Synthesis and properties of compounds of formamidindium disulfide with d-element tetrahalide anions

Article abstract of DOI:10.1134/S0036023613060107

Products of reactions of salts of d elements with formamidine disulfide dihydrochloride (FDSH₂Cl₂) in concentrated HCl and HBr solutions were synthesized and characterized. The following compounds were obtained: FDSH₂[CuCl₄] · H₂O, FDSH ₂[CoCl₄], FDSH₂[ZnCl₄], FDSH ₂[HgCl₄], and FDSH₂[HgBr₄]. The identity of these compounds was confirmed by X-ray diffraction; their compositions were derived from the results of chemical analysis and thermal analysis. The IR and Raman scattering spectra of the compounds indicate the presence therein of FDSH ₂ ²⁺ cation. It was established that FDSH ₂ ²⁺ transforms into formamidindium trisulfide cation (NH₂)₂C-S-S-S-C(NH₂) ₂ ²⁺ upon storage in air in hydrochloric acid solution.

Full text of DOI:10.1134/S0036023613060107

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2013, Vol. 58, No. 6, pp. 701–705. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © N.N. Golovnev, S.D. Kirik, A.A. Leshok, 2013, published in Zhurnal Neorganicheskoi Khimii, 2013, Vol. 58, No. 6, pp. 793–797.
PHYSICAL METHODS
OF INVESTIGATION
Synthesis and Properties of Compounds of Formamidindium
Disulfide with dꢀElement Tetrahalide Anions
N. N. Golovnev, S. D. Kirik, and A. A. Leshok
Siberian Federal University, Krasnoyarsk, Russia
Received April 10, 2012
Abstract—Products of reactions of salts of
d
elements with formamidine disulfide dihydrochloride
(
FDSH Cl2) in concentrated HCl and HBr solutions were synthesized and characterized. The following
2
compounds were obtained: FDSH [CuCl ] ⋅ H O, FDSH [CoCl ], FDSH [ZnCl ], FDSH [HgCl ], and
2
4
2 2 4 2 4 2 4
FDSH [HgBr ]. The identity of these compounds was confirmed by Xꢀray diffraction; their compositions
2
4
were derived from the results of chemical analysis and thermal analysis. The IR and Raman scattering spectra
2
+
of the compounds indicate the presence therein of FDSH2 cation. It was established that FDSH2 transꢀ
2+
2
+
forms into formamidindium trisulfide cation (NH ) C–S–S–S–C(NH ) upon storage in air in hydrochloꢀ
2
2
2 2
ric acid solution.
DOI: 10.1134/S0036023613060107
Thiourea (Tu) and its derivatives are used in hydroꢀ presumably result in reduction of FDS. Metal ions
2+
thermal preparation of metal sulfide films and as corꢀ with pronounced oxidative properties (Cu ) can oxiꢀ
rosion inhibitors [1, 2]. Acid solutions of thiourea are dize formamidine disulfide.
considered as a real alternative to cyanide solutions in
gold hydrometallurgy, and its use may have important
environmental advantages [3, 4]. Thiourea is oxidized
in aqueous medium; the product formed in the first
stage is formamidine disulfide (FDS), the possible catꢀ H O (
alytic activity of which in gold dissolution reaction has
In this work, FDSH Cl2
⋅
H O (
2
1
)
and products of
2
its interaction with salts of
d elements in concentrated
2
2
+
2−
⋅
HCl and HBr solutions, namely FDSH [CuCl ]
4
2
2
+
2−
2+
2−
2
), FDSH [CoCl ]
(3), FDSH [ZnCl ]
2
4
2
4
2+
2
2−
2+
2−
(
4
), FDSH [HgCl ]
(
5
)
, and FDSH [HgBr ]
4
2
4
been discussed in literature [4, 5].
(6), were isolated and characterized in order to study
the influence of the nature of a metal on thiourea–forꢀ
mamidine disulfide mutual transformations.
