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Synthesis and structural characterization of amido scorpionate rare earth metals complexes† Isabel Márquez-Segovia, Agustín Lara-Sánchez,* Antonio Otero,* Juan Fernández-Baeza, José Antonio Castro-Osma, Luis F. Sánchez-Barba and Ana M. Rodríguez The reactivity of hybrid scorpionate/cyclopentadienyl ligands in the form of the protio derivatives as a mixture of two regioisomers, namely bpzcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}-1,3-cyclopentadiene] and bpztcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene], with the tris(silylamide) precursors [M{N(SiHMe2)2}3(thf)x] of rare earth metals (including the group 3 metals scandium and yttrium) is related to the atomic radii of the metal centres. The reaction with the precursor containing the smallest ion, [Sc{N(SiHMe2)2}3(thf)], did not proceed even heating at reflux temperature in toluene. The reaction with the precursors that contain a medium-sized metal ion, i.e., [M{N(SiHMe2)2}3(thf)2] (M = Y, Lu), proceeded only at high temperature and gave good yields of the silylenediamide-containing derivatives [M{κ2-NN-Me2Si(NSiHMe2)2}(bpzcp)] (M = Y 1, Lu 2) and [M{κ2-NN-Me2Si(NSiHMe2)2}(bpztcp)] (M = Y 3, Lu 4) by an double activation of Si–H and Si–N bonds. However, the reaction with the precursors that contained the largest metal ions, i.e., [M{N(SiHMe2)2}3(thf )2] (M = Nd, Sm), proceeded rapidly at room temperature to afford the bis(silylamide) complexes [M{N(SiHMe2)2}2(bpzcp)] (M = Nd 5, Sm 6) and [M{N(SiHMe2)2}2(bpztcp)] (M = Nd 7, Sm 8). Additionally, the alkyl heteroscorpionate yttrium and lutetium com-

Received 14th March 2014, Accepted 2nd May 2014

plexes [M(CH2SiMe3)2(NNCp)] (M = Y, Lu) reacted with an excess of HN(SiHMe2)2 to give the mixed alkyl/

DOI: 10.1039/c4dt00770k

amide derivatives [M{N(SiHMe2)2}(CH2SiMe3)(bpzcp)] (M = Y 9, Lu 10) and [M{N(SiHMe2)2}(CH2SiMe3)(bpztcp)] (M = Y 11, Lu 12). The structures of the complexes were determined by spectroscopic methods

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and the X-ray crystal structures of 1, 3 and 5 were also established.

Introduction The rare earth metals (Group 3 metals and lanthanide elements) are a class of elements that offer unique properties in their coordination chemistry. For these elements the overwhelming dominance of M(III) complexes allows the potential preparation of a series of complexes with related structural and chemical properties. The main difference between the lanthanides therefore lies in the variation of the ionic radii of the elements (lanthanide contraction),1 which is significant and ranges from 0.75 Å for scandium (6 coordinate) to 1.03 Å for lanthanum (6 coordinate).1 The systematic variation of the

Departamento de Química Inorgánica, Orgánica y Bioquímica, Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, 13071-Ciudad Real, Spain. E-mail: [email protected]; Fax: +34926295318; Tel: +34926295300 † Electronic supplementary information (ESI) available: Figures, text, tables giving experimental details. Details of data collection, refinement, for complexes 1, 3 and 5. CCDC 990873, 990874 and 990875. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4dt00770k

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ionic radius while maintaining a common oxidation state across different elements is a feature that is not found in other regions of the periodic table. This unusual trend has a number of important implications ranging from the coordination chemistry and reactivity of these metals to the catalytic activity of their complexes. These facts have been discussed in various recent review articles.2 Furthermore, ancillary ligands with multiple coordinating sites and large steric bulk are favored to stabilize rare earth metal complexes and to prevent reactions that afford unexpected products. Poly( pyrazolyl)based (‘scorpionate’) compounds with multiple coordinating sites have been exploited as ancillary ligands in a broad range of transition-metal applications, including organometallic, catalytic, bioinorganic and supramolecular contexts.3 In this field, heteroscorpionate ligands derived from bis( pyrazolyl)methane can be structurally modified very easily, either by varying the substituents on the heterocycle or by changing the arm bearing an anionic functional donor group such as carboxylate, dithiocarboxylate, aryloxide, alkoxide, amide, cyclopentadienyl, acetamidate, thioacetamidate, amidinate

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amongst others, in order to tune both the electronic and steric properties.4 Although the literature concerning transition metals and heteroscorpionate ligands is extensive, the chemistry of these compounds with rare earth metals has been less widely explored.5 Furthermore, cyclopentadienyl ligands bearing an additional donor function arm are attracting increasing interest in the chemistry of early transition and rare earth metals because of their potential applications as catalysts in different processes.6 In this way, ligands that possess both a cyclopentadienyl ring and heteroatoms connected by an appropriate spacer are receiving considerable attention in synthesis and catalysis, as they lead to significant changes in both the steric and electronic effects on the metal centres.7 The easy preparation of heteroscorpionate ligands bearing a cyclopentadienyl anionic arm led us to develop and fully explore the potential offered by this type of ligand. In recent years some reports on the use of NNCp heteroscorpionates in main group, transition and rare earth coordination or organometallic chemistry have been published.7 Some of the complexes are highly efficient catalysts in polymerization reactions, especially the ring opening polymerization of cyclic esters, or in the hydroamination of aminoalkenes.7 As a continuation of our studies in this field, we report here the different reactivity of hybrid scorpionate/cyclopentadienyl ligands4d,h with tris(silylamide) rare earth metal precursors. The reactivity is affected by the nature of the metal centre employed. In the course of our study, we found that precursors containing medium-sized metal ions undergo an unusual double activation of Si–H and Si–N σ-bonds.8

Results and discussion Synthesis and structural characterization Amine elimination of rare earth (including scandium and yttrium) tris(silylamide)complexes [M{N(SiHMe2)2}3(thf)x]9 (M = Sc, Y, Nd, Sm, Lu) by reaction with one equivalent of the heteroscorpionate proligands bpzcpH and racemic-bpztcpH, as a mixture of two regioisomers, bpzcpH = 1-[2,2-bis(3,5dimethylpyrazol-1-yl)-1,1-diphenylethyl]-1,3-cyclopentadiene and 2-[2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl]-1,3-cyclopentadiene and bpztcpH = 1-[2,2-bis(3,5-dimethylpyrazol-1-yl)1-tert-butylethyl]-1,3-cyclopentadiene and 2-[2,2-bis(3,5dimethylpyrazol-1-yl)-1-tert-butylethyl]-1,3-cyclopentadiene,7e was the planned reaction to prepare the bis(silylamide) complexes [M{N(SiHMe2)2}2(NNCp)] (NNCp = hybrid scorpionate/ cyclopentadienyl ligand). The experimental conditions and the results of this reaction have been affected by the ionic radii of the different metal centres employed (see Scheme 1). Thus, the reaction of the heteroscorpionate proligands with an equimolar amount of the tris(silylamide) scandium (with the smallest ionic radius, 0.75 Å) complex [Sc{N(SiHMe2)2}3(thf )] in toluene did not proceed even on heating at reflux temperature for 24 hours (Scheme 1). The reaction of [M{N(SiHMe2)2}3(thf )2] (M = Y, Lu) (with the mid-range ionic radii, Y 0.90 Å; Lu 0.86 Å) with one equivalent of bpzcpH or bpztcpH

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Scheme 1 Different reactivity observed for [M{N(SiHMe2)2}3(thf)x] (M = Sc, Y, Nd, Sm, Lu) in the reactions with the hybrid scorpionate/cyclopentadiene proligands.

