Dioxygen Activation by a Macrocyclic Copper Complex Leads to a Cu2O2 Core with Unexpected Structure and Reactivity
Abstract We report the Cu I /O 2 chemistry of complexes derived from the macrocylic ligands 14-TMC (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and 12-TMC (1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane). While [(14-TMC)Cu I ] + is unreactive towards dioxygen, the smaller analog [(12-TMC)Cu I (CH 3 CN)] + reacts with O 2 to give a side-on bound peroxo-dicopper(II) species ( S P), confirmed by spectroscopic and computational methods. Intriguingly, 12-TMC as a N4 donor ligand generates S P species, thus in contrast with the previous observation that such species are generated by N2 and N3 ligands. In addition, the reactivity of this macrocyclic side-on peroxo-dicopper(II) differs from typical S P species, because it reacts only with acid to release H 2 O 2 , in contrast with the classic reactivity of Cu 2 O 2 cores. Kinetics and computations are consistent with a protonation mechanism whereby the TMC acts as a hemilabile ligand and shuttles H + to an i