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

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 CoCl2 followed by activation with NaEt3BH. 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 (Ph3P-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.

Automated summary

A metal-organic framework supported monoligated phosphine-cobalt complex has been developed as an active heterogeneous catalyst for aromatic C-H borylation and alkene hydroboration. The catalyst shows broad substrate scope and excellent functional group tolerance, leading to the synthesis of arene- and alkyl-boronate esters with high yields and selectivity. Notably, the catalyst exhibits high turnover number and can be recycled and reused multiple times.