Synthesis, structure and reactivity of NHC-nickel complexes containing carbonato ligands

Article abstract of DOI:10.1016/j.inoche.2013.03.011

Reactions of different alkane-bridged (n = 1-3) di-NHC precursors, bisimidazolium chlorides with the NiCl₂ in presents of K ₂CO₃ in acetonitrile give the corresponding 16-electron binuclear complexes of the type Ni(di-NHC)(μ-O)₂CO in moderate yield. The molecular structures of 1-3 have been determined by X-ray crystallography, which revealed a cis-chelating di-NHC on a slightly distorted square-planar nickel center with κ²-cabonato ligand. The influence of the different di-NHC ligands on the structure and reactivity of the complexes has been studied. The catalytic properties of the complexes were investigated in the Kumada reaction for cross-coupling of phenylmagnesium bromide with a variety of aryl halides. The complex 3 which has the longest linker between two NHCs shows the best catalytic activity in these reactions.

Full text of DOI:10.1016/j.inoche.2013.03.011

Inorganic Chemistry Communications 31 (2013) 74–78
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Synthesis, structure and reactivity of NHC–nickel complexes containing
carbonato ligands
Jin Guo , Lanlan Lv , Xiaojun Wang , Changsheng Cao ⁎, Guangsheng Pang , Yanhui Shi a,c,⁎
a
a
a
a,
b
a
School of Chemistry and Chemical Engineering and Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal University, Xuzhou,
Jiangsu, 221116, PR China
b
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, Jilin, 130012, PR China
State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, Jiangsu, 210093, PR China
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of different alkane-bridged (n = 1–3) di-NHC precursors, bisimidazolium chlorides with the NiCl2
Received 29 January 2013
Accepted 13 March 2013
Available online 22 March 2013
in presents of K
Ni(di-NHC)(μ-O)
2
CO
3
in acetonitrile give the corresponding 16-electron binuclear complexes of the type
2
CO in moderate yield. The molecular structures of 1–3 have been determined by X-ray crystal-
lography, which revealed a cis-chelating di-NHC on a slightly distorted square-planar nickel center with
2
κ -cabonato ligand. The influence of the different di-NHC ligands on the structure and reactivity of the complexes
Keywords:
has been studied. The catalytic properties of the complexes were investigated in the Kumada reaction for
cross-coupling of phenylmagnesium bromide with a variety of aryl halides. The complex 3 which has the longest
linker between two NHCs shows the best catalytic activity in these reactions.
N-heterocyclic carbene
Bidentate ligand
Nickel complex
Carbonato ligand
© 2013 Elsevier B.V. All rights reserved.
N-heterocyclic carbenes (NHCs) have attracted considerable atten-
tion and become an important class of ligands, due to their successful
application in organometallic chemistry and homogeneous catalysis
In this paper, we report the synthesis and characterization of
cis-chelating di-NHC nickel complexes containing κ -carbonato ligands,
2
in which di-NHC is mesityl bis(imidazol-2-ylidene) ligand with differ-
ent length of alkyl bridge (Scheme 1). To the best of our knowledge,
it is the first example of nickel–NHC complex containing carbonato
ligand. Investigations of these complexes in Kumada reaction revealed
that complex 3 which has the longest linker between two NHCs
shows the most catalytic activity for this reaction.
