FLASH VACUUM THERMOLYSIS AND MASS SPECTROSCOPY OF 9,10-DIHYDRO-9-SILAANTHRACENES

Article abstract of DOI:10.1016/S0040-4020(01)81380-6

The synthesis of 9,10-dibenzyl-9,10-diphenyl-9,10-dihydro-9-silaanthracene (8), and of some similarly substituted 9,10-dihydro-9-silaanthracenes is reported.Compound 8 was prepared with the aim of converting it by Flash Vacuum Thermolysis (FVT) into 9,10-diphenyl-9-silaanthracene (4), with 1,2-diphenylethane (5) as the expected byproduct.At lower temperatures, a surprisingly stable, dark green organic radical was formed, which was investigated by ESR and ENDOR spectroscopy and tentatively assigned the triphenylmethyl type structure 9.Both benzyl groups of 8 were efficiently cleaved off, presumably to give 4, and the yield of 5 was about 70percent at higher temperatures.However, no direct information on the existence of 4 was obtained, and it was concluded that it polymerizes under the conditions of reaction.Parallel to FVT experiments, the formation of ionized 9-silaanthracenes in the EI mass spectra of 8 and of analogues was investigated.Fragmentation leading to the ionized 9-silaanthracenes was found to be favoured by the presence of one or two phenyl groups at silicon in the precursor ion of a benzyl group and a hydrogen at the 10-carbon position.