Mono- and dinuclear pincer nickel catalyzed activation and transformation of C-Cl, C-N, and C-O bonds

Article abstract of DOI:10.1021/om500452c

Condensation of 2-NH₂C₆H₄P(Et)Ph (2) with pyrrole-2-carboxaldehyde generated 2-(C₄H₄N-2′-CH - N)C₆H₄P(Et)Ph (3). Treatment of 3 with NaH and followed by (DME)NiX₂ (X = Cl, Br) afforded mononuclear pincer nickel complexes [Ni{2-(C₄H₃N-2′-CH - N)C₆H₄P(Et)Ph}X] (4a, X = Cl; 4b, X = Br). Reaction of [2-NH₂C₆H₄P(Ph)]₂(CH₂)_n (5a, n = 3; 5b, n = 4) with pyrrole-2-carboxaldehyde or 5-tert-butyl-1H-pyrrole-2-carbaldehyde formed [2-(C₄H₄N-2′-CH - N)C₆H₄P(Ph)]₂(CH₂)_n (6a, n = 3; 6b, n = 4) and [2-(5′-tBuC₄H₃N-2′-CH - N)C₆H₄P(Ph)]₂(CH₂)₄ (6c). Respective treatment of 6a-c with NaH followed by (DME)NiX₂ (X = Cl, Br) gave the dinuclear nickel complexes [Ni{2-(5′-RC₄H₂N-2′-CH - N)C₆H₄P(Ph)}X]₂(CH₂)_n (7a, R = H, X = Cl, n = 3; 7b, R = H, X = Cl, n = 4; 7c, R = H, X = Br, n = 4; 7d, R = tBu, X = Cl, n = 4). Catalysis of the complexes for the activation and transformation of C-Cl, C-N, and C-O bonds was evaluated. Complex 7c exhibited excellent catalytic activity in the cross-coupling of aryl chlorides or aryltrimethylammonium iodides with arylzinc reagents as well as of aryl sulfamates with aryl Grignard reagents. The dinuclear nickel complexes 7b-d showed higher catalytic activity than the mononuclear complexes in each type of reaction.

Full text of DOI:10.1021/om500452c

Article
pubs.acs.org/Organometallics
Mono- and Dinuclear Pincer Nickel Catalyzed Activation and
Transformation of C−Cl, C−N, and C−O Bonds
Xia Yang and Zhong-Xia Wang*
CAS Key Laboratory of Soft Matter Chemistry and Department of Chemistry, University of Science and Technology of China, Hefei,
Anhui 230026, People’s Republic of China
S
* Supporting Information
ABSTRACT: Condensation of 2-NH2C6H4P(Et)Ph (2) with
pyrrole-2-carboxaldehyde generated 2-(C4H4N-2′-CHN)-
C6H4P(Et)Ph (3). Treatment of 3 with NaH and followed
by (DME)NiX2 (X = Cl, Br) afforded mononuclear pincer
nickel complexes [Ni{2-(C4H3N-2′-CHN)C6H4P(Et)Ph}-
X] (4a, X = Cl; 4b, X = Br). Reaction of [2-NH2C6H4P-
(Ph)]2(CH2)n (5a, n = 3; 5b, n = 4) with pyrrole-2-
carboxaldehyde or 5-tert-butyl-1H-pyrrole-2-carbaldehyde
formed [2-(C4H4N-2′-CHN)C6H4P(Ph)]2(CH2)n (6a, n =
3; 6b, n = 4) and [2-(5′-tBuC4H3N-2′-CHN)C6H4P-
(Ph)]2(CH2)4 (6c). Respective treatment of 6a−c with NaH
followed by (DME)NiX2 (X = Cl, Br) gave the dinuclear nickel complexes [Ni{2-(5′-RC4H2N-2′-CHN)C6H4P(Ph)}-
X]2(CH2)n (7a, R = H, X = Cl, n = 3; 7b, R = H, X = Cl, n = 4; 7c, R = H, X = Br, n = 4; 7d, R = tBu, X = Cl, n = 4). Catalysis of
the complexes for the activation and transformation of C−Cl, C−N, and C−O bonds was evaluated. Complex 7c exhibited
excellent catalytic activity in the cross-coupling of aryl chlorides or aryltrimethylammonium iodides with arylzinc reagents as well
as of aryl sulfamates with aryl Grignard reagents. The dinuclear nickel complexes 7b−d showed higher catalytic activity than the
mononuclear complexes in each type of reaction.
catalyst.6g Our group carried out the reaction of aryltrimethy-
INTRODUCTION
■
lammonium salts with organozinc reagents using Ni(PCy3)2Cl2
Transition-metal-catalyzed cross-coupling reactions are power-
or amido pincer nickels as the catalysts.6b,c,e Phenolic
ful tools for construction of C−C bonds in organic systhesis.1
derivatives are other types of versatile electrophiles. Aryl
Nucleophiles used in the cross-couplings include Grignard
triflates and sulfonates were most widely investigated in the
reagents and organozinc, -boron, -silicon, and -tin reagents.1,2
phenol-derived electrophiles.8 Less common phenol-based
Electrophiles are principally organic halides, especially
electrophiles such as esters, carbonates, carbamates, sulfamates,
bromides and iodides at the earlier stage.1−3 Organic chlorides
phenolate, and ethers were also developed in the past few
as the inert electrophiles have received intense attention over
years.8−10 Among them, sulfamates are attractive due to their
the past 15 years because of their lower cost and the wider
ease of preparation, significant stability under various reaction
diversity of available compounds in comparison with bromides
conditions, and the potential to direct the installation of other
and iodides.4 Some effective catalysts, including palladium,
functional groups onto an aromatic ring by C−H activation or
ortho metalation prior to cross-coupling.10d,j The reported
nickel, copper, iron, and cobalt catalysts, have been developed
for the C−Cl bond activation.2f,5 Representative examples
catalytic reactions using sulfamates as electrophilic partners
include Buchwald biarylphosphine/Pd catalysts,5b sterically
include Suzuki couplings,10b−i Kumada couplings,10j−l amina-
demanding trialkylphosphine/Pd catalysts,5c,d N-heterocyclic
tion reactions,10m−p and C−H bond functionalizations.10q,r
carbene/Pd catalysts,5e−g pincer nickel catalysts,5i,j butadiene/
Nickel, palladium, iron, and cobalt complexes were demon-
Ni catalysts,5k−m N-heterocyclic carbene/Fe and Co(acac)3
catalysts, etc.5q−s In recent years aromatic amines have gained
increasing attention as electrophiles through C−N bond
activation. However, the C−N bonds in an aromatic amine
are very inert. Hence, aromatic amines were usually trans-
formed to ammonium salts or diazonium salts to weaken the
C−N bonds before catalytic cleavage.6,7 For example, Wenkert
and Reeves respectively reported nickel- or palladium-catalyzed
reactions of aryltrimethylammonium salts with Grignard
reagents.6f,i MacMillan et al. reported the Suzuki coupling of
aryltrimethylammonium triflates using Ni(cod)2/IMes as the
strated to catalyze these transformations.10c−p For example,
FeCl2/SIMes catalyzes cross-coupling of aryl sulfamates and
primary or secondary alkyl Grignard reagents.10l Ni(Cl)(Cp)-
IMes catalyzes cross-coupling of aryl sulfamates and aryl
Grignard reagents.10j
Special Issue: Catalytic and Organometallic Chemistry of Earth-
Abundant Metals
Received: April 29, 2014
Published: September 23, 2014
© 2014 American Chemical Society
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We intended to develop highly effective and widely
applicable catalyst systems for the activation and transformation
of C−Cl, C−N, and C−O bonds. The use of bimetallic
catalysts was considered as an efficient way to achieve this aim.
Bimetallic catalysts have attracted considerable attention in
recent years due to the existence of cooperative catalytic
effects.11−14 The bimetallic cooperativity can improve the
activities and/or selectivities of the catalysts, make reaction
conditions milder, and lead to making the reaction more
efficient. A range of reactions such as ethylene polymer-
ization,12 ring-opening polymerization of cyclic esters,13 C−C
couplings,14 and asymmetric transformations11b,15 have been
carried out using bimetallic catalysts, and the cooperative effect
was observed in the reactions. On the basis of the achievements
of bimetallic catalysis indicated above and the studies of pincer
nickel catalysts by us and other groups,5j,6a−c,16 we designed
and synthesized bimetallic nickel complexes supported by
P,N,N-pincer ligands. These bimetallic complexes were proven
to effectively catalyze the activation of aryl C−Cl, C−N, and
C−O bonds. For the purpose of comparison, two related
monounclear complexes of nickel were also synthesized and
evaluated for the catalysis. Herein we report the results.
