Reactions of a Neutral Silylene Ruthenium Complex with Heterocumulenes: C=O Hydrosilylation of Isocyanates vs C=S Bond Cleavage of Isothiocyanate

Reactions of the neutral silylene ruthenium complex Cp*(CO)(H)Ru=Si(H){C(SiMe3)(3)} (2) with heterocumulenes were investigated. Treatment of 2 with ArNCO (Ar = Mes, Ph; Mes = 2,4,6-trimethylphenyl) resulted in hydrosilylation of ArNCO selectively at the C=O bond at room temperature to give the five-membered chelate complexes Cp*(CO)Ru[kappa N-2,Si-N(Ar)=C(H)OSi(H)-{C(SiMe3)(3)}] (3a, Ar = Mes; 3b, Ar = Ph). In contrast, the reaction of 2 with MesNCS led to cleavage of the C=S double bond to give the isocyanide complex Cp*(CO)Ru(CNMes){SSiH2C(SiMe3)(3)} (4). The structures of both types of products were unambiguously determined by X-ray crystallography.