Cu(II) complexes with anilido-imine ligands: Synthesis, characterization and catalysis on reverse atom transfer radical polymerization of styrene

Article abstract of DOI:10.1016/j.poly.2017.01.018

Several copper(II) complexes bearing bidentate anilido-imine ligands [(Ar′N[dbnd]CHC₆H₄-NAr)Cu]₂(μ-Cl)₂(Ar?=?Ar′?=?2,6-Me₂C₆H₃(1a); Ar?=?Ar′?=?2,6-Et₂C₆H

Full text of DOI:10.1016/j.poly.2017.01.018

Accepted Manuscript
Cu(II) Complexes with Anilido-Imine ligands: Synthesis, Characterization and
Catalysis on Reverse Atom Transfer Radical Polymerization of Styrene
Zhiqiang Hao, Anjie Ma, Bin Xu, Wei Gao, Ying Mu
PII:
S0277-5387(17)30031-1
DOI:
http://dx.doi.org/10.1016/j.poly.2017.01.018
POLY 12422
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
12 October 2016
11 January 2017
11 January 2017
Please cite this article as: Z. Hao, A. Ma, B. Xu, W. Gao, Y. Mu, Cu(II) Complexes with Anilido-Imine ligands:
Synthesis, Characterization and Catalysis on Reverse Atom Transfer Radical Polymerization of Styrene,
Polyhedron (2017), doi: http://dx.doi.org/10.1016/j.poly.2017.01.018
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Cu(II) Complexes with Anilido-Imine ligands: Synthesis,
Characterization and Catalysis on Reverse Atom Transfer
Radical Polymerization of Styrene
Zhiqiang Hao, Anjie Ma, Bin Xu, Wei Gao,* and Ying Mu
†College of Chemistry, Jilin University, Changchun 130012, China.
To whom correspondence should be addressed. E-mail: gw@jlu.edu.cn
Fax:+86-431- 8849055
Abstract
Several copper(II) complexes bearing bidentate anilido-imine ligands
[(Ar′N=CHC6H4-NAr)Cu]2(µ-Cl)2 (Ar = Ar′ = 2,6-Me2C6H3 (1a); Ar = Ar′ =
2,6-Et2C6H3 (1b); Ar = 3,5-(CF3)2C6H3, Ar′ = 2,6-iPr2C6H3 (1d); Ar = p-OMeC6H4, Ar′
= 2,6-iPr2C6H3 (1e)), (Ar′N=CHC6H4-NAr)CuCl (Ar = Ar′ = 2,6-iPr2C6H3 (1c)), and
that
bearing
tridentate
quinolinyl
anilido-imine
ligand
(2,6-iPr2C6H3N=CHC6H4-NAr)CuCl (Ar = 8-quinolinyl (1f)) were synthesized via
n
reactions of the corresponding ligands with BuLi and subsequent in-situ addition of
CuCl2. The X-ray diffraction analysis revealed that 1a and 1d are dinuclear, while 1f
with N,N,N-tridentate ligand is in monomeric form. In the presence of
2,2′-azobisisobutyronitrile (AIBN), these well-defined complexes showed moderate to
high activities in reverse ATRP of styrene. High conversions up to 86.5% were
obtained and polymers with controllable molecular weight and relatively narrow
polydispersity were produced.

Keywords: Copper complexes; Reverse-ATRP; Anilido-imine ligands
1. Introduction
Atom transfer radical polymerization (ATRP), discovered independently by
Sawamoto and Matyjaszewski in 1995, have received considerable attention in the
controllable polymerization area due to its broad range of applicable monomers, high
initiation efficiency, precise control of molecular weights, and mild reaction
conditions.[1] In ATRP, some transition metal complexes were used to control the
radical concentration at very low levels, thereby reduce the impact of irreversible
bimolecular terminations through the establishment of a shuttle between the active
radical chain and a dormant chain that is capped by a halogen atom.[1, 2] In this
process, a lot of alkyl halide were used as the resource of radical. In order to minimize
the amount of alkyl halide in the polymerization, the reverse ATRP using the
conventional radical generator and metal complexes were developed.[3] Various
complexes based on Cu,[4] Fe,[5] Ni,[6] and Ru[7] were widely investigated and used
as catalyst in ATRP and reverse ATRP, in which the copper complexes have received
special attention due to their high activities. On the other hand, it is well accepted that
the ligands in the catalysis systems can not only solubilize the transition-metal
complexes in the organic media but also adjust the redox potential of the metal center
for appropriate reactivity and dynamics for the atom transfer.[5a] In literatures,
various ligands are used to support the metal complexes, in which the nitrogen ligands
were mainly used for copper- and iron-mediate ATRP, while the phosphorus-based
ligands are mostly used for other transition metals such as rhenium, ruthenium,

