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Methylene-Bridged Bisphosphine Monoxide Ligands for Palladium-Catalyzed Copolymerization of Ethylene and Polar Monomers.

Yusuke MitsushigeHina YasudaBrad P CarrowShingo ItoMinoru KobayashiTakao TayanoYumiko WatanabeYoshishige OkunoShinya HayashiJunichi KurodaYoshikuni OkumuraKyoko Nozaki
Published in: ACS macro letters (2018)
A series of palladium complexes bearing a bisphosphine monoxide with a methylene linker, that is, [κ 2 - P , O -(R 1 2 P)CH 2 P(O)R 2 2 ]PdMe(2,6-lutidine)][BAr F 4 ] (Pd/BPMO), were synthesized and evaluated as catalysts for the homopolymerization of ethylene and the copolymerization of ethylene and polar monomers. X-ray crystallographic analyses revealed that these Pd/BPMO complexes exhibit significantly narrower bite angles and longer Pd-O bonds than Pd/BPMO complexes bearing a phenylene linker, while maintaining almost constant Pd-P bond lengths. Among the complexes synthesized, menthyl-substituted complex 3f (R 1 = (1 R ,2 S ,5 R )-2-isopropyl-5-methylcyclohexan-1-yl; R 2 = Me) showed the best catalytic performance in the homo- and copolymerization in terms of molecular weight and polymerization activity. Meanwhile, complex 3e (R 1 = t -Bu; R 2 = Me) exhibited a markedly higher incorporation of comonomers in the copolymerization of ethylene and allyl acetate (≤12.0 mol %) or methyl methacrylate (≤0.6 mol %). The catalytic system represents one of the first examples of late-transition-metal complexes bearing an alkylene-bridged bidentate ligand that afford high-molecular-weight copolymers from the copolymerization of ethylene and polar monomers.
Keyphrases
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