The Synthesis and Investigation of Liquid-Liquid Extraction Capability of N-Diphenylphosphino-N-ethylaniline and Its Chalcogenide Derivatives

Article abstract of DOI:10.1134/S1070427219060119

The aminophosphine ligand was synthesized by the reaction of N-ethylaniline with chlorodiphenylphosphine in the presence of triethylamine at low temperature. Oxidation of the ligand with elemental sulfur or selenium afforded the corresponding aminophosphi

Full text of DOI:10.1134/S1070427219060119

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2019, Vol. 92, No. 6, pp. 817−822. © Pleiades Publishing, Ltd., 2019.
MACROMOLECULAR COMPOUNDS
AND POLYMERIC MATERIALS
The Synthesis and Investigation
of Liquid‒Liquid Extraction Capability
of N-Diphenylphosphino-N-ethylaniline
and Its Chalcogenide Derivatives
a
a,
Y. Akkuşlu and Ö. Sarıöz *
a
Department of Chemistry, Faculty of Science and Arts, Niğde Ömer Halisdemir University, Niğde, Turkey
*
e-mail: ozsarioz4@yahoo.com
Received February 11, 2019; revised March 28, 2019; accepted May 19, 2019
Abstract—The aminophosphine ligand was synthesized by the reaction of N-ethylaniline with chlorodiphe-
nylphosphine in the presence of triethylamine at low temperature. Oxidation of the ligand with elemental sulfur
or selenium afforded the corresponding aminophosphine sulfide and selenide. The compounds were characterized
1
31
by elemental analyses, IR, H and P NMR. N-diphenylphosphino-N-ethylaniline and its chalcogen derivatives
2
+
2+
were used as ligands in solvent extraction of metal picrates such as Cd and Ni from the aqueous to the organic
phase. Influences of parameters such as pH of the aqueous phase, solvent, extraction time, and extractant concen-
tration were investigated to determine the extraction ability of ligands for metal ions. Results of the experiments
2
+
2+
showed that an extractability of 95.5 and 97.8%, respectively for Ni , and Cd at pH 2 could be achieved.
Keywords: Aminophosphines, chalcogenides, heavy metals, solvent extraction.
DOI: 10.1134/S1070427219060119
Pollution caused by metal ions in wastewater is a
common problem faced by many countries in recent
years. Ni2+ and Cd2+ ions in wastewater have been
especially recognized as key contaminants that damage
the environment and adversely affect human health
amine extractants have been reported for the extraction
and separation of the transition metal ions [14, 15].
Aminophosphines containing direct P–N bonds are
a well-known class of phosphorus compound. Over the
years, aminophosphine researches have gained prime
importance because of their acting as versatile ligands
in coordination chemistry; specific roles as catalysts
for various organic reactions and easy conversion to
chalcogenides, which possess ligating behavior, and
hence they find applications in catalysis and electronic
industries [16, 17]. Although aminophosphine ligands
may be constructed in large quantities through the
use of relatively simple condensation processes, and
from inexpensive starting materials, there are limited
studies focused on the possibility of effective use in the
extraction process of metal ions of aminophosphines and
chalcogenide derivatives [18].
[
1–6]. In spite of their toxicity, these metals are used
in a wide variety of industries such as plating and
cadmium–nickel battery, phosphate fertilizers, mining,
pigments, stabilizers and alloys, and find their way to
the aquatic environment through wastewater discharges
[3, 7]. Therefore, the recovery of cadmium and nickel is
necessary and very important to gain the metal values
and protect the environment. From this point of view, in
metal recovery, the solvent extraction is one of the favored
separation techniques because of its simplicity, speed and
wide scope [8–12]. Different types of extractants used
for the extraction of Cd(II) and Ni(II) include amines,
carboxylic acids, oximes and also organophosphorus
extractants [8, 13]. Also synergistic extraction systems
containing mixtures of organophosphorus extractants and
In this study, a new aminophosphine ligand
(N-diphenylphosphino-N-ethylaniline) and its sulfide
and selenide derivatives was synthesized and used as
8
17

818
AKKUŞLU, SARIÖZ
2
+
ligands in solvent extraction of metal picrates (Ni and
Cd ) from the aqueous to the organic phase.
