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.

本研究考察了四氮杂大环托罗科伦纳德（tropocoronand，TC）配体的钴(II)配合物与一氧化氮（nitric oxide，NO）的反应行为。当[Co(TC-5,5)]与气态一氧化氮反应时，分离得到{CoNO}8型单亚硝酰配合物[Co(NO)(TC-5,5)]并完成结构表征。与之相对，当[Co(TC-6,6)]暴露于气态一氧化氮中时，生成了{Co(NO)2}10型物种，且从反应混合物中分离得到亚硝酸根配合物[Co(NO2)(TC-6,6)]，并对其开展了结构与光谱学表征。通过与独立合成并表征的参比物质进行光谱比对，将该{Co(NO)2}10型物种归属为双核双亚硝酰钴配合物[Co2(NO)4(TC-6,6)]。上述结果首次为托罗科伦纳德环尺寸对钴(II)配合物的一氧化氮反应活性的影响提供了实验依据。