Showing papers on "Cobalt published in 1970"

Metallic alloys and exchange-enhanced paramagnetism: application to rare- earth--cobalt alloys.

Abstract: A phenomenological theory is presented of the magnetic properties of two-component alloys, one of whose components has a permanent magnetic moment, and the other an exchange-enhanced paramagnetic susceptibility. The paramagnetic susceptibility, magnetic-ordering temperature, and magnetization at low temperature are discussed in terms of this theory, and the results obtained are applied to cubic alloys $A{\mathrm{Co}}_{2}$ between rare earth ($A$) and cobalt.

The reaction of cobalt with manganese dioxide minerals

Abstract: The adsorption of cobalt, copper, and nickel from solution by a number of synthetic manganese dioxides has been studied, and compared with the release of ions during the reaction. It was found that the initial rapid uptake of all three ions was followed by a period of slow uptake which continued for the duration of the experiment. During the slow phase of the reactions the uptake of cobalt was greater than that of copper or nickel, and cobalt released more manganese into solution. It is suggested that cobalt is able to replace Mn3+ in the crystal lattice, and this theory is supported by arguments based on crystal field theory.

The hydration of divalent cations in aqueous solution. An X-ray investigation with isomorphous replacement

Abstract: With the method of isomorphous replacement direct information about the hydration of cations has been obtained. The study comprises two groups of isomorphous aqueous solutions, viz. one group composed of cadmium and calcium nitrate solutions and another with solutions of the nitrates of zinc, nickel, cobalt and magnesium. The divalent cations appear to have a clear-cut shell of 6 neighbouring water molecules. The cation–water distance is in close agreement with the distances mentioned in the literature for the unit M(H2O)62+. in crystalline substances. A second hydration shell of about 12 molecules of water can be discerned at a distance of about 4.2 A of the cation.

Cobalt‐samarium permanent magnets prepared by liquid phase sintering

Abstract: The preparation and measurement of magnetic properties of cobalt‐samarium permanent magnets prepared by liquid‐phase sintering are discussed. Energy products in excess of 15×106 G Oe were observed. Long time exposure to air at 150°C did not degrade the samples.

Effects of Atomic Configurational Changes on Hyperfine Interactions in Concentrated Iron‐Cobalt Alloys

Abstract: Concentrated Fe-Co alloys, effects of local atomic configurational changes on hyperfine interaction using Mossbauer spectroscopy

Influence of Interactions Between Impurities on the Appearance of Magnetic Moments in Copper-Cobalt Dilute Alloys

Abstract: A simple model is used to describe the magnetic properties of cobalt impurities in copper. Isolated impurities are nonmagnetic with a high spin-fluctuation temperature. Isolated pairs of neighbor cobalt atoms are very nearly magnetic: This gives rise to a large susceptibility and a large electronic specific heat, varying as the square of the concentration $C$. At low temperatures, only the group of three (or more) cobalt atoms carries a magnetic moment.

Crystalline cobalt, zinc, manganese, and iron alkoxides of glycerol

Abstract: A series of crystalline metal glycerolato complexes has been prepared. The preparation of the cobalt, zinc, manganese, and iron complexes [(1 )-(4)] was achieved by heating (above 110o) glycerol with metal acetates, carbonates, oxalates, oxides, or hydroxides. The structure of (1) has been determined by X-rays and contains Co-O-Co-O and Co-O-C-C-O rings. X-ray powder diffraction and i.r. data are given for (1)-(4). These show (1) and (2) to be isostructural and that (3) and (4) are variants of these. The insolubility of (I), (2), (3), and (4) is in accord with their polymeric nature.

Infrared Spectra of Carbon Monoxide Chemisorbed on Metal Films: A Comparative Study of Copper, Silver, Gold, Iron, Cobalt and Nickel

Abstract: Infrared spectra have been obtained of carbon monoxide chemisorbed on very thin metal films deposited at 113 K under ultrahigh vacuum conditions. On iron, cobalt and nickel the spectra are similar to those found with silica-supported metals, but the absorption bands appeared only at high coverage, indicating that only a part of the adsorbed gas is responsible for them. On copper, silver and gold the adsorbed carbon monoxide is infrared active at low coverages, with bands at 2105, 2160 and 2110 cm$^{-1}$ respectively. Only one absorption band occurs on each metal, and on copper and gold the absorbance increases linearly with coverage. The extinction coefficients are 1 $\times $ 10$^{-17}$ and 2 $\times $ 10$^{-17}$ molecule$^{-1}$ cm$^{2}$ on copper and gold respectively. The relations between frequency, surface potential and heat of adsorption on the noble metals are discussed in terms of $\sigma -$ and $\pi $-bonding.

Environmentally disintegratable plastic compositions comprising copolymers of ethylene and carbon monoxide and a degradation accelerator

Abstract: Compositions comprising (1) a copolymer of ethylene and 0.1 percent to 18 percent by weight of carbon monoxide, said percentage range being the proportion of carbon monoxide in the copolymer, and (2) an ultraviolet light degradable amount of an organometallic compound or salt of a common metal, e.g., ferricine, cobalt acetyl acetonate, etc., whereby film, articles of manufacture and especially packaging means, upon exposure to ultraviolet rays emitted by the sun are capable of accelerated deterioration thereby causing such materials including packaging means to decompose forming dust or flakes which may become embedded in the soil or carried away by rain water under those circumstances where they are thrown away out of doors so as to be exposed to natural environmental conditions.

