Rhenium and technetium complexes with tridentate S,N,O ligands derived from benzoylhydrazine a Department of Chemistry, Hanoi University of Sciences, 19 Le Thanh Tong, Hanoi, Viet Nam b
Trang 1Rhenium and technetium complexes with tridentate S,N,O ligands derived from benzoylhydrazine
a
Department of Chemistry, Hanoi University of Sciences, 19 Le Thanh Tong, Hanoi, Viet Nam
b
Institute of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstr 34-36, D-14195 Berlin, Germany
a r t i c l e i n f o
Article history:
Received 25 August 2009
Accepted 14 September 2009
Available online 29 September 2009
Keywords:
Rhenium
Technetium
Mixed-ligand complexes
Benzoylthioureas
X-ray structure
a b s t r a c t
A potentially tridentate ligand with an S,N,O donor set, H2L, is formed by the reaction of N-[(diethylam-inothiocarbonyl)benzimidoyl chloride with benzoylhydrazine Reactions of H2L with (NBu4)[MOCl4] com-plexes (M = Re, Tc) give five-coordinate, neutral oxo comcom-plexes of the composition [MOCl(L)]
Mixed-ligand complexes of rhenium(V) containing the tridentate L2ligand and bidentate
N,N-dialkyl-N0-benzoylthioureato ligands (R2btu) are formed in high yields when (NBu4)[ReOCl4] is treated with mixtures of H2L and HR2btu Another approach to the mixed-ligand products is the reaction of [ReOCl(L)] with an equivalent amount of HR2btu
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1 Introduction
The widespread use of the radionuclide99mTc in diagnostic
nu-clear medicine and the potential of the b-emitting radioisotopes
186
Re and188Re in radiotherapy cause a continuing interest in the
coordination chemistry of technetium and rhenium[1,2] In this
context, there is a permanent need for efficient chelating systems
Ligands, which are suitable for the stabilization of the {MV@O}3+
cores (M = Re, Tc) are of particular interest, since reduction of
[MO4]ions from the commercial generator systems with common
reducing agents frequently form oxometallates(V) Ligand systems,
which stabilize this core under physiological conditions are
tetra-dentate N,S,O chelators[3,4] However, the tuning of the biological
properties of the resulting complexes by variations in the
periph-ery of the ligands is difficult and sometime results in the formation
of different stereoisomers[4] Mixed-ligand approaches give access
to a smooth tuning of the ligand properties and, thus, of their
bio-logical behavior
Following the so-called mixed-ligand concept, many ‘3+1’
sys-tems, which are neutral complexes with a [MO]3+ core and a
mixed-ligand set of a dianionic tridentate ligand containing one
or more sulfur donor atoms, such as [SSS], [SOS], [SNS], [SNN], or
[ONS], and a monodentate thiolate were studied [5] Finally, it
was found that many of these ‘3+1’ complexes were relatively unstable in vitro and in vivo due to a ready substitution of the labile monothiolate RSby physiological thiols such as cysteine or gluta-thione[6] Generally, this may be explained by the 16 valence elec-tron nature of the five-coordinate ‘3+1’ complexes Replacement of the labile monothiolate by bidentate ligands results in so-called
‘3+2’ systems with a closed-shell electron configuration and, thus,
a higher stability is expected[7] Several ‘3+2’ mixed-ligand com-plexes with ligands carrying different donor sets such as [SNS]/ [PO][7], [NOS]/[NO][8], [NOS]/[NN][9], [NON]/[OO][10], [NOS]/ [SN] [11] or [ONO]/[PO] were studied[12] Some of them show interesting properties, which encourage further studies and the introduction of hitherto not regarded ligand systems in such considerations
In previous papers, we described synthesis and characterization
of a new class of tridentate N-(dialkylaminothiocarbonyl)benzam-idine ligands (H2R2tcba) which form stable, five-coordinate com-plexes of the composition [ReOCl(R2tcba)] (1) [13], and elucidated the coordination chemistry of N,N-dialkyl-N0 -ben-zoylthioureas, HR2btu, with rhenium and technetium (Scheme 1)
[14] The advantage of these two ligand classes is the convenience
of modifications in the periphery of their chelating system This al-lows the variation of fundamental properties of the products such
as solubility, polarity and lipophilicity and also gives access to bio-conjugation via the periphery of the tridentate ligands With com-plexes of the types 1 and 2, appropriate starting materials are available with the bidentate and tridentate ligands already in coor-dination positions, which are expected for the intended mixed-ligand compounds, and we could show that stable mixed-mixed-ligand
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* Corresponding author Tel.: +49 30 838 54002; fax: +49 30 838 52676.
