Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

Article abstract of DOI:10.1016/j.poly.2011.05.033

N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL²; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN) ₂] (X = Br, Cl) in methanol gave the adducts [ReX(CO) ₃(HLⁿ)] (1a X = Cl, n = 1; 1a0 X = Br, n = 1; 1b X = Cl, n = 2; 1b0 X = Br, n = 2; 1c X = Cl, n = 3; 1c0 X = Br, n = 3) in good yield. All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and 1H NMR spectroscopic methods. Moreover, the structures of HL ², HL³, HL³.(CH₃)₂SO and 1b0-H2O were also elucidated by X-ray diffraction. In 1b', the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms (jS,N3) forming a five-membered chelate ring, as well as three carbonyl and bromide ligands. The resulting coordination polyhedron can be described as a distorted octahedron. The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re ₂(L¹)2(CO)₆] (2a), [Re₂(L ²)₂(CO)₆] (2b) and [Re₂(L ³)₂(CO)₆] (2c) as determined by X-ray studies. Methods of synthesis were optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer structures are achieved by Re-S-Re bridges, where S is the thiolate sulphur from a jS,N3-bidentate thiosemicarbazonate ligand. Some single crystals isolated in the synthesis of 2b contain [Re(L⁴)(L²)(CO)₂] (3b) where L⁴ (=2-methylamine-5-(para-methylsulfanephenyl)-1,3,4- thiadiazole) is originated in a cyclization process of the thiosemicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen of the thiosemicarbazonate (jS,N²) affording a four-membered chelate ring.

Full text of DOI:10.1016/j.poly.2011.05.033

Polyhedron 30 (2011) 2146–2156
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, characterization, reactivity and computational studies of new
rhenium(I) complexes with thiosemicarbazone ligands derived
from 4-(methylthio)benzaldehyde
Ara Núñez-Montenegro a, Rosa Carballo a, José M. Hermida-Ramón b, Ezequiel M. Vázquez-López a,
⇑
a Departamento de Química Inorgánica, Facultade de Química, Edificio de Ciencias Experimentais, Universidade de Vigo, E-36310 Vigo, Galicia, Spain
b Departamento de Química Física, Facultade de Química, Edificio de Ciencias Experimentais, Universidade de Vigo, E-36310 Vigo, Galicia, Spain
a r t i c l e i n f o
a b s t r a c t
N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL1; R = Me, HL2 and
R = Ph, HL3) have been prepared and their reaction with fac-[ReX(CO)3(CH3CN)2] (X = Br, Cl) in methanol
gave the adducts [ReX(CO)3(HLn)] (1a X = Cl, n = 1; 1a0 X = Br, n = 1; 1b X = Cl, n = 2; 1b0 X = Br, n = 2; 1c
X = Cl, n = 3; 1c0 X = Br, n = 3) in good yield.
Article history:
Received 18 April 2011
Accepted 27 May 2011
Available online 6 June 2011
All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and 1H
NMR spectroscopic methods. Moreover, the structures of HL2, HL3, HL3ꢀ(CH3)2SO and 1b0ꢀH2O were also
elucidated by X-ray diffraction. In 1b0, the rhenium atom is coordinated by the sulphur and the azome-
Keywords:
Thiosemicarbazone
Thiadiazole
Rhenium complexes
Carbonyl complexes
Crystal structures
thine nitrogen atoms (j
S,N3) forming a five-membered chelate ring, as well as three carbonyl and bro-
mide ligands. The resulting coordination polyhedron can be described as a distorted octahedron.
The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re2(L1)2(CO)6] (2a),
[Re2(L2)2(CO)6] (2b) and [Re2(L3)2(CO)6] (2c) as determined by X-ray studies. Methods of synthesis were
optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer
structures are achieved by Re–S–Re bridges, where S is the thiolate sulphur from a
osemicarbazonate ligand.
j
S,N3-bidentate thi-
Some single crystals isolated in the synthesis of 2b contain [Re(L4)(L2)(CO)3] (3b) where L4 (=2-methyl-
amine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole) is originated in a cyclization process of the thio-
semicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen
of the thiosemicarbazonate (j
S,N2) affording a four-membered chelate ring.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
a novel amphiphilic block copolymer. These water soluble nano-
particles with red emission were used as biolabels for cell imaging
and gene transfection [18].
The current interest in the coordination chemistry of techne-
tium and rhenium is due to the widespread use of the radionuclide
99mTc in diagnostic nuclear medicine and the potential of the radio-
isotopes 186Re and 188Re in radiotherapy [1–4]. The redox and
configurationally stability of the fragment {M(CO)3}+ (M = Tc, Re),
beside the photophysic/photochemistry [5–9] and catalytic prop-
erties [10], make it a suitable candidate to metal node in metallo-
supramolecular architecture [11–14]. In the last years, the
developing of a normal pressure preparation of [M(H2O)3(CO)3]+
On the other hand, thiosemicarbazones (TSCs) constantly
attract the interest of chemist and pharmacist because of their well
known and remarkable biological and pharmacological properties;
that is why the sensible increase in the number of studies of their
antibacterial, antiviral, antifungal and antitumour activity as
Quiroga and Navarro have reported [19]. Modifications of the
thiosemicarbazone framework to find new compounds have been
studied, and relationships between the biological activity and
chelate formation are evident in a number of cases. These ligands
are very versatile; they may be neutral or anionic ligand and link
metal ions by different coordinative modes [20–22].
ꢁ
from saline solutions of MO4 in high yields and purity [15] has
opened the possibility of using this metallic centre in radiotherapy
and radio image [16,17].
Recently, bifunctional nanoparticles were successfully con-
In previous papers [23] we reported a list of thiosemicarbazone
ligands and their reactions with fac-[ReX(CO)3(CH3CN)2], which is
a common starting material for the synthesis of rhenium(I) com-
plexes. We have now extended these studies to thiosemicarbazones
derived 4-(methylthio)benzaldehyde. In addition, the choice of
structed by encapsulating hydrophobic ReI (phen) complexes with
⇑
Corresponding author.
E-mail address: ezequiel@uvigo.es (E.M. Vázquez-López).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.05.033

A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
2147
sulfur-containing species in the ligands is due to a strategy for the
construction of molecular based devices by the self-assembly of
sulphur-containing molecules onto noble metal (particularly gold)
surfaces [24,25]. The –SMe group allows a variety of pendant
functionality to be introduced and metal-binding domains are of
particular interest as they allow the introduction of specific elec-
tronic and photophysical properties [26].
