Perfluoroalkyl(dithiocarbamato) tellurium(ii) compounds

Article abstract of DOI:10.1039/b618240b

[NMe₄][R_fTe(SC(S)NR₂)₂] derivatives are selectively formed by the oxidation of [NMe₄]TeR _f (R_f = CF₃, C₂F₅) with [R₂NC(S)S]₂ (NR₂ = NEt₂, NBz ₂, N(CH₂)₄) in almost quantitative yields. An alternative route to obtain the dithiocarbamato complex anions offer reactions of Te[SC(S)NR₂]₂ (NR₂ = NEt₂, NBz₂) with equimolar amounts of Me₃SiR_f and [NMe₄]F. Some of the derivatives were recrystallized with bulky cations in order to determine the crystal structures. Structural elucidation by diffraction methods exhibit the structural feature of a distorted pentagonal planar environment (resembling "butterflies") around the tellurium centres. The carbamato tellurates can be transferred easily into the neutral derivatives, R_fTeSC(S)NR₂, upon treatment with Ag[BF ₄]. In solution they equilibrate with Te₂(R _f)₂ and [R₂NC(S)S]₂ and finally are transformed into Te(R_f)₂, Te[SC(S)NR₂] ₂, and Te[SC(S)NR₂]₄, respectively. All compounds are fully characterized by NMR spectroscopic methods (¹H, ¹³C, ¹⁹F, ¹²⁵Te). Additionally, synthesis and characterization of the hitherto unknown derivative [NMe₄]TeC ₂F₅ are described. The Royal Society of Chemistry.

Full text of DOI:10.1039/b618240b

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PAPER
www.rsc.org/dalton | Dalton Transactions
Perfluoroalkyl(dithiocarbamato) tellurium(II) compounds†
Wieland Tyrra,* Dieter Naumann,* Sigrid Buslei, Silke Kremer, Ingo Pantenburg and Harald Scherer
Received 13th December 2006, Accepted 22nd February 2007
First published as an Advance Article on the web 16th March 2007
DOI: 10.1039/b618240b
[NMe4][RfTe(SC(S)NR2)2] derivatives are selectively formed by the oxidation of [NMe4]TeRf (Rf = CF3,
C2F5) with [R2NC(S)S]2 (NR2 = NEt2, NBz2, N(CH2)4) in almost quantitative yields. An alternative route
to obtain the dithiocarbamato complex anions offer reactions of Te[SC(S)NR2]2 (NR2 = NEt2, NBz2)
with equimolar amounts of Me3SiRf and [NMe4]F. Some of the derivatives were recrystallized with
bulky cations in order to determine the crystal structures. Structural elucidation by diffraction methods
exhibit the structural feature of a distorted pentagonal planar environment (resembling “butterflies”)
around the tellurium centres. The carbamato tellurates can be transferred easily into the neutral
derivatives, RfTeSC(S)NR2, upon treatment with Ag[BF4]. In solution they equilibrate with Te2(Rf)2 and
[R2NC(S)S]2 and finally are transformed into Te(Rf)2, Te[SC(S)NR2]2, and Te[SC(S)NR2]4, respectively.
All compounds are fully characterized by NMR spectroscopic methods (1H, 13C, 19F, 125Te). Additionally,
synthesis and characterization of the hitherto unknown derivative [NMe4]TeC2F5 are described.
more than 90% yield.
Introduction
[NMe4]F + Me3SiC2F5 + Te → [NMe4]TeC2F5 + Me3SiF (1)
Due to the similar characters of sulfur and tellurium, inter-
chalcogen compounds have attracted attention during the past
The salt 1b was obtained as a pale ochre, moderately light-sensitive
decades. The lack of low-valent tellurium containing starting
solid which can be handled in ambient atmosphere for at least some
materials allowed investigations mainly on tellurium (IV) species
minutes. In comparison with 1a, it shows the same spectroscopic
clearly revealing the focus on dithiocarbamates as the prominent
characteristics.
ligands for these systems. In the 1980s and early 1990s, numerous
It must be noted that extension of the reaction (eqn (1)) to higher
organotellurium(IV) dithiocarbamates were synthesized and char-
perfluoroalkylsilanes did not give any evidence for the homologous
acterized by spectroscopic and diffractional methods.1 In contrast,
compounds, [NMe4]Te(n-C3F7) and [NMe4]Te(n-C4F9), but for
examples of organotellurium(II) dithiocarbamates are rare and,
perfluorinated carbanions of a composition that will be discussed
to our knowledge, structural determinations are limited to
elsewhere.7
three examples, dimethyldithiocarbamato(2-phenylazophenyl-
C,Nꢀ)tellurium(II),2
dimethyldithiocarbamato[2-(2-pyridyl)-
Oxidations of 1 with dithiuramdisulfides
phenyl]tellurium(II),3 and diethyldithiocarbamato{8-[(dimethyl-
amino)-1-naphthyl]}tellurium(II).4
Oxidations of [NMe4]TeRf (Rf = CF3 (1a), C2F5 (1b)) with
dithiuramdisulfides proceed selectively and quantitatively to give
the title compounds (cf. Scheme 1; top left to centre). Products
were obtained as yellow crystalline to waxy materials. Attempted
crystallization carried out in open glass beakers at ambient
atmosphere gave inhomogeneous products from which crystals
of [NMe4][RfTe(SC(S)NR2)2] (yellow) and Te[SC(S)NR2]2 (red)
were selected for X-ray diffraction studies. Furthermore, a not
yet identified derivative (colourless) has been observed implying
a decomposition process by loss of CF3H. The dithiocarbamato
compounds are stable on exposure to daylight in ambient atmo-
sphere and can be stored in ordinary glassware. The compounds
3a–f were characterized by NMR spectroscopic methods and data
obtained for the anions did not deviate from those measured for
the crystalline derivatives described below (Table 1). Negative ESI-
mass spectra did not show the anion peak but were dominated by
The inherent properties of trifluoromethyl-5 and pentaflu-
oroethyltellurates(0) in combination with their convenient
oxidizability6 leads to interesting aspects of further studies.
