Solvation cobalt

X-ray structural investigations on alcoholic solutions of a number of transition metal salts [We 69], such as iron(II) chloride, iron(II) bromide and cobalt(II) bromide, revealed that in the case of the two iron(II) salts the transition metal ion is surrounded by four alcohol molecules, in accordance with tetrahedral symmetry. In an alcoholic solution of cobalt(II) bromide, on the other hand, cobalt solvates containing two bromide ions and two solvent molecules could be detected. In more concentrated iron(II) chloride solutions, a dimeric complex of composition Fe2Cl6 was found. 

Cobalt, cis-chloroamminebis(l, 2-ethanediamine)-optical isomerism, 1,12 Cobalt, chlorobis(l,2-ethanediamine)-solvation, 1,503... 

Sometimes, the physicochemical properties of ionic species solubilized in the aqueous core of reversed micelles are different from those in bulk water. Changes in the electronic absorption spectra of ionic species (1 , Co ", Cu " ) entrapped in AOT-reversed micelles have been observed, attributed to changes in the amount of water available for solvation [2,92,134], In particular, it has been observed that at low water concentrations cobalt ions are solubihzed in the micellar core as a tetrahedral complex, whereas with increasing water concentration there is a gradual conversion to an octahedral complex [135],... 

In marked contrast to the majority of activated metals prepared by the reduction process, cobalt showed limited reactivity toward oxidative addition with carbon halogen bonds. Iodopentafluorobenzene reacted with 2 to give the solvated oxidative addition products CoL and Co(C,F5)2 or Co(C F )L The compound CoiOJF 2PEt, was isolated in 54% yield by addition of triethylphosphine to tne solvated materials. This compound was also prepared in comparable yield from 1 by a similar procedure. This compound had previously been prepared by the reaction of cobalt atom vapor with C6F5I(81). 

Tri-ethylene diamine Cobalt hydroxide [Co(en)3](OH)2 Cooxen Good solvating properties, extensive oxidative degradation, coloured (claret)... 

As we have seen, an area of major importance and of considerable interest is that of substitution reactions of metal complexes in aqueous, nonaqueous and organized assemblies (particularly micellar systems). The accumulation of a great deal of data on substitution in nickel(II) and cobalt(II) in solution (9) has failed to shake the dissociative mechanism for substitution and for these the statement "The mechanisms of formation reactions of solvated metal cations have also been settled, the majority taking place by the Eigen-Wilkins interchange mechanism or by understandable variants of it" (10) seems appropriate. Required, however, are more data for substitution in the other... 

The tetranuclear and trinuclear clusters will only be observed at low pressures [8], but all other species are very common under hydroformylation conditions. Complex 4 is an ionic complex that is formed in polar solvents [9] and even hexa-solvated, divalent cobalt species may form as the cation. Under practical conditions both the dimers and the hydrides are observed, thus depending on the hydrogen pressure there will be more or less of the hydride present. 

Up to now, the solubility decrease of cobalt complexes with these modiflers has not been explained satisfyingly. It is assumed that the changes in the solvatization characteristics observed are caused by different interactions of the solute with the mixture of organic components and CO2 the modifier-solute (olefin/aldehyde-complex) interaction probably is stronger than the solute-scC02 interaction. Future theoretical treatment may also improve the... 

A variety of geometries have been established with Co(II). The interconversion of tetrahedral and octahedral species has been studied in nonaqueous solution (Sec. 7.2.4). The low spin, high spin equilibrium observed in a small number of cobalt(Il) complexes is rapidly attained (relaxation times < ns) (Sec. 7.3). The six-coordinated solvated cobalt(ll) species has been established in a number of solvents and kinetic parameters for solvent(S) exchange with Co(S)6 indicate an mechanism (Tables 4.1-4.4). The volumes of activation for Co " complexing with a variety of neutral ligands in aqueous solution are in the range h-4 to + 1 cm mol, reemphasizing an mechanism. 

