Metallophosphorus Polymers

21 POLYMERS WITH METAL-PHOSPHORUS LINKAGES 8.21.1 Metallophosphorus Polymers [1-11] 

Various examples of high molecular weight polymers containing M-P covalent bonds are now known. Linear varieties are the best characterised, and these contain M-P bonds either in the main chain or in the side chain, for example, (8.349) through (8.355). Dendritic varieties have also been reported (8.356) [1,2]. Metallophosphazene polymers are dealt with in Chapter 7.8. 

Metallophosphorus polymers have potential applications as catalysts, luminescent materials, sensors, MRI contrast agents and so on. 

When the acetylenic groups are in the para positions on the aromatic ring, condensation with a metal phosphine leads to a linear polymer as in (8.358), but if these groups are in the ortho position a cyclic tetrameric ring is produced as in (8.357) [33]. With three pendant acetylenic groups, dendritic-type structures can be obtained as in (8.356). 

The exploration of metallophosphorus dendritic structures is still in its infancy, but in the example (8.356), a polymer containing 45 Pt atoms was obtained. In such structures, the metallophosphorus region may be either in the core, the main network or the terminal group of the dendrimer. Examples of each case are now known. 

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Certain metallophosphorus polymers can provide 3-way junctions and have the potential to be built into nano-sized frameworks (Chapter 8.21). In a similar way, nano-sized particles should be capable of construction from DNA since the latter can participate in 3-way junctions (Figure 11.50). 

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