A New Mode of Chemical Reactivity for Metal‐Free Hydrogen Activation by Lewis Acidic Boranes

Abstract

We herein explorew hether tris(aryl)borane Lewis acids are capableofcleaving H 2 outsideofthe usualLewisacid/ base chemistrydescribedbythe conceptoffrustratedLewispairs (FLPs).Instead of aLewisbaseweuse achemicalreductant to generate stable radicala nionso ftwoh ighlyh inderedb oranes: tris(3,5-dinitromesityl)borane and tris(mesityl)borane. NMR spectroscopicc haracterizationr eveals that thec orresponding borane radicalanionsactivate(cleave) dihydrogen, whilst EPR spectroscopicc haracterization, supportedb yc omputational analysis,reveals theintermediates alongthe hydrogen activation pathway. This radical-based, redox pathwayi nvolvest he homolyticc leavage of H 2 ,i nc ontrastt oc onventionalm odels of FLPchemistry, whichinvokeaheterolyticcleavage pathway. This represents anew mode of chemical reactivityfor hydrogen activation by borane Lewisa cids.

Design of frustrated Lewis pair in defective TiO2 for photocatalytic non-oxidative methane coupling

“…A polarized environment with highly tunable and exible distance is more desirable. Recently, solid frustrated Lewis pair (FLP) composed of long-distanced Lewis acid (LA) and Lewis base (LB) sites on the solid surface have proven e cient for H 2 , CO 2 and CO activation [9][10][11][12] . The existence of steric hindrance between LA and LB leads to the unremitting attraction between Lewis pairs rather than bonding with each other, which has been extensively studied on metal oxides with unsaturated metal centers and metal terminal hydroxyl groups mediated by oxygen vacancies, typically seen in defective CeO 2 and In 2 O 3−x (OH) y [13][14][15][16][17] .…”

Design of Frustrated Lewis Pair in Defective TiO2 for Photocatalytic Non-Oxidative Methane Coupling

“…A polarized environment with highly tunable and exible distance is more desirable. Recently, solid frustrated Lewis pair (FLP) composed of long-distanced Lewis acid (LA) and Lewis base (LB) sites on the solid surface have proven e cient for H 2 , CO 2 and CO activation [9][10][11][12] . The existence of steric hindrance between LA and LB leads to the unremitting attraction between Lewis pairs rather than bonding with each other, which has been extensively studied on metal oxides with unsaturated metal centers and metal terminal hydroxyl groups mediated by oxygen vacancies, typically seen in defective CeO 2 and In 2 O 3−x (OH) y [13][14][15][16][17] .…”