A dual host approach to NiSO4 extraction

Article abstract of DOI:10.1080/10610278.2011.631706

This paper reports the synthesis of sulphate extractants, N,N-bis-(2-dibutylamino-ethyl)-isophthalamide (1), pyridine-2,6-dicarboxylic acid bis-[(2-dibutylamino-ethyl)-amide] (2) and 3,4-diphenyl-1H-pyrrole-2,5- dicarboxylic acid bis-[(2-dibutylamino-ethy

Full text of DOI:10.1080/10610278.2011.631706

This article was downloaded by: [Florida International University]
On: 01 January 2015, At: 14:13
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Supramolecular Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/gsch20
A dual host approach to NiSO4 extraction
Gareth W. Bates a , James E. Davidson b , Ross S. Forgan b , Philip A. Gale a , David K.
Henderson b , Michael G. King c , Mark E. Light a , Stephen J. Moore a , Peter A. Tasker b &
Christine C. Tong a
a School of Chemistry, University of Southampton , Southampton , SO17 1BJ , UK
b School of Chemistry, University of Edinburgh , Edinburgh , EH9 3JJ , UK
c Falconbridge Technology Center , Falconbridge , Canada
Published online: 11 Nov 2011.
To cite this article: Gareth W. Bates , James E. Davidson , Ross S. Forgan , Philip A. Gale , David K. Henderson , Michael G.
King , Mark E. Light , Stephen J. Moore , Peter A. Tasker & Christine C. Tong (2012) A dual host approach to NiSO4 extraction,
Supramolecular Chemistry, 24:2, 117-126, DOI: 10.1080/10610278.2011.631706
To link to this article: http://dx.doi.org/10.1080/10610278.2011.631706
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Supramolecular Chemistry
Vol. 24, No. 2, February 2012, 117–126
A dual host approach to NiSO4 extraction
Gareth W. Batesa, James E. Davidsonb, Ross S. Forganb, Philip A. Galea*, David K. Hendersonb, Michael G. Kingc,
Mark E. Lighta, Stephen J. Moorea, Peter A. Taskerb and Christine C. Tonga
b
aSchool of Chemistry, University of Southampton, Southampton, SO17 1BJ, UK; School of Chemistry, University of Edinburgh,
Edinburgh, EH9 3JJ, UK; Falconbridge Technology Center, Falconbridge, Canada
c
(Received 8 July 2011; final version received 30 September 2011)
This paper reports the synthesis of sulphate extractants, N,N0-bis-(2-dibutylamino-ethyl)-isophthalamide (1), pyridine-
2,6-dicarboxylic acid bis-[(2-dibutylamino-ethyl)-amide] (2) and 3,4-diphenyl-1H-pyrrole-2,5-dicarboxylic acid bis-[(2-
dibutylamino-ethyl)-amide] (3), and demonstrates that, in combination with a commercially available oxime extractant
2-hydroxy-5-nonyl benzaldehyde oxime (P50), these dual host systems are better extractants for nickel(II) sulphate than the
metal salt extractant, 5-nonyl-3-dihexylaminomethyl-2-hydroxy-benzaldehyde oxime (4).
Keywords: anion binding; extraction; hydrometallurgy; hydrogen bonding
Introduction
allows the metal of interest to be recovered from more
complex and/or low-grade ore stocks. Other advantages
are that the process usually requires less energy in
comparison to pyrometallurgical techniques and the ore
processing can be carried out close to mine sites thus
removing high ore transport costs (8).
Base metals are important commodities in the modern
world and recently their demand and consumption have
increased significantly. In particular, nickel, which is used
mainly (.70%) in the production of stainless steel and
alloys, has seen demand outstrip supply mostly due to the
rising demand for steel, particularly in China (1, 2). As a
consequence of this, major new projects and sources of
nickel ores are required. Recent examples of such projects
are the Bulong (3) operation in Western Australia, which
produces nickel and cobalt from a lateritic ore and the
Koniambo site in New Caledonia which, when up to full
production in 2013, will aim to produce ca. 60,000 tons of
nickel per year (4).
Liquid–liquid solvent extraction is becoming increas-
ingly useful in extractive hydrometallurgy and involves
the use of chemical processes, such as the formation of
metal complexes, to selectively extract the metal of value
from an aqueous medium into an immiscible organic phase
(in practice high-boiling-point hydrocarbons, such as
kerosene, are used in large-scale solvent extraction
processes). This process affects the unit operations of
separation and concentration as part of a four-step
flowsheet (Figure 2) involving leaching, extraction,
stripping and electrowinning (9). Leaching involves the
dissolution of the metal from the ore to generate an
aqueous pregnant leach solution (PLS) using a range of
reactants, depending on the chemical composition of the
ore (9). Selective extraction of the metal of value involves
the transport of metal cation, metal salts or metallate
anions into a non-polar organic phase via complexation by
a hydrophobic ligand (9). The organic solubility of the
complex is crucial for the success and overall efficiency of
the extraction process. As a result, the complex ideally is
charge neutral and the ligand contains hydrophobic
groups, such as large and usually branched alkyl chains.
