Selective reduction of halo-nitro aromatic compounds using [Rh]/DHTANa as catalyst in an aqueous bi-phase system

Article abstract of DOI:10.1016/j.catcom.2016.05.016

The use of water as co-solvent for biphasic reactions and of easily recyclable water-soluble catalysts are highly desirable for the realization of greener processes. The selective reduction of halo nitroarenes to the corresponding haloanilines is a very important industrial transformation for the production of agrochemicals, pigments, bactericides and pharmaceuticals and is not easy to obtain. The application of a water soluble catalyst, prepared by rhodium species and a cheap thioligand, in the hydrogenation of some halonitroarenes is here described. Excellent conversions, good recyclability of the catalytic species embedded in the aqueous phase and very high selectivity are demonstrated.

Full text of DOI:10.1016/j.catcom.2016.05.016

Selective reduction of halo-nitro aromatic compounds using [Rh]/DHTANa as
catalyst in an aqueous bi-phase system
Vikas Damu Rathod, Stefano Paganelli, Oreste Piccolo
PII:
DOI:
Reference:
S1566-7367(16)30174-1
doi: 10.1016/j.catcom.2016.05.016
CATCOM 4663
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
19 February 2016
11 May 2016
22 May 2016
Please cite this article as: Vikas Damu Rathod, Stefano Paganelli, Oreste Pic-
colo, Selective reduction of halo-nitro aromatic compounds using [Rh]/DHTANa
as catalyst in an aqueous bi-phase system, Catalysis Communications (2016), doi:
10.1016/j.catcom.2016.05.016
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ACCEPTED MANUSCRIPT
Selective reduction of halo-nitro aromatic compounds using [Rh]/DHTANa as catalyst in an
aqueous bi-phase system
Vikas Damu Rathod a, Stefano Paganelli a, Oreste Piccolo* b
a Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, via Torino
155, 30172 Venezia Mestre, Italy;
b SCSOP, Via Bornò 5, 23896 Sirtori (LC) (Italy).
* Corresponding author at: Studio di Consulenza scientifica, Via Borno 5, 23896 Sirtori (LC), Italy;
Mobile +39-3356828222; Email address: orestepiccolo@tin.it
Abstract
The use of water as co-solvent for biphasic reactions and of easily recyclable water-soluble catalysts
are highly desirable for the realization of greener processes. The selective reduction of halo
nitroarenes to the corresponding haloanilines is a very important industrial transformation for the
production of agrochemicals, pigments, bactericides and pharmaceuticals and is not easy to obtain.
The application of a water soluble catalyst, prepared by rhodium species and a cheap thioligand, in
the hydrogenation of some halonitroarenes is here described. Excellent conversions, good
recyclability of the catalytic species embedded in the aqueous phase and very high selectivity are
demonstrated.
Key words Hydrogenation; Halonitroarenes; Haloanilines; Water soluble catalyst; Rhodium;
Thioligand.
1. Introduction
Homogeneous catalysis is an efficient tool to carry out a chemical process in a very active and
selective way but the major drawback of the homogeneous process is the separation of the
expensive catalyst from the product mixture that requires an energy intensive process such as

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distillation. In recent years the use of metallic species with suitable ligands has allowed chemists to
carry out reactions in biphasic systems so permitting an easy separation of the used catalyst,
confined in a phase different from that of reagents and products, and its re-use in recycling
experiments [1-3]. Since many years in our research group we are investigating highly efficient
hydroformylation and hydrogenations reactions using different water-soluble complexes derived
from the interaction between Rh species with natural or some commercially available thioligands
[4-6]. Very recently we addressed our activity to the use of a very simple molecule, e.g.
dihydrothioctic acid (DHTA), the reduced form of thioctic acid (THA), which presents two SH
groups capable, in principle, to work as a bidentate ligand for the rhodium atom (Scheme 1). The
presence of another functional group, COOH, in the molecule, when it is salified, favours the
solubility in water of Rh species (hereafter named [Rh]/DHTANa ) but also may create a potential
third bonding site for the metallic species [7].
Insert Scheme 1
A red-orange solution was obtained introducing [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene) in a
deaerated aqueous solution containing the sodium salt of the dihydrothioctic acid (DHTANa) and
using a molar ratio ligand/metal 1:1; it may be stocked under nitrogen at 4°C showing good stability
for medium-long time. After its treatment with H2 or with H2/CO, catalytic species, [Rh]/DHTANa,
were obtained and afforded very encouraging results in hydrogenation and hydroformylation
reactions of some simple model compounds [7]. Here we report the application of [Rh]/DHTANa in
the selective reduction of nitrobenzene (I) and of some halo-nitro aromatic compounds such as 1-
chloro-3-nitrobenzene (III) and 1-iodo-4-nitrobenzene (V). Furthermore, a different and greener
preparation of the catalytic species is also described and the activities of the catalysts prepared by

