Phosphorus selenide

Molecular {{chem2|P2Se5}} has a norbornane like structure with two phosphorus atoms with oxidation state +3 bridged by two diselenide units ({{chem2|\sSe\sSe\s}}, analogous to disulfide) and one selenide unit ({{chem2|\sSe\s}}).{{cite journal|last1=Blachnik|first1=R.|last2=Lönnecke|first2=P.|last3=Boldt|first3=K.|last4=Engelen|first4=B.|title=P2Se5|journal=Acta Crystallographica Section C|volume=50|issue=5|year=1994|pages=659–661|issn=0108-2701|doi=10.1107/S0108270193010534}} It was isolated by solvent (carbon disulfide) extraction from a {{chem2|P2Se5}} amorphous phase made from the elements.{{cite journal|last1=Blachnik|first1=Roger|last2=Lönnecke|first2=Peter|title=From P4Se3I2via P3Se4I to P2Se5|journal=Phosphorus, Sulfur, and Silicon and the Related Elements|volume=65|issue=1–4|year=1992|pages=103–106|issn=1042-6507|doi=10.1080/10426509208055329}}

{{chem2|P4Se3}} has been characterised crystallographically and has the same structure as the low temperature form of {{chem2|P4S3}}.{{cite journal|last1=Keulen|first1=E.|last2=Vos|first2=A.|title=The crystal structure of P4Se3|journal=Acta Crystallographica|volume=12|issue=4|year=1959|pages=323–329|issn=0365-110X|doi=10.1107/S0365110X59000950|doi-access=free}} It can be prepared from the elements. One preparation is to extract and recrystallise using tetralin.

The {{chem2|P4Se5}} molecule has the same structure as Phosphorus sulfides#P4S5.{{cite journal|last1=Penney|first1=G. J.|last2=Sheldrick|first2=G. M.|title=Crystal and molecular structure of tetraphosphorus pentaselenide|journal=Journal of the Chemical Society A: Inorganic, Physical, Theoretical|year=1971|pages=245|issn=0022-4944|doi=10.1039/j19710000245}} It was prepared by reacting {{chem2|P4Se3}} with bromine in Carbon disulfide.

This compound consists of polymeric chains of norbornane-like units joined by Se atoms.{{cite journal|last1=Ruck|first1=Michael|title=Darstellung und Kristallstruktur des ersten polymeren Phosphorselenidscatena-(P4Se4)x|journal=Zeitschrift für Anorganische und Allgemeine Chemie|volume=620|issue=10|year=1994|pages=1832–1836|issn=0044-2313|doi=10.1002/zaac.19946201028}} 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.

{{chem2|P4Se4}} has two crystalline forms α-{{chem2|P4Se4}} with the same molecular structure as Phosphorus sulfides#P4S4 and β-{{chem2|P4Se4}} with same molecular structure as Phosphorus sulfides#P4S4.{{cite journal|last1=Blachnik|first1=R.|last2=Lönnecke|first2=P.|last3=Nuß|first3=J.|title=Neues vom P4Se4|journal=Zeitschrift für Anorganische und Allgemeine Chemie|volume=620|issue=1|year=1994|pages=160–166|issn=0044-2313|doi=10.1002/zaac.19946200126}} A fully characterised compound {{chem2|(CuI)3P4Se4}} contains {{chem2|P4Se4}} with a β-{{chem2|P4S4}} structure.{{cite journal|last1=Pfitzner|first1=A.|last2=Reiser|first2=Sara|title=(CuI)3P4Se4: β-P4Se4Cages between Columns of Copper Iodide†|journal=Inorganic Chemistry|volume=38|issue=10|year=1999|pages=2451–2454|issn=0020-1669|doi=10.1021/ic981042f|url=https://epub.uni-regensburg.de/11784/1/49_%28CuI%293P4Se4%20b-P4Se4%20Cages%20between%20Columns%20of%20Copper%20Iodide.pdf}}

This has been reported to have the same structure as Phosphorus sulfides#P4S7.{{cite book|last=Corbridge|first=D.E.C|title= Phosphorus: Chemistry, Biochemistry and Technology|publisher= CRC Press, Taylor Francis Group|year=2013|page=808|isbn=978-1-4398-4088-7}}{{cite book |editor1=Devillanova, Francesco |title=Handbook of Chalcogen Chemistry –New Perspectives in Sulfur, Selenium and Tellurium |publisher=Royal Society of Chemistry |year=2007 |isbn=9780854043668}} One well-known textbook does not mention it at all.{{Holleman&Wiberg}}

Molecular {{chem2|P4Se10}} has been reported to share the same structure as phosphorus pentasulfide and phosphorus pentoxide,{{cite book|last1=Housecroft|first1=Catherine E|last2=Sharpe|first2=Alan G|year=2005|title=Inorganic Chemistry|edition=2d|publisher=Pearson education|pages=427|isbn=978-0-13-039913-7}} 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 {{chem2|P4Se10}}.{{cite journal|last1=Georgiev|first1=D.|last2=Mitkova|first2=M.|last3=Boolchand|first3=P.|last4=Brunklaus|first4=G.|last5=Eckert|first5=H.|last6=Micoulaut|first6=M.|title=Molecular structure, glass transition temperature variation, agglomeration theory, and network connectivity of binary P-Se glasses|journal=Physical Review B|volume=64|issue=13|pages=134204|year=2001|issn=0163-1829|doi=10.1103/PhysRevB.64.134204|bibcode=2001PhRvB..64m4204G}} The isoelectronic anion {{chem2|[Ge4Se10](4−)}} which has the adamantane like {{chem2|P4O10}} structure is known, an example is the sodium salt {{chem2|Na4[Ge4Se10]}}.{{cite journal|last1=Eisenmann|first1=B.|last2=Hansa|first2=J.|title=Crystal structure of tetrasodium decaselenotetragermanate, Na4[Ge4Se10]|journal=Zeitschrift für Kristallographie|volume=205|issue=Part-2|year=1993|pages=325–326|issn=0044-2968|doi=10.1524/zkri.1993.205.Part-2.325|bibcode=1993ZK....205..325E}}

{{chem2|P4Se6, P14Se, P4Se, P4Se2, P2Se}}, have been reported.

Phosphorus - selenium glasses have been examined using ³¹P-NMR and Raman spectroscopy. Glasses are formed in {{chem2|P_{x}Se_{1−x}|}} 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 {{chem2|P4Se3}}) where there is a tendency to crystallise. For x < 0.47 the glasses contain {{chem2|Se_{n}|}} chain fragments, pyramidal P units (P oxidation state +3), quasi-tetrahedral P units (P oxidation state +5, with P=Se double bond) and {{chem2|P2}} units (P in formal oxidation state +4). There is no evidence for an amorphous phase containing molecular {{chem2|P4Se10}}.

{{reflist}}{{Selenides}}{{Selenium compounds}}

Category:Inorganic phosphorus compounds

Category:Selenides