Cobalt carbon containing

In the nickel—carbon and cobalt—carbon systems, the nickel carbide (3 1) [12012-02-1], Ni C, and cobalt carbide (3 1) [12011-59-5] C03C, are isomorphous with Fe C and exist only at low temperatures. The manganese—carbon system contains manganese carbide (3 1) [12121 -90-3] Mn C, isomorphous with Fe C, and manganese carbide (23 6) [12266-65-8] isomorphous with chromium carbide (23 6) [12105-81 -6] These... 

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. 

Chrornium—cobalt—alurninum oxide [68187-11-1]—Cl Pigment Blue 36, Cl No. 77343. A blue—green pigment obtained by calcining a mixture of chromium oxide, cobalt carbonate, and aluminum oxide. It may contain small amounts (<1% each) of oxides of barium, boron, siUcon, and nickel. 

Lenhert and Hodgkin (15) revealed with X-ray diffraction techniques that 5 -deoxyadenosylcobalamin (Bi2-coenzyme) contained a cobalt-carbon o-bond (Fig. 3). The discovery of this stable Co—C-tr-bond interested coordination chemists, and the search for methods of synthesizing coen-zyme-Bi2 together with analogous alkyl-cobalt corrinoids from Vitamin B12 was started. In short order the partial chemical synthesis of 5 -de-oxyadenosylcobalamin was worked out in Smith s laboratory (22), and the chemical synthesis of methylcobalamin provided a second B 12-coenzyme which was found to be active in methyl-transfer enzymes (23). A general reaction for the synthesis of alkylcorrinoids is shown in Fig. 4. 

If the solid obtained here is allowed to stand in contact with a little concentrated sodium carbonate solution for several hours, the cobalt is converted to reddish cobalt carbonate and the colorless supernatant liquid contains sodium tetrakis(thiocyanato)mercurate (II). 

It is better to prepare the cobalt nitrate solution by dissolving 60g of cobalt carbonate in portions in 70ml of concentrated nitric acid and filtering the solution as the crystalline nitrate is deliquescent it may contain considerably more water than indicated by the 6-hydrate.]... 

The structures of the biologically active forms of B12 were solved relatively recently (1961) (78) and were shown to contain a cobalt atom surrounded by a corrin ring as shown in Fig. 16 (80). The crystal structure also showed a cobalt-carbon a bond which was quite surprising since the few compounds with cobalt-carbon a- bonds known at that time were quite unstable (79). The corrin ring is similar to the porphyrin ring, but its greater saturation imports less rigidity than the porphyrin. Corrinoids with the axial 5,6-dimethylbenzimidazole substituent are called cobalamins. Vitamin B12 with Co(III) and CN in the top axial position is... 

A nonactive electrode may include noble metals such as gold, silver, and platinum, the so-called sp-metals such as In, Ga, Cd, Bi, as well as transition (or d) metals such as nickel or cobalt. Carbon electrodes and semiconductors such as indium tin oxide [1], diamond [2], and conducting polymers may fall into the category of nonactive electrodes in appropriate solutions, as do composite materials that contain metal oxides or chalcogenides. The behavior of active electrodes in nonaqueous solution is discussed separately in the next chapter. 

CVD is an established method for the synthesis of CNTs [59, 60]. Supported transition metals that catalyze the growth of CNTs, such as iron, nickel, or cobalt, are situated in a tubular reactor, and CNTs are grown at elevated temperature on the surface of the catalyst particles by decomposition of a carbon-containing precursor. The catalyst particles have to be removed by chemical treatment /washing in order to obtain a metal-free final product. 

Cobalt-containing zeolites have been studied for polymerization of ethylene (155-157). The catalysts which were prepared by precipitating cobalt carbonate together with zeolites A, X, Y, and mordenite were not very selective, yielding large amounts of ethane as well as C3 and C4 hydrocarbons. 

There are two known oxides of cobalt, CoO and Co3C>4, but the existence of Co203 is uncertain. The lowest of these, CoO, can be obtained by the decomposition of the hydroxide or carbonate containing Co2+ ... 

Potassium Cobalti-nitrite, K3Co(N02)6. H20, is the most familiar example of this type. It is also known as cobalt yellow and Fischer s salt in honour of its discoverer.1. It is readily prepared by adding potassium nitrite to an aqueous solution of a soluble cobalt salt acidified with acetic acid. It results in a very pure condition when cobalt carbonate is suspended in an aqueous solution containing an equivalent amount of potassium carbonate or nitrite, and treated with nitrous fumes (resulting from the action of nitric acid upon arsenious oxide) until it has suffered complete decomposition.2 The amount of combined water varies from 0 to 4 molecules according to circumstances. 

Methylcobalamin (I, R = —CH3) and the vitamin Bi2 coenzyme (I, R = 5 -deoxyadenosyl) are the only known naturally occurring organometailic compounds. Both are derivatives of vitamin 8t2 (cyanocobalamin, I, R = —CN)and both can be synthesized from Bn but are best prepared from hydroxocobalamin. These and numerous other derivatives of Bn containing a cobalt-carbon bond are known, and provided the cobalt is bonded to a primary carbon atom the complexes are thermally very stable, but always photochemically labile as a result of homolytic cleavage of the cobalt-carbon bond. 

In recent years, we have seen an explosive interest in nanomaterials, in particular in nanofibers, nanofilaments, and nanotubes of the very different chemical composition. The interest arises from the specific mechanical and physicochemical properties of these nano objects, which allow them to be used, for example, as specific adsorbents, catalyst supports, reinforcing components of composite materials, and so on. The most cited generic types of nanomaterials are carbon nanofilaments and nanotubes. Numerous methods for preparing these carbon materials are known. However, the simplest method seems to be thermal pyrolysis of various carbon contain ing precursors (e.g., carbon monoxide, saturated and unsaturated hydro carbons, etc.) in the presence of special catalysts that are typically nanosized particles of nickel, cobalt, iron metals, or their alloys with different metals. 

The Cambridge Structural Database contains X-ray crystallographic data for aU reported compounds and complexes of cobalt that contain carbon (see X-ray Crystallography). The November 2002 version of this database lists 10403 structures containing cobalt, with the earhest, the Co(n) complex of the phthalocyaninate dianion, dating back to 1936. The Inorganic Crystal Stmcture Database contains stmctural data for cobalt compounds... 

These complexes, all of which contain cobalt within a macrocyclic ligand and an axial cobalt-carbon bond, have been found to be photosensitive and have been the subject of numerous photochemical studies. Space does not permit a detailed summary of all the studies which have been conducted on these classes of compounds, and we present here only a general summary of the various observations and discuss pertinent articles from the most recent literature. The reader is referred to an excellent review of the subject by Koerner von Gustorf et al. 108) which presents a detailed discussion of reports that appeared prior to 1975. 

Finally, a history of organometallic chemistry would be incomplete without mention of what surely is the oldest known organometallic compound, vitamin B12 coenzyme. This naturally occurring cobalt complex, whose structure is illustrated in Figure 13-6, contains a cobalt-carbon n bond. It is a cofactor in a number of enzymes that catalyze 1,2 shifts in biochemical systems ... 

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