Mercury and methylmercury complexes with a triazine-3-thione ligand

Article abstract of DOI:10.1016/j.poly.2005.10.013

Reactions of 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione LH₂OCH₃ with Hg(NO₃)₂ ? H ₂O and HgMeCl afforded monomeric compounds in which the triazine loses the methoxy group and binds to the mercury through the sulphur atom, acting as monodentate. The coordination number found around the metal ion in both complexes is two, giving a linear disposition. This coordination mode is different from the ones that have been previously reported, where the ligand acts as bidentate NS or bidentate NS bridging via the sulphur atom, and unusual behaviour for a triazine ligand. Complexes have been characterised by mass spectrometry, IR, multinuclear (¹H, ¹³C) NMR, and X-ray diffraction. The redox behaviour was explored by cyclic voltammetry and both complexes show Hg(II)/Hg(I) processes.

Full text of DOI:10.1016/j.poly.2005.10.013

Polyhedron 25 (2006) 1464–1470
www.elsevier.com/locate/poly
Mercury and methylmercury complexes with a triazine-3-thione ligand
a
a
a,
b
*
´
´
Elena Lopez-Torres , M Antonia Mendiola , Cesar J. Pastor
a
Departamento de Quı´mica Inorga´nica, Universidad Auto´noma de Madrid, Cantoblanco, 28049 Madrid, Spain
Servicio Interdepartamental de Investigacio´n, Universidad Auto´noma de Madrid, Cantoblanco, 28049 Madrid, Spain
b
Received 8 July 2005; accepted 18 October 2005
Available online 28 November 2005
Abstract
Reactions of 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione LH2OCH3 with Hg(NO3)2 Æ H2O and HgMeCl afforded
monomeric compounds in which the triazine loses the methoxy group and binds to the mercury through the sulphur atom, acting as
monodentate. The coordination number found around the metal ion in both complexes is two, giving a linear disposition. This coordi-
nation mode is different from the ones that have been previously reported, where the ligand acts as bidentate NS or bidentate NS bridg-
ing via the sulphur atom, and unusual behaviour for a triazine ligand. Complexes have been characterised by mass spectrometry, IR,
multinuclear (1H, 13C) NMR, and X-ray diffraction. The redox behaviour was explored by cyclic voltammetry and both complexes show
Hg(II)/Hg(I) processes.
Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Triazine; Mercury complexes; Methylmercury complexes; X-ray analysis
1. Introduction
to mercury speciation in water [7]. Mercury is a very toxic
element, in particular its alkyl derivatives, due to its action
as enzymatic blocking agent and affinity for thiol groups,
so selective complexation and extraction of this cation at
low concentrations levels are necessary [8,9].
The increasing interest in thiosemicarbazones (TSCs)
that has arisen in the last decades is related to their wide
range of biological and pharmacological properties, which
confers numerous applications, for example as antibacte-
rial, antiviral and anticancer agents [1–4]. In addition, in
our research group we have been interested in the prepara-
tion of potentiometric ion-selective electrodes (ISE), to
detect and if possible to remove toxic metals, as mercury
and copper. In particular, we have applied copper com-
plexes with the open chain ligand benzilbis(thiosemicarba-
zone) in the development of potentiometric sensors for
copper determination [5]. A macrocyclic thiohydrazone
ligand (derived from benzil) has been successfully used as
modified carbon paste electrode for voltamperometric
determination and speciation of copper in water samples
[6] and we have recently studied the application of a carbon
paste electrode modified with benzilbis(thiosemicarbazone)
Furthermore, triazine derivatives have traditionally
found applications in analytical chemistry as complexation
agents, in electrochemistry as multi-step redox systems and
as pesticide or herbicide components in agriculture. In the
last years, there has been a growing interest in these com-
pounds that have been used, for example, as templates in
multidimensional crystal engineering involving metal com-
plexes for producing nanometre sized oligonuclear coordi-
nation compounds, as scaffold in combinatorial chemistry,
as well as new building blocks in peptidomimetics and as
anticancer agents [10,11]. Therefore, the synthesis of mer-
cury compounds with triazines derived from thiosemicar-
bazones is an interesting topic to pursue.
Due to the electronic delocalisation, which is enhanced
upon deprotonation, TSC ligands are very versatile. This
fact, together with the presence of different types of donor
atoms, allows several coordination modes possible [12,13].
So that, depending on the metal coordination preferences a
*
Corresponding author. Tel.: +34 91 4974844; fax: +34 91 4974833.
