Regioselective Arene C–H Borylation with a MOF-Immobilized Iridium Bipyridine Catalyst

Postsynthetic ligand exchange and metalation have been
used to
immobilize iridium bipyridine precatalysts in MFU-4l with controlled loadings. The resulting materials, 1-Ir-x (x = 0.1–0.5),
exhibit high activity for catalytic C–H borylation of arenes,
and 1-Ir-0.5 achieves up to 1560 turnover numbers per
Ir for toluene substrate. Remarkably, 1-Ir-0.5 exhibits
high meta:para product regioselectivity
compared to a homogeneous catalyst analogue for arene substrates bearing
bulky triisopropylsilyl groups. Density functional theory (DFT) calculations
reveal that steric constraints imposed by metal-organic framework
(MOF) pore confinement increase the free energy barrier for para C–H activation, biasing product formation toward
the meta isomer.

后合成配体交换与金属化方法已被用于将联吡啶铱预催化剂固载于MFU-4l框架中，并实现可控的负载量。所得材料1-Ir-x（x = 0.1~0.5）在芳烃的催化C-H硼化反应中表现出优异的催化活性，其中1-Ir-0.5针对甲苯底物时，每铱原子的转化数最高可达1560。值得注意的是，当芳烃底物带有大位阻三异丙基硅基基团时，1-Ir-0.5相较于其均相催化剂类似物，展现出更高的间位:对位产物区域选择性。密度泛函理论（DFT）计算结果显示，金属有机框架（MOF）的孔道限域效应所引入的空间位阻约束，提升了对位C-H活化过程的自由能垒，进而使产物生成偏向间位异构体。