Cationic and neutral phenylmercury(II) complexes with heterocyclic thione ligands. X-ray structures of [HgPh(dmpymtH)][BF4] · H2O and [{HgPh}2(μ-dtu)]

Article abstract of DOI:10.1016/j.jorganchem.2008.10.035

The neutral complex [HgPh(dmpymt)] 1 (dmpymtH = 4,6-dimethylpyrimidine-2(1H)-thione) reacts with HBF₄ to give the cationic complex [HgPh(dmpymtH)][BF₄] 2. The X-ray molecular structure of the later revealed a [2+1] coordination spher

Full text of DOI:10.1016/j.jorganchem.2008.10.035

Journal of Organometallic Chemistry 694 (2009) 253–258
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Cationic and neutral phenylmercury(II) complexes with heterocyclic thione ligands.
X-ray structures of [HgPh(dmpymtH)][BF4] Á H2O and [{HgPh}2(
l-dtu)]
a
b
c
Sebastião S. Lemos a, , Danilo U. Martins , Victor M. Deflon , Javier Elena
*
a Instituto de Química, Universidade de Brasília, 70904-970 Brasília, DF, Brazil
b Instituto de Química de São Carlos, Universidade de São Paulo, CP 780, 13560-970 São Carlos, SP, Brazil
c Instituto de Física, Universidade de São Paulo, 13560-970, São Carlos, SP, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
The neutral complex [HgPh(dmpymt)] 1 (dmpymtH = 4,6-dimethylpyrimidine-2(1H)-thione) reacts with
HBF4 to give the cationic complex [HgPh(dmpymtH)][BF4] 2. The X-ray molecular structure of the later
revealed a [2+1] coordination sphere about the mercury(II) atom (CÀHgÀS and HgÁ Á ÁN). In the dinuclear
Received 27 September 2008
Received in revised form 18 October 2008
Accepted 20 October 2008
Available online 25 October 2008
complex [(HgPh)2(l-dtu)] 3 [dtuH2 = 2,4(1H,3H)-pyrimidinedithione or dithiouracil] the coordination
spheres are also [2+1] although dissimilar regarding the HgÁ Á ÁN secondary bonds. NMR spectroscopy
(1H, 13C and 199Hg) studies were undertaken in solution and the results discussed in the light of the X-
ray structures.
Keywords:
Phenylmercury(II) complexes
Heterocyclic thione ligands
X-ray structure
Ó 2008 Elsevier B.V. All rights reserved.
NMR spectroscopy
Secondary bonds
1. Introduction
enabling the nitrogen atoms to establish secondary interactions.
In order to illustrate the structural diversity of organylmercury(II)
The establishment of the coordination number of the HgII atom
in its complexes is crucial to understanding their properties. It has
been noticed, mainly by X-ray crystallography, that the mercury(II)
atom is, in addition to two strong bonds, usually being engaged in
intra- and/or intermolecular secondary bonds, giving rise to various
derivatives containing S, N or O donating atoms, originated mainly
due to secondary bonds, we will present hereafter some typical
cases. In addition to the primary coordination, C–Hg–S, the com-
plex methyl(pyridine-2-thiolato)mercury(II) exhibits intra-HgÁ Á ÁN
and intermolecular HgÁ Á ÁS interactions [5]; the methyl(2-mer-
capto-4-methylpyrimidinato)mercury(II) presents intermolecular
HgÁ Á ÁS and HgÁ Á ÁHg interactions [6]. Not surprisingly, the complex
methyl(2-methylthio-4-pyrimidinonato)mercury(II) is C–Hg–N
primarily coordinated with additional intra-HgÁ Á ÁO and intermo-
lecular HgÁ Á ÁN secondary interactions [7]. The complex phenyl
(diacetylmonoximemorpholine N-thiohydrazonate)mercury(II) is
C–Hg–S primarily coordinated with additional intramolecular
HgÁ Á ÁN interaction [8].
