The formation of polyhalogenosiloxanes from the insertion reactions of perhalogeno-ketones and cyclic silthianes

Abstract

The perhalogeno-ketones (CF₃)₂CO, (CF₃)(CF₂Cl)CO, and (CF₂Cl)₂CO cause fission of the silicon–sulphur bonds in cyclic silthianes to produce polyhalogenosiloxanes, some of which are telomers. Thus, [–Me₂SiOC(CF₃)₂S(CH₂)₂SC(CF₃)₂O–] has a degree of polymerization of about 9, though this decreases in the compounds of lower fluorine and higher chlorine content, and [–Me₂SiOC(CF₃)₂SCH₂CH₂CH₂SC(CF₃)₂O–] is monomeric. [–Me₂SiOC(CF₃)₂SC(CF₃)₂O–] appears to have very labile Si–O bonds, distilling as a monomer, but appearing to undergo immediate ring-expansion in the liquid. Me₂Si[OC(CF₂Cl)₂]₂S remains monomeric.