[1–7]. Poly NHCs are interesting subclass of NHC ligands that allow
the preparation of organometallic compounds with a variety of geome-
tries and chemical reactivities [8–13]. Among poly-NHC ligands,
di-NHCs with an aliphatic ―(CH ) ― linker are the first ones to be pre-
2 n
pared [14–17]. The easy preparation of this type of ligand has allowed a
controlled study of their coordination to metals by modifying the length
of the linker, and some important implications on the structural proper-
ties and reactivity of the resulting complexes have been investigated
In all cases, the nickel complexes were obtained upon stirring blue
2 2 2
slurry consisting of NiCl , imidazolium chloride (H LCl ) [28] and
K
2
CO in acetonitrile at 80 °C, which gradually turned yellow (2 days)
3
[
18–20]. In the literature only a few examples to synthesis of cis-
[29]. Subsequent workup afforded the new nickel complexes as yellow
solids in moderate yield. The effort to prepare Ni–NHC compound with
butyl bridged linker under similar conditions was not successful, while
most of the starting materials were recovered. No less than 4 equiva-
chelating di-NHC nickel(II) complexes of the type (di-NHC)NiL were
successful. A number of attempts have been reported to be unsuccess-
ful, leading only to intractable reaction mixtures [21] or to homoleptic
2
2
+
[
2
(di-NHC) Ni]
complexes [22,23]. One of successful attempts re-
2 2 3
lents of NiCl and K CO are essential for the reaction, otherwise the
sulted in the synthesis of a cis-chelating di-NHC nickel complex derived
from an imidazolium-linked ortho-cyclophane [24]. Douthwaite
et al. were able to prepare two types of cis-chelating di-NHC
product can only be obtained in lower yield with most starting mate-
rials and some unknown oily compounds. A trace amount of water in
the system does not harm the reaction; moreover, the reaction can be
nickel complexes: (di-NHC)Ni(PMe
21]. Bouwman [26] and Jothibasu [27] reported to obtain this type
of complex with two halide anions by heating bisimidazolium salts
with Ni(OAc) in presence of a large amount of low-melting salt
3
)(Cl) [25], (di-NHC)Ni(Me)
2
carried out under air atmosphere. However, using NiCl
2
2
⋅6H O as
[
starting material leads to no product under similar conditions. All com-
plexes are robust compounds that are slightly soluble in methanol and
DMSO, sparingly soluble in acetonitrile and THF, and insoluble in
DCM, diethyl ether and hexane. The solubility of the complex is getting
better as the bridged chain is getting longer. The square planar low-spin
2
4
Bu NX (X = Cl, Br) as an ionic liquid solvent in vacuo simultaneously.
1
nickel complexes are diamagnetic and give rise to clear H spectra and
⁎
Corresponding author at: School of Chemistry and Chemical Engineering and Jiangsu
13
13
C NMR spectra. However, the C of complex 1 is hard to achieve
Key Laboratory of Green Synthetic Chemistry for Functional Materials, Jiangsu Normal
University, Xuzhou, Jiangsu, 221116, PR China. Tel./fax: +86 516 83500349.
E-mail address: yhshi_2000@126.com (Y. Shi).
due to the poor solubility of the complexes in the most of the solvents.
The imidazolium NCHN is absent in the 1H NMR spectra of the
1387-7003/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.inoche.2013.03.011

J. Guo et al. / Inorganic Chemistry Communications 31 (2013) 74–78
75
(
)
N
O
N
O
n
4
eq. NiCl , 10 eq. K CO
N
N
n N
N
2
2
3
N
N
Ni
O
2
Cl
CH CN, 80 o
C
3
n = 1, H L1Cl ;
2
2
n = 1 (1);
n = 2 (2);
n = 3 (3)
n = 2, H L2Cl ;
2
2
n = 3, H L3Cl2
2
Scheme 1. Synthesis of palladium complexes (1–3).
complexes, confirming carbene generation [30]. For complexes 2 and 3
the carbene-C and carbonato-C were not observed in 13C NMR spectra,
probably due to peak broadening. Although carbonato-C was not
Yellow single crystals were obtained by slow evaporation from the
solutions of methanol for 1 and acetonitrile for complexes 2 and 3,
and their molecular structures were determined by X-ray diffraction
[32]. The molecular structures of 1–3 are shown in Figs. 1–3 and
selected bond distances and angles are collected in Table 1.