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the previous method (A) and the new method (B) are compared. Some spectroscopic analyses were
also performed to try to elucidate the nature of the catalytic species. Finally, a comparison study
among the new catalyst [Rh]/DHTANa, the well-known water soluble Rh/TPPTS complex (where
the ligand TPPTS is triphenylphosphine-3,3’,3’’-trisulfonic acid trisodium salt) and the home-made
heterogeneous 0.18 % Rh/Al2O3 [8,9] in the hydrogenation of the above substrates is also described.
2. Experimental
2.1 Materials and analysis
[Rh(COD)Cl]2, RhCl3, nitrobenzene, 1-chloro-3-nitrobenzene, 1-iodo-4-nitrobenzene, NaBH4,
Na2CO3, trioctylamine (TOA), diethyl ether, toluene, chloroform, tetrahydrofuran,
cyclopentylmethyl ether (CPME) and TPPTS were Aldrich products. Alumina was a Chimet S.p.A
product. Thioctic acid was a generous gift of Prochifar s.r.l. (Milan). GC analyses were carried out
on an Agilent 6850 A gas chromatograph (HP1column 30 m × 0.32 mm × 0.25 m) and GC–MS
analyses were performed by using an Agilent MS Network 5937 (HP-5MScolumn 30 m × 0.25 mm
1
13
× 0.25 m). H NMR and C-NMR spectra were recorded on a Bruker Avance 300, using CDCl3
or H2O/D2O as solvent. For TEM analysis one drop of the aqueous solution of each sample was
deposited on the chloroform cleaned carbon coated Cu TEM grid, the solvent was then evaporated
and the sample analyzed by using TEM Tecnai G2 (FEI) operating at 100kV with a 70 mm lens
and with a 2.0A˚ point-to-point resolution. Images were taken using Veleta (Olympus Soft Imaging
System).
2.2. [Rh]/DHTANa preparation
2.2.1 Method A [7]
The precursor of [Rh]/DHTANa (A) was prepared in situ by reacting, at room temperature under a
nitrogen purge, [Rh(COD)Cl]2 (12.4 mg, 0.025 mmol) with a solution of dihydrothioctic acid
1
sodium salt (DHTANa) (10.3 mg, 0.5 mmol) in 5 mL of de-aerated water. H-NMR (H2O/D2O): δ

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3.61 (m, 1H, S-CH), 3.12 (m, 2H, S-CH2), 2.08 (t, J = 7.2 Hz, 2H, CH2-COONa), 1.90-1.78 (m,
2H, HSCH2CH2CHSH), 1.72-1.30 (m, 8H, (CH2)3, 2 SH). The catalytic species [Rh]/DHTANa (A)
was then formed during the hydrogenation reaction.
2.2.2 Method B
50 mg of RhCl3 (0.23 mmol of Rh), 88 mg (0.83 mmol) of Na2CO3 and 10 mL of dry CPME were
introduced in a 150 mL stainless steel autoclave under nitrogen. The autoclave was pressurized with
0.5 Mpa of hydrogen and warmed at 25 °C for 24 hours under stirring. After this time, a solution of
49.7 mg (0.23 mmol) of DHTA, prepared as described above, in 2 mL of CPME was added
followed by 25.3 mg (0.24mmol) of Na2CO3 in 24 mL of de-aerated water; the resulting mixture
was stirred for 24 h at 25 °C under nitrogen atmosphere. The organic phase was removed and the
light gray coloured aqueous phase containing [Rh]/DHTANa (B) was used as such in catalysed
hydrogenation reactions. A sample was analysed by 1H-NMR (H2O/D2O) (Figure 1SP): δ 3.66 (m,
1H, S-CH), 3.18 (m, 2H, S-CH2), 2.43 (m, 1H, HSCH2CH(H)CHSH), 2.12 (t, J = 7.2 Hz, 2H, CH2-
COONa), 1.94 (m, 1H, HSCH2CH(H)CHSH), 1.78-1,45 (m, 6H, (CH2)3), 1.42-1.28 (m, 2H, 2SH).
2.3 General procedure for hydrogenation experiments in the presence of [Rh]/DHTANa
If not otherwise reported (see details in Tables) all the reactions were carried out following a
procedure similar to that below described for [Rh]/DHTANa catalyzed hydrogenation of 1-iodo-4-
nitrobenzene (V).
A 150-mL stainless steel reaction vessel was charged, under a nitrogen purge, with 312 mg (1.25
mmol) of V in 2 mL of toluene, 1 mL of 0.005 M solution of [Rh]/DHTANa , obtained by A or B
procedure, and 2 mL of degassed distilled water. The reactor was then pressurized with hydrogen (4
MPa) and heated at 80°C for 24h. The reactor was then cooled to room temperature, the residual
gases released and the reaction mixture analysed by GC and GC-MS. Before separation of the two

