Direct synthesis of (PhSe)4Ge and (PhTe)4Ge from activated hydrogenated germanium - Crystal structure and twinning of (PhTe)4Ge

Article abstract of DOI:10.1002/ejic.200390183

The germanium chalcogenolates (PhSe)₄Ge and (PhTe)₄Ge were synthesized from activated hydrogenated germanium (Ge*) and diphenyldiselenide or diphenylditelluride, respectively. (PhTe)₄Ge is the first homoleptic organotellurolate of germanium. It was characterized spectroscopically and by X-ray crystal structure analysis. (PhTe)4Ge crystallizes in the monoclinic space group P2₁/c with a = 12.8018(14), b = 9.1842(9), c = 23.690(3) A and β = 105.458(8)°. The molecules show a tetrahedral GeTe₄ core. Weak Te-Te interactions connect neighbouring tetrahedra to infinite helices along [010]. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Full text of DOI:10.1002/ejic.200390183

FULL PAPER
Direct Synthesis of (PhSe)4Ge and (PhTe)4Ge from Activated Hydrogenated
Germanium ؊ Crystal Structure and Twinning of (PhTe)4Ge
Sabine Schlecht*[a] and Karen Friese[b]
Keywords: Germanium / Tellurium / Van der Waals interactions / Active metals
The germanium chalcogenolates (PhSe)4Ge and (PhTe)4Ge
were synthesized from activated hydrogenated germanium 9.1842(9), c = 23.690(3) A and β = 105.458(8)°. The molecules
monoclinic space group P21/c with a = 12.8018(14), b =
˚
(Ge*) and diphenyldiselenide or diphenylditelluride, re-
spectively. (PhTe)4Ge is the first homoleptic organotellurolate
of germanium. It was characterized spectroscopically and by
show a tetrahedral GeTe4 core. Weak Te-Te interactions con-
nect neighbouring tetrahedra to infinite helices along [010].
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
X-ray crystal structure analysis. (PhTe)4Ge crystallizes in the Germany, 2003)
Introduction
In the last two decades, organochalcogenolates of group
14 elements have gained increasing importance as molecu-
lar precursors for IV/VI semiconductors.[1Ϫ3] In the case of
(1)
the homoleptic series (RCh)4E with Ch ϭ Se, S and E ϭ Ge,
Sn only rather elaborate and low-to-medium yield synthetic
routes are known in the literature.[4Ϫ6] Analogous tellurol-
ates (RTe)4E with E ϭ Ge or Sn have not been described
so far.
The activated germanium thus obtained indeed inserted
into the SeϪSe bond and TeϪTe bond of Ph2Se2 and
Ph2Te2 at surprisingly low temperatures to give homoleptic
(PhSe)4Ge (2) at 65 °C and (PhTe)4Ge (3) at room temper-
ature [Equation (2) and (3)].
Hence, a direct synthesis of this class of compounds from
R2Ch2 (R ϭ alkyl, aryl; Ch ϭ Se, Te) and the group 14
element is highly desirable, especially in the case of the
tellurium compounds.
(2)
(3)
Results and Discussion
The same type of direct reaction with Ph2Se2 has also
been observed for activated nanocrystalline tin and also
yielded the homoleptic product (PhSe)4Sn.[8]
Commercially available elemental germanium or tin pow-
der does not react with diorganodichalcogenides at temper-
atures below the decomposition temperature of these
organoelement compounds. Thus, a chemical activation of
germanium is necessary in order to make such a direct reac-
tion feasible.
We used solvochemically produced hydrogenated ger-
manium, which is highly reactive and a good reductand and
can be obtained from GeCl2·dioxane and Li[Et3BH] in
THF according to Equation (1).[7]
In the reaction of Ge* (1) with diphenyldiselenide at
65 °C in THF solvent, the selenolate 2 is obtained in 92%
yield. This yield is significantly higher than the 60Ϫ65%
yield that could be obtained in reactions of LiSePh with
GeCl4.[4,5] In addition, our direct synthesis from activated
germanium and Ph2Se2 does not produce any by-products
in significant amounts and therefore no separation proced-
ure is required.[5]
The reaction of 1 with Ph2Te2 is less straightforward, but
tellurolate 3 was obtained in 26% yield as a deep red solid.
