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

The syntheses of novel Group 5 and Group 6 hydrosilylamido complexes of the type R(ArN=)M{N(Bu-t)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 beta-agostic interaction with the Si-H bond. The Mo agostic hydrido complex (ArN=)(2)Mo{eta(3)-N(Bu-t)SiMe2-H}H is a pre-catalyst for the hydrosilylation of carbonyls. The stoichiometric reaction between benzaldehyde and (ArN=)(2)Mo{eta N-3(Bu-t)SiMe2-H}H gives the benzoxy complex (ArN=)(2)Mo{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.