In the past few years, N-heterocyclic carbenes (NHCs)[1]emerged as ligated versatile building blocks for a large variety of organometallic and coordination compounds.These ligands show a -donors and to generate rather stable metal-carbon bonds. Here, we want report a comparative theoretical study on stability and interaction energy of 5 and/or 6-membered-ring chelates in some of [Bis- 2H2]. The geometries of all molecules were optimized at both BP86, and B3LYP, levels of theory using def2-TZVPP basis set. In all cases the vibrational frequency analyses, calculated at the same level of theory and indicated that the optimized structures are at the stationary points corresponding to local minima without any imaginary frequency. Calculations were performed using the GAUSSIAN 09 program.The interaction energies were calculated for all compounds.NBO analyses were also carried out with the internal module GAUSSIAN 09. The result show that the interaction energy between the -membered-ring chelate of NHC complexes is significantly more than corresponding 5-membered-ring chelate.
