Bis(acetylacetonato-κ2 O,O′)(pyridine-κN)zinc(II)

In the title compound, [Zn(C5H7O2)2(C5H5N)], the metal atom has square-pyramidal coordination geometry with the basal plane defined by the four O atoms of the chelating acetylacetonate ligands and with the axial position occupied by the pyridine N atom. The crystal packing is characterized by a C—H⋯O hydrogen-bonded ribbon structure approximately parallel to [10].


Comment
The title compound, [Zn(II)(C 5 H 7 O 2 ) 2 (C 5 H 5 N)], is a mixed-ligand metal-organic precursor for chemical vapour deposition, with the Zn atom being five coordinate. Metal-organic (MO) complexes have been widely employed as precursors for chemical vapour deposition (CVD) for the growth of various thin films. The title complex, (I), has been synthesized and discussed here. Several such MOCVD precursors have been previously synthesized and characterized (Urs et al., 2001;Neelgund et al., 2007;Brahma et al., 2008; and references therein).
The structure of (I) with adopted atom-numbering scheme is shown in Fig 1. The coordination geometry around Zn(II) is square-pyramidal with the basal plane defined by four O atoms from two chelating acetylacetonate (acac) ligands and the axial position occupied by N atom from pyridine ring. The five-membered ring formed by acetylacetonate and Zn atom is significantly non-planar.
The geometric parameters for observed short contacts are listed in Table 1. Crystal packing diagram is shown in Fig 2. The intermolecular C13-H13···O2 and C14-H14..O3 interactions, combined together generate C-H···O bonded ribbon structure that is approximately parallel to [101]-direction. A short C4-H4A···O4 contact associated with methyl group is also observed in the crystal.
Potassium hydroxide (KOH) solution (10 mmol, 0.56 g; 30% ethanol-water mixture) was added gradually to achieve a pH of 6-7. After stirring at room temperature for 1 hr, the mixture yielded a precipitate, which was filtered off and dried in a vacuum. The product was recrystallized from ethanol, giving a pure hydrate complex. To obtain the title complex from the hydrate, an ethanol solution of the hydrate was prepared and added in a (1:1) molar ratio to ethanol solutions of pyridine and stirred for 12 hr. Single crystals suitable for X-ray diffraction were grown by slow evaporation of the resultant solution in ethanol at low temperature.

Refinement
The refections (1,0,0) and (1 1 0) were omitted as they were affected by extinction or absorption. Hydrogen atoms were placed in their stereochemically expected positions and refined with the riding options. The distances with hydrogen atoms are: C(aromatic)-H = 0.93 Å, C(methyl)-H = 0.96 Å, and U iso = 1.2 U eq (parent) [1.5 U eq (parent) for methyl groups]. Fig. 1. A view of (I) with non-H atoms shown as probability ellipsoids at 30% levels. 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 Rfactors(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.