It should be noted that this reaction proceeds smoothly at room temperature and in a reproducible manner. It contrasts with the thermolysis reactivity of some uranium(IV) ethynediolate complexes that were found to react at elevated temperature through ligand degradation or intramolecular C-H activation at the ligand backbone, resulting in the formation of ethenediolate-type complexes. The observed C-H activation of toluene in 9 is somehow reminiscent of the C-H activation at the coordinated 4dimethylaminopyridine (DMAP) ligand upon addition of CO to an activated Mg(I) dimer complex (see Figure ). 15g In this case, DFT calculations suggested that the C-H activation is induced by a "zig-zag" {C2O2} 2-intermediate similar to iso2 (Figure ). The major difference in the case of 2 lies in its lack of reactivity in toluene in the absence of CO2, even at elevated temperatures (up to 100 °C). Only upon addition of CO2 is a highly reactive system formed that allows intermolecular C-H activation on toluene.