Two cadmium(II) complexes with oxazoline-based ligands as effective catalysts for C-N cross-coupling reactions

Article abstract of DOI:10.1016/j.ica.2015.01.005

Binuclear [{(DMOX)CdCl}₂(μ-Cl)₂] (DMOX = 4,5-dihydro-2-(4,5-dihydro-4,4-dimethyloxazol-2-yl)-4,4-dimethyl-oxazole) (1) and mononuclear [(Dm-Pybox)CdCl₂] (Dm-Pybox = 2,6-bis[4′,4′-dimethyloxazolin-2′-yl]pyridine) (2) were obtained by reacting CdCl₂ with DMOX and Dm-Pybox ligands, respectively. In the solid state, the supramolecular structures of 1 and 2 feature helical chains fabricated by C-H-Cl hydrogen bond interactions. The C-N cross-coupling reactions catalyzed by the two complexes were also investigated in homogeneous system. The results show that binuclear complex 1 exhibit significantly enhanced catalytic activity for C-N cross-coupling reactions.

Full text of DOI:10.1016/j.ica.2015.01.005

Inorganica Chimica Acta 427 (2015) 226–231
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Two cadmium(II) complexes with oxazoline-based ligands as effective
catalysts for C–N cross-coupling reactions
a
a
a
a
b,
Wei-Guo Jia a, , Dan-Dan Li , Cuiping Gu , Yuan-Chen Dai , Ying-Hua Zhou , Guozan Yuan
⇑
⇑
,
En-Hong Sheng a
a 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
b School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan 243002, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Binuclear [{(DMOX)CdCl}2(l-Cl)2] (DMOX = 4,5-dihydro-2-(4,5-dihydro-4,4-dimethyloxazol-2-yl)-4,4-
dimethyl-oxazole) (1) and mononuclear [(Dm-Pybox)CdCl2] (Dm-Pybox = 2,6-bis[40,40-dimethyloxazo-
lin-20-yl]pyridine) (2) were obtained by reacting CdCl2 with DMOX and Dm-Pybox ligands, respectively.
In the solid state, the supramolecular structures of 1 and 2 feature helical chains fabricated by C–Hꢀ ꢀ ꢀCl
hydrogen bond interactions. The C–N cross-coupling reactions catalyzed by the two complexes were also
investigated in homogeneous system. The results show that binuclear complex 1 exhibit significantly
enhanced catalytic activity for C–N cross-coupling reactions.
Received 13 October 2014
Received in revised form 18 November 2014
Accepted 5 January 2015
Available online 12 January 2015
Keywords:
Pincer
Oxazoline
Cadmium
Catalysis
Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction
palladium. The palladium-catalyzed cross-coupling of aryl amine
with aryl halide and pseudo halide is most popular method in this
Tridentate oxazoline-based pincer ligands and bisoxazolines are
important ligands with broad application in asymmetric synthesis
and homogeneous catalysis in modern metal-organic chemistry
transformation [18,19]. Besides palladium, other catalytic systems
using manganese [20], iron [21], cobalt [22], nickel [23,24], copper
[25,26], indium [27], gold [28] and rhodium [29] have also been
reported for the same purpose. However, among these transition
metal complexes, cadmium complexes with oxazoline-based
ligands have not received much attention [30].
In this work, we report the synthesis and characterization of
two Cd(II) complexes with bisoxazolines and tridentate pybox pin-
cer ligands: [{(DMOX)CdCl}2(l-Cl)2] (1) and [(Dm-Pybox)CdCl2]
(2), and further examine their catalytic ability in direct C–N
cross-coupling of amine with aryl halide. Our preliminary results
indicate that Cd complex 1 shows promising catalytic activity in
C–N cross-coupling of amine with aryl halide. The elucidation of
solid state structures of the Cd complexes 1 and 2 were also
obtained through single crystal X-ray diffraction.
[1–4]. Typically, these type ligands are good
r-donors and weak
p-acceptors which can be easily modified using appropriate com-
mercially available amino alcohol precursors to attain the desired
steric-bulk or electronic properties. Within the past years, reports
about pincer and bisoxazolines transition metal complexes’ excep-
tional catalytic abilities have been reported [2–8]. Continuing our
research interests in bisoxazolines and pincer complexes due to
their rich chemistry [9–11], we seek to discover new transition
metal complexes and hope to exploit their chemistry in a variety
of potential catalytic applications.
