Full text of DOI:10.1134/S1070328418050044

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2018, Vol. 44, No. 5, pp. 353–358. © Pleiades Publishing, Ltd., 2018.
Syntheses, Characterizations, and Reactivity of Two Cu(I)-Amido
Complexes: Proposed Intermediate
1
in Cu(I)-Catalyzed Goldberg Reaction
X. F. Liu*, R. F. Li, Xiaoyi Fu, Hui Shen, Mingyue wen, and X. Feng**
College of Chemistry and Chemical Engineering, and Henan Key Laboratory of Function-Oriented Porous Materials,
Luoyang Normal University, Luoyang, 471934 P.R. China
*e-mail: liuxinfang6@126.com
*
*e-mail: fengx@lynu.edu.cn
Received August 22, 2017
Abstract—Reactions between dichloro-bridged copper(I) complexes and amides with different carbonyl sub-
stituents (CF , CH , and Ph) were reported. Two neutral Cu(I)-amido complexes, [Cu(Dppf)(MOAA)] (I)
3
3
and [Cu(Dppf)(MOTFAA)] (II) (Dppf = 1,1'-bis(diphenylphosphino)ferrocene, MOAA and MOTFAA =
deprotonated N-(4-methoxyphenyl) acetamide and N-(4-methoxyphenyl) trifluoroacetamide, respectively),
were synthesized in moderate to good yield and characterized by element analysis, 1H NMR and X-ray crys-
tallography method (СIF file CCDC no. 1015222 (I)). The results showed that the production of Cu(I)-
amido complxes were influenced by carbonyl substituent in the order of Ph > CF > CH . The substituent
3
3
effect also appeared in the N-arylation reactions of I and II with iodobenzene, which generated
another copper(I) complex Cu(Dppf)I (III) and two amides products [N-methyl-N-(4-methoxyphenyl)
acetamide] (А) and [N-methyl-N-(4-methoxyphenyl) trifluoroacetamide] (B) in different yield. The forma-
tion and transformation of the Cu(I)-amido complexes could indicate their dynamiccompetency as the inter-
mediates of Goldberg reaction.
Keywords: intermediate, amide, Goldberg reaction, mechanism
DOI: 10.1134/S1070328418050044
INTRODUCTION
and characterization difficult [7–10]. However, the
effect of substituent groups of amide on the synthesis
of intermediate was not reported. In theory, the sub-
stituent group, especially the carbonyl substituent near
the reactive site (NH substrate), could influence the
Lewis acidity of amide, and as well as the synthesis of
reaction intermediates.
At the beginning of twenty century, Irma Goldberg
reported his pioneering work on copper-mediated
Goldberg reaction [1]. From then on, the arylation of
amide has received considerable attentions [2]. How-
ever, original coupling reactions suffered from stoi-
chiometric amounts of copper salts, high reaction
temperature and long reaction time [3]. Recently,
many drawbacks of the classical reaction have been
overcome by adding organic ligand to the copper cat-
alyst [4, 5]. At present, Goldberg reaction has become
Herein, the reactions of dichloro-bridged cop-
per(I) precursor with amides bearing electron-, elec-
tron-donating and hindered carbonyl substituent
(
CF , CH , Ph) have been studied. Considering the
3 3
an efficient method to form C–N bonds in organic extreme air-sensitivity of reaction intermediate, 1,1′-
synthesis, pharmaceuticals and polymer science [6].
bis(diphenylphosphino)ferrocene (Dppf) with strong
chelating ability and reducibility was used as main
ligand to prepare precursor. Two Cu(I)-amido com-
plexes [Cu(Dppf)(MOAA)] (I) and [Cu(Dppf)-
Besides developing new ancillary ligands, the
mechanism study can help to improve the reaction
conditions and broaden the reaction scope. Isolation
and detection of intermediate is one of the most used
methods to unravel reaction mechanism. However,
only few intermediates were isolated in pure form due
to their light or air-sensitivity, making their isolation
(
MOTFAA)] (II) MOAA and MOTFAA is deproton-
ated N-(4-methoxyphenyl) acetamide and N-(4-
methoxyphenyl) trifluoroacetamide, respectively)
were prepared and characterized by IR, element anal-
1
ysis and H NMR. Their N-arylation reactions with
aryl halide were also reported.
1
The article is published in the original.
353

3
54
LIU et al.
1
EXPERIMENTAL
sensitivity of Cu(I) species. H NMR (400 MHz) was
collected on a Bruker ACF-400 spectrometer. Ele-
mental analyses for C, H, and N were carried out on a
Bio-Rad elemental analyzer. Thermogravimetric
Materials and methods. Dppf, trifluoroacetic acid,
-methoxy aniline and other chemicals were obtained
4
from commercial sources. All solvents were dried by (TG) analysis was carried out using an Exstar 6000
–1
common methods and freshly distilled prior to use.
