Gold(III)-iron(III) heteropolynuclear complexes ([Au{S2CNR2}2][FeCl4]) n (R = C4H9, iso-C4H9): Chemisorption synthesis, supramolecular self-organization, and thermal behavior

Article abstract of DOI:10.1134/S1070328416020032

The reactions of iron(III) dibutyl and di-iso-butyl dithiocarbamates [Fe(S₂CNR₂)₃] (R = C₄H₉, iso-C₄H₉) with anions [AuCl₄]^- in 2 M HCl are studied. The result of heterogeneous reactions of gold(III) chemisorption binding from a solution is the formation of gold(III)-iron(III) heteropolynuclear complexes of the ionic type. The crystal and supramolecular structures of polymer complexes ([Au{S₂CN(C₄H₉)₂}₂][FeCl₄]) _n (I) and ([Au{S₂CN(iso-C₄H₉)₂}₂][FeCl₄]) _n (II) are determined by X-ray diffraction analysis (CIF files CCDC 1407704 (I) and 1407802 (II)). The structure of complex I contains two centrosymmetrical structurally nonequivalent complex cations [AuS{₂CN(C₄H₉)₂}₂]⁺ (A and B) and complex anion [FeCl₄]^-. Structure II is formed by three isomeric complex cations [Au{S₂CN(iso-C₄H₉)₂}₂]⁺ (A, B, and C) and two anions [FeCl₄]^- related as conformers. The isomeric cations are involved in the formation of linear (?A?B?) _n (in I) or zigzag (?A?B?A...C...) _n (in II) polymer chains due to pairs of weak secondary interactions Au?S. The thermal behavior of the complexes is studied by simultaneous thermal analysis. Thermal destruction includes the thermolysis of the dithiocarbamate moiety of the complexes and anions [FeCl₄]^- with the reduction of gold(III), release of FeCl3, and partial formation of Fe₂O₃. The final thermolysis products are metallic gold and Fe₂O₃.

Full text of DOI:10.1134/S1070328416020032

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2016, Vol. 42, No. 2, pp. 104–115. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © A.V. Ivanov, O.V. Loseva, T.A. Rodina, A.V. Gerasimenko, E.V. Novikova, 2016, published in Koordinatsionnaya Khimiya, 2016, Vol. 42, No. 2, pp. 91–
102.
Gold(III)–Iron(III) Heteropolynuclear Complexes
([Au{S2CNR2}2][FeCl4])n (R = C4H9, iso-C4H9): Chemisorption
Synthesis, Supramolecular Self-Organization, and Thermal Behavior
A. V. Ivanova, *, O. V. Losevaa, T. A. Rodinab, A. V. Gerasimenkoc, and E. V. Novikovad
aInstitute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences,
Relochnyi per. 1, Blagoveshchensk, 675000 Russia
bAmur State University, sh. Ignat’eva 21, Blagoveshchensk, 675027 Russia
cInstitute of Chemistry, Far East Branch, Russian Academy of Sciences,
pr. Stoletiya Vladivostoka 159, Vladivostok, 690022 Russia
dBlagoveshchensk State Pedagogical University, ul. Lenina 104, Blagoveshchensk, 675000 Russia
*e-mail: alexander.v.ivanov@chemist.com
Received July 8, 2015
Abstract—The reactions of iron(III) dibutyl and di-iso-butyl dithiocarbamates [Fe(S2CNR2)3] (R = C4H9,
iso-C4H9) with anions [AuCl4]– in 2 M HCl are studied. The result of heterogeneous reactions of gold(III)
chemisorption binding from a solution is the formation of gold(III)–iron(III) heteropolynuclear complexes
of the ionic type. The crystal and supramolecular structures of polymer complexes
([Au{S2CN(C4H9)2}2][FeCl4])n (I) and ([Au{S2CN(iso-C4H9)2}2][FeCl4])n (II) are determined by X-ray dif-
fraction analysis (CIF files CCDC 1407704 (I) and 1407802 (II)). The structure of complex I contains two
centrosymmetrical structurally nonequivalent complex cations [Au{S2CN(C4H9)2}2]+ (A and B) and com-
plex anion [FeCl4]–. Structure II is formed by three isomeric complex cations [Au{S2CN(iso-C4H9)2}2]+ (А,
В, and С) and two anions [FeCl4]– related as conformers. The isomeric cations are involved in the formation
of linear (⋅⋅⋅А⋅⋅⋅В⋅⋅⋅)n (in I) or zigzag (⋅⋅⋅А⋅⋅⋅В⋅⋅⋅А⋅⋅⋅С⋅⋅⋅)n (in II) polymer chains due to pairs of weak secondary
interactions Au···S. The thermal behavior of the complexes is studied by simultaneous thermal analysis. Ther-
mal destruction includes the thermolysis of the dithiocarbamate moiety of the complexes and anions
[FeCl4]– with the reduction of gold(III), release of FeCl3, and partial formation of Fe2O3. The final thermol-
ysis products are metallic gold and Fe2O3.
