Large-scale synthesis of novel sterically hindered acenaphthene-based α-diimine ligands and their application in coordination chemistry

Article abstract of DOI:10.1016/j.jorganchem.2018.01.055

An efficient method to synthesize novel highly sterically hindered acenaphthene-based α-diimine ligands bearing bulky diarylmethyl moiety was achieved by two-step reactions. These reactions could be carried out on a scale of 100 g with no chromatography involved. On the basis of this method, a series of novel highly sterically hindered acenaphthene-based α-diimine Pd(II) and Ni(II) complexes, imidazolium precursors and the corresponding NHCs-metal complexes were also successfully synthesized. These novel complexes can offer great potential for metal-catalyzed polymerizations and organic reactions.

Full text of DOI:10.1016/j.jorganchem.2018.01.055

Accepted Manuscript
Large-scale synthesis of novel sterically hindered acenaphthene-based α-diimine
ligands and their application in coordination chemistry
Lihua Guo, Wenyu Kong, Yanjian Xu, Yuliang Yang, Rui Ma, Li Cong, Shengyu Dai,
Zhe Liu
PII:
S0022-328X(18)30073-1
10.1016/j.jorganchem.2018.01.055
JOM 20293
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 2 December 2017
Revised Date: 15 January 2018
Accepted Date: 29 January 2018
Please cite this article as: L. Guo, W. Kong, Y. Xu, Y. Yang, R. Ma, L. Cong, S. Dai, Z. Liu, Large-
scale synthesis of novel sterically hindered acenaphthene-based α-diimine ligands and their
application in coordination chemistry, Journal of Organometallic Chemistry (2018), doi: 10.1016/
j.jorganchem.2018.01.055.
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ACCEPTED MANUSCRIPT
Large-Scale Synthesis of Novel Sterically Hindered Acenaphthene-
based α-Diimine Ligands and Their Application in Coordination
Chemistry
Lihua Guoa,b*, Wenyu Konga, Yanjian, Xua, Yuliang Yanga, Rui Maa, Li Conga, Shengyu Daib*, Zhe
Liua*
a School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, 273165, China
b Chinese Academy of Science Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering,
University of Science and Technology of China, Hefei 230026, China
* Corresponding authors. Email: guolihua@qfnu.edu.cn (L. Guo), daiyu@ustc.edu.cn (S. Dai), liuzheqd@163.com (Z. Liu).
ABSTRACT: An efficient method to synthesize novel highly sterically hindered acenaphthene-based α-diimine ligands bearing
bulky diarylmethyl moiety was achieved by two-step reactions. These reactions could be carried out on a scale of 100 grams with
no chromatography involved. On the basis of this method, a series of novel highly sterically hindered acenaphthene-based α-
diimine Pd(II) and Ni(II) complexes, imidazolium precursors and the corresponding NHCs-metal complexes were also successfully
synthesized. These novel complexes can offer great potential for metal-catalyzed polymerizations and organic reactions.
Keywords: Diimine, Sterically hindered, α-diimine nickel complexes, α-diimine palladium complexes, N-heterocyclic carbene
silver complexes, N-heterocyclic carbene palladium complexes
Introduction
The α-diimine ligands are well-known to stabilize organome-
tallic complexes[1,2]. They are also the intermediate in the
synthesis of N-heterocyclic carbenes (NHCs)[3,4]. The α-
diimine ligands are usually derived from the condensation
reaction of a diketone with two equivalents of an alkyl or ar-
ylamine, often catalyzed by a Lewis or Brönsted acid. The aryl
substituent and the backbone of α-diimines can be easily tuned
with appropriate substituents, thus enabling the preparation of
arrays of ligands with independent control over the steric and
electronic effects at the metal center. These ligands have been
applied in metal-catalyzed polymerizations[5-10] and a signif-
icant number of useful organic reactions (supporting infor-
mation, Scheme S1)[11-15]. It revealed that the increase of
steric bulk at the ortho position of N-aryl moiety of the α-
diimines can benefit these transformations. For example,
Brookhart and coworkers[5-10] discovered that the incorpora-
tion of sterically bulky axial substituents (2,6-diisopropyl) in
the Ni(II) and Pd(II) α-diimine catalysts is crucial in the gen-
eration of high molecular weight polymer because the bulky
axial substituents dramatically retard the chain transfer rates.
Using the more bulky dibenzhydryl instead of diisopropyl, the
more thermally stable Ni(II) and Pd(II) α-diimine catalysts
can be obtained[16-20]. These benzhydryl-derived Pd(II) α–
diimine catalysts also generate polyolefins with high molecu-
lar weight and very low branching density[18]. The efficient
and general synthetic methods for the glyoxal and 2,3-
butadione derived ligands with bulky diarylmethyl moiety
have been achieved in the recent work (Scheme 1, I and
II)[18,21].
Scheme 1. Reported Procedure for the Synthesis of α-
Diimines and Our Current Work.
α-Diimine of acenaphthenequinone, so-called BIAN ligands,
are acknowledged as both oxdatively and thermally stable
ligands for transition metal centers. The extensive π-system of
the acenaphthene ring combined with the sterically modular
aniline provide a broad range of π-acceptor frameworks, offer
ing precise control over the steric, optical, and electronic
properties.[22-28] These transition metal BIAN complexes are
also used as popular olefin polymerization catalyst. Interest-
ingly, polyolefin microstructure may be successfully tailored
via in situ reduction of BIAN-ligated Ni(II)-based olefin
polymerization catalysts[29,30]. Nevertheless, the synthesis of
highly sterically hindered acenaphthene-based α-diimines
bearing bulky diarylmethyl moiety is usually rather difficult
since the reported strategies usually yield only monocon-
densed products[17,31,32]. Long recently reported a modified
synthetic procedure using trimetylaluminum as catalysts for an
acenaphthenequinone derived ligand bearing the bulky ben-

ACCEPTED MANUSCRIPT
R1
R1
zhydryl moiety[17]. However, only ~10% yield is achieved
and the column separation is also required, which is an obvi-
ously bottleneck for its wide applications (Scheme 1, III). In
this work, an efficient and general method to synthesize highly
sterically hindered acenaphthene-based α-diimine ligands
bearing bulky diarylmethyl moiety was achieved by two-step
reactions. On the basis of this method, a series of novel highly
sterically hindered acenaphthene-based α-diimine Pd(II) and
Ni(II) complexes, imidazolium precursors and the subsequent
NHCs-metal complexes were also synthesized.
NH2
O
O
Aryl
N
N
Aryl
Zn
Step 1. ZnCl2, AcOH
Cl
Cl
reflux, 4 h
R2
R1
R1
R1 = CH3, H, OCH3, F, t-Bu, Ph
R2 = CH3, OCH3, t-Bu, Cl
Step 2.
K oxalate
R1
, H2O, CH2Cl2, 1 h
R1
A1-A11
R2
Aryl =
Results and discussion
Aryl
R1
N
N Aryl
L1-L11
Synthesis of sterically hindered acenaphthene-based α-diimine
R1
ligands.
O
O
O
O
It was found that some sterically hindered diimines could be
successfully prepared by the “template method” of Rosa[33].
Diimine-ZnCl2 complex was synthesized by the reaction of
aniline and acenaphthenequinone in the presence of ZnCl2.
Subsequent demetalation of the ligand was obtained by treat-
ing diimine-ZnCl2 complex with an aqueous solution of potas-
sium oxalate, leading to free ligand in high yield. Inspired by
this work, this method is also applicable to the synthesis of
sterically hindered acenaphthene-based α-diimines bearing
bulky diarylmethyl moiety as indicated in Scheme 2. To test
the limitations of this methodology, a number of hindered
anilines with R1 group in 4-position of diarylmethyl moiety
and R2 group in 4-position of N-aryl rings were investigated in
the synthesis of acenaphthene-based dicondensed products.
This method presented good compatibility and high isolated
yields. Even the hindered group substituted anilines (R1 = tert-
butyl and phenyl) gave the products L3 and L5 in 69.5% and
80.1% yields respectively. Introducing the F group reduced
the reaction efficiency (L4, 20.2%). Notably, 100 gram-scale
preparation of L7 was achieved in 75.4% yield, which makes
it possible for large-scale synthesis of metal catalysts, espe-
cially robust α-diimine transition metal catalysts for olefin
polymerization[16-18]. The solid structures of L4 and L5 were
confirmed by single-crystal X-ray analysis (Scheme 2 and
supporting information, Table S2). They exhibit E/E (C=N
bond) isomeric preference in the crystalline state, like other α-
diimine compounds[34]. The 1H NMR spectrum, at room
temperature, of a CDCl3 solution of all diimines individually
shows only one set of signals. L7 was typically chosen to
study time dependence by 1H NMR analysis in CDCl3 and no
changes in the spectra can be observed within 36 h, indicating
no isomerization occurs on the NMR time scale (supporting
information, Figure S36). As a result, we predicted that the
only isomer may be also E/E configuration in the solution.
