Poly[[tris(μ2-acetato-κ2 O:O′)(4-chlorobenzene-1,2-diamine-κN)(μ3-hydroxido)dizinc] ethanol monosolvate]

The title compound, {[Zn2(CH3CO2)3(OH)(C6H7ClN2)]·C2H5OH}n, has alternating octahedrally and tetrahedrally coordinated Zn2+ ions. The octahedral coordination sphere is composed of one N atom of the monodentate diaminochlorobenzene ligand, three acetate O atoms and two bridging hydroxide ligands. The tetrahedral coordination sphere consists of three acetate O atoms and the hydroxide ligand. The zinc ions are bridged by acetate and hydroxide ligands. The result is a laddered-chain structure parallel to [100] with ethanol solvent molecules occupying the space between the chains. The diamine ligand chlorine substitutent is disordered over two equally populated positions as a result of a crystallographically imposed inversion center between adjacent ligands. The ethanol solvent molecule exhibits disorder with the two components having refined occupancies of 0.696 (11) and 0.304 (11). O—H⋯O hydrogen bonds form between the hydroxide ligand and the ethanol solvent molecule. N—H⋯O and N—H⋯N hydrogen bonding between the uncoordinated amine group and the acetate ligands and the coordinated amine group are also observed.

The title compound, {[Zn 2 (CH 3 CO 2 ) 3 (OH)(C 6 H 7 ClN 2 )]Á-C 2 H 5 OH} n , has alternating octahedrally and tetrahedrally coordinated Zn 2+ ions. The octahedral coordination sphere is composed of one N atom of the monodentate diaminochlorobenzene ligand, three acetate O atoms and two bridging hydroxide ligands. The tetrahedral coordination sphere consists of three acetate O atoms and the hydroxide ligand. The zinc ions are bridged by acetate and hydroxide ligands. The result is a laddered-chain structure parallel to [100] with ethanol solvent molecules occupying the space between the chains. The diamine ligand chlorine substitutent is disordered over two equally populated positions as a result of a crystallographically imposed inversion center between adjacent ligands. The ethanol solvent molecule exhibits disorder with the two components having refined occupancies of 0.696 (11) and 0.304 (11). O-HÁ Á ÁO hydrogen bonds form between the hydroxide ligand and the ethanol solvent molecule. N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonding between the uncoordinated amine group and the acetate ligands and the coordinated amine group are also observed.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Because of their large internal surface areas and uniformly structured cavities which small molecules may occupy, metalorganic frameworks (MOFs) are of inherent interest in areas such as gas storage, catalysis, chemical sensors and molecular separation (Dey et al., 2014;Kreno et al., 2012;Farha & Hupp, 2010). The title compound is an example of a one-dimensional MOF in which space between polymeric chains provides room for incorporation of small, noncovalently bonded molecules. To our knowledge, this compound is the first example of a mixed acetato and monodentetate diamine coordinated zinc compound with a one-dimensional chain structure.
The title compound exhibits a laddered-chain structure. The atom-labeling scheme for the basic repeating unit is shown  Space between the chains is occupied by approximately two-fold rotationally-disordered ethanol molecules (see figure   3). Calculations using PLATON (Spek, 2009) (3) and 2.03 (4) Å for the major and minor components of the disordered ethanol.
In addition to the hydrogen bonds involving the solvate molecule, N-H···O and N-H···N hydrogen bonding involving the uncoordinated amine group as the donor moiety and acetate ligands and the coordinated amine group as the acceptors are observed. Pertinent metrics involving these interactions are found in Table 1.
The benzene ring of the diamine ligand is planar with the atom having the largest deviation being C2, which sits 0.011 (6) Å above the plane. The two amine nitrogen atoms deviate only slightly from the benzene ring plane with N1 being 0.048 (13) Å and N2 being 0.005 (0.012) Å above the plane.
The identical synthetic strategy employed using symmetrically substituted diamines results in a molecular species (c.f., Geiger, 2012). We have prepared an analogue of the title compound employing 1,2-diamino-4-cyanobenzene as the diamine. The structure of the compound is virtually the same (although not isomorphous), but all attempts to obtain a structure of publishable quality have failed. Whether or not the use of unsymmetrically-substituted 1,2-diaminobenzene is a prerequisite for the formation of a Zn MOF of this structureal type is yet to be determined. We are exploring other unsymmetrically substuted diamines in hopes of better understanding this phenomenon.

Experimental
The title compound was prepared by the reaction of two equivalents of 1,2-diamino-4-chlorobenzene with zinc acetate dihydrate in refluxing ethanol. Slow evaporation of the solvent resulted in the formation of layers of extremely thin, colorless plates. The samples used for analysis were cut from carefully peeled apart layers.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. As a result of the unsymmetrical nature of the 1,2-diamino-4-chlorobenzene ligand, the chloro substitutent was refined with a site occupancy factor of onehalf in each of two positions. The ethanol solvate is rotationally disordered over two positions. It was refined with the C -C and C-O distances restrained to 1.54 and 1.43 Å, respectively, using DFIX. The anisotropic displacement parameters of the minor component were constrained to the same refined values of the major component using EADP.
The refined occupancies of the major and minor contributors are 0.696 (11) and 0.304 (11), respectively. The maximum shift/error for the disorder occupancies and the coordinates and anisotropic displacement parameters of the ethanol solvate were 0.000. In the final set of refinement cycles, the occupancies of the major and minor components were fixed at 0.7 and 0.3, respectively. The maximum residual electron density (0.98 e 3 ) and the deepest hole (-1.05 e 3 ) are located 1.10 Å and 0.86 Å, respectively, from the Zn2 atom.
All hydrogen atoms except those associated with the disordered ethanol solvent molecule were observed in difference fourier maps. The carbon-bonded hydrogen atoms were refined using a riding model with a C-H distance of 0.98 Å for the methyl carbon atoms and 0.95 Å for the phenyl carbon atoms. The atomic coordinates for the nitrogen-and oxygenbonded hydrogen atoms were refined using the restraints DFIX = 0.84 Å for O-H and 0.91 Å for N-H.
The methyl C-H and the O-H hydrogen atom isotropic displacement parameters were set using the approximation U iso = 1.5U eq . All other hydrogen atom isotropic displacement parameters were set using the approximation U iso = 1.2U eq .   Packing diagram emphasizing the location of the ethanol solvent molecules with respect to the polymer chain. Only one of the partially occupied Cl sites is represented and only the major contributor to the disorder model is represented.

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.