Copper(I) carbonyl ([Cu(NCMe)4−n(CO)n][BF4]); in situ spectroscopic, electrochemical and spectroelectrochemical studies

The substitution of one or more CH3CN ligands by CO in [Cu(CH3CN)4]+ results in the formation of a stable carbonyl complex [Cu(CH3CN)4−n(CO)n]+ which is characterized by an infrared absorption at 2125 cm−1. In acetonitrile, both complexes possess two redox pairs associated with the electro-deposition of Cu(I) to form Cu(s) and the stripping of the latter, in addition to the reversible oxidation of Cu(I) to Cu(II). The electro-deposition step and the oxidation of Cu(I) to Cu(II) are characterized by the loss of the carbonyl signal from the complex, whereas the stripping step and the reduction of Cu(II) to Cu(I) result in the reappearance of the Cu(I) carbonyl complex. A pronounced solvent effect is observed and the stability of Cu(I) in non-complexing solvents is increased by the carbonyl ligand.