The protonation of dimethyl sulfoxide: Spectroscopic examinations of [(CX3)2SOX]+MF6- (X=H, D; M=As, Sb) and the X-Ray Structure of [(CH3)2SOH+]4Ge3F16 4-

Article abstract of DOI:10.1002/cplu.201200037

Dimethyl sulfoxide (DMSO) reacts with the superacidic solutions of XF/MF5 and XF/GeF4 (X=H, D; M=As, Sb) under formation of the corresponding salts [(CX3)2SOX+]MF6- and [(CH3)2SOH+]4Ge3F16 4-, respectively. The salts are characterized by vibrational and NMR spectroscopy, and in the case of [(CH3)2SOH+]4Ge3F16 4- also by single-crystal X-ray analysis. The salt [(CH3)2SOH+]4Ge3F16 4- crystallizes in the monoclinic space group P21/c with two formula units in the unit cell. The crystal structure possesses an unusual anion consisting of a chain of three slightly distorted fluorine-bridged GeF6 octahedra. The vibrational spectra are compared to the quantum chemically calculated free [(CX3)2SOX+] cations. The described salts are isolated examples of completely protonated DMSO molecules in the condensed phase.

Full text of DOI:10.1002/cplu.201200037

DOI: 10.1002/cplu.201200037
The Protonation of Dimethyl Sulfꢀoxide: Spectroscopic
Examinations of [(CX3)2SOX]+MF6 (X=H, D; M=As, Sb)
and the X-Ray Structure of [(CH3)2SOH+]4Ge3F16
Mathias Hopfinger, Karin Lux, and Andreas Kornath*[a]
4ꢀ
Dedicated to Professor Klaus Jurkschat on the occasion of his 60th birthday
Dimethyl sulfoxide (DMSO) reacts with the superacidic solu-
group P21/c with two formula units in the unit cell. The crystal
structure possesses an unusual anion consisting of a chain of
three slightly distorted fluorine-bridged GeF6 octahedra. The vi-
brational spectra are compared to the quantum chemically cal-
culated free [(CX3)2SOX+] cations. The described salts are isolat-
ed examples of completely protonated DMSO molecules in the
condensed phase.
tions of XF/MF5 and XF/GeF4 (X=H, D; M=As, Sb) under for-
ꢀ
mation of the corresponding salts [(CX3)2SOX+]MF6 and
[(CH3)2SOH+]4Ge3F164ꢀ, respectively. The salts are characterized
by vibrational and NMR spectroscopy, and in the case of
4ꢀ
[(CH3)2SOH+]4Ge3F16 also by single-crystal X-ray analysis. The
4ꢀ
salt [(CH3)2SOH+]4Ge3F16 crystallizes in the monoclinic space
Results and Discussion
Introduction
ꢀ
Synthesis and properties of [(CX3)2SOX+]MF6 and
Dimethyl sulfoxide (DMSO) is a versatile and widely used
agent. It is prepared by oxidation of dimethyl sulfide, using
N2O4 or O2/N2O4 mixtures. Because of its outstanding proper-
ties as a solvent and its high dielelectric constant (er =46.7)
and dipole moment (4.3 D) it is also used as an aprotic solvent
in many chemical reactions, such as extractions in petrochem-
istry and in the textile industry. Moreover, DMSO is used as an
oxidizer and as a base (owing to the dimsyl anion, [H3C-SO-
CH2]ꢀ). DMSO is easily resorbed through the skin and therefore
used as a transmitter for pharmaceuticals.[1] Because DMSO is
a widely used agent in research and industry, it is important to
understand its acid/base properties. Protonated species of
DMSO in the diluted state were first observed by Olah et al. in
the superacidic medium FSO3H/SbF5 (“magic acid”).[2] At first,
the sulfur atom was assumed to be the basic center. Spieker-
mann and Schrader showed later, that in the same reaction
medium the S-H stretching vibration is absent in the Raman
spectrum.[3] Olah proposed the oxygen protonation of DMSO
in a later publication.[4] For the O-protonated DMSO molecule,
there are only very few examples mentioned in the literature.
