Carboxylation of an ansa-zirconocene dinitrogen complex:: Regiospecific hydrazine synthesis from N2 and CO2

Addition of 2 equiv of carbon dioxide to the ansa-zirconocene dinitrogen complex resulted in selective insertion into each zirconium nitrogen bond, forming a C-2 symmetric dicarboxylated diazenido compound. Treatment with excess Me(3)Sil furnished the ansa-zirconocene diiodide along with the N,N-dicarboxylated silylated hydrazine. New nitrogen-carbon bonds were also assembled by addition of methyl triflate. Tri- and tetrasubstituted hydrazines could be formed by treatment with water and Me(3)Sil, respectively. The regiochemistry of the N-2 carboxylation is controlled by the ansa-cyclopentadienyl ligand where the sterically demanding tert-butyl substituents and the C-2 symmetry of the dimer dictates the stereochemistry of CO2 insertion. These results demonstrate the ability of zirconium dinitrogen compounds to participate in heterocumulene insertion chemistry.