DOI: 10.1134/S1070328416020032
[CdCl4]2–, [Cd2Cl6]2–, [ZnCl4]2–) [17–23], gold(III)–
bismuth ([Au{S2CNR2}2]3X)n (X = [Bi2Cl9]3–,
INTRODUCTION
Coordination compounds of transition metals with
dithiocarbamate ligands are interesting because of
diverse areas of their practical application. They are
used as polymerization initiators for the preparation of
polystyrene and poly(methyl methacrylate) [1] and
precursors in the preparation of nanosized powders of
metal sulfides [2–6]. They manifest the properties of
sensors to chemical volatiles [7] and luminophores [8,
9] and spin traps of nitrogen(II) oxide in biological
systems [10]. The dithiocarbamate complexes exhibit
catalytic [9, 11], antibacterial [12, 13], and anticancer
activities [14–16]. In addition, the transition metal
dithiocarbamates are characterized by the capability of
chemisorption binding of gold(III) from solutions.
The efficient character of gold(III) binding has earlier
been established for dialkyl dithiocarbamates of a
series of metals, which resulted in the formation of
polymer heteronuclear complexes gold(III)–cad-
[Bi3Cl12]3–) [24, 25], and gold(III)–thallium(III)
([Au{S2CN(iso-C4H9)2}2][TlCl4])n [26] with a compli-
catedly organized supramolecular structure. There-
fore, it was of interest to study the interaction of
iron(III) dialkyl dithiocarbamates with solutions of
gold(III), the synthesis of the gold(III)–iron(III)
dithiocarbamate chloride complexes, and their struc-
tural organization and thermal behavior.
In this work, we studied the reactions of the
iron(III)
dialkyl
dithiocarbamate
complexes
[Fe(S2CNR2)3] (R = C4H9, iso-C4H9) with gold(III)
in acidic solutions. The heterogeneous reaction of
gold(III) binding with freshly precipitated iron(III)
dithiocarbamates is accompanied by the formation of
new gold(III)–iron(III) heteropolynuclear complexes
([Au{S2CN(C4H9)2}2][FeCl4])n
(I)
and
mium and gold(III)–zinc ([Au{S2CNR2}2]2X)n (X = ([Au{S2CN(iso-C4H9)2}2][FeCl4])n (II). The crystal
104

GOLD(III)–IRON(III) HETEROPOLYNUCLEAR COMPLEXES
105
and supramolecular structures of preparatively iso- experiment for complex I was carried out from a twin
lated complexes I and II were determined by X-ray crystal at a crystal–detector distance of 50 mm. Two
diffraction analysis, and the thermal behavior was domains are turned relatively to each other by 180°
studied by simultaneous thermal analysis (STA).
about the reciprocal vector [0 1 1]*. The first domain
gave 30147 reflections (6585 independent reflections).
The second domain gave 29553 reflections (6459
independent reflections). Two domains gave 11825
overlapped reflections (3120 independent reflections).
The final structure refinement was performed by the
experimental data for the first domain. The BASF
parameter refined in the SHELXTL/PC programs
was equal to 0.073(1). Structure II was determined by
a direct method and refined by the least-squares
method in the anisotropic approximation of non-
hydrogen atoms. An X-ray absorption correction was
applied by equivalent reflections. For both I and II,
EXPERIMENTAL
Sodium dibutyl and di-iso-butyl dithiocarbamates
obtained by the reaction of carbon sulfide (Merck)
with dibutyl- and di-iso-butylamine (Aldrich) in an
alkaline medium were characterized by MAS 13С
NMR spectroscopy (δ, ppm).
Na{S2CN(C4H9)2} · H2O: 208.3 (–S2CN=); 55.2
(=NCH2–); 30.0, 21.0 (–CH2–); 15.6, 14.9, 14.5 (2 :
1 : 1, –CH3).
