Technetium fluoride trioxide, TcO3F, preparation and properties

Article abstract of DOI:10.1021/ic070333y

TcO₄^- in HF solution reacts to form Tc ₃O₉F₄^- along with some TcO ₃F. Pure TcO₃F is obtained if a mixture of HF/BiF ₅ is applied. TcO₃F dimerizes in the solid state via fluoride bridges, similar to the structures of CrO₂F₂ and VOF₃. TcO₃F reacts in HF with AsF₅ or SbF ₅ under formation of TcO₂F₂⁺As(Sb) F₆^-.

Full text of DOI:10.1021/ic070333y

Inorg. Chem. 2007, 46, 5591−5595
†
Technetium Fluoride Trioxide, TcO F, Preparation and Properties
3
Joanna Supeł, Ulrich Abram, Adelheid Hagenbach, and Konrad Seppelt*
Institute of Chemistry, Freie UniVersit a¨ t, D-14195 Berlin, Fabeckstrasse 34-36,
D-14195 Berlin, Germany
Received February 21, 2007
-
-
TcO
HF/BiF
VOF . TcO
4
in HF solution reacts to form Tc
is applied. TcO F dimerizes in the solid state via fluoride bridges, similar to the structures of CrO
F reacts in HF with AsF or SbF under formation of TcO
+As(Sb)F -.
3
O
9
F
4
along with some TcO
3
F. Pure TcO
3
F is obtained if a mixture of
5
3
2 2
F
and
3
3
5
5
2
F
2
6
Introduction
Of the three known fluoride oxides of technetium(VII),
solutions, although the reported vapor pressure of TcO
should make the separation from HF readily possible.
F7
3
We have become interested in TcO
3
F after we obtained
namely TcO F, TcO , and TcOF , there exists the least
information about the first and oldest of the three.
TcOF
has been found only recently.1,2 It is prepared from
TcO by reaction with KrF and is a molecular species
3
F
2 3
5
ReO
3
F pure and solved its complicated crystal structure.9
The latter can be described as a cis oxide and fluoride-
bridged helical polymer with six-coordinated Re atoms. On
5
F
2 3
2
the other hand, MnO
even in the solid state.
The aim of this investigation is to find a simple way of
preparing TcO F and to evaluate its crystal structure as well
3
F is monomeric and pseudo tetrahedral
with a close to octahedral structure, as confirmed by NMR,
IR, and Raman spectroscopy, a single-crystal structure
determination, and local density functional calculations. It
is one of the only four existing molecular oxide pentafluo-
1
0
3
as some of its chemistry.
rides; the others are ReOF
TcO
reaction of Tc
method, and a crystal structure is now available. TcO
5
, OsOF
5
, and IOF
5
.
3
4
F
2 3
was first observed in 1982, and 1991. The
Experimental Section
2
7 6
O with XeF finally resulted in a preparative
Caution. Handling anhydrous HF or compounds that produce
5
2 3
F is
HF upon hydrolysis requires eye and skin protection.
in the solid state a fluoride-bridged polymer, with distorted
octahedral coordination around the Tc atoms, the two oxygen
atoms being in a cis position.
Radiation Precautions. 99Tc is a weak â-emitter. Manipulations
of 99Tc compounds are performed in a laboratory approVed for
the handling of such radioactiVe materials.
TcO
Tc /UF
amounts by fluorination of TcO
3
F might have been detected in the mass spectrum of
Materials and Apparatus. Sample handling is performed using
Teflon-PFA (polyperfluoroether-terafluoroethylene) tubes that are
sealed at one end and equipped at the other end with a metal valve
and thus connectable to a stainless steel vacuum line.
NMR spectra are recorded on a JEOL multinuclear instrument
6
2
O
7
4
mixtures. It was first prepared in weightable
7
2
at 150 °C. Later, it was
-
assumed that it is formed simply by dissolving TcO
4
in
anhydrous HF,3 but it has never been isolated from such
,8
1
99
-
at 400 MHz for H. Tc spectra are recorded relative to TcO
4
in
†
H
2
O as external standard. Raman spectra are recorded on a Bruker
Dedicated to Neil Bartlett on the occasion of his 75th birthday.
To whom correspondence should be addressed. E-mail: Seppelt@
*
RFS 100 FT-Raman spectrometer.
chemie.fu-berlin.de.