Dichloro-bridged copper(I) complex [(Dppf)Cu] (μ-
analyzer in nitrogen at a heating rate of 15°C min .
2
Electron spray ion (ESI) mass spectrum was measured
Cl) ] and substituted amides were synthesized accord- using a Waters Platform ZMD4000 LC/MS mass
2
ing to literatures [11, 12]. Synthetic procedures were spectrometer.
carried out under a nitrogen atmosphere using a stan-
The synthesis route of the Cu(I)-amido complexes
dard Schlenk flask considering the air and moisture- are shown in Scheme 1:
OCH3
O
PPh2
Ph2P
Cl
Cl
1
2
Fe
Fe
+
R
N
H
Cu
Cu
PPh2
Ph2P
O
PPh2
Cu
Sodium methoxide
CH2Cl2
R
Fe
N
Room temperature
(I, 80%)
48 h
PPh2
(II, 68%)
OCH3
R = CF (I), CH (II), Phenyl
3
3
Scheme 1.
Synthesis of complex I. Dichloro-bridged precursor
Synthesis of complex II. The synthesis was identical
[
(Dppf)Cu] (μ-Cl) ] (0.131 g, 0.1 mmol), 2,2,2-triflu- to that of complex I, except that 2,2,2-trifluoro-N-p-
2 2
oro-N-(4-methoxy-phenyl)-acetamide (0.055 g, tolyl-acetamide (0.051 g, 0.025 mmol) was used as
0
.25 mmol) and CH ONa (0.054 g, 1.0 mmol) were auxiliary ligand. Complex II was prepared as orange
3
crystals. The yield was 112 g (68%).
placed in a Schlenk tube and CH Cl (20 mL) was
2
2
–1
added via syringe under nitrogen atmosphere. The
IR (ν, cm ): 1614 ν(C=O), 1497 νPh(C=C), 1432
mixture was stirred at room temperature for 48 h. The νCp(C=C), 1262 ν(C–F), 1164 δPh(CH), 1095 ν(P–
1
solvent was removed by rotary evaporator. Yellow Ph), 1024 δCp(CH), 837 πCp(CH). H NMR
block crystals of complex I were obtained by re-crys- (400 MHz; CDCl ; δ, ppm): 7.49–7.41 (m., 12H, Ph),
3
tallization in diethyl ether. The yield was 0.131 g 7.36 (t., J = 7.4 Hz, 8H, Ph), 7.07 (d., J = 8.2 Hz, 2H,
(
80%).
Ph of amide), 6.98 (d., J = 8.0 Hz, 2H, Ph of amide),
4
.40 (s., 4H, Cp), 4.18 (s., 4H Cp), 3.78 (s., 3H,
–1
IR (ν, cm ): 1634 ν(C=O), 1481 νPh(C=C), 1435
OMe), 2.35 (s., 3H).
νCp(C=C), 1236 ν(C–F), 1165 δPh(CH), 1099 ν(P–
1
Ph), 1032 δCp(CH), 823 πCp(CH). H NMR
For C H NO F P FeCu
4
4
37
2
3
2
(
400 MHz; CD Cl ; δ, ppm): 7.45–7.37 (m., 12H,
2 2
Anal. calcd., %
Found, %
C, 62.17
C, 63.08
H, 4.39
H, 4.32
N, 1.65
N, 1.76
Ph), 7.33 (t., J = 7.3 Hz, 8H, Ph), 6.96 (d., J = 8.7 Hz,
H, Ph of amide), 6.67 (d., J = 8.7 Hz, 2H, Ph of
amide), 4.37 (s., 4H, Cp), 4.12 (s., 4H, Cp), 3.76 (s.,
H, OMe).
2
X-ray crystallography. A suitable yellow single crys-
tal of complex I with dimensions of 0.48 × 0.36 ×
3
0
.22 mm was selected for measurement. Diffraction
For C H NO F P FeCu
43
35
2
3
2
data for I was collected at 296(2) K using a Bruker
Anal. calcd., %
Found, %
C, 61.77
C, 61.98
H, 4.22
H, 4.52
N, 1.68
N, 1.73
SMART APEX II CCD area detector diffractometer
(MoK , λ = 0.71073 Å). A total of 30239 reflections
α
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SYNTHESES, CHARACTERIZATIONS, AND REACTIVITY
355
Table 1. Crystallographic data and refinement parameters Table 2. Selected bond distances (Å) and bond angles (deg)
of complex I
for complex I
Parameter
Value
Bond
d, Å
Fw
836.05
Cu–N
1.975(4)
2.237(1)
2.265(1)
1.437(6)
1.315(6)
Color; crystal form
Crystal system
Space group
a, Å
Yellow; block
Monoclinic
Cu–P(1)
Cu–P(2)
C(37)–N
N–C(36)
P2 /n
1
9.7292(7)
22.4542(15)
17.2056(12)
90.591(4)
b, Å
Angle
ω, deg
c, Å
NCuP(2)
NCuP(1)
128.6(1)
117.6(1)
112.4(5)
β, deg
V, Å3
3
758.6(5)
P(2)CuP(1)
Z
4
ρcalcd, g cm–3
were collected in the range of 2.39° ≤ θ ≤ 27.55° by
using the ω–2θ scan mode, of which 8754 were unique
1
.477
with R = 0.0497. The crystal structure was solved by
μ, mm–1
int
1.090
Direct Methods and refined by full-matrix least
2
squares on F using the SHELXL-97 software [13, 14].
