information:extraction
Organophosphorus(0), (I), and (II) compounds

Compounds where phosphorus exists in a formal oxidation state of less than III are uncommon, but examples are known for each class. Organophosphorus(0) species are debatably illustrated by the carbene adducts,, where NHC is an N-heterocyclic carbene. With the formulae (RP) and (R P), respectively, compounds of phosphorus(I) and (II) are generated by reduction of the related organophosphorus(III) chlorides:

Diphosphenes, with the formula R P, formally contain phosphorus-phosphorus double bonds. These phosphorus(I) species are rare but are stable provided that the organic substituents are large enough to prevent catenation. Bulky substituents also stabilize phosphorus radicals

Many mixed-valence compounds are known, e.g. the cage P (CH).