E-mail address: abram@chemie.fu-berlin.de (U Abram).
1 Present address: Institute of Chemistry and Biochemistry, Freie Universität Berlin,
Fabeckstr 34-36, D-14195 Berlin, Germany.
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Polyhedron
j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / p o l y
Trang 2complexes of the composition [MO(R2tcba)(R2btu)] (M = Re, Tc) (3)
can readily be prepared[15]
In extension of this work, we synthesized a novel tridentate
li-gand, H2L, by the reaction of
N-(diethylaminothiocarbonyl)benz-imidoyl chloride (R2tcbCl) with benzoylhydrazine and studied
its reaction patterns with common rhenium and technetium
complexes
2 Results and discussion
2.1 Synthesis and structure of H2L
Reactions of N-(N0,N0-dialkylaminothiocarbonyl)benzimidoyl
chlorides with primary amines have been shown to be a
conve-nient approach for the synthesis of bidentate S,N ligands[16]or
tridentate S,N,O, S,N,N or S,N,S chelators[13,17] The coordination
behavior of the obtained ligands strongly depends on the amines
used, since they significantly influence the basicity of the N donor
position and the denticity of the resulting ligand system While the
coordination chemistry of the bidentate ligands has been studied
with a variety of metal ions[18], the tridentate systems have
hith-erto only be used for the formation of rhenium and technetium
complexes[13,17]
The novel benzoylhydrazine derivative H2L is formed by the
reaction of N-(N0,N0-diethylaminothiocarbonyl)benzimidoyl
chlo-ride and benzoylhydrazine In the presence of the supporting base
NEt3, the reaction proceeds quickly and under mild conditions The
product can be isolated as colorless, microcrystalline, analytically
pure solid in high yields (Scheme 2) The progress of the reaction
can readily be checked by thin-layer chromatography and is conve-niently indicated by the formation of a colorless precipitate of NEt3HCl, which is almost insoluble in acetone
The IR spectrum of H2L is characterized by absorptions of the
NH stretches at 3225 and 3163 cm1and a very strong absorption
at 1655 cm1, which can be assigned to the C@O vibration The1H NMR spectrum reflects the hindered rotation around the C–NEt2
bond, which is typically indicated by broad singlet signals corre-sponding to the ethyl residues This has also been found for other thiocarbamoylbenzamidines[13,15–18]
Fig 1illustrates the structure of H2L together with the intramo-lecular hydrogen bond between the nitrogen atom of the benzoylhydrazone unit and the sulfur atom An additional inter-molecular hydrogen bond is established between N3 and O57 Se-lected bond lengths and angles are summarized inTable 1 The positions of the hydrogen atoms at the atoms N3 and N59 are indi-cated by peaks of electron density in the final Fourier maps of the structure refinement and the fact that they are involved in hydro-gen bonds This finding is also consistent with the bond lengths of the C–N bonds in the ligand framework, in which the C4–N5 bond
of 1.266(4) Å is within the expected range of a C@N double bond and the C4–N3 distance of 1.431(4) Å is a typical C–N single bond This is in perfect agreement with structure C ofScheme 3and a description as a benzoylhydrazone Such a bonding situation is hitherto without precedence for the thiocarbamoylbenzamidines under study In corresponding structures, such as derivatives with aromatic amines[13]or thiosemicarbazones[17], a hydrogen atom
N NH
N S
R1
R2
OH
R1R2 = Et2 or Morph
H N O
N S
R3
R4
R3, R4 = alkyl or aryl
Re O
O N N
R3
R4
N N
N S O
Re O Cl
R1
R2
H 2 R 2 tcba
HR 2 btu
N
N
N S M
O
O
N N
R3
R4
R1
R2
3
M = Re, Tc
Scheme 1 Related ligands and hitherto known rhenium complexes.
N Cl
N S Et
PhCONHNH2
Et3N, Me2CO
- Et3N.HCl
N NH
N S Et HN
O
H 2 L
Et 2 tcbCl
Scheme 2 Synthesis of H 2 L.
Fig 1 Molecular structure of H 2 L Thermal ellipsoids represent 50% probability [23]
Table 1 Selected bond lengths (Å) in H 2 L.
