Cobalt -dioxime complex

Donat and Bruland [217] conducted a direct determination of cobalt and nickel in seawater by differential pulse cathodic scanning voltammetry, preceded by absorptive collection of cyclohexane-1,2 dioxime complexes. 

Although square-planar configuration is customarily considered classical for v/c-dioximate of nickel(II), attempts have been made repeatedly over the years for preparing the above complexes in other configurations also. By employing weakly polar solvents and some other variations, success has been claimed in the preparation of mono(dioxime) complexes of nickel(II).42,43 The dichloro-bis(l,2-cyclohexanedione dioximato)nickel(II) has been shown to have an octahedral vie structure.44 Examples of tris(dioxime) complexes of transition metals in general45"18 and of bivalent atoms40,47 in particular are rare and structural details of only a tris(dioxime) complex of cobalt(III) are known.48 In a more recent publication,49 the crystal structure of tris(l,2-cyclohexanedione dioximo)nickel(II) sulfate dihydrate has been elucidated. 

The singlet nature of most bands in the IR spectra of cobalt complexes confirmed the Cs symmetry of their molecules. The C=N stretching vibration bands were appreciably shifted and intensified compared with those of the initial dioximes. Only one band of this type was observed for cobalt(III) complexes, and its position and intensity were more affected than those of cobalt(II) clathrochelates. 

The UV-vis spectra of the macrobicyclic cobalt(II) oximehydra-zonates contain two CTBs in the visible region (at 18 000-19 000 and at 24 000-25 000 cm-i). In the spectra of cobalt(III) complexes, a shoulder at 18 000t20 000 cm-i and a peak at 24 000-30 000 cm-i were observed. All the absorption bands for the tris-dioximate complexes occur at slightly higher energy than the corresponding lines in spectra of the oximehydrazonate compounds [186]. 

The fell values for most macrobicyclic tris-dioximates and Ne-nSn-sarcophaginates (n = 2, 3) increase with decreasing E values. The cobalt Se-sarcophaginates and boron-capped tris-benzyldioximates drop out of linear correlation for both low-spin cobalt(II) and cobalt(III) complexes. The lack of this correlation in the first case may be attributed to the absence of structural changes in passing from the cobalt(III) complex to the cobalt(II) complex. In the second case, an increased fen value may be attributed to the special rigidity of hexaphenyl-substituted cobalt clathrochelates. 

Jacques PA, Artero V, Pecaut J, Fontecave M (2009) Cobalt and nickel diimine-dioxime complexes as molecular electrocatalysts for hydrogen evolution with low overvoltages. Proc Natl Acad Sci U S A 106(49) 20627-20632. doi 10.1073/pnas.0907775106... 

The first reported chiral catalysts allowing the enantioselective addition of diethylzinc to aryl aldehydes in up to 60% cc were the palladium and cobalt complexes of 1,7,7-trimethylbicy-clo[2.2.1. ]heptane-2,3-dione dioxime (A,B)3. A number of other, even more effective catalysts, based on the camphor structure (C K, Table 26) have been developed. 

Benzoquinone, 3,5-di-t-butyl-cobalt complexes, 2, 398 Benzoquinone dioximates metal complexes... 

Complexes containing encapsulated metal ions (clathrochelates ) with the formula [M(dioxime)3(BR)2] are known with iron(II) 135, cobalt(ll) 136, cobalt(III) 137, and ruthenium(ll) 138 (Fig. 37) [205-220]. Generally, these macrobicyclic complexes are prepared by template synthesis from a mixture of... 

In contrast with the Schiff base salen, salicylaldehyde oxime (79) (salox) complexes of Co have received comparatively little attention, but a series of bis-bidentate divalent complexes of the form iraiis-Co(sa 1 ox)2( D M SO)2 have been reported.343 The heterocyclic bidentate oxime violurate (lH,3H-pyrimidine-2,4,5,6-tetrone 5-oximate, Hvi) (80) and its /V-methyl (mvi) and /V,/V -dimethyl (dmvi) derivatives form high-spin divalent [Co(vi)]+ and Co(vi)2 complexes, whereas [Co(vi)3] is low spin.344 The mixed-ligand Co(dmvi)2(phen) complex is also low spin. The crystal structure of m-Co(pxo)2Br2 (pxo = 2-acetylpyridine-l-oxide oxime) is isostructural with the Ni11 relative.345 The dichloro complex also adopts a cis configuration. The tridentate dioximes 2,6-diformyl-4-methylphenol dioxime and 2,6-diacetyl-4-methylphenol dioxime (Hdampo) form binuclear complexes of the type (81a) and (81b) respectively.346 Cobalt oxide nanoparticles were prepared by... 

Cyclohexane-1,2-dione dioxime (nioxime) complexes of cobalt (II) and nickel (II) were concentrated from 10 ml seawater samples onto a hanging mercury drop electrode by controlled adsorption. Cobalt (II) and nickel (II) reduction currents were measured by differential pulse cathodic stripping voltammetry. Detection limits for cobalt and nickel were 6 pM and 0.45 mM, respectively. The results of detailed studies for optimising the analytical parameters, namely nioxime and buffer concentrations, pH, and adsorption potential are discussed. 

Clathrochelates comprise a new type of coordination compound containing a metal ion both coordinately saturated and encapsulated by a single ligand.1 5 The ligands of one class of clathrochelates are derived from dioximes and various boron compounds.1,4 Typical examples of iron and cobalt clathrochelates of this structural class are shown in Fig. 19 and Table I. These complexes are readily prepared from iron(II) or cobalt(II) salts,... 

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