Syntheses and characterization of some mixed Te/Se polychalcogenide anions [TemSen]2-

Article abstract of DOI:10.1021/ic040026h

Several mixed Te/Se polychalcogenide anions [Te_mSe _n]^2- were synthesized at 293 K by reactions between Te_n^2- and Se_n^2- anions in N,N-dimethylformamide (DMF) in the presence of different-size ammonium or phosphonium cations, in some cases in the presence of metal species. The structures of these anions were determined by single-crystal X-ray diffraction methods. The crystal structures of (NEt₄]₂[Te ₃Se₆] (1) and [NEt₄]₂[Te ₃Se₇] (2) consist, respectively, of one-dimensional infinite _∞¹[Te₃Se₆ ^2-] and _∞¹[Te₃Se ₇^2-] anionic chains separated by NEt₄ ⁺ cations. In compound 1, each chain comprises Te₃Se ₅ eight-membered rings bridged by Se atoms. The Te₃Se ₅ ring has an open book conformation. The NMR spectrum of a DMF solution of [NEt₄]₂[Te₃Se₆] crystals at 223 K shows ⁷⁷Se resonances at δ = 290, 349, and 771 ppm and a single ¹²⁵Te resonance at δ = 944.7 ppm. In compound 2, each chain comprises Te₃Se₆ five- and six-membered rings bridged by Se atoms. The Te₃Se₆ ring can be regarded as an inorganic analogue of bicyclononane. The anion of [PPh₄]₂[Te₂Se₂] (4) contains a Se-Te-Te-Se chain with the terminal Se atoms trans to one another. The new compounds [PPN]₂[TeSe₁₀] (3), [NMe₄] ₂[TeSe₃]·DMF (5), and [NEt₄] ₂[TeSe₃] (6) contain known anions.

Full text of DOI:10.1021/ic040026h

Inorg. Chem. 2004, 43, 5436−5441
Syntheses and Characterization of Some Mixed Te/Se Polychalcogenide
Anions [TemSen]2-
Perumal Sekar and James A. Ibers*
Department of Chemistry, Northwestern UniVersity, 2145 Sheridan Road,
EVanston, Illinois 60208-3113
Received February 18, 2004
Several mixed Te/Se polychalcogenide anions [TemSen]2- were synthesized at 293 K by reactions between Ten2-and
Sen2- anions in N,N-dimethylformamide (DMF) in the presence of different-size ammonium or phosphonium cations,
in some cases in the presence of metal species. The structures of these anions were determined by single-crystal
X-ray diffraction methods. The crystal structures of [NEt4]2[Te3Se6] (1) and [NEt4]2[Te3Se7] (2) consist, respectively,
1
∞
1
∞
of one-dimensional infinite [Te3Se62-] and [Te3Se72-] anionic chains separated by NEt4+ cations. In compound
1, each chain comprises Te3Se5 eight-membered rings bridged by Se atoms. The Te3Se5 ring has an “open book”
conformation. The NMR spectrum of a DMF solution of [NEt4]2[Te3Se6] crystals at 223 K shows 77Se resonances
at δ ) 290, 349, and 771 ppm and a single 125Te resonance at δ ) 944.7 ppm. In compound 2, each chain
comprises Te3Se6 five- and six-membered rings bridged by Se atoms. The Te3Se6 ring can be regarded as an
inorganic analogue of bicyclononane. The anion of [PPh4]2[Te2Se2] (4) contains a Se−Te−Te−Se chain with the
terminal Se atoms trans to one another. The new compounds [PPN] [TeSe10] (3), [NMe4]2[TeSe3]‚DMF (5), and
2
[NEt4]2[TeSe3] (6) contain known anions.
Introduction
prepared by high-temperature solid-state or solventothermal
or solution methods, contain TeII or TeIV centers bonded to
Sen species (n ) 1, 2, or 5). We recently reported the
Although many polytelluride and polyselenide anions have
been isolated and their structures characterized by single-
crystal X-ray difffraction methods,1-10 the known mixed
Te/Se polychalcogenide anions [TemSen]p- are limited to
[TeSe2]2-,11 [TeSe3]2-,11,12 [Te(Se5)2]2-,13 [Te(Se5)3]4-,14 and
[{Te(Se2)}2(µ2-(Se2)]2-.14 These anions, which have been
2-
compound [PPh4]2[NEt4][CuTe7], which was synthesized
from the reaction in DMF of CuCl with a polytelluride
solution.15 A novel mixed Te/Se anion [Te3Se7]2- containing
five- and six-membered rings was isolated when we at-
tempted the synthesis of a hypothetical mixed [CuTe7-nSen]3-
anion by addition of polyselenide to the reaction that afforded
[CuTe7]3-. Also two other mixed Te/Se anions were isolated
from reactions of other metal sources such as HgCl2 and
Cr(CO)6 with polytelluride/polyselenide solutions in DMF.