Aromatic amines and their derivatives are important motifs
found in pharmaceuticals, natural products, fine chemicals as well
as functional materials [12–14]. There is strong interest in develop-
ing efficient synthetic protocols for preparing such molecules
[15–17]. In the past decade, transition metal-catalyzed C–N bond
formation have been considered as one of the most powerful and
reliable methods, with attention particularly being focused on
2. Experimental
2.1. Materials and physical measurements
Commercial reagents were analytical grade and used as
received from Aladdin and Energy chemical. All reactions were per-
formed in oven-dried or flame-dried glassware, and were moni-
tored by TLC using 0.25 mm silica gel plates with UV indicator
⇑
Corresponding authors.
E-mail addresses: wgjiasy@mail.ahnu.edu.cn (W.-G. Jia), guozan@ahut.edu.cn
(G. Yuan).
http://dx.doi.org/10.1016/j.ica.2015.01.005
0020-1693/Ó 2015 Elsevier B.V. All rights reserved.

W.-G. Jia et al. / Inorganica Chimica Acta 427 (2015) 226–231
227
Table 1
and then the solvent was removed with the rotary evaporator; the
resulting solid was washed with Et2O. The product was dried under
vacuum to give corresponding colorless complex 1 (73 mg, 96%). X-
ray-quality colorless crystals were grown via the slow diffusion of
Et2O into the CH2CN solution of complex 1 after 7 days. 1H NMR
Crystallographic data and structure refinement parameters for complexes 1 and 2.
1
2
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C
20H32Cd2Cl4N4O4
C30H38Cd2Cl4N6O4
913.26
monoclinic
P2(1)/n
10.1410(8)
16.2430(13)
11.4541(9)
98.1680(10)
1867.6(3)
2
759.10
monoclinic
P2(1)/n
10.4067(6)
12.7413(8)
11.7204(7)
112.6220(10)
1434.50(15)
2
(500 MHz, CDCl3)
d
4.60 (s, 4H), 1.61 (s, 12H). 13C NMR
(125 MHz, CDCl3) d 156.52, 85.84, 68.91, 28.67. Anal. Calc. for C20-
H32Cl4Cu2N4O4: C, 31.58; H, 4.24; N, 7.37. Found: C, 31.44; H, 4.35;
N, 7.50%. IR (KBr cmꢁ1): 2970(m), 2935(s), 1749(s), 1653(vs),
1483(s), 1435(vs), 1360(s), 1333(s), 1251(m), 1183(vs), 1012(s),
924(vs), 835(w), 637(m).
b (Å)
c (Å)
b (°)
V (Å3)
Z
Dcalc (mg/m3)
1.757
1.886
1.624
1.466
2.3. Preparation of mononuclear [(Dm-Pybox)CdCl2] (2)
l
(Mo K
a
) (mmꢁ1
)
F(000)
752
912
h range (°)
Limiting indices
2.23–27.43
ꢁ12, 13, ꢁ13, 16,
ꢁ15, 15
2.19–27.43
ꢁ13, 13, ꢁ21, 21,
ꢁ13, 14
A 50 mL round-bottomed flask was placed with Dm-pybox
(55 mg, 0.2 mmol), CdCl2 (37 mg, 0.2 mmol), 10 mL MeOH and
10 mL CH2Cl2 as solvent. The mixture was stirred at room temper-
ature for 5 h and then the solvent was removed with the rotary
evaporator; the resulting solid was washed with Et2O. The product
was dried under vacuum to give corresponding colorless complex 2
(87 mg, 95%). X-ray-quality colorless crystals were grown via the
slow diffusion of Et2O into the CH2Cl2 solution of complex 2 after
4 days. 1H NMR (500 MHz, CDCl3) d 8.26 (t, J = 7.80 Hz, 1H), 8.06
(d, J = 7.80 Hz, 2H), 4.50 (s, 4H), 1.62 (s, 12H). 13C NMR
(125 MHz, CDCl3) d 161.68, 142.88, 142.68, 125.64, 83.97, 67.93,
28.60. Anal. Calc. for C15H19Cl2CdN3O2: C, 39.39; H, 4.19; N 9.19.
Found: C, 39.25; H, 4.30; N, 9.07%. IR (KBr cmꢁ1): 3058(m),
2967(m), 2924(w), 2871(w), 1654(s), 1583(vs), 1491(m),
1459(m), 1392(s), 1371(vs), 1328(s), 1286(s), 1191(vs), 1143(w),
1080(m), 1016(m), 974(s), 942(vs), 836(s), 762(m), 677(s).
