Mechanistic Studies on the Carboxylation of Hafnocene and ansa-Zirconocene Dinitrogen Complexes with CO2

A DFT study on the carboxylation of hafnocene and ansa-zirconocene dinitrogen complexes with CO2 indicates that the most favorable initial CO2 insertion into M-N (M = Hf, Zr) proceeds by a stepwise path rather than a concerted [2 + 2] path. The calculated results explain the regioselectivity of the N-C formation in experiments. In addition, a comparative analysis of ring tension and charge distribution unveils the different activities of N-N bond cleavage in the CO and CO2 direct N-C bond formation reactions.