Refinement of the crystal structures of the tetrahedro-tetragermsmides ICtGe4, Rb 4 Ge 4 and Cs4Ge4

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324

Ζ. Kristallogr. NCS 220 (2005) 324-326

© by Oldenbourg Wissenschaftsverlag, München

Refinement of the crystal structures of the tetrahedro-tetragermsmides ICtGe4, Rb ⁴ Ge ⁴ and Cs4Ge4

H. G. von Schnering*

^J

, J. Llanos"

¹

, J.-H. Chang

¹

, K. Peters

¹

, E.-M. Peters

¹

and R. Nesper™

1 Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1,70569 Stuttgart, Germany

n Universidad Calölica del Norte, Departamento de Quimica, Av. Angamos 0610, Casilla 1208, Antofagasta, Chile

m ΕΤΗ Hönggeiberg - HCl, Laboratoriuni für Anorganische Chemie, Wolfgang-Pauli-Str. 10,8093 Zürich, Switzerland Received August 22,2005, accepted and available on-line August 31,2005; CSD nos. 409848,409849,409850

Abstract _

Ge4K4, cubic, P43n (no. 218), a = 12.784(1) A, V= 2089.3 Ä

³

, Ζ = 8, Rgt(F) = 0.034, wR^F

2

) = 0.086, Τ = 296 Κ.

Ge4Rb

4

, cubic, P43/i(no. 218), a = 13.198(2)Ä, V= 2298.9 Ä

³

, Ζ = 8, RgcfF) = 0.040, wR^F

²

) = 0.082, Τ = 296 Κ.

Cs4<3e4, cubic, P43n(no. 218), a = 13.654(2) Ä, V= 2545.5 A

3

, Ζ = 8, RgtfF) = 0.036, wRkJF

²

) = 0.085, Τ = 296 Κ.

Source of material

The compounds, first characterized by Schäfer and Klemm [1]

and by Busmann [2,3], were synthesized from the elements in encapsulated Ta-ampoules enclosed in evacuated quartz tubes (distilled alkali metal, germanium powder 100/20 mmol), heated up to 1123 Κ (Κ) and 1173 Κ (Rb, Cs), respectively, within 12 h and annealed at these temperatures for 24 h and finally slowly cooled down to room temperature within 40 h [4]. Residual alkali metal was removed by distillation (550 Κ, 1 Pa). Well-shaped

black crystals are formed with shiny faces of type {100}, {110}

and {111} for Κ and Rb but reddish-blue cubes for Cs. The com- pounds are very sensitive to oxidation and hydrolysis and have to be handled strictly under inert conditions.

Experimental details

Lattice parameters were determined from Guinier-Simon powder patterns [5] (Si standard, a = 5.43102 A; Cu Ka\ radiation, λ =

1.540598 A).

Discussion

The three germanides form the KGe structure type (cP64) as re- ported by Busmann [2,3]. The redetermination was done for higher accuracy parameters and the results agree within the standard deviations with Busmann's film data. Dominant units are tetra- hedrally distorted M\Gc4 heterocubanes (stellae quadrangulae) formed by anionic G e ^ tetrahedra and completed by four μ

³

bridging cations, which furthermore interconnect the units via/4

1

Μ—Ge exo-bonds [4-7]. In that way all atoms are sixfold hetero- atomic coordinated. The arrangement of the Mt.Ge.4, units repre- sents a hierarchical cluster displacement structure [8] of the CnSi type with 2+6 fluster centers at the positions 2a and 6c of the space group P43n obviously an optimal arrangement for tetra- hedrally distorted heterocubanes as derivative of a 2

³

-fold NaCl structure [6,7], The Ba4SiAs4 structure (cPll) is closely related with Si-centered Ba4ÄS4 heterocubanes [9,10], The

MAGG*

units around 2a have 43m symmetry with the homoatomic bond lengths d(Ge—Ge) = 2.563(3) A, 2.559(4) A and 2.560(3) A (af- ter librational corrections: 2.580 A, 2.574 A and 2.577 A) and with ά(μ

³

-Μ—Ge) = 3.510(4) A, 3.636(2) A and 3.770(1) A for M= K, Rb and Cs, respectively. The interconnecting distances are larger with ά(μ

γ

-Μ—Ge) = 3.617(2) A, 3.763(2) A and 3.822(2) A.

