Silver(I) Undecafluorodiantimonate(V)

Article abstract of DOI:10.1021/ic034616b

The reaction between AgBF₄ and excess of SbF₅ in anhydrous hydrogen fluoride (aHF) yields the white solid AgSb₂F ₁₁ after the solvent and the excess of SbF₅ have been pumped off. Reaction between equimolar amounts of AgSb₂F ₁₁ and AgBF₄ yields AgSbF₆. Meanwhile, oxidation of solvolyzed AgSb₂F₁₁ in aHF by elemental fluorine yields a clear blue solution of solvated Ag(II) cations and SbF ₆^- anions. AgSb₂F₁₁ is orthorhombic, at 250 K, Pbca, with a = 1091.80(7) pm, b = 1246.28(8) pm, c = 3880.2(3) pm, V = 5.2797(6) nm3, and Z = 24. The crystal structure of AgSb₂F ₁₁ is related to the already known crystal structure of H ₃OSb₂F₁₁. Vibrational spectra of AgSb ₂F₁₁ entirely match the literature-reported vibrational spectra of β-Ag(SbF₆)₂, for which a formulation of a mixed-valence Ag(I)/Ag(III) compound was suggested (Ag^IAg ^III(SbF₆)₄). On the basis of obtained results it can be concluded that previously reported β-Ag(SbF₆) ₂ is in fact Ag(I) compound with composition AgSb₂F ₁₁.

Full text of DOI:10.1021/ic034616b

Inorg. Chem. 2003, 42, 8337−8343
Silver(I) Undecafluorodiantimonate(V)
Zoran Mazej* and Primozˇ Benkicˇ
Department of Inorganic Chemistry and Technology, Jozˇef Stefan Institute,
JamoVa 39, SI-1000 Ljubljana, SloVenia
Received June 4, 2003
The reaction between AgBF and excess of SbF in anhydrous hydrogen fluoride (aHF) yields the white solid
4
5
AgSb2F after the solvent and the excess of SbF5 have been pumped off. Reaction between equimolar amounts
11
of AgSb2F and AgBF yields AgSbF . Meanwhile, oxidation of solvolyzed AgSb2F in aHF by elemental fluorine
11
4
6
11
yields a clear blue solution of solvated Ag(II) cations and SbF6- anions. AgSb2F is orthorhombic, at 250 K, Pbca,
11
3
with a ) 1091.80(7) pm, b ) 1246.28(8) pm, c ) 3880.2(3) pm, V ) 5.2797(6) nm , and Z ) 24. The crystal
structure of AgSb2F is related to the already known crystal structure of H3OSb2F . Vibrational spectra of AgSb2F
11
11
11
entirely match the literature-reported vibrational spectra of â-Ag(SbF ) , for which a formulation of a mixed-valence
6 2
I
III
Ag(I)/Ag(III) compound was suggested (AgAg (SbF ) ). On the basis of obtained results it can be concluded that
6 4
previously reported â-Ag(SbF ) is in fact Ag(I) compound with composition AgSb2F .
6 2
11
Introduction
diamagnetic white “â-Ag(SbF6)2”, where the formulation AgI-
AgIII(SbF6)4 is suggested.10 Even the valence isomerism in
the latter is not improbable (i.e., a similar phenomenon was
found for AgF211 and the disproportionation of [Ag(CF3)2]-
into [Ag(CF3)4]- 12). In a recent review of silver compounds
N. Bartlett remarked that it should not be excluded that the
postulated â-Ag(SbF6)2 is Ag(I) compound (AgSb2F11).13
There are no available data about AgSb2F11 in the literature
except that solid AgSb2F11 is produced after reductive
carbonylation of Ag(SO3F)2 and removal of excess SbF5
under vacuum at room temperature.14 Since â-Ag(SbF6)2 is
often given as an example of Ag(I)/Ag(III) compound, we
decided to elucidate if this compound really exists. We
prepared pure AgSb2F11 and found that its vibrational spectra
entirely match the vibrational data previously reported for
â-Ag(SbF6)2. In addition, it is also reported how single
crystals of AgSb2F11 can be prepared in aHF, despite its lack
of solubility.
The investigation of the silver chemistry in superacid
media dates to early 1957 when Ag(I) salts (AgAsF6 and
AgSbF6) were prepared by dissolution of AgF in anhydrous
hydrogen fluoride (aHF) acidified with corresponding Lewis
acids.1 Their crystal structures have been recently deter-
mined.2,3 A great number of Ag(II) compounds have been
synthesized and characterized (e.g., AgFAsF6, Ag(SbF6)2).4-10
Disproportionation of AgFAsF6 in aHF yields white AgAsF6
-
and a black mixed-valence pseudotrifluoride (AgF+)2AgF4 -
AsF6-.11 Another proposed mixed-valence Ag compound is
* To whom correspondence should be addressed. Phone: +386 1 477
3301. Fax: +386 1 477423 21 25. E-mail: zoran.mazej@ijs.si.
(1) Clifford, A. F.; Beachell, H. C.; Jack, W. M. J. Inorg. Nucl. Chem.
1957, 5, 57-70.
(2) Hagiwara, R.; Kitashita, K.; Ito, Y.; Tamada, O. Solid-State Sci. 2000,
2, 237-241.
(3) Matsumoto, K.; Hagiwara, R.; Ito, Y.; Tamada, O. J. Fluorine Chem.
2001, 110, 117-122.
(4) Lucier, G.; Mu¨nzenberg, J.; Casteel, W. J., Jr.; Bartlett, N. Inorg. Chem.
1995, 34, 2692-2698.
