Design and Synthesis of 4,4'-Disubstituted-[2,2']-Bipyridines for Catalyzing CO/Styrene Copolymerization with Palladium(Ⅱ)

A series of 4,4'-disubstituted-2,2']-bipyridines, featuring electron withdrawing/donating functional groups such as amino, chloro, nitro, ethoxycarbonyl, carboxy, methyl, methoxy and hydroxymethyl, have been synthesized and employed in the copolymerization of carbon monoxide(CO)and styrene. The available bipyridine and its derivatives were coordinated with palladium(Ⅱ)acetate for catalyzing the copolymerization of CO and styrene, and the concomitant polyketone was characterized by means of 13 C NMR, FTIR, differential scanning calorimetry(DSC)and element analysis techniques concerning its structure and thermal performance. The effect of different electron-donating and electron-withdrawing groups on catalyst performance and molecular weight of copolymer was studied under certain experimental condition. It has been proved that the enhancement of electron donating and conjugative effects on bipyridine ligand will not only improve the catalytic activity of the composition, but also increase the molecular weight of the as-prepared polyketone. The catalytic activity is the highest in hydroxymethyl substituted 2,2'-bipyridine ligand(1 356 g STCO/(g Pd · h)), when the molecular weight and polydispersity index of the polyketone are M n=8 502,M w=1 3440 and M w/M n=1.581, respectively.