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In memory of Lord Jack Lewis Cite this: Dalton Trans., 2015, 44, 3896
Brian F. G. Johnson,a William. P. Griffith,b Robin J. H. Clark,c John Evans,d Brian H. Robinsone and Paul R. Raithbyf
DOI: 10.1039/c4dt90196g
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Introduction – Brian F. G. Johnson Lord Jack Lewis, who recently died aged 86, was the 1970 Inorganic Professor at Cambridge for 25 years from 1970 to 1995. Highly energetic and extremely talented he was amongst a small band of pioneers who revolutionised Inorganic Chemistry and must be regarded as one of the true founding fathers of Modern Inorganic Chemistry. His research remained highly active well beyond retirement. Jack obtained his PhD at Nottingham under the guidance of Professor C. C. Addison (at that time deemed a physical chemist!) and worked on nonaqueous solvents, which in the 1950s, was a dominant theme in chemistry. His work included studies of dinitrogen tetroxide and liquid sodium both highly important inorganic liquids, the former as a component of rocket fuel and the latter as a coolant for reactors. On completion of his PhD he took up a lectureship at Sheffield where he developed a deep interest in the magneto-chemistry of transition metal compounds and a
Department of Chemistry, University of Cambridge, Cambridge, UK b Department of Chemistry, Imperial College, London, UK. E-mail: w.griffi[email protected] c Department of Chemistry, University College London, London, UK. E-mail: [email protected] d Chemistry, University of Southampton, Southampton, SO17 1BJ Southampton, UK. E-mail: [email protected] e Department of Chemistry, University of Otago, Dunedin, New Zealand. E-mail: [email protected] f Department of Chemistry, University of Bath, Bath, UK. E-mail: [email protected]
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complexes, recognising that such measurements gave an important guide to the stereochemistry of transition metal ions and the nature of inorganic structures. It was during this time that Jack realised the value of physiochemical techniques as structural probes and later was amongst the first to appreciate the value of mass spectroscopy and multinuclear NMR spectroscopy as probes to the nature of inorganic and organometallic compounds. After a short time at Sheffield he moved to Imperial College and then onto University College where he developed a deep and lasting collaboration with the late Sir Ronald Nyholm. They were a perfect team. Amongst many avenues of interest they were aware that apart from a few isolated compounds, e.g. mercurous compounds with a Hg–Hg bond, there were no examples of direct transition metal–transition metal bonds. Together they established routes to a number of such systems and nowadays such bonds are commonplace. Jack received the call to the Inorganic Chair at Manchester in 1961 and played a significant role in the construction of the new Chemistry Building. Here he retained his interest in inorganic magneto-chemistry and the synthesis of metal–metal bonds but also became interested in the factors which stabilised the transition metal–carbon sigma bond - in those days a rarity. At the same time together with Professor Arthur Birch he developed an interest in the reactivity of co-ordinated ligands. He and Birch discovered that the iron(tricarbonyl) unit stabilised the keto-form of phenol. It was this highly significant observation
which led Jack to consider the effect of other organometallic substrates such as ruthenium(tricarbonyl) on a variety of organic systems. The problem was finding a route to this ruthenium fragment. Eventually, trirutheniumdodecarbonyl was synthesised and shown to be an ideal precursor. However, most importantly the synthesis of this trinuclear compound was to lead Jack into an entirely new area of chemistry viz. that of transition metal clusters. This area possibly more than any other is the one that is most closely associated with Jack. At its conception few examples of these compounds had been established; this was to change entirely during the following years and was to lead to many tangential studies of the metallic surface, catalysis, and so on. Towards the last part of his work at Cambridge he turned his attention towards the chemistry and electronic properties of organometallic polymers, a highly successful venture in which he collaborated extensively with members of the Physics Department at the Cavendish Laboratories. In this tribute to Jack five leading workers in the field discuss their relationships with Jack, the impression he made upon them, and the value he gave from his deep and profound knowledge of his subject. They have chosen some of the papers he published during the periods outlined above. His initial periods at Nottingham, Sheffield and Imperial College, followed by his work with Nyholm at University College, in his first Chair at Manchester, his brief return to University College and then of course Cambridge. Interestingly his
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areas of research which varied widely from non-aqueous solvents to organometallic chemistry appeared to coincide with the area becoming established as a key research area within modern Inorganic Chemistry. Each of the authors has chosen papers which they feel demonstrate Jack’s interest and contribution at a particular stage of his career. All knew Jack well either as members of his research group or as colleagues in the various departments. Jack was an exceptionally charismatic character. He instantly commanded respect and his intrinsic goodness and deep understanding of his subject led countless students and colleagues to choose to work alongside him, to enjoy being with him and to benefit from him. He was warm, avuncular and firm, you knew where you stood with Jack. He strongly believed that research was only of value when correctly recorded and published and his amazing record of publication is witness to that. Most publications appeared in the various journals of the Royal Society of Chemistry although one can only be truly impressed by nineteen papers in Nature. In recognition of this very substantial contribution Jack received many diverse honours and awards. He was elected a Fellow of the Royal Society in 1973 and was awarded the Davy Medal in 1985, and their Royal Medal in 2004. Chemists throughout the World held Jack in high regard and amongst many such awards he was elected a member of the American Academy of Arts and Science (1983) and later the American Philosophical Society (1994). During the period 1986–1988 he was President of the Royal Society of Chemistry. He was knighted in 1982 and inducted into the House of Lords in 1989 taking the title Baron Lewis of Newnham. The government at that time recognised the need to have reputable and knowledgeable scientists in the House of Lords. He was an active member of the House serving on many committees primarily concerned with environmental issues. Jack and I worked closely together for 31 years. For me it was a truly wonderful and beneficial experience. I remember with great affection the very many times
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we discussed chemistry with the blackboard in his office covered with scribbled ideas, solutions and sometimes rubbish. Many others will vouch for that. Conferences were always invigorating with Jack around and we spent many exhilarating times at meetings through the world and all benefited from his presence. Jack Lewis was a remarkably brilliant chemist and a thoroughly decent man in every respect. He will always be held in the highest regard by those who had the good fortune to work with him or alongside him. His published work is a testament to his remarkable abilities as a Chemist and I very much hope that this series of papers will do justice to his memory.
Early years at Imperial College – William P. Griffith I first knew Jack in the year he spent with us at Imperial College (IC) as a lecturer (1956–1957); it was a seminal period for me and probably for IC inorganic chemistry. He gave an inspirational course on ‘crystal field theory’, a concept not widely known, to us at least, at that time. He also supervised my third-year 1956 undergraduate research project in the spring and summer terms on metal nitrosyl complexes: this went well, and when from 1957–1960 I did my PhD with Geoffrey Wilkinson (GW) this was the topic with which we continued. Jack would come over occasionally from UCL to discuss things with me and I would sometimes visit him at UCL, though the day-to-day running was of course by GW. We (Jack, Geoff and I) published eight papers together from this work, appearing from 1958–1961. Jack was immediately likeable and very easy to get on with. He was of course an excellent teacher and an enthusiastic supervisor, humorous, kind and understanding, with an extraordinary memory and grasp of detail. The account below covers his earliest papers, which I have defined as those from 1951 to 1957, with two post-1956
publications which carry an IC or Sheffield affiliation at the bottom of the papers. With papers written with a distinguished supervisor it is hard to assess the student’s contribution. I have chosen one example because, although written early in Jack’s Ph.D. career, he is the only co-author, and it receives extended mention in Addison’s review on N2O4.1 The paper is a fine illustration of the application of physical techniques (determination of reaction rates, electrical conductivities) together with inorganic preparations, and this balance of measurement and preparations exemplifies much of Jack’s subsequent work.2 The dissociation of liquid N2O4 to NO+ and NO3− had earlier been established by Addison; this paper describes the reaction of zinc metal with liquid N2O4, the rates of their reaction together, and the likelihood that the overall process is: Zn þ 2½ðNOþ ÞðNO3 Þ ! ZnðNO3 Þ2 þ 2NO
It was to be the precursor of many more papers by Addison on N2O4 and its remarkable reactivity. The second paper I have selected is one of the earliest produced by Jack when he was ‘independent’, in his first job as lecturer at Sheffield.3 His coauthor was Ralph Wilkins, already established on the staff at Sheffield, and who was later to edit with Jack an important book, “Modern Coordination Chemistry” in 1960 (see Robin Clark’s commentary below). While clearly owing its rationale to his earlier work with Addison on N2O4, this paper marks the start of what was to be a groundbreaking series on complexes of the nitrosyl ligand (NO). The rates of exchange of 36Cl (obtained from Amersham) between (Me4N)Cl and (Et4N)Cl with NOCl were measured: these are quite fast and were considered to arise from self-ionisation of NOCl to NO+ and Cl−. This was later to have profound implications for nitrosation reactions using NOCl. Another contribution I wish to highlight is the difficult and dangerous work on liquid metals, supported by AERE Harwell and representing a new departure for Addison and Jack.4 In this
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paper, plates of zinc, copper and molybdenum were dipped into liquid sodium solutions under argon at various contact angles to study the ‘wetting’ of the metals by the liquid; an ingenious torsion apparatus was devised for the work. The sodium metal was a commercial sample and the authors had to purify it by filtration at 150 °C through sintered glass. Under these circumstances it was found that zinc was wetted by sodium, but not copper or molybdenum. Later parts of this series dealt with the surface tension of liquid sodium, and these studies may have led to two later papers by Jack and Wilkinson on solutions of alkali metals in ethers. Jack’s work on chemical exchange was performed with D. B. (Brian) Sowerby, his first student at Sheffield where this work was done. The paper expands the aforementioned studies on 36 Cl exchange with NOCl,3 but here the substrates are POCl3, AsCl3 and SeOCl2, and represents a rare but useful contribution that Jack made to main-group chemistry.5 The paper reports exchange reactions between (R4N)36Cl (R = Me, Et) in CH3CN, nitrobenzene and CHCl3 with the substrates. For the first two, formation of [POCl4]− and [AsCl4]− was demonstrated, there being direct interaction between the oxychloride and 36 − Cl , first-order in Cl− and oxychloride. A final paper from Jack’s early career is the third of the eight papers that as a student I was a co-author with Jack and Geoffrey Wilkinson, and is typical of the series which we wrote on metal nitrosyl complexes.6 In these papers complexes already reported in the older German literature were examined by IR and other appropriate techniques such as Gouy magnetochemical measurements applied to solids as well as aqueous solutions. Here the brown complex [Fe(NO)(H2O)5]2+ (which causes the colour in the old ‘brown ring’ test for nitrates) is shown to contain high-spin iron with three unpaired electrons per metal atom. The cation in solution and various solids containing it were studied, as were several other low-spin nitrosyls of iron, cobalt and copper, with a view to understanding the bonding of the coordinated nitrosyl (NO+) ligand in such species.
