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9,10-Dicyanoanth racene-sen sitized irradiation of 7,8-di silabicyclo[2.2.2]octa-2,5-dienes 1 – 3 in the presence of MeOH resulted in the formation of dimethoxydisilanes and the corresponding aromatic compounds. A stepwise mechanism involving CSi bond cleavage by MeOH is proposed.

Dibenzo-7-silabicyclo[2.2.1]hepta-2,5-dienes (1a, 1b) are excellent electron donors because of effective σ-π conjugation between the orbitals of CC π bonds and SiC σ bonds. Some of their donor properties are demonstrated by the reactions with some electron acceptors. When 1a and 1b are mixed with tetracyanoethylene, facile formation of charge-transfer complexes was observed. In the 2,4,6-triphenylpyrylium tetrafluoroborate-sensitized photoreaction of 1b, the corresponding difluorosilane and anthracene were obtained in good yields. The structural and electronic features of radical cation 1a+• were provided by semiemperical molecular orbital calculation. In addition, the structure of 1a in crystals was determined by X-ray crystallography and compared with that obtained by the calculation.

Irradiation of silanorbornadienes 1 using 9,10-dicyanoanthracene as a sensitizer afforded two isomers 2 and 3 accompanied with anthracene. In the presence of molecular oxygen, dioxide 5 was obtained as an additional product. These reactions are explained in terms of the initial electron donor-acceptor interaction followed by skeletal rearrangement.