N
N
N
N
O
O
O
O
L2, 72.4%
L1, 67.6%
F
F
F
F
N
N
N
N
F
F
F
F
L3, 69.5%
L4, 20.2%
Ph
Ph
Ph
Ph
O
N
N
O
N
N
Ph
Ph
Ph
Ph
L5, 80.1%
L6, 86.2%
O
N
N
O
O
N
N
O
L8, 82.7%
L7, 81.7%; 100 g-scale 75.4%
O
O
O
O
Cl
N
L9, 74.2%
N
N
Cl
Cl
N
N
Cl
O
O
O
O
L10, 60.8%
An attempt to employ the anilines A12 and A13 as the sub-
strates yielded the unexpected monoimine products (support-
ing information, Scheme S2), which was consistent with pre-
vious literature reports[17]. Our efforts to obtain the putative
Zn(II) intermediate have been unsuccessful. MS analysis indi-
cated the presence of the monoimine-Zn complex while the
elemental analysis indicated the mixture of the monoimine and
the monoimine-Zn complex. The monoimine-Zn complex may
be unstable and free monoimine can be generated in the treat-
ment process. We reasoned that one important factor was that
the monoimine-Zn complexes exhibited poor solubility and
precipitated in the acetic acid in the reaction of step 1,
N
L11, 60.2%
Conditons: Step 1: acenaphthenequinone (1.32 mmol), aniline
(3.0 mmol), ZnCl2 (1.5 mmol), acetic acid (3 mL), refluxed for
4 h; Step 2: potassium oxalate (3.0 mmol), CH2Cl2 (20 mL),
H2O (3 mL), r. t. for 1 h. Isolated yields.
Scheme 2. Synthesis of α-Diimine Ligands.
2

ACCEPTED MANUSCRIPT
the ortho position of N-aryl moiety of the NHCs could benefit
the palladium-catalyzed organic reactions.[4] As a result, with
an easy access to the highly steric diimine, the acenaphthene-
based imidazolium precursors and the corresponding NHCs-
metal complexes bearing bulky diarylmethyl moiety were also
synthesized. Cyclocondensation with chloromethyl methyl
ether provided the precipitate of the imidazolium chloride salts
(Scheme 4a). These yellow solids were isolated by filtration
and washed with Et2O, giving in moderate to high yields of
74.1%, 89.5%, and 65.2% for S1, S2, and S3, respectively. All
of the imidazolium slats were fully characterized by 1H NMR,
13C NMR and ESI-MS. The resonance of imidazolium C-H
protons (NCHN) was observed downfield at δ =10.44, 10.47,
and 13.17 ppm, respectively. Subsequently, the novel NHC-
silver complex 3 which often acts as a NHC transfer agent in
the presence of suitable metal precursors[35] and NHC-
palladium complex 4 which can be generally used as catalyst
in numerous cross-coupling reactions[36-42] were convenient-
ly obtained in 70% and 81% yields, respectively (Scheme 4b).
All of these prepared complexes are air and moisture stable
and can be stored on a shelf for more than three months with-
out noticeable decomposition. Complexes 3 and 4 were fully
characterized by single crystal X-ray diffraction analysis (Fig-
ure 2). As expected, NHC-silver complex 3 is nearly linear
(CNHC-Ag-Cl 176.53(18)o) and the Ag-CNHC distance(2.101(6)
Å) is close to that of other NHC-Ag complexes[21]. The solid
structure of NHC-palladium complex 4 adopts slightly distort-
ed square-planar coordination geometry with the NHC and
pyridine trans to each other.
NH2
Step 2
O
O
L12, L13
Monoimines:
Aryl
N
O
Zn
ZnCl2, AcOH
Cl
Cl
R2
L12-ZnCl2
L13
A12: R2 = CH3
-ZnCl2
Precipitate in AcOH
A13:
R2 = Cl
NH2
A1
Aryl
Step 2
O
O
L1
Diimine:
Aryl
N
O
Zn
N
N Aryl
ZnCl2, AcOH
Zn
Cl
Cl
Cl
Cl
A1
Precipitate in AcOH
L14
-ZnCl2
Dissolve in AcOH
Scheme 3. Plausible Explanation for the Production of
Diimines and Monoimines.
preventing the formation of diimine- Zn complex (Scheme 3).
In order to confirm this hypothesis, a monoimine L14 (R1 =
CH3, R2 = CH3) was purposefully synthesized using p-toluene
sulfonic acid as conventional catalyst (see experimental sec-
tion). L12, L13, L14 and ZnCl2 were in-situ added to the ace-
tic acid respectively. The reaction mixture was refluxed under
stirring for 4 hours. In monoimine L14 system, solution was
obtained, while insoluble substances were observed in mo-
noimines L12 and L13 systems (supporting information, Fig-
ure S1). This experiment indicates that the modification of R1
and R2 can influence the solubility of monoimine-Zn complex-
es. As a result, the monocondensed products that are not pre-
cipitated in the solution can continue to react with anilines to
form the dicondensed products (Scheme 3).
Synthesis of sterically hindered acenaphthene-based α-diimine
palladium and nickel complexes.
A broad range of transition metal-BIAN complexes has now
been described.[5-15] A focal point has been generation of
robust, versatile α-diimine Pd(II) and Ni(II) catalysts for olefin
polymerization and some important organic reactions. As a
result, the coordination chemistry of these diimines with Pd(II)
and Ni(II) was next evaluated (Figure 1). The palladium com-
plex 1 was synthesized in 61.7% yield by the reaction of
diimine L7 with (COD)PdCl2 (COD = 1,5-cyclooctadiene),
while the nickel complex was generated in 83.9% yield by
reaction of diimine L7 with (DME)NiBr2 (DME = 1,2-
dimethoxyethane). The molecular structures of 1 and 2 were
determined by X-ray diffraction analysis (Figure 1). Despite
their large steric hindrance, the diimines leave sufficient room
around the metal center. In the solid state, the Pd center adopts
a square planar geometry while the Ni center adopts distorted
tetrahedron geometry. The effective blockage of the axial po-
sitions of the Pd and Ni center can be observed from these
structures. As mentioned in the introduction section, the pres-
ence of bulky ortho-aryl substituents in the ligand could retard
the chain transfer process and generate high molecular weight
polymer in olefin polymerization. Therefore, these Pd(II) and
Ni(II) complexes may have the potential to produce some
novel polyolefin materials.
Figure 1. Synthesis and the ORTEP diagrams of complexes 1
and 2. Thermal ellipsoids are shown at the 50% probability
level. Hydrogen atoms have been omitted for clarity. Selected
bond lengths (Å) and angles (deg): complex 1: Pd(1)-N(2) =
2.060(3), Pd(1)-N(1) = 2.071(3), Pd(1)-Cl(2) = 2 .2864(10),
Pd(1)-Cl(1) = 2.2877(12), N(2)-Pd(1)-N(1) = 81.61(11), N(2)-
Pd(1)-Cl(2) = 93.43(8), N(1)-Pd(1)-Cl(2) = 170.20(9), Cl(2)-
Pd(1)-Cl(1) = 91.23(4); complex 2: Ni(1)-N(2) = 2.037(7),
Ni(1)-N(1) = 2.043(7), Ni(1)-Br(2) = 2.3005(18), Ni(1)-Br(1)
= 2.3161(18), N(2)-Ni(1)-N(1) = 82.7(3), N(2)-Ni(1)-Br(2) =
102.7(2), N(1)-Ni(1)-Br(2) = 132.1(2), Br(2)-Ni(1)-Br(1) =
111.74(7).
Synthesis of the imidazolium chloride salts and corresponding
NHCs-metal complexes.
The N-heterocyclic carbenes (NHCs) have emerged as the
most powerful supporting ligands in metal-catalyzed organic
transformations because of their strong σ-donation toward
metal center. It has been reported the increase of steric bulk at
3

ACCEPTED MANUSCRIPT
(a)
All chemicals were commercially sourced, except those
whose synthesis is described. Aniline compounds of 2,6-
dibenzhydryl-4-methoxyaniline (A6), 2,6-dibenzhydryl-4-
methylaniline (A12) and 2,6-dibenzhydryl-4-chloroaniline
(A13), was synthesized according to previous methods[18].
