Synthesis, structure and catalytic polymerization activity of half-sandwich cyclometallated iridium complexes

Article abstract of DOI:10.1002/aoc.4239

A series of mononuclear half-sandwich cyclometallated iridium complexes with Schiff base ligands were synthesized in good yields. Five air-stable C,N-chelate mode complexes were obtained smoothly through metal-mediated C─H bond activation. Treatments of d

Full text of DOI:10.1002/aoc.4239

Received: 30 October 2017
DOI: 10.1002/aoc.4239
Revised: 27 November 2017
Accepted: 28 November 2017
F U L L P A P E R
Synthesis, structure and catalytic polymerization activity of
half‐sandwich cyclometallated iridium complexes
Zi‐Jian Yao1,2
| Peng Li1 | Kuan Li1 | Wei Deng1
1 School of Chemical and Environmental
Engineering, Shanghai Institute of
Technology, Shanghai 201418, China
2 Shanghai Key Laboratory of Molecular
Catalysis and Innovative Material,
Department of Chemistry, Fudan
University, Shanghai 200433, China
A series of mononuclear half‐sandwich cyclometallated iridium complexes with
Schiff base ligands were synthesized in good yields. Five air‐stable C,N‐chelate
mode complexes were obtained smoothly through metal‐mediated C─H bond
activation. Treatments of dimeric metal complexes [Cp*IrCl2]2 with ligands
L1–L5 afforded the corresponding C,N‐chelate mononuclear half‐sandwich
iridium(III) complexes 1–5. These iridium complexes exhibit high catalytic
activity for norbornene polymerization. Both steric and electronic effects of
the substituted groups have influences on the behaviors of the polymerization
process. All complexes were characterized using infrared and NMR spectros-
copies and elemental analysis. Molecular structures of complexes 1, 2 and 5
were further confirmed using single‐crystal X‐ray analysis.
Correspondence
Zi‐Jian Yao, School of Chemical and
Environmental Engineering, Shanghai
Institute of Technology, Shanghai 201418,
China.
Email: zjyao@sit.edu.cn
Funding information
Natural Science Foundation of Shanghai,
Grant/Award Number: 16ZR1435700;
National Natural Science Foundation of
China, Grant/Award Number: 21601125;
Shanghai Science and Technology Com-
mittee, Grant/Award Number:
16DZ2270100
KEYWORDS
catalysis, iridium(III) complex, polymerization, Schiff base, X‐ray analysis
1 | INTRODUCTION
such as good transparency, heat resistivity and high glass
transition temperature.[9]
Polynorbornenes (PNBs) have attracted considerable
attention during the past few years because of their supe-
rior physical and chemical properties, such as excellent
chemical stability and mechanical properties, high tensile
fracture value and so on.[1–5] There are three pathways for
norbornene polymerization: ring‐opening metathesis
polymerization (ROMP), cationic polymerization and
vinyl‐type polymerization (Scheme 1). The ROMP route
produces PNBs with double bonds retained in the poly-
mer backbone.[6] The polymers obtained via the cationic
or radical polymerization route often exhibit low molecu-
lar weights.[7] Different from the former two methods,
PNBs synthesized through the route of vinyl‐type addition
polymerization retain bicyclic motifs in the polymer
chain.[8] This type of PNB shows distinctive properties,
Many transition metal complexes have been explored to
date for the vinyl‐type polymerization of norbornene. After
the Ziegler–Natta catalyst was developed for olefin poly-
merization in the 1950s,[10] a series of metallocene catalysts
were synthesized including Cp2TiCl2,[11] Cp2Zr(CH3)3
[12]
and so on.[13–15] However, the industrial application of early
transition metallocene catalysts is limited because of their
sensitivity to air and moisture and the moderate catalytic
activity of these complexes for norbornene polymerization.
Thus late transition metal catalysts have attracted consider-
able interest in recent years. Up to now, there have been
several reports of catalysts containing late transition metal
centers for the olefin polymerization process, such as those
containing ruthenium,[16,17] nickel,[18–20] copper,[21–23]
rhodium[24,25] and so on.[26–30] These stable catalysts
Appl Organometal Chem. 2018;e4239.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4239

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YAO ET AL.
been widely used as ligands in coordination chemistry.
