Molybdothiol complex catalysts

One characteristic feature of the molybdothiol complex catalysts is the stimulating effect of ATP on the reduction of acetylene (9, 12, 13). Recently, the effect of ATP as well as ADP was found to depend upon the pH of the ATP solution added to the reaction mixture. In addition, the effect of added H2S04 is similar to that of ATP and ADP. 

In conclusion, subtle variations in the molybdothiol-complex catalysts—ligand substitution, coordination donor atom, and central metal ion—have large effects on the catalytic activity of acetylene reduction. The results presented here may offer useful information for a design of catalysts with optimal activity in such complex systems. 

In the reduction of acetylene with molybdothiol and molybdoselenol complex catalysts, the effects of structural variation in ligands, variety of coordination-donor atom, kind of transition-metal ion, and other factors have been surveyed systematically. These factors have profound effects on the catalytic activity. The Mo complexes of cysteamine (or selenocysteamine), its N,N-dimethyl derivative, and its /3-dimethyl derivative give ethylene, ethane, and 1,3-butadiene, respectively, as the major product. The Co (I I) complexes of cysteine and cysteamine show higher catalytic activity than do the corresponding Mo complexes, and the order of the activity in the donor atom, namely S >Se 0 in the Co(II) complexes is consistent with that in the Mo complex systems. On the basis of electron spin resonance (ESR) features of these Mo complex catalysts, a relationship between their ESR characteristics and catalytic activities is discussed. 

Table II. Catalytic Activity of Various Molybdothiol and Molybdoselenol Complex Catalysts in Acetylene Reduction...

Molybdenum iw)and Tungsteriw). The discussion about the nature of molybdenum(iv) in solution continues, evidence being presented for both mononuclear and dinuclear species. Mononuclear oxomolybdate(ii) complex anions have been demonstrated as models for the reduction of CN and N2 by molybdothiol catalyst systems. ... 

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