Neutral '3 + 1' mixed-ligand oxorhenium(v) complexes with tridentate [S,N,S] chelates and aminoalkanethiols: Synthesis, characterization and structure determination

Article abstract of DOI:10.1039/b001600o

'3 + l' Oxorhenium(v) complexes [ReO(SN(R')S)(SR)] (R' = Me, Et, Pr or Bu; SR = aminoalkane thiolate) have been synthesized by ligand exchange at www-trichloromonooxo-bis(triphenylphosphine)rhenium(v) with a mixture of HSN(R')SH and RSH in alkaline methanolic solution. The complexes were purified by column chromatography and characterized by elemental analysis, mass and IR spectroscopy and for selected compounds by ¹H NMR spectroscopy. The structures of those complexes have been determined by X-ray diffraction analysis and revealed a change in the co-ordination geometry from square pyramidal to trigonal bipyramidal,: depending on the chelating (SN(R')S) moiety. The alkyl group (R1) was found to be arranged syn to the oxorhenium group. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b001600o

View Article Online / Journal Homepage / Table of Contents for this issue
Neutral ‘3 ؉ 1’ mixed-ligand oxorhenium(V) complexes with
tridentate [S,N,S] chelates and aminoalkanethiols: synthesis,
characterization and structure determination‡
a
a
b
c
a
Matthias Friebe,*† Hartmut Spies, Wilhelm Seichter, Peter Leibnitz and Bernd Johannsen
a
Forschungszentrum Rossendorf, Institut für Bioanorganische und Radiopharmazeutische
Chemie, D–01314 Dresden, POB 510119, Germany
Institut für Organische Chemie, TU-Bergakademie Freiberg, Leipziger Straße 29,
b
D–09596 Freiberg, Germany
Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, D–12205 Berlin,
c
Germany
Received 28th February 2000, Accepted 24th May 2000
Published on the Web 29th June 2000
‘3 ϩ 1’ Oxorhenium() complexes [ReO(SN(RЈ)S)(SR)] (RЈ = Me, Et, Pr or Bu; SR = aminoalkane thiolate) have
been synthesized by ligand exchange at trans-trichloromonooxo-bis(triphenylphosphine)rhenium() with a mixture
of HSN(RЈ)SH and RSH in alkaline methanolic solution. The complexes were purified by column chromatography
1
and characterized by elemental analysis, mass and IR spectroscopy and for selected compounds by H NMR
spectroscopy. The structures of those complexes have been determined by X-ray diffraction analysis and revealed
a change in the co-ordination geometry from square pyramidal to trigonal bipyramidal, depending on the chelating
(
SN(RЈ)S) moiety. The alkyl group (RЈ) was found to be arranged “syn” to the oxorhenium group.
Introduction
Co-ordination compounds of technetium and rhenium play an
important role in the search for new radiopharmaceuticals for
1–4
99m
use in nuclear medicine. The γ-emitter Tc has widely been
used as the most important nuclide for diagnostic purposes for
186
188
many years, and Re and Re attract increasing interest, since
Ϫ
these nuclides emit β particles with therapeutically useful
Fig. 1 Complex [ReO (SN)(PPh )], where the amine thiol is bidentate
2
3
energies. While all isotopes of technetium are radioactive,
chemically analogous complexes of non-radioactive rhenium
are frequently employed in model studies. These complexes are
used as references to identify the analogous technetium
complexes e.g. by HPLC comparison and may be useful as
therapeutics.
co-ordinated to the cis-dioxorhenium() core.
efforts to synthesize the desired ‘3 ϩ 1’ compounds in a one
pot reaction starting from the precursor [ReOCl (PPh ) ] are
3
3 2
hampered by the parallel formation of cis-dioxorhenium()
9
complexes of the general type [ReO (SN)(PPh )] (Fig. 1).