´
E-mail addresses: elena.lopez@uam.es (E. Lopez-Torres), antonia.
mendiola@uam.es (M.A. Mendiola).
0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.10.013

E. Lo´pez-Torres et al. / Polyhedron 25 (2006) 1464–1470
1465
10ꢀ3 M) at 25 °C with a Metrohm Herisau model E-518
instrument. Electrochemical measurements were per-
formed with a BAS CV 27 voltammograph and a BAS
A-4 XY register using a glassy carbon (B 5 mm) as work-
ing electrode, a platinum wire as auxiliary, and a double
junction, with porous ceramic wick, Ag/AgCl as reference
electrode, standardized for the redox couple ferricinium/
ferrocene (E1/2 = +0.400 V, DEp = 60 mV). Cyclic voltam-
metry studies of LH2OCH3 and complexes were carried
out on 0.01 M solutions in dimethylformamide containing
0.1 M [NBu4][PF6] as supporting electrolyte. The range of
potential studied was between +1.0 and ꢀ2.2 V. All solu-
tions were purged with nitrogen steam for 5 min before
measurement and the working electrode was polished
before each experiment with diamond paste. The proce-
dure was performed at room temperature and nitrogen
atmosphere was maintained over the solution during the
measurements.
Ph
Ph
OMe
NH
N
N
H
S
Scheme 1. Drawing of LH2OCH3.
particular ligand can show different coordination behav-
iour, as we have established in previous works [14]. In fact,
we have characterized complexes of the title ligand acting
as bidentate NS giving monomeric complexes with some
organotin (IV) derivatives [15], as well as with nickel and
cobalt salts. With other metals, as cadmium, acts also as
bidentate bridging via the sulphur atom, giving dinuclear
structures [16].
The most usual type of coordination in compounds of
Hg(II) is a distorted octahedron with two bonds much
shorter than the other four. In extreme, this results in a lin-
ear-2 coordination in which case bonds are largely cova-
lent. This situation usually takes place with S-donor
ligands. The complexes [Hg(5-CF3-pyS2)] and [Hg(5-CF3-
MepyS2)] are examples of this type of coordination, where
the Hg(II) ion is bonded to two ligands via the sulphur
atoms, giving a linear SS disposition [17,18].
The aim of this work is the synthesis and characteriza-
tion of mercury complexes derived of 5-methoxy-5,6-di-
phenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione LH2OCH3
(Scheme 1), in order to get new complexes and to explore
their potential capability as modifiers of a carbon paste
electrode for mercury determination and kinetic speciation
in water samples. In this paper, we report the synthesis and
structural characterisation of two mercury compounds
with this cyclic ligand. In both complexes, and induced
by the metal structural preferences, the triazine acts as
monodentate through the sulphur atom, behaviour that
has not been observed previously.
2.2. Crystallography
Crystals were mounted on a glass fibre and transferred
to a Bruker SMART 6K CCD area-detector three-circle
diffractometer with a MAC Science Co., Ltd. Rotating
˚
Anode (Cu Ka radiation, k = 1.54178 A) generator
equipped with Goebel mirrors at settings of 50 kV and
110 mA. X-ray data were collected with a combination of
six runs at different u and 2h angles, 3600 frames. The data
were collected using 0.3° wide x scans and crystal-to-detector
distance of 4.0 cm. Empirical absorption corrections
(SADABS) [19] were applied using multiple measurements
of symmetry-equivalent reflections (ratio of minimum to
maximum apparent transmission: 0.373482 for complex 1
and 0.556564 for complex 2). The unit cell parameters were
obtained by full-matrix least-squares refinements of 5528
and 7730 reflections for complexes 1 and 2, respectively.
The raw intensity data frames were integrated with the
SAINT [20] program, which also applied corrections for
Lorentz and polarization effects. The software package
SHELXTL [21] version 6.10 was used for space group determi-
nation, structure solution and refinement. The space group
determination was based on a check of the Laue symmetry
and systematic absences and was confirmed using the struc-
ture solution. The structure was solved by direct methods
(SHELXS-97) [22], completed with difference Fourier synthe-
ses, and refined with full-matrix least squares using SHELXL-
2. Experimental
2
97 [23] minimizing xðF 2oꢀ F c2Þ . Weighted R factors (Rw)
2.1. Physical measurements
and all goodness of fit (S) are based on F2; conventional
R factors (R) are based on F. All non-hydrogen atoms were
refined with anisotropic displacement parameters. All scat-
tering factors and anomalous dispersions factors are con-
tained in the SHELXTL [24] 6.10 program library. H atoms
were found in a difference map, but were then positioned
geometrically and included as riding, with C–H = 0.95
IR spectra in the 4000–400 cmꢀ1 range were recorded
as KBr pellets on a Jasco FT/IR-410 spectrophotometer.
