Transition metal dithiophosphate complex

Transition metal dithiophosphate complexes are coordination compounds containing dithiophosphate ligands, i.e. ligands of the formula (RO)2PS−
2. The charge-neutral complexes tend to be soluble in organic solvents, especially when R is branched. Dithiophosphates are available with a wide variety of alkoxy groups. The range of complexes is similar to those for dithiocarbamate complexes.

Important members are zinc dialkyldithiophosphates, which are oil additives.[2][3]

Preparation

Dithiophosphate complexes are usually prepared by salt metathesis from preformed ligands. Dialkoxydithiophoric acid reacts with many metal oxides, chlorides, and acetates:[4]

3 (C2H5O)2PS2H + CrCl3(H2O)6 → Cr[(S2P(OC2H5)2]3 + 3 HCl + 6 H2O

Alternatively, salts, such as ammonium diethyldithiophosphate, can be used to prepare complexes by salt metathesis reactions:

2 NH4[(S2P(OC2H5)2] + NiCl2·(H2O)6 → Ni(S2P(OC2H5)2) + 6 H2O + 2 NH4Cl

Dithiophosphate complexes have also be prepared by oxidative addition of their disulfides:[5]

[(S2P(OC2H5)2]2 + Ni(P(OC6H5)3)4 → Ni(S2P(OC2H5)2)2 + 4 P(OC6H5)3

Ligand properties

Dithiophosphates, when bidentate, are classified as L-X ligands in the Covalent bond classification method. In the usual electron counting method, they are three-electron ligands. With respect to HSAB theory, they are classified as soft. In addition to the conventional representation, they are also described by a zwitterionic resonance structure (RO)2P+(S−)2.

Dithiophosphate ligands are prepared by alcoholysis of phosphorus pentasulfide:[4]

P4S10 + 8 C2H5OH → 4 (C2H5O)2PS2H + 2 H2S

Alternatively, the intermediate dialkoxydithiophoric acid can be deprotonated to give salts, such as ammonium diethyldithiophosphate, which can also be used to prepare complexes:

(C2H5O)2PS2H + NH3 → NH4[(S2P(OC2H5)2]

Selected homoleptic complexes

Homoleptic complexes have formulas M[S2P(OR)2]2 and M[S2P(OR)2]3.

  • Ni[S2P(OC6H11)2]2[6] violet[7]
  • Cu[S2P(OC6H4CH3)2]2[8]
  • Pd[S2P(OC2H5)2]2[9]
  • Pt[S2P(OC2H5)2]2[10] yellow, diamagnetic[7]
  • Cri[S2P(OC2H5)2]3[11] violet, paramagneticx
  • Ru[S2P(OC2H5)2]3[12] pink, paramagnetic
  • Ir[S2P(OCH(CH3)2)2]3[13]

References

  1. ↑ T. Ito; T. Igarashi; H. Hagihara (1969). "The Crystal Structure of Metal Diethyldithiophosphates. I. Zinc Diethyldithiophosphate" (PDF). Acta Crystallogr. B. 25 (11): 2303–2309. Bibcode:1969AcCrB..25.2303I. doi:10.1107/S0567740869005619.
  2. ↑ "Zinc dialkyl dithiophosphates". Molecule of the Week Archive.
  3. ↑ Spikes, H. (2004-10-01). "The History and Mechanisms of ZDDP". Tribology Letters. 17 (3): 469–489. doi:10.1023/B:TRIL.0000044495.26882.b5. ISSN 1023-8883. S2CID 7163944.
  4. 1 2 Coldbery, David E.; Fernelius, W. Conard; Shamma, Maurice; et al. (1960). "Chromium(III) O,O ′-Diethyl Dithiophosphate". In Eugene G. Rochow (ed.). Inorganic Syntheses. Vol. 6. p. 142. doi:10.1002/9780470132371.ch44. ISBN 978-0-470-13165-7.
  5. ↑ Losada, J.; Morán, M.; Muro, Carmen (1989). "A New Synthesis and the Electrochemical Behaviour of Nickel(II) Dithiophosphate and Dithiophosphinate Complexes". Transition Metal Chemistry. 14 (2): 127–130. doi:10.1007/BF01040606.
  6. ↑ Taş, Murat; Yaĝan, Mehtap; Batı, Hümeyra; Batı, Bek˙ir; Büyükgüngör, Orhan (2005). "Redetermination of Bis( O , O ′-dicyclohexyl phosphorodithioato)nickel(II)". Acta Crystallographica Section e Structure Reports Online. 61 (9): m1684 – m1685. doi:10.1107/S1600536805023895.
  7. 1 2 Rudzinski, Walter.; Behnke, George T.; Fernando, Quintus. (1977). "A Normal-Coordinate Analysis of Bis(O,O'-dialkyldithiophosphato)nickel(II) Complexes". Inorganic Chemistry. 16 (5): 1206–1210. doi:10.1021/ic50171a046.
  8. ↑ Yordanov, Nicola D.; Alexiev, Valentin; MacIcek, Josef; Glowiak, Tadeusz; Russell, David R. (1983). "Studies on Intermolecular Interactions of Metal Chelate Complexes. V. Copper(II) Dithiophosphate Complexes: An Example of an Inner Self-Redox Reaction". Transition Metal Chemistry. 8 (5): 257–261. doi:10.1007/BF00620863.
  9. ↑ Yordanov, N.D.; Ivanova, M.; Gochev, G.; MacIcek, J. (1993). "EPR Studies on Bis(diisopropyldithiophosphato)copper(II) Magnetically diluted in the corresponding palladium(II) and platinum(II) single crystals and crystal and molecular structure of bis(diisopropyldithiophosphato)palladium(II) host lattice". Polyhedron. 12: 117–124. doi:10.1016/S0277-5387(00)87061-8.
  10. ↑ Gianini, Michel; Caseri, Walter R.; Gramlich, Volker; Suter, Ulrich W. (2000). "Synthesis and characterization of liquid platinum compounds". Inorganica Chimica Acta. 299 (2): 199–208. doi:10.1016/S0020-1693(99)00499-5.
  11. ↑ Biscarini, Paolo; Franca, Roberto; Kuroda, Reiko (1995). "Chiral Discrimination of Complexes with D3 Symmetry. Synthesis and Characterization of Tris{O,O'-bis[(+)(S)-2-methylbutyl] dithiophosphato}chromium(III) Complexes (ΛΔ){Cr[(+)(S)(S)Mebdtp]3} and Λ-(-)589-, and Δ-(+)589{Cr[(+)(S)(S)Mebdtp]3} and Crystal Packing of Racemic Tris{O,O'-diethyl dithiophosphato}chromium(III), Cr[DDTP]3". Inorganic Chemistry. 34 (18): 4618–4626. doi:10.1021/ic00122a019.
  12. ↑ Jain, Prateek U.; Munshi, Pradip; Walawalkar, Mrinalini G.; Rath, Sankar Prasad; Rajak, Kajal Krishna; Lahiri, Goutam Kumar (2000). "Ruthenium Dithiophosphates: Synthesis, X-Ray Crystal Structure, Spectroscopic and Electrochemical Properties". Polyhedron. 19 (7): 801–808. doi:10.1016/S0277-5387(00)00316-8.
  13. ↑ Marsh, R. E. (1995). "Some Thoughts on Choosing the Correct Space Group". Acta Crystallographica Section B Structural Science. 51 (6): 897–907. Bibcode:1995AcCrB..51..897M. doi:10.1107/S0108768195008901.
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