We therefore decided to study the reactions of polyselenide
and polytelluride anions with one another in the presence of
different-size cations, in some instances in the presence of
metal sources. Here, we report the syntheses by such
reactions of six new mixed Te/Se compounds. Three of these
* To whom correspondence should be addressed. E-mail:
ibers@chem.northwestern.edu.
(1) Brese, N. E.; Randall, C. R.; Ibers, J. A. Inorg. Chem. 1988, 27, 940-
943.
(2) Sheldrick, W. S.; Braunbeck, H. G. Z. Naturforsch. B: Anorg. Chem.
Org. Chem. 1989, 44, 1397-1401.
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1990, 29, 390-391.
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Chem. Sci. 1991, 46, 63-67.
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593-601.
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Fenske, D. Z. Anorg. Allg. Chem. 1993, 619, 1247-1256.
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205.
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581.
5436 Inorganic Chemistry, Vol. 43, No. 17, 2004
10.1021/ic040026h CCC: $27.50 © 2004 American Chemical Society
Published on Web 07/22/2004

Mixed Te/Se Polychalcogenide Anions
contain previously unknown [TemSen]2- anions; among these
anions, two comprise infinite chains of Te/Se rings.
2.00 mmol) were dissolved in DMF (20 mL). The reaction mixture
was stirred at 293 K for 3 days. Only few black crystals of
[PPh4]2[Te2Se2] formed after the solution was layered with Et2O
(10 mL) at 293 K. Attempts to isolate compound 4 without
Cr(CO)6 in the reaction mixture afforded the known compound
[PPh4]2[TeSe10],7 as deduced from a crystal-structure determination.
(Details can be found in the Supporting Information.) The yield of
[PPh4]2[TeSe10] was 1.06 g, 0.66 mmol, 66% (based on PPh4Br).
Experimental Section
General Procedures. All manipulations were performed under
an inert atmosphere of N2 with the use of standard Schlenk-line
techniques or under Ar in a glovebox. Solvents were dried, distilled,
and degassed under N2 before use. Anhydrous N,N-dimethylfor-
mamide (DMF), purchased from Fisher Chemical, Fair Lawn, NJ,
was stored over activated molecular sieves and degassed with dry
N2 before use. Anhydrous diethyl ether (Et2O) and tetrahydrofuran
(THF) were distilled from Na and benzophenone. Compounds Li2Q
(Q ) Se, Te) were prepared from the stoichiometric reactions of
Li and Q in liquid NH3. CuCl (Strem Chemical Co., Newburyport,
MA), Cr(CO)6 (Pressure Chemical Co., Pittsburgh, PA), and PEt3
(Aldrich Chemical Co., Milwaukee, WI) were used as received.
Energy-dispersive analyses by X-ray (EDAX) were performed with
the use of a Hitachi 3500 scanning electron microscope equipped
with an X-ray detector. 77Se and 125Te NMR spectra were recorded
on an INOVA 400-MHz spectrometer with a 10-mm broadband
NMR probe with DMF-d7/DMF as the solvent. 77Se chemical shifts,
in ppm, were recorded at 76.287 MHz and referenced to an external
standard of a saturated solution of Ph2Se2 in CD2Cl2 (set to 460
ppm). 125Te chemical shifts, in ppm, were recorded at 126.234 MHz
and referenced to an external standard of a saturated solution of
Ph2Te2 in CD2Cl2 (set to 422 ppm). Electrospray mass spectra were
obtained on a Micromass Quattro II instrument. Elemental analyses
were performed by Oneida Research Services, Whitesboro, NY.
Synthesis of [NEt4]2[Te3Se6] (1). Li2Se (0.217 g, 2.34 mmol),
Se (0.552 g, 6.99 mmol), Li2Te (0.142 g, 1.00 mmol), Te (0.383 g,
3.00 mmol), and NEt4Cl (0.331 g, 2.00 mmol) were dissolved in
DMF (20 mL). The resulting yellow-green solution was stirred at
293 K for 2 h, filtered, and then layered with Et2O (10 mL). Black
crystals of [NEt4]2[Te3Se6] grew overnight at 293 K. Yield: 850
mg, 0.76 mmol, 76% (based on NEt4Cl). 77Se NMR (400 MHz,
DMF, 223 K, Ph2Se2): δ ) 290, 349, 771 ppm. 125Te NMR (400
MHz, DMF, 223 K, Ph2Te2): δ ) 944.7 ppm. ESI-MS (DMF)
m/z (%): 494 (70) [M+ - 4Se], 288 (24) [M+ - 5Se + Te], 238
(20) [M+ - 4Se + 2Te]. Anal. Calcd for C16H40N2Se6Te3: C 17.20,
H 3.61, N 2.51%. Found: C 17.13, H 3.43, N 2.41%.
