Phosphite (ion)

The IUPAC recommended name for phosphorous acid is 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.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 }} A well-known university-level textbook follows the IUPAC recommendations.Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier {{ISBN|0-12-352651-5}} In practice any reference to "phosphite" should be investigated to determine the naming convention being employed.

:File:Disodium hydrogen phosphite.png. 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."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 The structure of {{chem|HPO|3|2−}} is approximately tetrahedral.L. E. Gordon, W. T. A. Harrison. "Bis(melaminium) hydrogen phosphite tetrahydrate". Acta Crystallogr. 59 (2): o195–o197. {{doi|10.1107/S1600536803001247}}"Crystal chemistry of inorganic phosphites", J. Loub, Acta Crystallogr. (1991), B47, 468–473, {{doi|10.1107/S0108768191002380}}

{{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.

File:Phosphite-ion-resonance-structures-2D.png

Acid or hydrogen phosphites are called hydrogenphosphonates or acid phosphites. IUPAC recommends the name hydrogenphosphonates). They are anions HP(O)₂OH⁻. A typical derivative is the salt [NH₄][HP(O)₂OH].{{Greenwood&Earnshaw}} 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.{{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

}}

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.{{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}}

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⁻.

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}}. The iso-electronic sulfite ion, {{chem|SO|3|2−}} is known from its salts.

{{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 oomycetes (water molds). The situation is confusing because of the similarity in name between phosphite and phosphate (a major plant 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. Lemoynie[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.] 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.{{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 }}

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|−}}
• Organophosphorus
• 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}}

{{reflist}}

Category:Phosphorus oxyanions

Category:Functional groups

Category:Phosphorus(III) compounds