Calix[4]arene-based bis-phosphonites, bis-phosphites, and bis-O-acyl-phosphites as ligands in the rhodium(I)-catalyzed hydroformylation of 1-octene

New calix[4]arene-based bis-phosphonites. bis-phosphites and bis-O-acylphosphites were synthesized and characterized. Treatment of these P-ligands with selected rhodium and platinum precursors led to mononuclear complexes that were satisfactorily characterized. The solid state structure of the dirhodium(I) complex 14 has been determined by X-ray diffraction. The two rhodium centres are bridged by two chloro ligands; one rhodium atom is further coordinated b calix[4]arene phosphorus atoms and the other by cyclooctadicne, The new calix[4]arene P-ligands were tested in the Rh(I) catalyzed hydroformylation of 1-octene. All Rh(l) complexes catalyzed the reaction leading to high chemoselectivity with regard to the formation of aldehydes. Yields and n/isoselectivities depended on the reaction conditions. Average yields of 80% and n/iso-ratios of about 1.3 to 1.5 were observed. High yields of aldehydes can be achieved using the methoxy substituted P-ligands at low Rh:ligand ratios.