Di-μ-chlorido-bis[(1,10-phenanthroline-κ2 N,N′)(trichloroacetato-κO)copper(II)]

The title compound, [Cu2(C2Cl3O2)2Cl2(C12H8N2)2], features a centrosymmetric binuclear complex. The coordination geometry around the CuII atom is square-pyramidal, comprising two N atoms from a symmetrically chelating 1,10-phenanthroline ligand, one O atom from a trichloroacetate ligand and two Cl− anions. In addition, there is a weak intramolecular Cu⋯O interaction of 2.9403 (14) Å involving the carbonyl O atom of the trichloroacetate ligand. The central Cu2Cl2 core takes the form of a rhombus, owing to the disparate Cu—Cl bond lengths. Molecules are connected in the crystal structure by C—H⋯Cl and C—H⋯O interactions.

The title compound, [Cu 2 (C 2 Cl 3 O 2 ) 2 Cl 2 (C 12 H 8 N 2 ) 2 ], features a centrosymmetric binuclear complex. The coordination geometry around the Cu II atom is square-pyramidal, comprising two N atoms from a symmetrically chelating 1,10-phenanthroline ligand, one O atom from a trichloroacetate ligand and two Cl À anions. In addition, there is a weak intramolecular CuÁ Á ÁO interaction of 2.9403 (14) Å involving the carbonyl O atom of the trichloroacetate ligand. The central Cu 2 Cl 2 core takes the form of a rhombus, owing to the disparate Cu-Cl bond lengths. Molecules are connected in the crystal structure by C-HÁ Á ÁCl and C-HÁ Á ÁO interactions.
The Cu II atom in binuclear (I), Fig. 1, is coordinated by two Cl atoms, which form dissimilar Cu-Cl bond lengths, two N atoms from a symmetrically chelating 1,10-phenanthroline ligand, and one O atom from a trichloroacetate ligand, Table 1. The structure of (I) is centrosymmetric and the central Cu 2 O 2 has the form of a rhombus. The carbonyl-O2 atom forms a weak intramolecular Cu···O contact of 2.9403 (14) Å. The asymmetric mode of coordination of the carboxylate is reflected in the disparate C-O bond distances with the longer C13-O1 distance [1.270 (2) Å] being associated with the shorter Cu-O1 interaction, and the short C13-O2 distance [1.220 (2) Å] associated with the weaker Cu-O2 contact.
The resultant Cl 2 N 2 O donor set defines a square pyramid. This assignment is based on the value calculated for τ of 0.07 for the Cu atom, which compares to the τ values of 0.0 and 1.0 for ideal square pyramidal and trigonal bipyramidal geometries, respectively (Spek, 2009;Addison et al., 1984). In this description, the less tightly bound Cl i atom defines the axial site (i: 1 -x, 1 -y, 1 -z).
The observed coordination geometry in (I) resembles closely those found in the analogous structures with the carboxylate ligands being 2-anilinobenzoate (Jiang et al., 2007) and p-tolylthioacetate (Zheng et al., 2008).
In the crystal packing, molecules assembles into layers in the ac plane and are connected into the three dimensional architecture by C-H···Cl and C-H···O interactions, Fig. 2 and Table 2.
Experimental 1,10-Phenanthroline (1 mmol) was placed in one arm of a branched tube (Harrowfield et al., 1996) and a mixture of copper(II) chloride dihydrate (1 mmol) and trichloroacetic acid (1 mmol) in the other. Ethanol was then added to fill both arms, the tube was sealed and the ligand-containing arm immersed in a bath at 333 K, while the other was left at ambient temperature. After 3 d, crystals had deposited in the arm held at ambient temperature. They were filtered off, washed with acetone and ether, and air dried. Yield: 85%. M.p. = 530 K.

Refinement
H-atoms were placed in calculated positions [C-H 0.95 Å, U iso (H) = 1.2U eq (C)] and were included in the refinement in the riding model approximation.

Figure 2
A view in projection down the a axis of the unit-cell contents for (I). The C-H···Cl and C-H···O interactions are shown as orange and blue dashed lines, respectively.