sodium hydride and then Ni(DME)X2 (X = Cl, Br) generated
the nickel complexes [Ni{2-(C4H3N-2′-CHN)C6H4P(Et)-
Ph}X] (4a, X = Cl; 4b, X = Br). Similar treatment of 1 with
sodium followed by 0.5 equiv of 1,3-dibromopropane or 1,4-
dibromobutane gave [2-NH2C6H4P(Ph)]2(CH2)n (5a, n = 3;
5b, n = 4). Reaction of 5a,b with 2 equiv of pyrrole-2-
carboxaldehyde or 5-tert-butyl-1H-pyrrole-2-carbaldehyde pro-
duced the diimines [2-(5′-RC4H3N-2′-CHN)C6H4P-
(Ph)]2(CH2)n (6a, R = H, n = 3; 6b, R = H, n = 4; 6c, R =
tBu, n = 4). Deprotonation of 6a−c with sodium hydride
followed by treatment of the deprotonated species with
Ni(DME)X2 (X = Cl, Br) afforded the dinuclear nickel
complexes [Ni{2-(5′-RC4H3N-2′-CHN)C6H4P(Ph)}-
X]2(CH2)n (7a, R = H, X = Cl, n = 3; 7b, R = H, X = Cl, n
= 4; 7c, R = H, X = Br, n = 4; 7d, R = tBu, X = Cl, n = 4). 5a,b
are both known compounds, and they were characterized by
1H, 13C, and 31P NMR spectra.18 Compounds 2, 3, and 6a−c
were characterized by 1H, 13C, and 31P NMR spectroscopy and
elemental analyses. It is noteworthy that the respective NMR
spectra of 6a,b gave two sets of signals. For example, the 31P
NMR spectra of 6a showed two signals at δ −23.89 and
−27.58, respectively. The 31P NMR signals of 6b appeared at δ
−21.41 and −22.53, respectively. This is ascribed to the
presence of cis and trans isomers of the imines. On the basis of
RESULTS AND DISCUSSION
■
1
their H and 31P NMR spectra, the ratios of the isomers are
Synthesis and Characterization of Mono- and
Dinuclear P,N,N-Pincer Nickel Complexes. The synthesis
of the ligand precursors and mono- and dinuclear nickel
complexes is summarized in Scheme 1. Compound 1 is known
and was prepared according to the reported method.17 The
reaction of 1 with sodium metal and then EtBr yielded 2-
NH2C6H4P(Et)Ph (2). Condensation of 2 with pyrrole-2-
carboxaldehyde afforded the corresponding pyrrolylimine 2-
(C4H4N-2′-CHN)C6H4P(Et)Ph (3). Treatment of 3 with
about 2:1 for 6a and 1.1:1 for 6b. Compound 6c showed only
one set of NMR signals. Its 31P NMR signal appeared at δ
−24.64. This is ascribed to the steric hindrance of tBu groups,
which leads to the existence of only trans imines in the
molecule. Complexes 4a,b and 7a−d are diamagnetic crystalline
solids and were characterized by 1H, 13C, and 31P NMR
spectroscopy, HR-MS, and elemental analyses. The NMR
spectra of each of the complexes displayed one set of signals,
with no isomers being observed. For example, the 31P NMR
spectrum of each complex showed only one signal. The 1H and
13C NMR spectra of the complexes also matched their
respective structures. The HR-MS of 4a,b gave molecular ion
signals, whereas the HR-MS of 7a−d gave [M − X]+ fragment
signals.
Scheme 1. Synthesis of Mono- and Dinuclear P,N,N-Pincer
Nickel Complexes
The structures of complexes 4b and 7c were further
confirmed by single-crystal X-ray diffraction analyses. The
ORTEP drawing of complex 4b is presented in Figure 1, along
with selected bond lengths and angles. In the molecule the
central nickel atom is coordinated by P1, N1, N2, and Br
atoms, having a distorted-square-planar geometry. The N1−
Ni1−Br1 atoms (bond angle 178.65(10)°) is approximately
linear. The P1−Ni1−N2 atoms (bond angle 170.86(12)°) are
also near linear. The N1−Ni1−P1 and N1−Ni1−N2 angles
(87.05(10) and 83.88(14)°, respectively) are both slightly
smaller than a right angle. The Ni1−N1 distance of 1.898(3) Å
is slightly shorter than that of Ni1−N2 (1.906(3) Å), and both
are close to those in pincer nickel complexes [Ni(Cl){N(2-
Ph2PC6H4)2}] (1.895(3) Å)19 and [Ni(Cl){N{CH(Ph)P-
(Ph2)O}C6H4(PPh2)-2}] (1.893(5) Å).16h The Ni−P
distance of 2.1402(11) Å is within the normal range in the
pincer nickel complexes.16h,i,19
The ORTEP drawing of complex 7c is presented in Figure 2,
along with selected bond lengths and angles. The molecule is
centrosymmetric. Each nickel atom has a distorted-square-
planar geometry, and the two pincer nickel units are bridged by
a 1,4-butylene group attached to the P atoms. The distance
between Ni1 and Ni1i is 8.5129 Å. In each pincer nickel unit
the coordination environment of the central nickel atom is very
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catalytic efficiency at 20, 65, and 90 °C, respectively. However,
the above reactions also showed that higher temperature was
beneficial to improving the product yields (Table 1, entries 1−
Table 1. Optimization of Reaction Conditions and
Evaluation of Catalytic Activity of Complexes 4a,b and 7a−d
in the Cross-Coupling of p-MeOC6H4Cl with p-
a
MeC6H4ZnCl
complex
time
(h)
yield
b
entry
1
(amt (mol %))
solvent
T (°C)
(%)
7c (0.25)
7c (0.25)
7c (0.25)
7c (0.5)
7c (0.5)
7c (0.5)
7c (0.5)
THF/NMP
(1/1)
20
12
12
12
12
24
24
24
10
65
68
86
96
31
62
2
3
4
5
6
7
THF/NMP
(1/1)
65
90
90
90
90
90
THF/NMP
(1/1)
THF/NMP
(1/1)
Figure 1. ORTEP drawing (30% probability) of complex 4b. Selected
bond lengths (Å) and angles (deg): Ni1−P1 2.1402(11), Ni1−N1
1.898(3), Ni1−N2 1.906(3), Ni1−Br1 2.2866(7), N1−C7 1.318(5);
P1−Ni1−N1 87.05(10), N1−Ni1−N2 83.88(14), N2−Ni1−Br1
97.32(11), P1−Ni1−Br1 91.75(4), P1−Ni1−N2 170.86(12), N1−
Ni1−Br1 178.65(10).
THF/NMP
(1/1)
THF/NMP
(2/1)
THF/NMP
(1/2)
8
7c (0.5)
7c (0.5)
7c (0.5)
7c (0.5)
NMP
THF
DMA
90
90
90
90
24
24
24
24
40
34
67
30
9
10
11
THF/DMA
(1/1)
12
13
14
15
16
7a (0.5)
7b (0.5)
7d (0.5)
4a (1.0)
4b (1.0)
THF/NMP
(1/1)
90
90
90
90
90
24
24
24
24
24
79
85
88
66
76
THF/NMP
(1/1)
THF/NMP
(1/1)
THF/NMP
(1/1)
THF/NMP
(1/1)
a
Unless otherwise stated, p-MeC6H4ZnCl was prepared from p-
MeC6H4MgBr and ZnCl2 in the presence of 2 equiv of LiCl; 0.5 mmol
b
of p-MeOC6H4Cl, and 0.75 mmol of p-MeC6H4ZnCl. Isolated yield.
3). The reaction was markedly improved when the catalyst
loading was increased to 0.5 mol % and the reaction time was
lengthened to 24 h, an almost quantitative yield being achieved
(Table 1, entries 4 and 5). Solvents were also screened for the
7c-catalyzed reaction, including NMP, THF, DMA, 1/2 and 2/
1 mixtures of THF and NMP, and a 1/1 mixture of THF and
DMA. All of these solvents were proven to be less effective than
the 1/1 mixture of THF and NMP (Table 1, entries 6−11).
We then examined the catalysis of other complexes using the
optimized conditions. Complexes 7a,b,d were effective for the
cross-coupling reaction (Table 1, entries 12−14). However,
their activity is lower than that of 7c and the activity order is
approximately 7c > 7d > 7b > 7a. It seems that a longer linker
between the two pincer nickel units is beneficial to the catalytic
activity. A pincer nickel bromide also displayed catalytic activity
higher than that of its chloride partner (7a vs 7b) for unclear
reasons. The tBu group on the pyrrolyl ring seems to affect the
activity to a lesser extent (7b vs 7d). Mononuclear complexes
4a,b were also evaluated using the same reaction as above at 90
°C with 1 mol % of complex loadings. Both of them showed
activity lower than that of any of the complexes 7a−d. The
bromide 4b was also more active than chloride 4a (Table 1,
entries 15 and 16).
Figure 2. ORTEP drawing (30% probability) of complex 7c. Selected
bond lengths (Å) and angles (deg): Ni1−N1 1.899(3), Ni1−N2
1.896(3), Ni1−P1 2.1399(11), Ni1−Br1 2.2956(7); N1−Ni1−P1
86.57(11), N1−Ni1−N2 83.85(15), P1−Ni1−Br1 93.00(4), N2−
Ni1−Br1 96.46(11), P1−Ni1−N2 169.87(12), N1−Ni1−Br1
177.91(9).
similar to that in 4b. The Ni1−N1 distance of 1.899(3) Å is
almost same as that of Ni1−N2 (1.896(3) Å), and both are
close to the corresponding values in 4b. The Ni−P distance of
2.1399(11) Å is also very close to that in 4b (2.1402(11) Å),
whereas the Ni−Br distance of 2.2956(7) Å is slightly longer
than that in 4b (2.2866(7) Å).
