Kinetics of the outer-sphere oxidation of thiourea by heteropoly-α_plus-plus">2-17-tungsto-1-vanadodiphosphate anion

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• 作者：Thangamariyappan Shanmugaprabha ; Karuppaiah Selvakumar…
• 刊名：Transition Metal Chemistry
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：42
• 期：1
• 页码：95-103
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Catalysis; Physical Chemistry; Inorganic Chemistry; Organometallic Chemistry;
• 出版者：Springer International Publishing
• ISSN：1572-901X
• 卷排序：42

文摘

Kinetics of the oxidation of thiourea (tu) by heteropoly-α₂-17-tungsto-1-vanadodiphosphate anion, α₂-[P₂VVW₁₇O₆₂]7−p>, have been studied spectrophotometrically in aqueous acidic medium at 25 °C. At low pH (2.4–3.0), the neutral form of tu is the only reactive species. At higher pH (4.2–4.9), both neutral and deprotonated forms of tu participate in the reaction. The observed mixed-order kinetics suggest two parallel reactions: one in which the order in [tu] is unity, and a second in which it is two. In both cases, the order in [α₂-[P₂VVW₁₇O₆₂]7−p>] is unity. Based on the kinetic studies, a mechanism is proposed, in which a second-order proton-coupled electron transfer involving NH₂CSNH₂ and α₂-[P₂VVW₁₇O₆₂]7−p> proceeds through a sequential electron transfer, followed by proton transfer such that the reaction is an “activation-controlled” outer-sphere electron transfer process. By applying the Marcus equation, the self-exchange rate constants for the couples \({\text{NH}}_{2} {\text{CSNH}}_{2}^{ \cdot + }\)/NH₂CSNH₂ and α₂-[P₂VVW₁₇O₆₂]7−p>/α₂-[P₂VIVW₁₇O₆₂]8−p> were evaluated.