Reactivity, structure and electrospray mass spectrometry of pentafluoro- and pentachloro-phenoxy-substituted cyclotriphosphazenes

Abstract

The reaction of N 3P 3Cl 6 with the sodium salts of pentachloro- and pentafluorophenol, has been investigated. In contrast to the non- geminal substitution typified by other RO − nucleophiles, the regiochemistry of the reaction of C 6X 5O − (X=Cl and F) with N 3P 3Cl 6 is dominated by geminal substitution. The reaction of C 6Cl 5O − with N 3P 3Cl 6 in refluxing tetrahydrofuran yielded gem-N 3P 3Cl 2(OC 6Cl 5) 4 ( 1) as the major product. The fully substituted derivative N 3P 3(OC 6Cl 5) 6 ( 2) was attained in low yield from reaction in refluxing diglyme. In contrast, the reaction of C 6F 5O − with N 3P 3Cl 6 in refluxing tetrahydrofuran yielded the fully substituted product N 3P 3(OC 6F 5) 6 ( 3) after approximately 4 h. 31P NMR spectral results suggest the C 6F 5O − ion may be attacking in a ‘random’ fashion at low degrees of substitution, which is largely replaced by an electronic geminal-directing effect at tetrasubstitution. Single crystal X-ray crystallographic analyses have been carried out on compounds 1 and 3. Electrospray mass spectrometry has been evaluated as a general technique for characterizing cyclotriphosphazenes, N 3P 3R 6. If R=OEt or OPh, good positive ion spectra are observed but, in contrast, if R is more strongly electron withdrawing (Cl, C 6Cl 5O or C 6F 5O) negative ion spectra are obtained.