Preparation and characterization of the first organosulfonium azides

Article abstract of DOI:10.1515/znb-2009-0420

The first triorganosulfonium azides [Me₃S]N₃ and Ph₃S]N₃ were prepared by reaction of the corresponding sulfonium bromides/iodides with silver azide and characterized by spectroscopic methods. The molecular stru

Full text of DOI:10.1515/znb-2009-0420

Note
467
◦
H O or CH Cl /0
C
2
2
2
Preparation and Characterization of the
First Organosulfonium Azides
[R3S]X+AgN3 −−−−−−−−−−−−→ [R3S]N3
−AgX
R = Me, X = I (1)
R = Ph, X = Br (2)
Thomas M. Klapo¨tke, Burkhard Krumm, and
Matthias Scherr
Scheme 1.
Department Chemie und Biochemie, Ludwig-Maximilians-
Universita¨t Mu¨nchen, Butenandtstraße 5 – 13(D),
D-81377 Mu¨nchen, Germany
Nevertheless, along with [Ph3S]N3 (2) an unex-
pected minor product, identified as [Ph3S][Ag(N3)2],
was observed and isolated. The synthesis of a salt
of this new anion was optimized and is reported
elsewhere [5]. An attempt to react an oxonium salt,
[Me3O][BF4], with silver azide, to form an oxonium
azide, resulted only in the formation of hydrazoic acid
HN3, as detected in the 14N NMR spectrum.
Reprint requests to Prof. Dr. T. M. Klapo¨tke. Fax: +49 (0)89
2180 77492. E-mail: tmk@cup.uni-muenchen.de
Z. Naturforsch. 2009, 64b, 467 – 469;
received January 14, 2009
Dedicated to Professor Ingo-Peter Lorenz on the occasion of
his 65th birthday
Both salts 1 and 2 are colorless stable solids, which
burn upon contact with a flame with soot formation.
The ionic nature of the compounds in KBr and solu-
tion has been confirmed by vibrational and NMR spec-
troscopy. The antisymmetric stretching vibration of the
azide groups [νas(N3)] are found with high intensity in
the IR spectra and with very low intensity (1) or not at
The first triorganosulfonium azides [Me3S]N3 and
[Ph3S]N3 were prepared by reaction of the corresponding
sulfonium bromides/iodides with silver azide and character-
ized by spectroscopic methods. The molecular structure of
[Ph3S]N3 as well as that of the precursor, [Ph3S]Br, have
been determined by X-ray diffraction.
Key words: Sulfonium Azides, Chalcogen Azides,
all (2) in the Raman spectra around 2050– 1980 cm−1
.
X-Ray Crystallography
The symmetric stretching vibration νs(N3) can be as-
signed for both compounds at 1322/1321 cm−1 with
considerable intensity, as typical for ionic azides,
and is slightly shifted compared to that of NaN3
(1344 cm−1 [6]). As expected, the 14N NMR spectra of
both salts in D2O (1, −133(β)/−282(α/γ) ppm) and
CDCl3 (2, −130(β)/−277(α/γ) ppm) show two res-
onances for the ionic azide moiety, which confirm the
dissociation of the compounds in solution, independent
of the solvent nature.
Colorless crystals of 2 were obtained by diffusion of
n-hexane into a CH2Cl2 solution maintained at ambi-
ent temperature for 5 d. The compound crystallizes in
the monoclinic system, space group P21/n with four
molecules in the unit cell (Fig. 1).
Introduction
The chemistry of the chalcogen azides has been
well investigated in the last years [1]. Among the var-
ious possible oxidation states of the chalcogens, sele-
nium(IV) and tellurium(IV) possess the highest stabil-
ity, and the ionic chalcogen(IV) azides [R3Te]N3 and
[R3Se]N3 have been described and thoroughly charac-
terized recently [2, 3]. In addition, the first telluronium,
selenonium and sulfonium dinitramides have been syn-
thesized [4]. In this contribution, we report the prepa-
ration of the first sulfonium azides.
Similar to findings for the chalcogen atoms in se-
lenonium and telluronium salts, the sulfur atom in
the cation of 2 is trigonal-pyramidally coordinated
(AX3E). The three S – C distances (S1 – C1 1.776(3),
Results and Discussion
Triorganosulfonium halides can be reacted with
azide, in a similar fashion as selenonium or telluro-
nium halides, to form the corresponding sulfonium
azides. As the azide transfer agent, conveniently sil-
ver azide was used, in order to achieve complete con-
version by separation of the precipitating silver halide
(Scheme 1).
