Synthesis, characterization and catalytic activity of gold complexes with pyridine-based selone ligands

Article abstract of DOI:10.1016/j.ica.2016.06.023

Three neutral pyridine-based selone compounds, 2,6-bis(1-methylimidazole-2-selone)pyridine (Bmsp), 2,6-bis(1-ethylimidazole-2-selone)pyridine (Besp) and 2,6-bis(1-isopropylimidazole- 2-selone)pyridine (Bpsp) have been synthesized and characterized. Reactions of HAuCl₄ with pyridine-based selone ligands result in the formation of the complexes [Au(L)Cl₂]⁺[AuCl₂]^- (L = Bmsp (1); L = Besp (2) and L = Bpsp (3)), respectively. All compounds have been characterized by elemental analysis, NMR IR spectra and electrospray ionization mass spectroscopic (ESI-MS). The molecular structure of 2 has been determined by X-ray crystallography. Moreover, the gold complexes are efficiently catalyzed nitroarenes reduction to aromatic amines in the presence of sodium tetrahydroborate reducing agent in water.

Full text of DOI:10.1016/j.ica.2016.06.023

Inorganica Chimica Acta 450 (2016) 315–320
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Synthesis, characterization and catalytic activity of gold complexes
with pyridine-based selone ligands
⇑
Hai-Ning Zhang, Wei-Guo Jia , Qiu-Tong Xu, Chang-Chun Ji
College of Chemistry and Materials Science, Center for Nano Science and Technology, The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory
of Molecular-Based Materials, Anhui Normal University, Wuhu 241000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 April 2016
Received in revised form 26 May 2016
Accepted 10 June 2016
Available online 11 June 2016
Three neutral pyridine-based selone compounds, 2,6-bis(1-methylimidazole-2-selone)pyridine (Bmsp),
2,6-bis(1-ethylimidazole-2-selone)pyridine (Besp) and 2,6-bis(1-isopropylimidazole- 2-selone)pyridine
(Bpsp) have been synthesized and characterized. Reactions of HAuCl4 with pyridine-based selone ligands
result in the formation of the complexes [Au(L)Cl2]+[AuCl2]À (L = Bmsp (1); L = Besp (2) and L = Bpsp (3)),
respectively. All compounds have been characterized by elemental analysis, NMR IR spectra and electro-
spray ionization mass spectroscopic (ESI-MS). The molecular structure of 2 has been determined by X-ray
crystallography. Moreover, the gold complexes are efficiently catalyzed nitroarenes reduction to aromatic
amines in the presence of sodium tetrahydroborate reducing agent in water.
Keywords:
Selone
Gold
Complex
Catalyst
Reduction
Ó 2016 Elsevier B.V. All rights reserved.
1. Introduction
Imidazoline-2-chalcogenone ligands NHC = E (NHC = N-hetero-
cyclic carbene, E = S, Se) are good
r-donors and weak p-acceptors
Functionalized anilines are important structural motifs that are
found in a variety of agrochemicals, dyes, pharmaceuticals, and
pigments and other industrially useful products [1–6]. Therefore,
a variety of protocols for synthesizing functionalized anilines have
been developed [7–19]. The desirable method for the synthesis of
functionalized anilines is the reduction of nitroarenes using transi-
tion metal catalysts in the presence of sodium tetrahydroborate
(NaBH4) [20]. A number of homogeneous and heterogeneous cata-
lysts have also been reported as viable catalysts for this hydrogena-
tion. Heterogeneous gold catalysts have become an important
topic since the 1980s [21], since 2000 homogeneous gold catalysis
has become a highly active field [22,23]. Furthermore, occasionally
reactions typically catalyzed by homogeneous catalysts have also
been reported to be catalyzed by heterogeneous catalysts [24],
and occasionally reaction typically catalyzed by heterogeneous
catalysts have also been reported to be catalyzed by homogeneous
gold(III) complexes [25]. Gold-based catalysts supported by metal
oxides (such as TiO2, Fe2O3, Fe3O4, SiO2 and Al2O3) [26–32], carbon
nanotube [33], polymer [34,35], graphene oxide [36], and gold
complexes [37–40] are all good candidate for the hydrogenation
of nitroarenes due to their high catalytic activities.
which can be easily modified using appropriate available NHC pre-
cursors to attain the desired steric-bulk or electronic properties
[41–43]. Reports about transition metal complexes with imidazo-
line-2-chalcogenone ligands have been reported within past few
years [44–49]. And the catalytic activities of these complexes are
comparable with the most efficient metal-NHC complexes for
organic transformation [50–52]. However, the transition metal
complexes with selone ligands are reported rarely due to difficulty
in synthesis, handing and malodorous nature of the organosele-
nium ligands [46]. Continuing our research interests in imidazo-
line-2-chalcogenone metal complexes for their rich chemistry
[53–56], we try to prepare the gold complexes with pyridine-based
[57,58] selone ligands and hope to exploit their catalytic applica-
tions in hydrogenation of nitroarenes.
Herein, we report the synthesis and characterization of
three gold complexes with pyridine-based selone compounds:
[Au(L)Cl2]+[AuCl2]À (L = Bmsp (1), Bmsp = 2,6-bis(1-methylimida-
zole-2-selone)pyridine; L = Besp (2), Besp = 2,6-bis(1-ethylimida-
zole-2-selone)pyridine
and
L = Bpsp
(3),
Bpsp = 2,6-bis
(1-isopropylimidazole-2-selone)pyridine), and further examine
their catalytic ability in direct nitroarenes reduction to aromatic
amines in the presence of NaBH4 reducing agent in water. Our
preliminary results indicate that gold complexes show promising
catalytic activities in nitroarenes reduction reaction. The
elucidation of solid state structure of the gold complex 2 was also
obtained through single crystal X-ray diffraction.