The precipitate was filtered and dried in air to yield 3 as
a white solid. 0.9 g (56 %); m.p. 158–159°C; H NMR
2+
1
(
(
CDCl ) δ, ppm): 7.28–7.91 (m, 15H, aromatic), 3.39
3
3
1
q, 2H, CH ), 1.43 (t, 3H, CH ); P NMR (CDCl ) δ,
EXPERIMENTAL
2
3
3
–
1
ppm): 82.67 (s, JPSe = 701 Hz); IR (cm ): 1437 (PPh),
99 (PN), 707 (P=Se); Found (Calc. for C H NPSe):
8
Reactions were routinely carried out using Schlenk-
line techniques under pure dry nitrogen gas. Solvents
were dried and distilled prior to use. All other chemicals
were used in analytical grade, without further purification.
20 20
C, 62.84 (62.50); H, 5.12 (5.25); N, 3.34 (3.64)
Solvent extraction procedure. Transition metal
picrates were prepared by the stepwise addition of a 1 ×
10 M of metal nitrate solution to a 2.5 × 10 M aqueous
picric acid solution by shaking at 25°C for 1 h. The 1 ×
10 M solutions of the ligands were separately prepared
in dichloromethane and used as extractants. An organic
solution (10 mL) of ligand and an aqueous solution
3
1
1
–2
–5
P and H NMR spectra were taken on Bruker
UltraShield-400 spectrophotometer. Infrared spectra were
recorded on a Perkin Elmer FTIR System Spectrum BX.
Spectrophotometric measurements were performed by
Shimadzu UV-160 A UV-vis spectrophotometer.
–
2
(10 mL) containing 4 mL of the metal picrate solution
Preparation of Ph PN(C H )Ph. Triethylamine
2
2
5
and 6 mL of a buffer solution (for pH adjustment) were
placed in a stoppered flask, and stirred with a magnetic
stirrer at 25°C for 1 h in a water jacket. The mixture
was allowed to settle for 30 min for the completion
of phase separation. Then, after the two phases were
separated completely, concentrations of the nickel(II)
and cadmium(II) picrate remaining in the aqueous phase
were determined spectrophotometrically at 359 nm and
(
4.39 mL, 31.69 mmol) and Ph PCl (6.09 mL, 31.69 mmol)
2
were sequentially added with stirring to a solution of
N-ethylaniline (4 mL, 31.69 mmol) in THF (40 mL) at
0
it was filtered to remove precipitated triethylamine
hydrochloride. The resulting solution was evaporated
under reduced pressure and diethyl ether added (20 mL).
The solvent was removed under vacuum to give a white
solid of the crude product. The material was removed
from the flask and washed with diethyl ether and dried in
°C. The reaction mixture was stirred for 6 h and then
360 nm which are wavelength of maximum absorption of
metal picrates used in experiments, respectively. Blank
experiments showed that no picrate extraction occurred
in the absence of ligand. The percent of extraction E (%)
has been calculated as:
1
vacuo. 6 g (62%); m.p. 129–130 °C; H NMR (CDCl ) δ,
ppm): 7.28–7.92 (m, 15H, aromatic), 3.39 (q, 2H, CH ),
1
3
2
3
1
.42 (t, 3H, CH ); P NMR (CDCl ) δ/ ppm): 21.59
3 3
–1
(s); IR (cm ): 1434 (PPh), 925 (PN); Found (Calc. for
A – A
0
C H PN): C, 78.44 (78.67); H, 6.38 (6.60); N, 4.37
E = –––––– × 100,
(1)
2
0
20
A
(4.59).
0
Preparation of Ph P(S)N(C H )Ph. N-diphenyl-
phosphino-N-ethylaniline (1,3 g, 4.26 mmol) and S8
0.136 g, 4.26 mmol) were refluxed in toluene (30 mL)
for 6 h. The reaction mixture was concentrated to ca.
–2 mL in vacuo and diethylether (10 mL) was added.
2
2
5
where A is the absorbance in the absence of ligand and
0
A denotes the absorbance in the aqueous phase after
extraction. The picrate extraction studies were conducted
on three different samples and the average value of
percent picrate extracted, with a standard deviation,
was calculated. UV–Vis spectroscopy is a very simple,
accessible and convenient analytical instrument for
quantitative detection of metals [19]. UV–Vis appears
to be a convenient tool to study the distribution of metal
picrates between non-aromatic organic solvents and
aqueous solutions.
