Thorwart Thaddäus, Roth Daniel, Greb Lutz
Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
Chemistry. 2021 Jul 16;27(40):10422-10427. doi: 10.1002/chem.202101138. Epub 2021 May 21.
Given its earth abundance, silicon is ideal for constructing Lewis acids of use in catalysis or materials science. Neutral silanes were limited to moderate Lewis acidity, until halogenated catecholato ligands provoked a significant boost. However, catalytic applications of bis(perhalocatecholato)silanes were suffering from very poor solubility and unknown deactivation pathways. In this work, the novel per(trifluoromethyl)catechol, H cat , and adducts of its silicon complex Si(cat ) (1) are described. According to the computed fluoride ion affinity, 1 ranks among the strongest neutral Lewis acids currently accessible in the condensed phase. The improved robustness and affinity of 1 enable deoxygenations of aldehydes, ketones, amides, or phosphine oxides, and a carbonyl-olefin metathesis. All those transformations have never been catalyzed by a neutral silane. Attempts to obtain donor-free 1 attest to the extreme Lewis acidity by stabilizing adducts with even the weakest donors, such as benzophenone or hexaethyl disiloxane.
鉴于硅在地球上储量丰富，它是构建用于催化或材料科学的路易斯酸的理想选择。中性硅烷的路易斯酸性一直局限于中等水平，直到卤代邻苯二酚配体使其酸性显著增强。然而，双（全卤代邻苯二酚）硅烷的催化应用存在溶解性极差和失活途径不明的问题。在这项工作中，描述了新型的全（三氟甲基）邻苯二酚H cat及其硅配合物Si(cat ) (1)的加合物。根据计算得出的氟离子亲和力，1位列目前凝聚相中可获得的最强中性路易斯酸之一。1的稳定性和亲和力的提高使其能够催化醛、酮、酰胺或氧化膦的脱氧反应以及羰基-烯烃复分解反应。所有这些转化反应从未被中性硅烷催化过。试图获得无供体的1的实验表明，即使是与最弱的供体（如二苯甲酮或六乙基二硅氧烷）形成加合物，也证明了其极强的路易斯酸性。