Although all suspended Ge* was consumed after two hours
of stirring at room temperature and a clear red solution had
formed, we were not able to isolate pure 3 from that solu-
tion. Instead, a mixture of Ph2Te2, amorphous brownish
[a]
Philipps-Universität Marburg, Fachbereich Chemie
Hans-Meerwein-Strasse, 35032 Marburg, Germany
Fax: (internat.) ϩ 49-(0)6421/28-28917
E-mail: schlecht@chemie.uni-marburg.de
[b]
Max-Planck-Institut für Festkörperforschung
Heisenbergstrasse 1, 70569 Stuttgart, Germany
1411
Eur. J. Inorg. Chem. 2003, 1411Ϫ1415  2003 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1434Ϫ1948/03/0407Ϫ1411 $ 20.00ϩ.50/0

S. Schlecht, K. Friese
FULL PAPER
Table 2. Atomic coordinates and isotropic displacement parameters
of 3
Atom
x
y
z
Uiso
Ge
0.14730(8)
0.25306(6)
0.27185(5)
0.02920(5)
0.02559(5)
0.3212(7)
0.2708(9)
0.3187(11)
0.4195(10)
0.4664(9)
0.4212(8)
0.3340(7)
0.2895(9)
0.3345(12)
0.4256(13)
0.4716(10)
0.4270(9)
0.1342(8)
0.2310(8)
0.2967(9)
Ϫ0.2656(11)
Ϫ0.1748(10)
Ϫ0.1022(9)
0.1225(8)
0.2144(9)
0.2761(9)
0.2526(11)
0.1664(11)
0.0954(9)
0.01670(9)
0.23134(6)
Ϫ0.18240(6)
0.09922(7)
Ϫ0.07486(7)
0.2951(8)
0.82455(4)
0.88289(3)
0.80162(3)
0.72343(3)
0.88825(3)
0.8146(4)
0.7752(4)
0.7315(5)
0.7285(5)
0.7683(6)
0.8123(5)
0.8899(4)
0.9127(5)
0.9700(5)
0.0040(6)
0.9815(6)
0.9254(5)
0.6777(3)
0.6766(4)
0.6480(4)
0.8777(5)
0.8765(5)
0.8472(5)
0.9661(4)
0.9993(4)
0.0480(5)
0.0647(5)
0.0317(5)
0.9826(4)
0.0504(4)
0.0634(3)
0.0620(3)
0.0615(2)
0.0637(3)
0.052(3)
0.067(4)
0.082(5)
0.077(5)
0.087(5)
0.074(5)
0.059(4)
0.072(5)
0.081(6)
0.094(6)
0.109(7)
0.074(5)
0.059(4)
0.064(4)
0.071(5)
0.087(6)
0.082(5)
0.081(5)
0.063(4)
0.070(4)
0.078(5)
0.081(5)
0.076(5)
0.070(5)
Te1
Te2
Te3
Te4
C1
C2
C3
C4
C5
C6
C7
0.3988(9)
0.4432(10)
0.3873(12)
0.2864(13)
0.2351(10)
Ϫ0.2477(10)
Ϫ0.3591(9)
Ϫ0.4047(12)
Ϫ0.3392(15)
Ϫ0.2248(17)
Ϫ0.1779(11)
0.0011(10)
0.0652(10)
Ϫ0.0048(11)
0.3603(14)
0.2952(11)
0.3620(11)
0.0246(9)
Figure 1. Molecular structure of (PhTe)4Ge (3) (ORTEP repres-
entation[19]); thermal ellipsoids are represented at a 50% probabil-
ity level
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
germanium and product 3 was obtained after removal of
the tetrahydrofuran. This mixture was re-dissolved in di-
ethyl ether and the amorphous germanium was separated
by filtration. The filtrate was evaporated to dryness and
Ph2Te2 and 3 were separated by an extraction with ice-cold
Table 1. Experimental parameters for the X-ray diffraction meas-
urement and details concerning the structure determination for
GeTe4C24H20 (3)
Ϫ0.0489(11)
0.0221(13)
0.1571(12)
0.2256(11)
0.1649(10)
Crystal system
Space group
monoclinic
P21/c
12.8018(14)
9.1842(9)
˚
a [A]
˚
b [A]
˚
c [A]
23.690(3)
β [°]
105.458(8)
2684.6(5)
2.22
Prismatic
Dark red
0.02 ϫ 0.04 ϫ 0.03
Stoe IPDS II
ϕ ϭ 0; ω ϭ 0Ϫ180;
ϕ ϭ 90; ω ϭ 0Ϫ180
1
10
100
0.71073
2.3Ϫ59.5
Ϫ17, Ϫ17, Ϫ19;
Ϫ17, 17, 19
5.41
Gaussian
0.2766, 0.8018
22297
3
˚
diethyl ether in which only Ph2Te2 is soluble. The deep-red
product that remained was pure 3 and was recrystallized at
room temperature by slow evaporation of a concentrated
solution in diethyl ether.
