Extraction of chlororuthenium(III) complexes by triazole derivatives from hydrochloric acid solutions

Article abstract of DOI:10.1134/S0036023607050269

The extraction of ruthenium(III) by triazole derivatives from hydrochloric acid solutions has been studied. The extraction of ruthenium(III) is implemented by the ion-association mechanism. The composition of the extraction compound has been determined us

Full text of DOI:10.1134/S0036023607050269

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2007, Vol. 52, No. 5, pp. 800–805. © Pleiades Publishing, Inc., 2007.
Original Russian Text © N.G. Afzaletdinova, L.M. Ryamova, Yu.I Murinov, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 5, pp. 866–871.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Extraction of Chlororuthenium(III) Complexes
by Triazole Derivatives from Hydrochloric Acid Solutions
N. G. Afzaletdinova, L. M. Ryamova, and Yu. I Murinov
Institute of Organic Chemistry, Ufa Scientific Center, pr. Oktyabrya 71, Ufa, 450054 Bashkortostan, Russia
Ufa State Academy for Economics and Service, Ufa, Bashkortostan, Russia
Received March 21, 2006
Abstract—The extraction of ruthenium(III) by triazole derivatives from hydrochloric acid solutions has been
studied. The extraction of ruthenium(III) is implemented by the ion-association mechanism. The composition
of the extraction compound has been determined using electronic, 1H NMR, 13C NMR, and IR spectroscopy
and elemental analysis.
DOI: 10.1134/S0036023607050269
The extraction techniques of recovery, separation, as the diluent to study the extraction properties of this
and preconcentration of precious metals are significant compound. It was found that the maximal ruthe-
for hydrometallurgy, analytical chemistry, and decon- nium(III) recovery from hydrochloric solutions
tamination of industrial sewages from heavy and rare occurred when there was at least 10–15 vol % decanol
metals. Recently, the attention of researchers has been in the mixture with toluene (Fig. 1). In further experi-
drawn by the extraction of precious metals by sulfur- ments, 15 vol % decanol in toluene was used. Ruthe-
and nitrogen-containing compounds [1–4]. Recent pub- nium(III) extraction to toluene without decanol was
lications concern the synthesis of precious metal com- accompanied by the appearance of a third phase, which
plexes with triazole derivatives.
complicated the investigation; in the presence of
decanol, no third phase appeared.
The utility of triazole derivatives substituted in the
position 1 for the synthesis of ruthenium(III) com-
plexes was demonstrated in work [6], and the spectro-
chemical and electrochemical properties of the com-
plex [Ru(bpy)2(Phtrz)2](PF6)2 were studied. The spec-
trochemical and antitumor properties of complexes
[RuCl4L · DMSO], where L = 1,2,4-triazole, and the
isomers of ruthenium(III) complexes with 1,2,4-triaz-
ole were studied in works [7, 8].
The ruthenium trichloride used contained 46.66%
ruthenium(III) (TU 6-09-05-510-76). The salt was dis-
D
4
Ru(III)
3
2
However, there are no data on the extraction of
ruthenium with triazoles substituted in the position 1.
This work concerns the extraction of ruthenium(III)
with propiconazole (1-2-(2,4-dichlorophenylpropyl-
1,3-dioxolan-2-ylmethyl-1H-1,2,4-triazole).
EXPERIMENTAL
1
0
The sample contained at least 99.9% of the major
substance. Solutions were prepared from accurately
weighed portions of the extactant. The compound in the
form of a diastereoisomer mixture (55–65% cis isomer
and 35–45% trans isomer) is a pasty substance with
Tm = 18–20°C and Tb = 180°C at p = 13.3 Pa and an
insignificant water solubility (0.11 g/L at 20°C) [9].
The isomers differ by the opposite positions of the tria-
zole ring above and below the plane relative to the rest
of the molecule. Toluene mixed with decanol was used
10
20
30
40
50
60
c
, %
dec
Fig. 1. Effect of the decanol concentration on the ruthe-
nium(III) distribution ratio. c
= 3 mol/L. c
= 2 ×
HCl
Ru(III)
–4
10 mol/L. c = 0.1 mol/L. τ
= 1 h. Diluent: toluene.
extr
cont
800