Herein, a series of half‐sandwich iridium complexes are
reported. These C,N‐chelate mononuclear half‐sandwich
iridium(III) complexes (1–5) with Schiff base ligands were
obtained in good yields through metal‐mediated C─H
bond activation. In comparison with previously reported
iridium‐based catalysts,[31] these catalysts with Schiff base
ligands containing bulky naphthalene units exhibit higher
catalytic activity for norbornene polymerization in the
presence of methylaluminoxane (MAO) as co‐catalyst.
The electronic and steric effects on their catalytic behavior
in norbornene polymerization are also discussed.
SCHEME
norbornene
1
Three different types of polymerization for
exhibited moderate to good catalytic activities. Although
the late transition metal catalysts have been explored
widely, there are only a few iridium complexes reported
for vinyl‐type polymerization of norbornene.[31]
Due to easy preparation, high yield and good stability
of Schiff bases, these types of organic compounds have
2 | RESULTS AND DISCUSSION
2.1 | Synthesis and Characterization of
Iridium Complexes
According to the classical method,[32–34] Schiff base
ligands L1–L5 were synthesized in good yields by conden-
sation reactions of 2‐naphthaldehyde with corresponding
aniline with a 1:1 molar ratio in methanol. A few drops
of acetic acid were added to the reaction mixture to pro-
mote the condensation. The identity of all ligands was
1
confirmed from H NMR spectra and elemental analysis.
The 1H NMR spectra of all ligands showed the character-
istic single peak in the range 8.50–8.70 ppm, which indi-
cates the formation of imine CH═N group.
With the ligands L1–L5 in hand, we next explored the
reactivity between these Schiff base ligands and iridium
precursor ([Cp*IrCl2]2). In a Schlenk flask, ligand and
SCHEME
complexes
2
Synthesis of ligands and C,N‐chelate Ir(III)
TABLE 1 Selected bond lengths (Å) and angles (°) for complexes 1, 2 and 5
Bond lengths and angles
1
2
5
Ir(1)–C(1)
2.055(12)
2.054(6)
2.026(7)
Ir(1)–N(1)
Ir(1)–centroida
2.103(8)
2.196
2.086(5)
2.201
2.103(5)
2.197
Ir(1)–Cl(1)
2.401(3)
1.292(13)
1.436(14)
1.468(14)
77.8(4)
2.4056(15)
1.305(8)
1.433(7)
1.453(9)
78.5(2)
2.4097(17)
1.292(9)
1.439(8)
1.429(9)
77.3(2)
N(1)–C(11)
N(1)–C(12)
C(1)–C(10)
C(1)–Ir(1)–N(1)
C(1)–Ir(1)–Cl(1)
N(1)–Ir(1)–Cl(1)
C(2)–C(1)–Ir(1)
C(10)–C(1)–Ir(1)
C(11)–C(10)–C(1)
N(1)–C(11)–C(10)
84.7(3)
85.44(18)
86.40(14)
130.1(5)
114.1(5)
113.2(5)
118.0(6)
86.71(19)
84.90(16)
128.9(5)
116.2(5)
112.8(6)
117.1(6)
88.2(2)
128.7(8)
128.7(8)
112.7(9)
117.9(9)
aCentroid of the five Cp* carbon atoms coordinated to the metal center.

YAO ET AL.
3 of 8
NaOAc were added to a suspension of [Cp*IrCl2]2 in
degassed methanol under a nitrogen atmosphere. Then
the mixture was stirred at 60 °C for 8 h. As shown in
Scheme 2, the air‐stable mononuclear iridium complexes
1–5 were obtained through C─H bond activation in good
isolated yields after column chromatography on silica gel.
