4-Tetrafluoropyridyl silver(I), AgC5F4N, in redox transmetalations with selenium and tellurium23

Article abstract of DOI:10.1021/om201195j

Se(C₅F₄N)₂ and Te(C₅F ₄N)₂ were prepared via redox transmetalations of AgC ₅F₄N and the corresponding elements in good yields. The crystal structures of both derivatives exhibit infinite chains caused by a weak intermolecular contact between the chalcogen and one nitrogen atom with a T-shaped (ψ-pentagonal-bipyramidal) ligand arrangement. Crystallization of both reagents from dimethylsulfoxide gave single crystals of the corresponding 1:1 adducts that crystallize in infinite chains best expressed by the formula [E(C₅F₄N)₂?(μ-DMSO)]_∞ (E = Se, Te). In these cases, the coordination spheres of selenium and tellurium are square-planar (ψ-octahedral). Similar effects are found in the molecular structures of [Te(C₅F₄N)₂?TMTU] _∞ and [Te(C₆F₅)₂?TMTU] _∞ (TMTU = tetramethylthiourea). Differences in the Te-S interatomic distances clearly indicate the C₅F₄N ligand being significantly more electron-withdrawing in comparison with the C ₆F₅ group; that is, Te(C₅F₄N) ₂ is the stronger Lewis acid.

Full text of DOI:10.1021/om201195j

Article
pubs.acs.org/Organometallics
4-Tetrafluoropyridyl Silver(I), AgC5F4N, in Redox Transmetalations
with Selenium and Tellurium23
Said Aboulkacem, Dieter Naumann, Wieland Tyrra,* and Ingo Pantenburg
Institut fur Anorganische Chemie, Department fur Chemie, Universitat zu Koln, Greinstr. 6, D-50939 Koln, Germany
̈
̈
̈
̈
̈
S
* Supporting Information
ABSTRACT: Se(C5F4N)2 and Te(C5F4N)2 were prepared via
redox transmetalations of AgC5F4N and the corresponding
elements in good yields. The crystal structures of both derivatives
exhibit infinite chains caused by a weak intermolecular contact
between the chalcogen and one nitrogen atom with a T-shaped
(ψ-pentagonal-bipyramidal) ligand arrangement. Crystallization of
both reagents from dimethylsulfoxide gave single crystals of the
corresponding 1:1 adducts that crystallize in infinite chains best
expressed by the formula [E(C5F4N)2·(μ-DMSO)]∞ (E = Se, Te). In these cases, the coordination spheres of selenium and
tellurium are square-planar (ψ-octahedral). Similar effects are found in the molecular structures of [Te(C5F4N)2·TMTU]∞ and
[Te(C6F5)2·TMTU]∞ (TMTU = tetramethylthiourea). Differences in the Te−S interatomic distances clearly indicate the C5F4N
ligand being significantly more electron-withdrawing in comparison with the C6F5 group; that is, Te(C5F4N)2 is the stronger
Lewis acid.
temperature, Se(C5F4N)2 was sublimed out of the gray
remainder as colorless and air- and moisture-insensitive needles
in 53% yield (with respect to AgF), showing a melting point of
87 °C. The 19F NMR chemical shifts appear to be solvent-
dependent, changing from the noncoordinating solvent CDCl3
to DMSO-d6 (Table 1). Such behavior indicates an interaction
INTRODUCTION
■
The tetrafluoropyridyl group has already attracted considerable
interest in transition-metal1 as well as main group chemistry.2−4
On the basis of theoretical calculations,5 the electron-
withdrawing effect of the C5F4N ligand should be considered
to be higher than that of the isolobal C6F5 group. Together with
the knowledge that tetrafluoropyridyl silver(I) can be
synthesized conveniently and is a versatile tool for redox
transmetalations,3,4 we extended our investigations to reactions
of AgC5F4N with elemental selenium and tellurium.
Although several different methods are established for the
generation of bis(fluoroaryl)chalcogen(II) derivatives,6−11 the
ease and selectivity to use, for example, AgC6F5,12,13 in redox
transmetalations makes this route very appealing.