2
3
Present efforts aim to develop new co-ordination compounds
for imaging the brain in vivo, which requires being able to cross
the blood brain barrier (BBB), and to be bound by receptor
sites. Such studies favor oxotechnetium() and oxorhenium()
While a ratio of monodentate ligand (alkane-SH):tridentate
ligand (HSXSH, X = S or NR):[ReOCl (PPh ) ] precursor of
3
3 2
4
:1:1 normally increases the yield of the ‘3 ϩ 1’ complexes, we
observed a significant amount of the cis-dioxorhenium()
complex when using N-(2-dialkylamino)ethanethiol as
5–8
complexes containing amine groups, since the presence of
a basic amino group in the compound is a prerequisite for
binding at receptor sites.
a
monodentate ligand instead of a simple alkanethiol. Since the
formation of the cis-dioxorhenium() complex is due to the
reaction of the rhenium() precursor with traces of water
associated with the precursor and the N-(2-dialkylamino)-
ethanethiol ligand, using thoroughly dried [ReOCl (PPh ) ]
Our investigations focus on the relationship between molec-
ular structure, lipophilicity parameters and brain uptake of a
series of systematically altered ‘3 ϩ 1’ mixed ligand complexes,
where the equatorial co-ordination sphere is formed by a tri-
dentate chelate ligand together with a monodentate amino
group bearing a thiolate ligand. We consider this type of com-
plex as well suited because they can be varied at the chelate
site as well as the amine position. This enables us to introduce
specific pharmacophores possessing amino groups by simple
monodentate co-ordination via a thiolato sulfur. However,
3
3 2
precursor and a strict 1:1:1 stoichiometric ratio of mono-
dentate ligand:tridentate ligand:[ReOCl (PPh ) ] precursor,
3
3 2
are prerequisite to achieve higher ‘3 ϩ 1’ complex yields over
the cis-dioxorhenium() complex.
The use of tridentate (SN(RЈ)S) ligands offers the opportun-
ity to modify the lipophilicity of the complex by varying the
alkyl chains, while retaining the receptor binding properties.
‘3 ϩ 1’ Mixed ligand rhenium complexes containing tris-
chelating ligands such as [SOS] and [SSS] with alkane- and
†
Present address: Harvard Medical School, Department of Radiology,
arenethiolates as monodentate ligands have been described in
Goldenson B-1/254, 220 Longwood Ave., Boston, MA, 02115, USA.
E-mail: mfriebe@hms.harvard.edu
10
this journal. Preliminary pharmacological studies on some
technetium complexes of these types have been described
‡
Electronic supplementary information (ESI) available: analytical and
11
spectroscopic data. See http://www.rsc.org/suppdata/dt/b0/b001600o/
earlier, but no details on synthesis have been published.
DOI: 10.1039/b001600o
J. Chem. Soc., Dalton Trans., 2000, 2471–2475
2471
This journal is © The Royal Society of Chemistry 2000

View Article Online
The present report discusses the preparation and character-
ization of new oxorhenium() complexes, as well as crystal
structure determinations for selected compounds, of the
general formula [ReO(SN(RЈ)S)(SR)]. HSN(RЈ)SH symbolizes
the tridentate dithiol ligand HSCH CH N(RЈ)CH CH SH
where RЈ = Me (1), Et (2), Pr (3) or Bu (4). RSH represents
dialkylaminoethanethiols that serve as monodentate ligands
and are designated by letters. A general formula and numbering
scheme for the resulting complexes that contain both ligands is
given in Scheme 1.
the compounds using [NBu ][ReOCl ], the preferred precursor
4 4
for the preparation of [SOS] and [SSS] tridentate ligand bearing
10
complexes, resulted in even lower yields.
The rhenium compounds were purified by column chrom-
atography on silica gel with chloroform as the mobile phase.
However, chloroform–methanol (19:1) was used for eluting the
less lipophilic complexes (1a, 1b, 1d, 2a, 2b, 3a, 3b). After
removing the solvent, crystalline complexes were obtained from
dichloromethane by addition of a 1:1 quantity of methanol
containing two drops of water, followed by slow evaporation.
All of these complexes are very soluble in organic solvents such
as trichloromethane, dichloromethane, acetonitrile; slightly
soluble in methanol, ethanol; very slightly soluble in diethyl
ether and almost insoluble in n-heptane and water. Heating the
compounds in any of these solvents for several hours did not
result in decomposition.
2
2
2
2
Elemental analysis of the complexes confirms their formu-
lation comprising a 1:1 molar ratio of the tridentate and
1
monodentate ligands, with a M᎐O core. The H NMR spec-
᎐
troscopic investigations showed signal patterns typical for
the presence of both ligands in the proposed structure, but
the exact assignment of the signals is complicated by the
overlapping of many of the methylene protons (data not
shown).