Here, we report on the synthesis and characterization of
[NMe4]TeC2F5, the oxidations of the anions TeCF3− and TeC2F5
−
by dithiuramdisulfides, and an alternative route to obtain com-
pounds with the anions [RfTe(SC(S)NR2)2]−. Furthermore, the
aspect of their conversion into neutral species is reported, corrob-
orated by NMR spectroscopy and structural characterization for
selected examples.
Results and discussion
Tetramethylammonium pentafluoroethyltellurate(0),
[NMe4]TeC2F5 (1b)
−
[NMe4]TeC2F5 1b is prepared in a similar manner as described for
the lighter homologue5 [NMe4]TeCF3 1a according to eqn (1) in
ions of the carbamate and {[NMe4](SC(S)NR2)2]} . Also, EI mass
spectra (20 eV) did not give a deeper insight into the molecular
structure. The peak [RfTeSC(S)NR2]+ was detected in all spectra
with an intensity below 8%; [Te2(Rf)2]+ was always found as the
100%-peak.
Institut fu¨r Anorganische Chemie, Universita¨t zu Ko¨ln, Greinstr. 6,
50939 Ko¨ln, Germany. E-mail: tyrra@uni-koeln.de; d.naumann@uni-
koeln.de; Fax: +49 221 470 5196
19F NMR chemical shifts of [CF3Te(SC(S)NR2)2]− (3a-c) are
located around −20 ppm for the carbamato compounds and are
† Dedicated to Professor Alois Haas on the occasion of his 75th birthday.
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Scheme 1
−
significantly shifted from the resonance of the parent ion TeCF3
(d ≈ +1)5 and known CF3TeSR derivatives (d ≈ −27).8 This
is in perfect agreement with shifts of other trifluoromethyltel-
lurates(II).6 Exceptionally large couplings for Te(II) derivatives
confirm values previously reported for [CF3TeI2]−.6 Similar re-
lations might be applied to the C2F5-compounds 3d–f (d ≈
−83.4 0.3 (CF3); −86.5 0.7 (CF2)) irrespective of the solvent
(acetonitrile or DMF), although reference values for comparison
purposes are missing (Table 1).
representing roughly the arithmetic mean value of d(Te(Rf)2)12,13
and d(Te[SC(S)NR2]2)14 in the ratio 1 : 2.
Reactions of tellurium(II) dithiocarbamates with the system
Me3SiRf/F− (Rf = CF3, C2F5)
The compounds 3a–f were alternatively prepared starting from the
corresponding tellurium(II) dithiocarbamates and Me3SiRf/F− as
equivalents for perfluoroalkyl anions (cf. Scheme 1; top right
to centre). These reactions proceed selectively and quantitatively
under the chosen conditions. Thereby the exclusive attachment of
one perfluoroalkyl group to the tellurium(II) centre is achieved.
No evidence for the replacement of the dithiocarbamate ligands
by perfluoroalkyl groups was found.
13C NMR signals of the CF3 group in CF3Te derivatives and
of the CF2 group in C2F5Te derivatives are shifted downfield
by approximately 30 ppm compared with the parent ions.5,9 All
1
signals (13C, H) for the dithiocarbamato ligands are detected in
the expected region. The chemical shift of the NCS2 group of about
205 2.5 ppm implies an ionic rather than a covalent character
of the carbamate ligand.10,11
125Te NMR signals are located between the resonances
of Te(Rf)2 and Te[SC(S)NR2]2 at approximately 960 ppm
([CF3Te(SC(S)NR2)2]−) and 920 ppm ([C2F5Te(SC(S)NR2)2]−)
Synthesis of 3g–j and crystal structures of 3h, 3j and
bis(triphenylphosphoranyliden)ammonium trifluoromethyl(chloro)-
(dibenzyldithiocarbamato)tellurate(II) (3k)
The salts 3g–j were selectively prepared from the exchange
reactions of 3a–c by the bulky cations [Cs(15-crown-5)2]+ and
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Table 1 Compilation of NMR data of tetramethylammonium perfluoroalkylbis(dithiocarbamato)tellurates(II), [NMe4][RfTe(SC(S)NR2)2] 3
Compound
Solvent
3a
3b
3c
3d
3e
3f
MeCN/CD3CN DMF-d7
CD3CN
MeCN/CD3CN
DMF-d7
MeCN/CD3CN
19F
d(CF3)
−20.0, s
−20.3, s
−19.6, s
−83.7, ta
−86.3, q
160
−83.0, tb
−85.9, br
163
−83.5, ta
−86.1, q
158
d(CF2)
2J(Te,F)/Hz
1J(F,C)/Hz
287
381
289
381
285
379
285/322c
288/321c
287/325c
125Te
d
955
979
952
883
936
918
13C
d(CF3)
d(CF2)
d(CS2)
d(NCH2)
d(other)
125.3
123.4
124.3
121.4
117.8
202.5
47.1
121.6
116.7
200.4
52.4
121.3
117.7
206.5
54.5
127.2; 127.5;
128.6; 137.1
55.3
203.2
47.7
12.5
199.9
52.5
25.7
207.4
55.6
128.1; 128.3;
129.5; 137.9
56.1
11.6
25.6
d(NMe4)
56.1
54.9
55.3
54.8
1H
d(NCH2)
d(other)
d(NMe4)
4.0, 8H
1.2, 12H
3.1, 12H
3.7, 8H
2.0, 8H
3.4, 12H
5.2, 8H
3.9, 8H
1.2, 12H
3.1, 12H
3.7, 8H
2.0, 8H
3.4, 12H
5.2, 8H
7.4,d 20H
3.1, 12H
7.4,d 20H
3.1, 12H
a
3
3JF,F = 3.1 Hz. b JF,F = 2.5 Hz. c First value 1JF,C of CF3 group; second of CF2 group. d Centre of overlapping multiplets.