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Periods at UCL – Robin J. H. Clark Jack’s periods at UCL, particularly the first from 1957–1961, were strongly reflected in the book “Modern Coordination Chemistry” edited by J. Lewis and R. G. Wilkins.7 It immediately became standard reading for all research groups in Inorganic Chemistry at UCL and in many other institutions. Accordingly it influences the choice of papers here, especially in Jack’s first period at UCL. The first paper from this period I wish to draw special attention to is “Magnetic properties of some d3, d4 and d5 complexes.”8 in which temperaturerange magnetic susceptibility measurements on osmium, ruthenium, rhenium and iridium complexes with the d3, d4 and d5 configurations were discussed in terms of Kotani theory. The relative importance of the assumptions made in this theory were examined in the light of the magnetic results. This paper was the forerunner to a long series of studies of the magnetism of transition metal complexes of various electronic configurations (d1, d2, d3 and d8) and geometries (octahedral and tetrahedral) as well as of antiferromagnetic systems. Many such papers discuss the magnetic properties of the complexes studied with reference to the ligand field strengths, the interelectronic repulsions and the spin–orbit coupling of the ions, antiferromagnetism and magnetic exchange between the ions. In particular, those with D. J. Machin and F. E. Mabbs at UCL and later in Manchester, led to several further publications in this area. Another important paper from this period was on diarsine complexes of quadrivalent metals.9 The very versatile ligand o-phenylenebisdimethylarsine, o-C6H4(AsMe2)2 (Diars) was shown to form 8-coordinate complexes TiX4·2Diars, X = Cl or Br. The titanium atom is bonded to four chlorine and four arsenic atoms to form a molecule with the classical dodecahedral D2d symmetry of the [Mo(CN)8]4− ion. VCl4·2Diars was characterised likewise. This paper erased the long-held belief by inorganic chemists (including Al Cotton) that first-row transition metals such as Ti or V could not form
adducts in which the metal atom had a co-ordination number of eight. This research also demonstrated that ZrX4 and HfX4 (X = Cl or Br) formed isomorphous dodecahedral molecules, and later research (with D. L. Kepert) demonstrated that NbX4 behaved likewise, forming isomorphous dodecahedral complexes which were paramagnetic owing to the d1 configuration of the niobium(IV). Moreover, it was noted (with W. Errington) that the reaction of diarsine with ZrCl4 is much faster than that with HfCl4, leading to the suggestion that the closely similar elements Zr and Hf might very effectively be separated through the different rates of reaction of their halides with diarsine. Although this did prove to be the case, the procedure was not economic as diarsine remained too expensive a reagent. The chemistry of titanium(III) had been difficult to establish owing to the large air- and moisture sensitivity of both its starting materials and any products. The necessary vacuum-line techniques, as originally developed and described in a thesis by S. Herzog from Jena, Germany, enabled the syntheses and study of several Ti(III) complexes to be carried out.10 Their characterisation established the coordination chemistry, properties, electronic spectroscopy and magnetism of titanium(III) complexes. This allowed the recognition of the features in common with those of related vanadium(III) and chromium(III) complexes. Distortion of the ligand field from octahedral was established for both the ground and excited states of each complex and the various ligands were placed in the spectrochemical series. Conditions favouring the formation of covalent metal–metal bonds were discussed in a contribution from Lewis in 1964, attention being paid to the electron configuration and the effective electronegativity of the metal atom.11 The electronegativity of the d10s1 atoms, e.g. gold, was considered, and the formal similarity of these atoms to the halogens emphasised. The compounds [Ph3PAuMn(CO)5], [(Ph3PAu)2Fe(CO)4] and [Ph3PAu-Co(CO)4] were synthesised and their physical properties compared to those of Mn(CO)4I and Fe(CO)4I2. This
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paper led to the frequent use of the fragment Ph3PAu as an isolobal substitute for hydride in metal carbonyl cluster chemistry. It also encouraged extensive further studies on the syntheses and properties of metal–metal bonded complexes at UCL, notably by the Lewis group during his second period there, and later at Cambridge and elsewhere. The final paper I wished to highlight from Jack’s time at UCL was a study of metal complexes of unsaturated phosphines and arsines.12 Chelate complexes of general formula [LPtX2] (X = Cl, Br and I) were formed by tertiary phosphines and arsines (L) containing the pentenyl group having the general formula [CH2vCH(CH2)]3ER2 (E = P, As). In them, both the olefinic double bond as well as the phosphorus or arsenic atoms are coordinated to platinum(II). Although transition metal complexes of Group 15 donors and of olefins were well established by 1961, it was only then that the idea of using a ‘hybrid’ ligand containing both types of donor was realised by H. W. Kouwenhoven, J. Lewis and R. S. Nyholm,13 who reported chelate Pt(II) complexes of 4-pentenyldimethylarsine, CH2vCH(CH2)3AsMe2. This was extended in the full paper (above)12 to the ligands 4-pentenyldiphenylphosphine, CH2vCH(CH2)3PPh2, and PhE {(CH2)3CHvCH2}2 (E = P or As). The range of stable metal-monoolefin complexes could be extended, not with the above ligands but with more rigid ones such as (2-vinylphenyl)dimethylarsine, 2-CH2vCHC6H4AsMe2, and (2-allylphenyl)dimethylarsine, 2CH2vCHCH2C6H4AsMe2, and their PPh2 counterparts. Bromination of planar PtBr2 complexes of these AsMe2containing ligands gave octahedral Pt(IV)–C sigma-bonded species.
At Manchester– Brian H. Robinson The confluence of new routine physiochemical techniques, the installation of a high-pressure facility to synthesise metal carbonyls on site at Manchester, the rapport with a like-minded organic
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chemist, Professor Arthur Birch, his enthusiastic approach to research and the ability to attract enthusiastic and able postgraduate students and outstanding ‘lieutenants’, and Jack’s vision, created the platform for the prolific research output which resulted from his years at Manchester. As a new researcher the ‘buzz’ in Jack’s group with his enthusiasm and mentoring was stimulating. There were three research platforms, synthesis and spectroscopic analysis of carbonyl complexes especially metal carbonyl clusters, reactions of coordinated ligands and magnetochemistry, the first two following Jack to UCL and Cambridge. Jack’s time at Manchester was a transition period with the organometallic/carbonyl cluster research laying the groundwork for later advances at UCL and Cambridge. Modern spectroscopic techniques were embraced by Jack in his research and this was especially true for his investigations of metal carbonyl complexes. These complexes lent themselves to routine mass spectrometry (a technique ‘owned’ by the organic chemists at the time and something they were unhappy with as it meant the probe had to be cleaned often!) and this technique launched the work on metal carbonyl clusters which became a mainstay of the Lewis–Johnson collaboration. The paper that set the scene was “Polynuclear metal carbonyl hydrides of manganese, ruthenium, and osmium”.14 Here the fragmentation patterns and the IR spectra of carbonyl hydrides were shown, for the first time, to be indicative of M–H–M bridges and new synthetic routes reported. This key work showed that the preferential loss of carbonyl groups, and a detailed analysis of the isotope pattern, enabled the formula and skeletal structure to be determined without an X-ray structure, and this was reinforced by the identification of new, unusual, clusters with non-transition group elements.15,16 The synthesis and mass spectra of many polynuclear complexes were also reported17,18 and this work, together with the theoretical interpretation of vibrational spectra19,20 placed the Lewis group at the forefront of organometallic spectroscopy.
Papers describing detailed IR and NMR, sometimes magnetochemistry, studies of carbon-bonded platinumβ-acetylacetonate complexes further illustrated Jack’s leadership in the application of spectroscopic techniques to organometallic complexes.21 The acetylacetonate work provided a background for future studies on coordinated ligands but it was the influence of Arthur Birch which initially produced the forward-looking research directed at the propensity of coordinated ring systems to undergo electrophilic attack. This research cemented Jack’s reputation in classical organometallic chemistry. A memorable seminar was one given by Birch on his travels overseas, but it eventually became a heated discussion on the latest work on diene complexes with particular reference to Roly Pettit’s work in Texas and the importance of the transition metal! The key and most cited paper from this era is “Iron tricarbonyl complexes of some cyclohexadienes”,22 which describes the reaction of triphenylmethyl fluoroborate on 1,3-dieneiron complexes and the subsequent reactions with nucleophiles on the resulting dienyl cation. The investigation of metal olefin complexes became another off-shoot of the Lewis–Johnson collaboration resulting in a number of papers in the final years at Manchester.23 Jack continued his work on magnetochemistry, begun in University College, working with collaborators David Machin, Frank Mabbs and, later, Malcolm Gerloch, all of whom developed their independent careers. Jack’s significant contributions to the development of inorganic magnetochemistry while at Manchester were to introduce the subject into the curriculum, textbooks written with his collaborators and reviews. The papers which had the most impact were those describing the variable temperature magnetic behaviour of the polynuclear complexes with strong linear M–O–M interactions; Cu–carboxylates, Cr3 and Fe3 carboxylates, and, probably most importantly, FeIIIOFeIII cores in [Fe(salen)]2O.24 These d-block cluster complexes demonstrated strong Heisenberg
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exchange coupling, with resultant J values, and these exchange interactions, and the complexes stereochemistry, were interpreted using molecular orbital theory. The fundamental ideas on exchange coupling, developed in these papers stood the test of time, predating the metalloprotein and metalloenzyme work of the 1970s onwards dealing with ‘Type 3’ CuCu (hemocyanins) and FeOFe (hemerythrin) protein metal sites. (Thanks to Professor K. Murray for comments.)
