Schiff bases derived from mercury(II)-aminothiolate complexes as metalloligands for transition metals

Article abstract of DOI:10.1016/S0022-328X(00)00672-0

Mercury(II) complexes of aromatic aminothiolate ligands of formula [Hg(n-SC₆H₄NH₂)₂], n=3 (1) or 4 (2) and [RHg(n-SC₆H₄NH₂)], R=Me, n=3 (3) or 4 (4); R=Ph, n=3 (5) or 4 (6) have been obtained and characterized by infrared and ¹H, ¹³C and ¹⁹⁹Hg-NMR spectroscopies. The latter indicates that, in solution, complexes 1-6 have an essentially linear coordination about Hg(II). Unprecedented Schiff bases containing the Hg-S(thiolate) bond have been synthesized from 3-6 and salicylaldehyde yielding complexes of formula [RHg(n-SC₆H₄N=CHC₆H₄OH)], R=Me, n=3 (7) or 4 (8); R=Ph, n=3 (9) or 4 (10). The template reaction of 3 and 4 with M(CH₃COO)₂, M=Zn(II), Cd(II), and salicylaldehyde has afforded trimetallic complexes of formula [M^II{MeHg(n-SC₆H₄N=CHC₆H₄O)}₂], M=Zn, n=3 (11) or 4 (12); M=Cd, n=3 (13) or 4 (14). Complexes 7-14 have also been explored by use of infrared and NMR spectroscopies. The crystal structure determination of 2, 3, 5, 7 and 8 by X-ray diffraction shows that Hg(II) has an essentially linear coordination. The presence of additional secondary Hg?S interactions in all these complexes leads to an increase in the coordination number of Hg to 4 or 5. In 2, the interaction of each S-Hg-S unit with three neighbouring units gives rise to a polymeric chain, which can be considered as being formed by pairs of fused incomplete cubanes. In 3, 5, 7 and 8, secondary Hg?S bonds between pairs of C-Hg-S fragments yield Hg₂S₂ dimers. In 3, these dimers afford two-dimensional sheets by means of additional Hg?N secondary interactions. The crystal packing of the Hg₂S₂ dimers in 5, 7 and 8 is very similar and gives rise to one-dimensional chains by means of additional Hg?S bonds. The resulting polymeric zig-zag ladders can be described as formed by Hg₄S₄ pseudo-cubanes sharing opposite faces.

Full text of DOI:10.1016/S0022-328X(00)00672-0

Journal of Organometallic Chemistry 623 (2001) 137–148
www.elsevier.nl/locate/jorganchem
Schiff bases derived from mercury(II)–aminothiolate complexes as
metalloligands for transition metals
Xavier Almagro a, William Clegg b, Lourdes Cucurull-Sa´nchez b,
Pilar Gonza´lez-Duarte a,*, Montserrat Traveria a
a Departament de Qu´ımica, Uni6ersitat Auto`noma de Barcelona, 08193 Bellaterra, Barcelona, Spain
b Department of Chemistry, Uni6ersity of Newcastle, Newcastle upon Tyne, NE1 7RU, UK
Received 2 August 2000; accepted 15 September 2000
Abstract
Mercury(II) complexes of aromatic aminothiolate ligands of formula [Hg(n-SC6H4NH2)2], n=3 (1) or 4 (2) and [RHg(n-
1
SC6H4NH2)], R=Me, n=3 (3) or 4 (4); R=Ph, n=3 (5) or 4 (6) have been obtained and characterized by infrared and H, 13C
and 199Hg-NMR spectroscopies. The latter indicates that, in solution, complexes 1–6 have an essentially linear coordination about
Hg(II). Unprecedented Schiff bases containing the Hg–S(thiolate) bond have been synthesized from 3–6 and salicylaldehyde
yielding complexes of formula [RHg(n-SC6H4NꢀCHC6H4OH)], R=Me, n=3 (7) or 4 (8); R=Ph, n=3 (9) or 4 (10). The
template reaction of 3 and 4 with M(CH3COO)2, M=Zn(II), Cd(II), and salicylaldehyde has afforded trimetallic complexes of
formula [MII{MeHg(n-SC6H4NꢀCHC6H4O)}2], M=Zn, n=3 (11) or 4 (12); M=Cd, n=3 (13) or 4 (14). Complexes 7–14 have
also been explored by use of infrared and NMR spectroscopies. The crystal structure determination of 2, 3, 5, 7 and 8 by X-ray
diffraction shows that Hg(II) has an essentially linear coordination. The presence of additional secondary Hg···S interactions in
all these complexes leads to an increase in the coordination number of Hg to 4 or 5. In 2, the interaction of each S–Hg–S unit
with three neighbouring units gives rise to a polymeric chain, which can be considered as being formed by pairs of fused
incomplete cubanes. In 3, 5, 7 and 8, secondary Hg···S bonds between pairs of C–Hg–S fragments yield Hg2S2 dimers. In 3, these
dimers afford two-dimensional sheets by means of additional Hg···N secondary interactions. The crystal packing of the Hg2S2
dimers in 5, 7 and 8 is very similar and gives rise to one-dimensional chains by means of additional Hg···S bonds. The resulting
polymeric zig-zag ladders can be described as formed by Hg4S4 pseudo-cubanes sharing opposite faces. © 2001 Elsevier Science
B.V. All rights reserved.
Keywords: Mercury complexes; Aminothiolate ligands; Schiff base; X-ray crystallography; NMR spectroscopy
1. Introduction
thiolates [2]. With the aim of contributing to the study
of the main factors affecting their final structure, we
obtained and structurally characterized several Hg(II)
complexes with aliphatic aminothiol ligands, which un-
der appropriate conditions behave as monofunctional
thiols with a solubilizing amino group [3–7]. However,
not only does the question of what determines the
stereochemistry around mercury remain as yet unre-
solved, but also evaluation of the possible answer seems
rather intricate. As an example, two different mercury
complexes in both mononuclear and polymeric forms,
with linear and tetrahedral coordination, respectively,
were obtained with 3-dimethylamino-1-propanethiol
ligand from apparently identical synthetic procedures
[8].
Mercury–thiolate complexes are well known for their
unusual coordination environments and provide an
outstanding example of the structural diversity found in
the wide family of metal thiolates [1]. Thus, the occur-
rence of two-, three- and four-coordination geometries,
the presence of secondary mercury–sulfur interactions
and the range in size from discrete species to polymeric
structures are remarkable features, now well established
but difficult to predict, in the chemistry of Hg(II)
* Corresponding author.
E-mail address: pilar.gonzalez.duarte@uab.es (P. Gonza´lez-Du-
arte).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00672-0

