Molecular Catalytic Systems for Hydrogenation Chemistry

  Focus areas of the working group heterogenous catalysis Copyright: ITMC Aachen

Catalyst deactivation via the formation of stable dimers, trimers, or higher aggregates represents a wide-ranging problem in homogeneous catalysis. A general approach to avoid the buildup of such structures is based on the design of sterically demanding ligands using the respective repellent forces for keeping the monomeric catalysts maintained in solution.

 

Catalytic hydrogenation systems activated by tailored tridentate ligands

M. Meuresch, S. Westhues, W. Leitner, J. Klankermayer, Angew. Chem. Int. Ed. 2016, 55, 1392. Link
S. Westhues, M. Meuresch, J. Klankermayer, Angew. Chem. Int. Ed. 2016, 55, 12841. Link

In our group, we investigate the development of a tailored tridentate ligand enabling the synthesis of a molecular ruthenium-triphos catalyst, that could eliminate or minimize the dimerization as the major deactivation pathway.

The hydrogenation of non-activated aliphatic amides remains an enormous challenge for molecular catalysts and especially the reductive cleavage of lactams. With these rationally developed molecular catalysts, the hydrogenation was significantly improved and the challenging reduction of lactams to cyclic amines could be achieved. The novel catalyst design showed strongly increased performance and facilitated the hydrogenation of highly challenging lactam substrates to the corresponding azacycloalkane products in excellent yield with unprecedented activity and selectivity.

  Focus areas of the working group heterogenous catalysis Copyright: ITMC Aachen  

By taking into consideration the possibility of catalytic N-alkylation of amines with alcohols, the lactam reduction in the presence of alcohols selectively yielded the desired cyclic tertiary amines. The catalytic ruthenium-triphos system enabled the modular synthesis of cyclic tertiary amines from simple lactam substrates and secondary alcohols. Moreover, the catalytic cascade reaction facilitated the reduction of the lactams without the need of molecular hydrogen, as the alcohol served as the hydrogen transfer and alkylation reagent.

  Transfer-Hydration/Alkylation Copyright: ITMC Aachen

 

Hydrogenolysis depolymerization of waste polyesters and polycarbonates

S. Westhues, J. Idel, J. Klankermayer, Science Advances 2018, 4, eaat9669. Link

The development of ruthenium-triphos adapted systems enables the effective and selective hydrogenolysis-depolymerization of waste polyesters or polycarbonates to the respective value-added diols, enabling a recycling concept within the circular economy vision. The application of this catalytic system on a larger scale depolymerization revealed the tolerance of the catalyst toward various polymer additives. Moreover, the employment of the tailored catalytic system in a consecutive transformation/separation of polymer mixtures is also achieved.

  Hydrogenolysis of selected polyesters and polycarbonates Copyright: ITMC Aachen Hydrogenolysis of selected polyesters and polycarbonate consumer products