Nickel(II) Schiff base complexes: Synthesis, characterization and catalytic activity in Kumada-Corriu cross-coupling reactions

Article abstract of DOI:10.1016/j.poly.2016.05.037

The syntheses of ten new Ni(II) complexes 5a-5j with H₂L tridentate (ONO) Schiff-base ligand (2-((2-oxybenzylidene)amino)phenolate) have been described and fully characterized by means of elemental analysis, FT-IR, electronic, ¹H NMR and ¹³C NMR spectroscopy and single-crystal X-ray diffraction. In all [Ni(L)B] complexes (where B are imidazole, 4-benzylpyridine, 2-methyl-5-ethylpyridine, 3-hydroxymethylpyridine, 2-methylbenzimidazole, 2,6-dimethylpyridine, 4-methylpyridine, 2-isopropylbenzimidazole, 4-methylpiperidine or triphenylphosphine) the Schiff base completely deprotonates and coordinates to the metal ion as a dianionic tridentate ligand via the donor oxygens and nitrogen atoms. The coordination number of Ni(II) atoms is four with distorted square-planar stereochemistry. This is in a good agreement with the ligand field band position in their electronic spectra, as well as with the X-ray structure analysis for all complexes under study. Six selected complexes are used as catalysts for Kumada-Corriu cross-coupling reactions and exhibit a moderate to good catalytic activity in the synthesis of biaryl derivatives.

Full text of DOI:10.1016/j.poly.2016.05.037

Polyhedron 117 (2016) 90–96
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Nickel(II) Schiff base complexes: Synthesis, characterization
and catalytic activity in Kumada–Corriu cross-coupling reactions
b
c
b
d
Vladimír Kuchtanin a, , Lucia Klešcíková , Michal Šoral , Róbert Fischer , Zdenka Ru˚ zicková ,
⇑
ˇ
ˇ
ˇ ˇ
e
a
a
´
Erik Rakovsky , Ján Moncol’ , Peter Segl’a
a Institute of Inorganic Chemistry, Technology and Materials, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 81237
Bratislava, Slovak Republic
b Institute of Organic Chemistry, Catalysis and Petrochemistry, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 81237
Bratislava, Slovak Republic
c Central Laboratories, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, SK-812 37, Slovak Republic
d Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, CZ-532 10 Pardubice, Czech Republic
e Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, 84215 Bratislava, Slovak Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
The syntheses of ten new Ni(II) complexes 5a–5j with H2L tridentate (ONO) Schiff-base ligand (2-((2-oxy-
benzylidene)amino)phenolate) have been described and fully characterized by means of elemental anal-
ysis, FT–IR, electronic, 1H NMR and 13C NMR spectroscopy and single-crystal X-ray diffraction. In all [Ni(L)
Received 16 February 2016
Accepted 15 May 2016
Available online 24 May 2016
B] complexes (where
B are imidazole, 4-benzylpyridine, 2-methyl-5-ethylpyridine, 3-hydrox-
ymethylpyridine, 2-methylbenzimidazole, 2,6-dimethylpyridine, 4-methylpyridine, 2-isopropylbenzimi-
dazole, 4-methylpiperidine or triphenylphosphine) the Schiff base completely deprotonates and
coordinates to the metal ion as a dianionic tridentate ligand via the donor oxygens and nitrogen atoms.
The coordination number of Ni(II) atoms is four with distorted square-planar stereochemistry. This is in a
good agreement with the ligand field band position in their electronic spectra, as well as with the X-ray
structure analysis for all complexes under study. Six selected complexes are used as catalysts for
Kumada–Corriu cross-coupling reactions and exhibit a moderate to good catalytic activity in the synthe-
sis of biaryl derivatives.
Keywords:
Nickel(II) complexes
Schiff base
Kumada–Corriu reaction
Cross-coupling
Biaryl
Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Schiff-bases are a vital class of organic compounds. A large
number of metal complexes with a Schiff-base were reported with
various methods of in activation of small molecules, in addition to
being nano-precursors and with good redox capability. Attention is
paid to their potential applications in many areas, viz. optical uti-
lization [1–3], biology [4,5], catalysis [6–8] and corrosion inhibi-
tion [9,10], as well as to their thermal, magnetic and electrical
properties [11]. Nickel complexes play a prominent role in bioinor-
ganic redox enzyme systems [12,13] and square planar nickel com-
plexes in concert of some other factors can cause the cleavage of
plasmid DNA [14].
2.1. Synthesis of the nickel(II)complexes
The synthetic route of nickel complexes is shown in Scheme 1.
The organic precursor H2L 3 was prepared according to the litera-
ture by the condensation of salicylaldehyde (1) and 2-aminophenol
(2) in acetonitrile [15]. Subsequently, all complexes 5a–5j were
prepared by stirring an acetonitrile solution of Schiff base with
methanolic solution of Ni(OCOCH3)2Á4H2O and with relevant N-
donor ligands (pyridine, piperidine, imidazole and benzimidazole
derivatives) or triphenylphosphine in 1:1:1 molar ratio for 2 h
under reflux. The resulting red solutions were left to evaporate
slowly at ambient temperature. Complexation products were iso-
lated as red-brown (5a) or red (5b, 5d–5j) crystals and a red (5c)
powder in good yields (70–80%). The analytical data for these com-
plexes are in good agreement with the proposed molecular
formula.
