Bis{2-methoxy-6-[(4-methylphenyl)iminiomethyl]phenolato-κO 1}bis(thiocyanato-κN)zinc(II)

The Schiff base 2-[(4-methylphenyl)iminomethyl]-6-methoxyphenol (HL) forms a complex with a Zn2+ atom and two independent thiocyanate ions, [Zn(NCS)2(C15H15NO2)2], in which two phenolate O atoms the two independent Schiff base ligands are coordinated to thee Zn2+ atom. The protonated imine N atoms are involved in an intramolecular hydrogen bond with the phenoxide group. The Zn atom is also coordinated by two N atoms of two thiocyanate ligands. The coordination environment of the Zn atom is distorted-tetrahedral.

The Schiff base 2-[(4-methylphenyl)iminomethyl]-6-methoxyphenol (HL) forms a complex with a Zn 2+ atom and two independent thiocyanate ions, [Zn(NCS) 2 (C 15 H 15 NO 2 ) 2 ], in which two phenolate O atoms the two independent Schiff base ligands are coordinated to thee Zn 2+ atom. The protonated imine N atoms are involved in an intramolecular hydrogen bond with the phenoxide group. The Zn atom is also coordinated by two N atoms of two thiocyanate ligands. The coordination environment of the Zn atom is distortedtetrahedral.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: AT2651).

S1. Comment
The Schiff base ligands, the products of condensation of o-vanillin with amines, viewed several different kind of coordination modes with the centre metals (Sen et al., 2006). And, in early articles, researchers have reported three coordination modes of the Schiff base ligand, HL, derived from condensation of o-vanillin and p-toluidine. The first mode was that two O atoms of the Schiff base ligand were coordinated to the centre metal Yu et al., 2007;Zhao et al., 2007). The second one was that the ligands coordinate to centre metal through hydroxy O atom and the azomethine N atom (Iyere et al., 2004). The third one was that the centre metal only coordinated to the phenol O atoms . In fact, there was still another coordination mode of the Schiff base ligand. It was that all the three donor atoms were coordinated to centre metal, but without its X-ray crystallographic conformations (Maurya et al., 1994). Here we decribe the synthesis and crystal structure of a new zinc(II) complex ( Fig. 1), Zn(HL) 2 (NCS) 2 , involing the Schiff base HL, with the third coordination mode.
As shown in Fig. 1, the tridentate ligands coordinate to the Zn atom through two phenolic hydroxy O atoms and two isothiocyanate N atoms, forming a distorted tetrahedral geometry around the metal ion. The isothiocyanate group was not used as a bridged ligand, in the same way to the other Zn complexes with the ligand of isothiocyanate (Li, 2007;Zhang & Wang, 2007;Groeneveld et al., 1982).

S2. Experimental
The Schiff base was prepared by refluxing o-vanillin (10 mmol, 1.5251 g) and p-toluidine (10 mmol, 1.0700 g) in ethanol. The colour of the mixture changed from light yellow to orange. Then, for the preparation of the complex, the zinc sulfate heptahydrate (1 mmol, 0.2876 g) and potassium thiocyanate (0.1945 g, 2 mmol) in methanol (10 ml) was added to a methanol (30 ml) solution of the Schiff base ligand (2 mmol, 0.4826 g). Red crystals were obtained after 10 days.

S3. Refinement
The H atoms bonded to C and N atoms were positioned geometrically and refined using a riding model  The molecular structure of the title complex, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Crystal data
[Zn(NCS) 2 (C 15 H 15 NO 2 ) 2 ] M r = 664.13 Triclinic, P1 Hall symbol: -P 1 a = 9.3830 (2) Å b = 11.7146 (2) where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.30 e Å −3 Δρ min = −0.24 e Å −3 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.

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