Synthesis of [NMe4]2[TeSe3]‚DMF (5). Li2Se (0.217 g, 2.34
mmol), Se (0.552 g, 6.99 mmol), Li2Te (0.142 g, 1.00 mmol), Te
(0.383 g, 3.00 mmol), and NMe4Cl (0.219 g, 2.00 mmol) were
dissolved in DMF (20 mL). Red crystals of [NMe4]2[TeSe3]‚DMF
grew overnight at 293 K. Yield: 0.382 g, 0.65 mmol, 65% (based
on NMe4Cl). Anal. Calcd for C11H31N3OSe3Te: C 22.55, H 5.33,
N 7.17%. Found: C 22.63, H 4.96, N 7.31%.
Synthesis of [NEt4]2[TeSe3] (6). Li2Se (0.217 g, 2.34 mmol),
Se (0.552 g, 6.99 mmol), Li2Te (0.142 g, 1.00 mmol), Te (0.383 g,
3.00 mmol), NEt4Cl (0.166 g, 1.00 mmol), and PPh4Br (0.419 g,
1.00 mmol) were dissolved in DMF (20 mL). Red crystals of
[NEt4]2[TeSe3] grew overnight at 293 K. Yield: 0.437 g, 0.70 mmol,
70% (based on NEt4Cl). 77Se NMR (400 MHz, DMF, 223 K,
Ph2Se2): δ ) 477 ppm. 125Te NMR (400 MHz, DMF, 223 K,
Ph2Te2): δ ) 1088 ppm. Anal. Calcd for C16H40N2Se3Te: C 30.75,
H 6.45, N 4.48%. Found: C 30.83, H 6.63, N 4.54%.
Crystallography. Single-crystal X-ray diffraction data were
collected with the use of the program SMART16 on a Bruker Smart
1000 CCD diffractometer16 at 153 K with monochromatized Mo
KR radiation (λ ) 0.71073 Å). The diffracted intensities generated
by a scan of 0.3° in ω were recorded on four sets of 606 frames at
æ settings of 0°, 90°, 180°, and 270°, with an additional 50 frames
at æ ) 0°. The exposure times (s/frame) were 10 (for 4 and 6), 15
(for 1, 3, and 5), and 20 (for 2). Cell refinement and data reduction
were carried out with the use of the program SAINT.16 There was
no evidence of twinning in any of the data sets. Face-indexed
absorption corrections were made with the program XPREP.17 Then
the program SADABS was employed to make incident beam and
decay corrections.16 The structures were solved by direct methods
with the program SHELXS and refined by full-matrix least-squares
techniques with the program SHELXL in the SHELXTL-97 suite.17
Hydrogen atoms were generated in calculated positions and
constrained with the use of a riding model. The final models
involved anisotropic displacement parameters for all non-hydrogen
atoms. Except in the following instances, such refinements were
straightforward. For compound 1, there is Te/Se disorder at one
position, as judged both by bond distances and by refinement the
Te/Se occupancy, which converged to 0.53(4) and was subsequently
Synthesis of [NEt4]2[Te3Se7] (2). Li2Se (0.217 g, 2.34 mmol),
Se (0.552 g, 6.99 mmol), Li2Te (0.142 g, 1.00 mmol), Te (0.383 g,
3.00 mmol), CuCl (0.099 g, 1 mmol), PEt3 (0.2 mL), NEt4Cl (0.166
g, 1.00 mmol), and PPh4Br (0.419 g, 1.00 mmol) were dissolved
in DMF (20 mL). Black needles of [NEt4]2[Te3Se7] grew over a
few weeks at 278 K. Yield: 0.2 g, 0.17 mmol, 33% (based on
NEt4Cl). The synthesis could not be repeated successfully, either
from the above reaction or with the addition of PPh4Br to the
reaction system that afforded compound 1.
+
set to 0.50. There are two independent NEt4 cations in the
asymmetric unit, each lying on a mirror plane. The independent
atoms in these cations were refined with a series of restraints.
