Double salt crystal structure of hexasodium hemiundecahydrogen α-hexamolybdoplatinate(IV) heminonahydrogen α-hexamolybdoplatinate(IV) nonacosahydrate: dihydrogen disordered-mixture double salt

The title double salt containing two distinct, differently protonated hexamolybdoplatinate(IV) polyanions. The polyanion pairs both form dimers of the same formula, viz. {[H10 α-Pt2Mo12O48]}6− connected by seven interpolyanion O—H⋯O hydrogen bonds.

In our studies of Anderson-type heteropolyoxotungstates containing Pt IV , [H n -Pt IV W 6 O 24 ] (8-n)n = 0, 2, 2.5, 3, 3.5), we have found out that the gradual protonation is also a typical character of these compounds (Izarova et al., 2012). Furthermore, we have reported the stepwise protonation species in the nonavanadoplatinate(IV) series, viz. [H n PtV 9 O 28 ] (7Àn)À (n = 2 and 3) (Lee et al., 2008;Joo et al., 2011;Joo & Lee, 2015;Joo et al., 2015b). As well as the Pt IV a Keggin-type (Keggin, 1934) heteropolyoxometalate was formed, [-SiPt IV 2 W 10 O 40 ] 8À (Lee et al., 2003). The Pt IV ion shows a very rich chemical behavior when it forms POMs with Mo, W and V systems. We assume that the diversity of the Pt IV -containing POMs is caused by the starting material of the heteroatom, [Pt IV (OH) 6 ] 2À , and the similarities in the oxidation states and the ionic radii of addenda atoms (Pt 4+ ; 0.76, Mo 6+ ; 0.73, W 6+ ; 0.74 & V 5+ ; 0.68 Å ; Shannon, 1976) and the electron configuration of Pt 4+ (5d 6 ) that preferentially forms the six-coordinated octahedra. In particular, the selective protonation of the 3 (Table 1), the interpolyanion hydrogen bonds (Table 2 and Fig. 4), and the bond-valence sums (BVSs; Brown & Altermatt, 1985;Brese & O'Keeffe, 1991) The molecular entities in the crystal structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level. The H atoms of the polyanion are presented as small spheres of arbitrary radius and the H atoms of water molecules have been omitted for clarity. Bonds between coordinating OW molecules and Na + are indicated by dashed lines.

Figure 3
Difference-Fourier map around atoms H2 and H30. Calculated with atom H2 and H30 absent from the model.   (Lee & Sasaki, 1994;Joo et al., 1994) showed a bent structure (C 2v ) but the present polyanion shows a near planar structure. The protonated O atoms of [H 6 PtMo 6 O 24 ] 2À in the present structure show the same protonation scheme as one previously reported (Lee & Joo, 2006a,b), viz. four 3 -OC and two 2 -OB atoms are protonated. However, the protonation scheme of the previously reported polyanion in [H 6 PtMo 6 O 24 ] 2À  was different, consisting of five 3 -OC and one 2 -OB protonated O atoms. Five protonated polyanion species (A) and (B) were confirmed for the first time in the title compound. Four 3 -O and one 2 -O atoms are protonated in both polyanions, but the position of the unprotonated 3 -O atom differs (Fig. 2).
Confirmation of the protonated O atoms was strongly supported by the BVS analysis. The BVSs for protonated atoms O2C-O6C and O7B in polyanion (A) Table 2). It is notable that the water molecules O21W-O29W, do not show any interaction with the metal atoms and are bonded to other O atoms only by O-HÁ Á ÁO hydrogen bonds. The other H atoms of the polyanion (H3, H5 and H27) form hydrogen bonds with water molecules (Table 2).

Synthesis and crystallization
Crystals of title compound were prepared by the reaction of Na 2 MoO 4 Á2H 2 O and Na 2 Pt(OH) 6 at ca pH 1.80 as described in a previous report (Lee & Sasaki, 1994).

(I)
Crystal data  (2) 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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )