Kinetic investigations of the hydrogenation of diolefin ligands in catalyst Precursors for the asymmetric reduction of prochiral olefins, II[1]

Article abstract of DOI:10.1002/cber.19961290117

Highly active catalysts for the hydrogenation of CO₂ to formic acid in DMSO/NEt₃ are formed in situ from [{(cod)Rh{(μ-Cl)j₂] and various monodentate or bidentate ligands with phosphorus as the donor atom. Formic acid concentrations up to 2.3 ± 0.2 mol 1^-1 can be obtained in less than 6 hours at ambient temperature under a total initial pressure of 40 atm by using rhodium concentrations of 5 10^-3 mol 1^-1. The changes in catalytic activities observed upon structural changes of monodeniate ligands are discussed in terms of classical ligand parameters like basicity and steric demand of the PR₃ group, while with bidentate ligands R₂P(CH₂)_nPR₂ the chain length n plays a dominant role for the activity of the catalyst. The effects cannot be explained by a direct impact of the iigand on catalytically active inter-mediates only, but influences on the formation of these species must also be taiten into account. VCH Verlagsgesellsehaft mbH. 1996.