+
Compound 4 has two independent [Te2Se2]2- anions and four PPh4
Synthesis of [PPN]2[TeSe10] (3). Compound 3 was synthesized
in a manner similar to the synthesis of compound 1, but with the
substitution of [PPN]Cl (PPN ) bis(triphenylphosphine)iminium)
(1.148 g, 2.00 mmol) for NEt4Cl. When the solution was layered
with Et2O (10 mL), black crystals of [PPN]2[TeSe10] grew over-
night at 293 K. Layering additional Et2O (10 mL) to the parent
solution gave a second batch of [PPN]2[TeSe10] crystals. Total
yield: 1.27 g, 0.64 mmol, 64% (based on [PPN]Cl). Anal. Calcd
for C72H60N2P4Se10Te: C 43.36, H 3.03, N 1.40%. Found: C 43.60,
H 3.08, N 1.34%.
cations in the asymmetric unit. One of these anions is disordered
and could not be modeled in a totally satisfactory manner; atom
Te3 from the second [Te2Se2]2- anion occupies two different sites
in approximately a 0.62(1):0.38(1) manner.
Selected crystallographic data for compounds 1-6 are listed in
Table 1. Further crystallographic details can be found in the Sup-
porting Information.
(16) Bruker. SMART Version 5.054 Data Collection and SAINT-Plus
Version 6.45 Data Processing Software for the SMART System;
Bruker Analytical X-ray Instruments, Inc., Madison, WI, 2003.
(17) Sheldrick, G. M. SHELXTL DOS/Windows/NT Version 6.14; Bruker
Analytical X-ray Instruments, Inc., Madison, WI, 2003.
Synthesis of [ PPh4]2[Te2Se2] (4). Li2Se (0.217 g, 2.34 mmol),
Se (0.552 g, 6.99 mmol), Li2Te (0.142 g, 1.00 mmol), Te (0.383 g,
3.00 mmol), Cr(CO)6 (0.220 g, 1 mmol), and PPh4Br (0.838 g,
Inorganic Chemistry, Vol. 43, No. 17, 2004 5437

Sekar and Ibers
Table 1. Selected Crystallographic Data
[NEt4]2[Te3Se6]
[NEt4]2[Te3Se7]
[PPN]2[TeSe10]
[PPh4]2[Te2Se2]
[NMe4]2[TeSe3]‚DMF
(5)
[NEt4]2[TeSe3]
(1)
(2)
(3)
(4)
(6)
formula
fw
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
C16H40N2Se6Te3
1117.06
Pnma
14.4975(8)
13.1068(7)
15.8270(8)
90
90
90
3007.4(3)
4
C16H40N2Se7Te3
1196.02
Pbca
14.811(5)
12.795(4)
32.802(11)
90
90
90
6216(3)
8
C72H60N2P4Se10Te
1994.30
P21/c
11.0540(8)
18.427(1)
17.844(1)
90
95.441(1)
90
3618.3(5)
2
C96H80P4Se4Te4
2183.72
P1h
C11H31N3OSe3Te
585.87
P21/c
15.601(1)
11.7941(8)
11.8795(8)
90
107.992(1)
90
2079.0(2)
4
C16H40N2Se3Te
624.98
P21/c
8.5056(7)
13.467(1)
20.889(2)
11.346(1)
19.420(2)
20.000(3)
89.402(2)
76.282(2)
88.457(2)
4279.3(9)
2
97.097(1)
2374.5(3)
4
T (K)
153
2.467
101.60
0.024
0.060
153
2.556
110.03
0.065
0.208
153
1.830
55.72
0.059
153
1.695
31.72
0.086
153
1.872
66.82
0.029
153
F
calcd (g/cm3)
1.748
58.52
0.026
0.070
µ(Mo KR) (cm-1
R1(F)a
)
Rw(F2)b
0.199
0.254
0.071
2
2
2
4
2
2
2
2
2
a R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. b Rw(Fo ) ) [∑w(Fo - Fc )2/∑wFo ]1/2; w-1 ) σ2(Fo ) + (qFo )2 for Fo > 0; w-1 ) σ2(Fo ) for Fo e 0; q ) 0.03 for
1, 5, and 6; q ) 0.1 for 2, 3, and 4.
Figure 1. Sketch of part of the infinite chain of the 1 [Te3Se62-] anion in
[NEt4]2[Te3Se6] (1). The black circles are Se; the whit∞e circles are Te. The
disorder, which presumably results from the random “flipping” of the
Te3Se5 rings, is not shown.
Results
Syntheses. Six new mixed Te/Se compounds (1-6) re-
2-
sulted from reactions at 293 K of Ten2-and Sen anions in
N,N-dimethylformamide (DMF) in the presence of different-
Figure 2. Te3Se5 ring in [NEt4]2[Te3Se6] (1). Primed atoms are related to
size ammonium or phosphonium cations and, in some in-
stances, the presence of metal sources. With the exception
of compound 2, the syntheses are reproducible; the yields
are good except for that of compound 4. Three of these
compounds contain previously unknown [TemSen]2- anions.
