Octahedral Chromium(III) Complexes Supported by Bis(2-pyridylmethyl)amines: Ligand Influence on Coordination Geometry and Ethylene Polymerization Activity

This report describes the synthesis, structural characterization, and polymerization behavior of a series of chromium(III) complexes supported by bis(2-pyridylmethyl)alkylamine (BPA) ligands. The compounds are prepared in high yield by room-temperature reaction of the appropriate BPA ligand with CrCl 3 (THF) 3 . X-ray crystallographic studies reveal that the complexes' coordination geometries depend on the substituent at the 6-position of the pyridine ring. Unsubstituted ligands yield fac- { N -propyl- N, N -di(2-pyridylmethyl)amine}CrCl 3 ( 6A ) and fac- { N -hexyl- N, N -di(2-pyridylmethyl)amine}CrCl 3 ( 6B ), whereas 6-methyl-substituted ligands produce mer- { N -propyl- N, N -di(6-methyl-2-pyridylmethyl)amine}CrCl 3 ( 6C ) and mer- { N -hexyl- N, N -di(6-methyl-2-pyridylmethyl)amine}CrCl 3 ( 6D ). Moreover, ethylene polymerization studies indicate that, upon activation by methylalumoxane, the fac derivatives are 30−40 times more active than their mer counterparts.