The yields of these products were not changed largely for
ligands with electron‐donating or electron‐withdrawing
groups. All the complexes are slightly soluble in chloro-
form and dichloromethane but insoluble in nonpolar sol-
vents such as hexane and diethyl ether. The 1H NMR and
IR spectra of these C,N‐chelate iridium complexes are
revealing the coordination interaction between nitrogen
atom of the imine group and the metal center.[35]
To unambiguously elaborate the structures of these
iridium complexes, single‐crystal X‐ray diffraction mea-
surement of complexes 1, 2 and 5 was carried out. Suitable
single crystals were obtained by the slow diffusion of n‐
hexane into a saturated solution in dichloromethane.
Selected bond lengths and angles are given in Table 1,
and their crystallographic data are presented in Table 2.
As shown in Figure 1, these mononuclear complexes
exhibit similar solid‐state structures. Molecular structures
of complexes 1, 2 and 5 show that the geometry at the
metal center is that of a three‐legged piano stool, contain-
ing a Schiff base ligand, a Cp* ligand and a chloride
ligand. The Ir─CPh bond distances of 1, 2 and 5 are
2.055(12), 2.054(6) and 2.026(7) Å, respectively, which
are all located in the range of known values for these
bonds in analogous complexes.[36] The Ir─N bond lengths
of 1, 2 and 5 also compare well with similar bonds found
1
similar to each other. The H NMR spectra of all com-
plexes showed two sharp signals at approximately 1.50
and 8.50 ppm, which can be ascribed to the protons of
Cp* group and imine CH═N group, respectively. The
C═N bond stretching vibration of the ligands (1625–
1635 cm−1) in their IR spectra are shifted to lower fre-
quencies (ca 1615 cm−1) upon complex formation
TABLE 2 Crystal data and structure refinement for complexes 1, 2 and 5a
1
2
5
Formula
Formula weight
T (K)
C27H27ClNIr
593.14
C28H29ClIrNO
C27H26BrClNIr
623.17
672.05
193(2)
193(2)
203(2)
λ (Å)
0.71073
Monoclinic
P21/c
0.71073
Triclinic
P‐1
0.71073
Orthorhombic
P212121
8.3457(18)
12.714(3)
29.629(6)
90
Crystal system
Space group
a (Å)
7.7495(5)
15.9475(10)
18.5951(12)
90.00
8.3461(13)
11.2822(17)
13.037(2)
85.205(2)
75.532(2)
88.954(2)
1184.5(3)
2
b (Å)
c (Å)
α (°)
β (°)
96.8220(10)
90.00
90
γ (°)
V (Å3)
90
2281.8(3)
4
3144.0(12)
4
Z
ρcalcd (Mg m−3
)
1.727
1.747
1.420
μ (mm−1
)
5.982
5.770
5.614
F(0 0 0)
1160
612
1296
θ range (°)
1.103–26.998
15 966
1.619–27.550
8565
1.375–27.536
17 938
99.9
Reflections collected
Completeness to θ (%)
Data/restraints/param.
Goodness‐of‐fit on F2
98.9
98.6
9759 / 55 / 551
1.077
5377 / 0 / 295
1.116
7209 / 0 / 285
0.910
Final R indices
[I > 2σ(I)a]
R1 = 0.0317
wR1 = 0.0711
R1 = 0.0315
wR1 = 0.0972
R1 = 0.0279
wR1 = 0.0697
2
2
aR1 = ∑||F0| − |Fc||/∑|F0| (based on reflections with F0 > 2σF2). wR2 = [∑[w(F0 − Fc2)2]/∑[w(F02)2]]1/2; w = 1/[σ2(F02) + (0.095P)2]; P = [max(F02, 0) +
2
2Fc2]/3 (also with F0 > 2σF2).

4 of 8
YAO ET AL.
FIGURE 1 Molecular structures of 1, 2 and 5 with 30% probability ellipsoids
in reported analogous complexes.[37] The Ir(1)–C(1)–
C(10)–C(11)–N(1) five‐membered ring of 1 is almost pla-
nar with a dihedral angle of 3.02° between planes of
N(1)–Ir(1)–C(1) and C(1)–C(10)–C(11)–N(1). The sum of
the angles formed by the five‐membered ring of 539.7°
also confirmed the planarity of the cyclometallated moi-
ety. The molecular structures of 2 and 5 are very similar
to that of 1, including Ir(1)─C(1), Ir(1)─N(1) and Ir(1)─
centroid bond lengths, and the angles of cyclometallated
rings. We failed to obtain suitable single crystals of the
other iridium complexes for X‐ray analysis after efforts
were made.
