A novel organotellurium halide with tellurium presenting mixed oxidation states: Synthesis and structural characterization

Article abstract of DOI:10.1016/j.ica.2010.09.053

In this work we have investigated the reaction for the obtention of an uncommon complex salt of the organotellurium bromide class. The reaction was carried out without the isolation of the synthetic intermediates in one-pot procedure. The complex salt obt

Full text of DOI:10.1016/j.ica.2010.09.053

Inorganica Chimica Acta 365 (2011) 492–495
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A novel organotellurium halide with tellurium presenting mixed oxidation states:
Synthesis and structural characterization
Gleison Antônio Casagrande a, , Cristiano Raminelli a, Ernesto Schulz Lang b, Sebastião de Souza Lemos c
⇑
a Laboratório de Síntese e Caracterização Molecular, Universidade Federal da Grande Dourados, Rod. Dourados/Itahum, Km 12, 79.804-970, Douradosm, MS, Brazil
b Departamento de Química, Universidade Federal de Santa Maria, 97.105-900 Santa Maria, RS, Brazil
c Instituto de Química, Universidade de Brasília, 70.904-970, Brasília, DF, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
In this work we have investigated the reaction for the obtention of an uncommon complex salt of the
organotellurium bromide class. The reaction was carried out without the isolation of the synthetic inter-
mediates in one-pot procedure. The complex salt obtained presents the tellurium atoms with mixed oxi-
dation states (TeII and TeIV). The cationic unit [5-Br-2-CH3O–C6H3Te(ETU)]+ presents the TeII atom with a
‘‘T” shape coordination geometry, and the anionic unit [4-CH3O–C6H4TeBr4]ꢀ presents the TeIV atom with
an octahedral coordination geometry considering the TeꢁꢁꢁBr interaction of 3.600(6) Å from the dimeric
arrangement presented in the solid state. Intermolecular (TeꢁꢁꢁBr) secondary bonds, built up the crystal-
line/molecular structure. Solution NMR data are presented and discussed in the light of the X-ray
structure.
Received 21 July 2010
Received in revised form 16 September
2010
Accepted 27 September 2010
Available online 8 October 2010
Keywords:
Organotellurium halides
Mixed oxidation state
Secondary bonds
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
few examples were reported in the literature so far. It is very diffi-
cult to access this class of molecule due to relative instability of the
In recent years, the rich and extensive chemistry of organotellu-
rium halides have obtained special attention due to structural fea-
tures presented in the solid state, for example, the possibilities in
the participation of dimeric, polymeric and supramolecular
arrangements via secondary bonds of the type TeꢁꢁꢁX [1–3]. Organo-
tellurium halides are very reactive compounds which have been
widely applied in several types of reactions in the field of organic
synthesis such as arylation of olefins, detelluration of organotellu-
rium halides with the formation of new C–C bonds, replacement of
the tellurium halides moieties by other functionalities, etc. [4].
Reactions concerning halogenation of organotellurium species for
giving compounds of tellurium in low oxidation states were re-
ported in pioneering works by Klar and Schulz [5,6], as well as
the complexation of this species with thiourea derivatives were re-
ported by Foss and Maartmannmoe [7]. Complex salts showing
aryltellurinates anions of the type [ArTeX4]ꢀ (Ar = Ph, m-
O2NC6H4, p-NCC6H4; X = Cl, Br, I) stabilized for cations of the pyrid-
inium type have been widely investigated and fully characterized
by X-ray diffraction studies [8,9]. Moreover, telluronium cations
synthetic intermediates as, for example, the monohalides of
organotellurium. Occurrences of disproportionation reactions were
reported in previous work of our research group [12]. In recent
work, we have demonstrated the synthesis and structural charac-
terization of some symmetrical examples of molecules of this nat-
ure [13]. We demonstrated that the structural organization in the
solid state is more related to steric effects than electronic effects
of the organic groups bonded in the chalcogen atom [14]. Recently,
Beckmann and co-workers have investigated the halogenation
reaction of two diarylditellurides aiming to the obtention of the
new diarylditellurides with mixed oxidation states. The obtained
products RX2TeTeR (R = Ph, 2,6-Mes2C6H3; X = Cl, Br) were charac-
terized in the solid state by X-ray diffraction and structural details
revealed a dimeric organization from TeꢁꢁꢁX secondary bonds [15].
Secondary bonds of type TeꢁꢁꢁX and XꢁꢁꢁX play an important role
in supramolecular self-assembling of anions of the type [RTeX4]ꢀ
(R = organic groups; X = Cl, Br, I), which are present in various salt
complexes described in the literature [9,16]. Alcock has introduced
the ‘‘secondary bond” term in the literature for classifying chemical
bonds that have borderline forces between the classic covalent
bonds and weak van der Waals interactions [17]. The supramolec-
ular synthesis considers the self-assembling of the molecular enti-
ties based on the secondary bonds, and calls ‘‘tectons” the single
unities which acts in the formation of the supramolecular arrays
by secondary bonds [18].
of the type [Ar3Te]+ (Ar = Ph, Mes) stabilized for anions I3 and
ꢀ
ꢀ
SbF6 were also characterized in early works [10,11].
Organochalcogen halides containing chalcogen atoms with
mixed oxidation states in the same molecule are very rare and
In this work we present the synthesis and structural character-
ization of a rare unsymmetrical salt complex of the organotellurium
⇑
Corresponding author. Tel.: +55 67 3410 2114; fax: +55 3410 2112.
E-mail address: gleisoncasagrande@ufgd.edu.br (G.A. Casagrande).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.09.053