⇑
Corresponding author.
E-mail address: wgjiasy@mail.ahnu.edu.cn (W.-G. Jia).
http://dx.doi.org/10.1016/j.ica.2016.06.023
0020-1693/Ó 2016 Elsevier B.V. All rights reserved.

316
H.-N. Zhang et al. / Inorganica Chimica Acta 450 (2016) 315–320
pyridine dibromide (220.4 mg, 0.5 mmol), Se (94.8 mg, 1.2 mmol),
2. Experimental
K2CO3 (165.9 mg, 1.2 mmol). Yield: (245 mg 55%) (based on 2,6-bis
(isopropyllimidazolium)pyridine dibromide). Anal. Calcd. for
2.1. Materials and physical measurements
C
17H21N5Se2 (455.01): C, 44.83; H, 4.65; N, 15.39. Found: C,
44.88; H, 4.62; N, 15.36. 1H NMR (300 MHz, CDCl3): d 8.82 (d,
J = 8 Hz, pyridine, 2H), 8.04 (t, pyridine, 1H), 7.58 (d, J = 3 Hz,
imidazole, 2H), 7.02 (d, J = 3 Hz, imidazole, 2H), 5.39 (m, 2CH,
2H), 1.45 (d, J = 6 Hz, 4CH3, 12H). 13C NMR (500 MHz, CDCl3): d
155.30, 149.39, 139.72, 119.96, 119.93, 119.79, 119.7, 51.36,
22.28, 22.25 ppm. IR (KBr, cmÀ1): 3175 (w), 3132 (w), 3094 (w),
2970 (w), 2866 (w), 1666 (w), 1598 (m), 1572 (m), 1456 (s),
1416 (m), 1400 (m), 1385 (w), 1368 (w), 1337 (m), 1327 (w),
1277 (m), 1225 (s), 1153 (w), 1134 (w), 1113 (m), 1047 (w),
1018 (w), 991 (w), 883 (w), 835 (w), 804 (m), 781 (m), 718 (m),
685 (w), 664 (m), 584 (w), 554 (w), 500 (w).
Commercial reagents were analytical grade and used as received
from Aladdin and Energy chemical. All manipulations were carried
out under nitrogen using standard schlenk and vacuum-line tech-
niques. All solvents were purified and degassed by standard proce-
dures. The starting materials 2,6-bis(1-methylimidazolium)
pyridine dibromide, 2,6-bis(1-ethylimidazolium)pyridine dibro-
mide and 2,6-bis(1-isopropylimidazolium)pyridine dibromide
were synthesized according to the procedures described in the lit-
erature [55]. All catalytic reactions were monitored by TLC using
0.25 mm silica gel plates with UV indicator (60F-254). 1H and 13C
NMR were recorded on a 300 MHz or 500 MHz NMR spectrometer
at room temperature. IR spectra were recorded on a Niclolet
AVATAR-360IR spectrometer. Element analyses were performed
on an Elementar III vario EI Analyzer. Mass spectra were obtained
with MicroTof (Bruker Daltonics, Bremen, Germany) spectrometers.
2.5. Synthesis of complex [Au(Bmsp)Cl2][AuCl2] (1)
In a 25 mL Schlenk tube were placed with Bmsp (59.55 mg,
0.15 mmol), HAuCl4 (132 mg, 0.32 mmol), 5 mL methanol as sol-
vent. The mixture was stirred at room temperature overnight
and then the solvent was removed with a rotary evaporator; the
resulting solid was washed with methanol and diethyl ether, and
then dried in vacuo. The product was recrystallized from MeCN/
CH2Cl2 to give brown deep-red powder. Yield: (67.5 mg, 45%)
2.2. Synthesis of Bmsp
In a 25 mL Schlenk tube were placed with 2,6-bis(1-methylimi-
dazolium)pyridine dibromide (201.5 mg, 0.5 mmol), Se (94.8 mg,
1.2 mmol), K2CO3 (165.9 mg, 1.2 mmol) and 6.0 mL methanol as
solvent. The mixture was allowed to reflux for 12 h after which
the methanol was removed with a rotary evaporator. The remaining
solid was shaken with 3 Â 10 mL CH2Cl2 which was then filtered
and rotary evaporated. The product was recrystallized from
CH2Cl2/MeOH to give white solid. Yield: (258 mg 65%) (based on
2,6-bis(1-methylimidazolium)pyridine dibromide). Anal. Calcd.
for C13H13N5Se2 (397.20): C, 39.10; H, 3.28; N, 17.77. Found: C,
39.15; H, 3.30; N, 17.58. 1H NMR (300 MHz, CDCl3): d 8.90 (d,
J = 8 Hz, pyridine, 2H), 8.05 (t, pyridine, 1H), 7.54 (d, J = 3 Hz, imida-
zole, 2H), 6.92 (d, J = 3 Hz, imidazole, 2H), 4.52 (s, 2CH3, 6H). 13C
NMR (500 MHz, CDCl3): d 156.72, 149.40, 140.15, 120.95, 119.18,
118.97, 37.86 ppm. IR (KBr, cmÀ1): 3358 (w), 3281 (w), 3188 (w),
3165 (w), 3130 (w), 3099 (w), 1666 (w), 1624 (vs), 1571 (m),
1471 (vs), 1448 (s), 1395 (m), 1369 (m), 1290 (m), 1236 (m),
1121 (w), 1074 (w), 985 (w), 874 (w), 797 (m), 671 (w), 555 (w).
