Structural characterization of some 2-(dimethylamino)methyl-substituted phenylcopper compounds R4Cu4

Abstract

2-[(Dimethylamino)methyl] phenylcopper and its 5-methyl and 5-methoxy analogues are tetrameric in benzene. 5-Methyl-2-[(dimethylamino)methyl]phenylcopper is tetrameric in the solid state (X-ray structure determination). The bonding in this tetranuclear cluster (Cu---Cu 2.38 Å, multicenter bonded aryl groups) is discussed. NMR spectroscopy provides indications that Cu---N coordination observed in the solid is weak in solution. Mass spectra of 2-[(dimethylamino)methyl]phenylcopper (R4Cu4) and its 5-methyl analogue (5-MeR)4Cu4 reveal that the Cu4 cluster in both compounds has considerable stability. Although the R4Cu4+ ions in both spectra are very abundant, the R3Cu4+ (even electron species) forms the base peak in the RnCun part of the mass spectra. The occurrence in solution of an intercluster exchange between R4Cu4 and (5-MeR)4Cu4 with formation of the three possible mixed species R(5-MeR)3Cu4, R2(5-MeR)2Cu4 and R3(5-MeR)Cu4 was confirmed by the mass spectra, which show five patterns in the parent peak region separated by 14 mass units.