Ammonium tetrathiomolybdate is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula (NH₄)₂MoS₄. This bright red

ammonium Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...

salt is an important reagent in the chemistry of

molybdenum Molybdenum is a chemical element; it has Symbol (chemistry), symbol Mo (from Neo-Latin ''molybdaenum'') and atomic number 42. The name derived from Ancient Greek ', meaning lead, since its ores were confused with lead ores. Molybdenum minerals hav ...

and has been used as a building block in bioinorganic chemistry. The thiometallate (see metallate) 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 oS₄sup>2− anion. The compound is prepared by treating solutions of

molybdate In chemistry, a molybdate is a compound containing an oxyanion with molybdenum in its highest oxidation state of +6: . Molybdenum can form a very large range of such oxyanions, which can be discrete structures or polymeric extended structures, ...

, oO₄sup>2− with

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

in the presence of ammonia: :(NH₄)₂MoO₄ + 4 H₂S → (NH₄)₂MoS₄ + 4 H₂O MoS4

Reactions

The anion is also an excellent ligand. For example, with Ni(II) sources, it forms i(MoS₄)₂sup>2−. Much of the chemistry of the thiomolybdate results from studies on salts of quaternised organic cations, such as Et₄sub>2 oS₄and Ph₄sub>2 oS₄(Et = C₂H₅, Ph = C₆H₅). These organic salts are soluble in polar organic solvents such as

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not class ...

and DMF. The

thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition of a substance caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic ...

of H₄sub>2 oS₄leads to molybdenum trisulfide (MoS₃), ammonia (NH₃) and hydrogen sulfide (H₂S), beginning at 155 °C till 280 °C. : (NH₄)₂MoS₄ → 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 hydrogen. : MoS₃ + H₂ → MoS₂ + H₂S

Related compounds

Several related thio and seleno anions are known including (A = alkali metal cation, Ph₄sup>+, Et₄sup>+) *A₃ S₄ *A₃ bS₄ref name=Lee1/> *A₃ aS₄ref name=Lee1/> *A₂ oSe₄*A₂ S₄ ammonium tetrathiotungstate, *A₂ Se₄ , tetraethylammonium tetraselenotungstate *A eS₄*(C₅H₁₄NO)₂MoS₄ (

bis-choline tetrathiomolybdate Tiomolibdic acid (trade name Decuprate) is a chelating agent under investigation for the treatment of cancer and of Wilson's disease, a rare and potentially fatal disease in which the body cannot regulate copper. It is developed by Wilson Ther ...

) More complex tetrahedral anions include A₂ oS_4−''x''O_''x''and A₂ S_4−''x''O_''x''

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 Wilson's disease (also called hepatolenticular degeneration) is a genetic disorder characterized by the excess build-up of copper in the body. Symptoms are typically related to the brain and liver. Liver-related symptoms include vomiting, wea ...

, a hereditary copper metabolism disorder, in humans; it acts both by competing with copper absorption in the bowel and by increasing excretion. Clinical studies have shown ATTM can effectively lower copper levels faster than currently available treatments, and that fewer patients with an initial neurological presentation of their disease who are treated with ATTM experience neurological deterioration Various phase II clinical trial of ATTM for copper depletion in cancer have been performed. ATTM has also been found to have an inhibitory effect on

angiogenesis Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature mainly by processes of sprouting and ...

, potentially via the inhibition of Cu ion dependent membrane translocation process involving a non-classical secretion pathway. This makes it an interesting investigatory treatment for

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

age-related macular degeneration Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Some people experien ...

, and other diseases featuring excessive blood vessel deposition.

References

{{DEFAULTSORT:Ammonium Tetrathiomolybdate Molybdates Sulfides Ammonium compounds Thiometallates