EXTRACTION OF CHLORORUTHENIUM(III) COMPLEXES
801
solved in concentrated hydrochloric acid, followed by
D
Ru(III)
filtration, to free it from insolubles. The purified salt
corresponded to the composition RuCl3 · H2O as deter-
mined by elemental analysis. The salt was verified for
the absence of ruthenium(IV) by the potassium iodide
test and by measuring its electronic absorption spec-
trum in hydrochloric acid [10]. Solutions were prepared
by diluting the stock ruthenium solution in 6 M HCl.
The ruthenium(III) concentration was determined spec-
trophotometrically [11] as the absorption of the blue
ruthenium thiourea complex.
4
3
2
When ruthenium(III) solutions are stored for a long
period in acid solutions (3–6 mol/L), diffuse absorption
bands appear at 29 400–26 300 and 23 255–20 800 cm–1
in their electronic absorption spectra in addition to the
absorption band at 30 300 cm–1; these new bands are
due to partial oxidation of ruthenium(III) by atmo-
spheric oxygen and the appearance of minor ruthe-
nium(IV) in the solution [12]. The extraction was car-
ried out from fresh ruthenium(III) solutions at room
temperature (20 0.5)°C and the aqueous-to-organic
phase ratio of 1 : 1. Stirring was performed on an R-3
magnetic stirrer. Phase separation was clear and
occurred in 1–2 min after the contact was over. Elec-
tronic absorption spectra were recorded on a Specord
M40 spectrophotometer using glass and silica cells. IR
spectra were recorded as thin films on a Specord M80
spectrophotometer. The electrical conductivity of
extracts was measured in acetone on a Radelkis OK
102/1 conductometer.
1
0
20
40
60
80
100
τ
, min
cont
Fig. 2. Effect of the phase contact time on the ruthe-
nium(III) distribution ratio. c
0.1 mol/L. c = 3.0 mol/L.
–4
= 2 × 10 mol/L. c
=
Ru(III)
extr
HCl
D
Ru(III)
10
2
8
RESULTS AND DISCUSSION
6
We showed that extraction equilibrium during the
extraction of ruthenium(III) with propiconazole from
3 M HCl is acquired after 1 h (Fig. 2). All further
extraction experiments were carried out during this
equilibrium time. Preliminary experiments studied the
extraction of hydrochloric acid by the extractant in tol-
uene + 15% decanol solutions. Table 1 lists the chemi-
cal shifts for the signals from carbon atoms of the two
stereomers of the extractant and its extracts with hydro-
chloric acid. The signals from the carbon atoms in the
positions 3 and 3' in the extracts, isolated from 3 and 4
M HCl, experience the greatest additional chemical
shifts. It follows that the triazole nitrogen atom in the
position 4 is protonated.
1
4
2
0
2
3
4
5
6
7
HCl
8
c
, mol/L
Fig. 3. Effect of the hydrochloric acid concentration on the
–4
ruthenium(III) distribution ratio. c
= 1.5 × 10 mol/L.
Ru(III)
To choose the optimal parameters of ruthenium(III)
extraction by the extractant, we studied the metal
recovery as a function of hydrochloric acid concentra-
tion in the aqueous phase (Fig. 3; curves 1, 2). The
recovery increased with increasing HCl concentration
regardless of the extractant concentration. The effect of the
HCl concentration on the ruthenium(III) recovery was
studied until the HCl concentration reached 7.5 mol/L.
The peak ruthenium recovery was from 6 M HCl. It is
known [13] that in the range of the acidities studied
c
= (1) 0.05 and (2) 0.10 mol/L. τ
= 1 h.
extr
cont
[RuCl5 · (H2O)]2–. The increase in the ruthenium(III)
recovery with increasing acid concentration can be
interpreted as an increase in the concentration of the
ruthenium(III) extraction species. When the HCl con-
centration was higher than 6 mol/L, the ruthenium(III)
recovery decreased, which can be explained as arising
(2−6 M HCl), ruthenium exists as [RuCl4(H2O)2]– and from an increase in the [RuCl6]3– concentration and the
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

