Syntheses and Characterization of the Thermally Stable Cu(hexafluoroacetylacetonato)2(μ-diethyl 2-allylmalonate)

Abstract

Much attention has been paid to the structural chemistry of β-diketones and β-diketonates involving keto-enol tautomerism and the intramolecular hydrogen bond. For the majority of cases in keto-enol tautomerism, the keto form (1a) is far more stable. Such factors as intramolecular hydrogen bond and conjugation, however, increase the stability of the enol form (1b and 1c). The geometry of the gas phase acetylacetonate anion is predicted using ab initio molecular orbital theory. There are three stable conformers in the diketo geometry of the acetylacetonate anion; (1) a Cs structure with the carbonyls in an anti conformation (2a), (2) a C2 structure with the carbonyls pointed exo (2b), and (3) a C2v structure with the carbonyls endo (2c). A Cs structure (2a) is most stable and a C2v structure (2c) is least stable conformation of the gas phase acetylacetonate anion. Most β-diketonate ligands in metal complexes exhibit a C2v bonding modes (2c). 3 Any β-diketones, however, is not known to bind to two different metal atoms yielding onedimensional chain structure. In this paper we report the reaction of β-diketone with Cu(hfa)2 (hfa = hexafluoroacetylacetonate) and discuss the structural characterization and thermal stability of Cu(hfa)2(μ-deam) (deam = diethyl allylmalonate). Cu(hfa)2(μ-deam) was obtained by the reaction of Cu(hfa)2 and diethyl allylmalonate(deam) in benzene. Suitable crystals were harvested from slow cooling of a saturated hexane solution.