Synthesis, structure and catalytic properties of [Cp*Cr(C6F5)(Bn)(THF)] toward ethylene in the presence of AlEt3
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Treatment of [Cp*CrCl(C6F5)]2 with BnMgCl (Bn = benzyl) in Et2O/THF affords [Cp*Cr(C 6F5)(Bn)(THF)] (1) which has been isolated in 72% yield. This compound whose magnetic moment is equal to of 4.037 B has been characterized by NMR and single crystal X-ray analysis. Compound 1 alone does not polymerize ethylene when dissolved in toluene. However, addition of excess AlEt3 to a solution of 1 in toluene leads to a catalytically active system which readily oligomerizes ethylene under standard conditions. Oligomerization experiments carried out with  = 10-3 M and [AlEt3] = 9 10-2 M for 15 min lead to the production of ethylene oligomers with an activity of 280 kg mol Cr-1 h-1. The experimental molecular weight distribution observed at intermediate times during the reaction is satisfactorily accounted for by the Poisson distribution formula, which is indicative of a living polymerization system. These observations are in agreement with a catalytic cycle in which the growing alkyl chain is transferred from chromium to aluminum via a bimetallic complex in which the chromium and aluminum centers are bridged by an alkyl group and the growing polymer chain. 2005 Elsevier B.V. All rights reserved.
Journal of Organometallic Chemistry
author list (cited authors)
Ganesan, M., & P. Gabba, F.
complete list of authors
Ganesan, Mani||P. Gabbaï, François