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phases pH of the aqueous phase was checked and restored to initial pH value, if necessary, by
adding an aqueous solution of Na2CO3. The organic phase was separated, the aqueous phase
extracted with toluene (2 x 2mL) and the combined organic solution was finally concentrated under
vacuum to recover the reaction products. The aqueous phase, containing the catalyst, was recovered
and reused for further experiments.
3. Results and Discussion
3.1 Characterization of [Rh]/DTHANa
1H-NMR of catalyst, prepared by method B (Figure 1SP), permits, in our opinion, to have a clear
picture of Rhodium species in aqueous phase. Rhodium seems to be strongly chelated by DTHANa
as demonstrated not only by the shift of signals of hydrogen atoms in S-CH ( δ 3.66 vs 2.92) and S-
CH2 ( δ 3.18 vs 2.60) in [Rh]/DTHANa compared with the free ligand, but especially by the
differentiation of chemical shift of the 2 hydrogen atoms of methylene group HSCH2CH2CHSH ( δ
2.43 and 1.94) vs undifferentiated multiplet, between δ 1.90-1.78, of the same group in the free
ligand and also in the catalyst precursor, obtained by method A before hydrogen treatment, where
Rh-Cl bond should be still present. The identity of the proton signals of this methylene group in
[Rh]/DTHANa was confirmed by decoupling experiments.
TEM images of fresh prepared [Rh]/DTHANa (B), recycled [Rh]/DTHANa (B) and recycled
[Rh]/DTHANa (A) are reported as supplementary material (Figures 2-5SP respectively). No
relevant difference were observed for recycled catalysts prepared with methods A and B to confirm
that, after hydrogen treatment, the catalytic species, which are very reasonably rhodium
nanoparticles stabilized by the thioligand, are equivalent. Slight bigger aggregates were found in
fresh prepared [Rh]/DTHANa (B). It is reasonable considering that Rh(0) particles could aggregate
before the addition of the ligand, even if after the hydrogenation reaction more disperse catalytic
species were found.

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3.2 Catalytic experiments
A first set of hydrogenation experiments was carried out on nitrobenzene (I) as substrate (Scheme
2), by using a 1000/1 substrate to catalyst molar ratio in the aqueous biphasic system H2O/THF, at
80°C and 24h, under different H2 pressure (Table 1).
Insert Scheme 2
Insert Table 1
At 5 MPa of H2, aniline (II) was obtained with 100% yield (Entry 1). Upon decreasing the
hydrogen pressure up to 2 MPa, complete conversion and 99% selectivity to II were achieved
(Entry 2). After extraction of the organic products with diethyl ether, the catalyst, embedded in the
aqueous phase, was used in consecutive experiments; noteworthy, the catalytic activity and
selectivity to II remained almost unchanged even after three recycling experiments (Entries 3-5).
The reduction was also carried out lowering H2 pressure to 1 Mpa but a low conversion (65%) was
observed at the same reaction time (Entry 6). Very poor results were obtained using toluene/water
solvent mixture instead of THF/water (Entry 7). Good results were achieved in THF/water also
using [Rh]/DHTANa prepared by the B procedure and the catalyst remained stable at least for two
recycles (Entries 8-10); less satisfactory conversion resulted in toluene/water (Entry 11). Using
[Rh]/DHTANa prepared by A or B procedure, side reaction products as nitrosobenzene, N-
phenylhydroxylamine, azobenzene and azoxybenzene were undetected or present in negligible
amount (Entries 2-5). For comparison, a reaction was carried out also in the presence of 0.18%
Rh/Al2O3 at the same experimental conditions in THF/water: aniline (II) was obtained with 99%
yield (Entry 12). Furthermore, the recovered heterogeneous catalyst maintained its activity and
selectivity unchanged in a recycle experiment (Entry 13). Surprisingly this heterogeneous catalyst
afforded different reaction products working in toluene/water, being able to hydrogenate also the
aromatic ring (entry 14).