Na{S2CN(iso-C4H9)2} · 3H2O: 208.2 (–S2CN=); the positions of hydrogen atoms were calculated geo-
66.7 (=NCH2–); 28.0, 27.1 (1 : 1, –CH=); 23.0, 22.4,
20.8 (1 : 1 : 2, –CH3).
Iron(III) dialkyl dithiocarbamates were synthe-
sized by the precipitation of Fe3+ ions from the aque-
ous phase with the corresponding sodium dithiocar-
bamates [27].
metrically and included in the refinement by the rid-
ing model. Data were collected and edited and the unit
cell parameters were refined using the APEX2 [28]
and SAINT [29] programs. All calculations on struc-
ture determination and refinement were performed
using the SHELXTL/PC programs [30]. The main
crystallographic data and the refinement results for
structures I and II are presented in Table 1. Selected
bond lengths and angles are given in Table 2.
Synthesis of I and II. Polymeric bis(N,N-dibu-
tyldithiocarbamato-S,S')gold(III)
tetrachlorofer-
rate(III) (I) and bis(N,N-di-iso-butyldithiocarbam-
ato-S,S')gold(III) tetrachloroferrate(III) (II) were
synthesized by the interaction of freshly precipitated
[Fe(S2CNR2)3] (R = C4H9, iso-C4H9) with a solution
of AuCl3 in 2 M HCl. A solution (10 mL) of AuCl3 (in
2 M HCl) containing of gold (28 mg) was poured to
each black iron(III) dialkyl dithiocarbamate complex
(100 mg), and the resulting solutions were stirred for
60 min. The residual gold content and iron content in
the solution were determined on an atomic absorption
spectrometer (class 1, model 180-50, Hitachi). The
obtained black-brown precipitate was filtered off,
washed with water, and dried on a filter. The heteroge-
neous binding of gold(III) from a solution by the pre-
cipitates of iron(III) dithiocarbamates accompanied
by the formation of the gold(III)–iron(III) heteronu-
clear complexes of the ionic type includes the decom-
position of one of three ligands
The coordinates of atoms, bond lengths, and bond
angles were deposited with the Cambridge Crystallo-
graphic Data Centre (CIF files 1407704 (I) and
1407802
(II);
deposit@ccdc.cam.ac.uk
or
http://www.ccdc.cam.ac.uk).
Thermal behavior was studied by the STA method
including the simultaneous detection of thermogravi-
metry (TG) and differential scanning calorimetry
(DSC) curves. The study was carried out on an STA
449C Jupiter instrument (NETZSCH) in corundum
crucibles under caps with a hole providing a vapor
pressure of 1 atm for the thermal decomposition of the
sample. The heating rate was 5°C/min to 1250°C in
argon. The samples were recorded additionally in alu-
minum crucibles to reveal thermal effects more dis-
tinctly. The weighed samples were 4.120–4.443 mg,
the accuracy of temperature measurement was 1°C,
and that of weight change was 1 × 10–4 mg.
After thermal analysis, the residual substance was
examined on a JSM-35C JEOL analytical scanning
electron microscope equipped with a 35-SDS type
wave dispersive spectrometer (a secondary electron
image was used). The chemical composition was
determined qualitatively using the microprobe
method on a RONTEC energy dispersive spectrome-
ter integrated with a LEO-1420 scanning electron
microscope.
[Fe(S2CNR2)3] + H[AuCl4]
= [Au(S2CNR2)2][FeCl4] + CS2 + HNR2.
Crystals of compounds I and II for X-ray diffrac-
tion analysis were obtained after the completion of
their interaction with gold(III) by the dissolution of
precipitates of the chemisorbing complexes in acetone
followed by the slow evaporation of the solvent. Crys-
tallization gave yellow prismatic (I) and plate-like (II)
crystals.
X-ray diffraction analyses were carried out for sin-
gle crystals of complexes I and II on BRUKER Kappa
APEX2 and BRUKER Smart APEX2 diffractometers,
respectively (MoKα radiation, λ = 0.71073 Å, graphite
monochromator) at 170(1) and 200(2) K. The X-ray
RESULTS AND DISCUSSION
The unit cells of compounds I and II include two
and eight formula units [Au(S2CNR2)2][FeCl4] (R =
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 2 2016

106
IVANOV et al.
