{N-alkyl-N-[pyridin-2-ylmethylene] amine}dichloro palladium(II) complexes: synthesis, crystal structures and evaluation of their catalytic activities for ethylene polymerization
作者:Rui Chen、John Bacsa、Selwyn F Mapolie
DOI:10.1016/s0277-5387(03)00410-8
日期:2003.9
Three pyridinylimine palladium(II) complexes of the type [(C5H4N)HC=N-(CH2)n-CH3] PdCl2 (n = 4, 7, 11) were synthesized by reacting (COD)PdCl2 with the appropriate pyridyl-imine ligand. The crystal structure of the complex, where n = 7 was determined using single crystal X-ray crystallography and this displays a striking co-planar geometry, with the pyridine ring, the metal coordination sphere N(1)-C(5)-C(6)-N(2)-Pd and the alkyl backbone all being in the same plane. The three complexes prepared were evaluated as catalyst precursors for ethylene polymerization. Activation with methylaluminoxane (MAO) leads to the formation of an active catalyst species, which produces only high-density polyethylene. The effect of the chain length of the alkyl substituent at the imino nitrogen on the catalytic activity was evaluated. It was found that the molecular weight of the polymer increases as the chain length increases, although a higher level of MAO was required to reach optimum activity. (C) 2003 Elsevier Science Ltd. All rights reserved.