Besides theoretical studies,[5,6] the [H(Me2SO)2]2[PtCl6] and [H-
(Me2SO)2]2[OsCl6] complexes have been characterized by IR
spectroscopy.[7] So far, only two examples for hemiprotonated
DMSO species are characterized by single-crystal X-ray analysis:
4ꢀ
[(CH3)2SOH+]4Ge3F16 (X=H, D; M=As, Sb)
The protonation of DMSO was carried out at ꢀ658C using the
superacidic systems HF/AsF5, HF/SbF5, and HF/GeF4, respective-
ly, according to the Equations (1) and (2):
ðCX3Þ2SO þ XF=MF5 ! ½ðCX3Þ2SOXꢁþMF6
ꢀ
ð1Þ
ðX ¼ H, D; M ¼ As, SbÞ
4ðCH3Þ2SO þ 3GeF4 þ 4HF ! ½ðCH3Þ2SOHþꢁ4Ge3F16
4ꢀ
ð2Þ
Anhydrous hydrogen fluoride (aHF), which is the protonating
agent as well as the solvent, was used in large excess. After
aHF is condensed into an FEP ampoule at ꢀ1968C, dry DMSO
ꢀ
and AsF5 or GeF4 were added. In the case of the SbF6 salt, an-
timony pentafluoride was first condensed into the ampoule.
During the warm-up process, the DMSO reacts homogeneously
with the melting HF/Lewis acid mixture at ꢀ608C. The reaction
product precipitates as a colorless powder. The air-sensitive
ꢀ
salts [(CX3)2SOX]+MF6 (X=H, D; M=As, Sb) and [(CH3)2SOH+
4ꢀ
]4Ge3F16 remained in the FEP reactor after the excess aHF was
[(DMSO)2H][trans-Ru(DMSO)2Cl4]
(CH3)2SO.[8,9]
and
[(CH3)SOH]2(TeCl6)·2-
removed at ꢀ788C in vacuo. The salts are stable at ambient
temperature in an inert gas atmosphere. Single crystals suita-
ble for X-ray diffraction were grown after recrystallizing from
a solution in SO2.
The lack of X-ray structures containing only completely pro-
tonated DMSO molecules prompted us to investigate the for-
mation and stability of protonated DMSO in superacidic media,
such as HF/AsF5, HF/SbF5, and HF/GeF4.[10]
[a] M. Hopfinger, Dr. K. Lux, Prof. Dr. A. Kornath
Department of Chemistry, Ludwig-Maximilians-University
Butenandtstrasse 5-13, 81377 Munich (Germany)
E-mail: andreas.kornath@cup.uni-muenchen.de
476
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPlusChem 2012, 77, 476 – 481

Superacid Systems
The vibrations of the anion
4ꢀ
Ge3F16 in accordance with earli-
er studies of Bartlett and co-
ꢀ
workers of fluorobridged GeF5
polymers[12] are assigned as fol-
lows: The nonbridging GeꢀF
stretching vibrations are found
at 683 cmꢀ1, 614 cmꢀ1 (Ra and
IR) and 670 cmꢀ1 (Ra), respective-
ly. The stretching and bending
vibrations of the Ge-F-Ge chains
occur at 530 (IR), 488 (Ra), and
391 cmꢀ1. The bending vibra-
tions of the planar GeF4 units are
observed at 350 cmꢀ1. Overall,
we found a good agreement be-
tween the cations observed and
quantum chemically calculated
frequencies (RPBE1PBE/6-311G
and RPBE1PBE/6-311G(d,p)).
ꢀ
Figure 1. FT-Raman and FT-IR vibrational spectra of (CH3)2SO, [(CH3)2SOH+]AsF6ꢀ, [(CH3)2SOH+]SbF6
,
NMR spectra of
ꢀ
[(CH3)2SOD+]AsF6ꢀ, [(CD3)2SOD+]AsF6ꢀ, and [(CH3)2SOH+]4Ge3F164ꢀ; temperature at ꢀ1968C, laser wavelength at
(CH3)2SOH+AsF6 and
4ꢀ
[(CH3)2SOH+]4Ge3F16
1064 nm.
The NMR spectra of (CH3)2SOH+
AsF6 and [(CH3)2SOH+]4Ge3F16
Vibrational spectra
ꢀ
4ꢀ
in SO2 were recorded at ꢀ658C. The observed signals are sum-
marized in Table 2, together with the signals of DMSO reported
in the literature.
