Unusually stable palladium(IV) complexes: Detailed mechanistic investigation of C-O bond-forming reductive elimination
Unusually stable palladium(IV) complexes: Detailed mechanistic investigation of C-O bond-forming reductive elimination
复制标题
DOI：
10.1021/ja0541940
复制
发表时间：
2005-09-21
影响因子：
15
通讯作者：
Sanford, MS
中科院分区：
文献类型：
--
作者：
Dick, AR;Kampf, JW;Sanford, MS
本通讯描述了一个异常稳定的钯（IV）配合物家族的合成，包含两个螯合2-苯基吡啶配体和两个苯甲酸盐。这些配合物在加热后进行了干净的C−O键形成还原消除，并对这一催化相关过程的机理进行了详细的研究。溶剂效应、交叉实验、Eyring图（在cdcl3和DMSO中分别显示ΔS⧧为- 1.4±1.9和4.2±1.4）和Hammett分析（在对苯甲酸酯取代基取代时显示ρ = - 1.36±0.04）都表明，还原消除不是通过苯甲酸酯配体的初始解离进行的。相反，提出了一种涉及苯吡啶配体n臂预平衡解离的不寻常机制。
This communication describes the synthesis of a family of unusually stable palladium(IV) complexes containing two chelating 2-phenylpyridine ligands and two benzoates. These complexes undergo clean C−O bond-forming reductive elimination upon heating, and the mechanism of this catalytically relevant process has been studied in detail. Solvent effects, crossover experiments, Eyring plots (which show ΔS⧧of −1.4 ± 1.9 and 4.2 ± 1.4 in CDCl3and DMSO, respectively), and Hammett analysis (which shows ρ = −1.36 ± 0.04 upon substitution of thepara-benzoate substituent) all suggest that reductive elimination does not proceed via initial dissociation of a benzoate ligand. Instead, an unusual mechanism involving pre-equilibrium dissociation of the N-arm of the phenylpyridine ligand is proposed.