C[sbnd]S cross-coupling catalyzed by a series of easily accessible, well defined Ni(II) complexes of the type [(NHC)Ni(Cp)(Br)]

Article abstract of DOI:10.1016/j.jcat.2020.01.016

The synthesis, characterization and catalytic evaluation of a series of NHC-Ni(II) complexes 1-Ni (-Me), 2-Ni (-ⁿBu) and 3-Ni (-Bn) bearing a phthalimide fragment and a cyclopentadienyl (Cp) ligand is reported. The complexes were evaluated in C

Full text of DOI:10.1016/j.jcat.2020.01.016

Journal of Catalysis 383 (2020) 193–198
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CAS cross-coupling catalyzed by a series of easily accessible, well
defined Ni(II) complexes of the type [(NHC)Ni(Cp)(Br)]
⇑
Mario A. Rodríguez-Cruz, Simón Hernández-Ortega, Hugo Valdés , Ernesto Rufino-Felipe,
David Morales-Morales
⇑
Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México C.P. 04510, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis, characterization and catalytic evaluation of a series of NHC-Ni(II) complexes 1-Ni (-Me), 2-
Ni (-nBu) and 3-Ni (-Bn) bearing a phthalimide fragment and a cyclopentadienyl (Cp) ligand is reported.
The complexes were evaluated in CAS couplings of iodobenzene and a range of thiols. The reactions were
carried out using a catalyst loading of 5 mol % in DMF during 0.5–19 h. Being complex 2-Ni the one
exhibiting the best activity for these transformations yielding up to 96% of products in 0.5 h.
Ó 2020 Elsevier Inc. All rights reserved.
Received 25 November 2019
Revised 13 January 2020
Accepted 14 January 2020
Keywords:
CAS cross-coupling
Thioetherification reaction
NHC complexes
Nickel complexes
Thiolation reaction
Catalysis
1. Introduction
the first example of an NHC-based Ni(0) catalyst for CAS couplings
[61].
The functionalization of an aryl halide with a thiol or disulfide
compound in the presence of a catalyst produces the desired CAS
bond in a safe and green manner. This transformation has become
one of the most important catalytic reactions in organic synthesis,
since CAS bonds are present in important biological and pharma-
ceutical products, such as nelfinavir, vortioxethine, etcetera [1–4].
In addition, the design of more active and earth abundant based cat-
alysts has allowed the widespread use of this strategy, however,
catalysts based on transition metals such as Co [5], Rh [6], Pd
[7,8], Cu [3,9–19], and Ni [20-33] have been used for this purpose.
N-heterocyclic carbene (NHC) ligands have emerged as useful
scaffolds for the design of highly active catalysts [34–60]. They
form strong bonds with transition metals and are excellent
They assumed that the catalytic active species bis(NHC)-Ni(0)
formed by reacting [Ni(COD)2] with two equivalents of IBnÁHBr in
the presence of a base. Years later, Nicasio and co-workers
described the catalytic activity of a well-defined NHC-Ni(II) com-
plex [63]. This catalyst allowed yields up to 96% in 24 h using a cat-
alyst loading of 1–5 mol %. Later, Jun and Lee supported a series of
NHC-Ni(II) fragments on magnetite/silica nanoparticles, allowing
this material to be easily recovered and recycled [66]. Finally,
Puerta and Valerga prepared a series of cationic NHC-Ni(II) com-
plexes and tested them as catalysts for CAS couplings [68]. They
observed that the presence of electron-donor or electron-
withdrawing substituents in the thiophenol did not have any effect
in the catalytic performance of the complexes. Other transition
metals such as Pd(II) [62,65] and Cu(I)[69] have also been success-
fully used to prepare catalysts based on NHC ligands.
