title: Rhodium-complex-catalyzed asymmetric hydrogenation: transformation of precatalysts into active species.
abstract: The use of diolefin-containing rhodium precatalysts leads to induction periods in asymmetric hydrogenation of prochiral olefins. Consequently, the reaction rate increases in the beginning. The induction period is caused by the fact that some of the catalyst is blocked by the diolefin and thus not available for hydrogenation of the prochiral olefin. Therefore, the maximum reaction rate cannot be reached initially. Due to the relatively slow hydrogenation of cyclooctadiene (cod) the share of active catalysts increases at first, and this leads to typical induction periods. The aim of this work is to quantify the hydrogenation of the diolefins cyclooctadiene (cod) and norborna-2,5-diene (nbd) for cationic complexes of the type [Rh(ligand)(diolefin)]BF(4) for the ligands Binap (1,1'-binaphthalene-2,2'-diylbis(phenylphosphine)), Me-Duphos (1,2-bis(2,5-dimethylphospholano)benzene, and Catasium in the solvents methanol, THF, and propylene carbonate. Furthermore, an approach is presented to determine the desired rate constant and the resulting respective pre-hydrogenation time from stoichiometric hydrogenations of the diolefin complexes via UV/Vis spectroscopy. This method is especially useful for very slow diolefin hydrogenations (e.g., cod hydrogenation with the ligands Me-Duphos, Et-Duphos (1,2-bis(2,5-diethylphospholano)benzene), and dppe (1,2-bis(diphenylphosphino)ethane).
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Strasse 29a, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: Preetz
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Drexler
authors.forename: Christian
authors.initials: C
authors.lastname: Fischer
authors.forename: Zhenya
authors.initials: Z
authors.lastname: Dai
authors.forename: Armin
authors.initials: A
authors.lastname: Börner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumann
authors.forename: Anke
authors.initials: A
authors.lastname: Spannenberg
authors.forename: Richard
authors.initials: R
authors.lastname: Thede
authors.forename: Detlef
authors.initials: D
authors.lastname: Heller
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D005663:Furans / Q000737:chemistry; D006865:Hydrogenation; D007700:Kinetics; D008024:Ligands; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010720:Phosphines / Q000138:chemical synthesis*; D011407:Propane / Q000031:analogs & derivatives / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D005663:Furans; D008024:Ligands; D009942:Organometallic Compounds; D010720:Phosphines; D012997:Solvents; C018674:tetrahydrofuran; C045990:propylene carbonate; D012238:Rhodium; D011407:Propane; D000432:Methanol