Journal of Organometallic Chemistry 567 (1998) 143 – 150 New reactors and methods for the investigation of homogeneous catalysis Claude de Bellefon *, Nathalie Tanchoux, Sylvain Caravieilhes Laboratoire de Ge ´nie des Proce ´de ´s Catalytiques, CNRS URA 2211, CPE Lyon, BP 2077, F -69616 Villeurbanne Cedex, France Received 17 October 1998 Abstract New methods and reactors for the kinetic investigation of homogeneous catalysis are described. These are oriented towards the minimisation of the amount of catalyst required for testing new catalytic reactions, kinetics determination and/or catalyst selection. The use of the centrifugal partition chromatograph (CPC) as a chromatographic catalytic reactor for steady-state and transient kinetics is reported. Examples are given which involve monophasic and biphasic reductions. The former is the enantioselective reduction of acetophenone to 2-phenylethanol by isopropanol catalysed by a Rh/chiral diamine system. The biphasic reductions are: (i) the reduction of benzaldehyde into benzylic alcohol catalysed with a Ru/TPPTS complex and (ii) the reduction of dimethylitaconate into dimethylmethylsuccinate catalysed with a Rh/TPPTS complex, both reductions taking place in cyclohexane/water mixtures with sodium formate as the hydrogen transfer reagent. Finally, for first order reactions, analytical solutions are found which demonstrate that kinetic parameters can be readily obtained by using the CPC as a chromatographic reactor in the transient (pulse) mode. © 1998 Elsevier Science S.A. All rights reserved. Keywords: Homogeneous catalysis; Liquid/liquid catalysis; Batch reactor; Plug flow reactor; Kinetics 1. Introduction The separation, the recycling, the cost and the availability of the catalyst and of the ligand, the ligand/ catalyst to substrate specificity and the lack of reliable kinetic data and deactivation processes constitute tech- nological and scientific drawbacks that may seriously limit a wider application of homogeneous enantioselec- tive catalysis. The separation and recycling of the catalysts is a matter of active research and some reliable solutions do exist now [1]. Thus, numerous transition metal com- plexes based on homogeneous catalytic reactions can easily be made biphasic just by functionalisation of the ligands to make the catalyst water soluble. This is currently achieved by sulfonation of phenyl groups which are widely used as organic substituants in phos- phines ligands. The Rho ˆ ne-Poulenc/Ruhr Chemie Pro- cess for the hydroformylation of olefins uses a rhodium complex catalyst co-ordinated with the water soluble sodium salt of triphenylphosphinetrisulphonate (TPPTS) [2,3]. Separation of the product and recovery of the catalyst is thus achieved by simple decantation. Although the overall picture seems elegant and simple, the introduction of an other physical phase induces complexity in the process analysis. The cost of the catalyst is determinated not only by the precious metal often used (Rh, Pt) but also by the sophisticated chiral inductor co-ordinated to the metal centre. For example, the price of commercially avail- able diphosphine ligands lies between 100 and 500 dollars per gram whereas that of rhodium metal is only $20 per gram. With such expensive chemicals, a pre-in- dustrial study may become very expensive. More em- barrassing is the availability of the catalyst. New * Corresponding author. Tel.: +33 4 72431754; fax: +33 4 72431673; e-mail: cdb@lobivia.cpe.fr 0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved. PII S0022-328X(98)00677-9