Classification and Nomenclature of P Compounds

One way of classifying phosphorus compounds is according to the configuration adopted by the chemical bonds formed by the element. Until about 60 years ago almost the whole of phosphorus chemistry was concerned with trivalent (pyramidal) compounds and pentavalent (tetrahedral) compounds (Chapter 3). Inorganic phosphorus chemistry dominated the field and the extent of known organophosphorus chemistry was still very limited. Since that time, however, many more compounds, including those with alternative combinations of valency states (X.) and coordination schemes (o), have been discovered. 

Another way of classifying P compounds is according to the elements (E) to which they form a chemical linkage P-E of some kind. It is convenient to sometimes include within such groups, compounds which contain both P and E atoms, even if they are devoid of direct P-E linkages, that is, 

As already stated (Section 1.1), it is convenient at the present time to recognise four major classes 

Oxyphosphorus compounds, which contain covalent P-O linkages 

Carbophosphorus (organophosphorus) compounds which contain P-C linkages 

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