Three- and Five-Membered W/C/N Metallacycles Formed by Incorporation of Acetonitrile Molecules into Silyltungsten Intermediates†

Treatment of Cp*(CO)2W(NCMe)Me (Cp* = η5-C5Me5) with HSiR3 (R = Et, p-Tol) afforded N-silylated η2-iminoacyl tungsten complexes Cp*(CO)2W{κ2(C,N)-C(Me)N(SiR3)} (1a, R = Et; 1b, R = p-Tol). Analogous reactions in the presence of excess acetonitrile for a prolonged reaction time led to the formation of five-membered metallacycles Cp*(CO)2W{κ2(C,N)-C(Me)N−C(Me)N(H)} (2) and Cp*(CO)2W{κ2(C,N)-C(CH2SiR3)N−C(Me)N(H)} (3, R = p-Tol) through a C−N coupling of nitrile molecules and migration of a silyl group.