Trang 3locates on the nitrogen atom N5 and a double bond is established
between C4 and N3 It can also not be excluded that in solution
and/or in metal complexes of the compound the other conformers
ofScheme 3play a considerable role
2.2 [MOCl(L)] complexes (M = Tc, Re)
The reaction of H2L with the common technetium(V) precursor
(NBu4)[TcOCl4] in methanol at room temperature gives rapidly a
red solid of the composition [TcOCl(L)] (4) (Scheme 4) The infrared
spectrum of complex 4 exhibits a strong bathochromic shift of the
mC@Oband of about 150 cm1, together with the disappearance of
absorptions in the region above 3150 cm1, which correspond to
mNHstretches in the uncoordinated H2L Both results indicate
che-late formation with a large degree of p-electron delocalization
within the chelate rings and the expected double deprotonation
of the ligand An intense band appearing at 976 cm1can be
as-signed to the Tc@O vibration[19] The1H NMR spectrum provides
additional evidence for the proposed composition and molecular
structure of the complex The rotation around the C–NEt2 bond
in 4 is more restricted than that in the uncoordinated H2L This is
reflected by two sets of well resolved signals corresponding to
the methyl groups The corresponding signals of the methylene
protons are sparingly resolved and appear as a broad signal
Fig 2depicts the molecular structure of compound 4 as a
pro-totype compound for these types of complexes Selected bond
lengths and angles are listed inTable 2 The technetium atom
pos-sesses a distorted square–pyramidal coordination environment
with an oxo ligand in the apical position and the square plane
formed by the donor atoms of the tridentate ligand and the chloro
ligand This square plane is slightly distorted, with a main
devia-tion of 0.097(1) Å from a mean least-square plane for atom O57
The Tc atom is situated by 0.691(1) Å above the basal plane
to-wards the oxo ligand All O10–Tc–X angles (X = equatorial donor
atom) fall in the range between 107° and 112° This is in good agreement with the typical bonding situation of square–pyramidal
TcVO complexes[19] The Tc@O distance of 1.644(2) Å is within the expected range of a technetium–oxygen double bond[19] Despite the fact that the six-membered ring formed by Tc, S1, C2, N3, C4 and N5 is not planar with a maximum distortion from the mean least-square plane of 0.263(1) Å for the Tc atom, a reasonable delocalization ofp-electrons is observed Consequently, the C–S and C–N bonds inside the chelate ring possess partially double bond character The bonding situation in the five-membered che-late ring is similar to those in typical benzoylhydrazone complexes with shortened C58–N59 and lengthened C58–O57 bonds, being both in the range between carbon–nitrogen and carbon–oxygen single and double bonds
The reaction of H2L with (NBu4)[ReOCl4] is much slower than that with the analogous technetium starting material The ligand exchange product of the composition [ReOCl(L)] (5) can be isolated after a period of several hours as red, microcrystalline solid directly from the reaction mixture in good yield Addition of a supporting
S
N
Ph NH
Ph O
SH
N
Ph
N
O
S
H N Ph
N
O
S
N
Ph OH
SH
N Ph
OH
S
H N Ph
OH
A
C
E
B
D
F
R2
R1
R2
R1
R2
R1
R2
R1
R2
R1
R2
R1
Scheme 3 Conformers of H 2 L.
M
Cl
O Cl
+ NEt3, MeOH
N
N S
Et Et N
M O
N NH
N S
Et Et HN
O
+
- (HNEt3)Cl
M = Re, Tc
(4) M = Tc (5) M = Re
Fig 2 Molecular structure of [TcOCl(L)] (4) Thermal ellipsoids represent 50% probability [23] H atoms are omitted for clarity.
Table 2 Selected bond lengths (Å) and angles (°) in [TcOCl(L)] (4) and [ReOCl(L)](5).
