The major goal of the ERC project “NoNaCat” was the development of new catalysts for improved synthetic transformations, specifically related to (de)hydrogenations, which are of interest for organic chemistry in general and which are also of significant practical value for the chemical and life science industries. In this respect, the synthesis and exploration of both molecularly-defined catalysts and nano-structured materials, especially based on non-noble metals such as iron, cobalt and manganese, was proposed. Originally, we projected to synthesize >60 new molecular complexes and >200 supported nanoparticles for the planned target reactions. Indeed, in the past five years within this project more than 1000 new heterogeneous materials were prepared and tested in these model reactions. In addition, around 250 molecular catalysts were prepared and tested in comparison. Several synthesized materials were forwarded to European industries (Evonik, Hofmann LaRoche, Bayer, Symrise) for further testing in their industrial relevant processes. Regarding knowledge transfer students from France (University of Rennes) and Denmark (Aarhus) were trained in the preparation of our catalysts and to perform catalytic experiments including high pressure techniques. Apart from the methodological improvements and specific application examples vide infra, several interesting results have been achieved with respect to material sciences or organometallic chemistry. Some highlights are exemplarily mentioned here:
1. We discovered that unusual nickel silicides can be relatively easy synthesized for the first time following our pyrolysis approach. These materials constitute safe and stable nickel catalysts compared to presently used Raney Nickel and offer new opportunities for material sciences.
2. In comparison to other metals, the organometallic chemistry of group 6 PNP-pincer complexes, in particular of Mo, was poorly developed for a long time. To overcome this limitation, we developed a family of low-valent molybdenum complexes, supported by the pincer ligand (iPr2PCH2CH2)2NH. After suitable activation (NaBHEt3) some coordination compounds were found to be suitable catalysts for the hydrogenation of ketones and olefins.
3. Ruthenium PNP pincer complexes bearing supplementary cyclometalated C,N-bound ligands have been prepared and fully characterized for the first time. By replacing CO and H− as ancillary ligands in such complexes, additional electronic and steric modifications of this topical class of catalysts are possible. The advantages of the new catalysts are demonstrated in the general α-alkylation of ketones with alcohols as shown below.
4. Methanol synthesis from syngas (CO/H2 mixtures) is one of the largest manmade chemical processes with annual production reaching 100 million tons. The current industrial method proceeds at high temperatures (200–300 °C) and pressures (50–100 atm) using a copper–zinc-based heterogeneous catalyst. In contrast, we developed a molecularly defined manganese catalyst based on the ERC proposal that allows for low-temperature/low-pressure (120–150 °C, 50 bar) carbon monoxide hydrogenation to methanol.
