Macrocyclization of cyclic thiosemicarbazones with mercury salts

Article abstract of DOI:10.1016/S0040-4020(02)00016-9

A new cyclic Schiff base L¹H₃ derived from benzil and thiosemicarbazide has been prepared in the presence of NaBH₄. Reactions of the new molecule and the cyclic 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione L²H₂ with mercury chloride and nitrate are reported. Complexes of 1:2 stoichiometry are obtained from L¹H₃, but the reactions from L²H₂ yield complexes of the macrocyclic Schiff base 5,6,11,12-tetraphenyl-1,2,4,7,8,10-hexaaza-cyclododeca-4,6,10,12-tetraene-3, 9-dithione L³H₂, which indicates the macrocyclization of L²H₂. A mechanism for the cyclization reaction based on the rupture of the C-N single bond in L²H₂ is proposed. The electrochemical results of complex L³Hg makes it and its precursors, L²H₂ and L³H₂, outstanding candidates for mercury determination by appropriate electrode modification.

Full text of DOI:10.1016/S0040-4020(02)00016-9

TETRAHEDRON
Pergamon
Tetrahedron 58 (2002) 1525±1531
Macrocyclization of cyclic thiosemicarbazones with mercury salts
a
M. Aranzazu Blanco, Elena Lopez-Torres, M. Antonia Mendiola, Ernesto Brunet
a
a,p
b
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and M. Teresa Sevillac
a
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Departamento de Quõmica Inorganica, Universidad Autonoma de Madrid, Cantoblanco, 28049Madrid, Spain
b
  Â
Departamento de Quõmica Organica, Universidad Autonoma de Madrid, Cantoblanco, 28049Madrid, Spain
 Â
c
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Departamento de Quõmica Analõtica y Analisis Instrumental, Universidad Autonoma de Madrid, Cantoblanco, 28049Madrid, Spain
Received 25 May 2001; revised 22 October 2001; accepted 17 December 2001
AbstractÐA new cyclic Schiff base L1H3 derived from benzil and thiosemicarbazide has been prepared in the presence of NaBH4. Reactions
of the new molecule and the cyclic 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione L2H2 with mercury chloride and nitrate
are reported. Complexes of 1:2 stoichiometry are obtained from L1H3, but the reactions from L2H2 yield complexes of the macrocyclic Schiff
base 5,6,11,12-tetraphenyl-1,2,4,7,8,10-hexaaza-cyclododeca-4,6,10,12-tetraene-3,9-dithione L3H2, which indicates the macrocyclization of
L2H2. A mechanism for the cyclization reaction based on the rupture of the C±N single bond in L2H2 is proposed. The electrochemical results
of complex L3Hg makes it and its precursors, L2H2 and L3H2, outstanding candidates for mercury determination by appropriate electrode
modi®cation. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
products, open chain and cyclic structures can be obtained
by selecting the appropriate solvent, pH, temperature and
the presence of metal ions. Metal salts have been used as
templates to yield macrocyclic Schiff bases from diamine
and dicarbonyl precursors.22,23 In these cases the size of the
metal, its charge, acidic character and favorable geometries
have to be considered.
Schiff base macroligands derived from thiosemicarbazide
and their complexes are of signi®cant interest for their
pharmacological properties as antibacterial and anticancer
agents.1±8 Macrocyclic ligands allow selective complex-
ation and extraction of metallic cations and anions of
environmental importance.9±12 In particular, the accidental
liberation of mercury in the environment poses dreadful
toxicity problems, but only recent studies have considered
the reactivity of macroligands containing sulfur to entrap
this metal.13±18
In previous papers, we have reported the preparation of
several macroligands derived from thiosemicarbazide and
benzil.24,25 The obtained results showed the importance of
the reaction conditions to get different condensation
products: open chain, cyclic L2H2 and macrocyclic L3H2
compounds. We have also studied their complexation
reactions with transition metals ions, in order to know the
structural features of the formed complexes and their poten-
tial use in determination of metals.26±29 Some of the studied
copper complexes have been used for the preparation of
sensitive potentiometric sensors for this metal.30 The aim
of this work is to get hydrogenated molecules from the
same precursors, which would permit to obtain new
ligands with functionalized pendant arms by subsequent
reactions, and to study the interaction of the obtained
new molecules and the previously published [111] and
[212] condensation products,25,27 (see Scheme 1) with
mercury chloride and nitrate to determine their conduct
towards this toxic metal. The compounds have been
characterized by elemental analysis, mass spectrometry,
In the last few years, a great deal of research has been aimed
to design compounds highly selective and sensitive to heavy
metal ions, in order to detect, and if possible, remove them.
