Electrochemical synthesis and structural characterisation of cadmium and mercury complexes containing pyrimidine-2-thionate ligands

Article abstract of DOI:10.1002/ejic.200400848

The electrochemical oxidation of anodic metal (cadmium or mercury) in a cell containing an acetonitrile solution of the appropriate pyrimidine-2-thione (RpymSH) affords complexes [M(RpymS)₂] (M = Cd, Hg; R = 4-CF ₃, 4,6-CF₃,Me and 4,6-CF₃,Ph). When 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) was added to the electrolytic cell, adducts of cadmium and compounds with these coligands were obtained. All the compounds have been characterised by microanalysis, IR spectroscopy and, in the case of the compounds that were sufficiently soluble, by ¹H, ¹³C and ¹⁹⁹Hg NMR spectroscopy. The compounds [Cd(4-CF₃pymS)₂] (1), [Cd(4,6-CF ₃MepymS)₂(bipy)] (4), [Cd(4,6-CF₃PhpymS) ₂ (phen)] (6) and [Hg(4,6-CF₃MepymS)₂] (8) were also characterised by X-ray diffraction. Compound 1 presents a polymeric structure with the polymer chains interconnected by intermolecular C-H...N interactions. Compounds 4 and 6 adopt mononuclear structures, with weak inter- and intra-molecular C-H...π interactions, as well as π-π stacking interactions for compound 6. Compound 8 also presents a mononuclear structure with intermolecular π-π interactions between the pyrimidine rings and additional weak Hg...Hg contacts (3.484 A). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Full text of DOI:10.1002/ejic.200400848

FULL PAPER
Electrochemical Synthesis and Structural Characterisation of Cadmium and
Mercury Complexes Containing Pyrimidine-2-thionate Ligands
Antonio Rodríguez,[a] Antonio Sousa-Pedrares,[a] José A. García-Vázquez,[a]
Jaime Romero,[a] and Antonio Sousa*[a]
Dedicated to Professor V. I. Minkin on the occasion of his 70th birthday
Keywords: Cadmium / Electrochemistry / Heterocycles / Mercury / S ligands
The electrochemical oxidation of anodic metal (cadmium or
mercury) in a cell containing an acetonitrile solution of the
appropriate pyrimidine-2-thione (RpymSH) affords com-
plexes [M(RpymS)2] (M = Cd, Hg; R = 4-CF3, 4,6-CF3,Me and
(phen)] (6) and [Hg(4,6-CF3MepymS)2] (8) were also charac-
terised by X-ray diffraction. Compound 1 presents a poly-
meric structure with the polymer chains interconnected by
intermolecular C–H···N interactions. Compounds 4 and 6
4,6-CF3,Ph). When 2,2Ј-bipyridine (bipy) or 1,10-phenan- adopt mononuclear structures, with weak inter- and intra-
throline (phen) was added to the electrolytic cell, adducts of
cadmium and compounds with these coligands were ob-
tained. All the compounds have been characterised by micro-
analysis, IR spectroscopy and, in the case of the compounds
that were sufficiently soluble, by 1H, 13C and 199Hg NMR
spectroscopy. The compounds [Cd(4-CF3pymS)2] (1),
[Cd(4,6-CF3MepymS)2(bipy)] (4), [Cd(4,6-CF3PhpymS)2-
molecular C–H···π interactions, as well as π–π stacking inter-
actions for compound 6. Compound 8 also presents a mono-
nuclear structure with intermolecular π–π interactions be-
tween the pyrimidine rings and additional weak Hg···Hg
contacts (3.484 Å).
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
However, in comparison with the coordination chemistry
of transition metals, the chemistry of the main-group metals
with sulfur ligands remains much less developed.[18–22] In
many cases, the interaction of toxic metals with biological
systems involves bonding of the metal to the sulfydryl
groups present in enzymes. Hence, an insight into the chem-
istry of main-group thiolate compounds is important in
terms of understanding the aforementioned interaction and
for the design of detoxifying agents.[23,24] The generally
poor solubility of group 12 metal thiolate compounds
makes it difficult to structurally characterise these systems.
As part of our continuing interest in the chemistry of
sterically hindered thiolates,[25] we report here the electro-
chemical synthesis and characterisation of Cd and Hg com-
plexes with a number of substituted pyrimidine-2-thiones
(Scheme 1). This type of ligand, besides having solubilising
and bulky groups that might modify the degree of aggrega-
tion as a result of steric constraints, is one of the most ver-
satile sulfur ligands. These ligands can act as follows: (a) a
neutral monodentate ligand coordinated through the sulfur
atom,[26] through one of the nitrogen atoms,[27] and as a
bridging ligand through sulfur[28] or as an N,S-chelating li-
gand,[29,30] and (b) as an anionic ligand, in which case it
can be monodentate through the sulfur atom,[31] as an N,S-
chelating ligand,[32] as a binuclear bridging ligand through
Introduction
The chemistry of metal–sulfur complexes has attracted
much interest over the past decade because of the potential
relevance of such compounds to active sites in metalloen-
zymes and also for their ability to adopt geometries of vari-
able nuclearity and great structural complexity.[1–7] These
latter features are the result of the tendency of thiolate li-
gands to bridge metal centres to yield oligomeric or poly-
meric species, a situation that makes it difficult to obtain
and isolate crystals suitable for X-ray diffraction studies. It
has been shown[8–10] that the degree of association depends
intimately on both the reaction conditions and the nature
of the thiolate ligands. Moreover, these association phe-
nomena may be limited by incorporating steric constraints
by appropriate ligand design or introducing coligands to
block a number of coordination sites around the metal. Re-
cently, a great deal of effort has been made[11–17] to modify
the thiolate ligand by introducing a solubilizing group or a
bulky substituent that might modify the aggregation pro-
cess.
[a] Departamento de Química Inorgánica, Universidad de Santi-
ago de Compostela,
15782, Santiago de Compostela, Spain
2242
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200400848
Eur. J. Inorg. Chem. 2005, 2242–2254

Cadmium and Mercury Complexes Containing Pyrimidine-2-thionate Ligands
FULL PAPER
nitrogen and sulfur,[33] or sulfur only,[34] as a binuclear triply ing coligand to the cell. The compounds are air-stable and
bridging ligand through sulfur and one of the nitrogens[35] moderately soluble in organic non-polar solvents, but solu-
or the two nitrogen and sulfur atoms,[36,37] and as a trinu- ble in dimethyl sulfoxide or N,NЈ-dimethylformamide.
clear triply bridging system.[38]
The values of the electrochemical efficiency, defined as
the amount of metal dissolved per unit of charge, were close
to 0.5 molF–1 regardless of the presence or absence of ad-
ditional ligand. This observation, along with the evolution
of hydrogen at the cathode, is compatible with the following
mechanism:
Cathode: 2 RpymSH + 2 e–Ǟ 2 RpymS– + H2
Anode: M + 2 RpymS– Ǟ [M(RpymS)2] + 2 e–
(M = Cd, Hg)
Scheme 1.
In addition, and in order to reduce the nuclearity of the
homoleptic cadmium(ii) complexes, didentate N,NЈ-donor
coligands, such as 2,2Ј-bipyridine or 1,10-phenanthroline,
were added to the electrochemical cell. This modification
results in the preparation of monomeric mixed cadmium(ii)
complexes in one step.
or
M + 2 RpymS– + L Ǟ [M(RpymS)2L] + 2 e–
(M = Cd; L = bipy, phen)
Results and Discussion
Crystallographic Studies
Cadmium and mercury complexes of general formula
[M(RpymS)2] (M = Cd and Hg; R = 4-CF3, 4,6-CF3,Me
and 4,6-CF3,Ph) were easily prepared in reasonable yields
Crystal and Molecular Structure of [Cd(4-CF3pymS)2] (1)
Figure 1 shows a perspective view of compound 1 along
by a simple, one-step electrochemical method. Mixed com- with the atomic labelling scheme used. A selection of bond
plexes of cadmium with 2,2Ј-bipyridine or 1,10-phenan- lengths and angles (with estimated standard deviations) are
throline were also obtained by addition of the correspond- given in Table 1.
Figure 1. ORTEP diagram of the structure of [Cd(4-CF3pymS)2]x (1), showing 40% thermal ellipsoid probability. The hydrogen atoms and
the CF3 groups on C(5) and C(10) have been omitted for clarity. Symmetry codes: #1 = –x + 2, –y, –z + 1; #2 = –x + 1, –y, –z + 1.
Eur. J. Inorg. Chem. 2005, 2242–2254
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2243

