Platinum(II) complexes incorporating racemic and optically active 1-alkyl-3-phospholene P-ligands: Synthesis, stereostructure, NMR properties and catalytic activity

Three 1-alkyl-3-phospholene 1-oxides, such as the P-ethyl, P-isobutyl and P-isopentyl derivative were prepared in racemic and enantiopure forms. After deoxygenation, the cyclic phosphines were converted to the corresponding phosphine-boranes and phosphine-platinum complexes (PtCl2L2, where L 1-alkyl-3-phospholene). The new products were characterized by spectral methods, and the stereostructure of the complexes was also evaluated by high level quantum chemical calculations. The platinum complexes were tested in the hydroformylation of the styrene. The extent of the regioselectivity towards branched aldehyde exceeds that measured with earlier platinum complexes. However, the enantioselectivity remained below 29%. (C) 2013 Elsevier B. V. All rights reserved.