Azaphosphorus Compounds

Azaphosphorus compounds can be identified according to the valency state and the coordination number of the phosphorus atom. Although some wholly N coordinated examples are known, in the great majority of known azaphosphorus compounds at least some of the N atoms are replaced by other atoms, thus making them substituted azaphosphorus derivatives. Possible varieties are indicated in Table 7.1. 

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Azaphosphorus compounds (3) are considered to include any derivative with a P-N linkage, whether organic or inorganic (Chapter 7). These compounds can be divided ... 

If only P-0 linkages are present, the compounds can be termed normal phosphates. If, on the other hand, some of the oxygens are replaced by other atoms or groups, the compounds will be termed substituted phosphates. When X = H, the compounds are more widely known as phosphites (5.4a) or hypophosphites (5.4b) and these are dealt with in Section 5.5. When X = CR3 or NR2, the substituted phosphates are also carbophosphorus compounds (Chapter 6) or azaphosphorus compounds (Chapter 7), respectively. Substituted phosphates which contain a single P=0 linkage (5.4c) are referred to as phosphoryl compounds. 

The existence of ylidic compounds like (6.462a,b) has been reported [2,33-35], as well as similar type azaphosphorus compounds (7.133). Compounds of type (c) are not yet known although some of type (d) have been reported in recent years. 

The neutral complexes (7.142) all have long P-N bonds and represent the majority of presently known 6-coordinated azaphosphorus compounds (P-N 1.76 A, P=N 1.57 A). 

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