Table 1. Compilation of Selected NMR Data for Se(C5F4N)2
and Te(C5F4N)2 (21 °C, δ in ppm, J in Hz))
Se(C5F4N)2
CDCl3 DMSO-d6
−130.3, 2F −129.4, 2F −121.1, 2F −119.2, 2F
Te(C5F4N)2
solvent
δ(F-3,5)
CDCl3 DMSO-d6
δ(F-2,6)
δ(C-3,5)
δ(C-2,6)
δ(C-4)
−88.1, 2F
141.5
−91.6, 2F
142.6
−89.0, 2F
−92.3, 2F
a
b
142.7
a
143.3
142.8
142.8
RESULTS AND DISCUSSION
■
119.6
123.1
106.6
370
Redox transmetalations of AgC5F4N and selenium and
tellurium proceed in a similar manner as described for the
groups 12−15 elements3,4 (Scheme 1).
1JC,Se/1JC,Te
130
n.o.
δ(77Se)/δ(125Te) +218
+185
+427
+388
a
b
Values may be interchangeable. Not measured.
Scheme 1
of the lone electron pairs of the solvent molecules to the
relatively electron-poor selenium center, which is caused by the
strong electron-withdrawing effect of the attached C5F4N
groups.5
Three signals were detected in the 13C{19F} NMR spectrum
of Se(C5F4N)2 recorded in CDCl3. A sharp singlet at δ 119.6
Bis(4-tetrafluoropyridyl)selenium. The reaction of
AgC5F4N with red selenium in EtCN proceeded at ambient
temperature completely and selectively within 2 days. After
vacuum condensation of all volatile materials at room
Special Issue: Fluorine in Organometallic Chemistry
Received: December 1, 2011
Published: January 18, 2012
© 2012 American Chemical Society
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Organometallics
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was assigned to the 4-C atom of the C5F4N moiety directly
prepared in EtCN solution using intermediately formed
AgC5F4N and an excess of elemental tellurium following
Scheme 1. The reaction proceeded with quantitative con-
sumption of AgC5F4N over a period of 16 h at ambient
temperature to give Te(C5F4N)2 in 82% yield. The pale yellow
needles, insensitive to moisture and air, showed a melting point
of 79−81 °C. In contrast to reactions with elemental selenium,
the reaction time was shortened to around 4 h by raising the
temperature to +50 °C without formation of any byproduct. A
similar solvent dependence of the NMR data as observed for
Se(C5F4N)2 has to be applied to the tellurium derivative (Table
1). As already outlined for several other derivatives bearing this
organic substituent,3,4,14 unambiguous assignment of C-3,5 and
C-2,6 is more than difficult in most cases. Two overlapping
doublets are detected at δ 142.8 and 142.7, both exhibiting 1JF,C
couplings estimated to be around 250 Hz. A triplet at δ 106.6
with a 2JF,C coupling of 28 Hz and 125Te satellites (1JTe,C ≈ 370
Hz) was definitely attributed to the C-4 carbon atom. The
125Te NMR signal (CDCl3) was detected as a well-resolved
quintet of quintets at δ +427 showing 3JTe,F couplings of 25 Hz
1
attached to the selenium center with a JSe,C coupling of 130
Hz. The resonance of C-3,5 occurred at 141.5 ppm with a 2JSe,C
1
coupling of 8 Hz and that of C-2,6 at 143.3 ppm. The JF,C
couplings (taken from the 19F NMR spectrum) exhibited to be
259 and 250 Hz, respectively. The broadened 77Se{19F}NMR
resonance was detected at +218 ppm. Adduct formation with
donor solvents is best demonstrated by recording spectra in
DMSO-d6 (δ +185) and acetone-d6 (δ +192). In the latter
undecoupled 77Se NMR experiment, the selenium signal was
detected as a quintet due to the couplings with four
3
magnetically equivalent F-3,5 atoms and a JSe,F coupling of
4
12 Hz. The JSe,F coupling appeared to be smaller than 2 Hz
due to the digital resolution used in this NMR experiment.
