Bis{μ-2-[bis(pyridin-2-yl)methylidene]hydrazinecarbothioamidato}bis[bromidocopper(II)] methanol disolvate

In the centrosymmetric binuclear title compound, [Cu2Br2(C12H10N5S)2]·2CH3OH, the CuII ion adopts a slightly distorted square-pyramidal coordination geometry. The hydrazine carbothioamide moiety and one of the pyridyl rings together adopt an almost planar arrangement, with a maximum deviation of 0.052 (4) Å for the C atom of the thiourea moiety. There are two molecules of methanol solvent per complex in the asymmetric unit. The nonconventional intramolecular C—H⋯Br hydrogen bonds make the molecule more rigid, whereas the conventional N—H⋯N and O—H⋯Br intermolecular hydrogen-bonding interactions, supported with N—H⋯π interactions, establish a supramolecular linkage among the molecules in the crystal. An intermolecular C—H⋯O interaction is also present.


Ambili Aravindakshan Comment
Hydrazinecarbothioamides have been reported to have a great variety of biological activity. In most cases, the metal complexes show more activity compared to their metal free ligands (Moubaraki et al., 1998). Coupled systems of transition metal complexes are of special interest in various fields of science. The main reason probably is due to the phenomenon of interaction between metal centers lying at the crossover point of two widely separated areas, namely the physics of the magnetic materials and the role of polynuclear reaction sites in biological processes (Khan et al., 1985).
The title complex [Cu 2 Br 2 (C 12 H 10 N 5 S) 2 ].2(CH 3 OH) has a dimeric structure. The coordination geometry around each copper(II) ion is square pyramidal with a slight distortion (τ = 0.03). The S1 atom of the hydrazinecarbothioamide moiety, the imino N3 atom, pyridine N1 atom and the Br1 atom comprise the basal plane while the apical position is occupied by the N2A atom of the symmetry related half of the dimer with a longest bond length to the metal atom of 2.529 (3) Å. The hydrazinecarbothioamide moiety of the free ligand shows E configuration about the both C12-N4 and C6-N3 (Ainscough et al., 1991;Philip et al., 2005) whereas in the Cu II complex the coordinated hydrazinecarbothioamide moiety has E configuration with respect to C6-N3 and Z configuration about C12-N4. The atoms coordinated to metal centre found to exist in E configuration having N3 and N1 atoms cis to each other with respect to C5-C6 bond. A unique part of the Cu II complex and the dimeric unit generated by the association of the free pyridyl nitrogen with the Cu atom are shown along with the atom-labeling in Fig. 1 and 2 respectively. The two aromatic rings are twisted with a dihedral angle of 88.1 (2)° between the rings. The hydrazinecarbothioamide moiety and one of the pyridine ring comprising atoms C1-C6 and N1 are almost planar with maximum deviation of 0.052 (4) Å for the atom C12 of the ring. C12-S1 bond distance (1.727 (4) Å) is very close to the single bond (Duan et al., 1996) which suggests that the ligand is coordinated in the thiolate form. This phenomenon could also be further confirmed by the coplanar nature of the NH 2 group of the coordinated ligand with sp 2 character wich facilitates an extended conjugation of the hydrazinecarbothioamide moiety with the aromatic rings.
The intramolecular non-classical hydrogen bonding interactions (C1-H1···Br1 and C11-H11···Br1), Table 1, makes the complex more rigid. The intermolecular hydrogen bonding interactions (classical and non-classical) establish a supramolecular 1-D network by linking the adjacent molecules through the methanol present in the lattice and N-H···N in parallel fashion as shown in Fig. 3. Packing of the molecules also involves many very weak π..π interactions with centroid-centroid distances in the range 3.707 (2)-5.778 (2). However, there is an N-H···π interaction between the hydrogen attached at N5 atom and one of the pyridyl ring comprising atoms from C7-C11 and N2 of another molecule and also a lone-pair···π interaction between the Br1 atom and two different chelate rings comprising atoms Cu1, S1, C12, N3, N4 and Cu1, N1, N3, C5, C6.

Experimental
The title complex was prepared by adapting a reported procedure (Philip et al., 2006) by refluxing a mixture of methanolic solutions of 2-[di(pyridin-2-yl)methylidene]hydrazinecarbothioamide (2.573 g, 10 mmol) and CuBr 2 (2.230 g, 10 mmol) for four hours. Black colored crystals were collected, washed with few drops of methanol and dried over P 4 O 10 in vacuo. Single crystals of the title complex suitable for X-ray analysis were obtained by slow evaporation from its methanolic solution.

Refinement
All H atoms on C were placed in calculated positions, guided by difference maps, with C-H bond distances 0.93-0.96 Å. H atoms were assigned as U iso =1.2 U eq (1.5 for Me). N5-H5A and N5-H5B H atoms were located from difference maps and restrained using DFIX instructions. The O1-H1A (0.82 Å) hydrogen of the methanol solvent is also placed in calculated position guided by difference maps.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 R-factors(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.