Spectral and Electrochemical Features of some substituted Bis(2‐hydroxyaryloximato)Co(II), Ni(II), Pd(II), and Cu(II) Chelates. Crystal and Molecular Structure of Trans‐bis(propanone,1‐[2‐hydroxyphenyl]‐oximato)Ni(II)

Abstract

The reaction products of five 2‐hydroxyaryloximes with Ni(II), Pd(II), and Co(II) have been obtained and characterized by elemental analyses, conductometric measurements, magnetic moment determination, and spectroscopic methods (IR, 1H NMR, electronic absorption in solutions and in solid state). Cyclic voltammetry on mercury and carbon fibre electrodes has been employed to investigate the electrochemical behaviour in DMF solutions. The effect of substituents on the structure of the chelates and the electron distribution is assessed, discussed and compared with the behaviour of the corresponding copper(II) chelates. The structure of the title compound trans‐bis(propanone, 1‐[2‐hydroxyphenyl]‐oximato) nickel(II), Ni(C9H10NO2)2 was determined by X‐ray diffraction monoclinic system (space group P21/n), a = 11.894, b = 5.126, c = 13.668 Å, b̃ = 103.72°, Z = 2. The structure was refined by full‐matrix least squares to a conventional R = 0.03. Ni is on the equatorial plane and surrounded by two nitrogen and two oxygen at distances 1.884(3) Å and 1.825(2) Å, respectively.

Metal complexes of 3-thiophene carboxamides containing a pyridine ring

“…A similar wave at 1.98 V was observed for the parent ligand [15] and the small difference in E p a suggests that ligand may be liberated upon oxidation of the complex. A similar result has been reported in a different solvent for trans-bis(propanone,1-[2-hydroxyphenyl]-oximato) copper (II), another N, O ligand [44]. The cathodic portion of the scan revealed the presence of a wave with E p c at −0.40 V which was associated with reduction of the complex, Cu (L) 2 2+ /Cu(L) 2 + ; a quasi-reversible companion oxidation wave appears on the reverse scan near 0.29 V. Another process, ascribed to the reduction of Cu(L) 2 + , is observed as a broad wave beginning near −0.58 V and produces free copper which deposits on the electrode.…”

Spectral and thermal features of some novel iron(III) chelates with substituted 2-hydroxyaryloximes

“…Such information is relevant since hydroxyoximes are ambidentate with the possibility of a variety of coordination modes, depending among other factors upon hydrogen bonding, electron distribution and steric hindrance. In this respect we have already studied several transition metal complexes of aromatic hydroxyaryloximes to establish the chemical, electronic and redox properties of the various coordination geometries obtainable with the oxime systems [6,7]. Our results were found to be in accordance with well-established X-ray structure determinations of the trans square-planar geometry of some salicylaldoximates [7][8][9].…”

“…In the IR spectra of the ligands, the stretching mode of the oximino hydroxyl group was observed as an intense broad band at 3360-2_30 cm -I [6,7]. The variation in the position of this band reveals the influence of the substituents.…”

“…Since we know that the 2-hydroxyaryloxime ligands give an intense chargetransfer band with transition metals [6,7], it is reasonable to assign the band found at 510 nm as the charge-transfer band. This is in agreement with what was found for the Fe(III) low-spin octahedral complex [Fe(o-vanillinoxime)2(H20)2]Cl [14].…”

Crystal structure of trans-bis[2-hydroxy-5-methyl-phenonethanoneoximato- N,O]nickel(II), C18H20N2NiO4

“…From elemental analysis and spectroscopic data (IR and electronic exicitation) [1], it was deduced the composition of the compound Ni(mpox)2. Although a complete diamagnetism was expected for this compound, it is found to posess a little paramagnetism (1.42 BM) room temparature, which is lost after heating the compound at 413 Κ for 1 hour.…”