A. Rodríguez, A. Sousa-Pedrares, J. A. García-Vázquez, J. Romero, A. Sousa
FULL PAPER
Table 1. Selected bond lengths [Å] and angles [°] for [Cd(4- the ligand is coordinated in a way that is closer to the thion-
CF3pymS)2] (1).[a]
ato form than to the thione form of the free ligand.
The packing structure of 1 (Figure 2) shows that every
polymeric chain interacts with two parallel chains in the b
direction through non-classical C–H···N hydrogen bonds.
These interactions link the polymeric chains through weak
C(8)–H···N(2) hydrogen bonds. The hydrogen bonds involve
the uncoordinated pyrimidine nitrogen atoms, N(2), on
alternate ligands in one chain that are parallel to one an-
other and also parallel to the chain with the pyrimidyl pro-
tons bond at C(8) atom on ligands in the adjacent chains,
which are again parallel between themselves but almost per-
pendicular to the first ones. The bond lengths and angles
in this system are as follows: C···N = 3.422(7) Å, N···H =
2.58 Å and C–H···N = 150.3°.
Cd(1)–N(3)
Cd(1)–S(2)#1
Cd(1)–S(1)
S(2)–C(6)
N(3)–Cd(1)–S(2)#1
N(3)–Cd(1)–S(1)#2
2.336(4)
2.6347(12) Cd(1)–S(1)#2
2.6777(12) Cd(1)–S(2)
1.745(4)
96.89(11)
97.31(9)
Cd(1)–N(1)
2.457(4)
2.6733(11)
2.8011(11)
1.755(5)
S(1)–C(1)
N(1)–Cd(1)–S(2)#1 158.73(10)
N(1)–Cd(1)–S(1)#2 92.70(8)
N(3)–Cd(1)–S(1)
S(2)#1-Cd(1)–S(1)
N(3)–Cd(1)–S(2)
S(2)#1-Cd(1)–S(2)
S(1)–Cd(1)–S(2)
S(2)#1-Cd(1)–S(1)#2 99.56(3)
156.88(11)
99.54(4)
60.63(9)
89.76(4)
103.15(3)
N(1)–Cd(1)–S(1)
S(1)#2-Cd(1)–S(1)
N(1)–Cd(1)–S(2)
S(1)#2-Cd(1)–S(2)
61.71(9)
95.89(3)
85.41(8)
157.13(4)
[a] Symmetry codes: #1 = –x + 2, –y, –z + 1; #2 = –x + 1, –y, –z
+ 1.
The compound consists of polymeric chains along the a
axis with the cadmium atom hexacoordinated by two nitro-
gen atoms from two different thionate ligands and four
bridging sulfur atoms. Each ligand chelates one cadmium
metal and bridges an adjacent cadmium atom through the
exocyclic sulfur. A second ligand is almost perpendicular to
the first one and also chelates this cadmium atom and brid-
ges to the next cadmium atom in the chain. Each thionate
ligand acts as a binuclear triply bridging μ2-S,N(η2-S;η1-N)
five-electron-donor ligand: each atom of cadmium is in a
highly distorted [CdN2S4] octahedral environment with the
nitrogen atoms in cis positions. The bond angles between
the metal and the donor atoms that are in a trans disposi-
tion are in the range 151.6(3)–167.1(3)°, far from the ideal
value of 180°. The values for the angles described by the
donors in the cis positions are much lower than those ex-
Figure 2. The crystal packing of 1 viewed along the c axis. Dashed
lines show the C–H···N interactions.
These interactions result in the formation of layers paral-
pected for a regular octahedron, with values for the S–Cd– lel to the crystallographic ab plane that stack along the c
N angles of 61.1(3)° and 61.3(3)°.
axis.
A comparison of the structures of cadmium complexes
Three of the four Cd–S bond lengths are very similar and
are in the range 2.6347(12)–2.6777(12) Å. The other Cd–S with different pyridine and pyrimidine-2-thiones clearly
distance is longer at 2.8011(11) Å. These values are within demonstrates that the degree of aggregation depends to a
the range observed for other complexes containing CdN2S4 large extent on the steric effects created by the ligand sub-
units with μ2-S,N(η2-S;η1-N) bridging ligands; for example stituents. Thus, while the complex with pyridine-2-thione
2.638(6)–2.761(8) Å in the hexanuclear complex [{Cd(4,6- consists of [Cd(pyS)2]x,[41] a polymeric chain structure, the
Me2pymS)2}6][35] and 2.647–2.777 Å in other hexacoordi- increased steric constraints introduced by the methyl groups
nate thionate complexes.[39,40] However, the range for these in the case of 4,6-dimethylpyrimidine-2-thione reduce the
distances in the complex [Cd(pyS)2],[41] which has a similar tendency for polymerisation and the complex obtained is
chain structure, is much wider [2.543(5)–3.038(4) Å].
hexanuclear [Cd(4,6-Me2pymS)2]6.[35] The metal atom in
The Cd–N bond lengths of 2.336(4) and 2.457(4) Å are the latter complex is hexacoordinate as in [Cd(pyS)2]x.[41]
A
also close to the values found in other octahedral complexes higher degree of steric hindrance, such as in 3-trimethylsi-
of cadmium containing heterocyclic thionates as ligands; lylpyridine-2-thione, produces a dimer [Cd(3-Me3Sipyt)2]2,[45]
for example 2.42(2) and 2.53(2) Å in [Cd(pymS)2(phen)],[42] with each cadmium atom in a five-coordinate environment.
[Cd(4,6-CF3MepymS)2(bipy)] and [Cd(4,6-CF3PhpymS)2- In the case of 4-trifluoromethylpyrimidine-2-thione, the
(phen)] (see below).
presence of a CF3 group in the 4-position produces greater
The S–C bond lengths of 1.755(5) and 1.745(4) Å are in- steric hindrance than in pyridine-2-thione, but less hin-
termediate between the value found in free 4,6-dimethylpyr- drance than in 4,6-dimethylpyrimidine-2-thione. However,
imidine-2-thione[30] [1.686(4) Å] and 1-phenyl-4,6-dimeth- the steric hindrance introduced by the CF3 group is not
ylpyrimidine-2-thione[29] [1.676(2) Å], which exist in the sufficient to reduce the aggregation level and the complex
thione form in the solid state, and the values of 1.781(2) Å is also polymeric as in [Cd(pyS)2]x.[41] Naturally, other fac-
and 1.782(3) Å found in bis(2-pyrimidyl) disulfide[43] and tors such as reaction conditions, kinetic factors, nature of
bis(4,6-dimethyl-2-pyrimidyl) disulfide,[44] both of which the solvent, etc., can also play a role in the aggregation
possess a simple C–S bond. This observation suggests that process.[25,45]
2244
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2242–2254

Cadmium and Mercury Complexes Containing Pyrimidine-2-thionate Ligands
FULL PAPER
Molecular Structures of [Cd(4,6-CF3MepymS)2(bipy)] (4)
and [Cd(4,6-CF3PhpymS)2(phen)] (6)
Table 2. Selected bond lengths [Å] and angles [°] for [Cd(4,6-
CF3MepymS)2bipy] (4).[a]
Cd–N(3)
N(3)–C(7)
N(3)–C(11)
S–C(l)
N(3)–Cd–N(3)#l
N(3)#l-Cd–S
S–Cd–S#l
S–Cd–N(l)#l
N(3)#l-Cd–N(l)
S#l-Cd–N(l)
2.38(3)
1.25(4)
1.38(5)
1.68(3)
69.9(14)
94.2(8)
109.4(6)
118.5(6)
86.8(9)
118.5(6)
N(2)–C(2)
Cd–S
Cd–N(l)
1.35(4)
2.523(10)
2.56(2)
Figure 3 and Figure 4 show perspective views of com-
pounds 4 and 6, respectively, together with the atomic label-
ling schemes used. A selection of bond lengths and angles
(with estimated standard deviations) are given in Table 2
and Table 3, respectively.
The cadmium atoms in both 4 and 6 are located on a
twofold rotation axis; accordingly, their asymmetric units
contain one half of the bipyridine (4) or phenanthroline (6)
ligand, one pyrimidine-2-thionate ligand and one half of
the cadmium atom.
N(3)–Cd–S
150.9(7)
94.2(8)
86.8(9)
90.6(10)
63.5(7)
176.9(14)
N(3)–Cd–S#l
N(3)–Cd–N(l)#l
N(3)–Cd–N(l)
S–Cd–N(l)
N(l)#l-Cd–N(l)
[a] Symmetry code: #1 = –x, –y, z.
Figure 3. ORTEP diagram of the molecular structure of [Cd(4,6-CF3MepymS)2(bipy)] (4), with 40% thermal ellipsoid probability. The
hydrogen atoms have been omitted for clarity. Symmetry code: #1 = –x, –y, z.
Figure 4. ORTEP diagram of the molecular structure of [Cd(4,6-CF3PhpymS)2(phen)] (6), with 30% thermal ellipsoid probability. The
hydrogen atoms have been omitted for clarity. Symmetry code: #1 = –x + 2, y, –z + 1/2.
Eur. J. Inorg. Chem. 2005, 2242–2254
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2245