Mass spectra with chemical ionization (pos./neg.) in addition
to electrospray identified the postulated structures as the ions
of the highest mass. Complexes 1a–4g are ionizable by the
described CI (negative) procedure, which results in simple
spectra without fragmentation of the sample. The isotopic
185
187
patterns of Re/ Re were found for all of the proposed com-
Ϫ1
plexes. IR-stretching bands in the range from 940 to 960 cm ,
typical for the Re᎐O absorption, were obtained for the com-
᎐
plexes. UV spectra showed absorbances at 580, 397, 364, 305,
2
52 and 216 nm. All yields, elemental analysis, melting points
and spectroscopic data are summarized in Tables A and B in the
Electronic Supplementary Materials.
A detailed discussion of the structural investigations is given
for three representative complexes (1e, 2f and 3g).
Complex 1e
Scheme 1 General formula and numbering scheme of prepared
‘3 ϩ 1’ oxorhenium() complexes.
An ideal isotope pattern for rhenium complexes was observed
in the mass spectrum obtained for 1e. The molecular ion [M]
Ϫ
is the highest peak observed with no fragments detected. A
Results and discussion
Ϫ1
strong Re᎐O stretching vibration at 950 cm was measured
᎐
Neutral ‘3 ϩ 1’ oxorhenium() complexes [ReO(S(NRЈ)S)-
for 1e in the IR spectrum. Compared to the [ReOCl (PPh ) ]
3 3 2
Ϫ1
(
SR)], bearing the tridentate chelate ligand and N-(2-dialkyl-
precursor (980 cm ), this vibration is shifted to shorter
wavenumbers.
amino)ethanethiol derivatives, have been obtained according to
Scheme 2, by adding a 1:1 molar ratio mixture of the ligands
The crystal structure determination of complex 1e clearly
reveals the formation of a distorted square pyramidal complex
(
Fig. 2, Table 1). Three sulfur donors and one nitrogen donor
form the base plane and a short rhenium–oxygen bond form the
apex of the pyramid. The Re is located 0.994 Å above the basal
12
plane. The parameter τ introduced to classify fivefold co-
ordinate complexes as ideally trigonal bipyramidal (τ = 1) or
square pyramidal (τ = 0) was determined to be 0.47. The alkyl
substituent of the co-ordinated nitrogen is “syn” to the oxygen
Scheme 2 Pathways to the ‘3 ϩ 1’ co-ordinate rhenium() complexes.
to a stirred methanolic suspension of the precursor [ReOCl3-
of the Re᎐O group. Analysis of the crystallographic data of
᎐
(
PPh ) ] at 70 ЊC. In order to complete the reaction procedure
3 2
in an appropriate time the mixture was briefly refluxed in
methanol. Addition of an external base to the reaction mixture
seems to be essential. The compounds can be synthesized by
employing methanol or dichloromethane as solvent, and
sodium acetate or triethylamine as the base. The tendency to
form cis-dioxorhenium() compounds involving the bidentate
donor set of the aminoalkanethiol ligands, as mentioned above,
was always observed but could be minimized by the use of exact
1
:1:1 ratios and dried reactants and solvents. These conditions
lead to pure products but moderate yields. Attempts to prepare
Fig. 2 Crystal structure of complex 1e.
