{{Short description|Compound containing the P3– ion or its equivalent}} thumb|A portion of the structure of {{chem2|Cu3P}}, highlighting the highly crosslinked nature common to many transition metal phosphides (Cu = orange, P = purple). In chemistry, a '''phosphide''' is a compound containing the {{chem2|P(3−)}} ion or its equivalent. Many different phosphides are known, with widely differing structures.<ref>{{Greenwood&Earnshaw}}</ref> Most commonly encountered on the binary phosphides, i.e. those materials consisting only of phosphorus and a less electronegative element. Numerous are polyphosphides, which are solids consisting of anionic chains or clusters of phosphorus. Phosphides are known with the majority of less electronegative elements with the exception of Hg, Pb, Sb, Bi, Te, and Po.<ref name = "Schnering">Von Schnering, H.G. and Hönle , W. (1994) "Phosphides - Solid-state Chemistry" in ''Encyclopedia of Inorganic Chemistry''. R. Bruce King (ed.). John Wiley & Sons {{ISBN|0-471-93620-0}}</ref> Finally, some phosphides are molecular.

==Binary phosphides== Binary phosphides include phosphorus and one other element. An example of a group 1 phosphide is sodium phosphide ({{chem2|Na3P}}). Other notable examples include aluminium phosphide ({{chem2|AlP}}) and calcium phosphide ({{chem2|Ca3P2}}), which are used as pesticides, exploiting their tendency to release toxic phosphine upon hydrolysis. Magnesium phosphide ({{chem2|Mg3P2}}) also is moisture sensitive. Indium phosphide ({{chem2|InP}}) and gallium phosphide ({{chem2|GaP}}) are used as a semi-conductors, often in combination of related arsenides.<ref>{{Cite journal|last1=Blackman|first1=C. S.|last2=Carmalt|first2=C. J.|author-link2=Claire J. Carmalt|last3=O'Neill|first3=S. A.|last4=Parkin|first4=I. P.|last5=Molloy|first5=K. C.|last6=Apostolico|first6=L.|year=2003|title=Chemical vapour deposition of group Vb metal phosphide thin films|url=http://discovery.ucl.ac.uk/143120/1/Blackman_Group_VB_2_Corrected.pdf|journal=Journal of Materials Chemistry|volume=13|issue=8|pages=1930|doi=10.1039/b304084b}}</ref> Copper phosphide ({{chem2|Cu3P}}) illustrates a rare stoichiometry for a phosphide. These species are insoluble in all solvents - they are 3-dimensional solid state polymers. For those with electropositive metals, the materials hydrolyze: :{{chem2|Ca3P2 + 6 H2O → 3 Ca(OH)2 + 2 PH3}} thumb|160px|Coordination environment around Cu in {{chem2|Cu3P}}. Two pairs of Cu atoms are eclipsed.

==Polyphosphides==

thumb|Structure of the {{chem|P|7|3-}} subunit as found in M<sub>3</sub>P<sub>7</sub> (M = alkali metal).|left|110px thumb|left|Close up on the structure of SnP<sub>3</sub>, highlighting the bonding around P (violet) and Sn (gray). '''Polyphosphides''' contain {{chem2|P\sP}} bonds. The simplest polyphosphides would be derivatives of {{chem|P|2|4-}}. The free anions are rarely encountered because they are so basic. Most members follow the octet rule.

Well studied polyphosphides are derivatives of {{chem|P|7|3-}}.<ref>{{cite journal |doi=10.1002/zaac.19875520907 |title=Zur Chemie und Strukturchemie von Phosphiden und Polyphosphiden. 44. Tricäsiumheptaphosphid Cs<sub>3</sub>P<sub>7</sub>: Darstellung, Struktur und Eigenschaften |date=1987 |last1=Meyer |first1=Teodoro |last2=Hönle |first2=Wolfgang |last3=von Schnering |first3=Hans Georg |journal=Zeitschrift für Anorganische und Allgemeine Chemie |volume=552 |issue=9 |pages=69–80 }}</ref> This Zintl cluster anion is obtained with diverse alkali metal derivatives.

The nomenclature for polyphosphides can be deceptive. As confirmed by X-ray crystallography tin triphosphide and germanium triphosphide are not triphosphides, but '''hexaphosphide'''s. They consist of ruffled ''cyclo''-{{chem|P|6|6-}} subunits.<ref>{{cite journal |last1=Gullman |first1=Jan |last2=Olofsson |first2=Olle |title=The crystal structure of SnP<sub>3</sub> and a note on the crystal structure of GeP<sub>3</sub> |journal=Journal of Solid State Chemistry |date=1 November 1972 |volume=5 |issue=3 |pages=441–445 |doi=10.1016/0022-4596(72)90091-6 |url=https://www.sciencedirect.com/science/article/abs/pii/0022459672900916 |access-date=28 March 2024 |issn=0022-4596|url-access=subscription }}</ref> Another example of deceptive nomenclature is "thorium pentaphosphide", which consists of a polymeric polyphosphide related to Hittorf's phosphorus.<ref>{{cite journal |doi=10.3891/acta.chem.scand.25-1327 |title=The Crystal Structure of TlP<sub>5</sub> |date=1971 |last1=Olofsson |first1=Olle |last2=Gullman |first2=Jan |last3=Søtofte |first3=Inger |last4=Beronius |first4=P. |last5=Engebretsen |first5=Jan E. |last6=Ehrenberg |first6=L. |journal=Acta Chemica Scandinavica |volume=25 |pages=1327–1337 }}</ref>