The oxidation of cobalt(II) in the organic phase can be minimized by the addition of donor molecules, such as the solvating extractants. 

Arene-solvated cobalt atoms (U) and (1, obtained by reacting Co vapor and arenes, have been found by Italian workers to promote the conversion of a,d)-dialkynes and nitriles to alkynyl-substituted pyridines [87JOM(326)C33] (Scheme 4). 

Cobalt(II) R-dtp complexes have been the subject of several studies js3,34i) Co(ethyl-dtp)2 occurs in a tetrahedral non-solvated form in carbon tetrachloride but undergoes solvation in other non-aqueous solvents 3 9. The spectrochemical series for tetrahedral Co(S2PX2)2 (where X = F,... 

Whatever the precursor, the formation of an intermediate solid phase was always observed. It can be inferred from X-ray diffraction (Fig. 9.2.7) and infrared spectroscopy that this intermediate phase shows a lamellar, incompletely ordered structure (turbostratic structure) built up with parallel and equidistant sheets like those involved in the lamellar structure of the well-crystallized hydroxides Ni(OH)2 or Co(OH)2, these sheets are disoriented with intercalation of polyol molecules and partial substitution of hydroxide ions by alkoxy ions (29). The dissolution of this solid phase, which acts as a reservoir for the M(I1) solvated species, controls the concentration of these species and then plays a significant role in the control of the nucleation of the metal particles and therefore of their final morphological characteristics. For instance, starting from cobalt or nickel hydroxide as precursor in ethylene glycol, the reaction proceeds according to the following scheme (8) ... 

Dr. Kamiya has attempted to explain the role of the catalyst according to Reactions 13-15, and he has attempted to differentiate between these proposed reaction steps and the simplified Reactions 3 and 4. It is not clear to me what types of structures he is trying to portray by using the empirical formulae Co2+BrH and Co3+Br". There does not seem to be any evidence for any unusual complexes in these solutions, and there does not seem to be any need to postulate them. It really becomes a matter of semantics because nobody believes that in solution Br, for example, exists as such, but it must be solvated by or coordinated with other species. Dr. Kamiya also implies that the initiation step is a direct reaction of the hydrocarbon with Co (III) ion. To my knowledge, a reaction such as this in acetic acid solution has never been demonstrated. We have shown that the reaction between cobalt (III) acetate in acetic acid and toluene is negligibly slow. It would be more likely to consider the reaction... 

The square planar palladium complexes which give values of m of ca. 0.4 (Table 1) are known to react via a mainly associative mechanism so that the values of m are taken to indicate that Pd—Cl bond cleavage and leaving Cl solvation were both important in determining the reactivity trend for these complexes, i.e. there is a greater degree of M—Cl bond breaking in the transition state of palladium compared with cobalt. 

The use of solvating extractants in the recovery of gold and platinum-group metals (PGM) was described in the previous section. These extractants have also found some specialized applications in the extractive metallurgy of base metals. For example, they have been used in the recovery of uranium, the separation of zirconium and hafnium, the separation of niobium and tantalum, the removal of iron from solutions of cobalt and nickel chlorides, and in the separation of the rare-earth metals from one another. 

Stoyanov, E.S., Smirnov, I.V. Proton solvates, H+-nH2OmL, formed by diphosphine dioxides with chlorinated cobalt(III) dicarbollide acid. J. Mol. Struct. (2005), 740 (1-3), 9-16. 

Apart from its own susceptibility to oxidation or reduction, a solvent can affect redox equilibria by modifying the relative stabilities of oxidation states of solutes. Thus Cu+ is unstable in aqueous solution to disproportionation (Section 5.4) but it is quite stable in acetonitrile. This arises from the relative magnitudes of the solvation energies and entropies of Cu+ and Cu2+ in the different solvents. In ammonia, cobalt(III) is much more stable relative to cobalt(II) than in water. The... 

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