Tacticity control of polypropylene using a C2-symmetric family of catalysts

A family of C2-symmetric catalysts was designed and synthesized with the intent to polymerize propylene. The catalyst was designed to be C2-symmetric for the specific goal that the catalyst would have two identical sites for the propagation of the polymer and therefore eliminate some of the stereoerrors that occur in the propagation of the polymer chain. This catalyst would also operate under simple enantiomorphic site control and therefore the insertion of the monomer would be governed by the ligand surrounding the active site. The ligands were synthesized with increasing degrees of steric bulk with the intention to determine if a catalyst system could generate elastomeric polypropylene. Enantiomorphic site control polypropylene utilizes statistical methods to determine the Si and Re content of a given polymer chain as a function of the variable E. Polypropylene samples generated by the catalyst family were analyzed using high temperature pentad analysis of the methyl region to calculate the E value. The goal was to observe E to be equal to 0.78 provided that the number molecular weight of the polymer was 100,000. The catalyst systems generated polymers with values higher and lower than the desired 0.78, indicating too high or too low enantioselectivity of the catalyst systems respectively at Tp = 0?C.