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KMID : 1059519920360060894
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Journal of the Korean Chemical Society
1992 Volume.36 No. 6 p.894 ~ p.905
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Oxidation Reaction of Hydrazobenzene by Activated Catalysts of Oxygen Adducted Tetradentate Schiff Base Cobalt(Ⅱ) Complexes in Methanol Solvent. (Ⅱ)
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Chjo Ki-Hyung
Choi Yong-Kook
Kim Sang-Bock
Park Jong-Ki
Park Dong-Hwa
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Abstract
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Dioxygen binding and homogeneous catalytic oxidation of hydrazobenzene were investigated by employing tetradentate Schiff base Cobalt(Ⅱ) complexes such as Co(Ⅱ)(SED)(Py)2, Co(Ⅱ)(SOPD)(Py)2 and Co(Ⅱ)(SND)(Py)2 in saturated oxygen methanol solvent. The major product of hydrazobenzene (H2AB) oxidation by catalysts of superoxo type [Co(Ⅲ)(SED)(Py)O2] and [Co(Ⅲ)(SOPD)(Py)O2] complexes are trans-azobenzene (t-AB) and rate constants k for oxidation reaction was 7.692 × 10-2 M/sec for [Co(Ⅲ)(SED)(Py)O2] and 5.076 × 10-2 M/sec for [Co(Ⅲ)(SOPD)(Py)O2]. But cis-azobenzene (c-AB) are obtained as a major product with μ-peroxo type [Co(Ⅲ)(SED)(Py)]2O2 catalyst, and rate constant k is 1.266 × 10-2 M/sec. The rate constants of oxidation reaction has been studied spectrophotometrically and the rate law established. A mechanism involving a intermediate activated complexes of catalyst, hydrazobenzene and oxygen has been proposed. H2AB ＋ Co(Ⅱ)(Schiff base)(Py)2 ＋ O2 K↔MeOH Co(Ⅲ)(Schiff base)(Py)O2·H2AB ＋ Py k→ Co(Ⅱ)(Schiff base)(Py)2 ＋ t-AB ＋ H2O2(Scchiff base : SED and SOPD). H2AB ＋ 2Co(Ⅱ)(SND)(Py)2 ＋ O2 K↔MeOH [Co(Ⅲ)(SND)(Py)]2O2·H2AB ＋ 2Py k→ (Co(Ⅱ)(SND)(Py)2 ＋ c-AB ＋ H2O2
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