Martin H. G. Prechtl

Classical methods for oxidation and reduction of organic functional groups into its corresponding reduced or oxidized form usually demand strong and toxic oxidants/reductants along with many additives. Alternatively, to these reactions, it is desirable to use a clean, environmentally friendly reaction pathway, without the necessity of large amounts of aggressive and toxic reagents and by avoiding chemical waste products. In the past few years it has been shown that many reactions can be performed in more environmentally benign solvents by the use of metal pincer catalysts with cooperative and non-cooperative metal-ligand system.^[1]

In our studies, we found on the one hand that catalysts with non-cooperative ligands are not crucial for (alcohol) dehydrogenation reactions, but on the other hand and in strong contrast cooperative ligands are important for hydrogenation reactions. ^[2-4] Additionally, we observed that the choice of solvent may have a strong influence on the product selectivity in certain cases. For example, under polar protic conditions nitriles are converted into primary amines and under non-polar non-protic conditions nitriles are converted into coupled secondary imines.^[3] Moreover we found for the amination of alcohols with ammonia that catalysts with non-cooperative ligand systems are superior to cooperative ligand systems.^[4]

Acknowledgement: Acknowledgement goes to the MIWF-NRW (NRW Rückkehrerprogramm), DFG (Heisenberg-Program) and the COST Action “C-H Activation in Organic Synthesis (CHAOS)”.

[1] J.-H. Choi, H. Valdés, D. Pingen, M. H. G. Prechtl, “The Chemistry of Pincer Compounds”, 2018, Elsevier, Amsterdam.
[2] J.-H. Choi, L. E. Heim, M. Ahrens, M. H. G. Prechtl, Dalton Trans. 2014, 43, 17248-17254.
[3] J.-H. Choi, M. H. G. Prechtl, Chemcatchem 2015, 7, 1023–1028.
[4] D. Pingen, J.-H. Choi, H. Allen, G. Murray, P. Ganji, P. W. N. M. van Leeuwen, M. H. G. Prechtl, Dieter Vogt, Catal. Sci. Technol. 2018, 8, 3969-3976.