Density Functional Studies on Asymmetric Homogeneous Catalysis:

Rh-catalyzed Olefin Hydrogenation

Walter Thiel

Max-Planck-Institut für Kohlenforschung, Germany

For the title reaction, rhodium catalysts with chiral monodentate phosphorous ligands have become an interesting alternative to those with their bidentate counterparts. While maintaining high efficiency and enantioselectivity, they are more easily tunable to various types of substrates. The enantioselectivity of Rh-complexes with chelating P-ligands has been described by Halpern [1] using an "anti lock and key" principle according to which the major enantiomer of the product is formed from the less stable of the two diastereomeric pro-chiral catalyst-substrate complexes. While subsequent calculations [2] have confirmed these findings, it has been shown recently that Rh-catalysts containing chiral monodentate P-ligands [3] follow the "lock and key" principle. We present detailed DFT investigations of the enantioselective hydrogenation of itaconic acid using a chiral Rh(phosponite)2 catalyst, combined with kinetic simulations, to explain these differences [4]. This case study illustrates the use of density functional theory in mechanistic work on asymmetric homogeneous catalysis.

[1] A. S. C. Chan, J. J. Pluth, J. Halpern, J. Am. Chem. Soc. 1980, 102, 5952-5954.

[2] C. R. Landis, J. Halpern, J. Am. Chem. Soc. 1987, 109, 1746-1754.

[3] M. T. Reetz, A. Meiswinkel, G. Mehler, K. Angermund, M. Graf, W. Thiel, R. Mynott, D. G. Blackmond, J. Am. Chem. Soc. 2005, 127, 10305-10313.

[4] K. Angermund, M. Graf, W. Thiel, to be published.