in toluene at room temperature did not proceed and the starting materials were recovered, even after a reaction time of two days. However, when the reaction was carried out at 60 °C for 15 hours the formation of a new complex along with the amine HN(SiHMe2)2 and the silane Me2SiH2 was observed. The formation of Me2SiH2 indicates that some type of intramolecular Si–N and Si–H σ-bond activations may have taken place.8 The reaction of [Y{N(SiHMe2)2}3(thf )2] and bpztcpH was monitored by 1H NMR spectroscopy. At room temperature the reaction failed (Fig. S1a†) but when the reaction mixture was heated at 60 °C the reagents partially reacted to give a new complex, together with unreacted starting materials, and free HN(SiHMe2)2 and Me2SiH2 (Fig. S1b,† after 3 hours at 60 °C). Finally, after a reaction time of 15 hours the starting materials were completely consumed (Fig. S1c†). Under the latter experimental conditions the new silylenediamide rare earth complexes [M{κ2-NN-Me2Si(NSiHMe2)2}(bpzcp)] (M = Y 1, Lu 2) [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] and [M{κ2-NN-Me2Si(NSiHMe2)2}(bpztcp)] (M = Y 3, Lu 4) [bpztcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1tert-butylethylcyclopentadienyl] were obtained as pale brown solids in ca. 85% yield (Scheme 1). In these reactions a chelating (dimethylsilylene)bis(dimethylsilyl)amide ligand had been generated. To the best of our knowledge, this is one of the few examples of such an unusual double activation of Si–N and Si–H σ-bonds in rare earth metal complexes.8a,c For the larger metal ions (Nd 0.98 Å; Sm 0.96 Å), the formation of bis(silylamide) complexes [M{N(SiHMe2)2}2(bpzcp)] (M = Nd 5, Sm 6) and [M{N(SiHMe2)2}2(bpztcp)] (M = Nd 7, Sm 8) was observed when [M{N(SiHMe2)2}3(thf)2] (M = Nd, Sm) was reacted with

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Scheme 2

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Synthesis of mixed alkyl/amide complexes 9–11.

one equivalent of bpzcpH or bpztcpH in toluene at room temperature. These products were isolated as blue solids for neodymium complexes (5, 7) and as yellow solids for samarium complexes (6, 8) in ca. 75% yield (Scheme 1). Complexes 3, 4, 7 and 8 were obtained as racemic mixtures. Having prepared the complexes we considered an alternative way to prepare the corresponding bis(silylamide) yttrium and lutetium metal complexes by a protonolysis reaction of the previously reported dialkyl complexes containing hybrid scorpionate/cyclopentadienyl ligands, [M(CH2SiMe3)2(NNCp)],7a,e with two equivalents of the amine HN(SiHMe2)2 (Scheme 2). However, the mixed alkyl/amide complexes [M{N(SiHMe2)2}(CH2SiMe3)(bpzcp)] (M = Y 9, Lu 10) and [M{N(SiHMe2)2}(CH2SiMe3)(bpztcp)] (M = Y 11, Lu 12) were obtained even when the reactions were carried out with excess amine and for prolonged reaction times. The results suggest that the metals with a medium ionic radius may give rise to steric problems that preclude the simultaneous coordination of the scorpionate/cyclopentadienyl and two bis(dimethylsilyl)amide ligands. The silylenediamide complexes 1–4 were characterized by FTIR and NMR spectroscopy (see Experimental section). IR spectroscopy is an efficient tool to corroborate the presence of β-Si–H intramolecular agostic interactions. The Si–H stretching frequencies in the FTIR spectra of 1–4 are found in the region 2110 to 2163 cm−1 and the values are consistent with the absence of interactions between the Si–H moieties and the metal centres.10 Furthermore, the value of the 1JSiH coupling constant is generally a good tool to gauge the intensity of metal-β-Si–H agostic interactions.10 The 1JSiH values found for complexes 1–4 are in the range that is indicative of non-agostic interactions (178–180 Hz) observed for rare earth complexes.10 The observed 29Si NMR resonances range from −29.0 to −23.0 ppm for the NSiHMe2 and the SiMe2-bridge moieties. The 29Si{1H} NMR spectra of yttrium complexes 1 and 3 show one doublet due to 29Si–89Y coupling of the dimethylsilyl bridge11 and this suggests the existence of an appreciable Y⋯SiMe2 interaction in solution (Fig. 1). The room temperature 1H and 13C{1H} NMR spectra of compounds 1 and 2 (achiral compounds) exhibit a singlet for each of the H4, Me3 and Me5 pyrazole protons and carbons, indicating that the pyrazole rings are equivalent, along with two multiplets for the cyclopentadienyl protons and one set of signals for the silylenediamide moiety. A pseudo five-coordinate environment for these complexes can be proposed and a plane

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Fig. 1 (a) 29Si NMR spectrum of complex 1 in C6D6. (b) spectrum of complex 1 in C6D6.

29

Si{1H} NMR

of symmetry exists: i.e., a pseudo square pyramidal geometry (see Scheme 1). However, the room temperature 1H and 13C {1H} NMR spectra of complexes 3 and 4 (chiral compounds) show two singlets for the H4, Me3 and Me5 pyrazole protons and carbons, four multiplets for the cyclopentadienyl protons and one set of signals for the silylenediamide moiety. These results are consistent with a pseudo five-coordinate disposition for complexes 3 and 4. Thus, these spectroscopic data indicate that the hybrid scorpionate/cyclopentadienyl ligands are coordinated in a facial ‘tripodal’ fashion with a κ2NNη5-Cp coordination mode and a κ2-NN-silylenediamide ligand, resulting from activation of the Si–N and Si–H σ-bonds, is also coordinated. The phase-sensitive 1H NOESY-1D NMR spectra were also obtained in order to confirm the assignments of the signals for the H4, Me3 and Me5 groups of each pyrazole ring and for the SiMe2 and SiHMe2 groups of the silylenediamide moiety. The assignment of the 13C{1H} NMR signals was made on the basis of 1H–13C heteronuclear correlation (g-HSQC) experiments. The NMR spectra of complexes 5–8 show strong paramagnetic shifts, as one would expect, with broadness of field from −30.00 to 30.00 ppm. The FTIR spectra of the neodymium and samarium complexes show the characteristic Si–H stretching vibrations at 2104 to 2165 cm−1 for non-interacting Si–H moieties together with Si–H stretching frequencies at ca. 2000 cm−1 as shoulders, which are typical of Si–H moieties with weak agostic interactions with the metal centres10 (see Experimental section). The presence of the proposed agostic interactions was confirmed in the solid state in the crystal molecular structure of compound 5 (see below). A pseudo fivecoordinate environment for these complexes can be proposed

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with a pseudo square pyramidal geometry disposition (Scheme 1). FTIR and NMR data also confirmed the nature of the mixed alkyl/amide species 9–12. The FTIR spectra contain well resolved ν(SiH) bands at around 2150 cm−1 and this supports the absence of interactions between the Si–H moieties and the metal centres.10 The NMR spectra of complexes 9–12 show the resonances of both the alkyl (CH2SiMe3) and the silylamide [N(SiHMe2)2] ligands. The room temperature 1H and 13C{1H} NMR spectra of 9 and 10 (achiral compounds) show that the two pyrazole rings are equivalent, with a singlet observed for each of the H4, Me3 and Me5 pyrazole protons and carbons, two multiplets for the cyclopentadienyl protons and one set of signals for the alkyl and silylamide ligands. The room temperature NMR spectra of 11 and 12 (chiral compounds) show that the pyrazole rings are not equivalent, with a singlet observed for each of the H4, Me3 and Me5 pyrazole protons, four multiplets for the cyclopentadienyl protons, and two doublets for the methyl protons of the silylamide ligand [–N(SiHMe2)2]. Furthermore, the methylene protons of the (–CH2SiMe3) ligand are diastereotopic and give rise to AB systems due to the presence of the stereogenic carbon, Ca, of the heteroscorpionate ligand (see Fig. 2). A pseudo five-coordinate environment can be proposed for these complexes, with a symmetry plane present in complexes 9 and 10. These results are consistent with the proposed pseudo trigonal-bipyramidal structure (Scheme 2). For complexes 9–12 two isomers are possible, one with the silylamide ligand trans to the cyclopentadienyl ring (Scheme 3a) and another with the alkyl ligand trans to the cyclopentadienyl ring

Fig. 2 (a) 1H NMR spectrum of complex [Lu{N(SiHMe2)2}(CH2SiMe3)(bpztcp)] (10) in C6D6 at 25 °C. (b) 1H NOESY-1D experiment on irradiating the methylene protons of the CH2SiMe3 ligand.

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Scheme 3 Proposed structures for the two possible isomers of complexes [M{N(SiHMe2)2}(CH2SiMe3)(NNCp)] (9–12).

