General Properties of Cyclic Metaphosphates

Cyclic metaphosphates lack most of the useful properties of long-chain polyphosphates. The metal-complexing power of the lower members is very weak compared to that of the linear polyphosphates. 

Metaphosphates undergo various reactions with ammonia to produce amido derivatives, ammonium salts and cycloimidophosphates (Chapter 7). Alcohols will react under alkaline conditions to give monoalkyl straight-chain esters. 

FIGURE 5.28 Part of crystal structure of V3CS3P12O35. Shows how V atoms lie at centres of P12O35 rings, forming VO octahedra. (Adapted from U. SchuUce and M.T. Averbuch-Pouchot, ZAC, 621,1232, 1995.) 

Ample proof of metaphosphate ring structure has been given by x-ray structural analyses of crystalline salts. In solution, cyclic metaphosphates can be distinguished from chain polyphosphates in several ways  

Two-dimensional paper chromatography. Suitable techniques enable a clear separation of the lower manbers of both series to be effected (Chapter 14.2). 

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