Tetra-μ-acetato-κ8 O:O′-bis{[4-methyl-N-(4-methylphenyl)pyridin-2-amine-κN 1]copper(II)}

The title complex, [Cu2(CH3COO)4(C13H14N2)2], features a binuclear molecule, which lies about a crystallographic centre of inversion; the four acetate ions each bridge a pair of CuII atoms. The coordination of the metal atom is distorted octahedral within a donor set defined by four O atoms, the heterocyclic N atom and the second Cu atom. The pyridine ring is twisted with respect to the tolyl ring and forms a dihedral angle of 35.34 (9)°. A bifurcated N—H⋯(O,O) hydrogen bond is present, linking the amine group to two carboxylate O atoms derived from different acetate ions. In the crystal, C—H⋯π interactions link molecules into a supramolecular array in the bc plane.

The title complex, [Cu 2 (CH 3 COO) 4 (C 13 H 14 N 2 ) 2 ], features a binuclear molecule, which lies about a crystallographic centre of inversion; the four acetate ions each bridge a pair of Cu II atoms. The coordination of the metal atom is distorted octahedral within a donor set defined by four O atoms, the heterocyclic N atom and the second Cu atom. The pyridine ring is twisted with respect to the tolyl ring and forms a dihedral angle of 35.34 (9) . A bifurcated N-HÁ Á Á(O,O) hydrogen bond is present, linking the amine group to two carboxylate O atoms derived from different acetate ions. In the crystal, C-HÁ Á Á interactions link molecules into a supramolecular array in the bc plane.
The binuclear copper(II) complex, Fig. 1, is situated about a centre of inversion and features two Cu II atoms bridged by four acetate groups. The Cu-O bond distances lie in a narrow range, i.e. 1.9701 (13) to 1.9759 (13) Å, Table 1. The distorted octahedral coordination environment for the Cu atom is completed by a pyridine-N atom derived from the 4-methyl-N-ptolylpyridin-2-amine ligand and the second Cu atom [Cu···Cu i = 2.6480 (4) Å for i: 1 -x, 1 -y, 1 -z]. Two intramolecular N1-H···O interactions are noted in which the amine-H spans carboxylate-O atoms derived from different ligands, Table 2.
The dihedral angle formed between the pyridine and benzene rings of 35.34 (9) ° indicates the N-heterocycle is non-planar.
The major twist in the molecule occurs around the amine group as seen in the value of the C9-N2-C11-C12 torsion angle of -27.2 (3) °. In the crystal packing, contacts of the type C-H···π occur between methyl-H and pyridine rings, Table 2, and lead to the formation of supramolecular arrays in the bc plane, Fig. 2. Layers thus formed stack along the a axis, Fig. 3.

Experimental
Copper acetate (0.1 g, 0.5 mmol) dissolved in acetonitrile (15 ml) was added to a mixture of 4-methyl-N-p-tolylpyridin-2amine (0.2183 g, 1.1 mmol) and trimethyl orthoformate (10 ml). The mixture was heated at 323 K, the green precipitate was collected and recrystallization from its acetonitrile solution yielded green prisms of (I).