EI mass spectra were dominated by the molecular peak of the
radical cation [Se(C5F4N)2]+ being additionally the 100% peak
and that of [Se(C5F4N)]+ (16%), both displaying absolute
agreement of measured and calculated isotope patterns.
However, raising the reaction temperature to +50 °C to
accelerate the reaction was accompanied by loss of selectivity.
The starting material AgC5F4N was already completely
converted after 5 h, but among Se(C5F4N)2 (80%), presumably
the diselenane, Se2(C5F4N)2 (20%), was formed (Scheme 2).
4
as well as JTe,F couplings of approximately 3.5 Hz.
Unfortunately, 19F decoupled NMR spectra could not be
recorded. Similarly, as outlined for the homologous selenium
derivative, 20 eV EI mass spectra show the radical ion peak of
[Te(C5F4N)2]+ coincidentally being the 100% peak, and the
radical ion peak of [Te(C5F4N)]+ (32%) fully matching the
calculated isotope pattern.
Scheme 2
Molecular Structures of Bis(4-tetrafluoropyridyl)-
selenium, Se(C5F4N)2, and Bis(4-tetrafluoropyridyl)-
tellurium, Te(C5F4N)2. Selected bond lengths and angles are
summarized in Table 2. Both derivatives Se(C5F4N)2 and
Te(C5F4N)2 crystallize isostructurally in the monoclinic space
group P21/c (No. 14) with eight molecules per unit cell (Table
3) of two crystallographically independent molecules (Figure
1).
The basic arrangement (Table 2) of the tetrafluoropyridyl
units around the chalcogen atoms is V-shaped with C−E−C
angles of 95.47(12)° and 96.16(13)° for the selenium
compound and 90.86(18)° as well as 91.73(18)° for the
tellurium derivative (Figure 1) following Bent’s rule. The E−C
distances are by approximately 0.6 pm (Se) and 2.4 pm (Te)
longer and the C−E−C bond angles by approximately 0.8°
(Se) and 2.0° (Te) more acute than those of the closely related
pentafluorophenyl derivatives.8,9 The average value of the C−
Se distances of 191.8(3) pm matches that of the nonfluorinated
homologue (191.3(4) pm),15 while the mean angle C−Se−C
(95.82(13)°) underruns that of Se(C5H4N)2 (100.4(1)°) by
The formation of the diselenane is exclusively formulated on
comparison of 19F NMR data. NMR chemical shifts for the
closely related pentafluorophenyl derivatives8 support this
suggestion; the differences between Se(C5F4N)2 and
Se2(C5F4N)2 as well as Se(C6F5)2 and Se2(C6F5)2 are
accompanied by a low-field shift of the F-3,5 (F-2,6 for
Se(C6F5)2) and F-2,6 (F-3,5 for Se(C6F5)2) resonances by less
than 1 ppm. Fortunately, crystalline Se(C5F4N)2 was easily
removed from the brown oily residue by crystallization from
CH2Cl2 or by vacuum sublimation.
Bis(4-tetrafluoropyridyl)tellurium. In a similar manner as
described for the selenium derivative, Te(C5F4N)2 was
Table 2. Selected Bond Lengths and Angles of E(C5F4N)2 and the Adducts with DMSO and TMTU as Well as Te(C6F5)2·TMTU
(d in pm; < in deg)
Te(C5F4N)2·
TMTU
Se(C5F4N)2
Te(C5F4N)2
Se(C5F4N)2·OSMe2 Te(C5F4N)2·OSMe2 Te(C6F5)2·TMTU
d(E−C)
191.7(3)
191.4(3)
192.0(3)
95.47(12)
211.0(5)
212.0(5)
212.6(4)
91.73(18)
193.1(3)
193.2(3)
92.13(13)
213.7(4)
213.3(4)
86.80(14)
214.7(3)
214.3(3)
90.64(11)
215.6(2)
215.2(2)
87.69(6)
191.9(3)
213.1(4)
<(C−E−C)
d(E−X)
96.16(13)
90.86(18)
X = N
X = O
X = S
321.7(6)
314.6(6)
327.7(14)
312.4(12)
288.7(11)
289.8(14)
167.99(20)
168.25(19)
114.67(14)
285.0(8)
319.8(18)
329.5(30)
172.54(17)
165.54(20)
111.27(12)
315.1(6)
284.8(12)
162.54(22)
165.16(24)
118.35(15)
317.4(5)
<(C−E−X)
<(X−E−X)
170.79(20)
171.94(20)
162.77(28)
167.33(30)
172.32(8)
166.74(10)
108.09(18)
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Organometallics
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builds up infinite chains with the motif of a zipper with one
C5F4N group being directed on the chalcogen atom of the next
molecule in the chain and the other being directed by
approximately 90° to the center of the “zipper” (Figure 2).
