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-p yridyl; 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 t riphenylphosphine. Turnover frequencies of 2.2 X 10(3) (mel aldehyde m ol Rh-1. h(-1)) were found for most ligands with an oct-l-ene concentr ation of 0.84 M. The pyridylphosphines were up to two times faster. Th e selectivity of the hydroformylation is not affected by the modificat ions and in all cases aldehydes were formed with a n/b ratio of 2.8. P h(2)P(4-C6H4COOH) showed low catalytic activity under standard conditi ons. Preliminary experiments have shown that the new ligands in their protonated, water-soluble form do not produce active hydroformylation catalysts.