Among the many different strategies proposed, the prepa-
ration of electrochemical and ¯uorescent sensors should be
highlighted.19±21
The number and relative position of the donor atoms and
the cavity size in macrocyclic compounds confer these
molecules with special reactivity. From speci®c dicarbonyl
and diamine precursors, the structure of the condensation
product can be conditioned by controlling the reaction
conditions. Thus, [111], [112] and [212] condensation
1
IR and H and 13C NMR spectroscopy. We also explored
Keywords: thiosemicarbazones; mercury complexes; nitrogen macrocycles;
templates.
Corresponding author. Tel.: 134-91-397-4844; fax: 134-91-397-4833;
e-mail: antonia.mendiola@uam.es
the electrochemical behavior of the complexes by cyclic
voltammetry in order to check their potentiality as sensors
for mercury.
p
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00016-9

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M. A. Blanco et al. / Tetrahedron 58 (2002) 1525±1531
Scheme 1. Reaction of benzil and thiosemicarbazide studied in this work.
2. Results and discussion
medium should be in equilibrium with the various possible
ketal and hemiacetal forms, which react with thiosemi-
carbazide to form benzilthiosemicarbazone. The latter
should be also in equilibrium with the hemiacetalic form
whose intramolecular reaction leads to L2H2. In the absence
of NaBH4 the reaction ends here. But its presence induces
the loss of MeOH, probably due to acid±base reaction
with the relatively highly acidic NH bond. The elimination
of MeOH, which has also been observed when L2H2 was
treated with strongly basic organometallic compounds
(MeHgCl or Me2SnCl2), led to the formation of a strongly
electrophilic double bond that was easily reduced in situ by
NaBH4. The electron-donor effect of the NH makes the
remaining CvN bond much less electrophilic and unable
to react with NaBH4.
The reactions of benzil with thiosemicarbazide in various
conditions are summarized in Scheme 1. Compounds L1H3
and L2H2 were obtained in the presence or absence of
NaBH4, respectively. Compound L2H2 was easily trans-
formed into L1H3 with NaBH4. The latter compound was
also obtained in low yield by NaBH4 reduction of benzil-
bisthiosemicarbazone (Scheme 1). All analytical data are in
agreement with the proposed structures for L1H3 and L2H2
(see Section 4).
All attempts to reduce the remaining imine group present in
L2H2 and in the new L1H3 resulted unsuccessful in our
hands.
Complexation of L1H3 with mercury(II) chloride or nitrate
gave the corresponding complexes of metal/organic-ligand
A plausible mechanism for the formation of L1H3 and L2H2
is outlined in Scheme 2. Benzil dissolved in MeOH in acidic
Scheme 2. Proposed mechanism for the reaction of benzil and thiosemicarbazide in the presence or absence of NaBH4.

M. A. Blanco et al. / Tetrahedron 58 (2002) 1525±1531
1527
Figure 1. Experimental (trace A; FAB1) and theoretical (trace B) mass spectrum of L3Hg with enlarged isotope distribution.
