Cobalt III hydroxide

Cobalt(III) fluoride reacts with water forming a finely divided black precipitate of cobalt(III) hydroxide, Co(OH)3. 

When an oxygen-ozone mixture containing 3.5% ozone is passed through a solution of cobalt sulfate, cobalt (III) hydroxide precipitates. This precipitation is quantitative within the pH range 1.8 to 2.5. The overall reaction is... 

Kekule s instability criterion failed completely in the case of many coordination compounds, which were classified as molecular compounds by sheer dint of necessity although they were extremely resistant to heat and chemical reagents. For example, although hexaamminecobalt(III) chloride contains ammonia, it neither evolves this ammonia on mild heating nor does it react with acids to form ammonium salts. Also, addition of a base to its aqueous solution fails to precipitate hydrated cobalt(III) hydroxide. 

Tris(phenylbiguanido)cobalt(III) hydroxide, [Co(C6-H5C2N6H5) 3]-3H20 or [Co(C6H6C2N6H6) 3] (OH) 3, forms rose-red crystals which melt with decomposition near 200° and are insoluble in water and alcohol. The compound absorbs carbon dioxide from the atmosphere and liberates ammonia from solutions of ammonium salts on boiling. Boiling water and alkali have no action upon the complex base, but concentrated acids decompose it. The anhydrous material may be obtained by heating the hydrate to 145 to 150° for 24 hours, but it readily absorbs water on exposure to air. The substance is preserved in an atmosphere free from carbon dioxide. 

In a chilled mortar 5 g. of tris(phenylbiguanide)cobalt-(III) hydroxide is triturated with cold (10°) 2 N hydrochloric acid, drop by drop, until the mixture becomes slightly acid (approximately 15 ml. is required). From the clear red solution which first forms, orange crystals gradually separate. Cooling is essential, because otherwise the chloride tends to separate as an oil. After further cooling of the solution the crystals are separated by filtration and washed with 3 ml. of ice water. The crystals are dried over calcium chloride, dissolved in 6 ml. of dry alcohol, and precipitated by the slow addition of 90 ml. of cold (10°) acetone with stirring. The purified product is filtered, washed with... 

Figure 6.7 Dissolution of cobalt (III) hydroxide in the presence of acidic hydrogen peroxide.

The X-ray method was first applied (52) to a chelated inorganic molecule4) in the case of the most accessible product of the reaction of aqueous L(+)alanine with cobalt(III) hydroxide, the violet crystalline, a(+)-[Co(L-ala)s]. The absolute configuration of L(+)alanine is known and could be projected only on to the configuration shown. The configuration of the whole complex (IV) was thus established as D. 

The hydroxide is slowly transformed into the brownish-black cobalt(III) hydroxide on exposure to the air ... 

Cobalt nitrate solution adding a few drops of the reagent to a solution of the hypochlorite, a black precipitate of cobalt(III) hydroxide is obtained ... 

SYNS COBALT(III) HYDROXIDE COBALTIC HYDROXIDE COBALT TRIHYDROXIDE... 

The classic method of Ley and Winkler —dissolving freshly prepared cobalt(III) hydroxide oxide, CoO(OH), in an aqueous solution of glycine with heating—gives both products, with the mer isomer predominating (often this is the only isomer formed). 

Cobalt is present in almost all nickel ores. Previously there was no use for cobalt and as its value was less than that of nickel, it was not separated. Therefore, old nickel alloys contain much more cobalt than those of the present day. Two chemical methods are based on the oxidation of cobalt to three-valent ions. Cobalt is precipitated as cobalt(III) hydroxide by treating the solution with chlorine to oxidize the cobalt(II) to cobalt(III) and adding nickel carbonate to control the pH to 4 (27)... 

The first silica-based 14-membered ring zeolite, UTD-1, was synthesized by Balkus ct al. [7,22] using bis(pentamethylcyclopentadicnyl)cobalt(III) hydroxide as a structure-directing... 

To determine the valence of Co, the sample is carefully heated with 2 N KOH until NH3 can no longer be detected. The resulting blue liquid, which contains suspended cobalt (III) hydroxide, is treated with KI and NaHC03 in a flask closed off with a glass stopper, and is then carefully acidified. After standingfor one day, the I3 which separates is back-titrated with NagSsOg solution. 

Cobalt (III) hydroxide (prepared as on p. 1520) Is placed in a porcelain boat and reduced in a stream of hydrogen. The boat is heated by a tubular electric furnace whose temperature is regulated by a thermocouple connected to anon-off relay. For practical purposes, a temperature exceeding 300°C gives a sufficiently high reduction rate. The crystal structure and pyrophoric nature of the product (at room temperature) are related to the reduction temperature as follows ... 

Boas et al. prepared and separated the meridional isomers of the [Co(ai-02)2] type complexes (oti-a2 represents the dianion of the dipeptide H2 i-a2> where ai is the N-terminal residue). Seven methods were used to prepare bis(dipeptidato)-cobaltate(III) complexes (i) by oxygenation of cobalt(II), (ii) from cobalt(II) carbonate, (iii) from sodium tricarbonatocobaltate(III), (iv) from hexaamminecobalt-(III) chloride, (v) from hexakis(urea)cobalt(III) perchlorate, (vi) from cobalt(III) hydroxide oxide, (vii) from triammine(glycylglycinato)cobalt(III). The methods starting from Co" gave more minor products, Na3[Co(C03)3] 3 H2O gave less, and cobalt(III) hydroxide oxide gave very little of these products. Thus, the method (vi) was prefered. The peptides used were gly-gly, L-ala-gly, gly-L-ala, L-leu-gly, gly-L-leu, L-phe-gly, gly-L-phe, L-ala-L-ala, L-ala-D-ala, L-leu-L-leu. 

The cobalt(III) hydroxide produced can be re-dissolved as a cobalt(II) salt under acidic conditions, by using the corresponding acid with H2O2 as a reducing agent [368], e.g. ... 

But Kekuld s stability criterion, or to be more accurate, instability criterion failed completely in the case of many coordination compounds, especially the metal-ammines, which were classified as molecular compounds by sheer dint of necessity even though they were extremely resistant to heat and chemical reagents. For example, look at Figure 1. Although hexaamminecobalt(III) chloride contains ammonia, it neither evolves this ammonia on mild heating nor does it react with acids to form ammonium salts. Also, despite its cobalt content, addition of a base to its aqueous solution fails to precipitate hydrated cobalt(III) hydroxide. It remained for Alfred Werner to explain successfully the constitution of such compounds, but the time was not yet ripe. Before considering Werner s coordination theory, we must examine one more theory of coordination compounds, perhaps the most successful of the pre-Wemer theories, namely, the Blomstrand-J0rgensen chain theory. 

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