´
supramolecular arrangements. Grdenic [1] has proposed two kinds
of coordination numbers to better structurally describe such com-
plexes: (i) the primary coordination number (mercury-donating
atom bond distance appropriate for their covalent radii) and (ii)
effective coordination number (mercury-donating atom interac-
tions that are less than the sum of their van der Waals radii). It
has been pointed out that secondary bonds might be implicated in
the easy mobility of organylmercury(II) ion in living organisms [2].
The study of monoorganylmercury(II)-thione complexes has
been devoted mainly to the methylmercury(II) cation, probably be-
cause of its relevance in natural systems due to biological methyl-
ation of the mercury atom [3]. Usually the organylmercury(II)
moiety links primarily to sulfur atoms present in the cysteinyl
groups of polypeptides and completes its coordination sphere by
establishing secondary bonds with nearby donating atoms. Hetero-
cyclic compounds like pyrimidinethione/thiol have been consid-
ered good candidates for modeling this scenario [4]. In their
complexes, usually the mercury atom bounds to the sulfur atom,
Here, we present the preparation and structural studies both in
the solid state and in solution for some mono- and dinuclear com-
plexes of the phenylmercury(II) cation with pyrimidinethione
derivatives as ligands.
2. Experimental details
2.1. Materials
Phenylmercury(II) acetate and dtuH2 was purchased from
Aldrich and dmpymtH was prepared following a reported method
[9].
* Corresponding author. Tel.: +55 61 3799 4575; fax: +55 61 3273 4149.
E-mail address: sslemos@unb.br (S.S. Lemos).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.10.035

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S.S. Lemos et al. / Journal of Organometallic Chemistry 694 (2009) 253–258
Table 1
2.2. Instrumentation
Crystallographic data for [HgPh(dmpymtH)][BF4] Á H2O 2 and [{HgPh}2(
l-dtu)] 3.
Elemental analyses (C, H, N, S) were performed on a Fisions
MOD EA 1108 analyser. The infrared spectra (KBr pellets, 4000–
400 cmÀ1) were recorded on BOMEM BM 100 FT-IR spectrometer.
NMR spectra were recorded on a Varian MERCURY plus spectrom-
eter, 7.05 T, operating at 300.07 MHz for 1H, 75.46 MHz for 13C, and
53.74 MHz for 199Hg. Chemical shifts (d) are given in ppm relative
to SiMe4 (internal reference for 1H and 13C) and net HgMe2 (exter-
nal reference for 199Hg), checked against 1.0 molar solution of
HgCl2 in DMSO (d À1501.0) by using the substitution method [10].
Crystallographic data were collected at room temperature on a
2
3
Molecular formula
Formula weight
Crystal system
Space group
Temperature (°C)
Unit cell dimensions
a (pm)
C12H15BF4HgN2OS
522.72
Monoclinic
P21/n
C16H12Hg2N2S2
697.58
Monoclinic
P21/n
20(2)
20(2)
741.00(2)
1263.80(6)
1728.50(8)
90
95.166(3)
90
1.61212(12)
4
2.154
1621.93(7)
540.75(3)
2293.50(10)
90
98.873(3)
90
1.98746(16)
4
2.331
b (pm)
c (pm)
a
(°)
b (°)
(°)
Enraf–Nonius Kappa-CCD diffractometer, equipped with Mo K
a
c
Volume (nm3)
Z
radiation (0.71073 Å) and graphite monochromator. The cell
refinements were performed using the software Collect [11] and
Scalepack [12], and the final cell parameters were obtained on all
reflections. Data reduction was carried out using the software Den-
zo-SMN and Scalepack [12]. Since the absorption coefficients are
significant, absorption corrections were applied.
Dcalc. (g/cm3)
Absorption coefficient (mmÀ1
F(000)
)
9.717
984
15.637
1256
Crystal size (mm3)
0.04 Â 0.10 Â 0.17
3.22–27.12
À7 ? 8, À14 ? 16,
À19 ? 22
6848
3365/0.0296
27.12 (94.3%)
3365/200
0.02 Â 0.08 Â 0.16
3.15–27.57
À21 ? 21, À6 ? 7,
À29 ? 29
20036
4536/0.0624
27.57 (99.0%)
4536/199
h Range for data collection (°)
Limiting indices (h, k, l)
The structures were solved with SHELXS97 by direct methods [13].
