1,1-Difluoro-2,2,3,3-tetramethyl-1-silirane: synthesis and novel chemistry. Reinterpretation of difluorosilylene reaction mechanisms

A systematic investigation of the reaction of SiF2 with ethylene and six methyl-substituted ethylenes. I. Product yields and mechanistic conclusions

“…However, siliranes are also significantly less stable than VI. The ring-opened likely to be highly reactive (7). since the reaction disilac~clobutane must have the stvcture shown mixture likely contains SiF,, ring-opened biradical since the alternative SF2-C-C-SiF, structure isomers of the silirane and free radical polymer could not account for the observed isomerizations chains, all of which should be very reactive towards of alkene linkages in the TB polymer.…”

A systematic investigation of the reaction of SiF2 with ethylene and six methyl-substituted ethylenes. II. Characterization of polymeric products, open chain organosilicon derivatives, and 1,2-disilacyclobutanes

“…With the exception of the ( §IF,), derivative from DB, all of these compounds are isomers of the corresponding disilacyclohexanes (141, suggesting a common intermediate (8). The proposed structure of the (SiF,), derivative of DB is identical to one of the products observed by thermolysis of a tetramethylsilirane (8).…”

“…Rather, speculation concerning the me&-three types of products: 1,2-disilacyclobutanes, anism of the reaction of SiF, with unsaturated oropen chain compounds, and polymers. These ganic compounds has been based upon the strucproducts were characterized by a of tures of the volatile products (6)(7)(8) which are in fact "F, l3C, and 29Si nmr spectroscopy.…”

“…The strucThe formation of disilacyclobutanes in the §IF,-tures of the polymers are obviously the key to olefin reaction has been known for some time (2). answering the primary question of whether SiF2 (8) Subsequently, reactions of §IF, with ci,y-Zbutene Or Si2F4 (6) is the major attacking species in this (CB) and tralzs-2-butene (TB) were shown to be reaction. The answers to these structural questions highly stereospecific with~respect to alkyl configu-are provided ration, although it was not known whether this Experimenhl involved retention or inversion of alkyl stereochemistry (3).…”

“…With the exception of the ( §IF,), derivative from DB, all of these compounds are isomers of the corresponding disilacyclohexanes (141, suggesting a common intermediate (8). The proposed structure of the (SiF,), derivative of DB is identical to one of the products observed by thermolysis of a tetramethylsilirane (8). One other interesting observation is that the alkene gro~lp in each chain isomer is apparently formed between a carbon p to silicon plus a y carbon which was an alkyl group in the starting alkene.…”