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X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
In order to extend the current knowledge of the
2.2.2. Synthesis of [Hg(4-SC6H4NH2)2] (2)
chemistry of Hg(II) thiolates, we have undertaken the
synthesis and structural characterization of the com-
plexes obtained with Hg(II) and several aromatic
aminothiol ligands. The existence of an uncoordinated
amino group in the previous complexes has allowed for
further modification of the coordinated ligand by
means of condensation with the carbonyl group of
salicylaldehyde and subsequent formation of a Schiff
base. This, in turn, can behave as a metalloligand
towards different metal centres. All these results, to-
gether with the crystal structure of five of these com-
plexes are reported below.
This complex was obtained by a procedure analogous
to that used for 1. Light green solid was obtained, 0.857
g (93.2%). Anal. Calc. for C12H12HgN2S2: C 32.11; H
2.67; N 6.24; S 14.29. Found: C 32.04; H 2.63; N 6.24;
S 14.42%. IR (cm−1) 3384 and 3354 w(N–H); 1619 and
1595 l(N–H). Yellow laminar crystals were grown
from CH3CN solution.
2.2.3. Synthesis of [MeHg(3-SC6H4NH2)2] (3)
An excess of freshly prepared Ag2O was slowly added
to a suspension of MeHgCl (1.057 g, 4 mmol) in 250 ml
of water. The reaction mixture was allowed to stir for
24 h, at which time the AgCl formed and the unreacted
Ag2O were separated by filtration. Then, the 3-
HSC6H4NH2 ligand (0.425 ml, 4 mmol) was slowly
added to the previous filtrate containing CH3HgOH.
The resulting yellow solution was stirred for 12 h, at
which time the oil formed on the walls of the reaction
flask was separated from the solution and treated with
diethylether to give a white solid, 0.996 g (73.30%).
Anal. Calc. for C7H9HgNS: C 24.75; H 2.65; N 4.12; S
9.44. Found: C 24.82; H 2.41; N 4.21; S 9.28%. IR
(cm−1) 3399 and 3312 w(N–H); 1610 and 1582 l(N–
H). Colourless block-shaped crystals were formed in
CHCl3 solution.
2. Experimental
2.1. General
Only the preparations of complexes of formula
[Hg(n-SC6H4NH2)2], n=3 (1) or 4 (2) were carried out
by standard Schlenk techniques under a nitrogen atmo-
sphere. The organic solvents were dried by conven-
tional methods when used in the reactions carried out
in non-aqueous media. Commercial 3-aminothiophenol,
4-aminothiophenol and salicylaldehyde from Aldrich,
M(CH3COO)2 for M=Zn, Cd or Hg (Fluka), MeHgCl
(Alfa Aesar) and PhHgOOCCH3 (Fluka) were used as
supplied. MeHgOH was obtained in situ from MeHgCl
and Ag2O. Microanalyses were performed with a Carlo
Erba NA-1500 analyser. Infrared spectra were recorded
from KBr discs on a Perkin–Elmer 1710 spectrometer
2.2.4. Synthesis of [MeHg(4-SC6H4NH2)2] (4)
A solution of 4-SC6H4NH2 (0.417 ml, 3 mmol) in 10
ml of methanol was slowly added to an aqueous solu-
tion containing MeHgOH. This was prepared accord-
ing to the procedure described above from MeHgCl
(0.793 g, 3 mmol) in 250 ml of water and Ag2O in
excess. The reaction mixture was allowed to stir for 24
h and the resulting solid formed was separated by
filtration and washed with 10–20 ml of methanol.
Addition of this methanol to the filtrate afforded a
second crop of solid. Both showed coincident elemental
analyses. Total yield 0.996 g (73.30%). Anal. Calc. for
C7H9HgNS: C 24.75; H 2.65; N 4.12; S 9.44. Found: C
24.94; H 2.58; N 4.13; S 9.44%. IR (cm−1) 3419 and
3335 w(N–H); 1617 and 1594 l(N–H).
1
for the range 4000–400 cm−1. H and 13C-NMR spec-
tra were run from DMSO-d6 solutions on Bruker AC
250 or AM 400 spectrometers using tetramethylsilane
as internal standard for 1H and 13C chemical shifts. The
199Hg-NMR spectra were recorded from 0.1 M solu-
tions in DMSO-d6, in a Bruker AM 400 spectrometer
using HgI2 as external standard. The conversion of the
199Hg chemical shifts to the more common HgMe2
reference is l(HgMe2, ext)=l(HgI2, ext;
DMSO)−3106 ppm [9].
1 M/
2.2. Preparation of the complexes
2.2.5. Synthesis of [PhHg(3-SC6H4NH2)2] (5)
2.2.1. Synthesis of [Hg(3-SC6H4NH2)2] (1)
The 3-SC6H4NH2 ligand (0.212 g, 2 mmol) was
slowly added to a suspension of PhHgOOCCH3 (0.673
g, 2 mmol) in 80 ml of methanol. The reaction mixture
was allowed to stir for 24 h, at which time it was
concentrated and the solid filtered off and washed with
diethylether. Yield, 0.591 g, 73.51%. Anal. Calc. for
C12H11HgNS: C 35.87; H 2.74; N 3.49; S 7.98. Found:
C 35.51; H 2.62; N 3.49; S 8.16%. IR (cm−1) 3402 and
3313 w(N–H); 1619 and 1585 l(N–H). Single crystals
were obtained from CH2Cl2 solution containing a few
drops of isopropanol.
The 3-HSC6H4NH2 ligand (0.32 ml, 3 mmol) was
slowly added to a suspension of Hg(CH3COO)2 (0.478
g, 1.5 mmol) in 40 ml of acetonitrile and the mixture
stirred for 15 min to give a light green solid. The
precipitate was collected by filtration, washed with ace-
tonitrile and diethyl ether. Yield, 0.538 g (79.9%). Anal.
Calc. for C12H12HgN2S2: C 32.11; H 2.67; N 6.24; S
14.29. Found: C 32.02; H 2.67; N 6.19; S 13.99%. IR
(cm−1) 3491 and 3408 w(N–H); 1626 and 1594 l(N–
H).

