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Synthesis and Structure Determination of Tellurium Tetracyanide Solvates Pseudopolymorphism of Te(CN)4 and TeF4.

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DOI: 10.1002/anie.200500168
Synthesis and Structure Determination of
Tellurium Tetracyanide Solvates:
Pseudopolymorphism of Te(CN)4 and TeF4**
Dieter Lentz* and Małgorzata Szwak
Until recently, tellurium dicyanide (1), known since 1908,[1]
was the only binary cyano compound of tellurium. Its
chemistry has remained almost unexplored, and only a few
spectroscopic data have been published so far.[2] Very
recently, Klap&tke et al. reported the crystal structure determination of 1 and the synthesis of an extremely unstable
tellurium tetracyanide, which was characterized on the basis
of a Raman spectrum and its decomposition into 1 and
cyanogens.[3] Extremely explosive tellurium tetraazide was
obtained by Klap&tke et al.[4] and Christe et al.;[5] again
structural data are missing. To the best of our knowledge
further homoleptic tellurium(iv) pseudohalides are unknown.
In the course of our studies of pseudohalogen compounds
of the chalcogens we have investigated the reaction of
tellurium tetrafluoride with trimethylsilyl cyanide in acetonitrile and THF, and have isolated the crystalline solvates of
tellurium tetracyanide [{Te(CN)4(CH3CN)2}n] (2 a) and
[{Te(CN)4(thf)3}n] (2 b) [Eq. (1)]. The compounds easily lose
the solvate molecules and decompose readily both as solids
and in solution to give 1 (d(125Te, THF) = 547 ppm, d(13C,
THF) = 86.6 ppm) and cyanogen (n(CN, gas) = 2157 cm 1).
Nevertheless, we succeeded in characterizing 2 b and the
mixed substituted compounds TeFx(CN)4 x (x = 4, 2, 1) by
Te, 19F, and 13C NMR spectroscopy at low temperature and
in eludicating the structures of 2 a and 2 b by single-crystal Xray diffraction (Figures 2–4).[6]
The 125Te NMR spectrum (Figure 1) of a mixture of TeF4
and less than four equivalents of TMSCN at 100 8C exhibits
[*] Priv.-Doz. Dr. D. Lentz, M. Szwak
Fachbereich Biologie, Chemie, Pharmazie
Institut f9r Chemie – Anorganische und Analytische Chemie
Freie Universit=t Berlin
Fabeckstrasse 34–36, 14195 Berlin (Germany)
Fax: (+ 49) 30-8385-2424
[**] This work was supported by the Deutsche Forschungsgemeinschaft.
Supporting information for this article is available on the WWW
under or from the author.
Angew. Chem. Int. Ed. 2005, 44, 5079 –5082
Figure 1. 125Te NMR spectrum of TeFx(CN)4 x (x = 4, 2, 1) at 100 8C
(top) and 2 b at 80 8C (bottom) in [D8]THF; dimethyl telluride was
used as an external reference.
