Thiophosphate

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For the thiophosphate esters see organothiophosphates.

Thiophosphates (or phosphorothioates, PS) are chemical compounds and anions with the general chemical formula PS4-xOx3− (x = 0, 1, 2, or 3) and related derivatives where organic groups are attached to one or more O or S. Thiophosphates feature tetrahedral phosphorus(V) centers.[1]

Organic

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Main article: Organothiophosphate

Organothiophosphates are a subclass of organophosphorus compounds that are structurally related to the inorganic thiophosphates. Common members have formulas of the type (RO)3-xRxPS and related compounds where RO is replaced by RS. Many of these compounds are used as insecticides, some have medical applications, and some have been used as oil additives.[1]

Selected organothiophosphates
zinc dialkyldithiophosphate, an oil additive.
zinc dialkyldithiophosphate, an oil additive.[2] 
Phosphorothioates are the basis for antisense therapies.
Phosphorothioates are the basis for antisense therapies. 
Amifostine, which is used in cancer chemotherapy.
Amifostine, which is used in cancer chemotherapy. 
Chlorpyrifos, a popular insecticide. 
Malathion, a popular insecticide.
Malathion, a popular insecticide. 

Oligonucleotide phosphorothioates (OPS) are modified oligonucleotides where one of the oxygen atoms in the phosphate moiety is replaced by sulfur. They are the basis of antisense therapy, e.g., the drugs fomivirsen (Vitravene), oblimersen, alicaforsen, and mipomersen (Kynamro).[3]

Inorganic

The simplest thiophosphates have the formula [PS4-xOx]3-. These trianions are only observed at very high pH, instead they exist in protonated form with the formul [HnPS4-xOx](3-n)-.

Monothiophosphate

File:Thiophosphate-ion-3D-balls.png
Ball-and-stick model of the hypothetical monothiophosphate trianion.

Monothiophosphate is the anion [PO3S]3−, which has C3v symmetry. A common salt is sodium monothiophosphate (Na3PO3S). Monothiophosphate is used in research as an analogue of phosphate in biochemistry. Monothiophosphate esters are biochemical reagents used in the study of transcription,[4] substitution interference assays. Sometimes," monothiophosphate" refers to esters such as (CH3O)2POS-.[5]

Dithiophosphates

Dithiophosphate has the formula [PO2S2]3−, which has C2v symmetry. Sodium dithiophosphate, which is colorless, is the major product from the reaction of phosphorus pentasulfide with NaOH:[6]

P2S5 + 6 NaOH → 2 Na3PO2S2 + H2S + 2 H2O

Dithiophosphoric acid is obtained by treatment of barium dithiophosphate with sulfuric acid:

Ba3(PO2S2)2 + 3 H2SO4 → 3 BaSO4 + 2 H3PO2S2

Both Na3PO2S2 and especially H3PO2S2 are prone toward hydrolysis to their monothio derivatives.

Tri- and tetrathiophosphates

Trithiophosphate is the anion [POS3]3−, which has C3v symmetry. Tetrathiophosphate is the anion [PS4]3−, which has Td symmetry.

PxSy: binary thiophosphates and polyphosphates

There are a number of these anions known. There has been interest in compounds containing these anions due to their potential application as fast ion conductors for use in solid state batteries. The binary thiophosphates do not exhibit the extensive diversity of the analogous P-O anions but contain similar structural features, for example P is 4 coordinate, P-S-P links form and there are P-P bonds. One difference is thations may include polysulfide fragments of 2 or more S atoms whereas in the P-O anions there is only the reactive -O-O-, peroxo, unit.

  • PS3− is the analogue of the nitrate ion, NO3− (there is no PO3− analogue)- it was isolated as the tetraphenylarsonium salt[7]
  • PS4 3− is the sulfur analogue of PO43−, and like PO43− is tetrahedral.
  • P2S74− the pyrothiophosphate ion consisting of two corner sharing PS4 tetrahedra, analogous to the pyrophosphates.[8]
  • P2S104− An ion which can be visualised either as two PS4 tetrahedra joined by a disulfide link or a pyro-thiophosphate where the bridging -S- is replaced by -S4-.[9]
  • P2S62− with a structure consisting of two edge sharing tetrahedra. The structure is therefore similar to the isoelectronic Al2Cl6 dimer. The oxygen analogue, dimetaphosphate P2O6 2−, in contrast, is not known, the metaphosphates favour polymeric structures of chains or rings.[8]
  • P2S82− and P2S102− are related to P2S62− but their two bridging -S- atoms are replaced by -S-S- in P2S82− and by an -S-S-S- bridge in P2S102−.[10]
  • P2S64− These form water stable salts.[11] The anion has an ethane like structure and contains a P-P bond. The formal oxidation state of phosphorus is +4. The oxygen analogue is the hypodiphosphate anion, P2O64−.
  • P3S93− contains a six membered P3S3 ring. The ammonium salt is produced by reaction of P4S10 in liquid ammonia.[12] Another way of visualising the structure is that it is the P4S10 adamantane (P4O10) structure with a PS3+ vertex removed.
  • P4S84− contains a square P4 ring,[7] P5S105− contains a P5 ring and P6S126− a P6 ring.[10] These (PS2−)n cyclic anions contain P with an oxidation state +3. Note they are not trigonal as arsenic(III) is in arsenites, but are tetrahedral with two bonds to other phosphorus atoms and two to sulfur. The P6S126− anion is analogous to the P6O126− ring anion.[13]
  • P4S2− An unusual butterfly shaped ion, SP(P2)PS, which can be visualised as a P4 molecule where two P-S bonds replace one P-P bond.[14]
  • P7(S)33− is a sulfido heptaphosphane cluster anion.[7]

References

  1. ↑ 1.0 1.1 J. Svara, N. Weferling, T. Hofmann "Phosphorus Compounds, Organic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2006. doi:10.1002/14356007.a19_545.pub2
  2. ↑ H. Spikes "The history and mechanisms of ZDDP" Tribology Letters, Vol. 17, No. 3, October 2004. doi:10.1023/B:TRIL.0000044495.26882.b5.
  3. ↑ Kurreck, J., "Antisense technologies. Improvement through novel chemical modifications", European Journal of Biochemistry 2003, 270, 1628-1644.doi:10.1046/j.1432-1033.2003.03555.x
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ R. Klement "Phosphorus" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1., p. 571.
  7. ↑ 7.0 7.1 7.2 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ 8.0 8.1 Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition, 2013, D.E.C. Corbridge, CRC Pres, Taylor Francis Group, ISBN 978-1-4398-4088-7
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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