WATER-SOLUBLE TRIPODAL PHOSPHANE LIGANDS AND THEIR RHODIUM COMPLEXES

The synthesis of the water-soluble tripodal phosphane ligand is-1,3,5- (PPh2)(3)-1,3,5-[CH2(OCH2CH2)(x)OCH3]C6H6 (x = 30-160) (5) has been ac hieved in a four-step reaction sequence. The alcohol )(3)[cis,cis-1,3, 5-(PPh2)(3)-1,3,5-(CH2OH)(3)C6H6] (1) is converted to the correspondin g alcoholate 2, which forms the polyethylene glycol derivative 3 in a polyaddition reaction with oxirane. After methylation of the end group s of 3, the Ligand 5 is obtained by a combined photochemical/oxidative demolybdenation reaction. The watersoluble tripodal phosphane 5 and t he methoxymethyl functionalized tripodal ligand 6 react with Rh(PPh3)( 3)(CO)H to form the water-soluble and water-insoluble rhodium carbonyl hydride complexes 5a and 6a, respectively. The catalytic activity of the rhodium complex 5a in the hydroformylation of 1-hexene was found t o be comparable in a single-phase system (1-hexene/methanol) with that in the biphasic system (1-hexene/water). Only traces of alcohol were found, which demonstrates that the catalyst 5a displays higher selecti vity in hydroformylation than in hydrogenation.