Bis(4-hydroxy-3-methoxybenzaldehyde 4-phenylthiosemicarbazonato-N 1,S)nickel(II)

In the title compound, [Ni(C15H14N3O2S)2], the NiII atom lies on a center of symmetry. The deprotonated ligands act as N,S-donors, forming five-membered metalla-rings. The NiII atom is four-coordinated in a slightly distorted square-planar environment. In the crystal, the discrete complex molecules are linked by weak N—H⋯O hydrogen bonds, generating chains along [110]. The chains are further connected via weak O—H⋯N interactions into a layered network extending parallel to (001).

In the title compound, [Ni(C 15 H 14 N 3 O 2 S) 2 ], the Ni II atom lies on a center of symmetry. The deprotonated ligands act as N,Sdonors, forming five-membered metalla-rings. The Ni II atom is four-coordinated in a slightly distorted square-planar environment. In the crystal, the discrete complex molecules are linked by weak N-HÁ Á ÁO hydrogen bonds, generating chains along [110]. The chains are further connected via weak O-HÁ Á ÁN interactions into a layered network extending parallel to (001).

Related literature
For the crystal structure of the ligand, see: Oliveira et al. (2013). For the crystal structure of a similar complex, see: Akinchan & Abram (2000). For the coordination chemistry of thiosemicarbazone compounds, see: Lobana et al. (2009).

Synthesis and crystallization
Starting materials were commercially available and were used without further purification. 4-Hydroxy-3-methoxybenzaldehyde 4-phenylthiosemicarbazone was dissolved in THF (2 mmol/40 ml) with stirring maintained for 30 min, while the solution turns yellow. A solution of nickel acetate tetrahydrate (1 mmol/40 ml) in THF was added under continuous stirring. After 3 h the solvent was removed and the solid redissolved in methanol. Crystals suitable for X-ray diffraction were obtained by the slow evaporation of the solvent.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. All non-hydrogen atoms were refined anisotropic. Most C-H atoms were positioned with idealized geometry (methyl and O-H atoms allowed to rotate but no to tip) and were refined isotropic with U iso (H) = 1.2 U eq (C, N) (1.5 for methyl and O-H atoms) using a riding model. The H atoms attached to N1 and C8 were refined with varying coordinates and varying isotropic displacement parameters.

Results and discussion
Thiosemicarbazone derivatives are N,S-donors with a wide range of coordination modes (Lobana et al., 2009). As part of our interest on the coordination chemistry of thiosemicarbazone ligands, we report herein the synthesis and the crystal structure of a new Ni II complex with the 4-hydroxy-3-methoxybenzaldehyde 4-phenylthiosemicarbazone.
The Ni II atoms are four-coordinated in a slightly distorted planar environment by two bidentate deprotonated ligands forming discrete complexes. The asymmetric unit consists of one Ni II cation that is located on a centre of inversion and one anionic ligand that occupies a general position (Fig. 1). During complex formation signficant structural changes of the N-N-C-S fragment are observed. For the uncoordinated 4-hydroxy-3-methoxybenzaldehyde 4-phenylthiosemicarbazone ligand the N-N, N-C and C-S bond distances amount to 1.3792 (17) Å, 1.3404 (19) Å and 1.6962 (15) Å.
The distances indicate the double bond character for the N-N and C-S bonds, and the single bond character for the N-C bond (Oliveira et al., 2013).
For the title compound, the acidic hydrogen of the hydrazine fragment is lost and the negative charge is delocalized over the N-N-C-S fragment. Therefore, for the coordinated ligand the N-N, N-C and C-S bond distances amount to 1.407 (4)  Abram, 2000). The N-C bond distances indicate a considerable double bond character, while the N-N and C-S bond distances are consistent with an increased single bond character.
The ligands are coordinated to the metal as N,S-donors (Fig. 1), building a slightly distorted planar environment, typical for low spin, strong field and d 8 electronic configuration with Jahn-Teller effect. The maximal deviation from the least squares plane through all non-hydrogen atoms for the Ni1/C7/N2/N3/S1 ring amounts to 0.2373 (15) Å for N3.
Additionally, the dihedral angle between the two aromatic rings of the ligands is 42.270 (68)°, showing that they are not planar (Fig. 1).
The molecules are linked into chains along the a-b-direction forming a H-bonded coordination polymer (Fig. 2). The crystal packing is stabilized by intermolecular N-H···O and O-H···N hydrogen bonding (Table 1).

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 40% probability level.
Symmetry code for the generation of equivalent atoms: (i)-x + 1,-y + 2,-z.  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.