Synthesis, characterization, and structures of R3EOTcO 3 complexes (E = C, Si, Ge, Sn, Pb) and related compounds

Article abstract of DOI:10.1021/ic1001094

AgTcO₄ reacts with R₃ECI compounds (E = C, Si, Ge, Sn, Pb; R = Me, ⁱPr, ^tBu, Ph), ^tBu ₂SnCl₂, or PhMgCl under formation of novel trioxotechnetium(VII) derivatives. The carbon and

Full text of DOI:10.1021/ic1001094

Inorg. Chem. 2010, 49, 3525–3530 3525
DOI: 10.1021/ic1001094
Synthesis, Characterization, and Structures of R3EOTcO3 Complexes
(E = C, Si, Ge, Sn, Pb) and Related Compounds
Elisabeth Oehlke,† Roger Alberto,‡ and Ulrich Abram*,†
†
€
Institute of Chemistry and Biochemistry, Freie Universitat Berlin, Fabeckstrasse 34-36, D-14195 Berlin, Germany,
‡
and Institute of Inorganic Chemistry, University of Zu€rich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
Received January 18, 2010
i
AgTcO4 reacts with R3ECl compounds (E = C, Si, Ge, Sn, Pb; R = Me, Pr, tBu, Ph), tBu2SnCl2, or PhMgCl under
formation of novel trioxotechnetium(VII) derivatives. The carbon and silicon derivatives readily undergo decomposi-
tion, which was proven by 99Tc NMR spectroscopy and the isolation of decomposition products such as [TcOCl3-
(THF)(OH2)]. Compounds [Ph3GeOTcO3], [(THF)Ph3SnOTcO3], [(O3TcO)SntBu2(OH)]2, and [(THF)4Mg(OTcO3)2]
are more stable and were isolated in crystalline form and characterized by X-ray diffraction.
Introduction
preformed {ReO3} building blocks in Re2O7. Such reactivity
is not observed for the molecular technetium oxide, and other
precursors are required.
Coordination and organometallic compounds of tech-
netium(VII) are still relatively rare, especially with respect
to the well-known rhenium(VII) chemistry.1-4 This is mainly
The synthesis of {TcO3}þ complexes from pertechnetate
with chelating ligands in the presence of strong acids is
restricted to a comparatively small number of (preferably
tripodal) chelators and technetium fluorides.8,9 It is assumed
that the initially formed pertechnetic acid, HTcO4, or mixed
anhydrides formed from HTcO4 and strong acids serve as the
real precursors in such reactions. The synthesis of MeTcO3
and some related products from Me4Sn and Tc2O7 is one of
the rare examples in which the oxide is used as a precursor.10
Some stable trioxotechnetium(VII) compounds have been
prepared by the oxidation of technetium(V) compounds con-
taining powerful chelators. Derivatives of [99TcO3(tacn)]Br
(tacn = 1,4,7-triazacyclononane) are particularly remark-
able11 because their 99mTc analogues may serve as a new
approach to technetium-labeled bioconjugates for nuclear-
medical imaging.11b,12
-
due to the differences in the redox potentials of TcO4
-
and ReO4 (TcO4-/TcO2 = þ0.747 V vs ReO4-/ReO2 =
þ0.510 V),5 and the lack of suitable technetium(VII) pre-
cursors. The facile reduction of technetium(VII) limits the
number of compounds that are accessible for this oxidation
state, and the volatility of most of the readily accessible
technetium(VII) compounds restricts their use in routine
procedures with respect to the radioactivity of technetium.
Unlike Re2O7, which possesses a polymeric structure con-
sisting of tetrameric subunits with preformed tetrahedral and
octahedral units (Figure 1),6 Tc2O7 is a centrosymmetric
˚
˚
molecule with Tc-O distances of 1.68 A (terminal) and 1.84 A
(bridging).7 Thus, some of the reactivities of the oxides can be
explained by their structures, particularly the formation of
the trioxorhenim(VII) core can be predicted by means of the
(8) (a) Davison, A.; Jones, A. G.; Abrams, M. J. Inorg. Chem. 1981, 20,
4300. (b) Thomas, J. A.; Davison, A. Inorg. Chem. 1992, 31, 1976. (c) Thomas,
J. A.; Davison, A. Inorg. Chim. Acta 1991, 190, 231. (d) Joachim, J. E.;
Apostolidis, C.; Kanellakopulos, B.; Maier, R.; Ziegler, M. L. Z. Naturforsch.
1993, B48, 227. (e) Tooyama, Y.; Braband, H.; Springler, B.; Abram, U.; Alberto,
R. Inorg. Chem. 2008, 47, 257.
*To whom correspondence should be addressed. E-mail: abram@chemie.
fu-berlin.de. Phone: (49) 30 83854002. Fax: (49) 30 83852676.
