Laser powered homogeneous decomposition of 2,2-diethenylhexamethyltrisilane: Complex mechanism and gas-phase deposition of polycarbosilane

IR laser-induced SF6-photosensitized decomposition of gaseous 2,2-diethenylhexamethyltrisilane yields acetylene, volatile organylsilanes (vinyltrimethylsilane, trimethylsilane) and organyldisilanes (1,1- and 1,2-bis(trimethylsilyl)ethenes and 3,3-dimethyl-3,5-disilacyclopent-4-ene), and affords chemical vapour deposition of solid polycarbosilane film. The mechanism of the decomposition is discussed on the basis of quantification of gaseous products and scavenging experiments with buta-1,3-diene and revealed to involve both molecular and radical steps. The first experimental evidence on direct extrusion of central silylene unit from trisilanes is reported.