Dinitrogen Silylation and Cleavage with a Hafnocene Complex

Silylation of a hafnocene complex containing a strongly activated dinitrogen ligand, [(eta(5)-C5H2-1,2,4-Me-3)(2)Hf](mu(2),eta(2),eta(2)-N-2), by addition of CySiH3 resulted in N-Si and Hf-H bond formation and a compound poised for subsequent N-2 cleavage. Warming the silane addition product to 75 degrees 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 mu-formamidide ([NC(H)O]2(-)) ligand. Subsequent treatment with HCl yielded free formamide, demonstrating that an important organic molecule can be synthesized from N-2, CO, an organosilane, and protons.