Single crystals are handled with cooling to ∼ -140 °C under
nitrogen in a special device,11 and mounted on a Bruker SMART
CCD 1000 TK diffractometer using Mo KR radiation, a graphite
monochromator, a scan width of 0.3° in ω, and a measuring time
of 10 s per frame. Usually each compound is measured up to 2θ )
(
(
1) Le Blond, N.; Schrobilgen, G. J. Chem. Commun. 1996, 2479-2480.
2) Le Blond, N.; Mercier, H. P. A.; Dixon, D. A.; Schrobilgen, G. J.
Inorg. Chem. 2000, 39, 4494-4509.
(
3) Franklin, K. J.; Lock, C. J. C.; Sager, D. G.; Schrobilgen, G. J. J. Am.
Chem. Soc. 1982, 104, 5303-5306.
(
(
4) Gibson, J. K. J. Fluor. Chem. 1991, 55, 299-311.
5) Mercier, H. P. A.; Schrobilgen, G. J. Inorg. Chem. 1993, 32, 145-
151.
(9) Supeł, J.; Marx, R.; Seppelt, K. Z. Anorg. Allg. Chem. 2005, 631,
2979-2986.
(
6) Sites, J. R.; Baldock, C. R.; Gilpatrick, L. O. U.S.A.E.C. 1952, ORNL-
1327.
(10) Spandl, J.; Supeł, J.; Drews, T.; Seppelt, K. Z. Anorg. Allg. Chem.
2006, 632, 2222-2225.
(
(
7) Selig, H.; Malm, G. J. Inorg. Nucl. Chem. 1963, 25, 349-351.
8) Binenboyen, J.; El-Gad, U.; Selig, H. Inorg. Chem. 1974, 13, 319-
(11) Schumann, H.; Genthe, W.; Hahn, E.; Hossein, M.-B.; Helm, D. v. d.
J. Organomet. Chem. 1986, 28, 2561-2567.
321.
1
0.1021/ic070333y CCC: $37.00
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 14, 2007 5591
Published on Web 06/05/2007

Supeł et al.
Table 1. Crystal Data
+
+
-
+
-
chemical formula
fw
space group
a/pm
b/pm
c/pm
K Tc3O9F4·1.5 TcO3F
TcO3F
165.0
P21/c
568.9(3)
506.9(3)
930.5(5)
93.21(1)
267.93
-115
4
CrO2F2
122.0
P21/c
565.5(3)
485.3(2)
911.6(3)
92.95(5)
249.85
-120
4
VOF3
123.9
P21/c
556.9(6)
500.7(4)
934.1(7)
91.32(4)
260.40
-90
TcO2F3·TcO3F
352.0
P21/c
820.1(2)
1458.3(4)
530.5(2)
90.13(1)
634.47
-140
TcO2F2 SbF6 ·2HF
443.8
P21/c
TcO2F2 ·AsF6 ·2HF
396.9
P21/c
800.6
P21/c
827.2(1)
1414.8(1)
2474.9(3)
92.72(2)
2893.14
-100
852.9(2)
903.8(2)
1134.3(2)
108.14(1)
830.96
-100
512.6(3)
810.3(6)
1969.1(12)
95.57(2)
813.89
â/deg
6
3
V/10 pm
T/°C
-100
4
5.96
3.24
Z
4
4
3.67
3.16
4
4.42
3.69
4
5.06
3.55
-
1
µ/mm
4.62
3.676
5.18
4.09
4.40
3.24
-
1
Fcalcd/g cm
reflns
measured
independent
variables
17 631
8261
442
1876
660
47
8383
1612
46
2207
611
47
6137
1817
101
10 285
2544
136
9828
2377
135
2
θmax/deg
60.05
0.036
0.063
0.077
57.83
0.061
0.075
0.156
81.84
0.023
0.028
0.060
56.01
0.026
0.029
0.068
65.80
0.045
0.050
0.096
61.13
0.013
0.014
0.030
60.16
0.038
0.082
0.095
R1(I > 4σ(I)
R1
wR2(all data)
6
1° by 1800 frames, thus covering a full sphere. Semiempirical
deeply yellow colored cubes and a small amount of the light yellow
platelets of TcO F are formed. The cube-shaped crystal are brought
to the crystal structure determination.
absorption corrections are used by equalizing symmetry-equivalent
reflections (SADABS). Structures are solved and refined with the
SHELDRICK programs.12 Experimental details of the crystal
structure determinations are given in Table 1. NH
purchased from Oakridge NEI Laboratories. KTcO
addition of KCl and isolation of the less-soluble precipitate. AsF
and SbF are from laboratory stock, as is HF. AsF is used as such,
SbF vacuum distilled twice into a -78° trap before use. HF is
vacuum distilled once and kept in a stainless steel cylinder over
3
+‚AsF
-‚2HF. TcO
TcO
2
F
2
6
3
F (10-20 mg), dissolved in HF,
at -196 °C. The sample is
+
-
4
TcO
4
has been
is combined with 225 mg of AsF
5
4
is prepared by
warmed carefully to -10° (caution, pressure!), and a clear
yellow solution is formed. Brief warming to room temperature is
followed by slow cooling to -78°. Fine, needle-shaped yellow
crystals are formed. These are brought to the crystal structure
determination. The compound decomposes within days even if
stored at -40 °C.
