Influence of Tetraazamacrocyclic Ligands on the Nitric Oxide Reactivity of their Cobalt(II) Complexes

The reactions of cobalt­(II) complexes of tetraazamacrocyclic tropocoronand (TC) ligands with nitric oxide (NO) were investigated. When [Co­(TC-5,5)] was allowed to react with NO­(g), the {CoNO}8 mononitrosyl [Co­(NO)­(TC-5,5)] was isolated and structurally characterized. In contrast, a {Co­(NO)2}10 species formed when [Co­(TC-6,6)] was exposed to NO­(g), and the nitrito [Co­(NO2)­(TC-6,6)] complex was structurally and spectroscopically characterized from the reaction mixture. The {Co­(NO)2}10 species was assigned as the bis­(cobalt dinitrosyl) complex [Co2(NO)4(TC-6,6)] by spectroscopic comparison with independently synthesized and characterized material. These results provide the first evidence for the influence of tropocoronand ring size on the nitric oxide reactivity of the cobalt­(II) complexes.