(1) Alberto, R. Technetium. In Comprehensive Coordination Chemistry II;
McCleverty, J. A., Meyer, T. J., Eds.; Elsevier: Amsterdam, The Netherlands,
2004; Vol. 5, p 127.
(2) Abram, U. Rhenium. In Comprehensive Coordination Chemistry II;
McCleverty, J. A., Meyer, T. J., Eds.; Elsevier: Amsterdam, The Netherlands,
2004; Vol. 5, p 271.
(9) (a) Castreel, W. J.; Dixon, D. A.; LeBlond, N.; Mercier, H. P. A.;
Schrobilgen, G. J. J. Inorg. Chem. 1998, 37, 340. (b) Supel, J.; Abram, U.;
Hagenbach, A.; Seppelt, K. Inorg. Chem. 2007, 46, 5591. (c) LeBlond, N.;
Schrobilgen, G. J. Chem. Commun. 1996, 2479.
~
(3) Romao, C. C.; Royo, B. Rhenium. In Comprehensive Organometallic
Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds.; Elsevier: Oxford, U.K.,
2007; Vol. 5, p 833.
(4) Sattelberger, A. P.; Scott, B. L.; Poineau, F. Technetium. In Compre-
hensive Organometallic Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds.;
Elsevier: Oxford, U.K., 2007; Vol. 5, p 833.
€
(10) Herrmann, W. A.; Alberto, R.; Kiprof, P.; Baumgartner, F. Angew.
Chem. 1990, 102, 208.
(11) (a) Braband, H.; Abram, U. Inorg. Chem. 2006, 45, 6589. (b) Braband,
H.; Tooyama, Y.; Fox, T.; Alberto, R. Chem.;Eur. J. 2009, 15, 633.
(c) Kanellakopoulos, B.; Nuber, B.; Raptis, K.; Ziegler, M. Angew. Chem.
1989, 101, 1055.
(5) (a) Boyd, G. E. J. Chem. Educ. 1959, 36, 3. (b) Meyer, R. E.; Arnold,
W. D. Radiochim. Acta 1991, 55, 19.
(12) Alberto, R.; Braband, H.; Jones, N. A. PCT Int. Appl. 2009, 42
(CODEN: PIXXD2 WO 2009112823 A2 20090917).
€
(6) Krebs, B.; Muller, A.; Beyer, H. H. Inorg. Chem. 1969, 8, 295.
(7) Krebs, B. Angew. Chem., Int. Ed. 1969, 8, 381.
r
2010 American Chemical Society
Published on Web 03/10/2010
pubs.acs.org/IC

3526 Inorganic Chemistry, Vol. 49, No. 7, 2010
Oehlke et al.
Table 1. 99Tc NMR Data of R3EOTcO3 and Related Compounds
compound/solvent
δ(99Tc) in ppma
Δν1/2 in Hz
ref
13
Me3SiOTcO3/toluene
Me3SiOTcO3/(Me3Si)2O
Ph3COTcO3/THF
-0.07
11.24
67.27
3.00
44
8.78
42.70
68.30
25.15
6.97
not reported
75
1045
960
23
127
307
1572
374
102
Ph(O)COTcO3/PhCOCl
FTcO3/HF
11b
9a
iPr3SiOTcO3/THF
tBuMe2SiOTcO3 /THF
Ph3SiOTcO3/THF
Figure 1. Structures of Tc2O7 and Re2O7.
Ph3GeOTcO3/THF
Ph3PbOTcO3/THF
Another apparently suitable precursor for trioxotechne-
tium(VII) compounds, Me3SiOTcO3, is described in an early
report of Nugent,13 and its reactivity has been proven for the
synthesis of a number of arylimidotechnetium(VII) com-
pounds14 but has not yet found more attention for ongoing
reactions. This is readily understood by the reported sensi-
tivity of this compound, which is much higher than that of its
rhenium analogue. Me3SiOReO3 serves as important pre-
cursor for rhenium(VI) alkoxides and organometallic rhe-
nium oxides such as Re2O3Me6, Re2O4(CH2CMe3)4, or
R0ReO3 (R0 =aryl),15 and also the heavier congoners R3Ge-
OReO3 and R3SnOReO3 (R = alky, aryl) have been known
for a long time.16
(THF)Ph3SnOTcO3/THF
[(OH)tBu2SnOTcO3]2/THF
Me3SnOTcO3/THF
(THF)4Mg(OTcO3)2/THF
-5.10
-2.46
-1.2
-38
237
293
not reported
120
10
a With respect to TcO4- in H2O.
even under inert conditions. This is most probably due to the
reduction of technetium. The rate of decomposition of the
technetium(VII) compound depends on the solvents used
(THF > acetonitrile > (Me3Si)2O ≈ benzene) and can be
readily tracked by the decreasing intensity of the 99Tc NMR
signal.