Chlorobenzene was chosen as the reaction solvent for
the polymerization process because this polar solvent
was able to improve the catalytic performances in
vinyl‐type polymerization of norbornene. Experimental
results are summarized in Table 3. No catalytic activity
was observed for 1 in the absence of MAO (Table 3,
entry 1). Thus, the MAO co‐catalyst is essential for the
polymerization process. For the complex 1/MAO cata-
lytic system, the best molar ratio of Al/Ir was 2500
(Table 3, entry 6). The catalytic activity increased from
0.86 × 106 to 2.06 × 106 g PNB (mol Ir)−1 h−1 with an
increase of the Al/Ir molar ratio from 500 to 2500
(Table 3, entries 2–6). However, the catalytic activity
slightly decreased when the Al/Ir ratio was increased to
3000 (Table 3, entry 7). The influence of the reaction
temperature on the catalytic activity and Mv also
explored. For 1, the highest catalytic activity, up to
2.40 g × 106 g PNB (mol Ir)−1 h–1, was obtained at
60 °C at the optimal Al/Ir molar ratio (Table 3, entry
8). At a higher temperature of 90 °C, a decrease of cata-
lytic activity was obtained, probably because of the
decomposition or instability of the active species formed
by the catalytic precursors (Table 3, entry 9).[38] Other
co‐catalysts such as Me3Al, Et2AlCl and B(C6F5)3 were
also used in the reaction; however, no positive results
were obtained (Table 3, entries 8 and 10–12). For 3, the
highest catalytic activity of up to 2.72 × 106 g PNB
2.2 | Norbornene Polymerization
Based on previous work,[29,37] we explored the catalytic
behavior of these hemi‐labile iridium complexes.
Norbornene polymerization was carried out in the
presence of MAO as
a co‐catalyst (Scheme 3).
SCHEME
3
Vinyl‐type polymerization catalyzed by Ir(III)
complexes

YAO ET AL.
5 of 8
TABLE 3 Polymerization of norbornene catalyzed by complexes 1–5 activated by MAOa
o
c
entry
Catalyst
Al/Ni
T/ C
Yield/g
Activityb
Mv
Mv (106 g mol−1 b
Entry
Catalyst
1
Al/Ir
T (°C)
Yield (g)
Activity (106 g PNB (mol Ir)−1 h−1
)
)
1
0
30
0
—
—
2
1
1
1
1
1
1
1
1
1
1
1
2
3
4
5
500
30
30
30
30
30
30
60
90
60
60
60
60
60
60
60
0.43
0.49
0.60
0.85
1.03
0.97
1.20
0.65
0.23
0.13
0.08
1.03
1.36
1.24
1.27
0.86
0.98
1.20
1.70
2.06
1.94
2.40
1.30
0.46
0.26
0.16
2.06
2.72
2.48
2.54
1.23
1.37
1.61
1.89
1.95
1.80
2.17
1.88
1.02c
1.22d
0.90e
2.11
2.26
2.05
2.13
3
1000
1500
2000
2500
3000
2500
2500
2500
2500
2500
2500
2500
2500
2500
4
5
6
7
8
9
10
11
12
13
14
15
16
aPolymerization conditions: [norbornene] = 1.80 g; Vtotal = 10 ml; catalyst: iridium complexes 1–5, 1 μmol; reaction time: 30 min; solvent: chlorobenzene.
bMeasured in chlorobenzene at 25 °C using the Mark–Houwink coefficients.
cMe3Alused as co‐catalyst.
dEt2AlCl used as co‐catalyst.
eB(C6F5)3 used as co‐catalyst.