The compounds are readily soluble in DMF to afford very
air-sensitive solutions. However, crystals of these materials
are modestly air stable.
the corresponding unprimed atoms by the mirror plane through atoms Se3,
Te3, and Te2. Displacement ellipsoids are drawn at the 75% probability
level. Bond distances are shown. Bond angles are Se3-Te3-Se2,
88.24(1)°; Se2-Te3-Se2′, 176.43(1)°; Se3-Te2-Se4, 84.22(1)°; Se4-
Te2-Se4′, 167.89(2)°; Se4-Se1/Te1-Se2, 106.99(1)°; Se1/Te1-Se2-Te3,
97.48(1)°; Te3-Se3-Te2, 104.67(2)°; Se1/Te1-Se4-Te2, 94.36(1)°.
an “open book” conformation. The eight-membered rings
in the chain alternate in their orientation (Figure 1).
Bond distances and angles are shown in Figure 2. The
Te-Se distances not affected by disorder are typical of
Te-Se single bonds, for example, 2.501(1) Å in [TeSe2]2-.11
The (Se1/Te1)-Se2 and (Se1/Te1)-Se4 bond lengths at 2.43
Å are a superposition of such a Te-Se single bond with a
Se-Se single bond (typically, about 2.34 Å in length).
[NEt4]2[Te3Se6] is diamagnetic in the range 5-300 K. The
77Se NMR spectrum of a DMF solution of [NEt4]2[Te3Se6]
crystals at 223 K shows resonances at δ ) 290, 349, and
771 ppm, and the 125Te NMR spectrum of the same solution
shows a single resonance at δ ) 944.7 ppm. From the solid-
state structure (Figure 1), three 77Se and two 125Te resonances
are expected. However, it is improbable that the infinite chain
Structure of [NEt4]2[Te3Se6] (1). The crystal structure
of [NEt4]2[Te3Se6] consists of one-dimensional infinite
1
∞[Te3Se62-] anionic chains separated by NEt4 cations.
Each chain comprises Te3Se5 eight-membered rings bridged
by Se atoms (Figure 1). There is a crystallographically
imposed mirror plane passing through atoms Se3, Te2, and
Te3. From the refinement of the X-ray data, the 1 position
is occupied 50% by Se1 and 50% by Te1 (Figure 2). This
disorder results from the random “flipping” of the Te3Se6
rings along the chain and not from cocrystallization of the
hypothetical species [NEt4]2[Te2Se7] and [NEt4]2[Te4Se5],
because such cocrystallization would not be expected to
comprise 50% of each species. The Te3, Se2, Se2′, Te2, Se4,
Se4′ portion of the Te3Se5 ring is essentially planar (mean
deviation, 0.055 Å), with atoms Se1 and Te1 1.35 Å from
this plane. Thus, the Te3Se5 ring can be regarded as having
+
persists in solution. The 77Se resonances fall in the same
region as those reported for the [TeSe3]2-,11,18 [MTenSe8-n
]
2-
(M ) Zn, Cd, Hg; n ) 0-4),19 and [Sen]2- (n ) 2-6)18,20
5438 Inorganic Chemistry, Vol. 43, No. 17, 2004

Mixed Te/Se Polychalcogenide Anions
single bonds. This is the first example of a structure of a
mixed Se/Te compound containing fused five- and six-
membered rings.
Structure of [PPN]2[TeSe10] (3). The crystal structure of
3 contains a [TeSe10]2- anion. This anion has been reported
previously in [K(2,2,2-crypt)]2[TeSe10],13 [Ba(2,2,2-crypt)-
(en)][TeSe10]‚en0.5,13 and [PPh4]2[TeSe10].7 The structure of
[TeSe10]2- anion consists of two similar [Se5]2- chains
coordinated to a TeII center in a square-planar geometry to
form a spirocyclic ring. The [TeSe10]2- anion possesses a
crystallographically imposed inversion symmetry. The
Te-Se bond distances (Table 2) are longer than the typical
Te-Se single bond distance (2.53 Å),21 but comparable to
those in the related [TeSe10]2- anions.13
Figure 3. Sketch of part of the infinite chain of the 1 [Te3Se72-] anion in
[NEt4]2[Te3Se7] (2). The black circles are Se; the wh∞ite circles are Te.
