Molybdenum-Based Hydrogenation Catalysts

Based on socio-economic reasons and due to the rapid development of environmental protection, the chemical industry is under forced pressure to invent more sustainable processes for the manufacture of indispensable products such as pharmaceuticals, agrochemicals, dyes, or starting materials for the production of plastics. In this regard, a chemical transformation known as hydrogenation is ideally suited to address this challenge as this type of reaction is readily implemented on industrial scale and allows for the very efficient use of feedstock materials. The pertinent method relies on the cleavage of gaseous hydrogen, a process that is rather energy demanding owing to the stability of the hydrogen molecule. Consequently, hydrogenations have to be promoted by special materials referred to as catalysts. There are essentially two types of catalysts: heterogeneous catalysts are solid, insoluble, complex mixtures which usually operate under harsh reaction conditions, i.e., high temperatures and pressures. However, these compounds still allow for easy recycling and product separation. On the other hand, homogeneous catalysts typically consist of one active metal center and certain steering molecules, so-called-ligands, which confer solubility, stability and reactivity, even under very mild reaction conditions. These metal-ligand assemblies offer the advantage of tailoring for specific purposes through rational variation of the molecular framework and the corresponding catalytic reactions proceed with much higher selectivity compared to their heterogeneous counterparts. Yet, the vast majority of such catalytically active materials rely on the use of rare and expensive noble metals such as platinum, gold, iridium, or rhodium. Thus, modern society will face scarcity issues associated with the use of these elements. The present research project seeks to develop new hydrogenation catalysts based on molybdenum since this metal is cost-effective and more abundant compared to its precious congeners. The synthesized molybdenum-based compounds are then going to be tested for their catalytic activity in the homogeneous hydrogenation of a variety of industrially relevant molecules that are precursors to valuable products. The aim of the project is to develop competitive, homogeneous hydrogenation catalysts that can rival the activity of corresponding precious-metal-based compounds.