Rhodium complexes with a new chiral amino-phosphinite ligand and their behavior as pre-catalysts in the hydroformylation of styrene

The new amino-phosphinite chiral ligand (Sa)-4-((S)-1-(diphenylphosphinooxy)-3-methylbutan-2-yl)-4,5-dihydro-3H-dinaphtho[2,1-c:1′,2′-e]azepine (1) has been synthesized and the corresponding more stable oxide has been characterized by X-ray analysis. The ligand behavior in styrene hydroformylation using [Rh(acac)(CO)2] and [Rh(COD)2]BF4 as precursors has been studied. With both pre-catalysts, branched aldehyde 2-phenylpropanal was obtained in mild catalysis conditions with high yield and regioselectivity but as racemic mixture, indicating the loss of the ligand (1) during catalytic run. To support these results, the reactions of [Rh(acac)(CO)2] and [Rh(COD)2]BF4 with the ligand 1 have been performed and the pre-catalysts behavior under CO/H2 has been investigated.