The minimum energy required for the green path is 6.48 eV. Thus, the σ donation and π acceptance behavior of carbene are not observed here (brown path). This reaction follows the green path. In the green path, the HOMO electron pair of carbene is excited to the LUMO which is followed by the HOMO electron donation of N 2 . The complex is further stabilized by the back donation of electrons from carbene to the vacant π * orbital of N 2 . This is confirmed by the charge distribution of the diazo derivative where the central nitrogen is positively charged.