Activation of Silanes and Imidazolium Salts by Low Valent Bis(imino)pyridyl Ruthenium Complexes

The study of species containing metal-silicon bonds, such as transition metal silyl and silylene complexes is central to organosilicon chemistry. This thesis describes the synthesis, characterization, and reactivity of ruthenium silylene, silyl, and carbene complexes by the activation of silanes and imidazolium salts by low valent ruthenium complexes. Ru(0) complexes bearing bis(imino)pyridine ligands, [η2-N 3]Ru(η6-Ar) and {[N3]Ru}2(μ-N 2), where Ar = C6H6 or C6H5 Me, and [N3] = 2,6-(MesN=CMe)2C5H 3N, react with N-heterocyclic silicon(IV) compounds to yield Ru(II) silylene complexes of the type [N3]RU(X)(Y){Si(NN)}, (X = H, Cl and Y = H, Cl, CH3; Si(NN) = N,N\u27-bis(neopentyl)-1,2-phenylenedi(amino)silylene). The activation of two groups on the silane occurs in a stepwise fashion: initial oxidative addition of an Si-X bond, followed by 1,2-migration (α-elimination) of the Si-Y group to the metal. Reversible dissociation from the Ru(II) center leads to free silylene, which can be preferentially trapped with Ru(0) complexes to generate a zerovalent silylene complex, [N3]Ru(N2){Si(NN)}, which also contains a terminal dinitrogen ligand. As an analogous synthesis, the activation of imidazolium salts by [N3]Ru(0) complexes can lead to the formation of ruthenium N-heterocyclic carbine (NHC) complexes. Oxidative addition of the silicon-chloride bonds of alkylchlorosilanes MenSiCl4-n (n = 0, 1, 2, and 3) or cyclomethylenedichlorosilane (CH2)3SiCl2 to ruthenium(0) complexes [η 2-N3]Ru(η6-Ar) and {[N3]Ru} 2(μ-N2), yields 16 electron [N3]Ru(Cl)-SiMe nCl3-n or [N3]Ru(Cl)-Si(CH2)3 complexes. The solid state structures of these complexes exhibit distorted square pyramidal geometries with a silyl ligand trans to the vacant site. Treatment of chloro(organosilyl)ruthenium complexes with a phosphine(PMe 3) results in the addition of the phosphine to the ruthenium center to give 18 electron ruthenium(II) complexes. Reaction of [N3]Ru(Cl)(SiMe 2Cl) with ethylene yields the 18e- olefin adduct, which subsequently undergoes olefin insertion into a ruthenium silicon bond to form the l6e-[N3]Ru(Cl)(CH2CH2SiMe 2Cl) and [N3]Ru(Cl)(CH2CH2SiMe 2Cl)(CH2CH2) under excess ethylene. Each intermediate structure has been isolated and characterized