Based on the above, on this opportunity we report the synthesis,
characterization and catalytic evaluation of a series of NHC-Ni(II)
complexes bearing a phthalimide fragment and a cyclopentadienyl
(Cp) ligand. Interestingly, NHC complexes with a phthalimide moi-
ety have been successfully used as highly active catalysts in
Suzuki-Miyaura [70] and Mizoroki-Heck couplings [71]. Thus, we
envisioned that NHC-Ni(II) complexes including this fragment on
their structures may render active catalyst for the CAS cross-
coupling of iodobenzene and thiols.
r
-donor ligands, hence producing electron rich metal centers.
Furthermore, NHC complexes are easily prepared and their stereo-
electronic properties can be tuned in a facile manner. Despite all
these great features, the use of NHC complexes for the CAS
cross-coupling has been scarcely explored [61–69].
Fig. 1 shows some relevant examples of NHC compounds used
for this purpose. For instance, in 2007, Zhang and Ying described
⇑
Corresponding authors.
E-mail addresses: hvaldes@live.com.mx (H. Valdés), damor@unam.mx
(D. Morales-Morales).
https://doi.org/10.1016/j.jcat.2020.01.016
0021-9517/Ó 2020 Elsevier Inc. All rights reserved.

194
M.A. Rodríguez-Cruz et al. / Journal of Catalysis 383 (2020) 193–198
Previous works
This work
BF4
Bn
N
Bn
N
Ar
N
R
N
Ni
N
N
N
N
N
N
N
Ni
Ni
Ni
Cl
O
Ni
N
Bn
N
Bn
N
Ar
Br
O
R
Zhang and Ying
Nicasio
Puerta and Valerga
O
N
Si
O
O
O
O
MNP
Jun and Lee
Ar
N
Ar
N
Cl
Pd Cl
PPh3
N
N
Ph
Pd
Cl
Cu
L
N
Ar
N
Ar
Liu
Nolan
Hsu, Han and Shyu
Fig. 1. Examples of NHC-M complexes used for CAS couplings.
complexes reveals the absence of the signal of the proton NCHN
and signals characteristic for the presence of the Cp ligand at about
5.3 ppm. While the 13C{1H} NMR spectra show characteristic sig-
nals due to the carbenic carbon at 163.9 (1-Ni), 162.9 (2-Ni) and
165.1 (3-Ni) ppm respectively. In addition, mass spectrometry
analysis produced clean spectra showing peaks for the molecular
ions at 378 m/z (1-Ni), 501 m/z (2-Ni) and 454 m/z (3-Ni) respec-
tively. Finally, elemental analysis of the three compounds are also
in good agreement with the proposed structures.
Suitable crystals of (1-Ni) for its X-ray diffraction analysis were
obtained by slow diffusion of hexane into a concentrated solution
of the complex in CH2Cl2. The molecular structure of (1-Ni) (CCDC
1968553) (Table 1, Fig. 2) confirms the coordination of the NHC
ligand to the Ni(II) atom, and completing its coordination sphere
a Cp ligand and a bromide. The distance of the NHC-Ni bond is
1.873(4) Å and the average length of the Ni-Cp bond is 2.13 Å.
With the complexes on hand, we decide to evaluate their cat-
alytic activity in the CAS cross-coupling reactions of iodobenzene
with thiophenol, using potassium tert-butoxide as base and a cat-
alyst loading of 5 mol % in DMF at 100 °C. The reaction progress
was monitored at different times (15, 30, 60 and 90 min) (Fig. 3).
Showing complex (2-Ni) to reach a conversion of 13% at 15 min,
2. Results and discussion
The synthesis of the NHC ligand precursors was performed in a
single step (Scheme 1). Thus, the 1:1 reflux reaction (toluene) of
N-(2-bromoethyl)phthalimide and the corresponding 1-imidazole
for 24 h afforded the desired azolium salts in 91%, 98% and
73% yield for 1-methylimidazol (1), 1-butylimidazole (2) and
1-benzylimidazole (3) respectively. All compounds were character-
ized by NMR techniques, mass spectrometry and elemental analy-
ses. The spectroscopic data of compounds (1) and (2) were similar
to those described in the literature [70,72]. And as expected, the 1H
NMR spectra of (3) reveals loss of symmetry. Exhibiting the charac-
teristic signal of the acidic proton (NCHN) at 9.38 ppm. In addition,
in the 13C{1H} NMR spectra, the signal due to the procarbenic car-
bon is observed at 136.8 ppm. The mass spectra provide us further
information showing the molecular ion [M-Br]+ at 332.1 m/z. All
this information being in agreement with the proposed structure.
