Heteroleptic triphenylacetate-tetramethylaluminate complexes of lanthanum and neodymium. Coordination of La3+ with the π-system as the reason for the low catalytic activity of lanthanum complexes

Abstract

Triphenylacetate-tetramethylaluminate complexes [Ln(Ph3CCOO)2Al(CH3)4]2 (Ln = La, Nd) have been synthesized and structurally characterized. Their reaction with THF leads to the formation of the solvent-separated ion pairs [(Ph3CCOO)2Ln(THF)5]+[(Al(CH3)4]−. The tendency of the La3+ cation to interact with the π-electron system of phenyl rings has been revealed by molecular structure analysis for La-Al and Nd – Al tetramethylaluminate complexes in combination with the study of butadiene and isoprene polymerization by using catalyst system based on these complexes and aluminum alkyl cocatalysts. Coordination of Ln3+ cation by the π-electron conjugated system makes it difficult to form the catalytically active intermediates and decreases the catalytic activity.