{3,3′,5,5′-Tetramethoxy-2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato}copper(II)

In the title square-planar copper complex, [Cu(C20H22N2O6)], the Cu—N and Cu—O bond lengths are significantly longer than those of its isostructural nickel analog. The title structure is related to that of the corresponding monohydrate. There are significant differences in the conformations of the two complexes. While the monohydrate is mainly planar, in the title compound there is a slight twist in the two benzene rings at each end of the complex [dihedral angle = 13.14 (6)°]. All the atoms of the methoxy substitutents are in the plane of the ring to which they are attached (r.m.s. deviation = 0.0079 Å) except for one of the methoxy C atoms, which deviates slightly [0.309 (4) Å]. In the crystal, weak C—H⋯O intermolecular interactions link the molecules.

In the title square-planar copper complex, [Cu(C 20 H 22 N 2 O 6 )], the Cu-N and Cu-O bond lengths are significantly longer than those of its isostructural nickel analog. The title structure is related to that of the corresponding monohydrate. There are significant differences in the conformations of the two complexes. While the monohydrate is mainly planar, in the title compound there is a slight twist in the two benzene rings at each end of the complex [dihedral angle = 13.14 (6) ]. All the atoms of the methoxy substitutents are in the plane of the ring to which they are attached (r.m.s. deviation = 0.0079 Å ) except for one of the methoxy C atoms, which deviates slightly [0.309 (4) Å ]. In the crystal, weak C-HÁ Á ÁO intermolecular interactions link the molecules.

Experimental
Crystal data [Cu(C 20   conformations of the structures. While the monohydrate is mainly planar, in the title compound there is a slight twist in the two phenyl rings at each end of the complex (dihedral angle of 13.14 (6)°). All the atoms of the methoxy substitutents are in the plane of the ring to which they are attached except C7 which deviates slightly [0.309 (4) °]. There are weak C-H···O intermolecular interactions which link the molecules.

Experimental
The ligand synthesis was accomplished by adding a solution of (2 g, 33.3 mmol) ethylenediamine in 25 ml of methanol to a solution of (12.13 g, 66.6 mmol) 4,6-dimethoxysalicylaldehyde in 40 ml of methanol. The mixture was refluxed overnight while stirring. Then the mixture was evaporated under reduced pressure to afford yellow solids. The complex was synthesized by mixing a solution of (0.38 g, 1 mmol) N,N-ethylenebis(4,6-dimethoxysalicylaldimine) in 5 ml of CH 2 Cl 2 with a solution of (0.29 g, 1 mmol) copper acetate in 5 ml methanol. The solution mixture was stirred for 1 hour then filtered and layered with diethyl ether for crystallization. Single crystals of X-ray quality were obtained.

Refinement
H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with a C-H distances of 0.95 and 0.99 Å U iso (H) = 1.2U eq (C) and 0.98 Å for CH 3 [U iso (H) = 1.5U eq (C)].  Crystal data [Cu(C 20  Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.