M–O10 1.644(2) 1.647(9) C2–N6 1.333(3) 1.34(1) M–Cl 2.3356(6) 2.349(3) N3–C4 1.317(3) 1.30(1) M–S1 2.2878(6) 2.276(3) C4–N5 1.351(3) 1.37(1) M–N5 1.994 (2) 1.972(9) N5–N59 1.409(2) 1.43(1) M–O57 1.970(1) 1.967(7) N59–C58 1.281(3) 1.28(1) S1–C2 1.756(2) 1.74(1) C58–O57 1.340(2) 1.33(1) C2–N3 1.335(3) 1.36(1)
O10–M–Cl 108.03(6) 110.0(4) S1–M–O57 139.45(4) 139.4(2) O10–M–S1 108.62(6) 108.1(3) S1–M–Cl 82.92(2) 84.5(1) O10–M–N5 107.08(7) 107.9(5) N5–M–O57 77.57(6) 76.3(3) O10–M–O57 111.92(7) 112.5(4) N5–M–Cl 144.63(5) 141.2(3) S1–M–N5 89.99(5) 91.4(2) O57–M–Cl 85.55(4) 82.0(2)
Trang 4base like NEt3accelerates the rate of the reaction, but results in the
formation of side-products, which are mainly formed by solvolysis
of the complex 5 The IR spectrum of 5 reveals am(Re@O)frequency
at 991 cm1[19]and a strong bathochromic shift of the C@N band
as a consequence of the complex formation The1H NMR spectrum
of 5 is very similar to that of 4, except that the resolution of the
methylene proton signals is much better than in the spectrum of
the technetium compound and four overlapping multiplet signals
with ABX3coupling patterns of CH2protons can be identified in
the region between 3.9 and 4.1 ppm In the13C NMR spectrum of
5, the separated signals of two ethyl groups are also observed
due to the hindered rotation The resonances assigned for
C@N, C@S and C@O, respectively, appear at 166.69, 172.70 and
173.73 ppm
The molecular structure of 5 is virtually identical with that of its
technetium analogue Therefore, no extra figure is given for this
compound Selected bond lengths and angles are compared with
the corresponding values of 4 inTable 2 The atomic numbering
scheme ofFig 2has also been applied for the rhenium compound
As discussed for technetium compound 4, the metal atom in 5 has
a distorted square–pyramidal coordination sphere and is located
0.691(1) Å above the equatorial plane formed by S1, N5, O57 and
Cl The Re–O distance of 1.647(9) Å is within the typical range of
a rhenium–oxygen double bond[19] All other structural features
discussed above for the technetium complex holds also true for
the rhenium analogue
2.3 Mixed-ligand complexes of the composition [ReO(L)(R1R2btu)]
Mixed-ligand complexes of the composition [ReO(L)(R1R2btu)]
(6) can be synthesized by two different routes (Scheme 5) The first
approach concerns a two-step synthesis, in which 5 is used as the
starting compound This labile square–pyramidal complex is
trea-ted with equimolar amounts of benzoylthioureas in warm CH2Cl2/
MeOH and the mixed-ligand complexes are obtained in high yields
The complexes 6 can alternatively be prepared in one-pot
reac-tions from (NBu4)[ReOCl4] and stoichiometric amounts of the
tri-dentate benzamidine and bitri-dentate benzoylthioureas The yields
of such reactions are not significantly lower than those obtained
from the two-step procedure When the ligands are added
subse-quently, the supporting base should be added a few minutes after
the addition of the second ligand in order to avoid undesired side-reactions The products are readily soluble in CH2Cl2, but sparingly soluble in MeOH Single crystals of good quality are obtained by slow evaporation of CH2Cl2/MeOH mixtures of the complexes Infrared spectra of complexes 6 do not show any absorption in the regions above 3100 cm1, which indicates the expected double deprotonation of benzamidines and the single deprotonation of the benzoylthiourea ligands during complex formation Additionally, the sharp intense absorptions in the range between 1620 and
1690 cm1, which are assigned to themC@NandmC@Ostretches in the spectra of the non-coordinated benzamidines and ben-zoylthioureas shift to the range between 1500 and 1540 cm1
and appear as broad bands Intense bands each at 972 cm1are as-signed to the Re@O stretches [19] They appear about 20 cm1
bathochromically shifted with respect to the corresponding absorption in 5
Because of the hindered rotation around the C–NR2bonds and the rigidity of the tertiary amine nitrogen atoms in both the ben-zamidine and benzoylthiourea ligands, the1H NMR spectra of 6 are complicate Especially for complex 6b, the rigidity of the mor-pholinyl moiety in the coordinated morphbtuligand makes all eight protons of the morpholine ring magnetically inequivalent This is indicated by four well resolved multiplet signals with ABXY splitting patterns at 4.29, 4.34, 4.46 and 4.58 ppm of four different
CH2–O protons and four CH2–N protons appear in two multiplet signals at 3.74 and 3.89 ppm The13C NMR spectra of the com-plexes 6 are more simple, since they are only influenced by hin-dered rotation around the C–NR2bonds As the consequence, two separated signals for each CH2 and CH3 carbon atoms in NEt2
