Nickel(II) complex incorporating methylene bridged tetradentate dicarbene ligand as an efficient catalyst toward CC and CN bond formation reactions

Article abstract of DOI:10.1016/j.molcata.2014.10.031

For the evaluation of binding and catalytic nature of N-heterocyclic carbenes (NHCs) and their complexes, a new methylene bridged bis(aryloxy-NHC) ligand has been prepared. A novel air-stable Ni(II) complex bearing the new NHC ligand has been synthesized and characterized by elemental analysis, NMR (¹H and ¹³C) as well as ESI-mass spectrometry. The molecular structure of the complex was identified by means of single crystal X-ray diffraction analysis which revealed that the Ni(II) complex possesses a square planar geometry with the ligand coordinating with bi-negative tetradentate C₂O₂ fashion and the complex showed efficient catalytic activity toward the Suzuki-Miyaura cross-coupling reaction between aryl halides and arylboronic acids under phosphine free conditions. The new complex also catalyzed the amination of aryl chlorides in the presence of KO^tBu. Various aryl chlorides and amines can react smoothly to give the corresponding aminated products in moderate to high yields. Both secondary and primary amines are well tolerated under the optimal reaction conditions.

Full text of DOI:10.1016/j.molcata.2014.10.031

Accepted Manuscript
Title: Nickel(II) complex incorporating methylene bridged
tetradentate dicarbene ligand as an efficient catalyst towards
C-C and C-N bond formation reactions
Author: Muthukumaran Nirmala Govindan Prakash
Rangasamy Ramachandran Periasamy Viswanathamurthi Jan
Grzegorz Malecki Wolfgang Linert
PII:
S1381-1169(14)00486-5
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2014.10.031
MOLCAA 9333
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Accepted date:
18-10-2014
31-10-2014
Please cite this article as: M. Nirmala, G. Prakash, R. Ramachandran, P.
Viswanathamurthi, J.G. Malecki, W. Linert, Nickel(II) complex incorporating
methylene bridged tetradentate dicarbene ligand as an efficient catalyst towards C-C
and C-N bond formation reactions, Journal of Molecular Catalysis A: Chemical (2014),
http://dx.doi.org/10.1016/j.molcata.2014.10.031
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Nickel(II) complex incorporating methylene bridged tetradentate dicarbene
ligand as an efficient catalyst towards C-C and C-N bond formation reactions
a
a
a
Muthukumaran Nirmala , Govindan Prakash , Rangasamy Ramachandran, Periasamy
a
b
c
Viswanathamurthi,* Jan Grzegorz Malecki , Wolfgang Linert
a
Department of Chemistry, Periyar University, Salem-636 011, India.
b
Department of Crystallography, Silesian University, Szkolna 9, 40-006 Katowice, Poland.
c
Institute of Applied Synthetic Chemistry, Vienna University of Technology, Vienna, Austria.
*
To whom correspondence should be made, e-mail: viswanathamurthi72@gmail.com;
Fax: +91 427 2345124
1
Page 1 of 35

Abstract
For the evaluation of binding and catalytic nature of N-heterocyclic carbenes (NHCs) and their
complexes, a new methylene bridged bis(aryloxy-NHC) ligand has been prepared. A novel air-
stable Ni(II) complex bearing the new NHC ligand has been synthesized and characterized by
1
13
elemental analysis, NMR ( H and C) as well as ESI-Mass spectrometry. The molecular
structure of the complex was identified by means of single crystal X-ray diffraction analysis
which revealed that the Ni(II) complex possesses a square planar geometry with the ligand
2 2
coordinating with bi-negative tetradentate C O fashion and the complex showed efficient
catalytic activity towards the Suzuki-Miyaura cross-coupling reaction between aryl halides and
arylboronic acids under phosphine free conditions. The new complex also catalyzed the
t
amination of aryl chlorides in the presence of KO Bu. Various aryl chlorides and amines can
react smoothly to give the corresponding aminated products in moderate to high yields. Both
secondary and primary amines are well tolerated under the optimal reaction conditions.
Key words:
Dianionic bis(aryloxy-NHC) ligand
Ni-NHC complex
X-ray diffraction
Suzuki-Miyaura
C-N coupling reaction
2
Page 2 of 35

1
. Introduction
The first stable N-heterocyclic carbene reported by Arduengo et al [1] triggered the
development of stable singlet carbenes from laboratory interests to key compounds for manifold
applications, particularly in catalysis [2]. N-heterocyclic carbenes (NHCs) have been embraced
as spectator ligands in catalyst design with a remarkable speed [3] in past few decades. Due to
the strong metal carbon bond, carbene complexes give robust catalytic systems and so, a number
of transition metal complexes of multidentate NHCs containing phosphorous [4], oxygen [5], and
nitrogen [6] functionalities have been reported. Such ligands may significantly improve catalyst
stability and their potential hemilability provide ease of generation of vacant coordination site
and catalytically active species. The first catalytic application of NHCs in transition-metal
catalysis was reported by Herrmann et al, who realized the great potential of NHCs as ancillary
ligands in palladium mediated cross-coupling reactions [7] and in ruthenium mediated olefin
metathesis [8]. Nowadays, NHC-metal complexes have found wide applications in hydrogen
transfer reactions [9] and hydrosilylation reactions [10], especially C-C and C-N coupling
reactions [11, 12]. Especially, the NHC ligands bearing hemilabile donor functionalities like
nitrogen, oxygen or sulfur allow efficient stabilization of the catalytic species, while rapidly
opening the free coordination sites for incoming substrates.
Carbon–carbon bond formation is an essential process within the realm of organic
synthesis and of utmost importance for the generation of structural complexity and diversity [13].
Over the 30 years of research history on Suzuki-Miyaura cross-coupling, the palladium based
catalysts have been the most frequently investigated one for C-C coupling. To the uninitiated,
nickel might look like just the impoverished younger sibling of palladium in the field of
transition metal catalysis [14]. After all, the use of nickel-NHC-catalyzed cross-coupling has
skyrocketed and is currently experiencing a period of intensified interest [15]. In particular, some
of the Ni(II)-based NHC complexes exhibit higher catalytic activity than palladium based NHC
complexes [16]. Despite the aforementioned progresses, most of the established procedures
required high catalyst loading (usually ≥ 5 mol%) and excess usage of phosphine supporting
ligands [16b,17]. These results highlight the importance of performing control experiments while
3
Page 3 of 35