˚
S1 – C7 1.780(3) and S1 – C13 1.787(3) A) and C –
S – C angles (C1 – S1 – C7 104.83(12)◦, C1 – S1 – C13
104.61(12)◦ and C7 – S1 – C13 104.50(12)◦) are prac-
tically identical and comparable with the parame-
ters of other triphenylsulfonium cations, such as in
[Ph3S]Br · H2O, whose crystal structure was deter-
c
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468
Note
with a Nd : YAG laser (1064 nm) (as neat solids). NMR spec-
tra were recorded on a Jeol Eclipse 400 instrument at 25 ◦C,
and chemical shifts were determined with respect to external
Me4Si (1H, 399.8 MHz; 13C, 100.5 MHz) and MeNO2 (14N,
28.9 MHz). Mass spectrometric data were obtained from a
Jeol MStation JMS 700 spectrometer using the FAB tech-
nique. Elemental analyses: Analytical Service LMU.
Preparation of triphenylsulfonium bromide
Into a solution of phenylmagnesium bromide, prepared
from PhBr (41.8 mmol) and Mg (41.8 mmol) in THF
(40 mL), diphenyl sulfoxide (16.7 mmol) and freshly dis-
tilled trimethylsilyl chloride (41.8 mmol) were added at 0 ◦C.
After stirring for 30 min this mixture was treated with aque-
ous HBr (30 mL, 10 %) and the yellowish mixture extracted
with further 30 mL of aqueous HBr solution. The resulting
yellow solution was extracted with CH2Cl2 (2 × 30 mL),
dried over anhydrous Na2SO4 and concentrated in vacuo.
The sulfonium bromide [Ph3S]Br was obtained as a beige
solid in 25 % yield. – Raman: ν = 3050 (80), 1578 (64),
1172 (19), 1156 (24), 1077 (45), 1066 (28), 1028 (42),
999 (100), 704 (19), 687 (24), 612 (22), 503 (19), 413 (22),
255 (46), 228 (28) cm−1. – 1H NMR (CDCl3): δ = 7.76 –
Fig 1. Molecular structure of [Ph3S]N3 (2) in the crys-
˚
tal (hydrogen atoms omitted). Selected bond lengths (A)
and angles (deg): S1–C1 1.776(3), S1–C7 1.780(3), S1–C13
1.787(3), N1–N2 1.140(4), N2–N3 1.179(4); N1–N2–N3
179.4(3), C1–S1–C7 104.83(12), C1–S1–C13 104.61(12),
C7–S1–C13 104.50(12).
˚
mined as well (S – C 1.77 – 1.78 A, C – S – C 103–
106◦). The azide ion is almost linear (N1 – N2 – N3
179.4(3)◦) with slightly different N – N bond lengths
1
7.63 (m). – 13C{ H} NMR (CDCl3): δ = 134.4, 131.4,
˚
(N1 – N2 1.140(4) und N2 – N3 1.179(4) A). These
131.2, 124.5.
values are in the range of those found for [Ph3Te]N3
˚
˚
(1.16/1.81 A), [Me3Se]N3 (1.17/1.8 A) and [Ph3Se]N3
General procedure for the preparation of the triorganosulfo-
˚
(1.02/1.05 A, disordered azide) [2, 3]. In contrast to the
nium azides [R S]N (R = Me, Ph)
3
3
latter structures, in the structure of 2 interionic con-
tacts are only very weak, the S···N distances being
Into
a
solution of trimethylsulfonium iodide/tri-
˚
only 0.05 A smaller than the sum of the van der Waals
phenylsulfonium bromide (1.0 mmol) in water resp.
dichloromethane (10 mL), silver azide (1.0 mmol) was
added at 0 ◦C and the mixture stirred for 30 min at this
temperature. After further stirring at ambient temperature
for 2 h, the resulting precipitate (AgI/AgBr) was separated
by filtration. Concentration of the solutions in high vacuum
furnished the slightly yellowish resp. reddish solids in
almost quantitative yield. Recrystallization of 2 from a
CH2Cl2/n-hexane mixture gave colorless crystals.
˚
radii of sulfur and nitrogen (3.35 A [7]), which do not
require further discussion.
To our knowledge, the crystal structure of the sul-
fonium(IV) azide 2 is the only one determined for
a sulfur(IV) azide. A detailed investigation of crys-
tal structures of several covalent organosulfonyl(VI)
azides RSO2N3 has been published [8]. Furthermore,
a theoretical study of binary sulfur azides has been re-
ported [9].
Trimethylsulfonium azide [Me S]N (1)
3
3
Experimental Section
Raman: ν = 3010 (43), 2924 (100), 2034 [5, νas(N3)],
1439 (29), 1322 [98, νs(N3)], 1245 (17), 731 (71), 658 (96),
319 (16), 295 (23), 197 (12) cm−1. – IR (KBr): ν = 3298 m,
3223 w, 3007 vs, 2920 m, 2054 vs/2023 vs/1986 vs (νasN3),
1656 br, 1447 s, 1433 s, 1419 s, 1339 m, 1320 w, 1307 m,
1179 w, 1064 s, 1039 vs, 941 vs, 894 w, 731 w, 655 m,
All manipulations of air- and moisture-sensitive materials
were performed under an inert atmosphere of dry argon us-
ing flame-dried glass vessels and Schlenk techniques [10];
the solvents and reagents were distilled and stored under
dry nitrogen prior to use. The sulfonium salts [Me3S]I [11]
and [Ph3S]Br [12] were prepared according to literature pro-
cedures. Infrared spectra were recorded on a Perkin-Elmer
Spektrum One FT-IR instrument (as KBr pellets), and Raman
1
540 s cm−1. – 1H NMR (D2O): δ = 2.96. – 13C{ H} NMR
(D2O): δ = 26.9. – 14N NMR (D2O): δ = – 133 (Nβ ), –
282 (Nα/γ ). – FAB+ MS: m/z (rel. int.) = 79 (100) [M]+,
spectra on a Perkin-Elmer 2000 NIR FT spectrometer fitted 232 (24) [M + NBA]+, 385 (6) [M + 2 NBA]+.
