Coadsorption of carbon monoxide and copper atoms on rhodium electroplates

The partial removal of copper atoms from a preliminarily formed Cu_ad layer and the adsorption of Cu²⁺ cations in the presence of a CO_ads monolayer were demonstrated for Rh/Pt electrodes by means of transients of current and potentiodynamic and analytical measurements. The electrooxidation of the mixed CO_ads + Cu_ad layer in the course of anodic potential scans is shown to be accompanied by simultaneous removal of both species in a wide potentials range.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 367–370.Original Russian Text Copyright © 2005 by Gladysheva, Podlovchenko.     

Inactivation of acetyl-CoA synthase/carbon monoxide dehydrogenase by copper

Two recent crystal structures of acetyl-CoA synthase (ACS) from Moorella thermoacetica exhibited different metal contents and geometries at their active site, called the A-cluster. This led to the proposal of two catalytic mechanisms, one Ni-based, the other Cu-based. ACS was studied with respect to synthase activity, methyl group transfer activity, metal content, and EPR spectroscopy. Our results indicate that Cu is not required for catalysis and that it inactivates ACS by binding to the proximal site of the A-cluster. With Cu in this site, the A-cluster cannot accept a methyl group from the corrinoid-iron-sulfur protein, nor can it exhibit the NiFeC EPR signal after treatment with CO.     

Photoinduced carbon monoxide migration in a synthetic heme-copper complex

Time-resolved infrared (TRIR) flash photolytic techniques have been employed to initiate and observe the efficient dissociation of CO from a synthetic heme-CO/copper complex, [((6)L)Fe(II)(CO)..Cu(I)](+) (2), in CH(3)CN and acetone at room temperature. In CH(3)CN, a significant fraction of the photodissociated CO molecules transiently bind to copper (nu(CO)(Cu) = 2091 cm(-)(1)) giving [((6)L)Fe(II)..Cu(I)(CO)](+) (4), with an observed rate constant, k(1) = 1.5 x 10(5) s(-)(1). That is followed by a slower direct transfer of CO from the copper moiety back to the heme (nu(CO)(Fe) = 1975 cm(-)(1)) with k(2) = 1600 s(-)(1). Additional transient absorption (TA) UV-vis spectroscopic experiments have been performed monitoring the CO-transfer reaction by following the Soret band. Eyring analysis of the temperature-dependent data yields DeltaH(double dagger) = 43.9 kJ mol(-)(1) for the 4-to-2 transformation, similar to that for CO dissociation from [Cu(I)(tmpa)(CO)](+) in CH(3)CN (DeltaH(double dagger) = 43.6 kJ mol(-)(1)), suggesting CO dissociation from copper regulates the binding of small molecules to the heme within [((6)L)Fe(II)..Cu(I)](+)(3). Our observations are analagous to those observed for the heme(a3)/Cu(B) active site of cytochrome c oxidase, where photodissociated CO from the heme(a3) site immediately (ps) transfers to Cu(B) followed by millisecond transfer back to the heme.     

Haems as potential reagents for carbon monoxide

A study of the potential of a myoglobin model system based on dipiperidyltetraphenylporphinatoiron(II) for the spectrophotometric determination of carbon monoxide is reported. At room temperature, oxygen does not bind strongly at the iron centre and does not interfere. Nitric oxide, hydrogen sulphide and carbon dioxide interfere and must be removed before the determination if present in significant amounts. The main disadvantage of this novel method is the low sensitivity (about 300 ppm CO). Possible means of modifying the system to enhance the sensitivity and to further reduce the number of interfering species are discussed.     

Oxidation of carbon monoxide over a copper(II) oxide catalyst

Transient FTIR observations in conjuction with gas phase CO conversion measurements indicate an adsorbed CO species which seems not to participate directly in the oxidation reaction over a silica supported copper(II) oxide catalyst. This observation together with order of reaction determinations suggest that oxidation occurs via an Eley-Rideal mechanism.

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CO CO, (II), . , , , -.

     

Electroreduction of carbon monoxide on palladium electrodeposits in solutions containing copper ions

It is shown that the electroreduction of CO proceeds on electrolytic deposits of palladium (edPd) in 0.5 M H₂SO₄ + (1–5) mM CuSO₄ + CO(sat) solutions at the potentials more positive than the Cu²⁺/Cu equilibrium potential. Among the CO reduction products, methanol and formaldehyde are identified. The current efficiency with respect to CH₃OH exceeds 75% on edPd formed in 1% PdCl₂+0.5 M H₂SO₄ solutions. In addition, Cu⁺ ions, which probably form complexes with CO, are detected in the solution and are assumed to play the role of intermediate species in the mediator catalysis along with copper adatoms.     

Cobalt promoted copper manganese oxide catalysts for ambient temperature carbon monoxide oxidation

Low levels of cobalt doping (1 wt%) of copper manganese oxide enhances its activity for carbon monoxide oxidation under ambient conditions and the doped catalyst can display higher activity than current commercial catalysts.     

Mechanism of carbon monoxide oxidation on nickel oxide and its solid solutions

On the basis of studying the isotope exchange of oxygen and the position of the Fermi level in the system MiO–Li_xNi_1–xO, an explanation is proposed for the compensation effect in the reaction of CO oxidation on nickel oxide and its solid solutions.

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NiO–Li_xNi_1–xO CO .

