Low Oxidation State Cobalt Center Stabilized by a Covalent Organic Framework to promote Hydroboration of Olefins

Abstract

Site isolation of unstable catalytic species within a reticular material is an appealing strategy for mitigating catalyst decom position whil e creating catalysts with improved activity and robustness. The covalent organic framework (COF) based on single cobalt sites coordinated to 2,2’ - bipyridine ( COF bpy Co ) exploit s the isolated nature of the cobalt sites to stabilize low - valent single sites and catalyze the hydroboration of olefins. Terminal alkyl boronate esters were obtained using 1 mol % COF bpy Co loading starting from terminal alkenes a nd internal alkenes, thanks to a tandem isomerization - hydroboration proc ess . The catalytic activity of COF bpy Co was maintained after being recycled six times. Experimental and computational studies suggested the { (bpy •− )Co I (THF) 2 } moiety as the active catalytic species within the COF . The mechanism follows an oxidative boryl migration, followed by isomerization and reductive elimination to form the boronate ester.