Double Pseudo-Polymeric Gold(III)-Mercury(II) Complexes [Au(S2CNR2)2] nX [R2 = (CH2)6, (CH2)4O] Containing ([HgCl3]?) n, [HgCl4]2? and [Hg2Cl6]2? Anions: Chemisorption Synthesis, Principles of Supramolecular Self-Assembly, and Thermal Behavior

Article abstract of DOI:10.1134/S1070363219110185

Novel pseudo-polymeric complexes of gold(III)-mercury(II) with cyclic alkylene dithiocarbamate ligands: ([Au{S₂CN(CH₂)₆}₂][HgCl₃])_n, ([Au{S₂CN(CH₂)₆}₂]₂[HgCl₄]·H₂O)_n, and ([Au{S₂CN(CH₂)₄O}₂]₂[Hg₂Cl₆])_n have been obtained and structurally characterized. The sophisticated supramolecular structure of the obtained compounds is realized due to secondary non-valent Au?S interactions and includes mononuclear and binuclear cations and anions as structural units as well as cationic and anionic polymer chains. The thermal behavior of the obtained complexes has been studied by means of simultaneous thermal analysis. The products of thermal transformations of the complexes are reduced elemental gold and HgCl₂.

Full text of DOI:10.1134/S1070363219110185

ISSN 1070-3632, Russian Journal of General Chemistry, 2019, Vol. 89, No. 11, pp. 2273–2284. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Zhurnal Obshchei Khimii, 2019, Vol. 89, No. 11, pp. 1766–1779.
Double Pseudo-Polymeric Gold(III)–Mercury(II) Complexes
[Au(S2CNR2)2]nX [R2 = (CH2)6, (CH2)4O]
Containing ([HgCl3]–)n, [HgCl4]2–, and [Hg2Cl6]2– Anions:
Chemisorption Synthesis, Principles of Supramolecular
Self-Assembly, and Thermal Behavior
O. V. Losevaa, T. A. Rodinaa, and A. V. Ivanova,*
a Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences,
Blagoveschensk, 675000 Russia
*e-mail: alexander.v.ivanov@chemist.com
Received April 19, 2019; revised April 19, 2019; accepted for publication May 17, 2019
Abstract—Novel pseudo-polymeric complexes of gold(III)–mercury(II) with cyclic alkylene dithiocarbamate li-
gands: ([Au{S2CN(CH2)6}2][HgCl3])n, ([Au{S2CN(CH2)6}2]2[HgCl4]∙H2O)n, and ([Au{S2CN(CH2)4O}2]2[Hg2Cl6])n
have been obtained and structurally characterized. The sophisticated supramolecular structure of the obtained
compounds is realized due to secondary non-valent Au···S interactions and includes mononuclear and binuclear
cations and anions as structural units as well as cationic and anionic polymer chains. The thermal behavior of the
obtained complexes has been studied by means of simultaneous thermal analysis. The products of thermal trans-
formations of the complexes are reduced elemental gold and HgCl2.
Keywords: mercury(II) dithiocarbamates, chemisorption activity, gold(III)–mercury(II) dithiocarbamato-chlorido
complexes, supramolecular self-assembly
DOI: 10.1134/S1070363219110185
Dithiocarbamates and their derivatives have been
widely used in industry for flotation enrichment of sulfide
ores (as collecting reagents) [1] and in the production of
rubber (as curing additives) [2]. Metal dithiocarbamates
are convenient precursors for the preparation of semi-
conducting nanocrystalline powders and films of metal
sulfides [3–8], as well as heterometallic sulfides [9].
Gold(III) complexes with dithiocarbamate ligands have
exhibited antitumor activity [10–12], whereas gold(I)
dithiocarbamates have revealed luminescent properties
[13, 14].
bamates with gold(III) has revealed the efficient binding of
the latter from the solutions into the solid phase with the
formation of supramolecular heteronuclearAu(III)–Hg(II)
complexes [16, 17, 21].
This study aimed to evaluate the chemisorption activ-
ity of mercury(II) complexes with cyclohexamethylene-
and morpholinedithiocarbamate ligands with respect
to [AuCl4]–/HCl (2 M), to isolate the Au(III)–Hg(II)
complexes as individual forms of bound gold, and to
investigate their structure and thermal behavior.
Doubleionic-polymericcompounds([Au{S2CN(CH2)6}2]·
[HgCl3])n (1), ([Au{S2CN(CH2)6}2]2[HgCl4]·H2O)n (2),
and ([Au{S2CN(CH2)4O}2]2[Hg2Cl6])n (3) were prepared
via chemisorption of gold(III) from hydrochloric acid
solutions by mercury(II) dithiocarbamate complexes.
Freshly prepared mercury(II) cyclohexamethylene- and
morpholinedithiocarbamates were curdled light-yellow
precipitates, having a highly developed surface. As per
scanning electron microscopy data, they consisted of
We have earlier prepared and characterized the struc-
ture of a series of dithiocarbamate mercury(II) complexes:
[Hg2(S2CNR2)4] {R2 = (CH2)6 [15], (CH2)5 [16]; R = iso-
C3H7 [17]} and [Hg{S2CN(CH2)4O}2]n [18].1 Moreover,
the study of the interaction between mercury(II) dithiocar-
1
The systematization of structurally characterized dithiocarbamate
mercury(II) complexes has been previously described in detail
[19, 20].
