Main-group element compounds possessing multiple reaction centers - Systems between cooperativity, synergy and emergence

催化是在环境友好和经济的过程中将传统资源和替代资源转化为有价值的化学品的最有效的策略之一。目前的工业催化剂几乎完全包含贵金属和非贵金属，它们是稀有的(相应地昂贵的)，而且通常在(生态)毒性方面存在问题。因此，有必要提出替代概念，将丰富和更环保的主族元素作为活动地点。然而，到目前为止，过渡金属催化的机理情景并不完全适用于主族元素化合物的催化。主族元素化合物的氧化加成和还原消除在催化上最相关的顺序还没有得到。因此，开发新的小分子活化和转化模式以及加强互补策略是值得追求的。该项目的核心是通过含有铝、钙、镓、锗、镁、硅和锡的多核环保主族元素化合物来激活和催化小分子和惰性化学键。我们感兴趣的是当一个配基框架包含两个非常接近的活性位点时所产生的协同效应和突现效应。协作性或协同性描述了与同等的单活性中心催化剂混合物相比，多活性中心催化剂的反应活性增强。相反，突现效应是不可减少的，即观察到的化学转化不能通过使用单位催化剂来实现。我们不一定寻求建立过渡金属催化剂的直接替代品，而是开发主族元素化合物介导的键断裂和成键的新概念。

Catalysis is one of the most powerful strategies to convert both conventional and alternative resources to valuable chemicals in environmentally friendly and economical processes. Current industrial catalysts almost exclusively incorporate precious and non-precious transition-metals, which are scarce (and correspondingly expensive) and often problematic with regard to (eco)toxicity. Thus, there is a need for alternative concepts that incorporate abundant and more environmentally friendly main-group elements as active sites. However, mechanistic scenarios operative in transition-metal catalysis are so far not fully applicable in catalysis by main-group element compounds. The catalytically most relevant sequence of oxidative addition and reductive elimination has not yet been achieved for main-group element compounds. Consequently, the development of new modes of small molecule activation and transformation as well as the enhancement of complementary strategies are worthy of pursuit. This project is centered around the activation and catalytic functionalisation of small molecules and inert chemical bonds by means of polynuclear environmentally benign main-group element compounds incorporating aluminium, calcium, gallium, germanium, magnesium, silicon and tin. We are interested in both the cooperative and the emergent effects that arise when a ligand frame hosts two active sites in close proximity. Cooperativity or synergism describes the enhanced reactivity of a multi-site catalyst compared to an equivalent mixture of single-site catalysts. In contrast, emergent effects are irreducible, i.e., the observed chemical transformations are not accessible by using single-site catalysts. We do not necessarily seek to establish immediate substitutes for transition-metal catalysts, but rather to develop new concepts for bond breaking and making mediated by main-group element compounds.