Celestine Michael J, Joseph Lorne S, Holder Alvin A
Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Boulevard, Norfolk, VA 23529-0126, USA.
College of Mathematics and Science, University of the Virgin Islands, 2 John Brewers Bay, St Thomas, VI 00802-9990, USA.
Inorganica Chim Acta. 2017 Jan 1;454:254-265. doi: 10.1016/j.ica.2016.07.013.
The kinetics and mechanism of the oxidation of [Co(dmgBF)(OH)] (where dmgBF = difluoroboryldimethylglyoximato) by sodium hypochlorite (NaOCl) were investigated by stopped-flow spectrophotometry at 450 nm over the temperature range of 10 °C ≤ θ ≤ 25 °C, pH range of 5.0 ≤ pH ≤ 7.8, and at an ionic strength of 0.60 M (NaCl). The pK value for [Co(dmgBF)(HO)] was calculated as 5.27 ± 0.14 at I = 0.60 (NaCl). The redox process was dependent on pH and oxidant concentration in a complex manner, that is, k = ((k[H] + kK)/([H] + K))[OCl], where at 25.3 °C, k was calculated as 3.54 × 10 M s, and k as 2.51 × 10 M cm. At a constant pH value, while varying the concentration of sodium hypochlorite two rate constants were calculated, viz., k' = 7.56 s (which corresponded to a reaction pathway independent of the NaOCl concentration) and k' = 2.26 × 10 M s, which was dependent on the concentration of NaOCl. From the variation in pH, [Formula: see text], and [Formula: see text] were calculated as 58 ± 16 kJ mol, 46 ± 1 kJ mol, 34 ± 55 J mol K, and -6 ± 4 Jmol K, respectively. The self-exchange rate constant, k, for sodium hypochlorite (as ClO) was calculated to be 1.2 × 10 M s, where an outer-sphere electron transfer mechanism was assumed. A green product, [Co(dmgBF)(OH)(OH)]·1.75NaOCl, which can react with DMSO, was isolated from the reaction at pH 8.04 with a yield of 13%.
通过停流分光光度法，在10°C≤θ≤25°C的温度范围、5.0≤pH≤7.8的pH范围以及0.60M（NaCl）的离子强度下，于450nm处研究了次氯酸钠（NaOCl）氧化[Co(dmgBF)(OH)]（其中dmgBF = 二氟硼基二甲基乙二肟）的动力学和机理。在I = 0.60（NaCl）时，[Co(dmgBF)(HO)]的pK值计算为5.27±0.14。氧化还原过程以复杂的方式依赖于pH和氧化剂浓度，即k = ((k[H] + kK)/([H] + K))[OCl]，其中在25.3°C时，k计算为3.54×10 M s，k为2.51×10 M cm。在恒定pH值下，改变次氯酸钠浓度时计算出两个速率常数，即k' = 7.56 s（对应于与NaOCl浓度无关的反应途径）和k' = 2.26×10 M s，其依赖于NaOCl的浓度。根据pH变化，分别计算出[公式：见文本]和[公式：见文本]为58±16 kJ mol、46±1 kJ mol、34±55 J mol K和 -6±4 Jmol K。假设外层电子转移机理，计算出次氯酸钠（作为ClO）的自交换速率常数k为1.2×10 M s。从pH为8.04的反应中分离出一种绿色产物[Co(dmgBF)(OH)(OH)]·1.75NaOCl，其能与DMSO反应，产率为13%。