F(000)
1712
All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were generated geometrically and
treated by a mixture of independent and constrained
refinement. The crystallographic data as well as details
of data collection and refinements are summarized in
Table 1. Selected bond distances and bond angles are
shown in Table 2.
Crystal size, mm
θ Range, deg
Index range
0.48 × 0.36 × 0.22
2.39–27.55
–12 ≤ h ≤ 12,
–
–
29 ≤ k ≤ 25,
21 ≤ l ≤ 22
Supplementary material for structure I has been
deposited with the Cambridge Crystallographic Data
Centre (CCDC no. 1015222; www.ccdc.cam.ac.uk/
data_request/cif).
Reflections collected/unique (R ) 30239/8754 (0.0497)
int
N-Arylation reaction of complexes I and II with
iodobenzene are shown in Scheme 2. To a Schlenk
flask containing complex I or II (0.1 mmol), iodoben-
zene (0.020 g, 0.1 mmol) was added 25 mL DMF as
solvent under nitrogen atmosphere. The reaction mix-
ture was stirred at 110°C overnight. The reaction sys-
tem was concentrated to about 2 mL and left to stand
overnight at room temperature. Then a yellow powder
(III) was obtained by filtration. The N-arylation prod-
uct (А or В) was separated from the filtrate by TLC
using ethyl acetate–petroleumether (1 : 10) as devel-
oping solvent.
Reflections with I > 2σ(I)
Number of refinement parameters
R , wR (I > 2σ(I))
6162
479
0.0741, 0.1246
1
2
Goodness of fit on F 2
0.981
Largest diff. peak and hole, e Å3
0
.749/–0.487
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 44 No. 5 2018

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LIU et al.
O
R
PPh2
Fe
Cu
N
+
I
PPh2
OCH3
Complex I, II
PPh2
O
DMF, 110°C
Fe
Cu I + R
PPh2
N
Overnight
III
OCH3
A: R = CF , 65%
3
B: R = CH , 52%
3
Scheme 2.
III: yellow microcrystal, ESI MS (+): 617 6.4 Hz, 4H), 7.31–7.27 (d., J = 5.4 Hz, 1H), 7.16–7.13
Cu(Dppf)] .
+
(d., J = 6.7 Hz, 4H), 3.76 (s., 3H), 2.03 (s., 3H).
[
–1
А: yellow powder, 0.019 g, 65%. IR (ν, cm ): 1705,
RESULTS AND DISCUSSION
1
507, 1396, 1228, 1203, 1153, 1137, 1016, 957, 820, 767,
1
Dichloro-bridged copper(I) complex is designed as
reaction precursor to improve the solubility and stabil-
ity of Cu(I) catalyst. To get adequate amide anion,
7
48, 717. H NMR (400 MHz; DMSO; δ, ppm): 7.18
(
d., J = 8.8, 8.3 Hz, 6H), 7.05 (d., J = 9.0 Hz, 3H),
3
.32 (s., 3H).
ten-equivalent CH ONa is added to the reaction sys-
3
–1
tem. Considering the weak acidity of methanol (pK =
В: white powder, 0.013 g, 52% yield. IR (ν, cm ):
a
1
29.0 in DMSO), strong base CH ONa can easily
3
1
(
672, 1509, 1371, 1298, 1247, 1033, 832, 696. H NMR
remove the proton of all amide ligands. However, no
product was prepared when amide with bulky carbonyl
substituent (Ph) reacted with precursor, which shows
that steric substituent has a major effect on the forma-
tion of intermediate. The result looks like but is not
contradictory to the “One-pot” formation of N-aryl
benzamide because during which the intermediate can
soon convert into the N-aryaltion product and even
trace intermediate can be effective [15]. Electronic
substituent has a secondary effect on the coordination
400 MHz; DMSO; δ, ppm): 7.43–7.36 (d., J =
O
F(3)
C(42) C(41)
F(2)
F(1)
C(35)
O(1)
N
C(43)
Cu
P(2)
reaction. In detail, electron with drawing CF group
3
increases the acidity of amide, and thus, the amide
P(1)
anion is easily formed and high yield of intermediate I
(
80%) is prepared. Instead, electron-donating CH
3
group makes the corresponding amide have weak cid-
ity and intermediate II is prepared at moderate yield
(68%).