X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
139
2.2.6. Synthesis of [PhHg(4-SC6H4NH2)2] (6)
2.2.10. Synthesis of [PhHg(4-SC6H4NꢀCHC6H4OH)]
(10)
A solution of 4-SC6H4NH2 (0.649 g, 4.7 mmol) in 10
ml of methanol was slowly added to a suspension of
PhHgOOCCH3 (1.570 g, 4.7 mmol) in 40 ml of
methanol. The reaction mixture was allowed to stir for
24 h, at which time the resulting solid formed was
filtered off and washed with methanol. Yield, 1.430 g,
76.30%. Anal. Calc. for C12H11HgNS: C 35.87; H 2.74;
N 3.49; S 7.98. Found: C 35.62; H 2.67; N 3.52; S
8.02%. IR (cm−1) 3462 and 3372 w(N–H); 1614 and
1595 l(N–H).
The synthetic procedure is essentially the same as
that of 7. In this case, the suspension of 6 (0.418 g, 1.04
mmol) in 80 ml of toluene was kept under reflux until
complete dissolution and then salicylaldehyde (109.5 ml,
1.04 mmol) was added. The reflux was kept for 24 h,
and the reaction afforded a pale yellow solid. Yield,
0.227 g, 43.13%. Anal. Calc. for C19H15HgNOS: C
45.11; H 2.97; N 2.77; S 6.34. Found: C 45.52; H 3.06;
N 2.61; S 6.25%. IR (cm−1) 3044 w(C–H), 1611
w(CꢀN) and 1277 w(C–O).
2.2.7. Synthesis of [MeHg(3-SC6H4NꢀCHC6H4OH)]
(7)
2.2.11. Synthesis of
A mixture of 3 (0.353 g, 1.04 mmol) and salicylalde-
hyde (109.4 ml, 1.04 mmol) in 60 ml of toluene contain-
ing a small amount of p-toluenesulfonic acid in order to
catalyse the condensation reaction was added to a
reaction flask equipped with a mini Dean–Stark trap.
The final solution was refluxed for 3 h under a nitrogen
atmosphere, while the reaction was monitored by thin
layer chromatography. At this time solid NaHCO3 was
added in order to neutralize the remaining p-toluenesul-
fonic acid. The sodium salt thus formed and the excess
of NaHCO3 were separated by filtration and the filtrate
evaporated to dryness. The oily residue was treated
successively with diethyl ether, affording a pale yellow
solid. Yield, 0.134 g, 29.1%. Anal. Calc. for
C14H13HgNOS: C 37.98; H 2.93; N 3.16; S 7.22. Found:
C 37.52; H 2.94; N 3.09; S 7.10%. IR (cm−1) 2908
w(C–H), 1618 w(CꢀN) and 1280 w(C–O). Yellow
needles were obtained from a CHCl3–C6H6 solution.
[Zn{MeHg(3-SC6H4NꢀCHC6H4O)}2] (11)
A solution of Zn(CH3COO)2·2H2O (0.088 g, 0.40
mmol) in 25 ml of absolute ethanol was slowly added
with stirring to the pale yellow solution containing 3
(0.289 g, 0.85 mmol) and salicylaldehyde (84.2 ml, 0.80
mmol) in 50 ml of the same solvent. The resultant clear
yellow solution was refluxed for 3 h, at which time the
thin layer chromatography indicated that the initial
complex 3 had totally reacted. Concentration of the
solution to half of its initial volume afforded a yellow
solid. Yield, 0.206 g, 54.1%. Anal. Calc. for
C28H24Hg2N2O2S2Zn: C 35.36; H 2.54; N 2.95; S 6.74.
Found: C 35.45; H 2.75; N 2.95; S 6.56%. IR (cm−1
2907 w(C–H), 1610 w(CꢀN), 1541 and 1311 w(C–O).
)
2.2.12. Synthesis of
[Zn{MeHg(4-SC6H4NꢀCHC6H4O)}2] (12)
The synthetic procedure is analogous to that fol-
lowed for 11. However, in this case, the addition of
Zn(CH3COO)2·2H2O (0.088 g, 0.40 mmol) in 20 ml of
absolute ethanol to the yellow solution containing 4
(0.289 g, 0.85 mmol) and salicylaldehyde (84.2 ml, 0.80
mmol) in 40 ml of the same solvent gave rise to the
formation of a precipitate, which became soluble when
the mixture was heated. The reaction was completed
after 1 h of reflux. Concentration of the solution to 10
ml afforded a yellow solid. Yield, 0.217 g, 57.0%. Anal.
Calc. for C28H24Hg2N2O2S2Zn: C 35.36; H 2.54; N
2.95; S 6.74. Found: C 35.28; H 2.68; N 2.97; S 6.73%.
IR (cm−1) 2908 w(C–H), 1602 w(CꢀN), 1532 and 1327
w(C–O).
2.2.8. Synthesis of [MeHg(4-SC6H4NꢀCHC6H4OH)]
(8)
A similar procedure to that described for 7 was
followed. Thus, a solution of 4 (0.401 g, 1.8 mmol) and
salicylaldehyde (124.3 ml, 1.8 mmol) in 80 ml of toluene
containing a small amount of p-toluenesulfonic acid
was refluxed for 24 h. The final solid residue was dried
with diethyl ether, affording an orange solid. Yield,
0.359 g, 68.5%. Anal. Calc. for C14H13HgNOS: C 37.98;
H 2.93; N 3.16; S 7.22. Found: C 37.94; H 3.00; N 3.09;
S 7.07%. IR (cm−1) 2905 w(C–H), 1615 w(CꢀN) and
1283 w(C–O). Single crystals were grown by slow evap-
oration from acetone solution.
2.2.13. Synthesis of
2.2.9. Synthesis of [PhHg(3-SC6H4NꢀCHC6H4OH)] (9)
The synthetic procedure is analogous to that of 7. In
this case, a solution of 5 (0.381 g, 0.95 mmol) and
salicylaldehyde (99.8 ml, 0.95 mmol) was refluxed in 70
ml of toluene for 8 h, affording a pale yellow solid.
Yield, 0.368 g, 76.7%. Anal. Calc. for C19H15HgNOS: C
45.11; H 2.97; N 2.77; S 6.34. Found: C 45.34; H 3.00;
N 2.69; S 6.07%. IR (cm−1) 3045 w(C–H), 1624
w(CꢀN) and 1281 w(C–O).
[Cd{MeHg(3-SC6H4NꢀCHC6H4O)}2] (13)
The synthetic procedure is analogous to that fol-
lowed for 11. Thus, a solution of Cd(CH3COO)2·2H2O
(0.080 g, 0.30 mmol) in 10 ml of absolute ethanol was
added to the pale yellow solution containing 3 (0.221 g,
0.65 mmol) and salicylaldehyde (63.2 ml, 0.60 mmol) in
70 ml of the same solvent. A precipitate appeared after
30 min of reflux, which was maintained for 12 h.
Filtration of the warm solution afforded a yellow solid.