Accomplishments at Cambridge – John Evans Starting off a PhD just as Jack and Brian moved to Cambridge was a privilege that took me some years to appreciate. There was a special atmosphere of enthusiasm and optimism that allowed imagination to flow. There was a freedom to be inventive, only made possible by the resources that were available to us. Jack would regularly make his morning rounds through the group, and it was good when one was able to report some progress. Jack was able to keep his own pressures in the background and give you his full attention, a rare capacity. I know that he thoughtfully considered what might be a good path for me long before I knew it myself. It was his guidance that pointed me towards spectroscopies and catalysis, and it remains a challenge to apply one to inform the other. I remain in Jack’s debt. Two of the themes that emerged during the 1960s, namely the reactions of coordinated organic ligands and metal carbonyl clusters, flowered through the next decade. We can highlight three aspects concentrating on osmium cluster chemistry, all of which have proven to be very influential in coordination chemistry, heterogeneous catalysis and surface science. Coordinating organic ligands to clusters This field was transformed by the development of new methods of synthesising a solvation site within [Os3(CO)12] by oxidising a carbonyl group with Me3NO.25 The lability of the solvent molecule,
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CH3CN, created a low temperature entrypoint to observe the stepwise activation of ligands by the cluster. For example, C–H cleavage of the ethene in [Os3(CO)11(H2CvCH2)] could be tracked through the vinyl complex [Os3H(CO)10(HCvCH2)] to a vinylidene, [Os3H2(CO)9(CvCH2)]. In each stage there is loss of a carbonyl ligand and this is offset by the coordination of the new Os–H and Os–C bonds. The C2 ligand is initially coordinated to one osmium, moves to an edge in the vinyl complex, and spans the face of the cluster in the vinylidene. Similarly, a two-step route from [Os3(CO)12] via [Os3H2(CO)10], had been developed to the yield the cyclohexa-1,3-diene complex, [Os3(CO)10(C6H8)], in which the diene was coordinated to a single osmium vertex.26 The diene is also relatively labile and so the complex opened up selective ways to synthesise alkene and alkyne complexes, with differing ligands being coordinated to a vertex, edge or face of the cluster. High nuclearity metal clusters This field developed strongly from a detailed study of the thermolysis of [Os3(CO)12], which resulted in the isolation of penta- to octa-nuclear clusters.27 The shapes adopted by the clusters were intriguing and stimulated much development of cluster bonding theories, with these clusters showing a remarkable relationship to the electron counting methods developed by Professor Ken Wade in borane chemistry and then extended by Professor Mike Mingos. There was indeed a rationale behind the cluster in [Os6(CO)18] (a capped trigonal bipyramid) not adopting an octahedral cluster framework, and [Os7(CO)21] incorporating a cage with a capped octahedron geometry. Later it was shown that reduction of [Os6(CO)18] to its dianion, increasing the number of skeletal electron pairs from 6 to 7, did indeed result in a reorganization to an octahedral cage. This work inspired the development of pathways to new high nuclearity clusters of ruthenium and osmium at Cambridge. One of the trinuclear complexes which had been synthesized with a sol-
vating organic ligand was [Os3(CO)11( pyridine)].25 Pyrolysis of this complex provided a route to a metalated pyridine ligand, attached to both trinuclear, [Os3H(CO)10(NC5H4)] and pentanuclear clusters [Os5C(H)(CO)14(NC5H4)],28 with the latter also containing a carbide ligand. After chromatography on silica, the pentanuclear hydride, [Os5H(CO)15]− was also a significant product. This may have been a precursor to the elegant [Os10C(CO)24]2− cluster which was the predominant species after long reaction times. This complex has many features relevant to heterogeneous metal catalysts: the tetracapped octahedral cage is a fragment of the fcc metallic structure, there is an interstitial carbide, and each face is essentially a (111) surface saturated with CO as shown below. The idealised symmetry in solution is Td and as a result, the 13C NMR spectrum of the cluster exhibits just two resonances for the terminal carbonyls: one from the four capping Os(CO)3 and the other for the six Os(CO)2 centres of the core octahedron; there is no evidence for any rapid exchange of CO between the two sites. An Os(CO)3 unit contributes 0 electrons to the skeletal electron count, and so, with the core cluster being an octahedron, this cluster cage too could be accommodated in skeletal electron counting methods. Just as single-crystal surface science studies provide atomicscale definition of the events on heterogeneous catalysts with large metal particle sizes, the high nuclearity clusters provided calibration points for nanoparticulate catalysts.
Fluxionality of cluster complexes This absence of exchange observed in [Os10C(CO)24]2− is by no means universal
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and structural rigidity could not be taken for granted. With other researchers, such as Professor Brian Heaton working with the group of Professor Paolo Chini (Milan), characterising the structures of these complexes in solution proved to be challenging as a result of unexpectedly simple NMR spectra at room temperature. Hopping of ligands between sites and even fluxionality of the cluster cages could be monitored by variable temperature NMR studies. At Cambridge, an elegant and influential study was developed on [Os3(CO)10(PEt3)2] and [Os3(CO)9(PEt3)3], for which both 13C and 31P NMR played roles in the study.29 In both complexes, all the phosphines adopt the same sites: an equatorial location always with a P–Os–Os–CO axis. As a result, in the trisphosphine complex, which has an idealized symmetry local to the cluster of C3h, there are just two 13CO sites : axial and equatorial (2 : 1 ratio). These coalesce at 20 °C, demonstrating site mobility. For the ruthenium analogue the coalescence temperature was 10–20° lower, and this relates well with the proposed mechanism via an intermediate with a structure like that of Fe3(CO)12. Generally the relative stability of bridging sites decreases on descending a triad of transition elements. The phosphine also plays a role in lowering the barrier to bridge formation. The proposed mechanism involves the pairwise formation of two bridges from one axial CO from each of two metal centres as shown below. It is a selective process along a single Os–Os edge, and for the lower symmetry bisphosphine complex, this does not result in total CO scrambling. However, at higher temperatures, the two inequivalent PEt3 ligands exchange sites. So this second process, taken in combination the lower energy exchange by the bridged intermediate, does result in total CO site exchange. This kind of study probed the energy differences between ligand arrangements in the clusters, and the effects of the nature of the metal and auxiliary ligands on these energy differences. Such patterns could be relevant to mobility of metal surfaces with or without promoters and poisons, but such studies have yet to be carried out.
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The later years in Cambridge – Paul R. Raithby Arriving in Cambridge as a post-doc in 1976 to work with Jack and Brian was an amazing experience. The group was very enthusiastic and supportive and there was always a genuine excitement about the research being carried out. Jack led the team in his own inimitable style, making frequent visits to the synthetic and structural laboratories to see how we were getting on. With us, his approach was always to make suggestions and request that we carried out various reactions or make a particular series of measurements. If this did not happen, as it sometimes did not, his initial reaction was mild disappointment, which we all hated, as the last thing we wanted to do was disappoint Jack. It also ensured that we had done whatever Jack had asked us to do by the next time he came round! I was always hugely impressed by Jack’s encyclopedic knowledge of chemistry and the speed of his thought and reasoning. He could always quote you a paper that you needed to read about what you were doing, and, like the best chess players, think a dozen moves ahead of where your research project was at the moment, of course, bringing in many ideas that you had not thought of. Jack retained his exceptional intellect and sharpness of mind right up until his passing, and during our last meeting, about 10 days before he died, we talked about the chemistry that I am doing now and he was still able to make insightful comments as to the way the project should be developed. Jack retained an interest in the careers of all his PhD students and postdoctoral co-workers, and would fight
their cause decades after they left the group. I, and many others, owe Jack an enormous debt of gratitude for the enthusiasm for chemistry that he generated within us, and for the role model that he gave us to follow in our careers. By the mid-1980s Jack and Brian had firmly established the Cambridge cluster group as the premier team studying cluster carbonyls of the iron triad, and had determined the archetypal structural motifs for clusters with nuclearities between three and ten metal atoms. One of the driving forces for the research was to use cluster carbonyls as models for heterogeneous catalysis, where the cluster framework would provide a simple model for catalytic metal surfaces. Thus, the reactivity and manipulation of organic ligands once attached to the cluster surface was of great interest. Jack’s team carried out many reactions with alkenes and alkynes that were bonded to clusters but one of the most spectacular and elegant pieces of chemistry was the formation of a trinuclear osmium cluster in which a benzene ring was coordinated parallel to the triangular osmium unit, in a new face-capping mode. The cluster [Os3(CO)9(μ3-η2:η2:η2-C6H6)] was obtained from the deprotonation of [Os3(μ2-H)(CO)9(C6H7)] with [CPh3][BF4] and 1,8-diazabicyclo[5.4.0]undec-7-ene. The cluster was characterized by 1H NMR spectroscopy and a single-crystal X-ray diffraction study. A similar bonding mode for benzene was observed in the hexanuclear ruthenium cluster [Ru6C(CO)11(μ3-η2:η2:η2-C6H6)(η6-C6H6)], obtained using a different synthetic methodology. The cluster [Ru6C(CO)14(η6-C6H6)] was initially reduced with methanolic NaOH, to produce the [Ru6C(CO)12(η6-C6H6)]2− dianion, which was treated with [Ru(η6-C6H6)(PhCN)3]2+ to produce [Ru6C(CO)11(μ3-η2:η2:η2-C6H6)(η6-C6H6)].30
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A second target for the Lewis– Johnson group throughout the 1980s and 1990s was the synthesis of higher nuclearity osmium cluster carbonyls. The synthetic routes to these materials involved the pyrolysis or thermolysis of lower nuclearity clusters under a range of conditions. The nature and number of the products obtained was very sensitive to the conditions used and, in general, the yields of the products were low. However, the isolation and characterisation of these higher nuclearity clusters represents the identification of some of the first nano-clusters or particles, which are now of major importance in materials chemistry and catalysis. The two largest clusters synthesised and characterised by the Lewis–Johnson group were the dianions [Os17(CO)36]2− and [Os20(CO)40]2−. These clusters were obtained by the vacuum pyrolysis of [Os3(CO)10(NCMe)2] at temperatures above 260 °C and at initial pressures of ca. 10−3 Torr. The [Os17(CO)36]2− dianion contains a trigonal-bipyramidal core of 14 osmium atoms which is capped by three additional osmium atoms, while the [Os20(CO)40]2− dianion has a tetrahedral cubic close-packed metal core of 20 osmium atoms and represents the only example of a totally symmetric array of metal atoms of this nuclearity. It remains the largest osmium cluster carbonyl to have been isolated and structurally characterized, and the surface of this tetrahedral cluster is analogous to a fragment of a 111 metal surface.31 Jack was among the first to appreciate that if carbonyl clusters were to have practical applications in the area of catalysis the yields of these materials needed to be scaled up. It was unlikely that this goal would be achieved using thermolysis or pyrolysis methods because of the difficulties in controlling the products obtained. His group, therefore, started to explore cluster buildup reactions that occurred under much milder conditions, and much of this work involved addition reactions through the unsaturated cluster [Os3(μ-H)2(CO)10] and the lightly-ligated ligand cluster [Os3(CO)10(NCMe)2]. However, the addition of cationic metal fragments to anionic metal clusters also proved a low
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energy and effective way of building medium nuclearity cluster in good yields. This approach was elegantly illustrated in one of Jack’s last publications on cluster chemistry, namely the use of the [Ru(η5-C5H5)(NCMe)3]+ cationic fragment to produce mixed metal phosphine-stabilised clusters through anionic coupling reactions. For example, the room temperature reduction of [Os3(CO)11(PPh3)] with K/Ph2CO and subsequent coupling with [Ru(η5-C5H5)(NCMe)3][PF6] yielded the pentanuclear clusters [Os3(CO)11(PPh3){Ru(η5-C5H5)}2], [Os3H2(CO)11(PPh3){Ru(η5-C5H5)}2] and the tetranuclear cluster [Os3(CO)11(PPh3){Ru(η5-C5H5)}] in good yields.32 From the early 1990s, Jack opened up a new area of research involving the chemistry of monomeric, oligomeric, and polymeric platinum alkyne and polyyne materials. This work stemmed from the earlier transition metal cluster studies of metal alkynes because of his realisation of the interesting optical and electronic properties that these materials might have, particularly in the solidstate. His research, and the complementary work in Cambridge of Richard Friend and Andrew Holmes, on related organic materials, has led to the development of a new area of materials chemistry, and groups worldwide are now developing materials related to Jack’s original compounds for a range of optoelectronic applications. One of his first papers in the area described the synthesis of a range of new alkyne complexes of platinum and rhodium, where new routes involving the use of bis-trimethylstannyl(acetylide) complexes afforded high yields of high molecular weight organometallic rigid-rod polymers.33 In a later paper, in 1997, he showed elegantly that chemical manipulation of dinuclear platinum acetylidefunctionalised oligothiophene complexes could be used to fine tune the electronic properties of these systems.34
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References 1 C. C. Addison, Dinitrogen tetroxide, nitric acid, and their mixtures as media for inorganic reactions, Chem.