1H and 13C NMR spectra were recorded on a spectropho-
tometer Bruker AMX-300 using CDCl3 and DMSO-d6 as
solvents and TMS as reference. Fast atom bombardment
(FAB) mass spectra were recorded on a VG Auto Spec
instrument using Cs as the fast atom and m-nitrobenzilal-
cohol (mNBA) as the matrix. Conductivity data were
measured using freshly prepared DMF solutions (ca.
˚
and 0.99 A, and Uiso(H) = 1.2 Ueq(C). The coordinates
were refined as riding on the parent atom and the occu-
pancy and Uij were fixed.

1466
E. Lo´pez-Torres et al. / Polyhedron 25 (2006) 1464–1470
2.3. Syntheses
to acid–base reaction with the relatively high acidic N–H
bond, yielding LH, according to a mechanism previously
published. Reaction with mercury nitrate does not need
the presence of lithium hydroxide, which is necessary in
the reactions studied with other metal salts [15,16].
Conductivity measurements in DMF indicate the pres-
ence of non-ionic species in this solvent [27]. The mass
spectrometry indicates the different mercury/ligand ratio.
Mass spectrum of complex 1 shows a peak corresponding
to [HgL2 + 1]+, which indicates the presence of a specie
containing one mercury ion and two deprotonated ligands.
However, mass spectrum of complex 2 shows a peak at
482.0 amu, which is attributed to [HgMeL + 1]+ and corre-
sponds to the molecular ion. The other peaks observed are
probably due to molecular associations produced during
the experiment.
The X-ray analysis shows that the crystal structure of
complex 1 is made up of discrete centrosymmetric mole-
cules of [HgL2] (Fig. 1), which agrees with the spectro-
scopic data, but rules out the structure previously
proposed for this complex [26]. The mercury atom is
bonded to two sulphur atoms of two thiosemicarbazone
ligands in a linear disposition (S–Hg–S = 180.0°). Complex
2 consists of [HgMeL] entities (Fig. 2), where the mercury
is also in a linear disposition, bonded to the sulphur atom
of a triazine ligand and the methyl group (S–Hg–C =
175.7°). Crystallographic data and selected bond distances
and angles are given in Tables 1–3.
All reagents and other solvents were obtained from stan-
dard commercial sources and were used as received.
2.4. 5-Methoxy-5,6-diphenyl-4,5-dihydro-2H-
[1,2,4]triazine-3-thione, LH2OCH3
The characterisation of the ligand LH2OCH3 was previ-
ously published [24], although it was synthesised according
to a modified procedure [25].
Selected spectroscopic data: IR (KBr, cmꢀ1): 3184s and
1
3131s (NH), 1608w (C@N), 1550s (NCS), 846w (CS). H
NMR (300 MHz, CDCl3, 25 °C): 3.4 (s, 3H, OCH3), 6.9
(d, 1H, NH), 7.1–7.3 (m, 6H, Ph), 7.4 (m, 2H, Ph), 7.6
(m, 2H, Ph), 9.5 (d, 1H, NH), 13C NMR (300 MHz,
CDCl3, 25 °C): 169.7 (CS), 142.4 (CN), 141.7, 133.7,
129.3, 126.5, (Ph), 83.2 (CR4), 50.7 (CH3O).
2.5. [HgL2] (1)
This complex was prepared as previously reported [26].
M.p. 218 °C (D). KM (DMF, Xꢀ1 cm2 mlꢀ1): 25. m/z
(FAB+): 731 ([HgL2 + 1]+, 30%). Selected spectroscopic
data: IR (KBr, cmꢀ1): 1601w, 1581w (C@N), 1491s
1
(NCS), 815w (CS). H NMR (300 MHz, DMSO, 25 °C):
7.4–7.1 (m, Ph). 13C NMR (300 MHz, DMSO-d6, 25 °C):
174.7 (CS), 154.3, 153.2 (CN), 135.2, 134.4, 130.9, 129.5,
129.4, 129.0, 128.6, 128.1 (Ph). Single crystals of complex
1 suitable for X-ray analysis, were grown by slow evapora-
tion of a solution of the complex in acetonitrile.