Reflections/unique (Rint
)
11987/3265
(0.0233)
15662/4257
(0.0222)
Completeness to h (°)
27.43 (99.8%)
3265/0/154
1.069
0.0213, 0.0550
0.0246, 0.0572
0.539 and ꢁ0.314
27.44 (99.9%)
4257/0/212
1.024
0.0204, 0.0500
0.0232, 0.0518
0.249 and ꢁ0555
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
R1, wR2 [I > 2
R1, wR2 (all data)
r
(I)]a
Largest difference in peak and
hole(e Åꢁ3
)
P
P
P
P
||Fo| ꢁ |Fc||/ |Fo|; wR2 = [ w(|F2o| ꢁ |Fc2|)2/ w|Fo2|2]1/2
.
a
R1
=
Table 2
Selected bond distances and angles for complexes 1 and 2.
Bond distance (Å) in 1
Cd(1)–N(1)
Cd(1)–Cl(1)
Cd(1)–Cl(1A)
Bond angle (deg) in 1
N(1)–Cd(1)–N(2)
N(1)–Cd(1)–Cl(1A)
N(2)–Cd(1)–Cl(1)
N(2)–Cd(1)–Cl(2)
Cl(1)–Cd(1)–Cl(1A)
2.4. General procedure for the synthesis C–N cross coupling products
2.3369(16)
2.6235(6)
2.5318(6)
Cd(1)–N(2)
Cd(1)–Cl(2)
2.3962(16)
2.4230(6)
Bromobenzene derivatives (0.5 mmol, 1.0 equiv), 1 (19 mg,
0.05 mmol, 0.1 equiv) and potassium hydroxide (19 mg, 0.5 mmol,
1.0 equiv) were added in DMSO (0.5 mL), then the mixture was
stirred for 10 min at 110 °C before the addition of alkylamines
(1.0 mmol, 2.0 equiv). Next the reaction was stirred at 110 °C for
several hours, after which the crude reaction mixture was loaded
directly onto a column of silica gel and purified by column chroma-
tography to give the corresponding products.
71.78(6)
N(1)–Cd(1)–Cl(1)
N(1)–Cd(1)–Cl(2)
N(2)–Cd(1)–Cl(1A)
Cl(1)–Cd(1)–Cl(2)
Cl(2)–Cd(1)–Cl(1A)
90.10(4)
100.87(4)
94.91(4)
110.91(2)
110.18(2)
148.13(4)
145.92(4)
100.93(4)
85.507(19)
Bond distance (Å) in 2
Cd(1)–N(1)
Cd(1)–N(3)
2.3582(14)
2.4079(15)
2.4472(5)
Cd(1)–N(2)
Cd(1)–Cl(1)
2.3811(14)
2.4049(6)
Cd(1)–Cl(2)
2.4.1. 4-Phenylmorpholine (1a) [15]
Bond angle (deg) in 2
N(1)–Cd(1)–N(2)
N(1)–Cd(1)–Cl(1)
N(2)–Cd(1)–N(3)
N(2)–Cd(1)–Cl(2)
N(3)–Cd(1)–Cl(2)
Pale yellow solid, 90% Yield (73 mg). 1H NMR (500 MHz, CDCl3)
d 7.29 (t, J = 7.50 Hz, 2H), 6.92 (d, J = 7.50 Hz, 2H), 6.89 (t, J = 7.50
Hz, 1H), 3.87 (m, 4H), 3.16 (m, 4H).
68.40(5)
134.83(4)
135.98(5)
99.05(4)
96.43(4)
N(1)–Cd(1)–N(3)
N(1)–Cd(1)–Cl(2)
N(2)–Cd(1)–Cl(1)
N(3)–Cd(1)–Cl(1)
Cl(1)–Cd(1)–Cl(2)
68.41(5)
100.26(4)
99.84(4)
104.41(4)
124.87(2)
2.4.2. 4-(3-(Trifluoromethyl)phenyl)morpholine (2a)
Pale yellow solid, 32% Yield (37 mg). 1H NMR (300 MHz, CDCl3)
d 7.37 (t, J = 8.10 Hz, 1H), 7.11 (m, 2H),7.05 (m, 1H), 3.87 (t,
J = 4.80 Hz, 4H), 3.20 (t, J = 4.80 Hz, 4H). 13C NMR (125 MHz, CDCl3)
d 151.38, 129.60, 118.42, 116.22, 111.86, 66.70, 48.82. HRMS (ESI)
Calcd. for C11H12F3NO [M+H]+ 232.0944, found 232.0947.
