SIGMA-BOND METATHESIS REACTIONS INVOLVING LANTHANIDE-SILICON AND LANTHANIDE-HYDROGEN BONDS

Neutral lanthanide silyl complexes Cp*(2)LnSiH(SiMe(3))(2) (1, Ln = Sm; 2, Ln = Nd; 3, Ln = Y; Cp* = eta(5)-C(5)Me(5)) are synthesized by reaction of the corresponding alkyls Cp*(2)LnCH(SiMe(3))(2) with neat SiH2(SiMe(3))(2). These complexes are monomeric in solution, but form dimers in the solid state through intermolecular Ln...CH3-Si interactions. Mechanistic studies on this reaction indicate that it proceeds via a second-order autocatalytic process catalyzed by [CP*(2)LnH](2). Reactions of [Cp*(2)LnH](2) with Cp(2)WH(2) give the sigma-bond metathesis products Cp*(2)Ln(mu-eta(1),eta(5)-C5H4)(mu-H)(2)WCp (5, Ln = Sm; 6, Ln = Y), via activation of a C-H (and not a W-H) bond of the tungsten hydride. The lanthanide borohydride complexes Cp*(2)Ln(eta(2)-H(2)BMes(2)) (Mes = mesityl; 7, Ln = Sm; 8, Ln = Y) are obtained by the reaction of [Cp*(2)LnH](2) with [HBMes(2)](2).