1:2 stoichiometry. Their mass spectra show two peaks
at 735.5 and 268 amu, which correspond to the
C30H25N6S2Hg fragment and to the molecular ion of L1H3,
respectively. These data and the fact that conductivity
measurements in DMF agree with the complexes as being
non-electrolytes indicate that L1H3 is not modi®ed by
complexation, acts as a neutral ligand and that chloride
and nitrate ions are bonded to the mercury atom.
observed for the thione carbon atom in the 13C NMR spectra
of both complexes agrees with the coordination of the ligand
to the metal by the sulfur atom.14,31
We also studied the reactions of L2H2 with mercury chloride
and nitrate in order to compare its reactivity with the new
cyclic L1H3. The reaction with Hg(NO3)2 or HgCl2 gives a
mercury complex, whose mass spectrum shows peaks at 731
and 530amu, corresponding to the C 30H21N6S2Hg and
C30H22N6S2 species, respectively (Fig. 1). These data
suggest that the ligand does modify its structure when
The IR spectrum of [Hg(L1H3)2(NO3)2] shows poorly
resolved bands for the amine stretching vibrations shifted
to lower frequency, which suggests hydrogen bonding
between the molecules of the ligand in the complex. The
bands assigned to the thioamide I, and specially those to
the thioamide IV, have been shifted. This indicates that
the sulfur atom is bonded to the metal ion, each L1H3 ligand
acting as monodentate, with the mercury coordination
sphere completed by the nitrate anions. IR spectrum of the
chloride complex shows similar modi®cations with respect
to the free ligand, implying a similar coordination pattern
for the mercury ion. Therefore, it can be assumed that in
these complexes the mercury is in a pseudo-tetrahedral
environment, with two chloride ions and two organic
ligands bonded to the metal ion. The shift to higher ®eld
1
complexing with mercury. On the other hand, H NMR
spectrum of this complex shows the absence of both
amine nitrogens and OMe group thus indicating the loss
of the methoxy group and the secondary amine hydrogens.
13C NMR spectrum con®rms the absence of the methoxy
group and the presence of two imine carbons. IR spectra
show the absence of both amine and nitrate ion vibrations,
the shift to lower frequencies suffered by the thioamide I
and IV bands, and the presence of absorptions correspond-
ing to two imine groups.
All this evidence points to the formation of the L3Hg macro-
cycle shown in Scheme 1. Therefore, in contrast to L1H3, the

1528
M. A. Blanco et al. / Tetrahedron 58 (2002) 1525±1531
Scheme 3. Behavior of ligands L1H3 and L2H2 in the presence of Hg(II) (see text).
coordination of L2H2 with mercury(II) led to a macrocycli-
zation process, which yields a complex of the macrocycle
L3H2 acting as a bidentate anion ligand by loss of the amine
secondary hydrogens. Last but not least, we have studied the
reaction of L3H2, previously isolated from the reaction
between L2H2 and copper(II) chloride, with mercury nitrate.
The reaction yields a solid, whose IR, mass and NMR
spectra are totally coincident with those obtained from the
complex isolated from the reaction of L2H2 with mercury
nitrate. This, in our belief, con®rms the macrocyclization
reaction.
Concerning its mechanism, it may be assumed that both
L1H3 and L2H2 form in a ®rst step a complex by means of
sulfur coordination as shown in Scheme 3. The positive
charge developed in this atom should be delocalized through
the nitrogens, but in the case of L2H2, the presence of the
methoxy group should weaken the C±N bond as the hyper-
conjugative resonance forms of Scheme 3 suggest.
The results of AM1 semiempirical calculations on these
molecules support this assumption. The optimized geo-
metries of L1H3 and L2H2 displayed C(5)±N(4) bond lengths
Ê
(Fig. 2) of 1.459 and 1.465 A, respectively. Protonation at
sulfur, which has been used in the calculations to mimic
coordination to the metal, elongates those bonds to 1.473
1
and 1.491 A, respectively, i.e. less than 1% for L H3 but ca.
Ê
2% for L2H2.
Once the C(5)±N(4) bond is broken, the two ligands bonded
to the metal might interact in the way shown in Fig. 3, the
Figure 2. Calculated structures (AM1 semiempirical method) of ligands
L1H3 and L2H2 (see text).
