Snapshots of the oxidative-addition process of silanes to nickel(0)

Abstract

Addition of hydridosilanes, Ar 2SiHX, to the labile Ni(0) benzene complex [(dtbpe)Ni] 2(C 6H 6) ( 1; dtbpe=1,2-bis(di- tert-butylphosphino)ethane) gives mononuclear Ni(II) hydride silyl complexes of the formulation (dtbpe)Ni(μ-H)SiAr 2X ( 2, X=H, Ar=Mes; 3, X=H, Ar=Ph; 4, X=Me, Ar=Ph; 5, X=Cl, Ar=Ph). Although the crystal structures of two representatives of the series indicate square-planar coordination around nickel, in solution structures having apparent C 2 v symmetry are observed. We propose that this behavior is due to a fluxional process that involves η 2-SiH intermediates. Other data are also consistent with the facile reductive elimination of the silane to regenerate nickel(0) products. Oxidation of 2 and 3 with triphenylcarbenium tetrakis(pentafluorophenyl)borate results in silane elimination and formation of [(dtbpe)Ni(η 3-C 6H 5CPh 2) +][B(C 6F 5) 4 −] ( 6), the structure of which shows the CPh 3 − ligand bound to a Ni(II) center through a phenyl ring in an η 3-allylic fashion.