REGULAR PAPERS
The Structure Of Tas+ CF3C(O)NS(CF3)NS(CF3)NC(O)CF3-, A Salt With A Bis(Sulfinyl) Amide Anion
Lork, E.1; Müller, M.1; Mews, R.1
1Institute of Inorganic and Physical Chemistry University of Bremen, PO Box 330440 D-28334 Bremen, Germany Fax:+49-421-218 4267; e-mail: mews@chemie.uni-bremen.de
Received March 10, 2004. In Final Form April 12, 2004
Dedicated
to Professor Dr. Pedro J. Aymonino on the occasion of his 75th
birthday.
Abstract
The title compound TAS +
CF3C(O)N S(CF3)NS(CF3) NC(O)CF3-
(3) was isolated as a minor product from the reaction
of TAS-fluoride with CF3C(O)NS(CF3)F. The X-ray structure
of 3 is reported and the bonding situation in the anion is discussed.
Resumen
Como producto secundario de la reacción
entre TAS-fluoruro con CF3C(O)NS(CF3)F se pudo aislar el
compuesto TAS+ CF3C(O)NS(CF3)NS(CF3)
NC(O)CF3- (3) cuya estructura de rayos X se
reporta aqui. Se discuten
las caracteristicas de enlace del anión.
Introduction
Acyl-sulfur(IV)imides RN=SR'R" (R= ClC(O), FC(O), CF3C(O); R'=R"=Cl, F, CF3, R'=R"=F, Cl, CF3) are an extraordinary interesting class of compounds, not only because of spectroscopic reasons but also from a synthetic point of view. Investigations of the structures and conformations of FC(O)NSF2 [1], CF3C(O)NSF2 [2], and FC(O)NSCl2 [3] by gas phase electron diffraction, IR- and Raman-spectroscopy have been reported. In both the gas and in the liquid phase dominantly a syn-syn conformation (the acyl group syn-periplanar with respect to the SF2 bisector and the oxygen directed towards the sulfur ) is observed. If one of the sulfur bonded fluorines is exchanged by a CF3-group, as e.g. in FC(O)N=S(CF3)F [4] and CF3C(O)NS(CF3)F [5] unexpectedly the anti-syn conformer (acyl group in an anti-position) is dominant. Besides these structural differences due to the F/CF3 exchange also remarkable differences in the reactivity result from this exchange. While the C-N- bond in sulfur difluoride imides RC(O)NSF2 (R=F, CF3) is readily cleaved by fluoride ions to give salts with the sulfur difluoride imide anion (e.g. Cs+NSF2- [6,7] Hg(NSF2)2 [6-8] TAS+NSF2 [9]), with RC(O)NS(CF3)F no formation of the corresponding NS(CF3)F--salts is observed. Stable salts with the RC(O)NS(CF3)F2- anion were isolated [9].
Experimental, X-Ray Crystallography
The starting materials TASF [10] and CF3C(O)NS(CF3)F [11] were prepared according to the literature, both compounds were reacted as
described in our earlier paper [9]. Onto the frozen CH3CN solution
of 3 an equal volume of diethyl ether was condensed at –196°C on a
vacuum line. The reaction vessel was warmed to –30°C and kept at this
temperature for several days.
By slow diffusion of the ether into the CH3CN solution
single crystals of 3 were formed. From the cold solution they were
transferred to cooled KEL-F oil, single crystals were selected at the same
temperature under a microscope in an atmosphere of dry nitrogen. The single
crystals were mounted on a thin glass fibre.
The single-crystal X-ray structure determination (Table 1) was
carried out on a Siemens P4 diffractometer using Mo(Ka) radiation (0.71073 Å)
with a graphite monochromator. Refinement based on F2; R1 = åççFoç - çFcçç/åçFoç; wR2 = {å[w(Fo2 – Fc2)2/å[w(Fo2)2]}1/2.
Programs used: SHELX-97 [12] and DIAMOND [13]
The structures were solved by direct methods (SHELXS [12]).
Subsequent least-squares refinements (SHELXL-97-2 [12]) located the positions
of the remaining atoms in the electron density maps. All non-H atoms were
refined anisotropically.
CCDC-232900 (3) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk.