[PNP]+ using the corresponding iodides (cf. Scheme 1; centre to
bottom right). [NMe4]I was filtered off and all volatile components
were distilled off in vacuo yielding salts 3g–j nearly quantitatively
as bright yellow solids. Recrystallization from CH2Cl2/Et2O
mixtures in open glass beakers gave yellow crystals of 3h and
3j. These crystals were of the required quality for crystal structure
determinations.
Attempted cation exchange of 3c and [PNP]Cl was unsuc-
cessful. Instead of [PNP][CF3Te(SC(S)NBz2)2], some crystals of
[PNP][CF3TeCl(SC(S)NBz2)] (3k) were collected after crystalliza-
tion of the raw material from a CH2Cl2/Et2O mixture.
The ligand arrangement around the tellurium centres in the
structures of 3h (Tables 2 and 3, Fig. 1 and 2) and 3j (Tables 2
Fig. 2 Perspective view of the unit cell of compound 3h along the a-axis.
and 3, Fig. 3) is almost planar in a distorted pentagonal
fashion with two shorter and two longer Te–S contacts (3h:
˚
˚
2.696(2)/3.022(2) A; 2.703(2)/3.082(2) A; 3j: 2.711(1)/3.154(1)
˚
˚
A; 2.687(1)/3.069(2) A). The carbon tellurium bond (3h: 2.251(6)
A; 3j: 2.237(5) A) is slightly longer with respect to related motifs
˚
˚
2−
6
˚
found in the dimeric [CF3TeI(l-I)]2 dianion (2.205(3) A). The
angular sums around tellurium are 360.0◦ (3h) and 360.1◦ (3j),
respectively, again proving the planar ligand arrangement. As
a consequence, the anions must be regarded as “hypervalent”
[14-Te-5] species with two lone electron pairs occupying axial
sites. A similar motif has also been found for the hemi-adduct
of bis(diethyldithiocarbamato)tellurium(II) with 4,4ꢀ-bipyridyl.15
A slight tendency towards planar five-coordination by intermolec-
ular Te–S contacts is also discussed for the molecular structures
of some bis(dithiocarbamato)tellurium(II) derivatives.16,17
In comparison with the parent molecule 4 (see below), Te–S
bonds are elongated by up to approximately 0.2 A due to the
Fig. 1 Molecular structure and labelling scheme of [Cs(15-crown-5)2]-
[CF3Te(SC(S)N(CH2)4)2] 3h.
˚
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Table 2 Crystal data and structure refinement parameters for 3h, 3j, 3k, 4b and 6c
3h
3j
3k
4b
6c
Empirical formula
C31H56N2F3O10S4CsTe
1062.53
C47H46N3F3P2S4Te
1027.65
C52H44N2F3P2S2ClTe
1043.00
C10H16N2S4Te
420.09
C60H56N4S8Te
1217.17
Formula mass/g mol−1
Rotation angle range
0◦ ≤ x ≤ 180◦; w = 0◦
0◦ ≤ x ≤ 180◦; w = 90◦
Dx = 2◦
0◦ ≤ x ≤ 180◦; w = 0◦
0◦ ≤ x ≤ 180◦; w = 90◦
Dx = 2◦
0◦ ≤ x ≤ 180◦; w = 0◦
0◦ ≤ x ≤ 180◦; w = 90◦
Dx = 2◦
0◦ ≤ u ≤ 250◦
0◦ ≤ u ≤ 250◦
Increment
Du = 2◦
Du = 2◦
No. of images
Exposure time/min
Detector distance/mm
2h range/◦
Temperature/K
Index range
180
6
120
1.9–54.8
180
10
120
1.9–54.8
180
3
120
1.9–54.8
125
125
4
60
5
60
3.8–56.3
293(2)
−10 ≤ h ≤ 10
−15 ≤ k ≤ 15
−21 ≤ l ≤ 21
17701
3.8–56.3
293(2)
−20 ≤ h ≤ 20
−20 ≤ k ≤ 20
−15 ≤ l ≤ 16
32889
170(2)
150(2)
150(2)
−16 ≤ h ≤ 15
−16 ≤ k ≤ 16
−19 ≤ l ≤ 19
34762
−19 ≤ h ≤ 19
−18 ≤ k ≤ 17
−23 ≤ l ≤ 23
64295
−17 ≤ h ≤ 19
−18 ≤ k ≤ 18
−26 ≤ l ≤ 26
73923
Total data collected
Unique data
9754
9021
10567
3635
