A considerable amount of research effort has been dedicated both recently and in the past to nonselective ethylene oligomerization with the aim of improving the understanding of this industrially relevant catalytic process.[1] The mixtures of linear alpha olefins (LAO) produced by this process are in fact valuable commodity chemicals for a range of industrial and household applications depending on their molar mass distribution (detergents, surfactants, cosmetics, synthetic lubricants, etc).[2] Herein, we describe the synthesis, structural characterization of Cr(III) complexes bearing imine tridentate ligands [N,N,E] (E = O, N) of general formula [CrCl2(NNE)(THF)] and their use in ethylene oligomerization. Upon activation with methylaluminoxane (MAO), these chromium precatalysts showed good activity in ethylene oligomerization (TOF = 10,900-72,900 (mol ethylene)(mol Cr)-1×h-1 at 80 °C), producing mostly oligomers (73.9-99.4 wt% of total products). We discuss also the performance of these precatalysts, evaluating the role of the ligand, and the experimental parameters (cocatalyst type, [Al]/[Cr] molar ratio, temperature, and oligomerization time) on the activity and on the product distribution (oligomer/PE ratio). [1] (a) D.S. McGuinness, V. C. Gibson and J. W. Steed, Organometallics 2004, 23, 6288; (b) K. Tenza, M. J. Hanton, and A. M. Z. Slawin, Organometallics 2009, 28, 4852; (c) E. Kirillov, T. Roisnel, A. Razavi and J.-F. Carpentier, Organometallics 2009, 28, 2401; (d) F. Junges, M. C. A. Kuhn, A. H. D. P. dos Santos, C. R. K. Rabello, C. M. Thomas, J.-F. Carpentier and O. L. Casagrande Jr. Organometallics 2007, 26, 4010; (e) Y. Chen, W. Zuo, P. Hao, S. Zhang, K. Gao and W.-H. Sun, J. Organomet. Chem. 2008, 693, 750; (f) R. Gao, T. Liang, F. Wanga and W.-H. Sun, J. Organomet. Chem. 2009, 694, 3701; (g) B. L. Small, R. Rios, E. R. Fernandez, D. L. Gerlach, J. A. Halfen and M. J. Carney, Organometallics 2010, 29, 6723. [2] (a) P.W.N.N. Van Leeuwen, Homogeneous Catalysis, Kluwer Academic, Inc. Dordrecht, 2004, p 175; (b) D. Vogt, Oligomerization of ethylene to higher linear Rolefins. In Applied Homogeneous Catalysis with Organometallic Compounds, Eds., Wiley-VCH: Weinheim, Germany, 2000, p 245; (c) G. R. Lappin and J. D.Sauer, in Alpha Olefins Application Handbook, Marcel Dekker: New York, 1989, Vol. 37, p 1.

Ethylene oligomerization promoted by chromium complexes bearing imine tridentate ligands

251st National Meeting (2016)

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