Metal Organic Cobalt Salts

The degree of unsaturation in these oil-modified alkyds was controlled by the amount and type of unsaturated acid used in the formation of the polyester. These unsaturated polymers cured or "dried" through auto-oxldatlon by oxygen from the air which reacted with the unsaturated carbon atoms on the surface of the freshly deposited film. This crosslinking reaction, like that of the "drying" of oil-based paints, was catalyzed by heavy metal salts, such as lead or cobalt salts of organic acids. Alkyds, which are some of the most Important paint resins, are produced at an annual rate in excess of 300 thousand tons. 

Cobalt(II) acetylacetonate [14024-48-7] cobalt(II) ethyUiexanoate [136-52-7] cobalt(II) oleate [14666-94-5] cobalt(II) linoleate [14666-96-7] cobalt(II) formate [6424-20-0], and cobalt(II) resinate can be produced by metathesis reaction of cobalt salt solutions and the sodium salt of the organic acid, by oxidation of cobalt metal in the presence of the acid, and by neutralization of the acid using cobalt carbonate or cobalt hydroxide. 

Cobalt(Il) dicobalt(Ill) tetroxide [1308-06-17, Co O, is a black cubic crystalline material containing about 72% cobalt. It is prepared by oxidation of cobalt metal at temperatures below 900°C or by pyrolysis in air of cobalt salts, usually the nitrate or chloride. The mixed valence oxide is insoluble in water and organic solvents and only partially soluble in mineral acids. Complete solubiUty can be effected by dissolution in acids under reducing conditions. It is used in enamels, semiconductors, and grinding wheels. Both oxides adsorb molecular oxygen at room temperatures. 

Evaporation by heating a filtrate from precipitation of potassium cobaltinitrite caused it to turn purple and explode violently [1]. This was attributed to interaction of nitrite, nitrate, acetic acid and residual cobalt with formation of fulminic or methylnitrolic acids or their cobalt salts, all of which are explosive [2], Mixtures containing nitrates, nitrites and organic materials are potentially dangerous, especially in presence of acidic materials and heavy metals. A later publication confirms the suggestion of formation of nitro- or nitrito-cobaltate(III) [3],... 

Toxicity. Coball, like most oilier metals, is not entirely harmless, although ii is not in any way comparable lo the known toxic metals, such as mercury, cadmium, and lead. Inhalation of fine cobalt dust over long periods can cause an irritation of Ihe respiratory organs, which may result in chronic bronchitis. Complete recovery is usually achieved upon removal from the contaminated atmosphere. Cobalt salts can cause benign dermatoses, either in people new to handling them, or aflci prolonged exposure, usually several years. 

Solvent Dyes (see also Section 3.10). The 1 2 chromium and cobalt complex dyes devoid of any hydrophilic substituent have a considerable solubility in organic solvents, especially alcohols, ketones, and esters. Enhanced solubility can be achieved by converting the metal-complex sodium salts into salts of organic cations [57], Such cations may be cationic dyes, long-chain aliphatic ammonium ions, or protonated guanidines. For example, the bluish red solvent dye 34 reaches a solubility in organic solvents of up to 1000 g/L [58],... 

Cobalt catalysts were used for substitution reactions of organic halides [442] and a small-ring enol lactone [Eq. (201) 443]. The cobalt salt seems to be the most effective one among a few transition metal salts involving copper, nickel, [see Eq. (130)], and iron. Without the catalyst, Grignard reagent attacked the carbonyl carbon of the enol lactone to give a mixture of a few ketonic compounds in a low yield. 

The autoxidation reactions are promoted by catalysts which are organic salts of polyvalent heavy metals. By far the most powerful of these are cobalt salts, e.g. cobalt octanoate (2-ethylhexanoate, C4H9CH(C2H5)C00H) or cobalt naphthenate, and these are usually accompanied by other organic salts, e.g. of lead, zirconium or calcium. 

Proust was predominantly an accurate and ingenious experimenter. Besides his numerous memoirs on the compositions of minerals and artificial compounds of metals (gold, silver, platinum, copper, mercury, tin, antimony, zinc, iron, cobalt, nickel, etc.), including salts of organic acids, Proust published a... 

B. M. Tassaert noticed that a solution of a cobalt salt in ammonia becomes brown on exposure to air, the colour changing to wine-red on boiljhg, and Thenard in 1802 showed that oxygen is absorbed. Fremy and others showed that the cobalt becomes tervalent and the salt is associated with up tjo a maximum of six ammonia molecules, e.g. CoC NHs). Similar compounds, now called ammines, are formed by platinous and platinic salts, and in many cases there are isomers of particular compounds. In most cases their reactions are abnormal, the compounds not showing the qualitative tests for the metal and sometimes not for the acid radical, e.g., in CrC NHa), only two, atoms of chlorine are precipitated by silver nitrate. Water or organic amihes or bases such as pyridine, may replace ammonia. 

Cobalt Salts. Barker" studied the effects of cobalt stearate, cobalt naphthenate, and a proprietary boron-containing metal-organic complex on adhesion to brass. He concluded that, with properly optimized compounds, little or no benefit is obtained from the use of cobalt insofar as initial adhesion is concerned. All salts, however, improved steam-aged adhesion to some extent. Other studies tend to support these claims. 

Lead salts of organic acids, the original driers, function as polymerization catalysts throughout the entire paint film depth in contrast, cobalt salts function as surface driers. Hence, until recently, combinations of lead and cobalt driers have been used to achieve a uniform drying rate. Manganese and zirconium salts may be used in place of lead. Many organic acids have been used to form these heavy metal salts, but the most widely used salts are naphthenates, which are based on naphthionic acid, a residue of petroleum resinous. Other acids used to produce driers are octoic, tallic, rosin, and linolenic acids. 

The cobalt catalyst can be introduced into the reactor in any convenient form, such as the hydrocarbon-soluble cobalt naphthenate [61789-51 -3] as it is converted in the reaction to dicobalt octacarbonyl [15226-74-17, Co2(CO)g, the precursor to cobalt hydrocarbonyl [16842-03-8] HCo(CO)4, the active catalyst species. Some of the methods used to recover cobalt values for reuse are (11) conversion to an inorganic salt soluble ia water conversion to an organic salt soluble ia water or an organic solvent treatment with aqueous acid or alkah to recover part or all of the HCo(CO)4 ia the aqueous phase and conversion to metallic cobalt by thermal or chemical means. 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

In this method, a metal oxide or hydroxide is slurried in an organic solvent, neodecanoic acid is slowly added, and the mixture is refluxed to remove the water. Salts that are basic can be prepared by using less than stoichiometric amounts of acid. This method has been used in the preparation of metal salts of silver (80) and vanadium (81). The third method of preparation is similar to the fusion process, the difference is the use of finely divided metal as the starting material instead of the metal oxide or hydroxide. This method has been appHed to the preparation of cobalt neodecanoate (82). Salts of tin (83) and antimony (84) have been prepared by the fusion method, starting with lower carboxyHc acids, then replacing these acids with neodecanoic acid. 

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