a quintet at d = 1235.9 ppm (1J(125Te-19F) 2012 Hz) for TeF4,
a triplet at d = 815.9 ppm (1J(125Te-19F) 187 Hz) for
TeF2(CN)2, and a doublet at d = 332.1 ppm (1J(125Te-19F)
200 Hz) for TeF(CN)3. Correspondingly, the 19F NMR
spectrum exhibits three resonances with 125Te satellites at
d = 45.1 ppm (1J(125Te-19F) 2000 Hz) for TeF4, d =
12.8 ppm (1J(125Te-19F) 196 Hz) for TeF(CN)3, and d =
80.3 (1J(125Te-19F) 182 Hz) for TeF2(CN)2, respectively,
besides the signal of Me3SiF. Thus no intermolecular fluoride
exchange occurs on the NMR time scale at 100 8C. The small
F-125Te coupling constants of TeFx(CN)4 x (x = 1, 2) in
comparison with those of TeF4 and TeF2(OTeF5)2 (1J(125TeIV19
F) = 2812 Hz)[7] indicate that in these compounds the
fluorine atoms occupy the axial positions of the y-trigonalbipyramidal structure as predicted by the VSPER model and
as already been observed for TeF2(CF3)2[8] (1J(125Te-19F) =
234 Hz). In the case of TeF4, rapid intramolecular exchange
of the fluorine substituents takes place even at 100 8C. On
warming, the 125Te-19F scalar coupling disappears as a result of
fast intermolecular fluoride exchange. Because of the low
solubility of 2 b at 80 8C—a saturated solution contains
approximately 25–50 mmol 2 b in 0.7–1.0 mL [D8]THF—it was
difficult to obtain the 125Te and 13C NMR spectra. The 125Te
NMR spectrum of 2 b at 80 8C exhibits a single resonance at
d = 16.8 ppm which is shifted to d = 45.0 ppm on warming to
30 8C. The 13C NMR spectrum at 80 8C exhibits two signals
at d = 111.6 and 114.2 ppm, which can be assigned to the CN
substituents, besides the resonances of the solvent and
trimethylsilyl fluoride. No 125Te satellites could be detected
due to the bad signal-to-noise ratio. The low-temperature
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Raman spectrum ( 80 8C) of 2 b exhibits three bands for the
CN stretching modes at 2153 (m), 2178 (w), and 2185 cm 1
In the solid state the structures of 2 a and 2 b are very
different from the structure of an isolated Te(CN)4 molecule
calculated by ab initio methods[3] which has C2v symmetry (ytrigonal-bipyramidal structure including the electron lone
pair). Both 2 a and 2 b form a coordination polymer in the
shape of bent chains (Figures 2–4). Both compounds have
trigonal-pyramidal {Te(CN)3} units as building blocks, which
are connected by unsymmetrical CN bridges (TeC < TeN) to
form chains and expanding the coordination sphere of
tellurium. The Te C distances to the terminal CN groups
range from 2.086 to 2.217 D. In 2 a two short and one long
distance were found, whereas in 2 b one short and two slightly
longer distances were observed. The C-Te-C bond angles are
between 78 and 87 8 (one small and two larger angles).
The structures of 2 a and 2 b differ in the connection of the
{Te(CN)3} units and the coordination of the solvate molecules.
Figure 3. Polymer chain of 2 a (DIAMOND[16]).
Figure 4. Unit cell of 2 b (ORTEP,[15] 30 % ellipsoids, H atoms
Figure 2. Structure of one monomeric unit of 2 a (ORTEP,[15] 50 % ellipsoids, top) and 2 b (ORTEP,[15] 30 % ellipsoids, H atoms omitted,
bottom). Selected distances [E] and angles [8] in 2 a/2 b: Te1–C1
2.217(4)/2.166(7), Te1–C2 2.102(4)/2.157(7), Te1–C3 2.116(4)/
2.086(7), Te1–C4 2.397(3)/2.482(7), Te1–N4 2.601(4)/2.567(8); C4-Te1N4 91.0(1)/128.1(2), C1-Te1-C2 86.9(1)/78.2(3), C1-Te1-C3 79.1(1)/
84.4(3), C2-Te1-C3 86.0(1)/86.6(3), C1-Te1-C4 154.3(1)/148.2(3), C2Te1-N4 158.5(1)/149.1(3).
In 2 a the trigonal [Te(CN)3]-pyramid is completed by the
bridging ligand atoms C4 (dTe1-C4 = 2.397(3) D) und N4
(dTe1-N4 = 2.601(4) D) forming a strongly distorted square
pyramid as the coordination polyhedron. Both distances are
significantly larger than the sum of covalency radii.[9] The
bond angle to the bridging atoms (aC4-Te1-N4) is 91.0(1)8.
