Cohalt compounds

In aqueous solutions and in the absence of contplexing agents, cohalt compounds are stahlc only in the 2+ oxidation (cobaltous) state. In the complexcd state the cobaltous ion is relatively unstable, being readily oxidized to the 3+ oxidation (cohallic) slate. An extremely large number of 3-t- complex ions have been idenlilied. most of which are quite stable in aquenus media... 

Dicohalt edetate Cohalt compounds Forms stable metal complexes with... 

Cohalt and nitrogen form three nitrides, CoiNi. Co N. and CoN, products of nu tal/ammonia reaction and compound decomposition. All are gray-black or black in color. 

Cohalt and copper. Ternary compounds are not formed. The alloys are hardest which oontain nickel and oohalt in equal proportions. All are attacked by nitric acid, but are fairly resistant to sulphuric acid. Waehlert, Chem. Zentr., 1914, li, 919, from Oesterr. Zeitsch. Berg- und Butten-wesen, 1914, 62, 341, 357, 374, 392, 406. 

Because such alkylation proceeds by S l mechanism, even cobalt complexes derived from unreactive (in an Sjj2 sense) halides can be formed. The cohalt complexes are air-stable compounds, but are affected by direct daylight. The incorporated Co-C bond is weak and, therefore, photolysis of 33 sets free the anomeiic radical 11. In the presence of olefins 12 this radical adds to the double bond, followed by subsequent combination to give the insertion product 35 (Scheme 9). 

Selective hydrogenation of oe,)3 unsaturated compounds in the presence of cohalt catalysts... 

Production of the tetrasubstituted cyclopentenone (15a, 15b)) involves condensing the protected vinyl ether (16) with (12) via a Pauson-Khand reaction. Studies on the Pauson-Khand reaction , 1 have shown that upon condensing an unsymmetrical alkene with an unsymmetrical alkyne in the presence of a cohalt carbonyl compound give rise to mixtures of diastereomers (Fig 1) with the bulkier substituents of the alkene and alkyne being a to the carbonyl of the cyclopentenone. However, the stereochemistry a to the... 

Sodium cohalt carbonylate / -Hydroxycarboxylic acid esters from oxido compounds... 

Pentaamminechlorocobaltdll) chloride, [Co(NH3]s(CI)]Cl2, is a compound that oontains cohalt in the +3 oxidation state [left). Hexaaquacohalt(II) chloride, [Co(OH2)e]CI2, oontains cobalt in the +2 oxidation state right). 

Synthesis with cohalt complex compounds Benzene ring... 

OCA and OCM crosslinking can also take place in the presence of radicalic initiators. In the main, peroxides and hydroperoxides are used. Cold strengthening is achieved in the presence of some compounds containing transitional metals, for example, cohalt, vanadium salts, or ferrocyan compounds [33]. 

Cohalt arsenates are generally reported to he the components of some pigments referred to as cobalt violet (q.v.) however, recent work on these pigments has identified magnesium cobalt arsenate as the more hkely constituent (Corbeil et al., 2002). Magnesium arsenate is isostructural with cobalt arsenate, and substitution between the two compounds is likely. 

A FIGURE 3.8 Hydrates Cobalt(n) chloride hexahydrate is pink. Heating the compound removes the waters of hydration, leaving the blue anhydrous cohalt(n) chloride. 

Cohaltous chloride calcium hypochlorite Oxido compounds from ethylene derivatives... 

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