investigating the catalytic C-C coupling activity of any potential nickel catalyst. Unfortunately,
such highly active NHC-Ni(II) based catalysts for C-C coupling reactions remain scarce [18-20].
Further, the transition-metal-catalyzed amination of aryl halides has become one of the
most powerful methods to construct arylamines [21]. Most studies have focused on palladium
and copper complexes as catalysts [22, 23]. However, the development of a general, robust and
operationally simple catalytic system of Ni catalyzed C−N cross-coupling reactions has remained
significantly challenging [24]. Many groups have expanded Ni-catalyzed C−N cross-coupling to
include new electrophiles such as aryl tosylates, carbamates, sulfamates, methyl ethers,
phosphates, pivalates, and nitriles [25-27]. In 2007, Yang reported the first use of NHC
3 2
complexes of the type (Ph P) Ni(1-nap)Cl used in C-N coupling reactions [28-30]. All of these
methods have their own advantages; however they suffer from certain demerits like instability of
catalyst, high catalytic loading and requirement of severe conditions etc. Hence, the development
of stable catalytic system with NHC-Ni(II) catalysts those can be performed under mild
conditions has received much attention.
As part of our effort to develop a better catalytic system using metal NHC catalyst, here
we have reported a new air and moisture stable [31, 32] dianionic bis(aryloxy-NHC) ligand and
its Ni(II) complex as a promising catalyst for Suzuki-Miyaura C-C coupling as well as C-N
coupling.
2
. Results and discussion
2
.1 Synthesis of ligand precursors and metal complex: We prepared a ligand precursor 1-(2’-
methoxy phenyl) imidazole, with 62 % yield by CuI/K PO mediated coupling reaction between
-iodoanisole and imidazole. The reaction between 1-(2’-methoxy phenyl) imidazole, and an
3
4
2
excess of dibromomethane was stirred at 100 ⁰C for 48 h then cooled to room temperature. The
resultant white precipitate was collected, washed with acetone to afforded 1,1’-Di(2-methoxy-
phenyl)-3,3’-methylene diimidazolium dibromide as white solid. It was dissolved in 47 % HBr
and CH COOH (1/1 v/v) and refluxed at 110 ⁰C for 48 h. The mixture was cooled to room
3
temperature to give a white precipitate of 1,1’-di(2-hydroxy-phenyl)-3,3’-methylene
diimidazolium dibromide ligand H
4
LBr
2
in good yield (87%) after washing with acetone
(
Scheme 1). The new ligand H LBr obtained is highly air and moisture stable. It is not soluble
4 2
4
Page 4 of 35

in acetone, hexane, diethyl ether, but dissolves readily in CHCl
and DMSO.
3 2
, CH Cl2, EtOH, MeOH, DMF
O
N
N
(a)
2+
O
O
(Br-)2
N
N
N
N
.
H
H
(b)
2+
OH
HO
(Br-)2
N
N
N
N
.
H
H
H LBr2
4
Scheme 1. Synthesis of NHC ligand. Reagents and conditions: (a) CH Br , 100 ⁰C, 48 h; (b) 47
2
2
%
3
HBr, CH COOH, 110 ⁰C, 48 h.
Nickel complex (1) with NHC ligand were typically prepared from the mixture of dianionic
bis(aryloxy-NHC) ligand H LBr and Ni(OAc) .4H O in ethanol was allowed to react in the
presence of Et NBr and Et N at 80 ⁰C in air as depicted in Scheme 2 that afforded the
4
2
2
2
4
3
corresponding nickel complex in quantitative yield (82%) [31,32]. The complex 1 was also
obtained by the reaction of [NiCl (PPh ) ] with H LBr in ethanol in the presence of few drops of
2
3 2
4
2
3 4
Et N and Et NBr (Scheme 2). The complex was insoluble in chloroform, acetone, hexane, and
diethyl ether, but dissolve readily in DMF and DMSO, which may be due to higher degree of
organization in the solid state. The complex was stable not only in the solid phase for months
under air but also in DMSO and DMF solution for several months. They are also thermally stable
1
13
and will not melt over 300 ⁰C. The compounds were fully characterized by H & C NMR, mass
spectra and elemental analysis. The analytical data (C, H, N) of the compounds 1,1’-Di(2-
5
Page 5 of 35

4 2
methoxy-phenyl)-3,3’-methylene diimidazolium dibromide, H LBr and the nickel complex are
in good agreement with the proposed molecular formulae.
N
N
N
N
H LBr
Ni
H LBr2
4
2
4
[
NiCl (PPh ) ]
Ni(OAc) .4H O
2 2
2
3 2
O
O
(
a)
(a)
1
4 3
Scheme 2. : Reaction conditions: (a) Et NBr, Et N, EtOH, 80 ⁰C, 6 h
2
.2 Spectroscopic studies
IR spectra of free ligand were compared with new complex in order to confirm the
coordination of ligand to nickel metal. The ligand showed a strong band in the region 1545-1562
-1
-1
cm due to νN-C-N. This band has been shifted to higher frequency 1561-1573 cm in the metal
complex, indicating the coordination of ligand to metal through carbene carbon. In the spectra of
-1
free ligand, a strong band obtained around 1333 cm was assigned to phenolic C O stretching,
-1
which has been shifted to a higher frequency 1393 cm in complex indicating the participation
of phenolic oxygen in bonding. This has been further confirmed by the disappearance of the
-1
broad OH band around 3383 cm in complex due to the bonding of phenolic-OH group with
nickel metal via deprotonation. The electronic spectrum of complex 1 has been recorded in
dichloromethane and it displayed five bands in the region around 250-450 nm. The complex
exhibit intense absorption bands at energy below 300 nm which can be attributed to ligand
centered π-π* transitions. The absorption band around 350 nm has been assigned to transition
involving phenolate-based HOMO and NHC based LUMO with small contribution from metal d-
orbitals. The transition can be described to have mainly LLCT character. The band at ~400 nm is
likely to involve transition of ligand based orbitals, and the absorption tail beyond 430 nm is
attributed to d-d transition.
1
The H NMR spectra of ligand H
4
LBr
2
and its complex 1 show the signals in the expected
region (Fig S1 – S2, ESI†). The carbenic proton of the ligand exhibited a signal in the region
0.01 ppm. The imidazole ring backbone signals (H LBr , 8.07/8.24 ppm; 1, 7.89/7.94 ppm)
1
4
2
appear as singlet due to low coupling constant. Further, the spectra of ligand and the complex
6
Page 6 of 35

