Chemistry of Coordinatively Unsaturated Transition Metal-Dioxygen Complex

通过电子和立体设计制备了四种配位钴（II）席夫碱配合物及其低温形成的二氧加合物。研究了这些配位不饱和超氧钴（III）配合物[CoIII(SB)(O2)]的化学行为，得到了以下结果。(1) CoIII (SB) （O2）作为氧化剂的作用很低，通常可氧化的酚类化合物如三苯基膦不能被任何配位不饱和CoII (SB) （O2）氧化。然而，在酸或酰氯的存在下，三苯基膦被氧化为氧化三苯基膦，其中过氧化氢或过氧化二酰基是原位形成的氧化剂。(2) CoIII (SB) （O2）可定量还原邻醌生成半醌钴（III）配合物。另一方面，p-醌没有发生反应。这些结果表明，配位不饱和配合物中的配位超氧基团的电子密度比配位饱和配合物中的电子密度低。(3) CoIII (SB) （O2）的自由基反应性：与配合饱和的超氧钴（III）配合物在较低温度下可与苯氧自由基偶联，但未与苯氧自由基发生反应。CoIII (SB) （O2）的自由基活性较低可能是由于其电子态具有金属特性所致。(4) CoIII (SB) （O2）与苯甲酰氯反应生成过氧化二苯甲酰，发现其阴离子性质，认为过氧化二苯甲酰的形成是两分子苯甲酰过氧自由基的重组。

Electronically and sterically designed four coordinate cobalt (II) Schiff base complexes and their dioxygen adducts formed at low temperature were prepared. Chemical behavior of these coordinatively unsaturated superoxocobalt (III) complexes [CoIII(SB)(O2)] were investigated to find the following results.(1) CoIII (SB) (O2) as an oxidizing agent was found to be very low : normally oxidizable phenolic compounds as wsell as triphenylphosphin were not oxidized with any coordinatively unsaturated CoII (SB) (O2). However, in the presence of an acid or acyl chloride, triphenylphosophin was oxidized to triphenylphosphin oxide, where hydrogen peroxide or diacylperoxide formed in situ was the oxidizing agent.(2) CoIII (SB) (O2) was found ito reduce o-quinons to igve semiquinonatocobalt (III) complex quantitatively. On the other hand, no reaction took place with p-quinons. These results suggest that the electron density of the coordinated superoxo species in coordinatively unsaturated complex is poor compaired to that in coordinatively sturated one.(3) Radical reactivity of CoIII (SB) (O2) : no reaction with phenoxy radicals were found contrary to the case with coordinatively saturated superoxocobalt (III) complex, which can couple with phenoxy radicals at lower temperature. The less radical reactivity of CoIII (SB) (O2) may be attributed to its electronic stae having metal characteristics.(4) Anionic nature of CoIII (SB) (O2) was found in the reaction wiht benzoyl chloride to give dibenzoyl peroxide, of which formation is considered to recombination of two molecules of benzoylperoxy radical.