In two cases, we were able to isolate the decomposition
products of such reaction mixtures: (i) colorless crystals of
(Ph3Si)2O were isolated from the reaction of AgTcO4 with
1 equiv of Ph3SiCl in dry THF, and (ii) yellow crystals of
Presently, we are searching for suitable precursors for
convenient access to technetium(VII) complexes. As part of
this work, we report in the present paper about the syntheses
and properties of R3EOTcO3 complexes (E = C, Si, Ge, Sn,
Pb; R = alkyl, aryl) and related compounds.
i
i
[TcOCl3(OH2)(THF)] appeared when Pr3SiOTcO3 in Pr3-
SiCl was stored over a period of several weeks. The formation
of the first product can be understood by the assumption
of an equilibrium between Ph3SiOTcO3 and (Ph3Si)2O/
Tc2O7, as was also observed for analogous rhenium com-
pounds,17 while isolation of the technetium(V) oxychloride is
direct proof of the reductive and hydrolytic degradation of
the primary reaction product iPr3SiOTcO3. The formation of
trichlorooxotechnetium(V) from iPr3SiOTcO3 with an excess
of iPr3SiCl is reproducible; for crystallization of its THF/H2O
adduct, however, a well-balanced ratio between these ligands
is required. This is best achieved when carefully dried solvents
and glassware and a standard Schlenk technique are used.
The small amount of water that is required for hydrolysis/
complexation is then released from the glass walls and
migrates into the reaction mixture during the manipulations,
keeping in mind that the reactions are done at the 0.1 mmol
scale.
[TcOCl3(OH2)(THF)] is a solvent adduct of one of the
three known neutral technetium oxychlorides: TcO3Cl,
TcOCl4, and TcOCl3. None of these compounds has been
isolated in crystalline form so far. Previous reports describe
TcOCl3 as a product of the photochemical decomposition of
TcOCl4. It can also be synthesized directly by chlorination of
TcO2 at 300-350 °C. The IR spectrum of TcOCl3 shows a
strong band at 1017 cm-1, which can be assigned to the
TcdO vibration. The compound is sensitive to hydrolysis
and disproportionates with water to TcO2 and HTcO4.17
Results and Discussion
Reactions of AgTcO4 with 1 equiv each of Ph3CCl or
i
t
R3SiCl (R = Me, Pr, Ph, Me2 Bu) in dry tetrahydrofuran
(THF), (Me3Si)2O, benzene, or acetonitrile result in the
formation of Ph3COTcO3 or R3SiOTcO3. During the reac-
tions, the sparingly soluble, yellow AgTcO4 slowly dissolves
and colorless AgCl is precipitated. The reactions can readily
be tracked by 99Tc NMR. After about 15 min, the narrow
pertechnetate peak at δ=18.52 ppm (chemical shift in THF,
Δν1/2=30 Hz; reference value δ=0 ppm in H2O) disappears
and new singlets with larger half-line widths appear in the
same region of the spectra (cf. Table 1 and Figure 2). This
area is characteristic for tetrahedral technetium(VII) com-
plexes, and also the signal of TcO3F is detected there.9,11b
Compared to pertechnetate, all novel technetium(VII) com-
plexes show signals with larger line widths, which is in
agreement with the significant electrical quadrupole moment
of 99Tc (Q = -0.19(5) ꢀ 10-28 m2), which broadens the sig-
nals of compounds with low molecular symmetry.1,4
We were not able to isolate the R3EOTcO3 (E = C, Si)
compounds from the reaction solution in crystalline form.
The products are oils or jellylike compounds after removal
of the solvents. They solidify at temperatures < -10 °C and
undergo a rapid decomposition under the influence of mois-
ture, as can be seen by a prolonged darkening (from pale
yellow to dark brown) upon storage of the reaction mixtures
Yellow single crystals of [TcOCl3(OH2)(THF)] 2THF were
3
obtained by removal of the solvent from the reaction mixture
and recrystallization of the resulting reddish oil from a THF/
acetonitrile mixture under inert conditions. The crystals are
(13) Nugent, W. A. Inorg. Chem. 1983, 22, 965.
(14) Bryan, J. C.; Burrell, A. K.; Miller, M. M.; Smith, W. H.; Burns, C. J.;
Sattelberger, A. P. Polyhedron 1993, 12(14), 1769.
(15) (a) Stravropoulos, P.; Edwards, P. G.; Wilkinson, G.; Motevalli, M.;
Abdul Malik, K. M.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1985,
2167. (b) Cai, S.; Hoffman, D. M.; Huffman, J. C.; Wierda, D. A.; Woo, H.-G.
Inorg. Chem. 1987, 26, 3693. (c) Edwards, P.; Wilkinson, G. J. Chem. Soc.,
Dalton Trans. 1984, 2695.
(17) (a) Nelson, C. M.; Boyd, G. E.; Smith, W. T., Jr. J. Am. Chem. Soc.
1954, 76, 348. (b) Colton, R.; Tomkins, I. R. Aust. J. Chem. 1968, 21, 1981.