2
472
J. Chem. Soc., Dalton Trans., 2000, 2471–2475

View Article Online
Table 1 Selected bond lengths (Å) and angles (Њ) for complex 1e with
estimated standard deviations (e.s.d.s) in parentheses
Table 2 Selected bond lengths (Å) and angles (Њ) for complex 2f with
e.s.d.s in parentheses
Re–O(1)
Re–N(1)
Re–S(2)
Re–S(3)
Re–S(1)
S(1)–C(5)
1.663(10)
2.153(12)
2.270(3)
2.278(4)
2.293(3)
1.805(13)
S(3)–C(3)
C(3)–C(4)
N(1)–C(4)
N(1)–C(1)
C(1)–C(2)
N(1)–C(11)
1.80(3)
1.44(4)
1.45(2)
1.47(2)
1.50(2)
1.54(3)
Re–O(1)
Re–N(1)
Re–S(2)
Re–S(3)
Re–S(1)
S(1)–C(1)
1.698(4)
S(3)–C(7)
C(3)–C(4)
N(1)–C(3)
N(1)–C(5)
C(1)–C(2)
N(1)–C(2)
1.825(6)
1.502(9)
1.489(7)
1.511(7)
1.522(9)
1.492(7)
2.225(5)
2.269(2)
2.302(14)
2.292(14)
1.827(6)
O(1)–Re–N(1)
O(1)–Re–S(2)
N(1)–Re–S(2)
O(1)–Re–S(3)
N(1)–Re–S(3)
S(2)–Re–S(3)
O(1)–Re–S(1)
N(1)–Re–S(1)
S(2)–Re–S(1)
S(3)–Re–S(1)
99.3(5)
117.7(4)
82.4(3)
115.9(4)
82.1(4)
125.8(2)
106.3(4)
154.0(4)
89.7(12)
82.7(13)
C(5)–S(1)–Re
C(2)–S(2)–Re
C(3)–S(3)–Re
C(4)–N(1)–C(1)
C(4)–N(1)–C(11)
C(1)–N(1)–C(11)
C(4)–N(1)–Re
C(1)–N(1)–Re
C(11)–N(1)–Re
N(1)–C(1)–C(2)
113.1(4)
103.4(5)
102.8(10)
113.7(14)
103.0(2)
106.0(2)
113.0(9)
113.0(9)
107.8(12)
110.0(12)
O(1)–Re–N(1)
O(1)–Re–S(2)
N(1)–Re–S(2)
O(1)–Re–S(3)
N(1)–Re–S(3)
S(1)–Re–S(2)
O(1)–Re–S(1)
N(1)–Re–S(1)
S(2)–Re–S(3)
S(3)–Re–S(1)
96.5(2)
117.8(2)
83.1(14)
105.6(14)
157.5(12)
122.4(6)
119.1(2)
92.9(13)
90.2(6)
C(7)–S(3)–Re
C(1)–S(1)–Re
C(4)–S(2)–Re
C(2)–N(1)–C(3)
C(2)–N(1)–C(5)
C(3)–N(1)–C(5)
C(3)–N(1)–Re
C(5)–N(1)–Re
C(2)–N(1)–Re
N(1)–C(5)–C(6)
113.2(2)
103.1(2)
104.0(2)
112.4(4)
110.3(5)
108.2(4)
109.8(3)
107.5(3)
108.5(3)
115.1(5)
82.7(5)
Table 3 Selected bond lengths (Å) and angles (Њ) for complex 3g with
e.s.d.s in parentheses
Re–O(1)
Re–N(1)
Re–S(2)
Re–S(3)
Re–S(1)
S(1)–C(1)
1.698(6)
2.216(7)
2.279(3)
2.305(2)
2.270(2)
1.833(10)
S(3)–C(8)
C(3)–C(4)
N(1)–C(3)
N(1)–C(5)
C(1)–C(2)
N(1)–C(2)
1.825(9)
1.519(13)
1.498(11)
1.500(11)
1.489(9)
1.511(7)
O(1)–Re–N(1)
O(1)–Re–S(2)
N(1)–Re–S(2)
O(1)–Re–S(3)
N(1)–Re–S(3)
S(1)–Re–S(2)
O(1)–Re–S(1)
N(1)–Re–S(1)
S(2)–Re–S(3)
S(3)–Re–S(1)
95.2(3)
119.5(3)
83.6(2)
104.9(2)
159.7(2)
122.6(10)
117.4(3)
83.8(2)
C(8)–S(3)–Re
C(1)–S(1)–Re
C(4)–S(2)–Re
C(2)–N(1)–C(3)
C(2)–N(1)–C(5)
C(3)–N(1)–C(5)
C(3)–N(1)–Re
C(5)–N(1)–Re
C(2)–N(1)–Re
N(1)–C(5)–C(6)
109.9(3)
103.5(3)
103.3(3)
110.7(7)
108.9(7)
110.0(7)
108.7(5)
108.5(5)
110.0(5)
117.9(7)
Fig. 3 Crystal structure of complex 2f.
1
3–15
several ‘3 ϩ 1’ [ReO(S(NRЈ)S)(SR)]
oxorhenium()
and tetradentate N2S2
15a,b,c
complexes does not show any contact
interactions of the “syn” substituent with the oxo-group. The
formation of the syn isomer is consistent with numerous reports
of rhenium and technetium monooxo 3 ϩ 1 and tetradentate
N S complexes wherein the “syn” isomer is either the exclusive
84.1(9)
89.3(9)
2
2
13–15
or predominant (>90%) isomer formed.