Catalysis of Complexes 4a,b and 7a−d. (1). Catalytic
Coupling of Aryl Chlorides with Arylzinc Chlorides. The
reaction conditions were screened through the reaction of p-
MeOC6H4Cl with p-MeC6H4ZnCl using 7c as the catalyst. A
1/1 mixture of THF and NMP has been reported to be a
suitable solvent for a range of Negishi couplings. We also chose
this solvent for the preliminary condition screening. When 0.25
mol % of complex 7c was loaded, it showed relatively low
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In the reactions mentioned above, the zinc reagent p-
MeC6H4ZnCl was prepared from the corresponding Grignard
reagent and ZnCl2 in the presence of 2 equiv of LiCl. The zinc
reagent prepared from Grignard reagent and ZnCl2 in the
absence of LiCl resulted in a slightly lower product yield (Table
2). Deactivated, unactivated, and activated electrophilic
Table 3. Reaction of Aryl Chlorides with ArZnCl Catalyzed
by 7c or 4b
a
7c (0.5 mol %)
Ar1‐Cl + Ar2‐ZnCl ⎯⎯o⎯⎯r⎯4⎯b⎯⎯⎯(⎯1⎯⎯m⎯o⎯⎯l⎯%⎯⎯→) Ar1‐Ar2
THF/NMP (1/1)
90 °C, 12 or 24 h
Table 2. LiCl effect in 7c-Catalyzed Cross-Coupling
a
Reaction of Aryl Chlorides with ArZnCl
Ar1‐Cl + Ar2‐ZnCl ⎯T⎯⎯H7⎯⎯cF⎯(/⎯⎯0N⎯.5⎯M⎯m⎯P⎯o⎯=⎯l ⎯%⎯1⎯)→/1 Ar1‐Ar2
90°C
b
entry
Ar1
C6H5
Ar2
time (h)
yield (%)
c
1
p-MeOC6H4
p-MeOC6H4
p-MeC6H4
p-MeC6H4
p-MeC6H4
p-MeC6H4
24
24
12
12
12
12
94
16
86
82
93
68
d
2
C6H5
c
3
p-MeOC6H4
p-MeOC6H4
p-CF3C6H4
p-CF3C6H4
d
4
c
5
d
6
a
The reactions were performed with 0.5 mmol of aryl chlorides and
0.75 mmol of arylzinc chlorides according to the conditions indicated
b
c
by the above equation. Isolated yield. Arylzinc chlorides were
prepared from the corresponding Grignard reagents and ZnCl2 in the
presence of 2 equiv of LiCl. Arylzinc chlorides were prepared from
d
the corresponding Grignard reagents and ZnCl2 without LiCl additive.
substrates gave consistent results. The low reactivity of the
zinc reagent prepared from a Grignard reagent and ZnCl2
might be due to aggregation of the arylzinc reagent with the
coproduct MgCl2. The role of LiCl additive might be to break
the aggregation.20
The substrate scope was examnied using complex 7c under
the optimized conditions. Unactivated and deactivated aryl
chlorides, including PhCl, p-MeC6H4Cl, p-MeOC6H4Cl, and o-
MeOC6H4Cl, were proven to couple smoothly with p-
MeC6H4ZnCl, o-MeC6H4ZnCl, p-MeOC6H4ZnCl, and p-
Me2NC6H4ZnCl in the presence of 0.5 mol % of 7c (Table
3, entries 1−7). p-Me2NC6H4ZnCl showed higher reactivity
than the others. Its reaction with p-MeC6H4Cl can be carried
out at lower temperature and less loading of 7c (Table 3,
entries 4 and 5). o-MeC6H4ZnCl was less reactive than the
para-substituted phenylzinc reagents due to steric hindrance.
Reaction of o-MeOC6H4Cl with p-MeC6H4ZnCl gave a good
result on catalysis with 0.5 mol % of 7c, but the yield was lower
than that of p-MeOC6H4Cl under the same conditions (Table
1, entry 5 and Table 3, entry 7). Electron-poor aryl or
heteroaryl chlorides, including p-Et2NC(O)C6H4Cl, p-PhC-
(O)C6H4Cl, p-EtOC(O)C6H4Cl, p-CF3C6H4Cl, 2-chloropyr-
idine, and 2-chloro-4-methylquinoline, exhibited good reac-
tivity. Their reaction with electron-rich arylzinc reagents often
required less catalyst loading or lower reaction temperature and
gave excellent product yields (Table 3, entries 8−25). However,
p-NCC6H4Cl as an electron-poor electrophile showed relatively
low reactivity in comparison with those mentioned above. Its
reaction required much higher catalyst loading to achieve good
product yield (Table 3, entries 26 and 27). This is ascribed to
the coordination of the nitrile group with the catalyst species,
which decreases the catalytic activity of the active catalyst.21 p-
CF3C6H4ZnCl displayed relatively low reactivity due to its
electron-poor properties. It led to good reaction results only
when electron-poor aryl chlorides such as p-Et2NC(O)C6H4Cl,
p-PhC(O)C6H4Cl, and p-EtOC(O)C6H4Cl were employed
a
Unless otherwise stated, reactions were performed with 0.5 mmol of
aryl chlorides and 0.75 mmol of arylzinc chlorides according to the
conditions indicated by the above equation; arylzinc chlorides were
prepared from the corresponding Grignard reagents and ZnCl2 in the
presence of 2 equiv of LiCl. Isolated yield. The bath temperature was
40 °C. 0.25 mol % of 7c or 0.5 mol % of 4b was employed. 1 mol %
b
c
d
e
f
of 7c or 2 mol % of 4b was employed. 0.125 mol % of 7c or 0.25 mol
% of 4b was employed.
(Table 3, entries 28−30). As seen above, functional groups,
including OMe, NMe2, CF3, C(O)OEt, C(O)NEt2, PhC(O),
CN, and heteroaryl groups, are well tolerated. For comparison
the catalysis of complex 4b was tested in each reaction (Table
3). Under comparable conditions 4b exhibited lower activity
than 7c. This may be due to the existence of cooperative effects
in a bimetallic system.
(2). Catalytic Coupling of Aryltrimethylammonium Salts
with Arylzinc Chlorides. Complex 7c was chosen as the catalyst
for the condition screening using the reaction of PhNMe3 I
with p-MeOC6H4ZnCl in a 1/1 mixture of THF and NMP with
0.5 mol % of catalyst loading. The reaction temperature
+ −
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remarkably affected the product yields. When the temperature
changed from 25 to 65 °C the yields changed from 70 to 99%
(Table 4, entries 1−3). A series of solvents were screened,
14−17). In addition, KI additive was found to improve the
reaction of PhNMe3 Cl− and PhNMe3 OTf− with p-
MeOC6H4ZnCl. The former gave a 90% yield of 4-methoxy-
1,1′-biphenyl, and the latter led to the product in 93% yield
(Table 4, entries 18 and 19). The counterion effect may result
from interaction of the central metal with the anions during the
catalytic cycle. The iodide anion may provide better
stabilization to the central nickel atom or ion through
coordination. The weakly coordinating anion OTf− and
noncoordinating anion BF4− do not provide better stabilization
or provide less stabilizing actions.22
+
+
Table 4. Optimization of Reaction Conditions and
Evaluation of Catalytic Activity of Complexes 4a,b and 7a−d
+
in the Cross-Coupling Reactions of PhNMe3 X− with p-
a
MeOC6H4ZnCl
b
The catalysis of complexes 7a,b,d and 4a,b was evaluated at
65 °C in a 1/1 mixture of THF and NMP with 0.5 mol % (for
7a,b,d) or 1 mol % (for 4a,b) catalyst loadings (Table 4, entries
20−24). Complex 7d was proven to have activity close to that
of 7c. Complex 7b is more active than 7a. The activity of
complex 4b is higher than that of 4a and is close to that of 7a.
The activity order is 7c ≥ 7d > 7b > 7a ≅ 4b > 4a. This activity
order is approximately consistent with that for catalyzing
coupling of aryl chlorides with arylzinc reagents and shows that
the dinuclear complexes with 1,4-butylene as a linker are more
active than the complex with a 1,3-propylene linker or the
mononuclear complexes. In addition, a bulkier ligand seems to
be beneficial to the catalysis in this coupling (7b vs 7d).
The substrate scope was examined using complex 7c. We
noticed that a 0.25 mol % amount of 7c can drive most
coupling reactions to completion under the optimized
temperature and solvent conditions. For an electron-rich
arylzinc reagent such as p-Me2NC6H4ZnCl or activated
entry
complex
X
solvent
T (°C) yield (%)
1
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7c
7a
7b
7d
4a
4b
I
I
I
I
I
I
I
I
I
I
I
I
I
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/2)
THF/NMP (2/1)
THF
25
45
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
65
70
83
99
69
64
69
66
−
86
76
93
75
11
76
77
94
87
90
93
79
88
96
74
78
2
3
4
5
6
7
NMP
8
toluene
9
DMA
10
11
12
DMF
THF/DMA (1/1)
THF/DMF (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
THF/NMP (1/1)
c
13
14
15
16
17
OTf
BF4
Br
Cl
Cl
OTf
I
+ −
d
electrophile such as p-EtOC(O)C6H4NMe3 I 0.125 mol %
18
d
of 7c is able to drive the reaction to completion (Table 5,
entries 3, 10, 13, and 16). Unactivated and deactivated
aryltrimethylammonium salts can effectively react with para-
substituted phenylzinc chlorides (Table 5, entries 1−5).
However, the reaction of o-MeC6H4ZnCl with p-
19
20
21
22
I
I
e
23
I
e
+ −
24
I
MeOC6H4NMe3 I gave a relatively low product yield (Table
a
5, entry 7). Increasing catalyst loadings can improve the
reaction to a lesser extent. For example, 0.5 mol % of 7c led to
81% yield of the cross-coupling product. This results from the
hindering effect of the o-methyl group in o-MeC6H4ZnCl. The
Unless otherwise stated, reactions were carried out according to the
conditions indicated by the above equation using 0.5 mmol of
phenyltrimethylammonium salts and 0.75 mmol of p-MeOC6H4ZnCl;
p-MeOC6H4ZnCl was prepared from p-MeOC6H4MgBr and ZnCl2 in
the presence of 2 equiv of LiCl. Isolated yield. p-MeOC6H4ZnCl was
prepared from p-MeOC6H4MgBr and ZnCl2. 1 equiv of KI additive
b
c
+ −
o-methyl group in o-MeC6H4NMe3 I seems to affect the
d
+ −
reactions to a lesser extent. The reaction of o-MeC6H4NMe3 I
e
was employed. 1 mol % of catalyst was used.
with p-MeOC6H4ZnCl or p-Me2NC6H4ZnCl gave excellent
yields (Table 5, entries 8 and 10). The reaction of activated
including 1/2 and 2/1 mixtures of THF and NMP, THF, NMP,
toluene, DMA, DMF, a 1/1 mixture of THF and DMA, and a
1/1 mixture of THF and DMF. The results showed that all of
the solvents were less effective than the 1/1 mixture of THF
and NMP, although a 1/1 mixture of THF and DMA also led
to good results (Table 4, entries 4−12). The zinc reagent p-
MeOC6H4ZnCl used in the above reactions was prepared from
p-MeOC6H4MgBr and ZnCl2 in the presence of 2 equiv of
LiCl. When the LiCl additive was absent, the reaction resulted
in a much lower yield (Table 4, entry 13). The reason may be
same as that indicated in Catalytic Coupling of Aryl Chlorides
with Arylzinc Chlorides. The counterion effect was also
+ −
aryltrimethylammonium salts such as p-PhC(O)C6H4NMe3 I ,
+ −
+ −
p-EtOC(O)C6H4NMe3 I , and p-CF3C6H4NMe3 I with elec-
tron-rich and electron-poor arylzinc reagents (even o-
MeC6H4ZnCl) gave excellent yields (Table 5, entries 11−21).