2273

2274
LOSEVA et al.
(a)
(b)
10 μm
10 μm
E, keV
E, keV
Fig. 1. Particles size and shape and energy-dispersive spectra of the [Hg{S2CN(CH2)4O}2] (a) and [Au{S2CN(CH2)4O}2]2[Hg2Cl6]
(b) complexes.
sphere-like particles with diameter of 0.5 μm; the energy-
dispersive spectra reflecting the qualitative composition
of the starting complexes contained the peaks of Hg, C,
N, and S (see the data for [Hg{S2CN(CH2)4O}2]n inFig. 1a).
The interaction of mercury(II) dithiocarbamates with
H[AuCl4] solutions was accompanied by the rapid
change in the sorbents color to intense-yellow within
several minutes, the surrounding solutions being simulta-
neously discolored. The shape of the precipitate particles
was changed from spherical to elongated (6.8–8.3 μm,
diameter 1.4–2.5 μm). The energy-dispersive spectra
of the products evidenced the presence of Au and Cl
(Fig. 1b). The change in the chemical composition of
the complexes upon the chemisorption of gold from the
solution directly confirmed the formation of theAu(III)–
Hg(II) heteronuclear compounds in the studied systems.
Reactions (1) and (3) could be formally reduced to
chemisorption binding of an AuCl3 molecule with each
mononuclear [Hg(S2CNR)2] fragment of the complexes.
In the case of reaction (2), binding of gold(III) was ac-
companied by partial ion exchange and release of 1/2 of
mercury(II) in the solution.
IR spectra of the studied crystalline complexes con-
tained strong single absorption bands at 1522 (1) and
1537 (3) cm–1 assigned to the N–C(S)S bonds stretching
[22, 23]. However, the ν(С–N) values did not correspond
to the typical ranges of the corresponding single С–N
(1250–1360 cm–1) or double С=N (1640–1690 cm–1)
bonds. The frequencies of the experimental bands were
in between those ranges, closer to the high-frequency
part, evidencing partially double character of the formally
single N–C(S)S bond [24, 25]. Hence, the obtained data
suggested the shorter N–C(S)S bond length in structure 3.
Chemisorption interaction of mercury cyclohexameth-
ylenedithiocarbamate with H[AuCl4] mainly led to the
formation of compound 1 as platelet crystals, along with
needle-like crystals of complex 2. Hence, the binding
of gold(III) from the solution could be expressed by the
heterogeneous reactions (1) and (2).
Moreover, the bands of the thioureid group in the
spectra of the gold(III)–mercury(II) complexes were
shifted to higher frequency in comparison with the origi-
nal mercury(II) dithiocarbamates: [Hg2{S2CN(CH2)6}4]
and [Hg{S2CN(CH2)4O}2]n as well as the correspond-
ing sodium salts. Therefore, we concluded that the
rearrangement of the dithiocarbamate groups from the
coordination sphere of mercury(II) to that of gold(III)
was accompanied by the increase in the contribution of
the double bonding and, hence, the shortening of the N–
C(S)S bonds in complexes 1 and 3 in comparison with
mercury(II) dithiocarbamates.
[Hg2{S2CN(CH2)6}4] + 2H[AuCl4]
= 2[Au{S2CN(CH2)6}2][HgCl3] (1) + 2HCl,
[Hg2{S2CN(CH2)6}4] + 2H[AuCl4]
(1)
= [Au{S2CN(CH2)6}2]2[HgCl4] (2) + HgCl2 + 2HCl.
(2)
The binding of gold(III) with [Hg{S2CN(CH2)4O}2]n
gave complex 3 [reaction (3)].
2[Hg{S2CN(CH2)4O}2] + 2H[AuCl4]
The absorption bands of medium intensity at 1063 (1),
1059 cm–1 (3) and 972 (1), 993 cm–1 (3) were assigned
= [Au{S2CN(CH2)4O}2]2[Hg2Cl6] (3) + 2HCl.
(3)
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DOUBLE PSEUDO-POLYMERIC GOLD(III)–MERCURY(II) COMPLEXES
2275
(a)
to the asymmetric (νas) and symmetric (νs) stretching of
the C(S)S groups, respectively [23, 26]. Weak bands at
538–652 cm–1 were related to the ν(C–S) vibrations [27].
The 2851–2926 cm–1 range contained the absorption
bands due to symmetric and asymmetric stretching of the
С–H bonds in the methylene groups of the dithiocarba-
mate ligands. The spectrum of compound 1 contained the
band at 749 cm–1 assigned to rocking of the СН2 groups
which pointed at the presence of polymethylene chains
in the cyclic –N(CH2)6 fragments, whereas an additional
medium-intensity band at 959 cm–1 was assigned to the
С–С stretching [28]. A strong band with extremum at
1103 cm–1 in the spectrum of compound 3 was assigned
to the С–О–С polar group stretching in the N(CH2)4О
six-membered heterocycle [28].
(b)
(b)
The crystal structures of the obtained compounds
were elucidated by means of X-ray diffraction analy-
sis. The unit cells of the heteronuclear ionic-poly-
meric complexes 1–3 contained 4, 2, and 1 formu-
la units, respectively: [Au{S2CN(CH2)6}2[HgCl3],
[ A u { S 2 C N ( C H 2 ) 6 } 2 ] 2 [ H g C l 4 ] ∙ H 2 O , a n d
[Au{S2CN(CH2)4O}2]2[Hg2Cl6] (Table 1, Fig. 2).
