Catalytic reduction of 4-nitrobenzoic acid by cis-[Rh(CO)2(amine)2](PF6) complexes under water-gas shift reaction conditions: kinetics study

Rhodium(I) complexes of the type, cis-[Rh(CO)2(amine)2](PF6) where (amine = 3-picoline, 2-picoline, pyridine, 2,6-lutidina or 3,5-lutidine) dissolved in 80% aqueous amine solutions catalyzed the selective reduction of 4-nitrobenzoic acid to 4-aminobenzoic acid under CO atmosphere. The importance of...

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Bibliographic Details
Published in:Catalysis letters 2004-06, Vol.95 (3-4), p.143-150
Main Authors: FERNANDEZ, Celeste, LUJANO, Eduardo, MACIAS, Ursula, MARCANO, Josseilin, BARICELLI, Pablo J, LONGO, Clementina, MOYA, Sergio A, SOLORZANO, Maria G, ORTEGA, Marisol C, PARDEY, Alvaro J
Format: Article
Language:English
Subjects:
Acids
Catalysis
Chemical reduction
Chemistry
Exact sciences and technology
General and physical chemistry
Nitrobenzoic acid
Pressure dependence
Reaction kinetics
Rhodium
Selectivity
Shift reaction
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
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Summary:Rhodium(I) complexes of the type, cis-[Rh(CO)2(amine)2](PF6) where (amine = 3-picoline, 2-picoline, pyridine, 2,6-lutidina or 3,5-lutidine) dissolved in 80% aqueous amine solutions catalyzed the selective reduction of 4-nitrobenzoic acid to 4-aminobenzoic acid under CO atmosphere. The importance of these catalytic systems is their high chemo selectivity for the aromatic nitro group of the 4-nitrobenzoic acid with respect to the carboxylic group, allowing the production of the desired aromatic amine in high yields. The 4-aminobenzoic acid production depends on the nature of the coordinated amine. The Rh/3,5-lutidine system, the most active catalyst among tested, displays turnover frequencies for 4-aminobenzoic acid production of about 173 moles per mole Rh per day for [Rh] = 1 × 10−4 mol, [4-nitrobenzoic acid] = 3.82 × 10−3mol, 10 mL of 80% aqueous 3,5-lutidine, P(CO) = 0.9 atm at 100 °C. Analyses of kinetic results for the Rh/3,5-lutidine system show a first order dependence on 4-nitrobenzoic acid concentration, a non-linear dependence on CO pressure, a segmented Arrhenius plot and dependence on the nature of the reducing gas agent. These data are discussed in terms of a possible mechanism.
ISSN:1011-372X
1572-879X
DOI:10.1023/B:CATL.0000027287.78214.bf