groups and/or CH2–N and CH2–O atoms of the morpholinyl moiety are observed The chemical shifts of the aromatic carbon atoms, which can not be unambiguously assigned, are in the range be-tween 127 ppm and 136 ppm Resonances of the carbon atoms of the C@X groups (X = N, O, S) appear in the range from 163 ppm
to 187 ppm The very similar structures between benzoylthioureas and thiocarbamoylbenzamidines produce difficulties in the assign-ment of the C@X signals in the13C NMR spectra of the complexes Nevertheless, with respect to their analogous coordination sphere, the chemical shifts of the C@N, C@S and C@O signals of (L)2
in the two complexes should be essentially the same and appear at
163 ppm, 174 ppm and 176 ppm FAB+ mass spectra of the mixed-ligand complexes 6 show intense peaks of the molecular ions with the expected isotopic patterns Interestingly, fragments which result from the loss of R1R2NC„N residues of the R1R2 btu-ligand appear in all spectra as intense signals
The molecular structures of 6a and 6b are depicted inFig 3 Se-lected bond lengths and angles are given inTable 3 In these struc-tures, the rhenium atoms exhibit distorted octahedral coordination environments Axial positions are occupied by terminal oxo ligands and the oxygen atoms of the bidentate R1R2btuligands The tri-dentate thiocarbamoylbenzamidine ligands coordinate meridional and the remaining position of the equatorial coordination sphere is occupied by the sulfur atom of the R1R2btu ligand The metal atoms are located slightly above the mean least-square planes formed by the atoms S1, N5, O57 and S12 toward the oxo ligand with a distance of 0.410(2) Å for 6a and 0.381(3) Å for 6b The
Re@O distances of 1.644(8) and 1.659(7) Å are in the expected range of rhenium–oxygen double bonds
A remarkable structural feature in complexes 6 is the coordina-tion of the benzoylic oxygen atoms trans to the oxo ligands The Re–O15 bonds of 2.219(7) and 2.249(6) Å are at the upper limit
of trans-O@Re–O single bond lengths in Re(V) oxo complexes Sim-ilar values have previously been reported only for some complexes with small monodentate neutral ligands such as H2O, MeOH or
Me2CO [19] However, the C14–O15 bonds are not significantly shorter than corresponding distances in R1R2btuligands in other
N N
N S
Et Et N
Re O
O N N
R1
R2
HR1R2btu, Et3N
(TBA)[ReOCl4]
HR1R2btu,H2L,
Et3N
N N
N S
Et Et N
Re O
(5)
(6) a: R1 = R2 = Ph
b: NR1R2 = morpholinyl
Trang 5rhenium complexes[14] All Re–S11 and C12–S11 bond lengths are
in the typical range of Re–S single bonds and CAS bonds with par-tially double bond character as has been previously reported for oxorhenium(V) complexes with a variety of benzoylthiourea li-gands[19] In the benzamidine moiety, the Re–S1 and Re–N5 bond distances are lengthened by about 0.03–0.06 Å compared to the values in 5 Additionally, the Re–S1 bonds are by about 0.06 Å shorter than the Re–S11 bonds which are in their cis positions While the two chelate rings of the benzamidine ligands are almost planar, the six-membered rings of the benzoylthioureas are dra-matically distorted This is mainly due to the large deviations of the Re atoms of 1.448(6) Å (compound 6a) and 1.483(8) Å (com-pound 6b) from the least-square planes formed by the other atoms
of the chelate rings Nevertheless, a considerable delocalization of
p-electron density inside the chelate rings is observed for both the benzoylthiourea and the benzamidine ligands This is mainly indi-cated by the observation of almost identical bond lengths for all C–N bonds, which fall within the range between C–N single and double bonds The bond length equalization is also extended to the C2–N6 and C12–N16 bonds (1.33–1.36 Å), which are clearly shorter than expected for C–N single bonds The partial transfer
of electron density into these bonds well agrees with the 1H NMR spectra of the compounds, which indicate a rigid arrange-ment of –NR1R2moieties
3 Conclusions
We could demonstrate that the tridentate ligand H2L readily forms five-coordinate technetium and rhenium complexes of the composition [MOCl(L)] The remaining chloro ligand is labile and can readily be replaced by bidentate chelators such as N,N-dial-kyl-N0-benzoylthioureas The resulting mixed-ligand complexes can also be prepared in one-pot reactions starting from (NBu4) [ReOCl4] and mixtures of H2L and benzoylthioureas
The presented study on prototype compounds is the experi-mental basis of ongoing studies in our laboratory which deal with ligands of the same type, which contain anchor groups for the con-jugation to peptides or proteins
4 Experimental 4.1 Materials
All reagents used in this study were reagent grade and used without further purification Solvents were dried and freshly distilled prior use unless otherwise stated (NBu4)[ReOCl4],
Fig 3 Molecular structures of (a) [ReO(L)(Ph 2 btu)] (6a) and (b)
[ReO(L)(mor-phbtu)} (6b) Thermal ellipsoids represent 50% probability [23] H atoms are
omitted for clarity.
