Collect. Czech. Chem. Commun. 1990, 55, 1756-1762

Effect of triphenylphosphine on the cyclotrimerization of butadiene catalyzed by the TiCl4-EtAlCl2 system

Jindřich Poláček, Helena Antropiusová, Lidmila Petrusová and Karel Mach

The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, 182 23 Prague 8


Addition of PPh3 to the TiCl4 + n EtAlCl2 (n = 4-10) systems, which normally exhibit mostly Friedel-Crafts and polymerization activity towards butadiene, turns these systems into highly specific catalysts for the cyclotrimerization of butadiene to (Z, E, E)-1,5,9-cyclododecatriene. The effect of PPh3 lies in removal of AlCl3, which is formed in the reduction of TiCl4 with EtAlCl2 and in the disproportionation of EtAlCl2, for the AlCl3.PPh3 complex displays higher stability in comparison with the analogous complexes with ethylaluminium chlorides. The composition of the (η6-benzene)Ti(II) complexes, which are the catalytically active species, was determined by electronic absorption spectroscopy in the post-reaction mixtures.