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Kinetics and Mechanism of trans-[Cr(cyca)(OH)F]+Complex Oxidation by [Fe(CN)6]3- Ion in Strongly Alkaline Aqueous Solutions

Katafias A., Impert O., Kita P., Wrzeszcz G., Dominiak D.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 6

931-941

EN

Oxidation of the trans-[Cr(cyca)(OH)F]+ complex, where cyca = meso-5,5,7,12,14- hexamethyl-1,4,8,11-tetraazacyclotetradecane, by [Fe(CN)6]3- ion in strongly alkaline media has been studied. A long-lived intermediate chromium(V) species was detected basing on the EPR signal at giso = 1.986. The hyperfine structure of the main EPR signal is consistent with the d1-electron interactions with four equivalent or nearly equivalent nitrogen nuclei and [CrV=O(cycaox)]3+ formula, where cycaox = oxidized cyca, can be postulated for the intermediate CrV complex. Kinetics of the rate limiting stage - electron transfer from the chromium(III) complex - has been studied in details applying an excess of the reductant and [OH-] at ionic strength equal 2.0 M. The rate law: -d[FeIII] dt = d[CrIV] dt = 0,5k cb K[OH-] 1+ 0,5(K-1)[OH-] [CrIII][FeIII] is consistent with an outer-sphere electron transfer from the conjugate base (cb) of the reductant formed in a preequilibrium (K) step. Reactivity of the deprotonated chromium(III) complex is characterized by kcb 298 = 9.7,deltaH#= (44.1š 0.5) kJ_mol-1, deltaS# = (-78.0 š 2.0) JxK-1xmol-1 and the preequilibrium step -by K298 = 0.237, delta H0 = (11.5 š 1.8) kJ_mol-1, delta S0 = (26.6 š 5.8) JxK-1xmol-1.

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Wpływ preparatyki na właściwości fizyko-chemiczne i katalityczne nośnikowych katalizatorów rodowych (Rh/nośniki: SiO2, TiO2, MgO)

Szubiakiewicz E., Jóźwiak W. K., Dominiak D.

Przemysł Chemiczny

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2003

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T. 82, nr 8-9

786-789

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Synthesis and investigation of textural properties of silica gels

Ignaczak W., Jóźwiak K. W., Kaźmierczak A., Dominiak D., Rynkowski J., Szynkowska M. I.

Polish Journal of Chemical Technology

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2003

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Vol. 5, nr 3

35-38

EN

Texture properties and structure of silica gels prepared by so-gel processing using different types of solvents and doped with Fions have been investigated by evaluating the specific surface area and pore specific volume. Solids were characterized by nitrogen adsorption at 77 K. XRD measurements were used to determine structure and scanning electron micrographs studies (SEM) were applied to observe an image of silica.