Crystal structure and thermodynamic stability of an acetone solvate of bis(trifluoroacetylacetonato)copper(II)

Abstract

A solvate [Cu(CF3COCHCOCH3)2(CH3COCH3)] has been synthesized and characterized for the first time. According to X-ray structural data (diffractometer X8 APEX BRUKER, radiation MoKα, T = 150 K), it crystallizes in the monoclinic crystal system, space group P21/c, a = 8.9940(4) A, b = 22.3966(11) A, c = 8.1884(3) A, β = 92.705(2)°, V = 1647.59(12) A3, Z = 4, dcalc = 1.725 g/cm3, final R = 0.0272. The structure is molecular. In the equatorial plane the atom Cu(II) is surrounded with four oxygen atoms of two chelating ligands (CF3COCHCOCH3)−; Cu-O distances 1.927–1.937 A, O-Cu-O angles 86.18–93.30° and 170.18–175.67°. Square coordination of Cu is complemented to the square-pyramidal one by the oxygen atom of an acetone molecule behaving as an axial ligand; Cu-Oacetone 2.342 A, O-Cu-Oacetone 89.66–100.11°. In the studied compound disorder of one of the chelate ligands implies the co-existance of the molecules in the cis- and trans-configuration in the crystal under ratio 54.6:45.4. In air the solvate rapidly degrades losing acetone, while in a sealed vessel melts around 313 K. Temperature dependence of equilibrium vapor pressure of acetone over the complex was measured with the static spoon gauge technique, thermodynamic characteristics of its dissociation process being derived: [Cu(CF3COCHCOCH3)2(CH3COCH3)]s = [Cu(CF3COCHCOCH3)2]s + CH3COCH3g, ΔHav0 = 49.6(3) kJ/mol, ΔSav0 = 152(1) J/(mol K), ΔGav0 = 4.30(2) kJ/mol.