Proximity-Driven Synergic Copolymerization of Ethylene and Polar Monomers

Coordination copolymerization of ethylene and polar monomers is a promising strategy for preparing structurally well-defined functional polyolefin. However, the poisonous effect of polar groups on employed catalysts is the main obstacle to be overcome. To mimic the synergistic catalysis of multinuclear metal compounds in nature, herein, we report the copolymerization of ethylene with a series of unprotected polar monomers containing oxygen, nitrogen, and sulfur atoms using binuclear half-sandwich scandium complexes C1-Sc2 and C2-Sc2 bearing −CH2– and −CH2CH2– linkers, respectively. In the copolymerization of ethylene and para-methoxystyrene (pMOS), C1-Sc2 and C2-Sc2 exhibit 13 and 7 times greater activities, respectively, than the mononuclear analogue Sc1. For the polar olefins having a butylene spacer, the activities follow the trend C1-Sc2 > C2-Sc2 > Sc1, whereas for the polar olefins that are shorter or longer than the butylene spacer, C2-Sc2 shows the highest activity. Moreover, the synergic effects and the cooperative mechanism for ethylene and pMOS copolymerization with C1-Sc2 were supported by DFT calculations.