Structure of [PPh4]2[Te2Se2] (4). The crystal structure
of 4 contains a Se-Te-Te-Se chain with the terminal Se
atoms trans to one another. This anion is analogous to the
2-
homopolychalcogenide anions Se4 and Te42-. The two
independent [Te2Se2]2- anions in the unit cell are shown in
Figure 6. The [Te2Se2]2- anion has been proposed as one of
the intermediates in the scheme of converting a polytelluride
solution and elemental Se into [TeSe3]2-.12,18 77Se and 125Te
NMR data have been reported for this anion.18
Figure 4. Sketch of the fused rings in [NEt4]2[Te3Se7] (2). The black
circles are Se; the white circles are Te.
Structures of [NMe4]2[TeSe3]‚DMF (5) and [NEt4]2-
[TeSe3] (6). The crystal structures of 5 and 6 contain the
trigonal-pyramidal [TeSe3]2- anion. The Te-Se bond dis-
tances (Table 3) are shorter than a typical Te-Se single bond
distance (2.53 Å),21 but comparable to those in related salts
containing the [TeSe3]2- anion.11 The 77Se (δ ) 477 ppm)
and 125Te (δ ) 1088 ppm) NMR resonances of 6 at 223 K
are very close to the reported value for [K(2,2,2-crypt)]2-
[TeSe3]11 (77Se (δ ) 468 ppm) and 125Te (δ ) 1087 ppm)).
Figure 5. Te3Se6 ring in [NEt4]2[Te3Se7] (2). Displacement ellipsoids are
drawn at the 50% probability level. Bond distances are shown, except for
Se5-Se7′ ) 2.345(2) Å. Bond angles are Se1-Te1-Te2, 99.54(6)°; Se1-
Se2-Se3, 120.59(9)°; Se1-Se2-Se4, 118.22(9)°; Se2-Se1-Te1, 97.17-
(8)°; Se2-Se3-Te3, 100.77(7)°; Se2-Se4-Te2, 100.21(7)°; Se2-Se4-
Se5, 94.53(8)°; Se3-Se2-Se4, 121.13(9)°; Se3-Te3-Se6, 106.20(6)°;
Se3-Te3-Se7, 103.05(6)°; Se4-Te2-Te1, 95.67(5)°; Se4-Se5-Se6,
119.70(8)°; Se5-Se4-Te2, 102.93(7)°; Se5-Se6-Te3, 101.44(7)°; Se6-
Te3-Se7, 101.28(6)°.
Discussion
From crystallographic studies, rings of the Q8 type are
well-known for Q ) S and Se, but are very rare for Q ) Te.
22
Te8 rings are found in Cs3Te22 and Cs4Te28.23 From
spectroscopic studies, eight-membered rings of the Q8 type
are known for S/Se,24-27 S/Te,28 and 1,2-TeSeS6.28 Although
among the polycations a number of Te/Se ring systems
exist,29 such rings are far less common among the polyan-
ions.10 For example, the [Te8]2- anion does not exhibit a
ring structure, but rather comprises a Te2+ center coordi-
nated in a distorted square-planar fashion to [Te4]2- and
[Te3]2- chelating rings.30 Among Te/Se systems, disordered
anions. The observed 125Te NMR resonance at δ ) 944.7
ppm compares favorably with that of δ ) 1087 ppm for the
[TeSe3]2- anion.11
Structure of [NEt4]2[Te3Se7] (2). The crystal structure
of [NEt4]2[Te3Se7] consists of one-dimensional infinite
1
∞[Te3Se72-] anionic chains separated by NEt4 cations.
Each chain comprises fused five- and six-membered rings
of composition Te3Se6 bridged by Se atoms (Figure 3). These
rings alternate in their orientation along the chain. The
Te3Se6 ring (Figure 4) can be regarded as an inorganic
analogue of bicyclononane. The bridging Se atom in the
chain is bonded to a Te atom of the six-membered ring and
a Se atom of the six-membered ring from the next repeating
unit. Bond distances and angles are shown in Figure 5. The
Se-Se, Se-Te, and Te-Te bond distances are typical of
+
(21) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960.
(22) Sheldrick, W. S.; Wachhold, M. Angew. Chem., Int. Ed. Engl. 1995,
34, 450-451.
(23) Sheldrick, W. S.; Wachhold, M. J. Chem. Soc., Chem. Commun. 1996,
607-608.
(24) Laitinen, R. S.; Pakkanen, T. A. J. Chem. Soc., Chem. Commun. 1986,
1381-1382.
(25) Laitinen, R. S.; Pakkanen, T. A. Inorg. Chem. 1987, 26, 2598-2603.
(26) Chivers, T.; Laitinen, R. S.; Schmidt, K. J. Can. J. Chem. 1992, 70,
719-725.
(27) Steudel, R.; Papavassiliou, M.; Baumgart, F. Z. Naturforsch. B: Chem.
Sci. 1991, 46, 1674-1678.