The stripping stage involves the removal of the metal of
value from the organic phase and the hydrophobic ligand,
transferring it back to an aqueous solution from which the
metal is recovered by reduction of the pure metal salt,
Metallurgy is the extraction, purification and modifi-
cation of metals from their ores for a more useful purpose.
Currently, industry predominantly uses pyrometallurgical
smelting techniques in order to obtain metals; however,
these processes require large amounts of energy and
produce large volumes of pollutant and toxic gas
emissions (5). Hydrometallurgy involves the extraction
of metals from an aqueous solution of their ores (5).
Hydrometallurgical extraction/separation techniques
include selective crystallisation, selective reduction and
adsorption of ions onto solid matrices (5). An area of
increasing interest is extractive hydrometallurgy wherein
the metal of value is typically leached into an acidic
aqueous solution and subsequently transferred to a
hydrophobic organic solvent, thus separating and con-
centrating the metal of value. A typical flowsheet for this
process is illustrated in Figure 1 (5–7). This technique
*Corresponding author. Email: philip.gale@soton.ac.uk
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2011.631706
http://www.tandfonline.com

118
G.W. Bates et al.
Advanced
electrolyte
Pregnant Leach
Solution (PLS)
Separation &
concentration
Ore
Leach
Electrolysis
M
Leachant
(raffinate)
Depleted
electrolyte
Figure 1. The basic flowsheet for extractive hydrometallurgy.
usually by electrolysis. The organic phase containing the
regenerated hydrophobic ligand is recycled.
process as the decreasing pH hinders the complexation of
the metal ion to the ligand in the aqueous phase.
One way to overcome this problem is to use a ligand
system that can extract both the metal cation and attendant
sulfate anion(s) into the organic phase. Tasker and co-
workers have approached this problem by synthesising a
number of zwitterionic ditopic receptors in which the acid-
binding site is covalently attached to a salen-based metal-
binding site (11, 12). The system was designed so that
upon the coordination of the metal ion the two phenolic
protons would be displaced and protonate the tertiary
amine groups attached to the salen scaffold, which would
then bind the sulphate anion thus removing the excess
sulphuric acid generated in the extraction of the metal
(Scheme 3).
One of the most successful processes of this type
involves the extraction of copper from oxidic ores using
phenolic oxime ligands (Figure 3) to transport the copper
from the PLS (9).
An area of increasing interest is the extraction of
metals from sulphidic ores (1). In hydrometallurgical
processes, these ores have low solubility and therefore
cannot be effectively leached with dilute sulphuric acid
under ambient conditions. The ores can be converted into
their metal oxides by roasting in the presence of air
(Scheme 1). The roasting process produces SO2, which is a
major pollutant gas that has to be recovered through the
generation of sulphuric acid. This is capital intensive and
the production of sulphuric acid on mining sites is not
always economically viable (5, 8).
This approach has been extended to tripodal systems
(13) and to oxime-based metal salt extractants (Scheme 4)
which show significantly increased resistance to hydroly-
sis and in some instances increased extraction efficiencies
(14, 15).
New microbial leaching and high-pressure acid
leaching techniques involve conversion of the sulphidic
ore to the sulphate producing a PLS that can be used for the
liquid–liquid solvent extraction of the metal of value (7,
10). These leaching techniques are economically more
viable compared to the roasting technique as they avoid the
generation of SO2. However, if the sulphate PLS is
extracted with the commercial phenolic oxime ligand
system, then during the extraction step, sulphuric acid
builds up in the system (Scheme 2). This does not occur in
the process for oxidic ores as the sulphuric acid is recycled
for the leaching step. The buildup of sulphuric acid
significantly reduces the extraction efficiency of the
Such zwitterionic ditopic receptors have proven to be
useful for the extraction of copper(II) sulphate and the
introduction of hydrogen bonding groups to the pendent
arms of the receptor has been shown to improve the
sulphate selectivity (16) of the ditopic systems. However,
increasing the functionalisation of the ditopic receptors to
improve the affinity and selectivity of the receptors for
sulphate inevitably requires more complex synthesis and
ligands, which in turn increases the cost of manufacture
and decreases the mass transport efficiency (the mass of
extractant required per unit mass of metal recovered).
MSO4
MSO4
ML2
M + 0.5O2
MO
Electrowin
Leach
Strip
Extract
H2O+
power
H2O+
residues
H2SO4
2LH
H2SO4
Figure 2. A flowsheet for the liquid–liquid solvent extraction of metals from their oxidic ores (9).

Supramolecular Chemistry
119
have described the use of a cyclo[8]pyrrole in the
extraction of sulphate anions in the presence of nitrate.
Tripodal tris-urea functionalised tren-based receptors have
been reported by Custelcean and co-workers (20) as
functioning as selective crystallisation agents for SO422
.
This class of sulphate receptor has also been studied by
other groups (21). Additionally, Custelcean, Hay and co-
workers (22) have developed self-assembling urea
containing cage systems to arrange six urea groups around
sulphate. Gale and co-workers (23) have reported that
amido-indole and carbazole-functionalised diindolylureas
are selective for sulphate. Macrocyclic sulphate receptors
include Bowman–James’ (24) cyclic tetraamide/amine
system that forms sandwich complexes with SO242 and
Kubik’s (25) bis-cyclic peptide-based molecular oyster.
