Thiomolybdates

Of the many molybdenum sulfides which have been reported, only MoS, M0S2 and M02S3 are well established. A hydrated form of the trisulfide of somewhat variable composition is precipitated from aqueous molybdate solutions by H2S in classical analytical separations of molybdenum, but it is best prepared by thermal decomposition of the thiomolybdate, (NH4)2MoS4. MoS is formed by heating the calculated amounts of Mo and S in an evacuated tube. The black M0S2, however, is the most stable sulfide and, besides being the principal ore of Mo,... 

Persulfo-cyansaure, /. perthiocyanic acid, per-sulfocyanic acid, -molybditnsaure, /. per-thiomolybdic acid, tbiopermolybdic acid, -zyansaure, /. perthiocyanic acid. Perthiokoblensaure, /. perthiocarbonic acid, penianisch, a. Peru, Peruvian. 

Thiolates, generated in situ by the action of ammonium tetra-thiomolybdate on alkyl halides, thiocyanates, and disulfides, undergo conjugate addition to a, (1-unsaturatcd esters, nitriles, and ketones in water under neutral conditions (Eq. 10. II).29 Conjugate addition of thiols was also carried out in a hydrophobic ionic liquid [bmim]PF6/water-solvent system (2 1) in the absence of any acid catalyst to afford the corresponding Michael adducts in high to quantitative yields with excellent 1,4-selectivity under mild and neutral conditions (Eq. 10.12). The use of ionic liquids helps to avoid the use of either acid or base catalysts... 

Syntheses, Structures, and Reactions of Binary and Tertiary Thiomolybdate Complexes Containing the (0)Mo(Sx) and (S)Mo(Sx) Functional Groups (r = 1,2,4)... 

In terrestrial vegetation, molybdenum and sulfur interfere with copper-induced deficiencies (Gupta 1979). Copper poisoning in cattle and other ruminants is governed by dietary concentrations of molybdenum and sulfate (Lewis et al. 1967 Todd 1969 Buckley and Tait 1981 Eisler 1989). Molybdenum and sulfur in mammalian diets cause a decrease in the availability of copper because of the formation of the biologically unavailable copper-thiomolybdate complex (Aaseth and Norseth 1986). Cattle die when grazing for extended periods on pastures where the ratio of copper to molybdenum... 

Suttle, N.F. 1980. The role of thiomolybdates in the nutritional interactions of copper, molybdenum, and sulfur fact or fantasy Ann. N.Y. Acad. Sci. 355 195-207. 

Suttle, N.F. 1983b. A role for thiomolybdates in the Cu x Mo x S interaction in ruminant nutrition. Pages 599-610 in P. Bratter and P. Schramel (eds.). Trace Element-Analytical Chemistry in Medicine and Biology, Vol. 2. Walter de Gruyter, New York. 

Suttle, N.F. and A.C. Field. 1983. Effects of dietary supplements of thiomolybdates on copper and molybdenum metabolism in sheep. Jour Comp. Pathol. 93 379-389. 

Holmes-Maxted A process for removing organic sulfur compounds from coal gas. The gas, mixed with hydrogen, is passed over a metal thiomolybdate catalyst at 300 to 380°C, which converts the sulfur compounds to hydrogen sulfide which is then absorbed by iron oxide. Developed by E. B. Maxted at W. C. Holmes Company, UK, based on an invention made in 1937. More than 50 units were in operation by 1985. 

Mo use is not confined to prokaryotes similar enzymes are also formd in eukaryotes (including humans). Mo deficiency is rare, as are disorders of Mo metabolism, but symptoms may be induced if diets are rich in Cu or W, which are Mo antagonists. The direct toxicity of Mo is low, but Mo is an antagonist for Cu in cattle, where thiomolybdates formed in the rumen act as high-alfinity ligands for Cu. Hence intake of foods high in Mo can induce the disease molybdenosis (Mills and Davis 1987). 

Table 2 Structural Diversity Observed for Thiomolybdate(VI) Complexes of Copper(I)...

Mo NMR spectra have been reported for Cu1, Ag1 and Au1 complexes of the [MoOnS4 ]2 (n = 0-2) ions.28,29,32 41,49 The resonance position is characteristic of the complex and, as is seen clearly for the Cu1 systems, the chemical shift (from [Mo04]2-) decreases regularly (by ca. 500 p.p.m.) for each CuX unit bound to the thiomolybdate(VI) core. 

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