Synthesis and Structural Characterization of Cationic Rhenium(V) and Technetium(V) Dioxo Complexes Containing Four N-Heterocyclic Carbene Ligands

Cationic dioxorhenium and dioxotechnetium complexes of the composition [MO2(L1)4]+ (L1 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) have been prepared from various starting materials and studied spectroscopically and by X-ray crystallography. The metal-carbon distances range from 2.216(4) to 2.232(4) (angstrom) indicating mainly (sigma)-bonding.