Slow Reactant-Water Exchange and High Catalytic Performance of Water-Tolerant Lewis Acids
Slow Reactant-Water Exchange and High Catalytic Performance of Water-Tolerant Lewis Acids
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DOI：
10.1002/chem.201400240
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发表时间：
2014-06-23
影响因子：
4.3
通讯作者：
Hara, Michikazu
中科院分区：
文献类型：
--
作者：
Koito, Yusuke;Nakajima, Kiyotaka;Hara, Michikazu
用三甲基氧化膦（TMPO）的P-31核磁共振（NMR）谱研究了不同金属三氟甲磺酸盐在水中的刘易斯酸催化作用。TMPO分子与金属三氟甲磺酸盐的刘易斯酸中心直接相互作用，改变了TMPO分子原有的P-31 NMR化学位移和谱线宽度。[Sc（OTf）（3）]和[In（OTf）（3）]通过形成刘易斯酸-TMPO络合物而比其他金属三氟甲磺酸盐具有更大的P-31化学位移和线宽变化。这是由于刘易斯酸与TMPO之间存在强相互作用，导致[Sc（OTf）（3）TMPO]和[In（OTf）（3）TMPO]配合物的稳定性高于其他金属三氟甲磺酸盐-TMPO配合物。[Sc（OTf）（3）]和[In（OTf）（3）]对刘易斯酸催化羰基化合物在水中的反应的催化活性远上级其他三氟甲磺酸金属盐，表明三氟甲磺酸金属-羰基化合物配合物的高稳定性导致了这些反应的高催化性能。密度泛函理论（DFT）计算表明，[Sc（OTf）（3）]和[In（OTf）（3）]的低LUMO能级是它们与亲核试剂在水中形成稳定配位中间体的原因.
P-31 nuclear magnetic resonance (NMR) spectroscopic measurement with trimethylphosphine oxide (TMPO) was applied to evaluate the Lewis acid catalysis of various metal triflates in water. The original P-31 NMR chemical shift and line width of TMPO is changed by the direct interaction of TMPO molecules with the Lewis acid sites of metal triflates. [Sc(OTf)(3)] and [In(OTf)(3)] had larger changes in P-31 chemical shift and line width by formation of the Lewis acid-TMPO complex than other metal triflates. It originates from the strong interaction between the Lewis acid and TMPO, which results in higher stability of [Sc(OTf)(3)TMPO] and [In(OTf)(3)TMPO] complexes than other metal triflate-TMPO complexes. The catalytic activities of [Sc(OTf)(3)] and [In(OTf)(3)] for Lewis acid-catalyzed reactions with carbonyl compounds in water were far superior to the other metal triflates, which indicates that the high stability of metal triflate-carbonyl compound complexes cause high catalytic performance for these reactions. Density functional theory (DFT) calculation suggests that low LUMO levels of [Sc(OTf)(3)] and [In(OTf)(3)] would be responsible for the formation of stable coordination intermediate with nucleophilic reactant in water.