(c) Canterford, J. H.; Colton, R.; Tomkins, I. B. Inorg. Nucl. Chem. Lett. 1968, 4,
471.
(16) Schmidt, M.; Schmidbaur, H. Chem. Ber. 1959, 92, 2667.

Article
Inorganic Chemistry, Vol. 49, No. 7, 2010 3527
Figure 2. 99Tc NMR spectra of TcO4-, Ph3GeOTcO3, and (THF)Ph3SnOTcO3. A full collection of the spectra is deposited as Supporting Information.
˚
Table 2. Selected Bond Lengths (A) and Angles (deg) in [TcOCl3(OH2)(THF)]
Tc-O1
Tc-O2
Tc-O3
1.620(3)
2.037(3)
2.290(3)
Tc-Cl1
Tc-Cl2
Tc-Cl3
2.337(1)
2.316(1)
2343(1)
O1-Tc-O3
O1-Tc-O2
175.4(2)
96.8(2)
O1-Tc-Cl1
Cl1-Tc-Cl2
97.9(2)
89.49(6)
understood by the trans influence of the oxo ligand in
[TcOCl3(OH2)(THF)]. The positions of the hydrogen atoms
of the aqua ligand were derived from peaks of the electron
density in the final Fourier map. Both hydrogen atoms are
involved in hydrogen bonds to two solvent THF molecules in
the unit cell of the structure.
Because isolation of the R3SiOTcO3 and R3COTcO3
compounds in crystalline form was not successful, reac-
tions with the higher homologues germanium, tin, and lead
were carried out. The treatment of AgTcO4 with an equi-
valent amount of Ph3GeCl in dry THF at room tempera-
ture affords, after removal of AgCl and reduction of the
volume of the solvent, colorless crystals of the composition
Ph3GeOTcO3. The 99mTc NMR spectrum exhibits a signal
at 25.2 ppm, which indicates the formation of a tetrahedral
technetium(VII) compound. The IR spectrum reveals an
intense band at 895 cm-1 belonging to the TcdO vibration.
A broad band in the region of 800-850 cm-1 can be assig-
ned to the vibrations of the Tc-O-Ge bridge. Figure 4a
illustrates the molecular structure of Ph3GeOTcO3.
Selected bond lengths and angles for the complex are
presented in Table 3. The terminal TcdO bonds (1.669-
Figure 3. Molecular structure of [TcOCl3(OH2)(THF)]. THF hydrogen
atoms are omitted for clarity.
very sensitive and rapidly decompose upon contact with air
or moisture.
Figure 3 illustrates the molecular structure of [TcOCl3-
(OH2)(THF)]. Selected bond lengths and angles of the com-
plex are given in Table 2. The technetium atom is coordinated
in a distorted octahedral environment, with the oxo ligand
and coordinated THF molecule in the trans position to each
˚
other. The technetium atom is situated about 0.249 A above
the plane, which is formed from the aqua and three chloro
ligands, toward the oxo ligand. The Tc-O3 bond is slightly
longer than the Tc-O bonds in [TcCl4(THF)2] (Tc-O =
˚
˚
2.112 A), so far the only other structurally characte-
1.679 A) are within the expected range for Tc-O double
rized technetium-tetrahydrofuran complex.18 This can be
bonds. The Tc-O bond to the bridging oxygen atom is
˚
with 1.785(4) A slightly longer. The Tc-O-Ge bridge
(18) Hagenbach, A.; Yegen, E.; Abram, U. Inorg. Chem. 2006, 45, 7331.
exhibits an angle of 142.4(3)°.

3528 Inorganic Chemistry, Vol. 49, No. 7, 2010
Oehlke et al.
Figure 4. Molecular structures of (a) Ph3GeOTcO3 and (b) [(THF)Ph3SnOTcO3]. Hydrogen atoms are omitted for clarity.
˚
Table 3. Selected Bond Lengths (A) and Angles (deg) in Ph3GeOTcO3 and
[(THF)Ph3SnOTcO3]
NMR spectrum exhibits a signal at -5.1 ppm. The addition
of water results in a decrease of this signal and the appearance
of the narrow HTcO4/TcO4 signal at 18 ppm. The 119Sn
-
Ph3GeOTcO3
[(THF)Ph3SnOTcO3]
NMR spectrum shows a broad signal (line width 241 Hz) at
-110.138 ppm. There is no evidence of couplings between
technetium and tin. The IR spectrum reveals an intense band
at 887 cm-1, which can be assigned to the TcdO vibration.
A broad band in the region at 845 cm-1 can be assigned to the
vibration of the Tc-O-Sn bridge.
