Unsaturated Rings with Phosphorus and Carbon

The use of conventional valence bond formulae for unsaturated rings containing carbon and one phosphorus atom leads to the arrangements indicated in Table 6.22. Derivatives of most of these ring systems are known, but phosphinine (also named phosphorin or phosphabenzene) represents the only parent compound synthesised to date. It is the analogue of pyridine, C5H5N, and arsenin, 

The 1-H phosphirenes are a well-known class of compound, but relatively few derivatives of 2-H phosphirene have been prepared. Various derivatives of 2-phosphetenes are known as well as a few 

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