Hydrosilylation of a Dinuclear Tantalum Dinitrogen Complex:  Cleavage of N<sub>2</sub> and Functionalization of Both Nitrogen Atoms

Hydrosilylation of the ditantalum dinitrogen complex ([NPN]Ta)<sub>2</sub>(μ-H)<sub>2</sub>(μ-η:η-N<sub>2</sub>) proceeds via an addition reaction to produce ([NPN]TaH)(μ-H)<sub>2</sub>(μ-η<sup>1</sup>:η<sup>2</sup>-N−NSiH<sub>2</sub>Bu)(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 H<sub>2</sub> followed by N−N bond cleavage to generate a new intermediate with the formula ([NPN]TaH)(μ-N)(μ-NSiH<sub>2</sub>Bu)(Ta[NPN]); confirmation of N−N bond cleavage is evident from the <sup>15</sup>N-labeled isotopomer that displays an absence of <sup>15</sup>N−<sup>15</sup>N scalar coupling in the <sup>15</sup>N NMR spectrum. In the presence of additional silane, a second hydrosilylation and reductive elimination results to give ([NPN]Ta)<sub>2</sub>(μ-NSiH<sub>2</sub>Bu)<sub>2</sub>, a species in which each dinitrogen-derived N atom has been converted to a bridging silylimide ligand. This latter complex displays <i>C</i><sub>2</sub><i><sub>h</sub></i> symmetry both in solution and in the solid state.