The structures of these complexes consist of a slightly distorted
square-planar molecule with a nickel center surrounded by two oxygen
atoms from carbonate dianion and two carbon from the bicarbene
13
observed in C NMR, the structure was suggested by the absorption
−
1
of a single strong infrared absorption at 1656 and 1631 cm
1
for 1,
604 cm for 2 and 1657 and 1633 cm for 3, similar to the spectral
data for the other (μ-O) CO complexes [31].
−
1
−1
2
ligand in a cis-geometry. The two μ-O twisted out of the C
.16° for 3, 5.88° for 2, and 4.48° for 1 due to conformational constraints.
The Ni―C (carbene) distances in these complexes are rather similar
1.871(4) Å and 1.853(5) Å in 1; 1.864(3) and 1.881(3) in 2; 1.865(4)
2
Ni plane by
8
[
Å and 1.885(4) Å in 3], which are compatible with typical Ni―C carbene
bond lengths [26]. The bite angle of the bis-NHC ligand (C―Ni―C)
in the complexes changes slightly upon lengthening of the bridging
moiety, from 88.71(19)° for 1, 94.49(15)° for 2, and to 99.27(17)° for
3, which is a relatively small difference compared to the chelating
phosphanes [25]. This smaller effect in the bite angle is due to the imid-
azole rings twisted out of the coordination plane. The dihedral angle
between the coordination plane of the complex and the NHC ring
plane is increased with the increasing of the bridged length from
3
5.28° for 1, 56.99° for 2 to 77.43° for 3. The O―Ni―O bite angle of
the carbonato ligand, being 69.33(13)° in 1, 69.87(10) in 2 and
9.99(12)° in 3 is a little larger than that found for related carbonate
6
complexes [33]. C O has obviously character of double bond with the
bond length of 1.243(5) Å (C3―O3) in 1, 1.237(4) Å (C27―O3) in 2
and 1.223(5) Å (C3―O1) in 3. All other distances and angles lie in the
expected ranges and selected crystallographic data are shown in
Table 2.
Fig. 1. ORTEP drawing of 1 showing 50% probability thermal ellipsoids. The MeOH and
hydrogen have omitted for clarity.
The transition-metal catalyzed Kumada reaction has found wide
application in organic synthesis. The activity of these nickel complexes
Fig. 2. ORTEP drawing of 2 showing 50% probability thermal ellipsoids. The hydrogen
3
Fig. 3. ORTEP drawing of 3 showing 50% probability thermal ellipsoids. The CH CN and
have omitted for clarity.
hydrogen have omitted for clarity.

76
J. Guo et al. / Inorganic Chemistry Communications 31 (2013) 74–78
Table 1
Selected bond lengths (Å) and angles (deg) for complexes 1, 2, 3.
Distance (Å) and Angle (°)
Complex 1
Distance (Å) and Angle (°)
Complex 2
Distance (Å) and Angle (°)
Complex 3
Ni1―C1
Ni1―C2
Ni1―O1
Ni1―O2
C3―O1
C3―O2
C3―O3
C1―Ni1―C2
C1―Ni1―O1
O1―Ni1―O2
O2―Ni1―C2
O1―C3―O2
O1―C3―O3
O3―C3―O2
1.871(4)
1.853(5)
1.891(3)
1.891(3)
1.305(5)
1.287(5)
1.243(5)
88.71(19)
101.10(16)
69.33(13)
100.65(17)
112.1(4)
123.3(4)
124.6(4)
Ni1―C12
Ni1―C15
Ni1―O1
Ni1―O2
C27―O1
C27―O2
C27―O3
C12―Ni1―C15
C12―Ni1―O1
O1―Ni1―O2
O2―Ni1―C15
O1―C27―O2
O1―C27―O3
O3―C27―O2
1.864(3)
1.881(3)
1.881(2)
1.892(2)
1.309(4)
1.313(4)
1.237(4)
94.49(15)
96.52(13)
69.87(10)
99.16(13)
111.0(4)
123.9(4)
125.2(4)
Ni1―C1
Ni1―C2
Ni1―O2
Ni1―O3
C3―O2
C3―O3
C3―O1
C1―Ni1―C2
C1―Ni1―O2
O2―Ni1―O3
O3―Ni1―C2
O3―C3―O2
O1―C3―O2
O3―C3―O1
1.865(4)
1.885(4)
1.884(3)
1.878(3)
1.304(5)
1.322(5)
1.223(5)
99.27(17)
162.34(14)
69.99(12)
166.27(15)
110.5(4)
125.1(4)
124.4(4)
1
–3 in the Kumada reaction was tested. The reactions were conducted
11). The ratio of Grignard reagent to aryl halide affects both of the reac-
tion time and the yield of the product. The shorter reaction time and
higher yield were achieved with the higher ratio of Grignard reagent
to aryl halide (entries 12 and 13). The higher reaction temperature
does not effect the reaction very much, and the catalyst was still active
in the reflux temperature of THF.
