Redox Properties of Ferrocenyl Ene-diynyl-Bridged Cp*(dppe)M–C≡C–1,4-(C6H4) Complexes

Abstract

The complexes FcCH═C{1,4-C≡C–C6H4–C≡CM(dppe)Cp*}2 (Fc = ferrocenyl (FeCp(η-C5H4−); M = Fe (1), Ru (2)) were prepared from FcCH═C{1,4-C≡C–C6H4–C≡CSiMe3}2 (3) via a desilylation/metalation protocol in good (2; 65%) to excellent (1; 97%) yield. The iron compound 1 could also be prepared in a stepwise fashion by desilylation of 3 to give FcCH═C{1,4-C≡C–C6H4–C≡CH}2 (4), reaction with FeCl(dppe)Cp* to give the vinylidene complex FcCH═C{1,4-C≡C–C6H4–CH═C═Fe(dppe)Cp*}2](PF6)2 (5(PF6)2; 65%), and deprotonation. The cyclic voltammograms of 1 and 2 are characterized by an initial oxidation wave resulting from the overlap of two closely spaced oxidation processes, the potentials of which are sensitive to the identity of M, and a subsequent, one-electron-oxidation wave. Thus, while the dications 12+ and 22+ could be prepared by oxidation with 2 equiv of ferrocenium hexafluorophosphate and isolated as the PF6– salts 1(PF6)2 and 2(PF6)2 at low temperature, the monocations 1+ and 2+ could only be detected and studied as ...