The syn orientation
may be the thermodynamically preferred geometry caused
probably by a higher molecular orbital (MO) overlap of the
donating nitrogen lone pair and the empty metal orbitals. The
formation of the anti isomer is presumably due to kinetic
trapping as this isomer is either absent or observed only as a
minor constituent in N-substituted complexes of this kind.
Complex 2f
The molecular ion of complex 2f in the mass spectrum shows
the ideal isotopic pattern of Re/ Re. No other rhenium-
containing fragments were detected. The IR spectrum shows
Fig. 4 Crystal structure of complex 3g.
185
187
found identical to those of 1e and 2f. The molecular ion
M] was the signal of the highest mass with no fragments
the Re᎐O stretching vibration shifted to a shorter wavenumber
᎐
Ϫ
[
Ϫ1
of 944 cm . Additionally, the typical strong vibrations of the
detected. The IR spectrum revealed a Re᎐O stretching vibration
᎐
ethylene glycol group of the monodentate ligand were detected
Ϫ1
at 951.0 cm . Additionally, the strong vibration of the
Ϫ1
at 1436.7 and 1466.8 cm .
carbonyl group of the monodentate ligand was observed at
The crystal structural determination of complex 2f (Fig. 3,
Table 2) confirms that the basic structural features are similar to
those of 1e. The neutral nitrogen donor of the tris-chelating
ligand and the S(3) donor (monodentate ligand) are shifted out
of the former base plane to take up an axial position (N(1)–Re–
S(3) 157.5Њ compared to N(1)–Re–S(1) 154.0Њ for 1e), while the
sulfur atoms S(1) and S(2) are shifted more out of the former
equatorial base plane in the opposite direction. Thus, a new
equatorial plane is formed by O(1), S(1), S(2) around the
rhenium central atom and the 3-D structure is distorted to a
trigonal bipyramid (τ = 0.59). This phenomenon may be
effected by the longer alkyl side chain of the tridentate ligand.
Ϫ1
1
713.9 cm .
Structure determination of complex 3g reveals the expected
co-ordination mode for compounds such as [ReO(SNS)(S)]
Fig. 4, Table 3). The arrangement of oxygen, sulfur, nitrogen
(
and the metal center is similar to those of 1e and 2f. The N(1)–
Re–S(3) bond angle is larger (159.7Њ) than in 1e and 2f and
the molecular structure is even more distorted to a trigonal
bipyramid when compared to those of 1e and 2f. This is
confirmed in a higher value of the trigonality index τ (0.62).
Considering the studied species it seems that stronger distor-
tion between square pyramidal to trigonal bipyramidal is a
function of the alkyl chain length at the tris-chelating moiety.
However, some complexes described in the literature do not
follow this trend (Table 4). Only minor differences in τ values
have been observed between compounds with RЈ = ethyl and
Complex 3g
The isotope pattern in the mass spectrum of complex 3g was
J. Chem. Soc., Dalton Trans., 2000, 2471–2475
2473

View Article Online
Table 4 Trigonality index of prepared ‘3 ϩ 1’ complexes 1e, 2f, 3g
compared to data of other ‘3 ϩ 1’ complexes in the literature
g, as well as the tris-chelating ligands HSCH CH N(RЈ)CH -
2 2 2
CH SH (RЈ = Pr or Bu) were prepared in variation according to
2
18
the literature, whereas those where RЈ = Me or Et were syn-
19
thesized as described by Harley-Mason. Silica gel 60 (70–230
mesh), obtained from Merck, was used for column chromato-
graphy of rhenium() complexes. Chloroform and methanol
used for chromatography were of analytical grade.
UV/VIS spectra were recorded on a Specord M80 from Carl
Zeiss, infrared spectra (KBr pellets) on a FT-IR-SPECTRUM
‘
3 ϩ 1’
2
000 spectrophotometer from Perkin-Elmer and mass spectra
complex
R
RЈ
τ
Reference
on a Finnigan MAT 95 mass spectrometer. Elemental analyses
were performed on a Leco CHNS-932 elemental analyzer.
