1075732-70-5Relevant academic research and scientific papers
Silyl hydrides of tantalum supported by cyclopentadienyl-imido ligand sets: Syntheses, X-ray, NMR, and DFT studies
Ignatov, Stanislav K.,Rees, Nicholas H.,Merkoulov, Alexei A.,Dubberley, Stuart R.,Razuvaev, Alexei G.,Mountford, Philip,Nikonov, Georgii I.
, p. 5968 - 5977 (2009/04/13)
Reactions of the imido complex Cp(ArN)Ta(PMe3)2 (1, Ar = 2,6-diisopropylphenyl) with silanes afford the silyl hydrides Cp(ArN)Ta(PMe3)(H)(SiRnCl3-n) (2b-e) and Cp(ArN)Ta(PMe3)(H)(SiPhMeH) (2a) as the first kinetic products. However, the hydride compounds Cp(ArN)Ta(PMe3)(H)(SiR nCl3-n) are metastable and, first, rearrange in the presence of phosphine to the chlorides Cp(ArN)Ta(PMe3)(Cl)(SiHR nCl2-n) (5) and then decompose to Cp(ArN)Ta(PMe 3)(Cl)(H) (4) and eventually to Cp(ArN)Ta(PMe3)Cl 2 (3). Complexes with a smaller Ar' substituent at nitrogen (Ar′ = 2,6-dimethylphenyl) react faster, as do more Lewis acidic silanes. The occurrence of interligand hypervalent interactions in the tantalum complexes Cp(ArN)Ta(PMe3)(H)(SiRnCl3-n) has been revealed by X-ray structure analysis, DFT calculations, and the experimental determination of the sign of the coupling constant J(Si-H). The J(Si-H) was found to be negative for Cp(ArN)Ta(PMe3)(H)(SiMenCl 3-n) (J(Si-H) = -40 Hz for n = 1; J(Si-H) = -50 Hz for n = 0), indicative of the presence of Si-H bonding, but positive for Cp(ArN)Ta(PMe 3)(H)(SiMeHPh) (J(Si-H) = +14 Hz), suggesting the absence of direct Si-H interactions. A DFT study of the mechanism of silane coupling with the model imido complex Cp(MeN)Ta(PMe3)2 established the feasibility of the direct addition of silanes HSiMenCl3-n (n = 1-3) to the imido group to give the adduct Cp(MeN{→SiR 3-H})Ta(PMe3)2, as previously found in the related niobium chemistry.
