Tertiary trisilyloxonium ion in cationic ring-opening polymerisation of a model cyclic siloxane, octamethyl-1,4-dioxatetrasilacyclohexane

The formation of the cyclic trisilyloxonium ion is observed by the 29Si-NMR spectroscopy as a result of hydride transfer reaction between triethylsilane and Ph3C+ B(C6F5)4− in the presence of octamethyl-1,4-dioxatetrasilacyclohexane, 2D2. This ion is transformed by the reaction with another 2D2 molecule into the cyclic trisilyloxonium ion at the polymer chain end. The mechanism of polymerisation of 2D2 is discussed in relation with the mechanism of polymerisation of cyclic siloxanes.