Table 1. Crystallographic data, experimental details, and refinement parameters for structures I and II
Value
Parameter
I
II
Empirical formula
FW
C18H36N2S4Cl4FeAu
803.34
C18H36N2S4Cl4FeAu
803.34
Crystal system
Space group
a, Å
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
Triclinic
Monoclinic
P21/n
P1
9.9057(2)
11.7770(3)
13.0598(3)
79.2320(10)
89.8080(10)
84.8800(10)
1490.61(6)
15.6551(6)
15.0235(6)
26.233(1)
90
96.717(1)
90
6127.6(4)
Z
2
8
ρcalcd, g/cm3
1.790
1.742
μ, mm–1
F(000)
6.051
5.888
790
3160
Crystal size, mm
0.20 × 0.11 × 0.05
1.59–28.00
0.34 × 0.20 × 0.07
1.44–31.27
Data collection for θ range, deg
Ranges of reflection indices
Measured reflections
Independent reflections
Reflections with I > 2σ(I)
Refinement parameters
Goodness-of-fit
–13 ≤ h ≤ 13, –15 ≤ k ≤ 15, 0 ≤ l ≤ 17 –22 ≤ h ≤ 22, –21 ≤ k ≤ 21, –37 ≤ l ≤ 24
71525
7196
48960
18437 (Rint = 0.0321)
5820
279
1.085
14527
639
1.002
R factors for F 2 > 2σ(F2)
R1 = 0.0335, wR2 = 0.0840
R1 = 0.0309, wR2 = 0.0601
R factors for all reflections
R1 = 0.0482, wR2 = 0.0907
R1 = 0.0475, wR2 = 0.0648
Residual electron density (min/max), e/Å3
–2.517/0.774
–0.955/0.929
C4H9, iso-C4H9), respectively (Figs. 1 and 2). Com- (Table 2). The coordination of two Dtc ligands by gold
leads to the formation of a bicyclic system [CS2AuS2C]
with the metal atom in the spiro position. Small sizes
of the four-membered metallocycles [AuS2C] are
illustrated by the interatomic distances Au⋅⋅⋅C 2.831–
2.848 Å and S⋅⋅⋅S 2.840–2.856 Å, which are signifi-
cantly smaller than the sum of the van der Waals radii
of the corresponding pairs of atoms: 3.36 and 3.60 Å
[31, 32]. Thus, the positions of the gold and carbon
atoms in the discussed metallocycles are substantially
brought together, indicating the direct trans-annular
interaction between them and a high concentration of
the π-electron density delocalized inside the cycles.
The [AuS2C] groups are almost planar, and the
AuSSC and AuSCS torsion angles are close to 180°
(Table 2). The mutual arrangement of the discussed
plexes I and II contain structurally nonequivalent
complex cations [Au{S2CNR2}2]+: two cations in I
(R = C4H9) and three cations in II (R = iso-C4H9).
The cationic moiety of compound I is presented by
two
isomeric
centrosymmetrical
cations
[Au{S2CN(C4H9)2}2]+ including the Au(1) and Au(2)
atoms (hereinafter, cations А and В, Fig. 3a). In turn,
complex II contains noncentrosymmetrical cation A
with the Au(1) atom and centrosymmetrical cations В
and С with the Au(2) and Au(3) atoms, respectively
(Fig. 4). In each complex cation, the gold atom coor-
