Water-soluble and air-stable triruthenium carbonyl cluster Ru3 CO.9 TPPMS.3 TPPMSssodium diphenylphosphi-nobenzene-m-sulphonate. was used as catalyst precursor to hydrogenated acrylic acid in good yield. The cluster also catalyzed the hydroformylation of propylene with syngas in water, the main product is n-butyraldehyde; side-products are iso-butyraldehyde and a small amount of 1-butyl and isobutyl alcohols. At 1208C and propylene, CO and H2 partial pressures of 0.7 MPa, 2.0 MPa and 2.0MPa, respectively, catalytic turnover of 61.2 mol productsrmol cluster h and product n:i ratio of 15.9 were obtained. For ethylene hydroformylation, the main product is propanal; side-products are 3-pentanone, 1-propanol and 2-methyl-pent-2-en-1-al. The catalyst was characterized before and after the reaction by IR and. X-ray photoelectron spectroscopy and the results were discussed as related to the possible catalytic active species. q1999 Elsevier Science B.V. All rights reserved.