showed a series of signals for aromatic protons at 7.21-8.50 ppm. In addition, a clear singlet
4 2
appeared around 6.37 ppm for compounds H LBr and 1 corresponding to the methylene bridge
protons [33].
1
3
The C NMR spectra show the expected signals in the appropriate regions (Fig. S3–S4,
ESI†). The spectrum of ligand in DMSO-d shows the carbenic carbon signal in the region
38.02 ppm. For the uncoordinated ligand the imi-C and aryloxy carbon signals appeared in the
6
1
region 124.99-123.28 and 149.83 ppm respectively. Upon coordination and formation of new
nickel(II) complex a downfield shift is observed for the signals of imi-C (around 5 ppm), in
addition, the presence of peak in the region 148.76 ppm is assigned to aryloxy carbon
respectively. The nickel complex shows its carbenic carbon (Ni-Ccarbene) resonance at ca. 152.23
ppm, characteristic of the carbenic carbon bound to nickel [34]. It is worth of noting that only
1
3
one singlet was observed for the carbene carbon in C NMR spectrum of this complex. The
signals observed at 133.28-118.2 ppm in the spectra of ligand and complex is assigned to
aromatic carbons. The ESI mass spectrum of complex 1 showed a peak at m/z 389.09
+
corresponding to [M] (Fig. S6, ESI†).
2
.3 Structural studies
Even though the analytical and spectral data gave some idea about the molecular
formulae of the complex, they do not indicate the exact coordination of carbene-aryl oxygen
units in them. Hence, there is a need to prove this structure by X-ray crystallography. Single
crystals suitable for X-ray analysis were obtained from DMSO solution. The crystal data and
structure refinement parameters for complex 1 are summarized in Table S1 and is displayed in
supporting information (ESI†) and the selected bond length and bond angels are depicted in
Table 1. The ORTEP view and side view of the complex 1 along with atom numbering scheme
and packing arrangement of atoms in unit cell are given in fig 1-3. The single crystal X-ray
studies revealed that the complex was crystallized in a monoclinic system with space group
P21/n. As the coordination plane around Ni(II) ion in crystal adopts a square planar geometry, in
which two carbene atoms and two oxygen atoms occupy the basal plane. The nickel-Ccarbene bond
lengths [(1.835 (3), 1.846 (5) Å)] are analogous to those of other Ni(II)-NHC complexes [15d].
The Ni−O (phenolate) and Ni-Ccarbene bond distances of ~ 1.85 and ~1.84 Å are slightly smaller
7
Page 7 of 35

than those found in [Pt(II)salphen] (1.98 Å/ 2.03 Å) and [Mn(III)salphen] (1.91 Å/ 1.91 Å)
complexes, probably due to the less trans-effect of the NHC moieties which induce the strong
Ni-O bonds. Quite interestingly the solid-state molecular packing of complex 1 adopts a highly
planar structure [31-33]. While, the other previously reported complexes with aryloxide modified
biscarbene tetradentate NHC ligands generally showed bent framework due to the non-
conjugated C(10) methylene linker between two NHC moieties [31-33]. The stability of complex
in air is probably caused by the rigid structure of the tetradentate NHC ligand. These findings
indicate the character of the aryl oxygen coordinating to Ni(II) is similar to that of the salen
ligand [35]. The chelate bite angle of C(11)−Ni(1)−C(1) (91.51 (11)) is comparable to those of
various metal complexes with six membered chelate rings consisting of two imidazolylidene
rings and a bridged methylene group [36]. It is larger than the ideal angle and is probably due to
the less constraint of the six membered chelate rings. The angles of C(11)−Ni(1)−O(1),
C(1)−Ni(1)−O(1), C(11)−Ni(1)−O(2), C(1)−Ni(1)−O(2), O(1)−Ni(1)−O(2) are 175.60(9),
9
2.33(10), 92.28(9), 171.28(9) and 84.21(8) respectively. These parameters indicate that the Ni
atom takes square planar coordination geometry.
Table 1. Selected geometrical parameters for complex 1
Interatomic distances (Å)
Ni(1)−C(11)
1.835(3)
Ni(1)−C(1)
1.846(2)
Ni(1)−O(1)
Ni(1)-O(2)
1.8597(18)
1.8651(17)
Bond angles( )
C(11)−Ni(1)−C(1)
C(11)−Ni(1)−O(1)
C(1)−Ni(1)−O(1)
C(11)−Ni(1)−O(2)
C(1)−Ni(1)−O(2)
O(1)−Ni(1)−O(2)
91.51(11)
175.60(9)
92.33(10)
92.28(9)
171.28(9)
84.21(8)
8
Page 8 of 35

Fig. 1. ORTEP plot of complex 1. Thermal ellipsoids are drawn at the 50% probability level
Fig. 2. ORTEP drawing of complex 1 side view (50 % probability)
9
Page 9 of 35

Fig. 3. Packing diagram of complex 1
Therefore, the present structural variations among the complex reflect the attachment of
two carbenic carbons and two aryloxy groups onto one nickel atom. The use of two carbenic
carbon donor atoms represents an alternative strategy to efficiently modulate the coordination
environment around the center metal, mostly due to the different electric and/or steric influences
of the two carbenic groups.
3
. Catalysis
3
.1 Suzuki-Miyaura cross coupling
Evaluation of conditions for Suzuki-Miyaura cross coupling
Although using aryl halides as cross-coupling partners is the de facto standard, accessing the
desired halide coupling partner is not always trivial and can sometimes be extremely challenging.
To investigate a promising catalytic system, the screen was performed for a model reaction
between bromobenzene and phenylboronic acid. The results are depicted in Table 2. All the
reactions were run without any additive such as PPh as is often the case [37]. The progress of
3
the reaction was monitored by GC. It is a well-known fact that the choice of solvent significantly
1
0
Page 10 of 35

influences the Suzuki-Miyaura reactions. Thus, to study the effect of solvents in our system, we
performed a series of reactions between bromobenzene and phenylboronic acid in the presence
of different solvents such as toluene, THF, dioxane, EtOH, acetonitrile and iPrOH. Among them
toluene was the solvent of choice, which resulted in a high yield after 4 h (Table 2, entry 6). To
study the effect of amount of catalyst, the reactions were carried out at different amount of
catalysts ranging from 0.25 – 1 mol %. The yield increased as 42, 79 and 99 % respectively. An
increase in the catalyst mol % did not improve the yield further. Conversely, a decrease in
catalyst mol % diminished the yield of the product significantly (Fig. 4). Considering the pivotal
role of base in promoting the formation of nickel intermediates during the catalytic cycle,
different bases including K
2
CO
3
, NaOAc, Cs
2
CO
3
and K
3
PO
4
were screened. It was found that
CO is also an effective
K
3
PO and Cs CO were useful bases in these reactions at 110 ⁰C. Cs
4
2
3
2
3
base in this reaction as shown in fig. 4, but it is expensive when compared to other bases.
Furthermore, the results showed that 1.0 mol % catalyst in toluene was sufficient to push this
reaction and the most suitable reaction temperature was 110 ⁰C.
Table 2. Evaluation of conditions for Suzuki- Miyaura coupling of bromobenzene with
a
phenylboronic acid
Br
B(OH)
2
catalyst (1 mol%)
toluene, base, Temp.
PhB(OH)2
K3PO4
b
Entry
Solvent
Temp (⁰C) Time (h) Yield (%)
(
.equiv)
1.1
(.equiv)
1
2
3
4
5
6
7
8
9
Dioxane
Dioxane
iPrOH
2.2
2.2
2.4
2.6
2.6
2.6
2.6
2.6
2.6
2.6
90⁰C
90⁰C
85⁰C
85⁰C
110⁰C
110⁰C
85⁰C
85⁰C
70⁰C
85⁰C
2
4
45
52
15
29
91
>99
26
42
46
30
1.1
1.1
2
iPrOH
1.3
4
Toluene
Toluene
Acetonitrile
Acetonitrile
THF
1.3
2
1.3
4
1.3
4
1.3
6
1.3
12
12
10
EtOH
1.3
a
Reaction conditions: bromobenzene (1 mmol), phenylboronic acid (1.1-1.3 mmol),
PO (2.2-2.6 mmol), catalyst (1 mol %) and solvent (3 ml).
K
3
4
1
1
Page 11 of 35