3484
Observed data
Rmerg
7375
0.0390
5859
0.0947
8412
00513
0.6956/0.8778
Monoclinic
P21/n (no. 14)
15.394(1)
2472
0.0530
2203
0.1002
Transmission min/max
Crystal system
Space group
0.4023/0.7632
Triclinic
0.6679/0.8771
Monoclinic
P21/c (no. 14)
15.860(1)
14.887(1)
19.424(2)
0.6382/0.7575
Monoclinic
P21/n (no. 14)
8.094(1)
11.727(1)
16.101(2)
0.7701/0.9051
Tetragonal
¯
¯
P1 (no. 2)
P421c (no. 114)
˚
a/A
13.192(1)
13.178(1)
14.939(2)
87.97(1)
78.72(1)
61.22(1)
2, 2226.9(4)
R1 = 0.0689
wR2 = 0.1893
R1 = 0.0871
wR2 = 0.2030
15.406(2)
˚
b/A
14.710(1)
20.959(2)
˚
c/A
12.161(2)
a/◦
b/◦
c /◦
91.20(1)
94.08(1)
92.15(1)
3
˚
Z, Volume/A
4, 4584.9(6)
R1 = 0.0496
wR2 = 0.1166
R1 = 0.0824
wR2 = 0.1308
4, 4734.2(5)
R1 = 0.0383
wR2 = 0.1027
R1 = 0.0499
wR2 = 0.1107
4, 1527.1(3)
R1 = 0.0333
wR2 = 0.0615
R1 = 0.0624
wR2 = 0.0676
2, 2886.4(5)
R1 = 0.0436
wR2 = 0.0756
R1 = 0.0851
wR2 = 0.0874
R indexes [I > 2rI]
R indexes (all data)
R1 = R||Fo| − |Fc||/R |Fo|, wR2 = [Rw(|Fo|2 − |Fc|2)2/Rw(|Fo|2)2]1/2, S2 = [Rw(|Fo|2 − |Fc|2)2/(n − p)]1/2, with w = 1/[r2 (Fo)2 + (0.1000P)2]
for 3h w = 1/[r2 (Fo)2 + (0.0801P)2] for 3j, w = 1/[r2 (Fo)2 + (0.0728P)2 + 0.8236P] for 3k, w = 1/[r2 (Fo)2 + (0.0284P)2] for 4b and w = 1/[r2 (Fo)2 +
2
(0.0366P)2] for 6c, were P = (Fo + 2Fc2)/3. Fc* = kFc[1 + 0001 × |Fc|2 k3/sin(2h)]−1/4
.
◦
˚
Table 3 Interatomic distances (A) and angles ( ) for 3h, 3j, 3k, 4b and 6c (with estimated standard deviations in parentheses)
3h
3j
3k
4b
6c
Te–S11
Te–S12
Te–S21
Te–S22
3.022(2)
2.696(2)
3.082(2)
2.703(2)
2.251(6)
1.263(10)
1.251(10)
1.335(10)
1.695(6)
1.726(7)
1.702(7)
1.729(7)
1.345(8)
1.337(9)
Te–S111
Te–S112
Te–S211
Te–S212
Te–C1
3.154(1)
2.711(1)
3.069(2)
2.687(1)
2.237(5)
1.329(7)
1.343(7)
1.358(6)
1.692(5)
1.732(5)
1.696(5)
1.719(5)
1.347(6)
1.346(7)
Te–S1
Te–S2
3.083(1)
2.570(1)
Te–S111
Te–S112
Te–S211
Te–S212
2.898(1)
2.518(1)
2.896(1)
2.495(1)
Te–S11
Te–S12
2.755(1) 4x
2.723(1) 4x
Te–C1
Te–C1
2.204(3)
1.324(4)
1.331(4)
1.353(4)
1.689(3)
1.745(3)
C1–F11
C1–F12
C1–F13
C11–S11
C11–S12
C21–S21
C21–S22
C11–N12
C21–N22
C1-F11
C1–F11
C1–F12
C1–F13
C2–S1
C1–F12
C1–F13
C11-S111
C11–S112
C21–S211
C21–S212
C11–N12
C21–N22
C11–S111
C11–S112
C21–S211
C21–S212
C11–N12
C21–N22
1.688(3)
1.733(4)
1.686(4)
1.737(4)
1.325(5)
1.316(5)
C1–S11
C1–S12
1.707(5)
1.714(5)
C2–S2
C2–N1
Te–Cl
1.352(4)
2.726(1)
63.0(1)
C1–N1
1.357(6)
S11–Te–S12
S21–Te–S22
S11–Te–S21
S11–Te–S22
S12–Te–S21
S12–Te–S22
S12–Te–C1
S22–Te–C1
62.8(1)
62.1(1)
71.3(1)
133.4(1)
134.1(1)
163.8(1)
81.4(2)
82.4(2)
S111–Te–S112
S211–Te–S212
S111–Te–S211
S111–Te–S212
S112–Te–S211
S112–Te–S212
S111–Te–C1
61.0(1)
62.1(1)
162.1(1)
135.8(1)
136.6(1)
74.9(1)
78.4(2)
83.7(2)
S1–Te–S2
S111–Te–S112
S211–Te–S212
S111–Te–S211
S111–Te–S212
S112–Te–S211
S112–Te–S212
65.9(1)
66.1(1)
145.4(1)
148.5(1)
79.5(1)
S11–Te–S12
65.2(1) 4x
S2–Te–C1
S2–Te–Cl
S1–Te–C1
S1–Te–Cl
C1–Te–Cl
149.1(1)
127.5(1)
86.4(1)
169.5(1)
83.2(1)
R360.1
145.6(1)
S211–Te–C1
R360.0
R360.1
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Fig. 4 Molecular structure and labelling scheme of [PNP][CF3TeCl-
(SC(S)NBz2)] 3k.