(Scheme 3b). The absence of a response in the 1H NOESY-1D experiment (Fig. 2b) from the cyclopentadienyl protons on irradiating the methylene protons of the –CH2SiMe3 ligand suggests that the isomer in which the alkyl ligand is trans to the cyclopentadienyl ring is present (Scheme 3b). The molecular structures of complexes 1, 3·C7H8 and 5·C7H8 were determined by X-ray diffraction. The corresponding ORTEP drawings for complexes 1 and 3 are depicted in Fig. 3. The crystals of complex 3 contain a racemic mixture of enantiomers and the structure of the R enantiomer is depicted in Fig. 3. The crystallographic data and selected interatomic distances and angles are given in Table S1† and Table 1, respectively. The molecular structures of 1 and 3 determined by X-ray diffraction are in good agreement with the solution structures deduced from the spectroscopic data. The heteroscorpionate ligand is attached to the yttrium atom through two nitrogen atoms of pyrazole rings and the cyclopentadienyl ring in a κ2-NNη5-Cp coordination mode, which has the expected fac coordination fashion. In addition, the yttrium centre is coordinated to the chelating silylenediamide ligand. The angular structural parameter (τ value)12 has been reported as a quantitative tool to determine the extent to which five coordination geometries are more trigonal-bipyramidal or square-pyramidal. A value of zero indicates a perfectly square pyramidal geometry and a value of one indicates a perfectly trigonal bipyramidal geometry. The τ values assigned to complexes 1 and 3 (0.27 and 0.19, respectively) confirm that these complexes are slightly distorted square-pyramidal geometry, probably due to the constraints imposed by the chelating ligands. This distortion is manifested in the angles N(3)– Y(1)–N(1) 66.6(1)° and N(6)–Y(1)–N(5) 72.1(1)° for 1, and N(1)– Y(1)–N(3) 68.2(2)° and N(6)–Y(1)–N(5) 72.3(2)° for 3. The Y–N bond distances from the silylenediamide ligand range from 2.255(3) Å to 2.234(5) Å and correlate well with the corresponding distances found in other yttrium amide complexes.13 These bond lengths are shorter than the Y–N bond distances from the pyrazole ring [2.548(5)–2.512(4) Å], thus confirming that the N atoms of the silylenediamide ligand are attached to the yttrium centre in an anionic fashion. In these complexes, the C5H4 ring is symmetrically bonded to the metal centre with Y–C bond distances in the range 2.610(6)–2.669(4) Å. Furthermore, the metal centre, Y(1), is out of the plane

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core. The square tetragonal moiety is perpendicular to another coincident plane composed of C–Si–C and Y–Cp (centroid) (with a dihedral angle of 86.44° for complex 1 and 89.25° for complex 3). It is worth noting that the Y⋯SiMe2 length is 2.908(1) Å for complex 1 and 2.890(2) Å for complex 3, i.e., similar to M–Si σ-bond distances.10c,14 This finding suggests an appreciable interaction in the solid state and this remains in solution, as indicated by the spectroscopic data discussed above. The Y⋯Si contacts from the silylamide moiety are in the range 3.548 Å to 3.687 Å, i.e., longer than Y⋯Si contacts for which there are significant implications for the β-SiH agostic interaction of the silylamide fragment.10c The molecular structure of complex 5 (Fig. 4) is consistent with the structure proposed in Scheme 1. Crystallographic data and selected interatomic distances and angles are given in Table S1† and Table 2, respectively. The heteroscorpionate ligand is attached to the neodymium atom in a κ2-NNη5-Cp coordination mode with the expected fac coordination fashion. Additionally, the neodymium centre is coordinated to two silylamide ligands. The coordination environment of the neodymium atom can be described as a distorted squarepyramidal geometry. The τ value of 0.36 assigned to complex 5

Fig. 3 ORTEP drawings of compounds 1 (a) and 3 (b). Thermal ellipsoids are set at 30% probability and hydrogen atoms are omitted for clarity.

Table 1

Selected bond lengths [Å] and angles [°] for 1 and 3·C7H8

1 Y(1)–N(1) Y(1)–N(3) Y(1)–N(5) Y(1)–N(6) Y(1)–C(13) Y(1)–C(14) Y(1)–C(15) Y(1)–C(16) Y(1)–C(17) Y(1)–Si(2) N(6)–Y(1)–N(5) N(6)–Y(1)–N(3) N(5)–Y(1)–N(3) N(6)–Y(1)–N(1) N(5)–Y(1)–N(1) N(3)–Y(1)–N(1) N(6)–Y(1)–Si(2) N(5)–Y(1)–Si(2) N(5)–Si(2)–N(6)

3·C7H8 2.528(3) 2.512(4) 2.255(3) 2.240(3) 2.652(4) 2.636(4) 2.627(4) 2.647(4) 2.669(4) 2.908(1) 72.1(1) 131.4(1) 89.5(1) 106.8(1) 147.5(1) 66.6(1) 36.16(9) 35.91(9) 100.9(2)

Y(1)–N(1) Y(1)–N(3) Y(1)–N(5) Y(1)–N(6) Y(1)–C(13) Y(1)–C(14) Y(1)–C(15) Y(1)–C(16) Y(1)–C(17) Y(1)–Si(1) N(6)–Y(1)–N(5) N(6)–Y(1)–N(1) N(5)–Y(1)–N(1) N(6)–Y(1)–N(3) N(5)–Y(1)–N(3) N(1)–Y(1)–N(3) N(6)–Y(1)–Si(1) N(5)–Y(1)–Si(1) N(5)–Si(1)–N(6)

2.532(5) 2.558(5) 2.238(5) 2.234(5) 2.610(6) 2.630(6) 2.626(7) 2.634(7) 2.645(6) 2.890(2) 72.2(2) 93.1(2) 137.4(2) 148.7(2) 103.9(2) 68.2(2) 36.2(1) 36.1(1) 101.1(3)

defined by N(1), N(3), N(5) and N(6) by 0.786 Å for complex 1 and 0.736 Å for complex 3. The resulting silylenediamide ligand bites the yttrium at a right angle and the complex has a planar Y–N–Si–N tetragonal

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Fig. 4 ORTEP drawing of compound 5. Thermal ellipsoids are set at 30% probability and hydrogen atoms (except those attached to Si) are omitted for clarity.

Table 2

Bond lengths [Å] and angles [°] for 5·C7H8

Bond lengths Nd(1)–N(1) Nd(1)–N(3) Nd(1)–N(5) Nd(1)–N(6) Nd(1)–C(13) Nd(1)–C(14) Nd(1)–C(15) Nd(1)–C(16) Nd(1)–C(17)

Angles 2.606(7) 2.770(6) 2.397(6) 2.377(7) 2.779(7) 2.800(7) 2.781(7) 2.776(7) 2.806(7)

N(1)–Nd(1)–N(3) N(5)–Nd(1)–N(1) N(5)–Nd(1)–N(3) N(6)–Nd(1)–N(1) N(6)–Nd(1)–N(3) N(6)–Nd(1)–N(5)

63.1(2) 89.0(2) 152.0(2) 118.3(2) 92.6(2) 102.0(2)

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Table 3 Selected structural parameters (intramolecular distances Å and angles °) of β-SiH agostic interactions for 5·C7H8a

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Distances Nd(1)–H(I2)a Nd(1)–H(I3)a Nd(1)–H(I1)b Nd(1)–H(I4)b Nd(1)–Si(2)a Nd(1)–Si(3)a Nd(1)–Si(1)b Nd(1)–Si(4)b N(5)–Si(2)a N(5)–Si(1)b N(6)–Si(3)a N(5)–Si(4)b

Angles 2.731 2.950 3.887 3.573 3.192(3) 3.314(3) 3.808 3.587 1.687(7) 1.707(7) 1.669(7) 1.689(7)

Si(2)a–N(5)–Si(1)b Si(2)a–N(5)–Nd(1) Si(1)b–N(5)–Nd(1) Si(3)a–N(6)–Si(4)b Si(3)a–N(6)–Nd(1) Si(4)b–N(6)–Nd(1)

121.0(4) 101.4(3) 135.5(4) 128.2(4) 108.7(3) 122.9(3)

a Sia: Si atom involved in the agostic interaction; Sib: Si atom not involved in the agostic interaction; Ha: hydrogen atom bonded to Sia; Hb: hydrogen atom bonded to Sib. The hydrogen atoms were geometrically situated.

