Preparation and structures of aryloxy- and alkoxy-Ti(IV) complexes and their evaluation in ethylene oligomerisation and polymerisation
School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, Australia; Sasol Technology Ltd, PO Box 1183, Sasolburg 1947, South Africa
A range of aryloxy and alkoxy ligands, both monodenate and chelating, have been coordinated to Ti(iv) to yield complexes of the form [Ti(OAr) 2Cl 2], [Ti(ROO)Cl 3] and [Ti(ROO) 2Cl 2] (R = aryl, alkyl). The complexes vary in their Lewis base solvation and/or aggregation state, as revealed by X-ray crystallography of selected examples. The complexes have been evaluated as catalysts for ethylene oligomerisation and polymerisation following activation with alkylaluminium reagents (AlEt 3, methylaluminoxane). While polyethylene is the major product, ethylene oligomers also result, ranging from dimers to higher oligomers. The results indicate a number of different active species are formed upon activation, with oligomers likely arising through a metallacyclic mechanism. The findings are discussed in the context of the commercial Alphabutol dimerisation system [Ti(OR) 4], and the development of group 4 based ethylene trimerisation catalysts. © 2012 The Royal Society of Chemistry.
Active species; Aggregation state; Aryloxy; Group 4; Lewis base; Methylaluminoxane; Selected examples; Catalysts; Coordination reactions; Dimers; Ethylene; Oligomerization; Polymerization; X ray crystallography; Chlorine compounds