NH
+ 2H+
NH2
H N
2
NH2 C NH2
S
2
– 2e–
C S S
C
HN
EXPERIMENTAL
Tu
FDS
The following reagents were used in the work:
chemically pure grade Tu, HCl, HBr, ZnO; and pureꢀ
Scheme. Tu–FDS redox equilibrium.
forꢀanalysis grade HgO, CoCl2
H O
⋅
6H O, and CuCl2
⋅
2
Metal ions can exert different influence on equilibꢀ
2
.
2
ria between disulfides and their reduced species. For
example, on the one hand, transitionꢀmetal ions
Xꢀray diffraction patterns were obtained on an
X’Pert Pro (PANalytical) diffractometer (Cu radiaꢀ
K
2+
2+
3+
α
(
(
Pd , Pt , and Fe ) catalyze oxidation of thiols
SH) to disulfides (–SS–) [6], while on the other
tion, graphite monochromator,
2
θ
range of
5
°
–90 ,
°
⎯
air atmosphere). Thermoanalytical curves were
recorded on a NETZSCH 409 instrument (under
argon flow, heating rate of 10 K/min, temperature
hand, for instance for cistamine (NH (CH ) S–
2
2 2
S(CH ) NH2), the –SS– bond dissociates in the presꢀ
ence of palladium(II) [7], Hg(II), Ag(I) [8], Cu(II)
and Ni(II) [9] salts to yield thiol complexes of
2
2
range of 23–260 С, sample of 10–15 mg). IR spectra
°
were recorded as 0.1% mixtures with KBr in the range
cisteamine NH (CH ) SН
.
–1
2
2 2
of 400–4000 cm (FTIR Nicolet 6700). Raman scatꢀ
As it follows from Scheme 1, an increase in solution tering spectra were obtained for compounds
acidity should assist the reduction of FDS. Influence using an NXR FTꢀRaman module attachment for a
of ꢀelement ions on mutual redox transformations of Nicolet 6700 Fourierꢀtransform IR spectrometer (
thiourea and formamidine disulfide in strongly acidic 1064 nm). The spectrum of compound was recorded
solutions has been practically not studied. The formaꢀ on an Almega XR spectrometer ( = 785 nm). We
tion of stable thiourea complexes by metal ions can failed to obtain Raman scattering spectra from comꢀ
1, 4, and
5
d
λ
=
3
λ
701

702
GOLOVNEV et al.
(
285 Å =
3) (refcode FOINSI). For compound 1а Vm
29 Å [11]. Moreover, the a, b and c parameters
TG, %
DSC, mW/mg
0
3
2
100
change in similar trends in this series of compounds.
All the foregoing indicates that we have obtained a
monohydrate, which had characterized structurally in
the case of other two halide ions.
[
1]
90
80
70
60
50
40
–1
–2
–3
–4
–5
Synthesis of dꢀElement Compounds
In view of the fact that formamidine disulfide is staꢀ
+
ble only in strongly acidic aqueous solutions ([H ] >
2 mol/L) [12], as well as comparatively low thermodyꢀ
namic stability of [MX4] in an aqueous solution, the
synthesis was carried out at high medium acidity creꢀ
ated by 12 M HCl or 8 M HBr. Because of possible
contamination of the products with a chloride or broꢀ
[
1]
2–
50
100
150
T, °C
200
250
mide salt of formamidine disulfide, FDSH Cl
and M were taken in a ratio of 1 : 2. The synthesis was
conducted according to the reaction equations
⋅ H O
2
2 2
Fig. 1. Thermoanalytical curves for FDSH Cl · H O.
2+
2
2
2
pounds
2
and
6
. The resolution was 4–6 cm–1 in all the
FDSH Cl + MО + 4НX → FDSH [MX ]↓
2 2 2 4
cases. The elemental compositions of the specimens
were established by a Flash EA 1112 elemental anaꢀ
lyzer.