Table 3
Selected bond lengths (Å) and angles (°) in [ReO(L)(Ph 2 btu)] (6a) and [ReO(L)(morphbtu)] (6b).
Trang 6(NBu4)[TcOCl4] [20] were prepared by published methods.
HR1R2btu ligands[21]and
N-(diethylaminothiocarbonyl)benzimi-doyl chloride[16] were synthesized by the standard procedures
of Beyer et al
4.2 Radiation precautions
99Tc is a weak b-emitter All manipulations with this isotope
were performed in a laboratory approved for the handling of
radio-active materials Normal glassware provides adequate protection
against the low-energy beta emission of the technetium
com-pounds Secondary X-rays (bremsstrahlung) play an important role
only when larger amounts of99Tc are used
4.3 Physical measurements
Infrared spectra were measured as KBr pellets on a Shimadzu
FTIR-spectrometer between 400 and 4000 cm1 ESI mass spectra
were measured with an Agilent 6210 ESI-TOF (Agilent
Technolo-gies) All MS results are given in the form: m/z, assignment
Ele-mental analysis of carbon, hydrogen, nitrogen, and sulfur were
determined using a Heraeus vario EL elemental analyzer The
99Tc values were determined by standard liquid scintillation
count-ing NMR-spectra were taken with a JEOL 400 MHz multinuclear
spectrometer
4.4 Synthesis of the ligand H2L
N-(N0,N0-Diethylaminothiocarbonyl)benzimidoyl chloride
(1.227 g, 5 mmol) was dissolved in 10 mL dry acetone and slowly
added to a stirred mixture of benzoylhydrazine (680 mg, 5 mmol)
and NEt3(1.51 g, 15 mmol) in 10 mL of dry acetone The mixture
was stirred for 4 h at room temperature The formed precipitate
of NEt3HCl was filtered off and the filtrate was evaporated under
reduced pressure The residue was re-dissolved in 10 mL CH2Cl2
and extracted two times with brine solution (2 10 mL) The
or-ganic phase was dried over MgSO4and evaporated under reduced
pressure to dryness The resulting residue was treated with
dieth-ylether (15 mL) and stored at 20 °C for 24 h The crude product
was filtered off, dried under vacuum and recrystallized from
CH2Cl2/n-hexane Yield: 56% (0.991 g) Anal Calc for C19H22N4OS:
C, 64.38; H, 6.26; N, 15.81; S, 9.05 Found: C, 64.51; H, 6.42; N,
15.62; S, 9.00% IR (m in cm1): 3225(m), 3163(m), 3043(m),
2931(m), 1655(vs), 1542(vs), 1504(vs), 1481(vs), 1261(s),
1142(m), 1072(m), 1026(m), 779(m), 713(s), 694(s).1H NMR
(CDCl3; d, ppm): 0.92 (s, br, 3H, CH3), 1.00 (s, br, 3H, CH3), 3.40
(s, br, 2H, CH2), 3.76 (s, br, 2H, CH3), 7.36–7.48 (m, 6H, Ph), 7.77
(d, J = 7.2 Hz, 2H, Ph), 7.84 (d, J = 7.4 Hz, 2H, Ph)
4.5 Syntheses of complexes
4.5.1 [TcO(L)Cl] (4)
H2L (42 mg, 0.12 mmol) dissolved in 2 mL MeOH was added
dropwise to a stirred solution of (NBu4)[TcOCl4] (58 mg, 0.1 mmol)
in 1 mL MeOH The color of the solution immediately turned deep
red and a red precipitate deposited within a few minutes The red
powder was filtered off, washed with cold methanol and dried
un-der vacuum X-ray quality single crystals of 4 were obtained by