(mol Ir)−1 h–1 was observed under the optimal condi-
tions (Table 3, entry 14), which showed higher catalytic
activity (almost ten times) than the iridium complexes
with hydroxyindanimine ligands.[31] This very large dif-
ference also confirmed that suitable ligands can enhance
catalytic activity significantly. Although the catalytic
activities of the iridium complexes are of the same order
of magnitude, different activities were exhibited by com-
plexes 1–5. For example, 4 exhibited higher catalytic
activity than 1 and 2 (Table 3, entries 8, 13 and 15),
because the ortho‐substituted groups bonded to the
aromatic ring could inhibit the β‐H elimination in
the polymerization process.[38,39] In addition, due to
an electron‐deficient metal center being convenient for
olefin coordination and insertion, transition metal com-
plexes with electron‐withdrawing substituents bonded
to the ligands often show higher catalytic activity.[38]
Consequently, 3 with the 4‐trifluoromethyl group exhib-
ited higher catalytic activity than 1, 2, 4 and 5 (Table 3,
entries 8 and 13–16). The highest catalytic activity of
these iridium complexes is comparable with that
of reported iridium complexes,[37] but lower than
that of nickel and copper catalysts.[18,40,41]
The distinctive microstructure of the obtained PNBs
was confirmed using IR and NMR spectroscopies. All
polymers showed analogous IR spectra in which peaks
were observed at approximately 942 cm–1. These absorp-
tion peaks were identified to the ring system of
bicyclo[2.2.1]heptane indicating vinyl‐type polymeriza-
tion.[42] No absorptions were observed at 735 and
960 cm–1, which means that there are no ROMP struc-
tures of the PNBs. No resonance was observed at about
1
5.1 and 5.3 ppm in the H NMR spectrum of the PNB
assigned to the cis and trans forms of the double bond,
which generally indicates the presence of the ROMP
structure.[43–45] Meanwhile, the 1H NMR spectra also
proved that the polymers are vinyl‐type addition products.
1
The H NMR spectra of the PNBs showed four groups of
signals located in the range 1.0–3.0 ppm. But there are
no traces of the double bond at approximately 5.1 and
5.3 ppm in the 1H NMR spectra, which is typical for
ROMP PNB.[46,47] The 13C NMR spectrum shows the main
four groups of resonances at (51.3, 49.4, 48.8, 46.8, 44.5),
38.5, (37.8, 37.4, 34.7) and (30.5, 28.7) ppm, attributed to
carbons 2 and 3; carbons 1 and 4; carbon 7; and carbons
5 and 6, respectively. PNBs are soluble at room

6 of 8
YAO ET AL.
temperature in chlorobenzene and cyclohexane, which
indicates low stereoregularity.[29]
J = 7.5 Hz, Naph–H, 1H), 7.58–7.50 (m, Naph–H, 2H),
7.42 (t, J = 7.7 Hz, Ph–H, 2H), 7.29–7.24 (m, Ph, 3H). Ele-
mental analysis calcd for C17H13N (%): C, 88.28; H, 5.67;
N, 6.06; found (%): C, 88.32; H, 5.72; N, 5.96.
3 | CONCLUSIONS
1
L2: yellow solid; 1.15 g, 88%. H NMR (500 MHz,
CDCl3, δ, ppm): 8.64 (s, CH═N, 1H), 8.21–8.14 (m,
Naph–H, 2H), 7.92 (t, J = 8.5 Hz, Naph–H, 2H), 7.88 (d,
J = 8.0 Hz, Naph–H, 1H), 7.58–7.49 (m, Naph–H, 2H),
7.30 (d, J = 8.6 Hz, Ph–H, 2H), 6.96 (d, J = 8.7 Hz, Ph–
H, 2H), 3.85 (s, OCH3, 3H). Elemental analysis calcd for
C18H15NO (%): C, 82.73; H, 5.79; N, 5.36; found (%): C,
82.55; H, 5.70; N, 5.54.
In summary, a series of mononuclear half‐sandwich
iridium(III) complexes with 2‐naphthaldehyde‐based
ligands were synthesized through C─H bond activation
in good yields. Complexes 1, 2 and 5 were characterized
using single‐crystal X‐ray diffraction. Preliminary experi-
mental results demonstrate that these iridium complexes
exhibited high catalytic activity (2.72 × 106 g PNB (mol
Ir)–1 h–1) for norbornene polymerization in the presence
of MAO as a co‐catalyst. Both the electronic effect and
the steric hindrance of the substituents have influences
on polymerization behaviors. Further exploration of the
catalytic activity of these iridium complexes for catalytic
hydrogenation reactions is currently underway in our
laboratory.