confirms the distorted square-pyramidal geometry, probably due to the steric demand of the silylamide ligands and the constraints imposed by the heteroscorpionate ligand. This substantial distortion is manifested in the angles N(5)–Nd(1)– N(3), N(1)–Nd(1)–N(3) and N(6)–Nd(1)–N(5), which have values of 152.0(2), 63.1(2) and 102.0(2)°, respectively. The metal centre, Nd(1), is out of the equatorial plane defined by N(1), N(6) and the centroid of the Cp ring by 0.39 Å. The Nd(1)–N(3) bond distance, 2.770(6) Å, is slightly longer than the Nd(1)– N(1) distance, 2.606(7) Å, due to the trans effect of the bis (dimethylsilyl)amide ligand. The molecular structure of 5 unequivocally shows the presence of two asymmetric β-SiH monoagostic15 interactions of the silylamide ligands [one for each silylamide ligand: Si(3)–H(I3)⋯Nd(1) and Si(2)–H(I2) ⋯Nd(1)] (Table 3). The close Nd⋯Si contacts, Nd(1)–Si(2) of 3.192(3) Å and Nd(1)–Si(3) of 3.314(3) Å, are shorter than the Nd(1)–Si(1), 3.808 Å, and Nd(1)–Si(4), 3.587 Å, distances and they are comparable to the Nd–Si σ-bond distances.15,16 These data suggest an appreciable interaction in the solid state. Furthermore, the close Nd⋯H interactions,17 Nd(1)–H(I2)a of 2.731 Å and Nd(1)–H(I3)a of 2.950 Å (Table 3), complete the formation of agostically fused Nd–N–Si–H four-membered rings. For the ring Nd(1)–N(5)–Si(2)–H(I2) there is no torsion angle and the four atoms are located in the plane, whereas for the ring Nd(1)–N(6)–Si(3)–H(I3) the atoms N(6) and Si(3) are out the plane by 0.042 Å and 0.072 Å, respectively. The asymmetric agostic Nd⋯SiH interactions cause a significant contraction of both Nd–N–Si angles, Si(2)–N(5)–Nd(1) of 101.4(3)° and Si(3)–N(6)–Nd(1) of 108.7(3)°, which correspond to the Nd⋯Si contacts. The corresponding range observed for the amide precursor is 109.0(3)–123.2(2)°.9

Conclusions In conclusion, we report here a facile synthesis of a new family of silylamide heteroscorpionate rare earth compounds bearing

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a cyclopentadienyl group as a pendant donor arm. Different reactivities were found for the reactions of tris(silylamide) rare earth metal complexes and hybrid scorpionate/cyclopentadiene proligand compounds, with the reactivity dictated by the ionic radius of the metal centre employed. Thus, the metals with a medium ionic radius, e.g., yttrium and lutetium, gave rise to new silylenediamide derivatives 1–4 through an unusual double activation of Si–H and Si–N bonds. This is one of the few examples of such a double activation in rare earth metal complexes. However, the reaction with the amide precursors of neodymium and samarium, which have larger ionic radii, is very rapid at room temperature and affords the bis (silylamide) complexes 5–8 by amine elimination. Furthermore, mixed alkyl/amide Y and Lu complexes were obtained by protonolysis of the dialkyl complexes bearing hybrid scorpionate/cyclopentadienyl ancillary ligands with excess silylamine. Further studies are being carried out to examine the effect of changes to both the rare earth metal centre and the scorpionate ligand framework in the coordination chemistry and catalytic activity of the resulting complexes.

Experimental section All manipulations were performed under nitrogen using standard Schlenk techniques. Solvents were predried over sodium wire (toluene, n-hexane) and distilled under nitrogen from sodium (toluene) or sodium–potassium alloy (n-hexane). Deuterated solvents were stored over activated 4 Å molecular sieves and degassed by several freeze–thaw cycles. Microanalyses were carried out on a Perkin-Elmer 2400 CHN analyzer. 1H, 13C NMR and 29Si NMR spectra were recorded on a Varian Inova FT-500 (1H NMR 500 MHz, 13C NMR 125 MHz, and 99.5 MHz 29 Si NMR 470 MHz) spectrometer and referenced to the residual deuterated solvent. The NOESY-1D spectra were recorded with the following acquisition parameters: irradiation time 2 s and number of scans 256, using standard VARIANT-FT software. Two-dimensional NMR spectra were acquired using standard VARIANT-FT software and processed using an IPC-Sun computer. IR spectra were obtained on a Shimadzu IRPrestige-21 IR spectrophotometer equipped with a Pike Technologies ATR. Anhydrous trichlorides (YCl3, NdCl3, SmCl3, LuCl3) and HN(SiHMe2)2 were used as purchased (Aldrich and Strem). [MCl3(thf)x],18 Li[N(SiHMe2)2],19 [M{N(SiHMe2)2}3(thf)x],9 bpzcpH,7e bpztcpH,7e and [M(CH2SiMe3)2(NNCp)],7a,e were prepared according to literature procedures. Synthesis of [Y{κ2-NN-Me2Si(NSiHMe2)2}(bpzcp)] (1) A solution of bpzcpH (0.30 g, 0.69 mmol) in toluene (20 mL) was added dropwise to a solution of [Y{N(SiHMe2)2}3(thf )2] (0.44 g, 0.69 mmol) in toluene (20 mL). The reaction mixture was stirred for 15 h at 60 °C. Evaporation of the solvent gave a brown solid. The solid was recrystallized from toluene–hexane (10 : 1, 20 mL at −20 °C) to give pale brown crystals of compound 1. Yield: (0.43 g) 86%. Anal. Calcd for C35H49N6Si3Y:

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C, 57.8; H, 6.8; N, 11.6. Found: C, 57.9; H, 7.0; N, 11.3. IR (cm−1): 2922 (vs), 2853 (vs), 2163 [vs, ν(SiH)], 1556 [s, ν(CvN)], 1417 (w), 1379 (w), 1244 (vs), 976 (s), 901 (s), 758 (m). 1H NMR (C6D6, 297 K): δ = 6.96 (s, 1 H, CH), 5.18 (s, 2 H, H4), 2.43 (s, 6 H, Me3), 1.34 (s, 6 H, Me5), 7.12–6.84 (m, 10 H, Ph), 6.92 (m, 2 H, Hd–Cp), 5.81 (m, 2 H, Hc–Cp), 5.02 (m, 2 H, NSiHMe2), 0.50 (d, 3JHH = 3.0 Hz, 12 H, NSiHMe2), 0.63 (s, 6 H, SiMe2). 13 1 C{ H} NMR (C6D6, 297 K): δ = 68.5 (CH), 152.2, 143.2 (C3 or 5), 106.1 (C4′), 13.7 (Me3), 10.8 (Me5), 150.1–127.6 (Ph), 61.7 (Ca), 114.9 (Cb–Cp), 118.1 (Cc–Cp), 106.4 (Cd–Cp), 3.0 (SiMe2), 2.6 (NSiHMe2). 29Si NMR (C6D6, 297 K): −25.9 (m, SiMe2), −26.8 (ds, 1JSiH = 178.1 Hz, 2JSiH = 6.2 Hz, NSiHMe2). 29Si{1H} NMR (C6D6, 297 K): −25.9 (d, JSiY = 3.1 Hz SiMe2), −26.8 (s, NSiHMe2). Synthesis of [Lu{κ2-NN-Me2Si(NSiHMe2)2}(bpzcp)] (2) The synthetic procedure was the same as for complex 1, using bpzcpH (0.30 g, 0.69 mmol), [Lu{N(SiHMe2)2}3(thf )2] (0.50 g, 0.69 mmol) and toluene (20 mL) to give 2 as a pale brown solid. Yield: (0.52 g) 83%. Anal. Calcd for C35H49LuN6Si3: C, 51.7; H, 6.1; N, 10.3. Found: C, 51.8; H, 6.2; N, 10.1. IR (cm−1): 2915 (vs), 2875 (vs), 2150 [vs, ν(SiH)], 1549 [s, ν(CvN)], 1399 (w), 1321 (w), 1250 (vs), 958 (s), 879 (s), 748 (m). 1H NMR (C6D6, 297 K): δ = 7.03 (s, 1 H, CH), 5.35 (s, 2 H, H4), 2.68 (s, 6 H, Me3), 1.51 (s, 6 H, Me5), 7.17–6.84 (m, 10 H, Ph), 6.94 (m, 2 H, Hd–Cp), 5.79 (m, 2 H, Hc–Cp), 5.30 (m, 2 H, NSiHMe2), 0.54 (brs, 12 H, NSiHMe2), 0.30 (s, 6 H, SiMe2). 13C{1H} NMR (C6D6, 297 K): δ = 74.3 (CH), 144.3, 142.3 (C3 or 5), 108.6 (C4), 15.8 (Me3), 11.6 (Me5), 152.9–128.2 (Ph), 61.6 (Ca), 115.6 (Cb– Cp), 118.7 (Cc–Cp), 111.1 (Cd–Cp), 3.2 (SiMe2), 3.0 (NSiHMe2). 29 Si NMR (C6D6, 297 K): −23.8 (m, SiMe2), −25.9 (ds, 1JSiH = 178.9 Hz, 2JSiH = 5.9 Hz, NSiHMe2). 29Si{1H} NMR (C6D6, 297 K): −23.8 (SiMe2), −25.9 (NSiHMe2). Synthesis of [Y{κ2-NN-Me2Si(NSiHMe2)2}(bpztcp)] (3) The synthetic procedure was the same as for complex 1, using bpztcpH (0.23 g, 0.69 mmol), [Y{N(SiHMe2)2}3(thf )2] (0.44 g, 0.69 mmol) and toluene (20 mL) to give 3 as a pale brown solid. Yield: (0.39 g) 89%. Anal. Calcd for C27H49N6Si3Y: C, 51.4; H, 7.8; N, 13.3. Found: C, 51.7; H, 7.9; N, 13.0. IR (cm−1): 2984 (vs), 2888 (vs), 2163 [vs, ν(SiH)], 1560 [s, ν(CvN)], 1417 (w), 1351 (w), 1284 (vs), 988 (s), 874 (s), 763 (m). 1H NMR (C6D6, 297 K): δ = 6.30 (s, 1 H, CH), 5.32, 5.30 (s, 2 H, H4,4′), 2.45, 2.36 (s, 6 H, Me3,3′), 1.78, 1.66 (s, 6 H, Me5,5′), 2.57 (s, 1 H, CHa), 0.79 [s, 9 H, C(CH3)3], 7.03, 6.90 (m, 2 H, Hd,d′–Cp), 5.81, 5.75 (m, 2 H, Hc,c′–Cp), 5.17 (m, 2 H, NSiHMe2), 0.42 (d, 3 JHH = 2.4 Hz, 12 H, NSiHMe2), 0.67 (s, 6 H, SiMe2). 13C{1H} NMR (C6D6, 297 K): δ = 66.6 (CH), 151.6, 151.5, 142.0, 139.5 (C3,3′ or 5,5′), 107.7, 106.7 (C4,4′), 14.4, 14.3 (Me3,3′), 11.8, 10.9 (Me5,5′), 57.9 (Ca), 35.1 [C(CH3)3], 28.5 [C(CH3)3], 113.8 (Cb–Cp), 117.4, 113.7 (Cc,c′–Cp), 112.2, 110.2, (Cd,d′–Cp), 8.4 (SiMe2), 4.1, 4.3 (NSiHMe2). 29Si NMR (C6D6, 297 K): −22.9 (m, SiMe2), −26.8 (ds, 1JSiH = –79.9 Hz, 2JSiH = 5.8 Hz, NSiHMe2). 29Si{1H} NMR (C6D6, 297 K): −22.9 (d, JSiY = 3.3 Hz, SiMe2), −26.8 (NSiHMe2).