1 ppm) respect to the free ligands. Differently, the signal of the
N(2)–H proton moves around 2 ppm. This behaviour has been pre-
viously observed in rhenium(I) complexes of arylhydrazones [27]
and thiosemicarbazones [28] where the N(2)–H group is a member
of the chelate ring resulting after the O/S,N-coordination. However,
when the thiosemicarbazone is coordinated as a S-monodentate li-
gand, the N(2)–H proton signal behaves as the rest of the ligand sig-
nals [29].
The thiosemicarbazonate complexes (2a–c) may be isolated by
different ways depending of R (Scheme 3).
2. Results and discussion
In all cases the X-ray study of the crystals 2a, 2b, 2c (and
2cꢀ(CH3)2CO) showed the formation of binuclear thiosemicarbazo-
nate complexes (vide infra). In a similar fashion to those observed
in other rhenium(I) complexes of different thiosemicarbazone li-
gands [23], the deprotonation of the TSC ligand induces the labili-
zation of the halogen in the position occupied by sulphur atom
from other coordinated TSC (vide infra).
2.1. Synthesis and spectroscopic characterization
The ligands derived from 4-(methylthio)benzaldehyde thiosem-
icarbazone were obtained by refluxing a mixture of 4-(methyl-
thio)benzaldehyde and the corresponding thiosemicarbazide in
methanol/water solution for 2 h (Scheme 1).
Thiosemicarbazonate [Re2(L3)2(CO)6] 2c was identified as by-
product in the reaction of fac-[ReX(CO)3(CH3CN)2] and HL3 ligand,
probably due to the easy deprotonation of this ligand in soft reac-
tion conditions. This compound 2c may be obtained by longer
refluxing time than 1c and 1c0. However, to isolate the correspond-
ing derivatives of L1 and L2 (2a and 2b, respectively) was necessary
to reflux a mixture of [ReCl(CO)5] and the ligand in toluene for 2a
and the chloride adduct, 1b, with NaOH in methanol for 2b. In all of
them, the three carbonyl IR bands are consistent with a facial
geometry around rhenium atom.
Reaction of the three ligands with fac-[ReX(CO)3(CH3CN)2]
afforded six adducts (Scheme 2) with general formula fac-
[ReX(CO)3(HLn)].
The resulting solid depends substantially on the reaction time
and the R group nature. While, refluxing for 2 h affords adducts
1a, 1a0, 1b and 1b0 in good yield, the reaction time has to be short-
ened to avoid the formation of thiosemicarbazonate complexes
(via infra) in 1c and 1c0.
Elemental analysis and mass spectrometry confirmed the stoi-
chiometry [ReX(CO)3(HLn)]. The mass spectra of adducts show in
some cases a signal corresponding to the molecular ion, although
the peak due to the species [MꢁX]+ is more intense.
The 1H NMR spectra of these compounds in acetone-d6 show all
the proton signals shifted at low field respect to the free ligands
and, as expected, the signals for N(2)–H are absent due to the
deprotonation.
Furthermore, facial geometry around the rhenium atom is sug-
gested by the three strong bands
m
(C„O) in IR (sometimes col-
The ligand bands
lapsed) in the range 1895–2029 cmꢁ1
.
The reaction in methanol of 1b0 with NaOH in 1:2 relation yields
also the compound 2b too but, the X-ray analysis of the residual
single crystals obtained after storing the filtrate solution several
months showed the formation of 3b (Scheme 4). This compound
results of cyclization of a TSC yielding the thiadiazole ligand (2-
methylamine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole). In
corresponding to the N–H groups appear between 3099 and
3422 cmꢁ1 and are hardly modified by coordination (see [12] and
references therein).
In general, all proton signals in the 1H NMR spectra of the
complexes in acetone-d6 are shifted at low field (around 0.1–
NHR
7
8
H
H
MeOH/H2O
(1:1)
6
+
MeS
H
N
H2N
C
MeS
2
S
S
N
H
O
2
N
3
1
3
4
5
HL
HL1
HL2
HL3
R
H
NHR
1
Me
Ph
Scheme 1. Synthesis of the thiosemicarbazone ligands.
X
H
[ReX(CO)3(NCCH3)2]
OC
NHR
NH
S
N
H
MeS
S
N
N
Re
MeOH, reflux
NHR
OC
CO
R
H
H
X
Cl
Br
H
1a
1a'
1b
HL
1
SMe
Me Cl
1b' Me Br
1c
Ph
Cl
1c'
Ph
Br
Scheme 2. Synthesis of the rhenium(I) addutcs.

2148
A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
S
H
[ReCl(CO)5]
toluene, reflux
H
N
[Re2(L1)2(CO)6]
MeS
R1
S
R4
N
N
HL1
N
H
N
NH2
2a
(
)
R3 R2
(
)
H
N
R2
H
R2
N
R4
N
N
NaOH
MeOH
R4
R3
[ReCl(HL2)(CO)3]
[Re2(L2)2(CO)6]
S
R3
N
R1
N
S
N
R1
triazolidine-3-thione
N
1b
(
)
2b
( )
H
R3
thiadiazolidine-2-imine
N
S
R1
thiadiazole-2-imine
H
H
N
S
MeS
[ReBr(CO)3(CH3CN)2]
MeOH, reflux
N
[Re2(L3)2(CO)6]
Scheme 5. Products of cyclization of thiosemicarbazones.
HN
HL3
(
)
2c
(
)
monodentate group (i.e.: without additional chelating groups) are
scarce. Most of them are zinc [33] and copper [34] complexes but
always obtained by reaction with commercial thiadiazole ligands.
Scheme 3. Synthesis of the thiosemicarbazonate complexes.
SMe
2.2. Crystal and molecular structure of the ligands
S
H3C
The molecular structures of the free ligands are shown in Fig. 1
along with the atomic numbering scheme used. Selected bond
length and angles are listed in Table S1. The crystal structure of
HL1 had been previously reported by Yathirajan and coworkers [35].
Ligands HL2 and HL3 show E configuration around C(1)–N(2),
N(2)–N(3), N(3)–C(2) and C(2)–C(3) bonds. Apart from this, the dis-
tances C(1)–S(1), C(2)–N(3), N(2)–N(3) and N(2)–C(1) suggest that,
N
CH3
N
N
H
S
N
H
OC
OC
Re
N
H
CO
N
SMe
Scheme 4. The molecular structure of the compound 3b.
addition, the coordination mode of the thiosemicarbazonate li-
gand,
S,N2, affords a four-membered chelate ring different to
the usual five-membered chelate ring observed in the tiosemicar-
bazonate-
S,N3 such as 2b.
The presence of thiosemicarbazonate-
described before but the stabilizing factors of this coordination
mode against the usual
S,N3 mode is an open question. Bhattach-
j
j
j
S,N2 ligands has been
j
arya et al. [30] have attributed to steric stress on the coordination
sphere the formation of the four or five membered chelate ring in
rhuthenium(II) thiosemicarbazonate. However, experimental and
DFT studies with both linkage isomers of diorganolead(IV) and lea-
d(II) suggest that the mode-
mode
S,N2 an intermediary of the reaction. The isolation of 3b
from a virtually
S,N3-TSC complex (1b or 2b) suggest that other
j
S,N3 is slightly more stable, being the
j
j
paths may yield this coordination mode too.
