INOR 62 |
| Asymmetric hydrogenation is an area of considerable academic and industrial relevance. In particular Rh-based complexes involving easy to synthesize, BINOL-based monodendate phosphonites, phosphites and phosphoramidites have been reported as very active and economically interesting systems. Phosphoramidites were found to yield very high ee's up to 99.8 % in enantioselective rhodium-catalyzed hydrogenation of olefins. Up to now, only little is know about the mechanisms that lie on the basis of these unexpectedly high levels of enantioselectivity. In this contribution molecular dynamics calculations based on density functional theory are used for understanding this hydrogenation system. Two topics are discussed: (i) Which species act as the active catalyst either Rh bound to one or two MonoPhos-ligands? What is the probability of finding higher ligated species? (ii) Does the hydrogenation follows the Halpern mechanism, in which minor diastereomeric intermediate leads to the favored enantiomeric product, as in classical Rh-catalyzed olefin hydrogenation based on chiral chelating diphosphines? Therefore an efficient conformational sampling is performed of all possible pro-R and pro-S intermediates together with transition states at every stage of the catalytic cycle.
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Organometallic: Catalysis
8:30 AM-12:10 PM, Sunday, 10 September 2006 Moscone Center -- Room 310, Oral
Division of Inorganic Chemistry |
