Cleavage of siloxanes with organyltrifluoro- and diorganyldifluorosilanes

Abstract Hexamethyldisiloxane is cleaved with organyltrifluoro- or diorganyldifluorosilanes as low as 20°C in the absence of catalysts to form earlier unknown 1,1,1-trimethyl, 3-organyl-3,3-difluoro- or 1,1,1-trimethyl-, 3,3-diorganyl-3-difluorodisiloxanes with the general formula R 4- n SiF n - 1 OSi(CH 3 ) 3 ( n = 2-3) in 57-97% yield. The SiO bond in 1,1,3,3-tetramethyldisiloxane is broken with organyltrifluoro- or diorganyldifluorosilanes in a similar manner but more slowly to give 1,1-dimethyl-, 3-organyl-, 3,3-difluoro- or 1,1-dimethyl, 3,3-diorganyl-, 3-fluorodisiloxanes with the general formula R 4- n SiF n -1 OSi-H(CH 3 ) 2 ( n =2-3) in 50-70% yield. The reaction of phenyltrifluorosilane with 1,1,1,3,3,5,5,5-octamethyltrifluorosiloxane leads to 1,1,1,3,3-pentamethyl-, 5,5-difluoro-, 5-phenyltrisiloxane, whereas the reaction with tetrakis (trimethylsiloxy)siloxane gives tri(trimethylsiloxy)difluoro(phenyl)silane. Even under normal conditions of storage, the cleavage products disproportionate readily in different directions. The ability of these compounds to disproportionation depends on the nature of the substituents attached to the silicon atom and the number of fluorine atoms in the molecule.