Polyphosphazenes coordination compounds

The spacer units in 3.60 are assembled from polyphosphazenes that bear p-bromophc-noxy side groups via a lithiation reaction, and treatment with a diorganochlorophosphine to give 3.62. The chemistry is summarized in reaction sequence (45).107 Polymer 3.62 coordinates to a variety of metallo species,108 including osmium cluster compounds and cobalt carbonyl hydroformylation catalysts. When used as a polymeric hydroformylation catalyst, this latter species proved how stable the polyphosphazene backbone is under the drastic conditions often needed for these types of reactions. The weakest bonds in the molecule proved to be those between the phosphine phosphorus atoms and the aromatic spacer groups. 

Unlike most pol nmers (except poly(amino acids), poly (lactic acid), or poly(glycolic acid)), compounds such as XX hydrolyze slowly to yield ethanol, amino acid, phosphate, and ammonia. Thus, the polymer is biocompatible in the sense that it decomposes to materials that can be metabolized or excreted. Recent work in our laboratory has exploited the linkage of steroid molecules (XXI) to a polyphosphazene skeleton with a view to the utilization of these compounds as slow-release drugs. Furthermore, we have recently examined the use of poly[bis(methylamino)-phosphazene], [NP(NHCH3)2]n> a coordinative ligand for... 

---