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Later it was decided to explore the reduction of 1-chloro-3-nitrobenzene (III) and of 1-iodo-4-
nitrobenzene (V) to check the selectivity of the catalysts towards two different reactive groups.
Water soluble [Rh]/DHTANa showed good activity and high selectivity also working in the
hydrogenation of both III (Scheme 3) and V (Scheme 4).
Insert Scheme 3
Insert Table 2
In these experiments on substrate III, carried out in water/toluene at 80°C and 4 MPa of H2 for 24 h
and by using a 500/1 substrate to catalyst molar ratio, [Rh]/DHTANa, prepared by A or B method,
afforded the same results (Entries 1 and 5, Table 2); product IV was recovered with high yield and
selectivity and the catalyst was recycled three times without any relevant activity change (Entries
1-4, 5-8). On the contrary, the heterogeneous catalyst 0.18% Rh/Al2O3 was less selective affording
also 15-17% of dehalogenated side product II; however the catalyst activity and recyclability were
good (Entries 9 and 10).
Insert Scheme 4
Insert Table 3
In the case of a more demanding reaction, i.e. the reduction of compound V, in the aqueous biphasic
system H2O/toluene, at 60 °C and 4 Mpa H2 for 24 h and by using a 500/1 substrate to catalyst
molar ratio, a 85 % substrate conversion to VI was obtained and no dehalogenation was observed
(Entry 1, Table 3). Noteworthy, upon increasing the reaction temperature at 80 °C a quantitative
conversion was found and VI was recovered with 97% yield, being the side product II formed in a
very small amount (Entry 2). The catalyst, embedded in the aqueous phase, was recovered after the
separation of the organic phase and used in two recycle experiments. It was observed that a slight

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change in the pH occurred due to the formation of HI and a lower activity but similar selectivity
was found (unreported data); by restoring the initial pH adding the requested amount of Na2CO3
good results were obtained (Entries 3,4,6,7). As a possible explanation of the results observed
without any correction of pH, we can assume that some changes in the catalyst structure occur. As
a matter of fact, the isolated dried solid [Rh]/DHTANa , obtained by evaporation of water under
1
vacuum, was solubilized in CDCl3 : after carefully addition of a drop of conc. HCl, its H-NMR
showed a complex pattern spectrum where, besides the peaks tributable to the starting catalytic
species, some other signals were present(Figure 5SP). It is reasonable to assume that other species
are formed, probably due to the fact that the interaction of thiol groups and Rh species was partially
broken .
Also 0.18 % Rh/Al2O3 was investigated in the hydrogenation of V at the above reaction conditions:
disappointingly, the main product (60%) was aniline (II) (Entry 8). The catalyst maintained its
activity also in a recycle experiment but, again, aniline was the prevailing product (Entry 9). The
best result was obtained at 60°C and 1 MPa of H2: substrate conversion was complete and the
iodoaniline VI was obtained with 86% yield (Entry 11). Maybe milder reaction conditions should
be required to try to improve further the selectivity to the desired compound VI. Unfortunately the
recycle of this catalyst gave a very poor result (Entry 12). Finally, [Rh]DHTANa was compared
also to the well-known water soluble [Rh]/TPPTS complex: this catalytic system was very active
affording a total substrate conversion but aniline (II) was the only reaction product (Entries 13-15).
Moreover, the catalyst, at the reaction conditions adopted, strongly decomposed with formation of
rhodium black, so hampering any catalyst recycling.
4. Conclusions
The water soluble [Rh]-thioligand species, i.e., [Rh]/DHTANa, showed an interesting catalytic
activity, excellent selectivity and good recyclability not only in the reduction of nitrobenzene but
especially in the hydrogenation of some valuable aromatic halo-nitro compounds. Its preparation