Experimental Section
(5) Lucier, G.; Shen, Casteel, W. J., Jr.; Chaco´n, L.; Bartlett, N. J. Fluorine
Chem. 1995, 72, 157-163.
General Experimental Procedures. Volatile materials (BF3,
SbF5, aHF) were manipulated in an all-PTFE vacuum line equipped
with PTFE valves. The manipulation of the nonvolatile solids
sensitive to traces of moisture was accomplished in the dry argon
(6) Frlec, B.; Gantar, D.; Holloway, J. H. J. Fluorine Chem. 1982, 20,
385-396.
(7) Gantar, D.; Frlec, B.; Russell, D. R.; Holloway, J. H. Acta Crystallogr.,
Sect. C 1987, C43, 618-620.
(8) Gantar, D.; Leban, I.; Frlec, B.; Holloway, J. H. J. Chem. Soc., Dalton
Trans. 1987, 2379-2383.
(9) Casteel, W. J., Jr.; Lucier, G.; Hagiwara, R.; Borrmann, H.; Bartlett,
N. J. Solid State Chem. 1992, 96, 84-96.
(12) Dukat, W.; Naumann, D. ReV. Chim. Miner. 1986, 23, 589-603.
(13) Grochala, W.; Hoffmann, R. Angew. Chem., Int. Ed. 2001, 40, 2742-
(10) Cader, M. S. R.; Aubke, F. Can. J. Chem. 1989, 67, 1700-1707.
(11) Shen, C.; Zemva, B.; Lucier, G. M.; Graudejus, O.; Allman, J. A.;
Bartlett, N. Inorg. Chem. 1999, 38, 4570-4577.
2781.
(14) Willner, H.; Aubke, F. Angew. Chem., Int. Ed. Engl. 1997, 36, 2403-
2425.
10.1021/ic034616b CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/30/2003
Inorganic Chemistry, Vol. 42, No. 25, 2003 8337

Mazej and Benkicˇ
atmosphere of a drybox (M. Braun). The residual water in the
atmosphere within the drybox never exceeded 1 ppm. All reactions
were carried out in FEP vessels (height 300 mm, inner diameter
15.5 mm, outer diameter 18.75 mm) equipped with PTFE valves
and PTFE-coated stirring bars. Prior to their use all reaction vessels
were passivated with elemental fluorine.
Caution! aHF, BF3, SbF5, and elemental fluorine should only
be handled in a well-Ventilated hood, and protectiVe clothing should
be worn at all times!
Reagents. AgNO3 (Alkaloid Skopje, 99.7%), fluorine (Solvay,
99.98%), and BF3 (Union Carbide Austria GmbH, 99.5%) were
used as supplied. SbF5 (Merck, >98%) was redistilled in metal-
PTFE vacuum lines. Anhydrous HF (Fluka, purum) was treated
with K2NiF6 for several hours prior to use.
Preparation of AgBF4. AgBF4 was prepared by modified
method as described in the literature.15 A sample of 0.426 g (2.51
mmol) of AgNO3 was loaded into an FEP reaction vessel equipped
with a PTFE filter. A volume of 5 mL of aHF was condensed on
it at 77 K, and the reaction mixture was warmed to room
temperature. In few minutes a clear colorless solution was obtained
above the PTFE filter. The bottom part of the reaction vessel was
cooled to transfer the solution through the PTFE filter. After the
first portion of BF3 was added at room temperature, a white solid
precipitated immediately. Addition of gaseous BF3 was continued
until the pressure in the reaction vessel (2 bar) remained constant.
After 12 h the liquid phase was decanted away. Finally, the white
sample was dried by pumping the last traces of volatile components
away in a dynamic vacuum for 3 h. The product weight was 0.473
g; AgBF4 requires 0.488 g. The X-ray powder diffraction pattern
into an FEP reaction vessel, and aHF (2 mL) was condensed on it
at 77 K. Fluorine was slowly added at room temperature to the
final pressure of 2.1 bar. A clear blue solution formed in a few
minutes. Fluorine was added again to the final pressure of 3.2 bar.
After 1 day volatiles were pumped off at room temperature. The
resulting 0.109 g of blue solid was identified as Ag(SbF6)2 by
material balance (calcd 0.103 g), the Raman spectrum, and the X-ray
powder diffraction pattern.
Reduction of Ag(SbF6)2, Dissolved in aHF, by Elemental
Hydrogen. A sample of 0.215 g (1.48 mmol) of AgF2 was loaded
in a drybox into an FEP reaction vessel, and SbF5 (0.980 g) and
aHF (4 mL) were condensed on it at 77 K. The reaction vessel
was brought up to 298 K, and a clear blue solution formed in a
few minutes. Immediately after the addition of hydrogen at room
temperature to the final pressure of 4 bar, the solution changed its
color from blue to green. Finally, a white solid precipitated and
the solution became colorless. After volatiles were pumped off at
room temperature, 0.680 g of white solid was obtained. Raman
spectrum showed the mixture of AgSbF6 and AgSb2F11.
Attempt To Prepare Single Crystals of AgSb2F11 from
Saturated Solution in aHF. Preparation was carried out in a double
T-shaped apparatus made of two FEP tubes (19 mm o.d. and 6
mm o.d.). About 0.300 g of AgSb2F11 was loaded in a drybox into
the wider tube. Then aHF (∼7 mL) was condensed on it at 77 K
and the mixture was warmed to room temperature. The sample only
partly dissolved. The clear solution was poured into the narrower
tube. The narrower tube containing saturated solution was kept at
room temperature all the time of crystallization. Meanwhile, the
wider tube was cooled first by tap water (maintaining temperature
gradient of about 10 K for 7 days) and then to 263 K for an
additional 1 week, causing the evaporation of solvent from the
narrower into the wider tube. Cubic-shaped crystals formed on the
walls of the reaction vessel. Volatile components were slowly
pumped away. Raman spectra of obtained crystals showed only
the bands that can be assigned to AgSbF6.
was in agreement with literature data for AgBF4. The Raman
-
spectrum showed only bands that can be assigned to BF4
.
