Size-dependent reactivity of cobalt cluster ions with nitrogen monoxide: Competition between chemisorption and decomposition of NO

Reactions of NO molecules on cobalt cluster ions were studied in a beam-gas geometry by using a tandem mass spectrometer. Single-particle collision reactions of Co_mNO⁺ (m = 3–10) with NO were found to proceed in such a manner that NO decomposition dominates at m = 4–6 with the maximum reaction cross section at m = 5 and chemisorption dominates in m ≥ 7. On the other hand, in two-particle collision reactions of Co_n⁺ (n = 2–10) with NO, NO decomposition at n ≥ 5 and chemisorption of two NO molecules with Co atoms loss at n ≥ 8 were found to proceed. These results indicate that the size-dependency of the multiple collision reactions originates from secondary attacking of an NO molecule to primary products of the initial single collision reactions. The DFT calculation supports the scheme that both the decomposition and chemisorption of two-particle collision reactions proceed via a common intermediate, Co_mN₂O₂⁺, in which the two NO molecules are dissociatively chemisorbed on the cobalt cluster ion, and the size-dependency of the two-particle collision reactions is explained in terms of the structure of this reaction intermediate.     

Quadrupole polarizability and hyperpolarizability of carbon monoxide

Summary We report a study of the electric dipole-quadrupole (A _,,), quadrupole-quadrupole (C _,,), dipole-octopole (E _,) polarizability and the dipole-dipole-quadrupole (B _,,) hyperpolarizability of carbon monoxide. All values are obtained from finite-field self-consistent field (SCF) and fourth-order manybody perturbation theory (MP4) calculations. Our best values for the dipole-octopole polarizability areE _z,zzz=60.19 andE _x,xxx=–38.06e ² a ₀ ⁴ E _h ^–1 . For the dipole-dipole-quadrupole hyperpolarizability we reportB _zz,zz=–296,B _xz,xz=–170,B _xx,zz=88 andB _xx,xx=–178e ³ a ₀ ⁴ E _h ^–2 .     

Transition-metal-catalyzed carbonylation of allenes with carbon monoxide and thiols

In the presence of a catalytic amount of tetrakis(triphenylphosphine)platinum(0), allenes undergo carbonylative thiolation with carbon monoxide and thiols to provide the corresponding α,β- and β,γ-unsaturated thioesters in good yields. In contrast, the use of rhodium(I) catalysts such as RhH(CO)(PPh₃)₃ in place of Pt(PPh₃)₄ leads to copolymerization of allenes and carbon monoxide without incorporation of thio groups.     

Facile generation and morphology of Pd nanoparticles from palladacycles and carbon monoxide

Treatment of PdCys or palladium salts with carbon monoxide (1 atm) in DMF or toluene at room temperature results in a solution of palladium nanoparticles whose morphology depends on the PdCy or palladium salt. Unusual triangular shaped 2-12 nm nanoparticles result from PdCys 1 and 3.     

Coordination compounds of cobalt porphyrins with nitrogen monoxide

Complex formation of NO and the NO ₂ ⁻ ion with cobalt porphyrins bearing various substituents in the porphyrin macrocycle, viz., tetraphenylporphine (1), β-octabromo-meso-tetraphenylporphyrin (2), protoporphyrin IX (3), and 5,10,15,20-tetra(4N-carboxymethylene-pyridyl)porphyrin tetrabromide (4), was studied. The stability constants of the nitrosyl and nitrite extracomplexes in water and in ethanol were determined. Porphyrin 4 forms the most stable extracomplexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 715–718, April, 2007.     

Formation conditions and thermodynamic model predictions of carbon monoxide hydrates

With a fine accuracy and conciseness, Chen-Guo hydrate model has been widely applied to predict the hydrates formation conditions of different systems, including inhibitor containing systems and salt containing systems. However, the model could not predict the formation condition of carbon monoxide (CO) hydrates as the parameter values of CO required in the calculation are not available. In this work, CO hydrate formation pressures were measured at different temperatures in tetrahydrofuran (THF) solution first, then the parameter values of CO required in Chen-Guo model were fitted completely for the first time. On that basis, the hydrates formation conditions of different systems including CO were predicted by the model to verify the accuracy of the fitted values. The comparison between the predicted results and our experimental data (or literature data) shows that the absolute average deviation percentage (AADP) of structure I hydrates is no more than 1.481%, and the AADP of structure II hydrates is less than 6.796%. It is proved that the fitted parameter values of CO are credible, and Chen-Guo model is capable of predicting the formation conditions of CO hydrates. The experimental results and model modifications extend the applied range of Chen-Guo model and promote the development of CO hydrates thermodynamics research.     