(c)
(c)
In contrast to complex 1, whose centrosymmetric
[Au{S2CN(CH2)6}2]+ cations were structurally equiva-
lent, the gold(III) complex cations in compounds 2 and
3 existed in several isomeric forms, which could be
regarded as conformers, performing various structural
functions. It should be noted that structure 2 contained
both non-centrosymmetric cations A (with theAu1 atom)
and the centrosymmetric ones В and С (Au2 and Au3),
whereas both isomeric [Au{S2CN(CH2)4O}2]+ cations
A and В (Au1 and Au2) in complex 3 were centrosym-
metric (Table 2).
The central gold atoms (dsp2-hybrid state) formed
planar-tetragonal [AuS4] chromophores in the considered
cations, due to the binding of two dithiocarbamate groups
of the ligands, coordination of which was close to the S,S'-
isobidentate one: the Au–S bond length ranged between
2.3245 and 2.3496 Å (Table 2). Such coordination was
accompanied by the formation of two four-membered
[AuS2C] metallocycles combined via a common metal
atom. The coplanarity of the atoms in the cyclic fragments
was reflected in the AuSSC and SAuCS torsion angles
close to 180° (179.8°, 171.8°–178.8°, and 176.0°–177.7°
for complexes 1–3, respectively). Certain deviation of the
atoms from the plane could be represented at bending of
the [AuS2C] cycles along the S–S axis. The transannular
Fig. 2. Packing of structural units in the crystals of compounds
1 (a), 2 (b), and 3 (c).
distancesAu–C (2.830, 2.815–2.843, 2.818, and 2.822 Å)
and S–S (2.852, 2.850–2.871, 2.858, and 2.868 Å) in
complexes 1–3 were significantly shorter than the sums
of the van der Waals radii of the corresponding pairs of
atoms: 3.36 and 3.60 Å [29, 30], evidencing small size
of the metallocycles and significantly connivent positions
of the gold and carbon atoms.
The SCNC torsion angles of 179.9°–171.5° and
0.1°–7.3° pointed at the close to planar arrangement of
the atoms in the C2NC(S)S moiety of the dithiocarbamate
ligands. That fact, along with the higher strength of the
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LOSEVA et al.
Table 1. Crystallographic data, parameters of experiment and structure refinement for complexes 1–3
Value
Parameter
1
C14H24AuCl3HgN2S4
852.50
2
3
Empirical formula
C28H50Au2Cl4HgN4OS8 C20H32Au2Cl6Hg2N4O4S8
М
1451.52
Triclinic
P–1
1656.79
Triclinic
P–1
Crystal system
Space group
a, Å
Monoclinic
C2/c
20.9361(17)
12.0006(7)
8.8201(5)
90.00
10.0563(5)
12.7103(7)
17.4503(11)
94.268(2)
100.991(2)
99.500(2)
2146.6(2)
2
8.0591(4)
10.7044(5)
11.9505(6)
92.9340(10)
98.9860(10)
93.9650(10)
2118.1(2)
1
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
97.433(3)
90.00
2197.4(3)
4
Z
d
calc, g/cm3
2.577
2.246
2.714
μ, mm–1
14.395
11.053
15.602
F(000)
1584
1372
760
Crystal size, mm
Data collection range over θ
Indexes range
0.15×0.12×0.03
1.96–27.54
0.42×0.04×0.01
1.92–27.61
0.36×0.14×0.02
1.73–27.60
–27 ≤ h ≤ 26,
–14 ≤ k ≤ 15,
–9 ≤ l ≤ 11
–13 ≤ h ≤ 12,
–16 ≤ k ≤ 16,
–22 ≤ l ≤ 22
–10 ≤ h ≤ 10,
–13 ≤ k ≤ 13,
–1 5 ≤ l ≤ 15
Reflections measured
Independent reflections
Reflections with I > 2σ(I)
Refined parameters
GOOF
6685
22175
9933
2545 (Rint = 0.0492)
9917 (Rint = 0.0386)
4674 (Rint = 0.0745)
1914
117
7062
442
4279
211
1.029
0.977
1.050
R-Factors over F2 > 2σ(F2)
R1 = 0.0412,
wR2 = 0.0703
R1 = 0.0401,
wR2 = 0.0816
R1 = 0.0333,
wR2 = 0.0977
R-Factors over all reflections
R1 =0.0611,
R1 =0.0706,
R1 =0.0365,
wR2 = 0.0758
wR2 = 0.0887
wR2 = 0.0995
Residual electronic density (min/max), e/Å3
–1.654/1.829
–2.108/2.932
–1.837/2.218
N–C(S)S bonds (1.289–1.318 Å) as compared to the
N–CH2 ones (1.459–1.486 Å), resulted from the double
character contribution to the formally single bond due to
the sp2 admixing to the sp3-hybrid state of the nitrogen
and carbon atoms. It should be noted that the N–C(S)S
bonds in complexes 1 (1.318 Å) and 3 (1.306, 1.307 Å)
were noticeably shorter than in the corresponding origi-
nal mercury(II) complexes: [Hg2{S2CN(CH2)6}4] 1.326,
1.327 Å [15] and [Hg{S2CN(CH2)4O}2]n 1.335 Å [18],
as was expected from the IR spectroscopy data.