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Synthesis of [Lu{κ2-NN-Me2Si(NSiHMe2)2}(bpztcp)] (4) The synthetic procedure was the same as for complex 1, using bpztcpH (0.23 g, 0.69 mmol), [Lu{N(SiHMe2)2}3(thf )2] (0.50 g, 0.69 mmol) and toluene (20 mL) to give 4 as a pale brown solid. Yield: (0.40 g) 81%. Anal. Calcd for C27H49LuN6Si3: C, 45.2; H, 6.9; N, 11.7. Found: C, 45.5; H, 7.1; N, 11.5. IR (cm−1): 2953 (vs), 2817 (vs), 2110 [vs, ν(SiH)], 1551 [s, ν(CvN)], 1453 (w), 1328 (w), 1219 (vs), 975 (s), 839 (s), 753 (m). 1H NMR (C6D6, 297 K): δ = 6.34 (s, 1 H, CH), 5.41, 5.37 (s, 2 H, H4,4′), 2.82, 2.56 (s, 6 H, Me3,3′), 1.81, 1.75 (s, 6 H, Me5,5′), 2.65 (s, 1 H, CHa), 0.77 [s, 9 H, C(CH3)3], 7.14, 6.95 (m, 2 H, Hd,d′–Cp), 6.18, 5.54 (m, 2 H, Hc,c′–Cp), 5.21 (m, 2 H, NSiHMe2), 0.76, 0.58 (brs, 12 H, NSiHMe2), 0.77 (s, 6 H, SiMe2). 13C{1H} NMR (C6D6, 297 K): δ = 66.7 (CH), 155.0, 154.5, 140.6, 138.9 (C3,3′ or 5,5′), 108.5, 108.3 (C4,4′), 16.6, 15.4 (Me3,3′), 12.0, 11.1 (Me5,5′), 57.9 (Ca), 35.1 [C(CH3)3], 28.4 [C(CH3)3], 112.9 (Cb–Cp), 118.1, 112.6 (Cc,c′–Cp), 112.6, 112.1, (Cd,d′–Cp), 8.3 (SiMe2), 4.1, 4.2 (NSiHMe2). 29Si NMR (C6D6, 297 K): −23.5 (m, SiMe2), −27.4 (ds, 1JSiH = 178.5 Hz, 2JSiH = 5.3 Hz, NSiHMe2). 29Si{1H} NMR (C6D6, 297 K): −23.5 (SiMe2), −27.4 (NSiHMe2).

Synthesis of [Nd{N(SiHMe2)2}2(bpzcp)] (5) A solution of bpzcpH (0.30 g, 0.69 mmol) in toluene (20 mL) was added dropwise to a solution of [Nd{N(SiHMe2)2}3(thf )2] (0.47 g, 0.69 mmol) in toluene (20 mL). The reaction mixture was stirred for 2 h at room temperature. Evaporation of the solvent gave a blue solid. The solid was recrystallized from toluene–hexane (10 : 1, 20 mL at −20 °C) to give blue crystals of compound 5. Yield: (0.44 g) 77%. Anal. Calcd for C37H57N6NdSi4: C, 52.7; H, 6.8; N, 10.0. Found: C, 52.6; H, 6.9; N, 10.2. IR (cm−1): 2955 (vs), 2883 (vs), 2110 [vs, ν(SiH)], 2050 (m, sh), 1560 [s, ν(CvN)], 1493 (w), 1373 (w), 1248 (vs), 1032 (s), 903 (s), 723 (m). 1H NMR (C6D6, 297 K): δ = 16.80 (brs, lw = 480 Hz), 9.31 (brs, lw = 60 Hz), 8.83 (brs, lw = 90 Hz), 7.68 (brs, lw = 25 Hz), 7.60 (brs, lw = 25 Hz), 5.20 (brs, lw = 350 Hz), 4.75 (brs, lw = 15 Hz), 4.15 (brs, lw = 25 Hz), 2.75 (brs, lw = 250 Hz), 2.10 (brs, lw = 50 Hz), 1.25 (brs, lw = 250 Hz), 0.55 (s, lw = 5 Hz), 0.14 (brs, lw = 25 Hz), −1.18 (brs, lw = 125 Hz).

Synthesis of [Sm{N(SiHMe2)2}2(bpzcp)] (6) The synthetic procedure was the same as for complex 5, using bpzcpH (0.30 g, 0.69 mmol), [Sm{N(SiHMe2)2}3(thf)2] (0.48 g, 0.69 mmol) and toluene (40 mL), to give 6 as a yellow solid. Yield: (0.43 g) 73%. Anal. Calcd for C37H57N6Si4Sm: C, 52.4; H, 6.8; N, 9.9. Found: C, 52.8; H, 7.1; N, 9.7. IR (cm−1): 2975 (vs), 2897 (vs), 2150 [vs, ν(SiH)], 2030 (m, sh), 1571 [s, ν(CvN)], 1502 (w), 1384 (w), 1256 (vs), 1044 (s), 925 (s), 728 (m). 1H NMR (C6D6, 297 K): δ = 11.80 (brs, lw = 100 Hz), 8.48 (s, lw = 5 Hz), 7.61 (brs, lw = 45 Hz), 7.32 (brs, lw = 90 Hz), 7.09 (brs, lw = 20 Hz), 6.96 (brs, lw = 30 Hz), 4.55 (brs, lw = 100 Hz), 1.80 (brs, lw = 80 Hz), 1.19 (brs, lw = 250 Hz), 0.80 (brs, lw = 20 Hz), 0.11 (brs, lw = 20 Hz), −0.37 (brs, lw = 40 Hz), −1.22 (brs, lw = 20 Hz).