slow evaporation of a dichloromethane/methanol solution Yield:
50% (26 mg) Anal Calc for C19H20ClN4O2STc: Tc, 20.8 Found: Tc,
20.7% IR (m in cm1): 3055(w), 2985(w), 2932(w), 2870(w),
1504(vs), 1434(m), 1389(s), 1354(m), 1327(m), 1292(m),
1174(w), 1095(w), 1064(w), 1026(w), 976(s), 775(m), 698(s).1H
NMR (CDCl3; d, ppm): 1.30 (t, J = 7.1 Hz, 3 H, CH3), 1.37 (t,
J = 7.1 Hz, 3 H, CH3), 3.90–4.00 (m, 4 H, CH2), 7.32 (t, J = 7.4 Hz, 2
H, Ph), 7.36 (t, J = 6.9 Hz, 1 H, Ph), 7.42 (t, J = 7.7 Hz, 2 H, Ph),
7.50 (t, J = 7.3 Hz, 1 H, Ph), 7.84 (d, J = 7.9 Hz, 2 H, Ph), 8.01 (d,
J = 8.1 Hz, 2 H, Ph)
4.5.2 [ReO(L)Cl] (5) The red microcrystalline 5 was prepared from (NBu4)[ReOCl4] and H2L by a similar procedure as described for 4, except that the reaction time was increased and the precipitation of the prod-uct was finished only after 6 h Yield: 61% (36 mg) Anal Calc for
C19H20ClN4O2SRe: C, 38.67; H, 3.42; N, 9.49; S, 5.43 Found: C, 38.47; H, 3.50; N, 9.41; S, 5.22% IR (m in cm1): 3055(w), 2989(w), 2932(w), 1508(vs), 1438(m), 1389(m), 1326(m), 1292(m), 1145(w), 1072(w), 1026(w), 991(s), 775(m), 709(m), 691(s).1H NMR (CDCl3, d, ppm): 1.33 (t, J = 7.1 Hz, 3H, CH3), 1.39 (t, J = 7.1 Hz, 3H, CH3), 3.90 (m, 2H, CH2), 4.12 (m, 2H, CH2), 7.32 (t, J = 7.2 Hz, 2H, Ph), 7.38 (t, J = 7.0 Hz, 1H, Ph), 7.43 (t, J = 7.5 Hz, 2H, Ph), 7.51 (t, J = 7.4 Hz, 1H, Ph), 7.85 (d, J = 7.9 Hz, 2H, Ph), 8.05 (d, J = 8.3 Hz, 2H, Ph).13C NMR (CDCl3, d, ppm): 12.91, 13.20 (CH3), 47.41, 47.83 (N–CH2), 127.70, 127.78, 128.45, 128.65, 130.94, 131.76, 132.10 and 134.98(Ph), 166.69 (C@N), 172.70(C@S), 173.73 (C@O)
4.5.3 [ReO(L)(R1R2btu)] (6) Method 1 [ReO(L)Cl] (59 mg, 0.1 mmol) was dissolved in CH2Cl2 (10 mL) HR1R2btu (0.1 mmol) and three drops of NEt3were added under stirring The red colored solution was heated under reflux for
2 h and the solvent was removed under vacuum to dryness The resulting residue was either washed with cold MeOH or recrystal-lized from CH2Cl2/MeOH to give red crystalline products
Method 2 A mixture of H2L (35 mg, 0.1 mmol) and HR1R2btu (0.1 mmol) in 3 mL acetone was added to a solution of (NBu4) [ReOCl4] (58 mg, 0.1 mmol) in 3 mL CH2Cl2 After stirring at room temperature for 10 min, three drops of NEt3were added and the mixture was heated under reflux for 2 h This resulted in the for-mation of a dark red solution The solvent was removed in vacuo and the residue was treated as described in method 1
4.5.4 Data for [ReO(L)(Ph2btu)] (6a) Yield: 63% (56 mg) for method 1, 71% (63 mg) for method 2 Anal Calc for C39H35N6O3S2Re: C, 52.86; H, 3.98; N, 9.48; S, 7.24 Found: C, 52.00; H, 3.25; N, 9.37; S, 6.93% IR (m in cm1): 3055(w), 2978(w), 2924(w), 1512(vs),1450(s), 1427(vs), 1404(vs), 1334(m), 1257(m), 972(s), 694(s).1H NMR (CDCl3; d, ppm): 1.23 (t, 3H, CH3), 1.25 (t, 3H, CH3), 3.74 (m, 2H, CH2), 3.91 (m, 1H,
