Polyphosphonates and Polyphosphinates

Bis phosphonates (phosphonic anhydrides) (6.745b) can be obtained by the action of heat on some phosphonic acids (6.746), while methylene bis (phosphonates) (6.745f) with central carbon chains result from the condensation of a trialkyl phosphite with a halogenated hydrocarbon chain (6.747). Phosphorus pentachloride will convert some esters of this type into the corresponding chlorides (6.748). 

Methylene bis phosphinates (6.745e), with a central carbon chain, can be obtained from methyl phosphinic esters (6.253), or from methylphosphonous diesters, which, like phosphites, undergo Arbusov rearrangements with condensation (6.749). Methylene bis phosphinic acid can be obtained by reaction (6.750). This compound is reasonably stable in hot water, but on boiling it eventually gives methylene bis phosphonic acid, (H0)20P-CH2-P0(0H)2 [7]. 

Cyclic phosphonates (a), phosphonic anhydrides (b) and phosphinates (c) are known [8]. 

Because of their superior resistance to hydrolysis compared to the inorganic polyphosphates (Chapter 5.3), HEDPA and NMPA (Chapter 12.11) have become particularly important in liquid detergents, hard surface cleaners and stabilised bleaching formulations. Other applications are in textile processing and paper making, to control heavy metal ion concentrations, to reduce stains and to reduce water hardness. 

HEDPA will deflocculate and disperse suspensions of finely divided solids. It is more stable in acidic or alkaline solutions, but more expensive than polyphosphates. 

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Generally, these compounds form complexes with alkaline-earth metals that are less stable than the corresponding complexes of the polyphosphonic acids. WeiB and Hagele [96] investigated the chromatographic behavior of a variety of aliphatic and olefinic polyphosphonic and polyphosphinic acids, respectively, with 1 to 4 phosphorus atoms [87,88], that are applied in medicine and in pharmaceutical chemistry. 

In addition to structural isomers, stereoisomeric and, recently, rotational isomeric polyphosphonic and polyphosphinic acids can be separated. Most intriguing in this connection is the chromatogram in Fig. 3-103 of the sterically-crowded polyphosphonic acid 10,... 

Polymerization of monomers a and b proceed mostly via Michaelis-Arbu-zov type rearrangement involving cyclic phosphonium intermediates to form polyphosphinates or polyphosphonates. 

Fig. 3-102. Separation of an aromatic polyphosphinic and polyphosphonic acid of equal carbon backbone. — Chromatographic conditions see Fig. 3-96 solute concentrations 200 ppm each of 7 and 6.

The authors wish to thank Dr. M. M. Crutchfield for many stimulating discussions and for providing us with the polyphosphonate sample. We are also grateful to Dr. L. Maier for supplying us with samples of PMPA, PMPO, and the polyphosphinic acid. 

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