+
2HCl + Н О (М = Zn,Hg; X = Cl,Br),
2
FDSH Cl + MCl → FDSH [MCl ]↓
2
2
2
2
4
(
M = Cu,Co).
In a typical experiment, metal oxides or salts were
FDSH Cl ⋅ H O), which was obtained by the oxidaꢀ dissolved in 2 mL of concentrated HCl or HBr.
2 2
Formamidine disulfide dihydrochloride monohyꢀ
2+
–
drate [(NH ) СSSC(NH ) ]
⋅
2Cl
⋅
H O
2
2
2
2 2
(
2
tion reaction of thiourea with hydrogen peroxide in a FDSH Cl2
⋅
H O in an amount of 0.20 g was added to
2
2
hydrochloric acid medium, served as the starting subꢀ the obtained solution. Precipitates crystallized from
stance in the synthesis. Monohydrate FDSH Cl2
solutions within several days; they were filtered off and
) was prepared under slow precipiꢀ dried in air at room temperature. The yields of prodꢀ
tation conditions instead of the anhydrous salt as in ucts were in the range of 60–80%.
10]. This follows from the TG curve on which a
⋅
2
H O (compound
2
1
[
The synthesized compounds had the following colꢀ
weight loss corresponding to removal of one water
molecule and accompanied by an endotherm (Fig. 1)
is observed in the range of 80–100
is confirmed by the difference between unit cell
parameters contained in the Cambridge Structural
Database (CSD, refcode TFORCL01) [11] for
FDSH Cl (compound 1а) and those calculated for
our synthesized compound
graphic data obtained for fit well the regular change
in molar volume (Vm) in the following series of subꢀ Cu, 16.44.
2+
2−
ors: FDSH Cl
⋅
2−
H O (
2
1
), FDSH [ZnCl ]
(4),
2
2
2
2+
4
2
2
+
2−
°
С
. This conclusion FDSH
[HgCl
4
]
(
5
)
, and FDSH
2
[HgBr
4
]
(6)
2
2
+
2−
were white; FDSH [CuCl ]
⋅
H O (
2)
was yellowꢀ
was blue.
For C H Cl CuN OS anal. calcd. (%): C, 6.40;
4
2
2
2
+
2−
green; and FDSH [CoCl ]
(3)
4
2
10
4
4
2
2
2
H, 2.68; N, 14.92; S, 17.07; Cu, 16.92.
1 (Table 1). Crystalloꢀ
1
Found, %: C, 6.21; H, 2.47; N, 15.30; S, 17.70;
3
stances: FDSH Cl
H O (270
⋅
H O (Vm = 247
Å
)–FDSH Br2
⋅
For C H Cl N S Zn anal. calcd. (%): C, 6.68; H,
2
2
2
2
2 8 4 4 2
3
Å ) (refcode FOASBH)–FDSH2I2 ⋅ H O 2.24; N, 15.59; S, 17.84; Zn, 18.19.
2
2
Table 1. Crystallographic parameters of FDS compounds
Compound Space group , Å , Å
a
b
c
, Å
α
, deg
β
, deg
γ, deg
V
, Å3
1
1
2
3
4
5
6
a
Pbca
8.836
11.863
15.069
7.867
10.508
5.050
19.695
8.354
8.451
7.096
7.088
8.641
6.742
90.00
90.00
90.00
98.39
98.46
90.00
90.00
90.00
99.41
103.02
93.70
93.64
104.96
97.07
90.00
90.00
90.00
90.67
90.80
90.00
90.00
1828
494
P
P
P
P
P
P
2/a
2 /
1
n
9.699
1251
599
ꢀ1
ꢀ1
10.879
10.877
14.643
13.555
7.864
599
2 /
n
a
10.209
14.911
1248
1352
1
2 /
1
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 6 2013

SYNTHESIS AND PROPERTIES OF COMPOUNDS OF FORMAMIDINDIUM DISULFIDE
703
DSC, mW/mg
0
DSC, mW/mg
[
TG, %
00
TG, %
1]
100
1
0
98
96
94
92
90
88
95
–0.2
–0.4
–0.6
–
–
–
0.2
[
1]
90
85
80
75
0.4
0.6
–
0.8
1.0
–
–0.8
1.0
[
1]
–1.2
–
[
1]
40 60 80 100 120 140 160 180 200
t, °C
40
60 80 100 120 140 160 180 200
°
T,
C
2+
2
2−
Fig. 3. Thermoanalytical curves for FDSH [CuCl ]
H O.
