Preparation, Structure, and Photochemistry of 2-Disilanyl-1,4-benzoquinones

We synthesized 5-chloro- and 5-bromo-substituted 2-(pentamethyldisilanyl)-1,4-benzoquinones 1a and 1b, respectively. Their electronic absorption spectra showed significant intramolecular charge-transfer interaction between disilane and 1,4-benzoquinone moieties. The intramolecular σ(SiSi)–π* transition energies of 1a and 1b were lower than that of 2-(pentamethyldisilanyl)-5-t-butyl-1,4-benzoquinone (1c). X-ray crystallographic analysis of chloro-substituted derivative 1a revealed that the angle between the Si–Si bond and the quinone ring was 74° and also that the structure of 1a in the solid state was also advantageous for CT interaction. Photoreaction of 1a and 1b gave α-sila-m-quinonemethide derivatives 3a and 3b, respectively, which were trapped by acetone. Matrix isolation of 3a, 3b, and their 2-methyltetrahydrofuran-complexes were accomplished in glass matrixes.