802
AFZALETDINOVA et al.
Table 1. Chemical shifts for the signals from carbon atoms
in the 13C NMR spectra of reagent L and its complexes with
HCl (in CDCl3)
nificant values and the major species was a single-
charge chlororuthenium(III) complex [RuCl4(H2O)2]–.
The effect of the chloride ion concentration on the
ruthenium(III) recovery from 3 and 4 M HCl is illus-
trated by Fig. 4. The ruthenium(III) distribution ratio
increased with increasing sodium chloride concentra-
tion. This was likely on account of an increase in the
proportion of the extracted metal species in the aqueous
phase. Therefore, chloride ions have a salting-out effect
and favor extraction in the range of the sodium chloride
concentrations studied.
Cl
Cl
7
O
1
N
2
N
C6H2
O
5
3
C3H7
N
In order to elucidate the ruthenium(III) extraction
mechanism, we studied the distribution ratio DRu(III)
versus hydrogen ion concentration (solution ionic
strength, I = 4; NaCl + HCl; cHCl from 4.0 to 3.0 mol/L;
4
C
L
(HL)+(3 M HCl) (HL)+(4 M HCl)
in position
τ
cont = 1 h). The logD = f(pH) plot (Fig. 5) shows that
the hydrogen ion concentration affects the ruthe-
3
3'
∆
∆'
5
150.31
150.42
149.11
149.40
–1.20
145.87
146.40
–4.64
nium(III) distribution ratio: DRu(III) increases with
increasing ç+ concentration. The slope of the plot is −1.
This allows us to suggest that the extraction species is
the negatively charged species [RuCl4(H2O)2]–.
–1.02
–4.02
143.68
143.98
144.27 br
143.71 br
We recorded ruthenium(III) extraction isotherms
from 3 M HCl to extractant solutions in toluene + 15%
decanol. The slope method was used to estimate the
amount of the extractant that enters the composition of
the extraction compound. This amount is unity; that is,
there is one extractant molecule per ruthenium(III) ion
(Fig. 6).
5'
∆
6
0.59
54.06
54.55
0.91
0.03
54.49
55.00
1.34
53.15
53.61
6'
∆
∆'
7
0.94
1.39
From the combined experimental data, we derived
the equation below to describe extraction equilibrium;
this equation accounts for the fact that weakly basic
attractants can be protonated in contact with hydrochlo-
ric acid to yield ion associates [14].
106.03
106.11
106.37 br
105.89 br
7'
∆
0.34
–0.14
[RuCl4(H2O)2]– + H+ + L
{(HL)+ · [RuCl4(H2O)2]–}.
coextraction of hydrochloric acid. The main investiga-
tions on the extraction of ruthenium(III) were carried
out using 3 M HCl with τcont = 1 h at room temperature.
Under the chosen extraction parameters, DRu(III) had sig-
The unknown activity coefficients did not allow us
to calculate the thermodynamic constants of extraction.
Therefore, we used the concentration constants of
ruthenium extraction, which was calculated from
Kconc= [YRu3+
]
org/[XRu3+ ]aq ⋅ [S0 – (Y )
Ru3+ org][H+ – YRu(III)org]aq,
absorption band at 25 680 cm–1 with an attendant small
decrease in its intensity in the extract spectrum; this
spectral evolution was induced by the change in the
nature of the cation in the extraction complex. This pro-
vides evidence in favor of the extraction equation we
suggest (Fig. 7).
Here, [YRu3+
concentration in the organic phase, [XRu3+
]
org
was the equilibrium ruthenium(III)
]
was the
aq
equilibrium ruthenium concentration in the aqueous
phase, S0 was the starting extractant concentration [H+ –
YRu(III) ]aq. The concentration [H+] was set constant,
o
because [YRu(III) ] was insignificant (~ 10–4) and c H+
was fixed at 3 mol/L. The values calculated for the con-
centration constants of ruthenium(III) extraction are
listed in Table 2 (Kconc ~ 7.9 0.1).
The conductometric measurements in the organic
phases along the extraction isotherms in acetone
showed that these phases were electrolytes: λ ~
90−100 Ω–1 cm2 mol–1; this means that the extracted
species was a 1 : 1 electrolyte.
org
Comparing the electronic spectra of the aqueous
phase with the absorption spectrum of the extract
Having studied the temperature effect on ruthe-
obtained upon the extraction of ruthenium(III) with tol- nium(III) extraction by the triazole derivative, we found
uene from 3 M HCl, we observed broadening of the that the extraction capacity of the extractant increased
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

