Bridged fac-Tricarbonylrhenium(I)-Biscarbene Complexes: Synthesis, Characterization, and Molecular Dynamics

Six new biscarbene complexes of the type fac-[{CO)(3)-(ReBr)-Br-I(L)], where L represents a chelating bis(N-heterocyclic carbene) ligand consisting of two alkylene-bridged (R'), N-substituted (R) imidazoline moieties (1,1'-diR-3,3'-R'-diimidazoline-2,2'-diylidene), were synthesized. Spectroscopic methods and X-ray crystallography were employed to characterize the complexes in solution and the solid state. The observed dynamic behavior of the complexes in solution was examined in more detail by temperature-dependent H-1 NMR experiments and further analyzed by DFT calculations.