The synthesis, characterization, and ethylene polymerization behavior of a series of iron and cobalt halide complexes, LMX n (M ) Fe, X ) Cl, n ) 2, 3, X ) Br, n ) 2; M ) Co, X ) Cl, n ) 2), bearing chelating 2,6-bis(imino)pyridyl ligands L [L ) 2,6-(ArNCR 1 ) 2 C 5 H 3 N] is reported. X-ray diffraction studies show the geometry at the metal centers to be either distorted square pyramidal or distorted trigonal bipyramidal. Treatment of the complexes LMX n with methylaluminoxane (MAO) leads to highly active ethylene polymerization catalysts converting ethylene to highly linear polyethylene (PE). LFeX 2 precatalysts with ketimine ligands (R 1 ) Me) are approximately an order of magnitude more active than precatalysts with aldimine ligands (R 1 ) H). Catalyst productivities in the range 3750-20600 g/mmol‚h‚bar are observed for Fe-based ketimine catalysts, while Co ketimine systems display activities of 450-1740 g/mmol‚h‚bar. Molecular weights (M w ) of the polymers produced are in the range 14000-611000. Changing reaction conditions also affects productivity and molecular weight; in some systems, a bimodal molecular weight distribution is observed. On the basis of evidence gathered to date, the lower molecular weight fraction is a result of chain transfer to aluminum while the higher molecular weight fraction is produced by a combination of mainly -H transfer and some chain transfer to aluminum.

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Reactions of MnX 2 with the tridentate nitrogen donor ligands [2,6-{(2,4,6respectively, in good yield. Crystallographic studies on 1-3 reveal all three complexes to be pentacoordinate with geometries that can be best described as distorted trigonal bipyramidal (1, 2) or square pyramidal (3). Conversely, treatment of MnCl] with 2,6-diacetylpyridine) under similar reaction conditions results in self-assembly to afford the antiferromagnetically coupled polymetallic saltThe molecular structure of 4 shows a discrete dimanganese cation and polymeric manganese anion with each ionic unit supported by a 26-membered macrocyclic hexadentate nitrogen donor ligand.

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