Efficient copolymerization of ethylene with norbornene mediated by phosphine-sulfonate palladium catalysts

Abstract

A series of tBu-/Ar-substituted phosphine-sulfonate palladium catalysts Pd1-Pd6 {[κ2(P, O)-(tBu)ArP(C6H4SO2O)]Pd(Me)(DMSO)} (1: Ar = Ph; 2: Ar = 4-OMe-C6H4; 3: Ar = 4-CF3-C6H4; 4: Ar = 2-OMe-C6H4; 5: Ar = 2,5- (OMe)2-C6H3; 6: Ar = 2,4-(OMe)2-C6H3) were prepared to copolymerize ethylene with norbornene and its polar derivatives. Installing electron-donating OMe substituent on the nonchelating P-bound aryl was proven to enhance the properties of catalysts. The position and number of OMe substituent significantly influenced the copolymerization results. The E-NB copolymers generated from these catalysts showed both high comonomer incorporations (≥19.3 mol%) and high copolymer molecular weights (≥24.6 kg⋅mol−1), which has been proven to be difficult to achieve using this catalyst system. And for the obtained copolymers, their norbornene incorporations and Tg values conformed to a linear relationship. More importantly, these catalysts can efficiently mediate the copolymerizations of ethylene and polar norbornenes, along with high activities (up to 1.0 × 106 g⋅mol−1⋅h−1), high molecular weights (up to 182 kg⋅mol−1), and high incorporations (up to 36.7 mol%). This work provided an efficient method to synthesis cyclic olefin copolymer using late transition metal catalysts.