Reactions of silicon atoms with benzene: A matrix-spectroscopic study

The reaction of silicon atoms with benzene in argon at 10 K has been studied. The addition to the aromatic pi-system of benzene occurs in a [1,4]-fashion. Upon irradiation the pi-adduct 7-silabicyclo[2.2.1]heptadien-7-ylidene (2) rearranges to the formal C-C insertion product 1-silacycloheptatrienylidene (3). The structural elucidation of the new species is based on comparison of the experimental observations with density functional calculations.