Interaction of triethylaluminium with acetylacetonates of transition metals

Abstract

Abstract The reaction of AlEt 3 with acetylacetonates of Cr III , Fe III , Co III , Ni II and Pd II in benzene and cyclohexane has been studied in a wide range of initial ratios of AlEt 3 /M(acac) n . Quantitative analysis of the reaction mixture, performed with the help of UV spectra, showed that acetylacetonate ligands were transferred from the transition metals to aluminium. A scheme involving stepwise substitution of ethyl radicals by acetylacetonate ligands on AlEt 3 with further formation of an Al(acac) 3 -Et 2 Al(acac) mixture is proposed for Al/M n (M = Fe, Co, Ni). An increase of the Al/M ratio causes an increase of the Et 2 Al(acac) fraction. The only reaction product containing an acetylacetonate ligand is Et 2 (Al(acac) at Al/M = n . Cr(acac) 3 and Pd(acac) 2 interact with AlEt 3 forming Et 2 Al(acac) at any initial ratio of Al/M. Stabilization of intermediate organo-nickel and -palladium compounds has been observed in the interaction of AlEt 3 with Pd(acac) 2 and Ni(acac) 2 in benzene, which inhibited the reaction rate considerably. Magnetochemical measurements showed that Fe III , Co III , Ni II were reduced to the zerovalent state in their reaction with AlEt 3 (Al/Mn ⩾ n ). The content of the finely dispersed metal component is negligible small and the greater part of transition metal is present as M 0 complexes, where Et 2 Al(acac) formed in the reaction is the main stabilizing ligand.