CH2), 4.00 (m, 1H, CH2), 6.99(t, J = 7.9 Hz, 2H, Ph), 7.2–7.4(m, 19H, Ph), 7.79(d, J = 8.4 Hz, 2H, Ph), 7.99(d, J = 8.4 Hz, 2H, Ph).13C NMR (CDCl3; d, ppm): 13.35 (CH3), 13.38 (CH3), 46.58 (CH2), 47.49 (CH2), 127–136 (Ph), 163.20 (C@N, L2), 173.10 (C@S,
Ph2btu), 174.05 (C@S, L2), 176.18 (C@O, L2), 186.95 (C@O,
Ph2btu) FAB+MS (m/z): 909, 11%, [M+Na]+; 887, 40%, [M+H]+;
814, 6%, [MNEt2]+; 692, 65%, [MPh2NC„N]+
4.5.5 Data for [ReO(L)(morphbtu)] (6b) Yield: 40% (32 mg) for method 1, 59% (47 mg) for method 2 Anal Calc for C31H33N6O4S2Re: C, 46.31; H, 4.14; N, 10.55; S, 7.98 Found: C, 46.22; H, 4.04; N, 10.40; S, 8.12% IR (min cm1): 3062(w), 2978(w), 2926(w), 1520(vs),1488(vs), 1420(vs), 1350(s), 1311(s), 1234(m), 1110(m), 1065(m), 1026(m), 972(s), 771(m), 694(s).1H NMR (CDCl3; d, ppm): 1.23 (t, 3H, CH3), 1.25 (t, 3H,
CH3), 3.74 (m, 2H, morphNCH2), 3.89 (m, 2H, morphNCH2), 3.95– 4.05 (m, 4H, NCH2), 4.29 (m, 1H, morphOCH2), 4.34 (m, 1H, mor-phOCH2), 4.46 (m, 1H, morphOCH2), 4.58 (m, 1H, morphOCH2), 7.09 (t, J = 7.7 Hz, 2H, Ph), 7.21–7.27(m, 4H, Ph), 7.34–7.41 (m, 3H, Ph), 7.68(d, J = 7.1 Hz, 2H, Ph), 7.81(d, J = 8.3 Hz, 2H, Ph), 7.90 (d, J = 8.3 Hz, 2H, Ph) 13C NMR (CDCl3; d, ppm): 13.37 (CH3), 13,40 (CH3), 46.59 (NCH2), 47.57 (NCH2), 48.32 (NCH2), 49.81 (NCH), 67.12 (OCH ), 67.34 (OCH), 127.37, 127.72, 127.96,
Trang 7128.48, 129.56, 129.80, 130.42, 130.67, 131.44, 132.01, 135.42 and
136.47 (Ph), 163.25 (C@N, L2), 171.99 (C@S, morphbtu), 173.93
(C@S, L2), 176,19 (C@O, L2), 184.85 (C@O, morphbtu) FAB+
MS (m/z): 827, 9%, [M+Na]+; 805, 38%, [M+H]+; 692, 37%,
[Mmor-phC„N]+; 572, 35%, [ReO2(L2)]+
4.6 X-ray crystallography
The intensities for the X-ray determinations were collected on a
STOE IPDS 2T instrument with Mo Ka radiation (k = 0.71073 Å)
Standard procedures were applied for data reduction and
absorp-tion correcabsorp-tion Structure soluabsorp-tion and refinement were performed
withSHELXS97 andSHELXL97[22] Hydrogen atom positions were
cal-culated for idealized positions and treated with the ‘riding model’
option ofSHELXL More details on data collections and structure
cal-culations are contained inTable 1
Additional information on the structure determinations has
been deposited with the Cambridge Crystallographic Data Centre
(seeTable 4)
Supplementary data
CCDC 728398, 728399, 728400, 728401 and 728402 contain the
supplementary crystallographic data for this paper These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data
Cen-tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk
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Table 4
X-ray structure data collection and refinement parameters.
H 2 L [TcOCl(L)] (4) [ReOCl(L)] (5) [ReO(L)(Ph 2 btu)] (6a) [ReO(L)(morphbtu)] (6b) Formula C 19 H 22 N 4 OS C 19 H 20 ClN 4 O 2 STc C 19 H 20 ClN 4 O 2 ReS C 39 H 35 N 6 O 3 ReS 2 C 31 H 33 N 6 O 4 ReS 2
R 1 /wR 2 0.0505/0.0886 0.0288/0.0618 0.0749/0.1676 0.0534/0.1268 0.0735/0.1667
CSD deposit number CCDC-728398 CCDC-728400 CCDC-728399 CCDC-728401 CCDC-728402
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