Ferrocene-Containing (η6-Hexamethylbenzene)ruthenium(II) Methoxycarbenes: Synthesis, Structure, and Electrochemistry
Abstract
The (η6-hexamethylbenzene)dichlororuthenium(II) complexes [(η6-C6Me6)RuCl2(L)], where L = PMe3 (1), PPh3 (2), FcPPh2 (3; Fc = ferrocenyl), and Hdpf (4; Hdpf = (η5-C5H4PPh2)Fe(η5-C5H4COOH)), were reacted with terminal alkynes (FcC÷CH, Me3SiC÷CH, and PhC÷CH) in the presence of NaPF6 and methanol to give (η6-hexamethylbenzene)chlororuthenium(II) methoxycarbenes [(η6-C6Me6)Ru(=C(OCH3)CH2R)Cl(L)]PF6 (L/R = PMe3/Fc (1a), PPh3/Fc (2a), FcPPh2/Fc (3a), FcPPh2/H (3b), FcPPh2/Ph (3c), Hdpf/Fc (4a), Hdpf/H (4b), and Hdpf/Ph (4c)). All new compounds were characterized by NMR and IR spectroscopy and also studied by mass spectrometry in liquid matrix.
The solid-state structure of 4a.CH2Cl2 was determined by single-crystal X-ray diffraction. The electrochemical study of these bi- and trimetallic complexes displayed 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 redox change.
A redox dissymmetry of carbenes 1a-4c was observed, as these exhibit communication within the Ru-phosphine part while the carbene ferrocenyl group remains isolated and practically unaffected.