On the structure of hexahydroxocyclotriphosphazene

Hexahydroxocyclotriphosphazene geometry optimization at DFT level of theory produces 15 stable conformational isomers whereas at MP2 level only 14. Unlike other cyclotriphosphazenes, only one of them has planar cyclotriphosphazene ring. The preferred anti-planar conformation of O-H and P-N bonds connected with shorter and stronger P-N bonds and increased electron density transfer from oxygen and nitrogen to phosphorus atoms suggests that this feature originates in the interaction between oxygen lone pairs and out-of-plane πPN bonds. This feature cannot be explained by negative hyperconjugation which is connected with P-N bonds weakening.