The infrared and Raman spectra of (CH3)2SO, [(CH3)2SOH+
[(CH3)2SOH+]SbF6
,
[(CH3)2SOD+]AsF6
,
[(CD3)2SOD+
ꢀ
ꢀ
ꢀ
]AsF6
,
]AsF6ꢀ, and [(CH3)2SOH+]4Ge3F16 are shown in Figure 1 and
the observed frequencies are summarized in Table 1, together
with the quantum chemically calculated frequencies for the
(CX3)2SOX+ cations (X=H, D). The n(OH) is not observed in the
Raman spectrum but in the IR spectrum in the region 3367–
3089 cmꢀ1. The Raman band of the n(OD) is detected at
4ꢀ
ꢀ
(CH3)2SOH+AsF6
1
In the H NMR spectrum, the proton signal corresponding to
OH is detected at 7.45 ppm. This is consistent with the results
of Olah’s earlier NMR studies of DMSO in magic acid, where
this proton signal is observed in the 1H NMR spectrum at
6.26 ppm.[4] The proton signal of the methyl groups is detected
at 3.90 ppm as one singlet and it is therefore shifted downfield
by about 1.5 ppm relative to DMSO. Olah observed this signal
at 3.16 ppm.[4] One more strongly downfield-shifted signal
2412 cmꢀ1 ([(CH3)2SOD+]AsF6 ) and 2537 cmꢀ1 ([(CD3)2SOD+
ꢀ
ꢀ
]AsF6 ), respectively. The shift of the n(OD) to a higher frequen-
ꢀ
cy and the sharper band shape in [(CD3)2SOD+]AsF6 indicates
different crystal packing in the solid state. The intense bands
around 3000 cmꢀ1 are assigned to the nas(CH3) and ns(CH3).
They are about 50 cmꢀ1 blue-shifted to the corresponding
bands in DMSO. In case of the [(CD3)2SOD+] cation, these
bands are strongly red-shifted to 2287 cmꢀ1 and 2143 cmꢀ1, re-
spectively, according to the Teller–Redlich rule.[11] The d(CH3)
occur in the region between 1445 cmꢀ1 and 1332 cmꢀ1. The
new SOH bending mode is observed at 1150 cmꢀ1 (IR), and the
corresponding SOD bending mode at 866 cmꢀ1 ([(CD3)2SOD+
1
occurs in the H NMR spectrum at 11.0 ppm. This signal is as-
signed to residues of the superacid, namely H(HF)n+, as pro-
posed by Sommer and co-workers[13] The 13C NMR spectrum
shows one sharp signal corresponding to the two methyl
groups. It is detected at 35 ppm, about 5 ppm upfield-shifted
relative to DMSO. In the 19F NMR spectrum, the broadened
ꢀ
signal for the AsF6 anion is observed at ꢀ57 ppm. Residues of
ꢀ
+
]AsF6 ). Owing to the weakening of the SꢀO bond, caused by
H(HF)n are detected at ꢀ185 ppm.[13]
the protonation of oxygen atom, the n(SO) vibration is clearly
red-shifted from 1017 cmꢀ1 (DMSO) to 867 cmꢀ1 (protonated
DMSO). The nas(CS) vibration is observed in the region around
730 cmꢀ1.
4ꢀ
[(CH3)2SOH+]4Ge3F16
Owing to the absence of a deuterated NMR solvent, and there-
fore a reference substance, a small amount of an internal stan-
dard was placed between the outer NMR tube and the FEP in-
liner, a mixture of [D6]acetone and CFCl3, and the observed sig-
nals were referenced to this standard. These observed signals
At about 680, 580, and 365 cmꢀ1, the typical vibrations for
ꢀ
ꢀ
the AsF6 octahedron are observed. In case of the SbF6 octa-
hedron, the bands are observed at 645, 567, and 277 cmꢀ1
.
ChemPlusChem 2012, 77, 476 – 481
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chempluschem.org
477

A. Kornath et al.
Table 1. Selected experimental vibrational frequencies (cmꢀ1) of (CH3)2SOH+AsF6ꢀ, (CH3)2SOH+SbF6ꢀ, [(CH3)2SOH+]4Ge3F164ꢀ, (CH3)2SOD+AsF6ꢀ, (CD3)2SOD+
AsF6ꢀ and calculated vibrational frequencies (cmꢀ1) of (CH3)2SOH+, (CH3)2SOD+, (CD3)2SOD+.