The synthetic route for other anilines A1-A5, A7-A11 was
S1:R2= Me
S2:R2= OCH3
MeOCH2Cl
R2
R2
N
N
N
R2
N
R2
100 o
C
S3
Cl
:R2= Cl
1
shown in supporting information. H NMR spectra were ac-
(b)
Ag2O, CH2Cl2
quired in 5 mm NMR tubes at 298 K on Bruker DPX 500 or
Bruker Ascend Tm 400 spectrometers using TMS as an inter-
nal standard and CDCl3 as solvent. 13C NMR spectra were
acquired in 5 mm NMR tubes at 298 K on Bruker DPX 500 or
Bruker Ascend Tm 400 spectrometers. 13C NMR chemical
shifts were internally referenced to CH3Cl (77.16 ppm) for
chloroform-d1. Coupling constants are in Hz. All data pro-
cessing was carried out using XWIN-NMR version 3.6
(Bruker UK Ltd.). Elemental analysis was performed by the
Analytical Center of the University of Science and Technolo-
gy of China. Mass spectra of the anilines and some diimines
were recorded on a Thermo LTQ Orbitrap XL (ESI+). Mass
spectra of the complexes and some diimines were recorded on
a Atouflex Speed MALDI-TOF MS. X-ray Diffraction data
were collected at 298(2) K on a Bruker Smart CCD area detec-
tor with graphite-monochromated Mo Kα radiation (λ =
0.71073 Å).
N
O
O
N
Ag
Cl
3
O
O
N
N
Cl
PdCl2, Pyridine
K2CO3
S2
N
N
O
O
Pd
N
Cl
Cl
4
Scheme 4. (a) Synthesis of the Imidazolium Chloride Salts; (b)
Synthesis of Complexes 3 and 4.
Procedure for the Synthesis of Acenaphthene-based α-
Diimines.
N
N
Figure 2. Synthesis and the ORTEP diagrams of complexes 3
and 4. Thermal ellipsoids are shown at the 50% probability
level. Hydrogen atoms have been omitted for clarity. Selected
bond lengths (Å) and angles (deg): complex 3: Ag(1)-C(1) =
Bis(2,6-bis(di-p-tolylmethyl)-4-methylphenyl)acenaphthylene-
1,2-diimine (L1).
2.101(6), Ag(1)-Cl(1)
= 2.350(2), C(1)-Ag(1)-Cl(1) =
176.53(18); complex 4: Pd(1)-C(1) = 1.944(8), Pd(1)-N(3) =
2.117(7), Pd(1)-Cl(1) = 2.266(3), Pd(1)-Cl(2) = 2.287(3),
C(1)-Pd(1)-N(3) = 179.1(4), C(1)-Pd(1)-Cl(1) = 87.2(3), N(3)-
Pd(1)-Cl(1) = 91.9(2), C(1)-Pd(1)-Cl(2) = 90.3(3), N(3)-
Pd(1)-Cl(2) = 90.6(2), Cl(1)-Pd(1)-Cl(2) = 177.48(8).
Step 1: ZnCl2 (0.204 g, 1.5mmol) and acenaphthenequinone
(0.241 g, 1.32mmol) were suspended in glacial acetic acid (3
mL). 2,6-Bis(di-p-tolylmethyl)-4-methylaniline (1.49 g, 3.0
mmol) was added, and the reaction mixture was refluxed un-
der stirring for 4 h. The solution was allowed to cool to room
temperature, and a bright orange-red solid precipitated. The
solid was separated by filtration and washed with acetic acid
(3 × 3 mL) and diethyl ether (5 ×6 mL), to remove remaining
acetic acid. Drying under vacuum gave bright orange-red,
poorly soluble solid (1.21 g, 72.2%). According to the report-
ed literature[33,43,44], the solid is zinc diimine complex.
Step 2: The zinc was removed from the zinc diimine complex.
The product of the previous step was suspended in methylene
chloride (20 mL), and a solution of potassium oxalate (0.553 g,
3 mmol) in water (3 mL) was added. The reaction mixture was
stirred vigorously for 1 h. The two phases were separated, and
the organic layer was washed with water (3×10 mL) and dried
with MgSO4. After filtration the solvent was removed under
vacuum to afford the product as an orange powder (1.01 g,
93.6%), followed by recrystallization from dichloromethane
Conclusions
In summary, we have described an efficient method to syn-
thesize acenaphthene-based α-diimine ligands bearing bulky
diarylmethyl moiety. Most of products are accessible in mod-
erate to high yields, with no tedious purification involved.
These reactions also could be carried out on a scale of 100
grams. The coordination chemistry of these new bulky
diimines was investigated through the synthesis of the corre-
sponding Pd(II) and Ni(II) complexes. In addition, this meth-
odology also enables us to synthesize the novel imidazolium
precursors and the corresponding NHCs-metal complexes.
These novel diimines should find application in the stabiliza-
tion of reactive metallic species. Use of these diimines in ole-
fin coordination polymerization catalysts is being actively
pursued in our laboratory and we will continue to explore the
use of these new diimines.
1
and n-hexane. The total yield of two steps is 67.6%. H NMR
(500 MHz, CDCl3) δ 7.55 (d, J = 8.1 Hz, 2H, aryl-H), 6.99 –
6.83 (m, 22H, aryl-H), 6.72 (d, J = 5.6 Hz, 8H, aryl-H), 6.39
(d, J = 5.6 Hz, 8H, aryl-H), 6.12 (d, J = 5.1 Hz, 2H, aryl-H),
5.56 (s, 4H, CH(PhMe)2), 2.27 (s, 6H, Ar-CH3), 2.25 (s, 12H,
CH(PhMe)2), 1.88 (s, 12H, CH(PhMe)2). 13C NMR (126 MHz,
Experimental section
General Considerations.
4

ACCEPTED MANUSCRIPT
F
F
F
CDCl3) δ 163.55 (C=N), 146.71, 141.19, 140.08, 139.84,
F
135.25, 134.81, 132.53, 131.87, 129.92, 129.51, 129.48,
129.23, 128.78, 128.60, 128.56, 127.10, 126.58, 124.52, 50.74
(CH(PhMe)2), 21.64 (Ar-CH3), 21.08(CH(PhMe)2), 20.68
(CH(PhMe)2). ESI-MS (m/z): calcd for C86H77N2: [M+H]+
1137.6087, found: 1137.6063.
N
N
F
F
F
F
O
O
O
O
Bis(2,6-bis(bis(4-fluorophenyl)methyl)-4-
methylphenyl)acenaphthylene-1,2-diimine (L4).
N
N
Using the same procedure as for the synthesis of L1, L4
was obtained as an orange powder. The yields of step 1 and
step 2 are 30.2% (0.52 g) and 67.0% (0.31 g), respectively.
The total yield of two steps is 20.2%. A single crystal of L4
was obtained by layering methanol onto the DCM solution at
room temperature. 1H NMR (500 MHz, CDCl3) δ 7.67 (d, J =
8.2 Hz, 2H, aryl-H), 6.95 (dt, J = 11.5, 5.9 Hz, 10H, aryl-H),
6.88 – 6.81 (m,12H, aryl-H), 6.75 (dd, J = 8.5, 5.4 Hz, 8H,
aryl-H), 6.34 (t, J = 8.6 Hz, 8H, aryl-H), 6.08 (d, J = 7.1 Hz,
2H, aryl-H), 5.56 (s, 4H, CHAr2), 2.30 (s, 6H, Ar-CH3). 13C
NMR (126 MHz, CDCl3) δ 163.70 (C=N), 162.51 (C-F),
162.00 (C-F), 160.56 (C-F), 160.05 (C-F), 146.16, 139.85,
139.23, 139.21, 138.13, 138.10, 133.69, 131.61, 131.12,
131.06, 130.89, 130.82, 129.69, 129.62, 129.03, 128.01,
126.82, 124.33, 115.22, 115.05, 114.88, 50.04 (CHAr2), 21.63
(Ar-CH3). 19F NMR (471 MHz, CDCl3) δ -116.49 (s), -116.72
(s). MALDI-TOF-MS (m/z): 1169.06 [M+H]+.
O
O
O
O
Bis(2,6-bis(bis(4-methoxyphenyl)methyl)-4-
methylphenyl)acenaphthylene-1,2-diimine (L2).
