[1]Ferrocenophane Bridged by a 9-Silafluorenylidene Moiety

Sila[1]ferrocenophane bearing a 9-silafluorenylidene moiety (1) as a bridging unit was synthesized and isolated as a stable crystalline compound. Sila[1]ferrocenophane 1, which was newly obtained in this study, was characterized by spectroscopic analyses, a single-crystal X-ray diffraction (SC-XRD) analysis, and electrochemical measurements. Due to the characteristic 9-silafluorenyl moiety, 1 exhibited large electron affinity and a slightly higher oxidation potential relative to that of ferrocene. In addition, 1 was found to undergo ring-opening polymerization (ROP) triggered by thermolysis at a lower temperature relative to that of Ph2Sifc (1′, fc = 1,1′-ferrocenylidene). It also underwent ROP through reduction by KC8 to give the corresponding polymeric compound. The DFT calculations suggested that one-electron reduction of 1 would promote ring-opening polymerization, as shown in the experimental results.