Radical-controlled oxidative polymerization of 4-phenoxyphenol catalyzed by a dicopper complex of a dinucleating ligand

The oxidative polymerization of 4-phenoxyphenol (PPL) catalyzed by a dicopper complex with a dinucleating ligand, 1,2-bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane is described. The polymerization proceeded regioselectively to give crystalline unsubstituted poly(1,4-phenylene oxide) (PPO), in which mu-eta(2):eta(2)-peroxo dicopper(II) species is probably involved as the active dioxygen intermediate. A copper complex with a mononucleating ligand of the similar structure, I,1,l-tris(6-methylpyrid-2-yl)ethane, also catalyzed the oxidative coupling of PPL. The coupling selectivity for the dicopper/dinucleating ligand complex was close to that for the copper/mononucleating ligand complex. However, the initial reaction rate for the former was independent on the catalyst amount in a certain range, whereas that for the latter decreased with the decrease of the catalyst amount. (C) 2000 Elsevier Science B.V. All rights reserved.