Table 3. Crystal Data and Structure Refinement Parameters
for Se(C5F4N)2 and Te(C5F4N)2
Se(C5F4N)2
C10N2F8Se
formula mass (g mol−1) 379.08
Te(C5F4N)2
C10N2F8Te
427.72
empirical formula
rotation angle range
0° ≤ ω ≤ 180°; ψ = 0° 0° ≤ ω ≤ 180°; ψ = 0°
0° ≤ ω ≤ 160°; ψ = 90° 0° ≤ ω ≤ 62°; ψ = 90°
increment
Δω = 2°
170
Δω = 2°
121
no. of images
exposure time (min)
5
8
detector distance (mm) 120
120
2θ range (deg)
temperature (K)
index range
1.9−54.8
170(2)
1.9−54.8
120(2)
−26 ≤ h ≤ 26
−8 ≤ k ≤ 9
−19 ≤ l ≤ 20
32426
−31 ≤ h ≤ 32
−7 ≤ k ≤ 6
−20 ≤ l ≤ 20
22330
total data collected
unique data
observed data
Rmerg
5042
5189
3745
3752
0.0748
0.0436
transmission min/max
cryst syst
0.3345/0.7046
monoclinic
P21/c (No. 14)
2074.6(2)
732.0(1)
0.4727/0.7847
monoclinic
P21/c (No. 14)
2548.7(3)
590.9(1)
1602.4(2)
104.46(1)
8/2335.7(4)
R1 = 0.0361
wR2 = 0.0854
R1 = 0.0565
wR2 = 0.0968
283850
space group
a (pm)
Figure 2. Packing of E(C5F4N)2 along the crystallographic b axis
shown exemplarily for the selenium derivative.
b (pm)
c (pm)
1557.1(2)
107.13(1)
8/2259.8(4)
R1 = 0.0340
wR2 = 0.0813
R1 = 0.0489
wR2 = 0.0863
283849
However, no evidence is found for any kind of π-stacking
that is dominating the molecular structures of P(C5F4N)3 and
As(C5F4N)3.4 The E−N contacts within the chains are weak
(314.6(6)/321.7(6) pm, angle C−Se−N 171.94(20)/
170.79(20)° (Se); 312.4(12)/327.7(14) pm, angle C−Te−N
167.33(30)/162.77(28)° (Te)) but shorter than the sum of van
der Waals radii of the chalcogen atoms and nitrogen (∑(van
der Waals) Se−N = 345 pm; Te−N = 361 pm).16,17 This ligand
arrangement exceeds the basic ψ-tetrahedron to a ψ-trigonal
bipyramid with carbon and nitrogen forming the apexes and
one C5F4N ring and the two lone electron pairs being located in
equatorial positions (AB3E2). These findings might be
interpreted as packing effects rather than as structure-
determining Lewis acid base interactions as found in the
crystal structure of Hg(C5F4N)2.3
β (deg)
Z/volume (106·pm3)
a
R indexes (I > 2σI)
a
R indexes (all data)
CCDC reference
number
a
R1 = ∑||Fo| − |Fc||/∑|Fo|, wR2 = [∑w(|Fo|2 − |Fc|2)2/∑w(|Fo|2)2]1/2
,
and S2 = [∑w(|Fo|2 − |Fc|2)2/(n − p)]1/2, with w = 1/[σ2(Fo)2 +
(0.0478P)2] for Se(C5F4N)2 and w = 1/[σ2(Fo)2 + (0.0564P)2
+
0.3578·P] for Te(C5F4N)2, where P = (Fo + 2Fc2)/3. Fc* = kFc[1 +
2
0.001|Fc|2λ3/(sin 2θ)]−1/4
.
