Ru-3(CO)(9)(PPh3)(3) and Ru-3(CO)(9(P)Ph2CH2CH2Si(OMe)(3))(3) have been heterogenized in silica matrices by the sol-gel method. Gels prepared with Ru-3(CO)(9)(PPh2CH2CH2Si(OMe)(3))(3) were tested in the hydrogenation and isomerization of 1-hexene. At H-2-pressures of 16 psi in repeated runs (15h, 90degreesC) turnover numbers for 1-hexene hydrogenation were between 380 and 460. Isomerization products were trans-2-hexene, cis-2-hexene and trans-3-hexene. No cis-3-hexene, 2-methyl-1-pentene and 2-methylpentane were found. Leaching of ruthenium in each run was around 0.05% of ruthenium present in the original gel. UV-VIS and FT-IR spectra of the pure cluster compounds and the gels before and after the catalytic reactions showed that during the gel preparation some Ru-3 units remain intact, but are cleaved when the gel is heated under vacuum or used in catalytic hydrogenation reactions. (C) 2002 Elsevier Science B.V. All rights reserved.