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-η¹:η²-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 C_2h symmetry both in solution and in the solid state.