Synthesis and coordination chemistry of novel chiral P,S-ligands with a xylofuranose backbone: Use in asymmetric hydroformylation and hydrogenation

A series of novel chiral thioether-phosphite ligands derived fr om 1,2-O-is opropylidenexylofuranose have been synthesized. Reaction of these chiral li gands with [M(cod)(2)]BF4 (M = Ir, Rh; cod = 1,5-cyclooctadiene) yielded th e complexes [M(cod)(P-S)]BF4 10-15. The addition of H-2 to iridium complexe s 12-15 gave the cis-dihydridoiridium(III) complexes [IrH2(cod)(P-S)]BF4 19 -21, which are present in only one diastereoisomeric form. Iridium complexe s are active in the hydrogenation of itaconic acid and produce enantioselec tivities of up to 51% under atmospheric pressure. They have also been teste d in the Rh-catalyzed hydroformylation of styrene. We discuss hydroformylat ion results according to the solution structure of the species formed under hydroformylation conditions.