Hartmann Deborah, Schädler Marcel, Greb Lutz
Anorganisch-Chemisches Institut , Ruprecht-Karls-Universität Heidelberg , Im Neuenheimer Feld 275 , 69120 Heidelberg , Germany . Email:
Chem Sci. 2019 Jun 17;10(31):7379-7388. doi: 10.1039/c9sc02167a. eCollection 2019 Aug 21.
Although bis(catecholato)silanes have been known for several decades, their substantial Lewis acidity is not yet well described in the literature. Herewith, the synthesis and characterization of multiple substituted bis(catecholato)silanes and their triethylphosphine oxide, fluoride and chloride ion adducts are reported. The Lewis acidity of bis(catecholato)silanes is assessed by (Gutmann-Beckett, catalytic efficiency), (theoretical and relative experimental fluoride (FIA) and chloride (CIA) ion affinities) and (electrophilicity index) scaling methods. This comprehensive set of experimental and theoretical results reveals their general Lewis acidic nature and provides a consistent Lewis acidity trend for bis(catecholato)silanes for the first time. All experimental findings are supported by high-level DLPNO-CCSD(T) based thermochemical data and the Lewis acidity is rationalized by complementary chemical bonding analysis tools. Against the common belief that inductive electron withdrawal is the most important criterion for strong Lewis acidity, the present work highlights the decisive role of π-back bonding effects in aromatic ring systems to enhance electron deficiency. Thus, bis(perbromocatecholato)silane is identified and synthesized as the new record holder for silicon Lewis superacids.
尽管双（邻苯二酚）硅烷已为人所知数十年，但它们显著的路易斯酸性在文献中尚未得到充分描述。在此，我们报道了多种取代的双（邻苯二酚）硅烷及其三乙膦氧化物、氟化物和氯化物离子加合物的合成与表征。通过（古特曼 - 贝克特法、催化效率）、（理论和相对实验氟化物（FIA）和氯化物（CIA）离子亲和力）以及（亲电指数）标度方法评估了双（邻苯二酚）硅烷的路易斯酸性。这一系列全面的实验和理论结果揭示了它们普遍的路易斯酸性本质，并首次为双（邻苯二酚）硅烷提供了一致的路易斯酸性趋势。所有实验结果都得到了基于高水平DLPNO - CCSD(T)的热化学数据的支持，并且通过互补的化学键分析工具对路易斯酸性进行了合理化解释。与普遍认为诱导吸电子是强路易斯酸性最重要标准的观点相反，本工作突出了π - 反馈键合效应在芳环体系中增强电子不足方面的决定性作用。因此，双（全溴邻苯二酚）硅烷被鉴定并合成出来，成为硅路易斯超强酸的新纪录保持者。
