Pseudo-oxocarbons: the first complex of the 3,4-bis(dicyanomethylene)cyclobutane-1,2-dione dianion (cdcb2−); crystal structure of [{Cu2(cdcb)(MeCN)2}n]

Reaction of copper(II) ion with 3,4-bis(dicyanomethylene)cyclobutane-1,2-dione dianion (cdcb2–) led to a copper(I) complex, [{Cu2(cdcb)(MeCN)2}n]. The crystal structure of this first complex of cdcb has been determined; it consists of layers of Cu2(cdcb)(MeCN)2 units parallel to the ab planes. The redox system of this complex, investigated by electrochemistry and ESR spectroscopy, is formed by the dianion, the radical anion, the neutral species of cdcb and the CuI–CuII system.