Browsing by Author "Yaman, SO"

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    Electrochemistry of Acetate-, Carbonate-, Sulfate-, and Dihydrogenphosphate-Bridged Dirhodium(ii) Complexes
    (verlag Z Naturforsch, 2003) Yaman, SO; Önal, AM; Isci, H
    Complexes, [Rh-2(B-B)(4)L-2](n) (B-B = CH3CO2-, L = CH3CN, H2O, Cl-, Br-, SCN-; B-B CO32-, SO42-, H2PO4-, L = H2O, Cl-, Br-, SCN-) were prepared and their cyclic voltammograms (CV) and electronic absorption spectra were measured in solution. The CV of the complexes exhibits a reversible one-electron transfer from a metal-based orbital. Constant potential electrolysis at the oxidation peak potential of [Rh-2(O2CCH3)(4)(NCCH3)(2)] in acetonitrile yielded [Rh-2(O2CCH3)(4)(NCCH3)(2)](+), a mixed valent Rh(II)-Rh(III) cation complex. The formation of the mixed valent complex was monitored by measuring electronic absorption spectra of the solution in situ during the oxidative electrolysis. The reductive electrolysis of the mixed valent complex solution, in the same electrolysis cell, yielded the original electronic absorption spectrum of the starting complex. The changes in the oxidation and reduction potentials of the complexes with different axial ligands, L = H2O, Cl-, Br-, SCN-, are correlated to the relative energy changes of HOMO and LUMO of the complexes, which indicates the metal-axial ligand sigma- and pi-bonding interactions. Spectroscopic and CV data indicate that the degree of a-interaction is Cl- > Br- > SCN-, and that of pi-interaction is Br- > SCN- > Cl-.
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    Spectroelectrochemical Investigation of Pentacarbonyl(pyrazine)metal(0) (metal = Cr, Mo, W) Complexes of Group 6 Elements
    (Walter de Gruyter Gmbh, 2002) Yaman, SO; Esentürk, E; Kayran, C; Önal, AM
    The electrochemical behaviour of pentacarbony l(pyrazine) metal (0) complexes of the group 6 elements was studied by cyclic voltammetry in dichloromethane-(n-Bu)(4)NBF4 solvent-electrolyte couple at -20 degreesC vs. Ag/Ag+ or SCE reference electrode. Constant potential electrolyses of the complexes were carried out at their first oxidation peak potentials and monitored in situ by UV-Vis spectrometry. Electrolysis of W(CO)(5)pz produces [W(CO)(5)pz](+) and a similar electrochemical mechanism is expected both for Cr(CO)(5)pz and Mo(CO)(5)pz complexes. In situ low temperature constant current ESR electrolysis also confirmed the production of [W(CO)(5)pz](+) after the electron transfer.