catena-Poly[1-butyl-3-methylimidazolium [[dichlorido(methanol-κO)(propan-2-ol-κO)lanthanate(III)]-di-μ-chlorido]]

The title compound, (C8H15N2)[LaCl4(CH3OH)(C3H7OH)], consists of one 1-butyl-3-methylimidazolium (BMI+) cation and one hexahedral tetrachlorido(methanol)(propan-2-ol)lanthanate anion. The LaIII ion is eight-coordinate, with the LaIII ion bridged by a pair of Cl atoms, so forming chains propagating along the a-axis direction. Each LaIII ion is further coordinated by two isolated Cl atoms, one methanol and one propan-2-ol molecule. The coordinated methanol and propan-2-ol molecules of the anion form O—H⋯Cl hydrogen bonds with the Cl atoms of inversion-related anions. The BMI+ cation froms C—H⋯Cl hydrogen bonds with the Cl atoms of the anion. The anions are located in the C faces of the triclinic unit cell, with an inversion center in the middle of the La2Cl2 ring of the polymeric chain.

The title compound, in contrast to these examples, includes coordinated alcohol molecules and crystallized after mixing lanthanum chloride in 1-butyl-3-methylimidazolium chloride (BMICl) with a mixture of methanol and propan-2-ol ( Fig.   1). The bond lengths between La and the two non-bridging Cl atoms are 2.8232 (5) Å and 2.838 (1) Å, respectively. The La to bridging Cl distances are in the range of 2.8884 (6) Å and 3.0021 (8) Å. All the Cl atoms, except Cl4, exhibit short contacts to neighboring H atoms on the imidazolium rings or on alcohol molecules ranging from 2.653 Å to 2.909 Å.
In the crystal, H atoms in the imidazolium cations, such as H5A and H8A, form hydrogen bonds with chlorine Cl3 ( Fig.   2 and Table 1). The two H atoms in methanol (H2B) and propan-2-ol (H1D) form hydrogen bonds with atoms Cl2 and Cl1, respectively (Table 1). The [LaCl 4 (CH 3 OH)(i-C 3 H 9 OH)]anions are centered in the C faces of the triclinic unit cell, with an inversion center in the middle of La 2 Cl 2 ring, as shown in Fig. 3. The BMI + cation is on an inversion center, at position (1/2, 1/2, 1/2) in the unit cell.
Lanthanum chloride heptahydrate (0.708 g, 1.906 mmol) was mixed with BMICl (1.000 g, 5.725 mmol) in a small vial in a glove box. Equal amount of methanol and propan-2-ol were added carefully until the total dissolution of the mixture.
The vial was sealed and a colourless crystal appeared after cooling at 258 K for three weeks.

Refinement
The OH H atoms were located in a difference Fourier map and were freely refined. The C-bound H atoms were included in calculated positions and treated as riding atoms: C-H = 0.98, 0.97 and 0.96 Å for CH, CH 2 and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (parent C-atom), where k = 1.5 for CH 3 H atoms and k = 1.2 for all other H atoms. program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Figure 1
The molecular structure of the asymmetric unit of the title compound, with the numbering scheme and displacement ellipsoids drawn at the 50% probability level. H atoms have been omitted for clarify.

Figure 2
A view of the molecular structure of the title compound, with the dashed lines denoting the hydrogen bonding.

Figure 3
Crystal packing of the title compound viewed along the a axis. The [LaCl 4 (CH 3 OH)(i-C 3 H 9 OH)]anions are located about the inversion centers in the C faces of the triclinic unit cell.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq