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

18 July 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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.

Keywords

manganese alkyl complexes
alkene hydrogenation
migratory insertion

Supplementary materials

Title
Description
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Title
Supporting Information Alkene Hydrogenation Mn
Description
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Mn olefin hydrogenation
Description
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Mn dippe NPr
Description
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