rhodium, nickel, and palladium. The nitrogen-based ligands work particularly well for
copper-mediated ATRP, and it is well established that the coordination chemistry
shows great influence on the catalysis behavior of the complexes. For example, the
activity of copper complexes based on N-based ligands in ATRP decreases with the
number of coordinating sites as well as the number of linking carbon- atoms.[1e]
Recently we focused on the anilido-imine ligands, which features easy preparation
and fine-tuning of the steric and electronic properties at the metal centers. The
rare-earth-metal,[13] aluminum and zinc,[14] nickle,[15] and chromium[16]
complexes based on the anilido-imine ligands were proved to show moderate to high
activities in ε-caprolactone (lactide) ring-opening polymerization, norbornene
polymerization, and ethylene polymerization respectively. More recently, the iron(II)
complexes supported by these ligands have been demonstrated to be active for the
atom transfer radical polymerization (ATRP) of MMA. [17] Although, some copper
complexes bearing anilido-imine ligands have been reported,[18] their structure
features and catalysis performance were less focused. In extending this research, the
current study reports on the synthesis and full characterization of Cu(II) complexes
bearing anilido-imine ligands. The catalytic behaviors of these Cu(II) complexes
toward reverse ATRP polymerization of styrene are also presented.
2. Experimental
2.1. General procedures and methods
All manipulations involving air and moisture-sensitive compounds were carried
out under an atmosphere of dried and purified nitrogen using standard Schlenk or dry
box techniques. Toluene and hexane were dried over sodium/benzophenone and

distilled under nitrogen prior to use. Elemental analyses were performed on a Varian
12EL microanalyzer. NMR spectra were recorded on a Bruker-400 NMR
spectrometer at room temperature in CDCl3. The molecular weight and molecular
weight distribution of the polymers were measured on a TOSOH HLC 8220 GPC at
40 °C using THF as eluent at a flow rate of 1.0 mL/min. Polystyrene standards were
used for calibrations. The ligands LaH, LbH, LcH, and LfH were synthesized according
to the literature.[17]
2.2 ligands preparation and characterization
2.2.1. Preparation of LdH
n
An BuLi solution of hexane (8.3 mL, 16.5 mmol) was added to a THF (30 mL)
solution of 3,5-bis(trifluoromethyl)aniline (3.44 g, 15 mmol) at –40 ºC, and the
mixture was allowed to warm to room temperature overnight and then transferred into
a THF (20 mL) solution of ortho-C6H4F(CH=NC6H3iPr2-2,6) (2.83 g, 10 mmol) at
room temperature. After stirring for 24 h at 50 ºC, the reaction mixture was quenched
with 20 mL of H2O, The organic solution was dried with anhydrous MgSO4 and the
solvent was removed in vacuum to give a residue. Treatment of the residue with
column chromatography on silica gel eluting with petroleum ether affords the LdH as
1
yellow powder. Yield 2.07 g (42%). H NMR (400 MHz, CDCl3, 25 ºC): δ 1.18 (d,
12H, CH(CH3)2), 2.97–3.03 (m, 2H, CH(CH3)2), 7.01 (t, 1H, Ar-H), 7.16–7.23 (m, 3H,
Ar-H), 7.41–7.50 (m, 4H, Ar-H), 7.66 (s, 2H, Ar-H), 8.33 (s, 1H, Ar-CH=N), 11.56 (s,
1H, Ar-NH). 13C NMR (100 MHz, CDCl3, 25 ºC): δ 23.56 (s, 4C, ArC(CH3)2), 28.20
(s, 2C, ArC(CH3)2), 113.66, 115.32, 119.60, 121.93, 123.35, 124.64, 125.05, 132.30,

