Water gas shift reaction, catalyzed

Chemistry of the Water Gas Shift Reaction Catalyzed by Rhodium Complexes... 

The rates of the water gas shift reactions catalyzed by the systems derived from M(C0) (M = Cr, Mo, and W) were found to be inversely proportional to the CO pressure as indicated by straight line plots of rates of H2 production versus (l/PC0Kn t... 

This mechanistic scheme agrees with the experimental observations of the first order dependences on M(CO)fi and formate concentrations and the inverse first order dependence on CO pressure for the rate of production in the water gas shift reaction catalyzed by M(CO (M = Cr, Mo and W) in the presence of a base sufficiently strong to generate formate from CO by equation 2. 

Saito and coworkers134 reported on the homogeneous reverse water-gas shift reaction catalyzed by Ru3(CO)i2. Conditions employed were 20 ml of N-methyl-2-pyrrolidone solution 0.2 mmol Ru3(CO)i2 1 mmol bis(triphenylphosphine)immi-nium chloride and C02-H2 1 3 under 80 kg/cm2 at 160 °C. The major products were CO (15.1 mmol), H20 (21.6 mmol), and methanol (0.8 mmol). As no formic acid was detected, and because the authors only detected Ru cluster anion species H3Ru4(CO)i2, H2Ru4(CO)i22, and HRu3(CO)n, they concluded that the mechanism did not involve formic acid as an intermediate. Rather, they proposed that the mechanism proceeds by dehydrogenation of a metal hydride, C02 addition, and electrophilic attack from the proton to yield H20, as outlined in Scheme 48. 

The action nl catalysis cun he illustrated hy an cxample-the water gas shift reaction catalyzed by iron and chromium oxides. 

Nakamura J, Campbell JM, Campbell CT. Kinetics and mechanism of the water-gas shift reaction catalyzed by the clean and Cs-promoted Cu(l 10) surface - a comparison with Cu (111). J Chem Soc Faraday Trans. 1990 86( 15) 2725—34. 

DBU is an effective cocatalyst for the homogeneous water gas shift reaction catalyzed by Ru3(CO),2 or by Os3(CO),2 under basic conditions (83CL1837 85NKK503). 

Figure 22 Water-gas shift reaction catalyzed by FefCOjs. ...

W. A. R. Slegeir, R. S. Saplenra, R. Rayford, L. Lam, Role of homogeneous formate complexes in the water gas shift reaction catalyzed by the Group VI metal carbonyls, Organrane-tallics 1 (1982) 1728-1730. 

T. Yoshida, Y. Leda, S. Otsuka, Activation of water molecule. 1. Intermediates bearing on the water gas shift reaction catalyzed by platinum(O) complexes, J. Am. Chem Soc. 100 (1978) 3941-3942. 

R. Ziessel, Photocatalysis. Mechanistic studies of homogeneous photochemical water gas shift reaction catalyzed under mild conditions by novel cationic iridium(III) complexes, J. Am. Chem. Soc. 115 (1993) 118-127. 

The reduction of CO2 to HCOO might proceed through the formation of a metallocarboxylic species (eq. 6), which after chloride recoordination would give formate and the starting ruthenium complex (eq. 7). Such a complex [Ru(bpy)2(COOH)]+ has been identified and isolated during the thermal water-gas-shift-reaction catalyzed by [Ru(bpy)2(CO)(Cl)] [66]. It could be formed during catalysis, by nucleophilic attack of the Ru(0) complex on the CO2 molecule (eq.6). 

Photochemical Water-gas-shift Reaction Catalyzed by Novel Iridium(III) Complexes... 

This kind of attack is frequently encountered in water gas shift reactions catalyzed by molecular clusters. 

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