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

Abstract

The Laplaza-Cummins catalyst L₃Mo (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 d² transition metal may induce activity towards the inert CO₂ 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, TaL₃, will successfully bind to CO₂ in a mononuclear η² 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 CO₂ 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 CO₂ to the triamide catalyst. A similar scenario exists for mixed metal interactions involving a d² and d⁴ combination in a bridging dinuclear arrangement.