⇑
Corresponding author. Tel.: +421 2593 25 209; fax: +421 2524 93 198.
E-mail address: vladimir.kuchtanin@stuba.sk (V. Kuchtanin).
http://dx.doi.org/10.1016/j.poly.2016.05.037
0277-5387/Ó 2016 Elsevier Ltd. All rights reserved.

V. Kuchtanin et al. / Polyhedron 117 (2016) 90–96
91
Scheme 1. Synthesis of the nickel(II) complexes.
2.2. Characterization of the complexes
2.2.1. Infrared spectra
The
frequencies in complexes indicating weakening of the azomethine
band due to the coordination to the metal [16]. The (CAO) band
m
(C@N) band at 1625 cmÀ1 of the Schiff base shifts to lower
m
for all complexes appears at lower frequencies compared to that
for the free ligand, which is due to the participation of phenolic
oxygen on chelation [17].
2.2.2. 1H and 13C NMR spectra
The NMR analysis of compounds 5a–j suggested a partial or
dominant paramagnetic behavior of the central atom. A consider-
able line broadening was present in the 1H and 13C NMR spectra
of 5d and 5i. A dependence of the decrease of T2⁄ relaxation time
upon the distance from Ni(II) was observable, resulting in the
impossibility to assign (or even observe) some of the 13C signals
from the heterocyclic ligands. The NMR measurements of 5f, 5g
and 5j resulted in signals which were too broad to attempt a 2D
NMR analysis. The rapid T2 relaxation of the signals would cause
that the potentially observable signals would relax (and thus dis-
appear) already during the mixing and evolution period of the
2D NMR sequences. High-spin and ligand dependent behavior of
Ni(II) complexes was observed in past studies and described in
detail [18]. This behavior was noticed when measuring the spectra
of 5b in deuterated chloroform, while measurements of the same
substance in deuterated tetrahydrofuran yielded spectra with
sharp lines. Based on the above reasons, 1H and 13C NMR spectra
for the complexes 5f, 5g and 5j were not recordable, and therefore
are not included in Section 4.
Fig. 1. Molecular structure of complex 5a. Only one part of disordered ligand is
drawn.
Distortion is mainly caused by the presence of the double deproto-
nated tridentate L ligand (2-((2-oxybenzylidene)amino)phenolate),
which forms together with nickel atom one five- and one six-mem-
bered metallocycles [OANiAN angles are in the ranges 86–88° and
95–98°, respectively]. In all compounds is L bonded to the nickel
ion via two phenolate oxygen atoms [NiAO distances are in the
range 1.81–1.85 Å, See ESI Table S1] and iminic nitrogen atoms
[NiAN distances are in the range 1.82–1.89 Å, See ESI Table S1].
The crystal structures of two complexes 5b and 5h show two crys-
tallographic independent complex molecules (Figs. 2 and ESI S5).
The fourth coordination positions are occupied by the phosphorus
atom from triphenylphosphine ligand (5a) [NiAP distances are in
the range 2.11–2.15 Å, See ESI Table S1] or nitrogen atoms from
imidazole (5b), 4-benzylpyridine (5d), 2-methyl-5-ethylpyridine
(5e), 3-hydroxymethylpyridine (5f), 2-methylbenzimidazole (5g),
2,6-dimethylpyridine (5h), 4-methylpyridine (5i) or 2-isopropyl-
benzimidazole (5j) [NiAN distances are in the range 1.88–1.95 Å,
2.2.3. Electronic spectra
Ni(II) square-planar complexes typically have a single band at
about 22000 cmÀ1, and a second more intense band may be seen
near 23000 cmÀ1. Square complexes under study differ from those
with other coordination polyhedra in that the absorption below
10000 cmÀ1 is not seen [19].
2.2.4. X-ray crystallography
The molecular structures of nine complexes 5a, 5b, 5d–5j are
drawn in Figs. 1–5 and ESI Figs. S1–S4. The nickel atoms in all
compounds have a distorted square planar coordination geometry.

92
V. Kuchtanin et al. / Polyhedron 117 (2016) 90–96
Fig. 2. Molecular structure of complex 5b.
Fig. 4. Molecular structure of complex 5g. Only one part of disordered ligand is
drawn.
Fig. 3. Molecular structure of complex 5d. Only one part of disordered complex
molecule is drawn.
See ESI Table S1]. Similar square planar nickel(II) complexes with
1-methylimidazole and triphenylphosphine ligands have been
recently published by Salehi et al. [20] and Saha et al. [21].
Fig. 5. Molecular structure of complex 5j. Only one part of disordered ligand is
drawn.