Finally the coordination sphere is completed by two acetonitrile molecules which have very large Te N distances
(2.728(4), 2.866(4) D). The principal coordination in 2 b is
rather similar; however, the square pyramid is even more
distorted, and the dTe1-C4 (2.482(7) D) is larger. Furthermore
the angle C4-Te1-N4 of 128.1(2) 8 is much larger. Three THF
molecules are coordinated to the tellurium atom over very
large distances (2.700(7)–2.774(7) D) by dipole interactions.
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2005, 44, 5079 –5082
In both structures the volume attributed to the lone pair is
unoccupied by solvate molecules and ligands. Both compounds 2 a and 2 b can be described as [Te(CN)3]CN with the
ionic character being more pronounced in 2 b.
For comparison, the structures of the previously not
characterized solvates [TeF4(thf)2] (3 a)[6] (Figure 5) and
Figure 6. Unit cell of 3 b (ORTEP,[15] 50 % ellipsoids, view along 1̄00).
Selected distances [E] and angles [8]: Te–F(apical) 1.846(3)–1.847(4),
Te–F(basal) 1.873(4)–1.886(4), Te–F(Br9cke) 2.171(4)–2.23(4), Te1–C(arom.) 3.151(7)–3.449(7), Te2–C(arom.) 3.202(7)–3.356(7); F5-Te2-F9
95.33(9), F4-Te1-F5 100.39(9).
Figure 5. Crystal structure of 3 a (ORTEP,[15] 50 % ellipsoids). Selected
distances [E] and angles [8]: Te1–F1 1.966(2), Te1–F2 1.941(2), Te1–F3
1.862(2), Te1–F4 1.867(2), Te1–O1 2.448(2), Te1–O2 2.697; F1-Te1-F2
161.33(7), F3-Te1-F4 86.98(6), F1-Te-F3 80.97(6), F1-Te1-F4 84.74(7),
F2-Te1-F3 82.15(7), F2-Te1-F4 86.45, F3-Te1-O2 155.89, F4-Fe1-O1
160.89(7), O1-T1-O2 122.95.
[{TeF4(toluene)}n] (3 b)[6] (Figure 6) were elucidated by Xray crystallography. Unexpectedly, 3 a consists of monomeric
C2v-symmetric TeF4 units in accordance to the y-trigonalbipyramidal geometry expected by the VSEPR model and in
contrast to 2 a, 2 b, and 3 b. As expected, the distances to the
axial fluorine atoms are about 0.1 D longer than those to the
equatorial ones. Due to the steric influence of the electron
lone pair, the angles aF1-Te1-F2 and aF3-Te1-F4 are significantly
smaller than 180 and 1208, respectively. The distance dTe1-O1,
(2.448(2) D) is shorter than the distance dTe1-O2 (2.697(2) D)
and the comparable Te O distances in 2 b.
The structures of 2 a and 2 b can be compared to those of
3 b (Figure 6) and tellurium tetrafluoride,[10] in which trigonalpyramidal TeF3 units are completed by two bridging fluorine
atoms in cis position forming a square pyramid. The nearest
distances of the aromatic carbon atoms to the tellurium atom
range from 3.151(7) to 3.449(7) D. Thus these distances are
shorter than the sum of van der Waals radii (3.8 D).[11]
Tellurium tetrachloride forms a tetramer with a heterocubane
structure which is formed by connecting four TeCl3 units with
bridging chlorine atoms.[12]
It is surprising that with the same solvate molecule,
tetrahydofuran, TeF4 forms a pseudopolymorphic structure
with isolated TeF4 units, whereas Te(CN)4 forms a coordination polymer that can be better described as [{Te(CN)3(thf)3Angew. Chem. Int. Ed. 2005, 44, 5079 –5082
(m-CN)}n]. Further studies on the influence of solvate
molecules on the pseudopolymorphic structures[13] of tellurium halides and pseudohalides are underway in our group.