Molecular Structures of the 1:1 Adducts of Bis(4-
tetrafluoropyridyl)selenium, Se(C5F4N)2, and Bis(4-
tetrafluoropyridyl)tellurium, Te(C5F4N)2, with DMSO.
Selected bond lengths and angles are summarized in Table 2.
Both compounds form 1:1 adducts with the Lewis base DMSO
and crystallize isotypic in the monoclinic space group P21/c
(No. 14) with four molecules per unit cell (Table 4; Figure 3).
The basic molecular structure (Figure 3) shows a nearly ideal
planar arrangement of two C5F4N groups and two bridging
DMSO molecules coordinating as to be expected via the
oxygen atom. Marginal deviations from planarity are best
expressed by the angular sums around the chalcogen centers
being 359.70° for the selenium and 359.95° for the tellurium
derivative. The sterically active lone electron pairs occupy apical
positions as predicted for an AB2C2E2 kernel by the VSEPR
model.
Figure 1. View of the molecular structure of the two independent
molecules of E(C5F4N)2 shown exemplarily for the selenium
derivative.
The planar 4-fold coordination is extended in the solid state
to parallel infinite chains via edge-on bridging oxygen atoms
connecting the heavier chalcogen atoms along the crystallo-
graphic c axis (Figure 4). Planes of adjacent units are twisted by
more than 4°. This observation may be attributed to the higher
group electronegativity of the C5F4N group in comparison with
the isolobale C6F5 group and the nonfluorinated homologue on
the basis of theoretical calculations.5 Furthermore, E(C5F4N)2
97
1°. The averaged chalcogen oxygen distances (Se−O,
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Organometallics
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Table 4. Crystal Data and Structure Refinement Parameters
for Se(C5F4N)2·DMSO and Te(C5F4N)2·DMSO
Se(C5F4N)2·DMSO
Te(C5F4N)2·DMSO
empirical formula
C12H6N2OF8SSe
C12H6N2OF8STe
505.85
formula mass (g mol−1) 457.21
rotation angle range
0° ≤ ω ≤ 180°; ψ = 0° 0° ≤ ω ≤ 180°; ψ = 0°
0° ≤ ω ≤ 96°; ψ = 90° 0° ≤ ω ≤ 180°; ψ = 90°
0° ≤ ω ≤ 180°; ψ = 135°
increment
Δω = 2°
138
Δω = 2°
270
no. of images
exposure time (min)
5
3
detector distance (mm) 120
100
2θ range (deg)
temperature (K)
index range
1.9−54.8
150(2)
2.2−59.5
150(2)
−12 ≤ h ≤ 12
−22 ≤ k ≤ 22
−11 ≤ l ≤ 11
16540
−13 ≤ h ≤ 13
−24 ≤ k ≤ 24
−12 ≤ l ≤ 12
35962
Figure 4. View of the infinite chains of square-planar E-
(C5F4N)2·DMSO units extending along the crystallographic c axis
(viewed along a).
total data collected
unique data
observed data
Rmerg
3411
4449
2825
3235
0.0355
0.0808
comparison with the corresponding selenium compound. The
“solid state” formula of both compounds is best expressed by
[E(C5F4N)2·(μ-DMSO)]∞ (E = Se, Te).