EXTRACTION OF CHLORORUTHENIUM(III) COMPLEXES
803
D
logD
Ru(III)
Ru(III)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.72
2
0.68
0.64
1
0.60
0.56
–0.68 –0.64 –0.60 –0.56 –0.52 –0.48 –0.44
pH
0
0.5
1.0
1.5
2.0
, mol/L
c
NaCl
Fig. 4. Effect of the chloride ion concentration on the ruthe-
Fig. 5. Effect of the chloride ion concentration on the ruthe-
–4
–4
nium(III) distribution ratio. c
= 2 × 10 mol/L. c
=
nium(III) distribution ratio. c
0.05 mol/L. I = 4. n = –1.
= 2 × 10 mol/L. c
=
Ru(III)
extr
Ru(III)
extr
0.05 mol/L. c
= (1) 3 and (2) 4 mol/L.
HCl
logD
Ru(III)
A
–0.3
–0.4
–0.5
–0.6
–0.7
0.4
0.3
0.2
1
2
3
0.1
0
30
28
26
24
22
20
18
16
3
–1
λ × 10 , cm
–1.55 –1.50 –1.45 –1.40 –1.35 –1.30 –1.25 –1.20
l0gS
free
Fig. 7. Electronic absorption spectra for (1) the starting
ruthenium(III) solution in 3 M HCl, (2) the organic phase
after the extraction of ruthenium(III), and (3) the aqueous
phase after the extraction of ruthenium(III).
Fig. 6. Effect of the free extractant concentration on the
ruthenium(III) distribution ratio. c
= 3.0 mol/L. X
=
HCl
Ru(III)
–4
3 × 10 mol/L. τ
= 1 h. q = 1.
cont
insignificantly in response to increasing temperature
(Fig. 8). From the log logD = f(1/T) plot, we derived the atom N4 in the formation of an ion associated with the
enthalpy of extraction ∆H equal to 6.13 kcal/(mol K).
To verify the participation of the triazole nitrogen
ruthenium(III) ion [RuCl4(H2O)2]– during the extraction
1
of ruthenium(III) from 3 M HCl, we recorded H and
Q = –∆H = 2.3Rtanα
= –[4.575(–1.34)] = 6.13 kcal/ (mol ä).
13ë NMR spectra. Table 3 displays the chemical shifts δ
and additional chemical shifts ∆δ for the signals from
methylene and methyne protons (ëç2 and CH) in the
From the investigation of the temperature effect on
the ruthenium extraction, it follows that the extraction
reaction is endothermic.
1ç spectra of the extractant and its extract with HCl and
ruthenium(III).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