Other interesting aspect is the formation of the thiadiazole ring.
The cyclization processes of TSCs have been extensively studied by
Zelenin et al. [31] and it is known that different products may be
isolated depending of the substituent on the N(1) and C(2) atoms
(see Scheme 5) and the reagents (metal) used. These studies sug-
gest a strong dependence of the media. Landquist reported that
phenoxyacetone (1-phenyl)thiosemicarbazone undergoes atmo-
spheric oxidation in the reaction with basic alumina, yielding dif-
ferent products based on the triazoline-5-thione ring [32].
However, the product obtained is the thiadiazoline-5-phenylamino
when the reaction is performed with manganese dioxide. In the
present case, atmospheric oxidation seems to be enough to the
cyclization and formation of the thiadiazole-5-methylamine
complex.
Complexes of different thiadiazole ligands have been described
before (see for example Ref. [38]) although those with a single
Fig. 1. Molecular structures of HL2 (A), HL3 (B) and HL3ꢀ(CH3)2SO (C).

A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
2149
in spite of the usual delocalization of
p
electrons along the thio-
2.4. Crystal and molecular structures of [Re2(L1)2(CO)6](2a),
semicarbazide chain [36], the canonical form of the free ligand de-
picted in Scheme 1 is likely the main form in solid state. Z
configuration in the C(1)–N(1) bond has been related with the exis-
tence of the intramolecular hydrogen-bonding interaction N(1)–
Hꢀ ꢀ ꢀN(3) [21].
[Re2(L2)2(CO)6](2b), [Re2(L3)2(CO)6](2c) and [Re2(L3)2(CO)6]ꢀ(CH3)2CO
(2cꢀ(CH3)2CO)
Relevant length bonds and angles are included in Table 2. The
molecular structures showing the numbering schemes used are de-
picted in Fig. 2B.
In HL2, the molecule of the ligand can be considered essentially
planar: the angle between the ideal plane of the thiosemicarbazide
chain N(1)/S(1)/C(1)/N(2)/N(3)/C(2) and the carbon atoms that de-
fine the phenyl ring is 6.84(8)°. However, in HL3 and HL3ꢀ(CH3)2SO,
the presence of other phenyl ring as thiosemicarbazide substituent
changes the planarity of these molecules; the angle between the
general plane C(1)/N(2)/N(3)/C(2)/C(6) and the aromatic ring are
52.28° and 79.45°, respectively. On the other hand, the methylsulfa-
nyl residues are also coplanar with the phenyl rings (Table S1).
The molecular association is strongly dominated by the pres-
ence of hydrogen bonds. It is remarkable that only the thioamide
S(1) atom acts as an acceptor for hydrogen bonds, while the meth-
ylsulfanyl S(2) atom is not involved in any relevant hydrogen bond
interaction. In HL2, each TSC molecule is linked to other two mol-
ecules by N(1)–Hꢀ ꢀ ꢀS(1) and N(2)–Hꢀ ꢀ ꢀS(1) interactions (Table S2)
in a almost honeycomb grid parallel to ab crystallographic plane
(Fig. S1A). Weak interactions C(9C)–Hꢀ ꢀ ꢀS(1) and C(2)–Hꢀ ꢀ ꢀC(9A)
play a supportive role (C(9)–S(1) = 3.886 Å; C(2)–C(9) = 3.521 Å)
in packing of these sheets along the c axis therefore the 2-(methyl-
thio)phenyl fragments site in the voids of a neighbouring layer.
The phenyl group on the N(1) atoms is likely hindering the
establishment of intermolecular hydrogen bond interactions of
the group N(1)–H in the crystal of HL3. Thus, the molecules are
only coupled by N(2)–Hꢀ ꢀ ꢀS(1) hydrogen bonds and the dimers
associated in a brick-wall-like pattern by weak interactions involv-
As consequence of the ligand deprotonation, the rhenium coor-
dinates the sulphur atom of a neighbouring molecule at the posi-
tion occupied by the halogen atom creating dimers. In all the
cases, the thiosemicarbazonate groups are in the same side of the
Re2S2 fragment affording dissymmetric structures [23,24] although
centrosymmetric structures are also possible [28]. In 2a and 2b the
dimers are generated by a twofold axis. Anyway, the formation of
both types of Re2S2 diamonds does not impose important differ-
ences in bond lengths and angles (Table 2).
The rhenium atoms retains its octahedral coordination, but now
interacts with two sulphur atoms, and the sulphur belonging to the
partner in the dimer, is about 0.1 Å farther away than its own sul-
phur. In fact, the Re–S–Re bridge is relatively asymmetric, as in
others dimeric structures based on this type of interaction
[39,40]. In the diamond Re2S2, the bond angles are close to 90°
and the distances Re–Re are in both compounds is too long
(>3.75 Å) what it means any significant bonding interaction. The
aromatic rings are face-to-face stacked with different slipping de-
grade, and the –SMe group is orientated in opposite directions in
2a and 2b. The benzyl centroid–centroid distances, 4.671 Å in 2a
and 4.270 Å in 2b, may not rule out the expected poor attractive
face-to-face
p–p interaction between aromatic systems of same
electronic nature [41]. The more eclipsed distribution in 2b may
be due to the steric hindrance impose for the methyl group at N(1).
As observed in other TSC derivatives [13,23,27], the Re–N(3)
and Re–S(1) as C(2)–N(3) and N(2)–N(3) distances of the deproto-
nated ligand are statistically equivalents to the observed in
1b0ꢀH2O. However, the values of the C(1)–S(1) distance do show
slight modifications respect to the adduct. In addition, the angle
between the plane of the benzaldehyde ring and the thiosemicar-
bazide arm (11.99° in 2a, 17.98° in 2b, 36.65° in 2c and 35.10° in
2cꢀ(CH3)2CO) shows that ligand adopts a more planar disposition
in these complexes than in 1b0ꢀH2O (44.30°).
ing aromatic C–H groups as H-donors and other C–H groups or p-
clouds as acceptors (Fig. S1B). In HL3ꢀ(CH3)2SO, the solvent acts as
acceptor in hydrogen bonds activating the group N(1)–H although
the TSC molecules are coupled in a similar arrangement as the ob-
served in HL3 (Fig. S1C).
2.3. Crystal and molecular structure of [ReBr(CO)3(HL2)]ꢀH2O
(1b0ꢀH2O)
In the crystal structure of 2a, molecules of dimer are associated
by hydrogen bond involving thioamide N(1) hydrogen atoms, S(2)
atom and the oxygen carbonyl group trans to N(3) atom (Fig. S2B).