The complex molecules of 5b are connected through NAHÁ Á ÁO
hydrogen bonds between imidazole ligand and phenolate oxygen
atoms of L1 [NÁ Á ÁO distances are in the range 2.773(5)–2.826(6) Å
(See ESI Table S2)], forming supramolecular spiral (See ESI
Fig. S5). The two complex molecules of 5f are joined into
supramolecular ring R22(14) [22] (See ESI Fig. S6) through OAHÁ Á ÁO
hydrogen bonds between hydroxyl groups of 3-hydrox-
ymethylpyridine ligand and phenolate oxygen atoms of L1 [OÁ Á ÁO
distance of 2.743(5) Å (See ESI Table S2)]. The complex molecules
of 5g are linked through NAHÁ Á ÁO hydrogen bonds between imida-
zole ring and phenolate oxygen atoms of L1 [NÁ Á ÁO distance of
2.756(5) Å (See ESI Table S2)] into supramolecular zigzag chain
(See ESI Fig. S7). The crystal structure of 5j consists of complex
molecules and uncoordinated methanol molecules, which are con-
nected into supramolecular ring R44(16) [22] (See ESI Fig. S8)
through NAHÁ Á ÁO hydrogen bonds between imidazole rings of 2-
isopropylbenzimidazole ligand and methanol molecules [NÁ Á ÁO
distance of 2.802(5) Å (See ESI Table S2)], and OAHÁ Á ÁO hydrogen
bonds between methanol ligands and phenolate oxygen atoms of
L1 [OÁ Á ÁO distance of 2.662(5) Å (See ESI Table S2)]. The similar
supramolecular rings have been formed in crystal structure of

V. Kuchtanin et al. / Polyhedron 117 (2016) 90–96
93
(4-chloro-2-((2-(hydroxy)benzylidene)amino)phenolato)(1H-imi-
dazole)-nickel methanol solvate (refcode: ZUFVUT) [23]. On the
other hand, supramolecular zigzag chain have been observed in
crystal structure of (4-chloro-2-((2-(hydroxy)benzylidene)amino)
phenolato)-(2-methyl-1H-imidazole)-nickel methanol solvate (ref-
code: SUBJEG) [24].
activity, and the desired product 4-methoxybiphenyl (8a) was iso-
lated in 65–70% yields, despite of different ligands used (entries 2,
4 and 5). Moreover, the yields were even higher than that with Ni
(dppp)Cl2 (57%, entry 1). On the other hand, complexes 5b, 5g and
5j, containing the imidazole and the benzimidazole ligands were
less active. The presence of hydrogen atom attached to the nitro-
gen atoms probably governed the catalytic activity of 5b, 5g and
5j due to their facile deprotonation, and 4-methoxybiphenyl (8a)
was obtained in lower 49% and 42% yields (entries 3, 6 and 7),
respectively. Apart from the isolated yields, no homocoupling
side-products were detected by inspection of NMR spectra of the
crude reaction mixtures. To extend the utilization of the catalysts,
two complexes 5a and 5d, showing the best activity, were applied
in cross-coupling reactions of phenylmagnesium bromide (7) with
1-bromonaphthalene (6b) and 3-bromopyridine (6c). The reactions
were performed under same reaction conditions as described
above. Results again showed the good catalytic activity of both
complexes. The reaction of 1-bromonaphthalene (6b) provided
desired 1-phenylnaphtalene (8b) in very good 81% and 78% iso-
lated yields, respectively (entries 8 and 9), in comparison to the
reactions of 3-bromopyridine (6c), which afforded 3-phenylpyri-
dine (8c) in lower 60% and 62% yields (entries 10 and 11). It is
worth noting that complex 5d, bearing a pyridine ligand, was more
stable than 5a with a triphenylphosphino group. The latter species
was gradually decomposed by storage at room temperature for a
longer time, resulting in the loss of its activity.
2.3. Catalytic activity of the nickel(II)complexes
The catalytic activity of the selected Ni(II) complexes 5a–d, 5g
and 5j was readily examined in Kumada–Corriu cross-coupling
reaction [25], which is still one of the most attractive method for
the synthesis of biphenyl derivatives [26]. 4-Bromoanisole (6a)
and phenylmagnesium bromide (7) were chosen as initial model
substrates. All attempts were carried out in a Schlenk tube in the
presence of 2 mol% of nickel complexes for 24 h under argon atmo-
sphere (Table 1). Commercially available Ni(dppp)Cl2 was used as a
competitive catalyst. The results summarized in Table 1 show that
three of the tested complexes 5a,c and 5d exhibit good catalytic
Table 1
Kumada–Corriu cross-coupling reactions with the selected nickel(II) complexes 5a–d,
5g, 5j.a
MgBr
Ar
Ni cat. (2 mol%)
THF, r.t., 24 h
Ar Br
6a-c
8a-c
7
3. Conclusion
In conclusion, we have presented the synthesis and structural
study of ten nickel(II) Schiff base complexes. The crystal structures
of the presented complexes show, that nickel atoms in all com-
pounds have a distorted square planar coordination geometry.
