Bis{S-benzyl 3-[(phenyl)(pyridin-2-yl)methylidene]dithiocarbazato}zinc acetonitrile monosolvate

In the title compound, [Zn(C20H16N3S2)2]·CH3CN, two different Schiff base moieties coordinate to the central ZnII ion as tridentate N,N′,S-chelating ligands, creating a distorted octahedral environment [the smallest angle being 73.24 (6)° and the widest angle being 155.73 (7)°], with the two S atoms in cis positions. The dihedral angle between the mean planes of the two coordinating ligands is 83.65 (5)°. The crystal packing is consolidated by weak C—H⋯N hydrogen-bonding interactions.

In the title compound, [Zn(C 20 H 16 N 3 S 2 ) 2 ]ÁCH 3 CN, two different Schiff base moieties coordinate to the central Zn II ion as tridentate N,N 0 ,S-chelating ligands, creating a distorted octahedral environment [the smallest angle being 73.24 (6) and the widest angle being 155.73 (7) ], with the two S atoms in cis positions. The dihedral angle between the mean planes of the two coordinating ligands is 83.65 (5) . The crystal packing is consolidated by weak C-HÁ Á ÁN hydrogen-bonding interactions.

Experimental
Crystal data [Zn(C 20    eliminating the saccharinate anion and instead coordinating one metal ion with two tridentate deprotonated Schiff base moieties. Background on the coordination chemistry of hydrazine carbodithioates is given by Ravoof et al. (2010).
Similar Cu(II) complexes have been previously synthesized by Hossain et al. (1996).
There is one independent molecule in the asymmetric unit which contains the Zn II ion coordinated to two tridentate Schiff bases via the pyridyl nitrogen (N115, N215), azomethine nitrogen (N102, N202) and thiolate sulfur (S105, S205) atoms ( Fig. 1). A solvent acetonitrile molecule in also present in the lattice. The coordination of the metal ion is distorted octahedral with equatorial angles ranging from 73.24 (6)° to 120.54 (5)°. The angle between the planes containing the atoms of the tridentate chelating rings is 83.65 (5). The planes containing the benzyl rings attached to the sulfur atom on both Schiff bases are almost parallel to each other with an angle of 16.41 (10). Similarly, the benzyl rings on the ketone moiety of the two Schiff bases are also almost parallel with an angle of 11.69 (9)°. However, the pyridine rings of the ketone moiety of the two Schiff bases are at an angle of 66.52 (10)°.
The packing diagram viewed along the b axis shows an arrangement where the benzyl ring of the ketone moiety of Schiff base 2 are arranged in such a way that it is facing each other between molecules. The crystal packing is consolidated by weak C-H···N hydrogen bonding interactions (Table 2).

Experimental
Zinc saccharinate, [Zn(sac) 2 (H 2 O) 4 ]. 2H 2 O was prepared according to the method outlined in Ravoof et al. (2004). The 2benzoylpyridine Schiff base of S-benzyldithiocarbazate was prepared following the method by Hossain et al. (1996). The Schiff base was dissolved in acetonitrile (50 ml) and mixed with an equimolar quantity of zinc saccharinate in acetonitrile (25 ml). The resulting mixture was heated on a water bath until the volume reduced to about 30 ml. On standing overnight, the mixture yielded orange crystals which were filtered off, washed with acetonitrile and dried in a desiccator over anhydrous silica gel, overnight. Crystals of the zinc complex suitable for X-ray diffraction analysis were obtained by recrystallisation from a mixture of acetonitrile, THF and chloroform. Slow evaporation over 3 weeks yielded crystals suitable for diffraction experiments.

Refinement
H atoms were all located in difference maps, but those attached to C 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   Molecular packing diagram of the title compound viewed along the b axis. Hydrogen atoms are omitted for clarity.