˚
The Te–C bond length of 2.204(3) A is found in the range
of similar crystallographically characterized square-planar triflu-
2− 6
oromethyltellurates(II), [CF3TeI(l-I)]2
and [CF3Te(TeCF3)(l-
X)]2 (X = Cl, Br, I).6,22 The Te–Cl bond (2.726(1) A) is shorter
2−
˚
˚
by approximately 0.1 A in comparison with previously reported
Fig. 3 Molecular structure and labelling scheme of [PNP][CF3Te-
(SC(S)N(CH2)4)2] 3j.
data for [CF3Te(TeCF3)(l-Cl)]22− and related compounds.23 Again,
electron distribution in the dithiocarbamato ligands is best
described by the canonical structures depicted in Scheme 2.
additional coordination by the electronegative trifluoromethyl
group. C–S and C–N bond lengths indicate an electron
distribution in the ligand somewhere in between the canonical
forms A and B (Scheme 2) which is in absolute agreement with
estimations made on the basis of 13C NMR data in solution.
Synthesis of perfluoroalkyl(dithiocarbamato)tellurium(II) 5
The reactions of the compounds 3 and Ag[BF4] proceed selectively
in MeCN solution within 15 min to give the corresponding
derivatives 5 in quantitative yields. The formation of the sparingly
soluble salts [NMe4][BF4] and Ag[SC(S)NR2] appears to be the
driving force (cf. Scheme 1, centre to left). During the reaction the
colour of the mixture changes from bright yellow to orange, while
a white solid precipitates. Upon filtration and condensing off the
solvent in vacuo, derivatives 5 were isolated as intensive orange
solids unfortunately of insufficient purity.
Concomitant with the formation of 5 an equilibrium begins
to establish between the former, Te2(CF3)2 and the dithiuram
disulfide (Scheme 3). Upon prolonged storing of 5 in solution
irrespective of the solvent, a second equilibrium is observed
between the former and Te(Rf)2 and Te[SC(S)NR2]2 4. Finally,
the known14 equilibrium between 4 and Te[SC(S)NR2]4 6 and
dithiuramdisulfide occurs.
Scheme 2
The pyrrolidine rings appear to be planar in the crystal
structure of 3h, while significant folding is found for it in 3j.
Alternate stacking of the anions and cations occurs along the
a-axis leading to the exceptional planar molecular structure of
the whole anion due to lattice effects produced by this stacking.
In the crystal structure of 3j, the anions are incorporated in the
[PNP] framework allowing the pyrrolidine rings to exhibit their
characteristic folding.
No peculiarities are found concerning interatomic distances
and angles in both cations [Cs(15-crown-5)2] e.g. ref. 18 and 19 and
[PNP] e.g. ref. 6 and 20 in comparison with known structures. How-
ever, it should be noted that a disorder problem in the crown
ethers is possibly responsible for the R-values obtained for
3h.
As a consequence, the signals of five tellurium compounds
were detected in the 125Te,19F-HMBC spectra (cf. Fig. 5 for
The [CF3TeCl(SC(S)NBz2)]− anion in 3k (Tables 2 and 3;
Fig. 4) exhibits a distorted square planar ligand arrangement at
tellurium. As to be expected, ligand–Te–ligand angles vary from
63.0(1)◦ (S1–Te–S2)—due to the chelating bidentate character of
the dithiocarbamate ligand—to 127.5(1)◦ (S1–Te–Cl), while only
the two angles S1–Te–C1 (86.4(1)◦) and C1–Te–Cl (83.2(1)◦) are
close to the rectangle. As a consequence, the trans angles S1–
Te–Cl (169.5(2)◦) and especially S2–Te–C1 (149.1(1)◦) deviate
significantly from linearity. However, the angular sum around
tellurium is 360.1◦ suggesting that the lone electron pairs are
located above and below the plane as is expected for a [12-
Te-4] species. The Te–S2 bond is shorter than in the five-
coordinate species (3h and 3j) but significantly longer than in
comparable bis(dithiocarbamato)tellurium(II) compounds.16,17,21
Scheme 3
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The results of NMR investigations are summarized in Table 4.
All 1D NMR spectral data match the expectations and display the
typical splitting.
While the 19F NMR signals of the CF3 (5a–c) respectively CF2
(5d–f) groups are shielded by approximately 6 ppm in comparison
with the parent ions 3a–f, the 125Te NMR signals are deshielded by
approximately 150 ppm. The 13C NMR signal of the NCS2 group
is detected around 190 ppm whereas 205 2.5 ppm is observed
for 3a–f. These differences express different bonding situations in
3a–f and 5a–f and suggest a pronounced covalent nature of the
tellurium sulfur bonds in 5a–f.
EI mass spectra show the respective M+ peaks with intensities
lower than 10% and are dominated by the ions [Te2(Rf)2]+, [Te2Rf]+,
[TeSC(S)NR2]+ and [R2NCS]+.
Sign determination for the 2J(125Te,19F) couplings in 3a and 3d
Fig. 5 125Te,19F-HMBC spectrum of the decomposition products of 5d in
CD3CN.
The absolute values of the 2J(125Te,19F) coupling constants in 3a–c
and 3d–f are found to increase for the anionic species compared
with the neutral derivatives 5a–c as well as 5d–f. From previous
investigations,24 different signs were reported for the 2J(125Te,19F)
coupling constants of the molecules Te(CF3)2 and Te(C2F5)2 with
an opposite trend of the value when both molecules interact with
Lewis bases under the same conditions. Therefore, the sign of the
2J(125Te,19F) coupling constant of 3a and 3d was explored.
C2F5TeSC(S)NEt2 (5d) in CD3CN), while three of the signals
gave crosspeaks in the 19F{125Te} HMBC spectra. The signal of
Te[SC(S)NEt2]4 6a occurs at −543 ppm and cannot be displayed
in this figure due to technical limitations. The chemical shifts for
Te(C2F5)2 (1218 ppm)12, Te2(C2F5)2 (685 ppm)12, Te[SC(S)NEt2]2
(763 ppm)14 and Te[SC(S)NEt2]4 (−543 ppm)14 correspond to
reported values, while the resonance of 5d is located at 1028 ppm.
