{S-Benzyl 3-[(6-methylpyridin-2-yl-κN)methylidene]dithiocarbazato-κ2 N 3,S}zinc

The title compound, [Zn(C15H14N3S2)2], contains two chemically equivalent Schiff base anions that are coordinated to the ZnII ion as tridentate N,N′,S-chelating ligands, creating a distorted octahedral environment [the smallest angle being 75.40 (6)° and the widest angle being 162.87 (6)°], with the two S atoms in cis positions. The dihedral angle between the mean planes of the two coordinating ligands is 85.65 (5)°. Weak C—H⋯S hydrogen bonds are also observed.


Crouse Comment
The title compound was preferentially formed during the attempt to complex the tridentate Schiff base with zinc(II) saccharinate. The saccharinate anion was eliminated in this process and two tridentate deprotonated Schiff base moieties coordinated instead with the zinc(II) cation as determined by its infrared spectrum, elemental analysis and crystal structure analysis.
The bidentate ligands coordinate through their pyridine nitrogen, azomethine nitrogen and thiolate sulfur atoms. The environment around the Zn II ion is distorted octahedral (  ) for which C-N bond lengths ranging from 1.273 to 1.320 Å and N-N bond lengths of 1.374 to 1.379 Å were reported. In the title complex, the two ligands are coordinated to the zinc(II) ion in a meridional configuration, where the two thiolate S atoms (S105 & S205) and the two pyridine N atoms (N115 & N215) are cis to each other and the two azomethine N atoms trans (N102 & N202) as in other bis-ligand metal complexes of related NNS tridentate ligands . The angle between the planes defined by Zn1-S205-C204-N203-N202-C201-C214-N215 (minimum deviation: 0.001 and maximum deviation: 0.157 Å), and Zn1-S105-C104-N103 -N102-C101-C114-N115 (minimum deviation: 0.011 and maximum deviation: 0.212 Å) is 85.65 (5)° showing that the planes are almost orthogonal to each other thus defining an distorted octahedral arrangement.
The angle between the planes defined by the benzyl ring (C208-C213) and the pyridyl ring (C214-C219) is 84.39 (12)°; however, the angle between the planes defined by the corresponding benzyl (C108-C113) and pyridyl rings (C114-C119) in the other Schiff base moiety is 75.06 (12)°. Both planes of the benzyl ring moieties of the Schiff bases are slightly displaced at an angle of 15.05 (10)°, but the distance between them precludes π-π interaction. The pyridyl rings on both Schiff bases are almost orthogonal to each other at an angle of 85.06 (11)°.  . Although none of the bond angles in the complex conformed to the ideal values expected of a regular octahedral geometry, this appears to be supplementary materials sup-2 Acta Cryst. (2012). E68, m534-m535 common in six-coordinate metal complexes of Schiff base ligands derived from dithiocarbazic acid and is attributed to the restricted bite angles of the planar NNS tridentate ligands. Tarafder et al., 2001). Weak C-H···S hydrogen bonds are observed and may consolidate the crystal packing (Fig. 2, Table 2).
Further background on the coordination chemistry of hydrazine carbodithioates is given by Ravoof et al. (2010).

Experimental
Zinc(II) saccharinate, [Zn(sac) 2 (H 2 O) 4 ] . 2H 2 O was synthesized using a similar procedure as for the synthesis of Cu(II) saccharinate (Ravoof et al. (2004)). The title compound was synthesized following the procedure by Ali et al. (1997). The Schiff base was dissolved in acetonitrile (50 ml) and mixed with an equimolar quantity of zinc(II) saccharinate in acetonitrile (25 ml). The resulting mixture was heated on a water bath until the volume reduced to ca 30 ml. On standing overnight in the fridge, the mixture yielded yellow crystals suitable for X-ray analysis.

Refinement
H atoms were all located in difference maps; those attached to carbon atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C-H in the range 0.93-0.98, N-H in the range 0.86-0.89 Å) and U iso (H)(in the range 1.2-1.5 times U eq of the parent atom), after which the positions were refined with riding constraints.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq