Dioxime complexes

The macrocyclic bis(oximato)borates 130-131 and its tetramethylene analogue 132 are derivatives of the bisborylated dioxime complexes discussed above, in which one of the OBR2O groups has been substituted by a trimethylene or tetramethylene unit, respectively (Fig. 35). 

Tris(dioxime) complexes that are capped with a boryl group BR at only one end of the molecule are also known, e.g., with technetium(III) [227, 228] and rhenium(III) [229]. 

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. 

Blinc and Iladzi (23a) have shown that this frequency, which lies at about 1650-1820 cm-1 in a series of afe-dioxime complexes, is more probably the in-plane O-H deformation frequency, and that the O-H stretching frequency lies in the range 2340-2380 cm-1 they find the out-of-plane O-H vibration between 860 and 930 cm-1. It seems likely that the hydrogen atoms do not lie directly between oxygen atoms, but it is still uncertain whether they are symmetrically disposed with respect to the oxygen atoms or not. 

Banks and Barnum (18) have found that the visible spectra of a series of these nickel and palladium ric-dioxime complexes always show a band in... 

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. 

In the majority of cases, the formation of macrobicyclic metal tris-dioximates is stipulated by the interaction of the reactive oxime groups in tris-dioximate complexes with Lewis acids. The most efficient capping agents have proved to be trigonal organic and inorganic boron compounds. 

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]. 

Treher EN, Francesconi LG, Gougoutas JZ, Malley M, Nunn A (1989) Mono-capped tris dioxime complexes of technetium (III) synthesis and structural characterization of TCX (dioxime)3, B-R (X=C1, Br dioximedimethylglyoxime cyclohexanedioxime R=CFl3, C4FI9). Inorg Chem 28 3411-3416... 

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