Coordination Chemistry and Reactivity of a Cupric Hydroperoxide Species Featuring a Proximal H‑Bonding Substituent

At −90 °C in acetone, a stable hydroperoxo
complex
[(BA)­CuIIOOH]+ (2) (BA, a tetradentate
N4 ligand possessing a pendant −N­(H)­CH2C6H5 group) is generated by reacting [(BA)­CuII(CH3COCH3)]2+ with only
1 equiv of H2O2/Et3N. The exceptional
stability of 2 is ascribed to internal H-bonding. Species 2 is also generated in a manner not previously known in copper
chemistry, by adding 1.5 equiv of H2O2 (no base)
to the cuprous complex [(BA)­CuI]+. The broad
implications for this finding are discussed. Species 2 slowly converts to a μ-1,2-peroxodicopper­(II) analogue (3) characterized by UV–vis and resonance Raman spectroscopies.
Unlike a close analogue not possessing internal H-bonding, 2 affords no oxidative reactivity with internal or external substrates.
However, 2 can be protonated to release H2O2, but only with HClO4, while 1 equiv Et3N restores 2.