Products of the interaction of copper and benzenediazonium tetrafluoroborate in acetonitrile medium

The products of the chemical interaction of copper and a concentrated (≥0.05 M) benzenediazonium tetrafluoroborate (BDFB) solution in acetonitrile have been studied. It is proposed on the base of the obtained results that the intermediate of the copper dissolution-ionization, which corresponds to an absorption band with a maximum at 432 nm, is the mixed complex [Cu(N≡N−C6H5)(N≡C−CH3)3], which contains three acetonitrile molecules and the copper ion covalently bonded to an azophenyl radical. This complex is thermodynamically unstable and decomposes slowly into a colorless crystalline and a black amorphous phase. The crystalline phase was identified as [Cu(N≡C−CH3)4]BF4 by X-ray diffraction, while the amorphous phase is a mixture of oligomeric products of different lengths, which are formed as the result of the condensation of azophenyl and phenyl radicals.