Complexation of metal ions with 3,5-di-tert-butyl-1,2-benzoquinone-1-monooxime, ESR studies of radical intermediates

The possibility of chelate formation of 3,5-di-tert-butyl-o-benzoquinone-1- monooxime with Cu(II), Co(II), Ni(II), Mn(II), Pd(II) metal ions under N-2 and in air have been investigated. It was found that complexation of metals except Cu(II) and Mn(II) was accompanied by formation of various stable ra dical species under air. The complexation of Co(II) even under N-2 unlike o ther metal ions, results in the formation of very stable radical species, w hich are assigned to phenazinyl type radical. ESR examination of reduction of bis(3,5-di-tert-butyl-o-benzoquinone-1-monooximato)M(II) (M = Cu, Pd,) w ith triarylphosphines P(C6H4X)(3) (X = H, m-Cl, m-CH3, p-Et2N) reveal the f ormation of the N-(2-hydroxy-3,5-di-tertbutylphenyl)-4', 6'-di-tertbutyl-o- benzosemiquinone iminate radical. Finally, ESR spectra of Cu(II), Ni(II), a nd Mn(II) complexes at 300 and 130 K, as well as reaction of bis(oximato)Ni (II) with PPh3 have been studied.