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 C₂ symmetric dicarboxylated diazenido compound. Treatment with excess Me₃SiI 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 Me₃SiI, respectively. The regiochemistry of the N₂ carboxylation is controlled by the ansa-cyclopentadienyl ligand where the sterically demanding tert-butyl substituents and the C₂ 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.