(based on Bmsp ligand). Anal. Calcd. for
C13H13Au2Cl4N5Se2
(932.94): C, 16.74; H, 1.40; N, 7.51. Found: C, 16.77; H, 1.16; N,
7.50. 1H NMR (300 MHz, CD3OD): d 8.52 (t, pyridine, 1H), 8.17 (d,
J = 2 Hz, pyridine, 2H), 7.95 (d, J = 6 Hz, imidazole, 2H), 7.70 (d,
J = 2 Hz, imidazole, 2H), 4.25 (s, 6H). 13C NMR (500 MHz, CD3OD):
d 148.06, 143.98, 138.89, 125.57, 124.02, 121.55, 38.5. ppm. ESI-MS
(positive ions) for [Au(Bmsp)]3+: m/z 595.9160 (calcd for [Au
(Bmsp)]3+ 595.9167). IR (KBr, cmÀ1): 3421(w), 2943(w), 1816(w),
1672(m), 1627(s), 1562(m), 1508(w), 1476(s), 1440(m), 1408(w),
1379(w), 1300(w), 1238(m), 1138(w), 986(w), 878(w), 802(w),
734(w), 551(w), 501(w).
2.6. Synthesis of complex [Au(Besp)Cl2][AuCl2] (2)
Prepared by the same procedure as described above for 1, using
Besp (49.65 mg, 0.15 mmol) and HAuCl4 (132 mg, 0.32 mmol).
Yield: (77.3 mg, 50%) (based on Besp ligand). Anal. Calc. for C15H17
-
2.3. Synthesis of Besp
Au2Cl4N5Se2 (961.00): C, 18.75; H, 1.78; N, 7.29. Found: C, 18.72; H,
1.71; N, 7.22. 1H NMR (300 MHz, CD3OD) d 8.51 (t, pyridine,1H),
8.20 (d, J = 2 Hz, imidazole, 2H), 8.08 (d, J = 2 Hz, imidazole,2H),
7.97 (d, J = 2 Hz, pyridine, 2H), 4.70–4.72 (m, 4H, CH2), 1.60
(t, 2CH3, 6H). 13C NMR (500 MHz, CD3OD) d 148.08, 146.59,
143.99, 124.64, 123.90, 122.09, 47.19, 13.95. ESI-MS (positive ions)
for [Au(Besp)]3+: m/z 623.9461 (calcd for [Au(Besp)]3+ 623.9480).
IR (KBr, cmÀ1): 3395 (w), 3138 (w), 3070 (w), 2976 (w), 2929
(w), 2868 (w), 1732 (w), 1627 (w), 1597 (w), 1554 (w), 1458 (s),
1431 (m), 1398 (w), 1352 (w), 1301 (w), 1267 (m), 1221 (m),
1134 (w), 1088 (w), 1043 (w), 995 (w), 954 (w), 814 (w), 775
(w), 735 (w), 679 (w), 544 (w), 501 (w).
The synthesis procedure was similar to the ligand Bmsp to
afford the white solid Besp, using 2,6-bis(1-ethylimidazolium)pyr-
idine dibromide (217 mg, 0.5 mmol), Se (94.8 mg, 1.2 mmol),
K2CO3 (165.9 mg, 1.2 mmol). Yield: (213 mg 50%) (based on 2,6-
bis(1-ethylimidazolium)pyridine dibromide). Anal. Calcd. for
C15H17N5Se2 (426.98): C, 42.16; H, 4.01; N, 16.40. Found: C,
42.20; H, 4.05; N, 16.36. 1H NMR (300 MHz, CDCl3): d 8.86 (d,
J = 8 Hz, pyridine, 2H), 8.12 (t, pyridine, 1H), 7.57 (d, J = 3 Hz,
imidazole, 2H), 6.98 (d, J = 3 Hz, imidazole, 2H), 4.26 (m, 2CH2
4H), 1.46 (t, 2CH3, 6H). 13C NMR (500 MHz, CDCl3): d 155.73,
149.39, 139.91, 119.60, 119.35, 119.15, 45.34, 14.60 ppm. IR (KBr,
cmÀ1): 3177 (w), 3140 (w), 3097 (w), 2965 (w), 2864 (w), 1647
(w), 1605 (s), 1576 (m), 1533 (w), 1464 (s), 1408 (s), 1392 (s),
1354 (w), 1303 (m), 1281 (s), 1258 (s), 1223 (s), 1155 (m), 1134
(m), 1115 (m), 1076 (w), 1040 (w), 995 (w), 985 (w), 966 (w),
949 (m), 903 (w), 802 (s), 800 (s), 785 (m), 773 (m), 735 (w),716
(m), 688 (w), 655 (m), 599 (w), 509 (w).
2.7. Synthesis of complex [Au(Bpsp)Cl2][AuCl2]À (3)
Prepared by the same procedure as described above for 1, using
Bpsp (68.0 mg, 0.15 mmol) and HAuCl4 (132 mg, 0.32 mmol).