Mechanistic model of disproportionation of nitrogen monoxide on CaHY-type zeolite

Infrared spectra produced by adsorbing, by evacuating and by readsorbing NO on CaHY-type zeolite were examined. The absorption peaks were identified by comparing the spectra produced by adsorbing and by evacuating N₂O and NO₂. Based upon the experimental evidence, an eight-step mechanism was proposed for the behavior of NO on CaHY-type zeolite. A mechanistic model of the disproportionation reaction of NO was deduced from the variation of the spectra with time.     

Indole synthesis: palladium-catalyzed C-H bond amination via reduction of nitroalkenes with carbon monoxide

Nitroalkenes have been called ‘chemical chameleons’ due to their versatility in numerous synthetic transformations. Herein, we describe the first transition metal-catalyzed transformation of conjugated nitroalkenes into indoles. Under mild reaction conditions (1 atm carbon monoxide, 110 °C), palladium catalyzes the reductive cyclization of nitroalkenes to form a putative nitrosoalkene intermediate, which then rearranges to provide 3-arylindoles in high yields. Notably, this novel C-H bond amination takes advantage of carbon monoxide as an inexpensive stoichiometric reductant and produces carbon dioxide as the major byproduct.     

Electrochemical generation of a nickel–carbonyl complex, catalyst for the electroreductive coupling of organic halides and carbon monoxide into ketones

The nickel–carbonyl complex Ni(CO)bpy is involved in the nickel-catalysed electroreductive coupling of organic halides and carbon monoxide into ketones. The active species is obtained from a stoichiometric mixture of Ni⁰, 2,2′-bipyridine and CO. The electrochemical method used to generate this complex allows a good tuning of Ni⁰ production versus CO dissolution. We have shown that Ni(CO)bpy results from a CO equilibrium exchange between Ni(CO)₂bpy and Nibpy.     

A quantitative study of carbon monoxide and carbon dioxide evolution during thermal degradation of flame retarded epoxy resins

Thermogravimetric analysis (TGA) combined with infrared analysis of the evolved gases analysis (EGA) has been used to study the thermal degradation behaviour of epoxy resin both in air and nitrogen. The mass loss as a function of temperature has been correlated with the evolution of carbon monoxide (CO) and carbon dioxide (CO₂), and oxygen consumption as measured using an oxygen analyser. An analytical technique has been developed to quantitatively measure the carbon monoxide and dioxide gases evolved. The effect of a range of flame retardants containing phosphorus, nitrogen and halogen elements on CO and CO₂ evolution during thermal degradation of flame retarded epoxy resins has also been observed.     

Palladium(II)-catalyzed carboxylation of benzene and other aromatic compounds with carbon monoxide under very mild conditions

Aromatic compounds such as benzene, toluene, chlorobenzene, anisole, and naphthalene were carboxylated by palladium(II) acetate catalyst with carbon monoxide in the presence of potassium peroxodisulfate in trifluoroacetic acid (TFA) at room temperature under atmospheric pressure. The aromatic carboxylic acids were formed in good yields; for example, the carboxylation of benzene with carbon monoxide proceeds quantitatively under the optimal conditions.     

Property and structure of various platinum catalysts for low-temperature carbon monoxide oxidations

The oxidation of carbon monoxide (CO) has received more attention in the last two to three decades owing to its importance in different fields. To control this CO pollution, catalytic converters have been investigated. Different types of catalysts have been used in a catalytic converter for CO emission control purposes. Platinum (Pt)-based noble metal catalysts show great potential for CO oxidation in catalytic converters with high thermal stability and tailoring flexibility. Pt metal catalysts modified with promoters such as alkali metals and reducible metal oxides have received great attention for their superior catalytic activities in CO oxidation. Temperature, close environment of the catalyst, and chemical composition in the surface layer of the catalyst have a huge effect on the active phase dispersion and O₂ adsorption capacity of the Pt metal catalysts. The main difference in activities of Pt metal catalyst for CO oxidation in O₂ or H₂ atmosphere has found. The addition of supports in Pt metal catalysts has improved their performances and reduced their cost. These improvement strongly depends on the surface structure, morphology, number of active sites, and various Pt-O interactions. Many research articles have already been published in CO oxidation over Pt metal catalysts, but no review article dedicated to CO oxidation is available in the literature.     