A. Rodríguez, A. Sousa-Pedrares, J. A. García-Vázquez, J. Romero, A. Sousa
FULL PAPER
Table 3. Selected bond lengths [Å] and angles [°] for [Cd(4,6-
CF3PhpymS)2phen] (6).[a]
Cd(1)–N(3)#1
Cd(1)–S(1)
Cd(1)–N(1)
S(1)–C(1)
2.378(4)
2.4758(17)
2.570(4)
1.533(6)
Cd(1)–N(3)
Cd(1)–S(1)#1
Cd(1)–N(1)#1
2.378(4)
2.4758(17)
2.570(4)
N(3)#1-Cd(1)–N(3) 70.62(19)
N(3)#1-Cd(1)–S(1) 113.99(10)
N(3)–Cd(1)–S(1)#1 113.99(10)
N(3)#1-Cd(1)–N(1) 87.86(12)
N(3)–Cd(1)–S(1)
S(1)–Cd(1)–S(1)#1
N(3)–Cd(1)–N(1)
94.92(10)
144.89(11)
136.46(11)
S(1)–Cd(1)–N(1)
59.18(8)
S(1)#1-Cd(1)–N(1) 104.96(9)
S(1)–Cd(1)–N(1)#1 104.96(9)
N(3)–Cd(1)–N(1)#1 87.86(12)
N(1)–Cd(1)–N(1)#1 130.17(16)
[a] Symmetry code: #1 = –x + 2, y, –z + 1/2.
In both cases the molecular structure consists of discrete
molecular species, which shows that the presence of an ad-
ditional didentate coligand inhibits the polymerisation of
the complexes. In both compounds the cadmium atom is
hexacoordinated by the chelating nitrogen donors of the co-
ligand (bipy or phen) and two anionic pyrimidine-2-thion-
ate ligands, which also act in a didentate chelating (S,N)
manner.
The cadmium atom in compound 4 is in a distorted
[CdS2N4] octahedral environment. The disposition of the
ligands in 4 is such that the sulfur atoms occupy cis posi-
tions. The equatorial plane of the molecule can be consid-
Figure 5. Distorted trigonal-prismatic environment for [Cd(4,6-
CF3PhpymS)2(phen)] (6).
ered as being formed by the two nitrogen atoms from the [N(3) and N(3#1)] can be explained by the formation of a
2,2Ј-bipyridine molecule and two sulfur atoms from pyrimi- rigid five-membered chelating ring, while the pyrimidine-2-
dine-2-thionato ligands; these four atoms are not exactly thionate ligands form four-membered rings.
coplanar. In terms of the best plane that includes these four
The Cd–S bond lengths [2.523(10) for 4 and 2.4578(17) Å
donor atoms and the cadmium centre, the atoms N(3) and for 6] are similar to those found in other octahedral com-
S, which occupy trans positions, are both below this plane pounds of cadmium(ii) with heterocyclic thionate ligands
(by –0.514 and –0.318 Å respectively), while the atoms [2.588–2.5331 Å].[42,46] The Cd–NpymS bond lengths
N(3#1) and S(#1) are located above this plane (by +0.514 [2.56(2) Å and 2.570(4) Å for 4 and 6, respectively] are
and +0.318 Å respectively). The cadmium atom, however, clearly longer than those involving the metal and the nitro-
is in the plane defined above.
gen atoms of the bipyridine in 4 or phenanthroline in 6
These deviations produce N(3)–Cd–S and N(3#1)–Cd– [Cd–Nbipy = 2.38(3) Å and Cd–Nphen = 2.378(4) Å]. This
S(#1) bond angles of 150.9(7)°, which differ from the ideal situation is probably due to the fact that the chelate coordi-
value of 180°. In addition, the small angles of the chelate nation of the thionate ligand gives rise to a four-membered
rings, together with the elongation in the axial direction, ring, which causes an elongation of the C–N bond as the
cause the S–Cd–SЈ and S–Cd–N(3#1) angles to deviate sig- interaction with sulfur is more favourable and the thionate
nificantly from 90° [109.4(6) and 94.2(8)°, respectively].
ligand is rigid. However, these Cd–Nbipy and Cd–Nphen
In complex 6 the disposition of the 4-trifluoromethyl-6- bond lengths [2.38(3) Å] do not differ significantly from
phenylpyrimidine-2-thionate ligands differs from that found those found in other octahedral cadmium(ii) 2,2Ј-bipyridine
in [Cd(4,6-CF3MepymS)2(bipy)] (4). As in compound (4), and 1,10-phenanthroline complexes.[42,46]
the cadmium atom in 6 is also in a [CdS2N4] environment,
The thionate ring is nearly planar and the exocyclic sul-
although in this case the geometry is best described as dis- fur atom is also in the same plane. Other structural charac-
torted trigonal prismatic. This can clearly be seen by inspec- teristics of the thionate ligand and the 2,2Ј-bipyridine or
tion of the twist angle between the two parallel faces of the 1,10-phenanthroline unit are as one would expect and do
coordination polyhedron, as shown in Figure 5. These val- not warrant further discussion.
ues are 14.2° for N(3) and N(3#1), 10.5° for N(1) and S(1)
Compound 6 shows a wide variety of intra- and intermo-
and 10.5° for N(1#1) and S(1#1). The expected values are lecular interactions that involve the π clouds of the aromatic
0° for a regular trigonal-prismatic geometry and 60° for an rings.
octahedral one.
A view of the crystal packing of this compound is shown
In the structure, the three didentate ligands (two pyrimi- in Figure 6. Each molecule in the crystal lattice interacts
dine-2-thionates and one phenanthroline) link the two tri- with four neighbouring molecules: two through the phenan-
angular faces of the trigonal prism. The higher value of throline groups and two through the pyrimidine rings. Only
14.2° for the twist angle involving the phenanthroline ligand the interactions between the phenanthroline rings are
2246
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2242–2254

Cadmium and Mercury Complexes Containing Pyrimidine-2-thionate Ligands
FULL PAPER
shown in the figure (upper part of Figure 6). The crystal
packing is such that the phenanthroline rings are opposite
one another and π–π stacking occurs between the outer
rings of each phenanthroline unit (distance between
centroids = 3.597 Å). The rings of the phenanthroline
groups involved in the π interactions are arranged in such
a way that the six atoms of the ring do not completely
eclipse those of the other ring, meaning that the interaction
is not “perfect face alignment” but “offset or slipped stack-
ing” (distances between the corresponding atoms of the two
rings of 3.587, 3.588 and 3.616 Å). Figure 7 shows a view
perpendicular to the planes of the phenanthroline groups.
Figure 8. A view of complex 6 showing intramolecular C–H···π
bonds and intermolecular π–π interactions between phenyl rings.
It can be seen from Figure 8 that, besides the π–π stack-
ing interactions discussed above, each molecule in the crys-
tal lattice is involved in two other interactions through the
π clouds of the aromatic rings of the heterocyclic thione:
one of these interactions is intramolecular and the other is
intermolecular. The intramolecular interaction is of the C–
H···π type and occurs between the protons ortho to the
phenanthroline nitrogen (the most acidic protons in this
unit) and the phenyl groups in the 6-position of the pyrimi-
dine rings (H–centroid distance = 3.135 Å; C–centroid dis-
tance = 4.060 Å; C–H–centroid angle = 173.70°). It is inter-
esting to note the high level of directionality of this interac-
tion. In this situation each molecule is involved in two iden-
tical interactions of this type due to the presence of two
pyrimidine units in each molecule.
As far as the intermolecular interaction is concerned,
each pyrimidine ring takes part in a π–π stacking interac-
tion with a phenyl ring in the 6-position of a pyrimidine
ring in a neighbouring molecule. This π–π stacking interac-
tion is of the most common offset or slipped-stacking type.
This type of interaction is characterised by a distance be-
tween the centroids of the rings in question of about 3.8 Å.
In the case under discussion here the distance between the
centroids is 3.764 Å (the distances between the correspond-
ing atoms ranges between 3.637 and 3.899 Å).
Figure 6. Crystal packing diagram of 6; intermolecular π–π stack-
ing interactions between phenanthroline rings are represented by
dashed lines.
The compounds [Cd(4,6-CF3MepymS)2(bipy)] (4) and
[Cd(4,6-CF3PhpymS)2(phen)] (6) (Figure 9) have different
groups in the 6-position of the pyrimidine rings and, conse-
quently, the disposition of the pyrimidine ligands in the two
complexes is very different. These differences are clear when
one considers the dihedral angles R–C–CЈ–RЈ, where R or
Figure 7. Overlapping between phenanthroline rings of three neigh-
bouring molecules in 6.
A view of the interactions between one molecule in the RЈ is the group in the 6-position (Me or Ph) and C or CЈ
crystal lattice and neighbouring molecules through the pyr- is the carbon atom in the 6-position of the ring to which
imidine rings is shown in Figure 8 (see also lower part of the substituent is attached. These angles have values of
Figure 6).
110.0° when R = Me and 175.8° when R = Ph.
Eur. J. Inorg. Chem. 2005, 2242–2254
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2247