140
X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
Yield,
0.126
g,
42.1%.
Anal.
Calc.
for
2.3. X-ray crystallography
C28H24CdHg2N2O2S2·12EtOH: C 33.69; H 2.81; N 2.42;
S 6.42. Found: C 34.11; H 2.64; N 2.74; S 6.28%. IR
(cm−1) 2906 w(C–H), 1611 w(CꢀN), 1541 and 1312
w(C–O).
Crystals were examined and data collected on a
Stoe–Siemens four-circle diffractometer (5 and 8) and
on a Bruker AXS SMART CCD diffractometer (2, 3
and 7), in all cases with graphite-monochromated Mo–
,
Ka radiation (u=0.71073 A) and at low temperature.
2.2.14. Synthesis of
[Cd{MeHg(4-SC6H4NꢀCHC6H4OH)}2] (14)
Crystal data are given in Table 1. Semi-empirical ab-
sorption corrections were based on measurements of
equivalent reflections. The structures were solved by
standard heavy-atom and direct methods, and were
refined on all unique F2 values [10]. Disorder was
resolved for one ligand and for both OH groups in
compound 8, with the aid of geometrical and displace-
ment parameter restraints in refinement. Hydrogen
atoms were located in difference syntheses for com-
pounds 2, 3 and 7 and were refined with appropriate
constraints for C–H groups, but they were not located
for compounds 5 and 8. The largest residual electron
density peaks are close to heavy atoms. The crystal of
compound 5 was probably racemically twinned, with a
refined enantiopole parameter of 0.46(2) [11].
The synthetic procedure is analogous to that fol-
lowed for 11. Thus, a solution of Cd(CH3COO)2·2H2O
(0.080 g, 0.30 mmol) in 10 ml of absolute ethanol was
added to the pale yellow solution containing 4 (0.221 g,
0.65 mmol) and salicylaldehyde (63.2 ml, 0.60 mmol) in
40 ml of the same solvent. A yellow precipitate ap-
peared after 2 h of reflux, which was maintained for
two more hours. Rapid filtration of the warm solution
afforded an orange–yellow solid. Yield, 0.122 g, 40.8%.
Anal. Calc. for C28H24CdHg2N2O2S2·12EtOH: C 33.69;
H 2.81; N 2.42; S 6.42. Found: C 34.13; H 2.54; N 2.84;
S 6.64%. IR (cm−1) 2907 w(C–H), 1605 w(CꢀN), 1530
and 1320 w(C–O).
Table 1
Crystallographic data for [Hg(4-SC6H4NH2)2] (2), [CH3Hg(3-SC6H4NH2)] (3), [PhHg(3-SC6H4NH2)] (5), [CH3Hg(3-SC6H4NꢀCHC6H4OH)] (7),
[CH3Hg(4-SC6H4NꢀCHC6H4OH)] (8)
2
3
5
7
8
Formula
M
C12H12HgN2S2
449.0
C7H9HgNS
339.8
C12H11HgNS
401.9
C14H13HgNOS
443.9
C14H13HgNOS
443.9
Crystal system
Space group
Unit cell dimensions
Monoclinic
P21/n
Triclinic
Orthorhombic
Pna21
Monoclinic
C2/c
triclinic
(
(
P1
P1
,
a (A)
4.3066(3)
27.483(2)
10.7052(8)
8.1782(10)
10.2859(13)
10.6757(14)
102.286(2)
91.214(2)
91.164(3)
877.0(2)
4
7.172(2)
14.215(3)
23.597(5)
20.265(2)
6.8258(8)
40.774(5)
7.068(3)
13.687(5)
14.781(6)
101.74(3)
96.42(3)
102.83(3)
1346.5(9)
4
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
92.785(2)
93.966(3)
3
,
1265.5(2)
4
2.356
12.47
160
2405.6(9)
8
2.219
12.94
160
5626.5(11)
16
2.096
11.08
160
Z
Dcalc (g cm−3
)
2.574
17.71
160
2.190
11.57
160
v (mm−1
T (K)
)
Crystal size (mm)
qmax (°)
0.36×0.16×0.04
25.5
0.44×0.44×0.18
25.5
0.55×0.10×0.08
25.0
0.54×0.10×0.08
25.7
0.52×0.12×0.03
25.0
Transmission factor range
Reflections measured
Unique reflections
Rint
0.230–0.777
5446
2099
0.0951
167
0.0584
0.1526
1.199
0.154–0.953
7560
2872
0.1144
197
0.0582
0.1776
1.167
0.663–0.932
3203
2947
0.0401
142
0.0359
0.0888
1.045
0.093–0.382
11630
4673
0.0878
330
0.0591
0.1251
1.216
0.058–0.536
6732
4740
0.0503
410
0.1054
0.2617
1.145
Number of parameters
R (F, F2\2|)
Rw (F2, all data)
Goodness of fit
Maximum, minimum electron
2.29, −3.53
3.40, −2.55
2.40, −1.61
1.48, −1.43
4.12, −4.50
−3
,
density (e A
)

