NICKEL(0)-CATALYZED ALTERNATING COPOLYMERIZATION OF 2,6-OCTADIYNE WITH CARBON-DIOXIDE TO POLY(2-PYRONE)

A nickel(0) catalyst generated from Ni(COD)2 and tri-n-alkylphosphine effected efficient alternating copolymerization of 2,6-octadiyne (1) with CO2 to a new class of polymer of poly(2-pyrone) 2. Various factors such as reaction temperature, CO2 pressure, diyne concentration, and reaction solvent exerted influences on the alternating copolymerizability along with the copolymer yield and molecular weight. Under the reaction conditions, the reaction temperature of 60-degrees-C, the CO2 pressure of 20 kg/cm2, and the THF/MeCN solvent, and using a P(n-C8H17)3 ligand and the higher diyne concentration, 2 with the molecular weight of ca. 7000 was obtained in excellent yield. The formation of the 1:1 alternating copolymer was demonstrated by the comparison of C-13 NMR C=O and/or C=C absorptions of 2 with those of a co-oligomer and a homopolymer.