G.A. Casagrande et al. / Inorganica Chimica Acta 365 (2011) 492–495
493
halide family. The new salt complex presents the tellurium atoms
with mixed oxidation states in the same molecule. The dimeric
association via secondary bonds TeꢁꢁꢁBr are present in the solid state
but the NMR 125Te features suggest that such interactions are not
sustained in acetone-dimethylsulfoxide solution. Multinuclear
magnetic resonance has been used to demonstrate that such inter-
actions, when present in solution, induce a considerable low-field
shifting of the 125Te nucleus [19,20].
Bruker Tensor-27 spectrometer using KBr pellets. Elemental analy-
ses were obtained in a Perkin–Elmer CHN 2400 equipment.
2.2. Preparation of the salt complex
The salt complex was synthesized exploring a one-pot proce-
dure in agreement with the outline below:
ðiÞBr2
R0TeTeR0 ! R0TeBr
ðBrownÞ
ðiiÞETU
ðiiiÞR00TeBr3
!
R0TeðETUÞBr
!
½R00TeðETUÞꢂ½R0TeðBrÞ4ꢂ
ðYellowÞ
ðYellowÞ
2. Experimental
ðiÞ rt=5 min:
ðiiÞ Ethylenethiourea ðETUÞ; rt=15 min:
2.1. Chemicals and measurements
ðiiiÞ R00TeBr3; 45 ꢃC=1:5 h:
R0 ¼ p-CH3O—C6H4; R00 ¼ 5-Br-2-CH3O—C6H3
All manipulations were conducted under nitrogen by the use of
standard Schlenk techniques. Br2 and ethylenethiourea are analyt-
ical grade reagents (Sigma–AldrichÒ) and were used without puri-
fication. Organotellurium derivatives were synthesized according
to the literature methods [4,21] and methanol was dried with
Mg/I2 and distilled prior to use [22]. The X-ray structural determi-
nations were collected with a Bruker APEX II CCD area-detector dif-
Initially, Br2 (0.032 g, 0.2 mmol) was added to a red solution of
(4-CH3O–C6H4Te)2 (0.094 g, 0.2 mmol) in methanol (20 mL). After
stirring for 5 min, it was produced a brown solution of 4-CH3O–
C6H4TeBr. Afterwards, ethylenethiourea (0.0204 g, 0.2 mmol) was
added and the solution quickly turned yellow. To this solution the
organotellurium tribromide (0.088 g, 0.2 mmol) was added and
maintained under stirring at 45 °C for 1.5 h. After cooling at room
temperature the mixture was filtered and the slow evaporation of
the solvent gave yellow needle crystals.
fractometer and graphite-monocromatized Mo
Ka (0.7107 Å)
radiation. The structure was solved by direct methods using SHELXS
and SHELXL package implemented in the WINGX 2002 program [23].
All refinements were made by full-matrix least-squares on F2 with
anisotropic displacement parameters for all non-hydrogen atoms.
Hydrogen atoms were included in the refinement in calculated
positions. Crystal data and more details of the data collections
and refinements are shown in Table 1. All NMR spectra were re-
corded on a Varian Mercury plus spectrometer (7.05T) operating
at 94.74 MHz for 125Te. 125Te spectra were acquired in a mixture
of acetone-d6 and DMSO-d6 (9:1 by volume) and were externally
referenced to Me2Te checked against Te2Ph2 in CDCl3 (d =
450 ppm) [24]. The sample temperature was maintained at 300 K
during the acquisitions. The IR measurements were acquired in a
