Bis(butane-1,4-diammonium) di-μ-oxido-bis[trifluoridooxidomolybdate(V)] monohydrate

The title compound, (C4H14N2)2[Mo2O4F6]·H2O, was obtained by solvothermal reaction at 443 K for 72 h from a mixture of MoO3, HF, 1,4-diaminobutane (dab), water and ethylene glycol. The structure consists of [Mo2O4F6]4− anionic dimers containing strongly distorted MoO3F3 octahedra (with twofold symmetry), diprotonated dab cations and water molecules (twofold symmetry) in the ratio 1:2:1. The cohesion of the three-dimensional structure is ensured through N—H⋯O, N—H⋯F and O—H⋯F interactions.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: VN2059).

sup-1
Acta Cryst. Transition-metal oxofluoride hybrids have been intensively studied due to their interesting magnetic, optical and electrochemical properties (Nakajima et al., 2000). This paper presents a new organic-inorganic hybrid compound with molybdenum (V) and 1,4-butanediamine. To date, few hybrid oxofluoromolybdates (V) are reported in the literature.
[MoOF 5 ] 2monomers, [Mo 2 O 2 F 9 ] 3and [Mo 2 O 4 F 6 ] 4dimers were obtained with ammonium by Mattes et al. (1976Mattes et al. ( , 1980. Adil et al. (2007) reported the previous monomer with tren cations. Two other compounds, built up from [Mo 2 O 4 F 4 ] 2dimers with bipyridinium or phenanthrolinium, were synthesized by Chakravorti et al. (1983). It must be noted that the same author obtained many alkali metal molybdenum (V) (Mattes et al., 1980;Adil et al., 2007). Isolated water molecules are hydrogen bonded in a tetrahedral geometry with two -NH 3 cations and two fluorine atoms (Fig. 2). The inorganic anions and organic cations are connected by intermolecular hydrogen bonds ( Fig. 3 and Table 2), creating a two-dimensional network of hydrogen bonds parallel to (-102) between the inorganic anion sheets and organic cation layers.

Experimental
The starting chemical reactants were molybdenum trioxide (MoO 3 ), 1,4-diaminobutane, aqueous HF (48%), water and ethylenglycol in the molar ratio 1:20:55:278:103. The starting mixture was dissolved under solvothermal conditions at 170°C for 72 h. Single crystals were obtained after the evaporation of the solution at room temperature. Crystals suitable for X-ray diffraction were selected under a polarizing optical microscope.

Refinement
Non-hydrogen atoms were refined with anisotropic thermal factors. H atoms attached to nitrogen atoms were freely refined but their isotropic atomic displacement parameter was constrained to U iso (H) = 1.5 U eq (N). Hydrogen atoms attached to carbon atoms were treated in riding motion, with U iso (H) = 1.2 U eq (C). The independent H atom of the water molecule was located in a difference Fourier map and was refined using a SHELXL DFIX option. Small, unresolved disorder affects the organic cation and consequently, the deepest and highest residual peaks in the final difference Fourier supplementary materials sup-2 Acta Cryst. (2012). E68, m1520 map are located close to carbon atoms. All attempts to decrease these densities using split positions failed.

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.