(
1
The precipitate was filtered and dried in air to yield 2 as a
1
pale yellow solid. 1 g (70 %); m.p. 172–173°C; H NMR
(
2
8
CDCl ) δ, ppm): 7.28–7.92 (m, 15H, aromatic), 3.38 (q,
3
31
H, CH ), 1.41 (t, 3H, CH ); P NMR (CDCl ) δ, ppm):
2 3 3
0.06 (s); IR (cm ): 1436 (PPh), 909 (PN), 655 (P=S);
–
1
Found (Calc. for C H NPS): C, 71.47 (71.19); H, 5.68
2
0
20
(
5.97); N, 3.84 (4.15).
Preparation of Ph P(Se)N(C H )Ph. N-diphenyl-
RESULTS AND DISCUSSION
2
2
5
phosphino-N-ethylaniline (1,0 g, 3.27 mmol) and grey Se
0.258 g, 3.27 mmol) were refluxed in toluene (30 mL)
for 5 h. The reaction mixture was concentrated to ca.
–2 mL in vacuo and diethylether (10 mL) was added.
(
In this work, N-diphenylphosphino-N-ethylaniline (1),
was prepared via phosphination of N-ethylaniline, with
1
one equivalent of Ph PCl in the presence of triethylamine
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019

THE SYNTHESIS AND INVESTIGATION OF LIQUID‒LIQUID EXTRACTION CAPABILITY
819
2
+
Fig. 1. Synthesis of the aminophosphine and its chalcogen
derivatives.
Fig. 2. Dependence of log D on pH for extraction of Ni and
2+
Cd picrates with Ph PN(C H )Ph (1).
2 2 5
in tetrahydrofuran. Oxidation of 1 elemental sulfur or
selenium gave the corresponding sulfide (2), and selenide
The liquid-liquid extraction of metal picrates such as
2
+
2+
Ni and Cd from aqueous phase to organic phase was
carried out using aminophosphine (1) and its chalcogenide
derivatives as ligands (2 and 3). The effects of several
experimental parameters (pH, solvent, extraction time
and extractant concentration) were investigated in order
to find optimal operation conditions.
(3), respectively (Fig. 1). The aminophosphine ligand and
its chalcogen derivatives were characterized by elemental
1
31
analyses, IR, H and P NMR.
The 31P-{1H} NMR chemical shift of 1 is found at
2
8
1.6 ppm whereas those of 2 and 3 occur at 80.06 and
2.67 ppm, respectively. The chemical shift values
The effect of pH on the extraction of the metal
picrates was investigated in the pH range from 1 to 7. The
results indicate that the highest extraction efficiency was
obtained at pH 2. Usually, as seen in Table 1 extraction to
organic phase decreases as pH increases. When log D–pH
graph is examined, this tendency is clear (Figs. 2–4).
Here, D is the distribution ratio of metal picrates between
the organic and the aqueous phase. Thus, in the further
extraction studies, pH 2 was used.
of 1–3 are in accordance with the literature [20]. The
3
1
1
P–{ H} NMR spectrum of 3 consists of singlet with
7
7
1
Se satellites and the coupling constant value ( JPSe)
1
is 701 Hz. The H NMR spectra of 1–3 are consistent
with the proposed structures. In the IR spectra of 1–3,
the υ(PN) vibration is observed at 925 cm (for 1), 909
cm (for 2), and 899 cm (for 3). The υ(P–Ph) bands are
observed in region of 1435–1437 cm .Also, the P=S and
−
1
−1
−1
−1
P=Se double bonds in 2 and 3 exhibit vibrations around
For a good extraction efficiency the value of D
should be greater than 1.0. Based on this criterion, it
−
1
7
07 and 655 cm , respectively.
Table 1. Effect of pH on the percentage extraction of Ni and Cd2+ picrates with Ph PN(C H )Ph (1), Ph P(S)N(C H )Ph (2)
2
+
2
2
5
2
2
5
–
2
and Ph P(Se)N(C H )Ph (3) ([L] = 1 × 10 M in dichloromethane, the contact time: 1 h)
2
2
5
Extractability, %
pH
1
2
3
Ni2+
Cd2+
Ni2+
Cd2+
Ni2+
Cd2+
2
66.0 ± 3
75.4 ± 4
49.0 ± 3
52.3 ± 3
51.0 ± 2
62.2 ± 1
3
4
5
6
7
42.4 ± 2
30.2 ± 3
29.8 ± 1
9.4 ± 1
57.3 ± 2
36.9 ± 3
18.2 ± 1
10.6 ± 2
11.0 ± 2
8.6 ± 1
20.1 ± 2
12.3 ± 2
13.7 ± 1
9.1 ± 2
19.3 ± 2
12.7 ± 1
11.7 ± 2
13.8 ± 1
4.5 ± 1
40.7 ± 2
33.5 ± 2
35.2 ± 3
36.2 ± 2
14.4 ± 2
36.8 ± 3
10.5 ± 2
Not measured
Not measured
5.5 ± 1
7.4 ± 1
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019

820
AKKUŞLU, SARIÖZ
Fig. 3. Dependence of log D on pH for extraction of Ni2+ and Cd2+ picrates with Ph P(S)N(C H )Ph (2).
2
2
5
can be expected that a good extraction efficiency could
be achieved in the extraction of Cd2+ and Ni2+ picrates
at pH 2. The separation factor between the two metals
was then calculated as the ratio of the distribution ratios
extraction efficiency values of Cd2+ and Ni2+ ions with
ligand 1 is higher than that of compounds 2 and 3 for both
of the solvents. Also, the cation-binding affinities of all
ligands for Cd over Ni in both organic solvents were
found to be the highest.
2
+
2+
of two metals (SFCd/Ni = D /D ). Unlike the ligands 1
Cd Ni
and 2, selenide derivative (3) indicated a slight selectivity
for Cd2+ over Ni2+ in the pH range of 4–7. The Cd/Ni
separation factors are between 3.5 and 4.1 for ligand 3.
The effect of time on the extraction of metal
picrates (Ni2+ and Cd2+) with aminophosphine (1) and
chalcogenide derivatives (2, 3) was investigated. As
shown in Table 3 and Figure 5, the best extraction time was
30 min when aminophosphine (1) was used as extractant
for both metals, while it was 60 min for aminophosphine
chalcogenides (2 and 3). The extraction efficiency
decreased above these contact times. It is known that in
some instances P–N bonds are sensitive towards acid- or
base-catalyzed hydrolysis during complexation reactions
[21]. Decreasing of extraction efficiency over time is
possibly due to metal assisted hydrolysis of P–N bonds.
In the following study, the extraction time was fixed to
Two different organic solvents, dichloromethane and
chloroform, were used in the liquid–liquid extraction
experiments. As shown in Table 2, chloroform gave the
best extraction efficiency in case of using aminophosphine
(
1) as extractant. On the other hand, dichloromethane gave
the best extraction efficiency for chalcogenide derivatives
and 3. Thus, chloroform (for 1) and dichloromethane
for 2 and 3) was selected as the solvent throughout
the rest of the extraction study. The percentage of the
2
(
3
0 and 60 min for ligand 1 and ligands 2, 3 respectively.
When the ligand concentrations in organic phase
–
2
was increased to 5 × 10 M, the extraction percentage
2
+
2+
values of Cd and Ni picrates were 97.8, and 95.5 for
compound 1, while 78.5, and 67.6 for compound 2, and
8
6.2, and 73.8 for compound 3, respectively.
The tested extractant ligands were found to be efficient
2+
2+
for the liquid-liquid extraction of Ni and Cd picrates.
