Highly organic phase soluble polyisobutylene-bound cobalt phthalocyanines as recyclable catalysts for nitroarene reduction

Article abstract of DOI:10.1016/j.catcom.2016.01.022

A cobalt phthalocyanine (CoMPc) containing covalently linked polyisobutylene (PIB) groups as phase anchors that is both highly soluble in nonpolar organic solvents and phase selectively soluble in a liquid/liquid separation step is shown to be an effective recyclable homogeneous catalyst for nitroarene reduction in a semi-thermomorphic system. Electron-donating and electron-withdrawing substituents in the nitroarene are tolerated in this aniline synthesis and the catalyst is recyclable up to 10 cycles with little leaching and no detectable loss in reactivity after 10 cycles.

Full text of DOI:10.1016/j.catcom.2016.01.022

Highly organic phase soluble polyisobutylene-bound cobalt phthalocyanines
as recyclable catalysts for nitroarene reduction
Chih-Gang Chao, David E. Bergbreiter
PII:
DOI:
Reference:
S1566-7367(16)30022-X
doi: 10.1016/j.catcom.2016.01.022
CATCOM 4567
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
2 December 2015
20 January 2016
22 January 2016
Please cite this article as: Chih-Gang Chao, David E. Bergbreiter, Highly organic
phase soluble polyisobutylene-bound cobalt phthalocyanines as recyclable catalysts for ni-
troarene reduction, Catalysis Communications (2016), doi: 10.1016/j.catcom.2016.01.022
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ACCEPTED MANUSCRIPT
Highly Organic Phase Soluble Polyisobutylene-Bound Cobalt Phthalocyanines as Recyclable
Catalysts for Nitroarene Reduction
*
Chih-Gang Chao and David E. Bergbreiter
Department of Chemistry, Texas A&M University, P.O Box 30012, College Station, TX 77842-3012,
USA
*
bergbreiter@chem.tamu.edu
Abstract
A cobalt phthalocyanine (CoMPc) containing covalently linked polyisobutylene (PIB) groups as
phase anchors that is both highly soluble in nonpolar organic solvents and phase selectively soluble in a
liquid/liquid separation step is shown to be an effective recyclable homogeneous catalyst for nitroarene
reduction in a semi-thermomorphic system. Electron-donating and electron-withdrawing substituents in
the nitroarene are tolerated in this aniline synthesis and the catalyst is recyclable up to 10 cycles with little
leaching and no detectable loss in reactivity after 10 cycles.
Keywords
Thermomorphic; Metallophthalocyanine catalyst; Polyisobutylene; Nitroarene reduction; Catalyst
recycling
1. Introduction
Aromatic amines are important organic compounds due to their use in the syntheses of dyes [1],
pesticides [2], pharmaceuticals [3,4], and polymers [5]. Reduction of nitro compounds is one of most
widely used routes to this class of compounds. Classically reduction of nitroarenes to form anilines uses
hydrogenation with Pd/C [6]. More recently, there has been an increase in interest in homogeneous
catalysts that use more earth abundant metals [7-9], that are recyclable [10,11], or that use alternatives to
hydrogen as the penultimate reductant [12-15].
Metallophthalocyanines (MPcs) were originally developed as pigments [16] but are now also used as
photosensitizers, photodynamic therapy agents, and in molecular electronics [17,18]. MPcs can also be
used as catalysts. However, their use in homogeneous catalysis is less common than is the case for
porphyrins [19-21]. MPcs are less commonly used as homogeneous catalysts because MPcs have
-5
-7
solubility that is in the range of 10 to 10 M in organic solvents [22], a limitation that renders their use
as homogeneous catalysts problematic. Our success in synthesis of PIB-bound MPcs that dissolve in
hydrocarbon polymers and the activity of several MPcs as heterogeneous catalysts for nitroarene
reduction [23,24] suggested to us that PIB-modified MPcs could be recyclable homogeneous catalysts and
that this hypothesis could be tested by examining their use in nitroarene hydrogenation. Our hypothesis