Synthesis of AgSb2F11. In a drybox 1.85 mmol (0.361 g) of
AgBF4 was loaded into an FEP reaction vessel. Then an excess of
SbF5 (6.23 mmol, 1.350 g) and aHF (2 mL) were condensed on it
at 77 K. The reaction mixture was left stirring for few days at room
temperature. A clear colorless liquid phase was visible above a
nondissolved white solid all the time. Volatiles were slowly pumped
off at room temperature for few hours, leaving behind 1.041 g of
white solid corresponding to the composition of AgSb2F11 (calcd
1.038 g).
Reaction between AgSb2F11 and AgBF4. A sample of 0.150 g
(0.27 mmol) of AgSb2F11 and 0.052 g (0.27 mmol) of AgBF4 was
loaded in a drybox into an FEP reaction vessel. Then aHF (2 mL)
was condensed on the reaction mixture at 77 K. The reaction was
carried out at room temperature for 1 day. Solvent and released
BF3 were pumped off at room temperature. A white solid, 0.194 g,
which corresponded to the composition AgSbF6, was obtained
(calcd 0.186 g). The vibrational spectrum and X-ray powder
diffraction pattern were in agreement with literature data for
AgSbF6.
Preparation of Single Crystals of AgSb2F11. Preparation was
carried out in a double T-shaped apparatus made of two FEP tubes
of the same size separated by a common valve (19 mm o.d.). A
sample of 0.150 g (0.77 mmol) of AgBF4 was loaded in a drybox
into one tube. Then 0.500 g (2.31 mmol) of SbF5 and aHF (∼4
mL) were condensed on it at 77 K and the mixture was warmed to
233 K without stirring. The reaction mixture was slowly allowed
to warm to room temperature (1 day) and was left at room
temperature without stirring. After 2 days the valve separating both
tubes was opened. The tube containing the reaction mixture was
kept at room temperature. Meanwhile, the empty tube was first
cooled by tap water (maintaining temperature gradient of about 10
K for 1 month), then to 253 K for 1 week, to 223 K for an additional
1 week, and finally to 77 K for 1 day. In that way aHF, released
BF3, and the excess SbF5 slowly evaporated from one tube into
the empty one and colorless crystals were obtained. Crystals were
immersed in perfluorinated oil (ABCR, FO5960) in the drybox,
selected under the microscope, and transferred into the cold nitrogen
stream of the diffractometer. Some of the crystals were also mounted
into 0.3 mm quartz capillaries. Raman spectra of selected single
crystals were identical to the Raman spectrum of powdered
AgSb2F11 prepared by reaction between AgBF4 and excess SbF5
in aHF.
The remaining AgSbF6 (∼100 mg) was redissolved in 7 mL of
aHF. Immediately after the addition of elemental fluorine, a dark
green solid precipitated. Above it a clear blue solution was observed.
After 2 h volatiles were pumped away at room temperature. The
X-ray powder diffraction pattern of the isolated black-green solid
was of very poor quality. Only a few weak lines were observed
that could be tentatively attributed to AgF2, Ag(SbF6)2, and
- 11
(AgIIF+)2AgIIIF4-SbF6
.
Elemental Analysis. Silver was determined gravimetrically,16
and antimony was determined by redox titration.17 The content of
Oxidation of AgSb2F11 by Elemental Fluorine in aHF. A
sample of 0.100 g (0.18 mmol) of AgSb2F11 was loaded in a drybox
(16) Vogel, A. I. Vogel’s textbook of quantitatiVe inorganic analysis:
including elementary instrumental analysis, 4th ed.; Longman: Lon-
don, 1978; pp 433-435, 479.
(15) Clifford, A. F.; Kongpricha, S. J. Inorg. Nucl. Chem. 1957, 5, 76-
78.
8338 Inorganic Chemistry, Vol. 42, No. 25, 2003

SilWer(I) Undecafluorodiantimonate(V)
a
Table 1. Crystal Data and Structure Refinement for AgSb2F11
formula
fw
AgSb2F11
560.37
250
1091.80(7)
1246.28(8)
3880.2(3)
5.2797(6)
24
temp (K)
a (pm)
b (pm)
c (pm)
V (nm3)
Z
D
calcd (mg/m3)
4.230
λ (pm)
71.069
8.44
Pbca (No. 61)
1.209
µ (mm-1
)
space group
GOF indicator
R1; wR2 (I > 2.00σ(I))
0.0615; 0.1334
a R1 ) ∑|Fo| - |Fc|/∑|Fo|; wR2 ) [∑(w(Fo2 - Fc2)2/∑(w(Fo2)2]1/2; GOF
) [∑(w(Fo - Fc )2/(No - Np)]1/2, where No ) number of reflections and
Np ) number of refined parameters.
2
2
total fluoride ions was determined after total decomposition with a
fluoride ion selective electrode.18 The chemical analyses are given
in mass percents.
X-ray powder diffraction photographs were obtained using
the Debye-Scherrer technique with Ni-filtered Cu KR radiation.
Samples were loaded into quartz capillaries (0.3 mm) in a glovebox.
Intensities were estimated visually.
Figure 1. Infrared and Raman spectra of AgSb2F11.