The six-membered N(CH2)4О heterocycles (3) adopt-
ed the chair conformation, whereas the seven-membered
N(CH2)6 cycles exhibited either chair (1) or twisted chair
(2) conformation [31].
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DOUBLE PSEUDO-POLYMERIC GOLD(III)–MERCURY(II) COMPLEXES
2277
Table 2. Selected bond lengths (d), bond angles (ω), and torsion angles (φ) in complexes 1a, 2b, and 3c
Compound 1
Cation
Bond
Au1–S1
Au1–S2
Au1···S2b
S1–C1
S2–C1
N1–C1
N1–C2
d, Å
Bond
N1–C7
d, Å
2.333(2)
2.346(2)
3.647(2)
1.705(8)
1.749(7)
1.318(9)
1.486(8)
ω, deg
1.476(10)
1.527(10)
1.499(11)
1.517(11)
1.513(11)
1.499(11)
C2–C3
C3–C4
C4–C5
C5–C6
C6–C7
Angle
Angle
ω, deg
86.1(3)
111.3(4)
S1Au1S2
S1Au1S2a
Au1S1C1
75.11(7)
104.89(7)
87.5(2)
Au1S2C1
S1C1S2
Angle
φ, deg
Angle
φ, deg
178.2(5)
–175.8(5)
0.2(9)
Au1S1S2C1
S1Au1C1S2
S1C1N1C2
–179.8(4)
–179.8(4)
2.2(9)
S1C1N1C7
S2C1N1C2
S2C1N1C7
Anion
Bond
Hg1–Cl1
d, Å
Bond
Hg1–Cl2
Angle
d, Å
2.369(2)
ω, deg
2.7465(3)
ω, deg
Angle
Cl1Hg1Cl1c
Cl1Hg1Cl2
138.10(11)
94.18(5)
Cl2Hg1Cl2c
Cl1cHg1Cl2
106.81(2)
110.70(6)
Compound 2
Cation А
Bond
Au1–S1
Au1–S2
Au1–S3
Au1–S4
Au1···S3a
S1–C1
S2–C1
S3–C8
S4–C8
N1–C1
d, Å
Bond
N2–C9
N2–C14
C2–C3
C3–C4
C4–C5
d, Å
2.350(2)
2.341(2)
2.330(2)
2.327(2)
3.493(2)
1.739(8)
1.747(7)
1.728(6)
1.728(7)
1.289(10)
1.468(9)
1.476(9)
1.302(9)
1.483(8)
1.486(8)
1.483(11)
1.516(11)
1.517(12)
1.522(8)
1.512(13)
1.497(11)
1.536(11)
1.511(11)
1.524(12)
1.526(11)
C5–C6
C6–C7
C9–C10
C10–C11
C11–C12
C12–C13
C13–C14
N1–C2
N1–C7
N2–C8
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LOSEVA et al.
Table 2. (Contd.)
Compound 2
Cation А
Angle
S1Au1S2
S1Au1S3
S1Au1S4
S2Au1S3
S2Au1S4
ω, deg
Angle
Au1S1C1
Au1S2C1
Au1S3C8
Au1S4C8
S1C1S2
ω, deg
86.8(3)
86.8(3)
86.7(2)
86.8(2)
110.9(5)
75.48(7)
105.47(6)
178.86(7)
178.92(6)
103.61(6)
S3Au1S4
75.45(6)
φ, deg
S3C8S4
111.1(4)
φ, deg
Angle
Angle
Au1S1S2C1
Au1S3S4C8
S1Au1C1S2
S3Au1C8S4
S1C1N1C2
S1C1N1C7
177.6(5)
178.7(4)
177.9(4)
178.8(4)
2.1(11)
S2C1N1C2
S2C1N1C7
S3C8N2C9
S3C8N2C14
S4C8N2C9
S4C8N2C14
–177.1(6)
–0.5(11)
–1.2(9)
179.9(5)
179.6(5)
0.7(9)
178.8(6)
Cation В
Cation С
Bond
Au2–S5
d, Å
Bond
Au3–S7
Au3–S8
S7–C22
d, Å
2.336(2)
2.329(2)
3.702(2)
1.735(7)
1.723(8)
1.305(9)
1.473(9)
1.459(9)
1.534(11)
1.529(12)
1.510(8)
1.488(12)
1.503(12)
ω, deg
75.63(7)
104.37(7)
86.1(2)
86.6(2)
111.6(4)
φ, deg
2.341(2)
2.331(2)
1.729(8)
1.732(7)
1.311(8)
1.469(9)
1.471(9)
1.511(15)
1.502(15)
1.491(14)
1.507(9)
1.506(12)
Au2–S6
Au2···S2a
S5–C15
S8–C22
S6–C15
N4–C22
N4–C23
N4–C28
C23–C24
C24–C25
C25–C26
C26–C27
C27–C28
N3–C15
N3–C16
N3–C21
C16–C17
C17–C18
C18–C19
C19–C20
C20–C21
Angle
Angle
S7Au3S8
S7Au3S8b
Au3S7C22
Au3S8C22
S7C22S8
ω, deg
75.23(7)
104.77(7)
86.5(2)
86.8(2)
111.0(4)
φ, deg
S5Au2S6
S5Au2S6a
Au2S5C15
Au2S6C15
S5C15S6
Angle
Angle
Au2S5S6C15
S5Au2C15S6
S5C15N3C16
S5C15N3C21
S6C15N3C16
S6C15N3C21
178.4(4)
178.6(4)
–7.3(10)
174.9(6)
171.5(6)
–6.3(10)
Au3S7S8C22
S7Au3C22S8
S7C22N4C23
S7C22N4C28
S8C22N4C23
S8C22N4C28
171.8(4)
172.6(4)
4.7(10)
–177.3(6)
–178.2(6)
–0.1(10)
Anion
Bond
Hg1–Cl1
Hg1–Cl2
d, Å
2.468(2)
2.534(2)
Bond
Hg1–Cl3
Hg1–Cl4
d, Å
2.504(2)
2.467(2)
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DOUBLE PSEUDO-POLYMERIC GOLD(III)–MERCURY(II) COMPLEXES
2279
Table 2. (Contd.)
