Synthesis, electrochemical and theoretical studies of the Au(i)-Cu(i) heterometallic clusters bearing ferrocenyl groups

Abstract

Treatment of the polymeric alkynyl compounds (AuC2R)n (R = Fc, C6H4Fc; Fc = ferrocenyl) with the diphosphine PPh2C6H4PPh2 gave complexes (RC2Au)PPh2C6H4PPh2(AuC2R) (1, R = Fc; 2, R = C6H4Fc) with end-capped ferrocenyl groups. The reactions of 1 or 2 with Cu(NCMe)4PF6 result in formation of the heterotrimetallic aggregates [{Au3Cu2(C2R)6}Au3(PPh2C6H4PPh2)3](PF6)2 (3, R = Fc; 4, R = C6H4Fc), which consist of the alkynyl clusters [Au3Cu2(C2R)6]- wrapped by the cationic [Au3(PPh2C6H4PPh2)3]3+ belt. The novel compounds were characterized by NMR spectroscopy and ESI-MS measurements. The solid state structure of 3 is reported. Electrochemical properties of the complexes 1-4 have been studied. These data show that all six ferrocenyl units are oxidized in the clusters 3 and 4. The Fc groups of 3 are electronically coupled into each other, but in 4 behave essentially independently. Electronic structure calculations have been performed, showing good correlation with the X-ray and electrochemical studies.