For the mutation of heteroatom of N-heterocyclic carbene, the nitrogen atom is replaced by the phosphorous atom of 5 CN carbene. This carbene is termed as 6 CN carbene. The reaction of N 2 with 6 CN was also studied. It is observed that activation energy and reaction-free energy of this reaction are 11.6 kcal/mol and -10.1 kcal/mol respectively. Among all carbenes, the lowest activation energy for the formation of the diazo derivative is observed for the 6 CN carbene. This diazo derivative is the most stable too. Therefore, 6 CN is the best candidate for N 2 activation in our present Inquisition.