Unexpected Ring Expansion of a Four-Membered Cyclophosphazane

Nucleophilic substitution reactions of the N(R),N(R)-spiro-bridged octachlorobis­(cyclotriphosphazene), N3P3Cl4[N­(CH2)5CH3]2N3P3Cl4 (1), with sodium salts of alcohols (1,3-propanediol, 2,2,3,3,4,4-hexafluoro-1,5-pentanediol, and phenol) give ansa products (2–4) via an unexpected rearrangement. These products were characterized by elemental analysis, mass spectrometry, and 1H and 31P NMR spectroscopy. The molecular structures of compounds 3 and 4 were also established by X-ray crystallography. This new class of phosphazene structures consists of three fused P3N3 rings that arise from expansion of the four-membered phosphazane ring in 1 to a six-membered N3P3 ring during alcoholysis reactions.