Figure 3. Calculated structure for the possible transition state of Hg(II) templated macrocyclization of L2H2.

M. A. Blanco et al. / Tetrahedron 58 (2002) 1525±1531
1529
Scheme 4. Expected intermediate in the Hg(II) templated macrocyclization of L2H2.
metal being an excellent template to induce the observed
formation of the macrocycle.
3. Conclusions
The reaction of benzil with thiosemicarbazone in methanol
in the presence of NaBH4 led to a six-membered ring hetero-
cycle L1H3 that forms stable 2:1 complexes with Hg(II) as a
neutral ligand. The resulting heterocycle retains a NvC
bond whose low electrophilic character prevents its reduc-
tion by the hydride.
When the new C±N bonds are formed, the counter ions
acting as a base take two protons from the macrocyclic
structure and two molecules of methanol are lost as shown
in Scheme 4.
Cyclic voltammograms of L1H3, L2H3 and L3H2 in DMF
exhibit irreversible cathodic waves in the range expected
for this kind of molecules.32 The cyclic voltammogram of
[L3Hg], between 0.0 and 21.6 V (Fig. 4), shows a cathodic
peak at 20.517 V associated with an anodic one at
20.468 V. This couple corresponds with the reversible
redox mercury process. At more negative potentials two
peaks corresponding to ligand reduction processes are
observed (20.750 and 21.350V). One of them is slightly
shifted in relation with those of the free ligand (20.720 and
21.350V), which is in agreement with its bonding to the
mercury ion.
In the absence of NaBH4 a different heterocycle L2H2 is
obtained that contains a MeO group. Interestingly, the
presence of the methoxy group induces a different outcome
of its reaction with Hg(II) as compared to L1H3: the ring
opens and two molecules of L2H2, anchored by the metal,
react to give a macrocycle that binds as an anionic bidentate
ligand to the metal. Semiempirical calculations support the
proposed metal-template mechanism.
The electrochemical results of complex L3Hg makes it and
its precursors, L2H2 and L3H2, outstanding candidates for
mercury determination by appropriate electrode modi®-
cation.
4. Experimental
Microanalyses were carried out using a Perkin±Elmer 2400
II CHNS/O Elemental Analyser. IR spectra in the 4000±
400 cm21 range were recorded as KBr pellets on a
Bomen-100 spectrophotometer. Conductivity data were
measured using freshly prepared DMF solutions (ca.
1023 M) at 258C with a Metrohm Herisau model E-518
1
instrument. H and 13C NMR spectra were recorded on a
spectrophotometer Bruker AMX-300 using dimethylsul-
foxide-d6 as solvent and TMS as internal reference. Fast
atom bombardment mass spectra were recorded on a VG
Auto Spec instrument using Cs as the fast atom and m-nitro-
benzylalcohol (mNBA) as the matrix. Electronic impact
spectrum was recorded in the same instrument. Electro-
chemical measurements were performed with a BAS CV
27 voltammograph and a BAS A-4 XY register using a
glassy carbon (f 5 mm) as working 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 (E1/2ˆ10.400 V,
DEpˆ60mV). Cyclic voltammetry studies of ligands
and complex were carried out on 0.01 M solutions in
Figure 4. Cyclic voltammogram of L3Hg.

1530
M. A. Blanco et al. / Tetrahedron 58 (2002) 1525±1531
dimethylformamide containing 0.1 M [NBu4][PF6] as sup-
porting electrolyte. The range of potential studied was
between 11 to 21.6 V. All solutions were purged with
nitrogen for ®ve minutes before measurement and the
working electrode was polished before each experiment
with diamond paste. The procedure was performed at
room temperature and nitrogen atmosphere was maintained
over the solution during the measurements. IUPAC names
of compounds were obtained from ChemWeb: (http://
cwgen.chemweb.com/autonom/autonomsearch.html).