dinates two Dtc ligands through the S,S'-bidentate
mode. The coordination mode of the ligands is nearly
isobidentate: the maximum difference in Au–S bond
lengths is 0.01 Å. In noncentrosymmetrical cation A of atoms in cations B and С (structure II) deviates from
the coplanar arrangement due to tetrahedral distor-
tion. The geometry of the chromophores [AuS4] is
complex II, one of the Dtc ligands is noticeably more
strongly bound to the Au atom than the second ligand
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GOLD(III)–IRON(III) HETEROPOLYNUCLEAR COMPLEXES
107
Table 2. Selected bond lengths (d) and bond (ω) and torsion (φ) angles in structures I and II*
Compound I
Cation A
Cation B
Bond
d, Å
Bond
Au(2)–S(3)
Au(2)–S(4)
Au(2)⋅⋅⋅S(2)a
S(3)–C(10)
S(4)–C(10)
N(2)–C(10)
N(2)–C(11)
N(2)–C(15)
d, Å
Au(1)–S(1)
Au(1)–S(2)
Au(1)⋅⋅⋅S(3)
2.3328(11)
2.3369(11)
3.6869(13)
2.3408(13)
2.3329(13)
3.8600(12)
S(1)–C(1)
S(2)–C(1)
N(1)–C(1)
N(1)–C(2)
N(1)–C(6)
1.724(5)
1.741(4)
1.297(6)
1.479(6)
1.485(6)
1.737(5)
1.729(5)
1.297(6)
1.469(7)
1.472(7)
Angle
ω, deg
Angle
ω, deg
72.26(4)
87.2(2)
86.7(2)
110.7(2)
124.9(3)
124.4(4)
75.33(5)
86.6(2)
87.03(2)
110.9(3)
125.1(4)
124.0(4)
S(1)Au(1)S(2)
C(1)S(1)Au(1)
C(1)S(2)Au(1)
S(1)C(1)S(2)
N(1)C(1)S(1)
N(1)C(1)S(2)
S(3)Au(2)S(4)
C(10)S(3)Au(2)
C(10)S(4)Au(2)
S(3)C(10)S(4)
N(2)C(10)S(3)
N(2)C(10)S(4)
Angle
φ, deg
Angle
φ, deg
176.2(3)
176.6(3)
1.1(7)
–177.3(4)
–178.9(4)
2.7(7)
Au(1)S(1)S(2)C(1)
S(1)Au(1)C(1)S(2)
S(1)C(1)N(1)C(2)
S(1)C(1)N(1)C(6)
S(2)C(1)N(1)C(2)
S(2)C(1)N(1)C(6)
–178.2(2)
–178.4(2)
–179.6(3)
–1.0(6)
0.3(6)
178.9(3)
Au(2)S(3)S(4)C(10)
S(3)Au(2)C(10)S(4)
S(3)C(10)N(2)C(11)
S(3)C(10)N(2)C(15)
S(4)C(10)N(2)C(11)
S(4)C(10)N(2)C(15)
Anion
Bond
d, Å
Bond
d, Å
Fe–Cl(1)
Fe–Cl(2)
2.174(2)
2.183(2)
Fe–Cl(3)
Fe–Cl(4)
2.180(2)
2.193(2)
Angle
ω, deg
Angle
ω, deg
Cl(1)FeCl(2)
Cl(1)FeCl(3)
Cl(1)FeCl(4)
110.80(9)
111.24(8)
108.87(8)
Cl(2)FeCl(4)
Cl(3)FeCl(2)
Cl(3)FeCl(4)
109.99(8)
107.97(7)
107.92(8)
Compound II
Cation A
Bond
d, Å
Bond
S(3)–C(10)
d, Å
Au(1)–S(1)
Au(1)–S(2)
Au(1)–S(3)
Au(1)–S(4)
Au(1)⋅⋅⋅S(6)
Au(1)⋅⋅⋅S(7)
S(1)–C(1)
S(2)–C(1)
2.3398(7)
2.3498(7)
2.3282(7)
2.3316(7)
3.6857(8)
3.6824(8)
1.732(3)
1.730(3)
1.735(3)
1.312(3)
1.477(4)
1.482(3)
1.304(3)
1.476(3)
1.484(3)
S(4)–C(10)
N(1)–C(1)
N(1)–C(2)
N(1)–C(6)
N(2)–C(10)
N(2)–C(11)
N(2)–C(15)
1.733(3)
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IVANOV et al.
Table 2. (Contd.)
Compound II
Cation A
Angle
ω, deg
Angle
ω, deg
S(1)Au(1)S(2)
S(1)Au(1)S(3)
S(1)Au(1)S(4)
S(2)Au(1)S(3)
S(2)Au(1)S(4)
S(3)Au(1)S(4)
C(1)S(1)Au(1)
C(1)S(2)Au(1)
75.01(2)
104.26(2)
176.61(3)
