Water-soluble metal complexes and catalysts X-BIPHLOPHOS, a novel axially chiral diphosphine ligand: preparation and application in the asymmetric rhodium-catalyzed hydroformylation of styrene

A stereospecific synthesis of both enantiomers of the new axially chiral di phosphine ligand 2,2'-bis(diphenylphosphinomethyl)-4,4',6,6'-tetrachloro-1, 1'-biphenyl 5 called BIPHLOPHOS, starting from the readily available pure e nantiomers of 4,4',6,6'-tetrachlorodiphenic acid, was developed. The (-)-en antiomer was then tested in the homogeneous rhodium-catalyzed asymmetric hy droformylation of styrene. The ligand was used to prepare the complex IrH(C O)(PPh3)L-2 (L-2 = 5) 6, the crystal structure of which was determined and compared with the related complex RhH(CO)(PPh3)(BISBI). Additionally, ligan d 5 was sulfonated by classical methods to yield a uniform reaction product . This is in sharp contrast to the analogous ligands BISBI and NAPHOS, wher e sulfonation yields a complicated mixture of products. The sulfonated liga nd is excellently water-soluble and shows activities and regioselectivities in the hydroformylation of styrene comparable to the well-investigated lig and BISBI. (C) 1999 Elsevier Science S.A. All rights reserved.