Photolysis of organopolysilanes. The synthesis and reactions of stable silacyclopropenes

Unexpected photochemical reactions of 2-aryl- 2-ethynyltrisilane derivative

“…Compound 17 containing silacyclopropene moieties is generated, and then the photolysis of compound 17 may give silylene 14 and compound 12. A similar reaction mechanism is reported in the photoreaction of alkynyldisilane 18 in the presence of methanol by Ishikawa, Kumada, and their co-workers (Scheme 8) ( Ishikawa et al, 1980;Ishikawa and Kumada, 1981). Silacyclopropene 19 could be isolated, and the following photolysis gave bis(trimethylsilyl)acetylene 20 and dimesitylsilylene 21, the generation of which was suggested by the isolation of 22.…”

Silacyclopropene ring structure; X-ray crystal structure of 1,1-dimesityl-2-phenyl-3-trimethylsilyl-1-silacyclopropene

“…We have recently demonstrated that photolysis of 1 -phenylethynyl-and 1 -trimethylsilylethynyl-1,l -dimesityltrimethyldisilane results in the formation of a stable silacyclopropene? We now report the first X-ray crystallographic study of 1,l -dimesityl-2-phenyl-3-trimethylsilyl-1-silacyclopropene (1). Colourless crystals of (1) suitable for X-ray analysis were obtained by recrystallization from ethanol.…”

Photochemistry of 1,4-Bis(pentamethyldisilanyl)butadiyne: Formation of Silacyclopropene Intermediates

“…In photoadduct 1 , saturation of methoxy protons enhances the intensity of the olefinic proton, but no NOE enhancement of the olefinic proton is observed in photoadduct 2 . The structure of photoisomers 1 could also be distinguished from that of photoadduct 2 on the basis of the 1 H NMR spectra of the isomer pair 4a. The 1 H NMR of photoadduct 2 showed a downfield shift for the dimethylmethoxysilyl group due to the anisotropy effect of the C⋮C triple bond cis to this dimethylmethoxysilyl group compared to photoadduct 1 .…”

“…in 1962, although the proposed structure was soon shown to be incorrect, with the actual structure being the dimer of silacyclopropene, 1,4-disilacyclohexa-2,5-diene − In general, most of the silacyclopropenes are thermally stable, but they are extremely reactive toward atmospheric oxygen and moisture. These silacyclopropenes formed from the photolysis of alkynyl-substituted disilanes in methanol or acetone react readily with methanol or acetone.…”