Compound 2
Anion
Angle
Cl1Hg1Cl2
Cl1Hg1Cl3
Cl1Hg1Cl4
ω, deg
Angle
Cl2Hg1Cl3
Cl2Hg1Cl4
Cl3Hg1Cl4
ω, deg
104.52(7)
106.40(8)
116.43(8)
110.39(8)
109.93(7)
109.02(7)
Compound 3
Cation А
Cation В
Bond
Au1–S1
Au1–S2
Au1···S4b
S1–C1
d, Å
Bond
Au2–S3
Au2–S4
Au2···S1
S3–C6
d, Å
2.3245(14)
2.3435(14)
3.5766(14)
1.723(6)
1.734(5)
1.307(7)
1.477(7)
1.463(7)
1.523(9)
1.516(9)
1.433(7)
1.423(8)
ω, deg
2.3427(13)
2.3464(14)
3.2998(14)
1.725(6)
1.736(6)
1.306(7)
1.479(7)
1.467(7)
1.519(8)
1.500(8)
1.429(7)
1.430(7)
ω, deg
S2–C1
S4–C6
N1–C1
N1–C2
N1–C5
C2–C3
N2–C6
N2–C7
N2–C10
C7–C8
C9–C10
C8–O2
C9–O2
C4–C5
C3–O1
C4–O1
Angle
Angle
S1Au1S2
S1Au1S2a
Au1S1C1
Au1S2C1
S1C1S2
75.51(5)
104.49(5)
86.9(2)
S3Au2S4
S3Au2S4b
Au2S3C6
Au2S4C6
S3C6S4
75.41(5)
104.59(5)
86.5(2)
86.0(2)
86.1(2)
111.5(3)
φ, deg
111.9(3)
φ, deg
Angle
Angle
Au1S1S2C1
S1Au1C1S2
S1C1N1C2
S1C1N1C5
S2C1N1C2
S2C1N1C5
177.4(3)
177.7(3)
–6.9(8)
Au2S3S4C6
S3Au2C6S4
S3C6N2C7
S3C6N2C10
S4C6N2C7
S4C6N2C10
176.0(3)
176.5(3)
–4.3(8)
176.9(4)
172.2(4)
–3.9(8)
–174.9(4)
175.0(4)
4.4(7)
Anion
Bond
Hg1–Cl1
Hg1–Cl2
d, Å
Bond
Hg1–Cl3
Hg1–Cl1c
d, Å
2.7106(14)
2.4021(16)
ω, deg
2.3886(15)
2.5693(15)
ω, deg
Angle
Angle
Cl1Hg1Cl2
Cl1Hg1Cl3
Cl1Hg1Cl1c
Cl2Hg1Cl3
105.54(6)
96.47(5)
86.99(4)
132.22(6)
Cl2Hg1Cl1c
Cl3Hg1Cl1c
Hg1Cl1Hg1c
106.30(6)
116.89(5)
93.01(4)
Symmetry transformations: a (i) 1 – x, 1 – y, 1 – z; (ii) 1 – x, y, 1/2 – z; (iii) 1 – x, y, 3/2 – z. b (i) –x, 1 – y, –z; (ii) –x, –y, 1 – z; (iii) 1 – x, 1 – y, –z.
c (i) –x, –y, 1 – z; (ii) 1 – x, –y, 1 – z; (iii) c –x, 1 – y, –z.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 11 2019

2280
(a)
LOSEVA et al.
(a)
(b)
Fig. 4. Fragment of supramolecular cationic chain
(···[А···А]···B···)n in the structure of complex 2 (a) and
hydrated anion [HgCl4]2– (b). The secondary Au···S bonds
are shown by double dashed lines; hydrogen bonds are shown
by dashed lines.
the coordination number of the latter to 4 and thus forming
a zigzag (Cl2Hg1Cl2c angle 106.81°) ([HgCl3]–)n polymeric
chain oriented along the c crystal axis (Figs. 2a, 3b).
In the structure of complex 2, the discrete [HgCl4]2–
anions formed strongly non-equivalent bonds with the
outer-sphere Н2О molecules: O–H···Cl2 3.142 Å and
O1–H···Cl1 3.414 Å (Fig. 4b). The mercury atoms in
structure 3 were combined by the μ2-Cl1,Cl1c atoms, thus
forming centrosymmetric binuclear [Hg2Cl6]2– anions
(Fig. 5b): the atoms in the central four-member [Hg2Cl2]
metallocycle were coplanar, the Hg1···Hg1с distance be-
ing 3.832 Å.
