Polymerization of norbornene by palladium(II) complexes bearing ethylene-bridged bisindolinyl- or bis(l,2,3,4-tetrahydroquinolinyl) ligands

Novel moisture and air stable, cationic palladium(II) amine complexes (1-4) of the general type [Pd(N boolean AND N)(X)(2)](BF4)(2), [N boolean AND N = 1,2-bis(N-indolinyl)ethane (BIE) 1, 3; 1,2-bis(N-1,2,3,4-tetrahydroquinolinyl)ethane (BTQE) 2, 4; X = NCCH3, H2O] were found to catalyze the polymerization reaction of bicyclo[2.2.1]hept-2-ene at room temperature. The amorphous polymer products consist of 2,3-linked norbornene units; no indications for ring opened species could be observed. The polymerization activity of the diaqua-complexes 3, 4 is superior compared to their acetonitrile analogues due to a facile activation by a Wacker-type reaction. The cationic Pd(II)-compounds are inactive towards homo- and copolymerization reactions of polar monomers, like acrylates or carbon monoxide. However, addition of methylacrylate resulted in polynorbornene products with increased molecular weight and narrow molecular weight distributions. (C) 1998 Elsevier Science B.V.