We have prepared simple anion extractants, which,
alongside known anion, cation and metal salt extractants
(Figure 4), were tested in the extraction of nickel sulphate.
Figure 3. Commercial phenolic oxime copper extractants (9).
Results and discussion
N,N0-bis-(2-dibutylamino-ethyl)-isophthalamide (1) and
pyridine-2,6-dicarboxylic acid bis-[(2-dibutylamino-
ethyl)-amide] (2) were prepared by reaction of N,N-di-n-
butylethylenediamine with isophthaloyl dichloride and
pyridine 2,6-diacetyldichloride in 80% and 82% yield,
respectively. 3,4-Diphenyl-1H-pyrrole-2,5-dicarboxylic
acid bis-[(2-dibutylamino-ethyl)-amide] (3) was prepared
in 67% overall yield from 3,4-diphenyl-1H-pyrrole-2,5-
dicarboxylic acid (26) via the acid chloride.
Scheme 1. The materials balance for the recovery of SO2 by
acid generation.
One approach to reduce manufacturing cost is to use
simple small molecules to extract sulphuric acid from the
PLS independently from the extraction of the metal ion, a
strategy that has been successfully applied in the co-
extraction of Csþ and NO32 ions (17). A major advantage
of this ‘dual host’ approach compared to the ditopic ligand
approach is that it is much easier to achieve selectivity for
the metal cation and the sulphate anion with individual
components, whereas in the case of the ditopic receptor
selectivity for both the metal cation and the sulphate anion
need to be included in a single extractive ligand. A number
of groups have previously synthesised receptors that
exhibit selectivity towards sulphate and hydrogen sulphate
anions (18). Recently, Sessler, Moyer and co-workers (19)
X-ray quality crystals of 3 were obtained via slow
evaporation of a methanol solution. The crystal structure
revealed that a hydrogen-bonded dimer was formed in the
solid state by interactions between the pyrrole NH group
and a carbonyl group with a N2· · ·O10 distance of
˚
2.9872(16) A (Figure 5).
5-Nonyl-3-dihexylaminomethyl-2-hydroxy-benzal-
dehyde oxime (4) was prepared by the oximation of 5-
nonyl-3-dihexylaminomethyl-2-hydroxybenzaldehyde
MSO4 (aq)
Leaching
MS + 2O2
MSO4 (aq) + 2LH (org)
ML2 (org) + H2SO4 (org)
MSO4 (aq) + 2LH (org)
M +1/2 O2 + H2SO4 (aq)
Extraction
Stripping
Electrowinning
Net
ML2 (org) + H2SO4 (aq)
MSO4 (aq) + H2O
MS + 3
/2 O2 + H2O
M + H2SO4
Scheme 2. Material balance of phenolic oxime extraction of metals from sulphidic ores showing the generation of sulphuric acid during
the extraction step.

120
G.W. Bates et al.
Scheme 3. Expected binding of metal sulphates with salen-based zwitterionic receptors.
Scheme 4. Oxime-based metal salt extractants showing generic coordination of a mono-anion to the protonatable pendant amine arms.
(13) in 93% yield. The nickel complex of an analogue of
this ligand, 5-t-butyl-3-piperidinomethyl-2-hydroxy-ben-
zaldehyde oxime (5) (14), was prepared and single
crystals, suitable for X-ray diffraction, were grown by slow
evaporation from hexane. The structure (Figure 6) has a
square planar nickel centre on a point of inversion. The
oximic protons show bifurcated hydrogen bonding to both
arranged on opposite sides, above and below the plane of
the molecule. This will clearly be disadvantageous for the
binding of di-anions such as SO242, however, the related
copper complex has been demonstrated to be an efficient
extractant for a range of mono-anions (15).
˚
the phenolic oxygen (O23· · ·O1A 2.564 A) and the
Extraction results
˚
nitrogen on the piperidine ring (O23· · ·N62 2.831 A).
Compounds 1, 2 and 3 were investigated as sulphuric acid
extractants both on their own and as part of a dual host
system, in the presence of Ni(P50-H)2. A simple tertiary
More significantly due to the preferred hydrogen bonding
arrangement of the oxime, the anion-binding sites are
Figure 4. Anion, cation and metal salt extractants studied.

Supramolecular Chemistry
121
Figure 5. X-ray crystal structure of 3 showing the formation of the hydrogen-bonded dimer.
Figure 6. Structure of Ni(5-H)2 (30) showing the bifurcated hydrogen bonding of the oximic proton and the arrangement of the
piperidino anion-binding arms.

122
G.W. Bates et al.
Figure 8. Quantity of nickel in the organic phase as a
percentage of the amount of extractant in the system at
equilibrium. The lines are added as visual aids and do not
represent fitted data.