(60F-254). All solvents were purified and degassed by standard
procedures. The starting materials DMOX [31] and Dm-Pybox
[32] were synthesized according to the procedures described in
the literature. 1H and 13C NMR were recorded on a 300 MHz or
500 MHz NMR spectrometer at room temperature. Chemical shifts
(d) are given in ppm relative to CDCl3 (7.26 ppm for 1H and 77 ppm
for 13C) or internal TMS. High-resolution mass spectra (HRMS)
were obtained using APCI-TOF in positive mode. IR spectra were
recorded on a Niclolet AVATAR-360IR spectrometer. Element anal-
yses were performed on an Elementar III vario EI Analyzer.
2.4.3. 4-(4-(Trifluoromethyl)phenyl)morpholine (2b)
Pale yellow solid, 59% Yield (68 mg). 1H NMR (300 MHz, CDCl3)
d 7.50 (d, J = 8.70 Hz, 2H), 6.91 (d, J = 8.70 Hz, 2H), 3.87 (t,
J = 4.80 Hz, 4H), 3.24(t, J = 4.80 Hz, 4H). 13C NMR (125 MHz, CDCl3)
d 153.33, 126.43, 114.29, 66.61, 48.14. HRMS (ESI) Calcd. for C11-
H12F3NO [M+H]+ 232.0944, found 232.0944.
2.2. Preparation of binuclear complex [{(DMOX)CdCl}2(
l
-Cl)2] (1)
2.4.4. 4-(3-Methoxyphenyl)morpholine (3a)
Pale yellow solid, 37% Yield (36 mg). 1H NMR (300 MHz, CDCl3)
d 7.20 (t, J = 8.25 Hz, 1H), 6.53 (d, J = 8.25 Hz, 1H),6.45 (m, 2H), 3.86
(t, J = 4.80 Hz, 4H), 3.80 (s, 3H), 3.16 (t, J = 4.80 Hz, 4H). 13C NMR
A 50 mL round-bottomed flask was placed with DMOX (39 mg,
0.2 mmol), CdCl2 (37 mg, 0.2 mmol), 10 mL MeOH and 10 mL CH2-
Cl2 as solvent. The mixture was stirred at room temperature for 5 h
(125 MHz, CDCl3)
d 160.56, 152.63, 129.79, 108.39, 104.63,

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W.-G. Jia et al. / Inorganica Chimica Acta 427 (2015) 226–231
Fig. 1. (a) View of 1D intertwined supramolecular helical polymeric chains in 1 along the b-axis; (b) molecular structure of 1; (c) perspective views of intermolecular
hydrogen bonds in 1.
Table 3
1H), 4.41 (s, 2H), 3.82 (s, 3H), 3.56 (t, J = 6.00 Hz, 2H), 2.98 (t,
J = 6.00 Hz, 2H). 13C NMR (125 MHz, CDCl3) d 160.72, 151.88,
134.91, 134.41, 129.84, 128.45, 126.50, 126.34, 126.04, 107.90,
103.29, 101.52, 55.19, 50.62, 46.35, 29.10. HRMS (ESI) Calcd. for
C–Hꢀ ꢀ ꢀCl interactions in complexes 1 and 2.
Interaction
Hꢀ ꢀ ꢀCl (Å)
Cꢀ ꢀ ꢀCl (Å)
C–Hꢀ ꢀ ꢀCl (deg)
Complex 1
C(7)–H(7A)ꢀ ꢀ ꢀCl(1)
C
16H17NO [M+H]+ 240.1383, found 240.1381.
