Cobalt hydroxide, dehydration

In the case of Co(N03)3 at 2(X)°C, the powder was shown to consist of a mixture of C03O4 and CoO(OH). At the higher temperatures, 300°C and 400°C, only C03O4 particles were produced (Figure 7). The presence of a cobalt hydroxide in the low-temperature sample indicates that dehydration was incomplete. Thus, Co + did not precipitate out of solution unless sodium hydroxide was present, and then only at the higher temperatures. 

Cobalt(II) chloride hexahydrate [7791-13-1], C0CI2 6H20 is a deep red monoclinic crystalline material that deflquesces. It is prepared by reaction of hydrochloric acid with the metal, simple oxide, mixed valence oxides, carbonate, or hydroxide. A high purity cobalt chloride has also been prepared electrolyticaHy (4). The chloride is very soluble in water and alcohols. The dehydration of the hexahydrate occurs stepwise ... 

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). 

The adsorption of transition metal complexes by minerals is often followed by reactions which change the coordination environment around the metal ion. Thus in the adsorption of hexaamminechromium(III) and tris(ethylenediamine) chromium(III) by chlorite, illite and kaolinite, XPS showed that hydrolysis reactions occurred, leading to the formation of aqua complexes (67). In a similar manner, dehydration of hexaaraminecobalt(III) and chloropentaamminecobalt(III) adsorbed on montmorillonite led to the formation of cobalt(II) hydroxide and ammonium ions (68), the reaction being conveniently followed by the IR absorbance of the ammonium ions. Demetallation of complexes can also occur, as in the case of dehydration of tin tetra(4-pyridyl) porphyrin adsorbed on Na hectorite (69). The reaction, which was observed using UV-visible and luminescence spectroscopy, was reversible indicating that the Sn(IV) cation and porphyrin anion remained close to one another after destruction of the complex. 

Also, cobalt(II) fluoride can he prepared as a tetrahydrate, C0F2 4H2O hy dissolving cobalt(ll) hydroxide in hydrofluoric acid. The tetrahydrate is then dehydrated to anhydrous fluoride. Elemental fluorine combines with cohalt at 450°C forming mixtures of cobalt(II) and cobalt(III) fluorides. 

Cobaltous acetate. CAS 71-48-7], Co(CHiCO )>. is obtained as a pink salt by the dehydration of the tetrahydrate which is prepared by dissolving the hydroxide or carbonate in acetic acid. The tetrahydrate. which is the commercial form, is widely used in the preparation of catalysts, c.g.. OXO synthesis, and dryers for inks and vamlshes. 

Carbonic anhydrase is a zinc(II) metalloenzyme which catalyzes the hydration and dehydration of carbon dioxide, C02+H20 H+ + HC03. 25 As a result there has been considerable interest in the metal ion-promoted hydration of carbonyl substrates as potential model systems for the enzyme. For example, Pocker and Meany519 studied the reversible hydration of 2- and 4-pyridinecarbaldehyde by carbonic anhydrase, zinc(II), cobalt(II), H20 and OH. The catalytic efficiency of bovine carbonic anhydrase is ca. 108 times greater than that of water for hydration of both 2- and 4-pyridinecarbaldehydes. Zinc(II) and cobalt(II) are ca. 107 times more effective than water for the hydration of 2-pyridinecarbaldehyde, but are much less effective with 4-pyridinecarbaldehyde. Presumably in the case of 2-pyridinecarbaldehyde complexes of type (166) are formed in solution. Polarization of the carbonyl group by the metal ion assists nucleophilic attack by water or hydroxide ion. Further studies of this reaction have been made,520,521 but the mechanistic details of the catalysis are unclear. Metal-bound nucleophiles (M—OH or M—OH2) could, for example, be involved in the catalysis. 

Derivation By the action of hydrochloric acid on cobalt its oxide, hydroxide, or carbonate. Concentration gives (2) and dehydration (1). 

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