in a vial in the presence of 1 mol% of nickel catalysts 1–3 in THF
solution of 4-chloroanisole with phenylmagnesium bromide [34]
and the results were given in Table 3. Apart from the desired product
4
-methoxybiphenyl and
byproducts are observed in the reaction mixtures. All the complexes
–3 are able to catalyze the coupling of 4-chloroanisole with
a little amount of biphenyl, no other
1
To investigate the scope of the reaction, the alkyl halides (bromides
and chlorides) with different electronic and steric properties were cho-
sen in the reactions with complex 3 as catalyst. The results showed that
the complex 3 can not only catalyze the reaction with more reactive aryl
bromides, but also can catalyze the reaction in good to excellent yield
with less reactive aryl chlorides. However, the reaction with aryl
bromides typically went completion faster and gave higher yield than
that with aryl chlorides (entry 16 vs. entry 23 and entry 20 vs. entry
24). The higher yield was obtained for aryl bromides with electron-
donating group compared to that with electron-withdrawing group
(entry 18 vs. entry 19). The steric hindrance plays insignificantly role
in the reaction with methyl substituent (entry 16 vs. entry 17), whereas,
it does play important role in the reaction with methoxyl substituent
(entry 19 vs. entry 20).
phenylmagnesium bromide, however, the yield and rate depend to a
large extent on the complex used. Complex 1 showed very poor catalyt-
ic activity, whereas, the complex 3 showed the best catalytic activity in
these three complexes. For example, full conversion is achieved with 3
in 40 h, furnishing the desired product in 99% yield; whereas, the 76%
yield was achieved with 2 and the 23% with 1 in 40 h. Therefore, the
Ni complexes with longer alkyl linker between the two NHCs show
better result and the catalytic activity of the complexes are in the
trend of 3 > 2 > 1. Furthermore, the effect of the catalyst loading, the
ratio of starting materials, and reaction temperature on the reaction of
phenylmagnesium bromide with 4-chloroanisole catalyzed by 3 was
studied (entries 10–15). The results showed that decreased the catalyst
loading, the yield was decreased dramatically. For example, 36% of
desired product was obtained with 0.5 mol% of catalyst 3, while only
2
In summary, three of a novel class of Ni κ -carbonato complexes
1
1% of product was observed with 0.2 mol% of 3 (entry 10 vs. entry
with chelating bis(imidazol-2-ylidene) ligands have been synthesized
Table 2
Selected crystallographic data for complexes 1, 2 and 3.