Ge/Sn-O11
Ge/Sn-C1
Ge/Sn-C7
Ge/Sn-C13
Sn-O12
1.853(4)
1.905(7)
1.931(7)
1.923(8)
2.211(4)
2.132(5)
2.119(5)
2.119(5)
2.327(3)
1.738(4)
1.689(7)
1.684(6)
1.594(7)
Tc-O11
1.785(4)
1.677(5)
1.679(5)
1.669(5)
Tc-O13
Figure 4b depicts the molecular structure of [(THF)Ph3-
SnOTcO3]. Bond lengths and angles are compared to the
corresponding values of Ph3GeOTcO3 in Table 3. The bond-
ing situation in the tin compound is similar to that in Ph3-
Tc-O14
Tc-O15
Tc-O11-Ge/Sn
O11-Tc-O13
O11-Tc-O14
O11-Tc-O15
C1-Ge/Sn-O11
C1-Ge/Sn-C7
C7-Ge/Sn-C13
O11-Sn-O12
142.4(3)
108.8(2)
109.5(3)
110.0(3)
103.9(2)
116.4(3)
116.2(3)
147.3(2)
108.7(3)
110.8(2)
110.6(3)
91.7(2)
122.5(2)
123.3(2)
177.1(1)
˚
GeOTcO3. The terminal TcdO bonds (1.594-1.689 A) are
within the same range, and the bridging Tc-O bond of
˚
1.738(4) A is slightly shorter than the corresponding bond
in the germanium compound. The tin atom is coordinated in
a trigonal-bipyramidalenvironment. Thebridging oxoligand
and the oxygen atom of the THF molecule occupy the axial
positions, while the three phenyl residues are arranged equa-
torially.
Analogous Ph3SiOReO3 and Ph3GeOReO3 compounds
are described but not structurally characterized.19 A compari-
son of Ph3GeOTcO3 with the structurally studied Me3SiO-
ReO3 shows a number of similarities. The rhenium atom has
a tetrahedral coordination environment, with the RedO
The corresponding lead compound Ph3PbOTcO3 can be
synthesized by the treatment of AgTcO4 with an equivalent
amount of Ph3PbCl in dry THF. The compound was isolated
from the reaction mixture as a colorless powder and char-
acterizedby 99Tc NMR and IR spectroscopy. The 99TcNMR
spectrum exhibits a signal at 6.79 ppm. The IR spectrum
reveals, as for Ph3GeOTcO3 and (THF)Ph3SnOTcO3, an
intense band at 891 cm-1 belonging to the TcdO vibration
and a broad band in the region at 856 cm-1, which can be
assigned to the vibrations of the Tc-O-Pb bridge.
We were not able to isolate a crystalline tin compound with
˚
bonds (1.55-1.72 A) being in the range of typical RedO
double bonds. The Si-O-Re angle of 164° is somewhat
larger than the Ge-O-Tc angle in Ph3GeOTcO3. Moreover,
the bond between the rhenium atom and the bridging oxygen
˚
atom (1.67(8) A) is slightly shorter than the bridging Tc-O
bond in Ph3GeOTcO3.20
The analogous reaction of AgTcO4 and 1 equiv of Ph3SnCl
in dry THF resulted in the formation of the related tin
compound [(THF)Ph3SnOTcO3], which contains one addi-
tional coordinated THF molecule. In contrast to the reac-
tions of the carbon, silicon, or germanium compounds, no
rapid darkening of the reaction solution was observed.
Merely, a slight yellow color was detected after standing
for several days. [(THF)Ph3SnOTcO3] can be isolated as
colorless crystals directly from the reaction mixture. The
compound is stable in air but moisture-sensitive. The 99Tc
t
two pertechnetate units during reactions of Bu2SnCl2 with
2 equiv of AgTcO4, but its first hydrolysis product was the
tetranuclear [(O3TcO)SntBu2(OH)]2. The 99Tc NMR spectra
of the reaction mixture of the isolated and redissolved
complex show only one signal at -2.46 ppm with a line
width of 293 Hz. This indicates that hydrolysis proceeds
rapid, mainly because of traces of moisture in the tin com-
pound used. No 119Sn NMR signal was observed, which may
be explained by a rapid equilibrium between the hydroxo-
bridged dimer of Figure 5 and the related monomers in
solution. The monomers are already preformed in the so-
(19) (a) Schmidbaur, H.; Koth, D.; Burkert, P. K. Chem. Ber. 1974, 107,
2697. (b) Schoop, T.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Organo-
metallics 1993, 12, 571.
˚
lid-state structure, which is evident by two short [2.058(8) A]
˚
and two long [2.177(8) A] Sn-O bonds. Such a bonding
(20) Sheldrick, G. M.; Sheldrick, W. S. J. Chem. Soc. A 1969, 2160.
pattern and spectroscopic behavior is frequently observed for

Article
Inorganic Chemistry, Vol. 49, No. 7, 2010 3529
Figure 5. Molecular structure of [(O3TcO)SntBu2(OH)]2. Hydrogen
atoms are omitted for clarity.
t
˚
Table 4. Selected Bond Lengths (A) and Angles (deg) in [(O3TcO)Sn Bu2(OH)]2
Figure 6. Molecular structure of [(THF)4Mg(OTcO3)2]. Hydrogen
atoms are omitted for clarity.