132.61, 132.94, 133.27, 135.13, 138.18, 143.07, 144.05, 147.82, 165.68 (s, 1C, CH=N)
ppm.
2.2.2. Preparation of LeH
n
An BuLi solution of hexane (8.3 mL, 16.5 mmol ) was added to a THF (30 mL)
solution of 4-methoxyaniline (1.85 g, 15.0 mmol) at –30 ºC, and the mixture was
allowed to warm to room temperature overnight. The resulted lithium-salt solution
i
was slowly transferred into a solution of ortho-C6H4F(CH=NC6H3 Pr2-2,6) (2.83 g,
10.0 mmol) in 20 mL of THF at room temperature. After stirring for 12 h at 50 ºC, the
reaction was quenched with 15 mL of water, extracted with ethyl acetate, and
evaporated to dryness in vacuum affording a yellow solid. The solid was crystallized
from methanol to give LeH as yellow crystals. Yield 2.75 g (71.2%). NMR (400 MHz,
CDCl3, 25 ºC): δ 1.19 (d, 12H, CH(CH3)2), 3.02–3.09 (m, 2H, CH(CH3)2), 3.81 (s, 3H,
Ar-OMe), 6.76 (t, 1H, Ar-H), 6.92 (d, 2H, Ar-H), 7.10–7.27 (m, 7H, Ar-H), 7.34 (d,
1H, Ar-H), 8.30 (s, 1H, Ar-CH=N), 10.92 (s, 1H, Ar-NH). 13C NMR (100 MHz,
CDCl3, 25 ºC): δ 23.57 (s, 4C, ArC(CH3)2), 28.11 (s, 2C, ArC(CH3)2), 55.54 (s, 1C,
Ar-OCH3), 112.15, 114.64, 116.16, 117.28, 123.11, 124.45, 125.29, 132.07, 133.69,
134.89, 138.19, 147.92, 148.61, 156.41, 165.49 (s, 1C, CH=N) ppm.
2.3. Preparation and characterization of copper complexes
2.3.1 Preparation of complex 1a
n
A hexane solution of BuLi (2.00 M in hexane, 0.50 mL, 1.0 mmol) was added
dropwise to a solution of the free ligand LaH (0.33 g, 1.0 mmol) in 20 mL of THF at
−78 °C. After stirred for 1 h, the reaction mixture was gradually warmed to –40 ºC

and then CuCl2 (0.14 g, 1.0 mmol) was added in one portion. The reaction mixture
was allowed to warm to room temperature and stirred overnight. Evaporation of the
solvent and crystallization of the residues with toluene/hexane mixed solvent afford
the copper complex 1a as brown powder (0.63 g, 73.7%). Single crystals for X-ray
analysis were grown from dichloromethane/hexane at –30 ºC within several days as
brown blocks. Anal. Calcd for C46H46Cl2N4Cu2 (%): C, 64.78; H, 5.44; N, 6.57 Found:
C, 64.65; H, 5.58; N, 6.62. IR(KBr): ν (cm–1) 3123s, 3009m, 1609m, 1578m, 1460m,
1399vs, 1227w, 1163s, 1087w, 1037w, 772m, 743m, 670w.
2.3.2 Preparation of complex 1b
Complex 1b was prepared in a similar procedure to that for preparation of 1a.
n
Treatment of LbH (0.39 g, 1.0 mmol) in 25 mL THF with BuLi (2.0 M in hexane,
0.50 mL, 1.0 mmol) and then in situ addition of CuCl2 (0.14 g, 1.0 mmol) yield 1b in
a 74.6% yield (0.72 g). Anal. Calcd for C54H62Cl2N4Cu2: C, 67.20; H, 6.48; N, 5.81.
Found: C, 67.33; H, 6.58; N, 5.69. IR(KBr): ν (cm–1) 3130m, 2959s, 2834m, 1733s,
1460s, 1378s, 1243w, 1173m, 1071w, 837m, 814m, 744w, 619w.
2.3.3 Preparation of complex 1c
Following the same procedure described for 1a, treatment of LcH (0.44 g, 1.0 mmol)
with nBuLi (2.0 M in hexane, 0.50 mL, 1.0 mmol) and then in situ addition of CuCl2
(0.14 g, 1.0 mmol) afford complex 1c in a 76.7% yield (0.83 g). Anal. Calcd for
C31H39ClN2Cu:C, 69.12; H, 7.30; N, 5.20. Found: C, 68.94; H, 7.42; N, 5.03. IR(KBr):
ν (cm–1) 3158m, 2979s, 2827s, 2737w, 1734s, 1462m, 1416vs, 1249w, 1174m, 992m,
832m, 734w, 612w.

