Crystal structure of bis{S-hexyl 3-[4-(dimethylamino)benzylidene]dithiocarbazato-κ2 N 3,S}copper(II)

In the title complex, the CuII atom exhibits a square-planar coordination geometry and is located on a crystallographic inversion centre, leading to a trans configuration of the N,S-chelating ligands.


Chemical context
Bidentate Schiff bases of S-methyl or S-benzyl dithiocarbazates and their metal complexes have received considerable attention for their possible bioactivities (Chan et al., 2008;How et al., 2008;Ali et al., 2002;Chew et al., 2004;Crouse et al., 2004). As part of our ongoing structural studies on these S-containing Schiff bases Begum et al., 2015), we report herein the structure of a copper(II) complex with the (dimethylaminobenzylidene)dithiocarbazate ligand.

Structural commentary
In the crystal, the bis-chelated Cu II complex resides on a crystallographic inversion centre and the two chelating Schiff bases, in their deprotonated imino thiolate form, coordinate the metal centre via the azomethine nitrogen N1 and thiolate sulfur S1 atoms in a trans-planar configuration (Fig. 1). The Cu1-S and Cu1-N coordination bond lengths are of 2.2557 (6) and 2.0060 (14) Å , respectively, with an S1-Cu- ISSN 2056-9890 N1 chelating angle of 84.41 (5) . It is worth of note that copper(II) complexes with similar dithiocarbazate ligands assume a distorted tetrahedral configuration as well Manan, et al., 2011). In these derivatives the coordination distances are close comparable to those here reported. On the other hand the present Cu-S and Cu-N bond lengths are slightly longer with respect to those measured in the centrosymmetric complex with ligand bearing a benzyl group at the S atom [Cu-S = 2.165 (1), Cu-N = 1.929 (4) Å ; Tian, et al., 1998).

Supramolecular features
The crystal packing shows almost planar complexes piled along axis b with a stacking distance of 5.23947 (10) Å . (Fig. 2)

Synthesis and crystallization
A solution of Cu(CH 3 COO) 2 ÁH 2 O (0.10 g, 0.5 mmol, 15 mL methanol) was added to a solution of the N,N 0 -dimethyl-aminobenzaldehyde Schiff base of S-hexyldithiocarbazate (0.32 g, 1.0 mmol, 10 mL methanol). The resulting mixture was stirred at room temperature for seven hours. A dark reddish brown precipitate was formed, filtered off, washed with methanol and dried in vacuo over anhydrous CaCl 2 . Dark reddish brown single crystals of the compound, suitable for X-ray diffraction, were obtained by slow evaporation from a mixture of dichloromethane and acetonitrile (2:1), m.p. 437 K.

Database survey
The structure of the corresponding copper(II) complex with N,N 0 -dimethylaminophenyl but having a benzyl group replacing the hexyl alkyl chain at S has been reported (Tian, et al., 1998).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. All H atoms were fixed geometrically (C-H = 0.95-0.99 Å ) and refined as riding, with U iso (H) = 1.2 U eq (C). Drawing (ellipsoid probability at 50%) of the CuL 2 complex with atom labels of the crystallographic independent unit (primed atoms at Àx + 2, Ày, Àz + 1).

Bis{S-hexyl 3-[4-(dimethylamino)benzylidene]dithiocarbazato-κ 2 N 3 ,S}copper(II)
Crystal data [Cu(C 16  Special details Geometry. ENTER SPECIAL DETAILS OF THE MOLECULAR GEOMETRY Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).