b
Conversion determined by GC.
Fig. 4. Effect of catalyst (mol %) and base on Suzuki–Miyaura cross-coupling of bromobenzene
with phenylboronic acid
With an optimized catalytic system in hand, a number of structurally diverse aryl halides
and arylboronic acids were screened to demonstrate the general applicability and efficacy of this
protocol and the results are summarized in Table 3. To our delight all reactions took place
smoothly to give the corresponding biphenyls in good to high yields (Table 3, entry 1-16). The
reaction scope of this complex has been examined with a short series of aryl bromides bearing
electron-withdrawing and donating substituent undergo coupling reactions with arylboronic
acids, effectively affording the desired biaryls in excellent yields 84 - >99% (Table 3, entry 1-4,
1
4-16). The reaction of aryl iodides proceeded smoothly to produce the desired biphenyl
compounds in high yields 90-93 % (Table 3, entry 5-8). While the reaction of 4-nitrobenzene
with aryl boronic acid, the complex showed lower activity even when the reaction was
performed for 24 h (Table 3, entry 11). We have also examined the effectiveness of the current
catalytic system in the cross-coupling chemistry of aryl chlorides using 4-chlorobenzene, and 2’-
1
2
Page 12 of 35

chloroacetophenone with arylboronic acids. The desired biphenyls were isolated in 81, 83 and
4, 86 % yields respectively after 4 h.
8
a
Table 3. Complex 1 catalyzed Suzuki-Miyaura coupling of aryl halides and arylboronic acids
B(OH)2
X
catalyst ( 1 mol%)
toluene, K PO ,
R1
3
4
R
R
R
1
o
1
10 C, 4h
X = Br, Cl, I
Aryl boronic
acid
Time
(h)
Yield
(%)
c
d
Entry Aryl halide
product
b
TON TOF
1
2
Br
Br
B(OH)
B(OH)
B(OH)2
2
4
4
>99
88
99
88
25
22
H CO
3
2
H C
3
3
4
Br
4
4
CH
3
84
95
84
95
21
24
H CO
3
CH3
H
3
CO
Br
H
3
C
B(OH)
2
5
6
I
I
B(OH)2
4
4
92
90
92
90
23
23
H
CO
I
B(OH)2
H CO
3
3
H C
B(OH)2
3
7
4
4
CH
3
93
90
93
90
23
23
H CO
3
CH3
8
9
H CO
3
I
H C
3
B(OH)2
Cl
Cl
B(OH)
2
4
4
81
83
58
81
83
58
20
21
15
1
0
H
3
C
B(OH)
2
CH
3
1
1
1
O
2
N
Cl
B(OH)
2
24
O N
2
OCH3
OCH3
OCH3
2
3
B(OH)
2
4
4
84
86
84
86
21
22
Cl
OCH3
1
H
3
C
B(OH)
2
Cl
CH3
1
1
4
5
NC
NC
Br
Br
B(OH)
2
4
4
NC
NC
92
90
92
90
23
23
H
C
B(OH)
CH
3
3
2
Br
OCH3
1
6
B(OH)
2
4
92
92
23
OCH
3
a
3 4
Reaction conditions: aryl halide (1 mmol), arylboronic acid (1.3 mmol), K PO (2.6 mmol)
1
3
Page 13 of 35

and catalyst (1 mol %) in toluene (3 ml).
b
Conversion determined by GC.
c
Molar ratios of product formed with the catalyst used.
d
TOF = TON/time
Numerous monodentate free carbenes [38-40], bidentate bridged carbenes [41],
functionalized carbenes [16b, 42] and pincer-type ligands based on NHCs have been reported
and successfully applied in catalysis. The precise reaction mechanism remains to be elucidated.
Nevertheless, a few comments can be made. We believe that the catalytic C C coupling
reaction with nickel complex follows the “reductive elimination” pathway, extensively studied
by Liu, Xu, Xie and others [43]. The Ni(II) complexes are believed to be in situ reduced to active
Ni(0) species by the homocoupling of phenylboronic acid via a mechanism previously postulated
for related Pd(II) species and for other nickel based systems, which catalyze these reactions via a
Ni(0) ↔ Ni(II) cycle [43c, 44]. Accordingly, it is commonly accepted that, in a typical C C
coupling catalytic cycle, the strong σ-electron donating ability of a NHC ligand aids the initial
reduction and the oxidative addition [16b]. Moreover, the steric bulkiness of a NHC ligand can
increase the rate of the reductive elimination [44]. However, it is reasonable to consider that a
bulky NHC ligand may also hinder the coordination of incoming substrates to the center metal
and hence decrease the activity of center metal. In order to overcome the aforementioned
problem, the incorporation of additional donor functionalities in the side chains has been
particularly fruitful for catalytic applications as well. Especially, the hemilabile donor
functionalities based on nitrogen, oxygen or sulfur allow for efficient stabilization of the catalytic
species, while rapidly opening up free coordination sites for incoming substrates. Therefore, the
use of a flexible NHC ancillary ligand could constitute a solution. This trend agrees with our
working hypothesis that an increase in the stability of ligand could lead to improve catalytic
properties, possibly through the stabilization of the putative Ni(0) species. This prompted us to
develop a dazzling variety of these dianionic bis(aryloxy-NHC) nickel(II) complex 1 of type
2 2
[Ni(NHC) O ], because such structural variation may serve as an alternative strategy to modulate
the coordination sphere of the central metal by considering both the electronic and steric
environment of the nickel centre.
1
4
Page 14 of 35

