Phosphorus selenide

Phosphorus selenides are a relatively obscure group of compounds. There have been some studies of the phosphorus - selenium phase diagram and the glassy amorphous phases are reported. The compounds that have been reported are shown below. While some of phosphorus selenides are similar to their sulfide analogues, there are some new forms, molecular and the polymeric catena-. There is also some doubt about the existence of molecular.

Crystallographically confirmed compounds

Molecular has a norbornane like structure with two phosphorus atoms with oxidation state +3 bridged by two diselenide units and one selenide unit. It was isolated by solvent extraction from a amorphous phase made from the elements.

has been characterised crystallographically and has the same structure as the low temperature form of. It can be prepared from the elements. One preparation is to extract and recrystallise using tetralin.

The molecule has the same structure as [Phosphorus sulfides#P4S5|]. It was prepared by reacting with bromine in [Carbon disulfide|].

''catena''-{{chem2|P4Se4_{''x''}|}}

This compound consists of polymeric chains of norbornane-like units joined by Se atoms. As each P atom in the repeat unit is bonded to another P atom and to two Se atoms, each P atom has a formal oxidation state of +2.

Compounds confirmed spectroscopically

has two crystalline forms α- with the same molecular structure as α- and β- with same molecular structure as β-. A fully characterised compound contains with a β- structure.

This has been reported to have the same structure as [Phosphorus sulfides#P4S7|]. One well-known textbook does not mention it at all.

Molecular has been reported to share the same structure as [phosphorus pentasulfide|] and [phosphorus pentoxide|], but one well-known textbook does not mention it at all. A review examining P-Se amorphous phases did not confirm the presence of molecular. The isoelectronic anion which has the adamantane like structure is known, an example is the sodium salt.

Other compounds

, have been reported.

Phosphorus - selenium glasses

Phosphorus - selenium glasses have been examined using ³¹P-NMR and Raman spectroscopy. Glasses are formed in over the range of compositions 0 < x < 0.8 with a small window around 0.52 – 0.60 centred on 0.57 where there is a tendency to crystallise. For x < 0.47 the glasses contain chain fragments, pyramidal P units, quasi-tetrahedral P units and units. There is no evidence for an amorphous phase containing molecular.