X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
141

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X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
Table 3
Coupling constants (Hz) for complexes [Hg(3-SC6H4NH2)2] (1), [Hg(4-SC6H4NH2)2] (2), [CH3Hg(3-SC6H4NH2)] (3), [CH3Hg(4-SC6H4NH2)] (4),
[PhHg(3-SC6H4NH2)] (5), [PhHg(4-SC6H4NH2)] (6), [CH3Hg(3-SC6H4NꢀCHC6H4OH)] (7), [CH3Hg(4-SC6H4NꢀCHC6H4OH)] (8), [PhHg(3-
SC6H4NꢀCHC6H4OH)]
(9),
[PhHg(4-SC6H4NꢀCHC6H4OH)]
(10),
[Zn{CH3Hg(3-SC6H4NꢀCHC6H4O)}2]
(11),
[Zn{CH3Hg(4-
SC6H4NꢀCHC6H4O)}2] (12)
Compound
3J(H1–H2) 3J(H2–H3) 4J(H1–H3) 2J(Hg–H6)
3J(H7–H8) 3J(H8–H9) 3J(H11–H12
)
3J(H12–H13
)
3J(H13–H14
)
3-HSC6H4NH2 8.39
8.08
7.32
8.07
7.93
8.04
8.05
7.94
1
7.93
7.11
7.33
8.05
8.05
7.94
1.22
1.62
3
5
7
9
167.97
173.28
170.31
7.32
7.32
2.19
8.05
8.04
7.93
8.05
8.05
7.93
8.05
8.05
8.23
11
4-HSC6H4NH2 8.74
2
4
6
8
10
12
8.41
8.04
8.10
8.05
8.04
8.55
165.24
173.28
175.19
7.35
7.31
7.35
7.31
8.05
8.04
7.94
8.05
8.05
7.97
8.05
8.05
8.54
3. Results and discussion
sence of protons with a measurable coupling constant
with the mercury nucleus in 1, 2, 5 and 6 hinders the
use of the previous sequences. The 199Hg chemical shift
values found for 1, 2 and for 3, 4 (Table 5) are,
respectively, within the ranges given in the literature for
[Hg(SR)2] and [MeHg(SR)] compounds [2,15,16] con-
taining Hg(II) with digonal coordination. Reported
data for [PhHgX] complexes reduce to X=inorganic
anions [17] and they are not therefore a good reference
for establishing the coordination geometry of Hg(II) in
[PhHg(SR)] complexes 5, 6. On the other hand, consid-
ering that the 199Hg resonances indicate that the sec-
ondary Hg···S interactions present in the solid phase of
2 and 3 are absent in solution, it seems likely that the
same behaviour could be extended to 5. Thus, the fact
that its X-ray structure consists of linear C–Hg–S units
enables us to propose that the experimental chemical
shift values of −948 and −963 ppm are indicative of
3.1. Complexes of formula [Hg(n-SC6H4NH2)2], n=3
(1) or 4 (2) and [RHg(n-SC6H4NH2)], R=Me, n=3
(3) or 4 (4); R=Ph, n=3 (5) or 4 (6)
The reaction of [Hg(CH3COO)2], MeHgOH and
PhHgCH3COO with the aromatic aminothiols 3-
SC6H4NH2 and 4-SC6H4NH2 produces the title com-
plexes 1–6 with relatively good yields. They are slightly
soluble in common organic low coordinating solvents
such as CH3CN, CHCl3 and EtOH. However, consider-
ing complexes 3–6, solubility increases if the compound
contains the (3-SC6H4NH2)− aminothiolate ligand and/
or the MeHg+ species. Complexes 1–6 show a signifi-
cant tendency to decompose, mainly in solution but
also in the solid phase, yielding elemental mercury and
the corresponding disulfide. This tendency increases
with temperature, and solid complexes containing
MeHg+ are unstable above 8–10°C. Accordingly, all
complexes have to be kept at low temperature.
Analogous redox decomposition has already been re-
ported for solid [Hg(SPh)2] at 240°C [12].
digonal coordination about Hg(II) in
respectively.
5 and 6,
The crystal structures of [Hg(4-SC6H4NH2)2] (2),
[MeHg(3-SC6H4NH2)2] (3) and [PhHg(3-SC6H4NH2)2
(5) have been solved by X-ray diffraction. Selected
bond lengths and angles are given in Tables 6–8. The
Hg–S distance in the basic units of the three complexes
1
Complexes 1–6 have been fully characterized by H
and 13C-NMR spectroscopies (Tables 2–4 respectively).
The assignment of the signals has been deduced by
standard calculations and by comparison with the free
ligands and related literature data. In addition, 199Hg-
NMR data (Table 5) have allowed determination of the
coordination geometry about mercury(II) in solution.
In order to diminish considerably the registration time
of the 199Hg-NMR spectrum without decreasing the
signal-to-noise ratio, we have used the INEPT [13] and
RINEPT [14] pulse sequences for complexes 3 and 4 of
formula [MeHg(SC6H4NH2)]. Unfortunately, the ab-
,
(Figs. 1–3) lies within the range 2.35–2.39 A and
consequently it is in good concordance with the sum of
covalent radii of diagonally coordinated mercury with
sulfur atoms [18], and with that found in closely related
species [17,19].
The asymmetric unit of 2, one quarter of the unit
cell, contains one molecule of [Hg(4-SC6H4NH2)2] as
shown in Fig. 1a. The Hg atom presents a linear
two-coordination, with the S–Hg–S angle only slightly
bent (175.7°). The two Hg–S bonds are effectively

