RHODIUM-CATALYZED HYDROFORMYLATION OF HIGHER ALKENES USING AMPHIPHILIC LIGANDS

A variety of amphiphilic ligands has been synthesised comprising Ph(2)ArP (Ar=3-hydroxyphenyl, 4-carboxyphenyl), Ph(n)Ar(3-n)P (Ar = 4-PhCH(2)X, X = NEt(2), NMePh, NPh(2); n = 1-2) and Ph(n)Ar(3-n)P (Ar = 3/4-pyridyl; n = 1-2). In the hydroformylation of oct-l-ene (80 degrees C, 20 bar syngas, toluene) the ligands were shown to be comparable with triphenylphosphine. Turnover frequencies of 2.2 X 10(3) (mel aldehyde mol Rh-1. h(-1)) were found for most ligands with an oct-l-ene concentration of 0.84 M. The pyridylphosphines were up to two times faster. The selectivity of the hydroformylation is not affected by the modifications and in all cases aldehydes were formed with a n/b ratio of 2.8. Ph(2)P(4-C6H4COOH) showed low catalytic activity under standard conditions. Preliminary experiments have shown that the new ligands in their protonated, water-soluble form do not produce active hydroformylation catalysts.