Synthesis and electrochemistry property of new crowded multi-ferrocenyl substituted benzene derivatives

A series of new sterically crowded multi-ferrocenyl and ferrocenylethynyl substituted benzene derivatives, 1,2,4-triferrocenyl-3,5-diferrocenylethynylbenzene (2), 1,3,5-triferrocenyl-2,4-diferrocenylethynylbenzene (3), 1-indeny1-2-trimethylsily1-4,5-diferroceny1-3,6-diferrocenylethynylbenzene (4), 1-indeny1-2trimethylsily1-4,6-diferroceny1-3,5-diferrocenylethynylbenzene (5), 1-indenyl-2-trimethylsily1-3, 5-diferrocenyl-4,6-diferrocenylethynylbenzene (6) were synthesized by [2+2+2] cycloaddition reactions of 1,4-bis(ferrocenyl)butadiyne with cobalt clusters Co-2(CO)(6)(mu(2)-eta(2)-FcC equivalent to CH) and Co-2(CO)(6) (mu(2)-eta(2)-C9H7C equivalent to SiMe3) (1) [where C9H7 = indenyl, Fc = ferrocenyl, Me = methyl], and characterized by FT-IR, NMR, MS and elemental analysis. The crystal structures of compounds 1, 3-5 were determined by X-ray single crystal diffraction analysis for the first time. The electrochemical results of compounds 2-6 studied by cyclic voltammetry and square wave voltammetry indicate the wave splitting and the electronic interactions of 2-6 are related to the directly bonded ferrocenyl termini. Compounds 4-6 are three isomers, of which the molecular structures could be identified by their electrochemical properties and structural information. (C) 2016 Elsevier Ltd. All rights reserved.