The Ullmann-type coupling C-C cross-coupling reactions of different aromatic halides over highly active Pd nanoparticles embedded in a polycyanoethylphenyl methylsiloxane was studied by on-column reaction gas chromatography. In these experiments, catalysis and separation of educts and products are integrated by the use of a catalytically active gas chromatographic stationary phase, which allows very efficiently the measurement of reaction rate measurements by employing reactant libraries. Here the polysiloxane, used as stationary phase, was modified with catalytically highly active Pd nanoparticles and coated as a thin film of 500 nm onto the inner surface of the micro-capillary with an inner diameter of 250 mu m and serves both as solvent and selective stationary phase to allow the synchronous combination of catalysis and separation in a gas chromatographic reactor. Besides the biarylation reaction of aryl halides we observed the cyanation by transfer of nitrile-groups from the polysiloxane matrix in the presence of the Pd nanoparticles. Herein, we demonstrate by systematic on-column reaction chromatographic measurements and TEM investigations the synthetic applicability of multiphase (gas-liquid-solid) C-C cross-coupling as well as cyanation reactions in micro-capillary reactors. (C) 2009 Elsevier Ltd. All rights reserved.