The first N-heterocyclic carbene (NHC)-metal complexes was synthesized in 1968[1]. The isolation of the first free carbene by Arduengo in 1991, set the scene for an ever-growing interest and advancement in the field of NHC chemistry [2]. Shortly afterward, the use of these compounds in organometallic chemistry, particularly in catalysis, dramatically increased [3]. There are several reports on the structure and nature of metal—ligand bonding of Metal-NHC complexes [6-4]. Herein I summarize some recent researched works concerning the theoretical study on the structure and the nature of metal—ligand bonding in some Metal-Carben complexes by using the density functional method. The amount of natural charges of elements in the complexes, hybrid orbital types, WBI and molecular orbitals were calculated through NBO analysis. Also the AIM and EDA analyses were used to detect the presence of bond critical points (BCPs) and the nature of C→M bond in the complexes. The contributions of the electrostatic and the orbital interaction are estimated by energy decomposition analysis(EDA) and the strength of the σ donor and π acceptor bonding in the complexes are discussed by using ETS-NOCV scheme.