5
5
5
5
BiF
5
. BiF
5
is prepared from BiF
3
and elemental F
2
at 550 °C, as
described in ref 13.
TcO
mol) of SbF
BiF ) of TcO
the U-tube at -78°. About half of the HF is distilled off into a
198 °C cold trap. Warming to 0 °C and cooling to -78 °C gives
a large crop of yellow platelets, along with large colorless cubes
2
F
2
+SbF
6
-
‚2HF. A PFA U-tube is filled with 100 mg (0.46
+
-‚1.5TcO
K Tc
3
O
9
F
4
3
F. KTcO
4
(30 mg) is filled into a 8 mm
-
5
and connected to the preparation setup (TcO
F. The volatile TcO
4
, HF,
outer diameter PFA tube, and on a vacuum line 2 g (0.1 mol) of
anhydrous HF are condensed on it. The reaction mixture is warmed
to room temperature and shaken for 30-60 min. The clear yellow
solution is pumped to dryness in dynamic vacuum, leaving a brown
microcrystalline precipitate. Addition of more HF gives back the
yellow-brown solution at 25 °C, slow cooling to -30 °C gives large,
cubic-shaped brown crystals. The yield is estimated to be quantita-
5
3
3
F/HF mixture is distilled into
-
+
-
that are determined as H
spectrum (solid, -100 °C, cm ) 993(st), 982(m), 732(w), 710,
91, 669(st), 642(m), 586, 518, 407(m), 381, 322(m), 312(m), 285-
3
O SbF
6
by crystallography. Raman
-
1
6
(
-
+
tive, based on TcO
4
. The NH
4
salt can be prepared similarly,
but crystals of the K salt are of much better quality.
TcO F. An 8 mm outer diameter PFA tube is filled with 90 mg
0.3 mmol) of BiF and 2.5 g (0.125 mol) of HF. Under an inert
gas atmosphere and cooling to -78 °C, 30 mg (0.15 mmol) of
KTcO is added. The mixture is warmed to room temperature
+
-
2 2 6
m), 264, 240, 232(w), 201, 188, 176, 157, 122. TcO F SbF ‚2HF
+
melts in part at 40 °C under evolution of HF. After pumping off
the latter, a light yellow powder is obtained, with a Raman spectrum
3
(
5
+
- 14
2 2 6
of previously published TcO F SbF : Raman spectrum (solid,
2
6
-
1
5 °C, cm ): 992(st), 980(m), 748, 732, 720, 680(m), 666(st),
12(w), 550, 533, 410(m), 385, 327(m), 311(m), 290, 269, 246-
4
under shaking. Within 30 min at 25 °C the solution and solid
turn yellow. In a dynamic vacuum the mixture is pumped through
(m), 240, 207, 176, 130, 120.
15
VOF
3 2 5 2
(cf. ref 15 ). V O is fluorinated with undiluted F at
-
-
-
3
78 and -196 °C cooled PFA traps. TcO F is collected in the
78 °C trap. Addition of 1 mL of HF and very slow cooling to
78 °C within 2 weeks affords light yellow crystal plates. The
475 °C in a copper tube and sublimed into a PFA tube. Single
crystals are obtained by recrystallization from HF at -78 °C.
CrO F . K Cr O is dissolved in HF under formation of a brown
yield is estimated about 50%, mp 18.5 °C. Raman spectrum (solid,
2
2
2
2
7
-
1
-
100 °C, cm ): 943 (st), 933(st), 915(m), 466(w), 383(m), 366-
gas. Volatiles are condensed into a -30 °C cold PFA trap. Brown
99
(
m), 293(w), 228(w), 186(w), 139(w), 105(m). Tc NMR (SO
2
-
crystals appear on the cooled wall, whereas liquid HF condenses
FCl): 48.92 ppm, w1/2 ) 70 Hz (25 °C). 99Tc NMR (HF) 43.1
19
into the bottom of the tube. F NMR (SO FCl, -70 °C): δ )
2
ppm, w1/2 ) 225 Hz (-80 °C), 45.1 ppm, w1/2 ) 27 Hz (25 °C).