Using the same procedure as for the synthesis of L1, L2
was obtained as an orange powder. The yields of step 1 and
step 2 are 75.1% (1.39 g) and 96.4% (1.21g), respectively. The
total yield of two steps is 72.4%. 1H NMR (500 MHz, CDCl3)
δ 7.53 (d, J = 8.1 Hz, 2H, aryl-H), 7.00 (d, J = 8.4 Hz, 8H,
aryl-H), 6.93 (t, J = 7.6 Hz, 2H, aryl-H), 6.86 (s, 4H, aryl-H),
6.76 (d, J = 8.3 Hz, 8H, aryl-H), 6.69 (d, J = 8.5 Hz, 8H, aryl-
H), 6.11 (d, J = 8.3 Hz, 10H, aryl-H), 5.59 (s, 4H, CHAr2),
3.72 (s, 12H, OCH3), 3.35 (s, 12H, OCH3), 2.28 (s, 6H, aryl-
CH3). 13C NMR (126 MHz, CDCl3) δ 163.79 (C=N), 157.86
(C-O), 157.25 (C-O), 146.63, 139.75, 136.59, 135.17, 132.72,
132.19, 130.81, 130.51, 129.40, 129.16, 128.51, 127.58,
126.65, 124.48, 113.53, 113.25, 55.31 (OCH3), 54.84 (OCH3),
49.90 (CHAr2), 21.65 (aryl-CH3). ESI-MS (m/z): calcd for
C86H77N2O8: 1265.5680, found: 1265.5701 [M+H]+.
Bis(2,6-bis(di([1,1'-biphenyl]-4-yl)methyl)-4-
methylphenyl)acenaphthylene-1,2-diimine (L5).
Using the same procedure as for the synthesis of L1, L5 was
obtained as a yellow powder. The yields of step 1 and step 2
are 96.5% (2.23 g) and 83.0% (1.71 g), respectively. The total
yield of two steps is 80.1%. A single crystal of L5 was ob-
tained by layering methanol onto the DCM solution at room
temperature. 1H NMR (500 MHz, CDCl3) δ 7.50 (d, J = 7.6 Hz,
8H, aryl-H), 7.36 (dd, J = 17.2, 8.0 Hz, 18H, aryl-H), 7.29 (s,
2H, aryl-H), 7.28 (s, 2H, aryl-H), 7.22 (d, J = 7.5 Hz, 20H,
aryl-H), 7.07 – 7.00 (m, 20H, aryl-H), 6.86 (d, J = 8.0 Hz, 8H,
aryl-H), 6.80 (t, J = 7.7 Hz, 2H, aryl-H), 6.23 (d, J = 7.1 Hz,
2H, aryl-H), 5.83 (s, 4H, CHAr2), 2.36 (s, 6H, Ar-CH3). 13C
NMR (126 MHz, CDCl3) δ 163.94 (C=N), 146.79, 142.93,
141.64, 140.99, 140.37, 139.69, 138.80, 138.48, 133.02,
131.46, 130.29, 129.91, 129.58, 129.28, 128.76, 128.62,
128.40, 128.22, 127.94, 127.01, 126.92, 126.83, 126.67,
126.60, 126.44, 124.51, 50.91 (CHAr2), 21.58 (Ar-CH3).
MALDI-TOF-MS (m/z): 1634.18 [M+H]+.
Bis(2,6-bis(bis(4-(tert-butyl)phenyl)methyl)-4-
methylphenyl)acenaphthylene-1,2-diimine (L3).
Using the same procedure as for the synthesis of L1, L3
was obtained as an orange powder. The yields of step 1 and
step 2 are 78.1% (1.66 g) and 89.1% (1.36 g), respectively.
1
The total yield of two steps is 69.5%. H NMR (500 MHz,
CDCl3) δ 7.43 (d, J = 8.0 Hz, 2H, aryl-H), 7.15 (d, J = 8.3 Hz,
8H, aryl-H), 7.04 (d, J = 8.2 Hz, 8H, aryl-H), 6.95 (s, 4H, aryl-
H), 6.84 (dd, J = 16.8, 7.8 Hz, 10H, aryl-H), 6.70 (d, J = 8.1
Hz, 8H, aryl-H), 6.14 (d, J = 6.9 Hz, 2H, aryl-H), 5.66 (s, 4H,
CHAr2), 2.32 (s, 6H, aryl-CH3), 1.24 (s, 36H, (C(CH3)3), 0.98
(s, 36H, (C(CH3)3). 13C NMR (126 MHz, CDCl3) δ 163.64
(C=N), 148.40, 148.02, 146.68, 140.97, 140.03, 139.97,
132.45, 131.94, 129.58, 129.34, 129.26, 128.73, 128.01,
126.64, 124.95, 124.75, 124.65, 50.54 (CHAr2), 34.40
(C(CH3)3), 34.08 (C(CH3)3), 31.52 (C(CH3)3), 31.26 (C(CH3)3),
21.71 (aryl-CH3). ESI-MS (m/z): calcd for C110H125N2:
1474.9876, found: 1474.9915 [M+H]+.
5

ACCEPTED MANUSCRIPT
Bis(2,6-dibenzhydryl-4-methoxyphenyl)acenaphthylene-1,2-
diimine (L6).
148.54, 148.17, 142.94, 140.53, 140.01, 139.75, 133.38,
129.54, 129.44, 129.21, 128.66, 128.14, 126.68, 125.01,
124.79, 124.66, 114.32, 55.35 (OCH3), 50.70 (CHAr2), 34.38
(C(CH3)3), 34.05 (C(CH3)3), 31.49 (C(CH3)3), 31.22 (C(CH3)3).
ESI-MS (m/z): calcd for C110H125N2O2: 1505.9741, found:
1505.9735 [M+H]+.
Using the same procedure as for the synthesis of L1, L6
was obtained as a yellow powder. The yields of step 1 and step
2 are 98.7% (1.56 g) and 87.3% (1.20 g), respectively. The
total yield of two steps is 86.2%. 1H NMR (400 MHz, CDCl3)
δ 7.51 (d, J = 8.2 Hz, 2H, aryl-H), 7.10 (dd, J = 21.5, 6.6 Hz,
20H, aryl-H), 6.88 (d, J = 15.3 Hz, 10H, aryl-H), 6.66 (d, J =
15.1 Hz, 16H, aryl-H), 6.16 (d, J = 7.1 Hz, 2H, aryl-H), 5.68
(s, 4H, CHAr2), 3.66 (s, 6H, OCH3). 13C NMR (101 MHz,
CDCl3) δ 164.24 (C=N), 155.69 (C-O), 143.51, 142.82,
142.33, 139.84, 133.02, 129.72, 129.47, 129.34, 128.51,
128.08, 128.00, 127.83, 126.64, 126.11, 125.81, 124.25,
114.51, 55.23 (OCH3), 51.57 (CHAr2). ESI-MS (m/z): calcd
for C78H61N2O2: 1057.4733, found:1057.4777 [M+H]+.
Bis(4-chloro-2,6-bis(di-p-tolylmethyl)phenyl)acenaphthylene-
1,2-diimine (L9).
Using the same procedure as for the synthesis of L1, L9
was obtained as a yellow powder. The yields of step 1 and step
2 are 75.1% (1.30 g) and 98.7% (1.15 g), respectively. The
total yield of two steps is 74.2%. 1H NMR (500 MHz, CDCl3)
δ 7.60 (d, J = 8.2 Hz, 2H, aryl-H), 7.05 (s, 4H, aryl-H), 6.92 (q,
J = 8.2 Hz, 18H, aryl-H), 6.67 (d, J = 8.0 Hz, 8H, aryl-H),
6.40 (d, J = 7.9 Hz, 8H, aryl-H), 6.15 (d, J = 7.1 Hz, 2H, aryl-
H), 5.52 (s, 4H, CHAr2), 2.25 (s, 12H, Ar-CH3), 1.87 (s, 12H,
Ar-CH3). 13C NMR (126 MHz, CDCl3) δ 163.61 (C=N),
147.44, 140.09, 139.93, 139.10, 135.78, 135.32, 134.19,
129.75, 129.53, 129.33, 129.01, 128.98, 128.78, 128.60,
128.20, 127.62, 126.80, 124.51, 50.77 (CHAr2), 21.07
(CH(PhMe)2), 20.67 (CH(PhMe)2). ESI-MS (m/z): calcd for
C84H71Cl2N2: 1177.4994, found: 1177.4941 [M+H]+.
Bis(2,6-bis(di-p-tolylmethyl)-4-
methoxyphenyl)acenaphthylene-1,2-diimine (L7).
