Density functional theory studies for the role of N,N,N′,N′-tetramethylethylenediamine (TMEDA) in iron-catalyzed cross-coupling reactions between phenylmagnesium bromide and bromocycloheptane have been investigated using B3LYP-D3BJ functionals and the SMD (tetrahydrofuran) model. The results reveal that the whole catalytic cycle has two possible pathways: one in which main product P₁, named Path A, is obtained or another in which byproduct P₂, named Path B, is obtained. TMEDA-bound iron intermediates are responsible for the products of P₁ or P₂. The radical intermediate initiated by TMEDA–iron species starts the reaction, which just highlights the central role of TMEDA intermediates in the catalytic cycle. Different spin states of the iron species are checked. The calculated results are helpful for understanding the mechanisms of TMEDA involved in iron-catalyzed cross-coupling reactions. It shows that the rate-determining step to obtain main product P₁ in Path A is a reductive elimination step where Gibbs free energy in solvent THF, ΔG_sol, is 9.5 kcal/mol, and the rate-limiting step to obtain byproduct P₂ in Path B is the radical initiation step where Gibbs free energy in solvent THF, ΔG_sol, is 26.4 kcal/mol, which means that Path A to obtain main product P₁ is favored, which meets the experimental results.

中文翻译：

---

TMEDA 在铁催化 C(sp2)–C(sp3) 交叉偶联反应中的作用：使用 DFT 计算的机理研究

使用 B3LYP-D3BJ 泛函和 SMD（四氢呋喃）模型对N , N , N ', N '-四甲基乙二胺 (TMEDA) 在铁催化的苯基溴化镁和溴代环庚烷之间的交叉偶联反应中的作用进行了密度泛函理论研究。结果表明，整个催化循环有两种可能的路径：一种是获得主产物P ₁，称为路径A，另一种是获得副产物P ₂，称为路径B。结合 TMEDA 的铁中间体负责产生P ₁或P ₂的产物。由TMEDA-铁物质引发的自由基中间体开始反应，这凸显了TMEDA中间体在催化循环中的核心作用。检查铁物质的不同自旋状态。计算结果有助于理解TMEDA参与铁催化交叉偶联反应的机制。表明路径A中获得主产物P _{1 的}限速步骤为还原消除步骤，溶剂THF中的吉布斯自由能ΔG sol_{为9.5 kcal/mol，获得副产物}P的限速步骤为还原消除步骤。路径B中的₂为自由基引发步骤，溶剂THF中的吉布斯自由能ΔG sol_为26.4 kcal/mol，这意味着路径A有利于获得主产物P ₁，符合实验结果。