Table 1. Crystal data and structure refinement for TAS+CF3C(O)NS(CF3)NS(CF3)C(O)CF3- (3).
Empirical Formula |
C12H18F12N6O2S3 |
M |
602.50 |
T/K |
173(2) |
Wave length/ pm |
71.073 |
Crystal system |
triclinic |
Space group |
P-1 |
a/pm |
932.0(2) |
b/pm |
1095.5(2) |
c/pm |
1199.5(2) |
a/° |
92.560(10) |
b/° |
100.600(10) |
Γ/° |
93.840(10) |
U/nm3 |
1.1991(4) |
Z |
2 |
Dc/Mg m-3 |
1.669 |
m (MoKa) mm-1 |
0.425 |
F(000) |
608 |
Crystal size /mm3 |
0.8 x 0.7 x 0.6 |
q range/ ° |
2.55 to 27.50 |
Indexrange |
–12£h£12, –14£k£14, –15£1£15 |
Reflections collected |
11078 |
Independent Reflections |
5489 [R(int) = 0.0248] |
Completeness to theta= 27.50° |
99.9% |
Refinement |
Full-matrix least-squares on F2 |
Data/Restraints/Parameter |
5489/0/324 |
Goodness-of-fit on F2 |
1.021 |
R1, wR2 [I > 2s(I)] |
0.0358, 0.0933 |
R1, wR2 (all Data) |
0.0438, 0.0982 |
Extinction coefficient |
0.0173(15) |
Largest difference peak, hole/eÅ-3 |
0.369 / –0.327 e. Å-3 |
Results And Discussion
Recently we reported the reactions of FC(O)NS(CF3)F with TAS-fluoride ((Me2N)3S+Me3SiF2- (Tris(dimethylamino)sulfonium difluorotrimethylsilicate) [9]:
1 was characterized by NMR spectroscopy and X-ray crystallography, 2 was also isolated in almost quantitative yield and unequivocally characterised by 19F-NMR spectroscopy. Compound 2 seemed to the stable in solution, cleavage of the CN-bond was not observed. Therefore it was rather surprising that from our present attempt to crystallize 2 from CH3CN/diethylether at –30 °C. single crystals of 3 were isolated. The formation of 3 is rationalised by the equation.
TASF + 3 CF3C(O)NS(CF3)F → TAS+ CF3C(O)NS(CF3)NS(CF3)NC(O)CF3-
3
+ Me3SiF { + CF3C(O)F + CF3SF3}
The bridging nitrogen between the two acylsulfurimide moieties probably results from the decomposition of the primarily formed anion of salt 2. CN bond cleavage might be the next step, followed by attack of the resulting nucleophile at CF3C(O)NS(CF3)F. In a further step SC-bond cleavage should have occurred. Until now these speculations could not be confirmed by spectroscopic investigations.
X-ray structure of TAS+CF3C(O)NS(CF3)NS(CF3)C(O)CF3- (3)
3 crystallizes in the triclinic space
group P-1 with 2 molecules in the asymmetric unit. The structure of the anion
of 3 is presented in Figure 1, details of the structure determination of
3 are given in Table 1, Table 2 lists selected bond lengths and bond
angles.
The unique anion of 3 is an imino derivative of a hitherto unknown class
of compounds, of the bis(sulfinyl)amides (RS(O))2N-. The
corresponding bis(sulfonyl)amides (RS(O)2)2N- with various counterions (R=F, perfluoroalkyl) have been previously reported
and are presently investigated in many laboratories for their application as
electrolytes in batteries and fuel cells [14]. A mixed fluorosulfinyl – fluorosulfonyl-amide, TAS+ FS(O)2NS(O)F- was
prepared in our laboratory from FS(O)2NSO and TASF [15]. In a
similar way bis(sulfinyl)amides should be available from N-sulfinyl
sulfinamides, e. g. CF3S(O)NSO [16], and TASF.
According to the bond distances determined the amide is best
described as superposition of the two resonance structures B and B',
by C, because all SN distances are almost of equal length (163.2
(2)–164.0(2) pm). Compared to CF3-C(=O)-N=S(CF3)F (SN =
155.4(8) pm) the SN-bonds are significantly lengthened, while the CN bonds in 3 are shortened by approximately 5 pm, the CO distances are stretched by 2.5–2.9 pm. The negative charge is
delocalised over 9 bonds.
