Tetranuclear complexes {(μ4-TCNX)[Cu(Me3TACN)]4}(BF4)4 with TCNX=TCNE, TCNQ or TCNB (1,2,4,5-tetracyanobenzene) and Me3TACN=1,4,7-trimethyl-1,4,7-triazacyclononane

The title complexes were obtained as blue solids from the reaction of TCNX ligands with four equiv. of [(CH3CN)Cu(Me3TACN)](BF4). The poorly soluble (TCNB) or insoluble compounds (TCNE, TCNQ) exhibit nitrile stretching frequencies compatible with only a moderate metal-to-TCNX electron transfer. This observation stands in contrast to results obtained for previously reported tetranuclear species from the reaction of TCNX ligands with complex fragments containing d6-configurated metal centers (MnI, RuII, OsII). The TCNB complex was characterized in solution by cyclic voltammetry, 1H NMR, IR and UV–Vis spectroelectrochemistry and by EPR of the one-electron reduced form.