Figure 7. Quantity of sulphur in the organic phase as a
percentage of the amount of extractant at equilibrium at different
pH values in the in the system at equilibrium in the presence of
Ni(P50-H)2. The lines are added as visual aids and do not
represent fitted data.
compared to TOA. Unfavourable interactions of the anion
in the binding cavity with the lone pair on the pyridine ring
may be the reason why 1 is superior to 2. The weaker
performance of 3 is more difficult to explain but may be
due to the slightly different geometry of the amide arms
created by the pyrrole ring (cf. pyridine and benzene) not
allowing creation of the optimum anion-binding cavity
size for sulphate.
amine, tri-n-octylamine (TOA), was included for com-
parison as this is often used as a model for the commercial
ion pair extractant alamine 336 (27). The dual host systems
were also compared with the metal salt extractant 4.
pH profiles for sulphate loading were determined by
taking chloroform solutions containing 0.01 M of either 1,
2, 3 or TOA (0.02 M) and contacting the organic solutions
with 0.8 M aqueous sulphate solutions at different pH
values and recording the % sulphur uptake into the organic
phase. Dual host experiments were carried out in the same
manner but in the presence of 0.01 M Ni(P50-H)2. pH
profiles for Ni-content in the organic phase obtained from
this procedure represent the stripping of the nickel from
the ligand.
The metal salt complex, Ni(4-H)2 shows no selectivity
for sulphate versus hydrogen sulphate as expected from the
unfavourable arrangement of the anion-binding sites. All
other ligands show a plateau indicative of sulphate
selectivity (12). The increase in sulphur loading beyond
100% at pH ,1 shown by some of the systems is due to
extraction of HSO24 as this species dominates at low pH.
Equally, the drop in sulphur extraction exhibited by both 1
and 2 at low pH in the absence of Ni(P50-H)2 (see
Supplementary Information for graphs, available online)
can be attributed to the increased solubility of the HSO42
complex in the aqueous phase and has been observed
previously (28).
For the sulphate receptors the extraction strength order
was found to be 1 . 2 . 3 . TOA (Figure 7 and Table 1).
While this order does not change with the presence of
1
2
Ni(P50-H)2 in the system, there is a slight increase in pH
(S) for all ligands except 3 (see Supplementary
Information for graphs, available online). The results
show that the incorporation of hydrogen bonding groups
into the ligand systems enhances sulphate extraction when
1
The pH (Ni) of P50 varies by approximately 1 pH unit
over the series of sulphate extractants 3 , TOA , 1 , 2
(Figure 8 and Table 1). For comparison, when measured on
2
1
2
1
2
its own, Ni(P50-H)2 has a pH of 3.7. This shows that
while the presence of 1 has little or no effect on the nickel
Table 1. pH values estimated from the % uptake versus
equilibrium pH plots.
loading of P50, 2 significantly decreases (0.7 pH units) and
3 increases (0.4 pH units) extraction strength. TOA shows
a slight increase in extraction strength (0.2 pH units).
Although 4 begins to extract nickel at lower pH than the
1
1
2
1
2
pH Ni
pH S loading
(with Ni)
pH S loading
(without Ni)
Extractant
loa2ding
3 þ Ni(P50-H)2
2 þ Ni(P50-H)2
1 þ Ni(P50-H)2
TOA
Ni(4-H)2
Ni(P50)2
3.30
4.40
3.75
3.50
3.75
3.70
4.75
5.20
5.50
4.40
3.70
–
4.9
5.0
5.4
4.1
–
1
P50 systems, it has a pH value of 3.75 and the extraction
curve is very shallow and maximum loading (80%) is only
2
reached above pH 5. Interestingly, the Ni(P50-H)2 þ TOA
–
system initially follows the same trend but displays greater

Supramolecular Chemistry
123
spectra (electrospray mass spectrometry) were recorded
on a Micromass Platform single quadrupole spectrometer.
Analytical data were obtained on a CE-440 Elemental
Analyser by the University of Edinburgh Microanalytical
service or were performed by Medac Ltd (Chobham,
Surrey, United Kingdom). Inductively coupled plasma-
optical emission spectrometer (ICP-OES) analysis was
carried out using a Perkin-Elmer Optima 5300DV
spectrometer. The measurement of pH was carried out
using a Fisher Scientific AR50 pH meter fitted with a
CW711 pH probe. 5-Nonyl-3-dihexylaminomethyl-2-
hydroxybenzaldehyde (13) and 5-t-butyl-3-piperidino-
methyl-2-hydroxybenzaldehyde oxime (5) (14) were
prepared as previously reported. 2-Hydroxy-5-nonylben-
zaldehyde oxime (P50) was gratefully received from
Cytec Industries (Stamford, CT, USA). Thionyl chloride
was distilled from 10% (w/w) triphenyl phosphate and
stored under nitrogen. All other solvents and reagents were
purchased from commercial sources and used without
further purification unless otherwise stated.
Figure 9. Structure of [Ni(5)2(benzoate)2] showing the
octahedral coordination sphere of the nickel.
extraction above pH 3, again reaching maximum (100%)
above pH 5.
Crystal data for 3 and Ni(5-H)2 and [Ni(5)2(benzoate)2]
are given in the electrospray ionization (ESI).
