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

We have investigated the electronic ground-state structure and binding mode of CH 2 N 2 by ab initio multireference perturbation calculations CASPT2 and CASPT3, using correlation consistent cc-pVTZ basis sets. Our calculations suggest that the CH 2 −N 2 binding between the CH 2 (ã 1 A 1 ) and N 2 (X 1 Σ g + ) moieties consists of a “harpooning” σ, bond from N 2 to CH 2 and a π-like bond due to the back-transfer of electrons from CH 2 to N 2 . Despite the popular dipolar resonance structures employed to represent the CH 2 N 2 binding no charge transfer between the in situ CH 2 and N 2 is observed. Our CH 2 −N 2 dissociation energy is D e = 38.2 kcal/mol with respect to the CH 2 (ã 1 A 1 ) + N 2 (X 1 Σ g + ) adiabatic products or D e = 27.2 kcal/mol with respect to the ground X̃ 3 B 1 state of CH 2 . Taking into account zero point energy corrections, this value is reduced to D o = 21.6 kcal/mol.