Investigating reactivity and electronic structure of copper(II)-polypyridyl complexes and hydrogen peroxide

This work presents a detailed study of the reactivity of three mononuclear Cu-II complexes supported by derivatives of the tetradentate ligand N,N'-bis(2-pyridylmethyl)-1,2-ethylenediamine (bispicen). The Cu-II complexes are capable of performing C - H bond activation in the presence of NEt3 and H2O2 through what has been proposed computationally to be a [CuO](+) intermediate. A wavefunction-based quantum chemical investigation into the electronic structure of the proposed [CuO](+) intermediate reveals a triplet ground state predominantly consistent with an S = 1/2 Cu-II center ferromagnetically coupled to an oxyl radical, though contributions from the corresponding biradicaloid CM-oxen resonance structure may be nontrivial. Furthermore, correlation of the electronic structure of the proposed intermediate with analogous high-valent metal-oxo species capable of olefin epoxidation suggests that the Cu-II complexes might be also capable of olefin epoxidation in the presence of NEt3 and H2O2. To test this hypothesis experimentally, the Cu-II complexes are treated with NEt 3 and H2O2 in the presence of alkene substrates, resulting in the formation of epoxides.