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about the solubility and activity of PIB-modified MPcs has proven correct and we have shown here that a
PIB-bound CoMPc catalyst can be used as a homogeneous catalyst for nitroarene reduction and that this
catalyst can be quantitatively separated from products and recycled as discussed below.
2. Experimental
2.1. General procedures
Vinyl terminated PIB (Glissopal 1000) was provided by BASF [25]. Other reagents and solvents were
1
13
purchased from commercial sources and used without further purification. H and C NMR spectra were
recorded on Inova 300 or 500 MHz NMR spectrometers. IR spectra were obtained using a Shimadzu
Affinity-1S IR spectrometer. UV–Visible spectra were recorded on a Shimadzu UV-2600
spectrophotometer. A NexION 300D Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) was
used to determine the Co metal content in 6.
2.2. Synthesis of 2-6
1
13
The syntheses of 2-6 are detailed in the supplemental information along with H and C NMR
spectroscopic data.
2.3. General procedure for nitroarene reduction using hydrazine hydrate with 6 as a homogeneous catalyst
A biphasic mixture of 1 mmol of nitroarene and 0.4 mol% of catalyst 6 was prepared using 5 mL of
heptane and 5 mL of anhydrous ethylene glycol in a Schlenk tube. Then 5 equivalent of hydrazine hydrate
o
were added and the biphasic solution was stirred at 110 C under a N atmosphere for 24 h. While the
2
original biphasic mixture never became a single phase during this process, the ethylene glycol phase
visually appeared to increase in volume due to some heptane dissolution. In addition, some of the PIB-
bound MPc complex visually was present in that phase. After the reaction was complete, the biphasic
mixture was cooled down to ambient temperature. The polar ethylene glycol-rich phase was separated
from the heptane solution of the MPc and the product was isolated by chromatography from this polar
phase. The catalyst in the heptane phase was recycled for further experiments after addition of fresh
reagents and fresh ethylene glycol.
1
4
3
4
3
-Chloroaniline. H NMR (500 MHz, CDCl ),  7.10 (2 H, d, J = 8.8 Hz), 6.60 (2 H, d, J = 8.8 Hz), 3.50-
3
13
.80 (2 H, br); C NMR (125 MHz, CDCl ), 129.08, 123.12, 116.20.
3
1
-Bromoaniline. H NMR (300 MHz, CDCl ),  7.23 (2 H, d, J = 8.4 Hz), 6.56 (2 H, d, J = 8.4 Hz), 3.60-
3
13
.70 (2 H, br); C NMR (75 MHz, CDCl ), 131.97, 116.67, 110.15.
3

