Bis(acetato-κ2 O,O′)(4,4′-dimethyl-2,2′-bipyridine-κ2 N,N′)zinc

The molecular structure of the title compound, [Zn(CH3COO)2(C12H12N2)], consists of isolated molecules bisected by a twofold rotation axis which goes through the ZnII cation and halves the organic base through the central C—C bond. The ZnII ion is coordinated by two N atoms from one molecule of the aromatic base and four O atoms from two bidentate, symmetry-related acetate anions, which coordinate asymmetrically [Zn—O distances of 2.058 (2) and 2.362 (3) Å], while the two Zn—N bond distances are equal as imposed by symmetry [2.079 (2) Å]. The crystal structure is supported by a number of weak C—H⋯O interactions and C—H⋯π contacts, with no π–π interactions present, mainly hindered by the substituent methyl groups and the relative molecular orientation. The result is a three-dimensional structure in which each molecule is linked to eight different neighbors.

The molecular structure of the title compound, [Zn(CH 3 COO) 2 (C 12 H 12 N 2 )], consists of isolated molecules bisected by a twofold rotation axis which goes through the Zn II cation and halves the organic base through the central C-C bond. The Zn II ion is coordinated by two N atoms from one molecule of the aromatic base and four O atoms from two bidentate, symmetry-related acetate anions, which coordinate asymmetrically [Zn-O distances of 2.058 (2) and 2.362 (3) Å ], while the two Zn-N bond distances are equal as imposed by symmetry [2.079 (2) Å ]. The crystal structure is supported by a number of weak C-HÁ Á ÁO interactions and C-HÁ Á Á contacts, with nointeractions present, mainly hindered by the substituent methyl groups and the relative molecular orientation. The result is a three-dimensional structure in which each molecule is linked to eight different neighbors.

D-HÁ
Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009  The Zn(II) ion is coordinated by two nitrogen atoms from one molecule of the aromatic base and four oxygen atoms from two bidentate, symmetry related acetate anions (Fig. 1). A very similar compound, with Cu(II) as its central cation has been reported in Barquín et al., 2010. Donor atoms in the title compound can not fit in any regular polyhedron, but the three chelate ligands fulfill the vector bond valence postulate of the Vectorial Bond-Valence Model (for details on the theory see Harvey et al., 2006). The three ligand vectors, as defined therein, lay in a planar trigonal geometry with a sum of angles equal to 359.6 (2)° (ideal: 360°) and a resultant vector modulus of 0.03 v.u. (Ideal: 0.00 v.u.).
The crystal structure is supported by a number of weak C-H···O interactions (Table 1, entries 1,2) and C-H···π contacts (Table 1, entries 3 to 5). In spite of the presence of aromatic rings there are no π-π interactions in the structure, mainly hindered by the substituent methyl groups and the relative molecular orientation.
The overall effect of these weak interactions, uniformly distributed in space, is the formation of a three-dimensional structure where each molecule is linked to eight different neighbors. Fig. 2 presents a highly simplified packing view projected down c, where only the C-H···O bonds have been drawn, for clarity, and where the complex linkage can be envisaged.

Experimental
The title compound was obtained as an unexpected byproduct in an attempt to synthesize a Zn tetrathionate complex with the aromatic base. Solid Zn acetate dihydrate, 4,4′-Dimethylbipyridine and potassium tetrathionate, 0.050 mmol of each, were added to 5 ml of dimethylformamide. On standing, colorless blocks of the title compound could be extracted for diffraction experiments.

Refinement
All H atoms were confirmed in a difference map, further idealized and allowed to ride, with displacement parameters taken as U iso (H) = X × U eq (C) [(C-H) methyl = 0.96 A°, X = 1.5; (C-H) arom = 0.93 A°, X = 1.2] (CH 3 groups were also free to rotate as well).

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.