Synthesis and ESR Studies of Redox Reactivity of Bis(3,5-Di

Abstract

Complexing of 3,5-di-tert-butyl-1,2-benzoquinone-2-monooxime with Cu(II) in air and under N<inf>2</inf> gave Cu(qo)<inf>2</inf> and Cu(qo)<inf>2</inf>·H<inf>2</inf>O (where qo is 3,5-di-tert-butyl-1,2-benzoquinone-2-monooximato-anion) complexes, respectively. The ESR spectroscopy showed that the reduction of these complexes with P(PhX)<inf>3</inf> (X = H, m-Cl, m-CH<inf>3</inf>, p-Et<inf>2</inf>N-) and 1,4-bis(diphenyldiphosphino) butane (dppb) proceeds via the radical formation (phenoxazine, amino phenoxy and nitrene type radical intermediates) and pathways of reduction depend on the structure of these complexes. The reaction of Cu(qo)<inf>2</inf> with dppb and P(PhX)<inf>3</inf> phosphines gave essentially identical ESR spectra. At the same time, reduction of Cu(qo)<inf>2</inf>·H<inf>2</inf>O with PPh<inf>3</inf> result in entirely different unstable radical spectrum (g = 2.0046) which is further converted to another relatively stable Cu-containing radical signal (g = 2.0052). The unstable radical species attributed to nitrene type radicals. The initial complexes and all radical products were characterized by their ESR and optical spectra.