Reaction of p-CF3C6H4ZnCl with deactivated p-
+ −
MeOC6H4NMe3 I afforded th cross-coupling product in low
yield. The reaction cannot be further improved by increasing
catalyst loadings. The reaction of 2-pyridyltrimethylammonium
+ −
+ −
iodide with either p-MeC6H4NMe3 I or p-MeOC6H4NMe3 I
gave moderate yields. However, the reactions were markedly
improved by increasing the amount of 7c to 0.5 mol %,
affording the corresponding products in 99% and 91% yields,
respectively (Table 5, entries 23−26). In all the reactions the
CAr−N bonds of the aryltrimethylammonium salts are
selectively activated, although the CAr−N bonds are stronger
than the CMe−N bonds.23 A series of functional groups,
including OMe, NMe2, CF3, C(O)OEt, PhC(O), and pyridyl
groups, are tolerated.
−
investigated with Br−, Cl−, OTf−, and BF4 , respectively, as a
counterion in a 1/1 mixture of THF and NMP at 65 °C. The
tetrafluoroborate and triflate salts exhibited the lowest
reactivity. The bromide salt showed higher reactivity than the
chloride salt, the reaction of the former giving 94% product
yield and that of the latter giving 87% yield. However, both of
them were less reactive than the iodide salt (Table 4, entries
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Article
were used as reactants and 7c was used as the catalyst for the
screening of reaction conditions. The reaction gave a low yield
when it was performed in THF at room temperature for 12 h
with 0.5 mol % catalyst loading. The product yield was
markedly increased when the reaction time was prolonged to
24 h and the reaction temperature was raised to 35 °C (Table
6, entries 1−3). The reaction was further improved when the
Table 5. Reaction of Aryltrimethylammonium Iodides with
ArZnCl Catalyzed by 7c or 4b
a
7c (0.25 mol %)
Ar1‐NMe+3 I− + Ar2‐ZnCl ⎯o⎯⎯r⎯4⎯⎯b⎯⎯(⎯0⎯.5⎯⎯m⎯⎯o⎯⎯l⎯%⎯→) Ar1‐Ar2
THF/NMP (1/1)
65 °C, 12 h
b
yield (%)
entry
Ar1
Ar2
7c
4b
Table 6. Optimization of Reaction Conditions and
Evaluation of Catalytic Activity of Complexes 4a,b and 7a−d
1
2
Ph
Ph
Ph
p-MeOC6H4
p-Me2NC6H4
p-Me2NC6H4
p-MeC6H4
98
99
99
96
98
99
78
87
99
99
99
99
97
99
99
96
99
96
83
98
97
56
76
99
70
91
72
99
91
69
93
91
59
85
99
92
80
99
84
92
99
90
85
82
61
86
88
28
53
71
70
75
in the Cross-Coupling Reactions of PhOSO2NMe2 with p-
a
MeOC6H4MgBr
c
3
b
4
5
6
7
8
9
p-MeOC6H4
m-MeOC6H4
m-MeOC6H4
p-MeOC6H4
o-MeC6H4
entry
complex (amt (mol %))
solvent
T (°C)
yield (%)
p-MeC6H4
c
1
7c (0.5)
7c (0.5)
7c (0.5)
7c (0.75)
7c (0.75)
7c (0.75)
7c (0.75)
7a (0.75)
7b (0.75)
7d (0.75)
4a (1.5)
4b (1.5)
THF
THF
THF
THF
Et2O
dioxane
toluene
THF
THF
THF
THF
THF
25
35
35
35
35
35
35
35
35
35
35
35
8
27
69
88
38
34
78
69
82
87
65
71
p-Me2NC6H4
o-MeC6H4
c
2
3
p-MeOC6H4
p-Me2NC6H4
p-Me2NC6H4
p-MeC6H4
4
o-MeC6H4
5
c
10
o-MeC6H4
6
11
12
p-PhC(O)C6H4
p-EtOOCC6H4
p-EtOOCC6H4
p-EtOOCC6H4
p-EtOOCC6H4
p-EtOOCC6H4
p-CF3C6H4
p-CF3C6H4
p-PhC(O)C6H4
p-PhC(O)C6H4
p-EtOOCC6H4
p-MeOC6H4
2-Py
7
p-MeC6H4
8
c
13
p-MeC6H4
9
14
15
o-MeC6H4
10
11
12
p-MeOC6H4
p-MeOC6H4
p-MeC6H4
c
16
17
18
19
a
Unless otherwise stated, the reactions were run for 24 h using 0.5
mmol of PhOSO2NMe2 and 0.75 mmol of p-MeOC6H4MgBr.
Isolated yield. Reaction time was 12 h.
p-MeOC6H4
p-CF3C6H4
p-CF3C6H4
p-CF3C6H4
p-CF3C6H4
p-MeC6H4
b
c
d
20
21
22
23
catalyst loading was increased to 0.75 mol %, 88% yield being
achieved (Table 6, entry 4). Other solvents, including Et2O,
dioxane, and toluene, were also examined, and they were
proven to be less effective than THF (Table 6, entries 5−7).
Complexes 7a,b,d and 4a,b were tested under the optimized
conditions. Complex 7d showed almost the same activity as 7c,
and they are more active than 7b and 7a. The activity of
complex 4b is close to that of 7a and higher than that of 4a.
The activity order is 7c ≅ 7d > 7b > 7a ≅ 4b > 4a (Table 6,
entries 8−12). The results are consistent with those seen in
Catalytic Coupling of Aryl Chlorides with Arylzinc Chlorides
and Catalytic Coupling of Aryltrimethylammonium Salts with
Arylzinc Chlorides. Thus, the dinuclear complexes with a 1,4-
butylene linker are more active than the complexes with a 1,3-
propylene linker. The dinuclear complexes also exhibited higher
activity than the mononuclear complexes under comparable
conditions (7b vs 4a and 7c vs 4b).
Complexes 7c,d exhibited almost the same activity on the
basis of the above evaluation. We chose 7c as the catalyst to
examine the substrate scope under the optimized conditions.
PhOSO2NMe2 also reacted smoothly with p-Me2NC6H4MgBr
in the presence of 7c, giving p-Me2NC6H4Ph in 96% yield
(Table 7, entry 1). The deactivated aryl sulfamate p-
MeOC6H4OSO2NMe2 reacted with p-MeC6H4MgBr to afford
4-methoxy-4′-methylbiphenyl in 90% yield. No C−OMe bond
activation was observed. The reaction of p-Me2NC6H4MgBr
with p-MeOC6H4OSO2NMe2 gave an unusually low yield in
comparison with p-MeC6H4MgBr for unclear reasons. Increas-
ing the catalyst loading to 1 mol % resulted in a 99% yield of
the desired product (Table 7, entries 2−4). The reaction of o-
MeC6H4MgBr with p-MeOC6H4OSO2NMe2 gave a yield much
lower than that of p-MeC6H4MgBr (72% vs 90%). This is
ascribed to the steric hindrance of o-MeC6H4MgBr (Table 7,
d
24
2-Py
p-MeC6H4
25
2-Py
p-MeOC6H4
p-MeOC6H4
d
26
2-Py
a
Unless otherwise stated, reactions were carried out according to the
conditions indicated by the above equation using 0.5 mmol of
aryltrimethylammonium iodides and 0.75 mmol of arylzinc chlorides;
arylzinc chlorides were prepared from the corresponding arylmagne-
sium bromides and ZnCl2 in the presence of 2 equiv of LiCl. Isolated
yield. 0.125 mol % of 7c or 0.25 mol % of 4b was employed. 0.5 mol
% of 7c or 1 mol % of 4b was employed.
b
c
d
For comparison, the catalysis of complex 4b was tested for
each reaction (Table 5). Complex 4b showed good catalytic
activity in quite a few reactions tested but exhibited lower
activity than complex 7c in almost every case under comparable
conditions.
Several nickel-catalyzed cross-coupling reactions of aryltri-
methylammonium salts and arylzinc reagents have been
reported.6b,c,e The dinuclear complex 7c exhibited the highest
activity in comparison with the reported complexes. For
example, the Ni(PCy3)2Cl2-catalyzed reaction of p-
+ −
MeOC6H4NMe3 I with p-MeC6H4ZnCl required 2 mol %
catalyst loading and 90 °C reaction temperature.6e The same
reaction catalyzed by the pincer nickel complex [Ni(Cl){N(2-
Ph2PC6H4)(C(Ph)NC6H4Me-4′)}] required 1 mol %
catalyst loading and 85 °C reaction temperature.6b However,
the reaction catalyzed by 7c proceeded under milder conditions
(65 °C), required a lower catalyst amount (0.25 mol % 7c), and
gave a higher product yield (96%).
