The rhodium thiopyrimidine complex [Rh(SPymMe(2))(CO)(2)] was tethered to chemically modified SiO2 substrates and tested as a catalyst in the hydroformylation reaction of 1-heptene. Catalytic performance was monitored under different reaction conditions for several cycles, and compared with the catalytic behaviour of the Rh thiolate complex in a homogeneous medium. Anchoring of the rhodium complex to the modified SiO2 surface was performed by displacement of a CO ligand of the rhodium complex by a PR3 group. following a reaction pathway previously described for gem-dicarbonilic complexes. The XPS data revealed that the sulphur atom is released from the external surface of the solid catalyst during the hydroformylation reaction. However, the thiolate complex is still present in the inner pore network of the solid after the hydroformylation reaction. (C) 2002 Elsevier Science B.V. All rights reserved.