Ammonium thiomolybdates

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. 

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] ... 

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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