CO2 Utilisation and Transformation via Transition Metal Activation by Cobalt, Rhodium and Iridium

二氧化碳是一种相当不活泼的化合物，具有很高的热力学和动力学稳定性。它的丰度、无毒性、易于管理以及低廉的价格使这种物质成为化学合成的一个非常有趣的替代碳源。考虑到CCS技术的最新发展，以及2005年启动的欧盟二氧化碳排放交易计划，价格的进一步下跌似乎是合理的。这一趋势将在不久的将来导致二氧化碳利用的经济利益增加。不幸的是，到目前为止，只有少数化学过程是已知的，其中二氧化碳被用作工业规模的替代碳源。在使用之前，在这种过程中通常需要对二氧化碳进行活化，并且可以通过不同的方式实现。除了电化学方法或使用高能底物外，还可以应用各种金属配合物来实现活化，以便随后在化学计量或催化转化中使用CO2。在最简单的情况下，这种活化是通过一个二氧化碳分子和只有一个金属中心的相互作用进行的，导致二氧化碳配合物具有不同的配位模式，这取决于金属和共配体的氧化状态。本研究项目的主要目标是钴、铑和铱的二氧化碳配合物的合成及其性质的研究。这些化合物将在与氢或烯烃等模型底物的反应中进行评估，以建立它们的结构与二氧化碳配体的配位模式之间的关系，以及由此产生的配合物的反应活性，从而获得对金属介导的二氧化碳活化过程的基本见解。为了进一步了解辅助配体和溶剂的影响，这些参数将被系统地改变。所获得的信息将有助于开发利用金属钴、铑和铱的二氧化碳转化的新型定制催化系统。在这方面，本研究项目的长期目标之一是为改进二氧化碳加氢制甲酸和最终甲醇作为潜在燃料的方案的发展作出贡献。

Carbon dioxide is a rather unreactive compound of high thermodynamic and kinetic stability. Its abundance, non-toxicity, and simple manageability in connection with its low price make this substance a highly interesting alternative carbon source for chemical syntheses. Keeping the recent developments in CCS technologies (CCS = CO2 Capture and storage) as well as the European Union Emission Trading Scheme for CO2, launched in 2005, in mind, a further fall in price seems reasonable. This trend will lead to an increased economic interest in CO2 utilization in near future. Unfortunately, until now only a few chemical processes are known, in which carbon dioxide is utilized as an alternative carbon source in industrial scale. Prior to use, an activation of carbon dioxide is often necessary in such processes and can be achieved in different ways. Beside electrochemical methods or the use high energy substrates a variety of metal complexes can be applied to achieve activation in order to subsequently use CO2 in stoichiometric or catalytic transformations. In the simplest case, this activation proceeds via interaction of one carbon dioxide molecule and only one metal center leading to carbon dioxide complexes with varying coordination modes of the CO2 ligand in dependence of oxidation state of the metal and the co-ligands present. The main goals of this research project are the syntheses of such CO2 complexes of cobalt, rhodium and iridium and the investigation of their properties. These compounds will be evaluated in reactions with model substrates like hydrogen or alkenes to establish a relationship between their structures with respect to the coordination mode of the CO2 ligand and the resulting reactivity of the complexes in order to gain fundamental insights into the metal mediated CO2 activation process. For further information on the influence of auxiliary ligands and solvents, these parameters will be systematically varied. The information gained will help to develop novel tailor-made catalytic systems for CO2 transformations utilizing the metals cobalt, rhodium and iridium. In this connection, contributions to the development of improved protocols for the hydrogenation of carbon dioxide to formic acid and finally methanol as potential fuel are among the long term goal of this research project.