Using the same procedure as for the synthesis of L1, L7
was obtained as an orange powder. The yields of step 1 and
step 2 are 93.0% (1.60 g) and 87.8% (1.26 g), respectively.
1
The total yield of two steps is 81.7%. H NMR (500 MHz,
CDCl3) δ 7.56 (d, J = 8.2 Hz, 2H, aryl-H), 6.96 (d, J = 8.1 Hz,
8H, aryl-H), 6.93 (d, J = 8.1 Hz, 8H, aryl-H), 6.90 – 6.86 (m,
2H, aryl-H), 6.70 (d, J = 8.0 Hz, 8H, aryl-H), 6.65 (s, 4H, aryl-
H), 6.37 (d, J = 7.8 Hz, 8H, aryl-H), 6.15 (d, J = 7.1 Hz, 2H,
aryl-H), 5.57 (s, 4H, CHAr2), 3.65 (s, 6H, Ar-OCH3), 2.24 (s,
12H, Ar-CH3), 1.86 (s, 12H, Ar-CH3). 13C NMR (126 MHz,
CDCl3) δ 164.31 (C=N), 155.67 (C-O), 142.98, 140.84,
139.81, 139.74, 135.39, 134.92, 133.38, 129.86, 129.51,
129.45, 128.84, 128.58, 128.54, 127.17, 126.61, 124.51,
114.26, 55.33 (Ar-OCH3), 50.89 (CHAr2), 21.07 (Ar-CH3),
20.66 (Ar-CH3). ESI-MS (m/z): calcd for C86H77N2O2:
1169.5985, found:1169.5999 [M+H]+.
Bis(2,6-bis(bis(4-methoxyphenyl)methyl)-4-
chlorophenyl)acenaphthylene-1,2-diimine (L10).
Using the same procedure as for the synthesis of L1, L10
was obtained as a yellow powder. The yields of step 1 and step
2 are 68.8% (1.37 g) and 88.4% (1.10 g), respectively. The
total yield of two steps is 60.8%. 1H NMR (500 MHz, CDCl3)
δ 7.59 (d, J = 8.2 Hz, 2H, aryl-H), 7.04 (s, 4H, aryl-H), 6.98
(dd, J = 16.5, 8.2 Hz, 10H, aryl-H), 6.72 (dd, J = 13.8, 8.6 Hz,
16H, aryl-H), 6.14 (dd, J = 10.6, 8.0 Hz, 10H, aryl-H), 5.56 (s,
4H, CHAr2), 3.73 (s, 12H, Ar-OCH3), 3.36 (s, 12H, Ar-OCH3).
13C NMR (126 MHz, CDCl3) δ 163.93 (C=N), 158.15 (C-O),
157.53 (C-O), 147.36, 139.86, 135.48, 134.56, 134.16, 130.70,
130.40, 129.47, 129.16, 128.56, 128.13, 128.10, 126.86,
124.55, 113.77, 113.48, 55.34 (Ar-OCH3), 54.87 (Ar-OCH3),
49.95 (CHAr2). ESI-MS (m/z): calcd for C84H71Cl2N2O8:
1305.4587, found: 1305.4590 [M+H]+.
Bis(2,6-bis(bis(4-(tert-butyl)phenyl)methyl)-4-
methoxyphenyl)acenaphthylene-1,2-diimine (L8).
Using the same procedure as for the synthesis of L1, L8
was obtained as a yellow powder. The yields of step 1 and step
2 are 98.8% (2.11 g) and 83.7% (1.62 g), respectively. The
total yield of two steps is 82.7%. 1H NMR (400 MHz, CDCl3)
δ 7.47 (d, J = 7.7 Hz, 2H, aryl-H), 7.17 (d, J = 7.2 Hz, 8H,
aryl-H), 7.06 (d, J = 7.2 Hz, 8H, aryl-H), 6.86 (dd, J = 24.0,
7.4 Hz, 11H, aryl-H), 6.76 – 6.67 (m, 11H, aryl-H), 6.20 (d, J
= 6.4 Hz, 2H, aryl-H), 5.67 (s, 4H, CHAr2), 3.69 (s, 6H,
OCH3), 1.24 (s, 36H, C(CH3)3), 0.97 (s, 36H, C(CH3)3). 13C
NMR (101 MHz, CDCl3) δ 164.30 (C=N), 155.60 (C-O),
6

ACCEPTED MANUSCRIPT
Bis(4-(tert-butyl)-2,6-bis(di-p-
tolylmethyl)phenyl)acenaphthylene-1,2-diimine (L11).
is previously known[36]. 1H NMR (500 MHz, CDCl3) δ 8.04 –
7.99 (m, 2H, aryl-H), 7.70 (dt, J = 8.0, 3.4 Hz, 2H, aryl-H),
7.23 (t, J = 7.4 Hz, 4H, aryl-H), 7.17 (t, J = 7.3 Hz, 2H, aryl-
H), 7.05 (dd, J = 7.4, 3.3 Hz, 5H, aryl-H), 6.85 (d, J = 7.2 Hz,
4H, aryl-H), 6.78 (s, 2H, aryl-H), 6.59 (t, J = 7.7 Hz, 4H, aryl-
H), 6.42 (t, J = 7.4 Hz, 2H, aryl-H), 6.13 (d, J = 7.1 Hz, 1H,
aryl-H), 5.42 (s, 2H, CHAr2), 2.26 (s, 3H, Aryl-CH3). 13C
NMR (126 MHz, CDCl3) δ 189.82 (C=O), 162.41 (C=N),
145.96, 143.00, 142.49, 141.76, 133.26, 131.88, 131.79,
130.03, 129.90, 129.81, 129,71, 129.57, 129.56, 129.48,
128.72, 128.51, 128.47, 128.19, 127.84 , 127.57, 127.25,
126.97, 126.22, 125.55, 123.96, 121.54, 52.19 (CHAr2), 21.58
(Aryl-CH3). MALDI-TOF-MS (m/z): 604.07 [M+H]+.
Using the same procedure as for the synthesis of L1, L11
was obtained as a yellow powder. The yields of step 1 and step
2 are 72.6% (1.29 g) and 82.9% (0.96 g), respectively. The
total yield of two steps is 60.2%. 1H NMR (500 MHz, CDCl3)
δ 7.54 (d, J = 8.2 Hz, 2H, aryl-H), 7.09 (s, 4H, aryl-H), 6.93 (q,
J = 8.2 Hz, 16H, aryl-H), 6.87 – 6.83 (m, 2H, aryl-H), 6.69 (d,
J = 7.9 Hz, 8H, aryl-H), 6.38 (d, J = 7.8 Hz, 8H, aryl-H), 6.01
(d, J = 7.1 Hz, 2H, aryl-H), 5.55 (s, 4H, CHAr2), 2.24 (s, 12H,
Ar-CH3), 1.86 (s, 12H, Ar-CH3), 1.19 (s, 18H, C(CH3)3). 13C
NMR (126 MHz, CDCl3) δ 163.38 (C=N), 146.65, 145.70,
141.30, 140.31, 139.81, 135.08, 134.64, 131.10, 129.84,
129.61, 129.42, 128.67, 128.62, 128.46, 127.01, 126.56,
125.49, 124.31, 50.97 (CHAr2), 34.52 (C(CH3)3), 31.58
(C(CH3)3), 21.05 (Ar-CH3), 20.65 (Ar-CH3). ESI-MS (m/z):
calcd for C92H89N2: 1221.7026, found: 1221.7052 [M+H]+.
Procedure for 100 gram-Scale Synthesis of L7
.
Step 1: ZnCl2 (20.4 g, 150 mmol) and acenaphthenequinone
(24.1 g, 132 mmol) were suspended in glacial acetic acid (300
mL). 2,6-Bis(di-p-tolylmethyl)-4-methylaniline (149 g, 300
mmol) was added, and the reaction mixture was refluxed un-
der mechanical stirring for 4 h. The solution was allowed to
cool to room temperature, and a bright orange-red solid pre-
cipitated. The solid was separated by filtration and washed
with acetic acid (3 × 100 mL) and diethyl ether (5 ×150 mL),
to remove remaining acetic acid. Drying under vacuum gave
bright orange-red, poorly soluble solid (151 g, 87.8%). Step 2:
The zinc was removed from the zinc diimine complex. The
product of the previous step was suspended in methylene chlo-
ride (1000 mL), and a solution of potassium oxalate (55.3 g,
300 mmol) in water (500 mL) was added. The reaction mix-
ture was stirred vigorously by mechanical agitator for 1 h. The
two phases were separated, and the organic layer was washed
with water (3×200 mL) and dried with MgSO4. After filtration
the solvent was removed under vacuum to afford the product
as an orange powder (116 g, 85.9%). The total yield of two
steps is 75.4%.