These interactions form chains running along to c crystallographic
axis while the interaction N(1)–Hꢀ ꢀ ꢀS(2) associates these chains in
a sheet parallel to the bc crystallographic plane.
In 2b, molecules of dimer are associated in a sheet parallel to ab
crystallographic plane by N(1)–Hꢀ ꢀ ꢀS(2) hydrogen bonds
(Table S2). Moreover, the sheets are linked also by weak interac-
tions between C–H and oxygen carbonyl groups (Fig. S2C).
Molecules of dimer 2c are associated by hydrogen bond
involving N(1) hydrogen and oxygen carbonyl groups forming
chains running parallel to c crystallographic axis (Fig. S2D). In
2cꢀ(CH3)2CO, the presence of the solvent in the crystal only slightly
modifies the interactions between the chains. Consequently, the
interactions between molecules occurs of very similar way to the
observed in 2c, with the acetone molecules linked to these dimers
along to b crystallographic axis (Fig. S2E).
The molecular structure of 1b0ꢀH2O together with the number-
ing scheme used is depicted in Fig. 2A. Interatomic distances and
angles relative to the coordination sphere are included in Table 1.
The ligand HL2 is coordinated to rhenium atom through the sul-
phur and nitrogen N(3) atoms. This coordination mode changes the
configuration of the bond C(1)–N(2) from E, observed in the struc-
ture of free ligand HL2 (vide supra), to Z to form a five-membered
chelate ring. This ring is approximately planar and the angle re-
spect to the aromatic ring is 52.65°. The rhenium atom is octahe-
drally coordinated to three carbonyl carbon atoms in fac
arrangement, a bromide atom, the azomethine nitrogen and the
sulphur atom of the thiosemicarbazone, main distortion being in
the angle S–Re–N (Table 1). The bond distances Re–N(3), Re–S
and Re–Br are very similar to those observed previously in others
fac-Re(CO)3 adducts with TSC chelate ligands [12,23,28,37].
The molecular packing in the crystal seems dominated by the
water molecule. In spite that water hydrogen atoms were not
localized, the description of its role in the packing may be based
on the interatomic donor–acceptor distances. Thus, it behaves as
hydrogen bonding acceptor by interaction with the N(1)–H(1)
and N(2)–H(2) groups of the same 1b0 molecule and as a donor
with the bromine ligand (O1Wꢀ ꢀ ꢀBr1i = 3.195(16) Å, i = ꢁ1 + x, y,
z). In addition, an interaction with a neighbouring water molecule
yields the chains depicted in Fig. S2A. This kind of water associa-
tion has been described before [38].
2.5. Crystal and molecular structure of 3b
The molecular structure of compound 3b is depicted in Fig. 3.
Table 3 lists a selection of the bond distances and angles.
The rhenium atom is coordinated by the S(1) and N(2a) atoms
of a thiosemicarbazonate ligand, by a N(2b) atom of a thiadiazole
ring and three carbon carbonyl atoms. The
j
S,N2-coordination

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A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
Fig. 2. Molecular structures (hydrogen atoms are omitted for clarity) in 1b0 (A) 2a (B), 2b (C), 2c (D) and 2cꢀ(CH3)2CO (E).
mode of thiosemicarbazonate ligand and, consequently, the forma-
tion of a four-membered chelate ring is not usual but it has been
reported before in complexes of ruthenium(II), thallium(II), lea-
d(IV) and lead(II) (see for example Refs. [30,42–44].
The thiadiazole ligand is coordinated to rhenium by the N(2B)
atom and it adopts the tautomeric form usually observed in solid
and solution free ligand [45]. The Re–N(2B) distance is similar to
that found in other Zn(II)/Cu(II) complexes of monodentate thiadi-
azole [34]. The ligand reflects some delocalization in the C(1B)–
N(1B) bond as it is usually observed in thiosemicarbazone and thi-
osemicarbazonate complexes.
The molecules of complex are coupled in centrosymmetric di-
mers by hydrogen bond involving the N(1A)–Hꢀ ꢀ ꢀS(2B)i (0.86,
2.75, 3.540(3) Å and 154.2° i = ꢁx, ꢁy, 1 ꢁ z). Furthermore, these
dimers are associated in chains by an additional hydrogen interac-
tion involving N(1B)–Hꢀ ꢀ ꢀS(1A)ii (0.86, 2.70, 3.355(3) Å and 134.3°,
ii = ꢁx, 1 ꢁ y, ꢁz) interaction (Fig. S2F).
The comparison with the structure of HL2, 1b0, 2b and 3b allows
us to obtain a rather clear view of the electronic structure of the
last case. The C(1)–S(1), N(1)–C(1) and N(2)–N(3) bond distances
are clearly shortened while N(2)–C(1) is lengthened respect to
compound 2b. In fact, the values of these bonds are more similar
to these found in free ligand HL2 and adduct 1b0.
Coordinated ligand in 3b present configurations of the bonds re-
lated with the fragment C(2)/N(3)/N(2)/C(1)/N(1) like free ligands.
Furthermore, the Re–N(2) distance is clearly shorter than the Re–
N(3) distance in 1b0 and 2b. However, the Re–S(1) distance is
clearly longer than in all the five-membered chelate ring of 1b0
and 2a–2c. In fact, it is close to the Re–S bridge distance observed
in compounds 2. Similar behaviour of the M–S and M–N(2)/N(3)
distances has been reported before by Casas et al. for diorgano-
lead(IV) and lead(II) complexes [44].
2.6. Computational studies
The geometries in the ground state of the ligand HL2 and its rhe-
nium(I) complex 1b0 have been optimized at the DFT level with the
B3LYP functional. For the first row atoms we used the Duning

A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
2151
Table 1
Relevant interatomic distances (Å) and bond angles (°) for HL2 and 1b0ꢀH2O in
comparison with the theoretical data.
HL2
1b0
X-ray
Theoretical
X-ray
Theoretical
S(1)–C(1)
S(2)–C(6)
S(2)–C(9)
N(1)–C(1)
N(1)–C(10)
N(2)–C(1)
N(2)–N(3)
N(3)–C(2)
C(2)–C(3)
Re(1)–N(3)
Re(1)–S(1)
Re(1)–Br(1)
1.680(6)
1.741(7)
1.762(8)
1.341(7)
1.443(7)
1.349(6)
1.369(6)
1.273(7)
1.450(8)
1.7302
1.8355
1.8807
1.3559
1.4633
1.3929
1.3808
1.3061
1.4171
1.681(9)
1.755(8)
1.780(12)
1.324(11)
1.433(11)
1.342(10)
1.376(9)
1.300(10)
1.463(12)
2.222(7)
2.464(2)
2.6648(12)
1.7448
1.8263
1.8805
1.3592
1.4729
1.3673
1.4184
1.3191
1.4554
2.2415
2.5863
2.7283
Fig. 3. Molecular structure of 3b.