Several polyphosphides contain the cluster {{chem|P|11|3-}} ions and polymeric chain anions (e.g. the helical {{chem|(|P|-|)|''n''}} ion) and complex sheet or 3-D anions.<ref>{{Cite journal | doi = 10.1080/03086648708080608| title = Phosphides and Polyphosphides of the Transition Metals| journal = Phosphorus and Sulfur and the Related Elements| volume = 30| issue = 1–2| pages = 413–416| year = 1987| last1 = Jeitschko | first1 = W. | last2 = Möller | first2 = M. H. }}</ref> The range of structures is extensive. Potassium has nine phosphides: {{chem2|K3P}}, {{chem2|K4P3}}, {{chem2|K5P4}}, {{chem2|KP}}, {{chem2|K4P6}}, {{chem2|K3P7}}, {{chem2|K3P11}}, {{chem2|KP10.3}}, {{chem2|KP15}}. Eight mono- and polyphosphides of nickel also exist: ({{chem2|Ni3P}}, {{chem2|Ni5P2}}, {{chem2|Ni12P5}}, {{chem2|Ni2P}}, {{chem2|Ni5P4}}, {{chem2|NiP}}, {{chem2|NiP2}}, {{chem2|NiP3}}).<ref name = "Schnering"/>

Two polyphosphide ions, {{chem|P|3|4-}} found in {{chem|K|4|P|3}} and {{chem|P|4|5-}} found in {{chem2|K5P4}}, are radical anions with an odd number of valence electrons.<ref name = "Schnering"/>

==Preparation of phosphide and polyphosphide materials== There are many ways to prepare phosphide compounds. One common way involves heating a metal and red phosphorus (P) under inert atmospheric conditions or vacuum. In principle, all metal phosphides and polyphosphides can be synthesized from elemental phosphorus and the respective metal element in stoichiometric forms. However, the synthesis is complicated due to several problems. The exothermic reactions are often explosive due to local overheating. Oxidized metals, or even just an oxidized layer on the exterior of the metal, causes extreme and unacceptably high temperatures for beginning phosphorination.<ref>{{cite journal | last1 = von Schnering |first1 = Hans-Georg | last2 = Hönle | first2=Wolfgang | title = Bridging Chasms with Phosphides | journal = Chemical Reviews | year = 1988 | volume = 88 | pages = 243–273 | doi = 10.1021/cr00083a012}}</ref> Hydrothermal reactions to generate nickel phosphides have produced pure and well crystallized nickel phosphide compounds, {{chem2|Ni2P}} and {{chem2|Ni12P5}}. These compounds were synthesized through a solid-liquid reaction between {{chem2|NiCl2*12H2O}} and red phosphorus at 200&nbsp;°C for 24 and 48 hours, respectively.<ref>{{cite journal | author1 = Liu, Zongyi | author2 = Huang, Xiang | author3 = Zhu, Zhibin | author4 = Dai, Jinhui | title = A simple mild hydrothermal route for the synthesis of nickel phosphide powders | journal = Ceramics International | volume = 36 | year = 2010 | pages = 1155–1158 | doi = 10.1016/j.ceramint.2009.12.015 | issue = 3}}</ref>

Metal phosphides are also produced by reaction of tris(trimethylsilyl)phosphine with metal halides. In this method, the halide is liberated as the volatile trimethylsilyl chloride.

thumb|Structure of terminal phosphido complexes of Mo. A method for the preparation of {{chem2|K2P16}} from red phosphorus and potassium ethoxide has been reported.<ref>{{cite journal|title=Facile Conversion of Red Phosphorus into Soluble Polyphosphide Anions by Reaction with Potassium Ethoxide|first1=Alina|last1=Dragulescu-Andrasi|first2=L. Zane|last2=Miller|first3=Banghao|last3=Chen|first4=D. Tyler |last4=McQuade|first5=Michael|last5=Shatruk|journal= Angewandte Chemie International Edition|date=March 14, 2016|volume=55|issue=12|pages=3904–3908|doi=10.1002/anie.201511186|pmid=26928980|doi-access=free}}</ref>

==Molecular phosphides== Compounds with triple bonds between a metal and phosphorus are rare. The main examples have the formula {{chem2|P\tMo(NR2)3}}, where R is a bulky organic substituent.<ref>{{Cite journal | doi = 10.1021/cr9003709| pmid = 20175534| title = Early-Transition-Metal-Mediated Activation and Transformation of White Phosphorus| journal = Chemical Reviews| volume = 110| issue = 7| pages = 4164–77| year = 2010| last1 = Cossairt | first1 = B. M. | last2 = Piro | first2 = N. A. | last3 = Cummins | first3 = C. C. | citeseerx = 10.1.1.666.8019}}</ref>

==Organic phosphides== {{See also|Organophosphine|Phosphaalkyne}} Many organophosphides are known. Common examples have the formula {{chem2|R2PM}} where R is an organic substituent and M is a metal. One example is lithium diphenylphosphide.

==Natural examples== The mineral schreibersite {{chem2|(Fe,Ni)3P}} is common in some meteorites.

==References== {{Reflist|2}} {{Phosphides}} {{Monatomic anion compounds}}

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Category:Anions * Category:Phosphorus(−III) compounds