     

State of the copper ions in the catalysts for oxidation of carbon monoxide to carbon dioxide

The state of the copper ions in the catalysts for the oxidation of carbon monoxide to carbon dioxide, prepared by dissolving an activated copper-containing aluminum alloy in water followed by calcination (method A) and by impregnation of the support produced by dissolving activated aluminum in water with copper nitrate solution (method B), was investigated by diffuse reflection electronic spectroscopy. It was established that the catalysts contain Cu ²⁺ ions stabilized in fields of octahedral symmetry. The concentration of these ions depends on the method of synthesis of the catalyst, its copper content, and the pretreatment temperature. It is higher in the samples produced by impregnation than in the samples produced by fusion; increase in the amount of copper leads to a decrease while increase in the calcination temperature leads to an increase in the concentration of the above-mentioned ions. Treatment of the oxide systems with the reaction mixture does not affect the state and concentration of Cu ²⁺. The catalytic activity of the samples depends on the method of preparation and increases with decrease in the amount of Cu ²⁺ (O_h) and with increase in the content of the CuO phase in the system.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 786–790, April, 1992.     

Copolymerization of ethylene/carbon monoxide by a cationic hydridoaquopalladium complex

The cationic hydridoaquopalladium (II) complex, trans-[(PCy₃)₂Pd(H)(H₂O)]⁺BF^?₄, is an excellent catalyst for the ethylene/carbon monoxide alternating copolymerization in the presence of a bidentate phosphorus ligand and p-toluenesulphonic acid. © 1995 John Wiley & Sons, Inc.     

Replacement of carbon monoxide by π-ligands in fluorinated iron complex

Conclusions The -allylidene complex is formed in the photochemical reaction of with 1,3-butadiene and 1,3-cyclohexadiene, with subsequent replacement of the carbonyl group by the appropriate ligand.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2130–2131, September, 1977.     

Mechanochemical synthesis of calcium and copper ferrite catalysts for medium-temperature carbon monoxide conversion

The mechanochemical synthesis of calcium and copper ferrites has been investigated by X-ray powder diffraction, X-ray crystallography, thermogravimetric analysis, IR spectroscopy, sedimentation analysis, and chromatography. The effects of mechanical activation and heat treatment on the formation of calcium ferrite with a perovskite structure and copper ferrite with a mixed spinel structure are demonstrated. Calcium and copper ferrites calcined at low temperatures (450–500°C) are catalytically very active in the water-gas shift reaction. CO conversion on calcium and copper ferrites yields a number of by-products. The concentrations of these by-products in the condensate have been determined.     

Reduction of nitrobenzene catalyzed by immobilized copper catalyst under carbon monoxide and water

Catalytic activity for reduction of nitrobenzene to aniline (98%) and azobenzene (2%) using a poly(4-vinylpyridine)-immobilized Cu catalyst [Cu(II)/P(4-VP)] under a CO atmosphere in aqueous 2-ethoxyethanol was studied as a function of the various reaction parameters ([Cu], P(CO), T, and nitrobenzene/Cu molar ratio). Reaction rates were first-order in [Cu]_tot over 1.0–12.0?wt.% range and in P(CO) over the 6.8–27.2?atm range. The catalytic activity proved to be non-linear in nitrobenzene/Cu ratio over 41–500 molar ratio range. These results suggest that the rate-limiting step is preceded by reversible coordination of nitrobenzene to a carbonyl–Cu(I) immobilized species. A catalytic mechanism consistent with the data is proposed.     

Preparation of perlite-based carbon dioxide absorbent

A new highly efficient carbon dioxide absorbent consisting of sodium hydroxide, expanded perlite and acid-base indicator was prepared. The absorption efficiency, absorption capacity, flow resistance and color indication for the absorbent were tested and compared with some commercial products. The absorbent can reduce the carbon dioxide content in gases to 3.3 ppb (v/v) and absorbs not less than 35% of its weight of carbon dioxide. Besides its large capacity and sharp color indication, the absorbent has an outstanding advantage of small flow resistance in comparison with other commercial carbon dioxide absorbents. Applications in gas analysis and purification were also investigated.     

Hayashi ligand-based rhodium complex in carbon monoxide and molecular hydrogen-assisted reductive amination

The CO- and H₂-assisted reductive amination of carbonyl compounds catalyzed by stable chiral Hayashi ligand-based rhodium complex afforded the racemic amines in moderate yields. The racemic outcome of the process results from the elimination of the chiral ligand from the catalyst under the action of hydrogen or carbon monoxide as reductants.     

Nitrogen-containing carbon nanotubes as solid base catalysts

Nitrogen-containing carbon nanotubes (NCNT) are effective re-usable solid base catalysts, their activity for a Knoevenagel condensation being related to the amount of pyridinic nitrogen incorporated in the NCNT structure, which could be tuned by the synthesis parameters of the catalyst.     

Bis-arene-vanadium anions as reducing agents towards carbon dioxide and monoxide

A novel way of activating an alkali metal for the reduction of CO₂ and CO involves dissolving potassium in tetrahydrofuran containing [V(C₆H₆)₂], to give a solution of K[V(C₆H₆)₂] as the actual reducing agent. In contact with CO₂ or CO, the formal V⁻¹ derivative is immediately re-oxidized to the V⁰ complex and C₁ and C₂ products are formed.