The coordination of the NHC to Ni(II) was easily performed by
reacting [NiCp2] with the corresponding azolium salt in a THF/
DMF mixture (5:1) at reflux for 3 h. After purification, the com-
plexes were obtained in 15% (1-Ni), 54% (2-Ni) and 55% (3-Ni) yield
respectively (Scheme 1). In general, the 1H NMR spectra of the
Scheme 1. Synthesis of the NHC-Ni(II) complexes.

M.A. Rodríguez-Cruz et al. / Journal of Catalysis 383 (2020) 193–198
195
Table 1
Crystal data and structure refinement for (1-Ni).
Empirical formula
C19H18BrN3NiO2
Formula weight
Temperature
458.98
298(2) K
Wavelength
Crystal system
Space group
0.71073 Å
Orthorhombic
Pbca
Unit cell dimensions
a = 14.2496(5) Å
a
= 90ob = 7.1235(3) Å
b = 90°c = 37.0727(15) Å
3763.1(3) Å3
8
c
= 90o
Volume
Z
Density (calculated)
Absorption coefficient
F(0 0 0)
Crystal size
Theta range for data
collection
1.620 Mg/m3
3.173 mmÀ1
1856
0.378 Â 0.196 Â 0.100 mm3
2.197 to 25.363°.
Fig. 3. Time-course reaction profiles for the reaction of iodobenzene and thiophe-
nol. Reaction conditions: iodobenzene (0.25 mmol), thiophenol (0.25 mmol), KOtBu
(0.25 mmol) and [cat] (5 mol %) in DMF (3 mL) at 100 °C.
Index ranges
Reflections collected
Independent
À17ꢀhꢀ17, À8ꢀkꢀ7, À44ꢀlꢀ44
66,261
3451 [R(int) = 0.0789]
reflections
Once determined complex (2-Ni) to be the most active catalyst,
we were interested in exploring its catalytic activity towards dif-
ferent substrates. Thus, under the optimized reaction conditions
we explore the reactivity of a series of thiols, i.e. aliphatic, aromatic
and heterocyclic derivatives (Table 2). Although we observed good
activities of this complexes for thiophenol at times as short as
30 min, due to the nature of other substrates we stablished as stan-
dard reaction time 19 h. Under this conditions, complex (2-Ni)
exhibited moderate to high activities towards aliphatic and
Completeness to
theta = 25.242°
Absorption correction
Max. and min.
transmission
Refinement method
Data / restraints /
parameters
99.9%
Semi-empirical from equivalents
0.7452 and 0.5664
Full-matrix least-squares on F2
3451/201/282
Goodness-of-fit on F2
Final R indices
[I > 2sigma(I)]
R indices (all data)
Largest diff. peak and
hole
1.054
R1 = 0.0466, wR2 = 0.0953
R1 = 0.0811, wR2 = 0.1093
0.927 and À0.346 e.ÅÀ3
Table 2
CAS cross-coupling between iodobenzene and thiols catalyzed by NHC-NiBrCp
complexes.a.
Entry
HS-R
Product
Conversion (%)b
50
1
2
3
79
34
4
5
6
97
96c
91
88c
Fig. 2. Molecular structure of (1-Ni). The ellipsoids are represented at 50%
probability and hydrogen atoms were omitted for clarity. Selected bond lengths
(Å) and angles (°): Ni(1)-C(2) 1.873(4); Ni(1)-Br(1) 2.3144(7); Ni(1)-C(18) 2.152(9);
Ni(1)-C(19) 2.131(10); Ni(1)-C(20) 2.181(10); Ni(1)-C(21) 2.101(10); Ni(1)-C(22)
2.094(11); O(1)-C(9) 1.211(6); O(2)-C(11) 1.199(6); N(1)-C(2) 1.343(5); N(3)-C(2)
1.345(5); N(10)-C(9) 1.386(6); N(10)-C(11) 1.389(6); N(1)-C(2)-N(3) 104.3(4); C(2)-
Ni(1)-Br(1) 93.97(14); C(18)-Ni(1)-Br(1) 120–3(4); C(19)-Ni(1)-Br(1) 98.8; C(20)-Ni
(1)-Br(1) 112.1(4); C(21)-Ni(1)-Br(1) 147.5(5); C(22)-Ni(1)-Br(1) 159.3(5); C(9)-N
(10)-C(11) 112.6(4).
