Structures of Anhydrous and Hydrated Copper(II) Hexafluoroacetylacetonate

Crystal structure analyses are reported for anhydrous copper(II) hexafluoroacetylacetonate (Cu(hfac)2) and for two
of its hydrates. The anhydrous compound (Cu(hfac)2, 1:  P1̄; at 100 K, a = 5.428(1), b = 5.849(1), c = 11.516(3)
Å; α = 81.47(2), β = 74.57(2), γ = 86.96(2)°; Z = 1) contains centrosymmetric square-planar complexes with
close intermolecular Cu···F contacts. The geometry of the complex is similar to that previously reported for Cu(hfac)2·toluene. The monoaquo compound (Cu(hfac)2(H2O), 2:  P21/c; at 100 K, a = 10.8300(8), b = 6.5400(6), c =
21.551(3) Å; β = 90.282(8)°; Z = 4) consists of square-pyramidal molecules with apical H2O ligands, and close-lying F atoms in the sixth coordination sites. The major difference between this structure and the two other polymorphs
previously reported is the nature and direction of hydrogen bonds. The yellow-green solid formed from Cu(hfac)2
with excess H2O is identified as the trihydrate. In crystalline form it is the previously unreported [trans-Cu(hfac)2(H2O)2]·H2O (3:  P1̄; at 150 K, a = 8.3899(3), b = 9.6011(3), c = 11.4852(4) Å; α = 72.397(2), β = 79.161(2),
γ = 87.843(2)°; Z = 2). There is no conclusive evidence in favor of any solid with the composition Cu(hfac)2·2H2O.