Reactions of N-silylphosphoranimines with alcohols:: Synthesis and structure of cyclotriphosphazenes with nongeminal methyl and phenyl substituents

The reactions of Me3SiN=P(OR")RR' (R" = Ph, CH2CF3; R, R' = Me, Ph) with alcohols were investigated. With nonequivalent amounts of CF3CH2OH, the reactions produced high yields of the cyclic phosphazene (Me2PN)(3) and both the cis and trans isomers of nongeminally substituted [(Ph)(Me)PN](3). The isomers of this new cyclic phosphazene were separated by column chromatography and characterized by NMR and IR spectroscopy, elemental analysis, and X-ray crystallography. Crystals of the cis isomer 6a have a monoclinic crystal system, while the trans isomer 6b has a triclinic crystal system with two different molecules in an asymmetric unit. The bond lengths and bond angles are very similar to those of the simpler cyclic trimers (Me2PN)(3) and (Ph2PN)(3). A likely pathway for the formation of these compounds is discussed.