Vinyl-Functionalized Silanes and Disiloxanes with Electronically Communicated Ferrocenyl Units

Abstract

A new series of vinyl-functionalized polyferrocenyl organosilicon compounds, including triferrocenylvinylsilane, (CH2═CH)Si(Fc)3 (7) (Fc = (η5-C5H4)Fe(η5-C5H5)), 1,3-divinyl-1,1,3,3-tetraferrocenyldisiloxane, [(CH2═CH)(Fc)2Si]2O (8), and 1,3-divinyl-1,3-dimethyl-1,3-diferrocenyldisiloxane, [(CH2═CH)(Fc)MeSi]2O (9), have been synthesized via the low-temperature salt metathesis reaction of monolithioferrocene and the chlorosilanes (CH2═CH)SiCl3 and [(CH2═CH)(Cl)MeSi]2O. Compounds 7−9 were characterized by elemental analysis, multinuclear (1H, 13C, 29Si) NMR spectroscopy, and MALDI-TOF mass spectrometry. The molecular structures of the vinyl-functionalized silane 7 and divinyldisiloxanes 8 and 9 in the solid state have been determined by single-crystal X-ray analysis. Whereas tetraferrocenyl compound 8 possesses a linear disiloxane skeleton (Si−O−Si bond angle of 180.0(2)°), biferrocenyl 9 shows a bent arrangement of the disiloxane linkage (Si−O−Si angle of 143.2(2)°). The oxidation electrochemical behavior of polyferrocenyl molecules 7−9 has been examined by cyclic voltammetry and square wave voltammetry in dichloromethane solution, using hexafluorophosfate, [PF6]−, and tetrakis(pentafluorophenyl)borate, [B(C6F5)4]−, as supporting electrolyte anions of different coordinating ability. Compound 7 can be reversibly oxidized in three consecutive steps to the trication 73+. Divinyldisiloxanes 8 and 9 are reversibly oxidized in four and two one-electron-transfer steps, respectively, which suggests significant electronic interaction among the ferrocenyl redox centers linked by the short three-atom Si−O−Si bridge.