(Pentafluoropropionato-κO)tetrakis(trimethylphosphine oxide-κO)copper(II) pentafluoropropionate

The title compound, [Cu(C3F5O2)(C3H9OP)4](C3F5O2), comprises a cationic CuII complex and a disordered pentafluoropropionate counter-ion. The metal atom has a distorted square-pyramidal coordination environment formed by four O atoms originating from trimethylphosphine oxide molecules and the remaining one belonging to the monodentate pentafluoropropionate anion, which is situated in the basal plane of the pyramid. The molecules are held together in the crystal by a net of weak C—H⋯O and C—H⋯F hydrogen bonds. The counter anion is disordered over two sets of sites in a 0.629 (5):0.371 (5) ratio.

The title compound, [Cu(C 3 F 5 O 2 )(C 3 H 9 OP) 4 ](C 3 F 5 O 2 ), comprises a cationic Cu II complex and a disordered pentafluoropropionate counter-ion. The metal atom has a distorted square-pyramidal coordination environment formed by four O atoms originating from trimethylphosphine oxide molecules and the remaining one belonging to the monodentate pentafluoropropionate anion, which is situated in the basal plane of the pyramid. The molecules are held together in the crystal by a net of weak C-HÁ Á ÁO and C-HÁ Á ÁF hydrogen bonds. The counter anion is disordered over two sets of sites in a 0.629 (5):0.371 (5) ratio.
The title compound has one monocationic Cu II complex and one pentafluoropropionate counter-ion present in the asymmetric unit (Fig.1). The geometry around the Cu II ion is a distorted square-pyramid formed by four O atoms originating from trimethylphosphine oxide molecules and one from the monodentate pentafluoropropionate ion, which is located in the base plane of the pyramid. The corresponding bond lengths and angles are presented in Table 1. The geometrical features of the ligands are in good agreement with reported values. The counter-ion is disordered over two positions with refined site occupancies of 0.629 (5):0.371 (5). There are weak intramolecular C-H···O interactions between the methyl groups of three distinct trimethylphosphine oxides (P1, P2 and P4) involving the atoms C3, C5 and C10, that act as donors, and O5 (from the counter-ion), as well as O4 and O3 (from the oxide ligands), that act as acceptors, respectively ( Table 2). The C9 methyl group from P3 however, interacts with the counter-ion by weak C9-H9A···F7A hydrogen bonding with a C···F distance of 3.322 (6) Å, and a C-H-F angle of 150°. The packing is further stabilized by numerous weak intermolecular C-H···O and C-H···F interactions.
Experimental (C 2 F 5 COO) 2 Cu (1.04 mmol) was placed in a Schlenk tube, dissolved in 25 ml of freshly distilled acetonitrile, and copper powder (5 mmol) was added. The obtained suspension was stirred until the solution was pale yellow. Then PMe 3 (2.1 ml of a 1 M THF solution) was added and the reaction mixture was stirred for 18 h at ambient temperature, and filtered. The solvent was evaporated under reduced pressure, yielding [Cu 2 (PMe 3 ) 2 (µ-C 2 F 5 CO 2 ) 2 ] as a pale yellow, viscous oil. Crystals of the title Cu II complex suitable for X-ray studies were obtained after a few months, presumably upon slow oxidation by diffused air.

Refinement
All H atoms were positioned geometrically, with C-H = 0.98 and constrained to ride on their parent atoms with U iso (H) = 1.5U eq (C). The counter-ion was found to be disordered and modeled in two positions. Refinement included bond lengths restraints applied to the O8B-O7B, C17B-O7B and C17B-O8B as well as to ADPs of 'A' part.
Figures Fig. 1. The molecular structure of the title compound, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level; the other orientation of the disordered counter-ion has been omitted for clarity.