Yield: (87.3 mg, 55%) (based on Bpsp ligand). Anal. Calc. for C17H21
-
Au2Cl4N5Se2 (989.05): C, 20.64; H, 2.14; N, 7.08. Found: C, 20.70; H,
2.18; N, 7.15. 1H NMR (300 MHz, CD3OD) d 8.53 (t, pyridine, 1H),
8.25 (d, J = 2 Hz, imidazole, 2H), 8.12 (d, J = 2 Hz, imidazole, 2H),
7.99 (d, pyridine, 2H), 5.48 (m, CH, 2H), 1.57 (d, CH3, 6H), 1.28
(d, CH3, 6H). 13C NMR (500 MHz, CD3OD) d 148.08, 144.47,
137.10, 124.93, 121.99, 121.42, 54.40, 21.64, 21.00. ESI-MS
2.4. Synthesis of Bpsp
The synthesis procedure was similar to the ligand Bmsp to
afford the white solid Bpsp, using 2,6-bis(isopropyllimidazolium)

H.-N. Zhang et al. / Inorganica Chimica Acta 450 (2016) 315–320
317
(positive ions) for [Au(Bpsp)]3+: m/z 651.9778 (calcd for [Au
Table 2
(Bpsp)]3+ 651.9793). IR (KBr, cmÀ1): 3180 (w), 3134 (w), 3096
(w), 2976 (w), 2875 (w), 1672 (w), 1598 (s), 1573 (m), 1456 (s),
1416 (m), 1400 (m), 1385 (w), 1369 (w), 1337 (m), 1329 (w),
1311 (w), 1277 (m), 1224 (s), 1155 (w), 1136 (w), 1114 (m),
1069 (w), 1047 (w), 1022 (w), 991 (w), 889 (w), 843 (w), 804
(m), 787 (m), 718 (m), 685 (w), 664 (m), 590 (w), 559 (w), 503 (w).
Selected bond distances and angles for complex 2.
Bond distance (Å) in 2
Au(1)-Se(1)
Au(1)-Cl(1)
Au(2)-Cl(3)
Se(1)-C(3)
2.4391(6)
2.3496(15)
2.2491(3)
1.8882(6)
Au(1)-Se(2)
Au(1)-Cl(2)
Au(2)-Cl(4)
Se(2)-C(13)
2.4427(6)
2.3279(17)
2.2540(2)
1.8862(5)
Bond angle (deg) in 2
Se(1)-Au(1)-Cl(1)
Se(2)-Au(1)-Cl(1)
Cl(1)-Au(1)-Cl(2)
Cl(3)-Au(2)-Cl(4)
176.24(4)
90.94(5)
90.97(6)
177.22(9)
Se(1)-Au(1)-Cl(2)
Se(2)-Au(1)-Cl(2)
Se(1)-Au(1)-Se(2)
91.21(5)
175.56(5)
87.10(2)
2.8. General procedure for the reduction of nitroarenes to anilines
using gold catalysts
Gold complex (0.01 mmol, 0.02 equiv) was dissolved in water
(2.0 mL), then appropriate nitroarenes (0.5 mmol, 1.0 equiv) and
NaBH4 (2 mmol, 4.0 equiv) was added. Subsequently, the resulting
mixture was stirred at room temperature. After completion of the
reaction (monitored by TLC), the crude reaction mixture was
extracted with EtOAC (3 Â 2 mL). After solvents were removed in
vacuo from combined organic extracts, the crude products loaded
directly onto a column of silica gel and purified by column chro-
matography to give the corresponding products [59–61].
air and moisture in the solid state, and were soluble in common
organic solvents such as CH2Cl2, CHCl3 and THF. All compounds
were characterized by elemental analysis, NMR IR spectra as well
as electrospray ionization mass spectroscopic (ESI-MS). The 1H
NMR spectrum of Bmsp show signals at d 4.52, 6.92, 7.54, 8.05
and 8.90 ppm, which can be assigned to the methyl, imidazole,
and pyridyl groups, respectively. And the 13C NMR spectra show
singlet at about d 156.72 ppm for C = Se group in Bmsp, which also
prove the formation of the selone compound.
The mononuclear mixed-valent gold complexes [Au(L)Cl2]
[AuCl2]À (L = Bmsp (1); L = Besp (2) and L = Bpsp (3)) were
obtained by reacting HAuCl4 with three pyridine-based selone
ligands in MeOH at room temperature respectively (Scheme 2).
All gold complexes were confirmed by IR, NMR spectroscopy as
well as elemental analyses. The gold complexes are air and mois-
ture stable in the solid state, soluble in MeOH, MeCN, DMSO sol-
vents but slightly soluble in chlorohydrocarbon. The 13C NMR
chemical shift values for the C = Se group were comparable
(d 148.06 ppm (1), 148.08 ppm (2) and 148.08 ppm (3), respec-
tively) in comparison with free selone compounds.
2.9. X-ray crystallography for 2
Diffraction data of complex 2 was collected on a Bruker Smart
CCD diffractometer with graphite-monochromated MoKa radiation
(k = 0.71073 Å). All the data were collected at room temperature
and the structure was solved by direct methods and subsequently
refined on F2 by using full-matrix least-squares techniques
(SHELXL) [62], and SADABS absorption corrections [63] applied to
the data. The crystallographic data for complex 2 are summarized
in Table 1, and selected bond lengths and angles are shown in
Table 2.
Positive-ion electrospray ionization mass spectroscopic
(ESI-MS) studies further supported the formation of gold complex.
For example, the ESI-MS spectrum for [Au(Bmsp)Cl2][AuCl2]
showed peaks at m/z 595.9160, corresponding to [Au(Bmsp)]3+
(calcd for [Au(Bmsp)]3+ 595.9167).
