Phosphite anion: Difference between revisions

{{Short description|Ion}}

{{for|phosphites of the type P(OR)₃|Phosphite ester}}

| ImageFile = Phosphite ion.svg

| ImageFileL1 = Phosphite-ion-from-xtal-3D-balls.png

| ImageFileR1 = Phosphite-ion-from-xtal-3D-vdW.png

| IUPACName = Phosphonate

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 415680520

| SystematicName = Phosphite<ref>{{Cite web|title = Phosphorite - PubChem Public Chemical Database|url = https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=107908|work = The PubChem Project|location = USA|publisher = National Center for Biotechnology Information}}</ref>

| Section1 = {{Chembox Identifiers

| CASNo_Ref = {{cascite|changed|??}}

| CASNo = 15477-76-6

| PubChem = 406

| ChemSpiderID = 10449627

| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}

| MeSHName = Phosphorite

| ChEBI_Ref = {{ebicite|changed|EBI}}

| ChEBI = 16215

| ChEMBL =

| ChEMBL_Ref = {{ebicite|changed|EBI}}

| Gmelin = 1618

| KEGG =

| SMILES = P([O-])([O-])=O

| SMILES_Comment = hypervalent form

| SMILES1 = [H][P+]([O-])([O-])[O-]

| SMILES1_Comment = ionic form

| StdInChI = 1S/O3P/c1-4(2)3/q-3

| StdInChI_Ref = {{stdinchicite|changed|chemspider}}

| StdInChIKey = AQSJGOWTSHOLKH-UHFFFAOYSA-N

| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

| Section2 = {{Chembox Properties

| Formula = {{chem|HPO|3|2−}}

| MolarMass = 79.9810 g mol⁻¹

}}

| Section3 = {{Chembox Related

| OtherAnions = [[Phosphinite]]<br />

[[Phosphonite]]

}}

}}

A '''phosphite anion''' or '''phosphite''' in inorganic chemistry usually refers to [HPO₃]²⁻ but includes [H₂PO₃]⁻ ([HPO₂(OH)]⁻). These anions are the conjugate bases of [[phosphorous acid]] (H₃PO₃). The corresponding salts, e.g. [[sodium phosphite]] (Na₂HPO₃) are reducing in character.

==Nomenclature==

The IUPAC recommended name for phosphorous acid is [[phosphorous acid|phosphonic acid]]. Correspondingly, the IUPAC-recommended name for the {{chem|HPO|3|2−}} ion is [[phosphonate]]. In the US the IUPAC naming conventions for inorganic compounds are taught at high school, but not as a 'required' part of the curriculum.<ref>Physical setting/ chemistry core curriculum, The University of the State of New York, The State Education Department, http://www.p12.nysed.gov/ciai/mst/pub/chemist.pdf {{Webarchive|url=https://web.archive.org/web/20180329090703/http://www.p12.nysed.gov/ciai/mst/pub/chemist.pdf |date=2018-03-29 }}</ref> A well-known university-level textbook follows the IUPAC recommendations.<ref name = "Wiberg&Holleman">Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier {{ISBN|0-12-352651-5}}</ref> In practice any reference to "phosphite" should be investigated to determine the naming convention being employed.

==Salts containing HPO₃²⁻, called phosphonates or phosphites==

:[[File:Disodium hydrogen phosphite.png|thumb|left|132px|Structural formula of [[disodium hydrogen phosphite|Na₂HPO₃]]. The anion has C_3v symmetry.]]

From the commercial perspective, the most important phosphite salt is [[basic lead phosphite]]. Many salts containing the phosphite ion have been investigated structurally, these include [[sodium phosphite]] pentahydrate (Na₂HPO₃·5H₂O). (NH₄)₂HPO₃·H₂O, CuHPO₃·H₂O, SnHPO₃ and Al₂(HPO₃)₃·4H₂O.<ref>"Synthesis and crystal structures of aluminum and iron phosphites", D.M. Poojary, Y. Zhang, D.E. Cox, P.R. Rudolf, S. Cheng & A. Clearfield, ''J. Chem. Crystallogr.'' '''24''' (1994) 155–163</ref> The structure of {{chem|HPO|3|2−}} is approximately tetrahedral.<ref name = "Gordon">L. E. Gordon, W. T. A. Harrison. "Bis(melaminium) hydrogen phosphite tetrahydrate". ''Acta Crystallogr.'' '''59''' (2): o195–o197. {{doi|10.1107/S1600536803001247}}</ref><ref name = "Loub">"Crystal chemistry of inorganic phosphites", J. Loub, ''Acta Crystallogr.'' (1991), '''B47''', 468–473, {{doi|10.1107/S0108768191002380}}</ref>

{{chem|HPO|3|2−}} has a number of canonical resonance forms making it isoelectronic with [[bisulfite]] ion, {{chem|HSO|3|−}}, which has a similar structure.<ref name = "Greenwood"/>

[[File:Phosphite-ion-resonance-structures-2D.png|554x554px|center]]