Similar relations are found for the corresponding trifluoromethyl
derivatives 5a–c and the other pentafluoroethyl derivatives 5e
and 5f. In most cases compounds 4 and 6 crystallized from the
solutions as dark red (4) and yellow to orange (6) specimens.
The sign of this coupling constant can be obtained from 13C,19F
correlated spectra investigating the crosspeaks of the tellurium
satellites of the fluorine signals to the tellurium satellites of the 13
C
signals. The slope of these crosspeaks provides information on the
relative sign of the 2J(125Te,19F) coupling constant compared with
1
the sign of the J(13C,125Te) coupling constant. The correlation
2
spectra of 3a and 3d exhibit the J(125Te,19F) coupling constant
Table 4 Compilation of NMR data of perfluoroalkyl(dithiocarbamato)tellurium(II), RfTeSC(S)NR2 5
Compound
Solvent
3h
3h
3h
3h
5e
5f
CD3CN (CD2Cl2)
CD3CN (CD2Cl2)
CD3CN (CD2Cl2)
CD3CN
CD3CN
CD3CN
19F
d(CF3)
−26.4 (−26.6)
−26.1 (−26.0)
−25.7 (−26.3)
−84.0, tc
−91.9, q
[23] 38
−84.0, tc
−91.4, q
[23] 38
−83.9, br
−90.0,br
[n.o.] 36
284/315
d(CF2)
[3]2J(Te,F)/Hz
aJ(F,C)/Hz
197 (187)
371
196 (183)
371
198 (183)
371
283/317
283/317
125Te
d
1100 (1103)
1150 (1162)
1156 (1146)
119.7
1028
1078
1082
13C
d(CF3)
d(CF2)
d(CS2)
d(NCH2)
d(other)
119.8
118.7
120.5
115.6
n.o.
52.4
11.4
120.5
114.8
195.3
53.0
120.5
115.3
n.o.
58.8
128.6; 129.2;
129.9; 135.3
193.7
50.0
11.5
187.9
54.6
26.2
n.o.
58.7
128.5; 129.2;
129.9; 135.2
25.0
1H
d(NCH2)
d(other)
3.8, 4H
1.3, 6H
3.7, 4H
2.0, 4H
5.0, 4H
3.8, 4H
1.3, 6H
3.7, 4H
2.1, 4H
5.0, 8H
7.3,b 10H
7.3,b 10H
a First value 1JF,C of CF3 group; second of CF2 group. b Centre of overlapping multiplets. c3JF,F = 3.1 Hz.
1834 | Dalton Trans., 2007, 1829–1837
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1
to have the same sign as the J(13C,125Te) coupling constant for
both anions. This fact explains the increase of the value of the
2J(125Te,19F) coupling constant for both compounds.
1
The sign of the J(13C,125Te) coupling constant of 419 Hz of
Te(CF3)2 was found to be positive.24 The values of the 1J(13C,125Te)
coupling constants are 517 Hz for 3d and 662 Hz for 3a. The fact
that all three values are found in the same order of magnitude led
to the assumption of all three couplings having a positive sign. As
2
a consequence, the sign of the J(125Te,19F) coupling constant is
positive for both derivatives, 3a and 3d.
Structures of 4b and 6c
In bis(tetramethylendithiocarbamato)tellurium(II) (4b) (Tables 2
and 3; Fig. 6), the two dithiocarbamato moieties act as bidentate
chelating ligands as it is found in all the structures of related
compounds.16,17,21 The sulfur coordination around tellurium is
best described as a planar trapezoidal configuration with two
˚
˚
short (2.518(1); 2.495(1) A) and two long (2.898(1); 2.896(1) A)
˚
Te–S bonds. Carbon–sulfur bond lengths differ by 0.05 A as
well. Together with the quite short C–N bond the essentially
planar dithiocarbamate ligand may be seen somewhere between
2−
the canonical forms R2N+ CS2 and R2N–C(S)S−.
=
Fig. 7 Molecular structure and labelling scheme of Te(SC(S)NBz2)4 6c.
Fig. 6 Molecular structure and labelling scheme of Te(SC(S)N(CH2)4)2
4b.
Tetrakis(dibenzyldithiocarbamato)tellurium(IV) (6c) (Tables 2
¯
and 3; Fig. 7 and 8) crystallizes in the tetragonal space group P421c.
The space group symmetry requires that the Te atoms are found
on fourfold inversion axes. They are distorted dodecahedrally
coordinated to the 8 S atoms of the 4 dithiocarbamato ligands.
˚
The Te–S bond lengths of 2.723(1) and 2.755(1) A as well as the
˚
S–C bond lengths of 1.707(5) and 1.714(5) A deviate only slightly
from each other indicating that the negative charge of the ligand
is nearly ideally delocalised. The lone pair of electrons on Te(IV)
appears to be stereochemically inactive. Bond lengths and angles
match best with those reported for tetrakis[N-(2-hydroxyethyl)-N-
methyldithiocarbamato]tellurium(IV).25
Fig. 8 View of the unit cell of compound 6c.
was used as an external lock (5 mm tube) in reaction control
measurements while an original sample of the reaction mixture
was measured in a 4 mm insert. Due to the sensitivity of
NMR parameters to concentration for tellurium compounds, all
NMR experiments were performed with saturated solutions. The
13C,19F-HMQC spectra for sign determination, optimized for the
1J(13C,19F) coupling constant, were carried out using a 5 mm
inverse broadband probe head. The detection coil was tuned to
the fluorine frequency of 470.59 MHz, the decoupling coil to the
carbon frequency of 125.76 MHz. The 90◦ fluorine pulse was
14.0 ls, the 90◦ 13C pulse 12.5 ls.
