Ammonium tetrathiomolybdate

Ammonium tetrathiomolybdate
Other names

ammonium thiomolybdate
Identifiers
CAS number 15060-55-6 Y
ChemSpider 10764593 Y
RTECS number QA4668250
Jmol-3D images Image 1
Properties
Molecular formula H8N2MoS4
Molar mass 260.28 g/mol
Appearance red crystals
Melting point

decomp ~ 155 °C [1]
Basicity (pKb) decomposes
Structure
Crystal structure B. Hill, H.-W. Lerner and M. Bolte (2010). Acta Crystallographica E 66 (13). doi:10.1107/S1600536810003016. 
Hazards
Main hazards toxic
Related compounds
Related compounds (NH4)2[WS4],
MoS2
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ammonium tetrathiomolybdate is the chemical compound with the formula [NH4]2MoS4. 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).

Contents

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:[2]

[NH4]2[MoO4] + 4 H2S → [NH4]2[MoS4] + 4 H2O


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).[3] These organic salts are soluble in polar organic solvents such as acetonitrile and dmf.

The thermal decomposition of [NH4]2[MoS4] leads to molybdenum trisulfide (MoS3), ammonia (NH3) and hydrogen sulfide (H2S), beginning at 155 °C till 280 °C [1]

(NH4)2(MoS4) → MoS3 + 2 NH3 + H2S

MoS3 then decomposes again to molybdenum disulfide (MoS2) in a broad temperature range from 300 °C to 820 °C. Perfect decomposition to MoS2 under inert gas requires at least 800°C according to the following reaction,

MoS3 → MoS2 + S

but it can also be achieved at 450°C, if there is enough hygrogen.[4]

MoS3 + H2 → MoS2 + H2S

Related compounds

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

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, potentially via the inhibition of Cu ion dependent membrane translocation process involving a non-classical secretion pathway.[8] This makes it an interesting investigatory treatment for cancer, age-related macular degeneration, and other diseases featuring excessive blood vessel deposition.[9]

References

  1. ^ a b Prasad, T. P.; Diemann, E. ; Müller, A. (1973). "Thermal decomposition of (NH4)2MoO2S2, (NH4)2MoS4, (NH4)2WO2S2 and (NH4)2WS4". Journal of Inorganic and Nuclear Chemistry 35 (6): 1895. doi:10.1016/0022-1902(73)80124-1. 
  2. ^ 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 (11): 934. doi:10.1002/anie.198109341. 
  3. ^ Coucouvanis, D. (1998). Syntheses, Structures, and Reactions of Binary and Tertiary Thiomolybdate Complexes Containing the (O)Mo(Sx) AND (S)Mo(Sx) Functional Groups (x = 1, 2, 4). "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. Advances in Inorganic Chemistry 45: 1–73. doi:10.1016/S0898-8838(08)60024-0. ISBN 9780120236459. 
  4. ^ Brito, J. L. ; Ilija, M. ; Hernández, P. (1995). "Thermal and reductive decomposition of ammonium thiomolybdates". Thermochimica Acta 256 (2): 325. doi:10.1016/0040-6031(94)02178-Q. 
  5. ^ a b c Lee, S. C.; Li, J.; Mitchell, J. C.; Holm, R. H., (1992). "Group 5 Tetrathiometalates: Simplified Syntheses and Structures". Inorg. Chem. 31 (21): 4333–4338. doi:10.1021/ic00047a021. 
  6. ^ Srinivasan, B. R.; Poisot, M.; Näther, C.; Bensch, W. (2004). "Diammonium tetrathiotungstate(VI), [NH4]2[WS4], at 150 K". Acta Crystallographica E E60 (11): i136–i138. doi:10.1107/S1600536804023761. 
  7. ^ Goodman, J. T.; Rauchfuss, T. B., (2002). "Tetraethylammonium-tetrathioperrhenate [Et4N][ReS4]". Inorganic Syntheses 33: 107–110. 
  8. ^ Nickel, W (2003). "The Mystery of nonclassical protein secretion, a current view on cargo proteins and potential export routes". Eur. J. Biochem. 270 (10): 2109–2119. doi:10.1046/j.1432-1033.2003.03577.x. PMID 12752430. 
  9. ^ 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. http://archneur.ama-assn.org/cgi/content/full/60/3/379.