77
45
7
8
78
while the other two complexes did not show any activity at similar
times. Allowing to pass 30 min, complex (2-Ni) still exhibited the
best activity (96%) in comparison with (1-Ni, 89%) and (3-Ni,
60%). This trend was observed along time showing that is indeed
complex (2-Ni) the most active catalyst of the series. The behavior
observed is coherent with the fact that the N-substituent -nBu in
(2-Ni) gives place to a more electro-donating NHC ligand, in com-
parison with -Me (1-Ni) and -Bn (3-Ni) substituents, following the
trend -NnBu > -NMe > -NBn [73,74].
9
99
24c
10
99
96c
(continued on next page)

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M.A. Rodríguez-Cruz et al. / Journal of Catalysis 383 (2020) 193–198
aromatic thiols with electron-withdrawing substituents the con-
Table 2 (continued)
versions were above 96% in 30 min only (Entries 10, 11, Table 2).
Interestingly, substrates with ortho-substituents such as CH3, Cl,
F and CF3 were very active, reaching conversions above 77%. Note-
worthy the fact that the catalyst was very selective for the produc-
tion of the CAS cross-coupling products as no homocoupling
products were detected.
Entry
HS-R
Product
Conversion (%)b
11
99
97c
According to the results above, a potential mechanism based on
that proposed by Sun and Zhou [1] for the catalytic CASA couplings
of iodobenzene with thiols using our NHC-NiBrCp complexes may
proceed as shown in Scheme 2. The first step consisting in the coor-
dination of two thiolate ligands followed by dearomatization of the
Cp ligand to produce the 18e- species I. Which in turn produces the
active species II by reductive elimination of one mol of disulfide. The
Ni(0) intermediate then reacts with iodobenzene, followed by a
ligand exchange, and a reductive elimination regenerates the cata-
lyst and releases the desired product.
12
13
76
97
92c
14
15
5
1
3. Conclusion
In summary, we have prepared in a facile manner and in good
yields a series of NHC-Ni(II) complexes of the type [(NHC)Ni(Cp)
(Br)], including a phthalimide fragment at the NHC ligand. The
complexes were fully characterized including the unequivocal
determination of the molecular structure of compound (1-Ni) by
single crystal X-ray diffraction studies. The series of complexes
were tested as catalysts on the CAS cross-coupling of iodobenzene
and thiols, being complex (2-Ni) the best, this probably being
because the NHC ligand is the more electrodonating in comparison
with the other NHC ligands in (1-Ni) and (2-Ni).
In these reactions, the alkyl substrates having more hindered
substituents exhibited higher conversions than those having sub-
stituents with less steric demand. Regarding the thiophenols, those
with electron-withdrawing groups were very reactive, reaching
conversions above 90% in short periods of time (30 min). However,
the catalyst exhibited low activity towards heterocyclic thiols. This
catalytic system by being based on Ni is very promising for testing
in other cross coupling or similar reactions, and certainly exhibits
similar activity that some palladium-based catalysts in similar
CAS coupling processes.
a
Reaction conditions: iodobenzene (0.25 mmol), thiophenol (0.25 mmol), KOtBu
(0.25 mmol) and [cat] (5 mol %) in DMF (3 mL), 100 °C for 19 h. bConversions
obtained by GC-MS are based on residual iodobenzene and are the average of two
runs. c30 min
aromatic thiols, however, for the thiols including a heterocyclic
moieties the performance of the catalyst was low, this may be
the result of better complexation of these thiols, perhaps even in
a chelating manner, thus hampering the production of the coupling
products leading to more stable complexes, inactive in the
thioetherification process.
