Structure-stereospecificity relationships of propylene polymerization using substituted ansa-silylene(fluorenyl)(amido) titanium complexes

• New ansa-Fluorenylamidotitanium complexes with various substituents were synthesized.
• The complexes promoted syn-specific of aspecific propylene polymerization.
• The origin of the stereodefect in this polymerization system was revealed.

ansa-Fluorenylamidotitanium complexes bearing various substituents on the nitrogen and fluorene (2a-d) were synthesized. The structures of the complexes were characterized by 1H and 13C NMR, and X-ray crystal analyses were performed for complexes 2a, 2b and 2d. The coordination mode of the fluorenyl group to the metal center was changed from η3 to η1 when a bulky group was introduced on the nitrogen or 2,3-position of the fluorenyl ring. Syndiotactic-specificity of the catalyst for the propylene polymerization was reduced when bulky group was introduced on the nitrogen. Least-square fitting analysis of the steric pentad distributions revealed that the stereodefect was mainly formed by the chain migration without monomer insertion, which is accelerated by the η1-coordination of the fluorenyl group.

ansaFluorenylamidotitanium complexes bearing various substituents on the nitrogen and fluorene were synthesized to reveal the relationship between the structure and stereospecificity of propylene polymerization. Syndiotactic-specificity of the catalyst for the propylene polymerization was reduced when bulky group was introduced on the nitrogen.Figure optionsDownload as PowerPoint slide