DOI: 10.1002/chem.201404860
Full Paper
& Scorpionates
Polyimido Sulfur(VI) Phosphanyl Ligand in Metal Complexation Elena Carl and Dietmar Stalke*[a] In memory of Professor Lord Jack Lewis
Abstract: Herein, new complexes containing the [Ph2PCH2S(NtBu)3] anion are presented, supplying three imido nitrogen atoms and a remote phosphorus atom as potential donor sites to main group and transition-metal cations. The lithiated complex [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) is an excellent starting material in transmetalation reactions. Herein, the transition-metal complexes [M{(NtBu)3SCH2PPh2}2] (M =
Introduction Next to phosphorus/nitrogen chemistry, probably the richest line of action in main-group chemistry is sulfur/nitrogen chemistry. The wide range of coordination numbers one to six and oxidation states (+ I to + VI) affords an enormous variety of covalent molecules.[1] Ever since, the synthesis of polymeric (SN)x[2] and the discovery of its high-temperature superconducting properties,[3] the nature of the SN bond was under constant debate and the synthesis of SN multiple bonds was a rapidly emerging area.[4] Originally, sulfur dioxide SO2 and diimide S(NR)2 were believed to be hypervalent species with one lone pair and two S=O or S=N double bonds.[5] It was only much later that calculations indicated that the necessary d orbitals in the optimization merely serve as polarization functions and do not contribute to the covalent bonding by accommodating the additional valence electrons at the sulfur atom.[6] Charge-density investigations on SO2[7] and S(NtBu)2[8] discharged hypervalency and proved considerable electrostatics to be responsible for the bond shortening. The same is valid for the sulfate anion SO42.[9] After the syntheses to triimidosulfites S(NR)32 [Eq. (1)] and their oxidation to sulfur triimides S(NR)3 by halogens [Eq. (2)],[10] the triimidosulfonate anion RS(NR)3 is accessible in the reaction of sulfur triimide S(NR)3 with any organometallics, such as methyllithium [Eq. (3)].[11] To further augment the coordination abilities of the SN ligands, the diimidosulfinates[12] RS(NR)2 and triimidosulfonates RS(NR)3 provide a rich platform. They chelate the metal with two imido nitrogen atoms only and hold it tight like a scorpion with its two claws (Figure 1). The additional coordination site,
Mn (2), Ni (3), Zn (4)) were synthesized and structurally characterized. Their isotypical molecules show SN2 chelation and no employment of the adjacent phosphorus atom in coordination. The third pendent imido group is always twisted toward the vacant face of the tetrahedrally coordinated sulfur atom.
comparable to the sting of the scorpion, can be introduced if the sulfur di- or triimide is reacted with an organometallic compound providing an additional donor site, for example, a phosphorus atom (Scheme 1). 2 SðNRÞ2 þ 4 LiHNR ! ½Li4 fðNRÞ3 Sg2 þ 2 H2 NR
ð1Þ
½Li4 fðNRÞ3 Sg2 þ 2 X2 ! 2 SðNRÞ3 þ 4 LiX; X ¼ Cl, Br, I
ð2Þ
2 SðNRÞ3 þ 2 MeLi ! ½LiðNRÞ3 SMe2
ð3Þ
[a] E. Carl, Prof. D. Stalke Institut fr Anorganische Chemie, Georg-August-Universitt Tammannstrasse 4, 37077 Gçttingen (Germany) E-mail: [email protected] Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201404860. Chem. Eur. J. 2014, 20, 15849 – 15854
Figure 1. Hemilabile polyimido SN scorpionate with two N claws and an additional P sting for potential tripodal metal coordination.
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Scheme 1. Preparation of [(tmeda)Li{(NtBu)3SCH2PPh2}] (1).
The resulting ligands combine the abilities of Trofimenko’s scorpionates[13] with the hemilability of the Janus head ligands.[14] To broaden the field of polyimido sulfur phosphanyl ligands, tris(tert-butyl)sulfur(VI) triimide S(NtBu)3,[10, 11] instead of sulfur(IV) diimides S(NR)2, was used as the scaffold and starting material for the reaction with lithium diphenylphosphanylmethylides [(tmeda)LiCH2PPh2] (TMEDA = tetramethylethylenediamine). The resulting [(tBuN)3SCH2PPh2] anion in 1 is reminiscent to the [(tBuN)3SMe] anion with the S-bound methyl group further functionalized.[15] Sulfur/nitrogen compounds of this type have already been employed in the synthesis for various metal complexes with versatile coordination motifs,[11] but the combination with transition metals has rarely been touched to date.[16] One advantage of the sulfur triimides over the sulfur diimides is their additional coordination site that can be employed in the syntheses of heterobimetallic complexes.[3d] To explore the field of sulfur imides in combination with transition metals, the new Janus head scorpionate [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) and the transition metals manganese, nickel, and zinc were used in the syntheses. Those metals were chosen because of their divalent character and their easy availability.
Results and Discussion Ligand synthesis The linkage between the sulfur triimide and the phosphane was achieved by an equimolar reaction of lithium diphenyl phosphanyl methanide and tris(tert-butyl)sulfur triimide in a pentane/THF solution at dry-ice temperature to give [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) in 90 % yield (Scheme 1). Colorless crystals suitable for X-ray structure determination were obtained after storing the solution at 24 8C for five days. The crystal structure of 1 is depicted in Figure 2. The lithiated complex crystallizes in the orthorhombic space group P212121 with one molecule in the asymmetric unit. In the monomeric complex, the lithium cation is chelated in a distorted tetrahedral manner by only two nitrogen atoms of the three present imido groups and by the two nitrogen atoms of the chelating TMEDA donor base to saturate the coordination sphere of the lithium cation. Due to steric crowding, a tripodal coordination of the metal is prevented, and the third NtBu group is turned to the vacant site of the complex. The sulfur atom in the oxidation state VI is the presumably electronically depleted center of the ligand. It is also tetraheChem. Eur. J. 2014, 20, 15849 – 15854
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Figure 2. Molecular structure of 1. Anisotropic displacement parameters are depicted at the 50 % probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths [] and angles [8]: S1N1 1.5804(10), S1N2 1.5705(11), S1N3 1.5389(11), Li1N1 2.006(3), Li1N2 1.977(2), SC1 1.8181(12), PC1 1.8513(12), N1-S1-N2 97.49(5), S1-C1-P1 111.76(6), C1-S-N3 95.90(6), N1-Li1-N2 72.99(8), N4-Li1-N5 82.94(16).
drally distorted coordinated by the three nitrogen atoms and the phosphorus side arm. The SN bond lengths of the nitrogen atoms N1 and N2 are halfway in the range of the predicted values for a double (1.52 ) and a single (1.70 ) bond, reported in literature.[17] However, it is clear that hypervalency is not an option for sulfur–imido compounds and bond shortening is due to electrostatic reinforcement.[8, 18] Relatively to the SN1 and SN2 distances, the SN3 distance is shorter and quite close to the length of a double bond. The coordination to the lithium cation causes the elongation of the SN1/2 bonds, because the electron density of the nitrogen atoms has to be shared between the lithium cation and the electropositive sulfur atom. Consequently, the SN3 bond has to be the shortest (1.5389(11) ), due to the resulting enhanced electrostatic interaction between the negatively charged, non-chelating nitrogen atom and also due to the lower coordination number. The SC1 bond length shows the typical distance of 1.8181(12) . The phosphorus atom in the side arm is directed to the lithium cation but the distance of 3.718 is too long to be called a LiP bond, considering the mean value of all published LiP bond lengths in the CSD to be 2.58 and the LiP distance in, for example, the [(tmeda)LiPPh2]2 dimer of 2.61 .[19, 20] The related complex [(tmeda)Li{(NSiMe3)2SCH2PPh2}] is the sulfur(IV) diimide analogue of 1, in which the third nitrogen side arm is substituted by the lone pair of the sulfur(IV) atom.[12a] A superposition plot of the core of both complexes is depicted in Figure 3. A comparison of the bond angles and lengths of both complexes revealed that the SN distances in 1 are shorter in comparison to the SIV analogue (165.20(9) and
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Full Paper Transition-metal complexes
Figure 3. Superposition plot of 1 (gray) and [(tmeda)Li{(NSiMe3)SCH2PPh2}] (black). The S1, N1, and N2 atoms are projected onto each other.