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Note
469
1
δ = 7.69 – 7.59 (m). – 13C{ H} NMR (CDCl3): δ = 134.2,
131.2, 130.7, 124.6. – 14N NMR (CDCl3): δ = −130 (Nβ ),
−277 (Nα/γ). – FAB+ MS: m/z (rel. int.) = 264 (100) [M]+,
187 (7) [Ph2S]+.
Table 1. Crystal structure data for [Ph3S]Br· H2O and
[Ph3S]N3 (2).
[Ph3S]Br·H2O
[Ph3S]N3 (2)
C18H15N3S
305.40
Formula
Mr
C18H17BrOS
361.30
Crystal size, mm3
Crystal system
Space group
0.29×0.06×0.03
monoclinic
P21/n
11.8279(5)
10.5732(5)
13.1582(5)
92.857(4)
1643.50(12)
4
0.25×0.25×0.11
monoclinic
P21/n
11.9474(4)
10.8360(5)
12.9600(5)
95.613(4)
1634.98(11)
4
Reaction of [Me O][BF ] with silver azide
3
4
Into a solution of [Me3O][BF4] (0.6 mmol) in dichloro-
methane (3 mL) AgN3 (0.6 mmol) was added at 0 C and
˚
◦
a, A
˚
b, A
the mixture stirred for 30 min at that temperature. After
further stirring at ambient temperature, a sample for NMR
spectrosocopy was taken from the clear supernatant solu-
tion. No evidence was found for the formation of an oxo-
nium azide; as the main product hydrazoic acid was detected
[HN3: 14N NMR: δ = −136 (Nβ ), −177 (Nγ), −324 (Nα )].
˚
c, A
β, deg
3
˚
V, A
Z
Dcalcd, g cm−3
µ(MoKα ), cm−1
F(000)
1.460
1.241
2.624
736
0.197
640
hkl range
−13 ≤ h ≤ +14
−12 ≤ k ≤ +13
−16 ≤ l ≤ +16
3.9 – 26.0
9472
2005
0.055
−14 ≤ h ≤ +14
−13 ≤ k ≤ +13
−15 ≤ l ≤ +15
3.8 – 26.0
9209
2025
0.033
X-Ray structure determination
For both compounds, [Ph3S]Br · H2O and 2, an Oxford
Xcalibur diffractometer with an CCD area detector was em-
ployed for data collection using MoKα radiation. The struc-
tures were solved using Direct Methods and refined by full-
matrix least-squares on F2 (Table 1, SHELXS/L [13]). All
non-hydrogen atoms were refined anisotropically. The OR-
TEP plot (Fig. 1) is shown with displacement ellipsoids at
the 50 % probability level.
θ range, deg
Refl. measured
Refl. unique
Rint
Param. refined
R(F)/wR(F2) (all refls.)
GoF (F2)
3206
0.0746/ 0.0664
0.92
−0.40/0.61
3200
0.0570/ 0.0849
1.05
−0.24/0.54
−3
˚
∆ρfin (max/min), e A
CCDC 694100 and 693669 contain the supplementary
crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data request/cif.
Triphenylsulfonium azide [Ph S]N (2)
3
3
Raman: ν = 3150 (11), 3059 (80), 1578 (59), 1321 [36,
νs(N3)], 1183 (17), 1078 (40), 1024 (47), 1000 (100),
734 (15), 704 (18), 688 (27), 612 (28), 440 (23), 256 (42),
229 (28) cm−1. – IR (KBr): ν = 3434 br, 3050 w, 2036
vs/2012 vs/1993 vs [νas(N3)], 1634 w, 1473 s, 1443 s,
1404 w, 1384 w, 1316 w, 1159 w, 1100 w, 1064 s, 1021 w,
995 s, 931 w, 851 w, 752 vs, 701 w, 684 vs, 649 m, 642 w,
628 w, 611 w, 501 s, 496 s cm−1. – 1H NMR (CDCl3):
Acknowledgement
Financial support of this work by the University of Mu-
nich, the Fonds der Chemischen Industrie, and the Deutsche
Forschungsgemeinschaft (KL 636/10-1) is gratefully ac-
knowledged.
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