X-ray Structure Determination of AgSb2F11. Single crystal data
of AgSb2F11 were collected on a Mercury CCD area detector
coupled with a Rigaku AFC7S diffractometer using monochroma-
tized Mo KR radiation. Data were corrected for Lorentz, polariza-
tion, and absorption effects and processed using the Rigaku
Crystalclear software suite program package. The structure was
solved by direct methods (SHELXS) and expanded using Fourier
techniques. Some details of the single crystal data collection, data
processing, and refinement are given in Table 1.
Infrared and Raman Spectroscopy. The infrared spectra were
taken on a Perkin-Elmer FTIR 1710 spectrometer on powdered
samples between AgCl windows in a leak-tight brass cell. Raman
spectra were recorded on a Renishaw Raman Imaging Microscope
System 1000, with the 632.8 nm exciting line of a He-Ne laser.
observed, indicating that some AgSb2F11 was also present
(see Vibrational Spectra).3 In the Raman spectrum of AgSbF6
taken on a single crystal, no such band could be observed.
The main driving forces for the AgSbF6 (AgSb2F11) forma-
tion are the fluoride ion affinities (FIA) of SbF5 (2SbF5) and
the lattice energy differences between the AgF and the
complex fluoroanion salts AgSbF6 (AgSb2F11). The lattice
potential energy of AgSbF6 is estimated to be 580 kJ/mol.19
Using Jenkins et al.’s generalized volume-based Kapustinskii
equation,20 and using the crystal data for AgSb2F11, the lattice
potential energy of AgSb2F11 was estimated to be 493 kJ/
mol. However, the FIA of 2SbF5 is higher than that of SbF5
(about 165 kJ/mol higher for gaseus SbF5).19 These data
imply that AgSb2F11 is presumably the result of thermo-
dynamic control, whereas AgSbF6 is the more likely kinetic
product.
Results
Elemental Analysis. Calcd for AgSb2F11: Ag, 19.2%;
Sb, 43.5%; F, 37.3%. Found: Ag, 19.8%; Sb, 42.0; F, 36.3%.
Raman and IR spectra of the bulk of AgSb2F11 are
shown in Figure 1 and given in Table 2.
To confirm the composition AgSb2F11, two additional
experiments were performed. In the first experiment equi-
molar amounts of AgSb2F11 and AgBF4 reacted according
to the equation
Discussion
AgBF4 +AgSb2F11 aHF 8 2AgSbF6 + BF3
(2)
Syntheses. In highly acidic aHF the strong Lewis acid
SbF5 displaces the weaker acid BF3 from AgBF4, yielding
AgSb2F11:
298 K
The solvolysis of AgSb2F11 in aHF to AgSbF6 and SbF5
is in accordance with previous findings that washing with
aHF is an effective way to eliminate SbF5 from Sb2F11
salts.21 Released SbF5 displaces BF3 from AgBF4, yielding
AgSbF6.
aHF,SbF5
-
AgBF4 + 2SbF5
8 AgSb2F11 + BF3
(1)
298 K
If the excess of SbF5 in aHF is too low or pumping off of
the volatiles is too fast, then mainly AgSbF6 is obtained as
the final product. This explains why only AgSbF6 was
observed in the isolated solids of reactions of AgF with
excess of SbF5.1,3 However, in the Raman spectra of isolated
products a weak broad peak at 680 cm-1 was sometimes
Oxidation of solvolyzed AgSb2F11 by elemental fluorine
yields a clear solution with a blue color typical for solvated
(19) Jenkins, H. D. B.; Roobottom, H. K. Inorg. Chem. 2003, 42, 2886-
2893.
(20) Jenkins, H. D. B.; Roobottom, H. K.; Passmore, J.; Glasser, L. Inorg.
Chem. 1999, 38, 3609-3620.
(21) Bernhardt, E.; Bley, B.; Wartchow, R.; Willner, H.; Bill, E.; Kuhn,
P.; Sham, I. H. T.; Bodenbinder, M.; Bro¨chler, R.; Aubke, F. J. Am.
Chem. Soc. 1999, 121, 7188-7200.
(17) Ponikvar, M.; Pihlar, B.; Zˇemva, B. Talanta 2002, 58, 803-810.
(18) Ponikvar, M.; Sedej, B.; Pihlar, B.; Zˇemva, B. Anal. Chim. Acta 2000,
418, 113-118.
