Of cobalt compounds

The mauve colored cobalt(II) carbonate [7542-09-8] of commerce is a basic material of indeterminate stoichiometry, (CoCO ) ( (0 )2) H20, that contains 45—47% cobalt. It is prepared by adding a hot solution of cobalt salts to a hot sodium carbonate or sodium bicarbonate solution. Precipitation from cold solutions gives a light blue unstable product. Dissolution of cobalt metal in ammonium carbonate solution followed by thermal decomposition of the solution gives a relatively dense carbonate. Basic cobalt carbonate is virtually insoluble in water, but dissolves in acids and ammonia solutions. It is used in the preparation of pigments and as a starting material in the preparation of cobalt compounds. 

Cobalt(II) hydroxide [1307-86-4], Co(OH)2, is a pink, rhombic crystalline material containing about 61% cobalt. It is insoluble in water, but dissolves in acids and ammonium salt solutions. The material is prepared by mixing a cobalt salt solution and a sodium hydroxide solution. Because of the tendency of the cobalt(II) to oxidize, antioxidants (qv) are generally added. Dehydration occurs above 150°C. The hydroxide is a common starting material for the preparation of cobalt compounds. It is also used in paints and Hthographic printing inks and as a catalyst (see Paint). 

Prices of cobalt compounds are directiy related to the cost of cobalt metal which fluctuates widely. Zaire is the primary cobalt suppHer. The price of cobalt metal was 46.30/kg in July 1992, down from 76.75/kg in December 1991, but up from the 27.56/kg July 1991 price. Annual usage of cobalt in the western world averaged 15,950 t in 1980—1984. The nonmetaUic uses of cobalt were about 35% in 1984 and estimated to be 40% in 1990 (1,8,9). 

The high cost of cobalt metal has led to substitution such that alloys containing low or no cobalt are produced where possible. Because the cost of cobalt compounds in specialty appHcations is usually much less significant than in alloys, there is less incentive to develop alternatives. 

MiscelEneous. Small quantities of cobalt compounds are used in the production of electronic devices such as thermistors, varistors, piezoelectrics (qv), and solar collectors. Cobalt salts are useful indicators for humidity. The blue anhydrous form becomes pink (hydrated) on exposure to high humidity. Cobalt pyridine thiocyanate is a useful temperature indicating salt. A conductive paste for painting on ceramics and glass is composed of cobalt oxide (62). 

Cobalt is found in most natural foods. Although a necessary trace element, it is toxic to humans if ingested in large amounts. The human body does excrete in urine excessive amounts of cobalt compounds such as found in vitamin B ... 

X-edge spectra of cobalt compounds appear quite similar to those of manganese compounds. The ionic cobaltous salts and hydrates produce t3q>e I spectra. In Fig. 9 and 10 the spectra of the salts (except for CoBrj) have their principal maximum at 18-20 ev. Spectra of the cobaltic salts stabilized with a coordination sphere of ammonia or of ethylene diamine, shown in Figs. 11 and 12, are all very similar, are of typo I, and have their... 

Cobalt Compounds. In general the chemical properties arc intermediate between those of iron and nickel. The predominant oxidation stales of cobalt compounds, except for a large class of organumetallie compounds, are 2+ and 3+. Common usage assigns the terms cobaltous and cobaltic. respectively, to these. 

In parallel the cocatalysis of cobalt compounds with A7-hydroxyphthalimide 398 was developed extensively for oxidative radical reactions [434]. Ishii and colleagues showed that these conditions can be used in radical additions (Fig. 92). Ketyl radicals generated by hydrogen abstraction from secondary alcohols 396 add to a.p-unsaturated esters 397 affording 2,4-dihydroxy esters, which cyclized to lactones 399 under the reactions conditions [435]. Using 0.1 mol% of Co(OAc)2, 1 mol% of Co(acac)3, and 10 mol% of 398 under 1 atm of oxygen, the cyclic products 399 were isolated in 14—90% yield. As observed for similar reactions, Co(III) alone needs an induction period (see below). 

The high cost and toxicity of cobalt compounds has prompted a search for alternative materials that intercalate lithium ions. Examples of these are LiMn204 [iv], LiCoo.2Nio.8O2. LiNio.5Mni.504 [v], LiNio.5Mno.5O2 [vi], LiFeP04 [vii], Lix VO [viii], and LixMrVOz (M = Ca, Cu) [ix], etc. 

A selection of articles detailing synthetic methods used for the preparation of cobalt compounds and complexes and a list of useful starting materials for such syntheses are available. ... 

Werner and his co-workers (Tables I and II) proceeded in a very systematic fashion, and a series of cobalt compounds was not only made but was also identified, and properties were noted or measured (color, chemical reaction, electrical conductivity, and optical properties). Some of his students and co-workers continued to investigate cobalt compounds after having accepted positions in other universities or returned to their native countries. 

Another important use of cobalt compounds is as catalysts. A catalyst is a substance used to speed up a chemical reaction. The catalyst does not undergo any change itself during the reaction. Cobalt molybdate (C0M0O4) is used in the petroleum industry to convert crude oil to gasoline and other petroleum products. It is also used to remove sulfur from crude oil. 

Cobalt is an essential nutrient at low levels ( 40mgday ). In industrial settings, inhalation of high concentrations of cobalt compounds has led to hard-metal pneumoconiosis, which may result in interstitial fibrosis. Workers with this condition typically develop hypersensitivity to cobalt compounds (symptoms include coughing and wheezing). A few workers have developed skin hypersensitivity after dermal contact with cobalt and its compounds. Cobalt can cause cardiomyopathy and (if inhaled as a dust) interstitial lung disease. 

Lison D, De Boeck M, Verougstraete V, and Kirsch-Volders M (2001) Update on the genotoxicity and carcinogenicity of cobalt compounds. Occupational and Environmental Medicine 58(10) 619-625. 

Light can often be used to promote SRN1 reactions [2]. Indeed, the photo-chemically induced, cobalt-catalyzed carbonylation of haloarenes, PhCl included, readily occurs under phase-transfer conditions. This interesting methodology was first developed by Brunet, Sidot, and Caubere [23,69] and subsequently used for the carbonylation of various chloroarenes in the presence of catalytic amounts of cobalt compounds (Sect. 3.3). 

Here we report a eomparative study of catalytic properties of different type cobalt-containing compounds in alkene epoxidation by dioxygen in the presence of o-butyraldehyde (IBA) and provide some data, which allow us to clarify the reaction mechanism and the nature of the cafeilytic aetion of cobalt compounds. 

In 1735 the cobalt ore used by the glass maker was examined by Georg Brandt, a Swede, born at Riddarhytta in Vestmanland in 1694, and not to be confused with Hennig Brand, the Hamburg merchant, who obtained phosphorus from urine in 1669 (p. 76). Brandt isolated a new metal from the mineral in impure form in 1742 and called it cobalt. That it was really a new metal was confirmed by Bergman in 1790 and by Tassaert in 1799. The real study of the chemistry of cobalt compounds began with the researches of Thenard in 1802 and of Proust in 1806. 

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