SILICON-CARBON UNSATURATED-COMPOUNDS .52. THERMAL-REACTION OF PHENYL-1,2-BIS(TRIMETHYLSILYL)SILACYCLOPROP-2-ENES AND HENYL-1,2-BIS(TRIMETHYLSILYL)SILACYCLOPROP-2-ENES, PHENYL-1,2-BIS(TRIMETHYLSILYL)SILACYCLOPROP-2-ENES

Thermal reaction of 1-mesityl-, 1-o-tolyl-, and 1-p-tolyl- phenyl-1,2- bis(trimethylsilyl)silacycloprop-2-enes (1a-1c) has been studied. The thermolysis of 1b afforded -dimethyl-4-phenyl-1-o-tolyl-5-(trimethylsi lyl)-1, (2b), 1-o-tolyl-1,3-bis(trimethylsilyl)-1-silaindene (3b), and 1-o-tolyl-2,3-bis(trimethylsilyl)-1-silaindene (4b), while the thermo lysis of 1c produced tolyl-5-(trimethylsilyl)-1,3-disilacyclopent-4-en e (2c), 1-p-tolyl-1,3-bis(trimethylsilyl)-1-silaindene (3c), and 1-p-t olyl-2,3-bis(trimethylsilyl)-1-silaindene (4c). The thermolysis of 1b in the presence of phenyl(trimethylsilyl)acetylene afforded l]-1-o-tol yl-2-(trimethylsilyl)silacycloprop-2-ene (7b), together with 2b, 3b, a nd 4b, while the similar reaction of 1c produced (Z)- and (E)- thenyl] -1-o-tolyl-2-(trimethylsilyl)-1-silaindene, in addition to 2c, 3c, and 4c. The reactions of 1b and 1c in the presence of methyldiphenylsilan e produced Z and E isomers of 1-(2-methyl-2,2-diphenyl-1-o-tolyldisila nyl)- and 1-(2-methyl-2,2-diphenyl-1-p-tolyldisilanyl)- 2-phenyl-1,2-b is(trimethylsilyl)ethene, respectively. The structure of 7-tris(trimet hylsilyl)-1-silabenzo[b]norbornadiene (6a), which is produced from the reaction of 1a with phenyl(trimethylsilyl)acetylene, was reinvestigat ed. 6a crystallizes in the space group P2(1)/a with cell dimensions of a = 23.955(7) Angstrom, b = 12.664(1) Angstrom, c = 11.514(1) Angstro m, alpha = gamma = 90 degrees, beta = 98.76(2)degrees, V = 3452(1) Ang strom(3), Z = 4, and D-calcd = 1.095 g/cm(3). 7b crystallizes in the s pace group P2(1)/c with cell dimensions of a = 18.880(1) Angstrom, b = 9.4251(7) Angstrom, c = 20.938(3) Angstrom, alpha = gamma = 90.0 degr ees, beta = 115.069(6)degrees, V = 3374.9(3) Angstrom(3), Z = 4, and D -calcd = 1.065 g/cm(3).