Computational Details
Density functional theory (DFT) calculations were carried out using Gaussian09 suite of programs [53-55]. Geometry optimization was carried out using the density functional B3LYP and M06 methods and using two different basis sets 6-31+G(d) and 6-311++G(d,p) [56]. The results (relative energy values) obtained using M06/6-311++G(d,p) level of quantum chemical methods are provided in Tables 1 and 2, the results obtained using other three levels (as well as the corresponding absolute energy values) are given in supporting information. All the minima are characterized by zero negative frequencies and the transition states are characterized by one negative frequency. The Gibb’s free energy values are employed in the analysis. The bond dissociation energy values are estimated by breaking the L-C bond in which the L is a fully characterizable carbene unit.