Silicon-carbon unsaturated compounds : XIV. Formation and reactions of 1,1,2,2-tetratolyl-3,4-bis[bis(trimethylsilyl)methylene]-1,2-disilacyclobutanes

Abstract The photolysis of 1,1-di- o -tolyl-, 1,1-di- m -tolyl-and 1,1-di- p -tolyl-1-(trimethylsilylethynyl)trimethyldisilane gave the respective 1,1,2,2-tetratolyl-3,4-bis[(trimethylsilyl)methylene]-1,2-disilacyclobutanes. These compounds isomerized photochemically and thermally to give 1,1,2,2-tetratolyl-4,4-bis(trimethylsilyl)-3-[bis(trimethylsilyl)ethenylidene]-1,2-disilacyclobutanes in almost quantitative yield. The thermolysis of 1,1,2,2-tetra- m -tolyl- and 1,1,2,2-tetra- p -tolyl)-4,4-bis(trimethylsilyl)-3-[bis(trimethylsilyl)ethenylidene]-1,2-disilacyclobutane afforded two types of the 1,3-disilacyclobutane derivative, but 1,1,2,2-tetra- o -tolyl-4,4-bis(trimethylsilyl)-3-[bis(trimethylsilyl)ethenylidene]-1,2-disilacyclobutane yielded 1,1,3,3-tetra- o -tolyl-2,4-bis[bis(trimethylsilyl)ethenylidene]-1,3-disilacyclobutane as the sole product.