Crystal structure of catena-poly[hemi[1,3-bis(2,6-diisopropylphenyl)imidazolium] [[μ3-acetato-κ3 O:O:O′-tri-μ2-acetato-κ6 O:O′-dicopper(II)(Cu—Cu)]-μ-chlorido] dichloromethane sesquisolvate]

The title copper(II) complex, {(C27H37N2)[Cu4(CH3COO)8Cl]·3CH2Cl2}n, is a one-dimensional coordination polymer. The asymmetric unit is composed of a copper(II) tetraacetate paddle-wheel complex, a Cl− anion situated on a twofold rotation axis, half a 1,3-bis(2,6-diisopropylphenyl)imidazolium cation (the whole molecule being generated by twofold rotation symmetry) and one and a half of a dichloromethane solvent molecule (one being located about a twofold rotation axis). The central metal-organic framework comprises of a tetranuclear copper(II) acetate ‘paddle-wheel’ complex which arises from the dimerization of the copper(II) tetraacetate core comprising of three μ2-bidentate acetate and one μ3-tridentate acetate ligands per binuclear paddle-wheel complex. Both CuII atoms of the binuclear component adopt a distorted square-pyramidal coordination geometry (τ = 0.04), with a Cu⋯Cu separation of 2.6016 (2) Å. The apical coordination site of one CuII atom is occupied by an O atom of a neighbouring acetate bridge [Cu—O = 2.200 (2) Å], while that of the second CuII atom is occupied by a bridging chloride ligand [Cu⋯Cl = 2.4364 (4) Å]. The chloride bridge is slightly bent with respect to the Cu⋯Cu internuclear axis [Cu—Cl—Cu = 167.06 (6)°] and the tetranuclear units are located about a twofold rotation axis, forming the one-dimensional polymer that propagates along [101]. Charge neutrality is maintained by the inclusion of the 1,3-bis(2,6-diisopropylphenyl)imidazolium cation within the crystal lattice. In the crystal, the cation and dichloromethane solvent molecules are linked to the coordination polymer by various C—H⋯O and C—H⋯Cl hydrogen bonds. There are no other significant intermolecular interactions present.


S1. Synthesis and crystallization
To a solution of 1,3-bis(2,6-di-isopropylphenyl)imidazol-2-ylidine(0.22 g, 0.55 mmol) in dry toluene, at room temperature under nitrogen, was added anhydrous copper(II)acetate (0.09g, 0.5 mmol). The reaction mixture was stirred at room temperature for 12 h and the blue coloured precipitate, identified as 1,3-bis(2,6-di-isopropylphenyl)imidazolium copper(II) acetate, was removed by filtration. The filtrate was left to stand at 248 K in an enclosed vessel for 1 week and the precipitate was collected at the pump. Recrystallization of this solid (vapour diffusion from CH 2 Cl 2 /petrol) afforded an admixture of two crystalline products; one colourless (which proved to be 1,3-bis(2,6-di-isopropylphenyl)imidazolium chloride) and the other, small blue block-like crystals of the title compound. Physical separation of these two crystalline compounds and further recrystallization of the blue-coloured crystals from CH 2 Cl 2 /petrol afforded crystals suitable for Xray diffraction analysis.

S2. Refinement
The H atoms were included in calculated positions and refined as riding atoms: C-H = 0.95 -98 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms.

S3. Structural commentary
N-heterocyclic carbenes (NHCs) have been used as ancillary ligands for the preparation of transition metal based catalysts (Hopkinson et al., 2014), which are very useful in organic transformations (Faulkner et al., 2005;Bull et al., 2008). Binuclear Cu II carboxylate compounds are interesting because of their magnetic properties (Kato et al., 1964, Zhang et al., 2005Cotton et al., 2000) and electrochemical behaviour (Paschke et al., 2003). Herein, we report on the synthesis and crystal structure of the title copper(II) acetate coordination polymer. Here, acetate acts as a bridging bidentate chelating ligand, giving a typical paddle-wheel structure.
The asymmetric unit of the title compound, Fig. 1 In the crystal, the cation and dichloromethane solvent molecules are linked to the coordination polymer by various C-H···O and C-H···Cl hydrogen bonds (Table 1 and Fig. 3). There are no other significant intermolecular interactions present.
This structure is unique in that it possesses a halide bridge linking tetranuclear copper paddle-wheel units (for chloridebridged binuclear systems, see: Chen et al., 2015) and imidazolium salts interspersed within the crystal lattice (for imidazolium-functionalised acetate ligands, see: Suresh et al., 2015).

Figure 1
A view of the molecular structure of the asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view of the tetranuclear paddle-wheel unit of the title polymeric compound [symmetry codes: (a) -x, y,

Figure 3
A view along the b axis of the crystal packing of title compound. Colour code: coordination polymer black, organic cation red; CH 2 Cl 2 solvent molecules green and blue.

dicopper(II)(Cu-Cu)]-µ-chlorido] dichloromethane sesquisolvate]
Crystal data (C 27  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.70 e Å −3 Δρ min = −0.46 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.