Figure 1. X-ray Structure of TAS+ CF3C(O)NS(CF3)NS(CF3)NC(O)CF3- (3)
Table 2 Selected bond distances and bond angles in 3
N(1)-S(1) |
163.29(15) |
N(1)-S(2) |
164.01(15) |
S(1)-N(2) |
163.64(15) |
S(1)-C(3) |
183.7(2) |
N(2)-C(1) |
134.5(2) |
C(1)-O(1) |
122.9(2) |
C(1)-C(4) |
153.2(3) |
S(2)-N(3) |
163.18(16) |
S(2)-C(5) |
183.8(2) |
N(3)-C(2) |
133.7(2) |
C(2)-O(2) |
122.6(2) |
C(2)-C(6) |
153.7(3) |
S(3)-N(5) |
160.42(16) |
S(3)-N(6) |
161.70(16) |
S(3)-N(4) |
168.37(15) |
S(1)-N(1)-S(2) |
108.05(9) |
N(1)-S(1)-N(2) |
109.58(8) |
N(1)-S(1)-C(3) |
98.29(9) |
N(2)-S(1)-C(3) |
94.68(8) |
C(1)-N(2)-S(1) |
107.82(13) |
O(1)-C(1)-N(2) |
128.58(19) |
O(1)-C(1)-C(4) |
119.44(17) |
N(2)-C(1)-C(4) |
111.97(16) |
N(3)-S(2)-N(1) |
110.38(9) |
N(3)-S(2)-C(5) |
94.82(8) |
N(1)-S(2)-C(5) |
98.04(9) |
C(2)-N(3)-S(2) |
109.62(13) |
O(2)-C(2)-N(3) |
130.00(18) |
O(2)-C(2)-C(6) |
118.81(17) |
N(3)-C(2)-C(6) |
111.19(16) |
N(5)-S(3)-N(6) |
115.26(9) |
N(5)-S(3)-N(4) |
100.64(8) |
N(6)-S(3)-N(4) |
98.83(8) |
As mentioned in the introduction, of special interest is the conformation of the RC(O)-groups with respect to the –N=SRR’-group. The structure of the anion of 3 corresponds to the structure of CF3C(O)N=S(CF3)F [5], two CF3C(O)NSCF3-units are connected by N1. As observed for CF3C(O)NS(CF3)F both CF3C(O)-units adopt the anti- syn conformation: the CO-group is in an anti-position to the NSC bisector, the oxygen points towards the sulfur (Figure 2). The atoms CSNCO are coplanar (Figure 3), the distances S1O1 (268.1 pm) and S2O2 (274.5 pm) are considerably shorter than the sum of the v.d. Waals radii of sulfur and oxygen (330 pm) [17]. These distances are slightly shorter than in the neutral CF3C(O)NS(CF3)F, probably due to increased electrostatic interaction between O and S in the anion. This electrostatic interaction might be the reason for the unexpected conformation in acyl–S_trifluoromethyl sulphurimides. In both structures sulphur adopts nearly a ψ-trigonal bipyramidal coordination with the O..S_C atoms in axial positions. The angles O1..S1_C3 and O2..S2_C5 in 3 are 151.6° and 153.8°, respectively.
Figure 2. Conformation of the CF3C(O)NS(CF3)NS(CF3)NC(O)CF3- -anion (for clarity the F-atoms of the CF3-groups are omitted)
Figure 3. View showing the coplanarity of the atoms CSNCO and C and the ψ-trigonal bipyramidal environment of the sulphur atoms
Conclusions
From
the reaction of TASF with CF3C(O)NS(CF3)F, unexpectedly
TAS+CF3C(O)NS(CF3)NS
(CF3)NC(O)CF3- (3) was isolated and
characterized by X-ray crystallography. The anion of 3 is the first
member of a hitherto unknown class of compounds, of the bis(sulfinyl)amides [RS(NR’)]2N- and [RS(O)]2N-, respectively. Possible
direct pathways to these compounds, the reactions of RS(NR)F or RS(O)F with
LiN(SiMe3)2 or related amides or the addition of “naked”
anions (nucleophiles) [18] to RS(O)NSO will be followed in the future.
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