Metal Complexes of Free Radicals. Part II: Identification and structures of radical complexes of alkaline earth metals and zinc

The formation of chelate complexes between free radicals and closed‐shell metal ions is observed by ESR. spectroscopy. High resolution spectra of 1:1 complexes formed between the radical anion of glyoxal‐bis‐(N‐t‐butylimine) (GLIR) and Mg2+, Ca2+ and Zn2+ are completely analysed. The complexes formed in dimethoxyethane or tetrahydrofuran solutions are Ca(GLIR)+, Mg(GLIR)X, Zn (GLIR)X and Zn(GLIR)Y−2, where X = Cl−, Br−, I−, and Y = CN−, NCS−. The formation of the heterometallic, binuclear cyanide‐bridged complex Zn(GLIR)Fe(CN)63− is also described. Isotropic coupling constants are given for protons and 14N in GLIR as well as for the metal nuclei and magnetic nuclei in the groups X and Y. Stabilities, structures and ESR. parameters of these radical complexes are discussed.