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.
Bibliographical noteFunding Information:
We thank Don Truhlar and Bill Tolman for helpful discussions on the subjects of tunneling and bis(μ-oxo)dicopper complexes, respectively. This work was supported in part by the National Science Foundation (CHE-0203346).
- Binuclear copper complex
- C-H bond activation
- Hydrogen-atom transfer
- Kinetic isotope effect
- Oxygen activation