Compound
1
2
3
Empirical Formula
C
26
H
28
N
4
NiO
3
·3CH
3
OH
C
27
H
30
N
4
NiO
3
C
28 32 4 3 2 3
H N NiO ·C H N
Formula weight
Temperature/K
Crystal system
Space group
599.34
293(2)
Triclinic
P-1
517.24
293(2)
Orthorhombic
Pbcn
572.32
293(2)
Monoclinic
P2(1)/n
Crystal size/mm
0.30 × 0.22 × 0.20
11.530(5)
12.094(9)
12.416(7)
80.66(3)
63.53(3)
84.33(3)
1528.6(16)
2
0.20 × 0.18 × 0.18
21.8187(15)
17.2911(12)
16.2357(11)
90.00
90.00
90.00
6125.2(7)
8
1.122
0.30 × 0.22 × 0.20
9.2538(4)
15.6525(9)
20.3125(11)
90.00
94.285(3)
90.00
2933.9(3)
4
a/Å
b/Å
c/Å
α/°
β/°
γ/°
3
V/Å
Z
D
calcd./mg cm−
3
1.302
0.681
636
1.296
0.700
1208
−
1
Absorption coefficient/mm
F(000)
0.663
2176
θ range/°
Reflections collected/unique
1.71–28.48
5419/7734
1.50–25.00
33215/5403
[R(int) = 0.1041]
5403/420/322
1.178
1.64–25.19
16677/5270
[R(int) = 0.0905]
5270/3/353
0.848
[
R(int) = 0.2636]
Data/restrains/parameters
Goodness-of-fit on F
5409/0/367
0.976
2
Final R indices [I > 2σ (I)]
R
1
= 0.0628
wR = 0.1407
= 0.1128
wR = 0.1607
R
1
= 0.0439
wR = 0.0681
= 0.0908
wR = 0.0710
R
1
= 0.0490
wR = 0.1120
= 0.1139
wR = 0.1275
2
2
2
R indices (all data)
R
1
R
1
R
1
2
2
2

J. Guo et al. / Inorganic Chemistry Communications 31 (2013) 74–78
77
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1 (1)
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3 (1)
1 (1)
2 (1)
3 (1)
3 (0.5)
3 (0.2)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
3 (1)
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
p-OMe
o-Me
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
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Cl
Cl
Cl
Cl
Cl
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Br
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18
18
18
24
24
24
40
40
40
40
40
40
24
40
40
48
40
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40
48
40
40
40
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10
45
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p-Me
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We are grateful to the foundation of NSFC (21071121, 21172188
and 21104064), SRF for ROCS, SEM, PAPD, 333 Project for the Cultiva-
tion of High-level Talents (33GC10002), Graduate Foundation
2
(2001) 111–120.
25] R.E. Douthwaite, D. Haussinger, M.L.H. Green, P.J. Silcock, P.T. Gomes, A.M. Martins,
A.A. Danopoulos, Cationic nickel(II) complexes of chelating N-heterocyclic carbenes,
Organometallics 18 (1999) 4584–4590.
(
2012YZD008) of Jiangsu Normal University and the State Key Labora-
tory of Inorganic Synthesis and Preparative Chemistry at Jilin University
2013-03) for financial support.
[26] J. Berding, M. Lutz, A.L. Spek, E. Bouwman, Synthesis of novel chelating benzimidazole-
based carbenes and their nickel(II) complexes: activity in the Kumada coupling
reaction, Organometallics 28 (2009) 1845–1854.
(
[
[
[
27] H. Vinh Huynh, R. Jothibasu, Formation of homoleptic tetracarbene versus
cis-chelating dicarbene complexes of nickel(II) and applications in Kumada–
Corriu couplings, Eur. J. Inorg. Chem. 13 (2009) 1926–1931.
28] C. Cao, Y. Zhuang, J. Zhao, Y. Peng, X. Li, Z. Shi, G. Pang, Y. Shi, Binuclear palladium
complexes bridged by dicarbene with different lengths and their application in
Mizoroki–Heck reaction, Inorg. Chim. Acta 363 (2010) 3914–3918.