⋅
4
Fig. 2. Thermoanalytical curves for FDSH [ZnCl ]
.
2
4
2
Found (%): C, 6.28; H, 2.22; N, 15.65; S, 18.17;
Zn, 17.56.
For C H Cl CoN S anal. calcd. (%): C, 6.81; H,
2+
all comprise FDSH2 cation. Four of these comꢀ
pounds have chlorideꢀcontaining rhenium anions as
counterions, while the others contain Cl , Br , I , or
–
–
–
2
8
4
4
2
2.28; N, 15.87; S, 18.17; Co, 16.70.
−
NO3 anions.
Found (%): C, 6.52; H, 2.09; N, 15.97; S, 18.24;
Co, 16.81.
According to thermal analysis, most of the comꢀ
pounds prepared by us are free of water. As an examꢀ
ple, Fig. 2 shows thermoanalytical curves for one of
them. As follows from the TG curve (Fig. 3), the
For C H Cl HgN S anal. calcd. (%): C, 4.86; H,
.63; N,. 11.33; S, 12.97; Hg, 40.55.
2
8
4
4 2
1
Found (%): C, 4.57; H, 1.73; N, 11.06; S, 13.06;
Hg, 39.89.
2+
2
2−
weight loss experienced by FDSH [CuCl ]
in agreement with the presence of one molecule of
crystal water (calcd.: 4.80 wt %; found: 4.94 wt %).
⋅ H O is
2
4
For C H Br HgN S anal. calcd. (%): C, 3.57; H,
.20; N, 8.33; S, 9.54; Hg, 29.83.
2
8
4
4 2
1
2
+
Decomposition of FDSH structural fragment in
all the compounds started at 140–150
herm in the range of 150–160 (Figs. 1–3) on the
DSC curve corresponded to this process. Practically
Found (%): C, 3.69; H, 1.25; N, 8.46; S, 9.97; Hg,
9.16.
2
°С. An endotꢀ
2
°С
An interesting result was obtained in attempting to
2
+
2−
isolate FDSH [ZnBr ] . On keeping the reaction
2
4
complete coincidence in the thermolysis characterisꢀ
mixture for 5 months, white single crystals of formaꢀ
tics of FDSH Cl2
⋅
H O and the compounds with metꢀ
2
2
midindium trisulfide dibromide (NH ) C–S–S–S–
2
2
2+
als indirectly confirms the preservation of FDSH2
cation in the complexes. The composition of thermolꢀ
ysis products was not studied.
Calculated crystallographic characteristics confirm
the individuality of the compounds (Table 1).
2
2
+
⋅
2Br– precipitated from the solution. The
C(NH2)
structure of this compound was confirmed by Xꢀray
diffraction study; the crystallographic parameters calꢀ
culated were in agreement with those presented in
[
13], in which this compound was prepared by direct
2
2
+
2−
2+
2
2−
FDSH [CoCl ]
(3
)
and FDSH [ZnCl ]
(4)
were
oxidation of thiourea with bromine. The possibility of
incorporating sulfur into disulfide group in the
absence of additional oxidizers (except air oxygen) is
of interest.
4
4
isostructural with each other.