The complex molecules which contain imidazole, substituted imi-
dazoles or 3-hydroxymethylpyridine ligands act as a supramolecu-
lar reagent for a building of the hydrogen bonding coordination
networks.
The catalytic activity of the six Ni(II) complexes was examined
in the Kumada–Corriu cross-coupling reaction. Three of them
exhibited a good catalytic activity. On the other hand, other com-
plexes which contain imidazole ring show a lower catalytic activ-
ity. This is probably due to the fact that hydrogen atom attached
to nitrogen atom could be removed by phenylmagnesium bromide,
resulting in the structure change.
Entry
1
ArBr
Ni cat.
Product
Yieldc (%)
57
NiCl2 (dppp)b
MeO
Br
Br
Br
Br
Br
Br
MeO
Ph
8a
6a
6a
6a
6a
6a
6a
2
3
4
5
6
7
8
5a
5b
5c
5d
5g
5j
70
49
65
70
42
42
81
MeO
MeO
MeO
Me O
Me O
MeO
MeO
MeO
MeO
MeO
MeO
Ph
8a
Ph
8a
Ph
8a
Ph
8a
Ph
8a
4. Experimental
4.1. General
MeO
Br
Ph
8a
6a
6b
All the chemicals used were of reagent grade purity (Aldrich or
Sigma, Acros Organics, Alfa-Aesar, Merck and Mikrochem Trade)
and used without further purification. Carbon, hydrogen and nitro-
gen contents were determined by microanalytical methods
(Thermo Electron Flash EA 1112). Electron spectra (9000–
50000 cmÀ1) of the powdered samples in Nujol mulls were
recorded at room temperature on a Specord 200 spectrophotome-
ter (Carl Zeiss Jena). Infrared spectra in the region 400–4000 cmÀ1
were recorded on a Nicolet 5700 FT-IR spectrometer (Thermo Sci-
entific). Spectra of the solid samples were obtained by the ATR
technique at room temperature. Melting points were measured
on a Melting Point B-540 apparatus (Büchi) and stayed uncor-
rected. 1H NMR spectra were recorded on a Varian VRX-300 spec-
trometer (1H, 300 MHz) and Varian INOVA-600 spectrometer (1H,
600 MHz) in CDCl3, d8-THF and C6D6 using TMS as the internal
standard. TLC analysis was carried out using TLC Silica gel 60
5a
Br
Ph
8b
8b
9
5d
78
Br
Ph
6b
10
11
5a
5d
60
62
N
N
N
N
6c
8c
Br
6c
Ph
8c
Ph
Br
a
Reagents and conditions: ArBr (2 mmol), Ni cat. (2 mol%, 0.04 mmol), PhMgBr
(4 mmol, 1 M in THF), THF (2 mL), r.t., 24 h.
b
[1,3-Bis(diphenylphosphino)propane]dichloronickel(II).
Isolated yield.
c

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V. Kuchtanin et al. / Polyhedron 117 (2016) 90–96
F254 (aluminum sheets, Merck) and visualized by UV light or with
permanganate solution followed by heating. Flash column chro-
matography (FCC) was performed on Büchi system (Pump Manager
C-615 and Fraction Collector C-660) using Normasil 60 silica gel
(0.040–0.063 mm) (VWR). All solvents were dried and distilled
according to conventional methods. THF was stored over molecular
sieves and handled under inert atmosphere.
6.8, 1.1 Hz), 6.50 (ddd, 1H, J = 8.0, 7.2, 1.2 Hz), 3.77–3.65 (m, 2H),
2.84–2.71 (m, 2H), 1.75–1.66 (m, 2H), 1.62–1.51 (m, 1H), 1.50 (tt,
1H, J = 12.2, 2.5 Hz), 1.15–1.04 (m, 2H), 0.91 (d, 3H, J = 6.5 Hz);
13C NMR (151 MHz, CDCl3): d = 164.6, 163.2, 148.5, 139.4, 132.7,
132.5, 128.5, 121.0 (2ÂC), 117.1, 115.5, 114.5, 113.8, 47.8 (2ÂC),
34.9 (2ÂC), 30.3, 22.2; Elemental Anal. Calc.: C, 62.00; H, 5.75; N,
7.61; Found: C, 61.87; H, 5.61; N, 7.85%. IR (ATR) cmÀ1
:
m
(C@N)
1604 s, m(CAO) 1295 s, m(NiAO) 545 s, m(NiAN) 445 m, UV–Vis
4.2. Synthesis of the complexes
(NUJOL) kmax cmÀ1: 23500, 22200.
4.2.1. Preparation of Schiff base H2L
We added salicylaldehyde (22.38 g; 0.183 mol) to 2-hydrox-
yaniline (20 g; 0.183 mol) dissolved in acetonitrile (50 mL) and
the resulting solution was refluxed for 20 min, during which the
color turned yellow, and the red-orange microcrystalline solid pre-
cipitated. The solution was left to cool down, then it was filtered
and the solid was washed with cold methanol and air dried. Yield
(85%; 33.2 g).
