| This thesis describes the synthesis, structural studies, and stoichiometric and catalytic reactivity of novel Mo(IV) imido silylamide (R 1N)Mo(R2)(eta3-R1N-SiR 32-H)(PMe3)n (1: R 1 = tBu, Ar', Ar; R2 = Cl; R32 = Me2, MePh, MeCl, Ph 2, HPh; n = 2; 2: R1 = Ar, R2 = SiH2Ph, n = 1) and hydride complexes (ArN)Mo(H)(R)(PMe3 )3 (R = Cl (3), SiH2Ph (4)). Compounds of type 1 were generated from (R1N)Mo(PMe 3)n(L) (5: R1 = tBu, Ar', Ar; L = PMe3, eta2- C2H4) and chlorohydrosilanes by the imido/silane coupling approach, recently discovered in our group. The mechanism of the reaction of 5 with HSiCl3 to give (ArN)MoCl2(PMe 3)3 (8) was studied by VT NMR, which revealed the intermediacy of (ArN)MCl2(eta2-ArN=SiHCl)(PMe 3)2 (9). The imido/silyl coupling methodology was transferred to the reactions of 5 with chlorine-free hydrosilanes. This approach allowed for the isolation of a novel beta-agostic compound (ArN)Mo(SiH2Ph)(eta3-NAr-SiHPh-H)(PMe3) (10). The latter was found to be active in a variety of hydrosilation processes, including the rare monoaddition of PhSiH3 to benzonitrile. Stoichiometric reactions of 11 with unsaturated compounds appear to proceed via the silanimine intermediate (ArN)M(eta 2-ArN=SiHPh)(PMe3) (12) and, in the case of olefins and nitriles, give products of Si-C coupling, such as (ArN)Mo(R)(eta 3-NAr-SiHPh-CH=CHR')(PMe3)| (13: R = Et, R' = H; 14: R = H, R' = Ph) and (ArN)Mo(eta2-NAr-SiHPh-CHR=N)(PMe 3) (15). Compound 13 was also subjected to catalysis showing much improved activity in the hydrosilation of carbonyls and alkenes.;Hydride complexes 3 and 4 were prepared starting-from (ArN)MoCl2(PMe3)3 (8). Both hydride species catalyze a diversity of hydrosilation processes that proceed via initial substrate activation but not silane addition. The proposed mechanism is supported by stoichiometric reactions of 3 and 4, kinetic NMR studies, and DFT calculations for the hydrosilation of benzaldehyde and acetone mediated by 4. |