The Ge4

⁴

anions around 6c are significantly flattened to 42m disphenoids with d{Ge—Ge) = 2.556(2) A (4x), 2.583(2) A (2x) and 2.553(2) A (4x), 2.583(3) A (2x) and 2.553(2) A (4x), 2.587(3) A (2x) (mean values = 2.565(14) A, 2.563(16) A, and 2.564(18) A). This deformation is also reflected in the Μ—Ge distances which are in the ranges of 3. 369 A-3.476 A, 3.492 A - 3.619 A and 3.625 A - 3.797 A for the/*

³

bridges (μ

¹

connection range: 3.502 A - 3 . 614 A, 3.650 A - 3.761 A, 3.814 A - 3.919 A).

The small, but not significant tendency to change the Ge—Ge bonds in the series from potassium to cesium is confirmed by the vibrational force constants [11].

* Correspondence author

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K4Ge4, Rb4Ge4, Cs4Ge4

325

1. Tetrapotassium tetrahedro-tetragermsmide^ K4G&1

Table 1. Data collection and handling.

Crystal:

Wavelength:

μ·

Diffractometer, scan mode:

20nuul·

N(hkl WuUW,«:

Criterion for lobs, N(hkl) N(param)reiined:

Programs:

black shiny, {100} and {110} forms, size 0.3 χ 0.3 χ 0.3 mm

Mo Ka radiation (0.71073 A) 129.14 c m " ! .

SYNTEX PI, ω 6 9 . 2 6 ° 4 3 2 , 4 3 2

/obs > 2 a(Iobs), 411 2 5

SHELXTL-plus [12], ATOMS [13]

Table 2. Atomic coordinates and displacement parameters (in A2).

Atom Site * y ζ Un Un t/33 Un Un t/23

Ge(l) 8 e 0.07089(7) X X 0.0315(4) Un Un -0.0055(4) Un Ul2

Ge(2) 24i 0.06461(7) 0.31992(8) 0.42236(8) 0.0307(5) 0.0285(5) 0.0281(5) -0.0034(5) 0.0057(4) 0.0032(4)

K(l) Se 0.3327(2) X X 0.0380(9) Un Un -0.0038(9) Ul2 Un

K(2) 24/ 0.3359(2) 0.1401(2) 0.0651(2) 0.037(1) 0.040(1) 0.034(1) 0.002(1) -0.003(1) 0.001(1)

2. T e t r a r u b i d i i m i tetrahedro-tetragermsuMe, R h t G e i

Crystal:

Wavelength:

μ·

20mu:

N(hkl)measured, Nfhklhnaqot'·

Criterion for /obs, N(hkl)p: N(param)n fined:

Programs:

black shiny, {100} and {110} forms, size 0.2 χ 0.2 χ 0.2 mm

M o Ka radiation (0.71073 A) 2 7 1 . 1 5 c m_ ,_

SYNTEX PI, ω 55°

1 4 3 0 , 5 0 9 /obs > 2 <7f/obs), 4 0 4 2 5

Table 4. Atomic coordinates and displacement parameters (in A2).

Atom Site X y ζ Un Un 1/33 Un Un 1/23

Ge(l) Se 0.0685(1) X X 0.0273(5) Un Un -0.0048(6) Un Un

C3e(2) 24/ 0.0627(1) 0.3176(1) 0.4249(1) 0.0279(8) 0.0267(7) 0.0244(7) -0.0021(6) 0.0049(6) 0.0040(6)

Rb(l) ie 0.3318(1) X X 0.0338(5) Un Un -0.0031(6) Un Un

Rb(2) 24i 0.3355(1) 0.1405(1) 0.0637(1) 0.0324(8) 0.0361(8) 0.0309(7) 0.0026(6) -0.0050(7) 0.0013(7)

3. TetracesNim te&ri/i«d!r»-tefcrageniianide, C&tGet

Crystal:

Wavelength:

μ·

2θιαα·

Nihkljmasami, N(hkl)w0qae·

Criterion for /obs, N(hkl)ρ: N(param)afined:

Programs:

reddish-blue cube, size 0.3 χ 0.3 χ 0.3 mm M o Ka radiation (0.71073 A)

2 0 5 . 6 6 c m ' _ SYNTEX PI, ω 5 4 . 9 2 ° 3 0 4 7 , 5 5 8 /ob, > 2 of/obJ, 5 2 5 2 5

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326

K4Ge4, Rb4Ge4, Cs4Ge4

Table 6. Atomic coordinates and displacement parameters (in Ä2).