Inorganic Chemistry, Vol. 42, No. 25, 2003 8339

Mazej and Benkicˇ
17
Table 2. Comparison of Literature Data for â-Ag(SbF6)2 with Obseved Vibrational Wavenumbers for AgSb2F11 and Description of Vibrational
41
Modes for Sb2F11 on the Basis of Literature Data for Pd(CO)4(Sb2F11)2
â-Ag(SbF6)2
AgSb2F11
Pd(CO)4(Sb2F11)2
IRa
Ramana
IR
Raman
IR
Raman
assignmentb
719 (s, sh)
720 (12, sh)
700 (33, sh)
722 (m,sh)
706 (s)
713 (10)
718 (sh)
708 (vs)
714 (w)
709 (sh)
697 (w)
ν(SbFax)
ν(SbFax)
ν(SbFax)
697 (30)
692 (vs)
692 (vs)
690 (vs)
ν(SbF4eq
ν(SbF4eq
ν(SbF4eq
ν(SbF4eq
ν(SbF4eq
ν(SbF4eq
ν(SbF4eq
)
)
)
)
)
)
)
682 (100)
678 (100)
672 (sh)
655 (95)
645 (30, sh)
594 (15)
585 (15)
686 (m)
668 (s)
656 (s)
649 (m)
598 (w)
585 (w)
673 (s)
654 (s)
674 (m,sh)
656 (s)
640 (sh)
602 (m)
675 (s)
662 (s)
648 (sh)
604 (vw)
596 (w)
659 (93)
651 (30, sh)
600 (16)
602 (m)
590 (14)
515 (vw)
490 (ms)
526 (4)
490 (ms)
475 (sh)
503 (m)
484 (m)
ν(SbFSb)
ν(SbFSb)
368 (mw)
365 (1)
357 (w, sh)
349 (2)
312 (13, sh)
303 (32)
315 (s)
305 (s)
δ(SbFax)
δ(SbFax)
301 (sh)
298 (40)
305 (m)
275 (w)
283 (s)
278 (s)
290 (18)
285 (20, sh)
272 (2, sh)
233 (15)
267 (vs)
250 (sh)
228 (sh)
196 (vw)
δ(SbF4eq
δ(SbF4eq
δ(SbF4eq
δ(SbF4eq
)
)
)
)
230 (m)
201 (vw)
136 (vw)
153 (m)
δ(FSbF)
a Intensities are given in parentheses; vw ) very weak, w ) weak, m ) medium, ms ) medium strong, s ) strong, vs ) very strong, sh ) shoulder.
b ν ) stretching mode, δ ) deformation mode.
Ag(II) in superacid media. The final product of isolation was
Comparing the effective molar volumes of Ag+ and H3O+,
it is not so surprising that AgSb2F11 is structurally related to
H3OSb2F11.22 The calculated effective volume of the Ag+
cation is 0.00604 nm3, using Goldschmidt’s radius for Ag+
(0.113 nm)23 and taking the volume of the cation to be equal
to (4/3)πr3.20,24 The average effective volume of H3O+ can
be calculated by Veff(H3O+) ) [(Vunit cell/Z) - Vanion]. Using
the values of Vunit cell and Z known from the crystal structures
of H3OAsF625 and H3OSbF626 and using the average effective
volumes for the anions AsF6- (0.110 nm3) and SbF6- (0.121
nm3) obtained by the method of Jenkins et al.,20 the average
effective volume of H3O+ (0.00758 nm3) can be estimated.
The complex structure of AgSb2F11 reveals three crystal-
blue R-Ag(SbF6)2.8
AgSb2F11 + (1/2)F2 aHF 8 Ag(SbF6)2
(3)
298 K
In contrast, the fluorination of AgSbF6 in aHF proceeded
in a completely different manner. Addition of fluorine first
converts AgSbF6 to AgFSbF6.4 Further course of reaction
depends on the amount of aHF. In a small amount of aHF
(concentration of SbF5 is high), AgFSbF6 disproportionates
-
- 11
to AgSbF6 and black insoluble (AgF+)2AgF4 SbF6 . The
interaction of AgFSbF6 with a large amount of aHF leads to
simple solvolysis and AgF2 and Ag(SbF6)2 production.11
Since the fluorination of the product obtained in the AgBF4/
SbF5/aHF system yields a clear blue solution, it can be
concluded that AgSb2F11 is not contaminated with AgSbF6.
Otherwise, also some precipitation of black (AgF+)2AgF4-SbF6
or dark green AgF2 should occur.
-
lographically nonequivalent Sb2F11 anions (Figure 2). In
the ideal case the Sb2F11 unit has a linear Sb-F-Sb moiety,
together with eclipsed SbF4,eq groups. Then the dioctahedral
anion is centrosymmetrical (point group D4h).27 The eclipsed
conformation is rare but has been previously observed in
H3F2Sb2F11,28 N5Sb2F11,29 and Au(CO)2Sb2F11.30 Because of
their flexibility, Sb2F11 anions are usually distorted from D4h
symmetry, depending upon the counterions in the crystal
Additionally, it was found that the presence of hydrogen
in the solvent (aHF) can cause the reduction of solvated
cationic Ag(II) to Ag(I), yielding AgSbF6 and/or AgSb2F11
depending on the conditions of isolation.
(22) Zhang, D.; Rettig, S. J.; Trotter, J.; Aubke, F. Inorg. Chem. 1996, 35,
6113-6130.
(23) Dasent, W. E. Inorganic Energetics, 2nd ed.; Cambridge University
Press: Cambridge, UK, 1982.
(24) Marcus, Y.; Jenkins, H. D. B.; Glasser, L. J. Chem. Soc., Dalton Trans.
2002, 3795-3798.
(25) Mootz, D.; Wiebcke, M. Inorg. Chem. 1986, 25, 3095-3097.
(26) Abney, K. D.; Larson, A. C.; Eller, P. G. Acta Crystallogr., Sect. B
1991, B47, 206-209.
(27) Sham, I. H. T.; Patrick, B. O.; von Ahsen, B.; von Ahsen, S.; Wilner,
H.; Thompson, R. C.; Aubke, F. Solid-State Sci. 2002, 4, 1457-1463.
(28) Mootz, D.; Bartmann, K. Angew. Chem., Int. Ed. 1998, 27, 391-392.
(29) Vij, A.; Wilson, W. W.; Vij, V.; Tham, F. S.; Sheehy, J. A.; Christe,
K. O. J. Am. Chem. Soc. 2001, 123, 6308-6313.
(30) Willner, H.; Schaebs, J.; Hwang, G.; Mistry, F.; Jones, R.; Trotter, J.;
Aubke, F. J. Am. Chem. Soc. 1992, 114, 8972-8980.
The mass balance, chemical analysis, and chemical
behavior of isolated solid confirm the composition AgSb2F11.
