Mono‐Phosphine Metal‐Organic Framework‐Supported Cobalt Catalyst for Efficient Borylation Reactions

Abstract

Abstract We report a metal‐organic framework (MOF) supported monoligated phosphine‐cobalt complex, which is an active heterogeneous catalyst for aromatic C−H borylation and alkene hydroboration. The mono(phosphine)‐Co catalyst (MOF−P−Co) was prepared by metalation of a porous triarylphosphine‐functionalized MOF (MOF−P) with CoCl 2 followed by activation with NaEt 3 BH. The MOF catalyst has a broad substrate scope with excellent functional group tolerance to afford arene‐ and alkyl‐boronate esters in excellent yields and selectivity. MOF−P−Co gave a turnover number (TON) of 30,000 and could be recycled and reused at least 13 times in arene C−H borylation. Importantly, the attempt to prepare the homogeneous control (Ph 3 P−Co) using triphenylphosphine was unsuccessful due to the facile disproportionation reactions or intermolecular ligand exchanges in the solution. In contrast, the site isolation of the active mono(phosphine)‐Co species within the MOF affords the robust and coordinatively unsaturated metal complexes, allowing to explore their catalytic properties and the reaction mechanism.