1
L3: yellow solid; 1.27 g, 85%. H NMR (500 MHz,
CDCl3, δ, ppm): 8.58 (s, CH═N, 1H), 8.22 (s, Naph–H,
1H), 8.16 (d, J = 8.5 Hz, Naph–H, 1H), 7.97–7.92 (m,
Naph–H, 2H), 7.89 (d, J = 7.8 Hz, Naph–H, 1H), 7.67 (d,
J = 8.2 Hz, Naph–H, 2H), 7.61–7.53 (m, Ph–H, 2H), 7.30
(d, J = 8.1 Hz, Ph–H, 2H). 13C NMR (125 MHz, CDCl3,
δ, ppm): 161.95, 155.26, 135.29, 133.48, 133.06, 133.93,
128.90 (d, J = 3.6 Hz), 128.01, 127.93, 126.81, 126.43 (d, J
= 3.0 Hz), 123.80, 121.06. Elemental analysis calcd for
C18H12F3N (%): C, 72.24; H, 4.04; N, 4.68; found (%): C,
72.32; H, 4.05; N, 4.79.
4 | EXPERIMENTAL
4.1 | General
1
L4: yellow solid; 1.10 g, 90%. H NMR (500 MHz,
CDCl3, δ, ppm): 8.53 (s, CH═N, 1H), 8.24–8.18 (m,
Naph–H, 2H), 7.93 (t, J = 8.5 Hz, Naph–H, 2H), 7.89 (d,
J = 7.2 Hz, Naph–H, 1H), 7.59–7.50 (m, Naph–H, 2H),
7.23 (d, J = 8.8 Hz, Ph–H, 2H), 7.15 (t, J = 7.1 Hz, Ph–
H, 1H), 6.99 (d, J = 7.6 Hz, Ph–H, 1H), 2.41 (s, CH3,
3H). Elemental analysis calcd for C18H15N (%): C, 88.13;
H, 6.16; N, 5.71; found (%): C, 88.20; H, 6.22; N, 5.65.
L5: yellow solid; 1.35 g, 87%.1H NMR (500 MHz,
CDCl3, δ, ppm): 8.57 (s, CH═N, 1H), 8.20 (s, Naph–H,
1H), 8.14 (d, J = 8.5 Hz, Naph–H, 1H), 7.93 (t, J =
8.3 Hz, Naph–H, 2H), 7.89 (d, J = 7.8 Hz, Naph–H, 1H),
7.59–7.53 (m, Naph–H, 2H), 7.41 (s, Ph–H, 1H), 7.38 (d,
J = 8.0 Hz, Ph–H, 1H), 7.29 (t, J = 7.9 Hz, Ph–H, 1H),
7.19 (d, J = 7.8 Hz, Ph–H, 1H). 13C NMR (125 MHz,
CDCl3, δ, ppm): 161.33, 153.54, 135.22, 133.57, 133.07,
131.75, 130.50, 128.89, 128.80, 128.00, 127.82, 126.75,
123.81, 122.85, 120.06. Elemental analysis calcd for
C17H12BrN (%): C, 65.83; H, 3.90; N, 4.52; found (%): C,
65.90; H, 3.94; N, 4.47.
All the reactions of air‐ or moisture‐sensitive compounds
were performed under an atmosphere of nitrogen using
standard Schlenk techniques. All chemicals were pur-
chased from Sigma‐Aldrich. Norbornene was purified by
stirring it over calcium hydride at 60 °C for one day and
then distilled. Chlorobenzene was dried and distilled from
calcium hydride. Other chemicals were used without fur-
ther purification. 1H NMR (500 MHz) and 13C NMR
(125 MHz) spectra were measured with a Bruker DMX‐
500 spectrometer. IR (KBr) spectra were measured with
a Nicolet FT‐IR spectrophotometer. Elemental analysis
was performed with an Elementar Vario EL III analyzer.
