Meng Ling-Qi, Wang Jian-Sen, You Xiao-Xia, Zhong Rong-Lin, Gao Feng-Wei, Su Zhong-Min
Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, China.
School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun 130012, China.
Inorg Chem. 2024 Sep 23;63(38):17626-17638. doi: 10.1021/acs.inorgchem.4c02432. Epub 2024 Sep 5.
Iridium-catalyzed C-H borylation of aromatic and aliphatic hydrocarbons assisted by a directing group was theoretically investigated. Density functional theory (DFT) calculations revealed both Ir-catalyzed C(sp)-H and C(sp)-H borylations via an Ir/Ir catalytic cycle, where the tetra-coordinated (C, N)Ir(Bpin) complex with two vacant sites is an active species. Dramatically, the orientation of cyclometalation for C(sp)-H bond activation assisted by a directing group is different from the C(sp)-H one. The activation energy (Δ = 28.5 kcal mol) of the C(sp)-H bond via -chelation to form cyclometalation is lower than that (41.4 kcal mol) via -chelation. In contrast, the Δ (26.6 kcal mol) of the C(sp)-H bond via -chelation to form cyclometalation is lower than that (34.3 kcal mol) via -chelation. In addition, the rate-determining step of Ir-catalyzed C(sp)-H borylation is oxidative addition of the C(sp)-H bond, while that of C(sp)-H analogues is hydride migration. Such differences arise from not only the differences in the steric hindrance of the C(sp) and secondary C(sp) atoms but also the differences in the trans effect and steric effect of the two vacant sites of active species. These findings were expected to facilitate further studies on the design and synthesis of innovative ligands for Ir-catalyzed C-H borylation.
对导向基团辅助的铱催化芳烃和脂肪烃的C-H硼化反应进行了理论研究。密度泛函理论（DFT）计算表明，通过Ir/Ir催化循环可实现铱催化的C(sp)-H和C(sp)-H硼化反应，其中具有两个空位的四配位（C，N）Ir（Bpin）配合物是活性物种。引人注目的是，导向基团辅助的C(sp)-H键活化的环金属化取向与C(sp)-H的不同。通过-螯合形成环金属化的C(sp)-H键的活化能（Δ = 28.5 kcal/mol）低于通过-螯合的活化能（41.4 kcal/mol）。相反，通过-螯合形成环金属化的C(sp)-H键的Δ（26.6 kcal/mol）低于通过-螯合的活化能（34.3 kcal/mol）。此外，铱催化的C(sp)-H硼化反应的速率决定步骤是C(sp)-H键的氧化加成，而C(sp)-H类似物的速率决定步骤是氢化物迁移。这些差异不仅源于C(sp)和仲C(sp)原子空间位阻的差异，还源于活性物种两个空位的反位效应和空间效应的差异。这些发现有望促进对铱催化C-H硼化反应创新配体设计与合成的进一步研究。
