INTERACTION OF TRIETHYLALUMINIUM WITH ACETYLACETONATES OF TRANSITION METALS

Article abstract of DOI:10.1016/S0022-328X(00)99208-8

The reaction of AlEt3 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 AlEt3/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 AlEt3 with further formation of an Al(acac)3Et2Al(acac) mixture is proposed for Al/M < n (M=Fe, Co, Ni).An increase of the Al/M ratio causes an increase of the Et2Al(acac) fraction.The only reaction product containing an acetylacetonate ligand is Et2Al(acac) at Al/M=n.Cr(acac)3 and Pd(acac)2 interact with AlEt3 forming Et2Al(acac) at any initial ratio of Al/M.Stabilization of intermediate organo-nickel and -palladium compounds has been observed in the interaction of AlEt3 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 AlEt3 (Al/Mn <*> n).The content of the finely dispersed metal component is negligible small and the greater part of transition metal is present as M⁰ complexes, where Et2Al(acac) formed in the reaction is the main stabilizing ligand.