Properties: crystalline air stable substance; C17H19Br5N2O2STe2
F.W. (970.15); Yield: 0.192 g (82%) based on the ditelluride used;
Melting point: 121–123 °C; Anal. Calc. C, 21.05; H, 1.97; N, 2.89.
Found: C, 21.22; H, 1.92; N, 2.92%; 1H NMR: d 8.67 (sbroad, 2H,
NH), 6.8–8.4 (m, 7H, C–Harom.), 3.92–3.85 (m, 10H, CH2, OCH3);
13C{1H} NMR: d 176.66 (C@S), 138.4, 138.00, 137.50, 115.90,
115.70, 115.30, 114.10, 113.00 (Carom), 57.00, 55.85 (OCH3),
46.17, 42.60 (CH2); IR (KBr,
m
/cmꢀ1) 1579, 1522, 1462 (
s-N–H) [26].
ms-N–C@S)
[25], 1252 ( s-C–O) [26], 3292 (
m
m
3. Results and discussion
Table 1
3.1. X-ray studies
Crystal data and structure refinement for the complex.
The crystal X-ray data and the experimental conditions of the
analyses for the complex are given in Table 1. Table 2 summarizes
selected bond distances and angles for the title complex.
Fig. 1 shows the molecular structure present in the crystallo-
graphic asymmetric unit. Fig. 2 shows the dimeric association from
the secondary bond present in the solid state, the secondary inter-
actions are identified by dashed lines.
To the best of our knowledge, this complex salt is the first
organotellurium halide reported in the literature containing
unsymmetric organic groups bonded in the chalcogen atoms with
mixed oxidation states. The structure consists of one cationic unit
[5-Br-2-CH3O–C6H3Te(ETU)]+ containing the TeII atom and one an-
ionic unit [4-CH3O–C6H4TeBr4]ꢀ containing the TeIV atom. These
units interact with each other through one interionic secondary
bond Te(2)ꢁꢁꢁBr(1) of 3.2900(7) Å, this interaction is in agreement
with the value of 3.1757(13) Å for a similar compound [13]. On
the other hand, the anionic units interact with each other through
Empirical formula
Formula weight
Temperature(K)
Radiation; k (Å)
Crystal system
Unit cell dimensions
a (Å)
C17H19Br5N2O2STe2
970.15
295(2)
Mo K
triclínic P1
a
; 0.71073
ꢀ
9.3936(6)
b (Å)
c (Å)
11.7872(8)
13.2069(9)
109.531(4)
96.464(4)
104.259(4)
1304.96(15)
2/2.469
a
(°)
b (°)
c
(°)
Volume (Å3)
Z/density calculated (g cmꢀ3
)
Absorption coefficient (mmꢀ1
F(0 0 0)
)
9.987
892
Crystal size (mm)
Range for data collection h (°)
Index ranges
0.32 ꢄ 0.32 ꢄ 0.26
1.67 a 32.15
ꢀ14 6 h 6 14
ꢀ15 6 k 6 17
ꢀ19 6 l 6 16
27041
Reflections collected
Reflections unique
Table 2
9057
99.7
Bond lengths (Å) and angles (°) selected for the complex.
Completeness to theta maximum (%)
Absorption correction
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit F2
semi-empirical
0.1810 and 0.1423
9057/0/262
1.062
R1 = 0.0489
wR2 = 0.1210
R1 = 0.0781, wR2 = 0.1468
1.747 e ꢀ1.112
Bond lengths
Angles
S(1)–Te(2)
2.4467(13)
3.2900(7)
3.6000(6)
2.7221(7)
2.6650(6)
S(1)–Te(2)–Br(1)
C(11)–Te(1)–Br(2)#1
C(11)–Te(1)–Br(4)
C(21)–Te(2)–S(1)
Br(2)–Te(1)–Br(4)
170.09(2)
170.25(12)
89.91(12)
96.19(12)
178.97(2)
Br(1)–Te(2)
Te(1)–Br(2)#1
Br(1)–Te(1)
Br(2)–Te(1)
Final R indices [I > 2
r(I)]
R indices (all data)
Largest difference in peak and hole (e Åꢀ3
)
Symmetry transformations used to generate equivalent atoms: #1 x, y, z ꢀ 1.

