Reversible room temperature heterolytic activation of vinylic sp2 C–H bonds at a gallium center

The identification of molecular design principles which enable the activation of strong nonpolar bonds remains an open challenge, particularly for main-group elements. Inspired by reports of metal-framework cooperativity in gallium containing zeolites, we demonstrate the reversible room temperature activation of the sp2 C–H bonds of olefins by the gallium aminoxy complex Ga(TEMPO)3·THF (1) (TEMPO = (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) facilitated by metal-ligand cooperativity (MLC). Treatment of 1 with ethylene results in either reversible alkene ad-dition across the Ga–O–N unit forming a 3+2 cycloadduct or concurrently with the C–H bond of ethylene to form a Ga–vinyl species analogous to a putative intermediate required for silica supported single-site gallium catalysts to enter a Cossee-Arlman oligomerization cycle. Com-plex 1 reversibly activates a variety of alkenes and treatment of 1 with biologically derived olefins and a deuteron source (TEMPOD) resulted in deuterium incorporation at terminal alkene posi-tions. Our work highlights the blurred lines between MLC and metal-framework cooperativity and elucidates how a main-group element can be coaxed to perform a transformation tradition-ally ascribed to more noble members of the periodic table.