(18) Bjo¨rgvinsson, M.; Schrobilgen, G. J. Inorg. Chem. 1991, 30, 2540-
2547.
(19) Bollinger, J. C.; Ibers, J. A. Inorg. Chem. 1995, 34, 1859-1867.
(20) Cusick, J.; Dance, I. Polyhedron 1991, 10, 2629-2640.
(28) Chivers, T.; Laitinen, R. S.; Schmidt, K. J.; Taavitsainen, J. Inorg.
Chem. 1993, 32, 337-340.
(29) Beck, J. Coord. Chem. ReV. 1997, 163, 55-70.
Inorganic Chemistry, Vol. 43, No. 17, 2004 5439

Sekar and Ibers
Table 2. Selected Bond Distances (Å) and Angles (deg) for 3 and Related Compounds
[Ba(2,2,2-crypt)(en)][TeSe10]‚en0.5
b
[PPN]2[TeSe10]a (3)
[K(2,2,2-crypt)]2 [TeSe10]b
molecule 1
molecule 2
[PPh4]2[TeSe10]a,c
Te1-Se1
Te1-Se5
Se1-Se2
Se2-Se3
Se3-Se4
Se4-Se5
2.809(1)
2.808(1)
2.337(1)
2.377(1)
2.421(1)
2.401(1)
2.815(2)
2.824(2)
2.305(4)
2.349(4)
2.336(4)
2.311(4)
2.819(3)
2.823(3)
2.287(6)
2.316(6)
2.309(6)
2.248(6)
2.805(3)
2.821(3)
2.323(6)
2.341(6)
2.342(6)
2.314(6)
2.809(2)
2.870(2)
2.348(2)
2.388(3)
2.399(2)
2.347(2)
Te1-Se1-Se2
Se1-Se2-Se3
Se2-Se3-Se4
Se3-Se4-Se5
Se4-Se5-Te1
Se5-Te1-Se1
Se5′-Te1-Se1
105.57(3)
107.62(5)
103.33(4)
104.00(5)
103.95(3)
93.03(3)
104.0(1)
107.2(1)
103.2(1)
106.1(1)
105.2(1)
95.6(1)
104.2(2)
104.1(2)
100.2(2)
106.1(2)
108.8(2)
106.8(2)
73.2(2)
107.4(2)
99.34(7)
103.93(7)
104.88(10)
106.72(10)
109.95(8)
93.39(5)
106.6(2)
102.8(2)
107.3(2)
104.0(2)
105.3(2)
74.7(2)
86.97(3)
84.4(1)
86.62(5)
a This work. b Reference 13. c For this compound, ref 7 reports the synthesis and limited crystallographic characterization from X-ray powder diffraction
data.
Table 3. Selected Bond Distances (Å) and Angles (deg) for 5, 6, and Related Compounds
[NMe4]2[TeSe3]‚DMFa (5)
[NEt4]2[TeSe3]a (6)
Na2TeSe3
K2TeSe3
[K(2,2,2-crypt)]2[TeSe3]c
b
b
Te1-Se1
Te1-Se2
Te1-Se3
2.4724(4)
2.4598(4)
2.4853(4)
2.4822(3)
2.4767(3)
2.4714(4)
2.515(2)
2.499(2)
2.494(2)
2.500(4)
2.496(4)
2.478(4)
2.454(4)
2.465(4)
2.460(4)
Se1-Te1-Se2
Se1-Te1-Se3
Se2-Te1-Se3
105.74(1)
105.25(1)
105.65(1)
105.01(1)
106.47(1)
106.93(1)
100.4(1)
102.0(1)
102.9(1)
102.6(1)
105.6(1)
101.9(1)
108.9(1)
104.8(2)
107.4(1)
a This work. b Reference 12. c Reference 11.
centers. Thus, the Te3Se5 ring found in [NEt4]2[Te3Se6] (1)
and the fused five- and six-membered rings of composition
Te3Se6 found in [NEt4]2[Te3Se7] (2) are further examples of
mixed Te/Se rings.
Complex equilibria among multiple species are typical of
polytelluride and polyselenide solutions.18,20,35-41 The mixed
polytelluride/polyselenide solution in the present preparation
is no exception and probably displays even more complex
equilibria among Sen2-, Ten2-, and [TemSen]2- species.
+
Indeed, in the presence of NEt4 , [NEt4]2[Te3Se6] (1) is
isolated in 76% yield. In contrast, under the same conditions
but with a change of cation, we isolate completely different
products, including [PPN]2[TeSe10] (3) and [NMe4]2[TeSe3]‚
DMF (5). If the Se/Te ratio is increased from 2.3:1 originally
chosen to optimize the yield of 1, then red Se is produced
in these reactions. If the Se/Te ratio is decreased, then Te
2-
and Te4 are produced. Moreover, the reaction with the
(30) Schreiner, B.; Dehnicke, K.; Maczek, K.; Fenske, D. Z. Anorg. Allg.
