Ammonium tetrathiomolybdate

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Ammonium tetrathiomolybdate
Other names ammonium thiomolybdate
Identifiers
CAS number 15060-55-6
RTECS number QA4668250
Properties
Molecular formula H8N2MoS4
Molar mass 260.28 g/mol
Appearance red crystals
Melting point

decomp 300 °C

Basicity (pKb) decomposes
Hazards
Main hazards toxic
Related Compounds
Related compounds [NH4]2[WS4],
MoS2
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Ammonium tetrathiomolybdate is the chemical compound with the formula [NH4]2[MoS4]. This bright red ammonium salt is an important reagent in the chemistry of molybdenum and has been used as a building block in bioinorganic chemistry. The thiometallate anion has the distinctive property of undergoing oxidation at the sulfur centers concomitant with reduction of the metal from Mo(VI) to Mo(IV).

Preparation and structure

The salt contains the tetrahedral [MoS4]2- anion. The compound is prepared by treating solutions of molybdate, [MoO4]2- with hydrogen sulfide in the presence of ammonia:[1]

[NH4]2[MoO4] + 4 H2S → [NH4]2[MoS4] + 4 H2O
File:MoS4.png
The [MoS4]2- anion.


Reactions

The anion is also an excellent ligand. For example, with Ni(II) sources, it forms [Ni(MoS4)2]2-. Much of the chemistry of the thiomolybdate results from studies on salts of quaternised organic cations, such as [NEt4]2[MoS4] and [PPh4]2[MoS4] (Et = C2H5, Ph = C6H5).[2] These organic salts are soluble in polar organic solvents such as acetonitrile and dmf.

The thermal decomposition of [NH4]2[MoS4] leads to sulfides of composition MoSx (2< x< 3), which are of interest as catalysts for hydrodesulfurization.[3]

Related compounds

Several related thio and seleno anions are known including (A = alkali metal cation, [PPh4]+, [NEt4]+)

  • A3[VS4][4]
  • A3[NbS4][4]
  • A3[TaS4][4]
  • A2[MoSe4]
  • A2[WS4][5]
  • A2[WSe4]
  • A[ReS4][6]

More complex tetrahedral anions include A2[MoS4-xOx] and A2[WS4-xOx]

Uses

Ammonium tetrathiomolybdate was first used therapeutically in the treatment of copper toxicosis in animals. It was then introduced as a treatment in Wilson's disease, a hereditary copper metabolism disorder, in humans; it acts both by competing with copper absorption in the bowel and by increasing excretion. It has also been found to have an inhibitory effect on angiogenesis, making it an investigatory treatment for cancer, age-related macular degeneration, and other diseases featuring excessive blood vessel deposition.[7]

References

  1. Müller, A.; Diemann, E.; Jostes, R.; Bögge, H. (1981). "Transition Metal Thio Anions: Properties and Significance for Complex Chemistry and Bioinorganic Chemistry". Angewandte Chemie International Edition in English 20: 934. doi:10.1002/anie.198109341.
  2. Coucouvanis, D. (1998). "Syntheses, Structures, and Reactions of Binary and Tertiary Thiomolydate Complexes Containing the (O)Mo(Sx) and (S)Mo(Sx) Functional Groups (x = 1, 2, 4)". Advances in Inorganic Chemistry 45: 1–73.
  3. Alonso, G.; Berhault, G.; Aguilar, A.; Collins, V.; Ornelas, C.; Fuentes, S.; Chianelli, R. R. (2002). "Characterization and HDS Activity of Mesoporous MoS2 Catalysts Prepared by in Situ Activation of Tetraalkylammonium Thiomolybdates". J. Catal. 208: 359–369. doi:10.1006/jcat.2002.3553.
  4. 4.0 4.1 4.2 Lee, S. C.; Li, J.; Mitchell, J. C.; Holm, R. H., (1992). "Group 5 Tetrathiometalates: Simplified Syntheses and Structures". Inorg. Chem. 31: 4333–4338. doi:10.1021/ic00047a021.
  5. Srinivasan, B. R.; Poisot, M.; Näther, C.; Bensch, W. (2004). "Diammonium tetrathiotungstate(VI), [NH4]2[WS4], at 150 K". Acta Crystallographica Section E: Structure Reports Online E60: i136-i138. doi:10.1107/S1600536804023761.
  6. Goodman, J. T.; Rauchfuss, T. B., (2002). "Tetraethylammonium-tetrathioperrhenate [Et4N][ReS4]". Inorganic Syntheses 33: 107–110.
  7. Brewer GJ, Hedera P, Kluin KJ et al (2003). "Treatment of Wilson disease with ammonium tetrathiomolybdate: III. Initial therapy in a total of 55 neurologically affected patients and follow-up with zinc therapy". Arch Neurol 60 (3): 379–85. doi:10.1001/archneur.60.3.379. PMID 12633149.

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