3. Result and discussions
Pyridine-based selone compounds: 2,6-bis(1-methylimidazole-
2-selone)pyridine (Bmsp), 2,6-bis(1-ethylimidazole-2-selone)pyri-
dine (Besp) and 2,6-bis(1-isopropylimidazole- 2-selone)pyridine
(Bpsp) were prepared in one-pot via the reactions of pyridine
bridged imidazolium dibromide derivatives with selenium powder
in the presence of K2CO3 with moderate yields (50%) (Scheme 1)
[55]. All these compounds were thermally stable and inert toward
3.1. Structural description of [Au(Besp)Cl2][AuCl2] (2)
Crystal suitable for X-ray crystallography of 2 was obtained by
slow diffusion of hexane into concentrated solution of the complex
in acetonitrile solution. The molecular structure of 2 is solved in
the monoclinic crystal system and P2(1)/c space group. As can be
seen in Fig. 1, the coordination geometry of the central gold center
can be best described as a nearly square-planar geometry with two
Cl atoms and two Se atoms (Se(1)-Au(1)-Se(2) 87.10(2)°, Se(1)-Au
(1)-Cl(1) 176.24(4)°, Se(1)-Au(1)-Cl(2) 91.21(5)°, Se(2)-Au(1)-Cl(1)
90.94(5)°, Se(2)-Au(1)-Cl(2) 175.56(5)° and Cl(1)-Au(1)-Cl(2) 90.97
(6)°). Both selenium atoms and two chlorine atoms of Bptp ligand
adopt a cis disposition. Au-Clav average bond distance (2.338 Å) is
within the range normally found for Au-Cl bonds in Au(III) com-
plexes [64,65]. Bond distances around the gold ion with selenium
Table 1
Crystallographic data and structure refinement parameters for complex 2.
2
Empirical formula
Formula weight
Crystal syst., Space group
a (Å)
b (Å)
c (Å)
C15H17Au2Cl4N5Se2
960.99
Monoclinic, P2(1)/c
13.0360(7)
15.1772(8)
11.7753(6)
92.105(1)
2328.2(2), 4
2.742
16.187
b (°)
Volume (Å3), Z
Dc (mg/m3)
l
(Mo-K
a
) (mmÀ1
)
F(0 0 0)
1744
h range (°)
Limiting indices
Reflections/unique[R(int)]
Completeness to h (°)
1.563–27.499
À15, 16, À19, 19, À15, 14
19587/5254 [0.0384]
27.49 (98.2%)
5254/0/253
1.018
0.0312, 0.0747
0.0411, 0.0787
2.12/À1.82
Data/restraints/parameters
Goodness-of-fit on F2
R1, wR2 [I > 2
r
(I)]a
R1, wR2 (all data)
Larg. diff. peak/hole (e/ÅÀ3
)
a
R1
=
R
||Fo| À |Fc||/
R
|Fo|; wR2 = [
R
w(|F2o| À |F2c|)2/
R .
w|F2o|2]1/2
Scheme 1. Synthesis of pyridine-based selone ligands.

318
H.-N. Zhang et al. / Inorganica Chimica Acta 450 (2016) 315–320
Table 3
Screening of gold catalysts for 4-nitroanisole reduction.a,b
NO2
NH2
Gold catalysts 2 mol%
NaBH4, Water, RT
OMe
OMe
Entry
Catalyst
HAuCl4
Solvent
H2O
Time (h)
Yield (%)
Scheme 2. Synthesis of gold complexes (1–3) with pyridine-based selone ligands.
1
2
3
3
12
50
[(bmtp)AuCl2]Cl
H2O
3
[(betp)AuCl2]Cl
H2O
3
53
4
[(bptp)AuCl2]Cl
H2O
3
65
5
6
7
8
[(bmsp)AuCl2]AuCl2 (1)
[(besp)AuCl2]AuCl2 (2)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
[(bpsp)AuCl2]AuCl2 (3)
None
H2O
H2O
H2O
3
3
3
6
6
6
6
6
2.5
1
15
48
6
83
85
95
95
20
15
10
10
95
99
90
87
EtOH
DCM
DMSO
DMF
MeCN
H2Oc
H2Od
H2Oe
H2Of
H2Og
9
10
11
12
13
14
15
16
17
No reaction
a
Reaction conditions: 0.5 mmol nitrobenzene, 2.0 mmol sodium tetrahydrobo-
rate, gold catalysts (2 mol%), water (2 mL), room temperature.
b
Isolated yield.
30 °C.
80 °C.
Complex 3, 1 mol%.
Complex 3, 0.5 mol%.
No catalysts.
Fig. 1. Crystal structure of [(Besp)AuCl2][AuCl2], hydrogen atoms are omitted for
clarity.
c
d
e
f
g
(Au-Seav = 2.441 Å) are comparable to the distances observed in the
gold complexes containing selone ligands [66–68]. The Au-Se dis-
tances (2.4391(6) and 2.4427(6) Å) in complex 2, which are longer
than those of in Au(I) complex [AuCl(SeUr)] (Ur = NHC-derived
selenoureas ligands) (2.353–2.398 Å) [67] and [Au2{SeC6H4(CH2-
(7)Á Á ÁCl(4) = 154° and C(11)Á Á ÁCl(4) = 3.5417(1) Å; C(11)AH(11)Á Á Á
Cl(4) = 134°], which play crucial roles in the construction of 1D
network structure in the solid states.
NMe2)-2}2(l-dppf)] (2.4245(5) and 2.4250(8) Å) [68].
As shown in the Fig. 2, there are two forms of gold in 2 unit cell.
One Au is coordinated by two Se atoms of ligand and two Cl atoms,
the other Au is coordinated by two Cl atoms which as coordination
anion. The [AuCl2]À anions, arranged in a spiral, bridge two [Au
(Besp)Cl2]+ cations through long axial contacts. For [Au(Besp)
Cl2]+[AuCl2]À (2), cations (+) and anions (À) are arranged alterna-
tively in the solid state. This alternate arrangement of the oppo-
sitely charge Au(III)/Au(I) ions is favorable because it allows the
electrostatic interaction to be optimized in the solid state. More-
over, there is no Au(I)Á Á ÁAu(I) contract between adjacent [AuCl2]À
units as both the Au(I)Á Á ÁAu(I) distance (7.6478(4) Å) is longer than
4 Å [69]. There are two kinds of weak intermolecular CAHÁ Á ÁCl
hydrogen bonds between chlorine anion and carbon of ligand.