The final proof comes from the structure determination.
Structure. The preparation of single crystals of AgSb2F11
from saturated solution in aHF failed because of its solvolysis
in aHF. Only single crystals of AgSbF6 were obtained.
However, if the starting AgI compound is treated with a large
excess of SbF5 in a small amount of aHF at low temperature
and then volatiles are slowly removed, single crystals of
AgSb2F11 suitable for crystal structure determination can be
grown.
8340 Inorganic Chemistry, Vol. 42, No. 25, 2003

SilWer(I) Undecafluorodiantimonate(V)
depends not only on the nature of the cations but also on
packing effects. Another well-known example is N5Sb2F11
(R ) 155°, ψ ) 0°) where the eclipsed conformation results
+
from N5 acting as a spacer between two SbF4,eq units of
Sb2F11.29 As found for many other Sb2F11 compounds,22,29,33-36
a slight asymmetry of the Sb-Fb-Sb bridge in Sb2F11 units
of AgSb2F11 was observed (Table 3). Sb-Ft bonds are as
expected shorter (182.7-186.7 pm) and show a wider spread
than Sb-Fb bonds (201.7-204.2 pm). A slight lengthening
of some terminal Sb-Ft bonds appears to involve Ft engaged
in interionic contacts with Ag cations (Table 3, Figure 2).
Bond angles Feq-Sb-Fax are slightly wider than 90°, while
Feq-Sb-Fb angles are acute by about 3-6° (Table 4). A slight
lean of fluorine atoms in equatorial positions toward the
weakly bonded Sb-Fb-Sb moiety is in agreement with the
VSEPR theory of molecular structure.37,38 As for H3-
OSb2F11,22 Sb-Ft distances in AgSb2F11 are in general
slightly shorter than distances in corresponding SbF6- salts,
-
showing that Sb2F11 is a weaker nucleophile than SbF6 .
There are also three crystallographically nonequivalent
Ag+ cations in the crystal structure of AgSb2F11 (figures in
Supporting Information). Ag-F bond distances cover a wide
range and can be divided into two groups (247.2-263.4 and
269.1-294.7 pm). The Ag-F distances of the second group
are a little larger than that based on the sum of the Shanon
radii (261 pm)39 of fluorine and silver, taking into account
the coordination number (CN) 8 but still quite below the
sum of their respective van der Waals radii (315(8) pm).40,41
They can be compared to Ag-F distances found in
AgPdZr2F11,42,43 Ag2CuFeF7,42,44 and AgF (type II).42,45 In
the first two compounds the Ag atoms are 8-fold coordinated
by four shorter (AgPdZr2F11: 235.5 pm (4×); Ag2CuFeF7:
242.1 pm (2×) and 254.0 pm (2×)) and four longer contacts
(AgPdZr2F11: 279.8 pm (4×); Ag2CuFeF7: 278.8 pm (2×)
and 290.7 pm (2×)) that are similar to the distances found
in AgSb2F11. In AgF (type II) silver atoms are 8-fold
coordinated with equal Ag-F distances (255 pm).42,8,45 The
coordination of silver atoms in AgSb2F11 can be ap-
proximately written as 5 + 3 for Ag1 (CN ) 8), 6 + 3 for
Ag2 (CN ) 9), and 6 + 2 for Ag3 (CN ) 8).
Figure 2. Three crystallographically nonequivalent Sb2F11 units and their
interactions with Ag+ cations in the crystal structure of AgSb2F11 (thermal
ellipsoids are drawn at 40% probability level).
lattice. They exhibit a wide range of Sb-F-Sb bridging
angles in a staggered conformation. There are two primarily
distortional processes involved. First is bending of two SbF5
groups about Fb (bridging fluorine) which is expressed in
terms of the bridge angle R, and second is torsion of two
planar SbF4,eq groups from eclipsed to staggered conforma-
tion expressed in the torsion angle (ψ).31 In AgSb2F11 three
different bridge (143.5°, 148.3°, and 151.8°) and three
corresponding dihedral (37.1°, 22.5°, 18.0°) angles for three
crystallographically nonequivalent Sb2F11 units are found.
The bridging angles in AgSb2F11 are close to the values found
for the anions in structurally related H3OSb2F11 (R ) 145.9°,
148.3°, and 149.4°). Meanwhile, dihedral angles found in
AgSb2F11 show a larger distinction in comparison with H3-
OSb2F11 (ψ ) 29.5°, 21.2°, and 24.2°).22 In the literature an
explanation can be often found that an increase in ψ serves
to minimize steric repulsions between the nearest neighbor
F atoms on each octahedron as R decreases below 180°. For
example, ψ ) 0° when R approaches 180°, and ψ ) 45°
when R increases to ∼145°.32 However, the values of R and
corresponding ψ for Sb2F11 units found in the crystal structure
(33) Bruce, D. M.; Holloway, J. H.; Russell, D. R. J. Chem. Soc., Dalton
Trans. 1978, 1627-1631.
(34) Willner, H.; Bach, C.; Wartchow, R.; Wang, C.; Rettig, S. J.; Trotter,
J.; Jonas, V.; Thiel, W.; Aubke, F. Inorg. Chem. 2000, 39, 1933-
1942.
(35) Bernhardt, E.; Bley, B.; Wartchow, Willner, H.; R.; Bill, E.; Kuhn,
P.; Sham, I. H. T.; Bodenbinder, M.; Bro¨chler, R.; Aubke, F. J. Am.
Chem. Soc. 1999, 121, 7188-7200.
