Synthesis, characterization and use in enantioselective hydroformylation of (BINAPO)PtCl2 (BINAPO=2-diphenylphosphino-2 '-diphenylphosphinyl-1,1 '-binaphthalene), the first chiral catalyst with an atropisomeric hemilabile P,O-heterodonor ligand

Platinum(LI) complexes with the axially chiral phosphinyl phosphine (S)-BIN APO (1) have been prepared and their behaviour in solution has been studied by P-31-NMR spectroscopy. Reaction of PtCl2(PhCN)(2) with 1 in benzene lea ds to the isolation of a neutral complex, 4, which maintains the P,O-chelat e coordination of the ligand even in solvents of low polarity. The hemilabi le character of the ligand is apparent from the reactions with DMSO and wit h carbon monoxide which promote the cleavage of the chelate ring of 4 throu gh displacement of the oxygenated arm. Insertion of tin(LI) chloride into t he Pt-Cl bond takes readily place at room temperature affording only one of the possible trichlorostannato derivatives (6) with complete selectivity. In the presence of SnCl2, the platinum complex 4 originates a catalyst of r emarkable regioselectivity which, in the hydroformylation of styrene, is ab le to produce in up to 30% e.e. the branched aldehyde as the prevalent prod uct. (C) 1999 Elsevier Science B.V. All rights reserved.