New atropisomeric N–N ligands for CO/vinylarene copolymerization reaction

Abstract

New atropisomeric bidentate bipyridine-based ligands (3,3′-(ethylenedioxy)-2,2′-bipyridine 3; 3,3′-(propylenedioxy)-2,2′-bipyridine 4; 3,3′-(butylenedioxy)-2,2′-bipyridine 5) containing a bridge between the 3,3′ positions of the aromatic rings have been prepared. Together with the previously reported analogous ligands ((R)-3,3′-(1-methylethylenedioxy)-2,2′-bipyridine) 1 and ((S,S)-3,3′-(1,2-dimethylethylenedioxy)-2,2′-bipyridine) 2, they were used to synthesize the corresponding bis-chelated dicationic complexes [Pd(N–N)₂][PF₆]₂. Crystal structures and comparison of the data obtained by X-ray analysis on four of these complexes is reported. These palladium compounds were used as precatalysts in the CO/styrene and CO/4-Me-styrene copolymerization reactions, where they showed that small variations in the ligand backbone remarkably affects the productivity of the catalytic system.