(b)
(b)
The central mercury atom (sp3 hybrid state) was in
the distorted tetrahedral environment of chlorine atoms
each of the considered anions. A convenient parameter
to quantitively describe the geometry of the tetrahedral
polyhedrons in compounds 1–3 was τ4 = [360° – (α +
β)]/141° (α and β being two largest L–M–L angles)
[32]. The limiting values of that parameter proposed for
the fourfold coordination geometry of the central metal
atom pointed to a perfectly tetrahedral (τ4 = 1; α = β =
109.5°) or square-tetragonal (τ4 = 0; α = β = 180°) struc-
tures. The data in Table 2 showed that the τ4 values were
0.789, 0.945, and 0.787 for complexes 1–3, respectively.
Hence, the most regular tetrahedron was realized in the
case of tetrachloromercurate(II) ion (2); for other two
compounds, the contribution of the tetrahedral structure
to the polyhedron geometry was close to 79%.
Fig. 3. Fragments of the cationic ([Au{S2CN(CH2)6}2]+)n (a)
and anionic ([HgCl3]–)n (b) polymeric chains in compound
1. (Double dashed lines) show the secondary Au···S bonds
between the complex ions.
The anionic part of the considered compounds con-
tained either polymeric complex ion ([HgCl3]–)n (1) or
discrete ions [HgCl4]2– (2) or [Hg2Cl6]2– (3). The terminal
chlorine atoms in the [HgCl3]– and [Hg2Cl6]2– anions
formed much stronger bonds with the central mercury
atom than the bridging ones (Table 2). The bridging chlo-
rine atom Cl2 in each of the [HgCl3]– anions symmetri-
cally interacted with the neighbor metal atom, increasing
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DOUBLE PSEUDO-POLYMERIC GOLD(III)–MERCURY(II) COMPLEXES
2281
A single type of the nonvalent secondary bonds2
(Au···S) was realized in compounds 1–3. Nevertheless,
their supramolecular organization was significantly dif-
ferent. For example, pairs of symmetrical Au1···S2b and
Au1b···S2 3.647 Å secondary bonds in structure 1combined
the equivalent gold(III) cations in linear polymeric chains
([Au{S2CN(CH2)6}2]+)n, the Au···Au distance being
4.410 Å (Figs. 2a, 3a). The cations adjacent along the chain
were arranged so that the bisecting planes passing through
the [CS2AuS2C] bicyclic fragments formed an angle close
to the right one, 86.37° (Fig. 2a). The alternating cationic
and anionic polymeric chains in the crystal structure 1
were oriented along the с crystal axis (Fig. 2a).
(a)
(b)
The non-centrosymmetric isomeric cations А in
complex 2 were involved in the pairwise Au1···S3а and
Au1а···S3 3.493 Å secondary interactions, thus forming
the [Au2{S2CN(CH2)6}4]2+ supramolecular dications con-
taining the [Au{S2CN(CH2)6}2]+ mononuclear fragments
in the antiparallel orientation, the Au1–Au1a intradimer
distance being 4.019 Å (Fig. 4a). The weaker secondary
bonds (S2a···Au2 3.702 Å) between each of the discussed
binuclear cations with the neighbor centrosymmetric cat-
ions В led to the formation of the zigzag supramolecular
chains (···[А···А]···B···)n containing the binuclear and
mononuclear cations alternating along the chain: the Au-
1Au1Au2 and Au1Au2Au1 angles were 85.55° and 180°,
respectively, and the Au1···Au2 interatomic distance was
4.768 Å (Fig. 4a). The centrosymmetric discrete cations
C were located between the chains (Fig. 2b). Let us note
evident effect of the Au···S secondary bonds on the spa-
tial orientation of the bulky N(CH2)6 cyclic fragments.
For example, the pairs of the cyclic fragments in the
[Au2{S2CN(CH2)6}4]2+ supramolecular binuclear cations
showed opposite orientation, due to the interligand repul-
sion forces (Fig. 4a); the cyclic fragments in each cation
were located to the same side with respect to the [AuS4]
chromophore plane (cis-orientation). On the contrast, the
considered heterocycles revealed trans-orientation in the
mononuclear cations B and C.
Fig. 5. Fragment of polymeric cationic chain (···А···B···)n (a)
and structure of binuclear anion [Hg2Cl6]2– (b) in compound
3. The secondary Au···S bonds between the isomeric cations
are shown by double dotted lines.
theAu···S secondary bonds formed by the nonequivalent
gold atoms was different:Au1···S4 3.5766 Å andAu2···S1
3.2998 Å (for comparison, the sum of van der Waals
radii of gold and sulfur atoms equals 3.46 Å [29, 30]).
Hence, the formation of the linear supramolecular chain
(···А···B···)n oriented along the а crystal axis presumed
the formation of two pairs of asymmetrical secondary
bonds between each cation and the closest neighbors
(Fig. 5a). The mutual spatial orientation of the neighbor
cations could be characterized by the angle of 74.19°
between their bisecting planes passing through the
[CS2AuS2C] bicyclic fragments.
TheAu···S additional secondary interactions in supra-
molecular structures 1–3 led to the transformation of the
[AuS4] coordination polyhedron to the elongated tetragonal
pyramid [AuS5] (2,Au1) or elongated octahedron [AuS6].
The vertex sulfur atoms in those polyhedrons were shifted
from the ideal positions, since the S···Au–S angles devi-
ated from 90°. The S3аAu1S2 angle in the distorted pyramid
equaled 85.34° (Fig. 4a); the corresponding angles for the
octahedrons in complexes 1–3 were as follows: S2bAu1S1
84.74°, S2bAu2S5 68.56°, S4сAu1S2 86.78°, and S1Au2S4
86.37° (Figs. 3a–5a).