Thus, we chose aliphatic functional groups with different size,
namely tert-butyl, sec-butyl and iso-butyl. We observed that using
substrates with more steric hindrance, such as 2-methyl-2-
propanethiol and 2-butanethiol, lead to conversions up to 50%
and 79%, respectively, while using the less sterically demanding
substrates such as 2-methyl-1-propanethiol the conversion
decreased to 34%. Now, when the reaction was carried out using
4. Experimental
All reactions were carried out under nitrogen with standard
Schlenk techniques unless otherwise stated. All chemical com-
pounds were commercially obtained from Aldrich Chemical Co.
and used as received without further purification. The 1H and 13C
{1H} NMR spectra were recorded on a Bruker Ascend 500 spec-
trometer or on a JEOL GX300 spectrometer. Chemical shifts are
reported in ppm down field of TMS using the residual signals in
the solvent as internal standard. Elemental analyses were per-
formed on a Perkin Elmer 240. MS-Electrospray determinations
were recorded on a Bruker Daltonics-Esquire 3000 plus Electro-
spray Mass Spectrometer. Mass measurements in FAB+ were per-
formed at a resolution of 3000 using magnetic field scans and
the matrix ions as the reference material or, alternatively, by elec-
tric field scans with the sample peak bracketed by two (polyethy-
lene glycol or cesium iodide) reference ions.
General procedure for the synthesis of azolium salts
A solution of N-(2-bromoethyl)phthalimide (0.508 g, 2.0 mmol)
and the corresponding 1-imidazole (1.6 mmol) in toluene (5 mL)
was refluxed for 24 h. After this time, the solution was cooled to
Scheme 2. Proposed mechanism for CAS couplings catalyzed by [(NHC)Ni(Cp)(Br)]
complexes.

M.A. Rodríguez-Cruz et al. / Journal of Catalysis 383 (2020) 193–198
197
room temperature. The white solid was filtered and washed with
diethyl ether (20 mL).
20.2 (NCH2CH2CH2CH3), 14.0 (NCH2CH2CH2CH3). MS (FAB+): m/z
501 [M]+. Elem. Anal. Calcd. for C22H24BrN3NiO2: C, 52.74; H,
4.83; N, 8.39. Found: C, 52.35; H, 4.71; N, 8.40.
Azolium salt (1)
Complex (3-Ni)
For the synthesis of (1), 1-methylimidazole (0.135 g, 1.6 mmol)
was used. Yield: 0.489 g (91%). The spectroscopic data was similar
to those reported in the literature [70,72].
For the synthesis of (3-Ni), the azolium (3) (0.319 g, 0.8 mmol)
and [NiCp2] (0.378 g, 2.0 mmol) were used. Yield: 0.235 g (55%). 1H
3
NMR (500 MHz, CDCl3) d 7.81 (d, JH-H = 57.4 Hz, 4H, CHAr),
7.53–7.30 (m, 3H, CHAr), 7.23–7.13 (m, 2H, CHAr), 6.85 (d,
Azolium salt (2)
3
3JH-H = 91.6 Hz, 2H, CHIm), 6.28 (d, JH-H = 15.0 Hz, 1H, ACH2A),
5.90 (d, 3JH-H = 15.1 Hz, 1H, ACH2A), 5.59–5.45 (m, 1H, ImCH2CH2),
5.28 (s, 5H, CHCp), 4.89–4.66 (m, 1H, ImCH2CH2), 4.56–4.42 (m, 1H,
ImCH2CH2), 4.25–4.09 (m, 1H, ImCH2CH2). 13C NMR (126 MHz,
CDCl3) d 168.1 (C@O), 165.1 (Ni-Ccarbene), 136.6 (CAr), 134.5 (CHAr),
132.0 (CAr), 129.1 (CHAr), 128.2 (CHAr), 127.7 (CHAr), 123.7 (CHAr),
123.1 (CHIm), 122.9 (CHIm), 92.2 (CHCp), 55.9 (ACH2A), 49.9
(ImCH2CH2), 38.4 (ImCH2CH2). MS (FAB+): m/z 454 [M-Br]+. Elem.