2-((2,6-Dibenzhydryl-4-chlorophenyl)imino)acenaphthylen-1-
one (L13).
Using the same procedure as for the synthesis of L1, L13
was obtained as an orange powder. Our efforts to obtain the
putative Zn(II) intermediate have been unsuccessful. The total
yield is 69.4% (0.57 g). This compound is previously
known[45]. 1H NMR (400 MHz, CDCl3) δ 8.04 (d, J = 6.1 Hz,
2H, aryl-H), 7.73 (t, J = 9.3 Hz, 2H, aryl-H), 7.32 – 7.19 (m,
5H, aryl-H), 7.05 (t, J = 11.1 Hz, 6H, aryl-H), 6.96 (s, 2H,
aryl-H), 6.84 (d, J = 7.4 Hz, 5H, aryl-H), 6.60 (t, J = 7.4 Hz,
3H, aryl-H), 6.44 (t, J = 7.2 Hz, 2H, aryl-H), 6.16 (d, J = 7.0
Hz, 1H, aryl-H), 5.42 (s, 2H, CHAr2). 13C NMR (101 MHz,
CDCl3) δ 189.45 (C=O), 162.62 (C=N), 146.87, 142.68,
142.01, 140.93, 134.16, 132.06, 129.97, 129.88, 129.67,
129.61, 129.48, 129.42, 128.95, 128.79, 128.47, 128.35,
128.16, 128.10, 127.80, 127.33, 126.69, 125.94, 123.92,
121.84, 52.21 (CHAr2). ESI-MS (m/z): calcd for C44H31ClNO:
624.2094, found: 624.2007 [M+H]+.
Procedure for the Synthesis of Acenaphthene-based Mo-
noimines.
2-((2,6-Bis(di-p-tolylmethyl)-4-
methylphenyl)imino)acenaphthylen-1-one (L14).
The monoimine ligand L14 was purposefully synthesized to
investigate the solubility of monoimine-Zn(II) intermediates in
the acetic acid in the reaction of step 1. A mixture of 2,6-
bis(di-p-tolylmethyl)-4-methylaniline (2.97 g, 6 mmol, 1.0
equiv.) and acenaphthenequinone (1.09 g, 6 mmol, 1.0 equiv.)
were dissolved in 5 mL ethanol and 100 mL of CH2Cl2 con-
taining a catalytic amount of p-toluenesulfonic acid and stirred
for 48 h at room temperature. The solvent was evaporated at
reduced pressure to give the crude product, which was chro-
matographed on silica gel with petroleum ether-ethyl acetate
(v/v = 30:1). A 2.75 g amount of the product was obtained as
2-((2,6-Dibenzhydryl-4-methylphenyl)imino)acenaphthylen-1-
one (L12).
Using the same procedure as for the synthesis of L1, L12
was obtained as an orange powder. Our efforts to obtain the
putative Zn(II) intermediate have been unsuccessful. MS anal-
ysis indicated the presence of the monoimine-Zn complex
(MALDI-TOF-MS (m/z): 689.23 [M-2Cl+Na]+, see support-
ing information, Figure S84) while the elemental analysis in-
dicated the mixture of the monoimine ligands and the mo-
noimine-Zn complexes (Anal. Calcd for C45H33Cl2NOZn: C,
73.04; H, 4.49 N, 1.89; Found: C, 80.53; H, 5.10; N, 2.12).
The total yield of two steps is 69.4% (0.55 g). This compound
1
red powder in 69.5% yield. H NMR (500 MHz, CDCl3) δ
8.02 (dd, J = 10.8, 7.6 Hz, 2H, aryl-H), 7.76 -7.66 (m, 2H,
7

ACCEPTED MANUSCRIPT
aryl-H), 7.06-6.99 (m, 5H, aryl-H), 6.96 (t, J = 9.4 Hz, 4H,
aryl-H), 6.77 (s, 2H, aryl-H), 6.71 (d, J = 7.9 Hz, 4H, aryl-H),
6.32 (d, J = 7.8 Hz, 4H, aryl-H), 6.03 (d, J = 7.1 Hz, 1H, aryl-
H), 5.33 (s, 2H, CH(PhMe)2), 2.29 (s, 6H, CH(PhMe)2), 2.25
(s, 3H, Ar-CH3 ), 1.67 (s, 6H, CH(PhMe)2). 13C NMR (126
MHz, CDCl3) δ 190.09 (C=O), 162.56 (C=N), 146.08, 142.38,
140.19, 139.12, 135.60, 134.86, 133.14, 132.77, 131.98,
131.67, 130.24, 129.97, 129.76, 129.47, 129.42, 129.31,
128.93, 128.64, 128.43, 127.58, 127.56, 127.33, 126.86,
124.29, 122.22, 121.50, 51.53(CHAr2), 21.65 (Ar-CH3), 21.14
(Ar-CH3), 20.48 (Ar-CH3). ESI-MS (m/z): calcd for C49H42NO:
660.3266, found: 660.3275 [M+H]+.
Complex 2: A mixture of L7 (1.17 g, 1 mmol) and
(DME)NiBr2 (0.31 g, 1.0 mmol) (DME 1,2-
=
dimethoxyethane) were stirred in 10 mL of CH2Cl2 overnight
at room temperature. The solvent was removed, and the result-
ing powder was washed with hexane (3×10 mL) and dried
under vacuum to obtain a red solid (1.16 g, 83.9%). A single
crystal of complex 2 was obtained by layering hexane onto the
CH2Cl2 solution at room temperature. As a result of their par-
amagnetic nature, this complex could not be characterized by
1H and 13C NMR. MALDI-TOF-MS (m/z): 1307.33 [M-Br]+.
Anal. Calcd for C86H76Br2N2O2Ni: C, 74.42; H, 5.52; N, 2.02;
Found: C, 74.66; H, 5.47; N, 1.99.
In-situ Reaction of Monoimines L12-L14 with ZnCl2 in the
Acetic Acid.
Monoimine (0.2 mmol) and ZnCl2 (0.2 mmol) were added
in the glacial acetic acid (10 mL). The reaction mixture was
refluxed under stirring for 4 h. In monoimine ligand L14 sys-
tem, solution is obtained, while insoluble substances are ob-
served in monoimine ligand L12 and L13 systems (Figure S1).
Procedure for the Synthesis of the Imidazolium Chloride Salts.
Procedure for the Synthesis of
Complexes.
α-Diimine Pd(II) and Ni(II)
O
N
N
O
Pd
Cl
Cl
S1: L1 (1.32 mmol) and methoxy(methyl)chloride (65.9
mmol) were added to a nitrogen-flushed thick-walled reaction
vessel. The vessel was sealed and the reaction mixture was
Complex 1: A mixture of L7 (1.28 g, 1.1 mmol),
stirred at 100
℃ for 16h, during this time the mixture changed
(COD)PdCl2 (0.286 g, 1 mmol) in CH2Cl2 (20 mL) was stirred
for 3 days at room temperature. During stirring, the solid was
completely dissolved and the color of the solution was
changed from yellow to red. The desired compound can be
isolated from repeated recrystallized from n-hexane and di-
chloromethane. Alternatively, the desired compound can be
isolated at much higher yield using column chromatography.
The mixture was eluted on silica gel with first 1:1 hex-
anes/CH2Cl2, then pure CH2Cl2 as the mobile phase. The pure
compound was obtained as an orange solid (0.831 g, 61.7%).
A single crystal of complex 1 was obtained by layering hexane
from a murky brown suspension to a clear red solution. Cool-
ing of the reaction mixture to ambient temperature and the
subsequent addition of 20 ml of diethyl ether resulted in the
formation of a yellow precipitate. The resulting solid was fil-
tered off and washed with 50 ml of diethyl ether and dried in
vacuo to afford S1(1.16 g, 74.1%). 1H NMR (500 MHz,
CDCl3) δ 10.44 (s, 1H, N-CH), 7.79 (d, J = 8.2 Hz, 2H, aryl-
H), 7.10 (t, J = 7.6 Hz, 2H, aryl-H), 7.00 (s, 4H, aryl-H), 6.90
(d, J = 6.5 Hz, 8H, aryl-H), 6.82 (d, J = 6.2 Hz, 8H, aryl-H),
6.52 (s, 16H, aryl-H), 6.28 (d, J = 6.9 Hz, 2H, aryl-H), 5.12 (s,
4H, CHAr2), 2.32 (s, 6H, Ar-CH3), 2.22 (s, 12H, CH(PhMe)2),
1.96 (s, 12H, CH(PhMe)2). 13C NMR (126 MHz, CDCl3) δ
142.09, 141.27, 139.31, 138.57, 138.19, 137.88, 136.60,
136.35, 130.69, 129.51, 129.33, 129.20, 129.06, 129.00,
128.55, 126.77, 123.68, 121.10, 51.00 (CHAr2), 22.01 (Ar-
CH3), 21.03 (CH(PhMe)2), 20.73 (CH(PhMe)2). ESI-MS (m/z):
calcd for C87H77N2: 1149.6081, found: 1149.6082 [M-Cl-]+.
