Cobalt, chloro

The situation becomes more complicated if a given ionization reaction is studied in solvents that differ both in their EPD and EPA properties. This may be illustrated for the complex formation between Co and Cl ions. Qualitatively, stabilities of cobalt-chloro complexes usually decrease with increasing EPD strength of the solvent (25, 26). Quantitative measurements reveal, however, a number of irregularities which cannot be understood by considering the differences in solvent donicities. Accurate thermodynamic data have recently been determined for the reaction... 

Cobalt Chloro-tris-[trimethylphos-phan]- XIII/9b, 15... 

Cobalt Chloro-dimethy]-tris-[tri-methylphosphan)- XIII/9b, 120... 

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... 

Nickel and Cobalt. Often present with copper in sulfuric acid leach Hquors are nickel [7440-02-0] and cobalt [7440-48-4]. Extraction using an organophosphoric acid such as D2EHPA at a moderate (3 to 4) pH can readily take out the nickel and cobalt together, leaving the copper in the aqueous phase, but the cobalt—nickel separation is more difficult (274). In the case of chloride leach Hquors, separation of cobalt from nickel is inherently simpler because cobalt, unlike nickel, has a strong tendency to form anionic chloro-complexes. Thus cobalt can be separated by amine extractants, provided the chloride content of the aqueous phase is carefully controUed. A successhil example of this approach is the Falcon-bridge process developed in Norway (274). 

The sulfite group present in the heterocyclic ring of endosulfan is rapidly hydrolyzed by alkali. In the presence of atmospheric oxygen it then oxidizes divalent cobalt to cobalt(III). Phosphamidon, which contains a 2-chloro-2-diethylcarbamoyl group, ox-... 

The reductions by Fe(ll) of chloro(ethylenediaminetriacetatoacetate)cobaltate (III), Co(Y)CP , and its conjugate acid, Co(HY)CP, have been investigated by Pidcock and Higginson. At hydrogen-ion concentrations > 5x10 M... 

To date, the only reported cobalt(II) complexes involve 2-acetylpyridine N-oxide JV-dimethylthiosemicarbazone, 34 [189]. [Co(39-H)A] (A = Cl, Br) have magnetic moments suggestive of flattened tetrahedra, but calculations based on Tj symmetry yield values of Dq of about 330 cm and B values of 743 and 707 cm for the chloro and bromo complexes, respectively. 

Cobalt(II) alkoxides are known and monomeric forms are part of a wider review.413 The interest in these compounds pertains to a potential role in catalysis. For example, a discrete cobalt(II) alkoxide is believed to form in situ from a chloro precursor during reaction and performs the catalytic role in the decomposition of dialkyl pyrocarbonates to dialkyl carbonates and carbon dioxide.414 A number of mononuclear alkoxide complexes of cobalt(II) have been characterized by crystal structures, as exemplified by [CoCl(OC(t-Bu)3)2 Li(THF)].415 The Co ion in this structure and close relatives has a rare distorted trigonal-planar coordination geometry due to the extreme steric crowding around the metal. 

A combination of Co-mediated amino-carbonylation and a Pauson-Khand reaction was described by Pericas and colleagues [286], with the formation of five new bonds in a single operation. Reaction of l-chloro-2-phenylacetylene 6/4-34 and dicobalt octacarbonyl gave the two cobalt complexes 6/4-36 and 6/4-37 via 6/4-35, which were treated with an amine 6/4-38. The final products of this domino process are azadi- and azatriquinanes 6/4-40 with 6/4-39 as an intermediate, which can also be isolated and separately transformed into 6/4-40 (Scheme 6/4.11). 

In an interesting study, phthalocyanine complexes containing four anthraquinone nuclei (5.34) were synthesised and evaluated as potential vat dyes and pigments [18]. Anthraquinone-1,2-dicarbonitrile or the corresponding dicarboxylic anhydride was reacted with a transition-metal salt, namely vanadium, chromium, iron, cobalt, nickel, copper, tin, platinum or lead (Scheme 5.6). Substituted analogues were also prepared from amino, chloro or nitro derivatives of anthraquinone-l,2-dicarboxylic anhydride. 

The chemical reactivity of crown-ether complexes with neutral molecules has received little attention. Nakabayashi et al. (1976) have reported crown-ether catalysis in the reaction of thiols with l-chloro-2,4-dinitrobenzene. The catalytic activity was attributed to deprotonation of thiols by dicyclohexyl-18-crown-6 in acetonitrile solution. Blackmer et al. (1978) found that the rate of aquation of the cobalt(III) complex [333] increases on addition of... 

Bis(l-methylbenzotriazole)cobalt(II) nitrate, 3652 A-Chloro-4,5 -dimethy ltriazole, 1490 5-Cyano-4-diazo-4//-l,2,3-triazole, 1345... 

In a one-pot process for the preparation of the complexes from cobalt(II) nitrate, which is converted into the tetracarbonyl anion by the standard procedure [9], higher yields of (2) are claimed (R = Cl, 42% R = Br, 36% R = H, 30%) using cetyltrimethylammonium bromide as the catalyst. It is known that the cluster compounds are unstable under basic conditions and it was noted that, for example, in the preparation of the chloro compound, extended reaction times (4.5 hours) resulted in the total decomposition of the product [10]. 

The fact that from a chloro-cobalt complex a chloro-chromium complex is formed, suggests that the reaction must proceed through an intermediate state that enables the transfer of a chlorine atom from cobalt to chromium. The proposed mechanism for this reaction is ... 

A number of cobalt(III) encapsulated cage complexes have been used as electron-transfer agents their advantage over viologens is their long-term stability in photochemical cycles. The most effective complex is [CoL] where L is l-chloro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eico-sane at a concentration of 4 x 10 mol dm , this cage exhibits a similar ability to methylviolo-gen to produce Laser flash photolysis in sodium dodecyl sulfate and sodium laurate... 

Cyclizing ca-chloro Reissert compound 136 gives rise to tricyclic lactam 137 (72JHC541). In a study of the cobalt-mediated reaction of pyridones with alkynes, in the case of the N-hexynyl compound, C-H activation with... 

O6C6CI4OS2, Osmium, hexacarbonyl(di-/i-chloro)(dichloro)di-, 34 219 O6C0KN3C20H29, Cobalt(III), tricyano(cyclo-pentadienyl)-, (18-crown-6)potassium, 34 169... 

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