171.84(10) pm) because of the higher oxidation state of the sulfur atom. The P-C-S angle in the SIV ligand is a little smaller (108.79(9)8) than in 1, indicating a more pronounced inclination of the phosphorus atom to the lithium cation resulting in a closer LiP distance of 3.231 . The space-filling model of 1 is depicted in Figure 4 and demonstrates how the tBu groups hinder the phosphorus atom from coordinating the lithium cation in 1. The quartenary carbon atoms of the tBu groups are more fixed in the N1-S1-N2 plane, shielding the lithium cation perfectly.
Previously, it was reported that sulfur diimide derivatives are too redox active in reactions with metal halides and that these reactions most likely give rise to ligand scrambling via SN and SC bond cleavages.[21] Consequently, only the transmetalation of the NSCP ligand [Li{Me2PCH2S(NtBu)2}]2 with MgCl2 leads successfully to the magnesium complex [Mg{Me2PCH2S(NtBu)2}2].[12a] The explanation for that might be the diagonal relationship between lithium and magnesium in the periodic tables of elements and their similar cationic radius. For any other successful transmetalation reactions of S-phosphanyl-diimidosulfinate ligands reported in this paper, metal(II) bis(trimethylsilyl)amides were used.[12b] Despite of those limitations, we now reacted 1 with metal(II) bromides to investigate whether or not the SVI ligand is stable enough against redox scrambling. The metal halides are easier accessible than the metal(II) bis(trimethylsilyl)amides and easier to handle. The metal bromides are a softer reagent in comparison to the chlorides and more soluble in the required solvent. The general preparation route for the transition metal complexes 2 (Mn), 3 (Ni), and 4 (Zn) in yields of 25, 10, and 21 %, respectively, is shown in Scheme 2.
Scheme 2. Synthesis of [M{(NtBu)3SCH2PPh2}2] (M = Mn (2), Ni (3), Zn (4)).
Structural comparison
Figure 4. Space-filling model of 1 and [(tmeda)Li{(NSiMe3)2SCH2PPh2}]. The TMEDA ligand is omitted to provide high visibility of the lithium cation.
In the SIV ligand, the SiMe3 groups deviate significantly from the N1-S1-N2 plane (0.713 and 0.535 ), giving the phosphorus side arm extra space to approach the lithium cation more closely. In addition, the SiN bonds are much longer than the CN bonds, keeping the methyl groups away from the metal. The advantage of complex 1 is the presence of a third imido group. Together with the additional phosphorus side arm, it might provide a further coordination site for a second metal. Hence, ligand 1 offers the opportunity to generate heterobimetallic complexes with this second hemilabile donor site. Chem. Eur. J. 2014, 20, 15849 – 15854
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The complexes 2 (Mn), 3 (Ni), and 4 (Zn) are isotypical and crystallize in the monoclinic space group C2/c (2) or C2 (3 and 4) with half a molecule in the asymmetric unit, respectively. Representatively, the crystal structure of 2 is depicted in Figure 5 together with selected bond lengths and angles of 2, 3, and 4. The different transition-metal cations are coordinated similarly by the ligand. In the homoleptic complexes, the central metal cation is chelated by four of the six present NtBu groups in a distorted tetrahedral fashion. The negative charge is delocalized over the chelating SN2 unit indicated by the almost identical SN bond lengths. The two symmetry generated four membered SN2M rings (M = Mn2 + , Ni2 + and Zn2 + ) are connected via the metal(II) cation and twisted by 81.788 (2), 83.578 (3), and 85.388 (4). Again, the non-chelating pendent NtBu group of each ligand is turned toward the vacant site of the ligand, as was already observed in 1. Only in compound 2, the phosphorus side arm is inclined towards the metal but again the MnP distance (3.985 ) is too long to be called a firm coordination. However, this long-range interaction
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Full Paper sum of all SN distances in all three transition metal complexes is almost constant at 4.72(1) .[11a] The CSN3 unit responds flexibly to different electronic requirements induced by the various metal cations in terms of the sulfur atom being shifted relative to an otherwise fixed N3 environment. This again experimentally emphasizes the predominantly ionic SN bonding rather than valence expansion and d orbital participation in bonding. Assuming a classical S=N double bond in polyimido sulfur species would not explain the facile NR transfer in transimidation reactions with this class of compounds either (Table 1).[21]
Conclusion Figure 5. Molecular structure of [Mn{(NtBu)3SCH2PPh2}2] (2). Anisotropic displacement parameters are depicted at the 50 % probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths [] and angles [8]: 2: S1N1 1.5951(17), S1N2 1.5966(17), S1N3 1.5222(17), MnN1 2.1032(17), MnN2 2.1255(17), S1C1 1.8070(20), P1C1 1.858(2), N1-S1-N2 94.97(9), N1Mn-N2 67.61(6); 3 (Ni): S1N1 1.604(3), S1N2 1.593(3), S1N3 1.520(3), Ni N1 1.985(3), NiN2 1.964(3), S1C1 1.799(4), P1C1 1.847(4), N1-S1-N2 92.64(14), N1-Ni-N2 71.65(11); 4 (Zn): S1N1 1.595(2), S1N2 1.604(3), S1N3 1.522(3), ZnN1 2.005(2), ZnN2 2.013(2), S1C1 1.807(3), P1C1 1.849(3), N1-S1-N2 94.20(12), N1-Zn-N2 71.35(9).
might help to electronically supply the Mn2 + dication, because otherwise the phosphorus atom might have been turned away from the metal similar to 3 and 4. The MN distances are the shortest in 3 and the longest in 2, reflecting the different ion radii of Mn2 + (0.80 ), Ni2 + (0.69 ), and Zn2 + (0.74 ). Strictly speaking, only the Mn2 + dication is in the plane of the SN2 chelating ligand. The distance d in Figure 6 represents
Figure 6. Left: superposition plot of the SN3 core of the ligand and the chelated transition metals. The S, N1, and N2 atoms are projected onto each other. Right: schematically illustration of the distance d.
the deviation of the metal from the N1-S1-N2 plane and, as it is illustrated in the superposition plot, the nickel(II) cation deviates most from the N1S1N2 plane (d = 0.222 ), followed by zinc(II) (d = 0.165 ) and manganese(II) (d = 0.029 ). The dislocation of the metal from the ligand plane is unusual, because the two positively charged centres (the sulfur atom and the metal cation) getting in closer proximity and the SM distance decrease (S···Mn 2.835(6), S···Zn 2.7173(7), and S···Ni 2.6984(8) ). This deviation was first observed in a series of alkaline metal complexes [THF2M{(NSiMe3)2SR}2], R = Ph, N(SiMe3)2,[22] proceeding from Mg to Sr. The out-of-plane arrangement of the heavier alkaline earth-metal cations and the Ni2 + and the Zn2 + dications demonstrates the preference of the easier-to-polarize metal ions to interact with p-electron density located at the imide nitrogen atoms. Remarkable, the Chem. Eur. J. 2014, 20, 15849 – 15854
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We have shown the facile linkage of the sulfur triimide with lithium diphenylphosphanyl methanide motif to give the lithiated ligand [(tmeda)Li{(NtBu)3SCH2PPh2}] (1). The structural and geometrical differences to its sulfur(IV) diimide analogue [(tmeda)Li{(NSiMe3)2SCH2PPh2}] are marginal, but the advantages from the stronger redox stability of the first and the additional non-chelating imido group are obvious. We have also presented an easy pathway to transition-metal complexes of the polyimido sulfur phosphanyl ligand 1 through simple transition-metal halides and have shown their geometrical differences. This features ligand 1 to be a promising candidate for further monometallic and heterobimetallic complexes.