4.2 | Synthesis of Schiff Base Ligands L1–
L5
The Schiff base ligands L1–L5 were synthesized by a clas-
sical method. 2‐Naphthaldehyde (0.78 g, 5.0 mmol) and
aniline (5.0 mmol) were added to CH3CH2OH and heated
to reflux for 3 h in the presence of a catalytic amount of
CH3COOH. The resulting mixture was concentrated
under reduced pressure and stored at −10 °C overnight.
Further purification was achieved by filtration and wash-
ing three times with cold CH3OH. The obtained solid was
dried under vacuum.
4.3 | Synthesis of Mononuclear Complexes
1–5
In a 100 ml Schlenk flask, a mixture of [Cp*IrCl2]2
(0.1 mmol, 80 mg), NaOAc (0.6 mmol) and corresponding
ligands L1–L5 (0.2 mmol) was stirred at 60 °C in 15 ml of
methanol for 8 h under a nitrogen atmosphere. The mix-
ture was filtered and evaporated to give the crude prod-
ucts which were further purified by silica gel column
L1: yellow solid; 1.07 g, 93%. 1H NMR (500 MHz,
CDCl3, δ, ppm): 8.61 (s, CH═N, 1H), 8.23–8.13 (m,
Naph–H, 2H), 7.92 (t, J = 7.5 Hz, Naph–H, 2H), 7.88 (d,

YAO ET AL.
7 of 8
chromatography (PE:EA
cyclometallated mononuclear complexes in the yields of
73–83%.
=
10:1) to afford pure
chlorobenzene (3 ml) and fresh chlorobenzene (6 ml)
were added to a special polymerization bottle (50 ml)
under a nitrogen atmosphere. After stirring at 30 °C for
10 min, a certain amount of MAO was added into the
polymerization system via a syringe and the reaction
was started. After 30 min, acidic ethanol (Vethanol:Vconc.
1
Complex 1: red solid, 81% yield. H NMR (500 MHz,
CDCl3, δ, ppm): 8.48 (s, CH═N, 1H), 8.14 (s, Naph–H,
2H), 7.80–7.75 (m, Naph–H, 2H), 7.64 (d, J = 7.6 Hz,
Naph–H, 2H), 7.46–7.43 (m, Ph, 3H), 7.33–7.31 (m, Ph–
H, 2H), 1.50 (s, Cp*–H, 15H). IR (KBr, disk, ν, cm−1):
3050, 2917, 1612, 1600, 744, 697. Elemental analysis calcd
for C27H27ClNIr (%): C, 54.67; H, 4.59; N, 2.36; found (%):
C, 54.63; H, 4.57; N, 2.38.
= 20:1) was added to terminate the reaction. The
HCl
PNB was isolated by filtration, washed with ethanol and
dried at 80 °C for 24 h under vacuum. For all polymeriza-
tion procedures, the total reaction volume was 10.0 ml
(achieved by varying the amount of chlorobenzene when
necessary). The viscosity‐average molar masses (Mv) of
the norbornene polymers were obtained in chlorobenzene
at 25 °C using Mark–Houwink coefficients.
1
Complex 2: red solid, 76% yield. H NMR (500 MHz,
CDCl3, δ, ppm): 8.43 (s, CH═N, 1H), 8.12 (d, J =
13.0 Hz, Naph–H, 2H), 7.78–7.74 (m, Naph–H, 2H), 7.61
(d, J = 9.0 Hz, Naph–H, 2H), 7.46 (t, J = 7.5 Hz, Ph–H,
1H), 7.31 (t, J = 7.0 Hz, Ph–H, 1H), 6.95 (d, J = 8.5 Hz,
Ph–H, 2H), 3.87 (s, OCH3, 3H), 1.51 (s, Cp*–H, 15H). IR
(KBr, disk, ν, cm−1): 3045, 2916, 1615, 1596, 1265, 846,
753. Elemental analysis calcd for C28H29ClIrNO (%): C,
53.96; H, 4.69; N, 2.25; found (%): C, 53.88; H, 4.72; N,
2.28.