1
2
3
—
—
—
e
f
g
See Scheme 1
See Scheme 1
See Scheme 1
SC H5
SC H Cl-p
SC H Cl-p
SC H OCH -p
SC H OCH -p
CH3
0.47 This report
0.59 This report
0.62 This report
0.61 16
0.65 13
0.63 15
C H
2
5
Preparations
C H
3
7
H
6
trans-Trichloromonooxo-bis(triphenylphosphine)rhenium(V)
C H
6
4
2
5
[
ReOCl (PPh ) ] P. Triphenylphosphine (8.0 g, 30 mmol) was
3 3 2
C H N(C H )
6
4
2
4
2
5
2
2
2
heated to 90 ЊC in glacial acidic acid (150 ml), in order to give a
clear solution. Ammonium perrhenate (0.50 g, 1.85 mmol) was
dissolved in 16 ml of concentrated hydrochloric acid and added
dropwise over 10 minutes. The mixture was allowed to stay at
(
(
syn)
anti)
C H N(C H )
0.62 14
0.05 14
6
4
3
2
4
2
5
C H N(C H )
6
4
3
2
4
2
5
diethylaminoethyl. The non-sensitivity of the τ value is shown
for a complex with RЈ = H (τ = 0.61), that consequently is
more distorted to a trigonal-bipyramidal structure.
9
0 ЊC overnight. The resulting precipitate was separated by fil-
16
tration, washed with 3 × 20 ml of acetic acid and with 3 × 20 ml
of diethyl ether. The product was obtained quantitatively as a
green-yellow solid. Yield 3.07 g, 99% (Found: C, 55.9; H, 4.0;
Cl, 13.9. C H Cl ORe requires: C, 56.1; H, 4.0; Cl, 13.8%. IR
Unlike the “syn” oriented compounds, the τ value of the
anti” isomer tends to that of an ideal square-pyramidal
“
14
36 30
Ϫ1
3
arrangement even if RЈ = diethylaminoethyl. Thus, the distor-
tion from square pyramidal to trigonal bipyramidal geometry
observed is more distinct for the “syn” (SN(RЈ)S) species than
for “anti” oriented complexes or (SSS) and (SOS) tridentate
derived compounds described earlier. These findings might be
of interest with respect to in vivo and in vitro behavior since
differences in the solvate shells are likely between the square-
pyramidal and the trigonal bipyramidal arrangement of “syn”
oriented compounds as described here.
20
(
KBr): 980 cm (νReO).
[
ReO(SN(RЈ)S)(SR)] 1a–4e (General procedure). To a stirred
suspension of complex P (166 mg; 0.2 mmol) in a 0.15 M
methanolic solution of sodium acetate (10 ml), a mixture of the
SNS ligand (0.2 mmol) and the monodentate ligand (0.2 mmol)
in methanol (2 ml) was added. The suspension was stirred and
heated to 70 ЊC for approximately 40 minutes at which time the
greenish yellow starting metal compound had been changed to
dark green-brown. After cooling to room temperature, the reac-
tion mixture was diluted with dichloromethane and aqueous
hydrochloric acid (pH 4) was added. The aqueous phase was
separated and 2 ml of dichloromethane were added. The pH
was adjusted to 10 by adding sodium hydroxide. The organic
layer was isolated, dried over sodium sulfate and evaporated to
a final volume of 1 ml. The product was purified by liquid
chromatography on silica gel eluting with trichloromethane and
then trichloromethane–methanol (19:1) to yield the pure green
product as determined by TLC. The complexes were isolated as
green solids by complete removal of the solvent. After treating
the green solid with diethyl ether, the residue was dissolved in
dichloromethane (1 ml). X-Ray quality crystals were obtained
from these solutions by adding 1 ml of methanol containing
2 drops of water followed by slow evaporation.
17
Conclusion
New lipophilic ‘3 ϩ 1’ mixed-ligand rhenium() complexes
bearing tertiary amino groups are easily prepared starting from
trans-trichloromonooxo-bis(triphenylphosphine)rhenium().
The formation of cis-dioxorhenium() complexes as by-
products can be suppressed by strictly employing a 1:1:1 molar
ratio of the reactants and a brief drying of the rhenium()
precursor.