Fe
X-ray diffraction analysis of complex I is carried
out and the crystal structure is shown in Fig. 1. Unfor-
tunately, crystal II is easily efflorescent in air in less
than one minute, so its crystal structure is difficult to
be determined by X-ray diffraction method. Figure 1
shows that the Cu(I) centre is three-coordinated by
Fig. 1. Coordination environment of the Cu(I) centre in
complex I. Hydrogen atoms are omitted for clarity.
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SYNTHESES, CHARACTERIZATIONS, AND REACTIVITY
357
(a)
Complex II
Complex I
100
8
0
0
0
0
6
4
2
0
100
200 300 400 500 600
Temperature, °C
(b)
Fig. 3. TG curves of complexes I and II.
tative to discuss the thermal behaviour. The result
shows that I is stable from 50 to 245°C. There are two
obvious and continuous stages (~238–380°C) in the
process of thermal decomposition, corresponding to
the gradual decomposition of organic ligands. The
final residues are considered to be copperoxide and
ferric oxide, who account for 22.10% (calcd. 22.84%).
The TG experiments indicate complexes I and II are
thermally stable and qualified as reaction intermedi-
ates of Goldberg reaction.
Fig. 2. Views of the crystal packing linked by π π and C–
·
··
H···O interactions in complex I: 2D layer (a) and 3D
Stoichometric reactions of complexes I and II with
iodobenzene are performed under optimized condi-
tions (Scheme 2). Another Cu(I) complex (Dppf)CuI
supramolecular framework (b).
(
Scheme 2, III) has been isolated via concentration
one nitrogen atom (Cu–N (1.975(4) Å) from the
amide anion and chelated by two phosphine atoms
and settling process and identified by LC-MS-MS
analysis. The N-arylated amides A and B are obtained
(
Cu–P(1) 2.265(1), Cu–P(2) 2.237(1) Å) from the
in moderate yields (65 and 52%, respectively) and
Dppf ligand. The sum of all angles around the Cu(I)
1
+
confirmed by H NMR. Compared with CH , elec-
centre is 358.6(7)° and the Cu ion is 0.147(3) Å above
3
the plane P(1)–P(2)–N, which verifies the slight tron-withdrawing CF makes the intermediate react
3
deviation from ideal trigonal planar environment.
with iodobenzene at a relatively higher yield. Consid-
ering the well-known oxidative addition reaction (the
Complex I is assembled into a dimer via interdigi-
tation of aromatic rings with a face-to-face π···π inter- rate-limiting step of aryl halides activation), weak
actions (brown bond in Fig. 2a) with 3.662(5) Å for coordination of fluorine atom outweighing electronic
perpendicular distance and 3.826(2) Å for centroid effect increases the electron density of Cu(I) centre.
distance. The dimers are linked by four C–H···O As a result, complex I react with iodobenzene in a
interactionsinto a two-dimensional layer parallel to higher conversion than complex II.
the crystallographic yz plane (Fig. 2a). Adjacent layers
Thus, the catalytic cycle of Goldberg reaction is
simulated including the synthesis and N-arylation
reaction of intermediates. The intermediate features
Cu(I) surrounded by one N atom of amide anion and
are further connected by one weak C–H···O (orange
dotted line) and four C–H···F interactions (blue dot-
ted lines, Fig. 2b) into a three-dimensional suparmo-
lecular framework. Four relative strong C–H···F
interactions also play an important role in construct- two P atoms from Dppf. The formation of intermedi-
ing the crystal construction of I [16, 17]. These partly ate is mainly affected by steric effect of amide and is
explain why the crystal structure of I is more stable also affected by electronic effect in the order of CF >
3
than II.
CH . The N-arylation reaction of intermediate with
3
To determine the thermal competence of the inter- iodobenzene is more affected by weak coordination
mediates, TG analyses of complexes I and II were effect compared with electronic effect of the interme-
recorded (Fig. 3). Herein we selected I as a represen- diate.
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LIU et al.
ACKNOWLEDGMENTS
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Chem. Soc. Jpn., 1980, vol. 53, p. 1299.
The authors are grateful for the financial support
8
. Strieter, E.R., Bhayana, B., and Buchwald, S.L., J. Am.
from the National Natural Science Foundation of
China (nos. U1604143 and 21302082), Science and
Technology Development Project in Henan Province
Chem. Soc., 2009, vol. 131, p. 78.
9. Tye, J.W., Weng, Z., Johns, A.M., et al., J. Am. Chem.
Soc., 2008, vol. 130, p. 9971.
(
no. 172101410037) and China Scholarship Council
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