The X-ray crystal structure of germanium tellurolate 3 is
depicted in Figure 1. Details of the crystal structure deter-
mination are given in Table 1, and atomic coordinates can
be found in Table 2.
The structure of the molecule is similar to that of
(PhSe)4Ge and (PhSe)4Sn, of which an orthorhombic and
a monoclinic polymorph are known.[5] The germanium
centre is surrounded by an almost regular tetrahedron of
tellurium atoms. The GeϪTe bond lengths span from 257.5
pm to 258.2 pm (Table 3) and are similar to the distances
V [A ]
Calculated density [g/cm3]
Crystal shape
Crystal colour
Crystal size [mm]
Diffractometer
1st run; 2nd run
∆ω [°]
Exposure time [min]
Detector distance [mm]
Wavelength [A]
2Θ-range for data collection [°]
hklmin, hklmax
˚
Absorption coefficient [mmϪ1
Absorption correction
Tmin, Tmax
Total number of reflections
Unique reflections
Structure solution
Structure refinement
Parameters refined
R(obs) (Ͼ3σ)
]
Table 3. Selected bond lengths [pm] and bond angles [°] of 3
5949 (3149 Ͼ3σ)
[17]
Sir97
GeϪTe1
GeϪTe2
GeϪTe3
GeϪTe4
Te3ϪTe4Ј
257.51(10)
257.75(11)
258.24(10)
258.17(13)
393.23(8)
Te1ϪC1
Te2ϪC7
Te3ϪC13
Te4ϪC19
211.6(10)
211.7(8)
213.8(10)
213.4 (9)
Jana2000[18]
325
0.0418
0.0273
Rw(obs) (Ͼ3σ)
R(all)
Rw(all)
Twin matrix
0.0764
0.0276
(Ϫ1 0 0 | 0 1 0 |
Ϫ2/7 0 1)
0.867(1)
0.133(1)
0.408(9)
Te1ϪGeϪTe2
Te1ϪGeϪTe3
Te1ϪGeϪTe4
Te2ϪGeϪTe3
Te2ϪGeϪTe4
Te3ϪGeϪTe4
112.95(4)
111.54(3)
104.39(4)
104.76(4)
113.32(4)
110.03(4)
GeϪTe1ϪC1
GeϪTe2ϪC7
GeϪTe3ϪC13
GeϪTe4ϪC19
93.8(2)
94.8(3)
93.1(2)
93.7(3)
Volume fraction individual I
Volume fraction individual II
Extinction coefficient
1412
Eur. J. Inorg. Chem. 2003, 1411Ϫ1415

(PhSe)4Ge and (PhTe)4Ge from Activated Hydrogenated Germanium
FULL PAPER
found in the literature for other GeTe4 tetrahedra (e.g.
K2GeTe4: 250.8Ϫ264.0 pm;[9] Ag8GeTe6: 254.4 pm;[10]
Cs4GeTe: 253.7Ϫ262.3 pm[11]).
The angles around the four symmetrically independent
tellurium atoms range from 93.1° to 94.8° and are generally
more oblique than in the related selenium compounds
[(PhSe)4Ge (2): 96.2Ϫ96.7°; orthorhombic (PhSe)4Sn:
95.9Ϫ96.4°]. Only in monoclinic (PhSe)4Sn are similar
angles (93.5Ϫ95.6°) observed.