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1
4
-Aminobenzoic acid. H NMR (500 MHz, DMSO- d ),  7.59 (2 H, d, J = 8.5 Hz), 6.54 (2 H, d, J = 8.5
6
13
Hz), 5.70-5.84 (2 H, br); C NMR (125 MHz, DMSO- d )
6
1
4
3
4
3
3
4
-Aminotoluene. H NMR (500 MHz, CDCl ),  7.02 (2 H, d, J = 8.5 Hz), 6.65 (2 H, d, J = 8.5 Hz),
3
13
.50-3.60 (2 H, br), 2.30 (3 H, s); C NMR (125 MHz, CDCl ), 129.63, 127.59, 115.13, 20.34.
3
1
-tert-Butylaniline. H NMR (500 MHz, CDCl ),  7.19 (2 H, d, J = 9.0 Hz), 6.65 (2 H, d, J = 9.0 Hz),
3
13
.50-3.60 (2 H, br), 1.28 (9 H, s); C NMR (125 MHz, CDCl ), 141.32, 125.97, 114.87, 33.83,
3
1.46.
1
-Aminophenol. H NMR (500 MHz, DMSO- d ),  8.50-8.55 (1 H, br), 6.46 (2 H, d, J = 9.0 Hz), 6.42
6
13
(
2 H, d, J = 9.0 Hz); C NMR (125 MHz, DMSO- d )
6
1
13
1
,4-Diaminobenzene. H NMR (500 MHz, DMSO- d ),  6.57 (4 H, s), 3.25-3.40 (4 H, br); C NMR
6
(
125 MHz, DMSO-d ).
6
1
1
-Aminonaphthalene. H NMR (500 MHz, CDCl ),  7.82-7.89 (2 H, m), 7.48-7.55 (2 H, m), 7.34-7.41
3
1
3
(
2 H, m), 6.79-6.82 (1 H, m), 4.10-4.20 (2 H, br); C NMR (125 MHz, CDCl )  142.00, 134.28, 128.44,
3
126.26, 125.75, 124.74, 123.53, 120.72, 118.83, 109.57.
3. Results and discussions
In our initial studies, we first repeated others’ work that used an insoluble CoMPc as a heterogeneous
catalyst in ethylene glycol to reduce 4-chloronitrobenzene using hydrazine hydrate as the reducing agent
26]. However, extension of this work using the PIB-supported CoMPc 1 (Fig. 1) [27] in this same
[
solvent or in mixtures of polar solvents and heptane failed or led to incomplete reduction of 4-
chloronitroarene after 24 h at 80 °C (cf. Table S1). We addressed this problem by preparing a CoMPc
with PIB groups connected to the phthalocyanine core by electron-withdrawing groups (Scheme 1).
Starting with a thiol-ene reaction of vinyl-terminated PIB [28,29] with thioacetic acid, PIB thioacetate 2
was prepared. Hydrolysis of 2 formed the thiol PIB-SH 3 [30] that was allowed to react with 4-
nitrophthalonitrile in a nucleophilic aromatic substitution reaction to form the PIB-thiophthalonitrile 4
[
31]. Oxidation of 4 with m-chloroperbenzoic acid formed the PIB1240 sulfonyl phthalonitrile 5 [32].
Tetracyclization of 5 in the presence of CoCl then formed the desired PIB1240-bound MPc 6 [33]. The
2
phthalocyanine 6 so formed is a mixture of species with PIB in different orientations in the four quadrants
1
of the phthalocyanines. As a result, analysis affords a nondescript H NMR spectrum. However, 6 was
characterized by inductively coupled mass spectroscopy (ICP-MS) and UV-Visible spectroscopy. ICP-
MS analysis of a 1 g sample of 6 showed that it contained 0.0087 g of cobalt. This corresponds to an Mn
1
of 6770 Da that is higher than expected based on a H NMR spectroscopic analysis of the M of 5. This
n

ACCEPTED MANUSCRIPT
analysis of 5 compared the integrated intensity of a known amount of 1,1,2,2-tetrachloroethane internal
standard to the integration for the signals for the three aryl protons of 5 at 8.34, 8.29, and 8.07 and the
two protons in the –CH SO doublet of doublets of 5 at 3.13 and 2.99  of the PIB group and showed that
2
2
5
had a d.p. of 22 (a M of 1430 Da). This degree of polymerization is higher than that of the starting
n
1
thioacetate 2 which by a H NMR analysis had PIB groups with a d.p. of 20. The difference between 2
and 5 reflects fractionation of the PIB-bound species during the synthesis and purification steps in
Scheme 1. The purification steps leading to isolation of 6 either formed 6 with PIB groups with d.p.s of
26 or formed some 6b that did not contain Co. If we conservatively assume no further fractionation
occurred in forming 6 from 5, we calculate that 6 is ca. 87% metalated. Complex 6 has a max at 669 nm
that is slightly higher than that reported previously for 1 (max = 675 nm) (Fig. S1). This peak corresponds
to the Q band of the MPc. The shift of the Q band of 6 at 675 to the 669 nm band of 1 is consistent with
the introduction of an electron-withdrawing sulfonyl substituent.
1
Gratifyingly, the conversion of 4-chloronitrobenzene to 4-chloroaniline was 100% based on H NMR
spectroscopy when complex 6 was used as catalyst in the presence of 5 equivalents of hydrazine hydrate
instead of 1 (Scheme 2). In these experiments, the reduction was carried out over a period of 24 h at 110
-4
°
C using a 1/1 (vol/vol) mixture of a 4.0 x 10 M heptane solution of 6 and ethylene glycol. Under these
reactions conditions, the solution never becomes monophasic but it is rather partially thermomorphic –
the volume of the denser phase visually increases and some of 6 dissolves in this phase based on a slight
color change of the ethylene glycol rich phase. Fully thermomorphic systems including a 3/1
heptane/ethanol mixture, heptane/glyme (1/1, vol/vol) and heptane/n-propanol (1/1, vol/vol) were also
examined but reductions in these solvent mixtures only led to 83-95% conversion of the nitroarene to
aniline. Other thermomorphic systems using N,N-dimethylformamide, benzyl alcohol, and glycerol with
heptane were even less successful. Control experiments without any catalyst or with a PIB-bound metal
free phthalocyanine formed no product aniline. Thus, in subsequent studies of the generality and
o
recyclability of 6 in reductions of nitroarenes at 110 C, 6 was selected as the catalyst, 5 equivalents of
hydrazine hydrate was used as the reducing agent, and 1/1 (vol/vol) mixture of heptane and ethylene
glycol was used as the solvent mixture.

