Structural investigations of copper(II) complexes containing fluorine-substituted β-diketonate ligands

The crystal structures of the β-diketonate complexes Cu(pta)2, Cu(pta)2·EtOH, and Cu(F6-thd)2 (where pta is the anion of 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dione and F6-thd is the anion of 2,2-bis(trifluoromethyl)-6,6-dimethylheptane-3,5-dione) were determined. The solid-state structures of Cu(pta)2 and Cu(F6-thd)2 are square planar, while Cu(pta)2·EtOH is approximately square pyramidal with the EtOH ligand occupying the apical position. In each case, only one geometrical isomer (cis or trans) was observed in the crystals; arguments are presented that both isomers are present in bulk samples. Calculations of molecular volumes for structurally related Cu(II) complexes containing non-fluorinated versus fluorinated ancillary ligands show that fluorine substitution does not significantly affect packing efficiency in the solid-state; however, solvent coordination decreases packing efficiency slightly. [Cu(tdf)(py)(μ-C3F7CO2)]2 (where tdf is the anion of 1,1,1,2,2,3,3,7,7,8,8,9,9,9-tetradecafluorononane-4,6-dionate), a derived impurity from preparations of Cu(tdf)2, was isolated in low yield. The copper coordination geometries in the centrosymmetric structure are intermediate between square pyramidal and trigonal bipyramidal, with two unsymmetrically bridging μ,η1:η1-C3F7CO2 ligands.