3131 (NH); 1608 (CvN), 1550(thioamide I), 846 (thio-
1
amide IV). H NMR (300 MHz): (1H, s) 12.1; (1H, s)
10.0; (2H, m) 7.5, (8H, m) 7.4±7.2; (3H, s) 3.1. 13C NMR
(75 MHz): 169.7 (CS); 142.4 (CN); 141.7±126.5 (Ph); 83.2
(CH3O) and 50.7 (CR3).
4.1.3. 5,6,11,12-Tetraphenyl-1,2,4,7,8,10-hexaaza-cyclo-
dodeca-4,6,10,12-tetraene-3,9-dithione, L3H2. A solution
of copper chloride dihydrate (0.23 g, 0.70 mmol), in metha-
nol (50ml) was added to a solution of L 2H2 (0.41 g,
1.40mmol) in methanol (50ml). The mixture was stirred
for 2 h at room temperature. The cream solid L3H2 formed
was ®ltered off, washed several times with methanol and
dried in vacuo (yield 79%), mp 2058C. Anal.; Found: C,
67.82, H, 4.28, N, 15.75, S, 12.13; Calc. for C30H22N6S2:
C, 67.92, H, 4.15, N, 15.85, S, 12.07. m/z (FAB): 530.1
(C30H22N6S2, 100%). Selected spectroscopic data: IR
(cm21): 3057 (NH), 1599 and 1581 (CvN), 1480(thio-
4.1. Preparation of organic molecules
4.1.1.
5,6-Diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-
thione, L1H3. A solution of thiosemicarbazide (1.00 g,
10.64 mmol) in 80 ml of absolute methanol, 22 ml of 2 M
HCl and 0.6 ml of conc. HCl was added to a solution of
benzil (2.31 g, 10.64 mmol) in 80 ml of the same solvent
and some drops of conc. HCl under re¯ux. After 30min
NaBH4 (5.20g, 159.00mmol) was added in small amounts,
with effervescence. The reaction mixture was heated under
re¯ux for 8 h, and then the solvent was evaporated about a
half of the volume and a white solid was formed, which was
collected by ®ltration and recrystallized from CH2Cl2 (yield
73%), mp 1968C. Anal.; Found: C, 67.35; H, 4.78; N, 15.33;
S, 11.73; Calc. for C15H13N3S. C, 67.42; H, 4.87; N, 15.73;
S, 11.99. m/z (EI): 267 (C15H13N3S, 100%). Selected spectro-
scopic data: IR (cm21): 3375, 3187 and 3073 (NH), 1597
1
amide I), 866 (thioamide IV). H NMR (300 MHz): (11H,
m) 7.5±7.3. 13C NMR (75 MHz): 166.9 (CS), 156.6, 156.0
(CN), 134.9±128.6 (Ph).
4.2. Synthesis of mercury complexes
4.2.1. Derivatives of L1H3. [Hg(L1H3)2(NO3)2. A solution
of mercury(II) nitrate monohydrate (0.64 g, 1.87 mmol) in
30ml of absolute methanol was added to a solution of L 1H3
(1.00 g, 3.74 mmol) in 50 ml of the same solvent. The
mixture was stirred for 12 h at room temperature. The
pale yellow solid formed was ®ltered off, washed succes-
sively with absolute methanol and ether, and dried in vacuo
(yield 87%), mp 132±1348C. LM (DMF, V21 cm2 ml21): 45.
m/z (FAB): 735.3 (C30H25N6S2Hg, 65%). Selected spectro-
scopic data: IR (cm21): 3180, 3107 and 3064 (NH), 1614
1
(CvN), 1559 (thioamide I), 846 (thioamide IV). H NMR
(300 MHz): (1H, s) 11.5; (1H, s) 9.7; (2H, m) 7.7; (8H, m)
7.5±7.2; (H, s) 5.7. 13C NMR (75 MHz): 171.1 (CS); 145.3
(CN); 139.2±125.9 (Ph); 51.53 (CR3).
