Department of Chemistry - BMC, Uppsala University, 751 23, Uppsala, Sweden.
Institute of Organic Chemistry, Research Center for Natural Sciences, Budapest, Hungary.
Chemistry. 2021 Oct 1;27(55):13748-13756. doi: 10.1002/chem.202102575. Epub 2021 Sep 6.
[Bis(pyridine)iodine(I)] complexes offer controlled access to halonium ions under mild conditions. The reactivity of such stabilized halonium ions is primarily determined by their three-center, four-electron [N-I-N] halogen bond. We studied the importance of chelation, strain, steric hindrance and electrostatic interaction for the structure and reactivity of halogen bonded halonium ions by acquiring their N NMR coordination shifts and measuring their iodenium release rates, and interpreted the data with the support of DFT computations. A bidentate ligand stabilizes the [N-I-N] halogen bond, decreasing the halenium transfer rate. Strain weakens the bond and accordingly increases the release rate. Remote modifications in the backbone do not influence the stability as long as the effect is entirely steric. Incorporating an electron-rich moiety close by the [N-I-N] motif increases the iodenium release rate. The analysis of the iodine(I) transfer mechanism highlights the impact of secondary interactions, and may provide a handle on the induction of stereoselectivity in electrophilic halogenations.
[双(吡啶)碘(I)] 配合物在温和条件下提供卤鎓离子的可控通道。这种稳定卤鎓离子的反应性主要由其三中心、四电子 [N-I-N] 卤素键决定。我们通过获取它们的 N NMR 配位位移并测量它们的碘鎓释放速率，研究了螯合、应变、空间位阻和静电相互作用对卤键卤鎓离子的结构和反应性的重要性，并在 DFT 计算的支持下解释了数据。双齿配体稳定 [N-I-N] 卤素键，降低卤鎓转移速率。应变削弱了键，从而增加了释放速率。只要影响完全是空间的，骨架上的远程修饰就不会影响稳定性。在 [N-I-N] 基序附近引入富电子部分会增加碘鎓的释放速率。碘（I）转移机制的分析强调了次级相互作用的影响，并可能为诱导亲电卤化的立体选择性提供依据。