Anal. Calcd. for C25H22BrN3NiO2: C, 56.12; H, 4.14; N, 7.85. Found:
C, 56.10; H, 4.15; N, 7.66.
For the synthesis of (2), 1-butylimidazole (0.203 g, 1.6 mmol)
was used. Yield: 0.593 g (98%). The spectroscopic data was similar
to those reported in the literature [70,72].
Azolium salt (3)
For the synthesis of (3), 1-benzylimidazole (0.253 g, 1.6 mmol)
was used. Yield: 0.481 g (73%). 1H NMR (300 MHz, DMSO d6) d
9.38 (s, 1H, NCHN), 8.18–7.70 (m, 6H, CHAr), 7.54–7.21 (m, 5H, CHAr),
5.42 (s, 2H, ACH2A), 4.64–4.35 (m, 2H, Im-CH2CH2-), 4.08–3.90 (m,
2H, Im-CH2CH2-). 13C NMR (76 MHz, DMSO d6) d 167.6 (C@O), 136.8
(NCHN), 134.7 (CAr), 134.5 (CHAr), 131.4 (CAr), 128.9 (CHAr), 128.6
(CHAr), 127.8 (CHAr), 123.4 (CHIm), 123.2 (CHAr), 122.8 (CHIm), 51.8
(ACH2A), 48.1 (Im-CH2CH2-), 38.0 (Im-CH2CH2-). MS (ESI + ): m/z
332.1 [M-Br]+. Elem. Anal. Calcd. for C20H18BrN3O2: C, 58.26; H,
4.40; N, 10.19. Found: C, 58.17; H, 4.35; N, 10.01.
General procedure for the CAS cross-coupling
Under atmosphere of nitrogen, a solution of KOtBu (0.25 mmol)
and the corresponding catalyst (5 mol %) in DMF (3 mL) was stirred
at room temperature for 10 min. Then, iodobenzene (0.25 mmol)
and the respective thiol (0.25 mmol) were added to the solution.
The reaction was heated at 100 °C for the desired time. The reaction
mixture was cooled to room temperature and the organic phase ana-
lyzed by gas chromatography (GC-MS) (Quantitative analyses were
performed on an Agilent 6890 N GC with a 30.0 m DB-1MS capillary
column couple to an Agilent 5973 Inert Mass Selective detector).
General procedure for the synthesis of NHC-Ni(II) complexes
A solution of the corresponding bromide salt (1 eq) and [NiCp2]
(2.5 eq) in THF/DMF (6 mL) mixture (5:1) was refluxed for 3 h.
After this time the solution was cooled to room temperature and
all volatiles were removed under high vacuum. The crude solid
residue was dissolved in CH2Cl2 (1 mL) and purified by column
chromatography using silica gel. Elution with CH2Cl2 afforded the
separation of a red band that contained the desired complex.
Data collection and refinement for compound 1-Ni.
A red prism crystal of (1-Ni), was grown from CH2Cl2/Hexane and
mounted on glass fibers, then placed on a Bruker D8 adventure
j
geometry diffractometer with micro-focus X-ray source of Mo-
target X-ray source (k = 0.71073 Å). The detector was placed at a dis-
tance of 5.0 cm from the crystal, frames were collected with a scan
Complex (1-Ni)
For the synthesis of (1-Ni), the azolium (1) (0.100 g, 0.3 mmol)
width of 0.3 in x and exposure time of 5 s/frame. 66,261 reflections
and [NiCp2] (0.142 g, 0.8 mol) were used. Yield: 0.020 g (15%). 1H
were collected and integrated with the Bruker SAINT software pack-
age [75] using a narrow-frame integration algorithm. Systematic
absences and intensity statistics were used in orthorhombic system
and Pbca space group. The structure was solved using Patterson
methods using SHELXS-2014/7 program [76]. The remaining atoms
were located via a few cycles of least squares refinements and differ-
ence Fourier maps. Hydrogen atoms were input at calculated posi-
tions and allowed to ride on the atoms to which they are attached.