177.91(3)
105.74(2)
75.10(2)
C(10)S(3)Au(1)
C(10)S(4)Au(1)
S(1)C(1)S(2)
S(3)C(10)S(4)
N(1)C(1)S(1)
N(1)C(1)S(2)
N(2)C(10)S(3)
N(2)C(10)S(4)
87.51(9)
87.29(9)
111.0(2)
110.09(14)
124.0(2)
125.0(2)
125.0(2)
124.9(2)
87.18(9)
86.82(9)
Angle
φ, deg
Angle
φ, deg
Au(1)S(1)S(2)C(1)
S(1)Au(1)C(1)S(2)
S(1)C(1)N(1)C(2)
S(1)C(1)N(1)C(6)
S(2)C(1)N(1)C(2)
S(2)C(1)N(1)C(6)
178.2(2)
178.4(1)
–4.0(4)
178.8(2)
175.2(2)
–2.0(4)
Au(1)S(3)S(4)C(10)
S(3)Au(1)C(10)S(4)
S(3)C(10)N(2)C(11)
S(3)C(10)N(2)C(15)
S(4)C(10)N(2)C(11)
S(4)C(10)N(2)C(15)
–179.3(2)
–179.4(1)
170.1(2)
–8.0(4)
–9.5(4)
172.5(2)
Cation B
Cation C
Bond
d, Å
Bond
d, Å
Au(2)–S(5)
Au(2)–S(6)
Au(2)⋅⋅⋅S(1)
S(5)–C(19)
S(6)–C(19)
N(3)–C(19)
N(3)–C(24)
N(3)–C(20)
2.3349(7)
2.3355(7)
3.6103(8)
1.730(3)
1.736(3)
1.302(3)
1.471(3)
1.476(4)
Au(3)–S(7)
Au(3)–S(8)
Au(3)⋅⋅⋅S(2)
S(7)–C(28)
S(8)–C(28)
N(4)–C(28)
N(4)–C(29)
N(4)–C(33)
2.3409(7)
2.3364(7)
3.5893(8)
1.743(3)
1.736(3)
1.301(3)
1.476(3)
1.482(3)
Angle
ω, deg
Angle
ω, deg
S(5)Au(2)S(6)
C(19)S(5)Au(2)
C(19)S(6)Au(2)
S(5)C(19)S(6)
N(3)C(19)S(5)
N(3)C(19)S(6)
75.15(2)
87.14(9)
87.00(10)
110.5(2)
124.9(2)
124.6(2)
S(7)Au(3)S(8)
C(28)S(7)Au(3)
C(28)S(8)Au(3)
S(7)C(28)S(8)
N(4)C(28)S(7)
N(4)C(28)S(8)
75.08(2)
87.14(9)
87.44(9)
110.1(2)
124.9(2)
125.0(2)
Angle
φ, deg
Angle
φ, deg
Au(2)S(5)S(6)C(19)
S(5)Au(2)C(19)S(6)
S(5)C(19)N(3)C(20)
S(5)C(19)N(3)C(24)
S(6)C(19)N(3)C(20)
S(6)C(19)N(3)C(24)
174.7(2)
175.2(2)
–173.0(2)
2.4(4)
6.0(4)
–178.5(2)
Au(3)S(7)S(8)C(28)
S(7)Au(3)C(28)S(8)
S(7)C(28)N(4)C(29)
S(7)C(28)N(4)C(33)
S(8)C(28)N(4)C(29)
S(8)C(28)N(4)C(33)
–174.1(2)
–174.7(1)
2.7(4)
179.4(2)
–175.4(2)
1.3(4)
Anion D
Anion E
Bond
d, Å
Bond
d, Å
2.1957(8)
2.2001(10)
2.1919(13)
2.1874(9)
Fe(1)–Cl(1)
Fe(1)–Cl(2)
Fe(2)–Cl(5)
Fe(2)–Cl(6)
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GOLD(III)–IRON(III) HETEROPOLYNUCLEAR COMPLEXES
109
Table 2. (Contd.)
Compound II
Anion D
Anion E
Bond
d, Å
Bond
Fe(2)–Cl(7)
Fe(2)–Cl(8)
Angle
d, Å
Fe(1)–Cl(3)
Fe(1)–Cl(4)
2.1942(10)
2.1867(10)
2.1817(11)
2.1992(11)
Angle
ω, deg
ω, deg
109.47(5)
110.83(6)
109.64(6)
109.72(4)
108.48(4)
108.66(4)
Cl(1)Fe(1)Cl(2)
Cl(1)Fe(1)Cl(3)
Cl(1)Fe(1)Cl(4)
Cl(2)Fe(1)Cl(3)
Cl(2)Fe(1)Cl(4)
Cl(3)Fe(1)Cl(4)
107.57(4)
109.86(4)
109.30(4)
110.73(4)
109.95(4)
109.40(4)
Cl(5)Fe(2)Cl(6)
Cl(5)Fe(2)Cl(7)
Cl(5)Fe(2)Cl(8)
Cl(6)Fe(2)Cl(7)
Cl(6)Fe(2)Cl(8)
Cl(7)Fe(2)Cl(8)
а
* Symmetry transforms: –x + 1, –y + 1, –z + 2 (I).
close to the planar tetrahedral one with the low-spin
The supramolecular self-organization of com-
plexes I and II occurs by relatively weak secondary
(inner-orbital) dsp2-hybrid state of the gold(III) atom.
