Synthesis and Structure of Nongeminally Substituted Cyclic Phosphazenes with Haloalkyl and Thioester Functional Groups

Nongeminally substituted cyclic phosphazenes with various haloalkyl substituents were prepared using deprotonation−substitution reactions at the methyl groups of the cis isomers of nongeminally substituted cis-[Me(Ph)PN]3, 2.
Treatment of 2 with n-BuLi followed by reaction with organic halogenated reagents (RX = C2Cl6, BrC(O)CMe2Br,
and ICH2COOEt) at low temperature afforded the various cyclic derivatives cis-[(XCH2)(Ph)PN]3 (3, X = Cl, 4, Br,
and 5, I). The mono- and dibromoalkyl derivatives, cis-[Ph3(BrCH2)Me2P3N3], 6, and [Ph3(BrCH2)2MeP3N3], 7, were
also isolated along with 4 when the electrophile was dibromoethane. Reaction of cis-[Ph(BrCH2)PN]3, 4, with KSC(O)Me gave cis-[Ph(MeC(O)SCH2)PN]3, 8. The structures of all the cis cyclic phosphazenes were determined by
NMR spectroscopy and X-ray diffraction. All retained the basketlike shape with the hydrophobic phenyl groups
opposite the haloalkyl groups on the P3N3 ring. Thermal analysis of the new cyclic trimers indicates that ring-opening polymerization does not occur. The melting points and the thermal stabilities of haloalkyl cyclophosphazenes
were higher than those of the parent compound 2.