The coordination anion chloride form two CAHÁ Á ÁCl hydrogen
bonds with adjacent molecules [C(7)Á Á ÁCl(4) = 3.677(2) Å; C(7)AH
3.2. Catalytic reduction of nitroarenes
The reactivity of the gold complexes for the reduction of
nitroarenes was first studied using 4-nitroanisole as model sub-
strate. As shown in Table 3, the gold catalysts with selone ligands
are highly active in the 4-nitroanisole reduction, with the reaction
catalyzed by complex 3 reaching the yields of 95% within 3 h,
whereas for the reaction catalyzed by complex 1 and 2 the same
yield were achieved after 4 h of reaction time, respectively. More-
over, the catalytic activities using gold complexes with selone
ligands are better than those of gold complexes with thione ligands
[38] and HAuCl4. Then, the complex 3 was chosen as the optimal
catalyst to screen the various solvents (Table 3, entries 8–12). High
yield of 95% of the desired products was achieved within 3 h in
Fig. 2. View of 1D polymeric chains in complex 2.

H.-N. Zhang et al. / Inorganica Chimica Acta 450 (2016) 315–320
319
Table 4
reduced with NaBH4 to form gold particles (Fig. S6). Then the
reduction action occurred via electrons transfer from the donor
BHÀ4 to the acceptor nitroarene after both adsorbed onto the gold
particles surface. The hydrogen atom from the hydride attacked
nitroarene to reduce it to aromatic anilines after the electron trans-
fer to gold particles. There are still some gold complexes in solution
(confirmed by ESI-MS), which centrifugal separation after the cat-
alytic reaction. The nitroarene reduction procedure developed to
access gold complex and particle to containing homogeneous and
heterogeneous systems as previous reported [70].
Screening of substrates for nitroarenes reduction catalyzed by gold complexes 1, 2
and 3.a,b
Entry Substrate
Product
Catalyst Time
(h)
Yield
(%)
1
1
2
3
1
2
3
20
17
15
18
11
10
92
90
89
90
92
90
O2N
H2N
2
O2N
H2N
H2N
H2N
Cl
I
Cl
I
3
1
2
3
18
12
10
91
90
90
O2N
4. Conclusions
4
1
2
3
22
20
17
92
92
90
O2N
In summary, we have synthesized and characterized three novel
gold complexes with pyridine-based selone ligands. A combination
of spectroscopic studies and X-ray crystallographic study con-
firmed the molecular structure of all gold complexes. And these
gold complexes are highly catalyzed hydrogenation of nitroarenes
to aromatic anilines to proceed in the presence of sodium borohy-
dride reducing agent in water solvent. The reaction offers wide
functional group compatibility, broad substrate scope and proides
aromatic anilines in good to excellent yields.
CN
CN
5
1
2
3
15
12
10
90
87
90
O2N
H2N
OH
OH
6
1
2
3
15
11
9
90
92
89
O2N
H2N
H2N
H2N
H2N
7
1
2
3
13
11
7
93
91
95
O2N
Acknowledgments
8
1
2
3
12
11
9
87
89
90
O2N
This work was supported by the National Nature Science Foun-
dation of China (21102004), the NSF of Anhui province
(1408085MB32) and the Project-sponsored by SRF for ROCS and
National Training Programs of Innovation and Entrepreneurship
for Undergraduates (201410370040 and 201510370011).
9
1
2
3
6
6
5
93
95
95
O2N
O2N
OMe
CH3
OMe
CH3
10
1
2
3
4
4
3
89
90
91
H2N
Appendix A. Supplementary data
O
OH
11
12
1
2
3
30
24
20
90
87
89
O2N
O2N
H2N
H2N
Supplementary data (CCDC number 1470554 for compound 2)
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.ica.2016.06.023.
OH
CHO
NH2
1
2
3
12
10
9
91
90
93
NH2
References
a
Reaction conditions: 0.5 mmol nitrobenzene, 2.0 mmol sodium tetrahydrobo-
[1] K. Kondo, H. Ogawa, T. Shinohara, M. Kurimura, Y. Tanada, K. Kan, H.
Yamashita, S. Nakamura, T. Hirano, Y. Yamamura, T. Mori, M. Tominaga, A.
Itai, J. Med. Chem. 43 (2000) 4388–4397.
rate, gold catalyst (2 mol%), water (2 mL), room temperature.
b
Isolated yield.
[2] H.-U. Blaser, H. Steiner, M. Studer, ChemCatChem 1 (2009) 210–221.
[3] S. Kim, H. Choi, C. Baik, K. Song, S.O. Kang, J. Ko, Tetrahedron 63 (2007) 11436–
11443.
[4] A.M. Tafesh, J. Weiguny, Chem. Rev. 96 (1996) 2035–2052.
[5] J. Jiao, K. Murakami, K. Itami, ACS Catal. 6 (2016) 610–633.
[6] J.S. Carey, D. Laffan, C. Thomson, M.T. Williams, Org. Biomol. Chem. 4 (2006)
2337–2347.
[7] A. Krogul, G. Litwinienko, Org. Process Res. Dev. 19 (2015) 2017–2021.