Sn1-O1
Sn1-C1
Sn1-O2
Sn1-O20
2.24(1)
Tc1-O1
Tc1-O3
Tc1-O4
1.67(1)
1.651(9)
1.68(1)
2.187(9)
2.058(8)
2.177(8)
˚
Table 5. Selected Bond Lengths (A) and Angles (deg) in [(THF)4Mg(OTcO3)2]
Tc1-O1
Tc1-O2
Tc1-O3
Tc1-O4
1.706(9)
1.69(1)
1.67(2)
1.65(1)
Mg-O1
2.050(9)
2.074(9)
2.11(2)
2.11(2)
Mg-O11
Mg-O21
Mg-O31
Sn1-O1-Tc1
O1-Tc1-O3
Sn1-O2-Sn10
167.9(7)
109.5(4)
109.5(4)
O1-Sn1-O2
O1-Sn1-C1
82.6(4)
92.8(3)
O1-Mg-O10
O1-Mg-O11
O11-Mg-O21
178.8(9)
90.7(4)
90.5(4)
Mg-O1-Tc1
O1-Tc1-O2
O2-Tc1-O3
163.0(6)
110.6(6)
109.8(7)
diorganodistannoxanes and is also found for the parent tin
halides [tBu2SnX(OH)]2 (X = F, Cl, Br).21
Colorless crystals of the composition [(O3TcO)SntBu2-
(OH)]2 2THF were obtained directly from the reaction mix-
in a distorted octahedral environment with the two pertech-
netate units in the trans position to each other. The coordina-
tion environments of the two technetium atoms are almost
perfectly tetrahedral. The terminal TcdO bonds (1.65-1.69
3
ture. Figure 5 depicts the molecular structure of the com-
pound. Bond lengths and angles are summarized in Table 4.
[(O3TcO)SntBu2(OH)]2 contains two pentacoordinate tin
atoms, which are connected by two OH bridges. The asym-
metric unit contains only one-fourth of the dimeric molecule,
while the rest of the molecule is generated by inversion and
mirror symmetry. Consequently, the central Sn2O2 ring is
planar, and the atoms O1 and Tc1 are found in the same plane.
The hydrogen atoms of the OH bridges are both involved in
hydrogen bonds to the two cocrystallized THF molecules.
˚
A) are within the expected range for Tc-O double bonds. The
˚
Tc-O1 bond of 1.706(9) A is only slightly longer.
In summary, it can be stated that mixed anhydrides of
pertechnetic acid are readily accessible by the reactions of
AgTcO4 with compounds of the composition R3ECl (E = C,
Si, Ge, Sn, Pb), R2SnCl2, or RMgCl. 99Tc NMR is a valuable
tool to study their formation and decomposition in solution.
Particularly, the carbon and silicon compounds are of moderate
stability and slowly decompose in the reaction mixture under
reduction of the metal. The corresponding germanium, tin, and
lead compounds are of higher stability and can be isolated in
crystalline form. They may possess potential as precursors for
the synthesis of further technetium(VII) compounds.
˚
The terminal TcdO bonds (1.65-1.68 A) are within the
expected range for Tc-O double bonds. Unlike the situation in
Ph3GeOTcO3 and [(THF)Ph3SnOTcO3], theTc-O bond to the
˚
bridging oxygen atom O1 is with 1.67(1) A in the same range.
The reaction of AgTcO4 with 2 equiv of PhMgCl in THF
resulted in the formation of [(THF)4Mg(OTcO3)2]. It is most
likely that the first reaction product, PhMg(OTcO3), in
solution rapidly is involved in the Schlenk equilibrium of
Grignard reagents with PhMgPh and (O3TcO)Mg(OTcO3).
Stabilization of the latter compound by the formation of the
THF adduct might be one of the reasons that this equilibrium
is almost quantitatively shifted to the side of [(THF)4Mg-
(OTcO3)2], as is also indicated by the appearance of only one
99Tc NMR signal at -38 ppm.
[(THF)4Mg(OTcO3)2] is air- and moisture-sensitive and
rapidly decomposes at room temperature. It crystallizes as
colorless polyhedra. Figure 6 illustrates the molecular struc-
ture of the compound. Selected bond lengths and angles are
summarized in Table 5. The magnesium atom is coordinated
Experimental Section
Materials. All reagents were reagent-grade and were used
without further purification. Reactions were performed using a
standard Schlenk technique. Solvents were analytical-grade and
were flushed with argon and carefully dried prior to use.