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Table 1 Reduction of nitroarenes to corresponding aminoarenes and recyclability of 6 in ten cycles of
a, b
nitroarene reduction (Scheme 2)
c
Yield in each cycle
Entry
Nitroarene
d
1
2
3
4
5
6-10
1
2
3
4
5
6
7
8
4-chloronitrobenzene
4-bromonitrobenzene
4-nitrotoluene
74
63
56
68
70
50
46
75
74
71
81
84
72
69
69
-
74
73
79
77
70
69
72
-
73
76
82
81
75
68
71
-
72
75
78
82
74
68
65
-
75
71
80
86
79
65
74
-
4-tert-butylphenylnitrobenzene
4-nitrobenzoic acid
4-nitrophenol
4-nitroaniline
1-nitronaphthalene
a
-3
1
mmol of nitroarene, 4×10 mmol of 6, and 5 mmol of hydrazine hydrate were dissolved in 5 mL of ethylene glycol and 5 mL
o
b
of n-heptane and this mixture was stirred at 110 C under a nitrogen atmosphere for 24 h. After the nitroarene had been
completely reduced (as determined by H NMR spectroscopy), the reaction mixture was cooled and the bottom product-
1
containing layer was removed. Fresh nitroarene, hydrazine hydrate, and ethylene glycol were added to the flask for a subsequent
c
1
13
cycle. The yields reported are isolated yields of products that were pure by H and C NMR spectroscopy. The product
anilines were obtained by extracting the arylamine product from the ethylene glycol phase using ethyl acetate and further purified
d
using column chromatography. The yields for cycles 6-10 are an average yield for each of these five cycles based on the total
isolated yield for a combination of the product from the ethylene glycol phases for cycles 6-10.
The generality of this reduction and recyclability of these catalysts was tested with varied aryl
substituents on nitroarenes as shown in Table 1. 4-Chloro- and 4-bromonitrobenzene gave high isolated
yields and complete conversion of the starting nitroarene. Yields of 4-methyl- and 4-tert-butylaniline
were slightly lower in cycle 1, possibly due to the solubility of these aniline products in the heptane phase.
Nitroarenes with electron donating substituents like hydroxy and amino substituents also were
quantitatively converted to aniline products affording comparable isolated yields. Reduction of 1-
nitronaphthalene was also successful. However, this reduction product is a known carcinogen so
repetitive cycles were not performed. Consistent yields cycle-to-cycle were however observed for all the
nitroarenes studied, reflecting the high thermal and chemical stability associated with MPcs like 6 and the
high phase selective solubility of 6. This stability as well as the phase selectivity of 6 due to the PIB
support also makes it simple to recycle and to separate the homogeneous catalyst 6 from the aniline
products.
Recycling of the cobalt catalyst 6 was accomplished by cooling the reaction mixture to ambient
temperature. The less dense heptane-rich phase containing 6 was then physically separated by a gravity
separation from the ethylene glycol phase containing the product. The product was isolated from this
ethylene glycol phase. Visually no leaching of 6 into the ethylene glycol was seen in any of the 10
recycling experiments with any of the 7-nitroarene substrates in Table 1 with the product phase being a