Atom Site ίΛι UzL i/33 U12 U13 f23

Ge(l) 8e 0.06628(9) χ χ 0.0281(4) t/n U\\

Ge(2) 24/ 0.06169(9) 0.31521(9) 0.42812(9) 0.0262(6) 0.0249(6) 0.0236(6) Cs(l) 8e 0.33126(6) χ χ 0.0323(3) l/n t/n Cs(2) 24i 0.33580(5) 0.14183(5) 0.06409(6) 0.0334(4) 0.0341(4) 0.0302(4)

-0.0055(4) t/12 t/12

0.0033(5) 0.0058(5) -0.0038(5) -0.0014(3) C/i2 C/12

0.0017(3) -0.0055(3) 0.0035(3)

References

1. Schäfer, R.; Klemm, W.: Das Verhalten der Alkalimetalle zu Halb- metallen. IX. Weitere Beiträge zur Kenntnis der Silicide und Germanide der Alkalimetalle. Z. Anorg. Allg. Chem. 312 (1961) 214-220.

2. Busmann, E.: Die Kristallstniktur von KGe und isotypen Germaniden und Siliciden. Naturwissenschaften 47 (1960) 82.

3. Busmann, E.: Die Kristallstiukturen von KSi, RbSi, CsSi, KGe, RbGe und CsGe. Z. Anorg. AUg. Chem. 327 (1964) 260-273.

4. Llanos, J.: Neue Untersuchungen an den Germaniden der Alkalimetalle, vor allem an Verbindungen mit Ge4-Tetrahedrananionen. Dissertation, Universität Stuttgart 1984.

5. Simon, Α.: One Methode zur Untersuchung extrem luftempfindlicher Substanzen mit der Guinier-Methode. J. Appl. Crystallogr. 3 (1970) 11-18.

6. von Schnering, H. G.; Nesper, R.: Zusammenhänge der Strukturen von I- IV-Zintlphasen mit einfachen AB-Strukturtypen. Z. Kristallogr. 162 (1983) 202-204.

7. Nesper, R.: Structure and chemical bonding in Zintl-Phases containing lithium. Progr. Solid State Chem. 20 (1990) 1-45.

8. Canillo-Cabrera, W.; Caroca-Canales, N.; von Schnering, H. G.:

K2i-aNa2+0ln39 (δ = 2.8): A Cluster-Replacement Clathrate-Π Structure with an Alkali Metal Λ/ι »-Network. Z. Anorg. Allg. Chem. 620 (1994) 247-257.

9. Eisenmann, Β.; Jordan, Η.; Schäfer, Η.: Zintlphasen mit isolierten SiAs«- bzw. GeAs4-Anionen: Darstellung und Struktur von Ba4SiAs4 und Ba4GeAs4, sowie Sr4SiA£4 und Sr4GeAs4- Z. Anorg. Allg. Cliem. 475 (1981)74-80.

10. Nuss, J.; Hönle, W.; Peters, K.; von Schnering, H. G.: Tetrapnictido- titanate(IV) Af4TiXi (M = Sr, Ba; X = P, As), hierarchische Derivate der KGe-Stniktur K4Ge4. Z. Anorg. AUg. Chem. 622 (1996) 1879-1885.

11. Somer, M.; Aydemir, U.; Baitinger, M., von Schnering, H. G.: Vibrational Spectra of the Cluster Anion [i^]4" in K4£«, Rb4£4, Cs4£4 (E = Ge, Sn) and /J-Na4Sii4. Z. Anorg. Allg. Chem. (in press).

12. Sheldrick, G. M.: SHELXTL-plus. Structure Determination Software Suite. Release 4.1. Siemens Analytical X-Ray Instruments, Madison.

Wisconsin, USA 1990.

13. Dowty, E.: ATOMS. A Complete Program for Displaying Atomic Struc- tures. Version 6.0. Shape Software, Kingsport, Tennessee, USA 2002.