The IR spectrum of compound
(Fig. 4, Table 2) completely coincided with that given
in work [14] for FDSH Cl2. At the same time, a
1
obtained by us
2
decrease in weight corresponding to the loss of one
water molecule was observed on the TG curve (Fig. 1)
RESULTS AND DISCUSSION
with a plateau in the range of 90–150
mentally found decrease in weight was 7.18 wt %, with
°С (the experiꢀ
There are little data on the synthesis and stability of
formamidine disulfide compounds in the literature. In
part, this is explained by a low stability of formamidine
disulfide in weak acidic and especially in neutral and
basic solutions and its tendency to redox transformaꢀ
tions and catalytic decomposition in the presence of
the value calculated for FDSH Cl2
⋅
H O being equal to
indirectly confirms
2
2
7
.47 wt %). An endotherm at 83
°С
the loss of crystal water from the compound.
As it follows from Figs. 4 and 5, there are no signifꢀ
metal ions. The Cambridge Structural Database [11] icant differences between the IR and Raman scatterꢀ
contains the structures of eight FDS compounds; they ing spectra of FDSH
Cl ⋅ H O, on the one hand, and
2 2
2
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 6 2013

704
GOLOVNEV et al.
FDSH [HgCl ]
FDSH Cl · H O
2
2
2
2
4
FDSH [HgBr ]
2
FDSH Cl · H O
2 2 2
4
FDSH [HgCl ]
4
FDSH [ZnCl ]
2 4
2
FDSH [CuCl ] · H O
2
FDSH [CoCl ]
2 4
4
2
FDSH [ZnCl ]
2
4
800
600
400
200
Δν, cm–1
Fig. 5. Raman scattering spectra of formamidine disulfide
compounds.
FDSH [CoCl ]
2
4
is absent, and small differences are observed in other
1
600
1200
800
400
–1
, cm–1
frequencies (for example, 700 cm for
ν
(C–S)). The
ν
greatest differences were noted in the region of 3000–
–1
3
350 cm
follows: the researchers worked in one case with anhyꢀ
drous FDSH Cl2 and in the other with FDSH Cl
(
ν
(NH )). This fact may be explained as
2
Fig. 4. IR spectra of formamidine disulfide ionic comꢀ
pounds.
⋅
2
2
2
H O, which resulted in formation of various hydrogen
2
–
compounds containing anions of
d
ꢀmetal tetrahalides, bonds by NH2 group with Cl ions or O atoms (from
on the other. This indicates similar chemical surꢀ water).
roundings of disulfide groups in them. The observed
negligible shifts of some bands are explained by the
influence of hydrogen bonds. Therefore, the spectroꢀ
The Raman scattering spectrum of FDS
H O (Fig. 5, Table 3) features (C–S)/ (SCN2) bands
as(CN2) at 1057 cm–1
(SCN2)
⋅
2HCl
⋅
ν
β
2
–
1
2
2
+
at 666 and 558 cm
,
ν
,
δ
scopic results also agree with the presence of FDSH
cation in all the compounds.
–1
at 425 cm , assignment of which was made in accorꢀ
dance with [5]. The authors of work [5], based upon a
small difference between the length of S–S bond in
The assignment of bands in the IR spectra of
FDSH Cl to specific vibrations is ambiguous. For
2
2
FDS 2HCl and in rhombohedral sulfur the Raman
⋅
instance, some researchers [14] assigned the band at
72 cm–1 to
(NCN), while others [15] assigned it to
(S–S), etc. The IR spectra of FDSH Cl H O
scattering spectrum of which also features an intense
band with the same frequency, consider it more preferꢀ
4
ν
δ
⋅
2
2
2
–1
able to assign the band at 476 cm to
than to (CN2) [14]. Insignificant differences between
the spectra of FDS 2HCl H O and those of metalꢀ
(C=N)) containing compounds in the region of 350–800 cm
ν
(S–S) rather
obtained by us (Fig. 5) and in work [14] coincide comꢀ
pletely, but somewhat differ from the data of [15].