Rev., 1980, 80, 21–39, DOI: 10.1021/ cr60323a002. C. C. Addison and J. Lewis, The liquid dinitrogen tetroxide solvent system. Part X. The reaction of zinc with liquid nitrosyl chloride-dinitrogen tetroxide mixtures, J. Chem. Soc., 1951, 2843–2848, DOI: 10.1039/jr9510002843. J. Lewis and R. G. Wilkins, The chemistry of nitrosyl complexes. Part I. Evidence for the self-ionisation of liquid nitrosyl chloride from tracer studies, J. Chem. Soc., 1955, 56–59, DOI: 10.1039/jr9550000056. C. C. Addison, D. H. Kerridge and J. Lewis, Liquid metals. Part I. The surface tension of liquid sodium: the vertical-plate technique, J. Chem. Soc., 1954, 2861–2866, DOI: 10.1039/ jr9540002861. J. Lewis and D. B. Sowerby, Exchange of chlorine-36 between chloride ion and phosphorus oxychloride, arsenic trichloride, or selenium oxychloride, J. Chem. Soc., 1957, 336–342, DOI: 10.1039/jr9570000336. W. P. Griffith, J. Lewis and G. Wilkinson, Some nitric oxide complexes of iron and copper, J. Chem. Soc., 1958, 3993–3998, DOI: 10.1039/ jr9580003993. Modern Coordination Chemistry, ed. J. Lewis and R. G. Wilkins, Interscience Publ. Inc., London and New York, 1960. B. N. Figgis, J. Lewis, R. S. Nyholm and R. D. Peacock, Magnetic properties of some d3, d4 and d5 complexes, Discuss. Faraday Soc., 1958, 26, 103–109, DOI: 10.1039/ df9582600103. R. J. H. Clark, J. Lewis and R. S. Nyholm, Diarsine complexes of quadrivalent-metal halides, J. Chem. Soc., 1962, 2460, DOI: 10.1039/ jr9620002460. R. J. H. Clark, J. Lewis, D. J. Machin and R. S. Nyholm, Complexes of titanium trichloride, J. Chem. Soc., 1963, 379–387, DOI: 10.1039/jr9630000379. C. E. Coffey, J. Lewis and R. S. Nyholm, Metal–metal bonds. Part I. Compounds of gold(0) with the carbonyls of manganese, iron, and cobalt, J. Chem. Soc., 1964, 1741–1749, DOI: 10.1039/jr9640001741.
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12 M. A. Bennett, H. W. Kouwenhoven, J. Lewis and R. S. Nyholm, Metal complexes of unsaturated tertiary phosphines and arsines. Part I. Complexes of ligands containing the pentaenyl group, J. Chem. Soc., 1964, 4570–4577, DOI: 10.1039/ jr9640004570. 13 H. W. Kouwenhoven, J. Lewis and R. S. Nyholm, Complexes involving an olefinic tertiary arsine chelate group, Proc. Chem. Soc., London, 1961, 220, DOI: 10.1039/ps9610000185. 14 B. F. G. Johnson, R. D. Johnston, J. Lewis and B. H. Robinson, Polynuclear metal carbonyl hydrides of manganese, ruthenium, and osmium, Chem. Commun., 1966 (23), 851–852, DOI: 10.1039/ c19660000851. 15 B. F. G. Johnson, J. Lewis, I. G. Williams and J. Wilson, Mass spectra of polynuclear carbonyls: A new polynuclear carbonyl oxide of osmium, Chem. Commun., 1966 (12), 391–392, DOI: 10.1039/c19660000391. 16 B. F. G. Johnson, R. D. Johnston and J. Lewis, Chemistry of polynuclear compounds. Part XIV. Hexanuclear carbidocarbonylruthenium compounds, J. Chem. Soc. A, 1968, 2865– 2868, DOI: 10.1039/j19680002865. 17 J. Lewis, A. R. Manning, J. R. Miller and J. M. Wilson, Chemistry of polynuclear compounds. Part VII. The mass spectra of some polynuclear metal carbonyl complexes, J. Chem. Soc. A, 1966, 1663–1670, DOI: 10.1039/j19660001663. 18 B. F. G. Johnson, J. Lewis and P. A. Kilty, Chemistry of polynuclear compounds. Part XIII. The preparation and some reactions of dodecacarbonyltriosmium, J. Chem. Soc. A, 1968, 2859–2864, DOI: 10.1039/ j19680002859. 19 J. Lewis, A. R. Manning and J. R. Miller, Chemistry of polynuclear compounds. Part V. The vibrational spectra of some phosphine derivatives of manganese carbonyl, J. Chem. Soc. A, 1966, 845–854, DOI: 10.1039/ j19660000845. 20 H. M. Gager, J. Lewis and M. J. Ware, Metal–metal stretching frequencies in Raman spectra, Chem. Commun.,
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1966 (17), 616–617, DOI: 10.1039/ c19660000616. J. Lewis and C. Oldham, Metal-β-diketone complexes. Part III. Metal derivatives of some platinum-carbon bonded acetylacetone complexes, J. Chem. Soc. A, 1966, 1456–1462, DOI: 10.1039/j19660001456. A. J. Birch, P. E. Cross, J. Lewis, D. A. White and S. B. Wild, The chemistry of co-ordinated ligands. Part II. Iron tricarbonyl complexes of some cyclohexadienes, J. Chem. Soc. A, 1968, 332–340, DOI: 10.1039/ j19680000332. B. F. G. Johnson, T. Keating, J. Lewis, M. S. Subramanian and D. A. White, The chemistry of co-ordinated ligands. Part IV. Reactivity of cycloocta1,5-diene and its derivatives co-ordinated to palladium and platinum, J. Chem. Soc. A, 1969, 1793–1796, DOI: 10.1039/j19690001793. J. Lewis, F. E. Mabbs and A. Richards, The preparation and magnetic properties of some oxybridged binuclear iron(III) Schiffbase complexes, J. Chem. Soc. A, 1967, 1014–1018, DOI: 10.1039/ j19670001014. B. F. G. Johnson, J. Lewis and D. A. Pippard, The preparation, characterisation, and some reactions of [Os3(CO)11(NCMe)], J. Chem. Soc., Dalton Trans., 1981 (2), 407–412, DOI: 10.1039/dt9810000407. E. G. Bryan, B. F. G. Johnson and J. Lewis, 1,1,2,2,2,2,3,3,3,3-Decacarbonyl-1-(η-cyclohexa-1,3-diene)-triangulo-triosmium: A novel intermediate in synthetic osmium cluster chemistry, J. Chem. Soc., Dalton Trans., 1977 (14), 1328–1330, DOI: 10.1039/ dt9770001328. C. R. Eady, B. F. G. Johnson and J. Lewis, The chemistry of polynuclear compounds. Part XXVI. Products of the pyrolysis of dodecacarbonyl-triangulo-triruthenium and -triosmium, J. Chem. Soc., Dalton Trans., 1975 (23), 2606–2611, DOI: 10.1039/dt9750002606. P. F. Jackson, B. F. G. Johnson, J. Lewis, W. J. H. Nelson and M. McPartlin, The synthesis of the cluster dianion [Os10C(CO)24]2¬ by
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pyrolysis. X-Ray structure analysis of [N(PPh3)2]2 [Os10C(CO)24] and [Os5C (CO)14H(NC5H4)], J. Chem. Soc., Dalton Trans., 1982 (10), 2099–2107, DOI: 10.1039/dt9820002099. B. F. G. Johnson, J. Lewis, B. E. Reichert and K. T. Schorpp, Variable-temperature carbon-13 nuclear magnetic resonance spectra of phosphine-substituted dodecarbonyl-triangulo-triosmium, J. Chem. Soc., Dalton Trans., 1976 (14), 1403–1404, DOI: 10.1039/dt9760001403. M. P. Gomez-Sal, B. F. G. Johnson, J. Lewis, P. R. Raithby and A. H. Wright, Benzene in a new facecapping bonding mode: Molecular structures of [Ru6C(CO)11(μ3-η2:η 2:η2C6H6)(η6-C6H6)] and [Os3(CO)9(μ3η2:η2:η2-C6H6)], J. Chem. Soc., Chem. Commun., 1985 (23), 1682–1684, DOI: 10.1039/c39850001682. L. H. Gade, B. F. G. Johnson, J. Lewis, M. McPartlin, H. R. Powell, P. R. Raithby and W.-T. Wong, Synthesis and structural characterisation of the osmium cluster dianions [Os17(CO)36]2¬ and [Os20(CO)40]2¬ , J. Chem. Soc., Dalton Trans., 1994 (4), 521–532, DOI: 10.1039/ dt9940000521. R. Buntem, J. F. Gallagher, J. Lewis, P. R. Raithby, M.-A. Rennie and G. P. Shields, Use of the monocationic fragment [Ru(η5-C5H5)(MeCN)3]+ as an ionic coupling reagent in the synthesis of mixed-metal phosphine clusters, J. Chem. Soc., Dalton Trans., 2000 (23), 4297–4303, DOI: 10.1039/ b006746f. S. J. Davies, B. F. G. Johnson, M. S. Khan and J. Lewis, Synthesis of monomeric and oligomeric bis(acetylide) complexes of platinum and rhodium, J. Chem. Soc., Chem. Commun., 1991 (3), 187–188, DOI: 10.1039/c39910000187. J. Lewis, N. J. Long, P. R. Raithby, G. P. Shields, W.-Y. Wong and M. Younus, Synthesis and characterisation of new acetylide-functionalised oligothiophenes and their dinuclear platinum complexes, J. Chem. Soc., Dalton Trans., 1997 (22), 4283–4288, DOI: 10.1039/ a704708h.