2.7893(6)
3.7534(21)
172.86(13)
Complex 2
C(4)–H(4)ꢀ ꢀ ꢀCl(2)
C(8)–H(8B)ꢀ ꢀ ꢀCl(2)
C(12)–H(12A)ꢀ ꢀ ꢀCl(2)
2.7670(5)
2.8231(5)
2.8150(5)
3.6777(20)
3.7744(23)
3.6899(25)
166.40(20)
167.08(12)
150.39(15)
2.4.8. 2-(4-Methoxyphenyl)-1,2,3,4-tetrahydroisoquinoline (5b)
Pale yellow solid, 46% Yield (55 mg). 1H NMR (500 MHz, CDCl3)
d 7.16 (m, 4H), 6.98 (d, J = 9.25 Hz, 2H), 6.87 (d, J = 9.25 Hz, 2H),
4.30 (s, 2H), 3.78 (s, 3H), 3.45 (t, J = 6.00 Hz, 2H), 2.99 (t,
J = 6.00 Hz, 2H). 13C NMR (125 MHz, CDCl3) d 153.50, 145.36,
134.61, 128.67, 126.49, 126.24, 125.89, 118.02, 114.57, 55.63,
52.67, 48.43, 29.09. HRMS (ESI) Calcd. for C16H17NO [M+H]+
240.1383, found 240.1382.
102.14, 66.82, 55.11, 49.21. HRMS (ESI) Calcd. for C11H15NO2
[M+H]+ 194.1176, found 194.1178.
2.4.5. 4-(4-Methoxyphenyl)morpholine (3b)
Pale yellow solid, 21% Yield (20 mg). 1H NMR (300 MHz, CDCl3)
d 6.88 (m, 4H), 3.86 (t, J = 4.80 Hz, 4H), 3.77 (s, 3H), 3.05(t,
J = 4.80 Hz, 4H). 13C NMR (125 MHz, CDCl3) d 153.90, 145.57,
117.74, 114.44, 66.96, 55.48, 50.74. HRMS (ESI) Calcd. for
2.5. X-ray crystallography for 1 and 2
Diffraction data of complex 1 and 2 were collected on a Bruker
Smart CCD diffractometer with graphite-monochromated Mo K
a
C
11H15NO2 [M+H]+ 194.1176, found 194.1177.
radiation (k = 0.71073 Å). All the data were collected at room tem-
perature and the structures were solved by direct methods and
subsequently refined on F2 by using full-matrix least-squares tech-
niques (SHELXL) [33], and SADABS absorption corrections [34] applied
to the data. The crystallographic data for complexes 1 and 2 are
summarized in Table 1, and selected bond lengths and angles are
shown in Table 2.
2.4.6. 2-Phenyl-1,2,3,4-tetrahydroisoquinoline (4a)
Pale yellow solid, 96% Yield (72 mg). 1H NMR (500 MHz, CDCl3)
d 7.31 (t, J = 7.50 Hz, 2H), 7.19 (m, 4H), 7.01 (d, J = 7.50 Hz, 2H),
6.85 (t, J = 7.50 Hz, 1H), 4.43 (s, 2H), 3.58 (t, J = 6.00 Hz, 2H), 3.01
(t, J = 6.00 Hz, 2H). 13C NMR (125 MHz, CDCl3) d 150.51, 134.83,
134.42, 129.17, 128.49, 126.51, 126.29, 125.99, 118.63, 115.11,
50.69, 46.49, 29.08. HRMS (ESI) Calcd. for
210.1277, found 210.1276.
C15H15N
[M+H]+
3. Results and discussion
Binuclear [{(DMOX)CdCl}2(l-Cl)2] (1) and mononuclear pybox-
2.4.7. 2-(3-Methoxyphenyl)-1,2,3,4-tetrahydroisoquinoline (5a)
Pale yellow solid, 20% Yield (24 mg). 1H NMR (500 MHz, CDCl3) d
7.17 (m, 5H), 6.60 (d, J = 8.00 Hz, 1H), 6.51 (s, 1H) 6.39 (d, J = 8.00 Hz,
Cd complexes [(Dm-Pybox)CdCl2] (2) were obtained by reacting
CdCl2 with DMOX and Dm-Pybox in MeOH/CH2Cl2 co-solvent in
96% and 95% yields at room temperature respectively. The binuclear

W.-G. Jia et al. / Inorganica Chimica Acta 427 (2015) 226–231
229
Fig. 2. (a) Building unit; (b) 2D supramolecular structure; (c) View of 1D intertwined supramolecular helical polymeric chains in 2 along the b-axis.