Experimental Section All experiments were performed under dry argon gas atmosphere by using modified Schlenk techniques[23] or an argon drybox. Solvents were freshly distilled from sodium/potassium alloy prior to use. 1H, 13C, 31P, and 7Li NMR spectra were recorded at RT in dry [D8]THF by using a Bruker Avance III 300 MHz or Bruker DRX 500 MHz spectrometer. All chemical shifts d are given in ppm, relative to the residual proton signal of the deuterated solvent. All signals were assigned by H,H-COSY and C,H- and N,H- correlation spectra. Due to the paramagnetic character of 2 and 3, just broad and highly shifted signals were measured. EI mass spectra were recorded with a MAT 95 instrument. All starting materials were commercially available or synthesized according to the cited literature procedures. Elemental analyses were carried out in the Analytische Labor der Anorganischen Fakultt der Universitt Gçttingen.
Synthesis of [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) S(NtBu)3 (1.47 g, 6.00 mmol, 1.0 equiv) in THF (10 mL) was slowly added to a slurry of [(tmeda)LiCH2PPh2] (1.93 g, 6.00 mmol, 1.0 equiv) in n-pentane (30 mL) at 78 8C. After stirring at RT, the solution was filtered over Celite, reduced in volume (30 mL), and stored at 25 8C, giving colorless crystals after five days. The crystals were washed with n-pentane and dried (yield 3.07 g, 90 %). 1 H NMR (300.13 MHz): d = 1.28 (s, 27 H; C(CH3)3), 2.15 (s, 12 H; (CH3)2N), 2.30 (s br, 12 H; N(CH2)2N), 3.98 (s br, 2 H; SCH2P), 7.14– 7.23 (m, 6 H, o, p-H), 7.52–7.59 ppm (m, 4 H; m-H); 13C{1H} NMR (75.47 MHz): d = 34.07 (C(CH3)3), 46.01 ((CH3)2N), 52.19 (C(CH3)3), 58.72 (N(CH2)2), 64.54 (d, 1J (P,C) = 44.02 Hz; PCH2S), 128.16–128.28 (m, o, p-C), 134.25 (d, 3J (P,C) = 19.74 Hz; p-C), 142.70 ppm (d, 1J (P,C) = 16.9 Hz; ipso-C); 31P{1H} NMR (121.49 MHz): d = 24.22 ppm; 7 Li (116.64 MHz): d = 0.528 ppm; 15N NMR (30.42 MHz): d =
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Full Paper Table 1. Crystallographic data.
empirical formula formula weight CCDC no. crystal size [mm] symmetry setting space group a [] b [] c [] b [8] V [3] 1calcd [cm3] Z GoF q range [8] reflections measured independent reflections reflections used m [mm1] Flack x-parameter[24] F(000) transmission max./min. restraints/ parameter R1,[a] wR2[b] (all data) R1,[a] wR2[b] [I > 2s(I)] diff. peak/hole [e3]
1
2
3
4
C31H55LiN5PS
C50H78MnN6P2S2
C50H78NiN6P2S2
C50 H78N6P2S2Zn
567.77 1019315 0.10 0.05 0.05 orthorhombic
944.18 1019314 0.10 0.07 0.04 monoclinic
947.95 1019317 0.05 0.04 0.01 monoclinic
954.61 1019316 0.10 0.08 0.06 monoclinic
P212121 9.959(2) 16.962(2) 20.007(2) 90 3379.7(9) 1.116 4 1.073 1.574–26.394 136236 6921, Rint = 0.0309 6921 0.170 0.007(7)
C2/c 16.805(2) 13.033(2) 24.084(2) 102.44(2) 5151.0(12) 1.218 4 1.059 1.732–25.344 50751 4717, Rint = 0.0644 4717 0.438 –
C2 26.033(2) 9.369(2) 10.858(2) 99.50(2) 2612.0(8) 1.205 2 0.988 1.586–25.387 20288 4803, Rint = 0.0522 4803 0.551 0.038(8)
C2 26.054(2) 9.375 (2) 10.907(2) 99.56(2) 2627.0(4) 1.207 2 1.035 1.585–26.378 21432 5362, Rint = 0.0295 5362 0.646 0.028(5)
18 H; C(CH3)3), 1.40 (s, 36 H; C(CH3)2), 4.22 (s br, 4 H; SCH2P), 7.17–7.29 (m, 12 H; o, p-H), 7.51– 7.56 ppm (m, 10 H; m-H); 13 1 C{ H} NMR (75.47 MHz): d = 30.42 (C(CH3)3), 33.33 (C(CH3)3), 53.44 (C(CH3)3), 57.30 (C(CH3)3), 128.36– 128.97 (m, o,p-C), 133.80 ppm (d, 2 J(P,C) = 19.6 Hz; m-C), (PCH2S and ipso-C are not observed); 31 1 P{ H} NMR (121.49 MHz): d = 25.01; elemental analysis calcd (%) for C50H78N6P2S2Zn (954.61 g mol1): C 62.91, H 8.24, N 8.80, S 6.72; found: C 60.10, H 7.78, N 9.14, S 6.49.
