An Electron Spin Resonance Study of the Reaction of Nitrogen Dioxide with Metal Acetylacetonates

The reaction of nitrogen dioxide with several metal acetylacetonates was studied by electron spin resonance. Those metal complexes that have stable lower oxidation state, (i.e. Cu(II), Fe(III), Co(III), and VO(II)) react to form iminoxy radicals, while those metals not readily reduced (i.e. Zn(II), Cr(III), and Ce(III)) do not give iminoxy radicals. On the basis of the e.s.r. results, a simple mechanism was proposed to account for the formation of iminoxyacetylacetone radicals. A low temperature study of the e.s.r. spectra of the iminoxy-Cu(II)hexafluoroacetylacetonate suggested that a π-complex is formed between the organic radical and the Cu(II) compound.