X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
143

144
X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
,
Table 5
distance of 3.19 A, significantly shorter than the sum of
199Hg-NMR spectroscopic data of complexes 1–6
,
the corresponding van der Waals radii (3.5 A [2]). Thus,
the coordination number of Hg increases to 5 (2+3 in
terms of primary and secondary interactions) with
adoption of square-based pyramidal geometry (Fig.
1b), giving a chain polymer along the unit cell a axis.
The core of the chain contains parallel S–Hg–S pri-
mary units and is formed by fused Hg3S4 incomplete
cubanes when the secondary interactions are also con-
sidered; it is surrounded by a sheath of radiating aro-
matic substituents, all approximately parallel.
Complex
l
199Hg (ppm) a
[Hg(3-SC6H4NH2)2] (1)
[Hg(4-SC6H4NH2)2] (2)
[MeHg(3-SC6H4NH2)2] (3)
[MeHg(4-SC6H4NH2)2] (4)
[PhHg(3-SC6H4NH2)2] (5)
[PhHg(4-SC6H4NH2)2] (6)
−1079 (s)
−1135 (s)
−613 (q)
−645 (q)
−948 (s)
−963 (s)
a s singlet, q quartet.
The asymmetric unit of 3 is half a unit cell and
consists of two crystallographically independent
[MeHg(3-SC6H4NH2)2] molecules (Fig. 2a). Hg coordi-
nation is essentially linear, with an average C–Hg–S
angle of 175.5°, and the Hg–S and Hg–C distances are
in good agreement with literature data for related com-
pounds [17]. Each of these two molecules forms a
Table 6
,
Selected bond distances (A) and angles (°) for [Hg(4-SC6H4NH2)2]
(2); in this and other tables, primed atoms are related to unprimed
atoms by various symmetry operations
Hg(1)–S(1)
S(1)–C(11)
Hg(1)–S(2%)
Hg(1)–S(1¦)
2.361(3)
1.784(13)
3.252(3)
3.146(3)
Hg(1)–S(2)
S(2)–C(21)
Hg(1)–S(1%)
2.352(3)
1.787(12)
3.185(3)
centrosymmetric dimer with
a
symmetry-related
molecule through secondary Hg···S bonds, and the
anti-disposed aromatic substituents are approximately
perpendicular to the central Hg2S2 core (dihedral angles
of 88.7 and 85.3°), minimizing possible steric interac-
tions within the dimeric units. Further secondary bond-
ing, between amino groups and mercury, links the
dimers into sheet networks (Fig. 2b). The average
S(1)–Hg(1)–S(2)
C(11)–S(1)–Hg(1)
S(1)–Hg(1)–S(1¦)
175.75(11) C(21)–S(2)–Hg(1)
103.3(4) S(2%)–Hg(1)–S(1%)
84.06(10) S(1)–Hg(1)–S(2%)
101.7(4)
177.12(8)
79.12(9)
Table 7
,
Selected bond distances (A) and angles (°) for [CH3Hg(3-SC6H4NH2)]
(3)
,
Hg···N distance is 2.9 A, less than the sum of the van
,
der Waals radii (3.3 A [2]). As a result, the coordination
Hg(1)–C(11)
Hg(1)–S(1)
S(1)–C(12)
Hg(1)–N(2)
Hg(1)–S(2%)
2.074(14)
2.373(4)
1.747(15)
2.920(12)
3.417(4)
Hg(2)–C(21)
Hg(2)–S(2)
S(2)–C(22)
Hg(2)–N(1%)
Hg(1)–S(1%)
2.092(16)
2.379(4)
1.756(14)
2.905(13)
3.507(4)
number of Hg should be considered as 2+2, with a
geometry best regarded as pseudo-octahedral with two
cis-positions vacant.
The crystal structure of 5 also has two crystallo-
graphically independent molecules in the asymmetric
unit, which is here one quarter of the unit cell. The two
molecules of [PhHg(3-SC6H4NH2)2] differ significantly
only in the orientations of the aromatic substituents
(Fig. 3a). The average C–Hg–S angle for the essen-
tially linear coordination geometry is 176.6°. Each mer-
cury atom has two secondary Hg···S interactions with
C(11)–Hg(1)–S(1) 175.5(5)
C(12)–S(1)–Hg(1) 105.6(5)
S(1)–Hg(1)–S(1%)
C(21)–Hg(2)–S(2)
C(22)–S(2)–Hg(2)
174.8(5)
105.0(5)
94.71(10)
91.28(11) S(2)–Hg(2)–S(2%)
Table 8
,
Selected bond distances (A) and angles (°) for [PhHg(3-SC6H4NH2)]
(5)
,
average distance 3.26 A, to give 2+2 coordination, and
Hg(1)–C(7)
Hg(1)–S(1)
S(1)–C(1)
Hg(1)–S(1%)
Hg(1)–S(2%)
2.058(14)
2.363(4)
1.81(2)
3.229(5)
3.185(7)
Hg(2)–C(19)
Hg(2)–S(2)
S(2)–C(13)
Hg(2)–S(1%)
Hg(2)–S(2%)
2.074(15)
2.364(4)
1.76(2)
3.250(7)
3.357(5)
the result is a linking of the individual molecules into a
polymeric zig-zag ladder (Fig. 3b), surrounded by a
sheath of radiating aromatic substituents. The ladder
may be considered as composed of pseudo-cubanes,
each having one face opened up by lengthening of two
opposite Hg···S edges, and sharing opposite faces.
C(7)–Hg(1)–S(1)
C(1)–S(1)–Hg(1)
S(1%)–Hg(1)–S(1)
S(2%)–Hg(1)–S(1)
C(7)–Hg(1)–S(1%)
S(2%)–Hg(1)–S(1%)
S(2%)–Hg(1)–C(7)
174.9(6)
102.3(6)
89.88(11) S(1%)–Hg(2)–S(2)
85.22(17) S(2%)–Hg(2)–S(2)
95.0(5)
73.21(14) S(2%)–Hg(2)–S(1%)
97.4(8) S(2%)–Hg(2)–C(19)
C(19)–Hg(2)–S(2)
C(13)–S(2)–Hg(2)
178.2(7)
105.4(6)
83.72(18)
92.38(13)
97.8(8)
3.2. Complexes of formula
[RHg(n-SC6H4NꢀCHC6H4OH)] R=Me, n=3 (7) or
4 (8); R=Ph, n=3 (9) or 4 (10)
C(19)–Hg(2)–S(1%)
70.71(14)
89.1(5)
The synthetic procedures followed for obtaining
complexes 7–10 have afforded moderate-to-good
yields. Their solubility in common organic solvents is
dependent on the nature of R and the value of n. Thus,
,
equal (2.352(3), 2.361(3) A). The mercury atom of each
basic unit interacts with three neighbouring units by
means of Hg···S secondary bonds having an average