In both complexes, the triazine rings can be considered
˚
planar with a maximum deviation of 0.0498 A for C(3) in
˚
complex 1 and 0.0571 A for C(1) in complex 2. The sulphur
˚
atom is 0.260 A above this plane in complex 1 and
˚
2.6. [HgMeL] (2)
0.3385 A under in complex 2. The mercury atom is
˚
˚
0.5938 A above this plane and 0.2791 A under in complexes
1 and 2, respectively. The aromatic rings form with respect
to this plane dihedral angles of 44.9° for C(10)–C(15) and
36.95° for C(4)–C(9) in complex 1 and 47.22° and 31.92°,
respectively, in complex 2. An important change is
observed with respect to LH2OCH3, where the dihedral
angles are 95.07° and 36.94°, respectively, [24]. This change
in one of the phenyl rings could be explained by the loss of
the methoxy group, although it also could be attributed to
crystal packing. Owing to deprotonation, there is a consid-
erable electronic delocalisation through the thiosemicarba-
zone backbone, which is slightly larger in complex 2. As a
consequence all the C–N bonds have almost the same
length, which does not occur in LH2OCH3 (1.28–
Over a solution of LH2OCH3 (0.32 g, 1.1 mmol) and
LiOH Æ H2O (0.05 g, 1.1 mmol) in 50 ml of methanol was
drop wise added a solution of HgMeCl (0.27 g, 1.1 mmol)
in the same solvent. The solution was stirred at room tem-
perature for 6 h. Then it was evaporated until a yellow
solid appeared, which was filtered off and vacuum dried.
Yield 73%. m.p 140 °C. KM (DMF, Xꢀ1 cm2 mlꢀ1): 9.
m/z (FAB+): 482.0 ([HgMeL + 1]+, 100%). 696.0
([Hg2MeL + 1]+, 30%), 945 ([Hg2Me2L2]+, 4%), 961.1
([Hg2Me2L2]+, 2%). IR (KBr, cmꢀ1): 1598w, 1578w
(C@N), 1483s (NCS), 816w (CS). 1H NMR (300 MHz,
DMSO-d6, 25 °C): 7.3–7.5 (m, 10H, Ph), 0.89 (s, 3H,
CH3, J2(199Hg–1H) = 186 Hz). 13C NMR (300 MHz,
DMSO-d6, 25 °C): 176.5 (CS), 154.6, 153.1 (CN), 135.6,
135.4, 130.7, 129.6, 129.2, 129.1, 128.6, 128.5 (Ph), 9.4
(CH3). Single crystals suitable for X-ray analysis were
obtained by slow evaporation of a solution of the complex
in DMF.
˚
1.459 A). In the complexes, the thione bonds distances
˚
(1.755 and 1.763 A for complexes 1 and 2) are longer than
˚
in the precursor ligand (1.628 A) and they are closer to the
˚
value expected for a single bond (1.82 A) [28]. In addition
the N(3)–C(2)–C(3) angles are close to 120°, as would be
expected for sp2 hybridisation, while in LH2OCH3 is
108°, corresponding to sp3 hybridisation.
3. Results and discussion
Although there is no covalent bond between the mer-
cury atom and N(1) in complex 1 and N(3) in complex 2,
there is some interaction, because N–Hg distances are
In the synthesis of both complexes takes place the loss of
the methoxy group as a methanol molecule, probably due

E. Lo´pez-Torres et al. / Polyhedron 25 (2006) 1464–1470
1467
Fig. 1. Molecular structure of complex [HgL2] 1. Thermal ellipsoids are shown at 50% probability.
Fig. 2. Molecular structure of complex [HgMeL] 2. Thermal ellipsoids are shown at 50% probability.
˚
2.806 and 3.146 A, respectively, which are larger than the
The crystal structure of complex 1 belongs to the mono-
clinic system. In the crystal packing the mercury atoms are
placed in the eight corners and in the middle of a cube, giv-
ing a body-centred cubic packing.
˚
sum of the covalent radii (2.25 A), but shorter than the
sum of the Van der Waals radii (3.23 A). Some authors
˚
assume that if the Hg–N distance is lower than the sum
of the Van der Waals radii there is covalent bond [29].
The non-existence of a Hg–N bond in both complexes is
supported by the S–Hg–S angle, which is perfectly linear.
If the mercury ion would have to accommodate an addi-
tional bond with the nitrogen atom, there must be a change
in the sp hybridisation, which will be reflected in a devia-
tion of the angle [13].