Single-crystal structural analysis
Single crystals were picked from a Schlenk flask under argon atmosphere and covered with perfluorated polyether oil on a microscope 1240 2028 1020 1024 slide, which was cooled with a ni1.0000/0.9160 0.7453/0.6972 0.7453/0.7038 0.7454/0.6405 trogen gas flow by using the X434/434 0/285 1/285 1/285 TEMP2 device.[25] An appropriate crystal was selected by using a po0.0252, 0.0682 0.0505, 0.0814 0.0500, 0.0646 0.0345, 0.0654 larizing microscope, mounted on 0.0249, 0.0679 0.0351, 0.0745 0.0332, 0.0605 0.0290, 0.0636 the tip of a MiTeGenMicroMount 0.236/0.242 0.316/0.3020 0.267/0.234 0.410/0.182 or glass fiber, fixed to a goniometer rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi P P head, and shock cooled by the jjF jjF jj 1 ðF þ2F Þ PwðF F Þ , with w = ; P= 3 . [a] R1 = P jF j ; [b] wR2 = s ðF Þþðg PÞ þg P wðF Þ crystal-cooling device. The data for all structures were collected from shock-cooled crystals at 100(2) K on an Incoatec Mo Microsource[26] with mirror optics and APEX II de254.76 ppm (NtBu); elemental analysis calcd (%) for C31H55LiN5PS tector with a D8 goniometer. They were integrated with SAINT[27] 1 (567.77 g mol ): C 65.57, H 9.76, N 12.33, S 5.65; found: C 65.58, H and an empirical absorption correction (SADABS)[28] was applied. 9.52, N 12.00, S 5.99. The structures were solved by direct methods (SHELXS-97) and refined by full-matrix least-squares methods against F2 (SHELXL2012)[29] within the SHELXLE-GUI.[30] All nonhydrogen atoms were Synthesis of [M{(NtBu)3SCH2PPh2}2] (M = Mn (2), Ni (3), Zn(4)) refined with anisotropic displacement parameters. The C-bound hydrogen atoms were refined isotropically at calculated positions MBr2 (1.00 mmol, 0.5 equiv) and 1 (1.13 g, 2.00 mmol, 1.0 equiv) by using a riding model with their Uiso values constrained equal to were combined in an argon-filled drybox and dissolved in n-pen1.5 times the Ueq of their pivot atoms for terminal sp3 carbon tane (100 mL) at RT. After stirring overnight, the suspension was filatoms and 1.2 times for all other carbon atoms. Disordered moiettered over Celite, reduced in volume, and stored at 4 8C. Colorless ies were refined by using bond-length restraints and isotropic discrystals of 2 (yield 0.47 g, 25 %) and 4 (0.40 g, 21 %) were obtained placement parameter restraints. CCDC-1019315 (1), CCDC-1019314 after three days, and blue crystals of 3 (yield 0.19 g, 10 %) after 1 (2), CCDC-1019317 (3), and CCDC-1019316 (4) contain the supplefour weeks. Data for 2: H NMR (300.13 MHz): d = 0.11 (s br), 0.90 (s mentary crystallographic data for this paper. These data can be obbr), 1.30 (s br), 7.10 (s br), 7.70 ppm (s br); MS (EI) m/z (%): 943.4 tained free of charge from The Cambridge Crystallographic Data (4) [M + ], 673.2 (66) [M + NtBu, CH2PPh2], 570.1 (10) [M + 4 NtBu, + Centre via www.ccdc.cam.ac.uk/data_request/cif. SCH PPh ], 428.0 (5) [M 2 NtBu, SCH PPh ]; elemental analyo
c
o
2
2
2 o
2 2 c
2 o
2
2 2 o
2
2 o
1
2
2 c
2
2
sis calcd (%) for C50H78MnN6P2S2 (944.18 g mol1): C 63.64, H 8.35, N 8.91, S 6.80; found: C 62.38, H 8.08, N 9.25, S 7.18. Data for 3: 1 H NMR (300.13 MHz): d = 19.51 (s), 17.97 (s), 2.13 (s), 3.81 (s), 5.37 (s), 5.70 (s), 5.96 (s), 6.77 (s), 714 (s), 13.42 (s), 15.01 ppm (s); MS (EI) m/z (%): 946.4 (8) [M + ], 901.3 (14) [M + 3 CH3], 869.4 (6) [M + Ph], 798.4 (18) [M + NtBu3, Ph], 830.3 (22) [M + NtBu3, 3 CH3], 777.2 (38) [M + 2 Ph, CH3], 759.2 (100) [M + NtBu, 2 tBu, 4 CH3]; elemental analysis calcd (%) for C50H78NiN6P2S2 (947.95 g mol1): C 63.35, H 8.29, N 6.53, S 6.77; found: C 61.76, H 8.31, N 8.71, S 7.24. Data for 4: 1H NMR (300.13 MHz): d = 1.26 (s, Chem. Eur. J. 2014, 20, 15849 – 15854
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Acknowledgements We thank the Danish National Research Foundation (DNRF93), which funded the Center for Materials Crystallography (CMC), for partially supporting this research project and the Land Niedersachsen for providing the doctoral programme Catalysis for Sustainable Synthesis (CaSuS).
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Full Paper Keywords: lithium · N ligands · sulfur · transition metals · Xray diffraction [1] Recent review: D. Stalke, Chem. Commun. 2012, 48, 9559 – 9573. [2] F. P. Burt, J. Chem. Soc. 1910, 97, 1171 – 1174. [3] a) R. L. Greene, G. B. Street, L. J. Suter, Phys. Rev. Lett. 1975, 34, 577 – 579; b) M. M. Labes, P. Love, L. F. Nichols, Chem. Rev. 1979, 79, 1 – 15. [4] selected reviews: a) H. W. Roesky, Angew. Chem. Int. Ed. Engl. 1979, 18, 91 – 97; Angew. Chem. 1979, 91, 112 – 118; b) T. Chivers, Chem. Rev. 1985, 85, 341 – 365; c) R. Mews, P. J. Watson, E. Lork, Coord. Chem. Rev. 1997, 158, 233 – 273; d) R. Fleischer, D. Stalke, Coord. Chem. Rev. 1998, 176, 431 – 450; e) D. Stalke, Proc. Indian Acad. Sci. 2000, 112, 155 – 170; f) J. K. Brask, T. Chivers, Angew. Chem. Int. Ed. 2001, 40, 3960 – 3976; Angew. Chem. 2001, 113, 4082 – 4098; g) F. T. Edelmann, S. Blaurock, V. Lorenz, T. Chivers, Z. Anorg. Allg. Chem. 2008, 634, 413 – 415. [5] a) L. Pauling, J. Chem. Soc. 1948, 1461 – 1467; b) L. Pauling, The Nature of the Chemical Bond, Cornell University Press, Ithaca, 1939. [6] a) P. G. Mezey, E. C. Haas, J. Chem. Phys. 1982, 77, 870 – 876; b) W. Kutzelnigg, Angew. Chem. Int. Ed. Engl. 1984, 23, 272 – 295; Angew. Chem. 1984, 96, 262 – 286; c) D. W. J. Cruickshank, M. Eisenstein, J. Mol. Struct. 1985, 130, 143 – 156; d) D. W. J. Cruickshank, J. Mol. Struct. 1985, 130, 177 – 191; e) A. E. Reed, P. v. R. Schleyer, J. Am. Chem. Soc. 1990, 112, 1434 – 1445; f) J. Cioslowski, P. R. Surjn, J. Mol. Struct. THEOCHEM 1992, 255, 9 – 33; g) J. Cioslowski, S. T. Mixon, Inorg. Chem. 1993, 32, 3209 – 3216; h) J. A. Dobado, H. Martnez-Garca, J. M. Molina, M. R. Sundberg, J. Am. Chem. Soc. 1998, 120, 8461 – 8471; i) T. Stefan, R. Janoschek, J. Mol. Model. 2000, 6, 282 – 288; j) I. Love, J. Phys. Chem. A 2009, 113, 2640 – 2646. [7] S. Grabowsky, P. Luger, J. Buschmann, T. Schneider, T. Schirmeister, A. N. Sobolev, D. Jayatilaka, Angew. Chem. Int. Ed. 2012, 51, 6776 – 6779; Angew. Chem. 2012, 124, 6880 – 6884. [8] a) D. Leusser, J. Henn, N. Kocher, B. Engels, D. Stalke, J. Am. Chem. Soc. 2004, 126, 1781 – 1793; b) J. Henn, D. Ilge, D. Leusser, D. Stalke, B. Engels, J. Phys. Chem. A 2004, 108, 9442 – 9452. [9] M. S. Schmøkel, S. Cenedese, J. Overgaard, M. R. V. Jørgensen, Y.-S. Chen, C. Gatti, D. Stalke, B. B. Iversen, Inorg. Chem. 2012, 51, 8607 – 8616. [10] R. Fleischer, S. Freitag, D. Stalke, J. Chem. Soc. Dalton Trans. 1998, 193 – 197. [11] a) B. Walfort, A. P. Leedham, C. R. Russell, D. Stalke, Inorg. Chem. 2001, 40, 5668 – 5674; b) C. Selinka, D. Stalke, Eur. J. Inorg. Chem. 2003, 3376 – 3382; c) T. Schulz, D. Stalke, Eur. J. Inorg. Chem. 2010, 2185 – 2192. [12] a) M. M. Meinholz, S. K. Pandey, S. M. Deuerlein, D. Stalke, Dalton Trans. 2011, 40, 1662 – 1671; b) M. M. Meinholz, D. Stalke, Eur. J. Inorg. Chem. 2011, 4578 – 4584; c) M. M. Meinholz, M. Klemmer, E. Kriemen, D. Stalke, Chem. Eur. J. 2011, 17, 9415 – 9422; d) M. M. Meinholz, D. Stalke, Z. Na-