4.2.5. [Ni(L)(4-Bn-pyridine)] (5d)
This red compound was prepared by the same procedure as for
5a using 4-benzylpyridine (0.338 g; 0.002 mol) instead of
triphenylphosphine.
Yield: 73%, 1H NMR (600 MHz, CDCl3): d = 8.55 (br s, 2H), 8.14
(br s, 1H), 7.53 (d, 1H, J = 7.8 Hz), 7.38 (d, 1H, J = 7.6 Hz), 7.34–
7.30 (m, 2H), 7.28–7.24 (m, 1H), 7.18 (dd, 1H, J = 8.4, 6.8 Hz),
7.17–7.13 (m, 4H), 6.97 (dd, 1H, J = 8.1, 6.9 Hz), 6.88 (d, 1H,
J = 8.4 Hz), 6.72 (d, 1H, J = 8.1 Hz), 6.66 (dd, 1H, J = 7.6, 6.8 Hz),
6.53 (dd, 1H, J = 7.8, 6.9 Hz), 3.96 (br s, 2H); 13C NMR (151 MHz,
CDCl3): d = 164.2, 162.9, 149.4, 140.0, 132.9, 132.7, 129.1 (2ÂC),
128.9 (2ÂC), 128.6, 127.0, 121.2, 120.9, 117.4, 115.8, 114.7,
114.0, 41.3; Elemental Anal. Calc.: C, 68.38; H, 4.59; N, 6.38; Found:
4.2.2. [Ni(L)(PPh3)](5a)
We added a solution of nickel(II) acetate tetrahydrate (0.497 g;
0.002 mol) in MeOH (30 mL) and solid PPh3 (0.524 g; 0.002 mol) to
a solution of Schiff base H2L (0.426 g; 0.002 mol) in MeCN (30 mL).
The resulting solution was refluxed for 2 h and then left to evapo-
rate slowly at ambient temperature. Well shaped red-brown crys-
tals of complex 5a suitable for single crystal X-ray structure
analysis were collected after few days by filtration, washed with
methanol and finally dried at ambient temperature.
C, 68.55; H, 4.88; N, 6.12%. IR (ATR) cmÀ1
1295 s, (NiAO) 548 s,
(NiAN) 445 m, UV–Vis (NUJOL) kmax cmÀ1
23400, 22200.
: m(C@N) 1593 s, m(CAO)
m
m
:
Yield: 78%, 1H NMR (600 MHz, C6D6): d = 8.04 (s, 1H), 7.93 (br s,
6H), 7.31 (d, 1H, J = 8.2 Hz), 7.11 (d, 1H, J = 7.9 Hz), 7.09–7.02 (m,
9H), 6.99 (dd, 1H, J = 8.5, 6.9 Hz), 6.96 (dd, 1H, J = 8.2, 7.1 Hz),
6.88 (d, 1H, J = 8.2 Hz), 6.62 (d, 1H, J = 8.5 Hz), 6.57 (dd, 1H,
J = 7.9, 6.9 Hz), 6.55 (1H, dd, J = 8.2, 7.1 Hz); 13C NMR (151 MHz,
CDCl3): d = 167.0, 163.6, 148.4, 139.7, 135.0 (m, 6ÂC), 133.2,
132.5, 130.5 (3ÂC), 129.9 (only seen in HMBC, 3ÂC), 128.8, 128.6
(6ÂC), 122.4, 121.0, 118.6, 115.7, 114.7 (2ÂC); Elemental Anal.
Calc.: C, 69.96; H, 4.55; N, 2.63; Found: C, 69.72; H, 4.72; N,
4.2.6. [Ni(L)(2-Me-5-Et-pyridine)] (5e)
This red compound was prepared by the same procedure as for
5a using 2-methyl-5-ethylpyridine (0.242 g; 0.002 mol) instead of
triphenylphosphine.
Yield: 80%, 1H NMR (600 MHz, CDCl3): d = 9.25 (s, 1H), 8.09 (s,
1H), 7.55 (dd, 1H, J = 8.1, 1.2 Hz), 7.48 (br d, 1H, J = 7.7 Hz), 7.37
(dd, 1H, J = 7.9, 1.6 Hz), 7.14 (ddd, 1H, J = 8.6, 6.9, 1.6 Hz), 7.14
(br d, 1H, J = 7.7 Hz), 6.96 (ddd, 1H, J = 8.2, 7.1, 1.2 Hz), 6.73 (dd,
1H, J = 8.6, 0.9 Hz), 6.68 (dd, 1H, J = 8.2, 1.0 Hz), 6.64 (ddd, 1H,
J = 7.9, 6.9, 0.9 Hz), 6.53 (ddd, 1H, J = 8.1, 7.1, 1.0 Hz), 3.67 (s, 3H),
2.71 (br q, 2H, J = 7.7 Hz), 1.30 (br t, 3H, J = 7.7 Hz); 13C NMR
(151 MHz, CDCl3): d = 164.8, 163.2, 158.1, 150.4, 149.1, 139.5,
137.6, 137.3, 132.8, 132.7, 128.6, 125.2, 120.9, 120.7, 117.3,
115.5, 114.6, 113.8, 25.6, 25.1, 14.8. Elemental Anal. Calc.: C,
64.49; H, 5.15; N, 7.16; Found: C, 64.34; H, 5.51; N, 7.44%. IR
2.85%. IR (ATR) cmÀ1
:
m
(C@N) 1606 s,
m(CAO) 1311 m, m(NiAP)
1098 s,
m(NiAO) 527 s, m(NiAN) 454 s, UV–Vis (NUJOL) kmax
cmÀ1: 23500, 21250.