AgTcO4 was prepared from (NH4)TcO4 and AgNO3 following
a standard procedure.22
Physical Measurements. IR spectra were measured as KBr
pellets on a Shimadzu FTIR spectrometer between 400 and 4000
cm-1. Technetium elemental analyses were done by liquid
scintillation measurements. NMR spectra were taken with a
JEOL 400 MHz multinuclear spectrometer.
Radiation Precautions. 99Tc is a weak β- emitter (Emax =0.292
MeV) with a half-life of 2.12 ꢀ 105. Normal glassware provides
adequate protection against the weak β radiation when milligram
amounts are used. Secondary X-rays (bremsstrahlung), however,
(21) (a) Davies, A. G. Diorganotin Oxides and Hydroxides. In Compre-
hensive Organometallic Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds.;
Elsevier: Oxford, U.K., 2007; Vol. 3, p 847. (b) Chandrasekhar, V.; Singh, P.;
Gopal, K. Appl. Organomet. Chem. 2007, 21, 483. (c) Puff, H.; Hevendehl, H.;
€
Hofer, K.; Reuter, H.; Schuh, W. J. Organomet. Chem. 1985, 287, 163.
(22) Keller, C.; Kanellakopulos, B. Radiochim. Acta 1963, 1, 107.

3530 Inorganic Chemistry, Vol. 49, No. 7, 2010
Oehlke et al.
Table 6. X-ray Structure Data Collection and Refinement Parameters
[TcOCl3(OH2)(THF)] 2 THF Ph3GeOTcO3 ([THF)Ph3SnOTcO3] [(O3TcO)tBu2Sn(OH)]2 2 THF [(THF)4Mg(OTcO3)2]
3
3
formula
Mw
cryst syst
C12H26Cl3O5Tc
454.68
C18H15GeO4Tc
465.89
monoclinic
9.478(1)
38.683(4)
9.899(1)
90
101.68(1)
90
3554.2(6)
P21/n
8
1.741
2.486
17 510
7385
433
0.0499/0.0916
0.848
C22H23O5SnTc
584.09
monoclinic
18.720(1)
14.476(1)
16.780(1)
90
102.89(1)
90
4432.6(4)
P21/c
8
1.750
1.779
25 944
11 847
523
0.0470/0.1120
0.900
C24H54O12Sn2Tc2
968.05
monoclinic
16.406(5)
13.122(5)
9.959(5)
90
121.29(1)
90
1832.1(1)
C2/m
2
1.755
2.135
4903
1730
100
0.0577/0.0897
0.937
C16H32MgO12Tc2
636.73
orthorhombic
10.322(5)
16.50(2)
14.416(7)
90
90
90
2455(3)
Pbcn
4
1.723
1.205
8703
2164
152
0.0660/0.1361
0.746
triclinic
8.294(1)
10.725(1)
11.911(1)
104.19(1)
109.40(1)
97.40(1)
942.9(2)
P1
2
1.602
1.203
10 059
˚
a/A
˚
b/A
˚
c/A
R/deg
β/deg
γ/deg
3
˚
V/A
space group
Z
Dcalcd/g cm-3
μ/mm-1
no. of reflns
no. of indep reflns
no. of param
R1/wR2
5036
190
0.0502/0.1226
0.967
GOF
play a role when larger amounts of 99Tc are handled. All manipula-
tions were done in a laboratory approved for the handling of
radioactive materials. Particular care was taken during the manip-
ulation of volatile materials to avoid any contamination.
1 day. [(O3TcO)SntBu2(OH)]2 was obtained as colorless crystals.
Upon further concentration of the solution, more substance of
the compound was obtained as a colorless powder.
Data for [(O3TcO)SntBu2(OH)]2. Yield: 15% (15 mg). 99Tc
NMR (THF): δ -2.5 ppm. Δν1/2=293 Hz. 119Sn NMR (THF):
no signal.
Syntheses of [R3EOTcO3] (E = C, Si, Ge, Sn, Pb; R3 = Me,
iPr, tBu, Ph). AgTcO4 (0.1 mmol) was suspended in 3 mL of dry
THF, (Me3Si)2O, benzene, or MeCN, and the corresponding
R3ECl (0.1 mmol) was added. The mixture was stirred at room
temperature for 2 h, and the precipitated AgCl was removed by
filtration. In the case of Ph3GeCl, Ph3SnCl, and Ph3PbCl, the
solution was reduced under vacuum to 0.5 mL and stored at
-20 °C for 1 day. Ph3GeOTcO3 and (THF)Ph3SnOTcO3 were
deposited as colorless crystals from THF solutions and
Ph3PbOTcO3 as a colorless powder.
Syntheses of [(THF)4Mg(OTcO3)2]. AgTcO4 (0.1 mmol) was
suspended in 3 mL of dry THF, and 0.2 mmol of PhMgCl was
added. The mixture was stirred for 2 h at room temperature and
the precipitated AgCl removed by filtration. The solution was
reduced under vacuum until dryness, washed with benzene, and
recrystallized from THF. [(THF)4Mg(OTcO3)2] was obtained as
colorless crystals.