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Synthesis of [Nd{N(SiHMe2)2}2(bpztcp)] (7)

Synthesis of [Lu{N(SiHMe2)2}(CH2SiMe3)(bpzcp)] (10)

The synthetic procedure was the same as for complex 5, using bpztcpH (0.23 g, 0.69 mmol), [Nd{N(SiHMe2)2}3(thf )2] (0.47 g, 0.69 mmol) and toluene (40 mL), to give 7 as a blue solid. Yield: (0.40 g) 78%. Anal. Calcd for C29H57N6NdSi4: C, 46.7; H, 7.7; N, 11.3. Found: C, 46.9; H, 8.0; N, 11.1. IR (cm−1): 2958 (vs), 2875 (vs), 2104 [vs, ν(SiH)], 2018 (m, sh), 1660 [s, ν(CvN)], 1562 (w), 1454 (w), 1246 (vs), 1033 (s), 983 (s), 780 (m). 1H NMR (C6D6, 297 K): δ = 31.24 (brs, lw = 20 Hz), 21.04 (brs, lw = 30 Hz), 14.11 (s, lw = 5 Hz), 13.61 (brs, lw = 25 Hz), 12.69, 12.08, 11.99 (m, lw = 40 Hz), 8.08 (s, lw = 3 Hz), 7.81 (s, lw = 3 Hz), 7.13 (brs, lw = 45 Hz), 6.52 (s, lw = 2 Hz), 6.24 (s, lw = 2 Hz), 5.16 (s, lw = 5 Hz), 0.72 (brs, lw = 100 Hz), −3.13 (brs, lw = 350 Hz), −17.93 (brs, lw = 100 Hz), −18.32 (brs, lw = 100 Hz).

The synthetic procedure was the same as for complex 9, using HN(SiHMe2)2 (0.086 g, 0.64 mmol), [Lu(CH2SiMe3)2(bpzcp)]7a (0.25 g, 0.32 mmol) and toluene (20 mL) to give 10 as an orange solid. Yield: (0.22 g) 85%. Anal. Calcd for C37H54LuN5Si3: C, 53.7; H, 6.6; N, 8.5. Found: C, 53.9; H, 6.8; N, 8.3. IR (cm−1): 2942 (vs), 2815 (vs), 2150 [vs, ν(SiH)], 1548 [s, ν(CvN)], 1414 (w), 1398 (w), 1218 (vs), 941 (s), 908 (s), 743 (m). 1H NMR (C6D6, 297 K): δ = 6.86 (s, 1 H, CH), 5.21 (s, 2 H, H4), 2.53 (s, 6 H, Me3), 1.38 (s, 6 H, Me5), 7.20–6.94 (m, 10 H, Ph), 6.73 (m, 2 H, Hd–Cp), 5.71 (m, 2 H, Hc–Cp), −0.51 (s, 2 H, CH2SiMe3), 0.38 (s, 9 H, CH2SiMe3), 5.31 (m, 2 H, NSiHMe2), 0.53 (d, 3JHH = 3.2 Hz, 12 H, NSiHMe2). 13C{1H} NMR (C6D6, 297 K): δ = 69.3 (CH), 145.7, 142.2 (C3 or 5), 108.1 (C4), 15.3 (Me3), 11.9 (Me5), 149.2–128.7 (Ph), 60.9 (Ca), 110.4 (Cb–Cp), 118.1 (Cc–Cp), 111.2 (Cd–Cp), 35.7 (s, CH2SiMe3), 5.5 (CH2SiMe3), 3.7 (NSiHMe2). 29Si NMR (C6D6, 297 K): −23.6 (m, CH2SiMe3), −25.7 (ds, 1JSiH = 178.2 Hz, 2JSiH = 6.1 Hz, NSiHMe2).

Synthesis of [Sm{N(SiHMe2)2}2(bpztcp)] (8) The synthetic procedure was the same as for complex 5, using bpztcpH (0.23 g, 0.69 mmol), [Sm{N(SiHMe2)2}3(thf)2] (0.48 g, 0.69 mmol) and toluene (40 mL), to give 8 as a yellow solid. Yield: (0.38 g) 74%. Anal. Calcd for C29H57N6Si4Sm: C, 46.3; H, 7.6; N, 11.2. Found: C, 46.6; H, 7.9; N, 10.9. IR (cm−1): 2998 (vs), 2884 (vs), 2121 [vs, ν(SiH)], 2035 (m, sh), 1650 [s, ν(CvN)], 1548 (w), 1497 (w), 1284 (vs), 1045 (s), 987 (s), 787 (m). 1H NMR (C6D6, 297 K): δ = 11.95 (brs, lw = 30 Hz), 11.19 (brs, lw = 20 Hz), 8.39 (s, lw = 5 Hz), 8.00 (brs, lw = 60 Hz), 4.20, (s, lw = 2 Hz), 4.02 (s, lw = 2 Hz), 3.30 (brs, lw = 25 Hz), 3.24 (s, lw = 5 Hz), 3.02 (s, lw = 2 Hz), 2.64 (s, lw = 2 Hz), 1.89 (brs, lw = 50 Hz), 1.77 (brs, lw = 45 Hz), 1.20 (brs, lw = 50 Hz), 0.75 (s, lw = 5 Hz), −8.15 (brs, lw = 100 Hz), −8.55 (brs, lw = 150 Hz).

Synthesis of [Y{N(SiHMe2)2}(CH2SiMe3)(bpzcp)] (9) To a stirred solution of [Y(CH2SiMe3)2(bpzcp)]7e (0.30 g, 0.40 mmol) in cold (0 °C) toluene (20 mL) was added dropwise a solution of the amine HN(SiHMe2)2 (0.11 g, 0.80 mmol) in toluene (20 mL). The reaction mixture was warmed to room temperature and stirred for 6 h. The volatiles were removed under reduced pressure to afford 9 as a pale yellow solid. The solid was recrystallized from toluene–hexane (10 : 1, 20 mL at −20 °C) to give 9 as a pale yellow solid. Yield: (0.25 g) 86%. Anal. Calcd for C37H54N5Si3Y: C, 59.9; H, 7.3; N, 9.4. Found: C, 60.1; H, 7.6; N, 9.1. IR (cm−1): 2955 (vs), 2850 (vs), 2180 [vs, ν(SiH)], 1555 [s, ν(CvN)], 1428 (w), 1410 (w), 1244 (vs), 950 (s), 918 (s), 749 (m). 1H NMR (C6D6, 297 K): δ = 7.01 (s, 1 H, CH), 5.39 (s, 2 H, H4), 2.60 (s, 6 H, Me3), 1.54 (s, 6 H, Me5), 7.37–7.19 (m, 10 H, Ph), 6.98 (m, 2 H, Hd–Cp), 5.88 (m, 2 H, Hc–Cp), 0.08 (d, 2JYH = 2.8 Hz, 2 H, CH2SiMe3), 0.41 (s, 9 H, CH2SiMe3), 5.23 (m, 2 H, NSiHMe2), 0.50 (s, 12 H, NSiHMe2). 13 1 C{ H} NMR (C6D6, 297 K): δ = 74.6 (CH), 148.9, 144.6 (C3 or 5), 108.4 (C4), 15.6 (Me3), 11.0 (Me5), 150.0–127.0 (Ph), 61.8 (Ca), 115.4 (Cb–Cp), 118.1 (Cc–Cp), 110.4 (Cd–Cp), 30.4 (d, 1JYC = 37.1 Hz, CH2SiMe3), 4.9 (CH2SiMe3), 2.8 (NSiHMe2). 29Si NMR (C6D6, 297 K): −23.5 (m, CH2SiMe3), −26.7 (ds, 1JSiH = 180.1 Hz, 2JSiH = 5.4 Hz, NSiHMe2).

