COMPLEX ANTIMONY(III) OXOHALIDES
167
can be associated with a transformation of the rigid
The 19
F NMR spectrum of NH Sb BrF O (Fig. 5c)
4 2 4
fluoride sublattice involving local motions. Along with at 150 K is similar to those of the complexes
the rigid sublattice, reorientations of the complex KSb BrF O and RbSb BrF O. At 300 K, the spectra of
2
4
2
4
–
anion [Sb BrF O] are the most probable ionic NH Sb BrF O and NH Sb F [14] are virtually idenꢀ
2
4
4
2
4
4
2 7
motions at 350–450 K. The parameters of the NMR tical, differing only in the line widths and positions
spectra (the line width and shape and the second = 97 and 128 ppm, respectively). The observed
(
δ
moment) suggest high ionic mobility in the fluoride spectral pattern and the line width suggest the absence
sublattice above 480 K, which can be due to partial difꢀ of ionic motions in the fluoride sublattice with freꢀ
4
fusion of fluoride ions.
quencies above 10 Hz.
On heating to 420 K, the line in the 19
F NMR specꢀ
For a sample of KSb BrF O recooled from 500 to
2
4
19
3
00 K, the
F NMR spectrum is restored only parꢀ
trum of NH Sb BrF O becomes narrowed from 36 to
4
2
4
2
2
tially (
Δ
H
≈
27 kHz,
δ
≈
108 ppm, S2(F)
≈
20.5 G ; at
17.7 kHz (S2(F) decreases from ~24 to 15 G ). Most
least, a threeꢀcomponent spectral pattern). Apparꢀ
ently, such a spectral change arises from the beginning
of the decomposition of the complex.
likely, these changes are due to local motions in the
fluoride sublattice. At 420 K, the spectrum consists of
two components with different intensities (
12.5 and 42 kHz), which are
spaced apart at ~15 ppm. Above 440 K, the spectrum
2.5 kHz) with a Lorentzian
~90 ppm. The spectrum becomes highly
≈
60 : 40)
The 19F NMR spectrum of RbSb BrF O at 150– and different widths (
≈
2
≈
4
2
3
00 K shows an asymmetric line at
δ
95 ppm ( H =
Δ
7–39 kHz) (Fig. 5b), somewhat differing from the shows a narrow line (
Δ ≈
H
spectrum of the homoleptic analog RbSb2F7 at 300 K. profile at
δ
The asymmetry of the resonance line, as in the case of asymmetric and much wider (widening from 17.7 to
KSb BrF O, is due to the chemical shift anisotropy 38.5 kHz); the second moment increases as well. Since
2
4
and the nonequivalence of the structural positions of this complex does not melt or decompose at this temꢀ
the fluoride ions (at least three lines with different line perature, the narrow line is most likely attributable to
widths and positions overlap in the spectrum). Heating diffusion in the fluoride sublattice. However, its area at
1
9
from 150 to 300 K virtually does not affect the paramꢀ 500 K does not exceed 4% of the total area of the
F
eters of the 19
F
NMR spectrum of RbSb BrF O, which NMR spectrum, which is why local motions of fluoꢀ
2 4
corresponds to the rigid lattice. Above 300 K, the specꢀ rineꢀcontaining groups are still a dominant type of
tral pattern changes because of a transformation of the ionic mobility in the fluoride sublattice. Note that
19
rigid fluoride sublattice involving local motions. The recooling of
F
F from 500 K to ambient temperature,
19
19
NMR spectrum exhibits a new line with a monoꢀ the F NMR spectrum does not resume its original
tonically decreasing chemical shift (from
~42 to shape (Fig. 5c). This can be explained, as with
0 ppm) and a growing intensity as the temperature is KSb BrF , by the decomposition of the complex
NMR which begins at 496 K (thermal analysis data).
δ
2
2
O
4
19
elevated. Analysis of the derivative of the
F
spectrum in this temperature range reveals at least
three components at 145 10 (shoulder), 97, and
2–30 ppm. Heating from 380 to 450 K causes the
growth of the upfield and central components. The
shoulder at 145 10 vanishes almost completely and
the 19
NMR spectrum of RbSb BrF O consists of two
intense lines at
ing causes the growth and narrowing (to ~ 10 kHz) of
the line at = 25 ppm. At the maximum experimental
To sum up, when moving from the homoleptic
complexes MSb2F7 (M = K, Rb, and NH4) to the hetꢀ
eroleptic complexes MSb BrF O, the observed
δ
±
4
2
4
19
changes in the
F NMR spectra are due to the
δ
±
changes in the dynamic processes in the fluoride subꢀ
F
+
2
4
lattice, which depend on the cation M . On the whole,
δ
95 and 23 ppm (Fig. 5b). Further heatꢀ
introduction of bromide and oxygen ions into the comꢀ
plex anion of the complexes MSb2F7 reduces the ionic
δ
mobility in the resulting complexes MSb BrF O
.
2
4
temperature (500 K), the peak intensity of the upfield
line is higher by a factor of 1.7 than that of the line at
δ
≈
95 ppm (the ratio of the line widths is ~2 : 1). Analꢀ
ACKNOWLEDGMENTS
ysis of the above variations in the parameters of both
the lines in the 1
9
F
NMR spectrum (chemical shift,
This work was supported by the Far East Branch of
line width, and line intensity) with temperature, with the Russian Academy of Sciences, project no. 09ꢀIIIꢀ
consideration to NMR data for RbSb2F7 [14], suggests Vꢀ04ꢀ123.
that two forms of ionic motion can coexist in the fluoꢀ
ride sublattice of RbSb BrF O above 480 K. One can
2
4
REFERENCES
be associated with the reorientation of the complex
–
anion [Sb BrF O] (the line at
δ
= 95 ppm) and the
other, with the high mobility of fluoride ions (the line
at = 23 ppm), which is attributable to the diffusion
observed in the homoleptic analog RbSb2F7 above 450 K
2
4
1
. V. Ya. Kavun, N. F. Uvarov, A. B. Slobodyuk, et al.,
Russ. J. Electrochem. 41, 488 (2005).
δ
2
. L. A. Zemnukhova and R. L. Davidovich, J. Fluorine
Chem. 45, 71 (1989).
[
14]. On recooling of the complex RbSb BrF O to
2 4
19
ambient temperature, the
F
NMR spectrum virtually
3. L. A. Zemnukhova and R. L. Davidovich, Koord.
Khim. , 1572 (1982).
resumes its original shape (Fig. 5b).
8
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012