Metal complexes as antioxidants. VI. An electron spin resonance study of the transient cupric complexes formed in the reaction of cupric dialkyldithiocarbamates with alkylperoxy radicals and alkyl hydroperoxides

The epr spectra of three intermediate copper(II) complexes formed by oxidation of bis[N,N-dialkyl(dithiocarbamato-S,S′)] copper(II) by alkyl hydroperoxides and alkylperoxy radicals are reported. Isotropic and anisotropic spectra of the complexes formed from alkylperoxy radicals enriched with 17O are consistent with the following structures: [Cu(S2CNR2)(OS2CNR2)] (I), [Cu(OS2CNR2)2] (II), and [Cu(OS2CNR2)(O2S2CNR2)] (III). The isotropic 17O hyperfine interaction of I is 19.2 G while the anisotropic spectrum of II indicates that the two oxygen nuclei are equivalent. The anisotropic 17O hyperfine splitting constants are consistent with a structure for these complexes in which the S—O bond(s) is directed out of the plane of the complex and not coordinated to the copper.