494
G.A. Casagrande et al. / Inorganica Chimica Acta 365 (2011) 492–495
ꢀ
P1 crystallographic space group. This inversion center is located
in the middle point of the square formed by Te(1), Br(2), Te(1)#1,
Br(2)#1 atoms.
3.2. 125Te NMR studies
Due to the low solubility of the title complex crystals in conven-
tional organic solvents such as chloroform, benzene, and hexane,
our investigations for the solution behavior studies were elabo-
rated employing acetone-d6 and DMSO-d6 in a 9:1 proportion,
respectively. Moreover our attention was focused on 125Te NMR
once the 1H and 13C NMR spectra do not show significant structural
features for the dimeric complex in solution.
Two peaks were detected in the 125Te NMR spectra of the com-
plex in solution. One sharp peak appears in d = 1210.9 ppm and one
broad signal appears in d = 931.5 ppm. When the same experiment
is carried out for the standard compound [Et4N][PhTeBr4] only one
sharp signal is observed at d = 1199.8 ppm, this signal is assigned
for the anionic unit [PhTeBr4]ꢀ. For comparison purposes, we have
recorded the same experiment for the neutral compound PhTeBr3,
and in this case two sharp signals appeared in d = 1202.3 and
d = 824.8 ppm. These results show that the PhTeBr3 ionizes in
DMSO-acetone solution according to the equation: 2PhTeBr3 +
DMSO ? [PhTeBr4]ꢀ + [PhTe(DMSO)Br2]+ [13]. In the light of these
results and supported by the performed experiments we propose
that our complex ionizes in solution generating the corresponding
cationic and anionic units. Accordingly, the sharp peak that ap-
pears in d = 1210.9 ppm corresponds to the anionic unit [4-CH3O-
C6H4TeBr4]ꢀ, and the broad signal that appears in d = 931.5 ppm
is related to the cationic unit [5-Br-2CH3O–C6H3Te(ETU)]+. Based
on this behavior, we conclude that in solution occurs the disrup-
tion of the secondary bonds (TeꢁꢁꢁBr) responsible for the dimeric
association represented by dashed lines in the Fig. 2. It is worth
mentioning that in the complex [p-CH3O(C6H4)Te(ETU)][p-
CH3O(C6H4)TeI4] the 125Te NMR spectrum showed a broad signal
at 933.5 ppm, attributed to the [p-CH3O(C6H4)Te(ETU)]+ cation
Fig. 1. Molecular structure of the complex with emphasis in the secondary bond
Te(2)ꢁꢁꢁBr(1) of 3.2900(7) Å (all H-atoms have been omitted for clarity). Thermal
ellipsoids are drawn at the 50% probability level.
one secondary bond Te(1)ꢁꢁꢁBr(2)#1 of 3.600(6) Å, this interaction
is less than the sum of van der Waals radii for the same atoms
(Te and Br 4.00 Å) [27]. The latter secondary bond completes the
octahedral coordination sphere of the Te(1) atom, and is responsi-
ble by dimeric array organization of the structure in the solid state.
The analysis of the bond angles between S(1)–Te(2)–Br(1) of
170.09(2)° and C(21)–Te(2)–S(1) of 96.19(12)° for the Te(2) atom,
present in the cationic unit, shows that this atom has a ‘‘T” shape
coordination geometry and this is in agreement with other com-
pounds already mentioned in the literature [28]. Finally the
dimeric array is correlated by one inversion center belonging to
Fig. 2. Molecular structure and dimeric arrangement for the complex. Interionic secondary interactions are depicted in dashed lines (all H-atoms have been omitted for
clarity). Thermal ellipsoids are drawn at the 50% probability level. Symmetry transformations used to generate equivalent atoms: #1 x, y, z ꢀ 1.

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495
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4. Conclusion
The title complex presenting mixed oxidation states was syn-
thesized in a one-pot procedure in a good yield. The data refined
from the X-ray diffraction reveal the dimeric association of the
molecular entities formed via secondary bonds which are present
in the solid state. The comparison between 125Te NMR and X-ray
data show that the structure present in the solid state is not kept
in solution, moreover all secondary interactions (TeꢁꢁꢁBr) are bro-
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We gratefully acknowledge the CNPq (Conselho Nacional de
Desenvolvimento Científico e Tecnológico) and the FUNDECT
(Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e
Tecnologia do Estado do Mato Grosso do Sul) for financial support.
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Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2010.09.053.
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