transmission min/max
cryst syst
0.4068/0.7388
monoclinic
P21/c (No. 14)
958.6(1)
0.2663/0.7105
monoclinic
P21/c (No. 14)
969.1(1)
1778.3(2)
928.2(2)
98.52(1)
4/1581.9(3)
R1 = 0.0419
wR2 = 0.1069
R1 = 0.0571
wR2 = 0.1124
283852
space group
a (pm)
Molecular Structures of the 1:1 Adducts of Bis(4-
tetrafluoropyridyl)tellurium, Te(C5F4N)2, and Bis-
(pentafluorophenyl)tellurium, Te(C6F5)2, with Tetrame-
thylthiourea (TMTU). Selected bond lengths and angles are
summarized in Table 2. Both compounds were obtained as
crystalline solids upon slow evaporation of CHCl3 from 1:1
mixtures of the acid (Te compound) and the base
tetramethylthiourea, (Me2N)2CS (TMTU) (Table 5). The
monoclinic space group P21/c (No. 14) exhibited to be
predestined to solve all structures mentioned in this
contribution. For both compounds (Table 2), structural motifs
described for the DMSO adducts are nearly identical with
respect to (i) the polymeric nature, (ii) the ψ-octahedral
molecular structure (AB2C2E type), and (iii) the quasi ideal
ligand arrangement C2TeS2 within the plane (angular sum:
359.90°).
b (pm)
1794.5(2)
898.3(1)
c (pm)
β (deg)
96.35(1)
Z/volume (106·pm3)
4/1535.8(3)
R1 = 0.0376
wR2 = 0.0897
R1 = 0.0472
wR2 = 0.0942
283851
a
R indexes (I > 2σI)
a
R indexes (all data)
CCDC reference
number
a
R1 = ∑||Fo| − |Fc||/∑|Fo|, wR2 = [∑w(|Fo|2 − |Fc|2)2/∑w(|Fo|2)2]1/2
,
and S2 = [∑w(|Fo|2 − |Fc|2)2/(n − p)]1/2, with w = 1/[σ2(Fo)2 +
(0.0427P)2 + 2.0475P] for the Se compound and w = 1/[σ2(Fo)2 +
(0.0679P)2 + 0.4147P] for the Te derivative, where P = (Fo2 + 2Fc2)/3.
Fc* = kFc[1 + 0.001|Fc|2λ3/(sin 2θ)]−1/4
.
While interatomic Te−C distances of both compounds are
found to be marginally longer than the sum of covalent radii
(Te−C: 214 pm),17 the sum of Te−S van der Waals radii (Te−
S: 386−405 pm)16,17 is significantly underrun, implying strong
tellurium−sulfur interactions. The stronger electronegative
nature of the C5F4N ligand in comparison with the isolobal
C6F55 group is best demonstrated by the more acute C−Te−C
angle (≈3°), the elongated Te−C bond (≈1 pm), and the
significantly shorter Te−S bond (average value, 8.4 pm)
comparing the molecular structures of [Te(C5F4N)2·TMTU]∞
(Figure 5) and [Te(C6F5)2·TMTU]∞ (Figure 6). The decrease
in C−Te−C angles changing from the C6F5 to the C5F4N
group is consistent with Bent’s rule, which predicts that, if the
electronegativity difference between the central atom and the
ligand is greater, consequently, the bonding orbitals of the
tellurium center have more p character. However, structural
parameters of TMTU do not deviate from each other in both
structures.
Figure 3. View of the molecular structure of the adduct
E(C5F4N)2·DMSO (E = Se, Te).