Appendix A. Supplementary material
CCDC-917812, CCDC-917813 and CCDC-917814 contain the supple-
mentary crystallographic data for the paper. These data can be obtained
free of charge from The Director, CCDC, 12 Union Road, Cambridge, CB2
29] General procedures: Acetonitile was distilled over calcium hydride under the atmo-
sphere of argon. Dehydrated NiCl2 was obtained by heating NiCl2 · 6H O at 135 °C
2
under a stream of argon. All other chemicals were obtained from common suppliers
1
EZ UK or Fax: +44 1223 336033; Email:deposit@ccda.cam.ac.uk or
1
13
and used without further purification. H and C spectra were recorded on a Bruker
AV 400 MHz spectrometer at room temperature and referenced to the residual sig-
nals of the solvent. GC-MS was performed on an Agilent 6890-5973 N system with
electron ionization (EI) mass spectrometry. Elemental analyses were performed
on a EuroVektor Euro EA-300 elemental analyzer. IR spectra were recorded on KBr
pellets on a FTIR-Tensor 27 spectrometer.
http://www.ccdc.cam.ac.uk. Supplementary data to this article can be
found online at http://dx.doi.org/10.1016/j.inoche.2013.03.011.
References
[
30] Preparation of [Ni(L1)] (μ-O)
20 mL of CH CN was treated with NiCl
(1.2 g). The mixture was allowed to react at 80 °C for 2 days in air. The solution
2
CO (1): A solution of H
2
L1Cl
2
(0.46 g, 1 mmol) in
[1] W.A. Herrmann, N-heterocyclic carbenes: a new concept in organometallic catal-
3
2
(0.52 g, 4 mmol) and excess of K
2
CO
3
ysis, Angew. Chem. Int. Ed. 41 (2002) 1290–1309.

78
J. Guo et al. / Inorganic Chemistry Communications 31 (2013) 74–78
was filtered through Celite to remove excess NiCl and K CO and rinsed with Calcd for C28
2
2
3
H
32
N
4
NiO
10.66. H NMR (DMSO-d
J = 1.6 Hz, NCH), 6.92 (4H, s, C
m, CH ), 2.30 (6H, s, 4-CH ), 1.81 (12H, s, 2-CH
100 MHz): 140.1 (NCH), 137.0 (1-C ), 136.4 (NCH), 130.1 (3-C
(4-C ), 125.5 (2-C ), 48.1 (NCH ), 30.8 (CH ), 21.2 (4-CH ), 18.3 (2-CH
[31] D.W. Lee, C.M. Jensen, D. Morales-Morales, Reactivity of iridium PCP pincer com-
plexes toward CO and CO , Organometallics 22 (2003) 4744–4749.
3
: C, 63.30; H, 6.07; N, 10.55. found: C, 63.48; H, 5.93; N,
, 400 MHz): 7.57 (2H, d, J = 1.6 Hz, NCH), 7.16 (2H, d,
), 4.59 (4H, t, J = 6 Hz, NCH ), 2.66-2.62 (2H,
). C{ H} NMR (CD OD,
), 126.6
).
1
methanol. The filtrate was concentrated to approximately 2 mL, and addition of
6
diethyl ether (10 mL) led to precipitation of the product. Yield: 0.29 g, 56 %. IR
H
6 2
2
KBr): 3386, 1656[ν(C = O)], 1631[ν(C = O)], 1381, 1009, 669 cm− . Anal. Calcd
1
13
1
(
2
3
3
3
for C26
H
H
28
N
4
NiO
NMR(DMSO-d
J = 1.6Hz, NCH), 6.94 (4H, s, Ar-H), 6.53 (2H, s, CH
3
: C, 62.06; H, 5.61; N, 11.13. Found: C, 61.95; H, 5.58; N, 11.24.
