Jiazhen Chen
Northwestern
We report the synthesis and characterization of binuclear Sc half-sandwich complexes. Marked catalyst and cocatalyst nuclearity effects on product polymer microstructure are achieved in isoprene polymerization. The binuclear catalysts promote the cis-1,4- units formation in polyisoprene. Binuclear catalysts also regulate the isometric unit distributions and favor 3,4~3,4~3,4 blocks. Furthermore, the percentage of polyisoprene trans-1,4- units increases ~5x when binuclear cocatalyst is used in comparison to mononuclear cocatalyst. These results highlight the importance of both ion pairing and imposed nuclearity in these polymerizations, and indicate that both catalyst and co-catalyst nuclearities can be used to access specific polyisoprene polymer/copolymer microstructures.