Tetraatomic phosphorus molecules

Hydrated nickel(II) salts in the presence of the ligand p3 react with both white phosphorus and yellow arsenic, breaking up the structure of the tetraatomic P4 and As4 molecules to form triatomic cyclo-triphosphorus and cyc/o-triarsenic species. These fragments act as trihapto ligands yielding double sandwich complexes (equation 99).292 The compounds are air-stable both in the solid state and in solution. Upon reduction with NaBH the complexes of equation... 

Allotropic forms of phosphorus. Solid phosphorus exists in two distinct allotropic modifications and is also commonly encountered in a form consisting of a mixture of the two. White (or yellow) phosphorus is a translucent, waxlike solid which melts at 44°C, boils at about 290°C, and has a density of 1.83. When vaporized, the resulting gas consists of tetraatomic molecules (P4) up to a temperature of about 1500°C, whereupon these molecules partly dissociate into (and exist in equilibrium with) diatomic molecules (P2). White phosphorus is insoluble in water but is soluble in solvents such as ethyl ether and carbon disulfide. Great care should always be exercised in handling this form of phosphorus since it is highly flammable and very poisonous. Skin burns caused by phosphorus are exceedingly painful and very slow to heal. 

Examples of elements that normally exist as diatomic molecules include oxygen, hydrogen, nitrogen, chlorine, bromine and iodine (O2, H2, N2, CI2, Br2 and I2). Phosphorus exists as a tetraatomic molecule (P4), whereas a... 

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