2.6- diacetylpyridine bis

When a methanol solution containing a 1 1 molar ratio of cobalt(II) chloride to 2,6-diacetylpyridine bis(thiosemicarbazone), 28, is refluxed, [Co(28)Cl]Cl is formed [147]. Spectral studies indicate bonding as a SNNNS pentadentate... 

Diacetylpyridine bis(S-methylisothiosemicarbazone), 46, formed [Co(46-H)l2] H20 from a mixture of cobalt(II) acetate, 46, and hydrogen iodide in heated ethanol [203]. The complex is 7-coordinate with 46 functioning as a NNNNN pentadentate ligand. 

Solution studies of nickel(II) complexes of 2,6-diacetylpyridine bis(thiosemi-carbazone), 28, have been carried out [147]. From a refluxed methanolic solution containing 28 and nickel(II) chloride, [Ni(28)Cl2] was isolated which behaved as a 1 1 electrolyte in methanol [152], Based on spectral information it is proposed that the complex is a distorted octahedron with a SNNNS pentadentate ligand. 

A series of paramagnetic [NiL-2H] complexes have been isolated in which L = 2,6-diacetylpyridine bis(azacyclothiosemicarbazones) with Ni(II) assuming a distorted five-coordinate structure with d-d bands at about 7250, 10510, 12500, 14400, 19200 and 20500 cm [153], None of these Ni(II) complexes were reported to have activity against the P388 lymphocytic leukemia test system in mice. 

Diacetylpyridine bis(S-methylisothiosemicarbazone), 46, yields five-coordinate [Ni(46-H)]X (X = I, NCS) and six-coordinate [Ni(46-2H)] [203]. The latter compound is thought to be dimeric or polymeric with octahedral nickelfll) centers. 

Bis(semicarbazones) with N202 donor set form six-coordinate complexes with distorted octahedral geometry. The well-studied (potentially pentadentate) 2,6-diacetylpyridine bis(semicarbazone) (H2daps, 448) forms two type of crystals containing the same complex [Ni(Hdaps)2].1267 The ligands are coordinated through their pyridine and the inline N atoms and the O atom of one arm. 

Yet another hydrazine-based ligand, 2,6-diacetylpyridine bis(benzoic acid hydrazone) (dpbh 10) forms an interesting complex with La(N03)3 in which the coplanar penannular pentaden-tate dpbh coordinates together with three bidentate nitrate ions to give an 11-coordinated complex. One nitrate ion is disposed near the gap in the dpbh chain with the other two above and below the dpbh plane. Interatomic distances are La—N(ligand) = 2.769-2.790, La— O(ligand) = 2.507 and 2.560, and La—O(nitrate) = 2.563-2.648 A. 

Effect of Pressure on Proton-Coupled Electron Transfer Reactions of Seven-Coordinate Iron Complexes in Aqueous Solution It has been shown that seven-coordinate Fe(III) diaqua complexes consisting of a pentaaza macrocyclic ligand possess superoxide dismutase (SOD) activity, and therefore could serve an imitative SOD function.360 Choosing appropriate chemical composition of a chelate system yielded suitable pKa values for the two coordinated water molecules so that the Fe(III) complexes of 2,6-diacetylpyridine-bis(semicarbazone) (dapsox) and 2,6-diacetylpyridine-bis(semioxamazide) (dapsc) (see Scheme 7.12) would be present principally in the highly active aqua-hydroxo form in solution at physiological pH.361... 

Ligands in complexes I. = tetrathiafulvalenium, L2 = H2NCOC6H4NH3-2, L3 = 2-H2NC5H4NH, L4 = 2,6-diacetylpyridine-bis(2-furoylhydrazone)dimethyltin, L5 =N,N -dimethyl-5-nitro-2,2/-bi-imidazol-3/-ium, L6 = cytosinium, L7 = 8-methylaminoquinolinium, L8 = iV-(4-hydroxybenzylidene)-4-methoxyaniline, L9 = 8-meth-oxyquinolinium, 1.19 = (3-MePz)3SnBuCl2, T = thiamine, Pz = Pyrazole. cCentrosymmetric anion. 

Figure 4.44 Structure of [Sm(26)(N03)(0H)(H20)]+ [73], (Reproduced from Polyhedron, 23, F.B. Tamboura et al., Structural studies of bis-(2,6-diacetylpyridine-bis-(phenylhydrazone)) and X-ray structure of its Y(III), Pr(III), Sm(III) and Er(III) complex, 1191, 2004, with permission from Elsevier.)...

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