109.57 ppm, w1/2 = 300 Hz. Raman spectrum (solid, -100 °C):
959 (100), 941 (70), 655 (8), 592 (10), 539 (30), 498 (15), 431 (20),
397 (15), 339 (25), 277 (40), 238 (30), 186 (25), 164 (20), 150 (15),
1
9F NMR (SO
2
ClF, HF): very broad signal, centered about -50
ppm.
TcO
of HF, and 30 mg (0.15 mmol) of KTcO
above. After recrystallization from HF at -78 °C, a large crop of
2
F
3
‚TcO
3
F. BiF
5
(115 mg, 0.375 mmol), 2.5 g (0.125 m)
122 (35) cm-1
.
4
are reacted as described
(
13) Brauer, G. Handbuch der pr a¨ paratiVen Anorganischen Chemie I;
Ferdinand Enke Verlag: Stuttgart, 1975; p 219.
(
12) Sheldrick, G. Program for Crystal Structure Solution; Universit a¨ t
G o¨ ttingen; G o¨ ttingen, Germany, 1986; SHELXS; Universit a¨ t G o¨ ttin-
gen; G o¨ ttingen, Germany, 1997.
(14) Le Blond, N.; Dixon, D. A.; Schrobilgen, G. J. Inorg. Chem. 2000,
39, 2473-2487.
(15) Trevorrow, L. E. J. Phys. Chem. 1958, 62, 362.
5592 Inorganic Chemistry, Vol. 46, No. 14, 2007

3
Preparation and Properties of TcO F
Table 2. Selected Bond Lengths (pm) and Angles (deg)
+
-‚1.5TcO
F
3
K Tc
3
O F
9 4
-
3
Tc O
F
9 4
Unit
TcdO
Tc-F
167.3-169.1(4)
209.7-225.9(3)
103.3-106.0(2)
102.9-114.6(1)
269.6-284(4)
OdTcdO
Tc-F-Tc
+
K ‚‚‚F
+
K ‚‚‚O
281.2-321.4(4)
3
TcO F Unit
TcdO
Tc-F
OdTcdO
F-TcdO
168.7-175.4(4)
175.1-176.1(4)
108.2-111.3(2)
108.1-111.3(2)
3
TcO F
TcdO
167.4-173.8(1)
203.9, 213.3(1)
228.2(1)
103.2-105.4(4)
69.5(3)
Tc-F
Tc‚‚‚O
OdTcdO
F-Tc-F
CrO
157.4, 157.6(1)
2 2
F
CrdO
Cr-F
181.7, 186.7, 209.4(1)
222.9(1)
103.87(5)
Cr‚‚‚F
OdCrdO
F-Cr-F
+
-
73.21, 83.64, 152.51(4)
Figure 1. Asymmetric unit of K Tc3O9F4 ‚1.5TcO3F. For clarity, the
+
second K ion (K2) is omitted. Ortep representation, 50% probability
VOF
3
155.1(2)
ellipsoids.
VdO
V-F
V‚‚‚F
F-V-F
171.3, 178.9, 192.0, 197.2(2)
229.4(2)
72.9, 87.0, 91.6, 101.4, 153.6, 156.6(8)
Results
The present legal restrictions of handling radioactive,
volatile Tc compounds call for a simple, one-step procedure
at room temperature. Therefore, the original preparation from
TcO F ·TcO F
2
3
3
TcO
2
F
3
Chain
TcdO
Tc-F
OdTcdO
F-Tc-F
164.6, 165.6(5)
183.5, 184.8, 207.5, 209.3(4)
101.6(3)
TcO
We can show that by dissolving K TcO
no TcO F in appreciable amounts can be obtained, although
2 2
and F at 150 °C was not taken into consideration.
+
-
in anhydrous HF
80.2-81.1(3), 154.6
4
3
TcO F
167.8-170.6(6)
181.7(5)
3
TcdO
Tc-F
OdTcdO
3,8
it is obviously present in solution. From such solutions
large yellow crystals can be obtained, which according to
107.0-108.7(3)
+
-
TcO2F2+SbF6-‚2HF
164.8, 165.0(1)
181.7, 182.4(1)
221.0, 222.4(1)
103.16(6)
their crystal structure are K Tc
and Tables 1 and 2.