[CH3ꢀ]2SOH+ [CH3]2SOH+ [[CH3]2SOH+]4
[CH3]2SOH+
Ass.
[CH3ꢀ]2SOD+ [CH3]2SOD+
AsF6
Expt
Ra (Int)
Ass.
[CD3ꢀ]2SOD+ [CD3]2SOD+ Ass.
AsF6
Expt
Ra (Int)
ꢀ
4ꢀ
AsF6
SbF6
Ge3F16
Expt
IR
Calcd[a,c]
(IR/Ra)
Calcd[b,d]
(IR/Ra)
Calcd[a,e]
(IR/Ra)
Ra (Int)
3367-3089(m) 3580(93/68) n(OH)
3223(6.1/64) nas(CH3)
3058(7.0/74) nas(CH3) 2537(80)
3058(11/27) nas(CH3)
3043(18/83) nas(CH3)
nas(CH3)
2941(5.0/239) ns(CH3) 2287(80)
2940(16/1.1) ns(CH3) 2143(100) 2144(1.7/108) ns(CD3)
2538(54/33) n(OD)
2330(4.2/31) nas(CD3)
2327(4.0/8.7) nas(CD3)
2316(12/38) nas(CD3)
2314(0.8/16) nas(CD3)
3222(8.7/23) nas(CH3)
3025(64)
2937(91)
2412(16)
3037(43)
2943(63)
3050(22)
3031(13)
2950(86)
3042(74) 3042(m)
3207(17/77) nas(CH3)
3206(0.5/28) nas(CH3)
3081(3.7/227) ns(CH3)
3081(12/2.5) ns(CH3)
2ds(CH3)
2948(100)
2848 (m)
2632 (s)
2625(74/31) n(OD)
2144(5.2/0.8) ns(CD3)
1482(63/3.8) das(CH3)
1473(32/20) das(CH3)
1467(18/17) das(CH3)
1457(7.8/5.2) das(CH3)
1426(4.6/0.8) ds(CH3)
1399(5.9/1.9) ds(CH3)
1218(31/4.4) d(SOH)
1085(17/5.3) 1(CH3)
1034(39/4.1) 1(CH3)
1009(3.9/5.1) 1(CH3)
980(2.9/1.3) 1(CH3)
1394(49/0.7) das(CH3)
1385(19/16) das(CH3) 1042(12)
1376(8.5/16) das(CH3)
1370(12/1.2) das(CH3)
1322(11/0.8) ds(CH3)
1298(7.0/1.9) w(CH3)
1020(19/2.0) w(CH3) 866(34)
1000(14/1.3) 1(CH3)
930(7.7/2.7) 1(CH3)
895(9.4/0.3) d(SOD) 826(17)
1052 (18/2.9) das(CD3)
1036(5.1/5.1) das(CD3)
1033(21/5.3) das(CD3)
1030(11/3.4) das(CD3)
1024(3.0/2.3 das(CD3)
1016(5.1/1.2) ds(CD3)
903(8.7/3.1) d(SOD)
826(8.1/5.2) w(CD3)
1422(39)
1419(74)
1445(9.6)
1420(40) 1420(m)
1419(36)
1000(0.9)
1357(s)
1332(m)
1150(w)
1058(s)
1006(4.4) 1006(m)
937(w)
867(25)
766(12)
729(23)
762(26/2.0)
1(CD3)
1045(3.7)
992(1.9)
870(8.1)
733(20)
1045(3.2)
957(2.2)
870(36)
733(36)
695(100)
757(3.5/5.0) 1(CD3)
717(0.1/1.3) 1(CD3)
851(19)
730(14)
816(34/7.6)
799(84/1.1)
n(SO)
nas(CS) 773(17)
867(vs)
766(s)
692(13/14)
648(0.8/9.4) nas(CS)
590(3.6/28) ns(CS)
279(5.6/2.9) w(OH)
252(81/5.5) d(CSO)
n(SO)
662(8.2/16)
601(1.0/9.1) nas(CS)
543(2.9/25) ns(CS)
242(6.2/2.3) ds(CSO)
215(12/4.0) das(CSO)
n(SO)
704(2.8/5.3) ns(CS) 658(18)
648(2.1/16) d(CSO) 633(72)
321(5.8/1.7) d(CSO)
312(5.8/1.7) d(CSC) 302(6.8)
257(0.5/2.3) w(OH) 259(13)
670(16)
305(31)
371(7.6)
309(59)
235(1.0/3.1) d(CSC)
229(127/2.3) w(OH)
175(0.5/0.3) t(CH3)
148(0.6/0.9) t(CH3)
198(0.7/2.4) d(CSC)
171(103/1.6) w(OD)
124(0.5/0.1) t(CH3)
102(2.0/0.1) 1(CH3)
244(26/2.5)
t(CH3)
215(0.5/0.1) 1(CH3)
176(0.1/0.2) 1(CH3)
ꢀ
ꢀ
689(100)
577(6.5)
368(21)
AsF6ꢀ
689(100)
586(3.7)
368(22)
AsF6ꢀ
AsF6ꢀ
AsF6ꢀ
SbF6ꢀ
SbF6ꢀ
SbF6
AsF6ꢀ
AsF6ꢀ
AsF6ꢀ
AsF6ꢀ
AsF6
645(73)
567(12)
277(27)
677(98)
567(6.9)
365(31)
683(68)
670(5)
683(w)
n(GeꢀF)
non-bridging
n(GeꢀF)
non-bridging
n(GeF6)
n(chains)
n(chains)
d(chains)
d(GeF4)
614(2.8) 614(vs)
530(s)
488(2.1)
391(6.6) 391(s)
350(7.5) 350(s)
310(7.8)
