Alternative Conceptual Approach to the Design of Bifunctional Catalysts: An Osmium Germylene System for the Dehydrogenation of Formic Acid

The reaction of the hexahydride OsH6(PiPr(3))(2) with a P,Ge,P-germylene-diphosphine affords an osmium tetrahydride derivative bearing a Ge,P-chelate, which arises from the hydrogenolysis of a P-C(sp(3)) bond. This Os(IV)-Ge(II) compound is a pioneering example of a bifunctional catalyst based on the coordination of a sigma-donor acid, which is active in the dehydrogenation of formic acid to H-2 and CO2. The kinetics of the dehydrogenation, the characterization of the resting state of the catalysis, and DFT calculations point out that the hydrogen formation (the fast stage) exclusively occurs on the coordination sphere of the basic metal center, whereas both the metal center and the sigma-donor Lewis acid cooperatively participate in the CO2 release (the rate-determining step). During the process, the formate group pivots around the germanium to approach its hydrogen atom to the osmium center, which allows its transfer to the metal and the CO2 release.

Automated summary

The reaction of hexahydride OsH6(PiPr(3))(2) with a P,Ge,P-germylene-diphosphine leads to an osmium tetrahydride derivative with a Ge,P-chelate, serving as a bifunctional catalyst for formic acid dehydrogenation. The study reveals that hydrogen formation occurs exclusively on the coordination sphere of the metal center, while both the metal center and the sigma-donor Lewis acid cooperatively participate in CO2 release, which is the rate-determining step.