The activities of [Ni(NHC)
NHC complexes [15e,15d]. In addition, complex 1 effectively catalyzed the cross-coupling
between arylboronic acids and a range of aryl halides without the need of additives such as PPh
2 2
O ] complex 1 were superior to those of other reported nickel
3
.
The overall activity of our system, representing the first catalytic study on oxygen-functionalized
NHC nickel complexes, is nevertheless encouraging.
3
.2 Buchwald-Hartwig reactions
Evaluation of conditions for the complex 1 catalyzed amination reaction: Initial studies
focused on the coupling of chlorobenzene with aniline in dioxane at 90 ⁰C for 4 h in the presence
t
of 1.3 mmol of KO Bu as a base and 1 mol % of complex 1 as a possible catalyst precursor. It
was found that the bases used, drastically affect the reaction. For example, high yield of
t
diphenylamine was obtained when KO Bu was used as the base and in the presence of all other
t
bases such as NaO Bu, KOH, NaOH, K
2
CO
3
, Na
2
CO
3
and KHCO
3
, no reaction or only trace
amount of product was observed (Table 4, entry 1-7). To this end, we noticed that a strong base
was required to promote the reaction. We examined the effect of solvents with the aid of catalyst
on model reaction, and the results are described in Table 4. Out of different solvents tested
during the course of optimization, the solvent such as CH
3
CN, DMSO and iPrOH were found to
O could bring about only a little
be completely ineffective. Solvents such as THF, toluene and Et
2
conversion. However, when the reaction was carried out in dioxane, we were amazed and
delighted to observe a single-handedly magic effect of dioxane resulting in 96 % isolated yield at
the temperature of 90 ⁰C (Table 4, entry 7). To study the effect of amount of the catalyst, the
reactions were carried out at different amount of catalyst ranging from 0.15-1.0 mol %. When the
catalyst loading was lowered to 0.5 mol % a longer reaction time (12 h) was necessary to achieve
high yield. When the catalyst loading was further lowered to 0.25 mol %, the complex showed
much lower activity even when the reactions were performed for 12 h. In the presence of 0.15
mol %, inferior results were observed (Fig. 5). Complex 1, in which the carbene carbon chemical
shift was observed around 152.23 ppm, implying stronger σ-donation effect, which may be the
reason for more efficient amination reactions consistent with previous literature reports. Under
these conditions, complex 1 which has shown to be a convenient and highly active catalyst
precursor for the amination of aryl chlorides gave an encouraging yield after 4 h of reaction.
1
5
Page 15 of 35

a
Table 4. Evaluation of conditions for C N coupling reaction
Cl
NH2
H
N
Catalyst (1 mol %)
o
base, solvent, 90 C, 4 h
b
Entry
Base
Solvent
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
Temp (⁰C)
90 ⁰C
Yield (%)
t
1
2
3
4
5
NaO Bu
KOH
17
10
31
n. r
46
90 ⁰C
90 ⁰C
90 ⁰C
90 ⁰C
NaOH
K CO
2
3
Na
2
CO
3
6
KHCO
3
Dioxane
90 ⁰C
n. r
t
7
8
9
KO Bu
Dioxane
THF
90⁰C
65 ⁰C
153 ⁰C
85 ⁰C
190 ⁰C
110 ⁰C
83 ⁰C
35 ⁰C
90 ⁰C
90 ⁰C
96
39
t
KO Bu
t
KO Bu
DMF
82
t
10
11
12
13
14
15
16
KO Bu
CH
3
CN
n. r
n. r
74
t
KO Bu
DMSO
Toluene
iPrOH
t
KO Bu
t
KO Bu
n. r
41
t
KO Bu
2
Et O
t
c
KO Bu
Dioxane
DMF
n. r
n. r
t
c
KO Bu
a
All reactions were carried out using chlorobenzene (1 mmol), aniline (1.3 mmol),
base (1.3 mmol), catalyst (1 mol %), solvent (2 ml) at 90 ⁰C for 4 h.
b
Isolated yield after column chromatography
No catalyst was used; n.r: no reaction
c
1
6
Page 16 of 35

Fig. 5. Effect of catalyst (mol %) with respect to time on amination of aryl chlorides
Amination of aryl chlorides with primary amines: With an active catalyst in hand and reliable
conditions are identified for this Ni-catalyzed amination, we studied the scope of arylchlorides
with primary amines that undergo these amination reactions, and the results are summarized in
Table 5. All reactions proceeded smoothly and afforded the desired coupling products in
reasonable to excellent yields upon isolation. The results in Table 5 demonstrate that the catalytic
3 3
process is able to tolerate variety of functional groups and substitutions like CH , OCH , Cl, CN
and F. Various primary amines having both electron donating and electron withdrawing groups
underwent the reaction smoothly and gave rise to good to excellent product yields (Table 5, entry
2
a-2p). The relative substituents in the aryl chloride have hardly any influence on the coupling
reactions. For example, almost identical results were observed for an electron rich and electron
deficient aryl chlorides (Table 5, entry 2a-2b). The reactions of an amine containing a secondary
alkyl group still coupled with aryl chlorides afforded the products in higher yield 78-84 % (Table
5
, entry 2h, 2i, 2l). With regards to the reactivities of amines, the primary amines containing aryl
(
3k), and heteroaryl (2m) groups reacted well to furnish excellent yields (88-92 %). Sterically
hindered primary amines which are less reactive substrates were also tested under the optimal
reaction condition. To our delight, all reactions took place smoothly to give the aminated
products in good to high yields (Table 5, entry 2n). A sterically hindered chloroarene such as (3-
1
7
Page 17 of 35

chloro-phenyldimethylamine) gave the corresponding aminated products in excellent yields
Table 5, entry 2o, 2p).
(
a
Table 5. Complex 1 catalyzed coupling of arylchlorides with primary amines
H
catalyst (1 mol %), KOtBu
N
Ar-Cl
+
R-NH2
o
Ar
R
dioxane, 90 C 4 h
2b
H
H
H
N
N
H
3
C
N
F
2
a; 96 %
2b; 94 %
2
c; 90 %
H
N
H
N
H
CH3
N
OCH3
CH
3
2
d; 94 %
2
e; 98 %
2f; 89 %
H
N
H
H
H CO
H3C
N
H CO
3
N
3
2
g; 81 %
2h; 84 %
2i; 78 %
OCH3
OCH3
H
N
H
N
H
N
H CO
H3C
3
2
l; 84 %
2
j; 97 %
2k; 92 %
H
N
CH3
H
H
N
N
O
CH3
H3C
CH3
N
H C
3
CH3
2
m; 88 %
2
n; 94 %
2
o; 98 %
H
N
N
H3C
CH3
2
p; 91 %
a
All reactions carried out using aryl chlorides (1 mmol), primary amines (1.3
mmol), KO Bu (1.3 mmol), catalyst (1 mol %), and dioxane (2 ml) at 90 ⁰C for
t
4
h.
b
Isolated yield after column chromatography.
1
8
Page 18 of 35