The structure can be described as a heterocubane of Tc
3
O
9
F
4
3
‚1.5TcO F, see Figure
TcdO
Tc-F
Tc‚‚‚F
1
OdTcdO
F-Tc-F
F‚‚‚Tc‚‚‚F
Sb-F
and F atoms, where one corner Tc atom is missing. The
three oxygen atoms complete the distorted octahedral
coordination around the Tc atom. This cluster is considered
146.73(4)
77.30(4)
185.8-188.8, 195.6(1)
241.5(2)
F‚‚‚(H)-F
as the reaction product of three TcO
3
F molecules with one
2 2 6
TcO F
+AsF -‚2HF
-
F . Interestingly, there are TcO
3
F molecules also in the lattice
TcdO
Tc-F
Tc‚‚‚F
163.9, 164.5(4)
181.5, 181.8(4)
220.6, 223.3(4)
102.5(2)
as molecules. They are connected to the cluster Tc atoms
via very long contacts of the fluorine atoms (∼360-390 pm).
OdTcdO
F-Tc-F
F‚‚‚Tc‚‚‚F
As-F
+
145.9(2)
79.0(2)
169.5-173.0, 181.3(4)
249.4(5)
The K ions are coordinated to the oxygen atoms of the
3
clusters and to the TcO F molecules with typical distances
of 260-290 pm.
F‚‚‚(H)-F
This structure explains why TcO
solution, cannot simply be freed out of the solution or the
solid compound: The TcO F is kept in the solid state by
intermolecular interactions to K and F so that its vapor
pressure is severely lowered as compared to pure TcO F.
Not even by heating to ca. 80 °C under vacuum is any TcO
released. If the excess of HF is simply pumped off, the
3
F, although present in
equilibrium. This is done by adding the nonvolatile Lewis
+
-
+
-
acid BiF
salts. BiF
excess drives the fluorination reaction further to known
TcO
5
that forms very stable K BiF
6
3 6
and H O BiF
3
5
has to be added in a stoichiometrical amount,
+
-
3
2 3
F .
3
F
TcO4- + 2BiF + 3HF f BiF + H O BiF + TcO3F
-
+
-
5
6
3
6
formation reaction of TcO
compound.
3
F can turn back to the starting
TcO4- + 3BiF + 6HF f BiF
-
+
5
6
TcO4- + 3 HF h TcO F + H O + 2 F
+
-
+
-
2H O BiF + TcO2F3
3 6
3
3
Once this had been established, the preparation of TcO
3
F
If BiF
the co-crystallizate TcO
5
is applied in amounts between 1:2 and 1:3, then
‚TcO F is formed, see below.
+
+
is possible if the K and H
3
O ions are taken out of the
2
F
3
3
Inorganic Chemistry, Vol. 46, No. 14, 2007 5593

Supeł et al.
Figure 4. Raman spectrum of (TcO3F)2, solid, -100 °C. Arrows indicate
location and intensity of Raman lines of the PFA container.
Surprisingly we found that there exist two other oxide
fluorides with structures that are very much like that of
TcO
has been determined before, although with low precision.
As far as we know, the solid state of CrO has not been
described before. Our structure determinations are also shown
3 2 2 3 3
F, namely CrO F and VOF . The structure of VOF
Figure 2. Structure of TcO3F in the solid state, 50% probability ellipsoids.
Shown is one (extended) unit cell. TcO3F is a dimer via two slightly
asymmetric fluoride bridges with one additional long contact to a neighbor-
ing oxygen atom. The structures of CrO2F2 and VOF3 are very similar,
except that one (CrO2F2) and two (VOF3) oxygen atoms are replaced by
fluorine atoms. In these structures, the weak interaction between the dimeric
units is therefore also a fluoride bridge. Bond lengths and angles are listed
in Table 2.
1
5
2 2
F
6
in Figure 2. Lattice constants of VOF
are very similar, and all three belong to the same space group
P2 /c. In the sequence VOF , CrO , and TcO F, all
intermolecular forces within the dimeric units are getting
weaker, see Table 2. So TcO F is closest to a molecule in
the solid state, VOF is a polymer, and CrO lies
somewhere in between.
The dimeric form of TcO
spectrum of the solid, see Figure 4. The existence of three
3 2 2 3
, CrO F , and TcO F
1
3
2
F
2
3
3
3
2 2
F
3
F is also visible in the Raman
-1
TcdO stretching vibrations above 900 cm is in accord with
the low symmetry around the Tc atom, whereas the Tc-F
stretching vibrations cannot be located with certainty in
-
1
8
contrast to monomeric TcO
3
F (696 cm , m).