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was made simpler and cheaper than the previous reported one [7], without affecting its reactivity,
stability and recyclability characteristics. At the light of these results [Rh]/DHTANa seems a good
choice for the selective reduction of the nitro group when also a halo group is present in the same
molecule [10].
Acknowledgment
Funds for this research were given by Ca’Foscari University of Venice and by Studio di Consulenza
Scientifica. VDR thanks the Ministry of Education of the Italian Government (MIUR) for his PhD
grant. The authors are grateful to Dr. Laura Sperni (Ca’ Foscari University of Venice) for GC–MS
analyses.
References
[1] B. Cornils, W.A. Herrmann, I.T. Horvath, W. Leitner, S. Mecking, H. Olivier-Bourbigou, D.
Vogt (Eds.), Multiphase Homogeneous Catalysis, Wiley-VCH, Weinheim, 2005.
[2] F. Joò (Ed.), Aqueous Organometallic Catalysis, Kluwer Acad. Publ., Dordrecht,2001.
[3] B. Cornils, W.A. Herrmann (Eds.), Aqueous-Phase Organometallic Catalysis, 2nded., Wiley-
VCH, Weinheim, 2004.
[4] C. Bertucci, C. Botteghi, D. Giunta, M. Marchetti, S. Paganelli, Adv. Synth. Catal. 344 (2002)
556–562
[5] M. Marchetti, F. Minello, S. Paganelli, O. Piccolo, Appl. Catal. A: Gen. 373 (2010)76–80.
[6] S. Di Dio, M. Marchetti, S. Paganelli, O. Piccolo, Appl. Catal. A: Gen. 399 (2011) 205–210

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[7] S. Paganelli, O. Piccolo, P. Pontini, R. Tassini, V.D. Rathod, Catalysis Today, 247 (2015) 64-
69.
[8] O. Piccolo, A. Verrazzani, US 7087548 (2006)
[9] O. Piccolo, S. Paganelli, R. Tassini, V.D. Rathod, B. Onida, S. Fiorilli, 6th Int. Confer. on Green
and Sustainable Chemistry (GSC 6), Nottingham (UK) (2013), O 16
[10] H. K. Kadam, S. G. Tilve, RSC Adv., 5 (2015) 83391-83407.

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O
O
NaBH4
HS
OH
OH
S
S
SH
THA
DHTA
Scheme 1. Reduction of thioctic acid (TA) into dihydrothioctic acid (DHTA)
Scheme 2. Reduction of nitrobenzene (I)
Scheme 3. Reduction of 1-Chloro-3-nitrobenzene (III)

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Scheme 4 . Reduction of 1-Iodo-4-nitrobenzene (V)

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Table 1. Reduction of nitrobenzene (I)
Entry Catalyst (prep. method)a p(H2) (MPa) Conv. (%) II (%)
1
2
[Rh]/DHTANa (A)
[Rh]/DHTANa (A)
1° recycling
5
2
2
2
2
1
2
2
2
2
2
2
2
2
>99
>99
>99
>99
>99
65
>99
99
3b
98
4b
2° recycling
99
5b
3° recycling
97
6
[Rh]/DHTANa (A)
[Rh]/DHTANa (A)
[Rh]/DHTANa (B)
1° recycling
65
7c
27
27
8
>99
>99
90
>99
>99
90
9b
10b
11c
12d
13b
14e
2° recycling
[Rh]/DHTANa (B)
0.18%Rh/Al2O3
1° recycling
53
53
>99
>99
>99
99
99
0.18%Rh/Al2O3
-- f
Reaction conditions: substrate (I) = (0.62 g, 5 mmol); [Rh]/DHTANa 0.005M solution (1 mL),
a
(substrate I/ Rh molar ratio 1000/1); THF = 2 mL; H2O = 2 mL; T= 80°C; t = 24h. According to
paragraphs 2.2.1 and 2.2.2. b Reaction carried out by using the catalyst recovered from the previous
c
run. Toluene = 2 mL; H2O = 2 mL. d Substrate (I) = (0.62 g, 5 mmol); Rh/Al2O3 0.18 % (0.29 g),
e
(substrate I /Rh molar ratio = 1000/1); THF = 2 mL; H2O = 2 mL; T= 80°C; t = 24h. Toluene = 2
mL; H2O = 2 mL. f Product mixture: 73% cyclohexylamine and 27% dicyclohexylamine.

