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

我们提出了一系列的儿茶酚硅烷在气态，固态和溶液状态下的结构研究的各种方法，包括气体电子衍射，单晶和粉末X-射线衍射，CP/MAS-NMR以及DOSY-NMR光谱和ESI质谱。全卤代双邻苯二酚基硅烷的极端刘易斯酸性的发现最近引起了人们对这类化合物的关注。全氯衍生物的氟离子亲和力甚至超过五氟化锑，因此它有资格作为刘易斯超强酸。相比之下，简单的双（儿茶酚基）硅烷和三（儿茶酚基）硅酸盐已知近100年。然而，结构信息明显缺乏，因为这些化合物中的许多固化成玻璃状，并且可以采用各种形式的聚集。在过去甚至有关于平面四配位硅构型的推测。 为了进一步增强硅基刘易斯酸的刘易斯酸性，并提高其催化效率，需要了解分离的单体单元的结构（通过GED在拟议的研究中获得），可能发生的更高的聚集体（溶液中的DOSY-NMR，ESI-MS）及其在固态下的相互作用（单晶或粉末XRD和CP/MAS-NMR）。计划中的实验将提供足够的和冗余的信息，允许在不同的环境中的双（儿茶酚）硅烷类的结构的一个明确的声明。一系列的化合物与不同的空间体积和吸电子特性的各种取代基的研究将提供洞察力的键合情况，确定的酸性和聚集的偏好。因此，新的数据将澄清一个长期的争论，并为未来的发展提供基础。准备工作和光谱研究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.