Significant synergistic effects have been observed in
carboxylic acid/oxime mixtures of versatic acid 10 with
LIXw84-IC (2) and LIXw63 (29). However, in these cases,
the effect is probably due to direct coordination (31) of the
carboxylic acid forming an octahedral complex in a similar
manner to that seen in [Ni(5)2(benzoate)2] (32) (Figure 9)
and in oxime/diamine systems (33).
Preparation of compounds
N,N0-bis-(2-dibutylamino-ethyl)-isophthalamide (1)
Isophthaloyl dichloride (2.00 g, 9.9 mmol) in dichloro-
methane (50 ml) was added dropwise to a stirred solution
of N,N-dibutylethylenediamine (3.45 g, 20 mmol) and
triethylamine (5 ml) in dichloromethane (50 ml) with a
catalytic amount of dimethylaminopyridine (DMAP) and
the reaction mixture was stirred for 24 h. Water (100 ml)
was added and the organic layer separated, dried with
MgSO4, filtered and concentrated in vacuo. The resulting
oil was purified via a flash column chromatography (SiO2,
dichloromethane (DCM)/1% MeOH) to give the product
as a viscous yellow oil. Yield: 82%, 3.85 g; ESI-MS
Conclusions
We have shown that for sulphate binding, the ligands 1, 2
and 3 that contain hydrogen bonding functionality
outperform simple trialkylamines such as TOA. As part
of a dual host system, they show significant influence on
the nickel extraction strength of P50 oxime. The reason
behind these synergistic effects is not clear and will require
further investigation to elucidate. The dual host systems
also perform better than the metal salt reagent 4 as nickel
sulphate extractants. However, none of the systems
investigated show sufficiently strong extraction to be
applicable in industrial circuits.
1
m/z ¼ 475.5 [M þ H]þ. H NMR (400 MHz, CDCl3): d
0.88 (t, 2H), 125–1.35 (m, 8H), 1.38–1.46 (m, 8H), 2.45
(t, 8H), 2.63 (t, 4H), 3.48 (q, 4H), 6.97 (s, 2H); 7.49 (t, 1H),
8.33 (dd, 7.8 Hz, 2H), 8.23 (t, 1H). 13C NMR (100 MHz,
CDCl3): d 14.4, 21.1, 29.6, 37.9, 52.9, 54.0, 125.8, 129.2,
129.9, 135.6, 166.8. Elemental anal. Calcd for
C28H50N4O2: C, 70.84; H, 10.62; N, 11.80%. Found: C,
70.77; H, 10.53; N, 11.79%.
Experimental
General
Proton and 13C NMR were obtained using either a Bruker
AC250 (UoE) spectrometer or a DPX400 (UoS)
spectrometer and the chemical shifts reported in ppm.
The following abbreviations are used for spin multiplicity:
s ¼ singlet, d ¼ doublet, t ¼ triplet and m ¼ multiplet.
Fast atom bombardment (FAB)-MS was recorded using a
Kratos MS50TC spectrometer with a 3-nitrobenzyl
alcohol or thioglycerol matrix. Low-resolution mass
Pyridine-2,6-dicarboxylic acid bis-[(2-dibutylamino-
ethyl)-amide] (2)
Pyridine 2,6-diacetyldichloride (2.00 g, 9.8 mmol) in
dichloromethane (50 ml) was added dropwise to a stirred
solution of N,N-dibutylethylenediamine (3.45 g, 20 mmol)
and triethylamine (5 ml) in dichloromethane (50 ml) with a
catalytic amount of DMAP and the reaction mixture stirred

124
G.W. Bates et al.
for 24 h. Water (100 ml) was added and the organic layer
separated, dried with MgSO4, filtered and concentrated in
vacuo. The resulting oil was purified via a flash column
chromatography (SiO2, DCM/1% MeOH) to give the
product as a viscous orange oil. Yield: 80%, 3.73 g; ESI-
MS m/z ¼ 476.5 [M þ H]þ. 1H NMR (400 MHz, CDCl3):
d 0.88 (t, 12H), 1.26–1.35 (m, 8H), 1.41–1.49 (m, 8H),
2.49 (t, 8H), 2.67 (t, 4H), 3.56 (q, 4H), 8.00 (t, 1H), 8.33 (d,
2H), 8.43 (s, 2H). 13C NMR (100 MHz, CDCl3) d: 14.4,
20.1, 29.6, 37.8, 53.8, 54.5, 125.1, 139.2, 149.4, 164.0.
Elemental anal. Calcd for C27H49N5O2: C, 68.17; H,
10.38; N, 14.71%. Found: C, 68.15; H, 10.32; N, 14.70%.
CDCl3): d 0.51–1.60 (41H, m, AlkH), 2.50 (4H, t,
2 £ NCH2CH2), 3.79 (2H, s, ArCH2N), 6.76 (1H, m, ArH),
7.19 (1H, m, ArH), d 8.30 (1H, s, CHN). Elemental anal.
Calcd for C29H52N2O2: C, 75.60; H, 11.38; N, 6.08%.
Found: C, 74.10; H, 11.18; N, 5.95%. Discrepancy in
carbon analysis may be due to the presence of a small
amount of the sulphate salt of 4 in the analysis sample:
Calcd for C29H52N2O2(H)0.2(SO4)0.1: C 74.02; H, 11.18;
N, 5.95%. Found: C, 74.10; H, 11.18; N, 5.95%.
