An explicit discussion about the bonding nature and the binding process of the carbene -N 2 reaction is represented in Sec 3.2. It is observed that the diazo derivative is formed through the bonding -back-bonding phenomena of carbene. The HOMO of carbene has the σ type symmetry and the LUMO of carbene has the π type symmetry, and at the same time, the HOMO of N 2 is a σ type orbital and the LUMO of N 2 is a π type orbital. Thus, the electron donation of carbene to nitrogen is not possible in a straightforward way. The electron transfer and formation may occur through a complex pathway. The analysis of the molecular orbitals unveils that at first, the HOMO electron pair of carbene excited to the LUMO of carbene then the HOMO electron pair of N 2 is donated to the vacant HOMO of the carbene. In this process, the bonding is taken place. It is observed that the bonding process is completed before the transition state is reached. After crossing the transition state, the back-bonding takes place. The excited electron pair of carbene is donated to the vacant π * of N 2 to accomplish the back-bonding.