A. Rodríguez, A. Sousa-Pedrares, J. A. García-Vázquez, J. Romero, A. Sousa
FULL PAPER
Table 4. Selected bond lengths [Å] and angles [°] [Hg(4,6-CF3Me-
pymS)2] (8).[a]
Hg–S#l
Hg–S
N(2)–C(2)
N(2)–C(1)
S–C(l)
2.330(2)
2.330(2)
1.320(9)
1.325(7)
1.752(6)
180.0
90.0
90.0
90.0
90.0
N(1)–C(4)
Hg–N(1)
Hg–Hg#2
Hg–Hg#3
1.325(9)
2.773(6)
3.4845(5)
3.4845(5)
1.333(9)
114.3(8)
120.6(6)
115.1(6)
122.3(6)
115.2(7)
122.6(7)
N(1)–C(1)
S#l-Hg–S
N(2)–C(2)–C(6)
C(3)–C(2)–C(6)
C(2)–C(3)–C(4)
N(1)–C(4)–C(3)
N(1)–C(4)–C(5)
C(3)–C(4)–C(5)
S#l-Hg–Hg#2
S–Hg–Hg#2
S#l-Hg–Hg#3
S–Hg–Hg#3
Hg#2-Hg–Hg#3
C(l)-S–Hg
180.0
94.2(2)
[a] Symmetry codes: #1 = –x + 1, –y + 1, –z + 1; #2 = –x + 1, y,
–z + 1/2; #3 = –x + 1, y, –z + 3/2.
In compound 8 the whole molecule, except F(2), lies on
a mirror plane (symmetry code #4) and the mercury atom
is located on a centre of symmetry (symmetry code #1);
accordingly, the asymmetric unit contains one pyrimidine-
2-thionate ligand (apart from one of the fluorine atoms of
the CF3 group) and one half of the mercury atom. In the
molecule, the mercury atom is bonded to two sulfur atoms
in a linear disposition. The Hg–S bond length [2.330(2) Å]
is very similar to those found in other thionatomercury
complexes with a linear geometry.[11,47–49]
In the complex the two ligands are on different sides of
the line defined by the S–Hg–S bonds, and the pyrimidine
rings are in a staggered conformation. The ligands are ori-
ented in such a way that the N(1) atom is close to the mer-
cury atom (distance of 2.773 Å). This value is larger than
those observed in other mercury complexes containing het-
erocyclic donor nitrogen ligands, such as [Hg(pyS)(OAc)][50]
(2.210 Å) or [HgMepy](NO3)[51] [2.12(2) Å], but shorter
than the sum of the van der Waals radii (3.23 Å),[52] and
Figure 9. Views of complexes 4 (top) and 6 (bottom) illustrating
the disposition of the pyrimidine rings.
Molecular structure of [Hg(4,6-CF3MepymS)2] (8)
Figure 10 shows a view of compound 8 together with the comparable to the distances in other mercury thiolate com-
atomic numbering scheme. Selected bond lengths and plexes characterised by weak intramolecular Hg···N interac-
angles (with estimated deviations) are given in Table 4.
tions (2.798–2.980 Å).[46,53–55]
Figure 10. ORTEP diagram of the molecular structure of [Hg(4,6-CF3MepymS)2] (8), with 50% thermal ellipsoid probability. Symmetry
codes: #1 = –x + 1, –y + 1, –z + 1; #4 = x, y, –z + 1.
2248
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2242–2254

Cadmium and Mercury Complexes Containing Pyrimidine-2-thionate Ligands
FULL PAPER
The Hg···Hg distance [3.4845(5) Å] is much longer than rotated with respect to the adjacent ring, meaning that the
those found in elemental mercury[56] (3.02 Å), in mercury groups present on one ring do not eclipse those on other
clusters with mercury in an oxidation state of zero or in rings. This situation can clearly be seen in the diagram be-
dinuclear mercury(i) complexes (Hg22+, 2.5 Å).[57] However, low (Scheme 2), which shows a view perpendicular to the
the distance is close to or shorter than the sum of the van plane of the pyrimidine rings (along the crystallographic c
der Waals radii (1.7–2.0 Å)[58] and even shorter than that axis).
observed in most other mercury(ii) complexes (3.848–
3.578 Å).[59–63] It is also similar to the shortest Hg···Hg dis-
tance found in the case of tris(1,3-dimethyluracil-5-yl)mer-
curioxonium salt, which dimerises in two different ways
through weak Hg···Hg contacts [Hg···Hg distances in the
range 3.4552(6) to 3.5974(5) Å].[64]
The pyrimidine rings are planar and the sulfur atoms are
located in the same plane as the corresponding ring and the
Hg atom. The S–C bond length (1.752 Å) is close to those
found in many other complexes containing thionate ligands.
Scheme 2.
Each [Hg(4,6-CF3MepymS)2] unit is essentially planar
given that the pyrimidine ring is planar and both rings in
each unit are related by an inversion centre located on the
Spectroscopic Data
mercury atom. The pyrimidine rings of each unit are paral-
lel to the crystallographic ab plane. In the crystal packing
of the complex these units are arranged parallel to one an-
IR Spectra
The IR spectra of the complexes do not show bands due
to ν(N–H), which in the free ligands appear between 3200
and 3050 cm–1. This shows that deprotonation of the NH
group has occurred during the synthesis and, therefore, that
the ligand is coordinated in the thionato form. This conclu-
sion is supported by the shift to smaller wavenumbers of
the strong bands for ν(C=C) and ν(C=N), which appear
at 1600–1550 and 1570–1525 cm–1, respectively, in the free
ligands, on going from the free ligands to the complexes. In
addition, bands attributable to the ring breathing vibration
at ca. 1000 and 630 cm–1 are observed. These shifts provide
evidence that the nitrogen atom is bound to the metal
atom.[65,66] In addition, the mixed complexes show bands
typical for coordinated 2,2Ј-bypyridine[67] (770 and
730 cm–1) and 1,10-phenanthroline[67,68] (1530–1505, 840
and 720 cm–1).
other (Figure 11). The units are not superimposable but are
related through a rotation of 180° around an axis that
passes through the Hg centres and is parallel to the b axis,
followed by a translation about the c axis (1 – x, y, z +
0.5). In this arrangement the molecules are stacked in the
direction of the crystallographic c axis. Two types of inter-
molecular interaction are responsible for the packing ar-
rangement. On the one hand, an Hg–Hg interaction exists
between two units and this results in the Hg atoms being in
a linear arrangement parallel to the c axis (Hg–Hg distance
= 3.484 Å). On the other hand, a π–π stacking interaction
exists between the pyrimidine rings of the contiguous
[Hg(4,6-CF3MepymS)2] units (distance between the
centroids = 3.512 Å). In this case the π–π stacking interac-
tion gives rise to “perfect facial alignment”, as shown by
the angle formed by the centroids of the three consecutive
rings (165.56°). This angle is very close to the 180° that one
would expect for a complete interaction. It should also be
noted that, for each interaction of this type, each ring is
NMR Spectra
1
The H NMR spectra of the complexes do not contain a
signal for the NH proton of the free ligand, which shows
that the ligands are deprotonated in the complexes. The sig-
nals of all the protons of the pyrimidine ring and phenyl or
methyl groups in the complexes are slightly shifted with re-
spect to those of the free ligands. The NMR spectra of
mixed complexes show additional signals for 2,2Ј-bipyridine
and 1,10-phenanthroline at around δ = 7.6–9.2 ppm. These
signals are slightly shifted to lower field in comparison to
the corresponding signals in the free ligands. These changes
again provide evidence of coordination of the ligands to the
metal atom through the nitrogen atoms.[69–71] The 13C
NMR spectra of the free ligands 4,6-CF3MepymSH and
4,6-CF3PhpymSH show double the expected number of sig-
nals for C(2), C(6), CF3 and CH3, as the free ligands exist
in two tautomeric forms. This doubling in the number of
signals is not observed in the 13C NMR spectra of the metal
complexes. This situation provides evidence that, in solu-
Figure 11. Partial packing diagram of 8 showing intermolecular π–
π interactions and weak Hg···Hg contacts.
Eur. J. Inorg. Chem. 2005, 2242–2254
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2249