(3). Catalytic Coupling of Aryl Sulfamates with Aryl
Grignard Reagents. PhOSO2NMe2 and p-MeOC6H4MgBr
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can catalyze the reaction of aryl sulfamates with aryl Grignard
reagents.10j Complex 7c exhibited better catalytic results than
Ni(Cl)(Cp)IMes. For example, the Ni(Cl)(Cp)IMes-catalyzed
reaction of p-MeOC6H4OSO2NMe2 with PhMgBr at 40 °C
with 1 mol % catalyst loading gives the cross-coupling product
in 47% yield. However, the 7c-catalyzed reaction of p-
MeOC6H4OSO2NMe2 with p-MeC6H4MgBr at 35 °C and
0.75 mol % catalyst loading leads to 90% yield of cross-coupling
product.
The catalysts we present above show similar activity order for
each type of reaction, including the activation and trans-
formation of aryl C−Cl, C−N, and C−O bonds. The bimetallic
complexes with (CH2)4 linkers are more active than that with a
(CH2)3 linker and are superior to the monometallic systems.
This is ascribed to bimetallic cooperative activation of the
electrophilic substrate, as shown in Figure 3 (structure B). In
Table 7. Reaction of Aryl Sulfamates with Aryl Grignard
Reagents Catalyzed by 7c or 4b
a
7c (0.75 mol %)
or 4b (1.5 mol %)
Ar1‐OSO2NMe2 + Ar2‐MgBr ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→ Ar1‐Ar2
THF, 35 °C, 24 h
b
yield (%)
entry
Ar1
Ar2
7c
4b
1
2
3
Ph
p-Me2NC6H4
p-MeC6H4
96
90
78
99
72
81
93
99
99
97
99
99
86
78
83
89
99
92
83
83
46
91
43
62
89
93
92
89
80
78
72
56
61
83
90
56
p-MeOC6H4
p-MeOC6H4
p-MeOC6H4
p-MeOC6H4
o-MeC6H4
o-MeC6H4
2-naphthyl
2-naphthyl
p-EtOOCC6H4
p-EtOOCC6H4
p-EtOOCC6H4
p-CF3C6H4
p-CF3C6H4
p-CF3C6H4
p-CF3C6H4
2-Py
p-Me2NC6H4
p-Me2NC6H4
o-MeC6H4
c
4
5
6
7
8
9
p-MeOC6H4
p-Me2NC6H4
p-MeOC6H4
p-Me2NC6H4
p-MeC6H4
d
10
d
11
o-MeC6H4
d
12
p-MeOC6H4
p-MeC6H4
13
14
p-MeOC6H4
p-MeOC6H4
p-Me2NC6H4
p-MeC6H4
c
15
16
17
18
2-Py
p-MeOC6H4
a
Unless otherwise stated, reactions were performed with 0.5 mmol of
aryl sulfamates and 0.75 mmol of arylmagnesium bromides according
b
c
to the conditions indicated by the above equation. Isolated yield. 1
mol % of 7c or 2 mol % of 4b was employed. LiCl (2 equiv) was
d
added.
Figure 3. Possible catalytic cycle for the cross-couplings using the
bimetallic catalyst.
entry 5). Greater catalyst loadings did not further improve the
product yield. The reaction between o-MeC6H4OSO2NMe2
and p-MeOC6H4MgBr suffered the same situation, affording
only 81% product yield. However, p-Me2NC6H4MgBr behaved
better in the reaction with o-MeC6H4OSO2NMe2, the cross-
coupling product being isolated in 93% yield (Table 7, entries 6
and 7). 2-Naphthyl sulfamate is also a slightly sterically
hindered electrophile. However, it showed reactivity higher
than that of o-MeC6H4OSO2NMe2. Its reaction with either p-
MeOC6H4MgBr or p-Me2NC6H4MgBr gave the corresponding
products quantitatively (Table 7, entries 8 and 9). p-
EtOC(O)C6H4OSO2NMe2 can react with a Grignard reagent
in the presence of 2 equiv of LiCl. In the absence of LiCl,
partial addition products were observed. As an electron-poor
electrophile, it showed high reactivity, as expected. It reacted
smoothly with p-MeC6H4MgBr, p-MeOC6H4MgBr, and even o-
MeC6H4MgBr in the presence of 0.75 mol % of 7c, giving the
desired products in 97%−99% yields (Table 7, entries 10−12).
p-CF3C6H4OSO2NMe2 also reacted with p-MeC6H4MgBr, p-
MeOC6H4MgBr, and p-Me2NC6H4MgBr, respectively, in good
to excellent yields. However, it displayed lower reactivity in
comparison with p-EtOC(O)C6H4OSO2NMe2 (Table 7,
entries 13−16). 2-Pyridyl sulfamate is a good electrophile in
the reaction with p-MeC6H4MgBr or p-MeOC6H4MgBr in the
presence of 0.75 mol % of 7c, an excellent product yield being
achieved in each reaction (Table 7, entries 17 and 18). For
comparison, each reaction given in Table 7 was also carried out
in the presence of 4b. 4b exhibited good catalytic activity, but it
was lower than that of 7c.
structure B the aromatic ring of the electrophilic substrate
coordinates to one of the nickel atoms of the active bimetallic
species and the coordination promotes the oxidative addition of
the C−X bond at another nickel atom through changing the
electron distribution of the substrate. The length of the spacer
between the two pincer nickel units affects the efficiency of
bimetallic cooperation. This is supported by the experimental
fact that the bimetallic systems with (CH2)4 linkers (7b−d) are
more active than that with a (CH2)3 linker (7a) because an
appropriate separation between the two metal centers is
important for the cooperativity.11c In fact, the activity of 7a is
only slightly higher than that of mononuclear complex 4a in the
tested catalytic reactions. On the basis of the above analysis, a
possible catalytic cycle using 7b−d is proposed (Figure 3).
Thus, the dinuclear Ni(II) complex is converted to the
catalytically active nickel complex A at first through reduction
by an arylmagnesium or -zinc reagent. The reaction of A with
PhX results in complex B, which further transforms into the
oxidative addition species C. Reaction of C with the
arylmagnesium or -zinc reagent ArM forms E via D. Reductive
elimination of Ar-Ph from E regenerates the active catalyst A.
In previous studies of pincer nickel catalyzed cross-couplings,
Ni(I)/Ni(III) intermediates were suggested in most case-
s.5i,j,16a,l,k We also observed an obvious inhibitory action of the
free radical inhibitor 1,1-diphenylethylene to the reaction of p-
ClC6H4OMe with p-MeC6H4ZnCl catalyzed by 7c. However,
on the basis of current experimental results, we cannot
The nickel-catalyzed Kumada-type coupling of sulfamates is
very rare. Macklin and Snieckus reported that Ni(Cl)(Cp)IMes
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Hz), 119.8 (d, J = 10.3 Hz), 128.4, 128.5 (d, J = 14.2 Hz), 130.4 (s),
132.2 (d, J = 17.2 Hz), 132.7 (d, J = 3.1 Hz), 138.2 (d, J = 10.4 Hz),
150.5 (d, J = 18.5 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ −29.75.
Anal. Calcd for C14H16NP: C, 73.35; H, 7.03; N, 6.11. Found: C,
73.41; H, 7.00; N, 6.06.
determine the oxidation states of the nickels in the catalytic
cycle.
CONCLUSION
■
We have synthesized and characterized mono- and dinuclear
P,N,N-pincer nickel complexes. These complexes were shown
to be active catalysts for the cross-couplings of aryl chlorides or
aryltrimethylammonium salts with arylzinc reagents, as well as
of aryl sulfamates with aryl Grignard reagents. The reactions
covered a broad scope of substrates, including electron-rich and
-poor electrophiles and nucleophiles. A range of functional
groups were tolerated in the Negishi-type reactions. Hence,
these complexes are widely applicable catalysts for cross-
couplings. The dinuclear complexes with 1,4-butylene linkers
are more active than the complex with a 1,3-propylene linker.
Complex 7c displayed the highest activity in each type of
coupling reaction, and 7d exhibited comparable activity for the
activation and transformation of aryl C−N and C−O bonds.
Dinuclear complexes displayed catalytic activity higher than
that of the mononuclear complexes under comparable
conditions (7b vs 4a and 7c vs 4b). This is ascribed to
cooperative effects in a bimetallic system.
Synthesis of 2-(C4H4N-2′-CHN)C6H4P(Et)Ph (3). A mixture of
pyrrole-2-carboxaldehyde (0.43 g, 4.5 mmol), 2 (0.92 g, 4 mmol),
activated 4 Å molecular sieves (10 g), and toluene (60 mL) was heated
at 90 °C for 26 h with stirring. The mixture was cooled to room
temperature and filtered. The filtrate was concentrated under reduced
pressure, and the residue was recrystallized from ethanol to give yellow
1
crystals of 3 (0.95 g, 78%), mp 104−106 °C. H NMR (400 MHz,
CDCl3): δ 1.07 (dt, J = 7.6, 16.8 Hz, 3H, CH3), 1.92−2.02 (m, 1H,
CH2), 2.04−2.14 (m, 1H,CH2), 6.24−6.27 (m, 1H, Ar), 6.52−6.57
(m, 1H, Ar), 6.92 (s, 1H, Ar), 6.94−6.98 (m, 1H, Ar), 7.17 (t, J = 7.4
Hz, 1H, Ar), 7.22−7.30 (m, 4H, Ar), 7.33 (dt, J = 1.2, 7.6 Hz, 1H, Ar),
7.38−7.47 (m, 2H, Ar), 7.99 (s, 1H, CHN), 9.14 (b, 1H, NH).
13C{1H} NMR (101 MHz, CDCl3): δ 10.5 (d, J = 17.3 Hz), 19.6 (d, J
= 10.1 Hz), 110.4, 116.0, 117.5 (d, J = 1.8 Hz), 122.9, 125.4 (d, J = 1.3
Hz), 128.3 (d, J = 7.2 Hz), 128.5, 129.6, 131.1 (d, J = 3 Hz), 131.2,
133.3 (d, J = 19.3 Hz), 133.6 (d, J = 13.7 Hz), 138.8 (d, J = 12.3 Hz),
148.6, 154.3 (d, J = 15.4 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ
−19.76. Anal. Calcd for C19H19N2P: C, 74.49; H, 6.25; N, 9.14.