Experimental Section
All reactions were carried out in carefully dried apparatus under an
atmosphere of dry argon or under vacuum. TeF4 was handled in an
automatic drybox. Volatile solvents were carefully dried and condensed into the reaction vessel using a glass vacuum line system.
2 a: Acetonitrile (5 mL) was condensed into a 50-mL Schlenk
flask containing TeF4 (0.2 g, 1 mmol), which was dissolved by
warming the mixture to ambient temperature. Acetonitrile (4 mL)
was condensed into a 50-mL Schlenk flask containing TMSCN
(0.45 g, 4.5 mmol). After warming to ambient temperature both
solutions were cooled again to 35 8C. After flushing with argon the
TeF4 solution was added to the TMSCN solution by a Teflon tube. The
reaction mixture was allowed to warm slowly to 6 8C with stirring.
The colorless solution was placed in a refrigerator ( 30 8C). After
12 h 2 a was obtained as colorless platelets.
2 b: THF (15 mL) was condensed into a 50-mL Schlenk flask
containing TeF4 (0.1 g, 0.5 mmol), which was dissolved by warming
the mixture to ambient temperature. THF (20 mL) was condensed
into a 100-mL Schlenk flask containing TMSCN (0.25 g, 2.5 mmol),
which was dissolved at ambient temperature, and the mixture was
cooled to 68 8C. After flushing with argon the TeF4 solution ( 40 8C)
was added within 5 min to the stirred TMSCN solution using a Teflon
tube. The reaction mixture was warmed slowly to 6 8C (30 min
between 10 and 6 8C). Most of the solvent and the trimethylsilyl
fluoride (19F NMR, decett at d = 157 ppm) formed were removed
under vacuum at 68 8C. After warming to 8 8C to form a colorless
solution, the flask and the cold bath were placed in a refrigerator
( 84 8C). Colorless needle-shaped crystals of 2 b formed overnight.
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3 a: Crystals of 3 a were first obtained from the attempted
reaction of TeF4 with one equivalent of TMSCN in toluene after
crystallization of the nonvolatile residue from THF at 80 8C. The
compound can be obtained directly by crystallization of TeF4 from
3 b: Crystals of 3 b were obtained by slowly cooling a solution of
TeF4 (0.1 g, 0.5 mmol) in 1.5 mL of toluene to 84 8C.
NMR spectra: Approximately 5 to 10 mg of TeF4 was filled into 5mm NMR tube equipped with a magnetic stirring bar. Using a glass
vacuum line 0.5 mL of [D8]THF was condensed into the tube by
cooling with liquid nitrogen. After warming to ambient temperature,
the TeF4 dissolved completely. A further 0.3 mL of THF and
approximately 25 mg of TMSCN were condensed by cooling with
liquid nitrogen. The reaction mixture was warmed slowly to 6 8C
with stirring. The stirring bar was removed from the solution using a
magnet; the sample was cooled with liquid nitrogen and sealed under
vacuum. The samples were stored at 84 8C before the measurement.
NMR spectra were recorded using a JEOL Lambda 400 multinuclear
NMR spectrometer at temperatures between 100 and 20 8C.
Received: January 17, 2005
Revised: April 7, 2005
Published online: July 20, 2005
Keywords: cyanides · pseudohalogens · pseudopolymorphism ·
solid-state structures · tellurium
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[3] T. M. Klap&tke, B. Krumm, J. C. GJlvez-Ruiz, H. N&th, I.
