Tuning the Laplaza-Cummins 3-coordinate M[N(R)Ph]3 catalyst to activate and cleave CO2.

The Laplaza-Cummins catalyst L(3)Mo (L = N(R)Ar), is experimentally inactive towards carbon dioxide. Previous theoretical analysis identified the cause for this inactivity and suggested that a switch to a d(2) transition metal may induce activity towards the inert CO(2) molecule. In this manuscript we have tested this hypothesis by altering the central metal to Ta, Nb or V. Our calculations suggest that the tantalum analogue, TaL(3), will successfully bind to CO(2) in a mononuclear η(2) arrangement and, importantly, will strongly activate one C-O bond to a point where spontaneous C-O cleavage occurs. This prediction of a strongly exothermic reaction takes into consideration the initial barrier to formation, spin crossings, ligand bulk and even the choice of density functional in the calculations. The Nb analogue will likely coordinate CO(2) but reaction may not proceed further. In contrast, the V analogue faces an initial coordination barrier and is not expected to be sufficiently active to coordinate CO(2) to the triamide catalyst. A similar scenario exists for mixed metal interactions involving a d(2) and d(4) combination in a bridging dinuclear arrangement.