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.