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.