Structure Determination of Catecholato-Silanes in Different Phases and by Different Methods

我们拟采用气体电子衍射、单晶和粉末x射线衍射、CP/MAS-NMR、DOSY-NMR波谱和ESI质谱等多种方法研究一系列儿茶酚甲硅烷在气态、固态和溶液状态下的结构。过卤化双（儿茶酚）硅烷的极端路易斯酸的发现最近引起了这类化合物的注意。高氯衍生物的氟离子亲和力甚至超过了五氟化锑，因此它有资格成为路易斯超强酸。相比之下，简单的二（儿茶酚酸）硅烷和三（儿茶酚酸）硅酸盐已经被发现了将近100年。然而，结构信息明显缺乏，因为许多这些化合物凝固为玻璃状，并且可以采用各种形式的聚集。过去甚至有关于平面四坐标硅结构的猜测。为了进一步提高硅基路易斯酸的刘易斯酸度，提高其催化效率，需要了解分离单体单元的结构（在本研究中通过GED获得）、溶液中可能出现的高聚集（DOSY-NMR, ESI-MS）及其在固态（单晶或粉末XRD和CP/MAS-NMR）中的相互作用。计划中的实验将提供充分和冗余的信息，从而可以明确地说明在不同环境下双（儿茶酚ato）硅烷类的结构。对一系列具有不同立体体积和吸电子特征的取代基的化合物的研究将有助于深入了解决定酸性和聚集偏好的键合情况。因此，新的数据将澄清长期以来的争论，并为未来的发展提供基础。准备工作和光谱调查将在海德堡大学进行，气相结构测定将在比勒费尔德大学的核心设施GED@BI（气体电子衍射和小分子结构中心）进行。

We propose to study the structure of a series of catecholatosilanes in the gaseous, solid and solution state by a variety of methods including gas electron diffraction, single crystal and powder X-ray diffraction, CP/MAS-NMR as well as DOSY-NMR spectroscopy and ESI mass spectrometry. The finding of extreme Lewis acidities for perhalogenated bis(catecholato)silanes has very recently drawn the attention to this class of compounds. The fluoride ion affinity of the perchloro-derivative even exceeds that of antimony pentafluoride and thus it qualifies as a Lewis superacid. Simple bis(catecholato)silanes and tris(catecholato)silicates, in contrast, are known for almost 100 years. However, there is a distinct paucity in structural information, because many of these compounds solidify glassy and can adopt various forms of aggregation. There were even speculations about planar tetra-coordinate silicon configurations in the past. In order to further enhance the Lewis acidity of silicon based Lewis acids, and to improve their catalytic efficiencies, insights on the structure of the isolated monomeric units (obtained in the proposed study via GED), the possible occurrence of higher aggregates (DOSY-NMR in solution, ESI-MS) and their interaction in the solid state (single crystal or powder XRD and CP/MAS-NMR) are needed. The planned experiments will provide sufficient and redundant information that allows an unequivocal statement about the structure of the class of bis(catecholato)silanes in different environments. The study of a range of compounds with a variety of substituents differing in steric bulk and electron-withdrawing character will give insights into the bonding situation which determine the acidic properties and aggregation preferences. The new data will thus clarify a longstanding debate and provide a basis for future developments. The preparative work and spectroscopic investigations will be undertaken at the University of Heidelberg, gas phase structure determination will be undertaken within the core facility GED@BI (Centre of Gas Electron Diffraction and Small Molecule Structures) at Bielefeld University.