Two isomeric centrosymmetric cations
[Au{S2CN(CH2)4О}2]+ were alternated in the supra-
molecular cationic chains of complex 3: А and В (the
Au1···Au2 interatomic distance 4.030 Å). For each of the
cations, the observed secondary interactions involved the
gold atom and two diagonal sulfur atoms. The length of
2 The concept of secondary bonds was introduced for the first time
in [33] to describe the interactions at the distance comparable to
the sum of van der Waals radii of the corresponding pairs of atoms.
Thermal behavior of the complexes was studied
by means of simultaneous thermal analysis involving
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 11 2019

2282
LOSEVA et al.
synchronous recording of thermogravimetry (TG) and
differential scanning calorimetry (DSC) curves. Thermal
behavior of the studied substances was similar, as revealed
by the TG curves reflecting the formally single-stage ther-
molysis. The major mass loss of complexes 1 and 3 (64.00
and 66.69%) corresponded to the temperature ranges of
~195–340 and ~230–365°C, respectively. Differentiation
of those steeply descending sections of the TG curves re-
vealed the inflection points at 230.0 and 258.0°C, respec-
tively, pointing at the complex thermolysis of the cations
and anions simultaneously. Thermolysis of the cationic
part of the complexes led to the reduction of gold(III)
into elemental gold; heat-induced decomposition of the
anionic part was accompanied by the release of HgCl2
(followed by its evaporation). The high-temperature parts
of the TG curves at ~340–935 and ~365–850°С reflected
steady desorption of 12.49 and 6.98% of the volatile prod-
ucts, respectively. The residual mass at 1100°С [22.89 (1)
and 25.96% (3)] was close to the one expected for reduced
gold [calculated 23.10 (1) and 23.78% (3)] which was
almost quantitatively regenerated under relatively mild
conditions. Small spherical particles of metal gold were
observed during the crucibles examination.
self-assembly of the obtained substances. The study of
thermal behavior of the complexes revealed the conditions
of quantitative regeneration of the bound gold, HgCl2
being the byproduct of thermolysis.
EXPERIMENTAL
IR spectra were recorded using a PerkinElmer Spec-
trum 65 Fourier spectrometer (ATR, 400–4000 cm–1).
Dispersion state and morphology of the samples were
studied by means of high-resolution scanning electron
microscopy using a JSM 6390LV JEOL microscope (Ja-
pan) equipped with an Oxford INCA Energy 350-Wave
(England) microanalysis system with dispersion over
energy and wavelength. Qualitative chemical composi-
tion was determined using a microprobe technique with
an energy-dispersive spectrometer). Thermal behavior of
complexes 1 and 3 was studied by means of simultaneous
thermal analysis (TG and DSC) using a STA449C Jupiter
NETZSCH instrument (corundum crucible, heating rate
5 deg/min up to 1100°С, argon atmosphere, specimen
mass 1.828–5.424 mg; accuracy of temperature and mass
reading ±0.4°С and ±1×10–4 mg). The correction file re-
corded with an empty crucible was used during the data
processing; the instrument was calibrated with respect
to temperature and sensitivity prior to the measurement.
Melting points were determined independently using a
PTP(M) instrument (Khimlabpribor, Russia). Elemental
analysis was performed using a Euro EA-3000 automated
analyzer. Gold content was determined using an iCE
3000 atomic absorption spectrometer (Thermo Electron
Corporation, USA). Degree of gold binding from the
solutions (S, %) was calculated as S = [(с – сr)/с]×100%,
с and сr being starting and residual content of gold in the
solution, respectively.
The low-temperature part of the DSC curve for com-
plex 1 contained two weak endothermal effects, one
of them (extremum at 168.0°С) reflected the specimen
meting (extrapolated mp = 162.5°С; melting without
signs of decomposition was independently determined at
168–170°C using a glass capillary), whereas the second
one (extremum at 260.9°С) was assigned to vigorous
thermolysis of the sample and evaporation of the decom-
position products. The low-temperature part of the DSC
curve for compound 3 showed a single strong endother-
mal effect at 256.7°С (extrapolated process temperature
254.6°С) corresponding to the major mass loss stage and
assigned to thermal decomposition of the complex. Even
though the DSC curve did not show the endothermal melt-
ing effect distinctly, the phase transition was observed
in a glass capillary at 252–254°С. The high-temperature
part of the DSC curves contained an endothermal effect
of elemental gold melting: extrapolated mp = 1062.3
and 1062.6°С.
