Dinitrogen-Facilitated Reversible Formation of a Si–H Bond in a Pincer-Supported Ni Complex

Binding of dinitrogen to transition metal complexes typically involves coordination to a vacant site or a ligand substitution reaction with no formal change in oxidation state at the metal. Here, we report that dinitrogen binding to a PSiP pincer-supported Ni­(II) hydride results in reduction to a dinuclear Ni(0) bridging dinitrogen complex containing two Si–H agostic interactions and a monomeric Ni(0) terminal dinitrogen complex containing a Si–H agostic interaction, a rare example of dinitrogen facilitating formal reduction at the metal center and the formation of a Si–H bond. The process is reversible, and formation of the dinitrogen complexes is enthalpically driven. DFT calculations support the proposed equilibrium and provide information about the nature of the bonding in the unusual Ni(0) dinitrogen complexes. Similar behavior is also observed when CO binds to the Ni­(II) hydride, but in this case the reaction is irreversible.