Enantio- and Stereoselective Cyclopolymerization of Hexa-1,5-diene Catalyzed by Zirconium Complexes Possessing Optically Active Bis(phenolato) Ligands

摘要

Enantio-and stereoselective cyclopolymerization of hexa-1,5-diene was achieved by enantiomerically pure dichloro zirconium(IV) pre-catalysts 2 possessing chiral OSSO-type bis(phenolate) ligands (-)-1 and (+)-1 in combination with dried methylaluminoxane (dMAO) as an activator. The corresponding activities were recorded with quite high values up to 1,960 g mmol(2)(-1) h(-1), which are extremely larger than those of the related complexes. The microstructure analysis for the PMCPs furnished by pre-catalysts (Lambda,S,S)-2 and (Delta,R,R)-2 showed good isotacticity factors (alpha = 75-78) and relatively high proportions of trans-cyclopentane rings (sigma = 14-21). These enantiomeric PMCPs exhibited large specific optical rotations (alpha(D) = +28 to +32 degrees from (Lambda,S,S)-2, -26 to -34 degrees from (Delta,R,R)-2).