bonds1 Au⋅⋅⋅S of the nonvalent type between the com-
plex cations. In compound I, each of isomeric cations
A and B forms two pairs of these nonsymmetrical
bonds with the neighbors: Au(1)⋅⋅⋅S(3) and
Au(1)⋅⋅⋅S(3)b 3.6869; Au(2)⋅⋅⋅S(2)a and Au(2)⋅⋅⋅S(2)e
3.8600 Å, due to which linear polymer chains
[⋅⋅⋅A⋅⋅⋅B⋅⋅⋅]n oriented along the crystallographic axis x
are formed (Fig. 3a). The length of the discussed
bonds exceeds the sum of the van der Waals radii of
gold and sulfur (3.46 Å) [31, 32]. The Au(1)⋅⋅⋅Au(2)
The anionic moiety of complexes I and II is pre-
sented by ions [FeCl4]–, in each of which the central
iron atom (sp3-hybridization state) exists in the dis-
torted tetrahedral environment of four structurally
nonequivalent chlorine atoms (Fe–Cl 2.174–
2.2001 Å, angles ClFeCl 107.57°–111.24°). The struc-
ture of complex II includes two isomeric [FeCl4]–
anions D and E with the Fe(1) and Fe(2) atoms,
respectively (Fig. 5b, Table 2). The character of differ-
ences between the respective structural characteristics
of the nonequivalent gold(III) cations and iron(III)
anions (Table 2) makes it possible to classify them as
conformational isomers.
1
The concept of secondary bonds was proposed [33] for the
description of interactions characterized by the distances com-
parable with the sums of the van der Waals radii of the corre-
sponding atoms.
y
z
x
Fig. 1. Perspective view of the structure ([Au{S CN(C H ) } ][FeCl ]) (I) along the axis x.
2
4
9 2 2
4 n
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 2 2016

110
IVANOV et al.
y
z
x
Fig. 2. Perspective view of the structure ([Au{S CN(iso-C H ) } ][FeCl ]) (II) along the axis x.
2
4
9 2 2
4
n
(а)
S(4)f
S(2)
S(1)a
S(3)f
S(4)b
Au(1)
S(3)
Au(2)b
S(3)b
S(1)
S(2)g
S(2)a
(b)
Cl(4)
Cl(3)
Fe(1)
Cl(1)
Cl(2)
+
–
Fig. 3. (a) Fragment of the cationic polymer chain ([Au{S CN(C H ) } ] ) in complex I and (b) the tetrahedral anion [FeCl ] .
2
4
9 2 2
n
4
distance in the polymer chain is 4.953 Å. The [FeCl4]–
anions alternate at the right and left from the polymer
chains (Figs. 1 and 3b). It follows from the structural
fragment shown in Fig. 3a that in each gold(III) cation
only two diagonally oriented sulfur atoms are involved
in secondary binding: the atoms S(2) in cation A and
S(3) in cation B (Table 2).
gold(III) complex cations and two isomeric iron(III)
anions. All cations [Au{S2CN(iso-C4H9)2}2]+ are
involved in the construction of the polymer chain due
…
to pairs of nonsymmetrical Au S bonds. However, in
nonsymmetrical cation A, the sulfur atoms of only one
Dtc ligand, S(1) and S(2), are involved in binding,
whereas cations B and C present for binding the diag-
onally oriented atoms S(6), S(6)b and S(7), S(7)a,
More complicatedly organized supramolecular
structure II is caused by the presence of three isomeric respectively (Fig. 4, Table 2). Four nonequivalent
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GOLD(III)–IRON(III) HETEROPOLYNUCLEAR COMPLEXES
(а)
111
S(6)b
C(9A)
C(8B)
C(9B)
C(8A)
C(18)
C(16)
C(7A)
S(2)
S(1)
S(4)
S(3)
C(7B)
C(6)
C(11)
N(2)
Au(1)
C(10)
N(1)
C(17)
C(14)
C(1)
C(15)
C(2)
C(12)
C(3)
C(4)
C(5)
C(13)
S(7)a
(b)
S(1)b
C(26B)
C(27A)
C(26A)
C(25)
S(5)
S(6)
S(6)с
N(3)
C(27B)
C(24)
C(20)
C(19)
Au(2)
S(5)с
C(21)
C(22)
C(23)
S(7)d
(c)
S(2)
C(31B) C(32B)
C(31A)
C(32A)
C(30A)
C(29)
C(30B)
S(8)a
S(7)
N(4)
C(28)
Au(3)
C(33)
C(34)
C(35)
S(7)a
S(8)
C(36)
S(2)a
Fig. 4. Structures of isomeric complex cations (a) A, (b) B, and (c) C of compound II. Ellipsoids of 50% probability.