The absence of any band in the 2600-cmꢀ1 region in the
IR spectra of both complexes suggests the absence of any
thiol tautomer [30]. In the spectra, there are no bands in
the 3000–3300-cmꢀ1 region, which indicates the absence
of N–H bonds. Moreover bands attributable to the nitrate
group in complex 1 are not observed [31]. The absence of
these bands confirms that the ligand acts as a monoanion
L in this complex. The band corresponding to the CS moi-
ety is shifted to lower frequencies, indicating coordination
of the sulphur to the metal ion. The presence of two bands
There are p–p interactions between the phenyl rings,
with a distance of 3.817 A in complex 1 and 3.846 A in
complex 2.
˚
˚

1468
E. Lo´pez-Torres et al. / Polyhedron 25 (2006) 1464–1470
Table 1
Crystal data and structure refinement for complexes 1 and 2
1
2
Formula
M
C30H20N6S2Hg
729.23
C16H13N3SHg
479.94
Crystal system
Space group
a (A)
monoclinic
P2(1)/n
10.3574(2)
orthorhombic
P2(1)2(1)2(1)
5.9923(10)
˚
˚
b (A)
11.5451(2)
11.5016(3)
14.0288(3)
18.5810(3)
˚
c (A)
a (°)
b (°)
c (°)
90
90
90
90
98.9730(10)
90
1358.50(5)
3
˚
U (A )
1562.01(5)
Z
2
4
2041
18.882
904
1.064
9395
Dcalc (Mgmꢀ3
)
1.783
11.850
708
1.002
Absorption coefficient (mmꢀ1
F(000)
Goodness-of-fit on F2
Reflections collected
)
8487
Independent reflections [Rint
]
2469 [0.0443]
2872 [0.0539]
Completeness to h = 70.53° (%)
Absorption correction
Refinement method
Final R1 and wR2 [I > 2r(I)]
R indices (all data)
95.1
96.9
SADABS v. 2.03
SADABS v. 2.03
full-matrix least-squares on F2
R1 = 0.0286, wR2 = 0.0719
R1 = 0.0346, wR2 = 0.0756
full-matrix least-squares on F2
R1 = 0.0316, wR2 = 0.0783
R1 = 0.0335, wR2 = 0.0800
Table 2
one C@N band and the new band could be due to the
hydrazinic CN. These imine nitrogen atoms are non-coor-
dinate to the metal ion.
˚
Selected bond distances (A) for complexes [HgL2] 1 and [HgMeL] 2
[HgL2] 1
[HgMeL] 2
1
The H NMR spectra of both complexes show a multi-
Hg(1)–S(1)
Hg(1)–C(16)
N(1)–N(2)
N(1)–C(1)
N(2)–C(3)
N(3)–C(1)
N(3)–C(2)
S(1)–C(1)
C(2)–C(3)
2.3362(10)
2.3703(16)
2.086(8)
1.335(8)
1.312(9)
1.343(7)
1.341(7)
1.326(8)
1.763(7)
1.430(8)
plet in the aromatic region, corresponding to the phenyl
rings of the ligand. In complex 2 a signal at 0.89 ppm, cor-
responding to the CH3 group, can also be observed. The
absence of any signal corresponding to amine protons sup-
ports the ligand deprotonation. The absence of the singlet
attributable to the methoxy group at 3.4 ppm confirms
the loss of the inserted methoxy group. In the spectrum
of complex 2, the singlet corresponding to the methyl
group shows the satellites corresponding to the coupling
with the mercury ion with J2 = 186 Hz.
1.334(4)
1.336(4)
1.338(4)
1.326(4)
1.334(4)
1.755(3)
1.413(4)
Table 3
Selected angles (°) for complexes [HgL2] 1 and [HgMeL] 2
In the 13C NMR spectra the signals corresponding to the
methoxy group (50.7 ppm) and the tetrasubstituted carbon
atom (83.2 ppm) of LH2OCH3 have disappeared and a new
signal corresponding to an imine group is observed. The
imine groups are not bonded to the metal ion, as the X-
ray diffraction has established for complexes 1 and 2. In
addition the signal corresponding to the thione group is
deshielded, suggesting the presence of metal–sulphur
bonds. In complex 2, the signal of the methyl group bonded
to the mercury atom appears at 9.4 ppm.