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EDITORIAL
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In memory of Lord Jack Lewis Cite this: Dalton Trans., 2015, 44, 3896
Brian F. G. Johnson,a William. P. Griffith,b Robin J. H. Clark,c John Evans,d Brian H. Robinsone and Paul R. Raithbyf
DOI: 10.1039/c4dt90196g
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Introduction – Brian F. G. Johnson Lord Jack Lewis, who recently died aged 86, was the 1970 Inorganic Professor at Cambridge for 25 years from 1970 to 1995. Highly energetic and extremely talented he was amongst a small band of pioneers who revolutionised Inorganic Chemistry and must be regarded as one of the true founding fathers of Modern Inorganic Chemistry. His research remained highly active well beyond retirement. Jack obtained his PhD at Nottingham under the guidance of Professor C. C. Addison (at that time deemed a physical chemist!) and worked on nonaqueous solvents, which in the 1950s, was a dominant theme in chemistry. His work included studies of dinitrogen tetroxide and liquid sodium both highly important inorganic liquids, the former as a component of rocket fuel and the latter as a coolant for reactors. On completion of his PhD he took up a lectureship at Sheffield where he developed a deep interest in the magneto-chemistry of transition metal compounds and a
Department of Chemistry, University of Cambridge, Cambridge, UK b Department of Chemistry, Imperial College, London, UK. E-mail: w.griffi[email protected] c Department of Chemistry, University College London, London, UK. E-mail: [email protected] d Chemistry, University of Southampton, Southampton, SO17 1BJ Southampton, UK. E-mail: [email protected] e Department of Chemistry, University of Otago, Dunedin, New Zealand. E-mail: [email protected] f Department of Chemistry, University of Bath, Bath, UK. E-mail: [email protected]
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complexes, recognising that such measurements gave an important guide to the stereochemistry of transition metal ions and the nature of inorganic structures. It was during this time that Jack realised the value of physiochemical techniques as structural probes and later was amongst the first to appreciate the value of mass spectroscopy and multinuclear NMR spectroscopy as probes to the nature of inorganic and organometallic compounds. After a short time at Sheffield he moved to Imperial College and then onto University College where he developed a deep and lasting collaboration with the late Sir Ronald Nyholm. They were a perfect team. Amongst many avenues of interest they were aware that apart from a few isolated compounds, e.g. mercurous compounds with a Hg–Hg bond, there were no examples of direct transition metal–transition metal bonds. Together they established routes to a number of such systems and nowadays such bonds are commonplace. Jack received the call to the Inorganic Chair at Manchester in 1961 and played a significant role in the construction of the new Chemistry Building. Here he retained his interest in inorganic magneto-chemistry and the synthesis of metal–metal bonds but also became interested in the factors which stabilised the transition metal–carbon sigma bond - in those days a rarity. At the same time together with Professor Arthur Birch he developed an interest in the reactivity of co-ordinated ligands. He and Birch discovered that the iron(tricarbonyl) unit stabilised the keto-form of phenol. It was this highly significant observation
which led Jack to consider the effect of other organometallic substrates such as ruthenium(tricarbonyl) on a variety of organic systems. The problem was finding a route to this ruthenium fragment. Eventually, trirutheniumdodecarbonyl was synthesised and shown to be an ideal precursor. However, most importantly the synthesis of this trinuclear compound was to lead Jack into an entirely new area of chemistry viz. that of transition metal clusters. This area possibly more than any other is the one that is most closely associated with Jack. At its conception few examples of these compounds had been established; this was to change entirely during the following years and was to lead to many tangential studies of the metallic surface, catalysis, and so on. Towards the last part of his work at Cambridge he turned his attention towards the chemistry and electronic properties of organometallic polymers, a highly successful venture in which he collaborated extensively with members of the Physics Department at the Cavendish Laboratories. In this tribute to Jack five leading workers in the field discuss their relationships with Jack, the impression he made upon them, and the value he gave from his deep and profound knowledge of his subject. They have chosen some of the papers he published during the periods outlined above. His initial periods at Nottingham, Sheffield and Imperial College, followed by his work with Nyholm at University College, in his first Chair at Manchester, his brief return to University College and then of course Cambridge. Interestingly his
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areas of research which varied widely from non-aqueous solvents to organometallic chemistry appeared to coincide with the area becoming established as a key research area within modern Inorganic Chemistry. Each of the authors has chosen papers which they feel demonstrate Jack’s interest and contribution at a particular stage of his career. All knew Jack well either as members of his research group or as colleagues in the various departments. Jack was an exceptionally charismatic character. He instantly commanded respect and his intrinsic goodness and deep understanding of his subject led countless students and colleagues to choose to work alongside him, to enjoy being with him and to benefit from him. He was warm, avuncular and firm, you knew where you stood with Jack. He strongly believed that research was only of value when correctly recorded and published and his amazing record of publication is witness to that. Most publications appeared in the various journals of the Royal Society of Chemistry although one can only be truly impressed by nineteen papers in Nature. In recognition of this very substantial contribution Jack received many diverse honours and awards. He was elected a Fellow of the Royal Society in 1973 and was awarded the Davy Medal in 1985, and their Royal Medal in 2004. Chemists throughout the World held Jack in high regard and amongst many such awards he was elected a member of the American Academy of Arts and Science (1983) and later the American Philosophical Society (1994). During the period 1986–1988 he was President of the Royal Society of Chemistry. He was knighted in 1982 and inducted into the House of Lords in 1989 taking the title Baron Lewis of Newnham. The government at that time recognised the need to have reputable and knowledgeable scientists in the House of Lords. He was an active member of the House serving on many committees primarily concerned with environmental issues. Jack and I worked closely together for 31 years. For me it was a truly wonderful and beneficial experience. I remember with great affection the very many times
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we discussed chemistry with the blackboard in his office covered with scribbled ideas, solutions and sometimes rubbish. Many others will vouch for that. Conferences were always invigorating with Jack around and we spent many exhilarating times at meetings through the world and all benefited from his presence. Jack Lewis was a remarkably brilliant chemist and a thoroughly decent man in every respect. He will always be held in the highest regard by those who had the good fortune to work with him or alongside him. His published work is a testament to his remarkable abilities as a Chemist and I very much hope that this series of papers will do justice to his memory.
Early years at Imperial College – William P. Griffith I first knew Jack in the year he spent with us at Imperial College (IC) as a lecturer (1956–1957); it was a seminal period for me and probably for IC inorganic chemistry. He gave an inspirational course on ‘crystal field theory’, a concept not widely known, to us at least, at that time. He also supervised my third-year 1956 undergraduate research project in the spring and summer terms on metal nitrosyl complexes: this went well, and when from 1957–1960 I did my PhD with Geoffrey Wilkinson (GW) this was the topic with which we continued. Jack would come over occasionally from UCL to discuss things with me and I would sometimes visit him at UCL, though the day-to-day running was of course by GW. We (Jack, Geoff and I) published eight papers together from this work, appearing from 1958–1961. Jack was immediately likeable and very easy to get on with. He was of course an excellent teacher and an enthusiastic supervisor, humorous, kind and understanding, with an extraordinary memory and grasp of detail. The account below covers his earliest papers, which I have defined as those from 1951 to 1957, with two post-1956
publications which carry an IC or Sheffield affiliation at the bottom of the papers. With papers written with a distinguished supervisor it is hard to assess the student’s contribution. I have chosen one example because, although written early in Jack’s Ph.D. career, he is the only co-author, and it receives extended mention in Addison’s review on N2O4.1 The paper is a fine illustration of the application of physical techniques (determination of reaction rates, electrical conductivities) together with inorganic preparations, and this balance of measurement and preparations exemplifies much of Jack’s subsequent work.2 The dissociation of liquid N2O4 to NO+ and NO3− had earlier been established by Addison; this paper describes the reaction of zinc metal with liquid N2O4, the rates of their reaction together, and the likelihood that the overall process is: Zn þ 2½ðNOþ ÞðNO3 Þ ! ZnðNO3 Þ2 þ 2NO
It was to be the precursor of many more papers by Addison on N2O4 and its remarkable reactivity. The second paper I have selected is one of the earliest produced by Jack when he was ‘independent’, in his first job as lecturer at Sheffield.3 His coauthor was Ralph Wilkins, already established on the staff at Sheffield, and who was later to edit with Jack an important book, “Modern Coordination Chemistry” in 1960 (see Robin Clark’s commentary below). While clearly owing its rationale to his earlier work with Addison on N2O4, this paper marks the start of what was to be a groundbreaking series on complexes of the nitrosyl ligand (NO). The rates of exchange of 36Cl (obtained from Amersham) between (Me4N)Cl and (Et4N)Cl with NOCl were measured: these are quite fast and were considered to arise from self-ionisation of NOCl to NO+ and Cl−. This was later to have profound implications for nitrosation reactions using NOCl. Another contribution I wish to highlight is the difficult and dangerous work on liquid metals, supported by AERE Harwell and representing a new departure for Addison and Jack.4 In this
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paper, plates of zinc, copper and molybdenum were dipped into liquid sodium solutions under argon at various contact angles to study the ‘wetting’ of the metals by the liquid; an ingenious torsion apparatus was devised for the work. The sodium metal was a commercial sample and the authors had to purify it by filtration at 150 °C through sintered glass. Under these circumstances it was found that zinc was wetted by sodium, but not copper or molybdenum. Later parts of this series dealt with the surface tension of liquid sodium, and these studies may have led to two later papers by Jack and Wilkinson on solutions of alkali metals in ethers. Jack’s work on chemical exchange was performed with D. B. (Brian) Sowerby, his first student at Sheffield where this work was done. The paper expands the aforementioned studies on 36 Cl exchange with NOCl,3 but here the substrates are POCl3, AsCl3 and SeOCl2, and represents a rare but useful contribution that Jack made to main-group chemistry.5 The paper reports exchange reactions between (R4N)36Cl (R = Me, Et) in CH3CN, nitrobenzene and CHCl3 with the substrates. For the first two, formation of [POCl4]− and [AsCl4]− was demonstrated, there being direct interaction between the oxychloride and 36 − Cl , first-order in Cl− and oxychloride. A final paper from Jack’s early career is the third of the eight papers that as a student I was a co-author with Jack and Geoffrey Wilkinson, and is typical of the series which we wrote on metal nitrosyl complexes.6 In these papers complexes already reported in the older German literature were examined by IR and other appropriate techniques such as Gouy magnetochemical measurements applied to solids as well as aqueous solutions. Here the brown complex [Fe(NO)(H2O)5]2+ (which causes the colour in the old ‘brown ring’ test for nitrates) is shown to contain high-spin iron with three unpaired electrons per metal atom. The cation in solution and various solids containing it were studied, as were several other low-spin nitrosyls of iron, cobalt and copper, with a view to understanding the bonding of the coordinated nitrosyl (NO+) ligand in such species.
