Synthesis and Characterization of Polymer Metal Complexes and Their Catalytic Activity in Ethylene Oligomerization

A new polymeric ligand, 4,7-dihydroxy-1,10-phenanthroline/formaldehyde polymeric ligand [poly-(DHPF)], was synthesized via the polycondensation of 4,7-dihydroxy-1,10-phenanthroline and formaldehyde in an acidic medium. Polymer metal complexes, poly-[DHPF-M(II)Cl-2], were subsequently prepared with Co(II) and Ni(II) ions. The synthesized polymers were characterized by elemental and spectral analyses. The polymer metal complexes were evaluated as catalyst precursors for ethylene oligomerization, using methylaluminoxane as an activator. Different Al/M [M = Co(II) and Ni(II)] ratios were investigated at two different ethylene pressures. Poly-[DHPF-Co(II)Cl-2] (C-1) and poly-([DHPF-Ni(II)Cl-2] (C-2) were isolated as blue and green solids, respectively. Complex C-2 was found to be a more effective precatalyst than C-1 in the presence of a cocatalyst. Thus, C-2 exhibited the maximum activity of 1.92 x 10(6) g mol(-1) (Ni) h(-1) bar(-1) with an Al/Ni ratio of 3000: 1 at room temperature, whereas C-1 exhibited a maximum activity of 1.87 x 10(6) g mol(-1)(Co) h(-1) bar(-1) with a 5-atm pressure of ethylene. Upon increasing the Al/Co ratio at 1 atm pressure of ethylene, the catalytic activity of precatalyst increased and the process became more selective for higher oligomers. The catalytic activity and selectivity with 1-decene using C-1 were 3.16 x 10(5) g mol(-1)(Co) h(-1) bar(-1) and 72%, respectively, with 5 atm ethylene and an Al/Co ratio of 300:1. (C) 2013 Wiley Periodicals, Inc.