Direct Hydride/Silyl Exchange — Synthesis and X‐ray Study of the Bis(silyl) Complex [Cp2NbH(SiCl3)2]

Dorogov, Konstantin Yu.; Churakov, Andrei V.; Кузьмина, Л. Г.; Howard, Judith A. K.; Nikonov, Georgii I.

doi:10.1002/ejic.200300134

Cited by 20 publications

(27 citation statements)

References 39 publications

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“…[14-16, 28, 30] The same conclusion applies to complex 3 f [22] and the isolobal niobocene species [Nb(Cp) 2 -A C H T U N G T R E N N U N G (SiCl 3 ) 2 (H)]. [29] Such lack of IHI can be ascribed either to the diminished basicity of the hydride or to increased hyperconjugation between the chloride lone pairs and the s*A C H T U N G T R E N N U N G (Si À Cl) antibonding orbital of the chlorine atom lying [8]: Nb1ÀP1 2.534(3), Nb1ÀSi1 2.541(4), Nb1ÀN1 1.795(6), Si1ÀCl1 2.088(5), Si1ÀCl2 2.094(7), Si1ÀCl3 2.098(5), Nb1ÀH1 1.91(4), Si1ÀH1 2.32, P1ÀH1 2.39, Nb1ÀN1ÀC6 172.7(6), P1-Nb1-Si1 121.98(12), P1-Nb1-N1 88.6(2), Si1-Nb1-N1 98.8(2), Nb1-Si1-Cl1 113.7(3), Nb1-Si1-Cl2 116.05 (19), Cl1-Si1-Cl2 104.3(3), Nb1-Si1-Cl3 116.8(2), Cl1-Si1-Cl3 99.1(2), Cl2-Si1-Cl3 104.8(3).…”

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confidence: 58%

“…[22,29] However, the latter explanation appears to be less likely in light of the nonclassical structure of…”

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confidence: 88%

“…[29] Unlike [28] and the isolobal titanium complex [Ti(Cp) 2 - [15] there are no significant differences in the Si À Cl bond lengths within the trichlorosilyl group (a narrow range of 2.088(5)-2.098(5) is observed), which indicates the absence of any interligand hypervalent Si···H interaction. [14-16, 28, 30] The same conclusion applies to complex 3 f [22] and the isolobal niobocene species [Nb(Cp) 2 -A C H T U N G T R E N N U N G (SiCl 3 ) 2 (H)].…”

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confidence: 98%

“…[26] Unfortunately, the 29 Si NMR signals and H À Si coupling constants are not observable in this case [27] to establish the presence of any nonclassical interaction between the silyl and hydride ligands.…”

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confidence: 99%

“…[21e] The presence of agostic SiÀH···M bonding is con-clusively established by the measurement of large H À Si coupling constants (range 96-130 Hz) in the 29 Si NMR. [24] In the 1 H NMR spectra of silyl hydride complexes 3 the hydride resonates in the range 1.65-3.00 ppm, down-field shifted as a result of the anisotropy of the Nb=N bond.…”

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confidence: 99%

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Non‐Innocent Behaviour of Imido Ligands in the Reactions of Silanes with Half‐Sandwich Imido Complexes of Nb and V: A Silane/Imido Coupling Route to Compounds with Nonclassical SiH Interactions

Ignatov¹,

Rees

Merkoulov

et al. 2007

Chemistry A European J

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Reactions of imido complexes [M(Cp)(=NR')(PR''3)2] (M=V, Nb) with silanes afford a plethora of products, depending on the nature of the metal, substitution at silicon and nitrogen and the steric properties of the phosphine. The main products are [M(Cp)(=NR')(PR3)(H)(SiRnCl3-n)] (M=V, Nb; R'=2,6-diisopropylphenyl (Ar), 2,6-dimethylphenyl (Ar')), [Nb(Cp)(=NR')(PR''3)(H)(SiPhR2)] (R2=MeH, H2), [Nb(Cp)(==NR')(PR''3)(Cl)(SiHRnCl2-n)] and [Nb(Cp)(eta 3-N(R)SiR2--H...)(PR''3)(Cl)]. Complexes with the smaller Ar' substituent at nitrogen react faster, as do more acidic silanes. Bulkier groups at silicon and phosphorus slow down the reaction substantially. Kinetic NMR experiments supported by DFT calculations reveal an associative mechanism going via an intermediate N-silane adduct [Nb(Cp){=N(-->SiHClR2)R'}(PR''3)2] bearing a penta-coordinate silicon centre, which then rearranges into the final products through a Si--H or Si--Cl bond activation process. DFT calculations show that this imido-silane adduct is additionally stabilized by a Si--HM agostic interaction. Si--H activation is kinetically preferred even when Si--Cl activation affords thermodynamically more stable products. The niobium complexes [NbCp(=NAr)(PMe3)(H)(SiR2Cl)] (R=Ph, Cl) are classical according to X-ray studies, but DFT calculations suggest the presence of interligand hypervalent interactions (IHI) in the model complex [Nb(Cp) (==NMe)(PMe3)(H)(SiMe2Cl)]. The extent of Si--H activation in the beta-Si--HM agostic complexes [Cp{eta 3-N(R')SiR2--H}M(PR''3)(Cl)] (R''=PMe3, PMe2Ph) primarily depends on the identity of the ligand trans to the Si--H bond. A trans phosphine leads to a stronger Si--H bond, manifested by a larger J(Si--H) coupling constant. The Si--H activation diminishes slightly when a less basic phosphine is employed, consistent with decreased back-donation from the metal.

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confidence: 58%

“…[22,29] However, the latter explanation appears to be less likely in light of the nonclassical structure of…”

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confidence: 88%