Synthesis, X-ray crystal structures and thermal behavior of calcium β-diketonate complexes [Ca(fod)2(15-crown-5)] and [Ca(fod)(C3F7COO)(15-crown-5)] (Hfod = 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione)

Abstract

The synthesis of the Ca-β-diketonate complexes with 15-crown-5 [Ca(fod)2(15-crown-5)] (1), [Ca(fod)(C3F7COO)(15-crown-5)] (2), (Hfod = 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dione; 15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane) is described. The complex 1 has been prepared by reaction of metallic Ca with 1 equiv of 15-crown-5 and 2 equiv of Hfod in ethanol. The reaction of calcium covered by surface calcium hydroxide with excess of Hfod in presence of 15-crown-5 in boiling toluene results in the complex 2 as main product and complex 1 as by-product. The solvated complex [Ca(fod)(C3F7COO)(15-crown-5)](CH2Cl2) (3) was obtained by recrystallization from CH2Cl2-hexane solution of 2. The complexes 1, 2 were characterized by elemental analyses, IR-spectroscopy, NMR-spectroscopy. The molecular structures of 1, 3 were characterized by single-crystal X-ray diffraction method. Complexes 1, 3 have monomolecular structures. In 1 the calcium cation Ca2+ is outside the crown-ether cavity and coordinated by five O atoms of 15-crown-5 and four O atoms of two fod-ligands; the average Ca-Ofod distance is 2.38(2) Å and the average Ca-Ocrown distance is 2.64(2) Å. In the compound 3 the coordination environment of the Ca is set up by two O atoms of chelating fod ligand, one O atom of C3F7COO ligand and five O atoms of 15-crown-5 ligand. Ca atom is outside 15-crown-5 plane, β-diketonate and carboxylate ligands are in cis-position relative to 15-crown-5. The average Ca-Ofod bond distance 2.318(2) Å and Ca-OC3F7COO bond distance 2.311(2) Å are practically equal. The 1 and 2 are thermal stable in 50–227 °C and in 50–180 °C temperature ranges, respectively. In dynamic vacuum (residual pressure 10−2 Torr) complexes 1 and 2 sublimed in 70–110 °C temperature range congruently.