Abstract The biphasic hydroformylation reaction of oct-1-ene, has been investigated by using the water-soluble dinuclear complex [Rh 2 (μ-S t Bu) 2 (CO) 2 (TPPTS) 2] as precursor. Addition of ethanol as a cosolvent dramatically improved the yields but the good regioselectivity in linear aldehyde observed for neat oct-1-ene—water systems (97%) decreased to 83%(for 22% ethanol w/w). It is shown that the dinuclear framework cannot ...