Dinitrogen Silylation and Cleavage with a Hafnocene Complex

Silylation of a hafnocene complex containing a strongly activated dinitrogen ligand, [(η5-C5H2-1,2,4-Me3)2Hf]2(μ2,η2,η2-N2), by addition of CySiH3 resulted in N–Si and Hf–H bond formation and a compound poised for subsequent N2 cleavage. Warming the silane addition product to 75 °C triggered N–N scission, for which the requisite electrons were provided by silyl migration. Dinitrogen cleavage coupled to N–C bond formation was also accomplished by carbonylation of the silylated product, yielding an unprecedented μ-formamidide ([NC(H)O]2–) ligand. Subsequent treatment with HCl yielded free formamide, demonstrating that an important organic molecule can be synthesized from N2, CO, an organosilane, and protons.