The new water-soluble rhodium complex [Rh(mu-Pz)(CO)(TPPTS)](2) (I) with TPPTS tris-meta-sulfonatophenylphosphine and Pz = pyrazolate ligand, has been synthesized by the reaction of the rhodium precursor [Rh(acac)(CO)2] with TPPTS and pyrazol in aqueous solution under inert atmosphere and characterized by FT-IR, UV-vis, H-1 NMR, P-31 {H-1} NMR. This complex (1) shows high solubility and stability in water for long periods of time as demonstrated by UV-vis studies. The new rhodium complex was used as catalyst precursor during the two-phase catalytic hydroformylation of different olefins under the following reactions conditions: 373 K, 4981.3 kPa (CO/H-2 = 1: 1), 600 rpm and S/C= 100/1, obtaining as reaction order: 1-hexene > styrene > allylbenzene > 2,3-dimethyl-1-butene > cyclohexene. The catalytic activity of the complex (1) in the equimolar and real mixture of olefins with or without the presence of thiophene was also studied and practically no change in the total conversion to aldehydes was observed. This experiments shows that the binuclear complex (1) is resistant to possible sulphur poisons present in refinery cuts. (c) 2005 Elsevier B.V. All rights reserved.