Bis(1-methylpiperidinium) tetrachloridocuprate(II)

The structure of the title compound, (C6H14N)2[CuCl4], consists of two inequivalent 1-methylpiperidinium cations and a flattened tetrahedral [CuCl4]2− anion. Each organic cation exhibits a chair conformation with the methyl group in the equatorial position. They are segregated into alternating layers parallel to (100) and stacked along [100]. The first cation is arranged in parallel stacks in a herringbone pattern with rows of [CuCl4]2− anions fitting between the stacks and with a Cl− ion directed into the interior of the layer. The second organic cation forms distorted hcp layers that separate the other organic cation/[CuCl4]2− slabs. N—H⋯Cl hydrogen bonding between the cations and the anions consolidates the crystal packing.

The structure of the title compound, (C 6 H 14 N) 2 [CuCl 4 ], consists of two inequivalent 1-methylpiperidinium cations and a flattened tetrahedral [CuCl 4 ] 2À anion. Each organic cation exhibits a chair conformation with the methyl group in the equatorial position. They are segregated into alternating layers parallel to (100) and stacked along [100]. The first cation is arranged in parallel stacks in a herringbone pattern with rows of [CuCl 4 ] 2À anions fitting between the stacks and with a Cl À ion directed into the interior of the layer. The second organic cation forms distorted hcp layers that separate the other organic cation/[CuCl 4 ] 2À slabs. N-HÁ Á ÁCl hydrogen bonding between the cations and the anions consolidates the crystal packing.
The crystal structure of the title compound, (1-methylpiperidinium) 2 CuCl 4 , is comprised of a [CuCl 4 ] 2anion and two symmetrically inequivalent 1-methylpiperidinium cations. The [CuCl 4 ] 2anion displays the typical flattened tetrahedral geometry with an average trans Cl-Cu-Cl angle of 131.99° at 100 K, so no thermochromic phase transition is observed upon cooling to at least this temperature. Each 1-methylpiperidinium ion exhibits a chair conformation with the methyl group equatorial. Bond lengths and angles for the inorganic complex and organic cation conform to expected values (Ladd & Palmer, 1994). An ORTEP diagram of the asymmetric unit is presented in Figure 1. both sides of the cation #1 layer. Atom Cl1 is directed almost into the middle of the cation layer with the rows of complexes on either side of the layer offset from one another to provide spacing between the Cl1 atoms inside the layer. The closest intermolecular Cl···Cl contact distance is, thus, Cl1···Cl1 i = 5.891 (4) Å (i=-x, 1/2+y, 1/2-z) between Cl1 atoms from opposite rows of complexes. Cation #2 forms a layer at x = 0.5 to separate the cation #1/[CuCl 4 ] 2slabs at x = 0.0 and 1.0. In this layer the mean plane of the cation is closer to the layer plane with the normal forming an angle of 41.34° with respect to a.
The cations in this layer are arranged in a distorted hcp pattern with neighboring cations related by inversion, 2 1 rotation, or c-glide plane operations. A short, direct N11-H11···Cl1 hydrogen bond locks the Cl1 atoms into the interior of the cation #1 layer while a longer, less direct, and bifurcated N21-H21···Cl3 and ···Cl4 hydrogen bond links the cation #1/[CuCl 4 ] 2slabs to the cation #2 layer. A packing diagram for the structure viewed along [010] is presented in Figure 2.
Experimental 5 ml of 1-methylpiperidine were neutralized with concentrated HCl. This solution was mixed in a 2:1 molar ratio with copper(II) chloride dissolved in 6M HCl. Slow evaporation yielded yellow crystals of the title compound.

Refinement
All non-hydrogen atoms were refined with anisotropic displacement parameters. All hydrogen atoms were visible on electron density difference maps and freely refined to give N-H = 0.833-0.895 Å, methylene C-H = 0.913-1.03 Å. and methyl C-H = 0.945-0.97 Å. Fig. 1. ORTEP diagram of the asymmetric unit with atom labels. Displacement ellipsoids are drawn at the 50% level. The hydrogen bonding between N-H and Cl is indicated with dotted lines.