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turforsch. 2011, 66b, 981 – 984; e) M. M. Meinholz, E. Carl, E. Kriemen, D. Stalke, Chem. Commun. 2011, 47, 10948 – 10950. S. Trofimenko, Chem. Rev. 1993, 93, 943 – 980. a) F. Armbruster, I. Fernndez, F. Breher, Dalton Trans. 2009, 5612 – 5626; b) I. Kuzu, I. Krummenacher, J. Meyer, F. Armbruster, F. Breher, Dalton Trans. 2008, 5836 – 5865; c) M. Viciano, M. Sanaffl, E. Peris, Organometallics 2007, 26, 6050 – 6054; d) T. Stey, M. Pfeiffer, J. Henn, S. K. Pandey, D. Stalke, Chem. Eur. J. 2007, 13, 3636 – 3642; e) T. Stey, J. Henn, D. Stalke, Chem. Commun. 2007, 413 – 415; f) F. Baier, Z. Fei, H. Gornitzka, A. Murso, S. Neufeld, M. Pfeiffer, I. R denauer, A. Steiner, T. Stey, D. Stalke, J. Organomet. Chem. 2002, 661, 111 – 127. R. Fleischer, A. Rothenberger, D. Stalke, Angew. Chem. Int. Ed. Engl. 1997, 36, 1105 – 1107; Angew. Chem. 1997, 109, 1140 – 1142. C. Selinka, S. Deuerlein, T. Huser, D. Stalke, Inorg. Chim. Acta 2004, 357, 1873 – 1880. P. Rademacher, in Strukturen Organischer Molekle, VCH, New York, 1987. D. Leusser, B. Walfort, D. Stalke, Angew. Chem. Int. Ed. 2002, 41, 2079 – 2082; Angew. Chem. 2002, 114, 2183 – 2186. R. E. Mulvey, K. Wade, D. R. Armstrong, G. T. Walker, R. Snaith, W. Clegg, D. Reed, Polyhedron 1987, 6, 987 – 993. Cambridge Structural Database, release 5.34, 2012. a) R. Fleischer, D. Stalke, Organometallics 1998, 17, 832 – 838; b) D. Hnssgen, R. Steffens, Z. Anorg. Allg. Chem. 1983, 507, 178 – 182. R. Fleischer, D. Stalke, J. Organomet. Chem. 1998, 550, 173 – 182. www.stalke.chemie.uni-goettingen.de/virtuelles_labor/de.html. a) H. Flack, Acta Crystallogr. Sect. A 1983, 39, 876 – 881; b) H. D. Flack, G. Bernardinelli, J. Appl. Crystallogr. 2000, 33, 1143 – 1148. a) T. Kottke, R. J. Lagow, D. Stalke, J. Appl. Crystallogr. 1996, 29, 465 – 468; b) T. Kottke, D. Stalke, J. Appl. Crystallogr. 1993, 26, 615 – 619; c) D. Stalke, Chem. Soc. Rev. 1998, 27, 171 – 178. T. Schulz, K. Meindl, D. Leusser, D. Stern, J. Graf, C. Michaelsen, M. Ruf, G. M. Sheldrick, D. Stalke, J. Appl. Crystallogr. 2009, 42, 885 – 891. in SAINT v7.68 A in Bruker APEX2 v2012.2 – 0, Bruker AXS Inst. Inc., Madison, USA, 2012. G. M. Sheldrick, in SADABS-2012/1, Universitt Gçttingen, Germany, 2012. G. M. Sheldrick, Acta Cryst. Sect. A 2008, 64, 112 – 122. a) C. B. H bschle, G. M. Sheldrick, B. Dittrich, J. Appl. Cryst. 2011, 44, 1281 – 1284; b) P. M ller, R. Herbst-Irmer, A. L. Spek, T. R. Schneider, M. R. Sawaya, in Crystal Structure Refinement: A Crystallographer’s Guide to SHELXL, Vol. 8 (Ed.: P. M ller), Oxford University Press, Oxford, 2006.
Received: August 14, 2014 Published online on October 3, 2014
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& Scorpionates
Polyimido Sulfur(VI) Phosphanyl Ligand in Metal Complexation Elena Carl and Dietmar Stalke*[a] In memory of Professor Lord Jack Lewis
Abstract: Herein, new complexes containing the [Ph2PCH2S(NtBu)3] anion are presented, supplying three imido nitrogen atoms and a remote phosphorus atom as potential donor sites to main group and transition-metal cations. The lithiated complex [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) is an excellent starting material in transmetalation reactions. Herein, the transition-metal complexes [M{(NtBu)3SCH2PPh2}2] (M =
Introduction Next to phosphorus/nitrogen chemistry, probably the richest line of action in main-group chemistry is sulfur/nitrogen chemistry. The wide range of coordination numbers one to six and oxidation states (+ I to + VI) affords an enormous variety of covalent molecules.[1] Ever since, the synthesis of polymeric (SN)x[2] and the discovery of its high-temperature superconducting properties,[3] the nature of the SN bond was under constant debate and the synthesis of SN multiple bonds was a rapidly emerging area.[4] Originally, sulfur dioxide SO2 and diimide S(NR)2 were believed to be hypervalent species with one lone pair and two S=O or S=N double bonds.[5] It was only much later that calculations indicated that the necessary d orbitals in the optimization merely serve as polarization functions and do not contribute to the covalent bonding by accommodating the additional valence electrons at the sulfur atom.[6] Charge-density investigations on SO2[7] and S(NtBu)2[8] discharged hypervalency and proved considerable electrostatics to be responsible for the bond shortening. The same is valid for the sulfate anion SO42.[9] After the syntheses to triimidosulfites S(NR)32 [Eq. (1)] and their oxidation to sulfur triimides S(NR)3 by halogens [Eq. (2)],[10] the triimidosulfonate anion RS(NR)3 is accessible in the reaction of sulfur triimide S(NR)3 with any organometallics, such as methyllithium [Eq. (3)].[11] To further augment the coordination abilities of the SN ligands, the diimidosulfinates[12] RS(NR)2 and triimidosulfonates RS(NR)3 provide a rich platform. They chelate the metal with two imido nitrogen atoms only and hold it tight like a scorpion with its two claws (Figure 1). The additional coordination site,
Mn (2), Ni (3), Zn (4)) were synthesized and structurally characterized. Their isotypical molecules show SN2 chelation and no employment of the adjacent phosphorus atom in coordination. The third pendent imido group is always twisted toward the vacant face of the tetrahedrally coordinated sulfur atom.
comparable to the sting of the scorpion, can be introduced if the sulfur di- or triimide is reacted with an organometallic compound providing an additional donor site, for example, a phosphorus atom (Scheme 1). 2 SðNRÞ2 þ 4 LiHNR ! ½Li4 fðNRÞ3 Sg2 þ 2 H2 NR
ð1Þ
½Li4 fðNRÞ3 Sg2 þ 2 X2 ! 2 SðNRÞ3 þ 4 LiX; X ¼ Cl, Br, I
ð2Þ
2 SðNRÞ3 þ 2 MeLi ! ½LiðNRÞ3 SMe2
ð3Þ
[a] E. Carl, Prof. D. Stalke Institut fr Anorganische Chemie, Georg-August-Universitt Tammannstrasse 4, 37077 Gçttingen (Germany) E-mail: [email protected] Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201404860. Chem. Eur. J. 2014, 20, 15849 – 15854
Figure 1. Hemilabile polyimido SN scorpionate with two N claws and an additional P sting for potential tripodal metal coordination.