Experimental
The following derivatives were prepared according to literature
procedures: [NMe4]TeCF3,5 Me3SiC2F5,26 [NMe4]F,27 [PNP]X,28
((CH2)4NC(S)S)2,29
[Cs(15-crown-5)2]I,30
Te[SC(S)NR2]2.14
Me3SiCF3 (ABCR), elemental tellurium (Acros), and (Et2NC-
(S)S)2 (Fluka) were used as received. (Bz2NC(S)S)2 was received
from Prof. Dr Josef Hahn as a gift.
Schlenk techniques were used throughout all manipulations.
NMR spectra were recorded on Bruker AC 200 (routine 1H,
19F), AVANCE II 300, AVANCE 400 and DRX500 spectrometers.
Assignments were made on the basis of 1D and 2D NMR
(HMBC; HMQC) experiments. External standards were used in
all cases (1H, 13C: Me4Si; 19F: CCl3F; 125Te: Me2Te). Acetone-d6
Negative ESI mass spectra in MeCN solutions were run on
a Finnigan MAT 900 apparatus with a flow rate of 2 ll min−1.
Intensities are referenced to the most intense peak of a group.
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EI mass spectra (20 eV) were recorded on a Finnigan MAT 95
spectrometer. Isotope patterns for comparison were calculated
with the program Isopro.31 Visible decomposition points were
determined using the Stuart melting point apparatus SMP10. C,
H, N, and S analyses were carried out with a HEKAtech Euro EA
3000 apparatus. Details of crystal data and structure refinement
parameters are summarised in Table 2.
Method B. Due to the low solubility of Te[SC(S)N(CH2)4]2 in
glyme, the reactions were only performed with Te[SC(S)NEt2]2
and Te[SC(S)NBz2]2. To a mixture of 1.0 mmol of 4 and 1.2 mmol
of Me3SiRf in 10 mL glyme (−60 ◦C), 1.0 mmol [NMe4]F was
added in one portion. The mixture was stirred overnight, while the
temperature rose to room temperature. All volatile components
were condensed in vacuo giving the salts 3a, 3c, 3d, and 3f in
quantitative yields.
The NMR data are summarized in Table 1.
X-Ray crystal structure determinations
Tetramethylammonium
trifluoromethylbis(diethyldithiocar-
Data collection for X-ray structure determinations (Table 2)
were performed on a STOE IPDS I/II diffractometer using
bamato)tellurate(II), [NMe4][CF3Te(SC(S)NEt2)2] (3a). Mp
(decomp.) 100 ◦C; Found. C, 31.5; H, 5.8; N, 7.2%.
C15H32N3S4F3Te requires C, 31.8; H, 5.7; N, 7.4%.
˚
graphite-monochromated Mo-Karadiation (0.71073 A). The data
were corrected for Lorentz and polarization effects. A numerical
absorption correction based on crystal-shape optimization was
applied for all data.32 The programs used in this work are Stoe’s
X-Area,33 including X-RED and X-Shape for data reduction and
absorption correction,34 and the WinGX suite of programs,35
including SIR-9236 and SHELXL-9737 for structure solution and
refinement. The hydrogen atoms were placed in idealized positions
and constrained to ride on their parent atom. The last cycles of
refinement included atomic positions for all the atoms, anisotropic
thermal parameters for all the non-hydrogen atoms and isotropic
thermal parameters for all of the hydrogen atoms. Selected
interatomic distances and angles are given in Table 3.
Tetramethylammonium trifluoromethylbis(tetramethylendithio-
carbamato)tellurate(II), [NMe4][CF3Te(SC(S)N(CH2)4)2] (3b).
Mp (decomp.) 130 ◦C; Found. C, 32.2; H, 5.1; N, 7.9%.
C15H28N3S4F3Te requires C, 32.0; H, 5.0; N, 7.5%.
Tetramethylammonium trifluoromethylbis(dibenzyldithiocarb-
amato)tellurate(II),
[NMe4][CF3Te(SC(S)NBz2)2]
(3c). Mp
(decomp.) 101 ◦C; Found. C, 51.7; H, 5.0; N, 5.4%.
C35H40N3S4F3Te requires C, 51.5; H, 4.9; N, 5.2%.
Tetramethylammonium
pentafluoroethylbis(diethyldithio-
carbamato)tellurate(II), [NMe4][C2F5Te(SC(S)NEt2)2] (3d). Mp
(decomp.) 70 ◦C; Found. C, 31.1; H, 5.4; N, 6.7%. C16H32N3S4F5Te
requires C, 31.1; H, 5.2; N, 6.8%.
CCDC reference numbers 614394 (3h), 614395 (3j), 614396 (3k),
614397 (4b) and 614398 (6c).
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b618240b
Tetramethylammonium pentafluoroethylbis(tetramethylendithio-
carbamato)tellurate(II), [NMe4][C2F5Te(SC(S)N(CH2)4)2] (3e).
Mp (decomp.) 159 ◦C; Found. C, 31.0; H, 4.9; N, 7.0%.
C16H28N3S4F5Te requires C, 31.3; H, 4.6; N, 6.9%.
Tetramethylammonium pentafluoroethyltellurate(0) (1b). The
preparation procedure was the same as that used for 1a.5 An
amount of 2.00 g (15.7 mmol) elemental tellurium was suspended
in a solution of 2.14 g (11.1 mmol) Me3SiC2F5 in 80 mL
glyme at −60 ◦C. [NMe4]F (0.93 g; 10.0 mmol) was added
and the reaction mixture was allowed to warm up to ambient
temperature overnight. Excess tellurium was filtered off and all
volatile components were distilled off in vacuo at room temperature
giving a waxy solid which was washed twice with n-pentane. After
drying in vacuo, 1b was obtained as a malodorous, pale ochre solid
in 91% yield (2.92 g).