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Table 2. Reduction of 1-chloro-3-nitrobenzene (III)
Entry Catalyst (prep. method)a Conv.(%) IV (%) II (%)
1
2b
3b
4b
5
[Rh]/DHTANa (A)
1° recycle
>99
>99
98
>99
>99
98
-
-
2° recycle
-
3° recycle
99
99
-
[Rh]/DHTANa (B)
1° recycle
>99
>99
>99
99
>99
>99
99
-
6b
7b
8b
9c
10b
-
2° recycle
1
-
3° recycle
99
0.18%Rh/Al2O3
1° recycle
98
81
17
15
90
75
Reaction conditions: substrate (III) = (0.395 g, 2.5 mmol); [Rh]/DHTANa 0.005M solution (1 mL), (substrate III/ Rh
a
molar ratio 500/1); Toluene = 2 mL; H2O = 2 mL; T= 80°C; p(H2) = 4 MPa; t = 24h. According to paragraphs 2.2.1
and 2.2.2. bReaction carried out by using the catalyst recovered from the previous run; c Substrate (III) = (0.395 g, 2.5
mmol); 0.18 % Rh/Al2O3 (0.29 g), (substrate III / Rh molar ratio = 500/1); Toluene = 4 mL.

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Table 3. Reduction of 1-iodo-4-nitrobenzene (V)
Entry Catalyst (prep. method)a p(H2) (MPa) Conv. (%) VI (%) II (%)
1b
2
[Rh]/DHTANa (A)
[Rh]/DHTANa (A)
1° recycle
4
4
4
4
4
4
4
4
4
4
1
1
4
4
1
85
85
97
98
95
>99
99
96
38
40
78
86
15
-
-
2
>99
>99
>99
>99
>99
>99
97
3c
2
4c
2° recycle
5
5
[Rh]/DHTANa (B)
1° recycle
-
6c
1
7c
2° recycle
4
8d
0.18%Rh/Al2O3
1° recycle
60
57
22
14
6
9c
97
10e
11f
12c
13g
14h
15i
0.18% Rh/Al2O3
0.18% Rh/Al2O3
1° recycle
>99
>99
21
[Rh]/TPPTS
[Rh]/TPPTS
[Rh]/TPPTS
>99
>99
>99
>99
>99
>99
-
-
Reaction conditions: substrate (V) = (0.31 g, 1.25 mmol); [Rh]/DHTANa 0.005M solution (1 mL), (substrate V/Rh molar ratio
500/1); Toluene = 2 mL; H2O = 2 mL; T= 80°C; t = 24h. a According to paragraphs 2.2.1 and 2.2.2. b T= 60°C. c Reaction carried
out by using the catalyst recovered from the previous run. d Substrate (V) = (0.31 g, 1.25 mmol); 0.18 % Rh/Al2O3 (0.29 g)
(substrate V/Rh molar ratio = 500/1); Toluene = 4 mL; T= 60°C; t = 24h. e T = 80°C; t = 5h. f T= 60°C; t = 5h. g Reaction
conditions for experiments catalyzed by [Rh/TPPTS]: substrate (V) = (0.62 g, 2.5 mmol); [Rh(COD)Cl]2 = (0.00124 g, 0.0025
mmol), (substrate V/Rh molar ratio 500/1); TPPTS (triphenylphosphine-3,3’,3’’-trisulfonic acid trisodium salt) = (0.0085 g, 0.015
mmol), (Rh/TPPTS molar ratio 1/3); Toluene = 3 mL; H2O = 3 mL; T= 80°C; t = 24h. h Addition of 0.265 g (2.5 mmol) of
Na2CO3 ; i T= 60°C; t = 24h.

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Graphical abstract

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Highlights
[Rh]/DHTANa, a water-soluble catalyst.
[Rh]/DHTANa is suitable for selective hydrogenation of halonitro arenes.
[Rh]/DHTANa is easily recovered and reused with similar activity and selectivity.
New preparation of [Rh]/DHTANa is simple and greener.
[Rh]/DHTANa does not cause hydrogenolysis of carbon-halogen bond.