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Scheme 1. Preparation of [(tmeda)Li{(NtBu)3SCH2PPh2}] (1).
The resulting ligands combine the abilities of Trofimenko’s scorpionates[13] with the hemilability of the Janus head ligands.[14] To broaden the field of polyimido sulfur phosphanyl ligands, tris(tert-butyl)sulfur(VI) triimide S(NtBu)3,[10, 11] instead of sulfur(IV) diimides S(NR)2, was used as the scaffold and starting material for the reaction with lithium diphenylphosphanylmethylides [(tmeda)LiCH2PPh2] (TMEDA = tetramethylethylenediamine). The resulting [(tBuN)3SCH2PPh2] anion in 1 is reminiscent to the [(tBuN)3SMe] anion with the S-bound methyl group further functionalized.[15] Sulfur/nitrogen compounds of this type have already been employed in the synthesis for various metal complexes with versatile coordination motifs,[11] but the combination with transition metals has rarely been touched to date.[16] One advantage of the sulfur triimides over the sulfur diimides is their additional coordination site that can be employed in the syntheses of heterobimetallic complexes.[3d] To explore the field of sulfur imides in combination with transition metals, the new Janus head scorpionate [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) and the transition metals manganese, nickel, and zinc were used in the syntheses. Those metals were chosen because of their divalent character and their easy availability.
Results and Discussion Ligand synthesis The linkage between the sulfur triimide and the phosphane was achieved by an equimolar reaction of lithium diphenyl phosphanyl methanide and tris(tert-butyl)sulfur triimide in a pentane/THF solution at dry-ice temperature to give [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) in 90 % yield (Scheme 1). Colorless crystals suitable for X-ray structure determination were obtained after storing the solution at 24 8C for five days. The crystal structure of 1 is depicted in Figure 2. The lithiated complex crystallizes in the orthorhombic space group P212121 with one molecule in the asymmetric unit. In the monomeric complex, the lithium cation is chelated in a distorted tetrahedral manner by only two nitrogen atoms of the three present imido groups and by the two nitrogen atoms of the chelating TMEDA donor base to saturate the coordination sphere of the lithium cation. Due to steric crowding, a tripodal coordination of the metal is prevented, and the third NtBu group is turned to the vacant site of the complex. The sulfur atom in the oxidation state VI is the presumably electronically depleted center of the ligand. It is also tetraheChem. Eur. J. 2014, 20, 15849 – 15854
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Figure 2. Molecular structure of 1. Anisotropic displacement parameters are depicted at the 50 % probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths [] and angles [8]: S1N1 1.5804(10), S1N2 1.5705(11), S1N3 1.5389(11), Li1N1 2.006(3), Li1N2 1.977(2), SC1 1.8181(12), PC1 1.8513(12), N1-S1-N2 97.49(5), S1-C1-P1 111.76(6), C1-S-N3 95.90(6), N1-Li1-N2 72.99(8), N4-Li1-N5 82.94(16).
drally distorted coordinated by the three nitrogen atoms and the phosphorus side arm. The SN bond lengths of the nitrogen atoms N1 and N2 are halfway in the range of the predicted values for a double (1.52 ) and a single (1.70 ) bond, reported in literature.[17] However, it is clear that hypervalency is not an option for sulfur–imido compounds and bond shortening is due to electrostatic reinforcement.[8, 18] Relatively to the SN1 and SN2 distances, the SN3 distance is shorter and quite close to the length of a double bond. The coordination to the lithium cation causes the elongation of the SN1/2 bonds, because the electron density of the nitrogen atoms has to be shared between the lithium cation and the electropositive sulfur atom. Consequently, the SN3 bond has to be the shortest (1.5389(11) ), due to the resulting enhanced electrostatic interaction between the negatively charged, non-chelating nitrogen atom and also due to the lower coordination number. The SC1 bond length shows the typical distance of 1.8181(12) . The phosphorus atom in the side arm is directed to the lithium cation but the distance of 3.718 is too long to be called a LiP bond, considering the mean value of all published LiP bond lengths in the CSD to be 2.58 and the LiP distance in, for example, the [(tmeda)LiPPh2]2 dimer of 2.61 .[19, 20] The related complex [(tmeda)Li{(NSiMe3)2SCH2PPh2}] is the sulfur(IV) diimide analogue of 1, in which the third nitrogen side arm is substituted by the lone pair of the sulfur(IV) atom.[12a] A superposition plot of the core of both complexes is depicted in Figure 3. A comparison of the bond angles and lengths of both complexes revealed that the SN distances in 1 are shorter in comparison to the SIV analogue (165.20(9) and
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Figure 3. Superposition plot of 1 (gray) and [(tmeda)Li{(NSiMe3)SCH2PPh2}] (black). The S1, N1, and N2 atoms are projected onto each other.
171.84(10) pm) because of the higher oxidation state of the sulfur atom. The P-C-S angle in the SIV ligand is a little smaller (108.79(9)8) than in 1, indicating a more pronounced inclination of the phosphorus atom to the lithium cation resulting in a closer LiP distance of 3.231 . The space-filling model of 1 is depicted in Figure 4 and demonstrates how the tBu groups hinder the phosphorus atom from coordinating the lithium cation in 1. The quartenary carbon atoms of the tBu groups are more fixed in the N1-S1-N2 plane, shielding the lithium cation perfectly.
Previously, it was reported that sulfur diimide derivatives are too redox active in reactions with metal halides and that these reactions most likely give rise to ligand scrambling via SN and SC bond cleavages.[21] Consequently, only the transmetalation of the NSCP ligand [Li{Me2PCH2S(NtBu)2}]2 with MgCl2 leads successfully to the magnesium complex [Mg{Me2PCH2S(NtBu)2}2].[12a] The explanation for that might be the diagonal relationship between lithium and magnesium in the periodic tables of elements and their similar cationic radius. For any other successful transmetalation reactions of S-phosphanyl-diimidosulfinate ligands reported in this paper, metal(II) bis(trimethylsilyl)amides were used.[12b] Despite of those limitations, we now reacted 1 with metal(II) bromides to investigate whether or not the SVI ligand is stable enough against redox scrambling. The metal halides are easier accessible than the metal(II) bis(trimethylsilyl)amides and easier to handle. The metal bromides are a softer reagent in comparison to the chlorides and more soluble in the required solvent. The general preparation route for the transition metal complexes 2 (Mn), 3 (Ni), and 4 (Zn) in yields of 25, 10, and 21 %, respectively, is shown in Scheme 2.
Scheme 2. Synthesis of [M{(NtBu)3SCH2PPh2}2] (M = Mn (2), Ni (3), Zn (4)).
Structural comparison
Figure 4. Space-filling model of 1 and [(tmeda)Li{(NSiMe3)2SCH2PPh2}]. The TMEDA ligand is omitted to provide high visibility of the lithium cation.
