A Theoretical Investigation of the Structure and Bonding of Diazomethane, CH2N2

We have investigated the electronic ground-state structure and binding mode of CH2N2 by ab initio multireference perturbation calculations CASPT2 and CASPT3, using correlation consistent cc-pVTZ basis sets. Our calculations suggest that the CH2-N2 binding between the CH2 (ãA1) and N2 (XΣg) moieties consists of a “harpooning” σ, bond from N2 to CH2 and a π-like bond due to the back-transfer of electrons from CH2 to N2. Despite the popular dipolar resonance structures employed to represent the CH2N2 binding no charge transfer between the in situ CH2 and N2 is observed. Our CH2-N2 dissociation energy is De ) 38.2 kcal/mol with respect to the CH2 (ãA1) + N2 (XΣg) adiabatic products or De ) 27.2 kcal/mol with respect to the ground X̃B1 state of CH2. Taking into account zero point energy corrections, this value is reduced to Do ) 21.6 kcal/mol.