Tetrahedral complexes of cobalt(II) with L-histidine, histamine, imidazole, and N-acetyl-L-histidine

Abstract: In highly alkaline aqueous solutions, cobalt(I1) forms violet, tetrahedral, bis complexes with L-histidine, histamine, and N-acetyl-L-histidine. Imidazole similarly forms a tetrakis complex. Generation of the tetrahedral complexes is dependent on deprotonation of the imidazole ring pyrrole nitrogen for the L-histidine, histamine, and imidazole complexes, and on two amide hydrogen ionizations for the 2 : 1 N-acetyl-L-histidine complex. The tetrahedral complexes all possess four nitrogen donor atoms, at least two of which are negatively charged. Approximate, average pK, values for metal ion promoted pyrrole hydrogen ionizations from 2 : 1 complexes of L-histidine with cobalt(I1) and copper(I1) are 12.5 and 11.7, respectively. Minimization of steric crowding and reduction of charge repulsion appear to be the reasons for cobalt(I1) preferring a tetrahedral environment to an octahedral one in these cases. n a recent study of some oxygenation reactions, the I properties of several cobalt(I1) complexes of amino acids in oxygen-free solution were reported. For cobalt(I1) solutions containing L-histidine, raising the pH to about 12 produces a color change from pale pink-yellow to deep violet. This change has been ascribed to the conversion of octahedral 2 : 1 histidinecobalt(I1) complexes to a 2 : 1 tetrahedral complex accompanied by the deprotonation of the pyrrole nitrogen of histidine. The tetrahedral complex contains two bidentate histidines each carrying a 2 charge.3 Previous work in this laboratory indicated that the behavior of the violet cobalt(I1) complex of histidine was complicated. In the present paper we have more fully investigated the conditions necessary for the formation of the violet histidine complex of cobalt(I1). Compounds related to histidine have also been examined in an attempt to find the structural requirements for forming the violet color. Experimental Section The equivalent weights of all the high quality ligands obtained from commercial sources were checked by titrations with standard base. All experiments involving cobalt(I1) were carried out under scrupulously oxygen-free conditions, maintained by using tank nitrogen purified by passage through vanadium(I1) chloride scrubbers to remove any oxygen.‘ Spectra were recorded on a Cary 14R spectrophotometer. Because of the extended concentration range needed in some of the experiments, molar absorbances greater than 2 (at about 560 nm) were often obtained, even in I-mm cells. In such cases, the reference compartment contained a solution similar in composition to the test solution but of lower and known absorbance. The accuracy of the molar absorbances (at about 560 nm) recorded in this way was checked by comparing the molar absorbances at about 1100 nm, which were always less than 2. Circular dichroism was measured with a Durrum-Jasco ORD-UV-5 recording spectropolarimeter with a circular dichroism attachment. Values of pH were measured using a Radiometer Type TIT-1 titrator and associated GK 2021 B combined glass-calomel electrode and T 301 temperature compensator. All experiments were conducted at 24 =k 1 a. (1) This research was supported by a grant from the National Science ( 2 ) M. S . Michailidis and R. B. Martin, J . Amer. Chem. SOC., 91, 4683 (3) C. C. McDonald and W. D. Phillips, ibid., 85, 3736 (1963). (4) L. Meites, “Poldrographic Techniques,” Interscience Publishers, Foundation.

Optically active co-ordination compounds. Part XX. Reactions of 1,10-phenanthroline co-ordinated to cobalt(III)

Abstract: The reactivity towards nitration and oxidation of the known ions D(+)-[Co(en)2(phen)]3+ and D(+)-[Co(phen)3]3+ has been studied. (+)[Co(en)2(phen)] reacts rapidly at room temperature under normal nitrating conditions to give exclusively the 5-nitro-1, 10-phenanthroline derivative which is then slowly oxidised to the 1,10-phenanthroline-5,6-quinone (quinone hereafter) derivative. Both of these reactions occur with no racemisation at the cobalt.The reactivity of D(+)-[Co(phen)3]3+ towards nitration is much less; but D(+)-[Co(quinone)3]3+ has been prepared without loss of optical activity, by oxidation with nitric acid–sulphuric acid in the presence of bromide ion. Several chemical correlations of optical configurations emerge from the various reactions and the circular dichroism spectra are discussed in relation to the configurations thereby revealed. The tris-bipyridyl cobalt(III) ion has been obtained optically active, and its properties are described.A new synthesis of the free ligand 1,10-phenanthroline-5,6-quinone from the 5-nitro-derivative is described, together with a method for isolating the same compound from its cobalt complex.

Transition metal complexes of substituted alkynes. V. Compounds derived from Tri- and Tetra-cobalt carbonyl complexes

Abstract: Treatment of dodecacarbonyltetracobalt with several fluorocarbon alkynes has given complexes of stoicheiometry Co4(CO)10,(alkyne). For comparison, analogous complexes of the related hydrocarbon alkynes have also been prepared. Infrared, nuclear magnetic resonance, and mass spectra of the complexes are given and the probable structure of the complexes deduced. The reaction of both fluorocarbon and hydrocarbon alkynes with the cluster carbonyl compounds Co3(CO)9CY (Y = CH3, C6H5, CO2CH3) has also been investigated. The products obtained in these reactions include substituted benzenes and the two organocobalt complexes Co2(CO)6(alkyne) and Co2(CO)4(alkyne)3. The probable mode of formation of these compounds is discussed. The role played by the various complex types in the reactions of alkynes with cobalt carbonyls is also considered.