lattice
[a] Calculated on the PBE1PBE/6-311G level. [b] Calculated on the PBE1PBE/6-311G(d,p) level. [c] calculated IR and Raman intensities (unscaled) are given in
brackets ([km molꢀ1] and [ꢁ4 mꢀ1]). [d] Calculated IR and Raman intensities are given in brackets ([km molꢀ1] and [ꢁ4 mꢀ1]), scaling factor: 0.960. [e] Calculated
IR and Raman intensities are given in brackets ([km molꢀ1] and [ꢁ4 mꢀ1]), scaling factor: 0.937. v=very, s=strong, m=medium, w=weak, Ass.=assignment,
Int=intensity, IR=infrared, Ra=Raman.
Table 2. Summary of NMR chemical shifts in of (CH3)2SO,[13] (CH3)2SOH+
4ꢀ
of [(CH3)2SOH+]4Ge3F16 are comparable to the NMR signals of
4ꢀ
AsF6ꢀ, and [(CH3)2SOH+]4Ge3F16
.
(CH3)2SOH+AsF6ꢀ. In the H NMR spectrum, the proton signal
1
d [ppm] for d [ppm] for
d [ppm] for
Ass.
corresponding to OH is detected at 7.31 pm as a very broad
band. The methyl protons generate one signal at 4.31 ppm. In
the 13C NMR spectrum, apart from the reference signals only
one signal at 35.8 ppm is observed, which is assigned to the
methyl groups. In the 19F NMR spectrum also only one signal
ꢀ[b]
4ꢀ[b]
[CH3]2SO[a]
[CH3]2SOH+AsF6
[CH3]2SOH+]4Ge3F16
1H
1H
2.62
–
3.90
7.45
4.31
7.31
35.8
ꢀ112.0
CH3
OH
CH3
anion
13C 40.8
35.0
19F
–
ꢀ57.0
4ꢀ
at ꢀ112 ppm is observed. This signal belongs to the Ge3F16
[a] From reference [13] in CDCl3. [b] Observed NMR signals in SO2.
anion.
478
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ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPlusChem 2012, 77, 476 – 481

Superacid Systems
4ꢀ
Crystal structure of [(CH3)2SOH+]4Ge3F16
4ꢀ
Data collection for [(CH3)2SOH+]4Ge3F16 (1) was performed
with an Oxford Xcalibur3 diffractometer equipped with a Spell-
man generator (voltage 50 KV, current 40 mA) and a KappaCCD
detector, operating with MoKa radiation (l=0.7107 ꢁ). Data
collection at 123 K was performed using the CrysAlis CCD soft-
ware,[14] the data reductions were carried out using the CrysAlis
RED software.[15] The solution and refinement of the structure
was performed using the programs SHELXS[16] and SHELXL-
97[17] implemented in the WinGX software package[18] and final-
ly checked with the PLATON software.[19] The absorption cor-
rection was achieved with the SCALE3 ABSPACK multiscan
method.[20] In the crystal structure, the hydroxy hydrogen
atoms were localized in the difference map and refined iso-
tropically. The hydrogen atoms of the methyl groups were in-
cluded in the refinements in calculated positions. Selected
data and parameters of the X-ray determination are given in
Table 3.[21]
Figure 2. View of the molecular structure of [(CH3)2SOH+]4Ge3F164ꢀ (1) in the
crystal showing the 50% probability displacement ellipsoids. Methyl hydro-
gen atoms are omitted for clarity. [Symmetry code: i=2ꢀx, ꢀy, 1ꢀz].