(36) Willner, H.; Bodenbinder, M.; Bro¨chler, R.; Hwang, G.; Rettig, S. J.;
Trotter, J.; Von Ahsen, B.; Westphal, U.; Volker, J.; Thiel, W.; Aubke,
F. J. Am. Chem. Soc. 2001, 123, 588-602.
(37) Gillespie, R. J.; Hargittai, I. The VSEPR Model of Molecular Geometry;
Allyn and Bacon; Boston, 1991.
(38) Gillespie, R. J. Angew. Chem., Int. Ed. 1996, 35, 495-514.
(39) Shannon, R. D. Acta Crystallogr., Sect A 1976, A32, 751-767.
(40) Bondi, A. J. Phys. Chem. 1964, 68, 441-451.
(41) Hurlburt, P. K.; Rack, J. J.; Luck, J. S.; Dec, S. F.; Webb, J. D.;
Anderson, O. P.; Strauss, S. H. J. Am. Chem. Soc. 1994, 116, 10003-
10014.
22
of AgSb2F11 and H3OSb2F11 show that the correlation
between R and ψ is not generally valid and consequently
has no practical value since deformation of Sb2F11 units
(42) Mu¨ller, B. G. Angew. Chem., Int. Ed. Engl. 1987, 26, 1081-1097.
(43) Mu¨ller, B. G. Z. Anorg. Allg. Chem. 1987, 553, 205-211.
(44) Koch, J.; Hebecker, H. Naturwisseschaften 1985, 72, 431-432.
(45) Halleck, P. M.; Jamieson, J. C.; Pistorius, C. W. F. T. J. Phys. Chem.
Solids 1972, 33, 769-773.
(31) Burgess, J.; Fraser, C. J. W.; McRae, V. M.; Peacock, R. D.; Russell,
D. R. J. Inorg. Nucl. Chem. Suppl. 1976, 183-188.
(32) Casteel, W. J., Jr.; Dixon, D. A.; Mercier, H. P. A.; Schrobilgen, G.
J. Inorg. Chem. 1996, 35, 4310-4322.
Inorganic Chemistry, Vol. 42, No. 25, 2003 8341

Mazej and Benkicˇ
a
Table 3. Selected Bond Lengths (pm) in AgSb2F11
Sb1-F1
202.0(7)
184.3(8)
183.8(8)
186.7(9)
183.4(9)
185.7(7)
Sb2-F1
203.4(7)
185.1(8)
185.5(9)
184.4(8)
185.0(8)
184.5(7)
Sb3-F3
204.2(7)
184.9(8)
186.1(8)
185.9(7)
183.4(8)
185.0(7)
Sb4-F3
201.7(7)
186.2(8)
185.7(8)
182.9(8)
185.4(8)
185.2(8)
Sb1-F11
Sb1-F12
Sb1-F13
Sb1-F14
Sb1-F15
Sb2-F21
Sb2-F22
Sb2-F23
Sb2-F24
Sb2-F25
Sb3-F31
Sb3-F32
Sb3-F33
Sb3-F34
Sb3-F35
Sb4-F41
Sb4-F42
Sb4-F43
Sb4-F44
Sb4-F45
Sb5-F5
Sb5-F51
Sb5-F52
204.2(7)
184.8(8)
184.1(8)
Sb5-F53
Sb5-F54
Sb5-F55
182.7(9)
184.1(7)
185.4(7)
Sb6-F5
Sb6-F61
Sb6-F62
201.7(7)
186.1(8)
184.9(8)
Sb6-F63
Sb6-F64
Sb6-F65
185.4(8)
185.1(8)
185.7(7)
Ag1-F32
Ag15-F33
Ag1-F42
Ag12-F44
Ag16-F45
Ag1-F51
Ag1-F61
Ag16-F64
252.1(8)
260.0(7)
253.4(9)
272.8(9)
252.9(8)
249.4(8)
269.1(8)
286.4(8)
Ag2-F11
Ag28-F12
Ag2-F21
Ag28-F22
Ag23-F23
Ag26-F24
Ag2-F52
Ag2-F62
Ag26-F63
257.9(8)
257.1(8)
258.7(8)
255.0(9)
281.3(9)
261.3(8)
294.7(10)
247.2(8)
271.6(7)
Ag3-F13
Ag36-F15
Ag36-F31
Ag3-F35
Ag36-F41
Ag36-F54
Ag3-F55
Ag36-F65
254.5(10)
271.4(7)
261.2(8)
273.2(7)
262.2(8)
255.1(8)
263.4(8)
257.2(8)
a Symmetry operations used for generation of equivalent atoms: (1) x, y, z; (2) x + 1/2, -y + 1/2, -z; (3) -x, y + 1/2, -z + 1/2; (4) -x + 1/2, -y,
z + 1/2; (5) -x, -y, -z; (6) -x + 1/2, y + 1/2, z; (7) x, -y + 1/2, z + 1/2; (8) x + 1/2, y, -z + 1/2.