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Periods at UCL – Robin J. H. Clark Jack’s periods at UCL, particularly the first from 1957–1961, were strongly reflected in the book “Modern Coordination Chemistry” edited by J. Lewis and R. G. Wilkins.7 It immediately became standard reading for all research groups in Inorganic Chemistry at UCL and in many other institutions. Accordingly it influences the choice of papers here, especially in Jack’s first period at UCL. The first paper from this period I wish to draw special attention to is “Magnetic properties of some d3, d4 and d5 complexes.”8 in which temperaturerange magnetic susceptibility measurements on osmium, ruthenium, rhenium and iridium complexes with the d3, d4 and d5 configurations were discussed in terms of Kotani theory. The relative importance of the assumptions made in this theory were examined in the light of the magnetic results. This paper was the forerunner to a long series of studies of the magnetism of transition metal complexes of various electronic configurations (d1, d2, d3 and d8) and geometries (octahedral and tetrahedral) as well as of antiferromagnetic systems. Many such papers discuss the magnetic properties of the complexes studied with reference to the ligand field strengths, the interelectronic repulsions and the spin–orbit coupling of the ions, antiferromagnetism and magnetic exchange between the ions. In particular, those with D. J. Machin and F. E. Mabbs at UCL and later in Manchester, led to several further publications in this area. Another important paper from this period was on diarsine complexes of quadrivalent metals.9 The very versatile ligand o-phenylenebisdimethylarsine, o-C6H4(AsMe2)2 (Diars) was shown to form 8-coordinate complexes TiX4·2Diars, X = Cl or Br. The titanium atom is bonded to four chlorine and four arsenic atoms to form a molecule with the classical dodecahedral D2d symmetry of the [Mo(CN)8]4− ion. VCl4·2Diars was characterised likewise. This paper erased the long-held belief by inorganic chemists (including Al Cotton) that first-row transition metals such as Ti or V could not form
adducts in which the metal atom had a co-ordination number of eight. This research also demonstrated that ZrX4 and HfX4 (X = Cl or Br) formed isomorphous dodecahedral molecules, and later research (with D. L. Kepert) demonstrated that NbX4 behaved likewise, forming isomorphous dodecahedral complexes which were paramagnetic owing to the d1 configuration of the niobium(IV). Moreover, it was noted (with W. Errington) that the reaction of diarsine with ZrCl4 is much faster than that with HfCl4, leading to the suggestion that the closely similar elements Zr and Hf might very effectively be separated through the different rates of reaction of their halides with diarsine. Although this did prove to be the case, the procedure was not economic as diarsine remained too expensive a reagent. The chemistry of titanium(III) had been difficult to establish owing to the large air- and moisture sensitivity of both its starting materials and any products. The necessary vacuum-line techniques, as originally developed and described in a thesis by S. Herzog from Jena, Germany, enabled the syntheses and study of several Ti(III) complexes to be carried out.10 Their characterisation established the coordination chemistry, properties, electronic spectroscopy and magnetism of titanium(III) complexes. This allowed the recognition of the features in common with those of related vanadium(III) and chromium(III) complexes. Distortion of the ligand field from octahedral was established for both the ground and excited states of each complex and the various ligands were placed in the spectrochemical series. Conditions favouring the formation of covalent metal–metal bonds were discussed in a contribution from Lewis in 1964, attention being paid to the electron configuration and the effective electronegativity of the metal atom.11 The electronegativity of the d10s1 atoms, e.g. gold, was considered, and the formal similarity of these atoms to the halogens emphasised. The compounds [Ph3PAuMn(CO)5], [(Ph3PAu)2Fe(CO)4] and [Ph3PAu-Co(CO)4] were synthesised and their physical properties compared to those of Mn(CO)4I and Fe(CO)4I2. This
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paper led to the frequent use of the fragment Ph3PAu as an isolobal substitute for hydride in metal carbonyl cluster chemistry. It also encouraged extensive further studies on the syntheses and properties of metal–metal bonded complexes at UCL, notably by the Lewis group during his second period there, and later at Cambridge and elsewhere. The final paper I wished to highlight from Jack’s time at UCL was a study of metal complexes of unsaturated phosphines and arsines.12 Chelate complexes of general formula [LPtX2] (X = Cl, Br and I) were formed by tertiary phosphines and arsines (L) containing the pentenyl group having the general formula [CH2vCH(CH2)]3ER2 (E = P, As). In them, both the olefinic double bond as well as the phosphorus or arsenic atoms are coordinated to platinum(II). Although transition metal complexes of Group 15 donors and of olefins were well established by 1961, it was only then that the idea of using a ‘hybrid’ ligand containing both types of donor was realised by H. W. Kouwenhoven, J. Lewis and R. S. Nyholm,13 who reported chelate Pt(II) complexes of 4-pentenyldimethylarsine, CH2vCH(CH2)3AsMe2. This was extended in the full paper (above)12 to the ligands 4-pentenyldiphenylphosphine, CH2vCH(CH2)3PPh2, and PhE {(CH2)3CHvCH2}2 (E = P or As). The range of stable metal-monoolefin complexes could be extended, not with the above ligands but with more rigid ones such as (2-vinylphenyl)dimethylarsine, 2-CH2vCHC6H4AsMe2, and (2-allylphenyl)dimethylarsine, 2CH2vCHCH2C6H4AsMe2, and their PPh2 counterparts. Bromination of planar PtBr2 complexes of these AsMe2containing ligands gave octahedral Pt(IV)–C sigma-bonded species.
At Manchester– Brian H. Robinson The confluence of new routine physiochemical techniques, the installation of a high-pressure facility to synthesise metal carbonyls on site at Manchester, the rapport with a like-minded organic
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chemist, Professor Arthur Birch, his enthusiastic approach to research and the ability to attract enthusiastic and able postgraduate students and outstanding ‘lieutenants’, and Jack’s vision, created the platform for the prolific research output which resulted from his years at Manchester. As a new researcher the ‘buzz’ in Jack’s group with his enthusiasm and mentoring was stimulating. There were three research platforms, synthesis and spectroscopic analysis of carbonyl complexes especially metal carbonyl clusters, reactions of coordinated ligands and magnetochemistry, the first two following Jack to UCL and Cambridge. Jack’s time at Manchester was a transition period with the organometallic/carbonyl cluster research laying the groundwork for later advances at UCL and Cambridge. Modern spectroscopic techniques were embraced by Jack in his research and this was especially true for his investigations of metal carbonyl complexes. These complexes lent themselves to routine mass spectrometry (a technique ‘owned’ by the organic chemists at the time and something they were unhappy with as it meant the probe had to be cleaned often!) and this technique launched the work on metal carbonyl clusters which became a mainstay of the Lewis–Johnson collaboration. The paper that set the scene was “Polynuclear metal carbonyl hydrides of manganese, ruthenium, and osmium”.14 Here the fragmentation patterns and the IR spectra of carbonyl hydrides were shown, for the first time, to be indicative of M–H–M bridges and new synthetic routes reported. This key work showed that the preferential loss of carbonyl groups, and a detailed analysis of the isotope pattern, enabled the formula and skeletal structure to be determined without an X-ray structure, and this was reinforced by the identification of new, unusual, clusters with non-transition group elements.15,16 The synthesis and mass spectra of many polynuclear complexes were also reported17,18 and this work, together with the theoretical interpretation of vibrational spectra19,20 placed the Lewis group at the forefront of organometallic spectroscopy.
Papers describing detailed IR and NMR, sometimes magnetochemistry, studies of carbon-bonded platinumβ-acetylacetonate complexes further illustrated Jack’s leadership in the application of spectroscopic techniques to organometallic complexes.21 The acetylacetonate work provided a background for future studies on coordinated ligands but it was the influence of Arthur Birch which initially produced the forward-looking research directed at the propensity of coordinated ring systems to undergo electrophilic attack. This research cemented Jack’s reputation in classical organometallic chemistry. A memorable seminar was one given by Birch on his travels overseas, but it eventually became a heated discussion on the latest work on diene complexes with particular reference to Roly Pettit’s work in Texas and the importance of the transition metal! The key and most cited paper from this era is “Iron tricarbonyl complexes of some cyclohexadienes”,22 which describes the reaction of triphenylmethyl fluoroborate on 1,3-dieneiron complexes and the subsequent reactions with nucleophiles on the resulting dienyl cation. The investigation of metal olefin complexes became another off-shoot of the Lewis–Johnson collaboration resulting in a number of papers in the final years at Manchester.23 Jack continued his work on magnetochemistry, begun in University College, working with collaborators David Machin, Frank Mabbs and, later, Malcolm Gerloch, all of whom developed their independent careers. Jack’s significant contributions to the development of inorganic magnetochemistry while at Manchester were to introduce the subject into the curriculum, textbooks written with his collaborators and reviews. The papers which had the most impact were those describing the variable temperature magnetic behaviour of the polynuclear complexes with strong linear M–O–M interactions; Cu–carboxylates, Cr3 and Fe3 carboxylates, and, probably most importantly, FeIIIOFeIII cores in [Fe(salen)]2O.24 These d-block cluster complexes demonstrated strong Heisenberg
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exchange coupling, with resultant J values, and these exchange interactions, and the complexes stereochemistry, were interpreted using molecular orbital theory. The fundamental ideas on exchange coupling, developed in these papers stood the test of time, predating the metalloprotein and metalloenzyme work of the 1970s onwards dealing with ‘Type 3’ CuCu (hemocyanins) and FeOFe (hemerythrin) protein metal sites. (Thanks to Professor K. Murray for comments.)
