Bis(hydroxyammonium) hexachloridoplatinate(IV)–18-crown-6 (1/2)

In the title complex, (NH3OH)2[PtCl6]·2C12H24O6, the PtIV atom is coordinated by six chloride anions in a slightly distorted octahedral geometry. The Pt—Cl bond lengths are comparable to those reported for other hexachloridoplatinate(IV) species. The hydroxyammonium groups act as linkers between the [PtCl6]2− anion and the crown ether molecules. The anion is linked to two hydroxyammonium cations via O—H⋯Cl hydrogen bonds and each hydroxyammonium moiety is linked to a crown ether molecule by hydrogen bonds between ammonium H atoms and 18-crown-6 O atoms. The crown ether molecules have the classic crown shape in which all O atoms are located in the inner part of the crown ether ring and all –CH2– groups are turned to the outside.

In the title complex, (NH 3 OH) 2 [PtCl 6 ]Á2C 12 H 24 O 6 , the Pt IV atom is coordinated by six chloride anions in a slightly distorted octahedral geometry. The Pt-Cl bond lengths are comparable to those reported for other hexachloridoplatinate(IV) species. The hydroxyammonium groups act as linkers between the [PtCl 6 ] 2À anion and the crown ether molecules. The anion is linked to two hydroxyammonium cations via O-HÁ Á ÁCl hydrogen bonds and each hydroxyammonium moiety is linked to a crown ether molecule by hydrogen bonds between ammonium H atoms and 18-crown-6 O atoms. The crown ether molecules have the classic crown shape in which all O atoms are located in the inner part of the crown ether ring and all -CH 2 -groups are turned to the outside.

Related literature
For general background to supramolecular assemblies, see: Saalfrank & Demleitner (1999). For crystal structures of related compounds based on platinum complexes and crown ether molecules, see: Bulatov et al. (2012).

Comment
The crystal structure of the title complex contains one Pt atom coordinated by six Cl atoms in an octahedral geometry ( Fig. 1). The Pt-Cl1, Pt-Cl3, and Pt-Cl4 distances are 2.328 (3), 2.3202 (10), and 2.3184 (10) Å, respectively. The hydroxyammonium ions act as linkers between the [PtCl 6 ] 2moieties and the crown ether molecules. The O-H···Cl and N-H···O hydrogen bond parameters are given in Table 1. Association with the platinum complexes changes the conformation of the crown ether. Thus, the cavity of the free 18-crown-6 has two inward-turned CH 2 groups and two oxygens with the electron pairs facing outward and away from the center. In other words, the free crown ether does not display the true crown shape or cavity. However, in the presence of (NH 3 OH) 2 [PtCl 6 ], reorganization of the crown occurs to give the classic crown shape in which all oxygen atoms are located in the inner part of the crown ring and all CH 2 groups are turned to the outside.

Refinement
The OH hydrogen atom was located in a difference Fourier map but refined with fixed distances and angles (O-H = 0.84 Å and N-O-H = 109.47°) using a riding model with U iso = 1.5U eq of the parent atom. The NH 3 hydrogen atoms were also found in a difference Fourier map, but were subsequently constrained to ride on their parent atom, with N-H = 0.91 Å and U iso = 1.5U eq (parent atom). The other hydrogen atoms were positioned geometrically and constrained to ride on their parent atoms, with C-H = 0.99 and U iso = 1.2U eq (parent atom).

Computing details
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008b).  The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 1.49 e Å −3 Δρ min = −1.23 e Å −3 Absolute structure: Flack (1983), 2066 Friedel pairs Absolute structure parameter: 0.035 (6) 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