A. Rodríguez, A. Sousa-Pedrares, J. A. García-Vázquez, J. Romero, A. Sousa
FULL PAPER
Elemental analysis was performed with a Carlo–Erba EA micro-
analyser. IR spectra were recorded as KBr mulls on a Bruker IFS-
66V spectrophotometer. 1H and 13C NMR spectra were recorded
on a Bruker AMX 300 MHz instrument with CDCl3 or [D6]DMSO
as solvent. Chemical shifts are given relative to TMS as the internal
standard. 119Hg NMR spectra were recorded on a Bruker AMX500
spectrometer with CDCl3 as solvent. The mass spectra (FAB) were
recorded on a Micromass Autospec spectrometer, with 3-nitroben-
zyl alcohol as the matrix material.
tion, the ligand is coordinated to the metal in the thionate
form only.
The mercury complexes have δ(199Hg) values in the δ =
–1180 to –1213 ppm range. These values are similar to those
found in other mercury(ii) thionates in which a weak inter-
action between the metal atom and the heterocyclic nitro-
gen is observed.[11,49]
Mass Spectra
[4,6-CF3MepymSH]: This compound was obtained by direct reac-
tion between thiourea (2.428 g, 32 mmol) and 1,1,1-trifluoro-2,4-
pentanedione (5 g, 32 mmol) in ethanol in the presence of concen-
trated hydrochloric acid (1 mL) as a catalyst. The mixture was
heated under reflux for 2 h and the resulting dusty yellow solid was
filtered off. C6H5F3N2S (194.17): calcd. C 37.11, H 2.60, N 14.43,
The cadmium and mercury complexes were also charac-
terised by mass spectrometry using the positive-ion FAB
technique in 3-nitrobenzyl alcohol (NBA) as matrix. The
FAB spectra of [Cd(RpymS)2(bipy)] and [Cd(RpymS)2-
(phen)] show the molecular ion with the appropriate isotope
distribution, as well as peaks due to the fragments produced
by the loss of one and two thionate ligands. In the case of
[Cd(4,6-CF3MepymS)2(phen)] the peak due to the loss of
the 1,10-phenanthroline is also observed at m/z = 294.
The FAB mass spectra of both of the mercury com-
pounds, [Hg(RpymS)2], show the molecular ion peak at
m/z = 561 (R = CF3) and 589 (R = 4,6-CF3,Me) along
with peaks at m/z = 381 and 386, respectively, which are
associated with [Hg(RpymS)] formed by loss of one thion-
ate ligand.
S 16.51; found C 36.89, H 2.60, N 14.26, S 16.08. IR (KBr): ν =
˜
3100–3200 (m, br), 1615 (vs), 1590 (vs), 1440 (m), 1350 (vs), 1320
(w), 1200(s, br), 1130 (m), 1100 (m), 1030 (w), 970 (s), 920 (m), 860
(w), 850 (m), 705 (w), 660 (w), 595 (w), 570 (w), 530 (m), 510 (w),
1
470 (m), 450 (m), 370 (w) cm–1. H NMR (300 MHz, [D6]DMSO,
25°): δ = 14.40 (s, 1 H, NH), 7.19 (s, 1 H, H5), 2.39 (s, 3 H, CH3)
ppm. 13C NMR (300 MHz, [D6]DMSO): δ = 181.00 and 172.13 (s,
C2), 155.86 and 153.72 (q 2J
= 35 Hz, C4), 104.89 (s, C5),
13C-19
F
163.61 (s, C6), 119.27 and 119.67 (q, 1J
F = 275 Hz, CF3), 23.45
13C-19
and 18.46 (s, CH3) ppm. MS (FAB): m/z = 194 (4,6-CF3Me-
pymSH).
[4,6-CF3PhpymSH]: The precursor 1,1,1-trifluoro-4-phenyl-3-
buten-2-one was prepared previously. Benzaldehyde (5.22 g,
49 mmol) and 1,1,1-trifluoroacetone (5.21 g, 49 mmol) were added
to a solution of NaOH (9.93 g, 0.25 mol) in cold water (200 mL).
The mixture was allowed to reach room temperature, stirred for 6 h
and finally heated to 65 °C for 12 h. The organic compounds were
extracted with CH2Cl2, dried (MgSO4) and the solvent removed by
vacuum distillation to give a colourless liquid. (yield: 3.81 g, 39%).
1H NMR (300 MHz, CDCl3): δ = 6.8 (d, olefinic protons), 6.9 (d,
olefinic protons), 7.3 (m, Ph) ppm. 13C NMR (300 MHz, [D6]-
DMSO): δ = 180.53 (q, CF3), 150.44 (CO), 115–130 (C, phenyl
ring), 34.42 and 38.42 (C, olefinic) ppm.
Conclusions
In this report we have described the electrochemical syn-
thesis of a series of homoleptic and heteroleptic neutral cad-
mium(ii) complexes and homoleptic mercury complexes
with pyrimidine-2-thione derivatives. The ligands differ in
the nature, position and number of substituents in the het-
erocyclic ring.
In the case of [Cd(4-CF3pymS)2] (1), the presence of the
trifluoromethyl substituent is not sufficient to prevent the
association process and, as a consequence, the compound
is a polymer, with the metal atom in an [S4N2] octahedral
environment. However, the presence of coligands, such as
Dry ethanol (40 mL) was placed in a flame-dried round-bottomed
flask purged with argon, and sodium (0.45 g, 19.9 mmol) was
added at 0 °C. When effervescence had ceased, a solution of thio-
1,10-phenanthroline and 2,2Ј-bipyridine, in the coordina- urea (0.38 g, 4.99 mmol) in dry ethanol (30 mL) was added by can-
nula and the mixture was stirred for 15 min at room temperature.
A solution of the previously prepared 1,1,1-trifluoro-4-phenyl-3-
buten-2-one (1 g, 5 mmol) in dry ethanol was added to the reaction
mixture by cannula. The mixture was heated under reflux under
argon for 24 h. When the reaction was complete, the solvent was
removed and the resultant solid was added to water (50 mL). The
suspension was filtered and the alkaline solution was acidified to
pH 6 with AcOH. The resulting dusty yellow solid was filtered off
and washed with water until the washings were neutral. The solid
was dried under vacuum to give 1.1 g of a dusty orange solid. The
product was recrystallized from ethanol to give an orange solid.
Yield: 0.652 g (51%). C11H7F3N2S (256.25): calcd. C 51.50, H 2.75,
N 10.93, S 12.51; found C 51.40, H 2.81, N 11.02, S 12.39. IR
tion sphere of cadmium modifies the aggregation process
and the complexes [Cd(4,6-CF3MepymS)2bipy] (4) and
[Cd(4,6-CF3PhpymS)2bipy] (6) are monomers with the me-
tal atom in a different [S2N4] hexacoordinate environment
for both compounds − distorted octahedral for 4 and dis-
torted trigonal prismatic for 6. The crystal packing of com-
pound 6 shows the presence of C–H···π and π–π stacking
interactions. The groups involved in the C–H···π interac-
tions are in the 6-position of the pyrimidine rings.
Experimental Section
(KBr): ν = 3100–3200 (m, br), 1645 (m), 1610 (s), 1570 (s), 1550
˜
General Considerations: 4-Trifluoromethylpyrimidine-2-thione,
1,1,1-trifluoroacetone, 1,1,1-trifluoro-2,4-pentanedione, thiourea,
benzaldehyde, 1,10-phenanthroline and 2,2Ј-bipyridine are all com-
mercial products and were used as supplied. Cadmium (Aldrich)
was used as 2 × 2 cm plates. Mercury metal, a commercial product,
was washed with nitric acid and water prior to use.
(m), 1530 (m), 1490 (m), 1460 (m), 1450 (w), 1390 (vs), 1350 (m),
1330 (m), 1310 (w), 1260 (s), 1190 (vs), 1140 (m), 1110 (m), 1000
(s), 970 (w), 900 (m), 870 (w), 830 (s), 720 (m), 710 (w), 690 (s),
630 (m), 580 (m), 470 (w), 410 (w) cm–1. 1H NMR (300 MHz, [D6]-
DMSO): δ = 13.0 (s, 1 H, NH), 7.8 (s, 1 H, H5), 7.6 (m, Ph) ppm.
13C NMR (300 MHz, [D6]DMSO): δ = 169.30 (s, C2), 167.31 (q,
2250
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2242–2254