Data for [(THF)4Mg(OTcO3)2]. Yield: ca. 32% (20 mg). 99Tc
NMR (THF): δ -38.0 ppm. Δν1/2 =120 Hz.
Data for Ph3COTcO3. 99Tc NMR (THF): δ 67.3 ppm. Δν1/2
=
1045 Hz.
Data for Me3SiOTcO3. 99Tc NMR [(Me3Si)2O]: δ 11.2 ppm.
Δν1/2 =75 Hz.
Syntheses of [TcOCl3(OH2)(THF)]. AgTcO4 (0.1 mmol) was
suspended in 3 mL of dry THF, and 4.7 mmol (1 mL) of iPr3SiCl
was added. The mixture was stirred for 2 h at room temperature
and the precipitated AgCl removed by filtration. The solvent
was removed under vacuum and the obtained oil recrystallized
from a THF/acetonitrile mixture. [TcOCl3(OH2)(THF)] was
obtained upon standing for 3 weeks as extremely moisture-
sensitive, large yellow crystals. Yield: ca. 50% (23 mg).
X-ray Crystallography. The intensities for the X-ray determi-
nations were collected on a STOE IPDS 2T instrument with Mo
Data for iPr3SiOTcO3. 99Tc NMR (THF): δ 8.8 ppm. Δν1/2
=
127 Hz.
Data for Ph3SiOTcO3. 99Tc NMR (THF): δ 68.3 ppm. Δν1/2
=
1572 Hz.
t
Data for Me2 BuSiOTcO3. 99Tc NMR (THF): δ 42.7 ppm.
Δν1/2 =307 Hz.
Data for Ph3GeOTcO3. Yield: 90% (42 mg). IR (ν in cm-1):
3070 (w), 2963 (w), 1481 (w), 1427 (m), 1308 (w), 1261 (m), 1096
(s), 1022 (m), 937 (s), 895 (m), 806 (s), 737 (s), 694 (s), 459 (s).
99Tc NMR (THF): δ 25.2 ppm. Δν1/2 = 374 Hz.
˚
KR radiation (λ = 0.710 73 A) at 200 K. Standard procedures
were applied for data reduction and absorption correction.
Structure solution and refinement were performed with
SHELXS97 and SHELXL97.23 Hydrogen atom positions were
calculated for idealized positions and treated with the “riding
model” option of SHELXL, if not mentioned otherwise. More
details on data collections and structure calculations are con-
tained in Table 6. Additional information on the structure
determinations has been deposited with the Cambridge Crystal-
lographic Data Centre. The coordinates can be obtained, upon
request, from the Director, Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, U.K.
Data for (THF)Ph3SnOTcO3. Yield: 92% (54 mg). Anal.
Calcd for C22H23O5SnTc: Tc, 16.8. Found: Tc, 15.8. IR (ν in
cm-1): 3429 (w), 3067 (w) 3020 (w), 2966 (w), 1481 (w), 1427 (m),
1261 (w), 1076 (w), 1022 (w), 999 (w), 941 (st), 887 (st), 845 (st),
729 (m), 694 (m) 448 (m). 99Tc NMR (THF): δ -5.1 ppm. Δν1/2
237 Hz. 119Sn NMR (THF): δ -110.1 ppm Δν1/2 =241 Hz.
=
Data for Ph3PbOTcO3. Yield: 86% (51 mg). IR (ν in cm-1):
3051 (w), 2963 (w), 1566 (w), 1474 (w), 1427 (m), 1327 (w), 1096 (m),
1061 (m), 1018 (m), 995 (m), 930 (s), 891 (s), 802 (s), 721 (s) 687 (s),
436 (m). 99Tc NMR (THF): δ7.0 ppm. Δν1/2=102 Hz. 99Tc elemen-
tal analyses show too low values for this compound. This is mainly
due to absorption of a significant quantity of the weak β- radiation
Acknowledgment. We thank Prof. Jens Beckmann (FU
Berlin) for supplying us with the tin precursors.
˚
by the lead atom, which is only about 4 A apart from the technetium
Supporting Information Available: X-ray crystallographic
data in CIF format and 99Tc NMR spectra. This material is
available free of charge via the Internet at http://pubs.acs.org.
atom during measurements with this radiometric method.
Syntheses of [(O3TcO)SntBu2(OH)]2. AgTcO4 (0.2 mmol)
was suspended in 5 mL of dry THF, and 0.1 mmol of tBu2SnCl2
was added. The mixture was stirred for 2 h at room temperature
and the precipitated AgCl removed by filtration. The solution
was reduced under vacuum to 1.5 mL and stored at -20 °C for
(23) Sheldrick, G. M. SHELXS-97 and SHELXL-97, programs for the
€
solution and refinement of crystal structures; University of Gottingen:
€
Gottingen, Germany, 1997.