[Ni(4-H)2]
A solution of 4 (5 g, 10.9 mmol) in methanol (60 ml) was
added to a solution of nickel acetate tetrahydrate (1.37 g,
5.5 mmol) in methanol (60 ml) and stirred overnight. The
solvent was removed in vacuo to give a dark green viscous
oil. This was dissolved in dichloromethane (100 ml) and
washed with a pH 9 ammonia solution (2 £ 50 ml). The
organic layer was separated, dried with magnesium
sulphate, filtered and the solvent was removed in vacuo
to give the product as a sticky green solid. Yield: 80%,
4.3 g; FAB-MS m/z ¼ 980 [M þ H]þ.
3,4-Diphenyl-1H-pyrrole-2,5-dicarboxylic acid bis-[(2-
dibutylamino-ethyl)-amide] (3)
3,4-Diphenyl-1H-pyrrole-2-carboxylic acid124 (1.75 g;
5.7 mmol) was refluxed in thionyl chloride (40 ml) for
3 h. The thionyl chloride was evaporated and the resultant
solid was dissolved in dichloromethane (50 ml). This was
then added dropwise to a stirring solution of N,N-
dibutylethylenediamine (2 g, 12 mmol) and triethylamine
(5 ml) in dichloromethane (50 ml) with a catalytic amount
of DMAP. The reaction mixture was stirred for 48 h. Water
(100 ml) was added to the reaction mixture and the organic
layer was separated, dried with MgSO4, filtered and
concentrated in vacuo. The product was then recrystallised
from acetonitrile to give the product as a white powder.
[Ni(5-H)2]
A solution of 5 (1.03 g, 3.6 mmol) in methanol (60 ml) was
added to a solution of nickel acetate tetrahydrate (0.45 g,
1.8 mmol) in methanol (60 ml) and stirred overnight. The
solvent was removed in vacuo and the residue dissolved in
dichloromethane (100 ml) and washed with a pH 9
ammonia solution (2 £ 50 ml). The organic layer was
separated, dried with magnesium sulphate, filtered and the
solvent was removed invacuo to give the product as a green
crystalline solid which was recrystallised from hexane.
1
Yield 67%, 2.21 g; ESI-MS m/z ¼ 616.7 [M þ H]þ. H
NMR (400 MHz, CDCl3): d 0.84 (bt, 12H), 1.13 (m, 16H),
2.17 (m, 8H), 2.33 (bt, 4H), 3.28 (br, 4H), 6.09 (bt, 2H),
7.11–7.14 (m, 4H), 7.20–7.24 (m, 6H), 10.23 (s, 1H); 13
C
NMR (100 MHz, CDCl3) d 14.4, 20.1, 29.2, 37.6, 52.9,
53.8, 124.1, 126.2, 128.0, 128.9, 131.1, 133.8, 160.8;
Elemental anal. Calcd for C38H57N5O2: C, 74.11; H, 9.33;
N, 11.37%. Found: C, 74.04; H, 9.43; N, 11.36%.
1
Yield: 37%, 0.41 g; FAB-MS m/z ¼ 637 [M þ H]þ. H
NMR (250 MHz, CDCl3): d 1.15 (s, 9H, C(CH3)3), 1.45 (m,
2H, CH2), 1.50 (m, 4H, 2 £ CH2), 2.15 (m, 4H, 2 £ CH2),
3.22 (s, 2H, ArCH2N), 6.90 (s, 1H, ArH), 6.95 (s, 1H, ArH),
7.78 (s, 1H, ArCHN). 13C NMR (63 MHz, CDCl3): d 24.0,
25.0, 31.5, 33.5, 54.0, 58.0, 125.5, 131.5, 153.5. Elemental
anal. Calcd for C34H50N4O4Ni: C, 64.05; H, 7.85; N,
8.79%. Found: C, 64.10; H, 7.80; N, 8.50%.
5-Nonyl-3-dihexylaminomethyl-2-hydroxy-benzaldehyde
oxime (4)
5-Nonyl-3-dihexylaminomethyl-2-hydroxybenzaldehyde
(25 g, 60.2 mmol) was dissolved in toluene (50 ml) in a
250 ml 3-necked RB flask and the solution warmed to
458C. Hydroxylamine sulphate (6.36 g, 38.8 mmol) was
dissolved in water (30 ml) and warmed to 458C before
adding to the reaction flask. Sodium carbonate (4.11 g,
38.8 mmol) in water (30 ml) was added slowly to the
reaction mixture with stirring. The reaction was stirred
overnight (17 h) at 458C before cooling to room
temperature. The organic phase was separated and washed
with sulphuric acid solution (50 ml) followed by water
(2 £ 50 ml). The organic was dried over MgSO4 and the
solvent was removed under vacuum at 708C. Yield: 93%,
24 g; FAB-MS m/z ¼ 461 [M þ H]þ. 1H NMR (250 MHz,
[Ni(P50-H)2]
A solution of P50 (5.0 g, 19 mmol) in methanol (60 ml)
was added to a solution of nickel acetate tetrahydrate
(2.4 g, 9.5 mmol) in methanol (100 ml) and stirred
overnight. The solvent was removed in vacuo to give a
dark green viscous oil. This was dissolved in dichlor-
omethane (100 ml) and washed with a pH 9 ammonia
solution (2 £ 50 ml). The organic layer was separated,
dried with magnesium sulphate, filtered and the solvent

Supramolecular Chemistry
125
(2) Ndlovu, B.; Mahlangu, T. J. South. Afr. Inst. Min. Metall.
