Hydrosilylation of a Dinuclear Tantalum Dinitrogen Complex:  Cleavage of N2 and Functionalization of Both Nitrogen Atoms

Hydrosilylation of the ditantalum dinitrogen complex ([NPN]Ta)2(μ-H)2(μ-η:η-N2) proceeds via an addition reaction to produce ([NPN]TaH)(μ-H)2(μ-η12-N−NSiH2Bu)(Ta[NPN]), which contains a new N−Si bond and a terminal tantalum hydride; this species has been characterized by NMR spectroscopy and X-ray diffraction. This complex undergoes reductive elimination of H2 followed by N−N bond cleavage to generate a new intermediate with the formula ([NPN]TaH)(μ-N)(μ-NSiH2Bu)(Ta[NPN]); confirmation of N−N bond cleavage is evident from the 15N-labeled isotopomer that displays an absence of 15N−15N scalar coupling in the 15N NMR spectrum. In the presence of additional silane, a second hydrosilylation and reductive elimination results to give ([NPN]Ta)2(μ-NSiH2Bu)2, a species in which each dinitrogen-derived N atom has been converted to a bridging silylimide ligand. This latter complex displays C2h symmetry both in solution and in the solid state.