To a solution of benzilbisthiosemicarbazone (1.00 g, 2.91
mmol) (prepared by the procedure previously published)24
in 800 ml of absolute methanol under re¯ux was added
(1.08 g, 28.80 mmol) of NaBH4 in small amounts, with
effervescence. The mixture was re¯uxed for 8 h, and then
the solution was concentrated until a white solid precipi-
tated, which was ®ltered off and recrystallized in CH2Cl2,
(yield 15%). From the remaining solution, a dark yellow oil
was obtained.
1
(CvN), 1573 (thioamide I), 838 (thioamide IV). H NMR
(300 MHz): (2H, m) 7.8; (8H, m) 7.5±7.2; (1H, s) 6.1; (2H,
br.) 3.2. 13C NMR (75 MHz): 163.1 (CS); 148.1 (CN);
137.0±126.0 (Ph); 52.2 (CR3).
[Hg(L1H3)2Cl2]. A methanolic solution, 25 ml, of mer-
cury(II) chloride (0.26 g, 0.97 mmol) was added to a solu-
tion of L1H3 (0.50 g, 1.95 mmol) in 75 ml of methanol, at
room temperature. After being stirred and re¯uxed for 8 h,
the pale yellow solution was concentrated until a solid was
obtained, which was ®ltered off, washed with methanol
and dried in vacuo (yield 83%), mp 1388C. LM (DMF,
V21 cm2 ml21): 16. m/z (FAB): 735.5 (C30H25N6S2Hg,
10%), 268 (C15H13N3S, 65%). IR (cm21): 3170, 3103 and
3062 (NH), 1615 (CvN), 1570(thioamide I), 838 (thio-
To a warm solution of L2H2 (0.50 g, 1.68 mmol) in 200 ml
of absolute methanol, was added NaBH4 (0.64 g, 17.00
mmol) in small amounts, with effervescence. After 6 h
under re¯ux, the solvent was partially removed and a
white solid was formed, which was ®ltered off, and
recrystallized in CH2Cl2, (yield 68%).
1
amide IV). H NMR (300 MHz): (1H, s) 12.1; (1H, s)
10.4; (2H, m) 7.8; (8H, m) 7.5±7.2 (1H, s) 5.9. 13C NMR
(75 MHz): 166.6 (CS); 146.6 (CN); 137.7±125.7 (Ph); 51.1
(CR3).
4.1.2. 5-Methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]-
triazine-3-thione, L2H2. A solution of thiosemicarbazide
(1.14 g, 12.50mmol) in methanol (150ml), hydrochloric
acid (25 ml, 2 M), 1 ml of conc. HCl and a solution of benzil
(2.63 g, 12.50mmol) in methanol (100ml) were alterna-
tively added dropwise and slowly with strong stirring in
75 cm3 of methanol. After ®nishing the addition of all
reactants, the mixture was stirred over 8 h. Overnight a
crystalline solid was formed, which was ®ltered off, washed
and dried in vacuo (yield 95%), mp 2228C. Anal.; Found: C,
64.45; H, 5.09; N, 14.05. Calc. for C16H15N3OS: C, 64.64;
H, 5.05; N, 14.14%. m/z (FAB): 298 (C16H15N3SO11,
35%). Selected spectroscopic data: IR (cm21): 3184 and
4.2.2. Derivatives of L2H2. [L3Hg]. A suspension of
Hg(NO3)2´H2O (2.55 g, 7.43 mmol) in 100 ml of absolute
methanol was added to a solution of L2H2 (1.11 g,
3.70mmol) in 200ml of anhydrous methanol, at room
temperature. The mixture was stirred for 20h and the pale
yellow solid formed was ®ltered off, washed with methanol
and dried in vacuo (yield 59%), mp 2188C (D). LM (DMF,
V21 cm2 ml21): 25. m/z (FAB): 731 (C30H21N6S2Hg, 30%),
530(C 30H22N6S2, 5%). Selected spectroscopic data: IR

M. A. Blanco et al. / Tetrahedron 58 (2002) 1525±1531
1531
(cm21): 1601 and 1581 (CvN), 1491 (thioamide I), 815
Â
9. Beer, P. D.; Szemes, F.; Balzani, V.; Sala, M.; Drew, M. G. B.;
Dent, S. W.; Maestri, M. J. Am. Chem. Soc. 1997, 119, 11864.