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light yellow color. This qualitative observation of the absence of leaching was confirmed by UV
spectroscopic analysis of the product phase for the first cycle for the 4-chloronitrobenzene
reduction. While the product phase in these reactions has a yellow color, we were able to use UV-visible
spectroscopy to quantitatively asses leaching since 6 has a strong absorbance at 640 nm. These
experiments showed that the leaching of 6 into the product phase after the first cycle was <0.05 % of the
charged catalyst 6. An additional UV experiment was carried using the catalyst isolated from the tenth
cycle of a 4-chloronitrobenzene reduction which showed that the recovered catalyst had <0.01% leaching
into ethylene glycol.
The catalyst-containing heptane phase was reused by simply adding a new batch of nitroarene and
hydrazine hydrate in ethylene glycol to the recovered heptane solution of 6. As shown in Table 1, 6 was
able to catalyze at least 10 cycles of reaction with each substrate without significant changes in isolated
yield of product.
To confirm that the catalyst 6 had unchanged activity through these ten cycles, we carried out kinetic
studies following the conversion versus time for reductions of 4-chloronitrobenzene and 4-nitrobenzoic
acid as substrates in a cycle 11 and compared this plot to a similar conversion versus time plot for cycle 1
(
Fig. 2). In these experiments, we first carried out a reaction using a known amount of 6 in heptane and
1
ethylene glycol and a substrate nitroarene, following the conversion of the nitroarene versus time by H
NMR spectroscopy. Then, after the tenth cycle, we isolated the PIB-bound catalyst 6 from the heptane-
rich solution. The same amount of this catalyst 6 as was used in the reaction with fresh catalyst was then
used in an eleventh cycle and the conversion versus time was compared to the plot obtained with fresh
catalyst. As shown in Fig. 2, the conversion versus time between the first and the eleventh cycle are
unchanged for both substrates, indicating that the catalyst activity had not changed during these ten cycles
and separations. This is consistent with lack of change in isolated yields of products in Table 1 and with
the expected stability of the MPc catalysts.
Finally, we examined the spectrum of 6 by UV-Visible spectroscopy looking both at fresh 6 and at 6
that was isolated after eleven cycles of reduction and separation. As shown in Fig. 3, there is no obvious
change in the visible spectrum of 6 after eleven cycles of 4-chloronitrobenzene reduction and separation.
4. Conclusions
In summary, a highly heptane and organic solvent soluble PIB-supported CoMPc was
synthesized and was shown to be an effective and recyclable homogeneous catalyst for reduction
of nitroarenes using hydrazine hydrate as a reducing reagent under semi-thermomorphic
conditions at 110 ˚C. While a variety of solvents yielded product, the use of an equivolume
mixture of ethylene glycol and heptane as solvents worked best. The isolated yields of the reduced

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aniline products were consistently good for ten cycles with a variety of electron-donating and
electron-withdrawing substituents on the starting nitroarene. Because of the PIB-induced phase
selective solubility of the PIB-supported CoMPc, the catalyst can be recycled at least 10 times.
Kinetic studies show the catalyst has unchanged reactivity and UV-visible spectroscopy shows no
change in catalyst structure, results consistent with the expected thermal and kinetic stability of
MPc catalysts. We believe the solubility induced into these MPcs by PIB groups can be
employed to make other PIB-bound MPcs similarly useful in other homogeneously catalyzed
processes where a similar biphasic catalyst/product solution separation can facilitate both
catalyst/product separation and recycling.
Acknowledgements
Support of these catalyst studies by the Robert A. Welch Foundation (Grant A-0639) and the National
Science Foundation (Grant CHE-1362735), support of the hydrocarbon soluble metallophthalocyanine
synthesis by the National Priorities Research Program award (NPRP7-01263-1-230) from the Qatar
National Research Fund, and the gift of samples of Glissopal from BASF is gratefully acknowledged.
References
[
(
[
1] E. Merino, Synthesis of azobenzenes, the coloured pieces of molecular materials, Chem. Soc. Rev. 40
2011) 3835-3853.
2] E.R.A. Ferraz, G.A.R. de Oliveira, D.P. de Oliveira, The impact of aromatic amines on the
environment: risks and damages, Front Biosci 4 (2012) 914-923.
3] M. Breuer, K. Ditrich, T. Habicher, B. Hauer, M. Kesseler, R. Stuermer, T. Zelinski, Industrial
methods for the production of optically active intermediates, Angew. Chem., Int. Ed. 43 (2004) 788-824.
4] T. Henkel, R.M. Brunne, H. Müller, F. Reichel, Statistical investigation into the structural
complementarity of natural products and synthetic compounds, Angew. Chem., Int. Ed. 38 (1999) 643-
47.
5] X.-G. Li, M.-R. Huang, W. Duan, Y.-L. Yang, Novel multifunctional polymers from aromatic
diamines by oxidative polymerizations, Chem. Rev. 102 (2002) 2925-3030.
6] S. Nishimura, Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis, first ed.,
Wiley, New York, 2001.
7] R.V. Jagadeesh, G. Wienhofer, F.A. Westerhaus, A.-E. Surkus, M.-M. Pohl, H. Junge, K. Junge, M.
Beller, Efficient and highly selective iron-catalyzed reduction of nitroarenes, Chem. Commun. 47 (2011)
0972-10974.
[
[
6
[
[
[
1