2008, 108, 223–228.
(3) Donegan, S. Miner. Eng. 2006, 19, 1234–1245; Whitting-
ton, B.I.; Johnson, J.A.; Quan, L.P.; McDonald, R.G.; Muir,
D.M. Hydrometallurgy 2003, 70, 47–62.
was removed in vacuo to give the product as a sticky green
solid. Yield: 88%, 4.9 g; FAB-MS m/z ¼ 584 [M þ H]þ.
[Ni(5)2(benzoate)2]
(4) http://www.xstrata.com/assets/pdf/xni_koniambo_fact_
sheet_20081204.en.pdf.
(5) Habashi, F. A Textbook of Hydrometallurgy; Metallurgie
Extractive Quebec, Enr. Quebec, 1993.
(6) Tasker, P.A.; Tong, C.C.; Westra, A.N. Coord. Chem. Rev.
2007, 251, 1868–1877.
(7) Szymanowski, J. Hydroxyoximes and Copper Hydrometal-
lurgy; CRC Press, Inc. London, 1993.
Sodium benzoate (125 mg, 0.86 mmol) and 5 (250 mg,
0.86 mmol) were added to a solution of nickel nitrate
hexahydrate (127 mg, 0.43 mmol) in methanol (75 ml) and
stirred overnight. The solvent was removed in vacuo to
leave a green powder. Yield: 350 mg. X-ray quality
crystals were grown in low yield by layering of a
chloroform solution with hexane.
(8) Swaddle, T.W. Inorganic Chemistry; An Industrial and
Environmental Perspective; Academic Press, San Diego,
1997.
(9) Tasker, P.A.; Plieger, P.G.; West, L.C. In Comprehensive
Coordination Chemistry II; McCleverty, J.A., Meyer, T.J.,
Eds.; Elsevier: London, 2004; Vol. 9.
(10) Dreisinger, D. Hydrometallurgy 2006, 83, 10–20.
(11) White, D.J.; Laing, N.; Miller, H.A.; Parsons, S.; Coles, S.;
Tasker, P.A. Chem. Commun. 1999, 2077–2078; Coxall,
R.A.; Lindoy, L.F.; Miller, H.A.; Parkin, A.; Parsons, S.;
Tasker, P.A.; White, D.J. Dalton Trans. 2003, 55–64;
Galbraith, S.G. Ph.D. Thesis, University of Edinburgh,
2004.
(12) Galbraith, S.G.; Plieger, P.G.; Tasker, P.A. Chem. Commun.
2002, 22, 2662–2663.
(13) Akkus, N.; Campbell, J.C.; Davidson, J.; Henderson, D.K.;
Miller, H.A.; Parkin, A.; Parsons, S.; Plieger, P.G.; Swart,
R.M.; Tasker, P.A.; West, L.C. Dalton Trans. 2003, 10,
1932–1940.
Extraction studies
General procedure (sulphate extraction)
Stock solutions of 0.01 M ligand (0.02 M in the case of
TOA) were prepared in chloroform. Five millilitre
portions of the stock solutions were contacted with 5 ml
of 0.8 M aqueous sulphate solutions over a range of pH
values and stirred for 24 h. The aqueous and organic
phases were separated and the equilibrium pH of the
aqueous phase determined. Aliquots (0.5 ml) of the
organic phase were removed, evaporated to dryness in
vacuo and the residue redissolved in butan-1-ol for sulphur
determination by ICP-OES. From this plots of percentage
sulphur loading versus pH were generated.
(14) Forgan, R.S.; Davidson, J.E.; Galbraith, S.G.; Henderson,
D.K.; Parsons, S.; Tasker, P.A.; White, F.J. Chem.
Commun. 2008, 34, 4049–4051.
(15) Forgan, R.S.; Davidson, J.E.; Fabbiani, F.P.A.; Galbraith,
S.G.; Henderson, D.K.; Moggach, S.A.; Parsons, S.; Tasker,
P.A.; White, F.J. Dalton Trans. 2010, 33, 1763–1770.
(16) Galbraith, S.G.; Wang, Q.; Li, L.; Blake, A.J.; Wilson, C.;
Collinson, S.R.; Lindoy, L.F.; Plieger, P.G.; Schroeder, M.;
Tasker, P.A. Chem. A Eur. J. 2007, 13, 6091–6107.
(17) Kavallieratos, K.; Sachleben, R.A.; Berkel, G.J.V.; Moyer,
B.A. Chem. Commun. 2000, 187–188.
Metal salt 4
Procedure as above but using 0.01 M [Ni(4-H)2]. Butan-1-
ol solutions analysed for both nickel and sulphur contents
by ICP-OES. From this plots of percentage nickel and
sulphur loading versus pH were generated.