[8] J.L. Klinkenberg, J.F. Hartwig, Angew. Chem. Int. Ed. 50 (2011) 86–95.
[9] C. Zhu, G. Li, D.H. Ess, J.R. Falck, L. Kürti, J. Am. Chem. Soc. 134 (2012) 18253–
18256.
[10] T. Morofuji, A. Shimizu, J.-I. Yoshida, J. Am. Chem. Soc. 135 (2013) 5000–5003.
[11] M. Orlandi, F. Tosi, M. Bonsignore, M. Benaglia, Org. Lett. 17 (2015) 3941–3943.
[12] C.M. Lavoie, P.M. MacQueen, N.L. Rotta-Loria, R.S. Sawatzky, A. Borzenko, A.J.
Chisholm, B.K.V. Hargreaves, R. McDonald, M.J. Ferguson, M. Stradiotto, Nat.
Commun. 7 (2016).
[13] M. Fan, W. Zhou, Y. Jiang, D. Ma, Org. Lett. 17 (2015) 5934–5937.
[14] G. Wienhöfer, I. Sorribes, A. Boddien, F. Westerhaus, K. Junge, H. Junge, R.
Llusar, M. Beller, J. Am. Chem. Soc. 133 (2011) 12875–12879.
[15] X. Liu, S. Ye, H.-Q. Li, Y.-M. Liu, Y. Cao, K.-N. Fan, Mild Catal. Sci. Technol. 3
(2013) 3200–3206.
[16] X.-J. Yang, B. Chen, L.-Q. Zheng, L.-Z. Wu, C.-H. Tung, Green Chem. 16 (2014)
1082–1086.
[17] R.S. Downing, P.J. Kunkeler, H. van Bekkum, Cataly. Today 37 (1997) 121–136.
[18] R.A. Green, J.F. Hartwig, Org. Lett. 16 (2014) 4388–4391.
[19] Y. Aubin, C. Fischmeister, C.M. Thomas, J.-L. Renaud, Chem. Soc. Rev. 39 (2010)
4130–4145.
water solvent. Lower catalyst loading (1 mol% and 0.5 mol% 3)
attributed to longer reaction time (Table 3, entry 15–16). A control
experiment without the gold complex catalyst showed no reaction
(Table 3, entry 17).
With the optimal reaction conditions in hand, we started to
expand the scope and efficiency of this methodology. A series of
functionalized anilines were obtained in good to excellent yields
using three gold complexes with selone ligands as catalysts,
respectively (Table 4). As shown in Table 4, all gold catalyst were
found to be very active toward the reduction of various nitroarenes
in different reaction time. Electron-withdrawing and electron-
donating substituents on the aromatic backbone were able to give
the desired products in high yields. In the case of 4-nitroacetophe-
none and 4-nitrobenzaldehyde, the –CHO and –COMe groups were
reduced together with the nitro group.
It was interest to get the mechanism of the nitroarene reduction
using gold complexes catalysts. The gold complex peak (263 nm)
became weak and the new peak (317 nm) increase after 30 min
in UV–vis spectra (Fig. S5). When finished the reduction, some
black precipitate were detected. Thus we have carried out the reac-
tion of gold complex with NaBH4, which led to the formation of
black precipitate. We deduce that the gold complexes have been
[20] T. Aditya, A. Pal, T. Pal, Chem. Commun. 51 (2015) 9410–9431.
[21] M. Haruta, T. Kobayashi, H. Sano, N. Yamada, Chem. Lett. (1987) 405–408.
[22] A.S.K. Hashmi, L. Schwarz, J.-H. Choi, T.M. Frost, Angew. Chem. Int. Ed. 39
(2000) 2285–2288.

320
H.-N. Zhang et al. / Inorganica Chimica Acta 450 (2016) 315–320
[23] A.S.K. Hashmi, T.M. Frost, J.W. Bats, J. Am. Chem. Soc. 122 (2000) 11553–
11554.
[48] M. Minoura, V.K. Landry, J.G. Melnick, K. Pang, L. Marchio, G. Parkin, Chem.
Commun. (2006) 3990–3992.
[24] S. Carrettin, M.C. Blanco, A. Corma, A.S.K. Hashmi, Adv. Synth. Catal. 348 (2006)
1283–1288.
[49] A. Molter, F. Mohr, Coord. Chem. Rev. 254 (2010) 19–45.
[50] K. Srinivas, C. Naga Babu, G. Prabusankar, Dalton Trans. 44 (2015) 15636–
15644.
[51] G.K. Rao, A. Kumar, J. Ahmed, A.K. Singh, Chem. Commun. 46 (2010) 5954–
5956.
[52] K. Srinivas, A. Sathyanarayana, C.N. Babu, G. Prabusankar, Dalton Trans. 45
(2016) 5196–5209.
[53] W.G. Jia, Y.B. Huang, Y.J. Lin, G.L. Wang, G.X. Jin, Eur. J. Inorg. Chem. 2008
(2008) 4063–4073.
[54] W.-G. Jia, Y.-B. Huang, Y.-J. Lin, G.-X. Jin, Dalton Trans. (2008) 5612–5620.
[55] W.-G. Jia, Y.-B. Huang, G.-X. Jin, J. Organomet. Chem. 694 (2009) 3376–3380.
[56] W.-G. Jia, Y.-B. Huang, G.-X. Jin, J. Organomet. Chem. 694 (2009) 4008–4013.
[57] C. Khin, A.S.K. Hashmi, F. Rominger, Eur. J. Inorg. Chem. 2010 (2010) 1063–
1069.
[25] A.S.K. Hashmi, C. Lothschütz, M. Ackermann, R. Doepp, S. Anantharaman, B.