All non-hydrogen atoms of the molecules were clearly solved and
full-matrix least-squares refinement of these atoms with aniso-
tropic thermal parameters was carried on [14]. The C–H hydrogen
atoms were positioned stereochemically and were refined with
Reflections collected
Reflections unique/Rint
Completeness to h (°)
Data/parameters
2
Absorption correction
Maximum and minimum
transmission
fixed individual displacement parameters [Uiso(H) = 1.2Ueq (Csp
0.466 and 0.177
0.645 and 0.173
and Nsp2) or 1.5Ueq (Csp3 and OH)] using a riding model [14]. Tables
were generated by WINGX [15] and the structure representations by
PLATON [16]. Additional crystal data and more information about the
X-ray structural analyses are shown in Table 1.
Goodness-of-fit on F2
1.049
1.083
Final R indices [I > 2
R indices (all data)
r(I)]
R1 = 0.0334,
wR2 = 0.0814
R1 = 0.0462,
wR2 = 0.0861
0.730 and –0.591
R1 = 0.0533,
wR2 = 0.1389
R1 = 0.0941,
wR2 = 0.1624
1.849 and –1.351
2.3. Syntheses of the complexes
Largest difference in peak and
hole (e ÅÀ3
)
2.3.1. [HgPh(dmpymt)] 1
2.3.1.1. Method A. A suspension containing Hg(C6H5)(OOCCH3)
(HgPhAcO) (168.3 mg, 0.5 mmol) and C6H8N2S (dmpymtH)
(70.1 mg, 0.5 mmol) in toluene (20 mL) was heated to reflux under
continuous stirring when a clear solution has developed. The reflux
was continued for 2 h. The slow evaporation of the solution into a
beaker at room temperature produced colorless plates after six
weeks. Yield 186 mg (90%). M.p. 128–130 °C. Anal. Found: C,
34.76; H, 2.64; N, 6.80; S, 7.62%. C12H12HgN2S Calc.: C, 34.57; H,
2.90; N, 6.72; S, 7.69. IR (KBr): 3040(w), 1577(s), 1537, 1527(m),
1475(w), 1429(m), 1386(w), 1366(w), 1339(m), 1253(vs),
1023(w), 997(w), 950(w), 875(w), 726(s), 693(m), 669(w),
HgPhAcO
1) HBF4
dmpymtH
2) dmpymtH
HBF4
[HgPh(dmpymt)]
[HgPh(dmpymtH)][BF4]
2
1
Scheme 1. Summary of the synthetic procedure for obtaining the phenylmer-
cury(II) complexes.
549(w), 445(w) cmÀ1
.
Fig. 1. ORTEP plot of [HgPh(dmpymtH)][BF4] Á H2O 2 with the atom numbering. Thermal ellipsoids are scaled at 50%.

S.S. Lemos et al. / Journal of Organometallic Chemistry 694 (2009) 253–258
255
Fig. 2. ORTEP plot of [{HgPh}2(l-dtu)] 3 with the atom numbering. Thermal ellipsoids are scaled at 50%.
2.3.1.2. Method B. To
0.5 mmol) in acetonitrile (10 mL) was added
a
suspension of HgPhAcO (168.3 mg,
solution of
Table 2
Selected bond lengths (pm) and angles (°) for [HgPh(dmpymtH)][BF4] Á H2O 2.
a
dmpymtH (70.1 mg, 0.5 mmol) in acetonitrile (10 mL). A clear
solution resulted in a few minutes. The solution was magnetically
stirred for 2 h and filtered to remove any insoluble material. The
solution was allowed to evaporate at room temperature to approx-
imately 1 mL. Upon addition of hexane (3 mL) the product precip-
itated immediately. Yield 200 mg (95%).
Hg–S
Hg–C(6)
C(7)–S
C(7)–N(1)
C(7)–N(2)
HgÁ Á ÁN(1)
236.7(2)
207.1(6)
171.5(6)
133.9(7)
135.6(7)
289.4(4)
C(6)–Hg–S
C(7)–S–Hg
N(1)–C(7)–S
N(2)–C(7)–S
177.3(2)
95.5(2)
120.6(4)
118.6(4)
2.3.2. [HgPh(dmpymtH)][BF4] Á H2O 2
Table 3
Selected bond lengths (pm) and angles (°) for [{HgPh}2(l-dtu)] 3.
