New o-methoxyphenylcyclopentadienylchromium (III) complexes: Synthesis, structures and catalytic properties for ethylene polymerization

Abstract

Two new ligands 1-(2-methoxyphenyl)-3,4-diphenylcyclopentadiene ( 1) and 1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadiene ( 2), as well as their corresponding cyclopentadienylchromium complexes η 5-1-(2-methoxyphenyl)-3,4-diphenylcyclopentadienyl chromium dichloride ( 3) and η 5-1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadienyl chromium dichloride ( 4) were synthesized and characterized. Molecular structures of 3 and 4 were determined by single-crystal X-ray diffraction. Complexes 3 and 4 were tested as catalyst precursors for ethylene polymerization. When activated with Al( i Bu) 3 and Ph 3 C + B ( C 6 F 5 ) 4 - , complex 3 shows reasonable catalytic activity while 4 exhibits high catalytic activity for ethylene polymerization. The effects of temperature and Al/Cr ratio on the catalytic activity were studied. The molecular weight and melting temperature of the produced polyethylenes were determined.