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
Norbornane (also known as bicyclo .2.1eptane) is an organic compound and a saturated hydrocarbon with chemical formula C7H12. It is a crystalline compound with a melting point of 88 °C. The carbon skeleton is derived from cyclohexane ring with a ...
like structure with two phosphorus atoms with oxidation state +3 bridged by two
diselenide
Diselenide may refer to:
*Diselane, H-Se-Se-H
*Carbon diselenide, CSe2, a yellow-orange oily liquid with pungent odor
* Any organic chemical compound with a selenium-selenium bond, R-Se-Se-R
**Diphenyl diselenide, (C6H5)–Se–Se–(C6H5)
*Metal ...
units (, analogous to
disulfide
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
) 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
Tetralin (1,2,3,4-tetrahydronaphthalene) is a hydrocarbon having the chemical formula C10H12. It is a partially hydrogenated derivative of naphthalene. It is a colorless liquid that is used as a hydrogen-donor solvent.
Production
Tetralin is pro ...
.
The molecule has the same structure as
.
It was prepared by reacting with
bromine
Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simila ...
in
.
''catena''-
This compound consists of polymeric chains of
norbornane
Norbornane (also known as bicyclo .2.1eptane) is an organic compound and a saturated hydrocarbon with chemical formula C7H12. It is a crystalline compound with a melting point of 88 °C. The carbon skeleton is derived from cyclohexane ring with a ...
-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
.
One well-known textbook does not mention it at all.
Molecular has been reported to share the same structure as
and
,
but one well-known textbook does not mention it at all.
A review (2001) examining P-Se amorphous phases did not confirm the presence of molecular .
The isoelectronic anion which has the
adamantane
Adamantane is an organic compound with a formula C10H16 or, more descriptively, (CH)4(CH2)6. Adamantane molecules can be described as the fusion of three cyclohexane rings. The molecule is both rigid and virtually stress-free. Adamantane is the m ...
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 (corresponding to the compound ) where there is a tendency to crystallise. For ''x'' < 0.47 the glasses contain chain fragments, pyramidal P units (P
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
+3), quasi-tetrahedral P units (P oxidation state +5, with P=Se
double bond
In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...
) and units (P in formal oxidation state +4). There is no evidence for an
amorphous
In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal.
Etymology
The term comes from the Greek ''a'' ("wi ...
phase containing molecular .
References
{{Selenium compounds
Inorganic phosphorus compounds
Selenides