To a solution of 1 (208 mg, 0.5 mmol) in acetonitrile (20 mL) an
aqueous solution of HBF4 40% (0.08 mL, 0.5 mmol) was added un-
der continuous magnetic stirring. The stirring was continued for
15 min and the clear solution was allowed to evaporate at room
temperature resulting colorless needles after one week, one of
which was selected for diffraction studies. Yield 225 mg (86%).
M.p. 250–251 °C. Anal. Found: C, 27.81; H, 3.00; N, 5.96; S, 6.46%.
C12H15BF4HgN2OS Calc.: C, 27.57; H, 2.89; N, 5.36; S, 6.13%. IR
(KBr): 3616–2577(w), 1633(s), 1575, 1480(w), 1434(m), 1396(w),
1370(w), 1333(w), 1256(s), 1167(w), 1088-1025(vs), 886(w),
Hg(1)–S(1)
Hg(2)–S(2)
Hg(1)–C(6)
Hg(2)ÀC(11)
C(7)–S(1)
C(10)–S(2)
C(7)–N(1)
C(7)–N(2)
C(10)–N(2)
Hg(1)Á Á ÁN(1)
Hg(2)Á Á ÁN(2)
236.6(4)
236.5(4)
C(6)–Hg(1)–S(1)
C(11)–Hg(2)–S(2)
C(7)–S(1)–Hg(1)
C(10)–S(2)–Hg(2)
N(1)–C(7)–S(1)
N(2)–C(10)–S(2)
N(2)–C(7)–S(1)
178.3(4)
175.2(4)
93.6(5)
101.6(5)
117.2(10)
120.4(10)
115.8(10)
205.8(14)
208.4(15)
175.5(13)
176.6(13)
131.9(16)
134.0(17)
133.0(16)
277.4(11)
314.4(11)
741(s), 701(w), 544(w), 521(w), 451(m) cmÀ1
.
Fig. 3. Perspective view of the unit cell of [HgPh(dmpymtH)][BF4] Á H2O 2, showing the packing of the complex molecules parallel to the direction [100], in which the
pyrimidine and phenyl rings from distinct molecules are superposed. The dashed lines indicate hydrogen bonds.

256
S.S. Lemos et al. / Journal of Organometallic Chemistry 694 (2009) 253–258
2.3.3. [{HgPh}2(
l
-dtu)] 3
plex 3, the Hg(1)Á Á ÁN(1) and Hg(2)Á Á ÁN(2) distances are 274.4(11)
and 314.4(11), respectively. In complex this distance is
Prepared according to method A in the proportion HgPhAcO
(1 mmol) to dtuH2 (0.5 mmol). Colorless plates were collected after
two weeks, one of which was selected for diffraction studies. Yield
123.3 mg (35%). M.p. 181–183 °C. Anal. Found: C, 28.57; H, 2.14; N,
3.42; S, 8.59%. C16H12Hg2N2S2 Calc.: C, 27.55; H, 1.73; N, 4.02; S,
9.19. IR (KBr): 3060(w), 3043(w), 1574(w), 1532(vs), 1507(s),
1476(w), 1429(m), 1384(s), 1308(s), 1188(s), 1147(m), 1091(w),
2
289.4(4) pm, supporting secondary bonds in both complexes. In
addition, there is an array of hydrogen bonds, namely, N2–
H2Á Á ÁO1W (DA 275.7(7), O1W–H11WÁ Á ÁF1 (DA 277.2(8)) and
O1W–H12WÁ Á ÁF4 305.5(8) pm). The average deviation from ideal
planarity considering all atoms in the cation species of complex 2
is 8.91 pm. The phenyl ring bound to Hg(2) in 3 forms an angle
of 70.6(3)° with the plane formed by the remaining atoms of the
complex molecule (see Fig. 2), which shows an average deviation
of the fitted atoms of 4.55 pm from the planarity. The packing of
the molecules in the crystal structure of 2 is shown in Fig. 3 (Sup-
plementary material). The molecules are arranged in a head to tail
form, so that the pyrimidine and phenyl rings from distinct mole-
cules alternate in the staking parallel to the direction [10]. The dis-
tance between the molecules correspond to half of the cell
constant a. The molecules of complex 3 are piled up parallel to
the direction [10], as show in Fig. 4 (Supplementary material).
