Dihalodimethylsilanes from silicon atoms and methyl halides: a combined matrix-spectroscopic and density functional theory study

The reaction of silicon atoms with methyl halides 6a–d has been studied in an argon matrix at 10 K. It is shown that the product formation depends on the relative methyl halide/argon ratio. In the initial step triplet n-adducts T-5 are formed. T-5a–c can be identified spectroscopically. The next step can be induced photochemically. The primary photoproducts are the halomethylsilylenes S-1a–c. In case of methyl iodide 6d the reaction with silicon atoms leads spontaneously to silylene S-1d. In a diluted argon matrix all silylenes 1a–d can further be photoisomerized to the corresponding halosilenes 2a–d. In the presence of an excess of a methyl halide complexes of type 7a–d are formed. Longer irradiation transforms these adducts into the dihalodimethylsilanes 8a–d. The generation of the silanes 8a–d starting from silicon and a methyl halide images the results of the Rochow-Müller synthesis. The relevance of our findings to this important technical process is discussed. The structural elucidation of all new species is based on the comparison of the experimental observations with density functional theory calculations.