CO assisted N₂ functionalization activated by a dinuclear hafnium complex: A DFT mechanistic exploration

In this paper, the reaction mechanisms of CO assisted N₂ cleavage and functionalization activated by a dinuclear hafnium complex are studied using a density function theory (DFT) method. Several key intermediates (I_a, I_b, I_c and I_d) with axial/equatorial N=C=O coordination structures are found to be of importance along reaction pathways of CO assisted N₂ functionalization, which could provide a profound theoretical insight into the C-N bond formation and N-N bond cleavage. There are two different attack directions to insert the first CO molecule into the Hf-N bonds of the dinuclear hafnium complex, which lead to C-N bond formation. The calculated results imply that CO insertion into the Hf¹-N³ bond (Path A1) reacts more easily than that into the Hf²-N³ bond (Path A3). But for the insertion of the second CO insertion to give 2_A, there are two possibilities (Path A1 and Path A2) according to this insertion being after/before N-N bond cleavage. Two pathways (Path A1 and Path A2) are proved to be possible to form final dinitrogen functionalized products (oxamidide 2_A, 2_B and 2_C) in this study, which explain the formation of different oxamidide isomers in CO assisted N₂ functionalization activated by a dinuclear hafnium complex.