X-ray diffraction analysis of monocrystals 1–3 was
performed using a Bruker-Nonius X8 Apex CCD dif-
fractometer (MoKα radiation, λ = 0.71073 Å, graphite
monochromator) at 296(2) (1) and 150(2) K (2, 3). Data
collection was performed using a conventional proce-
dure of φ and ω narrow frames scanning. Absorption
was accounted for using SADABS software [34]. The
structures were solved via direct method and refined via
least squares method (over F2) under full-matrix aniso-
tropic approximation for non-hydrogen atoms. Positions
of hydrogen atoms were calculated from geometry and
included in the refinement using a riding model. Hydro-
gen atoms of the hydrated water molecules in compound
2 were localized via differential synthesis of the electron
In summary, we prepared, isolated, and characterized by
means of X-ray diffraction analysis the novel crystalline ionic-
polymericAu(III)–Hg(II) complexes ([Au{S2CN(CH2)6}2]·
[HgCl3])n, ([Au{S2CN(CH2)6}2]2[HgCl4]·H2O)n, and
([Au{S2CN(CH2)4O}2]2[Hg2Cl6])n containing three
types of polychloro(di)mercurate(II) ions. The Au···S
secondary interactions determined the supramolecular
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DOUBLE PSEUDO-POLYMERIC GOLD(III)–MERCURY(II) COMPLEXES
2283
density and refined under isotropic approximation with
Uiso(H) = 1.5Ueq(O) and distances O–H = 0.89(2) Å and
H···H = 1.45(2) Å. Data collection and processing as
well as refinement of unit cell parameters were performed
using APEX2 [34] and SAINT software [34]. Structure
refinement was performed using SHELXTL software
package [34]. Atomic coordinates, bond lengths, and
bond angles were deposited at the Cambridge Crystal-
lographic Data Centre [CCDC 1905389 (1), 1905390
(2), and 1905391 (3)].
during 30 min. Analysis of the solutions upon the in-
teraction revealed the binding degree of gold from the
solution of 99.9 (1, 2) and 99.7% (3). The formed yellow
precipitates were filtered off, washed, and dried on a filter.
Yield 98.4 (1, 2) and 98.9% (3). To prepare suitable single
crystals for X-ray diffraction analysis, the substance iso-
lated from the [Hg2{S2CN(CH2)6}4]–H[AuCl4]/2 M HCl
chemisorption system was dissolved in acetone. The small
amount of needle-like crystals of compound 2 were picked
out from the mass of yellow platelet crystals of complex
1 obtained via slow evaporation of the solvent. Yellow
platelet crystals of complex 3 were grown from methanol.
The initial sodium salts, Na(S2CNR2)·2H2O, were pre-
pared via the interaction of carbon sulfide (Merck) with
the corresponding cyclic N-donor base, hexamethylenei-
mine or morpholine (Aldrich) in an alkaline medium [22].
Na{S2CN(CH2)6}·2H2O. IR spectrum, ν, cm–1: 3369,
3295, 3167, 2983, 2923, 2851, 2105, 1638, 1622, 1484,
1448, 1429, 1407, 1366, 1339, 1283, 1258, 1244, 1187,
1168, 1095, 1067, 1046, 1009, 972, 953, 904, 850, 828,
764, 736, 678, 624, 562, 530, 479, 454, 440, 408.
Bis(N,N-cyclohexamethylenedithiocarbamato-
S,S')gold(III) trichloromercurate(II) (1). IR spectrum, ν,
cm–1:2977,2919,2851,1522,1499,1463,1428,1351,1270,
1232, 1200, 1177, 1158, 1096, 1064, 972, 959, 913, 866, 846,
819, 749, 611, 564, 511, 458, 438, 427, 420, 406. Found,
%: C 20.7; H 2.8; N 3.4; S 15.1. C14H24AuCl3HgN2S4.
Calculated, %: C 19.72; H 2.84; N 3.29; S 15.04.
Bis(morpholinedithiocarbamato-S,S')gold(III)
hexachlorodimercurate(II) (3). IR spectrum, ν, cm–1:
2987, 2926, 2858, 1537, 1459, 1423, 1383, 1356, 1297,
1267, 1243, 1212, 1103, 1059, 1019, 993, 878, 826, 652,
538, 456, 440, 428, 420, 411, 405. Found, %: C 14.7; H
1.9; N 3.4; S 15.7. C20H32Au2Cl6Hg2N4O4S8. Calculated,
%: C 14.50, H 1.95, N 3.38, S 15.48.
Na{S2CN(CH2)4O}·2H2O. IR spectrum, ν, cm–1:
3350, 3271, 3190, 2966, 2903, 2853, 2469, 2112, 1641,
1623, 1585, 1458, 1417, 1385, 1347, 1323, 1300, 1260,
1211, 1182, 1110, 1063, 1023, 976, 894, 871, 825, 676,
634, 577, 540, 482, 443, 420, 411, 403.
The mercury(II) dithiocarbamate complexes,
[Hg2{S2CN(CH2)6}4] [15] and [Hg{S2CN(CH2)4O}2]n
[18], were prepared via quantitative precipitation of Hg2+
ions from an aqueous phase with the corresponding so-
dium dithiocarbamates taken in 5% excess.3
[Hg2{S2CN(CH2)6}4]. IR spectrum, ν, cm–1: 2977,
2921, 2850, 1496, 1479, 1455, 1421, 1342, 1285, 1261,
1243, 1193, 1157, 1090, 1050, 1003, 990, 975, 952, 906,
875, 847, 826, 806, 765, 746, 619, 573, 536, 514, 489,
471, 439, 420, 402.
ACKNOWLEDGMENTS
Electron microscopy studies, determination of gold content
in the solutions, and recording of energy-dispersive spectra
were performed at the Analytical Center for Mineralogy and
Geochemical Studies, Institute of Geology and Nature Manage-
ment, Far Eastern Branch of the RAS. IR spectra were recorded
at the Center For Collective Usage, Kurnakov Institute of Gen-
eral and Inorganic Chemistry, Russian Academy of Sciences.
CONFLICT OF INTEREST
No conflict of interest was declared by the authors.
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