Cadmium and Mercury Complexes Containing Pyrimidine-2-thionate Ligands
FULL PAPER
C4), 110.42 (s, C5), 163.85 (s, C6), 118.54 (q, CF3), 122.98–135.32
860 (m), 840 (s), 830 (s), 815 (s), 770 (m), 720 (vs), 665 (s), 635 (m),
460 (w), 430 (w), 415 (w), 350 (w), 310 (w) cm–1. 1H NMR
(300 MHz, [D6]DMSO): δ = 7.60 (d, 2 H, H5), 8.60 (d, 2 H, H6);
phen: 8.87 (d, 2 H, H2/H9), 7.80 (dd, 2 H, H3/H8), 8.80 (d, 2 H, H7/
H4), 8.00 (s, 2 H, H6/H5) ppm. 13C NMR (300 MHz, [D6]DMSO): δ
= 170.12 (C2), 162.11 (C6), 154.21 (C4), 114.96 (C5), 127 (q, CF3),
149.62 (phen, C9/C2), 139.80 (phen, C4b/C6b), 139.33 (C4/C7),
128.74 (phen, C4a/C6a), 127.05 (phen, C5/C6), 125.13 (phen, C3/C8)
ppm. MS (FAB): m/z = 471 [Cd(4-CF3pymS)(phen)], 650 [Cd(4-
CF3pymS)2(phen)].
(phenyl ring) ppm. MS: m/z = 257.2 [M+], 511 [M2+].
Electrochemical Synthesis: All complexes were obtained by an elec-
trochemical procedure.[25] The cell was a 100-mL, tall-form beaker
fitted with a rubber bung. An acetonitrile solution of the thione
containing tetraethylammonium perchlorate (10 mg) was electro-
lysed using a platinum wire as the cathode and a cadmium plate as
a sacrificial anode suspended from another platinum wire. For the
synthesis of mercury compounds, the anode, which was in the bot-
tom of the vessel, was also connected through a platinum wire. For
the synthesis of mixed complexes, the corresponding co-ligand was
added to the solution phase. In all cases, hydrogen was evolved at
the cathode. The cells can be summarised as M(+)/CH3CN +
RpymSH + LЈ/Pt(–). During the electrolysis the yellow colour of
the solution faded and, at the end of the reaction, the solids were
isolated by filtration.
[Cd(4,6-CF3MepymS)2(bipy)] (4): Electrolysis of an acetonitrile
solution containing 4,6-CF3MepymSH (0.200 g, 1.03 mmol) and
bipyridine (0.080 g, 0.51 mmol) at 10 mA and 32 V for 2.75 h dis-
solved 73 mg of cadmium (Ef = 0.56). At the end of the experiment
the yellow solid was filtered off, washed with acetonitrile and di-
ethyl ether, and dried in vacuo. The compound was characterised
as
[Cd(4,6-CF3MepymS)2(bipy)].
Yield:
0.128 g
(38%).
[Cd(4-CF3pymS)2] (1): Electrochemical oxidation of a cadmium an-
ode in a solution of 4-(trifluoromethyl)pyrimidine-2-thione (4-
CF3pymSH; 0.150 g, 0.83 mmol) in acetonitrile (50 mL) at 14 V
and 10 mA for 1.5 h caused 36 mg of cadmium to be dissolved (Ef
= 0.52 molF–1). During the electrolysis hydrogen was evolved at
the cathode and at the end of the experiment a crystalline solid,
suitable for X-ray studies, had formed at the bottom of the vessel.
The yellow solid was filtered off, washed with acetonitrile and di-
ethyl ether and dried under vacuum. Yield: 0.102 g (52%).
C10H4CdF6N4S2 (470.69): calcd. C 25.5, H 0.9, N 11.9, S 13.6;
C22H16CdF6N6S2 (654.93): calcd. C 40.3, H 2.5, N 12.8, S 9.8;
found C 40.7, H 2.3, N 12.9, S 9.6. IR (KBr): ν = 1590 (m), 1565
˜
(vs), 1540 (vs), 1465 (m), 1435 (s), 1380 (vs), 1360 (m), 1310 (m),
1270 (vs), 1255 (s), 1220 (m), 1190 (m), 1135 (s), 1100 (m), 1010
(m), 1000 (m), 970 (m), 910 (m), 845 (s), 760 (s), 730 (m), 705 (s),
645 (w), 540 (m), 460 (w), 405 (w) cm–1. 1H NMR (300 MHz,
CDCl3): δ = 2.53 (s, 6 H, CH3), 6.87 (s, 2 H, H5); bipy: 8.91 (d, 2
H, H6/H6Ј), 7.82 (dd, 2 H, H5/H5Ј), 8.05 (dd, 2 H, H4/H4Ј), 8.23 (d,
2 H, H3/H3Ј) ppm. 13C NMR (300 MHz, CDCl3): δ = 184.07 (C2),
169.13 (C6), 155.17 (q, C4), 109.57 (s, C5), 24.33 (s, CH3), 122.49
(q, CF3), 150.62 (bipy, C2/C2Ј), 150.03 (bipy, C6/C6Ј), 140.17
(bipy; C5/C5Ј), 126.4 (bipy, C3/C3Ј), 112.8 (bipy, C4/C4Ј) ppm. MS
(FAB): m/z = 463 [Cd(4,6-CF3MepymS)(bipy)], 499 [Cd(4,6-CF3-
MepymS)2], 655 [Cd(4,6-CF3MepymS)2(bipy)].
found C 25.5, H 0.8, N 12.0, S 13.6. IR (KBr): ν = 1570 (s), 1550
˜
(vs), 1420 (m), 1345 (s), 1325 (vs), 1200 (s), 1175 (m), 1145 (m),
1110 (s), 830 (vs), 780 (m), 730 (s), 670 (s), 470 (m), 440 (m) cm–1.
1H NMR (300 MHz, [D6]DMSO): δ = 7.37 (d, 1 H, H5), 8.53 (d,
1 H, H6) ppm. 13C NMR (300 MHz, [D6]DMSO): δ = 183.34 (C2),
168.68 (C6), 154.17 (q, C4), 114.95 (C5), 120 (q, CF3) ppm.
Crystals of [Cd(4,6-CF3MepymS)2(bipy)] (4) suitable for X-ray
studies were obtained by recrystallisation of the initial product
from iPrOH.
[Cd(4-CF3pymS)2(bipy)] (2): Electrolysis of an acetonitrile solution
containing 4-CF3pymSH (0.150 g, 0.83 mmol), 2,2Ј-bipyridine
(0.065 g, 0.42 mmol) and a small amount of tetraethylammonium [Cd(4,6-CF3MepymS)2(phen)] (5): An acetonitrile solution of 4,6-
perchlorate (ca. 10 mg) at 10 mA and 16 V for 1.5 h dissolved
26 mg of cadmium (Ef = 0.44). At the end of the experiment the
white solid was filtered off, washed with acetonitrile and dried in
vacuo. The compound was characterised as [Cd(4-CF3pymS)2-
(bipy)] (2). Yield: 0.142 g (55%) C20H12CdF6N6S2 (626.88): calcd.
C 38.3, H 1.9, N 13.4, S 10.2; found C 38.0, H 1.9, N 13.5, S 10.2.
CF3MepymSH (0.200 g, 1.03 mmol) and phenanthroline (0.100 g,
0.55 mmol) was electrolysed at 10 mA during 2.75 h and 68 mg of
cadmium was dissolved from the anode (Ef = 0.53). At the end of
the electrolysis the solution was concentrated and the resulting
green solid was filtered off, washed with cold acetonitrile and di-
ethyl ether, dried under vacuum and identified as [Cd(4,6-CF3Me-
pymS)2(phen)]. Yield: 0.269 g (79%). C24H16CdF6N6S2 (678.95):
calcd. C 42.3, H 2.4, N 12.4, S 9.4; found C 42.0, H 2.4, N 12.6, S
IR (KBr): ν = 1585 (m), 1550 (vs), 1475 (w), 1460 (w), 1430 (m),
˜
1415 (s), 1335 (vs), 1240 (w), 1200 (vs), 1165 (w), 1150 (w), 1130
(m), 1110 (m), 1010 (m), 970 (m), 830 (m), 820 (m), 760 (s), 730 (m),
670 (s), 645 (w), 620 (w) cm–1. 1H NMR (300 MHz, [D6]DMSO): δ
9.0. IR (KBr): ν = 1570 (s), 1540 (vs), 1525 (w), 1505 (m), 1420
˜
(m), 1385 (vs), 1360 (s), 1300 (m), 1270 (vs), 1255 (vs), 1220 (m),
= 7.21 (d, 2 H, H5), 8.51 (d, 2 H, H6); bipy: 9.10 (d, 2 H, H6/H6Ј), 1175 (s), 1160 (m), 1005 (w), 970 (w), 915 (m), 840 (s), 770 (w), 725
7.60 (dd, 2 H, H5/H5Ј), 8.10 (dd, 2 H, H4/H4Ј), 8.80 (d, 2 H, H3/ (s), 705 (vs), 630 (w), 545 (m), 460 (m) cm–1. H NMR (300 MHz,
1
H3Ј) ppm. 13C NMR (300 MHz, [D6]DMSO): δ = 168.67 (C2),
[D6]DMSO): δ = 7.09 (s, 2 H, H5), 2.06 (s, 6 H, CH3); phen: 9.22
162.10 (C6), 154.45 (q, C4), 121 (q, CF3), 114.9 (C5), 149.12 (bipy,
(dd, 2 H, H2/H9), 8.80 (d, 2 H, H4/H7), 8.01 (dd, 2 H, H8/H3), 8.2
C2/C2Ј); 139.16 (bipy, C5/C5Ј), 125.38 (bipy, C3/C3Ј), 118.55 (bipy, (s, 2 H, H5/H6) ppm. 13C NMR (300 MHz, [D6]DMSO): δ = 184.07
C4/C4Ј) ppm. MS (FAB): m/z = 448 [Cd(4-CF3pymS)(bipy)], 627 (C2), 169.13(C6), 155.42 (q, C4), 122.50 (q, CF3), 109.34 (C5), 24.40
[Cd(4-CF3pymS)2(bipy)].
(CH3), 150.15 (phen, C9/C2), 141.82 (phen, C4b/C6b), 139.29 (phen,
C4/C7), 129.62 (phen, C4a/C6a), 127.50 (phen, C5/C6), 125.39(phen,
C3/C8) ppm. MS (FAB): m/z = 180 [phen], 294 [Cdphen], 487
[Cd(4,6-CF3MepymS)(phen)], 499 [Cd(4,6-CF3MepymS)2], 679
[Cd(4,6-CF3MepymS)2(phen)].
[Cd(4-CF3pymS)2(phen)] (3): A similar experiment to that described
above (12 V, 10 mA, 1.5 h) with 4-CF3pymSH (0.150 g, 0.83 mmol)
and phenanthroline (0.084 g, 0.467 mmol) in acetonitrile (50 mL)
dissolved 27 mg of cadmium (Ef = 0.46). The solid was filtered off,
washed with cold acetonitrile and diethyl ether, and dried under
vacuum. Yield: 0.122 g (45%). C22H12CdF6N6S2 (650.90): calcd. C
40.6, H 1.9, N 12.9, S 9.8; found C 40.6, H 1.8, N 12.9, S 9.9. IR
[Cd(4,6-CF3PhpymS)2(phen)] (6):
A similar experiment (6 V,
10 mA, 1 h) with 4,6-CF3PhpymSH (0.100 g, 0.55 mmol) and phen
(0.035 g, 0.19 mmol) in acetonitrile (50 mL) dissolved 18 mg of
(KBr): ν = 1610 (m), 1580 (m), 1550 (vs), 1525 (w), 1510 (w), 1500 cadmium (Ef = 0.48). Crystals suitable for X-ray studies were ob-
˜
(s), 1480 (m), 1415 (vs), 1335 (vs), 1320 (m), 1190 (s), 1160 (m),
1130 (w), 1110 (w), 1095 (w), 1070 (w), 1010 (m), 985 (m), 970 (w),
tained directly from the cell. The solid was filtered off, washed with
cool acetonitrile and diethyl ether, and dried under vacuum. Yield:
Eur. J. Inorg. Chem. 2005, 2242–2254
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2251

