(1,4,7,10-Tetraoxacyclododecane)(trideuteroacetonitrile)lithium perchlorate

In the title compound, [Li(C8H16O4)(CD3CN)]ClO4, the Li atom is pentacoordinate. The O atoms of the 12-crown-4 ether form the basal plane, whereas the N atom of the trideuteroacetonitrile occupies the apical position. The Li+ atom is displaced by 0.794 (6) Å toward the apical position from the plane formed by the O atoms because the Li+ atom is too large to fit in the cavity of the 12-crown-4 ether, resulting in a distorted square-pyramidal geometry about the Li+ atom.

In the title compound, [Li(C 8 H 16 O 4 )(CD 3 CN)]ClO 4 , the Li atom is pentacoordinate. The O atoms of the 12-crown-4 ether form the basal plane, whereas the N atom of the trideuteroacetonitrile occupies the apical position. The Li + atom is displaced by 0.794 (6) Å toward the apical position from the plane formed by the O atoms because the Li + atom is too large to fit in the cavity of the 12-crown-4 ether, resulting in a distorted square-pyramidal geometry about the Li + atom.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SI2247).

Comment
Crown ethers are important due to their remarkable selectivity toward complexation with metal ions through oxygen atoms on the crown ether ring. They have high conformational flexibility, act as host molecules for various guests (Jagannadh et al., 1999), and have a broad range of applications. Their importance has been studied in numerous fields such as molecular design (Lehn, 1973), supramolecular chemistry (Lehn, 1995), analytical chemistry (Doyle & McCord, 1998;Hayashita et al., 1992) and medicine (Frühauf & Zeller, 1991). The ionic title compound (I), a crown ether/Li + system, was prepared in a study aiming to develop a systematic methodology to understand the nature of these complexes. This methodology based on experimental crystallography may find application in characterization of host-guest type drug delivery systems.
Compound (I) crystallizes with discrete cations and anions. The Li + atom of the cation exhibits a distorted square pyramidal geometry. The four oxygen atoms of the 12-crown-4 ether (12C4) bond to lithium in the basal positions, and the acetonitrile nitrogen atom occupies the apical position. The 12C4 is in the frequently observed [3333] conformation approximating C 4 symmetry (Raithby et al., 1997;Jones et al., 1997). The oxygen atoms are nearly planar with a rms of 0.1325 (14) Å. The lithium atom is displaced out of this plane toward the apical position by 0.794 (6) Å. This displacement results from the Li + being too large to fit in the cavity of the crown ether. The two diagonal distances across the ring between the opposite oxygens are 3.611 (4) Å and 3.890 (4) Å resulting in an adjusted diameter of the cavity between 0.811 Å and 1.090 Å. This cavity is too small to accomodate the lithium ion whose ionic diameter is between 1.18 Å and 1.52 Å (Shoham et al., 1983;Dalley, 1978). The Li-N vector is nearly perpendicular to the plane of the 12C4 oxygen atoms forming a 89.8 (5)° angle.
The angles and distances involving lithium were statistically similar to the averages for 14 related compounds found in the Cambridge Structural Database (CSD; Version 1.11, September 2009 release; Allen, 2002). A Mogul structural check also confirmed that (I) exhibits typical geometrical parameters (Bruno et al., 2002).
The lithium complexes and the perchorate anions in the lattice of (I) are each stacked along a twofold screw axis to form columns along the a axis.
These two solutions were then mixed together according to a 1:1 molar ratio of 12C4/LiClO 4 .The final solution was kept in a desiccator and the solvent was allowed to evaporate gradually in order to produce a supersaturated solution. The supersaturated solution was stored at -20 °C refrigerator, until crystals formed after 48 hours. Two types of colorless crystals suitable for X-ray diffraction were obtained and separated from the solution, one of which was compound (I) the other being tris(1,4,7,10-tetraoxacyclododecane)-di-lithium diperchlorate (Guzei et al., 2010).
supplementary materials sup-2 Refinement All H and D atoms were placed in idealized locations and refined as riding, with C-H=0.99 Å and U iso (H) = 1.2U eq (C) for all hydrogen atoms, and C-D=0.98 Å and U iso (D)=1.5U eq (C) for all deuterium atoms. Fig. 1. Molecular structure of (I). The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms were omitted for clarity.

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.
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.