The weak dimer of TcO F can easily be broken up into a
3
monomer if other coordinating materials are present, as has
-
been shown already with the existence of Tc
The mixed compound TcO ‚TcO
when excess BiF is used in the formation reaction of TcO
is a (TcO polymer, very much like pure TcO , and
along its chain, TcO F molecules are attached, see Figure 5.
3
O
9
F
4
3
‚TcO F.
2
F
3
3
F, which is formed
5
3
F,
Figure 3. Comparison of the dimeric double fluorine bridged TcO3F (a)
with polymeric oxygen- and fluorine-bridged ReO3F (b).
2
F )
3 n
2 3
F
3
+
TcO
3
F could be a precursor to the TcO
3
cation, if the F
Once reacted, TcO
of the reaction mixtures, and yellow plates of crystalline
TcO F are formed upon cooling to -78 °C.
3
F and HF can be pumped together out
-
atom is taken away as F by a strong Lewis acid. It has
been assumed before that in TcO
Tc NMR signal at 160.7 ppm is due to TcO
solvated ion TcO ‚L has very recently been prepared, L )
-
4
/HF/AsF
5
solutions the
99
+
3
3
. Also the
+
The crystal structure, as shown in Figure 2 and Table 2,
proves it to be a dimer in the solid state, which means that
the Tc atoms are five-coordinate. Upon closer inspection of
the packing, a contact between the technetium atom and one
oxygen atom of an adjacent molecule is observed, raising
the coordination number to six. The crystal structures of
3
1
7
triazacyclononane.
Of interest here would be a very weakly solvated, almost
+
free TcO
3
cation, which is expected to have a high electron
affinity. Reaction of TcO
HF could be a simple mode of obtaining TcO
3
F and AsF
5
or SbF
5
in anhydrous
+
3
. This,
TcO
3
F is therefore very different from monomeric MnO
3
F
F
however, is not the case. In both reactions, only the
9
and polymeric ReO
is shown in Figure 3, while MnO
in all physical states.
3
3
F . The structure of TcO F and ReO
3
(
16) Edwards, A. J.; Taylor, P. J. Chem. Soc. D. Chem. Commun. 1970,
474-1475.
(17) Braband, H.; Abram, U. Inorg. Chem. 2006, 45, 6589-6591.
3
F is a molecular species
1
5594 Inorganic Chemistry, Vol. 46, No. 14, 2007

3
Preparation and Properties of TcO F
+
-
Figure 6. Zwitterionic unit TcO2F2 SbF6 ‚2HF, 50% probability ellipsoids
except H atoms), distances in pm.
(
Figure 5. Co-crystallizate TcO2F3‚TcO3F. 50% probability ellipsoids.
Shown is the polymeric chain of TcO2F3 with one loosely contacted TcO3F
molecule, distance in pm.
loss of HF can be observed in the Raman spectrum: The
final product shows exactly the previously published spec-
2 2 6
trum of TcO F .
+SbF
- 14
technetium-containing product TcO
2
F
2
+As(Sb)F
6
-‚2HF is
+
-
3
obtained, besides some H O (As,Sb)F
6
. These materials can
In summary, we do not state that a largely uncoordinated
cation could not exist, but it would need a different
approach, most likely the presence of HF should be avoided.
+
+
easily be distinguished after crystallization: the TcO
F
2 2
salts
TcO
3
+
are yellow prisms, the H
3
O salts are large, colorless cubes.
+
The two TcO
F
2 2
cations in both salts are virtually identical,
+
Acknowledgment. We gratefully acknowledge support
from the Deutsche Forschungsgemeinschaft and the Fonds
der Chemischen Industrie.
see Figure 6. The bisphenoidal shape of the TcO
2
F
2
is
+SbF
-
,14 including two
-) and one to the
similar to the structure in TcO
F
2 2
6
further contacts, here one to SbF
6
-(AsF
6
(
HF)
2
unit, so that the technetium atoms gain a (distorted)
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
+AsF
-
‚2HF decomposes
octahedral coordination. TcO
F
2 2
6
+
-
slowlyevenat-40°C,whereascrystalsofTcO
2
F
2
‚SbF ‚2HF
6
are stable to about -30 °C. Above this temperature, HF is
+
-
liberated, leaving TcO
F
2 2
‚SbF
6
as a beige powder. The
IC070333Y
Inorganic Chemistry, Vol. 46, No. 14, 2007 5595