Homogeneous and two-phase dimerization of olefins catalyzed by tungsten complexes. The role of imido ligands and Lewis acids

Organoimido CI4WVI = NAr (Ar = aryl) (1) complexes catalyze the dimerizatio n of propene and ethene in presence of alkylaluminum derivatives. Similar r esults are obtained with the in situ formed tungsten system based on the mi xture WCl6/aniline/alkylaluminum. For most cases, 2,3-dimethylbutenes are t he main dimers formed from propene. However, in some instances, propene met athesis reactions can be promoted. The Cl2WIV = NPh(PMe3)(3) 3 complex is a n efficient catalyst for ethene dimerization when promoted by AICl(3). The reaction can be carried out using acidic chloroaluminates as the solvent wi th 3 without an additional cocatalyst. Cationic species are proposed as the active intermediate. (C) 1999 Elsevier Science B.V. All rights reserved.