Cyclic voltammetry of the ligand LH2OCH3 and complex
1 have been previously published [26]. Complex 1 shows a
reversible redox couple at E1/2 = ꢀ0.492 V. On scanning
from +1.0 to ꢀ2.2 V cyclic voltammogram of complex 2
shows a redox couple at E1/2 = ꢀ0.275 V, corresponding
to a Hg(II)/Hg(I) process (Fig. 3) and two irreversible catho-
dic peaks corresponding to ligand reduction processes at
ꢀ1.325 and ꢀ1.825 V. Analysis of the redox couple in the
interval 25–800 mV sꢀ1 shows a lineal variation of ipc versus
[HgL2] 1
[HgMeL] 2
N(2)–N(1)–C(1)
N(1)–N(2)–C(3)
C(1)–N(3)–C(2)
N(3)–C(1)–N(1)
N(3)–C(1)–S(1)
N(1)–C(1)–S(1)
N(3)–C(2)–C(3)
N(3)–C(2)–C(4)
C(3)–C(2)–C(4)
N(2)–C(3)–C(2)
N(2)–C(3)–C(10)
C(2)–C(3)–C(10)
C(1)–S(1)–Hg(1)
S(1)#1–Hg(1)–S(1)
C(16)–Hg(1)–S(1)
118.1(3)
119.6(3)
116.5(3)
125.6(3)
116.6(2)
117.8(2)
119.6(3)
115.8(3)
124.6(3)
119.8(3)
115.2(3)
125.1(3)
94.01(11)
180.00(2)
117.5(5)
120.5(5)
117.1(5)
125.9(6)
119.9(5)
114.2(4)
118.6(5)
117.6(5)
123.8(5)
119.1(6)
115.9(5)
125.0(5)
102.0(2)
175.7(3)
attributable to C@N bonds could indicate the formation of
a new imine group, due to the loss of the methoxy group of
the ligand LH2OCH3, although the great electronic delo-
calisation in the ring probably leads to there being only

E. Lo´pez-Torres et al. / Polyhedron 25 (2006) 1464–1470
1469
paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the
Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge, CB2 1EZ, UK, fax: +44 1223 366
033, e-mail: deposit@ccdc.ac.uk or on the web www:
http://www.ccdc.cam.ac.uk.
Acknowledgements
We thank DGICYT (Project BQU2001-0151) for finan-
cial support.
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rate is observed, and the ipa/ipc ratio is close to the unity.
These results suggest a diffusion controlled quasirreversible
process [32]. The reduction process Hg(II)/Hg(I) is more dif-
ficult in complex 1, where the mercury atom is bonded to
two sulphur atoms due to the fact that electronic density
over the metal ion is bigger than when the environment is
formed by one sulphur and one carbon atom, as occurs in
complex 2.
´
´
[12] J.S. Casas, A. Castineiras, M.C. Rodrıguez-Arguelles, A. Sanchez, J.
˜
¨
´
´
´
´
Sordo, A. Vazquez-Lopez, E.M. Vazquez-Lopez, J. Chem. Soc.,
4. Conclusions
Dalton Trans. (2000) 2267.
[13] J.S. Casas, M.S. Tasende, J. Sordo, Coord. Chem. Rev. 209 (2000)
197.
Reactions of the ligand LH2OCH3 with two mercury
salts lead to the formation of the corresponding coordina-
tion compounds, where the ligand has lost the methoxy
group and acts as a monoanion. The methylmercury deriv-
ative is only obtained in the presence of basic medium.
In both complexes the ligand acts as monodentate and
binds to the mercury ion through the sulphur atom, giving
a linear disposition around the metal. This coordination
mode is usually observed in mercury complexes, although
coordination only via the sulphur atom is not frequent in
triazines and it is observed for the first time in this partic-
ular ligand.
The results obtained confer good prospects for com-
pound 2 to be used to prepare new sensors for the highly
toxic HgMe+ ion. Development of these sensors is very
important due to alkyl mercury derivatives are great envi-
ronmental pollutants and could affect food and soils (some
compounds are used as pesticides in the treatment of seeds
and can be introduced in natural waters).
´
´
[14] E. Lopez-Torres, M.A. Mendiola, C.J. Pastor, B. Souto Perez, Inorg.
Chem. 43 (2004) 5222, and references therein.
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[15] E. Lopez-Torres, M.A. Mendiola, C.J. Pastor, J.R. Procopio, Eur. J.
Inorg. Chem. (2003) 2711.
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[16] E. Lopez-Torres, M.A. Mendiola, Polyhedron 24 (2005) 1435.
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[18] A. Rodrıguez, A. Sousa-Pedrades, J.A. Garcıa-Vazquez, J. Romero,
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CCDC 256950 for complex 1 and 269350 for complex
2 contain the supplementary crystallographic data for this

1470
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