The main difference between (PhTe)4Ge (3) and the other
related compounds becomes evident when looking at the
spatial arrangement of the molecules. In the orthorhombic
compounds the molecules are arranged in such a way that
the tetrahedral cores are relatively isolated from each other
and, consequently, the intertetrahedral SeϪSe distances are
significantly longer than the intratetrahedral distances
[(PhSe)4Ge: intratetrahedral distances: 374.7Ϫ397.4; short-
est intertetrahedral distance: 468.5 pm; orthorhombic
(PhSe)4Sn: intratetrahedral distances: 403.2Ϫ424.6 pm;
shortest intertetrahedral distance: 434.9 pm]. In the mono-
clinic polymorph of (PhSe)4Sn some of the intertetrahedral
distances (the shortest is 382.3 pm) are shorter than the
intratetrahedral distances (404.1Ϫ414.4 pm), yet still too
long to assume SeϪSe interactions. In (PhTe)4Ge (3) the
shortest intertetrahedral TeϪTe distance is 393.2 pm, which
is significantly shorter than all intratetrahedral distances
Figure 2. Projection of the crystal structure of 3 along [010]; TeϪTe
interactions are indicated as dashed lines (ORTEP representa-
tion[19]); thermal ellipsoids are represented at a 50% probability
(407.44Ϫ431.0 pm). Furthermore, this distance is well be- level
low the sum of the van der Waals radii (440 pm)[12] and in
this case it is indeed reasonable to assume weak, attractive
TeϪTe interactions. These interactions connect Te atoms of
neighbouring tetrahedra and lead to the formation of hel-
ical chains consisting of germanium and tellurium atoms
along the crystallographic b direction (see Figure 2 and 3).
The type of helix that is formed by the tellurium and ger-
manium atoms in the backbone of the chain resembles the
[9]
anionic chain of tetrahedra in K2GeTe4 and the chain of
tellurium atoms found in the tellurium subchloride
Te3Cl2,[13] except for the differences in the bond angles. The
observed TeϪTe distance in 3 is similar to that observed in
other compounds, for example in Te[N(SiMe3)2]2 (377
pm),[14] with van der Waals interactions between the tellur-
ium atoms. These distances are longer than the interchain
distance in elemental tellurium (350 pm),[15] but they are
again similar to the TeϪTe distances at the van der Waals
gap of extended layered tellurides such as Ta2Te3,[16] where
a value of 373 pm was found.
Figure 3. Helical chain of interconnected tetrahedra of GeTe4 units
(ORTEP representation[19]); thermal ellipsoids are represented at a
50% probability level
these compounds ideal candidates for molecular precursors
leading to IV/VI semiconductors. Investigations on the low-
temperature synthesis of germanium() chalcogenides from
(PhSe)4Ge and (PhTe)4Ge are currently under way.
Conclusion
Activated hydrogenated germanium 1 allows the direct
one-step synthesis of (PhSe)4Ge (2) and (PhTe)4Ge (3) from
Ph2Se2 or Ph2Te2 and 1 in an oxidative addition leading
directly to the tetravalent germanium species. The homolep-
tic tellurolate 3 shows short intertetrahedral TeϪTe con-
tacts that lead to the formation of helical chains consisting
of germanium and tellurium atoms in this compound. The
Experimental Section
All manipulations were carried out under dry, oxygen-free argon,
except where stated otherwise. Li[Et3BH] (1  in THF), diphenyldi-
telluride, diphenyldiselenide and tetrahydrofuran were purchased
easy accessibility of (PhSe)4Ge (2) and (PhTe)4Ge (3) makes from Aldrich. GeCl2·dioxane was purchased from ABCR. THF
Eur. J. Inorg. Chem. 2003, 1411Ϫ1415 1413

S. Schlecht, K. Friese
FULL PAPER
was dried over CaH2 under argon atmosphere and freshly distilled
prior to use. The reactions were carried out in standard Schlenk
twinning by reticular merohedry. The two individual lattices have
the hk0 plane in common and generally all reflections l ϭ 7n over-
glassware. Activated hydrogenated germanium (1) was prepared as lap completely, while reflections l ϶ 7n correspond to reflections
described in the literature.[7]
of a single individual. This implies that it is inevitable to consider
the twinning operation in the refinement process. If the two twin
individuals were of equal volume, orthorhombic Laue symmetry
2/m2/m2/m would be simulated for the overall diffraction pattern.
The reduction of the symmetry of one individual to Laue class
2/m leaves the remaining four symmetry operations 2Ј/mЈϪ2Ј/mЈ as
possible choices for the twinning operation. We chose the mirror
plane perpendicular to a* as twin law corresponding to the matrix
(Ϫ1 0 0 | 0 1 0 | Ϫ2/7 0 1).
