Applications of Phosphonates Phosphonate Layer Structures

In contrast to metalphosphinate polymers (6.263), phosphonate salts of Zr, V and other cations can form layer-type complexes which in many ways resemble those formed by phosphate salts (Chapter 5.7). 

They contain ionic layers interleaved with neutral or hydrophobic layers. Similar type layers are formed by other salts such as VO (RPO3) 2H2O and M (RPO3) HjO, where M = Zn, Mg, Zn, etc., R = Ph, CgHii, etc. (Chapter 5.5). 

The phosphite structures (6.302) are retained only by triesters and a few diester salts. Monoesters and most diesters exist in the tetrahedral phosphonate form. 

Trimethyl phosphite is one of the products obtained initially on methanolysis of P4O9 (6.304), while mixtures of mono and diesters (in phosphonate form) are obtained on alcoholysis of the lower oxide P4O6 (6.305). 

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