Highly water-soluble arene-ruthenium(II) complexes: application to catalytic isomerization of allylic alcohols in aqueous medium

Arene-ruthenium(II) derivatives [RuCl2(eta(6)-C6H5OCH2CH2OH)(L)] (L = P(OMe)(3) (2a), P(OEt)(3) (2b), P((OPr)-Pr-i)(3) (2c), P(OPh)(3) (2d), PPh3 (2e)) have been prepared from the dimer [{RuCl(mu-Cl)(eta(6)-C6H5OCH2CH2OH)}(2)] and the appropriate P-donor ligand. The hydroxyethoxy substituent on the arene induces water-solubility of the resulting complexes (up to 755 g L-1); in particular derivative 2a being one hundred times more soluble in water than its p-cymene congener [RuCl2(eta(6)-p-cymene){P(OMe)(3)}]. Compounds 2a-e are active catalysts for isomerization of allylic alcohols into the corresponding ketones in aqueous medium. The best performances are obtained with derivatives 2a-c which have shown the highest activity reported to date for the isomerization of aromatic or disubstituted substrates in water.