Energetics of C−H Bond Activation of Fluorinated Aromatic Hydrocarbons Using a [Tp′Rh(CNneopentyl)] Complex

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• 作者：Meagan E. Evans ; Catherine L. Burke ; Sornanong Yaibuathes ; Eric Clot ; Odile Eisenstein ; William D. Jones
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：September 23, 2009
• 年：2009
• 卷：131
• 期：37
• 页码：13464-13473
• 全文大小：297K
• 年卷期：v.131,no.37(September 23, 2009)
• ISSN：1520-5126

文摘

C−H bond activation of fluorinated aromatic hydrocarbons by [Tp′Rh(CNneopentyl)] resulted in the formation of products of the type Tp′Rh(CNneopentyl)(aryl_F)H. The stability of the Rh−C_aryl product is shown to be strongly dependent on the number of ortho fluorines and only mildly dependent on the total number of fluorine substituents. Complexes with aryl groups containing two ortho fluorines have barriers to reductive elimination that are 5 kcal mol⁻¹ higher than for those with a single ortho fluorine. Competition experiments along with ΔG_re values allow for the determination of relative Rh−C_aryl bond strengths and illustrate the large ortho fluorine effect on the strength of the Rh−C_aryl bond. A large change in Rh−C_aryl bond strength was measured for small changes in the respective calculated C−H bond strengths. Relating M−C to C−H bond strengths resulted in a line (slope = 2.14) that closely matches the theoretically calculated value (slope = 1.96). This is the first experimental quantization of an ortho fluorine effect as predicted by theory.