4ꢀ
Table 3. Crystal structure data for [(CH3)2SOH+]4Ge3F16 2SO2 (1).
Formula
C8H28F16Ge3O8S6
966.43
0.3ꢂ0.1ꢂ0.1
P21/c
Mr [gmolꢀ1
]
crystal size [mm3]
crystal system
space group
a [ꢀ]
b [ꢀ]
monoclinic
7.9406(11)
27.224(2)
7.8817(11)
90.0
3094
2
2.093
3.460
952
123(2)
ꢀ9 ꢂ h ꢂ +5
ꢀ27 ꢂ k ꢂ +33
ꢀ9 ꢂ l ꢂ +9
5956
2961
0.0250
199
Table 4. Selected bond distances and angles of 1 with estimated stan-
dard deviations in parentheses; symmetry codes: i=x, 0.5ꢀy, z.
c [ꢀ]
Bond distances [ꢁ]
g [8]
V [ꢁ3]
Z
S1ꢀC1
S1ꢀC2
S1ꢀO1
S2ꢀC3
S2ꢀC4
S2ꢀO2
Ge1ꢀF1
Ge1ꢀF2
1.758(4)
1.766(4)
1.593(3)
1.770(4)
1.755(4)
1.587(3)
1.763(2)
1.788(2)
Ge1ꢀF3
Ge1ꢀF4
Ge1ꢀF5
Ge1ꢀF6
Ge2ꢀF6
Ge2ꢀF7
Ge2ꢀF8
–
1.762 (2)
1.782(2)
1.762(2)
1.921(2)
1.914(2)
1.744(3)
1.746(2)
–
1calcd [gcmꢀ3
]
m(MoKa) [cmꢀ1
F(000)
]
T [K]
hkl range
Bond angles [8]
C1-S1-C2
O1-S1-C1
O1-S1-C2
C3-S2-C4
102.0(2)
98.0(2)
101.6(2)
101.2(2)
O2-S2-C4
O2-S2-C3
Ge1-F6-Ge2
101.7(2)
98.3(2)
144.8(2)
measured reflections
unique reflections
Rint
parameters
R(F)/wR(F2)[a] (all reflections)
weighting Scheme[b]
GoF (F2)[c]
0.0381/0.0654
0.0343/0.0
0.948
1.066/ꢀ0.709
Oxford XCalibur
SHELXS-97/SHELXL-97[16,17]
agreement with the semiprotonated (Me2SO)2H+ cation de-
scribed in the literature.[8,22] The SꢀO bond lengths of
1 (1.593(3) ꢁ, 1.587(3) ꢁ) are, as expected, larger than the cor-
responding value in crystalline Me2SO (1.513 ꢁ).[23] In compari-
son with the hemiprotonated (Me2SO)2H+ cation (SꢀO bond
lengths 1.531(4) ꢁ and 1.536(4) ꢁ),[21] the SꢀO bond lengths of
1 are elongated. The cation Me2SOH+ forms a pyramid with
angles between 98.0(2)8 and 102.0(2)8.
D1max, D1min [ꢁꢀ3
device type
]
solution/refinement
[a] R1 =Sj jF0 j-jFc j j/SjF0 j. [b] wR2 =[S[w(F0 ꢀFc2)2]/S[w(F0)2]]1/2
;
w=
2
2
2
[sc2(F0 )+(xP)2 +yP]ꢀ1
;
P=(F02 +2Fc2)/3. [c] GoF={S[w(Fo -Fc2)2]/(nꢀp)}1/2
(n=number of reflections; p=total number of parameters).