1
(thioamide IV). H NMR (300 MHz): (m) 7.4±7.1. 13C
Â
10. Costa, J.; Delgado, R.; Drew, M. G. B.; Felix, V. J. Chem.
Soc., Dalton Trans. 1998, 1063.
NMR (75 MHz): 174.7 (CS); 154.3 and 153.2 (CN);
135.4±128.1 (Ph).
Â
Â
11. Al Shihadeh, Y.; Benito, A.; Lloris, J. M.; Martõnez-ManÄez,
R.; Pardo, T.; Soto, J.; Marcos, M. D. J. Chem. Soc., Dalton
Trans. 2000, 1199.
A solution of HgCl2 (0.88 g, 3.20 mmol) in 11 ml of metha-
nol was added to a solution of L2H2 (1.93 g, 6.50mmol) in
200 ml of the same solvent at room temperature. The
solution was stirred for 12 h and partially concentrated.
The yellow solid formed was ®ltered off, washed with
methanol and dried in vacuo (yield 30%), mp 2188C (D).
m/z (FAB): 731 (C30H21N6S2Hg, 30%); 530 (C30H22N6S2,
15%). Selected spectroscopic data: IR (cm21): 1602 and
12. Atkinson, I. A.; Chartres, J. D.; Everett, G. E.; Ji, X-K.;
Lindoy, L. F.; Mathews, O. A.; Meehan, G. V.; Skelton,
B. W.; Wei, G.; White, A. H. J. Chem. Soc., Dalton Trans.
2000, 1191.
Â
13. Costa, J.; Delgado, R.; Drew, M. G. B.; Felix, V. J. Chem.
Soc., Dalton Trans. 1999, 4331.
1
14. Popovic, Z.; Matkovic-Calogovic, D.; Soldin, Z.; Pavlovic,
G.; Davidovic, N.; Vikic-Topic, D. Inorg. Chim. Acta 1999,
294, 35.
1597 (CvN), 1485 (thioamide I), 815 (thioamide IV). H
NMR (300 MHz). (m) 7.4±7.2. 13C NMR (75 MHz): 174.7
(CS); 154.3 and 153.2 (CN); 135.4±128.1 (Ph).
15. Hennig, C.; Hallmeier, K. H.; Zahn, G.; Tschwatschal, F.;
Hennig, H. Inorg. Chem. 1999, 38, 38.
Â
16. Bermejo, E.; CastinÄeiras, A.; Domõnguez, R.; Carballo, R.;
To a suspension of the macrocyclic ligand L3H2 (0.13 g,
0.24 mmol) in 150 ml of absolute methanol was added a
suspension of Hg(NO3)2´H2O (0.08 g, 0.24 mmol) in 15 ml
of the same solvent. The mixture was stirred for 12 h. The
white solid obtained was ®ltered off, washed with methanol
and dried in vacuo. The ®ltrate was concentrated and a
yellow solid precipitated (yield 65%), mp 2188C (D). m/z
(FAB): 731.1 (C30H21N6S2Hg, 40%), 529 (C30H21N6S2,
20%). Selected spectroscopic data: IR (cm21): 3055 (NH),
1601 and 1597 (CvN), 1485 (thioamide I), 815 (thioamide
È
Maichle-Mossmer, C.; Strahle, J.; West, D. X. Z. Anorg.
Allg. Chem. 1999, 625, 961.
È
Â
17. Bermejo, E.; Carballo, R.; CastinÄeiras, A.; Domõnguez, R.;
È
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0103) and indirect funding from FYSE-ERCROS S. A.
are gratefully acknowledged.
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