J. Riess
Jun 1, 1969
Citations
0
Influential Citations
11
Citations
Journal
Annals of the New York Academy of Sciences
Abstract
Phosphorus is covalently bonded to its substituents in probably all of its compounds. Of importance in its chemistry there are, in addition to the monophosphorus compounds, the more highly condensed molecules, in the skeletons of which phosphorus alternates with atoms of other elements to give (a) chain oligomers and polymers, (b) rings of various sizes, and (c) highly cross-linked polymers. Indeed, the polyphosphoric acids, their salts and esters, as well as the phosphonitrilic chlorides, are among the most thoroughly investigated and best known families of inorganic chain and ring molecules. Catenation through P-P bonds is less commonly encountered, other than in three-dimensional intractible network polymers. Redistribution of the bonds to phosphorus occurs in the range of temperatures normally used in the laboratory and results in an exchange of substituents or parts between the molecules which are present. A state of dynamic equilibrium may usually be attained with respect to this exchange. Together with hydrogen and fluorine, phosphorus is one of the three nuclei for which nuclear magnetic resonance data are readily available; this is another feature which renders the investigation of its redistribution reactions relatively easy. Moreover, it is the only one of these three nuclei which can take branching positions in molecular structures. I n the first part of this review, the redistribution of monofunctional substituents on phosphorus-based central moieties will be briefly reviewed. Special attention will be given to some recent quantitative investigations of phosphorus ligand exchanges involving the redistribution of coordination bonds. In the second part, we shall describe and discuss the molecular constitution of some equilibrium-controlled families of phosphorus compounds (homologous series) obtained when one of the exchanging substituents is difunctional. The published data will be presented in terms of equilibrium-controlled size distributions of molecular species or fragments. Mention will be made of some phosphorusbased families in which equilibrium is not reached with respect to structural reorganization through bond exchange. This report is limited to single-phase mixtures (liquids, solutions, or glasses). Unless equilibrium data are reported, we d o not intend to describe systematically the preparative use which has been made of some scrambling reactions such as transesterifications or “metathesis.” Also we shall not review all the mishaps, dismutations, or other forms of unexpected decompositions that may be attributed to bond-exchange processes and that have been recorded when people have tried to isolate phosphorus compounds with mixed substituents, especially in the case of