Found: C, 74.27; H, 6.21; N, 9.15.
Synthesis of [Ni{2-(C4H3N-2′-CHN)C6H4P(Et)Ph}Cl] (4a). A
solution of compound 3 (0.67 g, 2.2 mmol) in THF (10 mL) was
added dropwise to a suspension of NaH (0.1 g, 60% dispersion in
mineral oil, 2.5 mmol) in THF (5 mL) at 0 °C with stirring. The
resultant mixture was stirred for 6 h at room temperature. This
solution was then transferred into a suspension of (DME)NiCl2 (0.55
g, 2.5 mmol) in THF (10 mL) at about −80 °C. The mixture was
warmed to room temperature and stirred for 12 h. Volatiles were
removed in vacuo. The residue was dissolved in CH2Cl2 and the
solution filtered by the use of a cannula fitted with filter paper. The
filtrate was concentrated to give red crystals of complex 4a (0.67 g,
76%), mp 178−180 °C. 1H NMR (400 MHz, CDCl3): δ 1.49 (dt, J =
7.6, 20.8 Hz, 3H, CH3), 1.98−2.12 (m, 1H, CH2), 2.54−2.66 (m, 1H,
CH2), 6.29−6.34 (m, 1H, Ar), 6.95 (d, J = 3.9 Hz, 1H, Ar), 7.16 (t, J =
7 Hz, 1H, Ar), 7.20 (s, 1H, Ar), 7.35 (t, J = 8.0 Hz, 1H, Ar), 7.39−7.52
(m, 5H, Ar), 7.68−7.78 (m, 2H, Ar), 7.80 (d, J = 2.4 Hz, 1H, CH
N). 13C{1H} NMR (101 MHz, CDCl3): δ 8.9, 18.6 (d, J = 32.1 Hz),
114.6 (d, J = 10.3 Hz), 116.0 (d, J = 3.9 Hz), 122.4 (d, J = 1.3 Hz),
124.4, 124.9, 125.7 (d, J = 6.5 Hz), 129.2 (d, J = 10.6 Hz), 129.7, 131.1
(d, J = 2.9 Hz), 131.9 (d, J = 9.4 Hz), 132.3 (d, J = 1.4 Hz), 133.4 (d, J
= 1.9 Hz), 141.5 (d, J = 1.4 Hz), 142.4, 150.0 (d, J = 2.1 Hz), 154.4 (d,
J = 20.3 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 31.32. MS: m/z
398.0568 [M]+; calcd for C19H18ClN2NiP 398.0250. Anal. Calcd for
C19H18ClN2NiP: C, 57.13; H, 4.54; N, 7.01. Found: C, 57.48; H, 4.67;
N, 6.88.
EXPERIMENTAL SECTION
■
All air- or moisture-sensitive manipulations were performed under
nitrogen using standard Schlenk techniques. Toluene and dioxane
were distilled under nitrogen over sodium, THF and diethyl ether
were distilled under nitrogen over sodium/benzophenone;, CH2Cl2
was distilled under nitrogen over calcium hydride, and NMP, DMF,
and DMA were dried over 4 Å molecular sieves, fractionally distilled
under reduced pressure, and stored under a nitrogen atmosphere.
CDCl3 and DMSO-d6 were purchased from Cambridge Isotope
Laboratories and stored over activated molecular sieves. (DME)-
NiCl2,24 (DME)NiBr2,24 2-(phenylphosphino)aniline (1),17 2,2′-
(propane-1,3-diylbis(phenylphosphinediyl))dianiline (5a), 2,2′-(bu-
tane-1,4-diylbis(phenylphosphinediyl))dianiline (5b),18 Grignard re-
agents,25 and aryl sulfamates10e were prepared according to the
reported methods. Aryltrimethylammonium salts were obtained either
by purchasing from commercial vendors or by preparation according
to the procedures we used previously.6e NMR spectra were recorded
on a Bruker av300 or Bruker avance III 400 spectrometer at ambient
temperature. The chemical shifts of H and 13C NMR spectra were
1
referenced to TMS or internal solvent resonances; the 31P NMR
spectra were referenced to external 85% H3PO4. Elemental analysis
was performed using an Elementar Vario EL Cube instrument. The
mass spectrometry analysis was performed on a Bruker Autoflex Speed
MALDI TOF mass spectrometer.
Synthesis of [Ni{2-(C4H3N-2′-CHN)C6H4P(Et)Ph}Br] (4b).
Complex 4b was synthesized using the same procedure as for 4a.
Thus, compound 3 (0.674 g, 2.2 mmol) was treated with NaH (0.1 g,
60%, 2.5 mmol) and the resulting sodium salt was further treated with
(DME)NiBr2 (0.772 g, 2.5 mmol) to generate a dark red crystalline
Synthesis of 2-NH2C6H4P(Et)Ph (2). Sodium (0.46 g, 20 mmol)
was added to a solution of (2-aminophenyl)phenylphosphine (4.02 g,
20 mmol) in THF (60 mL), and the resulting clear red solution was
stirred overnight at room temperature. The reaction mixture was
cooled to about −80 °C, and a solution of ethyl bromide (2.18 g, 20
mmol) in THF (50 mL) was added dropwise with stirring. The
reaction mixture was warmed to ambient temperature and stirred for a
further 48 h. An aqueous solution of ammonium chloride (20% w/w, 3
mL) was added, and the solvents were removed under reduced
pressure. Water (45 mL) and dichloromethane (30 mL) were added to
the residue. The organic layer was separated, and the water phase was
extracted with dichloromethane (2 × 30 mL). The combined organic
phase was dried over MgSO4 and filtered, and the solvent was removed
under reduced pressure. The crude product was distilled under
reduced pressure to give a colorless liquid (1.97 g, 43%), bp 92 °C/0.1
mmHg. 1H NMR (400 MHz, CDCl3): δ 1.11 (dt, J = 7.6, 17.6 Hz, 3H,
CH3), 1.96−2.12 (m, 2H, CH2), 4.18 (b, 2H, NH2), 6.63−6.67 (m,
1H, Ar), 6.76 (dt, J = 1.2, 7.6 Hz, 1H, Ar), 7.11−7.22 (m, 2H, Ar),
7.25−7.33 (m, 3H, Ar), 7.35−7.41 (m, 2H, Ar). 13C{1H} NMR (101
MHz, CDCl3): δ 10.2, 19.4, 115.5 (d, J = 2.7 Hz), 118.8 (d, J = 2.4
1
solid of complex 4b (0.83 g, 85%), mp 186−188 °C. H NMR (400
MHz, CDCl3): δ 1.47 (dt, J = 7.6, 21.2 Hz, 3H, CH3), 2.07−2.21 (m,
1H, CH2), 2.63−2.76 (m, 1H, CH2), 6.31 (s, 1H, Ar), 6.97 (d, J = 3.2
Hz, 1H, Ar), 7.15 (t, J = 6 Hz, 1H, Ar), 7.31 (t, J = 8 Hz, 1H, Ar), 7.35
(s, 1H, Ar), 7.38−7.53 (m, 5H, Ar), 7.66−7.79 (m, 2H, Ar), 7.89 (d, J
= 1.6 Hz, 1H, CHN). 13C{1H} NMR (101 MHz, CDCl3): δ 8.9,
19.2 (d, J = 33.8 Hz), 114.5 (d, J = 10.2 Hz), 116.3 (d, J = 3.7 Hz),
122.5 (d, J = 1.1 Hz), 125.3, 125.7, 125.9 (d, J = 6.5 Hz), 129.1 (d, J =
10.5 Hz), 129.8, 130.3, 131.1 (d, J = 3 Hz), 132.1 (d, J = 9.2 Hz),
132.3 (d, J = 1.2 Hz), 133.4 (d, J = 1.8 Hz), 142.7, 149.9 (d, J = 1.8
Hz), 154.1 (d, J = 20.2 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ
35.46. MS: m/z 441.9783 [M]+; calcd for C19H18BrN2NiP 441.9744.
Anal. Calcd for C19H18BrN2NiP: C, 51.41; H, 4.09; N, 6.31. Found: C,
51.77; H, 4.08; N, 6.36.
Synthesis of [2-(C4H4N-2′-CHN)C6H4P(Ph)]2(CH2)3 (6a). A
mixture of pyrrole-2-carboxaldehyde (0.82 g, 8.7 mmol), compound 5a
5870
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(1.77 g, 4 mmol), 4 Å molecular sieves (15 g), and toluene (60 mL)
was heated at 90 °C for 26 h with stirring. The mixture was cooled to
room temperature and then filtered. The filtrate was concentrated
under reduced pressure. The residue was recrystallized from ethanol to
and filtered by the use of a cannula fitted with filter paper. The filtrate
was concentrated to give red crystals of 7a (0.41 g, 47%), mp 198−200
°C. 1H NMR (400 MHz, DMSO-d6): δ 2.16 (b, 2H, CH2), 2.71−2.85
(m, 2H, CH2), 3.66 (b, 2H, CH2), 5.75 (s, CH2Cl2), 6.30 (d, J = 2.4
Hz, 2H, Ar), 6.98−7.02 (m, 6H, Ar), 7.26 (d, J = 6.8 Hz, 2H, Ar),
7.40−7.47 (m, 6H, Ar), 7.55 (t, J = 7.2 Hz, 2H, Ar), 7.75 (d, J = 8.4
Hz, 2H, Ar), 7.92 (d, J = 6.8 Hz, 4H, Ar), 8.45 (s, 2H, CHN).