ACCEPTED MANUSCRIPT
[
8] X. Dai, X. Cui, H. Yuan, Y. Deng, F. Shi, Cooperative transformation of nitroarenes and biomass-
based alcohols catalyzed by CuNiAlOx, RSC Adv. 5 (2015) 7970-7975.
[
[
9] I. Bauer, H.-J. Knölker, Iron catalysis in organic synthesis, Chem. Rev. 115 (2015) 3170-3387.
10] M. Shokouhimehr, T. Kim, S.W. Jun, K. Shin, Y. Jang, B.H. Kim, J. Kim, T. Hyeon, Magnetically
separable carbon nanocomposite catalysts for efficient nitroarene reduction and Suzuki reactions, Appl.
Catal., A 476 (2014) 133-139.
[
11] S.M. Islam, K. Ghosh, A.S. Roy, R.A. Molla, N. Salam, T. Chatterjee, M.A. Iqubal, Polystyrene
anchored ruthenium(II) complex catalyzed carbonylation of nitrobenzene and amines for the synthesis of
disubstituted ureas, J. Organomet. Chem. 772-773 (2014) 152-160.
[
12] B. Zeynizadeh, D. Setamdideh, NaBH4/Charcoal: A new synthetic method for mild and convenient
reduction of nitroarenes, Synth. Commun. 36 (2006) 2699-2704.
13] T. Schabel, C. Belger, B. Plietker, A mild chemoselective Ru-catalyzed reduction of alkynes, ketones,
and nitro compounds, Org. Lett. 15 (2013) 2858-2861.
14] K. Bhaumik, K.G. Akamanchi, Nitroarene reduction using Raney nickel alloy with ammonium
chloride in water, Can. J. Chem. 81 (2003) 197-198.
15] M. Periasamy, M. Thirumalaikumar, Methods of enhancement of reactivity and selectivity of sodium
borohydride for applications in organic synthesis, J. Organomet. Chem. 609 (2000) 137-151.
[
[
[
[
[
16] A.B. Sorokin, Phthalocyanine metal complexes in catalysis, Chem. Rev. 113 (2013) 8152-8191.
17] J.G. Young, W. Onyebuagu, Synthesis and characterization of di-disubstituted phthalocyanines, J.
Org. Chem. 55 (1990) 2155-2159.
18] D. Villemin, M. Hammadi, M. Hachemi, N. Bar, Applications of microwave in organic synthesis: an
[
improved one-step synthesis of metallophthalocyanines and a new modified microwave oven for dry
reactions, Molecules 6 (2001) 831-844.
[
19] Q.H. Xia, H.Q. Ge, C.P. Ye, Z.M. Liu, K.X. Su, Advances in homogeneous and heterogeneous
catalytic asymmetric epoxidation, Chem. Rev. 105 (2005) 1603-1662.
[
(
[
20] A.J. Esswein, D.G. Nocera, Hydrogen production by molecular photocatalysis, Chem. Rev. 107
2007) 4022-4047.
21] C.-M. Che, V.K.-Y. Lo, C.-Y. Zhou, J.-S. Huang, Selective functionalisation of saturated C-H bonds
with metalloporphyrin catalysts, Chem. Soc. Rev. 40 (2011) 1950-1975.
22] F. Ghani, J. Kristen, H. Riegler, Solubility properties of unsubstituted metal phthalocyanines in
different types of solvents, J. Chem. Eng. Data 57 (2012) 439-449.
23] P. Verma, M. Bala, K. Thakur, U. Sharma, N. Kumar, B. Singh, Iron and palladium(II)
phthalocyanines as recyclable catalysts for reduction of nitroarenes, Cat. Lett. 144 (2014) 1258-1267.
[
[