Tetramethylammonium pentafluoroethylbis(dibenzyldithiocarb-
amato)tellurate(II), [NMe4][C2F5Te(SC(S)NBz2)2] (3f). Mp (de-
◦
comp.) 85 C; Found. C, 49.2; H, 4.7; N, 4.9%. C36H40N3S4F5Te
requires C, 50.0; H, 4.7; N, 4.9%.
Synthesis of bis(15-crown-5)caesium trifluoromethylbis(dithi-
ocarbamato)tellurates(II) (3g–i) and bis(triphenylphosphoranyl-
iden)ammonium
trifluoromethylbis(tetramethylendithiocarba-
mato)tellurate(II) (3j). Equimolar amounts (0.5 mmol) of 3a–c
and [Cs(15-crown-5)2]I or [PNP]I were dissolved in 10 mL MeCN
at room temperature. The mixture was stirred for approximately
Mp (decomp.) 115 ◦C; Found. C, 22.2; H, 4.0; N, 4.4%.
C6H12NF5Te requires C, 22.5; H, 3.8; N, 4.4%. dH (DMF-d7)
1
2
3.41 ([NMe4]+); dF (DMF-d7) −66.6 (q, 2F, J(Te,F) = 108 Hz,
1 h. Completeness of the exchange was monitored by H NMR
3
3
1J(F,C) = 299 Hz, J(F,F) = 10 Hz), −83.5 (t, 3F, J(Te,F) =
spectroscopy (missing signal of the [NMe4] ion). [NMe4]I was
filtered off, and the solvent was evaporated to dryness. The
residue was washed with two small portions of n-pentane and
recrystallized from CH2Cl2/diethyl ether mixtures (v/v = 1 : 1)
in open glass beakers. The salts 3g–j were isolated as pale yellow
crystals in better than 90% yields. NMR data of the anions did
not deviate from those listed in Table 1.
12 Hz; 1J(F,C) = 283 Hz, 3J(F,F) = 10 Hz), dTe{F} (DMF-d7) 140,
d
C{F} 120.1 (s, 2J(Te,C) = 76 Hz), 95.1 (s, 1J(Te,C) = 574 Hz), 54.4
(qdec, 1J(C,H) = 144 Hz, 3J(C,H) = 4 Hz).
Synthesis of tetramethylammonium perfluoroalkylbis(dithio-
carbamato)tellurates(II) (3a–f).
Method A. An amount of 0.54 g (2.0 mmol) 1a (0.32 g
(1.0 mmol) 1b) was dissolved in 15 mL (10 mL) MeCN. 2.0 mmol
(1.0 mmol) of the corresponding dithiuramdisulfide 2 was added in
one portion. Directly after the addition, the colour of the reaction
mixture changed from ochre to bright yellow–orange. Stirring was
continued for up to 1 h. The solvent was removed in vacuo, giving
waxy orange residues. Washing twice with n-pentane and drying in
vacuo at ambient temperature gave the intensive yellow salts 3a–f
in nearly quantitative yields.
Bis(15-crown-5)caesium
trifluoromethylb◦is(diethyldithiocarb-
amato)tellurate(II) (3g). Mp (decomp.) 125 C; Found. C, 35.3;
H, 5.7; N, 3.1%. C31H60N2O10S4F3TeCs requires C, 34.9; H, 5.7;
N, 2.6%.
Bis(15-crown-5)caesium trifluoromethylbis(tetramethylendithio-
carbamato)tellurate(II) (3h). Mp (decomp.) 135 ◦C; Found. C,
35.1; H, 5.4; N, 2.9%. C31H56N2O10S4F3TeCs requires C, 35.0; H,
5.3; N, 2.6%.
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Bis(15-crown-5)caesium trifluoromethylbis(dibenzyldithiocarb-
amato)tellurate(II) (3i). Mp (decomp.) 133 C; Found. C, 46.9;
H, 5.4; N, 2.5%. C51H68N2O10S4F3TeCs requires C, 46.6; H, 5.2; N,
2.1%.
5 W. Tyrra, N. V. Kirij, D. Naumann and Yu. L. Yagupolskii, J. Fluorine
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120 ◦C; Found. C, 54.8; H, 4.8; N, 3.7%. C47H46N3P2S4F3TeCs
requires C, 54.4; H, 4.5; N, 4.1%.
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To a well stirred solution of 1 mmol 3 either in MeCN or glyme,
1 mmol Ag[BF4] was added at room temperature. Directly after
the addition, the colour of the reaction mixture changed from
bright yellow into intensively orange, while [NMe4][BF4] and
Ag[SC(S)NR2] precipitated as white solids. Stirring was continued
for approximately 30 min and completeness of the reaction was
checked by 19F NMR spectroscopy. The precipitate was filtered
off and all volatile compounds were removed in vacuo giving
the derivatives 5 as viscous dark orange materials which were
washed with n-pentane. Elemental analyses revealed in all cases
impurities by the corresponding dithiuramdisulfide. Due to the
decomposition processes in solution, attempts to recrystallize
the compounds remained unsuccessful. The results of NMR
examinations are given in Table 4.
Acknowledgements
Financial support by the Fonds der Chemischen Industrie is
gratefully acknowledged. We are indebted to Dr Mathias Scha¨fer
(Institut fu¨r Organische Chemie, Universita¨t zu Ko¨ln) for running
the negative ESI mass spectra and PD Dr Angela Mo¨ller for
helpful discussions.
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