Die binuklearen Produkte der Umsetzung von Grignardreagenzien mit Acetylacetonaten der späten 3d-Elemente und ihre katalytische Wirkung bei der Kreuzkopplung

Binuclear Reaction Products of Grignard Compounds and Transition Metal Acetylacetonates - Catalysts of Cross Coupling In THF Grignard compounds react with transition metal acetylacetonates forming the binuclear complexes (THF)₂Mg(acac)₂M^IIX₂ (M^II ? Fe, Co, Ni; X ? Cl, Br). A characteristic component of these compounds is the octahedral moiety (THF)₂Mg(acac)₂. The coordination of two cis-positioned oxygen donors of this moiety to an M^IIX₂-group builds up a second (tetrahedral) coordination centre. The structure of the binuclear complexes and their vis-spectra are discussed in detail. The new compounds are cross coupling catalysts of acylhalides and Grignard reagents. Probably in the course of the catalytic process the acylhalides are activated at the unsaturated transition metal centre (increase of the coordination number), but the Grignard reagent at the magnesium centre (substitution of one of the weakly bound THF-ligands). This model also explains the different catalytic activity of (THF)₂Mg(acac)₂FeCl₂ and (THF)₂Mg(acac)₂NiBr₂.