400 MHz): 7.78 (2H, d, J = 1.6Hz, NCH), 7.23 (2H, d,
), 2.26 (6H, s, 4-CH ), 1.97
CO (2): A solution of H L2Cl
CN was treated with NiCl (0.52 g, 4 mmol)
(1.2 g). The mixture was allowed to react at 80 °C for
days in air. The solution was filtered through Celite to remove excess NiCl
H
6 2
6 2
H
1
6
,
H
6 2
H
6 2
2
2
3
3
2
3
(
(
2H, s, 2-CH
0.47 g, 1 mmol) in 20 mL of CH
CO
3
). Preparation of [Ni(L2)] (μ-O)
2
2
2
2
3
2
[32] Preliminary examination and data collection were carried out on a Rigaku Mercury
CCD device at the window of a sealed X-ray tube with graphite-monochromated
and excess of K
2
3
2
2
α
Mo K radiation. Absorption correction was performed by the SADABS program.
and K
2
CO
3
, rinsed with methanol. The filtrate was concentrated to approximately
All the structures were solved by directed methods using the SHELXS-97 program
and refined by full-matrix least squares techniques on F . The guest solvent mole-
2
2
mL, and addition of diethyl ether (10 mL) led to precipitation of the product.
Yield: 0.34 g, 65%. IR (KBr): 3440, 1604 [ν(C = O), s], 1489, 1445, 1399, 1273,
cules in 2 are highly disordered and cannot be modeled, thus the SQUEEZE routine
of PLATON was applied to remove the contributions of the solvent molecules to
the scattering.
244, 853, 831, 758, 739, 714, 687 cm− . Anal. Calcd for C27
2.70; H, 5.85; N, 10.83. found: C, 62.54; H, 5.72; N, 11.01. 1H NMR (DMSO-d
00 MHz): 7.61(2H, s, NCH), 7.16 (2H, s, NCH), 6.93 (4H, s, Ar-H), 5.30 (4H, m,
1
1
30 4 3
H N NiO : C,
6
6
,
4
[33] S. Uozumi, H. Furutachi, M. Ohba, H. Okawa, D.E. Fenton, K. Shindo, S. Murata, D.J.
Kitko, Dinuclear nickel(II) complexes of an unsymmetric “end-off” compartmental
ligand: conversion of urea into cyanate at a dinuclear nickel core, Inorg. Chem. 37
(1998) 6281–6287.
[34] General Procedure for Kumada reaction: An oven-dried 4 mL vial containing a
stirrer bar was charged with catalyst (1 mol%) and alkyl halides (0.5 mmol, 62
μL) in the glove box. A 1 M solution of phenylmagnesium bromide in THF
(1.5 mmol, 1.5 mL) was added dropwise into the mixture with stirring. GC
yield is based on using dodecane as internal standard. All catalytic reactions
were performed in duplicate and were found to be consistent.
13
1
CH
2
), 2.30 (6H, s, 4-CH
40.2 (NCH), 136.7 (1-C
3
), 1.85 (12H, s, 2-CH
), 136.6 (NCH), 129.9 (3-C
), 21.2 (4-CH ), 18.6 (2-CH ). Preparation of [Ni(L3)] (μ-O)
3): A solution of H L3Cl (0.49 g, 1 mmol) in 20 mL of CH CN was treated with
(0.52 g, 4 mmol) and excess of K CO (1.2 g). The mixture was allowed to
react at 80 °C for 2 days in air. The solution was filtered through Celite to remove
excess NiCl and K CO , and rinsed with methanol. The filtrate was concentrated
3
). C{ H} NMR (CD
3
OD, 100 MHz):
), 124.7
CO
1
6
H
2
6 2
H ), 127.1 (4-C
6 2
H
(
(
2-C ), 50.8 (CH
H
6 2
2
3
3
2
2
2
3
NiCl
2
2
3
2
2
3
to approximately 2 mL, and addition of diethyl ether (10 mL) led to precipitation
of the product. Yield: 0.36 g, 68 %. IR (KBr): 3449, 3114, 3082, 2950, 1657
1
[ν
(C = O), sh], 1633 [ν(C = O), sh], 1491, 1460, 1410, 1370, 1225, 706 cm− . Anal.