N(1)–C(1)–N(2)
N(1)–C(1)–S(1)
N(2)–C(1)–S(1)
C(1)–N(2)–N(3)
C(2)–N(3)–N(2)
N(3)–C(2)–C(3)
C(1)–N(1)–C(10)
C(6)–S(2)–C(9)
N(3)–Re(1)–S(1)
N(3)–Re(1)–Br(1)
S(1)–Re(1)–Br(1)
116.2(5)
123.2(4)
120.6(4)
119.6(5)
117.1(5)
120.8(6)
123.7(5)
103.8(4)
114.92
125.71
119.38
120.80
118.37
122.42
123.37
102.83
116.0(8)
122.4(7)
121.6(7)
122.9(7)
113.7(7)
126.5(9)
124.9(9)
104.3(5)
78.99(18)
83.7(2)
116.07
121.95
121.98
123.50
112.61
128.56
123.25
102.84
79.20
crystal packing and hydrogen bonding will affect the experimental
bond lengths since the theoretical calculations do not consider the
effect of the chemical environment.
The observed IR bands with the relative intensities and calcu-
lates wavenumbers (scaled) and assignments are given in Table
4. Fig. 5 shows a comparison between the experimental FT-IR spec-
tra and the theoretical results. The assignment of the calculated
wavenumbers was aided by the animation option of MOLDEN pro-
gram [46] which gives a visual presentation of the vibrational
modes. The IR spectra calculated agree with experimental and
the main differences may be again attributed to crystal effect.
In general, the assignment is similar to that reported recently
for the ethylmethyl ketone thiosemicarbazone [47]. The present
study confirms the conclusions reported by Rao and Venkataragh-
avan [48] respect to the stretching frequencies in N–C@S groups. In
compounds where the thiocarbonyl group is linked to one or two
nitrogen atoms, strong vibrational coupling effects are possible
and the C@S vibrations are difficultly localized. Thus, bands around
860 and 580 cmꢁ1 in both HL2 and 1b0 have its origin in strongly
coupled transitions involving the entire thiosemicarbazide chain.
Although this set of vibrations in complex 1b seems slightly shifted
80.72
86.56
86.54(7)
D95V basis set and for Re the Los Alamos ECP was employed. Fre-
quency and force constants were obtained and the minimum nat-
ure of each conformation was established. Table 1 includes a
comparison of the bond distances and angles while Fig. 4 shows
the structural overlay of the resulting geometries and those deter-
mined by X-ray studies.
In general, the predicted bond lengths and angles are in agree-
ment with the values based on the X-ray structure data. The largest
differences for HL2 are in the S(1)–C(1) and S(2)–C bond distances
and in the Re–S(1) and Re–Br(1) distances for the structure of 1b0.
Although these differences may come from the approximated char-
acter of the basis sets employed, more likely the influence of the
Table 2
Relevant interatomic distances (Å) and angles (°) for 2a, 2b, 2c and 2cꢀ(CH3)2CO.a
2a
2b
2c
2cꢀ(CH3)2CO
Re(1)–N(3)/N(3A)
Re(1)–S(1)/S(1A)
Re(1)–S(1)#1/S(1B)
Re(2)–N(3B)
Re(2)–S(1B)
Re(2)–S(1A)
N(1)/N(1A)–C(1)/C(1A)
N(1B)–C(1B)
C(1)/C1(A)–N(2)/N(2A)
C(1B)–N(2B)
N(2)/N(2A)–N(3)/N(3A)
N(2B)–N(3B)
C(2)/C(2A)–N(3)/N(3A)
C(2B)–N(3B)
2.203(10)
2.461(3)
2.553(3)
2.203(6)
2.4650(18)
2.5507(19)
2.214(8)
2.451(3)
2.558(3)
2.183(9)
2.454(3)
2.553(3)
1.351(12)
1.368(12)
1.320(13)
1.266(13)
1.394(11)
1.419(11)
1.264(12)
1.319(13)
1.786(11)
1.799(10)
2.188(5)
2.4517(18)
2.5508(18)
2.197(6)
2.4615(18)
2.5519(18)
1.358(9)
1.363(8)
1.281(8)
1.291(8)
1.394(7)
1.401(7)
1.303(8)
1.297(8)
1.794(7)
1.784(7)
1.346(10)
1.310(11)
1.327(10)
1.355(14)
1.753(10)
1.349(9)
1.280(9)
1.399(8)
1.303(9)
1.778(8)
S(1)/S(1A)–C(1)/C(1A)
S(1B)–C(1B)
N(3)/N(3A)–Re(1)–S(1)/S(1A)
N(3)/N(3A)–Re(1)–S(1)#1/S(1B)
S(1)/S(1A)–Re(1)–S(1)#1/S(1B)
N(3B)–Re(2)–S(1B)
79.0(3)
90.5(2)
81.95(8)
78.30(17)
91.91(16)
82.38(6)
78.6(2)
91.8(3)
82.14(10)
78.1(2)
95.6(4)
82.14(10)
97.85(10)
97.62(10)
77.97(14)
90.27(14)
82.51(6)
78.57(15)
90.28(14)
82.30(6)
97.58(6)
97.36(6)
N(3B)–Re(2)–S(1A)
S(1B)–Re(2)–S(1A)
Re(1)–S(1A)–Re(1)#1/Re(2)
Re(2)–S(1B)–Re(1)
a
Symmetry transformations used to generate equivalent atoms: #1 = ꢁx, y, ꢁz + 3/2.

2152
A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
and azomethinic nitrogen atoms (mode j
S,N3). However, the reac-
tion with an excess of NaOH affords, in addition to 2, some single
Table 3
Bond lengths [Å] and angles [°] for 3b.
crystals of a thiosemicarbazonate complex where the ligand is
j
thiadiazole ligand resulting of the cyclization of a thiosemicarba-
zone. Work is in progress to obtain amounts of this compound
and determine the mechanism of formation.