Chem. 1993, 619, 1414-1418.
(31) Nagata, K.; Hayashi, H.; Miyamoto, Y. Fukuoka UniV. Sci. Rep. 1988,
18, 21-33.
(32) Nagata, K.; Hayashi, H.; Miyamoto, Y. Fukuoka UniV. Sci. Rep. 1988,
18, 35-46.
Figure 6. Structure of the ordered (top) and disordered (bottom) [Te2Se2]2-
anions in [PPh4]2[Te2Se2] (4). Displacement ellipsoids are drawn at the 50%
(top) and 30% (bottom) probability levels. Bond distances are shown, but
are not representative for the disordered anion in which Te3/Te3A ) 0.62:
0.38. Bond angles for the ordered anion are Se1-Te1-Te2, 113.52(3)°;
Se2-Te2-Te1, 109.12(3)°.
(33) Wachhold, M.; Sheldrick, W. S. Z. Naturforsch. B: Chem. Sci. 1997,
52, 169-175.
(34) Kretschmann, U.; Bo¨ttcher, P. Z. Naturforsch. B: Anorg. Chem. Org.
Chem. 1985, 40, 895-899.
(35) Sharp, K. W.; Koehler, W. H. Inorg. Chem. 1977, 16, 2258-2265.
(36) Teller, R. G.; Krause, L. J.; Haushalter, R. C. Inorg. Chem. 1983, 22,
1809-1812.
(37) Schultz, L. D.; Koehler, W. H. Inorg. Chem. 1987, 26, 1989-1993.
(38) Schultz, L. D. Inorg. Chim. Acta 1990, 176, 271-275.
(39) Raymond, C. C.; Dick, D. L.; Dorhout, P. K. Inorg. Chem. 1997, 36,
2678-2681.
(40) Ahrika, A.; Paris, J. New J. Chem. 1999, 23, 1177-1180.
(41) Ahrika, A.; Robert, J.; Anouti, M.; Paris, J. New J. Chem. 2001, 25,
741-746.
Te0.32Se7.6831 and Te1.05Se5.95 32 rings have been claimed, and
the Te4Se2 33 ring has been reported. An ordered Te3Se3 ring
14
is found in Cs4Te9.74Se13.26
.
The structure of Rb2TeSe4,34
determined from X-ray powder data, is believed to contain
an infinite chain of Te2Se4 six-membered rings sharing Te
5440 Inorganic Chemistry, Vol. 43, No. 17, 2004

Mixed Te/Se Polychalcogenide Anions
+
+
mixed countercations PPh4 and NEt4 , effective for the
isolation in high yield of certain [MTe7]3- species,15,42,43
produced [NEt4]2[TeSe3] (6), a new salt of the known
[TeSe3]2- anion.11 The presence of a metal species further
complicates matters. Thus, [PPh4]2[Te2Se2] (4) could only
be synthesized in the presence of Cr(CO)6.
Acknowledgment. This work was supported by the U.S.
National Science Foundation through Grant CHE9819385.
We are indebted to Dr. Regine Herbst-Irmer of the Uni-
versity of Go¨ttingen for her help with the refinement of
the disordered NEt4 cations in compound 1. We thank
Dr. Kwasi Mitchell for the magnetic susceptibility measure-
ments.
+
This work demonstrates that new [TemSen]2- species, some
with unprecedented structures, can be isolated reproducibly
and in good yield from mixed polytelluride/polyselenide
solutions.
Supporting Information Available: X-ray crystallographic data
in CIF format for [NEt4]2[Te3Se6] (1), [NEt4]2[Te3Se7] (2), [PPN]2-
[TeSe10] (3), [PPh4]2[Te2Se2] (4), [NMe4]2[TeSe3]‚DMF (5), [NEt4]2-
[TeSe3] (6), and [PPh4]2[TeSe10]. This material is available free of
charge via the Internet at http://pubs.acs.org.
(42) McConnachie, J. M.; Ansari, M. A.; Bollinger, J. C.; Salm, R. J.; Ibers,
J. A. Inorg. Chem. 1993, 32, 3201-3202.
(43) Smith, D. M.; Roof, L. C.; Ansari, M. A.; McConnachie, J. M.;
Bollinger, J. C.; Pell, M. A.; Salm, R. J.; Ibers, J. A. Inorg. Chem.
1996, 35, 4999-5006.
IC040026H
Inorganic Chemistry, Vol. 43, No. 17, 2004 5441