通过外层和内层电子转移途径，水合亚铁离子对二氧化氯的还原作用。

Chlorine dioxide reduction by aqueous iron(II) through outer-sphere and inner-sphere electron-transfer pathways.

作者信息

Wang Lu, Odeh Ihab N, Margerum Dale W

机构信息

Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.

出版信息

Inorg Chem. 2004 Nov 15;43(23):7545-51. doi: 10.1021/ic048809q.

DOI:10.1021/ic048809q

PMID:15530106

Abstract

The reduction of ClO(2) to ClO(2)(-) by aqueous iron(II) in 0.5 M HClO(4) proceeds by both outer-sphere (86%) and inner-sphere (14%) electron-transfer pathways. The second-order rate constant for the outer-sphere reaction is 1.3 x 10(6) M(-1) s(-1). The inner-sphere electron-transfer reaction takes place via the formation of FeClO(2)(2+) that is observed as an intermediate. The rate constant for the inner-sphere path (2.0 x 10(5) M(-1) s(-1)) is controlled by ClO(2) substitution of a coordinated water to give an inner-sphere complex between ClO(2) and Fe(II) that very rapidly transfers an electron to give (Fe(III)(ClO(2)(-))(H(2)O)(5)(2+))(IS). The composite activation parameters for the ClO(2)/Fe(aq)(2+) reaction (inner-sphere + outer-sphere) are the following: DeltaH(r)++ = 40 kJ mol(-1); DeltaS(r)++ = 1.7 J mol(-1) K(-1). The Fe(III)ClO(2)(2+) inner-sphere complex dissociates to give Fe(aq)(3+) and ClO(2)(-) (39.3 s(-1)). The activation parameters for the dissociation of this complex are the following: DeltaH(d)++= 76 kJ mol(-1); DeltaS(d)++= 32 J K(-1) mol(-1). The reaction of Fe(aq)(2+) with ClO(2)(-) is first order in each species with a second-order rate constant of k(ClO2)- = 2.0 x 10(3) M(-1) s(-1) that is five times larger than the rate constant for the Fe(aq)(2+) reaction with HClO(2) in H(2)SO(4) medium ([H(+)] = 0.01-0.13 M). The composite activation parameters for the Fe(aq)(2+)/Cl(III) reaction in H(2)SO(4) are DeltaH(Cl(III))++ = 41 kJ mol(-1) and DeltaS(Cl(III))++ = 48 J mol(-1) K(-1).

摘要

在0.5 M高氯酸中，水合亚铁离子将二氧化氯还原为亚氯酸盐的过程通过外层（86%）和内层（14%）电子转移途径进行。外层反应的二级速率常数为1.3×10⁶ M⁻¹ s⁻¹。内层电子转移反应通过形成FeClO₂²⁺进行，该离子被观测为中间体。内层途径的速率常数（2.0×10⁵ M⁻¹ s⁻¹）受配位水的二氧化氯取代控制，从而形成二氧化氯与亚铁离子之间的内层配合物，该配合物能非常迅速地转移一个电子生成(Fe(III)(ClO₂⁻)(H₂O)₅²⁺)(IS)。二氧化氯/水合亚铁离子反应（内层 + 外层）的复合活化参数如下：ΔH(r)⁺⁺ = 40 kJ mol⁻¹；ΔS(r)⁺⁺ = 1.7 J mol⁻¹ K⁻¹。Fe(III)ClO₂²⁺内层配合物解离生成水合铁离子(Fe³⁺(aq))和亚氯酸盐(ClO₂⁻)（39.3 s⁻¹）。该配合物解离的活化参数如下：ΔH(d)⁺⁺ = 76 kJ mol⁻¹；ΔS(d)⁺⁺ = 32 J K⁻¹ mol⁻¹。水合亚铁离子(Fe²⁺(aq))与亚氯酸盐(ClO₂⁻)的反应对各物种均为一级反应，二级速率常数k(ClO₂⁻) = 2.0×10³ M⁻¹ s⁻¹，该值比在硫酸介质（[H⁺] = 0.01 - 0.13 M）中水合亚铁离子(Fe²⁺(aq))与亚氯酸(HClO₂)反应的速率常数大五倍。在硫酸中，水合亚铁离子(Fe²⁺(aq))/氯(III)反应的复合活化参数为ΔH(Cl(III))⁺⁺ = 41 kJ mol⁻¹和ΔS(Cl(III))⁺⁺ = 48 J mol⁻¹ K⁻¹。