Protonated DMSO [(CH3)2SOH+]4Ge3F16 (1) crystallizes in
The cations Me2SOH+ are connected with the anion Ge3F16
4ꢀ
4ꢀ
the monoclinic space group P21/c with two formula units in
the unit cell. A view of the molecular structure is shown in
Figure 2. Table 4 contains details of selected geometric param-
eters.
through strong hydrogen bonds. The donor–acceptor distan-
ces are 2.573(3) ꢁ (O1···F2) and 2.621(3) ꢁ (O2···F4). Each
4ꢀ
Ge3F16 anion establishes four hydrogen bonds parallel to the
c axis through the fluorine atoms F2 and F4. For symmetry
codes and geometric parameters of the hydrogen bonds see
Figure 3.
The SꢀC bond lengths of the cation (CH3)2SOH+ are be-
tween 1.755(4) ꢁ and 1.770(4) ꢁ. These values are in good
ChemPlusChem 2012, 77, 476 – 481
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chempluschem.org
479

A. Kornath et al.
ture. In the crystal structure of
4ꢀ
[(CH3)2SOH+]4Ge3F16
a
novel
anion is found. The anion of this
compound consists of a fluorine-
bridged chain of three slightly
distorted GeF6 octahedra.
Experimental Section
CAUTION
Avoid contact with these com-
pounds and note that HF burns
the skin and causes irreparable
damage. Safety precautions such
as viton gloves and face protection
should be taken when using and
handling these materials!
Figure 3. View of the cell along the a axis, showing the 50% probability displacement ellipsoids. Methyl hydrogen
atoms are omitted for clarity. [Symmetry codes: i=1+x, y, 1+z; ii=x, y, ꢀ1+z].
Chemicals
The (CH3)2SO and (CD3)2SO were
obtained from Merck and distilled
4ꢀ
The anion Ge3F16 is the first representative of a trigermani-
prior to use. HF (Messer Griessheim) was first trap-to-trap distilled
in vacuo and then dried with fluorine for two weeks in a stainless-
steel pressure cylinder. The DF was prepared from dried CaF2 and
D2SO4, distilled in vacuo and dried with fluorine for two weeks in
a stainless-steel pressure cylinder. The D2SO4 was prepared by the
reaction of D2O with SO3 which has been isolated from Oleum
(65% SO3; Merck) by trap-to-trap condensation. SbF5 (Merck) was
distilled three times through Vigreux columns under a flow of dry
nitrogen at atmospheric pressure, and finally purified by trap-to-
trap distillation in vacuo.
um hexadecafluorido chain. The anion forms a chain of three
slightly distorted octahedrons, which are linked in staggered
conformation by the bridging fluorine atoms F6 and F6i
(Figure 2). The angles are in the range of 86.2(1)8 to 93.7(1)8
and 173.4(1)8 to 180.08. The Ge-F-Ge angle between two GeF6
octahedrons is 144.8(2)8. This value is in the same range as ob-
served by Bartlett et al. for (XeF5)GeF5 (Ge-F-Ge: 140.7(1)8) and
(ClO2)GeF5 (Ge-F-Ge: 143.2(2)8 and 148.1(3)8).[12] In these com-
ꢀ
pounds, the GeF5 anions build chains of GeF6 octahedra in
the solid state. The GeꢀF bond lengths (Ge1-F1, F2, F3, F4, and
4ꢀ
Equipment and instrumentation
F5) of the anion Ge3F16
are between 1.744(3) ꢁ and
2ꢀ
1.788(2) ꢁ. These values are in the typical range for a GeF6
octahedron observed in the literature.[24] The lengths of GeꢀF
bonds involved in hydrogen bonding (Ge1ꢀF2 and Ge1ꢀF4)
are slightly longer than Ge1ꢀF1, Ge1ꢀF3, and Ge1ꢀF5. The
All synthetic work and sample handling was performed employing
standard Schlenk techniques and a stainless-steel vacuum line. Su-
peracid reactions were carried out in FEP ampoules which were
closed with stainless-steel valves. All reaction vessels and the stain-
less-steel line were dried with fluorine prior to use. Infrared spectra
of the samples in a cooled cell were recorded on a Bruker Vertex
80v spectrophotometer. The Raman spectra were recorded on
ꢀ
same is observed in the case of SbF6 anions, as described by
Minkwitz et al.[25] The bond lengths of the bridging fluorine
atom F6 (Ge1ꢀF6: 1.921(2) ꢁ, Ge2ꢀF6: 1.914(2) ꢁ) are, as ex-
pected, longer than the nonbridging GeꢀF bonds. In the case
of the GeF5ꢀ, the bond length of the bridging fluorine atoms
are also longer (XeF5)GeF5: 1.890(1) ꢁ and (ClO2)GeF5:
1.887(1) ꢁ, 1.888(2) ꢁ), but they are about 29 pm shorter than
in the Ge3F164ꢀ anion.