Re(1)–N(2A)
Re(1)–N(2B)
Re(1)–S(1A)
S(1A)–C(1A)
S(1B)–C(1B)
S(1B)–C(2B)
S(2A)–C(6A)
S(2A)–C(10A)
S(2B)–C(6B)
S(2B)–C(10B)
2.181(3)
2.204(3)
2.5408(12)
1.730(4)
1.740(4)
1.748(4)
1.764(4)
1.786(4)
1.765(4)
1.775(5)
N(1A)–C(1A)
N(1A)–C(9A)
N(3B)–C(2B)
N(3B)–N(2B)
N(2B)–C(1B)
N(3A)–C(2A)
N(3A)–N(2A)
N(2A)–C(1A)
N(1B)–C(1B)
N(1B)–C(9B)
1.322(4)
1.443(5)
1.289(4)
1.387(4)
1.320(4)
1.281(4)
1.379(4)
1.329(4)
1.318(5)
1.465(5)
S,N4. In this complex, the rhenium atom is also coordinated by a
3. Experimental
3.1. Materials and methods
N(2A)–Re(1)–N(2B)
N(2A)–Re(1)–S(1A)
N(2B)–Re(1)–S(1A)
C(2B)–N(3B)–N(2B)
C(1B)–N(2B)–N(3B)
C(2A)–N(3A)–N(2A)
83.26(10)
64.07(8)
86.22(8)
113.3(3)
112.8(3)
116.5(3)
C(1A)–N(2A)–N(3A)
C(1B)–N(1B)–C(9B)
N(1A)–C(1A)–N(2A)
N(1A)–C(1A)–S(1A)
N(2A)–C(1A)–S(1A)
114.7(3)
123.0(3)
124.4(3)
125.1(3)
110.5(2)
All solvents used for synthesis were dried over appropriate dry-
ing agents, degassed using a vacuum line and distilled under an Ar
atmosphere [49]. Adducts [ReX(CO)3(CH3CN)2] were synthesized
following Farona and Kraus’ published methods [50] from the cor-
responding [ReX(CO)5] [51].
Elemental analyses were carried out on a Fisons EA-1108. Melt-
ing points (mp) were determined on a Gallenkamp MFB-595 and
they are uncorrected. Mass spectra were recorded on a Hewlett–
Packard 5989A spectrometer operating under ESI conditions. Infra-
red spectra were recorded from KBr pellets on a Bruker Vector
22FT. The 1H NMR spectra were obtained on a Bruker ARX-400
spectrometer from acetone-d6 solutions.
to lower wavenumbers with the coordination in the complex 1b;
the results confirm the insensitive character of the C–S stretching
mode in the thiosemicarbazide group in the present ligands.
On the other hand, the tioether group in HL2 shows two stretch-
ing modes around 1023 cmꢁ1 and other weaker around 627 cmꢁ1
,
which are hardly modified with the coordination to the metal
centre.
3.2. General synthesis of the ligands HL1, HL2 and HL3
In summary, in this work we have described the synthesis of six
rhenium carbonyl halide complex and thiosemicarbazones derived
from 4-(methylthio)benzaldehyde (1). The corresponding thiose-
micarbazonate complexes (2) may be obtained using toluene as
solvent or by reaction of the complex with equimolecular amount
of NaOH. X-ray studies show that the thiosemicarbazone or thiose-
micarbazonate ligands form the five-membered chelate ring by
coordination to the rhenium by the usual mode, i.e., the sulfur
4-(Methylthio)benzaldehyde was dissolved in dry methanol
(30 mL) and added to a stirred solution of the corresponding thio-
semicarbazide in H2O (10 mL). The reaction mixture was heated
under reflux for 2 h and then cooled to room temperature, and a
precipitate was deposited within a few minutes. This resulting so-
lid was filtered off and dried under vacuum.
Fig. 4. Structural overlay calculated (red) and X-ray (CPK coloured) molecules of HL2 (A) and 1b0 (B). (For interpretation of the references to colour in this figure legend, the
reader is referred to the web version of this article.)

A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
2153
Table 4
Calculated vibrational wavenumbers (scaled) and measured infrared bands positions and assignments for HL2 and 1b0.
HL2
1b0
Theoretical
Exp.
405
Assignmenta
Theoretical
Exp.
Assignmenta
Int.
Int.
405
cring
432
476
481
497
501
519
539
43
29
13
35
432
471
476
491
c
c
c
NCNN, cN–H, cring
N–H,
c
c
CO
N–H,
CO
dCO,
dCO
dCO,
x
ring
498
507
532
547
567
23
8
54
0.5
103
509
540
550
x
ring, tMe
dNC(S)N, C–S2
NC(S)N
dNC(S)N
36
7
519
559
xring
m
dNC(S)N, mC–S2
c
m(N2–H)
604
606
615
623
660
666
60
33
22
20
3
617
634
c
c
c
m
m
CO,
CO,
CO,
CO, dNC(S)N
CMe–S2
c
c
c
NCNN
CNN
NC(S)N
627
1
m
Me–S2, dring
652
671
650
670
728
803
811
827
902
925
74
4
36
29
19
2
663
694
744
800
813
833
898
927
c
c
(N1–H),
ring
c
(NCN)
12
dNC(S)N, dring
dNC(S)N, dring
dring
719
727
831
841
881
922
966
985
7
2
725
748
825
868
875
910
966
1014
dNCNN, dring
c
c
c
ring, dCNN
ring
ring
c
ring
dCN, dring
(C–H)
Me–S
48
16
11
42
12
60
27
16
11
23
66
268
43
272
121
39
2
14
59
129
318
409
c
dCNN, dring
CH
Me–S
NN, CN,
q
c
936
979
c
m
m
ring
q
965
Me–N1, dNC(S)N
CPh–S2
m
m
c
ring
1023
1031
1113
1168
1190
1246
1385
1397
1404
1421
1443
1468
1044
1093
1161
1179
1262
1385
dNCNN
dNCNN,
dNCNN, dring
dring, dNCNN
dC–H, dN–H
1067
1082
144
25
1092
m
m
C–S2, dring
Me–N1, dNC(S)N
q
Me–N
dN–H,
Me–S
tMe–S
dN–H, dring
xMe(N)
1305
1322
1397
59
163
82
1338
1356
1394
dCN, dring
c
m
m
CN, dN–H
CN, dC–H
1402
1429
dN–H,
dN–H,
m
m
NN
CN
1515
1558
1568
1815
1855
1930
233
350
237
1012
904
711
1527
1550
1581
1876
1884
1907
dNH
dNH, mCN
1535
114
1532
mCN, dring
m
m
m
m
CN, dring
COas
COas
COs
am – stretching, d – in-plane bending,
c
– out-of-plane bending,
q
– rocking, t – torsion,
x
– wagging.
3.2.1. Data for HL1
3.2.3. Data for HL3
Thiosemicarbazide (455 mg, 5.00 mmol)/4-(methylthio)benzal-
dehyde (761 mg, 5.00 mmol). White solid. Yield: 1022 mg
(84.0%). M.p.: 199 °C. Anal. Calc. for C9H11N3S2 requires: C, 47.9;
H, 4.9; N, 18.7; S, 28.4. Found: C, 47.8; H, 4.9; N, 18.6; S, 28.1%.