Amination of aryl chlorides with secondary amines: In order to check the versatility of our
catalyst, we decided to study the expanded substrate scope of the catalyst 1 with a variety of aryl
chlorides with secondary amines. As can be seen from Table 6, all reactions proceed smoothly to
give the corresponding aminated products in good to high yield (entry 3a-3o). The relative
positions of the substituents in the aryl chloride have hardly any influence on the coupling
reactions. O/m/p-chlorotoluene underwent the reaction smoothly and produces almost identical
results (Table 6, entry 3a-3c). Higher yields of products 3d (97 %) and 3e (88 %) could be
obtained for the reaction involving m and p-chloro anisoles. In addition, dimethylamino p-
substituted aryl chlorides were also tolerated to give the corresponding coupling product in high
yields (Table 6, entry 3g). Considering the wide synthetic utility of substituted amines, we also
examined the amination of aryl chlorides with other amines such as piperidine, pyrrolidine, N-
methyl benzylamine and N-methylaniline. For the reactions of piperidine with aryl chlorides to
give good yields (Table 6, entry 3h-3k, 3m). On extending the scope to pyrrolidine, aminated
products were obtained in moderate yields (Table 6, entry 3n, 3o).
a
Table 6. Complex 1 catalyzed coupling of arylchlorides with secondary amines
R1 catalyst (1 mol %), KOtBu
Ar N
R1
Ar-Cl
NH
o
dioxane, 90 C 4 h
R2
R2
3b
R
N
O
3
3
3
3
3
3
3
a (R = H)
b (R = m-CH3) 93 %
c (R = p-CH3) 98 %
d (R = m-OCH ) 97 %
e (R = p-OCH3) 88 %
92 %
R
N
3
3
3
3
h (R = H)
i (R = p-CH3) 91 %
j (R = m-OCH ) 85 %
79 %
3
3
k (R = p-OCH ) 80 %
3
f (R = p- F)
g (R = p- NMe ) 90 %
96 %
2
R
N
N
O
N
N
3
N
3
n (R = H)
74 %
l; 94 %
3m; 90 %
3
o (R = p-CH
3
) 72 %
a
Reaction conditions: All reactions were carried out using aryl chlorides (1
mmol), secondary amines (1.3 mmol), KO Bu (1.3 mmol), catalyst (1 mol
t
%
), and dioxane (2 ml) at 90 ⁰C for 4 h.
b
Isolated yield after column chromatography.
1
9
Page 19 of 35

Amination of hetero aryl chlorides with primary amines: Encouraged by these promising
results, we turned our attention to cross-coupling reactions between nitrogen containing
heteroaryl chlorides and primary amines catalyzed by 1 mol % of catalyst are summarized in
Table 7. Nitrogen containing heterocycles containing amino substituents are of particular
importance for pharmaceutical applications. However, the C N coupling reactions between
nitrogen containing heteroaryl electrophiles and primary amines are challenging, presumably
because of the coordinating properties of both pyridines and primary amines. Such reactions
proceed smoothly to give the corresponding aminated products in good yields under optimized
condition. The reaction of 2-chloropyridine was carried out with octylamine to obtain N-octyl-3-
aminopyridine (Table 7, entry 4a) in 92% yield. Next, several substituted heteroaryl chlorides,
underwent this amination reaction encompassed with 2-pyridyl and 3-pyridyl chlorides
containing both electron-donating and electron- withdrawing substituents in the ortho and para
position are well-tolerated, these reactions affording the corresponding aminated products in
good to excellent yields ranging from 61 to 96% (Table 7, entry 4b–4j). It is worth mentioning
that complex 1 can also catalyze the amination of heteroaryl chlorides with primary amines,
which is more sustainable for the synthesis of heterocyclic amines.
a
Table 7. Complex 1 catalyzed coupling of hetero arylchlorides with primary amines
t
catalyst (1 mol %), KO Bu
Heteroaryl- Cl
R-NH2
Heteroaryl-NH-R
o
dioxane, 90 C 4 h
4b
CN
CN
O
N
H
N
N
H
4
N
4
NHoctyl
a; 92 %
N
c; 67 %
4
b; 85 %
S
S
H
H
H
N
N
CF
3
N
CF3
N
N
4
N
4
f; 86 %
OCH3
d; 87 %
4e; 96 %
CN
CF3
N
CN
N
5C N
N
5
N
H
H
N
5C N
N
H
4
g; 80 %
4h; 68 %
4
i; 61 %
2
0
Page 20 of 35

N
5C N
N
H
4
j; 72 %
a
Unless otherwise specified, all reactions were carried out using
t
hetero aryl chlorides (1 mmol), primary amines (1.3 mmol), KO Bu
1.3 mmol), catalyst (1 mol %), and dioxane (2 ml) at 90 ⁰C for 4
h.
(
b
Isolated yield after column chromatography.
Based on previous literature reports [45], it appears to us that both steric and electronic
effects combine to mediate the coupling process. Initially, the electron donor properties of the
carbene facilitate the activation of aryl chlorides. A secondary effect may be provided by the
hemilabile donor functionality based on oxygen in the side chains for efficient stabilization of the
catalytic species. Accordingly, the Ni(II)-NHC complex 1 may formally be regarded as an
intermediate (oxidative adduct) in the catalytic cycle and hence it has the possibility for
generating Ni(0) species in situ by attack of nucleophiles and subsequent reductive elimination
prior to the normal catalytic cycle [46]. This new protocol provides an extremely convenient,
highly efficient and less expensive alternative for the synthesis of aryl amines. Studies are
currently underway in our laboratory to further expand the scope of this methodology as well as
to ascertain mechanistic details of this process.
4
. Conclusions
The present work reveals that the “one metal ion + one ligand” approach, i.e., using a
tetradentate NHC ligand to form robust Ni(II) complex, is an appealing strategy to develop
highly efficient organonickel(II) complex of the type [Ni(C )] which was synthesized from bis
] in presence of ethanol and Et N at
0 ⁰C afforded the corresponding complex 1. Crystal structure of the complex has been
2
O
2
(
aryloxy-NHC ligand) and Ni(OAc)
2
.4H
2
O or [NiCl
2
(PPh
3
)
2
3
8
described. For enhancing the rigidity of the stable Ni(II) complex supported by tetradentate NHC
ligand, our studies demonstrate that the simultaneous coordination of two carbenic carbons and
two aryloxy groups to one nickel centre can be used as an alternative strategy to significantly
improve the catalytic activity of Ni(II) complex. This is because this structural variation can
2
1
Page 21 of 35