4.2.3. [Ni(L)(Im)] (5b)
This red compound was prepared by the same procedure as for
using imidazole (0.136 g; 0.002 mol) instead of
triphenylphosphine.
5a
(ATR) cmÀ1
: m(C@N) 1600 s, m(CAO) 1311 s, m(NiAO) 545 m, m
Yield: 75%, 1H NMR (600 MHz, d8-THF): d = 12.18 (br s, 1H), 8.50
(br s, 1H), 7.81 (br s, 1H), 7.65 (dd, 1H, J = 8.1, 1.3 Hz), 7.44 (dd, 1H,
J = 8.0, 1.7 Hz), 7.12 (br s, 1H), 7.11 (ddd, 1H, J = 8.4, 6.8, 1.7 Hz),
7.06 (br s, 1H), 6.85 (dd, 1H, J = 8.4, 0.9 Hz), 6.84 (ddd, 1H, J = 8.1,
7.0, 1.3 Hz), 6.58 (dd, 1H, J = 8.1, 1.0 Hz), 6.55 (ddd, 1H, J = 8.0,
6.8, 0.9 Hz), 6.39 (ddd, 1H, J = 8.1, 7.0, 1.0 Hz); 13C NMR
(151 MHz, CDCl3): d = 166.3, 164.5, 150.3, 141.3, 137.0, 133.4,
132.9, 128.8, 126.3, 122.4, 122.2, 118.0, 116.7, 115.7, 115.0,
114.4; Elemental Anal. Calc.: C, 56.86; H, 3.88; N, 12.43; Found:
(NiAN) 445 m, UV–Vis (NUJOL) kmax cmÀ1: 23250, 21200.
4.2.7. [Ni(L)(3-hydroxymethylpyridine)] (5f)
This red compound was prepared by the same procedure as for
5a using 3-hydroxypyridine (0.218 g; 0.002 mol) instead of
triphenylphosphine.
Yield: 75%, Elemental Anal. Calc.: C, 60.21; H, 4.25; N, 7.39;
Found: C, 60.48; H, 4.01; N, 7.46%. IR (ATR) cmÀ1
:
m
(C@N) 1606 s,
C, 56.99; H, 3.48; N, 12.56%. IR (ATR) cmÀ1
(CAO) 1302 m, (NiAO) 523 s, (NiAN) 447 m, UV–Vis (NUJOL)
kmax cmÀ1: 23000, 22100.
:
m(C@N) 1603 s,
m
m
(CAO) 1313 s,
m(NiAO) 544 s, m(NiAN) 449 m, UV–Vis (NUJOL)
m
m
kmax cmÀ1: 23350, 21500.
4.2.4. [Ni(L)(4-Me-piperidine)] (5c)
4.2.8. [Ni(L)(2-Me-benzimidazole)] (5g)
This red compound was prepared by the same procedure as for
5a using 4-methylpiperidine (0.198 g; 0.002 mol) instead of
triphenylphosphine.
This red compound was prepared by the same procedure as for
5a using 2-methylbenzimidazole (0.624 g; 0.002 mol) instead of
triphenylphosphine.
Yield: 72%, (600 MHz, CDCl3): d = 8.04 (s, 1H), 7.46 (dd, 1H,
J = 8.0, 1.3 Hz), 7.32 (dd, 1H, J = 7.8, 1.6 Hz), 7.17 (ddd, 1H, J = 8.5,
6.8, 1.6 Hz), 6.96 (ddd, 1H, J = 8.1, 7.2, 1.3 Hz), 6.85 (dd, 1H,
J = 8.5, 1.1 Hz), 6.67 (dd, 1H, J = 8.1, 1.2 Hz), 6.63 (ddd, 1H, J = 7.8,
Yield: 70%, Elemental Anal. Calc.: C, 62.73; H, 4.26; N, 10.45;
Found: C, 62.56; H, 4.12; N, 10.68%. IR (ATR) cmÀ1
s,
:
m
(C@N) 1582
m(CAO) 1309 s, m(NiAO) 526 m, m(NiAN) 448 m, UV–Vis (NUJOL)
kmax cmÀ1: 23200, 22400.