Mass spectrum [m/z (%)]: 226.05 [M]+. IR data (KBr, cmꢁ1):
4-Phenyl-3-thiosemicarbazide (836 mg, 5.00 mmol)/4-(methyl-
thio)benzaldehyde (761 mg, 5.00 mmol). Yellow solid. Yield:
1123 mg (70.4%). M.p.: 185 °C. Anal. Calc. for C15H15N3S2 requires:
C, 59.7; H, 5.0; N, 13.9; S, 21.2. Found: C, 59.4; H, 5.1; N, 13.7; S,
21.0%. Mass spectrum [m/z (%)]: 302.08 [M]+. IR data (KBr, cmꢁ1):
3422s, 3384s, 3267m
m
(NH); 1593s; 815m. 1H NMR data (ppm):
3331s, 3151m m
(NH); 1594m; 810m. 1H NMR data (ppm): 10.64s
10.44s (1) d(N(2)–H); 8.13s (1) d(C(2)–H); 7.88s (1) d(N(1)–H);
7.73d (2) d(C(5,7)–H); 7.49s (1) d(N(1)–H); 7.29d (2) d(C(4,8)–H);
2.52s (3) d(S(CH3)–H).
(1) d(N(2)–H); 9.88s (1) d(N(1)–H); 8.22s (1) d(C(2)–H); 7.75d (2)
d(C(5,7)–H); 7.35d (2) d(C(4,8)–H); 7.80d (2) 7.36t(2) 7.19t(1)
d(N(1)–R1); 2.53s (3) d(S(CH3)–H).
Single colourless crystals were obtained after slow evaporation
of an acetone or DMSO solutions of the ligand.
3.2.2. Data for HL2
4-Methyl-3-thiosemicarbazide
(521 mg,
5.00 mmol)/4-
(methylthio)benzaldehyde (761 mg, 5.00 mmol). Pale-yellow solid.
Yield: 1148 mg (89.2%). M.p.: 190 °C. Anal. Calc. for C10H13N3S2 re-
quires: C, 50.2; H, 5.5; N, 17.6; S, 26.7. Found: C, 50.0; H, 5.3; N,
17.3; S, 25.5%. Mass spectrum [m/z (%)]: 240.06 [M]+. IR data
3.3. General synthesis of the complexes [ReX(CO)3(HLn)] (1)
To a solution of fac-[ReX(CO)3(CH3CN)2] (X = Cl, Br) in dry meth-
anol (15 mL) was added the corresponding equimolar quantity of
the ligand HLn. The mixture was heated under reflux for 2 h
(R = H, Me) and for 1 h (R = Ph), whereupon the colour changed
from colourless-pale yellow to deep yellow. The resulting solutions
were concentrated in vacuo to ca. 3 mL and stored at room temper-
ature after dropwise addition of diethyl ether until saturation. Yel-
low solids formed were filtered off and vacuum dried.
(KBr, cmꢁ1): 3352m, 3099m (NH); 1592s; 813m. 1H NMR data
m
(ppm): 10.36s (1) d(N(2)–H); 8.29s (1) d(N(1)–H); 8.09s (1)
d(C(2)–H); 7.69d (2) d(C(5,7)–H); 7.28d (2) d(C(4,8)–H); 3.14d (3)
d(C(9)–H); 2.52s (3) d(S(CH3)–H).
Single colourless crystals were obtained after slow evaporation
of the mother liquor.

2154
A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
Fig. 5. Comparison between the experimental FT-IR spectra and the theoretical results in HL2 (A) and 1b0 (B).
3.3.1. Data for 1a (HL1, X = Cl)
3.3.3. Data for 1b (HL2, X = Cl)
Yield: 63 mg (39.9%). M.p.: 193.7 °C. Anal. Calc. for
Yield: 124 mg (78.5%). M.p.: 187 °C. Anal. Calc. for
C12H11ClN3O3S2Re requires: C, 27.1; H, 2.1; N, 7.9; S, 12.0. Found:
C13H13ClN3O3S2Re requires: C, 28.6; H, 2.4; N, 7.7; S, 11.7. Found:
C, 27.4; H, 2.1; N, 7.8; S, 11.8%. Mass spectrum [m/z (%)]: 496
C, 28.9; H, 2.4; N, 7.7; S, 11.1%. Mass spectrum [m/z (%)]: 510
[MꢁCl]+. IR data (KBr, cmꢁ1): 3373m, 3273m, 3184m
m
(NH);
[MꢁCl]+. IR data (KBr, cmꢁ1): 3369m, 3212s
m(NH); 2022vs,
2025vs, 1900vs
m
(COfac); 1594s; 813w. 1H NMR data (ppm):
1919vs m
(COfac); 1594s; 811w. 1H NMR data (ppm): 12.16s (1)
12.32s (1) d(N(2)–H); 8.78s (1) d(C(2)–H); 8.20s (2) d(N(1)–H);
7.86d (2) d(C(5,7)–H); 7.40d (2) d(C(4,8)–H); 2.57s (3) d(S(CH3)–H).
d(N(2)–H; 8.81s (1) d(C(2)–H); 8.52s (0.5) 8.18s (0.5) d(N(1)–H);
7.83d (2) d(C(5,7)–H); 7.41d (2) d(C(4,8)–H); 3.17s (3) d(N(1)–
R1); 2.57s (3) d(S(CH3)–H).
3.3.2. Data for 1a0 (HL1, X = Br)
Yield: 50 mg (34.5%). M.p.: 190 °C. Anal. Calc. for
12H11BrN3O3S2Re requires: C, 25.1; H, 1.9; N, 7.3; S, 11.1. Found:
C
3.3.4. Data for 1b0 (HL2, X = Br)
C, 25.3; H, 1.8; N, 7.3; S, 10.8%. Mass spectrum [m/z (%)]: 574
Yield: 114 mg (72.2%). M.p.: 179.9 °C. Anal. Calc. for
13H13BrN3O3S2Re requires: C, 26.5; H, 2.2; N, 7.1; S, 10.8. Found:
[M]+, 496 [MꢁBr]+. IR data (KBr, cmꢁ1): 3374m, 3277m, 3189m
C
m(NH); 2025vs, 1922vs, 1895vs
m
(COfac); 1595s; 814w. 1H NMR
C, 26.6; H, 2.1; N, 7.1; S, 10.1%. Mass spectrum [m/z (%)]: 510
data (ppm): 12.35s (1) d(N(2)–H); 8.77s (1) d(C(2)–H); 8.23s (2)
d(N(1)–H); 7.78d (2) d(C(5,7)–H); 7.43d (2) d(C(4,8)–H); 2.57s (3)
d(S(CH3)–H).