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Synthesis of [Y{N(SiHMe2)2}(CH2SiMe3)(bpztcp)] (11) The synthetic procedure was the same as for complex 9, using HN(SiHMe2)2 (0.11 g, 0.80 mmol), [Y(CH2SiMe3)2(bpztcp)]7e (0.24 g, 0.40 mmol) and toluene (20 mL) to give 11 as a pale yellow solid. Yield: (0.39 g) 89%. Anal. Calcd for C29H54N5Si3Y: C, 53.9; H, 8.4; N, 10.8. Found: C, 54.1; H, 8.6; N, 10.6. IR (cm−1): 2983 (vs), 2891 (vs), 2188 [vs, ν(SiH)], 1554 [s, ν(CvN)], 1424 (w), 1349 (w), 1283 (vs), 975 (s), 849 (s), 784 (m). 1H NMR (C6D6, 297 K): δ = 6.48 (s, 1 H, CH), 5.34, 5.32 (s, 2 H, H4,4′), 2.41, 2.31 (s, 6 H, Me3,3′), 1.79, 1.68 (s, 6 H, Me5,5′), 2.54 (s, 1 H, CHa), 0.84 [s, 9 H, C(CH3)3], 7.01, 6.88 (m, 2 H, Hd,d′–Cp), 5.84, 5.73 (m, 2 H, Hc,c′–Cp), −0.05 (dd, 2JHH = 11.3 Hz, 2JYH = 2.8 Hz, 1 H, CH2SiMe3), −0.19 (dd, 2JHH = 11.3 Hz, 2JYH = 2.8 Hz, 1 H, CH2SiMe3), 0.54 (s, 9 H, CH2SiMe3), 5.19 (m, 2 H, NSiHMe2), 0.42 (s, 12 H, NSiHMe2). 13C{1H} NMR (C6D6, 297 K): δ = 67.3 (CH), 151.4, 150.8, 142.4, 139.3 (C3,3′ or 5,5′), 107.6, 106.4 (C4,4′), 15.1, 14.8 (Me3,3′), 11.4, 10.6 (Me5,5′), 57.4 (Ca), 35.5 [C(CH3)3], 28.8 [C(CH3)3], 114.1 (Cb–Cp), 116.8, 113.4 (Cc,c′–Cp), 112.4, 111.2, (Cd,d′–Cp), 33.4 (d, 1JYC = 37.4 Hz, CH2SiMe3), 4.7 (CH2SiMe3), 4.3, 4.0 (NSiHMe2). 29Si NMR (C6D6, 297 K): −25.9 (ds, 1JSiH = 178.4 Hz, 2JSiH = 5.3 Hz, NSiHMe2). Synthesis of [Lu{N(SiHMe2)2}(CH2SiMe3)(bpztcp)] (12) The synthetic procedure was the same as for complex 9, using HN(SiHMe2)2 (0.11 g, 0.80 mmol), [Lu(CH2SiMe3)2(bpztcp)]7a (0.28 g, 0.40 mmol) and toluene (20 mL) to give 12 as a pale orange solid. Yield: (0.39 g) 82%. Anal. Calcd for C29H54LuN5Si3: C, 47.6; H, 7.4; N, 9.6. Found: C, 47.5; H, 7.5; N, 9.4. IR (cm−1): 2989 (vs), 2894 (vs), 2184 [vs, ν(SiH)], 1559 [s, ν(CvN)], 1431 (w), 1357 (w), 1279 (vs), 980 (s), 844 (s), 787 (m). 1 H NMR (C6D6, 297 K): δ = 6.30 (s, 1 H, CH), 5.32, 5.30 (s, 2 H, H4,4′), 2.55, 2.49 (s, 6 H, Me3,3′), 1.74, 1.64 (s, 6 H, Me5,5′), 2.71 (s, 1 H, CHa), 0.79 [s, 9 H, C(CH3)3], 6.92, 6.85 (m, 2 H, Hd,d′– Cp), 6.42, 5.58 (m, 2 H, Hc,c′–Cp), −0.35 (d, 2JHH = 10.2 Hz, 1 H,

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CH2SiMe3), −0.70 (d, 2JHH = 10.2 Hz, 1 H, CH2SiMe3), 0.44 (s, 9 H, CH2SiMe3), 5.31 (m, 2 H, NSiHMe2), 0.58 (d, 3JHH = 3.1 Hz, 6 H, NSiHMe2), 0.51 (d, 3JHH = 3.0 Hz, 6 H, NSiHMe2). 13C{1H} NMR (C6D6, 297 K): δ = 66.8 (CH), 153.6, 151.2, 140.2, 139.7 (C3,3′ or 5,5′), 108.3, 108.0 (C4,4′), 16.4, 15.5 (Me3,3′), 12.2, 11.4 (Me5,5′), 58.6 (Ca), 35.5 [C(CH3)3], 28.7 [C(CH3)3], 110.2 (Cb–Cp), 114.3, 111.3 (Cc,c′–Cp), 117.0, 111.1, (Cd,d′–Cp), 31.7 (CH2SiMe3), 5.6 (CH2SiMe3), 3.9, 3.7 (NSiHMe2). 29Si NMR (C6D6, 297 K): −26.3 (ds, 1JSiH = 181.4 Hz, 2JSiH = 5.2 Hz, NSiHMe2). X-ray crystallographic structure determination For X-ray structure analyses the crystals of compound 1, 3·C7H8 and 5·C7H8 were mounted on a glass fiber with Paratone-N oil and transferred to a Bruker X8 APEX II CCD diffractometer with a graphite-monochromated Mo-Kα radiation source (λ = 0.71073 Å). Data were integrated and corrected for Lorentz polarization effects using SAINT20 and were corrected for absorption effects using SADABS.21 Space group assignments were based upon systematic absences, E statistics, and successful refinement of the structures. Structures were solved by direct methods with the aid of successive difference Fourier maps and were refined against all data using the SHELXTL software package.22 The thermal parameters for all non-hydrogen atoms were refined anisotropically and the hydrogen atoms were assigned to ideal positions and refined using a riding model with an isotropic thermal parameter. Compound 3·C7H8 crystallized with some disordered toluene molecules in the asymmetric unit. The squeeze option23 was used to eliminate the contribution of the electron density from the intensity data. The derived quantities (Mr), F(000), and Dx in the crystal data are corrected with the contribution from this disordered solvent.

Acknowledgements We gratefully acknowledge financial support from the Ministerio de Economia y Competitividad (MINECO), Spain (Grant Nos. CTQ2011-22578 and Consolider-Ingenio 2010 ORFEO CSD 00006-2007).

Notes and references 1 R. D. Shannon, Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Cryst., 1976, 32, 751. 2 See for example: (a) M. Zimmermann and R. Anwander, Chem. Rev., 2010, 110, 6194; (b) Molecular Catalysts of the Rare Earth Elements, ed. P. W. Roesky, Springer-Verlag, Heidelberg, 2010; (c) P. L. Arnold and I. J. Casely, Chem. Rev., 2009, 109, 3599; (d) G. Zi, Dalton Trans., 2009, 9101; (e) P. M. Zeimentz, S. Arndt, B. R. Elvidge and J. Okuda, Chem. Rev., 2006, 106, 2404; (f) S. Arndt and J. Okuda, Adv. Synth. Catal., 2005, 347, 339; (g) J. Gromada, J.-F. Carpentier and A. Mortreux, Coord. Chem. Rev., 2004,

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248, 397; (h) S. Hong and T. J. Marks, Acc. Chem. Res., 2004, 37, 673; (i) Z. Hou and Y. Wakatsuki, Coord. Chem. Rev., 2002, 231, 1; ( j) G. A. Molander and J. A. C. Romero, Chem. Rev., 2002, 102, 2161. 3 See for example: (a) S. Trofimenko, Scorpionates: The Coordination Chemistry of Polypyrazolylborate Ligands, Imperial College Press, London, 1998; (b) C. Pettinari, Scorpionates II: Chelating Borate Ligands, Imperial College Press, London, 2008; (c) A. Otero, J. Fernández-Baeza, A. LaraSánchez and L. F. Sánchez-Barba, Coord. Chem. Rev., 2013, 257, 1806; (d) G. Türkoglu, C. P. Ulldemolins, R. Müller, E. Hübner, F. W. Heinemann, M. Wolf and N. Burzlaff, Eur. J. Inorg. Chem., 2010, 2962; (e) A. Otero, J. FernándezBaeza, A. Lara-Sánchez, J. Tejeda and L. F. Sánchez-Barba, Eur. J. Inorg. Chem., 2008, 5309; (f ) C. Pettinari and R. Pettinari, Coord. Chem. Rev., 2005, 249, 663; (g) H. R. Bigmore, S. C. Lawrence, P. Mountford and C. S. Tredget, Dalton Trans., 2005, 635; (h) J. N. Smith, J. T. Hoffman, Z. Shirin and C. J. Carrano, Inorg. Chem., 2005, 44, 2012; (i) M. Costas, M. P. Mehn, M. P. Jensen and L. Que Jr., Chem. Rev., 2004, 104, 939; ( j) N. Marques, A. Sella and J. Takats, Chem. Rev., 2002, 102, 2137. 4 See for example: (a) X. L. Liu, X. Y. Zhang, H. B. Song and L. F. Tang, Organometallics, 2012, 31, 5108; (b) M. W. Jones, J. E. Baldwin, A. R. Cowley, J. R. Dilworth, A. Karpov, N. Smiljanic, A. L. Thompson and R. M. Adlington, Dalton Trans., 2012, 41, 14068; (c) A. Otero, J. Fernández-Baeza, A. Antiñolo, J. Tejeda, A. Lara-Sánchez, L. Sánchez-Barba, I. López-Solera and A. M. Rodríguez, Inorg. Chem., 2007, 46, 1760; (d) A. Otero, J. Fernández-Baeza, A. Antiñolo, J. Tejeda, A. Lara-Sánchez, L. F. Sánchez-Barba, M. Sánchez-Molina, A. M. Rodríguez, C. Bo and M. UrbanoCuadrado, Organometallics, 2007, 26, 4310; (e) D. Adhikari, G. Zhao, F. Basuli, J. Tomaszewski, J. C. Huffman and D. J. Mindiola, Inorg. Chem., 2006, 45, 1604; (f ) H. Kopf, C. Pietraszuk, E. Hübner and N. Burzlaff, Organometallics, 2006, 25, 2533; (g) B. S. Hammes, B. S. Chohan, J. T. Hoffman, S. Einwächter and C. J. Carrano, Inorg. Chem., 2004, 43, 7800; (h) A. Otero, J. Fernández-Baeza, A. Antiñolo, J. Tejeda, A. Lara-Sánchez, L. Sánchez-Barba, A. M. Rodríguez and M. A. Maestro, J. Am. Chem. Soc., 2004, 126, 1330; (i) J. N. Smith, Z. Shirin and C. J. Carrano, J. Am. Chem. Soc., 2003, 125, 868. 5 (a) Z. Zhang and D. Cui, Chem. – Eur. J., 2011, 17, 11520; (b) A. Otero, A. Lara-Sánchez, J. Fernández-Baeza, C. Alonso-Moreno, I. Márquez-Segovia, L. F. Sánchez-Barba, J. A. Castro-Osma and A. M. Rodríguez, Dalton Trans., 2011, 40, 4687; (c) G. Paolucci, M. Bortoluzzi, M. Napoli, P. Longo and V. Bertolasi, J. Mol. Catal. A: Chem., 2010, 317, 54; (d) Z. Zhang, D. Cui and A. A. Trifonov, Eur. J. Inorg. Chem., 2010, 2861; (e) A. Otero, J. Fernández-Baeza, A. LaraSánchez, C. Alonso-Moreno, I. Márquez-Segovia, L. F. Sánchez-Barba and A. M. Rodríguez, Angew. Chem., Int. Ed., 2009, 48, 2176; (f ) A. V. Pawlikowski, A. Ellern and A. D. Sadow, Inorg. Chem., 2009, 48, 8020; (g) R. G. Howe, C. S. Tredgdet, S. C. Lawrence, S. Subongkoj and

