Tris[(1,4,7,10,13,16-hexa­oxacyclo­octa­deca­ne)rubidium] heptaantimonide–ammonia (1/4)

Fabian Mutzbauer; Nikolaus Korber

doi:10.1107/S1600536811041237

. 2011 Oct 22;67(Pt 11):m1551. doi: 10.1107/S1600536811041237

Tris[(1,4,7,10,13,16-hexaoxacyclooctadecane)rubidium] heptaantimonide–ammonia (1/4)

Fabian Mutzbauer ^a, Nikolaus Korber ^a,^*

PMCID: PMC3246972 PMID: 22219792

Abstract

The crystal structure of the title compound, [Rb(C₁₂H₂₄O₆)]₃[Sb₇]·4NH₃, fills the gap between the already known Zintl anion ammoniates {[Cs(18-crown-6)]₃Sb₇}₂·9NH₃ [Wiesler (2007 ▶). Dissertation, Universität Regensburg, Germany] and [K(18-crown-6)]₃Sb₇·4NH₃ [Hanauer (2007 ▶). Dissertation, Universität Regensburg, Germany]. As in the two known compounds, the antimony cage anion in this crystal structure is coordinated by three alkali cations. The coordination spheres of each of the cations are saturated by 18-crown-6 molecules. The ammonia molecules of crystallization are situated between the crown ethers. The neutral, molecular [Rb(18-crown-6)]₃Sb₇ units are interconnected by multiple dipole–dipole interactions between ammonia and 18-crown-6.

Related literature

Rb₃Sb₇ can be obtained by a high-temperature solid-state reaction (Hirschle & Röhr, 2000a ▶) like the homologous Cs₃Sb₇ phase (Hirschle & Röhr, 2000b ▶). By dissolving these solids in solvents like ethylenediamine or liquid ammonia in the presence of chelating ligands like crown ether or cryptand molecules, new solvent-rich compounds can be crystallized from the mother liquor, see: Critchlow & Corbett (1984 ▶); Adolphson et al. (1976 ▶); Kummer et al. (1976 ▶); Hanauer (2007 ▶); Wiesler (2007 ▶). For the isotypic structure [K(18-crown-6)]₃Sb₇·4NH₃, see: Hanauer (2007 ▶). For the specification of nortricyclane analogue cluster anions, see: Hönle & von Schnering (1978 ▶); Somer et al. (1989 ▶).

Experimental

Crystal data

[Rb(C₁₂H₂₄O₆)]₃[Sb₇]·4NH₃
M _r = 1969.73
Monoclinic,
a = 15.000 (3) Å
b = 17.484 (4) Å
c = 25.158 (5) Å
β = 90.98 (3)°
V = 6597 (2) Å³
Z = 4
Mo Kα radiation
μ = 5.08 mm⁻¹
T = 123 K
0.3 × 0.2 × 0.1 mm

Data collection

Stoe IPDS1 diffractometer
Absorption correction: numerical (X-RED/X-SHAPE in X-AREA; Stoe & Cie, 2005 ▶) T _min = 0.453, T _max = 0.648
88182 measured reflections
12127 independent reflections
9417 reflections with I > 2σ(I)
R _int = 0.090

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.083
S = 0.96
12127 reflections
617 parameters
H-atom parameters constrained
Δρ_max = 1.66 e Å⁻³
Δρ_min = −0.74 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2005 ▶); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2001 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811041237/hp2013sup1.cif

e-67-m1551-sup1.cif^{(44.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811041237/hp2013Isup2.hkl

e-67-m1551-Isup2.hkl^{(592.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

The compound Rb₃Sb₇ can be obtained by a high temperature solid state reaction (Hirschle & Röhr, 2000a) like the homologous Cs₃Sb₇ phase (Hirschle & Röhr, 2000b). By dissolving these solids in solvents like ethylenediamine or liquid ammonia in the presence of chelating ligands like crown ether or cryptand molecules, new solvent rich compounds can be crystallized from the mother liquor (Critchlow & Corbett, 1984; Adolphson et al., 1976; Kummer et al., 1976; Hanauer, 2007; Wiesler, 2007). There is a line of crystal structures documented showing a distinct progression from the pure solid crystal to a solvent rich crystal. In the pure solid phase, the anion is coordinated directly by cations. The solvent rich crystal structures contain cations which are coordinated by chelating ligands and/or solvent molecules. This yields anionic cluster molecules which only feature weak ion-dipole interactions. The here presented [Rb(18-crown-6)]₃Sb₇.4NH₃ compound is isostructural to the crystal structure of [K(18-crown-6)]₃Sb₇.4NH₃ (Hanauer, 2007). Each rubidium cation binds exclusively to one crytallographically independent Sb₇ cage in an η⁴-like fashion. To complete a coordination number of ten for each metal atom, it is saturated by one 18-crown-6 molecule (Fig. 1). Four ammonia molecules are localized between the three crown ether ligands of each unit. These solvent molecules interact by hydrogen bonding with crown ether molecules and ammonia molecules of adjacent [Rb(18-crown-6)]₃Sb₇ × 4NH₃ units. Therefore, the structure can be described as a packing of isolated [Rb(18-crown-6)]₃Sb₇ units. This packing and the orientation of these units is shown in Figure 2. The nortricyclane analogue cluster anions were specified by von Schnering et al. They defined the cluster by its height H and the quotient Q between H and the average of the three bonding distances between the three atoms of the triangular base area (Hönle & von Schnering, 1978; Somer et al., 1989). The presented Sb₇ anion shows characteristic values for this kind of cage of H = 3.8653 (5) Å and Q = 1.33.

Experimental

All preparations were carried out in an atmosphere of dryed argon (99.9996%). 173 mg Rb₃Sb₇ (0.156 mmol), 41 mg 18-crown-6 (0.156 mmol) and 100 mg [Ni(CO)₂(PPh₃)₂] (0.156 mmol) were placed in a baked out reaction vessel inside a glove box. Afterwards ammonia (99.99990%) was condensed onto the solids until a filling level of about 15 ml solvent was achieved. A light brown suspension resulted. After 3 month of storage at 233 K a dark brown solution could be obtained and dark brown crystals could be isolated.