Cobalt 2 oxidation state

XPS results are very similar. The Co 2p splitting values 15.5 0.1 eV are equal within experimental error, the N(amine)/Co atomic ratios are 1.7 and 1.3, respectively, and the individual Co/Mn surface and bulk ratios are approximately equal at each pH. This latter result indicates that the sorption process occurs predominately on the surface at pH 6 and 7. The Co 2p splitting results are intermediate between values measured for Co(III) and Co(II)-containing compounds. To account for the Co 2p splitting result, a cobalt material with such an intermediate splitting or a mixture of the two cobalt oxidation states must be present. A survey of representative cobalt-containing materials (19,24,26) reveals that Co 2p splittings at about 15.5 eV are not common. 

This compound was shown by neutron powder diffraction to adopt an unprecedented structure in which chains of C0O4 squares share comers to form chains that are linked to form a layer by H-bridges. The average cobalt oxidation state is 1.1+ and the C0O2 sheets in the starting material have been replaced with CoOHo,7 sheets in the oxide hydride product, which is consistent with a mechanism in which oxide vacancies created by oxide ion deintercalation are filled by intercalation of hydride ions. 

An interesting coupling of acyl halide with Michael acceptors involves an organo-metallic intermediate and photochemical step as well as an electroreduction. The electrochemical reduction, however, is used to reduce the intermediate cobalt oxidation state [115]. 

We start by naming the complex cation. The ligands are named alphabetically with ammine first and then chloro. There are four ammonias and two chlorides, so the prefixes tetra- and di- are used. The cobalt oxidation state is determined by tracing the charges back as follows The net charge on the complex cation must be 1 + to balance the one 1 — chloride anion. Since there are two 1 — chlorides in the coordination sphere, the cobalt must be 3+ in order for the net charge on the cation to come out as 1+. With all this in mind, the full name of the compound is... 

Such low doping levels contrast with the high cobalt oxidation state reachable in the Na CoOi compounds by varying x. However, considering... 

Keeping in mind the problem linked to the cobalt oxidation states on each side of the trivalent cobalt, it is rather interesting to explore the oxides in which the d" magnetic cations allow an electron conduction at the level of the eg orbitals. Such an idea is inspired by the n-type metalli-city of tetravalent perovskite cobaltite such as SrCoOs-g. In the latter, the oxygen nonstoichiometry, 6 0.05, is responsible for the electron creation ( Co ) in the Co" matrix. The much lower resistivity,... 

Also, in anhydrous conditions, silver reacts with fluorine and forms silver difluoride AgFj and cobalt gives cobalt(III) fluoride, C0F3, these metals showing higher oxidation states than is usual in their simple salts. 

Like iron and the next transition element, nickel, cobalt is not generally found in any oxidation state above + 3, and this and + 2 are the usual states. The simple compounds of cobalt(III) are strongly oxidising ... 

As already noted, the simple salts in this oxidation state are powerful oxidising agents and oxidise water. Since, also, Co(III) would oxidise any halide except fluoride to halogen, the only simple halide salt is C0F3. Cobalt(lll) Jluoride, obtained by reaction of fluorine with cobalt(II) fluoride it is a useful fluorinating agent. 

For this reaction, charcoal is a catalyst if this is omitted and hydrogen peroxide is used as the oxidant, a red aquopentammino-cobalt(lll) chloride, [Co(NH3)jH20]Cl3, is formed and treatment of this with concentrated hydrochloric acid gives the red chloro-p0itatnmino-coba. t(lll) chloride, [Co(NH3)5Cl]Cl2. In these latter two compounds, one ammonia ligand is replaced by one water molecule or one chloride ion it is a peculiarity of cobalt that these replacements are so easy and the pure products so readily isolated. In the examples quoted, the complex cobalt(III) state is easily obtained by oxidation of cobalt(II) in presence of ammonia, since... 

Cobalt has an odd number of electrons, and does not form a simple carbonyl in oxidation state 0. However, carbonyls of formulae Co2(CO)g, Co4(CO)i2 and CoJCO),6 are known reduction of these by an alkali metal dissolved in liquid ammonia (p. 126) gives the ion [Co(CO)4] ". Both Co2(CO)g and [Co(CO)4]" are important as catalysts for organic syntheses. In the so-called oxo reaction, where an alkene reacts with carbon monoxide and hydrogen, under pressure, to give an aldehyde, dicobalt octacarbonyl is used as catalyst ... 

In the chemistry of nickel, we observe the continuing tendency for the higher oxidation states to decrease in stability along the first transition series unlike cobalt and iron, the -e3 state is rare and relatively unimportant for nickel and the +2 state is the only important one. 

Many competitive programs to perfect a metallic anode for chlorine arose. In one, Dow Chemical concentrated on a coating based on cobalt oxide rather than precious metal oxides. This technology was patented (9,10) and developed to the semicommercial state, but the operating characteristics of the cobalt oxide coatings proved inferior to those of the platinum-group metal oxide. 

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. 

Metal-Catalyzed Oxidation. Trace quantities of transition metal ions catalyze the decomposition of hydroperoxides to radical species and greatiy accelerate the rate of oxidation. Most effective are those metal ions that undergo one-electron transfer reactions, eg, copper, iron, cobalt, and manganese ions (9). The metal catalyst is an active hydroperoxide decomposer in both its higher and its lower oxidation states. In the overall reaction, two molecules of hydroperoxide decompose to peroxy and alkoxy radicals (eq. 5). 

The net result is formation of water and a high concentration of free radicals. The cobalt cycles between the two oxidation states. Lead and 2irconium salts cataly2e drying throughout the film and are called through driers. Calcium salts show Httle, if any, activity alone, but may reduce the amount of other driers needed. 

Oxidation catalysts are either metals that chemisorb oxygen readily, such as platinum or silver, or transition metal oxides that are able to give and take oxygen by reason of their having several possible oxidation states. Ethylene oxide is formed with silver, ammonia is oxidized with platinum, and silver or copper in the form of metal screens catalyze the oxidation of methanol to formaldehyde. Cobalt catalysis is used in the following oxidations butane to acetic acid and to butyl-hydroperoxide, cyclohexane to cyclohexylperoxide, acetaldehyde to acetic acid and toluene to benzoic acid. PdCh-CuCb is used for many liquid-phase oxidations and V9O5 combinations for many vapor-phase oxidations. 

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