A. Rodríguez, A. Sousa-Pedrares, J. A. García-Vázquez, J. Romero, A. Sousa
FULL PAPER
0.119 g (36%). C34H20CdF6N6S2 (803.08): calcd. C 50.8, H 2.5, N C6), 155.60 (q, C4), 118.70 (CF3), 112.58 (s, C5), 24.40 (s, CH3)
10.4, S 8.0; found C 50.4, H 2.3, N 10.4, S 7.9. IR (KBr): ν = 1615
ppm. 119Hg NMR (500 MHz, CDCl3): δ = –1207 ppm. MS (FAB):
˜
(s), 1559 (m), 1540 (w), 1515 (w), 1500 (m), 1430 (w), 1400 (w), m/z = 386 [Hg(4,6-CF3MepymS)], 588 [Hg(4,6-CF3MepymS)2], 386
1380 (vs), 1318 (s), 1300 (m), 1241 (m), 1180 (s), 1150 (s), 1135 (s), [Hg(4,6-CF3MepymS)].
1000 (s), 840 (m), 810 (w), 780 (s), 720 (w), 730 (m), 715 (w), 700
1
(m), 650 (w), 640 (m) cm–1. H NMR (300 MHz, [D6]DMSO): δ =
8.41 (s, 2 H, H5); phen: 9.07 (dd, 2 H, H2/H9), 8.79 (d, 2 H, H4/
H7), 8.00 (dd, 2 H, H3/H8), 8.20 (s, 2 H, H5/H6) ppm; signals at δ
= 7.39–7.84 ppm were assigned to the phenyl group.
Crystallisation from ethanol/acetone gave monocrystals suitable for
X-ray studies.
X-ray Crystal Structure Determinations: X-ray data were collected
on a Bruker Smart CCD 1000 diffractometer for 1 and 6, and on
an Enraf–Nonius CAD4 diffractometer in the cases of 4 and 8,
with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å).
The data were collected at 293 K for all structures. The ω-scan
technique was employed to measure intensities for all crystals. De-
composition of the crystals did not occur during data collection.
Absorption effects in compounds 1 and 6 were corrected with SA-
DABS.[72] Absorption in 4 and 8 was corrected by semi-empirical
Ψ scans. All the structures were solved by direct methods and re-
fined[73] by full-matrix least-squares based on F2. For all the com-
plexes, hydrogen atoms were also included in idealised positions
and refined with isotropic displacement parameters. All non-hydro-
gen atoms in the structures were refined anisotropically with the
exception of compound 4, in which only the heavy atoms (mercury
and sulfur) were refined anisotropically due to the poor quality of
the high-angle data. The CF3 groups of compounds 1 and 6 are
disordered over two positions with occupancies 51:49 and 57:43 for
the groups on C(5) and C(10) in compound 1 and 63:37 for the CF3
group in compound 6. Atomic scattering factors and anomalous
dispersion corrections for all atoms were taken from the Inter-
national Tables for X-ray Crystallography.[74] The crystal data and
summary of data collection and structure refinement for these com-
pounds are given in Table 5. The structures were visualised with
ORTEP3.[75]
[Hg(4-CF3pymS)2] (7): A solution of acetonitrile (50 mL) contain-
ing 4-CF3pymSH (0.150 g, 0.83 mmol) was electrolysed at 10 mA
during 2 h. No precipitation occurred initially, but within several
hours a white solid had formed and this was filtered off, washed
with acetonitrile, dried and identified by elemental analysis. Yield:
0.096 g (41%). C10H4F6HgN4S2 (558.87): calcd. C 21.5, H 0.7, N
10.0, S 11.5; found C 22.0, H 0.6, N 10.3, S 11.2. IR (KBr): ν =
˜
1550 (vs), 1420 (s), 1350 (vs), 1330 (vs), 1280 (w), 1200 (s), 1175
(w), 1110 (s), 1005 (w), 975 (s), 845 (m), 830 (m), 750 (w), 730 (m),
1
670 (s), 630 (w), 455 (w), 365 (w) cm–1. H NMR (300 MHz, [D6]
DMSO): δ = 7.43 (d, 2 H, H5), 8.61 (d, 2 H, H6) ppm. 13C NMR
(300 MHz, [D6]DMSO): δ = 176.95 (C2), 160.45 (C6), 153.85 (q,
C4), 111.98 (C5), 121.49 (q, CF3) ppm. 119Hg NMR (500 MHz
CDCl3): δ = –1213 ppm. MS (FAB): m/z = 560 [Hg(4-CF3pymS)2],
381 [Hg(4-CF3pymS)].
[Hg(4,6-CF3MepymS)2] (8): A similar procedure was used to that
described for [Hg(4-CF3pymS)2]. 4,6-CF3MepymSH (0.200 g,
1.03 mmol) was electrolysed at 10 mA during 2 h. At the end of the
experiment a microcrystalline white solid had formed and this was
filtered off, washed with acetonitrile, dried and identified by ele-
mental analysis. Yield: 0.114 g (38%). C12H8F6HgN4S2 (587.94):
calcd. C 24.6, H 1.4, N 9.6, S 11.0; found C 24.6, H 1.2, N 9.5, S
11.1. IR (KBr): ν = 1580 (vs), 1535 (s), 1385 (vs), 1310 (w), 1270
˜
(s), 1255 (m), 1220 (m), 1170 (m), 1140 (m), 1110 (m), 1025 (w),
975 (m), 920 (w), 865 (s), 845 (s), 780 (w), 750 (w), 710 (vs), 680 CCDC-240151–240154 (for 1, 4, 6 and 8, respectively) contain the
1
(w), 635 (w), 565 (w), 550 (m), 485 (w), 450 (w), 370 (w) cm–1. H
supplementary crystallographic data for this paper. These data can
NMR (300 MHz, CDCl3): δ = 7.18 (s, 2 H, H5), 2.47 (s, 6 H, CH3) be obtained free of charge from The Cambridge Crystallographic
ppm. 13C NMR (300 MHz, CDCl3): δ = 177.13 (s, C2), 170.80 (s, Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Table 5. Crystal data and structure refinement for 1, 4, 6 and 8.
1
4
6
8
Empirical formula
Formula mass
Crystal System
Space group
a [Å]
b [Å]
c [Å]
C10H4CdF6N4S2
470.69
C22H16CdF6N6S2
C17H10Cd0.50F3N3S
401.54
monoclinic
C2/c
23.3377(11)
13.6311(7)
10.5163(5)
90
108.391(1)
90
3174.6(3)
8
1.680
0.891
1600
C12H8F6HgN4S2
654.93
orthorhombic
Aba2
15.911(3)
17.930(4)
9.098(2)
90
90
90
2595.5(9)
4
1.676
587.94
orthorhombic
Ibam
7.632(2)
31.855(6)
6.969(1)
90
90
90
1684.3(6)
4
2.301
triclinic
¯
P1
7.0419(2)
10.3710(4)
11.3981(3)
81.768(1)
78.624(1)
70.736(1)
767.63(4)
2
α [°]
β [°]
γ [°]
Volume [Å3]
Z
Dc [Mgm–3]
μ(Mo-Kα) [mm–1]
F(000)
2.036
1.758
452
1.069
1296
9.395
1096
Crystal size [mm]
T [K]
No. of reflections collected 5131
0.25 × 0.05 × 0.05
293
0.42 × 0.26 × 0.06
293
748
0.35 × 0.20 × 0.10
293
10 808
0.80 × 0.25 × 0.05
293
893
No. of indept. reflections
3674
432
1.069
0.0836
0.1958
3908
1.052
0.0570
0.1476
484
1.064
0.0212
0.0493
Goodness of fit on F2
0.956
0.0481
0.1092
R[a]
wR2[b]
[a] R = Σ(|Fo| – |Fc|)/Σ|Fo|. [b] wR2 = {Σ[w(|Fo|2 – |Fc|2)2]/Σ(w|Fo2|2)}1/2
.
2252
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2242–2254