Ϫ1
IR absorptions between 940 and 960 cm are observed for
the Re᎐O stretching vibration and mass spectrometry data con-
firm the proposed composition of the ‘3 ϩ 1’ complexes. X-Ray
structural measurements of the representative complexes 1e, 2f
᎐
and 3g with “syn” arrangement of RЈ with respect to the R᎐O
᎐
group show a high degree of distortion in geometry from
square pyramidal to trigonal bipyramidal (1e < 2f < 3g). Hence
the co-ordination geometry seems to be related to the alkyl
chain length RЈ for such ‘3 ϩ 1’ [ReO(SN(RЈ)S)(SR)] com-
plexes as described above. Thus an influence of the tridentate
ligand in the ‘3 ϩ 1’ geometry and related parameters such as
lipophilicity, hydrogen-bonding capacity, and co-ordination of
solvent molecules is likely and has to be taken into consider-
ation for the development of in vivo pharmaceuticals. The
resulting non-radioactive complexes give a valuable basis for
potential rhenium based radio-therapeutics and are useful
as defined reference substances for HPLC identification of
Crystal structure determination
Reflections were collected on an Enraf-Nonius CAD-4 dif-
fractometer using graphite-monochromated Mo-Kα radiation
for complex 1e and Cu-Kα radiation for 2f and 3g. The
structures were solved by Patterson methods (SHELXS 86).
Non-hydrogen atoms were located from successive Fourier dif-
ference maps, and hydrogen atoms were calculated at idealized
positions using a riding model. Final refinement was done by
2
full-matrix least squares on F . For programs used and sources
of scattering factor data see refs. 21 and 22. Crystal data are
symmarized in Table 5.
CCDC reference number 186/2005.
99m
analogous Tc-technetium radiodiagnostics.
See http://www.rsc.org/suppdata/dt/b0/b001600o/ for crystal-
lographic files in .cif format.
Experimental
General procedures
Acknowledgements
We are grateful to Dr S. Machill from TU Dresden for record-
ing the mass spectra.
Ammonium perrhenate was obtained from Aldrich. Amino
alkanethiols 2-dimethyl- and 2-diethyl-aminoethanethiol (a, b)
were purchased from Fluka. The other applied ligands c, d, e, f,
2
474
J. Chem. Soc., Dalton Trans., 2000, 2471–2475

View Article Online
Table 5 Crystallographic data of complexes 1e, 2f, and 3g
1
e
2f
3g
Molecular formula
Molecular mass
C H N O ReS
497.69
C H N O ReS
567.78
C H N O ReS
3
537.76
1
1
23
2
2
3
15 29
2
3
3
14 27
2
2
Space group
Symmetry
a/Å
b/Å
c/Å
P2 /n
P2 /n
P2 /a
1
1
1
Monoclinic
11.767(3)
11.422(9)
13.299(6)
111.11(4)
1668(2)
4
Monoclinic
14.758(3)
10.064(10)
14.860(7)
118.32(2)
1942.9(10)
4
Monoclinic
12.630(4)
12.017(2)
14.817(4)
114.680(10)
2043.4(9)
4
β/Њ
V/Å
3
Z
T/K
µ/mm
296(2)
7.662
178(2)
15.386
298(2)
6.260
Ϫ1
Reflections
unique
observed [I > 2σ(I)]
R1 (observed)
wR2 (observed)
R
3441
3279
0.0545
0.1442
0.0243
3987
3851
0.0457
0.1247
0.0296
4900
3959
0.0695
0.1714
0.0250
1
5 (a) M. Papadopoulos, I. Pirmettis, C. Raptopoulou, E. Chiotellis,
M. Friebe, R. Berger, H. Spies and B. Johannsen, Appl. Radiat.
Isot., 1998, 49, 961; (b) A. Mahmood, K. E. Baidoo and S. Z.
References
1
2
K. Schwochau, Angew. Chem., 1994, 106, 2349.
E. Deutsch, K. Libson, S. Jurisson and L. F. Lindoy, Prog. Inorg.
Chem., 1987, 30, 75.
rd
Lever, in Proceedings of the 3 International Symposium on
Technetium in Chemistry and Nuclear Medicine, Padova, September
6–8, 1989, p. 119; (c) A. Mahmood, M. H. Kuchma, E. Freiberg,
3
4
B. Johannsen and H. Spies, Top. Curr. Chem., 1996, 176, 77.
P. L. Beaumier, P. Venkatesan, J. L. Vanderheyden, W. D. Burgua,
L. L. Kunz, A. R. Fritzberg, P. G. Abrams and A. C. Morgen, Jr.,
Cancer Res., 1991, 51, 769.
th
J. Goldstone, A. Davison and A. G. Jones, Proceedings of the 5
International Symposium on Technetium in Chemistry and Nuclear
Medicine, Academia Cusanus, Bressanone, September 6–9, 1998,
p. 253.