1
onto the CH2Cl2 solution at room temperature. H NMR (400
MHz, CDCl3) δ 7.66 (d, J = 8.1 Hz, 2H, aryl-H), 7.27 (s, 3H,
aryl-H), 7.26 – 7.24 (m, 5H, aryl-H), 6.97 (d, J = 7.8 Hz, 8H,
aryl-H), 6.84 (t, J = 7.7 Hz, 2H, aryl-H), 6.73 (d, J = 7.7 Hz,
8H, aryl-H), 6.69 (s, 4H, aryl-H), 6.27 (d, J = 7.8 Hz, 8H, aryl-
H), 6.12 (s, 4H, CHAr2 ), 6.04 (d, J = 6.9 Hz, 2H, aryl-H),
3.63 (s, 6H, Ar-OCH3), 2.25 (s, 12H, Ar-CH3), 1.82 (s, 12H,
Ar-CH3). 13C NMR (101 MHz, CDCl3) δ 178.00 (C=N),
158.69 (C-O), 145.61, 139.87, 138.86, 138.80, 136.24, 135.99,
135.41, 129.98, 129.90, 129.60, 128.99, 128.91, 127.39,
127.06, 123.52, 114.88, 55.31 (Ar-OCH3), 51.67 (CHAr2),
21.18 (Ar-CH3), 20.70 (Ar-CH3). MALDI-TOF-MS (m/z):
1309.36 [M-Cl]+. Anal. Calcd for C86H76Cl2N2O2Pd: C, 76.69;
H, 5.69; N, 2.08; Found: C, 76.93; H, 5.57; N, 2.06.
S2: Using the same procedure as for the synthesis of S1, S2
1
was obtained as a yellow powder (1.44 g, 89.5%). H NMR
(500 MHz, CDCl3) δ 10.47 (s, 1H, N-CH), 7.79 (d, J = 8.1 Hz,
2H, aryl-H), 7.12 (t, J = 7.4 Hz, 2H, aryl-H), 6.89 (broad peak,
16H, aryl-H), 6.69 (s, 4H, aryl-H), 6.53 (s, 16H, aryl-H), 6.32
8

ACCEPTED MANUSCRIPT
(d, J = 6.7 Hz, 2H, aryl-H), 5.12 (s, 4H, CHAr2), 3.66 (s, 6H,
OCH3), 2.22 (s, 12H, CH(PhMe)2), 1.96 (s, 12H, CH(PhMe)2).
13C NMR (126 MHz, CDCl3) δ 161.23 (C-O), 143.29, 138.36,
137.72, 136.70, 136.46, 129.52, 129.38, 129.19, 129.14,
129.09, 129.01, 128.56, 126.79, 124.16, 123.67, 121.15,
115.52, 55.57 (OCH3), 51.22 (CHAr2), 21.05 (CH(PhMe)2),
20.74 (CH(PhMe)2). ESI-MS (m/z): calcd for C87H77N2 O2:
1181.5980, found: 1181.5978 [M-Cl-]+.
Complex 4: the mixture of PdCl2 (44 mg, 0.25 mmol), S2
(305 mg, 0.25 mmol), K2CO3 (344 mg, 2.5 mmol) and pyri-
o
dine(1.4 mL) was stirred at 80 C for 24 h under a nitrogen
atmosphere. After cooling to room temperature,10 mL di-
chloromethane was added, and then the reaction mixture was
diluted in CH2Cl2, pass through a pad of silica covered with
celite, and eluted with CH2Cl2.The solvents were removed
under reduced pressure to furnish the desired product, which
was recrystallized in a CH2Cl2/hexane mixture to remove
completely the pyridine. The pure palladium complex was
finally obtained after filtration and drying under a high vacu-
S3: Using the same procedure as for the synthesis of S1, S3
was obtained as a yellow powder (1.03 g, 65.2%). H NMR
1
(500 MHz, CDCl3) δ 13.17 (s, 1H, N-CH), 7.68 (d, J = 8.2 Hz,
2H, aryl-H), 7.16 (s, 4H, aryl-H), 7.10 – 6.96 (m, 17H, aryl-H),
6.48 – 6.41 (m, 17H, aryl-H), 6.22 (d, J = 6.9 Hz, 2H, aryl-H),
5.25 (s, 4H, CHAr2), 2.18 (s, 12H, CH(PhMe)2), 1.93 (s, 12H,
CH(PhMe)2). 13C NMR (126 MHz, CDCl3) δ 144.08, 138.18,
137.86, 137.75, 137.36, 136.55, 136.53, 130.36, 130.22,
129.57, 129.36, 129.21, 129.03, 128.65, 128.42, 126.58,
123.60, 121.58, 51.07 (CHAr2), 21.11 (CH(PhMe)2), 20.79
(CH(PhMe)2). ESI-MS (m/z): calcd for C85H71Cl2N2:
1189.4989, found: 1189.4974 [M-Cl-]+.
um (Yellow solid，Yield: 288 mg, 81%). Single crystal of 4
was obtained by layering hexane onto the CH2Cl2 solution at
room temperature. 1H NMR (400 MHz, CDCl3) δ 9.25 (s, 2H,
aryl-H), 7.76 (s, 1H, aryl-H), 7.35 (s, 2H, aryl-H), 7.14 (s, 10H,
aryl-H), 6.89 (s, 12H, aryl-H), 6.51 (s, 2H, CHAr2), 6.37 (d, J
= 43.0 Hz, 12H, aryl-H), 6.10 (s, 8H, aryl-H), 5.64 (s, 2H,
CHAr2), 3.68 (s, 6H, OCH3), 2.22 (s, 12H, CH(PhMe)2), 1.85
(s, 12H, CH(PhMe)2). 13C NMR (101 MHz, CDCl3) δ 158.81
(C-O), 157.72, 152.21, 144.39, 142.76, 140.95, 138.76, 138.00,
134.90, 131.25, 130.56, 129.59, 128.39, 127.89, 127.85,
127.37, 125.92, 125.18, 124.32, 124.28, 121.56, 116.41, 55.34
(OCH3), 50.48 (CHAr2), 21.04 (CH(PhMe)2), 20.81
(CH(PhMe)2). MALDI-TOF-MS (m/z): 1284.31 [M-C5H5N-
2Cl]+. Anal. Calcd for C92H81Cl2N3O2Pd: C, 76.84; H, 5.68; N,
2.92; Found: C, 76.77; H, 5.80; N, 2.96.
Procedure for the Synthesis of N-heterocyclic Carbene (NHC)
Complexes.
Acknowledgment
This work was supported by National Natural Science Foundation
of China (NSFC, 21304054 and 51703215), Foundation of Qufu
Normal University (xkJ201603), College Students Innovation
Project (2017A032).
Complex 3: S2 (254 mg, 0.21 mmol) was dissolved in
CH2Cl2 (5 mL) and Ag2O (23.2 mg, 0.1 mmol) was added.
The mixture was sheltered from light and stirred at 25
16 h.The solution was filtered on a pad of celite and evapo-
rated to give 3 as a yellow solid (70 , 189 mg). Single crystal
℃ for
Appendix A
CCDC numbers of L4, L5, 1, 2, 3 and 4 are 1583392, 1583395,
1583396, 1583398, 1583400 and 1583401 respectively. These
data can be obtained free of charge from the Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
％
of 3 was obtained by layering diethyl ether onto the CH2Cl2
1
solution at room temperature. H NMR (400 MHz, CDCl3) δ
7.59 (d, J = 7.8 Hz, 2H, aryl-H), 7.07 – 6.97 (m, 2H, aryl-H),
6.83 (d, J = 6.9 Hz, 7H, aryl-H), 6.76 (d, J = 7.2 Hz, 9H, aryl-
H), 6.67 (s, 12H, aryl-H), 6.55 (d, J = 6.5 Hz, 8H, aryl-H),
6.19 (d, J = 6.4 Hz, 2H, aryl-H), 5.26 (s, 4H, CHAr2), 3.65 (s,
6H, OCH3), 2.21 (s, 12H, CH(PhMe)2), 1.97 (s, 12H,
CH(PhMe)2). 13C NMR (101 MHz, CDCl3) δ 159.96 (C-O),
143.75, 139.56, 139.48, 139.20, 139.10, 139.09, 135.88,
135.73, 129.77, 129.55, 129.31, 129.16, 129.10, 129.00,
128.73, 128.53, 126.89, 126.18, 123.76, 121.77, 114.91, 55.28
(OCH3), 50.86 (CHAr2), 21.08 (CH(PhMe)2), 20.73
(CH(PhMe)2). MALDI-TOF-MS (m/z): 1287.27 [M-Cl]+.
