Energetics of C-H Bond Activation of Fluorinated Aromatic Hydrocarbons Using a [Tp′Rh(CNneopentyl)] Complex
Energetics of C-H Bond Activation of Fluorinated Aromatic Hydrocarbons Using a [Tp′Rh(CNneopentyl)] Complex
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DOI：
10.1021/ja905057w
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发表时间：
2009-09-23
影响因子：
15
通讯作者：
Jones, William D.
中科院分区：
文献类型：
--
作者：
Evans, Meagan E.;Burke, Catherine L.;Jones, William D.
[Tp'Rh(CNneopentyl)]激活氟化芳烃的C-H键，形成了Tp'Rh(CNneopentyl)（芳基(F)）H型产物。rh - c -芳基产物的稳定性强烈依赖于邻氟的数量，而仅轻微依赖于氟取代基的总数。含有两个邻位氟的芳基配合物的还原消除障碍比含有单个邻位氟的配合物高5千卡摩尔（-1）。竞争实验和δ G(re)（双匕首）值可以测定rh - c -芳基键的相对强度，并说明邻位氟对rh - c -芳基键强度的巨大影响。rh - c -芳基键强度变化很大，而各自计算的C-H键强度变化很小。将M-C与碳氢键强度联系起来，得到一条与理论计算值（斜率= 1.96）非常吻合的线（斜率= 2.14）。这是理论预测的邻氟效应的第一个实验量化。
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 similar to 5 kcal mol(-1) higher than for those with a single ortho fluorine. Competition experiments along with Delta G(re)(double dagger) 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.