Showing papers on "Cobalt published in 1974"

Studies on the gorwth of Thiobacillus ferrooxidans. 3. Influence of uranium, other metal ions and 2:4-dinitrophenol on ferrous iron oxidation and carbon dioxide fixation by cell suspensions.

Abstract: Suspensions ofThiobacillus ferrooxidans in Warburg flasks oxidized ferrous iron and coupled14CO2 fixation to the oxidation. The sulphates of zinc, cobalt, copper, nickel or uranium (0.1–1.0 M) depressed the rate of Fe2+ oxidation: nickel and uranyl ions were the most inhibitory. Uranyl, copper and nickel ions inhibited iron-dependent CO2-fixation, the two former producing a marked uncoupling effect on CO2-fixation, similar to that produced by 2:4-dinitrophenol. Molybdate also inhibited iron oxidation. Incorporation of14C-labelled amino acids and glucose was largely dependent on energy from ferrous-iron oxidation and was also strongly inhibited by uranyl sulphate. Kinetic analysis of the inhibition of iron-oxidation by uranium indicated mixed competitive and non-competitive inhibition. Little binding of238U,63Ni or59Fe toT. ferrooxidans was observed and the effects of uranium were concluded to result mainly from loose binding at sites on the cell membrane concerned with iron-oxidation and possibly the transport of other metals. Molybdate probably interfered with sulphate-dependent steps of iron oxidation. Uncoupling of CO2-fixation probably resulted in part from interference with energy metabolism and could depend on transport of uranyl ions through the cell membrane. CO2-fixation by an uraniumtolerant culture (U+) was less sensitive to uranyl-inhibition than that by the wild-type strain (U−), but iron oxidation and CO2-fixation were much more sensitive to uranium when the U− organisms were previously cultured on thiosulphate rather than ferrous iron.

X-ray photoelectron spectra of cobalt compounds

Abstract: The X-ray photoelectron spectra of a variety of cobalt(II) and cobalt(III) complexes have been investigated. Intense satellite lines were observed for the 2p, 3s and 3p peaks in the case of the high spin cobalt(II) compounds, but not for low spin cobalt(III) complexes. The satellites of the 2p levels are best explained as arising from shake-up processes, whereas those of the 3s and 3p levels are thought to arise largely from multiplet (exchange) splitting of the levels. Multiplet splitting of the 2p level is small and responsible for an increase in the doublet separation of the 2p1/2, 2p3/2 spin-orbit levels of the high spin cobalt(II) compounds. The chemical shifts for cobalt differ for the 2p, 3s and 3p levels of the high spin cobalt(II) compounds. Those of the 2p and 3p levels of diamagnetic cobalt(III) and low spin cobalt(II) complexes are equal. The difference in the case of the high spin cobalt(II) compounds is thought to be due to the presence of unpaired 3d electrons.

Compounds Derived from Alkynes and Carbonyl Complexes of Cobalt

Abstract: Publisher Summary This chapter discusses the development of metal carbonyl chemistry. Solutions of octacarbonyldicobalt in hydrocarbon solvents can be prepared by a high–pressure reaction between a cobalt compound, such as cobalt carbonate, and a mixture of carbon monoxide and hydrogen. Solutions of octacarbonyldicobalt in petroleum solvents react readily at room temperature with a large variety of alkynes to give complexes of general formula Co2(CO)6(RC2R´). Octacarbonyldicobalt decomposes readily at about 50°–60°C to give dodecacarbonyltetracobalt, and this thermal degradation reaction provides a convenient synthesis of Co4(CO)12 on a small scale. The rate of exchange of carbon monoxide with several other CO2(CO)6(RC2R´) complexes in hexane is investigated. The mercury carbonylcobalt compound Hg[Co(CO)4]2 is obtained by the treatment of the anion [Co(CO)4]– with mercury salts, such as Hg(CN)2 and by the treatment of Co2(CO)8 with Na/Hg. Hg[Co(CO)4]2 is obtained as orange air-stable crystals of m.p. 81°–82°C. The infrared spectrum of the solutions of the compound in CS2 show vco at 2028 and 1967 cm–l, and the nuclear magnetic resonance (NMR) spectrum of the CS2 solution shows the cyclopentadienyl proton resonance as a sharp singlet at δ 5.00. The unsymmetrical isomer 2,4–bis(pentafluorophenyl)–3,5–diphenylcyclopentadienone–n–cyclopentadienylcobalt is the only product isolated from the reaction of (π–C5H5)CO(CO)2 and C6H5C=CC6F5. The involvement of metalocyclopentadiene intermediates in the cyclotrimerization of alkynes has been established for some metal systems.

Catalyst for electroless deposition of metals

Abstract: A solvent method for the metallization of a non-conductive surface with gold, nickel or copper is shown whereby on a substrate a thermosensitive coordination complex of palladium is deposited; the complex has the formula LmPdXn wherein L is a ligand or unsaturated organic radical, X is a halide, alkyl group or a bidentate ligand and m is an integer from 1 to 4 and n is from 0 to 3; trimethyl phosphite palladium dichloride complex is an appropriate illustration of the complex; the palladium complex is applied on the substrate in a suitable non-aqueous solution such as tetrahydrofuran solution; the complex is then baked in air at elevated temperature; the exposure to high temperature decomposes the complex leaving a residue which is catalytic to the deposition of gold, nickel, cobalt or copper from an electroless bath thereof; the non-conductive material is then immersed in an electroless bath to metallize the areas which have been rendered catalytic; the preferred thermosensitive coordination complex of palladium is trimethyl phosphite palladium dichloride; a requirement for a proper thermal exposure of the complex is that the substrate is capable of withstanding the elevated temperatures such as above 210°C; illustrative organic substrates are polyimides, polysulfones, silicones, vulcanizates, fluoroplastics, polyphenylene sulfides, polyparabanic acids, and polyhydantoin, etc.

