Phosphorus-nitrogen rings cyclophosphazenes

Allcock, H.R., Phosphorus-Nitrogen Compounds Academic Press New York, 1972 Allen, C.W., "Cyclophosphazenes and Related Compounds" in The Chemistry of Inorganic Rings, Ed. I. Haiduc and D.B. Sowerby, Academic Press, in press. 

As a consequence of this internal molecular stretching along the two-fold axis, atom P, appears to be in a pseudo-tetrahedral situation, the four associated phosphorus-nitrogen bonds being practically equal. Such a Td-like environment for a phosphorus atom belonging to a trimeric ring is unique in cyclophosphazenes and may explain the peculiar NMR behaviour manifested by P3 (see above). 

The four other peaks are of minor importance and their intensities within the series fluctuate in a rather random manner. However, the m/z 135 signal, which characterizes the N3P3 cyclophosphazene ring itself, is ever observed as the outcome of the fragmentation this observation, quite trivial in cyclophosphazenes, supports once more the non-aromatic Dewar islands electronic structure for phosphorus nitrogen rings37... 

PNMR spectroscopy and generates heterocycles that are hybrids of r-electron-rich (S-N) and tt-electron-precise ring systems (cyclophosphazenes, see Phosphorus-Nitrogen Compounds). 

Examples of cyclophosphazenes with ring systems containing elements other than phosphorus or nitrogen continue to be reported. The linear phosphazene [Ph2(H2N)Pi N.i P(NH2)Ph2]+Cl is cyclized by antimony pentachloride to give the compound (35). This result contrasts with... 

Cyclophosphazenes are a group of inorganic heterocyclic rings containing an alternate arrangement of phosphorus and nitrogen atoms [45-48]. 

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