==Salts containing HP(O)₂OH⁻==

Acid or hydrogen phosphites are called hydrogenphosphonates or acid phosphites. IUPAC recommends the name hydrogenphosphonates). They are anions HP(O)₂OH⁻. Aypical derivative is the salt [NH₄][HP(O)₂OH].<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref><ref name = "Loub"/> Many related salts are known, e.g., RbHPHO₃, CsHPHO₃, TlHPHO₃. These salts are prepared by treating [[phosphorous acid]] with the metal [[carbonate]]. These compounds contain a layer polymeric anion consisting of HPO₃ tetrahedra linked by hydrogen bonds. These layers are interleaved by layers of metal cations.<ref>{{cite journal

| vauthors = Kosterina EV, Troyanov SI, Kemnitz E, Aslanov LA

| title=Synthesis and Crystal Structure of Acid Phosphites RbH₂PO₃, CsH₂PO₃, and TlH₂PO₃

| journal=Russian Journal of Coordination Chemistry

| year=2001|volume=27|pages=458–462

| doi=10.1023/A:1011377229855

| issue=7| s2cid=91297300

}}</ref>

Organic esters of hydrogen phosphites are anions with the formula HP(O)₂OR⁻ (R = organic group). One commercial example is the [[fungicide]] [[fosetyl-Al]] with the formula [C₂H₅OP(H)O₂]₃Al.<ref>{{cite encyclopedia |author=Franz Müller |author2=Peter Ackermann |author3=Paul Margot |title=Fungicides, Agricultural, 2. Individual Fungicides|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|publisher=Wiley-VCH|place=Weinheim|year=2012|doi=10.1002/14356007.o12_o06|isbn=978-3-527-30673-2}}</ref>

==Salts containing H₂P₂O₅²⁻, called diphosphites or pyrophosphites==

Pyrophosphites (diphosphites) can be produced by gently heating acid phosphites under reduced pressure. They contain the ion {{chem|H|2|P|2|O|5|2−}}, which can be formulated [HP(O)₂O−P(O)₂H]²⁻.<ref name = "Greenwood"/><ref name = "Loub"/>

==Parallels in arsenic chemistry==

In contrast to the paucity of evidence for {{chem|PO|3|3−}}, the corresponding arsenic ion, ortho-[[arsenite]], {{chem|AsO|3|3−}} is known. An example is Ag₃AsO₃ as well as the polymeric meta-arsenite {{chem|(AsO|2|−|)|''n''}}.<ref name = "Greenwood"/> The iso-electronic [[sulfite]] ion, {{chem|SO|3|2−}} is known from its salts.<ref name = "Greenwood"/>

<!--==Synthesis of phosphite esters==

:PCl₃ + 3 ROH + 3 R′₃N → P(OR)₃ + 3R′₃NHCl-->

==Use as fungicides==

{{missing information|section|mechanism of antifungal/antiprotozoal action|date=March 2022}}

Inorganic phosphites (containing {{chem|HPO|3|2−}}) have been applied to crops to combat fungus-like pathogens of the order [[oomycete]]s (water molds). The situation is confusing because of the similarity in name between phosphite and [[phosphate]] (a major plant [[plant nutrition|nutrient]] and [[fertilizer]] ingredient), and controversial because phosphites have sometimes been advertised as fertilizers, even though they are converted to phosphate too slowly to serve as a plant's main phosphorus source. In fact, phosphites may cause phytotoxicity when a plant is starved of phosphates.<ref name=Thao/> Lemoynie<ref>[http://www.spectrumanalytic.com/support/library/pdf/Phosphites_and_Phosphates_When_distributors_and_growers_alike_could_get_confused.pdf "Phosphites and Phosphates: When Distributors and Growers alike could get confused!" by Jean-Pierre Leymonie. Courtesy of ''New Ag International'', September 2007 edition.]</ref> and others have described this complicated situation and noted that calling phosphites fertilizers avoided the regulatory complication and negative public perceptions that might have been incurred by registering them as fungicides.<ref name=Thao>{{cite journal |last1=Thao |last2=Yamakawa |year=2008 |title=Phosphite (phosphorous acid): Fungicide, fertilizer or bio-stimulator? |journal=Soil Science and Plant Nutrition |volume=55 |issue=2 |pages=228–234 |doi= 10.1111/j.1747-0765.2009.00365.x|s2cid=95723306 |doi-access=free }}</ref>

A major form of inorganic phosphite used in agriculture is [[monopotassium phosphite]]. This compound does serve as a potassium fertilizer.

* [[Hypophosphite]] – {{chem|H|2|PO|2|−}}

* [[Phosphine]] – PH₃ and the organic phosphines PR₃

* [[Phosphine oxide]] – OPR₃

* [[Phosphinite]] – P(OR)R₂

* [[Phosphonite]] – P(OR)₂R

* [[Phosphinate]] – OP(OR)R₂

* [[Phosphonate]] – organic phosphonates OP(OR)₂R

* [[Phosphate]] – {{chem|PO|4|3−}}

* [[Organophosphate]] – OP(OR)₃

*{{cite book | title=The Chemistry of the Elements |edition=2nd|author1=A. Earnshaw |author2=Norman Greenwood | year=1997| pages=513–514}}

[[Category:Phosphorus oxyanions]]

[[Category:Functional groups]]

[[Category:Phosphorus(III) compounds]]