Electrocatalysis by metal phthalocyanines in the reduction of carbon dioxide

Abstract: It is shown that cobalt and nickel phthalocyanines are active catalysts for the electrode reduction of carbon dioxide.

Catalytic process for reducing nitrogen oxides to nitrogen

Abstract: A catalyst compositions for reducing nitrogen oxide comprising, as its chief ingredient, an intimate mixture of A. titanium (Ti) as component A, with B. at least one metal selected from the group consisting of molybdenum (Mo), tungsten (W), iron (Fe), vanadium (V), nickel (Ni), cobalt (Co), copper (Cu), chromium (Cr), and uranium (U), as component B, in the form of their oxides, and a process for reducing nitrogen oxides to nitrogen, which comprises contacting a gaseous mixture containing nitrogen oxides and molecular oxygen and a reducing gas with aforesaid catalyst compositions at an elevated temperature.

Preparation and spectroscopic studies of cobalt(II) derivatives of blue copper proteins.

Abstract: Preparation of cobalt(II) derivatives of type 1 copper proteins has been extended to include bean plastocyanin and azurin from Pseudomonas aeruginosa. Fluorescence quenching data suggest that Co(II) binds to the type 1 site of both apoplastocyanin and apoazurin. Electronic absorption spectral measurements have been made for cobalt(II)-stellacyanin, cobalt(II)-plastocyanin, and cobalt(II)-azurin. In each case two visible bands with moderate intensities and two rather strong ultraviolet absorption peaks are observed. The intensity pattern and the separation of the two ultraviolet bands in the Co(II) derivatives correspond closely to the two intense, low-lying absorption peaks in the analogous, type 1 copper proteins. The evidence suggests that the intense, two-band systems represent ligand-to-metal charge transfer transitions in both Cu(II) and Co(II) derivatives. It is proposed that the transitions in each case originate in the 3pπ and 3pσ orbitals of a cysteine sulfur ligand at the type 1 site. The visible absorption bands in the Co(II) derivatives are assigned to d-d transitions. The large 4P splitting observed indicates that the type 1 Co(II) site is of low symmetry. The d-d band pattern suggests that the high-spin Co(II) center is either distorted tetrahedral or five-coordinate. The observed band intensities are in much closer accord with the values for Co(II) complexes known to have distorted tetrahedral structures.

Structural investigations of amorphous transition element films I. Scanning electron diffraction study of cobalt

Abstract: Thin films of cobalt, prepared in ultra-high-vacuum at 4 K and examined in situ by scanning electron diffraction, are shown to be amorphous with a radial distribution function similar to that obtained theoretically by serial deposition of atoms in the computer-simulated model developed by Bennett. The effects of removal of lossy electrons (by velocity filtering), subtraction of substrate background, and multiple scattering on the diffraction profile are investigated and discussed.

Structural investigations of amorphous transition element films: II. Chromium, iron, manganese and nickel

Abstract: Thin films of iron, chronium, manganese and nickel have been prepared in ultra high vacuum at 4 K and examined by scanning electron diffraction. Amorphous structures have been identified in iron, chromium and manganese and their respective interference functions found to be similar to each other and to that for cobalt. An argument is given supporting the concept of a truly amorphous phase devoid of crystalline order, as distinct from a miorocrystalline array. This argument is based not only on experimental structural results but on computer-simulated models together with magnetic and electron transport measurements. No evidence was found of an amorphous phase in clean nickel films. Some explanations are suggested for the inconsistencies between the present and earlier work, particularly in the case of nickel and iron.

The role of cobalt and molybdenum sulphides in hydrodesulphurisation catalysts: A review☆

Abstract: Although originally in the form of cobalt and molybdenum oxides, the usual hydrodesulphurisation catalysts undergo extensive reduction and sulphurisation before and during the hydrodesulphurisation process. Many researches have been devoted to the study of the relationship between the properties of the oxides and the catalytic activity. Much less work has been concerned with the role of the sulphides. The purpose of the present review is to summarise the information which has been gained concerning the role of cobalt and molybdenum sulphides in hydrodesulphurisation and hydrotreating catalysts. We first briefly review the structure of the various cobalt or molybdenum sulphides and of the only compound sulphide, CoMo 2 S 4 , at present known. A second part is devoted to the results concerning the adsorption properties and the catalytic activity of the simple sulphides. Cobalt sulphides exhibit no significant activity. The discussion is centered on MoS 2 . A third part is concerned with the roie of mixed or compound sulphides in catalysis. The possible action of oxides or of oxygen containing phases present with the sulphides is first discussed. Some results suggest that the sulphides might be the only active phases in catalytic conditions. Catalysis by the sulphides should be explained by some promoting effect of cobalt on MoS 2 . The possible mechanisms for this promoting effect are reviewed. An extensive study of e.p.r. signals of hydrodesul-phurisation catalysts has been made. E.p.r. signals of cobalt-molybdenum sulphides are briefly discussed in this connection.