13C{1H} NMR (101 MHz, DMSO-d6): δ 19.0, 24.7, 114.9, 115.6,
122.0, 126.3, 129.1, 131.5 (d, J = 19.3 Hz), 132.0, 133.3, 139.2, 142.3,
153.1, 153.7. 31P{1H} NMR (162 MHz, DMSO-d6): δ 28.04. MS: m/z
744.9958 [M − Cl]+; calcd for C37H32ClN4Ni2P2 745.0498. Anal.
Calcd for C37H32Cl2N4Ni2P2·0.15CH2Cl2: C, 56.08; H, 4.09; N, 7.04.
Found: C, 56.09; H, 4.14; N, 6.91. 7a cocrystallizes with CH2Cl2, and
the CH2Cl2 molecules can be partially removed under vacuum. The
1
afford pale yellow crystals of 6a (1.26 g, 53%), mp 102−104 °C. H
NMR (400 MHz, CDCl3): δ 1.38 (b, 0.6H, CH2), 1.63 (b, 1.4H,
CH2), 2.22 (b, 2H, CH2), 2.60−2.80 (m, 2H, CH2), 6.17 (b, 2H, Ar),
6.59 (d, J = 25.7 Hz, 4H), 6.78 (b, 0.6H, Ar), 6.88 (b, 1.4H, Ar), 6.96−
7.13 (m, 4H, Ar), 7.23−7.37 (m, 8H, Ar), 7.38−7.52 (m, 4H, Ar), 8.15
(s, 1.4 H, CHN), 8.18 (s, 0.6H, CHN), 10.57 (b, 1.4H, NH),
11.42 (b, 0.6H, NH). 13C{1H} NMR (101 MHz, CDCl3): δ 21.8 (t, J
= 13.6 Hz), 25.5 (t, J = 12.5 Hz), 27.0 (t, J = 12.1 Hz), 110.1, 110.3,
117.4, 117.6, 117.8, 124.06, 124.12, 125.5, 128.6 (d, J = 7.4 Hz), 128.9,
129.0, 129.4, 129.5, 130.8, 130.9, 131.9, 132.1, 133.9, 134.1, 134.4 (d, J
= 21 Hz), 135.1 (d, J = 15.4 Hz), 136.1 (d, J = 12.5 Hz), 150.0, 154.0
(d, J = 16.8 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ −23.89,
−27.58. Anal. Calcd for C37H34N4P2·0.8EtOH: C, 73.18; H, 6.17; N,
8.84. Found: C, 73.25; H, 6.10; N, 8.84.
1
CH2Cl2 signal can be observed in its H NMR spectrum (δ 5.75).
Synthesis of [Ni{2-(C4H3N-2′-CHN)C6H4P(Ph)}Cl]2(CH2)4
(7b). Complex 7b was synthesized using the same procedure as for
7a. Thus, the sodium salt prepared from 6b (0.61 g, 1 mmol) and NaH
(0.092 g, 60% dispersion in mineral oil, 2.3 mmol) was treated with
(DME)NiCl2 (0.51 g, 2.3 mmol) afforded, after workup, a red
Synthesis of [2-(C4H4N-2′-CHN)C6H4P(Ph)]2(CH2)4 (6b).
Compound 6b was synthesized using the same procedure as for 6a.
Thus, the reaction of pyrrole-2-carboxaldehyde (0.82 g, 8.7 mmol)
with 5b (1.82 g, 4 mmol) in toluene (60 mL) in the presence of 4 Å
molecular sieves (15 g) afforded, after similar workup, pale yellow
1
crystalline solid of complex 7b (0.54 g, 67%), mp 238−240 °C. H
NMR (400 MHz, CDCl3): δ 2.05−2.25 (m, 4H, CH2), 2.38−2.54 (m,
2H, CH2), 2.55−2.68 (m, 2H, CH2), 5.30 (s, CH2Cl2), 6.30−6.36 (m,
2H, Ar), 6.93 (d, J = 3.9 Hz, 2H, Ar), 7.05 (t, J = 7.4 Hz, 2H, Ar), 7.14
(s, 2H, Ar), 7.17−7.21 (m, 2H, Ar), 7.31−7.50 (m, 10H, Ar), 7.60 (d,
J = 2.7 Hz, 2H, Ar), 7.70−7.82 (m, 4H, Ar + CHN). 13C{1H} NMR
(101 MHz, CDCl3): δ 23.9, 24.2, 25.8 (dd, J = 1.6, 13.9 Hz), 53.6
(CH2Cl2), 114.8 (d, J = 10.4 Hz), 115.7 (d, J = 3.9 Hz), 122.1, 124.3,
124.7, 126.1 (d, J = 6.5 Hz), 129.2 (d, J = 10.7 Hz), 129.7 (s), 131.2
(d, J = 2.8 Hz), 131.9 (d, J = 9.6 Hz), 132.5, 133.4, 141.1, 142.4, 150.2,
153.8 (d, J = 9.6 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 27.61.
MS: m/z 760.9639 [M − Cl]+; calcd for C38H34ClN4Ni2P2 761.0609.
Anal. Calcd for C38H34Cl2N4Ni2P2: C, 57.27; H, 4.30; N, 7.03. Found:
C, 57.24; H, 4.12; N, 7.02. 7b cocrystallizes with CH2Cl2 (indicated by
the NMR spectra), and the CH2Cl2 molecules can be removed by
pumping the sample for a long time.
1
crystals of compound 6b (2.10 g, 86%), mp 116−118 °C. H NMR
(400 MHz, CDCl3): δ 1.30−1.46 (m, 1H, CH2), 1.47−1.68 (m, 3H,
CH2), 1.90−2.02 (m, 1H, CH2), 2.14−2.26 (m, 1H, CH2), 2.27−2.38
(m, 1H, CH2), 2.63−2.75 (m, 1H, CH2), 6.11−6.18 (m, 2H, Ar), 6.23
(b, 1H, Ar), 6.48 (b, 1H, Ar), 6.54 (b, 1H, Ar), 6.62 (b, 1H, Ar), 6.84
(dd, J = 4.4, 7.2 Hz, 1H, Ar), 6.91−6.99 (m, 2H, Ar), 7.07 (t, J = 7.2
Hz, 1H, Ar), 7.12−7.18 (m, 2H, Ar), 7.27−7.38 (m, 8H, Ar), 7.46−
7.58 (m, 4H, Ar), 7.93 (s, 1H, CHN), 8.12 (s, 1H, CHN), 10.13
(b, 1H, NH), 10.49 (b, 1H, NH). 13C{1H} NMR (101 MHz, CDCl3):
δ 23.9 (d, J = 11.8 Hz), 24.7 (d, J = 10.2 Hz), 25.7 (t, J = 15.0 Hz),
26.4 (t, J = 14.3 Hz), 110.2 (d, J = 4.1 Hz), 117.1, 117.5, 118.4, 124.0,
124.4, 125.3 (d, J = 3.3 Hz), 125.5, 128.3 (d, J = 7.3 Hz), 128.6, 128.7,
129.2 (d, J = 8.8 Hz), 129.7, 130.7 (d, J = 12.1 Hz), 131.6 (d, J = 2.0
Hz), 132.4 (d, J = 9.3 Hz), 133.7 (d, J = 15.6 Hz), 133.8 (d, J = 19.8
Hz), 134.5, 134.6, 134.7, 136.3 (d, J = 11.6 Hz), 137.7 (d, J = 12.1
Hz), 150.0, 150.4, 154.7 (d, J = 16.6 Hz), 155.0 (d, J = 13.3 Hz).
31P{1H} NMR (162 MHz, CDCl3): δ −21.41, −22.53. Anal. Calcd for
Synthesis of [Ni{2-(C4H3N-2′-CHN)C6H4P(Ph)}Br]2(CH2)4
(7c). Complex 7c was synthesized using the same procedure as for
7a. Thus, the sodium salt prepared from 6b (0.61 g, 1 mmol) and NaH
(0.092 g, 60% dispersion in mineral oil, 2.3 mmol) was treated with
(DME)NiBr2 (0.71 g, 2.3 mmol) to afford dark red crystals of complex
C38H36N4P2: C, 74.74; H, 5.94; N, 9.17. Found: C, 74.58; H, 6.01; N,
8.95.
1
7c (0.75 g, 85%), mp 244−246 °C. H NMR (400 MHz, CDCl3): δ
2.00−2.16 (m, 2H, CH2), 2.17−2.34 (m, 2H, CH2), 2.36−2.56 (m,
2H, CH2), 2.66−2.82 (m, 2H, CH2), 6.32 (b, 2H, Ar), 6.95 (d, J = 3.2
Hz, 2H, Ar), 7.07 (t, J = 3.2 Hz, 2H, Ar), 7.16 (dd, J = 3.6, 8.0 Hz, 2H,
Ar), 7.26 (s, 2H, Ar), 7.29−7.50 (m, 10H, Ar), 7.63 (d, J = 1.6 Hz, 2H,
Ar), 7.68−7.78 (m, 4H, Ar + CHN). 13C{1H} NMR (101 MHz,
CDCl3): δ 24.5, 24.8, 25.7 (dd, J = 2.2, 13.7 Hz), 114.9 (d, J = 10.3
Hz), 115.9 (d, J = 3.6 Hz), 122.1, 125.1, 125.5, 126.2 (d, J = 6.5 Hz),
129.1 (d, J = 10.7 Hz), 131.2 (d, J = 2.8 Hz), 132.0 (d, J = 9.5 Hz),
132.4, 133.4, 142.1, 142.7, 150.2 (d, J = 1.6 Hz), 153.5 (d, J = 20.4
Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 31.57. MS: m/z 805.0887
[M − Br]+; calcd for C38H34BrN4Ni2P2 805.0129. Anal. Calcd for
C38H34Br2N4Ni2P2: C, 51.52; H, 3.87; N, 6.32. Found: C, 51.23; H,
3.95; N, 6.31.
