Tetra-μ-acetato-κ8 O:O′-bis[(N-ethylpyrimidin-2-amine)copper(II)](Cu—Cu)

In the centrosymmetric title molecule, [Cu2(CH3COO)4(C6H9N3)2], each of the four acetate groups bridges a pair of CuII atoms [Cu—Cu = 2.6540 (4) Å]. The distorted octahedral geometry of the metal atom is completed by an N-donor atom of the N-ethylpyrimidin-2-amine ligand: an intramolecular N—H⋯O hydrogen links its N—H group to an acetate carboxylate O atom. In the crystal, C—H⋯O interactions link the molecules into a supramolecular chain along the b axis.

In the centrosymmetric title molecule, [Cu 2 (CH 3 COO) 4 -(C 6 H 9 N 3 ) 2 ], each of the four acetate groups bridges a pair of Cu II atoms [Cu-Cu = 2.6540 (4) Å ]. The distorted octahedral geometry of the metal atom is completed by an N-donor atom of the N-ethylpyrimidin-2-amine ligand: an intramolecular N-HÁ Á ÁO hydrogen links its N-H group to an acetate carboxylate O atom. In the crystal, C-HÁ Á ÁO interactions link the molecules into a supramolecular chain along the b axis.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB5613).
The binuclear copper(II) complex, Fig. 1, is situated about a centre of inversion and features two Cu atoms bridged by four acetate groups. The Cu-O bond distances lie in a narrow range of 1.953 (1) to 1.978 (2) Å, Table 1. The coordination environment for each Cu atom is completed by an N atom derived from the N-ethylpyrimidin-2-amine ligand and the second Cu atom [Cu···Cu i = 2.6540 (4) Å for i: 1 -x, 1 -y, 1 -z]. The resulting hexa-coordinated geometry is based on an octahedron.
An intramolecular N3-H···O1 interaction contributes to the stability of the dinuclear molecule, Table 2. The N-heterocycle is effectively planar as seen in the C8-N3-C9-C10 torsion angle of -166.6 (2) °. In the crystal packing, the presence of C-H···O interactions connect dinuclear molecules into supramolecular chains along the b axis, Fig. 2 and Table 2.

Experimental
Copper acetate (0.1 g, 0.5 mmol) was dissolved in acetonitrile (15 ml) and mixed with a solution of N-(pyrimidin-2yl)ethylamine (0.2 g, 1.1 mmol) dissolved in acetonitrile (15 ml). The blue precipitate that formed was recrystallized from acetonitrile to yield blue prisms of (I).

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.93 to 0.97 Å) and were included in the refinement in the riding model approximation, with U iso (H) set to 1.2 to 1.5U equiv (C). The N-bound H-atom was located in a difference Fourier map and was refined with a distance restraint of N-H 0.86±0.01 Å; the U iso value was freely refined Figures   Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 35% probability level. Primed atoms are related by the symmetry operation i: 1 -x, 1 -y, 1 -z.