Carbonylation of Coordinatively Unsaturated Iron Complexes

The reactivity of transition metal complexes towards small molecules is an increasingly important topic in organometallic chemistry. With energy prices on the rise and limited supplies of fossil fuels, transformations that involve incorporating small molecules such as CO, H2 , N2 , or CO 2 into complex chemicals can prove valuable in developing more sustainable chemistry. In order to achieve more efficient processes, it is important to understand the bonding and coordination properties of transition metals to such small molecules. This is typically done by examining the interactions of specific ligands with specific metal centers in different oxidation and spin states. In this regards, an important small molecule is carbon monoxide. In combination with iron, it is linked to a number of processes in industrial chemistry, from the water-gas shift reaction that converts it to carbon dioxide and hydrogen, to the Fischer-Tropsch reaction in which it is incorporated into liquid linear hydrocarbons. In addition, carbon monoxide coordination to iron plays an important role in Nature. Moreover, since carbon monoxide gas is highly toxic and humans are unable to detect it without using appropriate technology, the development of new sensing materials is desirable. Disadvantages of previously reported optochemical systems are the rather high detection threshold, the lack of CO sensing capacity in ambient air, potential interference of other airborne chemical compounds, as well as the high costs of precious metals. The objective is to obtain insights into their electronic properties and features that may allow the coordination and functionalization of more challenging substrates such as dihydrogen or carbenes as well as to find new materials which may possess potential for catalytic applications and/or CO gas sensing in future investigations. Moreover, this study may be useful for the future synthesis of iron complexes containing alkylidene ligands - which are electronically very similar to CO - as olefin metathesis catalysts, an as yet illusive reaction as iron is concerned. In addition, these investigations may also lead to new chromogenic CO sensing materials. Notwithstanding this, the present studies are important for the development of more environmentally friendly and sustainable reactions. Iron is the most abundant transition metal in the earth crust, essentially non-toxic, inexpensive, and ubiquitously available. Accordingly, such investigations are important for the rational design of well-defined iron catalysts.

In sum, this project generated a fundamental understanding of new concepts in the area of Reactivity of Base Metal Complexes towards Small Molecules. This led to the development of well-defines, stable iron-based complexes which in other project were used in catalytic reactions formerly restricted to noble metals, and resulted in the development of new, environmentally benign catalytic processes. This is of particular importance, since iron is the most abundant transition metal in the earth crust, essentially non-toxic, inexpensive, and ubiquitously available.The reactivity of transition metal complexes towards small molecules is an increasingly important topic in organometallic chemistry. With energy prices on the rise and limited supplies of fossil fuels, transformations that involve incorporating small molecules such as CO, H2, N2, or CO2 into complex chemicals can prove valuable in developing more sustainable chemistry. In the course of this project, we were able to develop well-defined iron complexes which were able to prepare various CO complexes, which is a prerequisite for the formation of hydride complexes. The latter are important for the application as hydrogenation catalysts. With this study we were able to understand the bonding and coordination properties of iron complexes towards such small molecules. This study may also allow for the finding of new materials which may possess potential for CO gas sensing in future investigations.In addition, we also started to develop related chemistry with other base metals such as molybdenum. The outcome of this project is documented in 15 publications in highly ranked peer-reviewed journals.