Synthesis of [Ni{2-(5′-tBuC4H2N-2′-CHN)C6H4P(Ph)}-
Cl]2(CH2)4 (7d). Complex 7d was synthesized using the same
procedure as for 7a. Thus, the sodium salt prepared from 6c (0.72
g, 1 mmol) and NaH (0.092 g, 60% dispersion in mineral oil, 2.3
mmol) was treated with (DME)NiCl2 (0.51 g, 2.3 mmol) to form,
after similar workup, a red crystalline solid of complex 7d (0.39 g,
43%), mp 160−162 °C. 1H NMR (400 MHz, CDCl3): δ 1.40 (s, 18H,
CH3), 1.90−2.04 (m, 2H, CH2), 2.05−2.21 (m, 2H, CH2), 2.48−2.64
(m, 2H, CH2), 2.81−2.92 (m, 2H, CH2), 5.30 (s, CH2Cl2), 6.31 (dd, J
= 2.0, 4.0 Hz, 2H, Ar), 6.86 (d, J = 4.0 Hz, 2H, Ar), 6.93 (t, J = 7.2 Hz,
2H, Ar), 7.17−7.20 (m, 2H, Ar), 7.24−7.32 (m, 4H, Ar), 7.40 (dt, J =
2.0, 7.6 Hz, 4H, Ar), 7.46−7.52 (m, 4H, Ar), 7.72−7.77 (m, 4H, Ar +
CHN). 13C{1H} NMR (101 MHz, CDCl3): δ 24.4, 24.7, 25.5 (d, J
= 15.3 Hz), 31.1, 34.0, 114.0 (d, J = 10.8 Hz), 115.3 (d, J = 4.4 Hz),
123.7, 124.2, 124.6, 125.0 (d, J = 6.4 Hz), 129.1 (d, J = 10.9 Hz),
Synthesis of [2-(5′-tBuC4H3N-2′-CHN)C6H4P(Ph)]2(CH2)4
(6c). Compound 6c was synthesized using the same procedure as
for 6a. Thus, the reaction of 5-tert-butyl-1H-pyrrole-2-carbaldehyde
(1.31 g, 8.7 mmol) with compound 5b (1.82 g, 4 mmol) in toluene
(60 mL) in the presence of 4 Å molecular sieves (15 g) afforded, after
similar workup, a pale yellow crystalline solid of 6c (1.18 g, 41%), mp
50−52 °C. 1H NMR (400 MHz, CDCl3): δ 1.31 (s, 18H, CH3), 1.41−
1.53 (m, 2H, CH2), 1.54−1.67 (m, 2H, CH2), 1.83−1.93 (m, 2H,
CH2), 1.96−2.07 (m, 2H, CH2), 5.97 (d, J = 3.7 Hz, 2H, Ar), 6.41 (d,
J = 3.7 Hz, 2H, Ar), 6.92 (dd, J = 3.5, 7.4 Hz, 2H, Ar), 7.13 (t, J = 7.6
Hz, 2H, Ar), 7.18−7.25 (m, 8H, Ar), 7.30 (dt, J = 1.2, 7.6 Hz, 2H, Ar),
7.33−7.40 (m, 4H, Ar), 7.86 (s, 2H, CHN), 9.26 (b, 2H, NH).
13C{1H} NMR (101 MHz, CDCl3): δ 26.8 (d, J = 11.2 Hz), 27.9 (m),
30.4 (s), 31.9 (s), 105.6 (s), 117.0 (s), 117.6 (s), 125.1 (s), 128.3 (dd,
J = 11.1, 7.2 Hz), 129.6 (s), 129.9 (s), 130.8 (s), 133.3 (t, J = 18.3 Hz),
139.2 (d, J = 12.2 Hz), 148.1 (s), 148.6 (s), 154.6 (d, J = 15.8 Hz).
31P{1H} NMR (162 MHz, CDCl3): δ −24.64. Anal. Calcd for
C46H52N4P2·1.3EtOH: C, 74.57; H, 7.70; N, 7.16. Found: C, 74.28; H,
7.72; N, 7.50.
Synthesis of [Ni{2-(C4H3N-2′-CHN)C6H4P(Ph)}Cl]2(CH2)3
(7a). A solution of 6a (0.60 g, 1 mmol) in THF (10 mL) was
added dropwise to a suspension of NaH (0.092 g, 60% dispersion in
mineral oil, 2.3 mmol) in THF (5 mL) at 0 °C with stirring. The
mixture was further stirred at room temperature for 6 h. The resulting
solution was then transferred into a suspension of (DME)NiCl2 (0.51
g, 2.3 mmol) in THF (10 mL) at about −80 °C with stirring. The
mixture was warmed to room temperature and stirred for 12 h.
Volatiles were removed in vacuo. The residue was dissolved in CH2Cl2
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129.9, 130.4, 131.1 (d, J = 2.9 Hz), 131.9 (d, J = 2.2 Hz), 132.0 (d, J =
10.1 Hz), 133.5 (d, J = 1.5 Hz), 143.3 (d, J = 1.7 Hz), 148.0, 154.3 (d,
J = 20.9 Hz), 170.8 (d, J = 4.4 Hz). 31P{1H} NMR (162 MHz,
CDCl3): δ 22.15. MS: m/z 873.1777 [M − Cl]+; calcd for
C46H50ClN4Ni2P2 873.1861. Anal. Calcd for C46H50Cl2N4Ni2P2·
0.1CH2Cl2: C, 60.34; H, 5.51; N, 6.11. Found: C, 60.34 H, 5.51 N,
6.11%. 7d cocrystallizes with CH2Cl2, and the CH2Cl2 molecules can
be partially removed under vacuum. The CH2Cl2 signal can be
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (Grant No. 21172208 and 21372212) and
the National Basic Research Program of China (Grant No.
2009CB825300). We thank Prof. S.-M. Zhou for the crystal
structure determination and Prof. H.-L. Jiang for help in
structural refinements.
1
observed in its H NMR spectrum (δ 5.30).
X-ray Crystallography. Single crystals of complexes 4b and 7c
were respectively mounted in Lindemann capillaries under nitrogen.
Diffraction data were collected on an Oxford Diffraction Gemini S
Ultra diffractometer with mirror-monochromated Cu Kα radiation (λ
= 1.54184 Å). The structures were solved by direct methods using
SHELXS-9726 and refined against F2 by full-matrix least squares using
SHELXL-97 (for 4b) or SHELXL-2013 (for 7c).27 Hydrogen atoms
were placed in calculated positions. Due to large thermal vibration and
disorder of the CH2Cl2 molecules in 7c crystals, ISOR restraints were
applied to the Uij values of the carbon and chlorine atoms. Crystal data
and experimental details of the structure determinations are given in
Table S-1 (Supporting Information).
General Procedure for the Negishi Cross-Coupling of Aryl
Chlorides. A thick-walled Schlenk tube was charged with aryl chloride
(0.5 mmol), NMP (1.5 mL), and complex 4b (0.005 mmol) or 7c
(0.0025 mmol). To the stirred mixture was added ArZnCl solution
(1.5 mL, 0.5 M solution in THF, 0.75 mmol) by syringe. The reaction
mixture was stirred at 90 °C (bath temprature and the Schlenk tube
was sealed) for 12 h. Water (10 mL) and several drops of acetic acid
were successively added. The mixture was extracted with Et2O (3 × 10
mL). The combined organic phase was dried over anhydrous Na2SO4,
concentrated by rotary evaporation, and purified by column
chromatography (silica gel).
REFERENCES
■
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Water (10 mL) and several drops of acetic acid were successively
added. The resulting mixture was extracted with Et2O (3 × 10 mL).
The extracts were dried over anhydrous Na2SO4, filtered, and
concentrated. The residue was purified by column chromatography
on sillca gel.
General Procedure for Reaction of ArMgBr with Aryl
Sulfamates. A Schlenk tube was charged with aryl sulfamate (0.5
mmol), THF (1.5 mL), and complex 4b (0.0075 mmol) or 7c
(0.00375 mmol). To the stirred mixture was added ArMgBr solution
(1.5 mL, 0.5 M solution in THF, 0.75 mmol) slowly by syringe. The
mixture was stirred at 35 °C for 24 h. Water (10 mL) and several
drops of acetic acid were successively added. The mixture was
extracted with Et2O (3 × 10 mL). The combined organic phase was
dried over anhydrous Na2SO4, concentrated by rotary evaporation, and
purified by column chromatography (silica gel).
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ASSOCIATED CONTENT
■
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6660. (q) Gosmini, C.; Begouin, J.-M.; Moncomble, A. Chem.
S
* Supporting Information
Commun. 2008, 3221. (r) Hatakeyama, T.; Nakamura, M. J. Am.
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Text, figures, tables, and CIF files giving characterization data
for all compounds prepared in this paper and X-ray
crystallographic data for complexes 4b and 7c. This material
is available free of charge via the Internet at http://pubs.acs.org.
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41, 1500.
AUTHOR INFORMATION
■
(6) (a) Zhang, X.-Q.; Wang, Z.-X. Org. Biomol. Chem. 2014, 12, 1448.
(b) Zhang, X.-Q.; Wang, Z.-X. J. Org. Chem. 2012, 77, 3658.
(c) Zhang, Q.; Zhang, X.-Q.; Wang, Z.-X. Dalton Trans. 2012, 41,
10453. (d) Guo, W.-J.; Wang, Z.-X. Tetrahedron 2013, 69, 9580.
(e) Xie, L.-G.; Wang, Z.-X. Angew. Chem., Int. Ed. 2011, 50, 4901.
(f) Reeves, J. T.; Fandrick, D. R.; Tan, Z.; Song, J. J.; Lee, H.; Yee, N.
Corresponding Author
*E-mail for Z.-X.W.: zxwang@ustc.edu.cn.
Notes
The authors declare no competing financial interest.
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dx.doi.org/10.1021/om500452c | Organometallics 2014, 33, 5863−5873

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