modulate both the electric and steric environment of the nickel centre in a straight forward
manner. The complex was found to be an active catalyst in Suzuki-Miyaura cross-coupling
reaction. The reaction progresses efficiently at low catalyst loading (1 mol %, complex 1). This
new protocol is effective for many electronically diverse aryl halides and arylboronic acids,
providing biphenyl derivatives in good to excellent yields. Furthermore, this catalyst system has
been demonstrated to C N cross coupling reactions. The reaction can tolerate a wide array of
substrates. Under mild conditions, all reactions performed very well to give corresponding
aminated products in moderate to almost quantitative yield, enriching a convenient and
alternative method for the amination of aryl chlorides in extremely short reaction times. We hope
that nickel will continue to gain recognition, not only as an inexpensive substitute for palladium,
but also possessing a number of inherent properties that provide a complement to catalysis by
other metals.
5
. Experimental section
5
.1 General considerations
Unless otherwise noted, all experiments with metal complex and the NHC ligand were
carried out without taking precautions to exclude air and moisture. All catalytic reactions were
carried out under an atmosphere of dry Ar or N using standard Schlenk techniques. All solvents
2
were reagent grade or better. All reagents were purchased from Aldrich chemical Co. and used as
received without further purification. Thin-layer chromatography (TLC) was performed on
Merck 1.05554 aluminum sheets precoated with silica gel 60 F254, and the spots were visualized
with UV light at 254 nm or under iodine. Column chromatography purifications were performed
by Merck silica gel 60 (0.063–0.200 mm). Microanalysis of carbon, hydrogen and nitrogen were
carried out using a Vario EL III elemental analyzer at SAIF, Cochin, India. Infrared spectra of
−1
the ligands and the metal complex were recorded as KBr discs in the range of 4000−400 cm
using a Nicolet Avatar model FT-IR spectrophotometer. Electronic spectra of the ligand and its
complex have been obtained in dichloromethane using a Shimadzu UV - 1650 PC
1
13
spectrophotometer in 800-200 nm range. H (300.13 MHz) and C (75.47 MHz) NMR spectra
were taken in DMSO-d or CDCl at room temperature with a Bruker AV400 instrument with
6
3
chemical shifts relative to tetramethylsilane. Electrospray ionization mass spectra were recorded
2
2
Page 22 of 35

by liquid chromatography–mass spectrometry quadrupole time-of-flight Micro Analyzer
Shimadzu) at SAIF, Panjab University, Chandigarh. Melting points were determined in open
(
capillary tubes on a Technico micro heating table and are uncorrected. The catalytic yields were
determined using ACME 6000 series GC-FID with DP-5 column of 30 m length, 0.53 mm
diameter and 5.00 μm film thickness. 1-(2’-methoxy phenyl)imidazole and the nickel metallic
precursor [NiCl
.1.1 Synthesis of 1-(2’-methoxy phenyl) imidazole
CuI (0.0952 g, 0.5 mmol) and K PO (4.245 g, 20.0 mmol) were added to a 100 ml flask
2 3 2
(PPh ) ] were prepared according to literature methods [47,48].
5
3
4
equipped with stirrer and reflux condenser. 2-Propanol (10 ml), ethylene glycol (11 ml, 20.0
mmol), 2-iodoanisole (1.3 ml, 10.0 mmol), and imidazole (0.82 g, 12.0 mmol) were added at
room temperature. The reaction mixture was heated at 80°C for 72 h to furnish a pale yellow
suspension, and then allowed to cool to room temperature. Water (ca. 5 ml) was added, and the
mixture was extracted with diethyl ether (3 ×10 ml). The combined organic phases were washed
with brine and dried over Na SO . The solvent was removed by rotary evaporation to yield the
2
4
crude product as a deep yellow residue that was purified by column chromatography on silica gel
using a solvent mixture (hexane/ ethyl acetate = 20/ 1) afforded 1-(2’-methoxy phenyl)imidazole
1
(
62 % yield) as yellow solid. H NMR (300.13 MHz, CDCl
3
): 3.64 (s, 3H, OCH
3
), 6.92 (s, 1H,
imi-H), 7.04 (s, 1H, imi-H), 7.21-7.28 (m, 1H, Ar-H), 6.84 (d, 1H, J = 7.5 Hz, Ar-H), 7.48 (s,
1
H, NCHN), 7.61 (t, 1H, Ar-H), 8.24 (d, 1H, J = 7.5 Hz, Ar-H).
5
.1.2 Synthesis of 1,1’-di(2-methoxy-phenyl)-3,3’-methylene diimidazolium dibromide
To a suspension of 1-(2’-methoxy phenyl)imidazole (3.48 g, 20.0 mmol) in
dibromomethane (5.0 ml, 71 mmol) was stirred at 100°C for 48 h, and then stored at room
temperature. The resultant white precipitate was filtered and washed with acetone and then dried
under air. Yield: 82 %. Anal. Calcd for C21
H
22
O
2
N
4
Br
2
: C, 48.30; H, 4.25; N, 10.73 %. Found:
1
C, 48.42; H, 4.40; N, 10.81 %. Mp: 42-46 ⁰C. H NMR (300.13 MHz, DMSO-d ) : δ 3.90 (s, 6H,
6
OMe), 5.67 (s, 4H, CCH
2 2
N), 6.82 (s, 2H, NCH ), 7.43 (dd, J = 7.5 Hz; J = 4.4 Hz, 2H, Ar-H),
7
.59 (d, J = 7.5 Hz, 2H, Ar-H), 7.66 (d, J = 7.5 Hz, 2H, Ar-H), 7.85 (t, 2H, Ar-H), 7.94 (s, 2H,
1
3
6
imi-H), 8.04 (s, 2H, imi-H), 9.82 (s, 2H, NCHN). C NMR (75.47 MHz, DMSO-d ): δ 29.24
2
3
Page 23 of 35