(2.6235(6) Å and 2.5318(6) Å) are longer than the axial
(2.4230(6) Å). The bond length of N–Cd are 2.3962(16) Å and
2.4230(6) Å, respectively, which is slightly longer than those
observed in the [Cd2L2X2] (X = Cl, Br, I) [36] and [Cd(1-
tza)(phen)(NO3)] (1-tza = tetrazole-1-acetic acid) [37]. As seen in
Fig. 1(a), the molecular units are linked into a helical chain along b
axis via the strong intermolecular hydrogen bonds, and form 1D
intertwined supramolecular helical polymeric chains in 1 along
the b-axis. Each helix is linked by C–Hꢀ ꢀ ꢀCl intermolecular hydrogen
bonds [C(7)ꢀ ꢀ ꢀCl(1) = 3.7534(21) Å; C(7)–H(7A)ꢀ ꢀ ꢀCl(1) = 172.86°]
(Fig. 1(c), Table 3) [38,39]. To the best of our knowledge, such helical
chains constructed by C–Hꢀ ꢀ ꢀX interactions (X = halogen) is very
rare [40,41].
Table 4
Initial studies toward morpholine with bromobenzene.
Br
O
10 mol% Cd complex
Air, Solvent, 110°C, 4h.
+
N
O
N
H
0.5 mmol
1.0 mmol
1a
Entry
[Cd] (10 mol%)
Base (1 equiv)
Solvent
Yield(%)a,b
1
2
3
4
5
6
7
CdCl2
KOH
KOH
KOH
KOH
KOH
K2CO3
K3PO4
DMSO
DMSO
DMSO
DMF
NMP
DMSO
DMSO
31
45
90
4
2
NR
NR
2
1
1
1
1
1
3.2. Structural description of mononuclear [(Dm-Pybox)CdCl2] (2)
The X-ray structure of 2 show two asymmetric units crystal-
lized in the monoclinic space group P21/c (Fig. 2(a)). As expected,
pyridine-based pincer ligand is coordinated to Cd in a tridentate
fashion by the pyridyl nitrogen and two oxazoline nitrogen atoms.
The coordination sphere around the Cd(II) atom is best described
as midway between trigonal bipyramidal and square pyramidal
in structure [35]. The Cd–N distances (2.3582(14), 2.3811(14)
and 2.4079(15) Å) in 2, which are compatible with a typical single
bond length between the cadmium center and the nitrogen atom
reported in the previous literature, and can be compared with oth-
ers Cd complexes containing the 3N ligand set [42,43].
a
Isolated yield.
b
Reaction condition: 1 equiv base, 0.5 mL DMSO as solvent, under air, 110 °C.
complexes 1 and mononuclear 2 were characterized by IR and ele-
mental analysis. Both compounds are stable towards air and mois-
ture in the solid state. Crystals suitable for X-ray crystallography of
1 and 2 were obtained by slow diffusion of diethyl ether into con-
centrated solution of the complexes in dichloromethane solution.
3.1. Structural description of binuclear complex [{(DMOX)CdCl}2(
Cl)2] (1)
l
-
As shown in the Fig. 2(b), there are two forms of chlorides in 2
unit cell. Both are coordinating Cl complexed to the Cd center, but
only one chlorine atoms form three C–Hꢀ ꢀ ꢀCl hydrogen bonds with
As shown in Fig. 1(b), the crystal structure of 1 consists of binu-
clear units, connected by Cl anion, and each Cd atom is coordinated
by two N atoms of DMOX ligand and three Cl atoms. The Cd(II) metal
is five-coordinate and exhibits distorted square-pyramidal geome-
adjacent
molecules
[C(4)ꢀ ꢀ ꢀCl(2) = 3.678 Å;
C(4)–H(4)ꢀ ꢀ ꢀC
l(2) = 166°, C(8)ꢀ ꢀ ꢀCl(2) = 3.774 Å; C(8)–H(8B)ꢀ ꢀ ꢀCl(2) = 167° and
C(12)ꢀ ꢀ ꢀCl(2) = 3.690 Å; C(12)–H(12A)ꢀ ꢀ ꢀCl(2) = 150°] (Table 3),
which play crucial roles in the construction of 2D network structure
in the solid states. Two intertwined helical chains (one is right-
try, with
s index of 0.08 [35]. The equatorial Cd–Cl bonds

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W.-G. Jia et al. / Inorganica Chimica Acta 427 (2015) 226–231
Table 5
Reaction of alkylamines with halobenzenes derivatives.