The distance between the packed molecules in this case corre-
sponds to the cell constant b.
1021(w), 997(w), 807(s), 726(s), 693(s), 448(w) cmÀ1
.
3. Results and discussion
3.1. Syntheses
The neutral complexes have been synthesized in reasonable
yields with displacement of acetic acid in mild conditions. We have
proved the feasibility of the reversible protonation/deprotonation
of the coordinated ligand in one typical case (Scheme 1).
3.2. X-ray structures
3.3. NMR spectroscopy
The atomic numbering used is shown in Figs. 1 and 2 for com-
plexes 2 and 3, respectively. Selected bond distances and bond an-
gles are shown in Tables 2 and 3 for compounds 2 and 3,
respectively. The Hg–C bond distance of 207.1(6) pm observed in
2 is close to the average value 206 pm reported for Hg–C(Ph) com-
pounds [17]. In the dinuclear complex 3 there is an asymmetry
both in the Hg–C bond distances 205.8(14) and 208.4(15) pm and
in the bond angles C–Hg–S being 178.3(4)° and 175.2(4)°. The
Hg–S bond distances are similar in both compounds and close to
237.6(3), reported for [Hg(C6H5)(C5H4NS)] [18]. The C–S bond dis-
tances are those of the expected single bonds for the thiol form
usually observed for such derivatives, particularly in the case of
2, although in some cases the thione form can be stable enough
to direct the metallation to the NH site as observed in [HgPh(DAB-
Rd)], where HDABRd is 5-(4-dimethylaminobenzylidene)rhoda-
nine [19]. Assuming the van der Waals radius of mercury
reported by Carty and Deacon [20] of 173 pm, the summation for
HgÁ Á ÁS and HgÁ Á ÁN will be 353 and 328 pm, respectively. In com-
Table 4 lists the NMR data of complexes 1–3. One striking fea-
ture of 1H NMR spectra of 1 and 2 is the absence of NH resonance
S
H
N
N
4
4
3
3
5
2
5
2
1
N
S
S
1
N
6
6
H
H
dmpymtH2
dtuH2
Scheme 2. Draw of the complexing agents (thione form) with numbering scheme
for NMR purpose.
Fig. 4. Perspective view of the unit cell of [{HgPh}2(l-dtu)] 3, showing the packing of the complex molecules parallel to the direction [010].

S.S. Lemos et al. / Journal of Organometallic Chemistry 694 (2009) 253–258
257
Table 4
1H, 13C{1H}, and 199Hg{1H} NMR data of complexes 1– 3 in DMSO-d6 solutions (d in ppm; J in Hz).
Compound
d
1H
d
13C{1H}
d
199Hg{1H}a
1
2.276 (s, 6H, Me)
23.47 (C4-Me/C6Me)
115.41 (C5H)
127.95 (CHp)
À1012.5 (82)
6.947 (s, 1H, C5H)
7.239 (tt, 3J = 7.2, 4J = 1.5, 1H, CHp)
7.367 (t, 3J = 7.5, 2H, CHm
)
128.53 (CHm)
7.481(dd, 3J = 7.5, 4J = 1.5, 2H, CHo – flanked by 3J(1H– 199Hg) 168
137.03 (CHo)
166.20 (C4/C6)
175.96 (CS)
2
2.368 (s, 6H, Me)
22.37 (C4-Me/C6Me)
116.22 (C5H)
À1080.5 (350)
7.178 (s, 1H, C5H)
7.250 (tt, 3J = 7.2, 4J = 1.5, 1H, CHp)
127.97 (CHp)
128.42 [CHm,
3J (13C– 199Hg) = 192]
7.479(dd, 3J = 8.0, 4J = 1.5, 2H, CHo – flanked by 3J(1HÀ199Hg) 180
136.70 [CHo, 2J (13C– 199Hg) = 112]
9.02 (s, br, NH)
156.84 (CHi)
167.02 (C4/C6)
172.42 (CS)
3
7.069 (d, J = 5.5, 1H, C5H)
116.78
125.20
À1027.5 (250)
7.227 (tt, 3J = 7.2, 4J = 1.5, 2H, CHp)
127.76
128.09
128.25
128.78
7.343 (t, 3J = 7.5, 4H, CHm
7.485 (dd, 3J = 6.6, 4J not
)
resolved, 4H, CHo – flanked by 3J(1H–199Hg) 168)
136.89 (C5)
138.07
8.056 (d, J = 5.5, 1H, C6H)
153.92
159.26 (C6)
174.39 (C2)
175.59 (C4)
a
Values in parentheses are the line widths at half height (in Hz).
