Mechanism of intramolecular C–H bond activation in [(LCu)2(μ-O)2]2+ (L=1,4,7-trialkyl-1,4,7-triazacyclononane): quantum mechanical/molecular mechanical modeling

N -dealkylation in [(LCu) 2 (μ-O) 2 ] 2+ (L=1,4,7-tribenzyl-1,4,7-triazacyclononane) is predicted by quantum–mechanical/molecular–mechanical calculations using density functional theory to take place with the dioxocopper core in a bis(μ-oxo) geometry via a mechanism involving internal hydrogen atom transfer of an equatorially located benzylic H to an oxo oxygen atom. This step is followed by a very-low barrier hydroxyl group rebound to generate an aminal that is hydrolyzed to an aldehyde on aqueous workup. There is some polar character to the H atom-transfer transition state so that it is weakly sensitive to aromatic substitution. At 233 K, tunneling plays a significant role in the kinetics.