X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
145
complexes with R=Me are clearly more soluble than
those with R=Ph. Within each group, complexes with
n=3 are more soluble than those with n=4. The main
feature of the infrared spectrum of 7–10 is the absorp-
tion band at about 1280 cm−1, which corresponds to
the stretching frequency of the C–O group in N-aryl-
salicylaldimines [18] and is thus indicative of the pres-
ence of the condensed salicylaldehyde. Complexes 7–10
1
have been characterized by H and 13C-NMR as shown
1
in Tables 2–4, respectively. In the H-NMR spectrum
of 7–10 the resonance at ca. 9 ppm and the absence of
that at ca. 5 ppm, due to the N–CH and NH2 protons,
Fig. 1. The structure of [Hg(4-SC6H4NH2)2] (2): (a) the asymmetric unit without H atoms, showing atom numbering; (b) a section of the polymeric
chain of linked incomplete Hg3S4 cubanes.
Fig. 2. The structure of [MeHg(3-SC6H4NH2)2] (3): (a) the asymmetric unit without H atoms, showing the atom numbering; (b) part of the sheet
network resulting from Hg···S and Hg···N secondary interactions.

146
X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
Fig. 3. The structure of [PhHg(3-SC6H4NH2)2] (5): (a) the asymmetric unit without H atoms, showing the atom numbering; (b) a section of the
zig-zag ladder formed through Hg···S interactions.
respectively, are indicative of the formation of the
Schiff base. However, owing to the complexity of the
aromatic region in these spectra (7, 8 and 9, 10 contain
two and three aromatic rings, respectively), 2D 1H-
NMR spectra were also recorded. These, together with
for 7. The asymmetric unit is one eighth of the unit cell
in 7 and one half of the unit cell in 8, but this difference
affects the details of the packing of the individual
ladders in the two crystal structures and not the overall
form of these ladders themselves. The thiolate sub-
stituents have bond lengths and angles similar to those
of related Schiff bases. Common to both 7 and 8 is the
E disposition of the benzene rings within each sub-
stituent, minimizing steric repulsions, and the presence
of intramolecular O–H···N hydrogen bonds between
hydroxyl and imine groups; the average N···O distance
1
the H-NMR data of the uncondensed parent amine
complexes 3–6 and of the free salicylaldehyde allowed
1
definite assignment of all H resonances in complexes
7–10. Their 13C-NMR spectrum also shows a consider-
able number of peaks due to the aromatic carbon nuclei
within the range 115–140 ppm. The tentative assign-
ment of these resonances (Table 4) has been based on
standard calculations considering the n-HSC6H4NꢀC-
HC6H4OH molecule and on comparison among the
four complexes. In this case, the parent complexes 3–6
cannot be taken as reference, given that their 13C
resonances shift 1–6 ppm upon formation of the Schiff
base.
,
for the two independent molecules of 7 is 2.62 A, but
Table 9
,
Selected bond distances (A) and angles (°) for [CH3Hg(3-
SC6H4NꢀCHC6H4OH)] (7)
Hg(1)–S(1)
Hg(1)–C(11)
S(1)–C(12)
Hg(1)–S(1%)
Hg(1)–S(2%)
2.383(3)
2.071(12)
1.767(13)
3.240(3)
3.128(3)
Hg(2)–S(2)
Hg(2)–C(21)
S(2)–C(22)
Hg(2)–S(1%)
Hg(2)–S(2%)
2.379(3)
2.092(12)
1.771(13)
3.160(3)
3.251(3)
The molecular structures of complexes 7 and 8 are
closely related, and so they are described together (Ta-
bles 9 and 10). The asymmetric unit in each case
consists of two independent molecules of [MeHg(n-
SC6H4NꢀCHC6H4OH)] with n=3 for 7 (Fig. 4a) and 4
for 8 (Fig. 5a). There are no significant differences in
the geometric parameters for the primary coordination
of the metal centres in these two structures. In each
case the mercury coordination is essentially linear (aver-
age C–Hg–S angles 178.5 and 176.4°), and overall
geometric features are similar to those of compound 3.
However, in both structures the further Hg···S sec-
ondary interactions raise the coordination number to
2+2 and produce the same kind of ladder polymer as
for 5, shown in different views in Fig. 4b and Fig. 5b.
The ladder for 8 is somewhat more distorted than that
C(11)–Hg(1)–S(1) 178.7(4)
C(12)–S(1)–Hg(1) 105.2(4)
C(21)–Hg(2)–S(2)
C(22)–S(2)–Hg(2)
178.3(5)
102.3(4)
Table 10
,
Selected bond distances (A) and angles (°) for [CH3Hg(4-
SC6H4NꢀCHC6H4OH)] (8)
Hg(1)–S(1)
Hg(1)–C(1)
S(1)–C(2)
Hg(1)–S(1%)
Hg(1)–S(2%)
2.369(7)
2.05(4)
1.77(3)
3.491(7)
3.353(7)
Hg(2)–S(2)
Hg(2)–C(15)
S(2)–C(16)
Hg(2)–S(1%)
Hg(2)–S(2%)
2.384(8)
2.11(3)
1.74(3)
3.294(8)
3.316(7)
C(1)–Hg(1)–S(1) 176.5(11)
C(2)–S(1)–Hg(1) 100.7(9)
C(15)–Hg(2)–S(2)
C(16)–S(2)–Hg(2)
176.2(10)
96.7(11)