Synthesis and properties of copolymers of ethylene/carbon monoxide with styrene/carbon monoxide

The terpolymerization of ethylene, styrene, and carbon monoxide was accomplished by two different palladium‐based catalysts: a phosphine‐based ligand system and a nitrogen‐based ligand system. The range of possible compositions and the composition dependence of the properties of the resulting polymers were determined. These polymers were essentially carbon monoxide versions of the ethylene styrene interpolymers recently presented by Dow. A comparison between the two families of polymers is attempted. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 752–757, 2000     

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.     

Trace carbon monoxide and hydrogen conversion prior to cryogenic distillation of air

Liquid Nitrogen is required in the semiconductor industry. This is generally produced by cryogenic distillation of air. However, trace levels of Carbon Monoxide and Hydrogen need to be removed from Nitrogen prior to its use in the semiconductor industry. This may be accomplished by catalytic conversion of trace Carbon Monoxide and Hydrogen to Carbon dioxide and Water, respectively. These impurities (Carbon dioxide and Water) are then removed by adsorption from air. The latest technology is to incorporate the catalytic conversion into adsorption based thermal swing pre-purification units, which are already used to remove Water and Carbon dioxide from air prior to its cryogenic distillation. Our experiments show that even though Hydrogen is converted to Water by a catalytic reaction, presence of Carbon dioxide in this stream significantly lowers the performance of the catalyst by as much as five-fold. Also, Hydrogen removal by the novel metal Pd catalyst does not follow a typical catalyst behavior but an adsorption breakthrough type behavior, i.e. for a constant inlet concentration the outlet concentration of Hydrogen breaks through at some time and then increases with time. On the other hand, Carbon monoxide conversion on a Hopcalite type catalyst follows typical catalyst behavior, i.e. for a constant inlet concentration the outlet concentration of Carbon monoxide is constant and does not change with time. Experimental data demonstrating these effects followed by a theoretical explanation are presented.     

Cobalt-catalyzed synthesis of -caprolactam and nylon-6 from aminopentene and carbon monoxide

-Caprolactam and nylon-6 oligomers were synthesized from 4-pentene-1-amine and/or 3-pentene-1-amine and carbon monoxide using Co₂(CO)₈ as catalyst. The results show that the volatile fraction of the product mixture is composed of -caprolactam, 3-methyl-2-piperidinone and 3-ethyl-2-pyrrolidinone, while the solid residue mainly consists of nylon-6 oligomers. The addition of excess PEt₃ as ligand can significantly improve the regioselectivity to -caprolactam. Using 3-pentene-1-amine as starting material leads to the same results as 4-pentene-1-amine due to rapid C=C bond isomerization.     

The interaction of formohydroxamic acid with nitrogen: FTIR matrix isolation and ab initio studies

Argon matrix infrared spectra of the complexes formed between formohydroxamic acid, HCONHOH (FHA) and nitrogen have been recorded. The experimental results indicate formation of two isomeric complexes in which the nitrogen atom of the N₂ molecule is attached to the NH or OH groups of FHA. Theoretical studies of the structure and spectral characteristics of the complexes were carried out on the MP2 level with the 6-311++G(2d,2p) basis set. The calculated vibrational frequencies for the complexes present in the matrices are in good agreement with the experimental data.     

Determination of carbon monoxide in ambient air using piezoelectric crystal sorption detection

A new piezoelectric quartz crystal (PQC) sorption detector was developed to monitor carbon monoxide (CO) at sub-ppm level in ambient air. Out of the 28 coating materials studied, the palladium(II) acetamide complex with a 1:10 mole ratio of Pd(II) to acetamide was found to be the best. The detection is based on a non-reversible gas/coating interaction with sensitivity depending on gas flowrate. For 5-15 min exposure at a flowrate of 50 ml/min, the working ranges were found to vary from 0.7 to 40 ppm (total exposure from 8 to 160 μg CO) and detection limits (S/N=2) from 0.7 to 2 ppm CO (total exposure to 8 μg CO). The repeatability at 10 ppm CO was 11.8% (R.S.D. for n=3). The sensor lifetime was found dependent on exposure up to 160 μg CO or not exceeding 1000 Hz accumulative shift of frequency to avoid saturation of active sites at the crystal surface. No interference to CO detection was found for H₂, H₂S, SO₂, NO₂, CO₂, HCHO, gasoline and water vapors at concentrations much higher than ambient air. Compared to existing CO monitor, the PQC detector developed has advantages of adequate selectivity, high sensitivity, fast response and a much lower detection limit for detecting CO at sub-ppm levels. However, it is limited by the total exposure to a maximum of 160 μg CO that restricts its application to intermittent monitoring of low CO concentration. The present work has demonstrated the advantages of using strong non-reversible interaction to enhance PQC sensitivity, as the total exposure can be adjusted easily by a suitable control of the gas flowrate.