Ainooson M.K., Guzei I.A., Spencer L.C., Darkwa J.
Department of Chemistry, University of Johannesburg, Auckland Park Kingsway Campus, Auckland Park 2006, South Africa; Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, United States
Ainooson, M.K., Department of Chemistry, University of Johannesburg, Auckland Park Kingsway Campus, Auckland Park 2006, South Africa; Guzei, I.A., Department of Chemistry, University of Johannesburg, Auckland Park Kingsway Campus, Auckland Park 2006, South Africa, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, United States; Spencer, L.C., Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, United States; Darkwa, J., Department of Chemistry, University of Johannesburg, Auckland Park Kingsway Campus, Auckland Park 2006, South Africa
A series of tridentate (O^N^N) and bidentate (N^N) iron, cobalt and nickel complexes were prepared from {2,4-di-tert-butyl-6-[(2-(3,5-RR-pyrazol-1-yl- ethylimino)methyl]-phenol}, R = H (L1), Me (L2), Ph (L3), [(3,5-di-tert-butyl-2- ethoxy-benzylidene)-[2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]amine (L4), and (4-(4-tert-butyl-benzylidene)-[2-(3,5-dimethyl-pyrazol-1-yl)ethyl]-imine) (L5). Ligands L1-L5 were reacted with MX2 (M = Fe, Co, Ni; X = Cl, Br) to form three types of complexes. Whereas tridentate O∧N∧N bound complexes were formed with Fe(II) and Co(II) salts (1-6), reactions involving Ni(II) salts resulted in hydrolysis of the Schiff base ligands used to form a novel tetranuclear cubane-like cluster [Ni4(3,5-Me2pza) 4Cl8] (7) (pza = (3,5-dimethylpyrazol-1yl)ethylamine) and mononuclear [Ni(3,5-R2pza)Br2] (R = H (8); R = Me (9) complexes. Molecular structures of five complexes (1, 5-7 and 9), determined by single-crystal X-ray diffraction, confirmed that ligand hydrolysis occurred in the nickel reactions. All three nickel complexes showed good to excellent activity towards ethylene oligomerization with activities up to 10 726 kg (mol Ni h)-1. © 2013 Elsevier Ltd. All rights reserved.