Marchetti, H. Bertagnolli, F. Rominger, Chem. Eur. J. 16 (2010) 8012–8019.
[26] X. Liu, L. He, Y.-M. Liu, Y. Cao, Acc. Chem. Res. 47 (2014) 793–804.
[27] B.S. Takale, M. Bao, Y. Yamamoto, Org. Biomol. Chem. 12 (2014) 2005–2027.
[28] Y. Zhou, Y. Zhu, X. Yang, J. Huang, W. Chen, X. Lv, C. Li, C. Li, RSC Adv. 5 (2015)
50454–50461.
[29] A. Corma, P. Concepción, P. Serna, Angew. Chem. Int. Ed. 46 (2007) 7266–7269.
[30] A. Corma, P. Serna, H. García, J. Am. Chem. Soc. 129 (2007) 6358–6359.
[31] K.-I. Shimizu, Y. Miyamoto, T. Kawasaki, T. Tanji, Y. Tai, A. Satsuma, J. Phys,
Chem. C 113 (2009) 17803–17810.
[32] F. Cárdenas-Lizana, S. Gómez-Quero, M.A. Keane, ChemSusChem 1 (2008)
215–221.
ˇ
´
[33] M. Cano, P. Villuendas, A.M. Benito, E.P. Urriolabeitia, W.K. Maser, Mater.
Today Commun. 3 (2015) 104–113.
[34] X. Zhang, Z. Su, Adv. Mater. 24 (2012) 4574–4577.
[35] S. Wu, J. Dzubiella, J. Kaiser, M. Drechsler, X. Guo, M. Ballauff, Y. Lu, Angew.
Chem. Int. Ed. 51 (2012) 2229–2233.
[36] Y. Zhang, S. Liu, W. Lu, L. Wang, J. Tian, X. Sun, Sci. Technol. 1 (2011) 1142–1144.
[37] A. Corma, C. González-Arellano, M. Iglesias, F. Sánchez, Appl. Catal. A: Gen. 356
(2009) 99–102.
[58] M. Pazicky, A. Loos, M.J. Ferreira, D. Serra, N. Vinokurov, F. Rominger, C. Jäkel,
A.S.K. Hashmi, M. Limbach, Organometallics 29 (2010) 4448–4458.
[59] W.-G. Jia, H. Zhang, T. Zhang, D. Xie, S. Ling, E.-H. Sheng, Organometallics 35
(2016) 503–512.
[60] A. Saha, B. Ranu, J. Org. Chem. 73 (2008) 6867–6870.
[61] H. Yang, Y. Li, M. Jiang, J. Wang, H. Fu, Chem. Eur. J. 17 (2011) 5652–5660.
[62] G. Sheldrick, SHELXL-97, a Program for Refining Crystal Structures, University
of Göttingen, Germany, 1997.
[38] W.-G. Jia, Y.-C. Dai, H.-N. Zhang, X. Lu, E.-H. Sheng, RSC Adv. 5 (2015) 29491–
29496.
[39] A.S.K. Hashmi, G.J. Hutchings, Angew. Chem. Int. Ed. 45 (2006) 7896–7936.
[40] D. Pflasterer, A.S.K. Hashmi, Chem. Soc. Rev. 45 (2016) 1331–1367.
[41] A. Liske, K. Verlinden, H. Buhl, K. Schaper, C. Ganter, Organometallics 32 (2013)
5269–5272.
[63] G. Sheldrick, SADABS v. 2.01, Bruker/Siemens area detector absorption
correction program, Bruker AXS, Madison, WI, USA, 1998.
[64] K.J. Kilpin, W. Henderson, B.K. Nicholson, Inorg. Chim. Acta 362 (2009) 3669–
3676.
[65] O. Crespo, M.C. Gimeno, A. Laguna, S. Montanel-Pérez, M.D. Villacampa,
Organometallics 31 (2012) 5520–5526.
[42] D.M. Buck, D. Kunz, Organometallics 34 (2015) 5335–5340.
[43] S.V.C. Vummaleti, D.J. Nelson, A. Poater, A. Gomez-Suarez, D.B. Cordes, A.M.Z.
Slawin, S.P. Nolan, L. Cavallo, Chem. Sci. 6 (2015) 1895–1904.
[44] H. Braunschweig, R.D. Dewhurst, A. Schneider, Chem. Rev. 110 (2010) 3924–
3957.
[45] G.R. Owen, Chem. Soc. Rev. 41 (2012) 3535–3546.
[46] N. Ghavale, S.T. Manjare, H.B. Singh, R.J. Butcher, Dalton Trans. 44 (2015)
(1900) 11893–11900.
[66] M.T. Aroz, M.C. Gimeno, M. Kulcsar, A. Laguna, V. Lippolis, Eur. J. Inorg. Chem.
2011 (2011) 2884–2894.
[67] D.J. Nelson, F. Nahra, S.R. Patrick, D.B. Cordes, A.M.Z. Slawin, S.P. Nolan,
Organometallics 33 (2014) 3640–3645.
[68] O. Crespo, M.C. Gimeno, A. Laguna, M. Kulcsar, C. Silvestru, Inorg. Chem. 48
(2009) 4134–4142.
[69] J.H.K. Yip, R. Feng, J.J. Vittal, Inorg. Chem. 38 (1999) 3586–3589.
[70] S.S. Zalesskiy, A.E. Sedykh, A.S. Kashin, V.P. Ananikov, J. Am. Chem. Soc. 135
(2013) 3550–3559.
[47] P. Ai, A.A. Danopoulos, P. Braunstein, Dalton Trans. 45 (2016) 4771–4779.