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Published on 06 May 2014. Downloaded by Northeastern University on 29/10/2014 00:00:24.

6

7

8

9

10

P. Mountford, Chem. Commun., 2006, 223; (h) J. Otero, J. Fernández-Baeza, A. Antiñolo, J. Tejeda, A. Lara-Sánchez, L. Sánchez-Barba, E. Martínez-Caballero, A. M. Rodríguez and I. López-Solera, Inorg. Chem., 2005, 44, 5336; (i) C. S. Tredgdet, S. C. Lawrence, B. D. Ward, G. R. Howe, A. R. Cowley and P. Mountford, Organometallics, 2005, 24, 3136. (a) V. C. Gibson and S. K. Spitzmesser, Chem. Rev., 2003, 103, 283; (b) Y. Qian, J. Huang, M. D. Bala, B. Lian, H. Zhang and H. Zhang, Chem. Rev., 2003, 103, 2633; (c) U. Siemeling, Chem. Rev., 2000, 100, 1495; (d) H. Butenschön, Chem. Rev., 2000, 100, 1527. (a) A. Otero, A. Lara-Sánchez, C. Nájera, J. Fernández-Baeza, I. Márquez-Segovia, J. A. Castro-Osma, J. Martínez, L. F. Sánchez-Barba and A. M. Rodríguez, Organometallics, 2012, 31, 2244; (b) K. Manna, S. Xu and A. D. Sadow, Angew. Chem., Int. Ed., 2011, 50, 1865; (c) K. Manna, A. Ellern and A. D. Sadow, Chem. Commun., 2010, 46, 339; (d) A. Otero, J. Fernández-Baeza, A. Lara-Sánchez, A. Antiñolo, J. Tejeda, E. Martínez-Caballero, I. Márquez-Segovia, I. López-Solera, L. F. Sánchez-Barba and C. Alonso-Moreno, Inorg. Chem., 2008, 47, 4996; (e) A. Otero, J. Fernández-Baeza, A. Antiñolo, A. Lara-Sánchez, J. Tejeda, L. Sánchez-Barba, E. Martínez-Caballero and I. López-Solera, Organometallics, 2008, 27, 976. (a) L. N. Jende, C. Maichle-Mössmer, C. Schädle and R. Anwander, J. Organomet. Chem., 2013, 744, 74; (b) F. Chen, S. Fan, Y. Wang, J. Chen and Y. Luo, Organometallics, 2012, 31, 3730; (c) J.-C. Buffet and J. Okuda, Dalton Trans., 2011, 40, 7748; (d) H. F. Yuen and T. J. Marks, Organometallics, 2009, 28, 2423. (a) S. Arndt, T. P. Spaniol and J. Okuda, Chem. Commun., 2002, 896; (b) R. Anwander, O. Runte, J. Eppinger, G. Gerstberger, E. Herdtweck and M. Spiegler, J. Chem. Soc., Dalton Trans., 1998, 847; (c) J. L. Atwood, W. E. Hunter, R. D. Rogers, J. Holton, J. McMeeking, R. Pearce and M. F. Lappert, J. Chem. Soc., Chem. Commun., 1978, 140; (d) M. F. Lappert and R. J. Pearce, J. Chem. Soc., Chem. Commun., 1973, 126. (a) H. J. Yuen and T. J. Marks, Organometallics, 2008, 27, 155; (b) W. Hieringer, J. Eppinger, R. Anwander and

This journal is © The Royal Society of Chemistry 2014

Paper

11 12

13 14

15 16 17

18

19

20 21

22 23

W. A. Herrmann, J. Am. Chem. Soc., 2000, 122, 11983; (c) L. J. Procopio, P. J. Carroll and D. H. Berry, J. Am. Chem. Soc., 1994, 116, 177. P. S. Coan, L. G. Hubert-Pfalzgraf and K. G. Caulton, Inorg. Chem., 1992, 31, 1262. (a) M.-A. Muñoz-Hernandez, T. S. Keizer, P. Wei, S. Parkin and D. A. Atwood, Inorg. Chem., 2001, 40, 6782; (b) J. Muller and R. Boese, J. Mol. Struct., 2000, 520, 215; (c) A. W. Addison, T. N. Rao, J. Reedijk, K. J. Van Rijn and G. C. Verschoor, J. Chem. Soc., Dalton Trans., 1984, 1349. S. Sun, K. Nie, Y. Tan, B. Zhao, Y. Zhang, Q. Shen and Y. Yao, Dalton Trans., 2013, 42, 2870. (a) W. J. Evans, T. J. Boyle and W. J. Ziller, J. Organomet. Chem., 1993, 462, 141; (b) N. S. Radu, T. D. Tilley and A. L. Rheingold, J. Am. Chem. Soc., 1992, 114, 8293. C. Meerman, G. Gerstberger, M. Spiegler, K. W. Törnroos and R. Anwander, Eur. J. Inorg. Chem., 2008, 2014. J. Eppinger, M. Spiegler, W. Hieringer, W. A. Herrmann and R. Anwander, J. Am. Chem. Soc., 2000, 122, 3080. (a) W. J. Evans, J. H. Meadows, A. L. Wayda, W. E. Hunter and J. L. Atwood, J. Am. Chem. Soc., 1982, 104, 2008; (b) B. Lobovskii, G. L. Soloveichik, A. B. Erofeev, B. M. Bulichev and V. K. Bel’skii, J. Organomet. Chem., 1982, 235, 151; (c) V. K. Bel’skii, A. N. Sobolev, B. M. Bulychev, T. Kh. Alikhanova, A. Kurbonbekov and U. Mirsaidov, Koord. Khim., 1990, 16, 1963. (a) R. Anwander, Top. Organomet. Chem., 1999, 2, 1; (b) J. Eppinger, E. Herdtweck and R. Anwander, Polyhedron, 1998, 17, 1195. (a) W. J. Evans, J. L. Shreeve, J. W. Ziller and R. J. Doedens, Inorg. Chem., 1995, 34, 576; (b) G. R. Willey, T. J. Woodman and M. G. B. Drew, Polyhedron, 1997, 16, 3385. SAINT+ NT ver. 6.04. SAX Area-Detector Integration Program, Bruker AXS, 1997–2001. G. M. Sheldrick, SADABS version 2.03. A Program for Empirical Absorption Correction, University of Göttingen, Göttingen, Germany, 1997–2001. Bruker AXS SHELXTL version 6.10. Structure Determination Package, Bruker AXS, Madison, WI. A. L. Spek, Acta Crystallogr., Sect. A: Fundam. Crystallogr., 1990, 46, C-34.

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