III International Conference

PP-II-93OPTICALLY ACTIVE AMMONIUM SALTS AS MODIFIERS OF CATALYSTS OFHYDROGEN TRANSFER HYDROGENATION OF ACETOPHENONENindakova L.O., Shainyan B.A., Lebed F.M.A.E. Favorskii Irkutsk Institute of Chemistry SB RAS, Irkutsk, RussiaE-mail: nindakova@istu.eduThe possibility of enantioselective hydrogen transfer hydrogenation of secondary ketoneson colloidal particles formed from the cyclooctadiene rhodium(I) complexes in the presenceof optically active ammonium salts derived from R,R-(+)-tartaric acids is demonstrated on theexample of acetophenone.As we have earlier shown [1] catalytic enantioselective hydrogenation of acetophenonewith hydrogen transfer on individual cationic rhodium diamine complexes 1 leads toprecipitation of elemental rhodium of cubic structure with the average size of particles of ca.45 Å, which is followed by an increase of the catalyst turnover number (TON) and decreaseof enantioselectivity.MeMeOOCH 2 NMe 2CH 2 NMe 2RhMe 2 NCH 2Me 2 NCH 2OO+MeTfO -MeMeMeOOCH 2 NMe 2 RCH 2 NMe 2 R+ 2Cl -12, R = octyl, benzylThe presence of elemental rhodium in the precipitates points to reduction of the transitionmetal under the reaction conditions to zero oxidation state that should be followed byformation of metal clusters with the size governed by the nature of stabilizers. The visuallyobserved precipitation of rhodium black is the final stage of aggregation of smaller particles,that means that the solutions of the catalysts starting from some moment should be consideredonly as arbitrarily homogeneous ("quasihomogeneous").Indeed, in the system the conditions exist, which according to the state of the art notions[2] may promote formation of ultradisperse metal particles, namely, the use of readilyreducible transition metal complexes as pre-catalysts, relatively high temperature, andpresence of stabilizers of nanoclusters.We have simulated the conditions of formation of colloid metal particles by introductionof optically active quaternary ammonium salts 2 into the system.Kinetic curves for catalytic hydrogen transfer hydrogenation of acetophenone on[Rh((4S,5S)-2,2-dimethyl-4,5-bis(dimethylaminomethyl)-1,3-dioxolane) 2 ] + CF 3 SO 3-1 and331