289.2 pm; Te−O, 284.9 pm) are significantly shorter than the
sum of van der Waals radii (Se−O, 340 pm; Te−O, 360
pm),16,17 implying strong dative interactions between the O-
electron donor and the E-electron acceptor. The significantly
shorter Te−O contacts may be interpreted in terms of a
significantly higher Lewis acidity of the tellurium derivative in
CONCLUSION
■
The oxidative potential of fluoroorgano silver derivatives has
been again impressively demonstrated in reactions of AgC5F4N
with the elements selenium and tellurium. Although
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Table 5. Crystal Data and Structure Refinement Parameters
for Te(C5F4N)2·TMTU and Te(C6F5)2·TMTU
Te(C5F4N)2·TMTU
Te(C6F5)2·TMTU
empirical formula
C17H12N2F10STe
C15H12N4F8STe
559.95
formula mass (g mol−1) 593.95
rotation angle range
0° ≤ ω ≤ 180°; ψ = 0° 0° ≤ ω ≤ 180°; ψ = 0°
0° ≤ ω ≤ 136°; ψ = 90° 0° ≤ ω ≤ 50°; ψ = 90°
increment
Δω = 2°
158
Δω = 1°
230
no. of images
exposure time (min)
7
3
detector distance (mm) 120
120
2θ range (deg)
temperature (K)
index range
1.9−54.8
150(2)
1.9−54.8
170(2)
−13 ≤ h ≤ 13
−26 ≤ k ≤ 26
−11 ≤ l ≤ 12
27617
−13 ≤ h ≤ 12
−25 ≤ k ≤ 26
−11 ≤ l ≤ 10
19191
total data collected
unique data
observed data
Rmerg
4509
4224
3625
3992
0.0412
0.0296
transmission min/max
cryst syst
0.5134/0.8333
monoclinic
P21/c (No. 14)
1032.8(1)
2070.0(2)
946.4(1)
0.5289/0.8513
monoclinic
P21/c (No. 14)
1062.5(1)
2031.9(1)
901.5(1)
space group
a (pm)
b (pm)
c (pm)
β (deg)
90.86(1)
90.59(1)
Z/volume (106·pm3)
4/2023.0(3)
R1 = 0.0273
wR2 = 0.0656
R1 = 0.0390
wR2 = 0.0716
283853
4/1946.1(2)
R1 = 0.0195
wR2 = 0.0485
R1 = 0.0211
wR2 = 0.0495
283854
a
Figure 5. View of the molecular structure of Te(C5F4N)2·TMTU
(top) and the infinite chains of square-planar Te(C5F4N)2·TMTU
units extending along the crystallographic c axis (viewed along a)
(bottom).
R indexes (I > 2σI)
a
R indexes (all data)
CCDC reference
number
a
R1 = ∑||Fo| − |Fc||/∑|Fo|, wR2 = [∑w(|Fo|2 − |Fc|2)2/∑w(|Fo|2)2]1/2
,
and S2 = [∑w(|Fo|2 − |Fc|2)2/(n − p)]1/2, with w = 1/[σ2(Fo)2 +
(0.0452P)2] for the tetrafluoropyridyl and w = 1/[σ2(Fo)2
+
(0.0233P)2 + 1.1399P] for the pentafluorophenyl compound, where
P = (Fo + 2Fc2)/3. Fc* = kFc[1 + 0.001|Fc|2λ3/(sin 2θ)]−1/4
.
2
trimethylsilyl derivatives bearing the individual fluorinated
group have to be prepared in advance, the general utility of
AgRf reagents as oxidative organylation reagents makes them
promising candidates for further synthetic approaches in all
fields of metalorganic and even organic chemistry due to the
reduced number of unwanted byproducts as formed in
transformations using lithium or magnesium derivatives.
Especially, the involvement of the strong electron-withdrawing
C5F4N substituent opens new horizons in several fields.
The chalcogen compounds prepared may become the basis
of further investigations in the fields of synthetic chemistry as
well as material sciences.
EXPERIMENTAL SECTION
■
General Information. Schlenk techniques were used throughout
all manipulations. NMR spectra were recorded on a Bruker AC 200
spectrometer (19F, 13C) and a Bruker AvanceII 300 spectrometer (13C,
77Se, 125Te). External standards were used in all cases (13C, Me4Si; 19F,
CCl3F; 77Se, Me2Se, 125Te, Me2Te). Couplings to heteronuclei given
are respective to the spin-1/2 nuclei 77Se and 125Te. Acetone-d6 was
used as an external lock (5 mm tube) in reaction control
measurements, while an original sample of the reaction mixture was
placed in a 4 mm insert. Mass spectra were run on a Finnigan MAT 95
Figure 6. View of the molecular structure of Te(C6F5)2·TMTU (top)
and the infinite chains of square-planar Te(C6F5)2·TMTU units
extending along the crystallographic c axis (viewed along a) (bottom).
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dx.doi.org/10.1021/om201195j | Organometallics 2012, 31, 1559−1565

Organometallics
Article
spectrometer using the electron impact method (20 eV). Intensities
are referenced to the isotopes 80Se and 130Te, respectively. Visible
decomposition points were determined using the apparatus Stuart
SMP10. CHN analyses were carried out with a HEKAtech Euro EA
3000 apparatus.
