Phenylene-bridged cross-conjugated 1,2,3-trisilacyclopentadienes

Abstract

1,2,3-Trisilacyclopentadienes are obtained from the reactions of cyclotrisilene c-Si₃R₄ (R = iPr₃C₆H₂) with phenyl and diphenyl acetylene, respectively. With 1,4-diethynyl benzene the cross-conjugated bridging of two of the Si₃C₂ cycles by a para-phenylene linker is achieved. UV/vis spectroscopy indicates a small but significant effect of cross-conjugation, which is confirmed by TD-DFT calculations. The formation mechanism of the 1,2,3-trisilacyclopentadienes is elucidated by VT NMR.