Ammonium tetrathiomolybdate
Encyclopedia
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).
, [MoO4]2- with hydrogen sulfide
in the presence of ammonia:
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
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,
but it can also be achieved at 450°C, if there is enough hygrogen.
More complex tetrahedral anions include A2[MoS4-xOx] and A2[WS4-xOx]
, 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. This makes it an interesting investigatory treatment for cancer
, age-related macular degeneration, and other diseases featuring excessive blood vessel deposition.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula [NH4]2MoS4. This bright red ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
salt is an important reagent in the chemistry of molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
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 molybdateMolybdate
In chemistry a molybdate is a compound containing an oxoanion with molybdenum in its highest oxidation state of 6. Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state.The...
, [MoO4]2- with hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
in the presence of ammonia:
- [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). These organic salts are soluble in polar organic solvents such as acetonitrileAcetonitrile
Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...
and dmf
Dimethylformamide
Dimethylformamide is an organic compound with the formula 2NCH. Commonly abbreviated as DMF , this colourless liquid is miscible with water and the majority of organic liquids. DMF is a common solvent for chemical reactions...
.
The thermal decomposition of [NH4]2[MoS4] leads to molybdenum trisulfide (MoS3), ammonia (NH3)
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
and hydrogen sulfide (H2S)
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
, beginning at 155 °C till 280 °C
- (NH4)2(MoS4) → MoS3 + 2 NH3 + H2S
MoS3 then decomposes again to molybdenum disulfide (MoS2)
Molybdenum disulfide
Molybdenum disulfide is the inorganic compound with the formula MoS2. This black crystalline sulfide of molybdenum occurs as the mineral molybdenite. It is the principal ore from which molybdenum metal is extracted. The natural amorphous form is known as the rarer mineral jordisite. MoS2 is less...
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.
- MoS3 + H2 → MoS2 + H2S
Related compounds
Several related thio and seleno anions are known including (A = alkali metal cation, [PPh4]+, [NEt4]+)- A3[VS4]
- A3[NbS4]
- A3[TaS4]
- A2[MoSe4]
- A2[WS4]
- A2[WSe4]
- A[ReS4]
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 diseaseWilson's disease
Wilson's disease or hepatolenticular degeneration is an autosomal recessive genetic disorder in which copper accumulates in tissues; this manifests as neurological or psychiatric symptoms and liver 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
Angiogenesis
Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over terminology, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for the formation of new blood...
, 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
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, age-related macular degeneration, and other diseases featuring excessive blood vessel deposition.