Thermal parameters were refined for all hydrogen atoms using a
Ueq = 1.2 Å. The final cycle of refinement was carried out on all
non-zero data using SHELXL-2014/7 [76]. Absorption correction
was applied using SADABS program [77].
NMR (500 MHz, CDCl3)
d 7.97–7.69 (m, 5H, CHAr), 6.91
3
(d, JH-H = 23.2 Hz, 2H, CHIm), 5.48–5.28 (m, 6H, CHCp (5H) and
ImCH2CH2- (1H)), 4.73 (br. s, 1H, ImCH2CH2-), 4.43 (br. s, 1H,
ImCH2CH2-), 4.26 (s, 3H, ACH3), 4.18–4.08 (m, 1H, ImCH2CH2-).
13C NMR (126 MHz, CDCl3) d 168.1 (C@O), 163.9 (Ni-Ccarbene),
134.4 (CHAr), 132.0 (CAr), 124.0 (CHAr), 123.7 (CHIm), 122.5 (CHIm),
92.1 (CHCp), 49.7 (ImCH2CH2), 39.4 (ACH3), 38.3 (ImCH2CH2). MS
(FAB+): m/z 378 [M-Br]+. Elem. Anal. Calcd. for C19H18BrN3NiO2:
C, 49.72; H, 3.95; N, 9.16. Found: C, 50.57; H, 3.90; N, 9.14.
Complex (2-Ni)
Cyclopentadienyl ring is forming a dihedral angle of 44.8(4)°
with carbene ligand. The carbene ligand and isoindolinedione frag-
ment are coplanar and adopt a geometry similar to a stair.
Cyclopentadienyl ring is disordered and was refined in two con-
tributors using a variable site occupational factors (SOF), the ratio
of SOF was 0.52/0.48. 201 parameters were used in the refinement
as follow: 15 for SAME/SADI, 30 for DELu and 156 for SIMU instruc-
tions. In the last refinement, two reflections were omitted
For the synthesis of (2-Ni), the azolium (2) (0.205 g, 0.5 mmol)
and [NiCp2] (0.236 g, 1.3 mol) were used. Yield: 0.135 g (54%). 1H
NMR (500 MHz, CDCl3) d 8.03–7.80 (m, 2H, CHAr), 7.80–7.62 (m,
3
2H, CHAr), 6.93 (d, JH-H = 30.5 Hz, 2H, CHIm), 5.58–5.42 (m, 1H,
ImCH2CH2), 5.34 (s, 5H, CHCp), 4.91–4.77 (m, 1H, NCH2CH2CH2CH3),
4.77–4.65 (m, 1H, ImCH2CH2), 4.65–4.55 (m, 1H, NCH2CH2CH2CH3),
4.49–4.36 (m, 1H, ImCH2CH2), 4.19–4.08 (m, 1H, ImCH2CH2),
2.09–1.92 (m, 1H, NCH2CH2CH2CH3), 1.92–1.79 (m, 1H,
NCH2CH2CH2CH3), 1.48 (h, J = 7.3 Hz, 2H, NCH2CH2CH2CH3), 1.04
(t, 3JH-H = 7.3 Hz, 3H, NCH2CH2CH2CH3). 13C NMR (126 MHz, CDCl3)
d 168.1 (C@O), 162.9 (Ni-Ccarbene), 134.4 (CHAr), 132.0 (CAr), 123.7
(CHAr), 122.6 (CHIm), 122.3 (CHIm), 92.2 (CHCp), 52.1 (NCH2CH2CH2-
CH3), 49.7 (ImCH2CH2), 38.4 (ImCH2CH2), 33.0 (NCH2CH2CH2CH3),
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We would like to thank Chem. Eng. Luis Velasco Ibarra, Dr. Fran-
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