Electron rich and geometrical constrained substituents in molecular silicon compounds - planar(ized) SiIV for bond activation and optoelectronic materials

几十年来，人们一直在积极研究用于光电子应用的均相催化剂和材料-过渡金属络合物是人们感兴趣的焦点。然而，通过丰富的主族元素化合物来替代通常有毒的、难以分离的和稀有的过渡金属是可取的。此外，主族化合物在异常成键情况下的反应活性是当前基础研究的主要兴趣。本文给出的方法是合成和研究具有富电子和几何约束取代基的硅(IV)化合物。所提出的多齿或大环氨基/酚基/吡咯取代基的性质回答了一系列基本和应用问题。(Pro)手性取代基将有助于阐明四价硅(IV)的平面反转--这是这类物质中立体动力学的一个理论上很久就知道但被实验忽视的方面。取代基的几何扭曲导致了反应活性的增强：Lewis-酸性显著增加，而富电子取代基的亲核性保持较高。产生了小的HOMO-LUMO间隙，导致了具有强sigma键的小分子活化的新的反应可能性。一方面，取代基参与氧化还原反应与硅(IV)的超配位能力相结合是可能的，导致了硅(IV)上的正式氧化加成。另外，所建议的化合物具有很强的两亲性，可以激发特定底物的异解键活化。平坦化的概念最终将使第一个分子、平面、四价硅(IV)物种的实现成为可能，它具有丰富的有趣的结构、反应和光学特征。所提出的结构在合成上是简单易懂的，量子理论研究揭示了这样的化合物非常有吸引力-例如具有比参考Lewis酸B(C6F5)3更强的Lewis酸度和相当大的可见光吸收-中性四价硅(IV)化合物的非常不寻常的性质。受主性质和模数合成提供了用于产生例如非线性光学效应的施主官能团的容易安装。提出的概念允许对硅(IV)化合物中取代基和平坦化对立体动力学、反应性和光物理的影响进行综合考察。首先，简要讨论与给定目标有关的有希望的结果。

Homogeneous catalysts and materials for optoelectronic applications have been actively investigated for several decades - with transitions metal complexes in the spotlight of interest. However, an alternative for the often toxic, hard to separate and rare transition metals by abundant main group element compounds is desirable. Moreover, the reactivity of main group compounds in unusual bond situations is of major current interest in fundamental research. The herewith given approach deals with the synthesis and investigation of silicon(IV) compounds equipped with electron rich und geometrically constrained substituents. The nature of the proposed polydentate or macrocyclic amido/phenolato/pyrrolo-substituents gives answer to a series of fundamental as well as applied problems. (Pro)chiral substituents will allow for the elucidation of the planar inversion of tetravalent silicon(IV) - a theoretically long known, but experimentally neglected aspect of stereodynamics in this substance class. The geometrical distortion by the substituents leads to augmented reactivity: the Lewis-acidity increases substantially whereas the nucleophilicity of the electron rich substituents remains high. Small HOMO-LUMO gaps are resulting, leading to new reaction possibilities in the activation of small molecules with strong sigma-bonds. On one hand, the participation of the substituents in redox reactions combined with the ability of hypercoordination at silicon(IV) is plausible, leading to formal oxidative additions at silicon(IV). Alternatively, the strong amphiphilic character of the proposed compounds could provoke heterolytic bond activation of specific substrates. The concept of planarization finally will enable the realization of the first molecular, planar, tetravalent silicon(IV) species, with plenty of interesting structural, reactive and optical features. The proposed structures are synthetically straightforward accessible and quantum theoretical considerations reveal such compounds as highly attractive - with e.g. stronger Lewis-acidity than the reference Lewis acid B(C6F5)3 and considerable absorption of visible light - highly unusual properties of neutral, tetravalent silicon(IV) compounds. The acceptor properties and the modular synthesis offers the easy installation of donor functionalities for the creation of e.g. non-linear optical effects. The proposed concept allows for the integrated examination of the influence of substituents and planarization in silicon(IV)-compounds on stereodynamics, reactivity and photo physics. First promising results in relation to the given objectives are shortly discussed.