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[6] Crystal structure analysis: Colorless crystals of 2 a, 2 b, 3 a, and
3 b were obtained as described above. A few crystals were
transferred with a pipette onto a piece of filter paper, which was
mounted in a stream of cold nitrogen onto an apparatus
described in the literature.[14] A suitable crystal was selected
using a microscope, mounted onto a glass fiber using silicon
grease, and transferred into the cold gas stream of a diffractometer without interrupting the cooling. BRUKER-AXS,
SMART CCD, MoKa, l = 0.71073 D, T = 173 K. 2 a: C8H6N6Te,
Mw = 313.79, monoclinic, P21, a = 6.006(1), b = 8.328(2), c =
11.976(2) D, b = 92.097(8)8, V = 598.6(2) D3, Z = 2, 1calcd =
1.741 Mg m 3, m(MoKa) = 2.464 mm 1, 7471 measured reflections, 3597 [R(int) = 0.014] crystallographically independent
reflections, empirical absorption correction (SADABS[17]),
least squares refinement (SHELXL-97[18]), anisotropic temperature factors, H atoms isotropic on calculated positions (riding
model), 138 refined parameters, GOOF = 1.083, R1 = 0.0188 [I >
2s(I)], wR2 = 0.0488 (all data), 1(max./min) = 0.996 and
0.383 e D 3, Flack parameter 0.00(2); a displacement of C4
and N4 converges at R1 = 0.0200, therefore the assignment of the
nitrogen and carbon atoms is unambiguous. 2 b: C16H24N4O3Te,
Mw = 447.99, monoclinic, P21/c, a = 8.473(2), b = 11.030(3), c =
20.505(6) D, b = 92.627(7)8, V = 1914.3(9) D3, Z = 4, 1calcd =
1.554 Mg m 3, m(MoKa) = 1.574 mm 1, 17 163 measured reflections, 3927 [R(int) = 0.113] crystallographically independent
reflections, least squares refinement (SHELXL-97[18]), anisotropic temperature factors, H atoms isotropic on calculated
positions (riding model), 217 refined parameters, GOOF =
1.035, R1 = 0.0566 [I > 2s(I)], wR2 = 0.1474 (all data), 1(max./
min) = 1.416 and 0.851 e D 3, no attempt was made to refine
the disorder of some of the C atoms of the THF molecules which
resulted in very large anisotropic displacement parameters on
split-atom positions. 3 a: C8H16F4O2Te, Mw = 347.81, triclinic, P1̄,
a = 6.816(2), b = 9.390(2), c = 10.465(2) D, a = 109.140(4), b =
101.744(6), g = 100.421(5)8, V = 596.9(2) D3, Z = 2, 1calcd =
1.935 Mg m 3, m(MoKa) = 2.524 mm 1, 7429 measured reflections, 3579 [R(int) = 0.0134] crystallographically independent
reflections, empirical absorption correction (SADABS[17]), least
squares refinement (SHELXL-97[18]), anisotropic temperature
factors, H atoms isotropic on calculated positions (riding model),
137 refined parameters, GOOF = 1.059, R1 = 0.0191 [I > 2s(I)],
wR2 = 0.0475 (all data), 1(max./min) = 0.984 and 0.501 e D 3.
3 b: C7H8F4O2Te, Mw = 295.73, triclinic, P1̄, a = 7.583(2),
b = 10.446(2), c = 13.131(3) D, a = 107.632(4), b = 96.929(4),
g = 108.243(4)8, V = 914.4(3) D3, Z = 4, 1calcd = 2.148 Mg m 3,
m(MoKa) = 3.260 mm 1, 11 412 measured reflections, [R(int) =
0.0239] crystallographically independent reflections, empirical
absorption correction (SADABS[17]), least squares refinement
(SHELXL-97[18]), anisotropic temperature factors, H atoms
isotropic on calculated positions (riding model), 222 refined
parameters, GOOF = 1.166, R1 = 0.0384 [I > 2s(I)], wR2 =
0.0735 (all data), 1(max./min) = 1.437 and
0.903 e D 3.
CCDC-259967 (2 a), CCDC-259968 (2 b), CCDC-259969 (3 a),
and CCDC-260727 (3 b) contain the supplementary crystallographic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
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2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2005, 44, 5079 –5082
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solvated, structure, synthesis, determination, tef4, pseudopolymorphism, tetracyanide, tellurium
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