Vinyl-Functionalized Silanes and Disiloxanes with Electronically Communicated Ferrocenyl Units

A new series of vinyl-functionalized polyferrocenyl organosilicon compounds, including triferrocenylvinylsilane, (CH2=CH)Si(Fe)(3) (7) (Fe = (eta(3)-C5H4)Fe(eta(5)-C5H5)), 1,3-divinyl-1,1,3,3-tetraferrocenyldisiloxane, [(CH2=CH)(Fe)(2)Si](2)O (8), and 1,3-divinyl-1,3-dimethyl-1,3-diferrocenyldisiloxane, [(CH2=-CH)(Fe)MeSi](2)O (9), have been synthesized via the low-temperature salt metathesis reaction of monolithioferrocene and the chlorosilanes (CH2=CH)SiCl3 and [(CH2=CH)(Cl)MeSi](2)O. Compounds 7-9 were characterized by elemental analysis, multinuclear (H-1, C-13, Si-29) 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)degrees), biferrocenyl 9 shows a bent arrangement of the disiloxane linkage (Si-O-Si angle of 143.2(2)degrees). 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 7(3+) 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.