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

Abstract

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 NCO 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.