GAS-PHASE REACTIONS OF SILYL CATIONS WITH WATER

In the gas phase, the (CH3)(3)SiOSi(CH3)(2)(+) and (CH3)(2)Si+OSi(CH3) CH2 ions were formed in the external source of a FT-ICR mass spectrome ter by fragmentation of (CH3)(3)SiOSi(CH3)(3)(.+). In the cell, the el ectrophilic center of these ions reacts with water to give product-ion s which undergo, spontaneously or upon collision, sequential losses of methane and water. The reactions of D2O and (H2O)-O-18 indicate that a permutation of the oxygen atom of the reactant and that of water tak es place prior to the dissociation of the product-ions. This means tha t both oxygens Flay a symmetric role in an intermediate step of the re action pathway. (C) Academie des Sciences/Elsevier, Paris.