A new β-octamolybdate(VI) salt based on 1,4-bis(2-methyl-1H-imidazol-1-yl)butane

The title compound, bis[2,2′-dimethyl-3,3′-(butane-1,4-diyl)diimidazol-1-ium] β-octamolybdate(VI), (C12H20N4)2[Mo8O26], was produced by hydrothermal reaction of an acidified aqueous solution of Na2MoO4 and 1,4-bis(2-methyl-1H-imidazol-1-yl)butane (hereafter L). The structure of the title compound consists of the β-octamolybdate anions having a center of symmetry, and protonated [H2 L]2+ cations, which link the β-octamolybdate anions, generating a supramolecular chain via hydrogen bonds.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BG2208).
In recent times a remarkable approach to the construction of multifunctional materials is being realized exploting the ability of polyoxometalates to coordinate to different transition-metal organic units (Hagrman et al., 1997;Li et al., 2008). The POMs, acting as unusual inorganic ligands are introduced into a variety of POM-based coordination polymers with desired properties (Bu et al., 2001;Wu et al., 2002). During our ongoing studies of related materials, we obtained the title compound, (I), and present its crystal structure here.
The asymmetric unit of compound (I) contains a complete (C 12

Experimental
A mixture of Na 2 MoO 4 .2H 2 O (0.242 g, 1.0 mmol) and L (0.218 g, 1.0 mmol) in water (10 ml) was adjusted with HCl (2M) to pH = 3. Then the mixture was placed in a 23 ml Teflon-lined autoclave and kept under autogenous pressure at 150 °C for 2 days. After the mixture was cooled to room temperature at 10°C.h -1 , colorless crystals of the title compound were obtained.

Refinement
All H atoms on C atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 -0.97 Å, and U iso =1.2U eq (C). The H atoms of N2 and N4 were located in a difference Fourier map and then refined isotropically, with restrained N-H (0.87 (3)Å) and U iso =1.5U eq (N).
supplementary materials sup-2 Figures Fig. 1. A view of the molecule of (I). Displacement ellipsoids are drawn at the 30% probability level. All crystallographic related oxygen atoms are unlabled for clarity. Symmetry code: Ball-stick representation of the one-dimensional supramolecular structure of (I).
Crystal data (C 12   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.