All extraction efficiency values of N-diphenylphosphino-
N-ethylaniline were higher than those of its chalcogenid
derivatives (2 and 3). The greater degree to which this
is observed in the aminophosphine (1) may be related to
the stronger σ donor ability of aminophosphine (1) vs. its
chalcogenid derivatives (2 and 3). On the other hand, the
2+
Fig. 4. Dependence of log D on pH for extraction of Ni and
2
+
2+
Cd picrates with Ph P(Se)N(C H )Ph (3).
extraction efficiency values of Cd picrate were higher
2
2
5
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THE SYNTHESIS AND INVESTIGATION OF LIQUID‒LIQUID EXTRACTION CAPABILITY
821
Table 2. Effect of solvent on the percentage extraction of Ni and Cd2+ picrates with Ph PN(C H )Ph (1), Ph P(S)N(C H )Ph
2
+
2
2
5
2
2
5
–
2
(
2), and Ph P(Se)N(C H )Ph (3) at pH 2 ([L] = 1 × 10 M; the contact time: 1 h)
2
2
5
Extractability, %
Solvent
1
2
3
Ni2+
Cd2+
Ni2+
Cd2+
Ni2+
Cd2+
Dichloromethane
Chloroform
66.0 ± 3
75.4 ± 4
49.0 ± 3
20.4 ± 3
52.3 ± 3
51.0 ± 2
26.2 ± 3
62.2 ± 1
35.4 ± 1
69.1 ± 4
75.9 ± 4
25.7 ± 2
Table 3. Effect of extraction time on the percentage extraction of Ni and Cd2+ picrates with Ph PN(C H )Ph (1), Ph P(S)
2
+
2
2
5
2
–
2
N(C H )Ph (2) and Ph P(Se)N(C H )Ph (3) at pH 2 ([L] = 1 × 10 M; solvent: chloroform for ligand 1, dichloromethane for
2
5
2
2
5
ligands 2 and 3)
Extractability, %
Extraction time,
min
1
2
3
Ni2+
Cd2+
Ni2+
Cd2+
Ni2+
Cd2+
3
6
9
1
0
71.4 ± 2
69.1 ± 4
66.7 ± 4
62.4 ± 3
76.8 ± 4
75.9 ± 4
67.4 ± 1
67.1 ± 4
44.8 ± 2
49.0 ± 3
43.4 ± 3
42.5 ± 4
48.1 ± 2
52.3 ± 3
47.0 ± 1
45.9 ± 2
48.5 ± 3
51.0 ± 2
47.2 ± 1
46.7 ± 2
53.7 ± 1
62.4 ± 1
51.5 ± 3
50.8 ± 3
0
0
20
2
+
than that of Ni , which can be explained by high affinity
can extract cadmium under these conditions [22]. Also,
nickel is available in both leach liquors from ores and
in secondary sources at lower pH. Most of the work in
hydrometallurgy is related to extract metals at pH as low
as possible [8]. N-diphenylphosphino-N-ethylaniline
shows good efficiency and affinity for metal ions at pH 2
according to obtained results, which makes it suitable for
solvent extractions in acidic media.
of “soft” phosphorus, or relatively less “softer” sulfur and
selenium toward soft Cd cations.
2
+
According to our results, ligands 1–3 were effective
for extraction of metal ions at pH 2. In most of the
industrial processes cadmium is present in acidic solutions
and it becomes necessary to search for an extractant that
CONCLUSIONS
In conclusion, the synthesis and metal extraction
abilities of N-diphenylphosphino-N-ethylaniline and its
chalcogen derivatives were studied. The results showed
that aminophosphine derivatives (1–2) are efficient
2
+
ligands for the extraction of metal picrates such as Cd
2
+
and Ni from an aqueous to an organic phase. The
2+
2+
maximum extraction efficiency values of Cd and Ni
picrates were 97.8, and 95.5 for N-diphenylphosphino-
N-ethylaniline, while 78.5, and 67.6 for sulfide, and 86.2,
and 73.8 for selenide, respectively, at pH 2. This makes
the ligands suitable for solvent extraction study at low pH.
ACKNOWLEDGMENTS
This study was supported financially by the Research
Projects Unit of Niğde Ömer Halisdemir University with
project no. FEB 2015/34.
Fig. 5. Dependence of log D on extraction time for extraction
of Cd and Ni picrates.
2
+
2+
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019

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AKKUŞLU, SARIÖZ
CONFLICT OF INTEREST
Technology, 2013, vol. 118, pp. 209–216.
1. El-Nadi, Y.A., Separation & Purification Reviews, 2017,
1
The authors declare the absence of a conflict of interest
vol. 46, pp. 195-215.
that requires disclosure in this article.
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