Difluorosilylene polymerization

Difluorophosphoryl(trifluoromethyl) peroxide, 16 135, 136 reactions of, 16 136 Difluoropolysulfanes, 16 302, 325-327 NMR of, 16 325, 326 separation of, 16 327 Difluorosilylene, 29 15-36 alternate layer reactions, 29 26-27 in nuclear recoil systems, 29 22 polymerization, 29 15 reaction mechanisms with alkenes and alkynes, 29 17-19 under co-condensation conditions, 29 28-32, 34-35... 

Difluorosilylene has always been considered the exceptional case of the silylene family. Unlike other silylenes, difluorosilylene had been believed to be quite inactive chemically in the gas phase (73). As a result, most studies of its chemistry were carried out under cocondensation conditions (73, 103, 104, 106, 108). At — 196°C, difluorosilylene forms a pale yellowish condensate, which polymerizes and forms small quantities of volatile perfluoropolysilanes (10% of the total yield) when the reaction trap is warmed to room temperature. 

When such an (SiF2) polymer (or oligomer) mechanism was cited in the literature, one could not but wonder whether difluorosilylene behaved as a carbene analogue at all. With considerable foresight, Gaspar and Herold stated more than a decade ago (39), in view of the poor Si—Si n interaction and the relative weakness of Si—Si single bond, it is very likely that characteristic reactions of difluorosilylene other than polymerization will be found in the near future. ... 

Having clarified the points mentioned above, it seems possible now to draw some conclusions about the reaction mechanism. The reactions of SiF2 in the gas phase seem rather simple. Difluorosilylene behaves quite similarly to the chemistry of other silylenes. The initial attack of SiF2 at the carbon-carbon double bond is followed by rearrangement whenever possible. Otherwise it may lead to polymerization. For example, CH2=CHF reacts according to the mechanisms in Scheme 6. 

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