X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
147
Fig. 4. The structure of [MeHg(3-SC6H4NꢀCHC6H4OH)] (7): (a) the asymmetric unit without H atoms, showing the atom numbering; (b) the
ladder viewed from a direction approximately perpendicular to one equivalent to Fig. 3b.
Fig. 5. The structure of [MeHg(4-SC6H4NꢀCHC6H4OH)] (8): (a) the asymmetric unit without H atoms, showing the atom numbering; (b) the core
of the ladder structure common to this and compounds 5 and 7.

148
X. Almagro et al. / Journal of Organometallic Chemistry 623 (2001) 137–148
the hydrogen bonding does not occur throughout the
structure of 8 because of two-fold disorder in the
orientations of the hydroxyphenyl groups (Fig. 5b).
use of specific strategies in order to increase the solubil-
ity of the complexes derived from [RHg(n-SC6H4Nꢀ
CHC6H4O)] metalloligands seems to be a prior require-
ment for pursuing their study.
3.3. Complexes of formula
[MII{MeHg(n-SC6H4NꢀCHC6H4O)}2], M=Zn, n=3
(11) or 4 (12); M=Cd, n=3 (13) or 4 (14)
4. Supplementary material
The three basic synthetic procedures reported [19] in
obtaining the title complexes can be summarized as
follows: (i) reaction of metal ion and Schiff base in the
presence of added base, (ii) reaction of primary amine
with bis-(salicylaldehyde) metal complex, (iii) template
reaction. All of these have been assayed for different
divalent metals (Mn, Ni, Pd, Cu, Zn, Cd) with both
aminothiolate derivatives of MeHg+ and PhHg+.
However, the low solubility of the compounds or mix-
tures obtained has not allowed the synthesis of pure
complexes except for 11–14. For these complexes, the
template reaction procedure has afforded the best yield
for the shortest reaction time and for the minimum
volume of solvent required to run the reaction in solu-
tion. Complexes 11 and 12 are somewhat soluble in
most organic solvents. However, 13 and 14 are only
soluble in hot DMSO, DMF and pyridine. As already
described, complexes with n=3 are more soluble than
their analogues with n=4. The main features of the
infrared spectrum of 11–14 are in concordance with the
coordination of Zn(II) and Cd(II) to the [MeHg(n-
SC6H4NꢀCHC6H4OH)] metalloligand by means of the
imine N and the O atom of the deprotonated OH
group. This is mainly shown by the frequency of the
stretching vibration of CꢀN and C–O groups, which
are shifted 5–30 cm−1 downwards and 30–50 cm−1
upwards, respectively, if compared with those of the
parent complexes 7–10. This coordination is confirmed
Five crystallographic files in CIF format have been
deposited at the Cambridge Crystallographic Data Cen-
tre, CCDC nos. 147377–147381. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
This work was supported by the DGICYT, Ministe-
rio de Educacio´n y Ciencia, Spain, through Project
PB97-0216. Financial support from EPSRC (UK) and
Bruker AXS Ltd. (UK) is also acknowledged. LC is
indebted to La Caixa (Spain) for a British Council-La
Caixa Fellowship.
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1
by the H and 13C-NMR data of Zn(II) complexes 11
and 12, Tables 2–4, respectively, as well as by prelimi-
nary information of the X-ray structure of 12. The
1
comparison of the H-NMR data of 11 and 12 with
those of 7 and 8, respectively, shows a decrease in the
degree of overlapping of the signals corresponding to
the aromatic protons of the salicylaldehyde moiety. A
similar comparison of the 13C-NMR data indicates that
the values of the chemical shifts corresponding to the
carbon nuclei of CꢀN and C–O groups in 11 and 12 are
shifted ca. 10 ppm downfield upon the complex forma-
tion. At this stage, the poor quality of the crystals
obtained for 12 only allows us to infer that it has a
trimetallic ZnHg2 molecular structure with an essen-
tially linear coordination of Hg to the methyl carbon
and thiolate sulfur atoms, and with tetrahedral N2O2
coordination about the Zn atom. With regard to the
Cd(II) complexes 13 and 14, their low solubility in
practically all solvents has hindered us from recording
[18] G.C. Percy, D.A. Thorton, J. Inorg. Nucl. Chem. 34 (1972) 3357.
[19] R.H. Holm, G.W. Everett, Jr., A. Chakravorty, Prog. Inorg.
Chem. 7 (1966) 83.
1
their H and 13C-NMR spectra, as well as from making
attempts to obtain single crystals. Consequently, the