Rhodium complexes associated with the fluorous phosphine P(C6H4-4-OCH2C7F15)3 (1) are active catalysts in the hydroformylation of 1-octene in biphasic fluorous systems (TOF 380 h(-1)). Selectivity in aldehydes was as much as 99% and regioselectivity in the linear aldehyde up to a n/iso ratio of 2.8. The system was efficiently recycled for two consecutive runs without decreasing conversion or selectivity. The loss of Rh in the organic layer after the first run was 0.78%. The activity increased using perfluoromethylcyclohexane as a sole solvent (TOF 1040 h(-1)). Under pressure of CO/H-2 (40 bar) the hydrido species [RhH(CO)(1)(3)] and [RhH(CO)(2)(1)(2)] were detected by high pressure NMR spectroscopy. (C) 2003 Elsevier B.V. All rights reserved.