(PhSe)4Ge (2): GeCl2·dioxane (232 mg, 1.0 mmol) was reduced to
Ge* (1) by 2.0 mL of a 1.0  solution of Li[Et3BH] in THF as
described previously.[7] The resulting 1 was suspended in 60 mL of
THF and Ph2Se2 (624 mg, 2.0 mmol) was added. The reaction mix-
ture was heated to gentle reflux for 4 h and a clear yellow solution
was obtained. This was allowed to cool to room temperature and
then the THF was removed under vacuum. The yellow solid ob-
tained was washed with 10 mL of hexane and dried again. The
product was identified as (PhSe)4Ge (2)[5] by 1H, 13C and 77Se
NMR spectroscopy, elemental analysis and powder diffraction
data. Yield: 641 mg (92%).
Although in the structure solution process (with the program
SIR97[17]) all reflections were taken into account (i.e. also the over-
lapping ones) no problems were encountered and the positions of
all heavy atoms were easily identified. Structure refinement em-
ploying the above -described twin law was carried out with the
program Jana2000.[18] Hydrogen atoms were taken from the differ-
ence Fourier synthesis map.
(PhTe)4Ge (3): GeCl2·dioxane (232 mg, 1.0 mmol) was reduced
with 2.0 mL of a 1  solution of Li[Et3BH] in THF as described
above. The resulting 1 was suspended in 60 mL of THF and Ph2Te2
(818 mg, 2.0 mmol) was added. The reaction mixture was stirred at
room temperature for 2 h and a clear red solution formed. The
THF was quickly evaporated under vacuum and an orange-red
powder remained. Diethyl ether (40 mL) was added and the solu-
tion was filtered. The filtrate was evaporated to dryness under va-
cuum and the remaining mixture of Ph2Te2 and 3 was extracted
with 3 ϫ 5 mL of ice-cold diethyl ether. A dark red solid remained.
Yield: 232 mg (26%). 1H NMR (300 MHz, CD2Cl2, 25 °C):
δ ϭ 7.19 (t, 8 H), 7.38 (t, 4 H), 7.61 (t, 8 H) ppm. 13C NMR
(75 MHz, CD2Cl2, 25 °C): δ ϭ 129.1, 130.0, 141.5 ppm. IR (nujol
mull): ν˜ 1573 cmϪ1 (w), 1153 (w), 1014 (w), 996 (w), 688 (m), 450
(m, νTe-C), 252 (m, νGe-Te), 238 (m, νGe-Te), 178 (w). MS (EI,
70 eV): m/z (%) ϭ 766 (2) [(PhTe)2Ge(Te)(TeC2H3)]ϩ, 561 (10)
[(PhTe)Ge(Te)(TeC2H3)]ϩ, 410 (20) [Ph2Te2]ϩ, 305 (50)
[(PhTe)Ge(C2H3)]ϩ, 206 (30) [PhTeH]ϩ, 154 (42) [TeC2H3]ϩ, 77
(100) [Ph]ϩ. C24H20GeTe4 (891.01): calcd. C 32.32, H 2.24; found
C 32.03, H 2.51.
CCDC-190899 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge at
www.ccdc.ac.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge
CB2 1EZ, UK; fax: (internat.) ϩ44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
Acknowledgments
S.S. thanks the Fonds der Chemischen Industrie and the BMBF for
a Liebig-Fellowship. Financial support by the BMBF is gratefully
acknowledged. We are grateful to Prof. Dr. Martin Jansen for his
continuous support.
X-ray Crystallographic Study: The overall distribution of intensities
in the diffraction pattern of Ge(TePh)4 (3) can be explained assum-
ing a monoclinic lattice with a ϭ 12.8018(14), b ϭ 9.1842(9), c ϭ
23.690(3) A and β ϭ 105.458(8) and an additional twinning opera-
tion (Figure 4). Two twin individuals of different volume fractions
have to be taken into account. The twinning can be classified as
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1414
Eur. J. Inorg. Chem. 2003, 1411Ϫ1415

(PhSe)4Ge and (PhTe)4Ge from Activated Hydrogenated Germanium
FULL PAPER
ing system, Institute of Physics, Academy of the Czech Repub-
[17]
A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, A.
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[I02446]
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[18]
ˇ ˇ
ˇ
V. Petricek, M. Dusek, JANA2000 Ϫ crystallographic comput-
Eur. J. Inorg. Chem. 2003, 1411Ϫ1415
1415