Table 4. Selected Bond Angles (deg) in AgSb2F11
F11-Sb1-F1
F12-Sb1-F1
F13-Sb1-F1
F14-Sb1-F1
F11-Sb1-F15
F12-Sb1-F15
F13-Sb1-F15
F14-Sb1-F15
84.3(3)
86.1(4)
84.4(4)
86.5(4)
95.2(4)
93.1(4)
96.1(4)
94.3(4)
F21-Sb2-F1
F22-Sb2-F1
F23-Sb2-F1
F24-Sb2-F1
F21-Sb2-F25
F22-Sb2-F25
F23-Sb2-F25
F24-Sb2-F25
Sb1-F1-Sb2
84.3(4)
85.8(4)
85.6(4)
86.5(4)
94.0(4)
92.5(4)
96.2(4)
95.2(4)
148.3(4)
F31-Sb3-F3
F32-Sb3-F3
F33-Sb3-F3
F34-Sb3-F3
F31-Sb3-F35
F32-Sb3-F35
F33-Sb3-F35
F34-Sb3-F35
84.7(3)
86.9(4)
82.7(3)
86.1(4)
96.0(4)
93.8(4)
96.6(4)
93.3(4)
F41-Sb4-F3
F42-Sb4-F3
F43-Sb4-F3
F44-Sb4-F3
F41-Sb4-F45
F42-Sb4-F45
F43-Sb4-F45
F44-Sb4-F45
Sb3-F3-Sb4
85.3(4)
85.7(4)
86.1(4)
86.5(4)
91.1(4)
92.1(4)
97.5(4)
95.7(4)
151.8(4)
F51-Sb5-F5
F52-Sb5-F5
F53-Sb5-F5
F54-Sb5-F5
F51-Sb5-F55
F52-Sb5-F55
F53-Sb5-F55
F54-Sb5-F55
85.0(4)
84.8(4)
86.7(4)
85.9(3)
92.4(4)
94.7(4)
95.8(4)
94.6(4)
F61-Sb6-F5
F62-Sb6-F5
F63-Sb6-F5
F64-Sb6-F5
F61-Sb6-F65
F62-Sb6-F65
F63-Sb6-F65
F64-Sb6-F65
Sb5-F5-Sb6
85.0(3)
86.5(4)
84.7(3)
86.5(4)
93.1(4)
92.7(4)
97.1(3)
94.3(4)
143.5(4)
Vibrational Spectra. Vibrational spectra of AgSb2F11 are
the same as for “â-Ag(SbF6)2” (AgIAgIII(SbF6)4),10 demon-
strating that AgSb2F11 and “â-Ag(SbF6)2” are one and the
Ag(SbF6)2”) and a blue solution from which R-Ag(SbF6)2
was isolated.10 All these data suggest that in all cases partial
reduction of Ag(II) occurred. The first cause could be the
presence of the impurities in starting materials serving as
reducers. This is not surprising since cationic solvated
Ag(II) in aHF acidified with Lewis acids is known to be a
very strong oxidizer and it can be easily reduced.46 The
second reason could be the influence of the acidity of aHF.
When an large excess of SbF5 was added to R-Ag(SbF6)2, it
was irreversibly converted in aHF to a white insoluble solid.10
From literature data it is well-known that increased acidity
of aHF favors a low oxidation state in the cation.47,48-50
The preparation and crystal structure determination of other
ASb2F11 compounds (A ) monovalent cation) are in
progress.
-
same compound. Sb2F11 anions strongly deviate from D4h
symmetry and have no symmetry (point group C1). Partial
-
assignment of Sb2F11 anions was made on the basis of
comparison with M(CO)4(Sb2F11)2 (M ) Pd, Pt)35 which
contain two crystallographically nonequivalent distorted
Sb2F11- anions. The bands in the regions 585-692 and 697-
722 cm-1 are assigned to Sb-Feq and Sb-Fax stretchings,
respectively; meanwhile, bands around 500 cm-1 are typical
for Sb-F-Sb bridging. The rest of the bands were assigned
to bending deformations.
Conclusions
On the basis of obtained results it can be concluded that
“â-Ag(SbF6)2” (formulated as mixed-valence Ag(I)/Ag(III)
compound) is in fact an Ag(I) compound (AgSb2F11). In the
original method of preparation of “â-Ag(SbF6)2” by solvoly-
sis of Ag(SO3F)2 in liquid SbF5, a change of color from black
brown to greenish blue and finally to yellow was observed.10
Additionally, the attempts of the same authors to repeat the
synthesis of previously reported R-Ag(SbF6)2 always gave
a fair amount of white insoluble solid (postulated to be “â-
Acknowledgment. The authors gratefully acknowledge
the financial support of the Ministry of Education, Science
(46) Zˇemva, B.; Hagiwara, R.; Casteel, W. J., Jr.; Lutar, K.; Jesih, A.;
Bartlett, N. J. Am. Chem. Soc. 1990, 112, 4846-4849.
(47) Zˇemva, B. C. R. Acad. Sci. Paris Ser. II 1998, 1, 151-156.
(48) Elder, S. H.; Lucier, G. M.; Hollander, F. J.; Bartlett, N. J. Am. Chem.
Soc. 1997, 119, 1020-1026.
(49) Hwang, I. C.; Seppelt, K. Z. Anorg. Allg. Chem. 2002, 628, 765-
769.
(50) O’Donnell, T. A. Eur. J. Inorg. Chem. 2001, 21-34.
8342 Inorganic Chemistry, Vol. 42, No. 25, 2003

SilWer(I) Undecafluorodiantimonate(V)
obtained by reaction between AgSb2F11 and AgBF4 in aHF, Raman
and IR spectra of Ag(SbF6)2 obtained by reaction between AgSb2F11
and F2 in aHF, Raman and IR spectra of the solid isolated after
reaction between AgSbF6 and F2 in aHF. This material is available
free of charge via the Internet at http://pubs.acs.org.
and Sport of the Republic of Slovenia. We thank Dr. Maja
Ponikvar for the chemical analyses.
Supporting Information Available: X-ray crystallographic file
in CIF format, figures of coordination of silver atoms by Sb2F11
units, figures of the Raman spectrum of AgBF4, Raman spectrum
of AgSbF6 taken on single crystal, Raman spectrum of AgSbF6
IC034616B
Inorganic Chemistry, Vol. 42, No. 25, 2003 8343