4.5 | X‐ray Crystallography
Diffraction data for 1, 2 and 5 were collected using a
Bruker Smart APEX CCD diffractometer with graphite‐
monochromated Mo Ka radiation (λ = 0.71073 Å). All
the data were collected at room temperature, and the
structures were solved by direct methods and subse-
quently refined on F2 by using full‐matrix least‐squares
techniques (SHELXL).[48] SADABS[49] absorption correc-
tions were applied to the data, all non‐hydrogen atoms
were refined anisotropically and hydrogen atoms were
located at calculated positions. All calculations were per-
formed using the Bruker program Smart.
1
Complex 3: red solid, 78% yield. H NMR (500 MHz,
CDCl3, δ, ppm): 8.50 (s, CH═N, 1H), 8.19 (d, J =
16.5 Hz, Naph–H, 2H), 7.80–7.76 (m, Naph–H, 4H),
7.80–7.76 (m, Ph, 2H), 7.50 (m, J = 7.5 Hz, Ph, 1H), 7.34
(t, J = 7.5 Hz, Ph–H, 1H), 1.51 (s, Cp*–H, 15H). IR (KBr,
disk, ν, cm−1): 3055, 2916, 1612, 1587, 1322, 835, 750. Ele-
mental analysis calcd for C28H26F3ClIrN (%): C, 50.86; H,
3.96; N, 2.12; found (%): C, 50.81; H, 3.92; N, 2.22.
1
Complex 4: red solid, 73% yield. H NMR (500 MHz,
ACKNOWLEDGMENTS
CDCl3, δ, ppm): 8.41 (s, CH═N, 1H), 8.14 (d, J = 3.0 Hz,
Naph–H, 2H), 7.80 (q, J = 8.5 Hz, Naph–H, 2H), 7.47 (d,
J = 7.0 Hz, Ph, 1H), 7.30–7.27 (m, Ph, 4H), 7.20 (d, J =
7.5 Hz, Ph–H, 1H), 2.31 (s, CH3, 3H), 1.51 (s, Cp*–H,
15H). IR (KBr, disk, ν, cm−1): 3041, 2909, 1614, 1588,
764, 748. Elemental analysis calcd for C28H29ClIrN (%):
C, 55.38; H, 4.81; N, 2.31; found (%): C, 55.35; H, 4.82;
N, 2.25.
This work was supported by the National Natural Science
Foundation of China (no. 21601125), the Chenguang
Scholar of Shanghai Municipal Education Commission
(no. 16CG64), the Natural Science Foundation of Shang-
hai (no. 16ZR1435700), Shanghai Science and Technology
Committee (16DZ2270100), the Shuguang Scholar of
Shanghai Municipal Education Commission (no.
16SG49), the Shanghai Municipal Education Commission
(Plateau Discipline Construction Program) and Local
Institutions Capacity Training of Shanghai Science and
Technology Commission (no. 15120503600).
1
Complex 5: red solid, 83% yield. H NMR (500 MHz,
CDCl3, δ, ppm): 8.48 (s, CH═N, 1H), 8.15 (d, J = 5.5 Hz,
Naph–H, 2H), 7.86 (s, Ph–H, 1H), 7.79 (t, J = 9.0 Hz,
Naph–H, 2H), 7.61 (d, J = 7.5 Hz, Ph–H, 1H), 7.48 (t, J
= 8.0 Hz, Naph–H, 2H), 7.33 (t, J = 8.0 Hz, Ph–H, 2H),
1.53 (s, Cp*–H, 15H). IR (KBr, disk, ν, cm−1): 3048,
2913, 1617, 1558, 747, 697. Elemental analysis calcd for
C27H26BrClNIr (%): C, 48.25; H, 3.90; N, 2.08; found (%):
C, 48.35; H, 3.82; N, 2.06.
ORCID
Zi‐Jian Yao http://orcid.org/0000-0003-1833-1142
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How to cite this article: Yao Z‐J, Li P, Li K, Deng
W. Synthesis, structure and catalytic
polymerization activity of half‐sandwich
cyclometallated iridium complexes. Appl
Organometal Chem. 2018;e4239. https://doi.org/
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