Hydridosilylamido complexes of Ta and Mo isolobal with Berry's zirconocenes: Syntheses, β-Si-H agostic interactions, catalytic hydrosilylation, and insight into mechanism

Abstract

The syntheses of novel Group 5 and Group 6 hydrosilylamido complexes of the type R(ArN)M{N(tBu)SiMe2-H}X (M = Ta, R = Cp; M = Mo, R = ArN; X = Cl, H, OBn, Me) are described. The various substituents in the X position seem to play the key role in determining the extent of β-agostic interaction with the Si-H bond. The Mo agostic hydrido complex (ArN)2Mo{η3-N(tBu)SiMe2-H}H is a pre-catalyst for the hydrosilylation of carbonyls. The stoichiometric reaction between benzaldehyde and (ArN)2Mo{η3-N(tBu)SiMe2-H}H gives the benzoxy complex (ArN)2Mo{N(tBu)SiMe2-H}(OBn), which showed a similar catalytic reactivity compared to the parent hydride. Mechanistic studies suggest that a non-hydride mechanism is operative.