Cadmium and Mercury Complexes Containing Pyrimidine-2-thionate Ligands
FULL PAPER
[34]
[35]
Y. K. Au, K. K. Cheung, W. T. Wong, J. Chem. Soc. Dalton
Trans. 1995, 1047–1057.
R. Castro, J. A. García-Vázquez, J. Romero, A. Sousa, R. Prit-
chard, C. McAuliffe, J. Chem. Soc. Dalton Trans. 1994, 1115–
1120.
Acknowledgments
We thank the Ministerio de Educación y Cultura of Spain and the
Xunta de Galicia for financial support.
[36]
[37]
[38]
A. Rodríguez, J. A. García-Vázquez, A. Sousa-Pedrares, J. Ro-
mero, A. Sousa, Inorg. Chem. Commun. 2003, 6, 619–622.
A. Rodríguez, J. A. García-Vázquez, A. Sousa-Pedrares, J. Ro-
mero, A. Sousa, J. Organomet. Chem. 2004, 689, 557–563.
R. Castro, M. L. Durán, J. A. García-Vázquez, J. Romero, A.
Sousa, E. E. Castellano, J. Zukerman-Schpector, J. Chem. Soc.
Dalton Trans. 1992, 2559–2563.
L. Raston, A. H. White, Aust. J. Chem. 1976, 29, 739–742.
A. McCleverty, S. Gill, R. S. Z. Kowalski, N. A. Bailey, H. Ad-
ams, K. W Lumbard, M. A. Murphy, J. Chem. Soc. Dalton
Trans. 1982, 493–503.
B. Hursthouse, O. F. Z. Khan, M. Mazid, M. Moteralli, P. O.
O’Brien, Polyhedron 1990, 9, 541–544.
R. Castro, M. L. Durán, J. A. García-Vázquez, A. Sousa, A.
Castiñeiras, W. Hiller, J. Strähle, Z. Naturforsch. 1992, 47b,
1067–1074.
[1] E. S. Raper, Coord. Chem. Rev. 1985, 61, 115–184.
[2] E. S. Raper, Coord. Chem. Rev. 1996, 153, 199–225.
[3] E. S. Raper, Coord. Chem. Rev. 1997, 165, 475–567.
[4] B. Krebs, G. Henkel, Angew. Chem. Int. Ed. Engl. 1991, 30,
769–788.
[5] I. G. Dance, Polyhedron 1986, 5, 1037–1104.
[6] P. G. Blower, J. R. Dilworth, Coord. Chem. Rev. 1987, 76, 121–
185.
[7] J. R. Dilworth, J. Hu, Adv. Inorg. Chem. 1993, 40, 411–459.
[8] K. Tang, M. Aslam, E. Block, T. Nicholson, J. Zubieta, Inorg.
Chem. 1987, 26, 1488–1497.
[9] E. Block, M. Gernon, H. Kang, S. Liu, J. Zubieta, J. Chem.
Soc. Chem. Commun. 1988, 1031–1033.
[10] E. Block, M. Gernon, H. Kang, G. Ofori-Okai, J. Zubieta, In-
org. Chem. 1989, 28, 1263–1271.
[11] E. Block, M. Brito, M. Gernon, D. McGowty, H. Kang, J.
Zubieta, Inorg. Chem. 1990, 29, 3172–3181.
[12] I. Casals, P. González-Duarte, J. Sola, J. Vives, M. Font-Bardia,
X. Solans, Polyhedron 1990, 9, 769–771.
[13] E. Block, M. Gernon, H. Kang, S. Liu, J. Zubieta, Inorg. Chim.
Acta 1990, 167, 143–146.
[39]
[40]
[41]
[42]
[43] S. Furberg, J. Solbakk, Acta Chem. Scand. 1973, 27, 2536–
2542.
[44]
[45]
J. A. Castro, J. Romero, J. A. García-Vázquez, A. Castiñeiras,
A. Sousa, Polyhedron 1995, 14, 2841–2847.
R. Castro, J. A. García-Vázquez, J. Romero, A. Sousa, A. Cas-
tiñeiras, W. Hiller, J. Strähle, Inorg. Chim. Acta 1993, 211, 47–
54.
[14] E. Block, M. Gernon, H. Kang, G. Ofori-Okai, J. Zubieta, In-
org. Chem. 1991, 30, 1736–1747.
[15] E. Block, G. Ofori-Okai, H. Kang, J. Zubieta, Inorg. Chim.
Acta 1991, 188, 7–13.
[16] W. Wojnowski, B. Becker, L. Walz, K. Peters, E.-M. Peters,
H. G. von Schnering, Polyhedron 1992, 11, 607–612.
[17] H.-O. Stephan, G. Henkel, Inorg. Chim. Acta 1994, 219, 1–2.
[18] A. Sousa-Pedrares, I. Casanova, J. A. García-Vázquez, M. L.
Durán, J. Romero, A. Sousa, J. Silver, P. J. Titler, Eur. J. Inorg.
Chem. 2003, 678–686.
[19] D. Dakternieks, K. Jurkschat, R. Tozer, J. Hook, E. R. S. Tiek-
ink, Organometallics 1997, 16, 3696–3706.
[20] J. Fernández, M. B. Hurthouse, M. Laguna, R. Terrota, J. Or-
ganomet. Chem. 1999, 574, 207–212.
[21] S. R. Foley, G. P. A. Yap, D. S. Richeson, J. Chem. Soc. Dalton
Trans. 2000, 1663–1668.
[22] R. Jurkschat, V. Pieper, S. Seemeyer, M. Schurmanm, M. Bies-
mans, I. Verbruggen, R. Willem, Organometallics 2001, 20,
868–880.
[46]
[47]
[48]
[49]
A. Sousa-Pedrares, J. Romero, J. A. García-Vázquez, M. L.
Durán, I. Casanova, A. Sousa, Dalton Trans. 2003, 1379–1388.
E. S. Gruff, S. A. Koch, J. Am. Chem. Soc. 1990, 112, 1245–
1247.
P. A. W. Dean, V. Manivannan, J. J. Vitall, Inorg. Chem. 1989,
28, 2360–2368.
J. Tallón, J. A. García-Vázquez, J. Romero, M. S. Louro, A.
Sousa, Q. Chen, Y. Chang, J. Zubieta, Polyhedron 1995, 14,
2309–2317.
S. Wang, J. P. Fackler, Inorg. Chem. 1989, 28, 2615–2619.
R. T. C. Brownlee, A. J. Canty, M. F. MacKay, Aust. J. Chem.
1978, 31, 1933–1036.
A. Bondi, J. Phys. Chem. 1964, 68, 441–451.
J. L. Atwood, D. E. Berry, S. R. Stobart, M. J. Zaworotko, In-
org. Chem. 1983, 22, 3480–3482.
A. Castiñeiras, W. Hiller, J. Strähle, J. Bravo, J. S. Casas, M.
Gayoso, J. Sordo, J. Chem. Soc. Dalton Trans. 1986, 1945–1948.
D. St. Black, G. B. Deacon, G. L. Edwards, B. M. Gatehouse,
Aust. J. Chem. 1993, 46, 1323–1326.
[50]
[51]
[52]
[53]
[54]
[55]
[56]
[57]
[58]
[59]
[60]
[61]
[62]
[63]
[64]
[65]
[66]
[23] E. Block, G. Ofori-Okai, J. Zubieta, J. Am. Chem. Soc. 1989,
N. N. Greenwood, E. Earnshaw, Chemistry of the Elements,
2nd ed., 1997, p. 1205.
K. Wurst, J. Strähle, Z. Anorg. Allg. Chem. 1991, 595, 239–250,
and references cited therein.
A. J. Canty, G. B. Deacon, Inorg. Chim. Acta 1980, 45, L225–
L227.
111, 2327–2329.
[24] M. M. Jones, Met. Ions Biol. Syst. 1983, 16, 47–83.
[25] J. A. García-Vázquez, J. Romero, A. Sousa, Coord. Chem. Rev.
1999, 193–195, 691–745.
[26] R. López Garzón, M. D. Gutiérrez Valero, M. L. Godino-Sal-
ido, B. K. Kepler, B. Nuber, J. Coord. Chem. 1993, 30, 111–
123.
R. D. Schluter, G. Krauter, W. S. Rees, J. Cluster Sci. 1997, 8,
123–154.
[27] A. C. Skapski, K. A. Woode, Acta Crystallogr. Sect. B 1979,
J. S. Casas, A. Castiñeiras, I. Haiduc, A. Sánchez, J. Sordo,
E. M. Vázquez-López, Polyhedron 1997, 16, 781–787.
J. S. Casas, E. M. Vázquez-López, J. Zukerman-Schpector, J.
Chem. Soc. Dalton Trans. 1996, 1973–1978.
P. Biscarini, E. Foresti, G. Pradella, J. Chem. Soc. Dalton Trans.
1984, 953–957.
35, 59–62.
[28] P. Karagiannidis, S. K. Hadjikakou, P. Aslanidis, A. Hountas,
Inorg. Chim Acta 1990, 178, 27–34.
[29] L. R. Battaglia, R. Battistuzzi, A. Bonamartini Corradi, C.
Rizzolie, P. Sgarabotto, J. Crystallogr. Spectrosc. Res. 1993, 23,
937–942.
[30] J. Abbot, D. M. L. Goodgame, Y. Jeeves, J. Chem. Soc. Dalton
Trans. 1978, 880–884.
[31] L. Petrilli, F. Caruso, E. Rivarola, Main Group Met. Chem.
1994, 17, 439–446.
[32] P. K. Baker, P. D. Jackson, M. E. Harman, M. B. Hursthouse,
J. Organomet. Chem. 1994, 468, 171–174.
[33] H. Engelking, S. Karentzopoulos, G. Reusmann, B. Krebs,
Chem. Ber. 1994, 127, 2355–2361.
A. J. Canty, C. L. Raston, A. H. White, Aust. J. Chem. 1978,
31, 677–684.
F. Zamora, M. Sabat, M. Janik, C. Siethoff, B. Lippert, Chem.
Commun. 1997, 485–486.
R. C. Paul, H. S. Makhni, P. Singh, S. L. Chadha, Z. Anorg.
Allg. Chem. 1970, 377, 108–112 references cited therein.
R. D. Kross, V. A. Fassel, M. Hargoshes, J. Am. Chem. Soc.
1956, 78, 1332–1335.
Eur. J. Inorg. Chem. 2005, 2242–2254
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2253

A. Rodríguez, A. Sousa-Pedrares, J. A. García-Vázquez, J. Romero, A. Sousa
FULL PAPER
[67] A. A. Schilt, R. C. Taylor, J. Inorg. Nucl. Chem. 1959, 9, 211–
221.
[68] R. G. Inskeep, J. Inorg. Nucl. Chem. 1963, 24, 763–776.
[69] S. Yamazaki, Polyhedron 1985, 4, 1915–1923.
[70] T. A. Annan, R. K. Chadha, D. G. Tuck, K. D. Watson, Can.
J. Chem. 1987, 65, 2670–2676.
[73] G. M. Sheldrick, SHELX-97, Program for the solution and re-
finement of crystal structures, University of Göttingen, Ger-
many, 1997.
[74] International Tables for X-ray Crystallography, vol. C, Kluwer,
Dordrecht, 1992.
[75] ORTEP3 for Windows: L. J. Farrugia, J. Appl. Crystallogr.
1997, 30, 565.
[71] H. E. Mabrouk, D. G. Tuck, J. Chem. Soc. Dalton Trans. 1988,
2539–2543.
Received: October 08, 2004
[72] G. M. Sheldrick, SADABS, An empirical absorption correction
program for area detector data, University of Göttingen, Ger-
many, 1996.
2254
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2242–2254