804
AFZALETDINOVA et al.
Table 2. Distribution and constants of ruthenium(III) ex- Table 3. Chemical shifts δ (ppm) for the proton signals in
traction with triazole derivatives
the 1H NMR spectra of reagent L and its complexes with HCl
and ruthenium(III)(in CDCl3)
Equilibrium ruthenium(III)
concentration, mol/L
Concentration
constant
of extraction
Cl
XRu(III)
YRu(III)
Cl
cextr = 0.04 mol/L (Kav = 7.1 0.1)
7
O
4.6 × 10–4
1.3 × 10–4
2.45 × 10–4
3.65 × 10–4
4.7 × 10–4
6.25 × 10–4
7.1
7.2
7.0
7.1
7.3
6
1
2
8.6 × 10–4
1.31 × 10–3
1.67 × 10–3
2.18 × 10–3
CH2
N
N
O
5
3
C3H7
N
4
C in po-
sition
L
(HL)+ (3 M HCl) {(HL)+ · [RuCl4 (H2O)2]–}
cextr = 0.05 mol/L (Kav = 9.5 0.1)
3.35 × 10–4
1.55 × 10–4
3.25 × 10–4
5.0 × 10–4
6.3 × 10–4
8.1 × 10–4
9.3
9.2
3
3'
∆
7.60
7.60
7.91 br
0.31
7.98 br
0.38
7.1 × 10–4
1.39 × 10–3
1.1 × 10–3
1.78 × 10–3
7.4
10.6
10.9
5
7.88
7.98
8.46
8.54
0.58
0.56
4.67
4.71
0.24
0.20
6.56
5'
∆
∆'
6
6'
∆
∆'
8.62 br
0.74
cextr = 0.06 mol/L (Kav = 7.1 0.1)
2.8 × 10–4
1.9 × 10–4
3.85 × 10–4
6.15 × 10–4
7.6 × 10–4
9.5 × 10–4
7.1
7.2
7.0
7.1
7.3
4.43
4.51
4.77 br
0.34
5.8 × 10–4
9.25 × 10–4
1.14 × 10–3
1.44 × 10–3
H+
6.32
From the interpretation of the chemical shifts for the
extractant and its extract with HCl and ruthenium(III),
it also follows that the greatest additional chemical
shifts are experienced by the signals from methyne and
methylene protons in the positions 3, 5, and 6: 0.37,
0.38, 0.74, and 0.34 ppm for the ruthenium(III) com-
plex and 0.31, 0.58, and 0.24 ppm for the complex of
the extractant with hydrochloric acid. The proton signal
in the ç+L complex appears at 6.32 ppm in the ruthe-
nium(III) complex {(H+L) · [RuCl4(H2O)2]–} and at
6.56 ppm in the hydrochloric acid complex [ç+L].
These data also confirm the ruthenium(III) extraction in
the form of ion associates. The extractant is protonated
at the triazole nitrogen atom N4.
logD
Ru(III)
–0.30
–0.35
–0.40
–0.45
To confirm the extractant protonation via the triaz-
ole nitrogen atom N4, we recorded 13C NMR spectra for
the extractant and its complexes with hydrochloric acid
and ruthenium(III) isolated from 3.0 M HCl (Table 4).
The signals from the carbon atoms in the positions 3, 5,
6, and 7 experience the greatest additional chemical
shifts. In the hydrochloric acid complex, the signals
from the carbon atoms in the same positions also
experience the greatest additional chemical shift.
These distinction of the spectra of the complexes from
the extractant spectrum also confirms our suggestion
that ruthenium(III) is extracted as the ion associate
[RuCl4(H2O)]– · (H+L) with the extractant being proto-
nated at the triazole nitrogen atom N4.
b = –1.34
r = 0.99
–0.50
–0.55
–0.60
–0.65
–0.70
3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50
3
1/Τ × 10 , K–1
Fig. 8. Effect of temperature on the ruthenium(III) distribu-
–4
The IR spectra of the ruthenium(III) complex with
the extractant were also recorded. The ν(Ru−Cl)
tion ratio. c
3.0 mol/L.
= 2 × 10 mol/L. c = 0.05 mol/L. c
=
Ru(III)
extr
HCl
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

EXTRACTION OF CHLORORUTHENIUM(III) COMPLEXES
805
Table 4. Chemical shifts δ (ppm) for the carbon signals in
the 13C NMR spectra of reagent L and its complexes with
HCl and ruthenium(III) in (CDCl3)
elemental analysis of the extraction complex confirms
our suggested composition: Ru : C : N = 1 : 4 : 1.
In summary, the extraction of ruthenium(III) from
3.0 M HCl solution is due to ion association. Ion asso-
ciates are formed through the protonation of the triazole
nitrogen atoms in the position 4.
Cl
Cl
7
O
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N
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N
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C3H7
N
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(HL)+ (3M HCl) {(HL)+ · [RuCl4 (H2O)]–}
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3'
∆
150.31
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149.11
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5'
∆
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6'
∆
∆'
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143.68
143.98
144.27 br
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145.26 br
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53.61
54.06
54.55
0.91
0.94
106.37
54.49
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1.39
105.72 br
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106.11
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∆
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appear as a strong broad band at 320 cm–1. Along with
the absorption band at 320 cm–1, there is absorption due
to the ν(Ru–O) stretches at 390 cm–1, which appears as
a weak absorption band and matches the literature data
for the mer configuration [17]; this is another piece of
evidence in favor of the entrance of [RuCl4(H2O)2]–
ruthenium ions into the extracted species. The bending
vibrations δ(éç) appear as a weak absorption band at
1650 cm–1. The librational vibrations of water mole-
cules ρ(ç2é) appear as a weak band at 648 cm–1. The
(6), 403 (2000).
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manowski, Proceedings of ISEC, Cape Town, 2002
(Cape Town, 2002), p. 988.
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RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007