Monocyclopentadienyl titanium catalysts:ethene polymerisation versus ethene trimerisation

The chemistry of monocyclopentadienyl titanium complexes with pendant arene groups on the cyclopentadienyl ligand is reviewed, with an emphasis on cationic titanium dialkyl derivatives and their performance in catalytic olefin conversion. In these cationic species, the pendant arene group can coordinate in intramolecular fashion to the metal centre. The effect of this arene coordination on catalytic olefin conversion depends strongly on the nature of the bridge between the cyclopentadienyl and arene moieties. Whereas intramolecular arene coordination is generally detrimental to styrene and propene polymerisation performance, it causes a dramatic switch in ethene conversion behaviour, resulting in high activity and selectivity for catalytic trimerisation of ethene to 1-hexene. Possible reasons for this behaviour are discussed. (C) 2003 Elsevier B.V. All rights reserved.