Accomplishments at Cambridge – John Evans Starting off a PhD just as Jack and Brian moved to Cambridge was a privilege that took me some years to appreciate. There was a special atmosphere of enthusiasm and optimism that allowed imagination to flow. There was a freedom to be inventive, only made possible by the resources that were available to us. Jack would regularly make his morning rounds through the group, and it was good when one was able to report some progress. Jack was able to keep his own pressures in the background and give you his full attention, a rare capacity. I know that he thoughtfully considered what might be a good path for me long before I knew it myself. It was his guidance that pointed me towards spectroscopies and catalysis, and it remains a challenge to apply one to inform the other. I remain in Jack’s debt. Two of the themes that emerged during the 1960s, namely the reactions of coordinated organic ligands and metal carbonyl clusters, flowered through the next decade. We can highlight three aspects concentrating on osmium cluster chemistry, all of which have proven to be very influential in coordination chemistry, heterogeneous catalysis and surface science. Coordinating organic ligands to clusters This field was transformed by the development of new methods of synthesising a solvation site within [Os3(CO)12] by oxidising a carbonyl group with Me3NO.25 The lability of the solvent molecule,
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CH3CN, created a low temperature entrypoint to observe the stepwise activation of ligands by the cluster. For example, C–H cleavage of the ethene in [Os3(CO)11(H2CvCH2)] could be tracked through the vinyl complex [Os3H(CO)10(HCvCH2)] to a vinylidene, [Os3H2(CO)9(CvCH2)]. In each stage there is loss of a carbonyl ligand and this is offset by the coordination of the new Os–H and Os–C bonds. The C2 ligand is initially coordinated to one osmium, moves to an edge in the vinyl complex, and spans the face of the cluster in the vinylidene. Similarly, a two-step route from [Os3(CO)12] via [Os3H2(CO)10], had been developed to the yield the cyclohexa-1,3-diene complex, [Os3(CO)10(C6H8)], in which the diene was coordinated to a single osmium vertex.26 The diene is also relatively labile and so the complex opened up selective ways to synthesise alkene and alkyne complexes, with differing ligands being coordinated to a vertex, edge or face of the cluster. High nuclearity metal clusters This field developed strongly from a detailed study of the thermolysis of [Os3(CO)12], which resulted in the isolation of penta- to octa-nuclear clusters.27 The shapes adopted by the clusters were intriguing and stimulated much development of cluster bonding theories, with these clusters showing a remarkable relationship to the electron counting methods developed by Professor Ken Wade in borane chemistry and then extended by Professor Mike Mingos. There was indeed a rationale behind the cluster in [Os6(CO)18] (a capped trigonal bipyramid) not adopting an octahedral cluster framework, and [Os7(CO)21] incorporating a cage with a capped octahedron geometry. Later it was shown that reduction of [Os6(CO)18] to its dianion, increasing the number of skeletal electron pairs from 6 to 7, did indeed result in a reorganization to an octahedral cage. This work inspired the development of pathways to new high nuclearity clusters of ruthenium and osmium at Cambridge. One of the trinuclear complexes which had been synthesized with a sol-
vating organic ligand was [Os3(CO)11( pyridine)].25 Pyrolysis of this complex provided a route to a metalated pyridine ligand, attached to both trinuclear, [Os3H(CO)10(NC5H4)] and pentanuclear clusters [Os5C(H)(CO)14(NC5H4)],28 with the latter also containing a carbide ligand. After chromatography on silica, the pentanuclear hydride, [Os5H(CO)15]− was also a significant product. This may have been a precursor to the elegant [Os10C(CO)24]2− cluster which was the predominant species after long reaction times. This complex has many features relevant to heterogeneous metal catalysts: the tetracapped octahedral cage is a fragment of the fcc metallic structure, there is an interstitial carbide, and each face is essentially a (111) surface saturated with CO as shown below. The idealised symmetry in solution is Td and as a result, the 13C NMR spectrum of the cluster exhibits just two resonances for the terminal carbonyls: one from the four capping Os(CO)3 and the other for the six Os(CO)2 centres of the core octahedron; there is no evidence for any rapid exchange of CO between the two sites. An Os(CO)3 unit contributes 0 electrons to the skeletal electron count, and so, with the core cluster being an octahedron, this cluster cage too could be accommodated in skeletal electron counting methods. Just as single-crystal surface science studies provide atomicscale definition of the events on heterogeneous catalysts with large metal particle sizes, the high nuclearity clusters provided calibration points for nanoparticulate catalysts.
Fluxionality of cluster complexes This absence of exchange observed in [Os10C(CO)24]2− is by no means universal
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and structural rigidity could not be taken for granted. With other researchers, such as Professor Brian Heaton working with the group of Professor Paolo Chini (Milan), characterising the structures of these complexes in solution proved to be challenging as a result of unexpectedly simple NMR spectra at room temperature. Hopping of ligands between sites and even fluxionality of the cluster cages could be monitored by variable temperature NMR studies. At Cambridge, an elegant and influential study was developed on [Os3(CO)10(PEt3)2] and [Os3(CO)9(PEt3)3], for which both 13C and 31P NMR played roles in the study.29 In both complexes, all the phosphines adopt the same sites: an equatorial location always with a P–Os–Os–CO axis. As a result, in the trisphosphine complex, which has an idealized symmetry local to the cluster of C3h, there are just two 13CO sites : axial and equatorial (2 : 1 ratio). These coalesce at 20 °C, demonstrating site mobility. For the ruthenium analogue the coalescence temperature was 10–20° lower, and this relates well with the proposed mechanism via an intermediate with a structure like that of Fe3(CO)12. Generally the relative stability of bridging sites decreases on descending a triad of transition elements. The phosphine also plays a role in lowering the barrier to bridge formation. The proposed mechanism involves the pairwise formation of two bridges from one axial CO from each of two metal centres as shown below. It is a selective process along a single Os–Os edge, and for the lower symmetry bisphosphine complex, this does not result in total CO scrambling. However, at higher temperatures, the two inequivalent PEt3 ligands exchange sites. So this second process, taken in combination the lower energy exchange by the bridged intermediate, does result in total CO site exchange. This kind of study probed the energy differences between ligand arrangements in the clusters, and the effects of the nature of the metal and auxiliary ligands on these energy differences. Such patterns could be relevant to mobility of metal surfaces with or without promoters and poisons, but such studies have yet to be carried out.
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The later years in Cambridge – Paul R. Raithby Arriving in Cambridge as a post-doc in 1976 to work with Jack and Brian was an amazing experience. The group was very enthusiastic and supportive and there was always a genuine excitement about the research being carried out. Jack led the team in his own inimitable style, making frequent visits to the synthetic and structural laboratories to see how we were getting on. With us, his approach was always to make suggestions and request that we carried out various reactions or make a particular series of measurements. If this did not happen, as it sometimes did not, his initial reaction was mild disappointment, which we all hated, as the last thing we wanted to do was disappoint Jack. It also ensured that we had done whatever Jack had asked us to do by the next time he came round! I was always hugely impressed by Jack’s encyclopedic knowledge of chemistry and the speed of his thought and reasoning. He could always quote you a paper that you needed to read about what you were doing, and, like the best chess players, think a dozen moves ahead of where your research project was at the moment, of course, bringing in many ideas that you had not thought of. Jack retained his exceptional intellect and sharpness of mind right up until his passing, and during our last meeting, about 10 days before he died, we talked about the chemistry that I am doing now and he was still able to make insightful comments as to the way the project should be developed. Jack retained an interest in the careers of all his PhD students and postdoctoral co-workers, and would fight
their cause decades after they left the group. I, and many others, owe Jack an enormous debt of gratitude for the enthusiasm for chemistry that he generated within us, and for the role model that he gave us to follow in our careers. By the mid-1980s Jack and Brian had firmly established the Cambridge cluster group as the premier team studying cluster carbonyls of the iron triad, and had determined the archetypal structural motifs for clusters with nuclearities between three and ten metal atoms. One of the driving forces for the research was to use cluster carbonyls as models for heterogeneous catalysis, where the cluster framework would provide a simple model for catalytic metal surfaces. Thus, the reactivity and manipulation of organic ligands once attached to the cluster surface was of great interest. Jack’s team carried out many reactions with alkenes and alkynes that were bonded to clusters but one of the most spectacular and elegant pieces of chemistry was the formation of a trinuclear osmium cluster in which a benzene ring was coordinated parallel to the triangular osmium unit, in a new face-capping mode. The cluster [Os3(CO)9(μ3-η2:η2:η2-C6H6)] was obtained from the deprotonation of [Os3(μ2-H)(CO)9(C6H7)] with [CPh3][BF4] and 1,8-diazabicyclo[5.4.0]undec-7-ene. The cluster was characterized by 1H NMR spectroscopy and a single-crystal X-ray diffraction study. A similar bonding mode for benzene was observed in the hexanuclear ruthenium cluster [Ru6C(CO)11(μ3-η2:η2:η2-C6H6)(η6-C6H6)], obtained using a different synthetic methodology. The cluster [Ru6C(CO)14(η6-C6H6)] was initially reduced with methanolic NaOH, to produce the [Ru6C(CO)12(η6-C6H6)]2− dianion, which was treated with [Ru(η6-C6H6)(PhCN)3]2+ to produce [Ru6C(CO)11(μ3-η2:η2:η2-C6H6)(η6-C6H6)].30
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A second target for the Lewis– Johnson group throughout the 1980s and 1990s was the synthesis of higher nuclearity osmium cluster carbonyls. The synthetic routes to these materials involved the pyrolysis or thermolysis of lower nuclearity clusters under a range of conditions. The nature and number of the products obtained was very sensitive to the conditions used and, in general, the yields of the products were low. However, the isolation and characterisation of these higher nuclearity clusters represents the identification of some of the first nano-clusters or particles, which are now of major importance in materials chemistry and catalysis. The two largest clusters synthesised and characterised by the Lewis–Johnson group were the dianions [Os17(CO)36]2− and [Os20(CO)40]2−. These clusters were obtained by the vacuum pyrolysis of [Os3(CO)10(NCMe)2] at temperatures above 260 °C and at initial pressures of ca. 10−3 Torr. The [Os17(CO)36]2− dianion contains a trigonal-bipyramidal core of 14 osmium atoms which is capped by three additional osmium atoms, while the [Os20(CO)40]2− dianion has a tetrahedral cubic close-packed metal core of 20 osmium atoms and represents the only example of a totally symmetric array of metal atoms of this nuclearity. It remains the largest osmium cluster carbonyl to have been isolated and structurally characterized, and the surface of this tetrahedral cluster is analogous to a fragment of a 111 metal surface.31 Jack was among the first to appreciate that if carbonyl clusters were to have practical applications in the area of catalysis the yields of these materials needed to be scaled up. It was unlikely that this goal would be achieved using thermolysis or pyrolysis methods because of the difficulties in controlling the products obtained. His group, therefore, started to explore cluster buildup reactions that occurred under much milder conditions, and much of this work involved addition reactions through the unsaturated cluster [Os3(μ-H)2(CO)10] and the lightly-ligated ligand cluster [Os3(CO)10(NCMe)2]. However, the addition of cationic metal fragments to anionic metal clusters also proved a low
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energy and effective way of building medium nuclearity cluster in good yields. This approach was elegantly illustrated in one of Jack’s last publications on cluster chemistry, namely the use of the [Ru(η5-C5H5)(NCMe)3]+ cationic fragment to produce mixed metal phosphine-stabilised clusters through anionic coupling reactions. For example, the room temperature reduction of [Os3(CO)11(PPh3)] with K/Ph2CO and subsequent coupling with [Ru(η5-C5H5)(NCMe)3][PF6] yielded the pentanuclear clusters [Os3(CO)11(PPh3){Ru(η5-C5H5)}2], [Os3H2(CO)11(PPh3){Ru(η5-C5H5)}2] and the tetranuclear cluster [Os3(CO)11(PPh3){Ru(η5-C5H5)}] in good yields.32 From the early 1990s, Jack opened up a new area of research involving the chemistry of monomeric, oligomeric, and polymeric platinum alkyne and polyyne materials. This work stemmed from the earlier transition metal cluster studies of metal alkynes because of his realisation of the interesting optical and electronic properties that these materials might have, particularly in the solidstate. His research, and the complementary work in Cambridge of Richard Friend and Andrew Holmes, on related organic materials, has led to the development of a new area of materials chemistry, and groups worldwide are now developing materials related to Jack’s original compounds for a range of optoelectronic applications. One of his first papers in the area described the synthesis of a range of new alkyne complexes of platinum and rhodium, where new routes involving the use of bis-trimethylstannyl(acetylide) complexes afforded high yields of high molecular weight organometallic rigid-rod polymers.33 In a later paper, in 1997, he showed elegantly that chemical manipulation of dinuclear platinum acetylidefunctionalised oligothiophene complexes could be used to fine tune the electronic properties of these systems.34
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References 1 C. C. Addison, Dinitrogen tetroxide, nitric acid, and their mixtures as media for inorganic reactions, Chem.