(18) Kang, S.O.; Powell, D.; Bowman-James, K. J. Am. Chem.
Soc. 2005, 127, 13478–13479; Kubik, S.; Kirchner, R.;
Nolting, D.; Seidel, J. J. Am. Chem. Soc. 2002, 124, 12752–
12760; Sessler, J.L.; Katayev, E.; Pantos, G.D.; Ustynyuk,
Y.A. Chem. Commun. 2004, 1276–1277; Sessler, J.L.;
Katayev, E.; Pantos, G.D.; Scherbakov, P.; Reshetova,
M.D.; Khurstalev, V.N.; Lynch, V.; Ustynyuk, Y.A. J. Am.
Chem. Soc. 2005, 127, 11442–11446; Katayev, E.; Boev,
N.; Khurstalev, V.N.; Ustynyuk, Y.A.; Tananaev, I.G.;
Sessler, J.L. J. Org. Chem. 2007, 72, 2886–2896.
(19) Eller, L.R.; Stepien, M.; Fowler, C.J.; Lee, J.T.; Sessler,
J.L.; Moyer, B.A. J. Am. Chem. Soc. 2007, 129,
11020–11021.
Dual host
Procedure as above but with the addition of 0.01 M
[Ni(P50-H)2] to the ligand stock solutions. Butan-1-ol
solutions analysed for both nickel and sulphur contents by
ICP-OES. From this plots of percentage nickel and sulphur
loading versus pH were generated.
Acknowledgements
We are grateful to the EPSRC and Crystal Faraday (PAG, GWB,
CCT) and Falconbridge for funding. Additionally, we are grateful
to the EPSRC for access to the crystallographic facilities at the
University of Southampton.
(20) Custelcean, R.; Moyer, B.A.; Hay, B.P. Chem. Commun.
2005, 5971–5973; Custelcean, R.; Remy, P.; Bonnesen,
P.V.; Jiang, D.; Moyer, B.A. Angew. Chem. Int. Ed. 2008,
47, 1866–1870.
(21) Wu, B.; Liang, J.J.; Yang, J.; Jia, C.D.; Yang, X.J.; Zhang,
H.R.; Tang, N. Janiak, C. Chem. Commun. 2008, 1762–
1764; Zhuge, F.Y.; Wu, B.A.; Liang, J.J.; Yang, J.; Liu, Y.Y.;
Jia, C.D.; Janiak, C.; Tang, N.; Yang, X.J. Inorg. Chem.
2009, 48, 10249–10256.
References
(1) King, M.G. J. Minerals Metals Mater. Soc. 2005, 57,
35–39.

126
G.W. Bates et al.
(22) Custelcean, R.; Barsano, J.; Bonnensen, P.V.; Kertesz, V.;
Hay, B.P. Angew. Chem. Int. Ed. 2009, 48, 4025–4029.
(23) Gale, P.A.; Hiscock, J.R.; Jie, C.Z.; Hursthouse, M.B.;
Light, M.E. Chem. Sci. 2010, 1, 215–220.
(24) Hossain, M.A.; Llinares, J.M.; Powell, D.; Bowman-
James, K. Inorg. Chem. 2001, 40, 2936–2937.
Pranolo, Y.; Zhu, Z.; Wang, W.; Hydrometallurgy, 2010,
104, 45–52.
(30) Barnard, K.R.; Nealon, G.L.; Ogden, M.I.; Skelton, B.W.
Solvent Extr. Ion Exch. 2010, 78, 778–792.
(31) Henderson, D.K.; Davidson, J.E.; Tasker, P.A.; Parson, S.;
White, F. Private communication to the Cambridge
Structural Database, deposition number CCDC 660851,
2007.
(25) Kubik, S.; Kirchner, R.; Nolting, D.; Seidel, J. J. Am. Chem.
Soc. 2002, 124, 12752–12760.
(26) Navakhun, K.; Gale, P.A.; Camiolo, S.; Light, M.E.;
Hursthouse, M.B. Chem. Commun. 2002, 2084–2085.
(27) Bell, K.J.; Westra, A.N.; Warr, R.C.; Chartres, J.; Elis, R.;
Tong, C.C.; Blake, A.J.; White, F.J.; Tasker, P.A.;
Schroder, M. Angew. Chem. Int. Ed. 2008, 47, 1745–1748.
(28) Henry, D.C.R.;, Ph.D. Thesis, University of Edinburgh
2007.
(32) Henderson, D.K.; Davidson, J.E.; Tasker, P.A.; Parson, S.;
White, F. Private communication to the Cambridge
Structural Database, deposition number CCDC 660850,
2007.
(33) Hultgren, V.M.; Atkinson, I.M.; Beddoes, R.L.; Collison,
D.; Garner, C.D.; Helliwell, M.; Lindoy, L.F.; Tasker, P.A.
Chem. Commun. 2001, 573–574.
(29) Cheng, C.Y. Hydrometallurgy, 2006, 84, 109–117; Cheng,
C.Y.; Boddy, G.; Zhang, W.; Godfrey, M.; Robinson, D.J.;