SILICON-COMPOUNDS WITH STRONG INTRAMOLECULAR STERIC INTERACTIONS .56.THE DIFFERENT MODES OF DECOMPOSITION OF HEXA-T-BUTYLCYCLOTRISILANE

On heating, hexa-t-butylcyclotrisilane (1) undergoes decomposition, pr esumably by way of Si-Si bond homolysis, isobutene elimination, 1,2-hy drogen shift, and subsequent ene-reactions, to furnish ca-t-butyl-5-me thylene-1,2,3,7,8,9-hexasilanonane; the structure of this product has been confirmed by NMR study and X-ray diffraction. However, photolysis of 1 proceeds through tetra-t-butyldisilene which dimerizes with loss of isobutene to produce the highly strained hepta-t-butylcyclotetrasi lane (10) in low yield. X-ray crystal structure analysis of this compo und reveals a slightly folded four-membered ring with two very long (2 53.8(4) pm) Si-Si bonds.