V. Kuchtanin et al. / Polyhedron 117 (2016) 90–96
95
4.2.9. [Ni(L)(2,6-Me2-pyridine)] (5h)
Final crystal data and structure refinement parameters are
given in Supplementary Table S2. The crystal structures were
drawn using the OLEX2 program [33]. The crystallographic data for
5a, 5b, and 5d–5j have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication CCDC Nos.
1406133–1406143.
This red compound was prepared by the same procedure as for
5a using 2,6-dimethylpyridine (0.214 g; 0.002 mol) instead of
triphenylphosphine.
Yield: 75%, 1H NMR (600 MHz, CDCl3): d = 8.09 (s, 1H), 7.56 (dd,
1H, J = 8.2, 1.2 Hz), 7.52 (t, 1H, J = 7.6 Hz), 7.36 (dd, 1H, J = 8.0,
1.9 Hz), 7.11 (ddd, 1H, J = 8.2, 6.9, 1.9 Hz), 7.09 (d, 2H, J = 7.6 Hz),
6.95 (ddd, 1H, J = 7.9, 7.2, 1.2 Hz), 6.66 (dd, 1H, J = 8.2, 1.0 Hz),
6.65 (dd, 1H, J = 7.9, 1.2 Hz), 6.62 (ddd, 1H, J = 8.0, 6.9, 1.0 Hz),
6.52 (ddd, 1H, J = 8.2, 7.2, 1.2 Hz), 4.17 (s, 6H); 13C NMR
(151 MHz, CDCl3): d = 165.0, 163.4, 160.2 (2ÂC), 148.9, 139.4,
138.1, 132.6 (2ÂC), 128.5, 122.4 (2ÂC), 121.0, 120.6, 117.4, 115.3,
114.3, 113.7, 26.5 (2ÂC); Elemental Anal. Calc.: C, 63.71; H, 4.81;
4.4. Kumada–Corriu cross-coupling reactions with the selected nickel
(II) complexes; General procedure
A
Schlenk tube was charged with a catalyst 5 (2 mol%,
0.04 mmol), sealed with a rubber septum, evacuated and filled
with argon. THF (2 mL) was added followed by aryl bromide 6
(2 mmol). After stirring for 10 min, the solution of phenylmagne-
sium bromide (7) (4 mmol, 1 M in THF) was added drop-wise via
syringe, and stirring continued at ambient temperature for 24 h.
Upon reaction completion, sat. aq. NH4Cl solution was added, and
the mixture was stirred for additional 10 min. Then, the mixture
was extracted with Et2O (3 Â 50 mL). Combined organic layers
were dried over MgSO4, and the solvent was evaporated in vacuo.
The product was isolated by column chromatography (hexanes/
ethyl acetate) to provide desired coupled product 8. The isolated
yields of 8a–c, depending on the catalyst, are summarized in
Table 1.
N, 7.43; Found: C, 63.52; H, 4.75; N, 7.59%. IR (ATR) cmÀ1
: m
(C@N) 1603 s,
m(CAO) 1311 s, m(NiAO) 545 s, m(NiAN) 440 m,
UV–Vis (NUJOL) kmax cmÀ1: 23250, 21700.
4.2.10. [Ni(L)(4-Me-pyridine)] (5i)
This red compound was prepared by the same procedure as for
5a using 4-methylpyridine (0.186 g; 0.002 mol) instead of
triphenylphosphine.
Yield: 75%, 1H NMR (600 MHz, CDCl3): d = 8.52 (br s, 2H), 8.16
(br s, 1H), 7.54 (br s, 2H), 7.54 (d, 1H, J = 7.9 Hz), 7.39 (d, 1H,
J = 7.8 Hz), 7.20 (dd, 1H, J = 8.5, 6.6 Hz), 6.98 (dd, 1H, J = 8.0,
7.0 Hz), 6.90 (d, 1H, J = 8.5 Hz), 6.74 (d, 1H, J = 8.0 Hz), 6.66 (dd,
1H, J = 7.8, 6.6 Hz), 6.54 (dd, 1H, J = 7.9, 7.0 Hz), 2.38 (br s, 3H);
13C NMR (151 MHz, CDCl3): d = 164.3, 163.0, 149.8, 149.4, 140.1,
132.9, 132.7, 128.6, 125.2, 121.2, 121.0, 117.4, 115.8, 114.7,
114.0, 21.3; Elemental Anal. Calc.: C, 62.86; H, 4.44; N, 7.72; Found:
4.4.1. 4-Methoxybiphenyl (8a)
The general procedure above was followed using 4-bro-
moanisole (6a) (250 lL, 2 mmol) and phenylmagnesium bromide
(7) (4 mL, 4 mmol, 1 M in THF). FCC on silica gel (hexanes/ethyl
acetate, 98:2) provided product 8a as a colorless solid in various
yields, depending on the catalyst: Yields/catalyst: [210 mg (57%)/
NiCl2(dppp); 258 mg (70%)/5a; 180 mg (49%)/5b; 240 mg
(65%)/5c; 258 mg (70%)/5d; 156 mg (42%)/5g; 154 mg (42%)/5j].
