Voltammetric anodic dissolution (VAD) applied to the quantitative analysis of coating discontinuities – influence of electrodeposition parameters

A voltammetric anodic dissolution (VAD) technique was used to quantify disruption and fault levels in nickel deposits on a copper substrate. This technique was based on a comparison of the charge passivation densities of the substrate with and without coating. The chosen system was electrolytic nickel coating on copper substrate, applied from a commercial Watts bath without additives under galvanostatic conditions. The results show the VAD technique to be useful in detecting variations in coating porosity and discontinuities caused by different applied deposition currents and charge densities. A minimum of porosity level was also detected in coating thicknesses obtained at a charge density of about 1200 mC cm^–2. With higher deposition charge densities, a coating fragmentation process (disruption) generating spheric-like particles was observed.     

An unusual dichromium(II,II) compound bearing di-2-pyridyl ketone oximate ligands and prepared by the ligand-assisted reduction of a trichromium(III,III,III) complex in air

The reaction of the oxide-centred triangular, trichromium(III,III,III) complex [Cr₃O(O₂CCMe₃)₆(H₂O)₃](O₂CCMe₃) with di-2-pyridyl ketone oxime, (py)₂CNOH, in MeCN under aerobic and refluxing conditions yields the pivalate-free, dichromium(II,II) complex [Cr₂{(py)₂CNO}₄] · 2H₂O (1 · 2H₂O). The dinuclear complex can also be prepared by the reaction of [Cr(CO)₆] with (py)₂CNOH in refluxing MeCN/H₂O in air. The two high-spin Cr^II atoms are doubly bridged by two 2.1110 oximate ligands, while a chelating 1.0110 (py)₂CNO⁻ ion completes distorted trigonal bipyramidal coordination at each metal centre. The dimers are stabilized by intramolecular stacking interactions between the terminal (py)₂CNO⁻ ligands, and the structural effects of these interactions are discussed.