Au⋅⋅⋅S bonds are observed between the adjacent iso- the Au(2)Au(1)Au(3) angle is 159.76°. In addition, the
meric cations [Au{S2CN(iso-C4H9)2}2]+: Au(1)⋅⋅⋅S(6)
3.6857, Au(1)⋅⋅⋅S(7) 3.6824, Au(2)⋅⋅⋅S(1) 3.6103, and
Au(3)⋅⋅⋅S(2) 3.5893 Å. The bonds result in the forma-
isomeric gold(III) complex cations in polymer chains
of compounds I and II are characterized by different
spatial orientations (Figs. 3a and 5a).
tion
of
zigzag
supramolecular
chains
The presence of secondary interactions in the poly-
[⋅⋅⋅A⋅⋅⋅В⋅⋅⋅A⋅⋅⋅C⋅⋅⋅]n (Fig. 5a). The distances are mer chains results in the formation of extended dis-
torted octahedral chromophores [AuS6] by each gold
Au(1)⋅⋅⋅Au(2) 3.933 and Au(1)⋅⋅⋅Au(3) 4.018 Å, and
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 2 2016

112
IVANOV et al.
(а)
S(2)
S(6)
Au(1)
Au(2)
Au(3)
S(4)
S(1)
S(3)
S(7)
(b)
Cl(2)
Cl(6)
Cl(1)
Cl(5)
Fe(2)
Fe(1)
Cl(4)
Cl(7)
Cl(3)
Cl(8)
+
Fig. 5. (a) Fragment of the cationic polymer chain ([Аu{S CN(iso-C H ) } ] ) in complex II and (b) the isomeric anions
2
4
9 2 2
n
–
[FeCl ] . Ellipsoids of 50% probability.
4
The [FeCl4]– anions are localized at the right and
left from the polymer chains (Figs. 2 and 5b). Anions
D form short contacts only with centrosymmetrical
cations B in the polymer chains. The Cl(1)⋅⋅⋅S(5) dis-
tances (3.531 Å) are somewhat shorter than the sum of
atom. It should be mentioned that the sulfur atoms,
which are not involved in the secondary interactions
Au⋅⋅⋅S, namely, S(1) and S(4) in complex I and S(3),
S(4), S(5), and S(8) in complex II, form reliably stron-
ger inner-cation covalent Au–S bonds (Table 2).
DSC, mW/mg
15
TG, %
−27.92%
а
100
90
80
70
60
50
40
30
c
10
5
1062.5°C
96.6°C
111.8°C
80
100
140
1063.6°C
b
−56.09%
0
27.56%
−5
−15.65%
1000
200
400
600
800
1200
T, °C
Fig. 6. (a) TG and (b) DSC curves for complex I. The low-temperature DSC region (c) was recorded in an aluminum crucible.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 2 2016

GOLD(III)–IRON(III) HETEROPOLYNUCLEAR COMPLEXES
(а)
113
15 kV
×140
100 µm 0200
10 58 BES
I × 103, rel. units
(b)
C
3
Fe
2
O
1
0
Fe
Fe
7
0
1
2
Au
3
4
5
6
8
9
10
(c)
8
6
4
2
0
C
Au
Au
Au
10
0
1
2
3
4
5
E, keV
6
7
8
9
Fig. 7. (a) Slag particles with metallic gold balls after the thermal analysis of complex I and the energy dispersive spectra of (b)
slag and (c) reduced gold.
the van der Waals radii of chlorine and sulfur atoms ents in the dithiocarbamate ligands demonstrate a
(3.55 Å) [31, 32]. Anions Е are isolated.
similar character of thermal transformations. In par-
ticular, complex I exhibits thermal stability up to
~90°С (Fig. 6). The TG curve shows the two-stage
process of mass loss (Fig. 6, a). The main mass loss
The thermal behavior of compounds I and II was
studied by the STA method using a combined detec-
tion of TG and DSC curves. Complexes I and II char-
acterized by different structures of the alkyl substitu- equal to 56.09% of the initial value (the calculated
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 2 2016

114
IVANOV et al.
value is 55.29%) falls onto the first steeply-descending Education and Science of the Russian Federation
region of the TG curve (~90–330°С), indicating that (project no. 1452.2014/9).
the thermolysis proceeds simultaneously by the cation
and anion with the reduction of gold(III) to metal and
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Translated by E. Yablonskaya
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 2 2016