Anal. Calcd for C87H76AgClN2O2: C, 78.87; H, 5.78; N, 2.11;
Found: C, 78.99; H, 5.77; N, 2.16.
Appendix B. Supplementary data
Supplementary data related to this article can be found at
http://dx.doi.org/.
References
[1] G. Van Koten, K. Vrieze, Organomet. Chem. 21 (1982)
151.
[2] V. Rosa, S. A. Carabineiro, T. Aviles, P. T. Gomes, R.
Welter, J. M. Campos, M. R. Ribeiro, J. Org. Chem. 693
(2008) 769.
[3] A. J. Arduengo, R. L. Harlow, M. A. Kline, J. Am.
Chem. Soc. 113 (1991) 361.
9

ACCEPTED MANUSCRIPT
[4] X. B. Lan, Y. W. Li, Y. F. Li, D. S. Shen, Z. F. Ke, F. S.
[29] W. C. Anderson, J. L. Rhinehart, A. G. Tennyson, B. K.
Long, J. Am. Chem. Soc. 138 (2016) 774.
[30] W. C. Anderson, B. K. Long, ACS Macro Lett. 5 (2016)
1029.
Liu, J. Org. Chem. 82 (2017) 2914.
[5] L. K. Johnson, C. M. Killian, M. Brookhart, J. Am.
Chem. Soc. 117 (1995) 6414.
[6] L. K. Johnson, S. Mecking, M. Brookhart J. Am. Chem.
Soc. 118 (1996) 267.
[31] Q. Ban, J. Zhang, T. L. Liang, C. Redshaw, W. H. J.
Sun, Organomet. Chem. 713 (2012) 151.
[7] L. H. Guo, C. L. Chen, Sci. China Chem. 58 (2015)
1663.
[8] L. H. Guo, S. Y. Dai, X. L. Sui, C. L. Chen, ACS Catal.
6 (2016) 428.
[32] H. Liu, W. Z. Zhao, X. A. Hao, C. Redshaw, W. Huang,
W. H. Sun, Organometallics 30 (2011) 2418.
[33] V. Lodeiro, T. Rosa, G. Avilés, B. Aullon, C. Covelo,
Inorg. Chem. 47 (2008) 7734.
[9] L. H. Guo, W. J. Liu, C. L. Chen, Mater. Chem. Front. 1
(2017), 2487.
[34] J. A. Moore, K. Vasudevan, N. J. Hill, G. Reeske, A. H.
Cowley, Chem. Commun. 27 (2006) 2913.
[10] L. H. Guo, H. Y. Gao, Q. R. Guan, H. B. Hu, J. A.
Deng, J. Liu, F. S. Liu, Wu, Q. Organometallics 31
(2012) 6054.
[11] A. M. Kluwer, T. S. Koblenz, T. Jonischkeit, K. Woelk,
C. J. Elsevier, J. Am. Chem. Soc. 127 (2005) 15470.
[12] H. Guo, Z. Zheng, F. Yu, S. Ma, A. Holuigue, D. S.
Tromp, C. J. Elsevier, Y. Yu, Angew. Chem., Int. Ed. 45
(2006) 4997.
[13] L. Li, P. S. Lopes, V. Rosa, C. A. Figueira, M. A. N. D.
A. Lemos, M. T. Duarte, T. Aviles, P. T. Gomes, Dalton
Trans. 41 (2012) 5144.
[14] L. Li, P. S. Lopes, C. A. Figueira, C. S. B. Gomes, M. T.
Duarte, V. Rosa, C. Fliedel, T. Avilés, P. T. Gomes, Eur.
J. Inorg. Chem. 2013 (2013) 1404.
[15] J. S. Ouyang, Y. F. Li, D. S. Shen, Z. F. Ke, F. S. Liu,
Dalton Trans. 45 (2016) 14919.
[16] J. L. Rhinehart, L. A. Brown, B. K. Long, J. Am. Chem.
Soc. 135 (2013) 16316.
[17] J. L. Rhinehart, N. E. Mitchell, B. K. Long, ACS Catal. 4
(2014) 2501.
[18] S. Y. Dai, X. L. Sui, C. L. Chen, Angew. Chem. Int. Ed.
54 (2015) 9948.
[35] J. A. Deng, H. Y. Gao, F. M. Zhu, Q. Wu, Organometal-
lics 32 (2013) 4507.
[36] X. B. Lan, Y. W. Li, Y. F. Li, D. S. Shen, Z. F. Ke, F. S.
Liu, J. Org. Chem. 82 (2017) 2914.
[37] X. B. Lan, F. M. Chen, B. B. Ma, D. S. Shen, F. S. Liu,
Organometallics 35 (2016) 3852.
[38] C. J. O’Brien, E. A. B. Kantchev, C. Valente, N. Hadei,
G. A. Chass, A. Lough, A. C. Hopkinson, M. G. Organ,
Chem. Eur. J. 12 (2006) 4743.
[39] M. G. Organ, S. Calimsiz, M. Sayah, K. H. Hoi, A. J.
Lough, Angew. Chem. Int. Ed. 48 (2009) 2383.
[40] A. Chartoire, X. Frogneux, A. Boreux, A. M. Z. Slawin,
S. P. Nolan, Organometallics 31 (2012) 6947.
[41] T. Tu, W. W. Fang, J. Jiang, Chem. Commun. 47 (2011)
12358.
[42] T. Tu, Z. M. Sun, W. W. Fang, M. Z. Xu, Y. F. Zhou,
Org. Lett. 14 (2012) 4250.
[43] D. Zhang, E. Nadres, M. Brookhart, O. Daugulis, Or-
ganometallics 32 (2013) 5136.
[44] K. V. Vasudevan, M. Findlater, A. H. Cowley, Chem.
Commun. (2008) 1918.
[45] S. Kong, C. Y. Guo, W. Yang, L. Wang, W. H. Sun, R.
Glaser, J. Org. Chem. 725 (2013) 37.
[19] L. H. Guo, C. Zou, S. Y. Dai, C. L. Chen, Polymers 9
(2017) 122.
[20] L. H. Guo, S. Y. Dai, C. L. Chen, Polymers 8 (2016) 37.
[21] B. G. Guillaume, A. S. Maxime, L. S. Anthony, T. Ber-
nard, N. H. R. Joost, E. M. István, Dalton Trans. 39
(2010) 1444.
[22] K. Hasan, E. Zysman-Colman, J. Phys. Org. Chem. 26
(2013) 274.
[23] U. El-Ayaan, A. Paulovicova, S. Yamada, Y. J. Fukuda,
Coord. Chem. 56 (2003) 373.
[24] J. Y. Wang, R. Ganguly, Y. X. Li, J. Diaz, H. S. Soo, F.
Garcia, Inorg. Chem. 56 (2017) 7811.
[25] N. J. Hill, I. Vargas-Baca, A. H. Cowley, Dalton Trans.
(2009) 240.
[26] I. L. Fedushkin, A. A. Skatova, V. A. Chudakova, G. K.
Fukin, Angew. Chem. Int. Ed. 42 (2003) 3294.
[27] K. Vasudevan, A. H. Cowley, Chem. Commun. (2007)
3464.
[28] H. Schumann, M. Hummert, A. N. Lukoyanov, V. A.
Chudakova, I. L. Fedushkin, Z. Naturforsch. B: Chem.
Sci. 62 (2007) 1107.
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Highlights
An efficient method to synthesize novel highly sterically hindered
acenaphthene-based α-diimine ligands bearing bulky diarylmethyl moiety was
achieved. On the basis of this method, novel highly sterically hindered
acenaphthene-based α-diimine Pd(II) and Ni(II) complexes and N-heterocyclic
carbenes-metal complexes were successfully synthesized.