5
6
B. Johannsen, M. Scheunemann, H. Spies, P. Brust, J. Wober,
R. Syhre and H.-J. Pietzsch, Nucl. Med. Biol., 1997, 23, 429.
S. K. Meegalla, K. Plössl, M. P. Kung, S. Chumpradit, D. A.
Stevenson, S. A. Kushner, W. T. McElgin, P. D. Mozley and
H. F. Kung, J. Med. Chem., 1997, 40, 9.
B. K. Madras, A. G. Jones, A. Mahmood, R. E. Zimmerman,
B. Garada, B. L. Holman, A. Davison, P. Blundell and P. C. Meltzer,
SYNAPSE, 1997, 22, 239.
16 M. Glaser, H. Spies, R. Berger, F. E. Hahn, T. Lügger and
B. Johannsen, Inorg. Chim. Acta, 1997, 257, 143.
17 T. Fietz, Ph.D. Thesis, Technische Universität Dresden, 1996.
18 J. Corbin, A. Miller, N. Parayadath, S. Wherland and A. Bruce,
Inorg. Chim. Acta, 1984, 90, 41.
19 J. Harley-Mason, J. Chem. Soc., 1947, 326.
20 N. P. Johnson, C. J. Lock and G. Wilkinson, J. Chem. Soc., 1964,
1054.
21 C. K. Fair, MOLEN, An Interactive Structure Solution
Procedure, Enraf-Nonius, Delft, 1990; M. C. Burla, M. Camalli,
G. Casarano, C. Giaccovazzo, G. Polidori, R. Spagna and D.
Viterbo, SIR, J. Appl. Crystallogr., 1989, 22, 398; G. Reck, R. G.
Kretschmer and G. Walter, CELLGRAF, Program for
Representation of Organic and Inorganic Crystal Structures,
Federal Institute for Material Research and Testing, Berlin, 1992;
W. Kraus and G. Nolze, POWDER CELL 1.6, Program for
representation and variation of crystal structures and calculation
of the related X-ray diffraction diagrams for polycrystalline
samples, Federal Institute for Material Research and Testing,
Berlin, 1995.
7
8
9
S. Z. Lever, K. E. Baidoo, A. Mahmood, K. Matsumura, U. Scheffel
and H. N. Wagner, Nucl. Med. Biol., 1994, 21, 157.
M. Friebe, R. Jankowsky, H. Spies, W. Seichter and B. Johannsen,
Polyhedron, 1998, 17, 3711.
1
0 H. Spies, T. Fietz, H.-J. Pietzsch, B. Johannsen, P. Leibnitz, G. Reck,
D. Scheller and K. Klostermann, J. Chem. Soc., Dalton Trans., 1995,
2
277.
1
1
1 H. Spies, R. Syhre and H.-J. Pietzsch, Plzen. Lek. Sb., 1990, 62, 85.
2 A. W. Addison, T. N. Rao, E. Reedijk, J. van Run and G. C.
Verschoor, J. Chem. Soc., Dalton Trans., 1984, 1349.
1
3 M. Papadopoulos, I. Pirmettis, C. Tsoukalas, B. Nock, T. Maina,
C. P. Raptopoulou, A. Terzis, H.-J. Pietzsch, M. Friebe, H. Spies,
B. Johannsen and E. Chiotellis, Inorg. Chim. Acta, 1999, 295, 1.
4 M. Papadopoulos, I. Pirmettis, M. Pelecanou, C. P. Raptopoulou,
A. Terzis, C. I. Stassinopoulou and E. Chiotellis, Inorg. Chem.,
1
22 G. M. Sheldrick, SHELXS 86, Structure solving Program,
University of Göttingen, 1986; SHELXL 93, Crystal Structure
Refinement, University of Göttingen, 1993.
1
996, 35, 7377.
J. Chem. Soc., Dalton Trans., 2000, 2471–2475
2475