(
OCH
C), 123.4 (imi-C), 123.8 (Ar-C), 124.5 (Ar-C), 142.4 (NCHN), 155.6 (C-O).
.1.3 Synthesis of 1,1’-di(2-hydroxy-phenyl)-3,3’-methylene diimidazolium dibromide
LBr
A solution of 1,1’-di(2-methoxy-phenyl)-3,3’-methylene diimidazolium dibromide (3.91
3 2
), 58.21 (CCH N), 116.1 (Ar-C), 119.4 (Ar-C), 121.1 (Ar-C), 122.6 (Ar-C), 122.7 (imi-
5
(
H
4
2
)
g, 7.91 mmol) in 47 % HBr (30 ml) and CH COOH (30 ml) was refluxed at 110°C for 48 h. The
3
mixture was stored at room temperature, and the resultant white precipitate was collected and
washed with acetone. Yield 87 %. Mp: 54-61⁰C. White solid. Anal. Calcd for C19
H
18
O
2
N
4
Br
2
: C,
-
1
4
1
2
6.18; H, 3.67; N, 11.34 %. Found: C, 46.27; H, 3.71; N, 11.42 %. IR (KBr, cm ): 3383 (O-H),
333 (C-O), 1562 (N-C-N), 3046 (CHC=C), 1418 (C-O). UV λmax( max) : 344 (12489), 318 (16791),
1
75 (4542). H NMR (300.13 MHz, DMSO-d
6
): δ 5.42 (s, 4H, CCH
2
N), 6.71 (s, 2H, NCH
2
), 7.38
(
(
(
dd, J = 7.5 Hz; J = 4.4 Hz, 2H, Ar-H), 7.42 (d, J = 7.5 Hz, 2H, Ar-H), 7.51 (t, 2H, Ar-H), 8.07
s, 2H, imi-H), 8.24 (s, 2H, imi-H), 8.56 (d, J = 7.5 Hz, 2H, Ar-H), 10.01 (s, 2H, NCHN), 11.08
1
3
s, 2H, OH). C NMR (75.47 MHz, DMSO-d
6
): δ 149.83 (C-O), 138.02 (NCHN), 130.9 (Ar-C),
1
24.99 (imi-C), 123.28 (imi-C), 121.52 (Ar-C), 121.47 (Ar-C), 119.35 (Ar-C), 116.82 (Ar-C),
2
+
1
2
18.4 (Ar-C), 118.2 (Ar-C), 57.64 (CCH N). ESI-MS (m/z): calcd. 167.18 [M-2Br] (z = 2).
2
+
Found, 167.15 [M-2Br]
5
.1.4 Synthesis of {1,1’-di(2-hydroxy-phenyl)-3,3’-methylene diimidazolin-2,2’-diylidene}
nickel(II) complex.Ni (L) 1
A suspension of Ni(OAc)
2
·4H
2
O (0.0455 g, 0.183 mmol) or [NiCl
LBr (0.082 g, 0.165 mmol) and Et
0.165 g, 0.785 mmol), Et N (74.0 μl, 0.531 mmo1) was added, and the mixture was gently
2
(PPh
3
)
2
] (0.1197 g,
0
.183 mmol) in ethanol (15 ml) was treated with H
4
2
4
NBr
(
3
stirred at 80⁰C for 6 h. The precipitated greenish yellow powder of complex 1 was filtered and
the solid was thoroughly washed with small amount of ethanol and diethyl ether. Single crystals
suitable for X-ray determination was grown in DMSO solution of 1 for one month at room
temperature. Yield: 82 %. Mp: >300⁰C. Greenish yellow solid. Anal. Calcd for C19
H
14
O
2
N
4
Ni:
-1
C, 58.66; H, 3.63; N, 14.40 %. Found: C, 58.74; H, 3.70; N, 14.51 %. IR (KBr, cm ): 1393 (C-O),
1573 (N-C-N), 3114 (CHC=C), 1417 (C-O). UV λmax( max) : 430 (<1000), 399 (3500), 369 (14421),
1
3
30 (15291). H NMR (300.13 MHz, DMSO-d
6
): δ 5.89 (s, 4H, CCH
2
N), 7.64 (t, 2H, Ar-H), 7.89
2
4
Page 24 of 35

(
s, 2H, imi-H), 7.94 (s, 2H, imi-H), 8.14 (t, 2H, Ar-H), 8.24 (d, J = 7.5 Hz, Ar-H) 8.41 (d, J = 7.5
1
3
Hz, 2H, Ar-H). C NMR (75.47 MHz, DMSO-d
6
): δ 60.58 (CCH
2
N), 120.66 (imi-C), 121.32
(
imi-C), 124.6 (Ar-C), 126.17 (Ar-C), 128.56 (Ar-C), 131.19 (Ar-C), 132.76 (Ar-C), 133.28 (Ar-
+
+
C), 148.76 (C-O), 152.23 (Ni-C). ESI-MS (m/z): calcd. 389.03 [M] . Found: 389.09 [M] .
5
.2 Catalysis
5
.2.1 General procedure for the Suzuki-Miyaura reaction: The typical procedure is as
follows. A two necked 25 ml flask fitted with a reflux condenser and septum was charged with
aryl halides (1 mmol), aryl phenylboronic acid (1.3 mmol), K PO (2.6 mmol) and catalyst (1
3
4
mol %) in 3 ml toluene. The reaction mixture was immediately heated with vigorous stirring in
an oil bath at 110⁰C under argon atmosphere for an appropriate period of time. The reaction
mixture was cooled to room temperature. A 1:1 mixture of diethyl ether/ water (20 ml) was
added. The organic layer was separated and the aqueous layer extracted with another 10 ml
4
portion of diethyl ether, and dried with anhydrous MgSO . The solution was then filtered.
Conversions and yields of the reactions were determined by GC using dodecane as internal
standard.
5
2
.2.2 General procedure for the Buchwald-Hartwig reaction: Under an N atmosphere,
t
KO Bu (1.3 mmol), complex 1 (1 mol %), dioxane (2 ml), amines (1.3 mmol) and aryl chlorides
(
1.0 mmol) were successively added into a Schlenk tube. The mixture was stirred vigorously at
9
0⁰C for 4 h. Then the solvent was removed under reduced pressure and the residue was purified
by column chromatography on silica gel (eluent: PE/EA = 15:1) to give the pure products. The
reported yields are the average of two runs.
The catalytic reactions have been given in Tables 4-7. The resulting amines were identified by
1
13
comparison of the H & C NMR data with those previously reported (ESI†).
5
.3 X-ray crystallography
2
5
Page 25 of 35

Crystal of complex 1 was mounted on glass fibers used for data collection. Crystal data
were collected at 295 K using a Gemini A Ultra Oxford Diffraction automatic diffractometer.
Graphite monochromated Mo-Kα radiation (λ = 0.71073 Å) was used throughout. The
absorption corrections were performed by the multi-scan method. Corrections were made for
Lorentz and polarization effects. The structures were solved by direct methods using the program
SHELXS [49]. Refinement and all further calculations were carried out using SHELXL [49].
The H atoms were included in calculated positions and treated as riding atoms using the
SHELXL default parameters. The non-hydrogen atoms were refined anisotropically using
2
weighted full-matrix least squares on F . Atomic scattering factors were incorporated into the
computer programs.
Acknowledgment
The authors express their sincere thanks to Department of Science and Technology, New Delhi,
for financial support for this work under the DST FAST TRACK Scheme (No. SR/FT/CS-
6
6/2011). One of the authors (MN) thanks DST-SERB for the award of fellowship.
Electronic supplementary information (ESI) available:
1
13
NMR ( H and C) and mass spectra of ligand and the complex. Catalysis protocols,
1
13
characterization data for aminated products and selected H and C NMR spectra of coupling
products. CCDC 985756. These data can be obtained free of charge from the Cambridge
Crystallographic Data center via www.ccdc.cam.ac.uk/data_request/cif.
2
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4
Chemical Co., Inc. are: PdCl
2
(99%) = RMB 8.8X10 per mol; PdCl
2
(dppp) = RMB
(98%) = RMB
(97%) = RMB
5
5
3
1
3
.98X10 per mol; PdCl
2
(PCy
3
)
2
(95%) = RMB 9.1X10 per mol; NiCl
2
3
4
.3X10 per mol; NiCl
2
(dppp) = RMB 8.3X10 per mol; NiCl
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(PCy
3
)
2
5
.1X10 per mol
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