In the SIV ligand, the SiMe3 groups deviate significantly from the N1-S1-N2 plane (0.713 and 0.535 ), giving the phosphorus side arm extra space to approach the lithium cation more closely. In addition, the SiN bonds are much longer than the CN bonds, keeping the methyl groups away from the metal. The advantage of complex 1 is the presence of a third imido group. Together with the additional phosphorus side arm, it might provide a further coordination site for a second metal. Hence, ligand 1 offers the opportunity to generate heterobimetallic complexes with this second hemilabile donor site. Chem. Eur. J. 2014, 20, 15849 – 15854
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The complexes 2 (Mn), 3 (Ni), and 4 (Zn) are isotypical and crystallize in the monoclinic space group C2/c (2) or C2 (3 and 4) with half a molecule in the asymmetric unit, respectively. Representatively, the crystal structure of 2 is depicted in Figure 5 together with selected bond lengths and angles of 2, 3, and 4. The different transition-metal cations are coordinated similarly by the ligand. In the homoleptic complexes, the central metal cation is chelated by four of the six present NtBu groups in a distorted tetrahedral fashion. The negative charge is delocalized over the chelating SN2 unit indicated by the almost identical SN bond lengths. The two symmetry generated four membered SN2M rings (M = Mn2 + , Ni2 + and Zn2 + ) are connected via the metal(II) cation and twisted by 81.788 (2), 83.578 (3), and 85.388 (4). Again, the non-chelating pendent NtBu group of each ligand is turned toward the vacant site of the ligand, as was already observed in 1. Only in compound 2, the phosphorus side arm is inclined towards the metal but again the MnP distance (3.985 ) is too long to be called a firm coordination. However, this long-range interaction
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Full Paper sum of all SN distances in all three transition metal complexes is almost constant at 4.72(1) .[11a] The CSN3 unit responds flexibly to different electronic requirements induced by the various metal cations in terms of the sulfur atom being shifted relative to an otherwise fixed N3 environment. This again experimentally emphasizes the predominantly ionic SN bonding rather than valence expansion and d orbital participation in bonding. Assuming a classical S=N double bond in polyimido sulfur species would not explain the facile NR transfer in transimidation reactions with this class of compounds either (Table 1).[21]
Conclusion Figure 5. Molecular structure of [Mn{(NtBu)3SCH2PPh2}2] (2). Anisotropic displacement parameters are depicted at the 50 % probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths [] and angles [8]: 2: S1N1 1.5951(17), S1N2 1.5966(17), S1N3 1.5222(17), MnN1 2.1032(17), MnN2 2.1255(17), S1C1 1.8070(20), P1C1 1.858(2), N1-S1-N2 94.97(9), N1Mn-N2 67.61(6); 3 (Ni): S1N1 1.604(3), S1N2 1.593(3), S1N3 1.520(3), Ni N1 1.985(3), NiN2 1.964(3), S1C1 1.799(4), P1C1 1.847(4), N1-S1-N2 92.64(14), N1-Ni-N2 71.65(11); 4 (Zn): S1N1 1.595(2), S1N2 1.604(3), S1N3 1.522(3), ZnN1 2.005(2), ZnN2 2.013(2), S1C1 1.807(3), P1C1 1.849(3), N1-S1-N2 94.20(12), N1-Zn-N2 71.35(9).
might help to electronically supply the Mn2 + dication, because otherwise the phosphorus atom might have been turned away from the metal similar to 3 and 4. The MN distances are the shortest in 3 and the longest in 2, reflecting the different ion radii of Mn2 + (0.80 ), Ni2 + (0.69 ), and Zn2 + (0.74 ). Strictly speaking, only the Mn2 + dication is in the plane of the SN2 chelating ligand. The distance d in Figure 6 represents
Figure 6. Left: superposition plot of the SN3 core of the ligand and the chelated transition metals. The S, N1, and N2 atoms are projected onto each other. Right: schematically illustration of the distance d.
the deviation of the metal from the N1-S1-N2 plane and, as it is illustrated in the superposition plot, the nickel(II) cation deviates most from the N1S1N2 plane (d = 0.222 ), followed by zinc(II) (d = 0.165 ) and manganese(II) (d = 0.029 ). The dislocation of the metal from the ligand plane is unusual, because the two positively charged centres (the sulfur atom and the metal cation) getting in closer proximity and the SM distance decrease (S···Mn 2.835(6), S···Zn 2.7173(7), and S···Ni 2.6984(8) ). This deviation was first observed in a series of alkaline metal complexes [THF2M{(NSiMe3)2SR}2], R = Ph, N(SiMe3)2,[22] proceeding from Mg to Sr. The out-of-plane arrangement of the heavier alkaline earth-metal cations and the Ni2 + and the Zn2 + dications demonstrates the preference of the easier-to-polarize metal ions to interact with p-electron density located at the imide nitrogen atoms. Remarkable, the Chem. Eur. J. 2014, 20, 15849 – 15854
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We have shown the facile linkage of the sulfur triimide with lithium diphenylphosphanyl methanide motif to give the lithiated ligand [(tmeda)Li{(NtBu)3SCH2PPh2}] (1). The structural and geometrical differences to its sulfur(IV) diimide analogue [(tmeda)Li{(NSiMe3)2SCH2PPh2}] are marginal, but the advantages from the stronger redox stability of the first and the additional non-chelating imido group are obvious. We have also presented an easy pathway to transition-metal complexes of the polyimido sulfur phosphanyl ligand 1 through simple transition-metal halides and have shown their geometrical differences. This features ligand 1 to be a promising candidate for further monometallic and heterobimetallic complexes.
Experimental Section All experiments were performed under dry argon gas atmosphere by using modified Schlenk techniques[23] or an argon drybox. Solvents were freshly distilled from sodium/potassium alloy prior to use. 1H, 13C, 31P, and 7Li NMR spectra were recorded at RT in dry [D8]THF by using a Bruker Avance III 300 MHz or Bruker DRX 500 MHz spectrometer. All chemical shifts d are given in ppm, relative to the residual proton signal of the deuterated solvent. All signals were assigned by H,H-COSY and C,H- and N,H- correlation spectra. Due to the paramagnetic character of 2 and 3, just broad and highly shifted signals were measured. EI mass spectra were recorded with a MAT 95 instrument. All starting materials were commercially available or synthesized according to the cited literature procedures. Elemental analyses were carried out in the Analytische Labor der Anorganischen Fakultt der Universitt Gçttingen.
