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Rethinking Basic Concepts - Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes

preprint
submitted on 17.07.2019 and posted on 18.07.2019 by Stefan Weber, Berthold Stöger, Luis F. Veiros, Karl Kirchner
An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is environmentally benign and atom economic, implementing an inexpensive, earth abundant non-precious metal catalyst. The most efficient pre-catalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- and disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 oC, while 1,2-disubstituted alkenes require a reaction temperature of 60oC. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar was applied. A mechanism based on DFT calculations is presented.

Funding

Austrian Science Fund - P29584-N28

History

Email Address of Submitting Author

karl.kirchner@tuwien.ac.at

Institution

Vienna University of Technology

Country

Austria

ORCID For Submitting Author

0000-0003-0872-6159

Declaration of Conflict of Interest

There is no conflict of interest

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