[MꢁBr]+. IR data (KBr, cmꢁ1): 3406s, 3296s
m(NH); 2025vs,
1921vs, 1896vs
m
(COfac); 1592s; 814w. 1H NMR data (ppm):
12.13s (1) d(N(2)–H; 8.73s (1) d(C(2)–H); 8.20s (0.5) 8.08s (0.5)

A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
2155
d(N(1)–H); 7.77d (2) d(C(5,7)–H); 7.42d (2) d(C(4,8)–H); 3.17s (3)
d(N(1)–R1); 2.57s (3) d(S(CH3)–H).
Yellow single crystals of 1b0ꢀH2O suitable for X-ray diffraction
were obtained by slow evaporation of an acetone solution.
3.3.5. Data for 1c (HL3, X = Cl)
Yield: 76 mg (41.6%). M.p.: 213 °C. Anal. Calc. for
C18H15ClN3O3S2Re requires: C, 36.5; H, 2.3; N, 7.1; S, 10.5. Found:
C, 36.6; H, 2.5; N, 6.9; S, 10.5%. Mass spectrum [m/z (%)]: 572
[MꢁCl]+. IR data (KBr, cmꢁ1): 3398m, 3252m
m(NH); 2025vs,
1901vs m
(COfac); 1566s; 810w. 1H NMR data (ppm): 12.24s (1)
d(N(2)–H); 10.23s (1) d(N(1)–H); 8.87s (1) d(C(2)–H); 7.84d (2)
d(C(5,7)–H); 7.43d (2) d(C(4,8)–H); 7.50d(4) 7.39t(1) d(N(1)–
R1); 2.58s (3) d(S(CH3)–H).
3.3.6. Data for 1c0 (HL3, X = Br)
Yield: 96 mg (56.5%). M.p.: 213 °C. Anal. Calc. for
C18H15BrN3O3S2Re requires: C, 33.2; H, 2.3; N, 6.5; S, 9.8. Found:
C, 34.2; H, 2.2; N, 6.7; S, 9.2%. Mass spectrum [m/z (%)]: 572
[MꢁBr]+. IR data (KBr, cmꢁ1): 3433s, 3255m
m(NH); 2029vs,
1936vs, 1905vs
m
(COfac); 1565s; 810w. 1H NMR data (ppm):
12.26s (1) d(N(2)–H); 10.20s (1) d(N(1)–H); 8.86s (1) d(C(2)–H);
7.76d (2) d(C(5,7)–H); 7.44d (2) d(C(4,8)–H); 7.49d(4) 7.39t(1)
d(N(1)–R1); 2.57s (3) d(S(CH3)–H).
3.4. Synthesis of complexes [Re2(Ln)2(CO)6] (2)
3.4.1. Synthesis of [Re2(L1)2(CO)6] (2a)
A solution of [ReCl(CO)5] (100 mg, 0.26 mmol) and an equimo-
lar amount of HL1 (62.2 mg, 0.26 mmol) in dry toluene was
heated under reflux for 15 h. The pale yellow precipitate formed
was filtered out, washed with chloroform and vacuum dried. Sin-
gle yellow crystals of 2a suitable for X-ray diffraction were ob-
tained by slow evaporation of a methanol solution of 1a0. Yield:
113 mg (69.7%). M.p.: 292.1 °C. Anal. Calc. for C24H20N6O6S4Re2
requires: C, 29.1; H, 2.0; N, 8.5; S, 12.9. Found: C, 28.8; H, 1.7;
N, 8.3; S, 11.8%. Mass spectrum [m/z (%)]: 989 [M]+. IR data
(KBr, cmꢁ1): 3488s, 3381s
m(NH); 2023vs, 1921vs, 1901vs,
1882vs
m
(COfac); 1596s; 808w. 1H NMR data (ppm): 8.23s (1)
d(C(2)–H); 8.13d (2) d(C(5,7)–H); 7.11d (2) d(C(4,8)–H); 7.01s
(2) d(N(1)–H); 2.60s (3) d(S(CH3)–H).
3.4.2. Synthesis of [Re2(L2)2(CO)6] (2b)
To
a
solution of fac-[ReCl(CO)3(HL2)] (1b) (100 mg,
0.18 mmol) in methanol was added an excess of NaOH and the
mixture was heated under reflux for 2 h. The pale yellow precip-
itate formed was filtered out, washed with chloroform and vac-
uum dried. Single yellow crystals of 2b suitable for X-ray
diffraction were obtained by slow evaporation of a MeOH solu-
tion of 1b. Yield: 27 mg (42.2%). M.p.: >250 °C. Anal. Calc. for
C
26H24N6O6S4Re2 requires: C, 30.7; H, 2.4; N, 8.3; S, 12.6. Found:
C, 30.9; H, 2.2; N, 8.3; S, 11.6%. Mass spectrum [m/z (%)]: 1017
[M]+. IR data (KBr, cmꢁ1): 3428m
(NH); 2027vs, 2011vs,
1941vs, 1916vs
(COfac); 1577s; 810w. 1H NMR data (ppm):
m
m
8.22s (1) d(C(2)–H); 8.19d (2) d(C(5,7)–H); 7.28d (2) d(C(4,8)–
H); 7.10s (1) d(N(1)–H); 2.84s(3) d(N(1)–R1); 2.69d (3) d(C(6)–H).
3.4.3. Synthesis of [Re2(L3)2(CO)6] (2c)
To a solution of fac-[ReBr(CO)3(CH3CN)2] (100 mg, 0.23 mmol)
in methanol was added HL3 (70 mg, 0.23 mmol). The yellow-col-
oured solution was heated under reflux for 2 h. The resulting yel-
low precipitate was filtered out and vacuum dried. Single yellow
crystals of 2c and 2cꢀCH3COCH3 suitable for X-ray diffraction
were obtained directly from the mother liquor and by slow evap-
oration of an acetone solution of 2c, respectively. Yield: 100 mg

2156
A. Núñez-Montenegro et al. / Polyhedron 30 (2011) 2146–2156
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m
(NH); 2029vs, 2020vs, 1934vs, 1900vs, 1876vs m(COfac); 1588m;
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1000 diffractometer at 293 K using graphite monochromated Mo
Ka radiation (k = 0.71073 Å), and were corrected for Lorentz, polar-
ization and absorption effects [52]. The structures were solved by
direct methods using the program SHELXS97. All non-hydrogen
atoms were refined on F2 with anisotropic thermal parameters
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positions and refined as riders. Graphics were produced with PLA-
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In the present study, the geometries of the ligand and the com-
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(DFT) and the B3LYP functional. All atoms were described by a
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basis set and the LANL2DZ effective core potential.
Acknowledgements
This research was supported by the European Rural Develop-
ment Fund and the Spanish Ministry of Science and Innovation
through project CTQ2010-19386/BQU.
Appendix A. Supplementary data
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Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.ca-
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