Gas kinetic studies on silanones and silylenes.

This thesis describes work on short-lived gaseous intermediates in organosilicon chemistry. The first part of this thesis discusses experiments carried out to verify the existence of the intermediate species dimethylsilanone, Me2SiO, containing a silicon-oxygen double bond, while the second part discusses the kinetics of the thermal decomposition of three chloromethyldisilanes to give silylenes and some of the insertion reactions of these silylenes. Three types of experiment were undertaken to verify the existence of dimethylsilanone. Using octamethylcyclotetra-siloxane, (Me2SiO)4, as a thermal source of Me2SiO, co-pyrolyses of (Me2SiO)4 with alkenes and dienes were carried out to observe any formation of cyclic adducts between the hydrocarbons and the intermediate, Me2SiO. Pyrolyses of (Me2SiO)4 with chloromono-silanes were also carried out to determine whether the intermediate, Me2SiO, would insert into the silicon-chlorine bond or bonds in the chloromonosilanes, to give linear chloromethylsiloxanes. The formation of cyclic adducts and insertion products would provide good evidence for the independent existence of Me2SiO. Finally, co-pyrolyses of (Me2SiO)4 with another cyclic siloxane, (MePhSiO)3, were undertaken to determine whether cyclic siloxanes containing both Me2SiO and MePhSiO units would be formed. Again formation of these 'mixed' siloxanes would provide further evidence for the existence of Me2SiO. In the work on silylenes, in the second part of this thesis, the thermal decomposition of three chloro-disilanes was studied and the Arrhenius parameters determined in each case. The three chlorodisilanes were : pentamethyl- chlorodisilane, Me5Si2Cl; 1,1,2,2-tetrachloro-l,2-dimethyl- disilane, Me2Si2Cl4; and 1,1,2-trime thyl-1,2 ,2-trichlorodisilane, Me3Si2Cl3. Some of the insertion reactions of the silylenes generated were also studied, especially insertion into the silicon-hydrogen and silicon-chlorine bonds.