Rhodium cationic complexes using dithioethers as chiral ligands. Application in styrene hydroformylation

Addition of the dithioethers (-)-DIOSR2 (R = Me, Pr-i) (2,3-O-isopropylidene-1,4-dimethyl (and diisopropyl) thioether-L-threitol) to a dichloromethane solution of [Rh(COD)(2)]ClO4, (COD = 1,5-cyclooctadiene) yielded the mononuclear complexes [Rh(COD)(DIOSR2)]ClO4. X-ray diffraction methods showed that the [Rh(COD)((DIOSPr2)-Pr-i)]ClO4 complex had an square-planar coordination geometry at the rhodium atom with the Pr-i groups in anti position. Cyclooctadiene complexes react with carbon monoxide to form dinuclear tetracarbonylated complexes [(CO)(2)Rh(mu-DIOSR2)(2)(CO)(2)](ClO4)(2). [Rh(COD)(DIOSR2)]ClO4 are active catalyst precursors in styrene hydroformylation at 30 atm and 65 degrees C which give conversions of up to 99% with a regioselectivity in 2-phenylpropanal as high as 74%. In all cases enantioselectivities are low. (C) 1998 Elsevier Science S.A. All rights reserved.