The Influence of Alkali Metal Ions on the Stability and Reactivity of Chromium(III) Superoxide Moieties Spanned by Siloxide Ligands.
The Influence of Alkali Metal Ions on the Stability and Reactivity of Chromium(III) Superoxide Moieties Spanned by Siloxide Ligands.
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DOI：
10.1002/chem.201900236
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
M. Wind;S. Hoof;C. Herwig;B. Braun‐Cula;C. Limberg
中科院分区：
文献类型：
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作者：
M. Wind;S. Hoof;C. Herwig;B. Braun‐Cula;C. Limberg
近年来，氧化还原失活的Lewis酸性金属离子的存在已变得明显，它可以决定性地影响在O2活化过程中、在分子络合物和金属酶中形成的金属-O2部分的反应活性。超氧化物物种通常作为主要中间体形成，但它们大多太不稳定，无法进行彻底的调查。本文报道了一系列铬(Ⅲ)超氧化物配合物[L2Cr]M2 O2(THF)y(L=-OSiPh2OSiPh2O-，M+=Li+，Na+，K+，y=4，5)，它们可在低温下进行光谱研究和部分结晶。它们的不同之处只在于所结合的两个Lewis酸性碱金属反离子(M+)，因此可以证明M+的性质在很大程度上决定了它与超氧化物配体的相互作用。这种相互作用反过来又显著影响了这些络合物对含有羟基的底物的稳定性和反应活性。此外，我们还表明，稳定性和反应活性也高度依赖于溶剂(四氢呋喃和腈)，因为给体溶剂与碱金属离子配位，因此也影响它们与超氧化物部分的相互作用。总之，这些结果提供了关于这类超氧化物的光谱性质、结构和行为之间的关联的全面而详细的图景，这可能对其他系统具有示范作用。
In recent years, it has become clear that the presence of redox-inactive Lewis acidic metal ions can decisively influence the reactivity of metal-dioxygen moieties that are formed in the course of O2 activation, in molecular complexes, and metalloenzymes. Superoxide species are often formed as the primary intermediates but they are mostly too unstable for a thorough investigation. We report here a series of chromium(III) superoxide complexes [L2 Cr]M2 O2 (THF)y (L=- OSiPh2 OSiPh2 O- , M+ =Li+ , Na+ , K+ and y=4, 5), which could be accessed, studied spectroscopically and partly crystallized at low temperatures. They only differ in the two incorporated Lewis acidic alkali metal counterions (M+ ) and it could thus be shown that the nature of M+ determines considerably its interaction with the superoxide ligand. This interaction, in turn, has a significant influence on the stability and reactivity of these complexes towards substrates with OH groups. Furthermore, we show that stability and reactivity are also highly solvent dependent (THF versus nitriles), as donor solvents coordinate to the alkali metal ions and thus also influence their interaction with the superoxide moiety. Altogether, these results provide a comprehensive and detailed picture concerning the correlation between spectroscopic properties, structure, and behavior of such superoxides, that may be exemplary for other systems.