Synthesis of [(tmeda)Li{(NtBu)3SCH2PPh2}] (1) S(NtBu)3 (1.47 g, 6.00 mmol, 1.0 equiv) in THF (10 mL) was slowly added to a slurry of [(tmeda)LiCH2PPh2] (1.93 g, 6.00 mmol, 1.0 equiv) in n-pentane (30 mL) at 78 8C. After stirring at RT, the solution was filtered over Celite, reduced in volume (30 mL), and stored at 25 8C, giving colorless crystals after five days. The crystals were washed with n-pentane and dried (yield 3.07 g, 90 %). 1 H NMR (300.13 MHz): d = 1.28 (s, 27 H; C(CH3)3), 2.15 (s, 12 H; (CH3)2N), 2.30 (s br, 12 H; N(CH2)2N), 3.98 (s br, 2 H; SCH2P), 7.14– 7.23 (m, 6 H, o, p-H), 7.52–7.59 ppm (m, 4 H; m-H); 13C{1H} NMR (75.47 MHz): d = 34.07 (C(CH3)3), 46.01 ((CH3)2N), 52.19 (C(CH3)3), 58.72 (N(CH2)2), 64.54 (d, 1J (P,C) = 44.02 Hz; PCH2S), 128.16–128.28 (m, o, p-C), 134.25 (d, 3J (P,C) = 19.74 Hz; p-C), 142.70 ppm (d, 1J (P,C) = 16.9 Hz; ipso-C); 31P{1H} NMR (121.49 MHz): d = 24.22 ppm; 7 Li (116.64 MHz): d = 0.528 ppm; 15N NMR (30.42 MHz): d =
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empirical formula formula weight CCDC no. crystal size [mm] symmetry setting space group a [] b [] c [] b [8] V [3] 1calcd [cm3] Z GoF q range [8] reflections measured independent reflections reflections used m [mm1] Flack x-parameter[24] F(000) transmission max./min. restraints/ parameter R1,[a] wR2[b] (all data) R1,[a] wR2[b] [I > 2s(I)] diff. peak/hole [e3]
1
2
3
4
C31H55LiN5PS
C50H78MnN6P2S2
C50H78NiN6P2S2
C50 H78N6P2S2Zn
567.77 1019315 0.10 0.05 0.05 orthorhombic
944.18 1019314 0.10 0.07 0.04 monoclinic
947.95 1019317 0.05 0.04 0.01 monoclinic
954.61 1019316 0.10 0.08 0.06 monoclinic
P212121 9.959(2) 16.962(2) 20.007(2) 90 3379.7(9) 1.116 4 1.073 1.574–26.394 136236 6921, Rint = 0.0309 6921 0.170 0.007(7)
C2/c 16.805(2) 13.033(2) 24.084(2) 102.44(2) 5151.0(12) 1.218 4 1.059 1.732–25.344 50751 4717, Rint = 0.0644 4717 0.438 –
C2 26.033(2) 9.369(2) 10.858(2) 99.50(2) 2612.0(8) 1.205 2 0.988 1.586–25.387 20288 4803, Rint = 0.0522 4803 0.551 0.038(8)
C2 26.054(2) 9.375 (2) 10.907(2) 99.56(2) 2627.0(4) 1.207 2 1.035 1.585–26.378 21432 5362, Rint = 0.0295 5362 0.646 0.028(5)
18 H; C(CH3)3), 1.40 (s, 36 H; C(CH3)2), 4.22 (s br, 4 H; SCH2P), 7.17–7.29 (m, 12 H; o, p-H), 7.51– 7.56 ppm (m, 10 H; m-H); 13 1 C{ H} NMR (75.47 MHz): d = 30.42 (C(CH3)3), 33.33 (C(CH3)3), 53.44 (C(CH3)3), 57.30 (C(CH3)3), 128.36– 128.97 (m, o,p-C), 133.80 ppm (d, 2 J(P,C) = 19.6 Hz; m-C), (PCH2S and ipso-C are not observed); 31 1 P{ H} NMR (121.49 MHz): d = 25.01; elemental analysis calcd (%) for C50H78N6P2S2Zn (954.61 g mol1): C 62.91, H 8.24, N 8.80, S 6.72; found: C 60.10, H 7.78, N 9.14, S 6.49.
Single-crystal structural analysis
Single crystals were picked from a Schlenk flask under argon atmosphere and covered with perfluorated polyether oil on a microscope 1240 2028 1020 1024 slide, which was cooled with a ni1.0000/0.9160 0.7453/0.6972 0.7453/0.7038 0.7454/0.6405 trogen gas flow by using the X434/434 0/285 1/285 1/285 TEMP2 device.[25] An appropriate crystal was selected by using a po0.0252, 0.0682 0.0505, 0.0814 0.0500, 0.0646 0.0345, 0.0654 larizing microscope, mounted on 0.0249, 0.0679 0.0351, 0.0745 0.0332, 0.0605 0.0290, 0.0636 the tip of a MiTeGenMicroMount 0.236/0.242 0.316/0.3020 0.267/0.234 0.410/0.182 or glass fiber, fixed to a goniometer rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi P P head, and shock cooled by the jjF jjF jj 1 ðF þ2F Þ PwðF F Þ , with w = ; P= 3 . [a] R1 = P jF j ; [b] wR2 = s ðF Þþðg PÞ þg P wðF Þ crystal-cooling device. The data for all structures were collected from shock-cooled crystals at 100(2) K on an Incoatec Mo Microsource[26] with mirror optics and APEX II de254.76 ppm (NtBu); elemental analysis calcd (%) for C31H55LiN5PS tector with a D8 goniometer. They were integrated with SAINT[27] 1 (567.77 g mol ): C 65.57, H 9.76, N 12.33, S 5.65; found: C 65.58, H and an empirical absorption correction (SADABS)[28] was applied. 9.52, N 12.00, S 5.99. The structures were solved by direct methods (SHELXS-97) and refined by full-matrix least-squares methods against F2 (SHELXL2012)[29] within the SHELXLE-GUI.[30] All nonhydrogen atoms were Synthesis of [M{(NtBu)3SCH2PPh2}2] (M = Mn (2), Ni (3), Zn(4)) refined with anisotropic displacement parameters. The C-bound hydrogen atoms were refined isotropically at calculated positions MBr2 (1.00 mmol, 0.5 equiv) and 1 (1.13 g, 2.00 mmol, 1.0 equiv) by using a riding model with their Uiso values constrained equal to were combined in an argon-filled drybox and dissolved in n-pen1.5 times the Ueq of their pivot atoms for terminal sp3 carbon tane (100 mL) at RT. After stirring overnight, the suspension was filatoms and 1.2 times for all other carbon atoms. Disordered moiettered over Celite, reduced in volume, and stored at 4 8C. Colorless ies were refined by using bond-length restraints and isotropic discrystals of 2 (yield 0.47 g, 25 %) and 4 (0.40 g, 21 %) were obtained placement parameter restraints. CCDC-1019315 (1), CCDC-1019314 after three days, and blue crystals of 3 (yield 0.19 g, 10 %) after 1 (2), CCDC-1019317 (3), and CCDC-1019316 (4) contain the supplefour weeks. Data for 2: H NMR (300.13 MHz): d = 0.11 (s br), 0.90 (s mentary crystallographic data for this paper. These data can be obbr), 1.30 (s br), 7.10 (s br), 7.70 ppm (s br); MS (EI) m/z (%): 943.4 tained free of charge from The Cambridge Crystallographic Data (4) [M + ], 673.2 (66) [M + NtBu, CH2PPh2], 570.1 (10) [M + 4 NtBu, + Centre via www.ccdc.cam.ac.uk/data_request/cif. SCH PPh ], 428.0 (5) [M 2 NtBu, SCH PPh ]; elemental analyo
c
o
2
2
2 o
2 2 c
2 o
2
2 2 o
2
2 o
1
2
2 c
2
2
sis calcd (%) for C50H78MnN6P2S2 (944.18 g mol1): C 63.64, H 8.35, N 8.91, S 6.80; found: C 62.38, H 8.08, N 9.25, S 7.18. Data for 3: 1 H NMR (300.13 MHz): d = 19.51 (s), 17.97 (s), 2.13 (s), 3.81 (s), 5.37 (s), 5.70 (s), 5.96 (s), 6.77 (s), 714 (s), 13.42 (s), 15.01 ppm (s); MS (EI) m/z (%): 946.4 (8) [M + ], 901.3 (14) [M + 3 CH3], 869.4 (6) [M + Ph], 798.4 (18) [M + NtBu3, Ph], 830.3 (22) [M + NtBu3, 3 CH3], 777.2 (38) [M + 2 Ph, CH3], 759.2 (100) [M + NtBu, 2 tBu, 4 CH3]; elemental analysis calcd (%) for C50H78NiN6P2S2 (947.95 g mol1): C 63.35, H 8.29, N 6.53, S 6.77; found: C 61.76, H 8.31, N 8.71, S 7.24. Data for 4: 1H NMR (300.13 MHz): d = 1.26 (s, Chem. Eur. J. 2014, 20, 15849 – 15854
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Acknowledgements We thank the Danish National Research Foundation (DNRF93), which funded the Center for Materials Crystallography (CMC), for partially supporting this research project and the Land Niedersachsen for providing the doctoral programme Catalysis for Sustainable Synthesis (CaSuS).
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Received: August 14, 2014 Published online on October 3, 2014
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