Rev., 1980, 80, 21–39, DOI: 10.1021/ cr60323a002. C. C. Addison and J. Lewis, The liquid dinitrogen tetroxide solvent system. Part X. The reaction of zinc with liquid nitrosyl chloride-dinitrogen tetroxide mixtures, J. Chem. Soc., 1951, 2843–2848, DOI: 10.1039/jr9510002843. J. Lewis and R. G. Wilkins, The chemistry of nitrosyl complexes. Part I. Evidence for the self-ionisation of liquid nitrosyl chloride from tracer studies, J. Chem. Soc., 1955, 56–59, DOI: 10.1039/jr9550000056. C. C. Addison, D. H. Kerridge and J. Lewis, Liquid metals. Part I. The surface tension of liquid sodium: the vertical-plate technique, J. Chem. Soc., 1954, 2861–2866, DOI: 10.1039/ jr9540002861. J. Lewis and D. B. Sowerby, Exchange of chlorine-36 between chloride ion and phosphorus oxychloride, arsenic trichloride, or selenium oxychloride, J. Chem. Soc., 1957, 336–342, DOI: 10.1039/jr9570000336. W. P. Griffith, J. Lewis and G. Wilkinson, Some nitric oxide complexes of iron and copper, J. Chem. Soc., 1958, 3993–3998, DOI: 10.1039/ jr9580003993. Modern Coordination Chemistry, ed. J. Lewis and R. G. Wilkins, Interscience Publ. Inc., London and New York, 1960. B. N. Figgis, J. Lewis, R. S. Nyholm and R. D. Peacock, Magnetic properties of some d3, d4 and d5 complexes, Discuss. Faraday Soc., 1958, 26, 103–109, DOI: 10.1039/ df9582600103. R. J. H. Clark, J. Lewis and R. S. Nyholm, Diarsine complexes of quadrivalent-metal halides, J. Chem. Soc., 1962, 2460, DOI: 10.1039/ jr9620002460. R. J. H. Clark, J. Lewis, D. J. Machin and R. S. Nyholm, Complexes of titanium trichloride, J. Chem. Soc., 1963, 379–387, DOI: 10.1039/jr9630000379. C. E. Coffey, J. Lewis and R. S. Nyholm, Metal–metal bonds. Part I. Compounds of gold(0) with the carbonyls of manganese, iron, and cobalt, J. Chem. Soc., 1964, 1741–1749, DOI: 10.1039/jr9640001741.
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12 M. A. Bennett, H. W. Kouwenhoven, J. Lewis and R. S. Nyholm, Metal complexes of unsaturated tertiary phosphines and arsines. Part I. Complexes of ligands containing the pentaenyl group, J. Chem. Soc., 1964, 4570–4577, DOI: 10.1039/ jr9640004570. 13 H. W. Kouwenhoven, J. Lewis and R. S. Nyholm, Complexes involving an olefinic tertiary arsine chelate group, Proc. Chem. Soc., London, 1961, 220, DOI: 10.1039/ps9610000185. 14 B. F. G. Johnson, R. D. Johnston, J. Lewis and B. H. Robinson, Polynuclear metal carbonyl hydrides of manganese, ruthenium, and osmium, Chem. Commun., 1966 (23), 851–852, DOI: 10.1039/ c19660000851. 15 B. F. G. Johnson, J. Lewis, I. G. Williams and J. Wilson, Mass spectra of polynuclear carbonyls: A new polynuclear carbonyl oxide of osmium, Chem. Commun., 1966 (12), 391–392, DOI: 10.1039/c19660000391. 16 B. F. G. Johnson, R. D. Johnston and J. Lewis, Chemistry of polynuclear compounds. Part XIV. Hexanuclear carbidocarbonylruthenium compounds, J. Chem. Soc. A, 1968, 2865– 2868, DOI: 10.1039/j19680002865. 17 J. Lewis, A. R. Manning, J. R. Miller and J. M. Wilson, Chemistry of polynuclear compounds. Part VII. The mass spectra of some polynuclear metal carbonyl complexes, J. Chem. Soc. A, 1966, 1663–1670, DOI: 10.1039/j19660001663. 18 B. F. G. Johnson, J. Lewis and P. A. Kilty, Chemistry of polynuclear compounds. Part XIII. The preparation and some reactions of dodecacarbonyltriosmium, J. Chem. Soc. A, 1968, 2859–2864, DOI: 10.1039/ j19680002859. 19 J. Lewis, A. R. Manning and J. R. Miller, Chemistry of polynuclear compounds. Part V. The vibrational spectra of some phosphine derivatives of manganese carbonyl, J. Chem. Soc. A, 1966, 845–854, DOI: 10.1039/ j19660000845. 20 H. M. Gager, J. Lewis and M. J. Ware, Metal–metal stretching frequencies in Raman spectra, Chem. Commun.,
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1966 (17), 616–617, DOI: 10.1039/ c19660000616. J. Lewis and C. Oldham, Metal-β-diketone complexes. Part III. Metal derivatives of some platinum-carbon bonded acetylacetone complexes, J. Chem. Soc. A, 1966, 1456–1462, DOI: 10.1039/j19660001456. A. J. Birch, P. E. Cross, J. Lewis, D. A. White and S. B. Wild, The chemistry of co-ordinated ligands. Part II. Iron tricarbonyl complexes of some cyclohexadienes, J. Chem. Soc. A, 1968, 332–340, DOI: 10.1039/ j19680000332. B. F. G. Johnson, T. Keating, J. Lewis, M. S. Subramanian and D. A. White, The chemistry of co-ordinated ligands. Part IV. Reactivity of cycloocta1,5-diene and its derivatives co-ordinated to palladium and platinum, J. Chem. Soc. A, 1969, 1793–1796, DOI: 10.1039/j19690001793. J. Lewis, F. E. Mabbs and A. Richards, The preparation and magnetic properties of some oxybridged binuclear iron(III) Schiffbase complexes, J. Chem. Soc. A, 1967, 1014–1018, DOI: 10.1039/ j19670001014. B. F. G. Johnson, J. Lewis and D. A. Pippard, The preparation, characterisation, and some reactions of [Os3(CO)11(NCMe)], J. Chem. Soc., Dalton Trans., 1981 (2), 407–412, DOI: 10.1039/dt9810000407. E. G. Bryan, B. F. G. Johnson and J. Lewis, 1,1,2,2,2,2,3,3,3,3-Decacarbonyl-1-(η-cyclohexa-1,3-diene)-triangulo-triosmium: A novel intermediate in synthetic osmium cluster chemistry, J. Chem. Soc., Dalton Trans., 1977 (14), 1328–1330, DOI: 10.1039/ dt9770001328. C. R. Eady, B. F. G. Johnson and J. Lewis, The chemistry of polynuclear compounds. Part XXVI. Products of the pyrolysis of dodecacarbonyl-triangulo-triruthenium and -triosmium, J. Chem. Soc., Dalton Trans., 1975 (23), 2606–2611, DOI: 10.1039/dt9750002606. P. F. Jackson, B. F. G. Johnson, J. Lewis, W. J. H. Nelson and M. McPartlin, The synthesis of the cluster dianion [Os10C(CO)24]2¬ by
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pyrolysis. X-Ray structure analysis of [N(PPh3)2]2 [Os10C(CO)24] and [Os5C (CO)14H(NC5H4)], J. Chem. Soc., Dalton Trans., 1982 (10), 2099–2107, DOI: 10.1039/dt9820002099. B. F. G. Johnson, J. Lewis, B. E. Reichert and K. T. Schorpp, Variable-temperature carbon-13 nuclear magnetic resonance spectra of phosphine-substituted dodecarbonyl-triangulo-triosmium, J. Chem. Soc., Dalton Trans., 1976 (14), 1403–1404, DOI: 10.1039/dt9760001403. M. P. Gomez-Sal, B. F. G. Johnson, J. Lewis, P. R. Raithby and A. H. Wright, Benzene in a new facecapping bonding mode: Molecular structures of [Ru6C(CO)11(μ3-η2:η 2:η2C6H6)(η6-C6H6)] and [Os3(CO)9(μ3η2:η2:η2-C6H6)], J. Chem. Soc., Chem. Commun., 1985 (23), 1682–1684, DOI: 10.1039/c39850001682. L. H. Gade, B. F. G. Johnson, J. Lewis, M. McPartlin, H. R. Powell, P. R. Raithby and W.-T. Wong, Synthesis and structural characterisation of the osmium cluster dianions [Os17(CO)36]2¬ and [Os20(CO)40]2¬ , J. Chem. Soc., Dalton Trans., 1994 (4), 521–532, DOI: 10.1039/ dt9940000521. R. Buntem, J. F. Gallagher, J. Lewis, P. R. Raithby, M.-A. Rennie and G. P. Shields, Use of the monocationic fragment [Ru(η5-C5H5)(MeCN)3]+ as an ionic coupling reagent in the synthesis of mixed-metal phosphine clusters, J. Chem. Soc., Dalton Trans., 2000 (23), 4297–4303, DOI: 10.1039/ b006746f. S. J. Davies, B. F. G. Johnson, M. S. Khan and J. Lewis, Synthesis of monomeric and oligomeric bis(acetylide) complexes of platinum and rhodium, J. Chem. Soc., Chem. Commun., 1991 (3), 187–188, DOI: 10.1039/c39910000187. J. Lewis, N. J. Long, P. R. Raithby, G. P. Shields, W.-Y. Wong and M. Younus, Synthesis and characterisation of new acetylide-functionalised oligothiophenes and their dinuclear platinum complexes, J. Chem. Soc., Dalton Trans., 1997 (22), 4283–4288, DOI: 10.1039/ a704708h.
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