FERROCENE-CONTAINING (ETA(6)-HEXAMETHYLBENZENE)RUTHENIUM(II) METHOXYCARBENES - SYNTHESIS, STRUCTURE, AND ELECTROCHEMISTRY

The (eta(6)-hexamethylbenzene)dichlororuthenium(II) complexes [(eta(6) -C6Me6)RuCl2(L)], where L = PMe3 (1), PPh3 (2), FcPPh(2) (3; Fc = ferr ocenyl), and Hdpf (4; Hdpf = (eta(5)-C5H4PPh2)Fe(eta(5)-C5H4COOH)), we re reacted with terminal alkynes (FcC=CH, Me(3)Sic=CH, and PhC=CH) in the presence of NaPF6 and methanol to give (eta(6)-hexamethylbenzene)c hlororuthenium(II) methoxycarbenes [(eta(6)-C6Me6)Ru(=C(OCH3)CH2R)Cl(L )PF6 (L/R = PMe3/Fc (1a) PPh3/Fc (2a), FcPPh(2)/Fc (3a), FcPPh(2)/H (3 b), FcPPh(2)/Ph (3c), Hdpf/Fc (4a), Hdpf/H (4b), and Hdpf/Ph (4c)). Al l new compounds were characterized by NMR and IR spectroscopy and also studied by mass spectrometry in liquid matrix. The solid-state struct ure of 4a.CH2Cl2 was determined by single-crystal X-ray diffraction. T he electrochemical study of these bi- and trimetallic complexes displa yed that upon oxidation, the Ru-ferrocenyl phosphine moiety undergoes a ferrocene/ferrocenium redox process followed by a Ru(II) --> Ru(III) oxidation which is, however, markedly influenced by the preceding red ox change. A redox dissymmetry of carbenes 1a-4c was observed, as thes e exhibit communication within the Ru-phosphine part while the carbene ferrocenyl group remains isolated and practically unaffected.