Mp 88–89 °C [Mp 90–91 °C (EtOH)] [34].
C, 62.55; H, 4.68; N, 7.81%. IR (ATR) cmÀ1
1322 s, (NiAO) 546 s,
(NiAN) 450 m, UV–Vis (NUJOL) kmax cmÀ1
23350, 22100.
: m(C@N) 1594 s, m(CAO)
m
m
:
4.2.11. [Ni(L)(2-iPr-benzim)]ÁMeOH (5j)
1H NMR (300 MHz, CDCl3): d = 7.60–7.53 (m, 4H), 7.46–7.41 (m,
2H), 7.35–7.32 (m, 1H), 7.03–6.98 (m, 2H), 3.87 (s, 3H).
This red compound was prepared by the same procedure as for
5a using 2-izopropylbenzimidazole (0.320 g; 0.002 mol) instead of
triphenylphosphine.
Yield: 76%, Elemental Anal. Calc.: C, 64.37; H, 5.45; N, 9.09;
4.4.2. 1-Phenylnaphthalene (8b)
The general procedure above was followed using 1-bromonaph-
thalene (6b) (280 lL, 2 mmol) and phenylmagnesium bromide (7)
Found: C, 64.38; H, 5.12; N, 9.21%. IR (ATR) cmÀ1
m
:
m(C@N) 1601 s,
(CAO) 1312 s, m(NiAO) 545 s, m(NiAN) 445 m, UV–Vis (NUJOL)
kmax cmÀ1: 23750, 22200.
(4 mL, 4 mmol, 1 M in THF). FCC on silica gel (hexanes/ethyl acet-
ate, 98:2) provided product 8b as a colorless oil [35] in various
yields, depending on the catalyst: Yields/catalyst: [330 mg
(81%)/5a; 320 mg (78%)/5d].
4.3. X-ray crystallography
1H NMR (600 MHz, CDCl3): d = 7.94–7.93 (m, 1H), 7.89–7.88 (m,
1H), 7.63–7.61 (m, 2H), 7.56–7.49 (m, 3H), 7.48–7.45 (m, 4H),
7.38–7.36 (m, 1H).
Data collection for 5a, 5b and 5e–5i were collected on a Bruker-
Nonius KappaCCD diffractometer at 150 K or Oxford Diffraction
Xcalibur S CCD diffractometer at 293 K, with graphite monochro-
mated Mo K
a Bruker APEX II CCD Ultra diffractometer with a micro-focused
rotating anode (Mo K radiation) and multilayer monochromator
at 100 K. The diffraction intensities were corrected for Lorentz
and polarization factors. The semi-empirical absorption correc-
a radiation. Intensity data for 5d was collected using
4.4.3. 3-Phenylpyridine (8c)
The general procedure above was followed using 3-bromopy-
ridine (6c) (195 lL, 2 mmol) and phenylmagnesium bromide (7)
a
(4 mL, 4 mmol, 1 M in THF). FCC on silica gel (hexanes/ethyl acet-
ate, 75:25) provided product 8c as a colorless oil [35] in various
yields, depending on the catalyst: Yields/catalyst: [185 mg
(60%)/5a; 192 mg (62%)/5d].
tions were made by multi-scans method using SADABS or SCALE
3
ABSPACK algorithm within CRYSALISPRO. The structures were solved by
the direct or charge-flipping methods using programs SHELXT [27],
1H NMR (600 MHz, CDCl3): d = 8.85 (dd, 1H, J = 2.4, 0.8 Hz), 8.58
(dd, 1H, J = 4.8, 1.7 Hz), 7.84 (ddd, 1H, J = 7.9, 2.4, 1.7 Hz), 7.56–7.55
(m, 2H), 7.47–7.44 (m, 2H), 7.38 (tt, 1H, J = 7.4, 1.2 Hz), 7.33 (ddd,
1H, J = 7.9, 4.8, 0.8 Hz).
SIR2014 [28], OLEX2.solve [29] or SUPERFLIP [30], and refined by the
full-matrix least squares procedure with SHELXL [31] (ver. 2014/7)
or CRYSTALS [32] (ver. 14.61). Geometrical analysis was performed
using SHELXL or CRYSTALS. The positions of all hydrogen atoms have
been constrained for all compounds using AFIX (SHELXL) or RIDE
(CRYSTALS) commands.
Acknowledgements
The anionic ligand L1 of 5a, 5e, 5g, 5h and 5j, and full complex
molecule of 5d are positional disorders. The positionally disor-
dered parts were restrained using SAME and/or SADI, EXYZ a RIGU
The authors wish to thank VEGA projects No. 1/0056/13,
1/0770/15 and 1/0488/14 and APVV project No. APVV-14-0078
for the financial support.
commands in SHELXL
.

96
V. Kuchtanin et al. / Polyhedron 117 (2016) 90–96
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CCDC 1406133–1406143 contains the supplementary crystallo-
graphic data for 5a, 5b, and 5d–5j. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
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