Photocatalysis. Mechanistic studies of homogeneous photochemical water gas shift reaction catalyzed under mild conditions by novel cationic iridium(III) complexes
- Ecole Europeenne des Hautes Etudes, Strasbourg (France) URM 46 du CNRS, Strasbourg (France)
The photochemical water gas shift reaction (WGSR) catalyzed, under mild conditions (25[degrees]C, 1 atm CO, visible light, pH = 7), by [([eta][sup 5]-Me[sub 5]C[sub 5])Ir[sup III](bpy)X][sup +] (bpy = 2,2[prime]-bipyridine, X = H, Cl), [([eta][sup 5]-Me[sub 5]C[sub 5])Ir[sup III](phen)X][sup +] (phen = 1,10-phenanthroline, X = H, Cl), or [([eta][sup 5]-Me[sub 5]C[sub 5])Ir[sup III](bpyRR[prime])Cl][sup +] (R = R[prime] = COOH, COOiPr, Br, NO[sub 2], NMe[sub 2] in the 4,4[prime]-positions or R = R[prime] = COOH, R = H and R[prime] = SO[sub 3]H in the 5,5[prime]-positions of the bpy ligand) has been investigated. A turnover frequency for H[sub 2] formation of 32 h[sup [minus]1] was obtained in an aqueous phosphate buffer containing [([eta][sup 5]-Me[sub 5]C[sub 5])Ir[sup III](bpy-4,4[prime]-(COOH)[sub 2]Cl)][sup +] as catalyst, over a 7-h irradiation period at a constant CO pressure of 1 atm. An increase of 1 order of magnitude in catalytic activity was observed for the bpy ligand substituted with two carboxylate groups in the 4,4[prime]- or 5,5[prime]-positions or with one sulfonate group in the 5-position (over the nonsubstituted bpy equivalent). Conversely, catalytic activity was lost when the bpy was substituted with two dimethylamino groups. The presence of an electron withdrawing group on the bpy-chelate was shown to decrease the activation energy of the process (E[sub a] = 14.6 kJ mol[sup [minus]1] for R = COOH, E[sub a] = 22.2 kJ mol[sup [minus]1] for R = COOiPr), cf. the unsubstituted ligand (E[sub a] = 29.6 kJ mol[sup [minus]1] for R = H). 64 refs., 8 figs., 5 tabs.
- OSTI ID:
- 6783985
- Journal Information:
- Journal of the American Chemical Society; (United States), Vol. 115:1; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON MONOXIDE
PHOTOCHEMICAL REACTIONS
IRIDIUM COMPLEXES
CATALYTIC EFFECTS
WATER
ACTIVATION ENERGY
CARBON DIOXIDE
CATALYSTS
CATIONS
CRYSTAL STRUCTURE
HOMOGENEOUS CATALYSIS
HYDROGEN
IRRADIATION
NUCLEAR MAGNETIC RESONANCE
CARBON COMPOUNDS
CARBON OXIDES
CATALYSIS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
COMPLEXES
ELEMENTS
ENERGY
HYDROGEN COMPOUNDS
IONS
MAGNETIC RESONANCE
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RESONANCE
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400500 - Photochemistry