Bimetallo-radical carbon-hydrogen bond activation of methanol and methane

被引：57

作者：

Cui, WH ^{[1
]}

Zhang, XP ^{[1
]}

Wayland, BB ^{[1
]}

机构：

[1] Univ Penn, Dept Chem, Philadelphia, PA 19104 USA

来源：

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY | 2003年 / 125卷 / 17期

关键词：

D O I：

10.1021/ja034494m

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

Carbon-hydrogen bond cleavage reactions of CH3OH and CH4 by a dirhodium(II) diporphyrin complex with a m-xylyl tether (·Rh(m-xylyl)Rh·(1)) are reported. Kinetic-mechanistic studies show that the substrate reactions are bimolecular and occur through the use of two Rh(II) centers in the molecular unit of 1. Second-order rate constants (T = 296 K) for the reactions of 1 with methanol (k(CH3OH) = 1.45 × 10-2 M-1 s-1) and methane (k(CH4) = 0.105 M-1 s-1) show aclear kinetic preference for the methane activation process. The methanol and methane reactions with 1 have large kinetic isotope effects (k(CH3OH)/k(CD3OD) = 9.7 ± 0.8, k(CH4)/k(CD4) = 10.8 ± 1.0, T = 296 K), consistent with a rate-limiting step of C-H bond homolysis through a linear transition state. Activation parameters for reaction of 1 with methanol (ΔH = 15.6 ± 1.0 kcal mol-1; ΔS = -14 ± 5 cal K-1 mol-1) and methane (ΔH = 9.8 ± 0.5 kcal mol-1; ΔS = -30 ± 3 cal K-1 mol-1) are reported. Copyright © 2003 American Chemical Society.

引用

页码：4994 / 4995

页数：2

共 18 条

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