Rhenium and technetium complexes with N-heterocyclic carbenes – A review

The coordination chemistry of technetium and rhenium with N-heterocyclic carbenes of the dimethylimidazol-2-ylidene and 1,2,4-triazol-5-ylidene types is reviewed. Compounds containing the metals in the oxidation states “+7”, “+5” and “+1” are introduced. General trends and differences in the chemical behaviour of the complexes, particularly between the different metal cores (oxo, nitrido, imido) of Tc(V) and Re(V) compounds, are discussed. The influence of electronic and steric factors for the stabilisation of the metal complexes is explored.