a
Bruker MultiRAM spectrometer using a Nd:YAG laser (l=
1064 nm) and a Ge detector, and on a Jobin Yvon T64000 spec-
trometer using an Ar+ laser tube (l=514.5 nm) from Spectra Phys-
ics. For the recording of the Raman spectra, the samples were
placed in a glass cell cooled with liquid nitrogen. The NMR spectra
were recorded on
a Delta JEOL 400 ecx NMR spectrometer
(400 Mhz). X-ray diffraction studies were performed with an Oxford
Xcalibur3 diffractometer equipped with a Spellman generator (volt-
age 50 KV, current 40 mA) and a KappaCCD detector, operating
with MoKa radiation (l=0.7107 ꢁ).
The solvent molecules SO2 lie in the gaps along the c axis
(Figure 3).
Conclusion
ꢀ
Synthesis of [(CX3)2SOX+]AsF6
A single-protonated DMSO molecule was prepared and charac-
terized by vibrational and NMR spectroscopy. Its structure was
determined by single-crystal X-ray analysis. Protonated DMSO
was synthesized in superacidic media, such as HF/AsF5, HF/
SbF5, and HF/GeF4. DMSO is protonated at the oxygen atom,
which is undoubtedly shown by the vibrational spectroscopic
data and the elongated SꢀO bond length in the X-ray struc-
(CH3)2SO (78 mg, 1.0 mmol) or (CD3)2SO (84 mg, 1.0 mmol) was
transferred into a FEP reactor, followed by condensation of 1.5 g of
XF (X=H, D). Then, AsF5 (187 mg, 1.1 mmol) was distilled to the
frozen XF at ꢀ1968C. The reaction mixture was warmed up to
ꢀ608C for 5 min and then cooled to ꢀ788C. The excess XF was re-
moved in a dynamic vacuum at ꢀ788C.
480
www.chempluschem.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemPlusChem 2012, 77, 476 – 481

Superacid Systems
ꢀ
Synthesis of [(CH3)2SOH+]SbF6
ˇ
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SbF5 (217 mg, 1.0 mmol) was distilled into a FEP reactor at
ꢀ1968C, followed by 1.5 g of HF. The mixture was warmed to 208C
to form the superacid. The reactor was then cooled to ꢀ1968C,
and (CH3)2SO (78 mg, 1.0 mmol) was added to the frozen supera-
cid. The reaction mixture was warmed up to ꢀ608C for 5 min and
then cooled to ꢀ788C. The excess HF was removed in a dynamic
vacuum at ꢀ788C.
4ꢀ
Synthesis of [(CH3)2SOH+]4Ge3F16
[14] CrysAlisCCD, Version 1.171.35.11 (release 16–05–2011 CrysAlis
171.NET), Oxford Diffraction Ltd., 2011.
(CH3)2SO (78 mg, 1.0 mmol) or (CD3)2SO (84 mg, 1.0 mmol) was
transferred into a FEP reactor, followed by condensation of 1.5 g of
XF (X=H, D). Then, GeF4 (111 mg, 0.75 mmol) was distilled to the
frozen HF at ꢀ1968C. The reaction mixture was warmed up to
ꢀ608C for 5 min and then cooled to ꢀ788C. The excess HF was re-
moved in a dynamic vacuum at ꢀ788C. Single crystals suitable for
X-ray diffraction were grown after recrystallizing from a solution in
SO2 at ꢀ408C.
[15] CrysAlisRED, Version 1.171.35.11 (release 16–05–2011 CrysAlis 171.NET),
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Acknowledgements
This study has been supported by the Deutsche Forschungsge-
meinschaft. Many thanks go to the Department of Chemistry,
Ludwig-Maximilian University, Munich and to Theresa Soltner for
the measurement of the crystal data.
Keywords: ab initio calculations
sulfoxide · superacid systems · vibrational spectroscopy · X-ray
diffraction
· protonated dimethyl
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Published online on April 18, 2012
ChemPlusChem 2012, 77, 476 – 481
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chempluschem.org
481