ACCEPTED MANUSCRIPT
[
24] U. Sharma, N. Kumar, P.K. Verma, V. Kumar, B. Singh, Zinc phthalocyanine with PEG-400 as a
recyclable catalytic system for selective reduction of aromatic nitro compounds, Green Chem. 14 (2012)
289-2293.
25] BASF, http://www.performancechemicals.basf.com/ev/internet/polyisobutene/en/content/EV3/polyis
obutene/glissopal (accessed November 29, 2015).
26] U. Sharma, P. Kumar, N. Kumar, V. Kumar, B. Singh, Highly chemo- and regioselective reduction
2
[
[
of aromatic nitro compounds catalyzed by recyclable copper(II) as well as cobalt(II) phthalocyanines,
Adv. Synth. Catal. 352 (2010) 1834-1840.
[
27] N. Priyadarshani, C.W. Benzine, B. Cassidy, J. Suriboot, P. Liu, H.-J. Sue, D.E. Bergbreiter,
Polyolefin soluble polyisobutylene oligomer-bound metallophthalocyanine and azo dye additives, J.
Polym. Sci., Part A: Polym. Chem. 52 (2014) 545-551.
[
28] A.B. Lowe, Thiol-ene "click" reactions and recent applications in polymer and materials synthesis: a
first update, Polym. Chem. 5 (2014) 4820-4870.
[
[
29] C.E. Hoyle, C.N. Bowman, Thiol–ene click chemistry, Angew. Chem., Int. Ed. 49 (2010) 1540-1573.
30] M. Roskamp, S. Enders, F. Pfrengle, S. Yekta, V. Dekaris, J. Dernedde, H.-U. Reissig, S. Schlecht,
Multivalent interaction and selectivities in selectin binding of functionalized gold colloids decorated with
carbohydrate mimetics, Org. Biomol. Chem. 9 (2011) 7448-7456.
[
31] C.C. Leznoff, S.M. Marcuccio, S. Greenberg, A.B.P. Lever, K.B. Tomer, Metallophthalocyanine
dimers incorporating five-atom covalent bridges, Can. J. Chem. 63 (1985) 623-631.
32] B. del Rey, U. Keller, T. Torres, G. Rojo, F. Agulló-López, S. Nonell, C. Martí, S. Brasselet, I.
[
Ledoux, J. Zyss, Synthesis and nonlinear optical, photophysical, and electrochemical properties of
subphthalocyanines, J. Am. Chem. Soc. 120 (1998) 12808-12817.
[
33] C.M. Older, S. Kristjansdottir, J.C. Ritter, W. Tam, M.C. Grady, Development of commercially
viable thermomorphic catalysts for controlled free radical polymerization, Chem. Ind. 123 (2009) 319-
28.
3
o
Fig. 1. A PIB-bound CoMPc complex that is soluble at 10 wt% in heptane or CH Cl at 25 C.
2
2

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Fig. 2. Conversion versus reaction time profile for the first and eleventh cycle for nitroarene reductions
catalyzed by 6 with two different nitroarenes: (a) 4-chloronitrobenzene and (b) 4-nitrobenzoic acid.
Fig. 3. UV-Vis spectrum of a heptane solution of 6 before and after eleven cycles of 4-chloronitrobenzene
reduction.

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Scheme 1. Synthesis of 6.

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Scheme 2. Nitroarene reduction using the heptane-soluble PIB-bound cobalt phthalocyanine catalyst 6.
Graphical Abstract
Highlights
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A new highly soluble polyisobutylene supported cobalt phthalocyanine complex was synthesized.
This CoMPc was shown to be a homogeneous catalyst for nitroarene reduction.
This CoMPc catalyst could be separated from products by liquid/liquid separation.
This CoMPc catalyst was recyclable with very low leaching and no loss in reactivity