for the former while the later presents it as a broad signal at
9.02 ppm (see Scheme 2). Another characteristic is that in 2, the
methyl groups are magnetically equivalent both in the 1H and
13C NMR spectra, which is a consequence of chemical exchange
of the NH group upon thione-coordination to the mercury(II) atom.
The coupling constants 3J(1H–199Hg) and 3J(13C–199Hg) of the phe-
nyl group attached to the HgII atom are in the range of reported
values for other similar phenylmercury(II) complexes [21]. The
199Hg NMR spectra of the analogous compounds [HgPh(HTu)]
and [HgPh(Tu-SMe)] (H2Tu = 2-thiouracil) in DMSO solutions
showed resonances at 1072.7 and 1258.0 ppm, concluded to be
S- and N-coordinated, respectively [7]. Usually one observe a low
field shift of the 199Hg resonance with increasing coordination
number; the complex [Hg(C6H4C5H4N(Hstsc) showed a major peak
at 868 ppm, which was attributed to the three-coordinated HgCNS
isomer [22]. The 199Hg NMR data of compounds 1–3 present only
one reasonably sharp peak for each one. Based on the reported
chemical shifts mentioned above it is concluded that, at room tem-
perature DMSO solutions, the primary coordination number of the
mercury atom is two (CÀHgÀS) in all complexes, although coordi-
nating solvents i.e. dimethylsulfoxide or acetonitrile might be
interacting too. For instance, the 199Hg chemical shift of 2 is
À1105.5 ppm in acetonitrile and À1080.5 ppm in dimethylsulfox-
ide, at the same concentrations. Besides its resonance line width
at half height in dimethylsulfoxide solution is about five times that
observed in acetonitrile solution. It is worth mentioning that in 3
the 13C NMR spectrum showed some nonequivalence of the phenyl
groups, the peaks from (dtu) being identified by comparison with
those of a dinuclear tin complex [23], whereas only one resonance
was observed in the 199Hg NMR spectrum. It can be explained by
the almost equivalence of the mercury(II) sites [7].
form, i.e., dmpymt, as judged by the absence of bands in the
3190–2600 cmÀ1 region, assigned to the N–H and C–H vibrations
of the free ligand. In complex 2 this region is rather complicated
and extends from 3616 to 2577 cmÀ1. The N–H stretching bands
are also absent in complex 3. All complexes exhibit the expected
‘‘NCS I, II and III bands” due to strong vibrational coupling effects
[24]. Although complex 3 shows a strong absorption band at
807 cmÀ1 (absent in free dtuH2), which could be related to C@S
vibration [8,19], it most probably comes from nonequivalent phe-
nyl groups. In the IR spectrum of complex 2, the BF4-absorption
bands are seen in the region 1088–1025 cmÀ1
521 cmÀ1
s).
(mas) and
(m
Acknowledgement
Financial support from FINEP CT-INFRA (970/01) and CNPq is
gratefully acknowledged.
Appendix A. Supplementary material
CCDC 695970 and 695971 contain the supplementary crystallo-
graphic data for 2 and 3. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif. Supplementary data associated with
this article can be found, in the online version, at doi:10.1016/
j.jorganchem.2008.10.035.
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