Se(C5F4N)·DMSO were placed in idealized positions and constrained
to ride on their parent atom. The last cycles of refinement included
atomic positions for all of the atoms, anisotropic thermal parameters
for all of the non-hydrogen atoms, and isotropic thermal parameters
for all of the hydrogen atoms. A numerical absorption correction was
applied after optimization of the crystal shape.21,22 Crystallographic
data for the structures have been deposited with the Cambridge
Crystallographic Data Centre as a supplementary publication. The
deposition numbers are found in the last row of Tables 3−5. Copies of
the data can be obtained, free of charge, on application to CHGC, 12
Union Road, Cambridge CB2 1EZ, U.K. (Fax: +44 1223 336033 or E-
mail: deposit@ccdc.cam.ac.uk).
Materials. 4-Trimethylsilyl-2,3,5,6-tetrafluoropyridine,
Me3SiC5F4N,3 bis(pentafluorophenyl)tellurium, Te(C6F5)2,10,12 and
red selenium18 were prepared following reported procedures. All other
chemicals were purchased from commercial suppliers and used as
received. AgF is best used if powdery and having a pale brown color.
Synthesis of Se(C5F4N)2. To a solution of AgC5F4Nprepared
from 2 mmol of AgF and 2.4 mmol of Me3SiC5F4Nin 5 mL of
EtCN was added a more than double excess of red selenium (0.20 g).
The reaction mixture was stirred for 2 days at room temperature. The
solution was taken off via a pipet, and all volatile components were
distilled off in vacuo until dryness. The remaining colorless solid was
sublimed at reduced pressure (60 °C, 6 mbar), giving crystals for XRD
measurements. Recrystallization from CH2Cl2 for several days at −20
°C gave crystals of comparable quality. Se(C5F4N)2 (0.20 g) was
obtained (53% yield relative to AgF) with a visible melting point of 87
°C. Anal. Calcd for C10F8N2Se (379.07): C, 31.69; N, 7.39. Found: C,
31.58; N, 7.28. 19F NMR (CDCl3): δ −88.1 (m, 2F, F-2,6, 1JF,C ≈ 250
Hz), −130.3 (m, 2F, F-3,5, 1JF,C ≈ 259 Hz,); (DMSO-d6): δ −91.6 (m,
2F, F-2,6), −129.4 (m, 2F, F-3,5). 13C{19F} NMR (CDCl3): δ 143.3
ASSOCIATED CONTENT
■
S
* Supporting Information
CIF files giving crystallographic data for the structures
determined in this paper. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: tyrra@uni-koeln.de.
2
1
(s, C-2,6), 141.5 (s, C-3,5, JSe,C = 8 Hz), 119.6 (s, C-4, JSe,C = 130
Hz); (DMSO-d6): 142.8 (s, C-2,6, 3JSe,C = 3 Hz), 142.6 (s, C-3,5, 2JSe,C
= 7 Hz), 123.1 (s, C-4, 1JSe,C not resolved). 77Se{19F} NMR (CDCl3):
ACKNOWLEDGMENTS
■
3
δ + 218; (DMSO-d6): +185; (acetone-d6): +192 (qi, JSe,F ≈ 12 Hz,
Financial and infrastuctural support by the Universitat zu Koln
is gratefully acknowledged.
̈
̈
19F coupled). EI-MS (20 eV, 100 °C): m/z = 380 (M+, 100%), 230
([M − C5F4N]+, 16%).
Reactions performed in the same stoichiometry, but for 5 h at +50
°C, gave evidence for the formation of Se(C5F4N)2 (80%; 19F NMR
(EtCN; external lock acetone-d6): δ −91.1 (F-3,5), −130.0 (F-2,6))
and Se2(C5F4N)2 (20%; 19F NMR (EtCN; external lock acetone-d6): δ
−91.3 (F-3,5), −129.3 (F-2,6)).
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1
(dm, C-3,5, JF,C ≈ 246 Hz), 106.6 (t, C-1, JC,F = 28 Hz, JTe,c = 370
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