N-heterocyclic carbenes are most accessible organic ligands in both organometallic and coordination chemistry, which is reflected by thousands of applications involving NHC-bearing metal complexes in areas ranging from homogeneous catalysis to material science [1]. The chemistry of N-heterocyclic carbenes (NHCs) and their metal complexes has advanced significantly over the last two decades in the field of organometallic catalysis and medicinal chemistry [2]. Herein we report a theoretical study on structure and nature of C→Re bonds in some derivatives of [(NHC(R))4Re(O)(Y)] (Y= OMe, Cl R=H, CH3, F, Cl, Br) complexes at PBE1PBE/def2-SVP level of theory. The interaction energies between [NHC(R)]4 and Re(O)Y in optimized structures of [(NHC(R))4Re(O)(Y)] (Y= OMe, Cl R=H, CH3, F, Cl, Br) complexes were calculated at PBE1PBE/def2-TZVP level of theory. The data showed that the C→Re bonds in the complexes especially with electron donating substituents are stronger than the other complexes. Also the results showed that the calculated interaction energies increase with changing R substituents in studied complexes, from F to Br atoms.
