Abstract
Reactions of carbene complex [Cp(IPORu(pyr)(2)][BF4] (6, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with excess acetonitrile and LiCl in THF afford complexes [Cp(IPr)Ru(NCCH3)(2)][PF6] (7) and Cp(IPr)RuCl (8), respectively. Complex 8 was characterized by NMR and X-ray diffraction analysis. Addition of hydrosilanes to 8 results in silane sigma-complexes Cp(IPr)Ru(eta(2)-HSiR3) Cl (4), which were characterized by NMR and X-ray studies of Cp(IPr)Ru(eta(2)-HSiMeCl2)Cl (4b) and Cp(IPr)Ru(eta(2)-H3SiPh)Cl (4d). The hydrogen silicon coupling constants of complexes 4 show an unusual trend in that the J(H-Si) values increase from the less-chlorinated complex Cp(IPr)Ru(eta(2)-HSiMe2Cl)Cl (4c) to the trichloro derivative Cp(IPr)Ru(eta(2)-HSiCl3)Cl (4a). Reaction of Cp(IPr)RuCl (8) with two equivalents of HSiCl3 gave the ruthenate complex [IPrH](+)[CpRuCl(H) (SiCl3)(2)](-), characterized by NMR and X-ray study. Addition of hydrosilanes to the cationic complex [Cp(IPr)Ru(NCCH3)(2)][BAr4F] (9) furnished very unstable cationic silane sigma-complexes [Cp(IPr)Ru(eta(2)-HSiR3)(NCCH3)](+) (5), characterized by low-temperature NMR. Reaction of complex 9 with two equivalents of HSiCl3 gives the neutral bis(silyl) complex CpRu(NCCH3)(H)(SiCl3)(2) and [IPrH][BAr4F]. Catalytic studies showed that 9 is a poorer catalyst for hydrosilylation of benzaldehyde, benzonitrile, and pyridine than its phosphine analogue [Cp((Pr3P)-Pr-i)Ru(NCCH3)(2)][BAr4F]. The reason for this reduced activity was assigned to the easy dissociation of carbene from the former catalyst.