Thiomolybdate , ammonium

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... 

When hydrogen sulfide is passed into a strongly ammoniacal solution of copper(II) and molybdate(VI) ions, the initial copper-(II) sulfide precipitate is redissolved, the copper is reduced to the copper(I) state by sulfide ion, and the compound CuNH4MoS4, copper(I) ammonium thiomolybdate(VI), precipitates. The compound has been reported previously by Debray,1 who was unable to characterize it. The following method of preparation is based upon Debray s work and gives superior yields and higher purity. 

Alternatively, the compound can be obtained by letting the deep-red solution, obtained after mixing the solutions, stand at room temperature for 2-4 hours. In this case the product is usually contaminated with crystals of ammonium tetrathio-molybdate(VI), (NH4)2MoS4. The compound also can be obtained in poor yields by dissolving freshly precipitated copper(II) sulfide in ammoniacal ammonium molybdate solution saturated with hydrogen sulfide. Undissolved copper(II) sulfide is removed by filtration after 3-5 minutes, and the copper(I) ammonium thiomolybdate(VI) is obtained by boiling as above. 

The deep green crystals are converted to a red powder on grinding. The material is unaffected by air, but with water it decomposes slowly to form soluble ammonium thiomolybdate and insoluble copper(I) sulfide. The compound crystallizes in the tetragonal space group 14 with unit-cell dimensions of a = 8.000 ... 

Ammonium thiomolybdate, (NH4)2MoS4, was reacted with the metal chloride (AX ) to obtain the precursor compound. 

Fig. 10 (a) Low-resolution TEM images of MoS, nanotubes grown by the decomposition of ammonium thiomolybdate (b) HREM image of the MoSj nanotube. (Reproduced with permission from ref. 21). 

Recently, open-tipped MoS2 nanotubes were prepared by the decomposition of ball-milled ammonium thiomolybdate powder under a H2 + thiophene atmosphere, and used as a catalyst for the methanation of CO with H2.143 The conversion of CO to CH4 was achieved at a much lower temperature compared to polycrystalline MoS2 particles, and there was no deterioration even after 50 h of consecutive catalyzing cycles. This observation is of importance in the context of energy conversion of global C02. 

Of thef/iio-aciV/scorrespondhisfto the sulphides of molyhdemmi, two have been prepared, namely, hexathiomolybdic acid, HMoS . and per-thiomolybdic acid, H MoSj. The former has been obtained by decomposition of the ammonium salt with hydrochloric acid the latter is precipitated as a reddish-brown powder on the addition of dilute acetic acid to a solution of its potassium salt, KHM0S5.-... 

Ammonium oxymolybdenum complexes with amines These complexes are prepared by the acid/base reaction of an acidic molybdenum source such as molybdenum trioxide, molybdic acid, ammonium molybdate [41] and ammonium thiomolybdates with oil-soluble amines [42], The preferred aminic compounds are lubricant additives known as dispersants, examples being succinimides and Mannich-type bases, as in Reactions (4.42) and (4.43) [41] ... 

Spending thioamides in the best yields. Thiolysis of iminium salts derived from amides and oxalyl chloride or phosphoric trichlorides with ammonium tetra-thiomolybdate 40 occurs below room temperature within 2 h (Eq. 10) [32]. It is advantageous that the by-products are easily separated, although H2S is needed in order to prepare 40. 

A steady loss of catalytic activity with the reaction time was observed over two catalysts and the rate of deactivation of in situ activated catalyst is much quicker than ex situ activated catalyst. In ammonium sulphide solution the total amount of sulphur is in excess in comparison with their stoichiometric value for M0S2 plus CoS. After impregnation in ammonium sulphide solution, both the CogSg and thiomolybdate complexes will be formed which is conformed from X-ray diffraction measurements. However, after pre-reduction in the presence of H2 these phases were disappeared. It can be understood that the... 

Several thiosalt precursors such as ammonium thiotungstate (NH4)2WS4 (known as ATT) and tetraalkylammonium thiotungstates (NR4)2WS4 were also used to synthesize WS2 (29). Besides, ammonium thiomolybdate (NH4)2MoS4 (known as ATM) and tetraalkylammonium thiomolybdates (NR4)2MoS4 were also used to obtain M0S2. 

The complexity of the oxide-sulfide transformation leads to some difficulties in sulfiding, for example, tungsten sulfide or other sulfide phases if in interaction with a nonoptimized support. In this respect, the use of thiosalts and more particularly thiomolybdates and thiotungstates represents an interesting alternative to the classical sulfidation of oxides. Ammonium thiomolybdate (NH)2MoS4 (ATM) was first synthesized by Kruss [53] in 1884. Later, Alonso et al. described an improved way of preparing ATM [54]. The synthesis of ammonivun thiotungstate (ATT)... 

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