Stereo- and enantioselective polymerization of hexa-1,5-diene on heterogeneous Ziegler-Natta catalysts obtained with the use of optically active internal donors

Abstract

Pure racemates and individual enantiomers of diethyl 2,3-diisopropylsuccinate ((+,−)-DIPS and (−)-DIPS) and 2,3-diisopropyl-1,4-dimethoxybutane ((+,−)-DPDMB and (+)-DPDMB) were prepared. The synthesized compounds and diethyl phthalate were used as internal donors for the preparation of heterogeneous Ziegler-Natta catalysts. Polymerization of hexa-1,5-diene was carried out on these catalysts. The obtained samples of poly(methylene-1,3-cyclopentane) were studied by 13C NMR spectroscopy and polarimetry. The induction of optical activity to polymer is observed with (−)-DIPS as the internal donor. The induction value makes up 15–20% from the value recorded in the case of optically active metallocene catalysts. The emergence of induction may be associated with the presence of close contact between the titanium atom and the donor molecule within the active site of catalyst, as well as with the fact that the donor molecule either deactivates a part of the stereospecific titanium centers or influences the structure of the titanium centers during their formation and development.