Lanthanum(III)-Catalyzed Disproportionation of Hydrogen Peroxide: A Heterogeneous Generator of Singlet Molecular Oxygen—1O2 (1Δg)—in Near-Neutral Aqueous and Organic Media for Peroxidation of Electron-Rich Substrates
作者:Véronique Nardello、Jacques Barbillat、Jean Marko、Peter T. Witte、Paul L. Alsters、Jean-Marie Aubry
DOI:10.1002/chem.200390045
日期:2003.1.20
disproportionation, this chemical source of (1)O(2) is able to generate (1)O(2) not only in basic media, but also under neutral and slightly acidic conditions. In addition, this La-based catalyst system has a very low tendency to induce unwanted oxygenating side reactions, such as epoxidation of alkenes. These two characteristics of the heterogeneous lanthanum catalyst system allow non-photochemical (i.e., "dark")
通过监测镧(iii)盐在1270 nm处的特征IR发光,研究了过氧化氢分解为单线态分子氧-(1)O(2)((1)Delta(g))-的现象。如果非均相催化剂是在原位生成的,则发现该过程是由La(III)进行非均相催化的。在水中和甲醇中,(1)O(2)生成的产率均估计为45 +/- 5%。pH对(1)O(2)生成速率的依赖性对应于从pH 4.5到13的钟形曲线,在pH 8处具有最大值。对H(2)O(2)的影响的研究表明一旦引入一当量的H(2)O(2),就开始了(1)O(2)的形成。然后,它急剧增加到两个等效值,并且在上面更平稳。不同于迄今为止已知的用于H(2)O(2)歧化的所有其他金属盐催化剂系统,(1)O(2)的这种化学来源不仅可以在碱性介质中,而且在中性和弱酸性条件下也可以生成(1)O(2)。另外,该基于La的催化剂体系具有非常低的趋势,以引起不希望的氧化副反应,例如烯烃的环氧化。非均相