δ
⋅
⋅
Thus, in work [15], the bands assigned to
ν
(NH2) lie at
2
–1
–1
ν
–1
3
240 and 2995 cm , the band at 1687 cm
(
Table 2. Fundamental vibration frequencies in the IR spectra of FDS compounds
Compound
Vibration frequencies, cm–1
1
2
3
4
5
6
1657vs*
1665vs
1662s
1610w
1607br
1610w
1611w
1611w
1609m
1521w
1405m
1392m
1397w
1396m
1404w
1404m
666w
472m
474w
465w
465br
457w
457w
423w
425w
418w
418w
421w
422w
1537w
1531w
1532w
1532w
1529w
662w
663w
657w
660m
669m
1662s
1665vs
1656vs
*
Here and in Table 3, band intensity notations: vs stands for very strong, s stands for strong, m stands for medium strength, w stands for
weak, and br stands for broad.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 6 2013

SYNTHESIS AND PROPERTIES OF COMPOUNDS OF FORMAMIDINDIUM DISULFIDE
705
Table 3. Fundamental vibration frequencies in the Raman scattering spectra of FDS compounds
Compound
Vibration frequencies, cm–1
1
1612w
1615w
1621w
n/o*
1530w
1528w
1530w
n/o
1419m
1417w
1420w
1417w
666s
558vs
559vs
560s
474vs
460m
462s
425s
340s
3
666m
665s
423m
423m
420w
346s
5
338m
337m
6
658m
553s
453w
*
Not observed.
2
2
+
4. X. Yang, M. S. Moats, and J. D. Miller, Miner. Eng. 23
98 (2010).
. G. K. Parker and G. A. Hope, Miner. Eng. 21, 489
2008).
. A. V. Eremin, V. G. Antonov, N. S. Panina, et al., Ross.
Khim. Zh. 53 (1), 135 (2009).
,
indicate that they all contain FDSH cation. The difꢀ
6
–1
ferences observed in the region of 200–350 cm are
due to the appearance of additional bands assigned to
the
Therefore, thermaoanalytical, IR, and Raman
scattering data for FDSH Cl2 H O and compounds
5
6
(
ν
(M–Cl) stretching vibrations.
⋅
7. I. A. Efimenko, Kh. I. Gasanok, N. A. Ivanova, et al.,
2
2
with
dꢀmetal tetrahalide anions do not have any signifꢀ
Koord. Khim. 26, 117 (2000).
icant differences. This indicates the existence of an
8. M. S. Bharara, S. Parkin, and D. A. Atwood, Main
2
+
Group Chem.
. D. Carrillo, P. Gouzerh, and Y. Jeannin, Polyhedron
837 (1989).
0. P. W. Preisler and L. Berger, J. Am. Chem. Soc. 69, 322
1947).
1. Cambridge Structural Database. Version 5.32 (Univ. of
Cambridge, UK, November 2010).
2. N. Madhiri, R. Olojo, and R. H. Simoyi, Phys. Chem.
Chem. Phys. 5, 4149 (2003).
3. A. D. Tol, A. D. Natu, and V. G. Puranik, Mol. Cryst.
Liq. Cryst. 469 (1), 69 (2007).
4. P. Bombicz, I. Mutikainen, M. Krunks, et al., Inorg.
4 (3), 217 (2005).
FDSH2 doubleꢀcharged cation in them and the same
chemical surrounding of disulfide group in all the
compounds; that is, the disproportionation or reducꢀ
tion of FDS to thiourea (see Scheme 1), which should
be assisted by the formation of its complexes with metal
ions, is not observed under the conditions studied.
9
8,
2
1
1
1
1
1
1
(
REFERENCES
1
2
3
. V. Stavila, K. H. Whitmire, and I. Rusakova, Chem.
Mater. 21, 5456 (2009).
. N. Bao, L. Shen, T. Takata, et al., J. Phys. Chem.
Chim. Acta 357, 513 (2004).
C
111, 17527 (2007).
5. J. P. Shubha and Puttaswamy, J. Sulfur Chem. 30, 490
(2009).
. L. F. Kozin, S. A. Kozina, and A. K. Bogdanova, Theor.
Exp. Chem. 39, 132 (2003).
Translated by M. Makarov
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 6 2013