Reactions of Hydrido(hydrosilylene)tungsten Complexes with α,β-Unsaturated Carbonyl Compounds: Selective Formation of (η3-Siloxyallyl)tungsten Complexes

Hydrido(hydrosilylene)tungsten complexes (C5Me4R1)(CO)2(H)WSi(H)[C(SiMe3)3] [R1 = Me (1a), R1 = Et (1b)] reacted with α,β-unsaturated carbonyl compounds R2C(O)CHCHR3 (R2 = Me, R3 = H or Ph; R2 = OMe, R3 = H) at room temperature to give exo-anti (η3-siloxyallyl)tungsten complexes (C5Me4R1)(CO)2W[η3-R3HCCHCR2OSiH2{C(SiMe3)3}] almost quantitatively and regioselectively. Possible reaction mechanisms involving a [2+4] cycloaddition process are proposed.