Entry
1
Substrate
Br
Product
Time (h)
4
Yield (%)a,b
90
92
I
N
O
1a
72
32
Cl
2
1.5
Br
N
O
F3C
F3C
F3C
2a
59
37
O
N
2b
3
10
Br
O
N
H3CO
H3CO
H3CO
3a
21
92
N
O
3b
4
5
4
Br
N
4a
10
46
20
Br
H3CO
H3CO
N
H3CO
5a
N
5b
a
Isolated yield
b
Reaction condition: 0.5 mmol bromobenzyl derivatives, 1.0 mmol alkylamines, 5 mol% complex 1, 1.0 mmol KOH, 0.5 mL DMSO as solvent, under air, 110 °C.
handed, and the other left-handed) are generated around the crys-
tallographic 2(1) axis with a pitch of 16.2430(13) Å, which is equal
to the b axis length. Each helix is linked by C–Hꢀ ꢀ ꢀCl intermolecular
hydrogen bonds [C(4)ꢀ ꢀ ꢀCl(2) = 3.678 Å; C(4)–H(4)ꢀ ꢀ ꢀCl(2) = 166°]
along the b axis, and form 1D intertwined supramolecular helical
polymeric chains in 2 (Fig. 2(c)).
Using iodobenzene as a coupling partner led to a high yield (92%),
while, chlorobenzene gave a moderate yield (72%) (Table 5, entry 1).
Morpholine with electron-withdrawing and electron-donating sub-
stituents on the aromatic backbone were investigated to provide the
4-phenylmorpholine core in high yields and efficient conversion of
electron-deficient benzene was achieved at shorter reaction time
(Table 4, entries 2–3). Regioisomers were obtained with 1-bromo-
4-(trifluoromethyl)benzene, and the m- and p-substituted products
were isolated with 32% and 59% yields, respectively (Table 5, entry
3). Similar non-regioselective couplings were observed for the para
methoxy substituted bromo benzenes substrates. This suggests that
the transformation proceeds via a benzyne intermediate [30].
Another amine substrate, 1,2,3,4-tetrahydroisoquinoline, reacted
well under the standard conditions, as shown in Table 4: 2-phe-
nyl-1,2,3,4-tetrahydroisoquinoline (4a), 2-(4-methoxyphenyl)-
1,2,3,4-tetrahydroisoquinoline (5a), and 2-(3-methoxyphenyl)-
1,2,3,4-tetrahydroisoquinoline (5b) were obtained from the bromo-
benzene and 1-bromo-4-methoxybenzene in 92%, 46% and 20%
yields, respectively.
3.3. C–N cross-coupling of amine with aryl halide
Next, we explored the chemistry of Cd(II) in C–N cross-coupling
of amine with aryl halide. The initial reaction was carried out with
0.5 mmol of bromobenzene and morpholine in 0.5 mL DMSO under
air in the presence of KOH. Coupling product yield of 31% was
obtained in the presence of 10 mol% CdCl2 catalysts (Table 4, entry
1). However, the reaction with 10 mol% complex 1 gave 1a in 90%
yield, and complex 2 provided 1a in 45% yield (Table 4, entries 2,
3). These results illustratetheimportanceofthe ligand configuration
andthecooperativebimetallic catalyticeffectonthistransformation
[44,45]. Next, we chose complex 1 and subjected the catalyst to dif-
ferent solvent and base (Table 4, entries 4–7). To our delight, 90%
yield was achieved with DMSO as the solvent and KOH as the base.
With the optimal conditions in hand, we began to expand the
scope for this methodology. A series of C–N coupling products were
obtained in good to excellent yields (Table 5, entries 1–5).
4. Conclusions
In conclusion, wehave reported thesynthesisof twooxazolineCd
complexes: binuclear [{(DMOX)CdCl}2(l-Cl)2] (1) and mononuclear

W.-G. Jia et al. / Inorganica Chimica Acta 427 (2015) 226–231
[16] J.F. Hartwig, Acc. Chem. Res. 41 (2008) 1534.
231
Pybox Cd(II) complex [(Dm-Pybox)CdCl2] (2). Both complexes have
been fully characterized and molecular structures were determined
by X-ray diffraction analysis. The intermolecular C–Hꢀ ꢀ ꢀCl hydrogen
bonds play crucial roles in the construction of 1D/2D structure in the
solid states of the two complexes. We also demonstrated that com-
plex [{(DMOX)CdCl}2(l-Cl)2] (1) is efficient in catalyzing C–N cross-
coupling of amine with aryl halide possibly via benzyne
intermediate.
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This work was supported by the National Nature Science Foun-
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Foundation of the Anhui Higher Education Institutions of China
(KJ2011A146), and the Project-sponsored by SRF for ROCS, SEM,
Special and Excellent Research Fund of Anhui Normal University.
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