Fluorinated β-Diketonates of the First Row Divalent Transition Metals: New Approach to the Synthesis of Unsolvated Species.

An original low-temperature solid-state route for the preparation of metal β-diketonates in their unsolvated forms has been suggested. Four new first row divalent transition metal β-diketonates, M(hfac)[sub2] (M = Mn (1), Fe (2), Co (3), and Ni (4); hfac = hexaluoroacetylacetonate), have been isolated in quantitative yield. Compounds 1-3 have been obtained by comproportionation reaction between the corresponding M(hfac)3 and metal powder. Ni(hfac)[sub2] (4) has been synthesized by oxidation of metallic nickel with Cu(hfac)[sub2]. All products have been characterized spectroscopically and by X-ray powder and single crystal diffraction techniques. The solid state structures of 1-4 feature polynuclear molecules, in which the coordinatively unsaturated metal centers fulfill an octahedral environment by Lewis acid-base interactions with the oxygen atoms of diketonate ligands acting in chelating-bridging fashion. Title transition metal diketonates have been shown to retain their polynuclear structures upon sublimation-deposition procedure as well as in solutions of non-coordinating solvents. In coordinating solvents the molecules of 1-4 quickly form the mononuclear M(hfac)[sub2]L[sub2] (L = donor solvent) complexes. [ABSTRACT FROM AUTHOR]