Thiophosphate

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For the thiophosphate esters see organothiophosphates.

A thiophosphate (or phosphorothioate) is a family of compounds and anions with the general chemical formula PS4-xOx3- (x = 0, 1, 2, or 3). The state of protonation is usually not specified. They could be bound to as many as three protons for the neutral H3PS4-xOx species. Two protons correspond to the related monoanions, and one proton for the dianions. The trianions are highly basic and do not exist in appreciable concentrations in solution. Thiophosphates are tetrahedral anions, with the phosphorus at the center of the tetrahedron.

Monothiophosphate[edit]

Ball-and-stick model of the monothiophosphate ion

Monothiophosphates are formally derived from the anion PO3S3-, which has C3v symmetry.. A number of insecticides feature organic monothiophosphate center, including diazinon, parathion, and malathion. They have the formula (RO)2PS(OAr), where R = methyl or ethyl and Ar = an aryl or related group. Coordination complexes by oxygen and sulphur are known.[1]

In the laboratory monothiophosphate is used as an analogue of phosphate in biochemistry. Monothiophosphate esters are biochemical reagents used in the study transcription,[2] substitution interference assays.

Dithiophosphates[edit]

X-ray structure of O,O′-diethyl dithiophosphate anion from ammonium salt[3]

Dithiophosphates are formally derived from the anion PO2S23-, which has C2v symmetry. This species is the major product from the reaction of base (e.g., NaOH) with phosphorus pentasulfide. The sodium salt has the nominal formula Na3PO2S2, but is invariably hydrated. The main application of this dithiophosphate salt is in the purification of molybdenite ore. Organic thiophosphates feature the (RO)2PS2- anion (R = alkyl, aryl), e.g. NH4S2P(EtO)2. Zinc dithiophosphate, e.g., Zn(S2P(OR)2)2, are used as oil additives (R = alkyl).

Trithiophosphates[edit]

Trithiophosphates are formally derived from the anion POS33-, which has C3v symmetry.

PxSy binary thiophosphates and polyphosphates[edit]

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[4]
  • 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.[5]
  • 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-.[6]
  • 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.[5]
  • 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-.[7]
  • P2S64– These form water stable salts.[8] 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.[9] 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,[4] P5S105– contains a P5 ring and P6S126– a P6 ring.[7] 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.[10]
  • 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.[11]
  • P7(S)33– is a sulfido heptaphosphane cluster anion.[4]

References[edit]

  1. ^ Poat JC et al. (1990). "A thiophosphate bridged platinum–zinc hetero-bimetallic complex: [(Me2PhP)2Pt{OSP(OR)2}2ZnCl2". J. Chem. Soc., Chem. Commun.: 1036–1038. 
  2. ^ Lorsch JR, Bartel DP, Szostak JW. (1995). "Reverse transcriptase reads through a 2'–5' linkage and a 2'-thiphosphate in a template". Nucleic Acids Res. 23 (15): 2811–2814. doi:10.1093/nar/23.15.2811. PMC 307115. PMID 7544885. 
  3. ^ Okuniewski, Andrzej; Becker, Barbara (2011). "Ammonium O,O′-diethyl dithiophosphate". Acta Cryst. E 67 (7): o1749–o1750. doi:10.1107/S1600536811022811. 
  4. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 509–510. ISBN 0-08-022057-6. 
  5. ^ a b Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition, 2013, D.E.C. Corbridge, CRC Pres, Taylor Francis Group, isbn: 978-1-4398-4088-7
  6. ^ Aitken, Jennifer A.; Canlas, Christian; Weliky, David P.; Kanatzidis, Mercouri G. (2001). "[P2S10]4-: A Novel Polythiophosphate Anion Containing a Tetrasulfide Fragment". Inorganic Chemistry 40 (25): 6496–6498. doi:10.1021/ic010664p. ISSN 0020-1669. 
  7. ^ a b Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, pp. 734–735, ISBN 0-12-352651-5 
  8. ^ Gjikaj, Mimoza; Ehrhardt, Claus (2007). "New Hexachalcogeno–Hypodiphosphates of the Alkali Metals: Synthesis, Crystal Structure and Vibrational Spectra of the Hexathiodiphosphate(IV) Hydrates K4[P2S6] · 4 H2O, Rb4[P2S6] · 6 H2O, and Cs4[P2S6] · 6 H2O". Zeitschrift für anorganische und allgemeine Chemie 633 (7): 1048–1054. doi:10.1002/zaac.200600339. ISSN 0044-2313. 
  9. ^ Wolf, G.-U.; Meisel, M. (1982). "Beitr�ge zur Chemie von Phosphorverbindungen mit Adamantanstruktur. VII[1]. �ber Darstellung und Eigenschaften von Nonathio-cyclotriphosphat". Zeitschrift f�r anorganische und allgemeine Chemie 494 (1): 49–54. doi:10.1002/zaac.19824940106. ISSN 0044-2313. 
  10. ^ Ebert, M.; Nassler, J. (1989). "The Ring Acid, H6P6O12 and Ring Acid, H4P4O10and Their Salts". Phosphorus, Sulfur, and Silicon and the Related Elements 41 (3-4): 462–462. doi:10.1080/10426508908039741. ISSN 1042-6507. 
  11. ^ Rotter, Christiane; Schuster, Michael; Karaghiosoff, Konstantin (2009). "An Unusual Binary Phosphorus−Tellurium Anion and Its Seleno- and Thio- Analogues: P4Ch22−(Ch = S, Se, Te)". Inorganic Chemistry 48 (16): 7531–7533. doi:10.1021/ic901149m. ISSN 0020-1669.