2.3.3 Preparation of complex 1d
Following the same procedure described for 1a, treatment of LdH (0.49 g, 1.0 mmol)
with nBuLi (2.0 M in hexane, 0.50 mL, 1.0 mmol) and then in situ addition of CuCl2
(0.14 g, 1.0 mmol) afford 1d as brown powder (0.86 g, 72.8%). Single crystals for
X-ray analysis were grown from hexane at –30 ºC within several days as brown
blocks. Anal. Calcd for C54H50Cl2F12N4Cu2: C, 54.92; H, 4.27; N, 4.74. Found: C,
54.80; H, 4.37; N, 4.59. IR(KBr): ν (cm–1) 3145m, 2971s, 2819m, 1728s, 1454m,
1401vs, 1264m, 1166m, 1006w, 969m, 809m, 748w.
2.3.3 Preparation of complex 1e
Following the same procedure described for 1a, treatment of LeH (0.39 g, 1.0 mmol)
with nBuLi (2.0 M in hexane, 0.50 mL, 1.0 mmol) and then in situ addition of CuCl2
(0.14 g, 1.0 mmol) afford 1e as brown powder (0.71 g, 73.4%). Anal. Calcd for
C52H58Cl2Cu2N4O2: C, 64.45; H, 6.03; N, 5.78 Found: C, 64.60; H, 5.87; N, 5.92.
IR(KBr): ν (cm–1) 3138m, 2953s, 2815m, 1739s, 1462m, 1399s, 1260m, 1143m,
1059w, 962m, 837m, 664w.
2.3.3 Preparation of complex 1f
Following the same procedure described for 1a, treatment of LfH (0.41 g, 1.0 mmol)
with nBuLi (2.0 M in hexane, 0.50 mL, 1.0 mmol) and then in situ addition of CuCl2
(0.14 g, 1.0 mmol) afford 1f as purple powder (0.40 g, 78.9%). Red crystals for X-ray
analysis were grew from the mixture of toluene and dichloromethane/hexane at –30
ºC within several days. Anal. Calcd for C28H28ClN3Cu: C, 66.52; H, 5.58; N, 8.31.
Found: C, 66.68; H, 5.44; N, 8.42. IR(KBr): ν (cm–1) 3131m, 2940w, 1590m, 1468s,

1395vs, 1340m, 1160s, 1089w, 832w, 740m, 657w.
2.4. Polymerizations
In the glovebox, a Schlenk tube was loaded with the catalyst and then corresponding
equivalent of styrene, AIBN and toluene were added in sequence. The tube was then
immersed in an oil at the desired temperature to polymerize under stirring. After the
desired time, the reaction was poured into 30 mL of cold ethanol, filtered, washed
with plenty of ethanol, and dried under vacuum.
2.5. Crystal structure determination
The crystals were mounted on a glass fiber using the oil drop. Data obtained with
the ω−2θ scan mode were collected on a Bruker SMART 1000 CCD diffractometer
with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å). The structures were
solved by direct methods, and refined with full-matrix least squares on F2. All
non-hydrogen atoms were refined anisotropically and hydrogen atoms were
introduced in calculated positions with the displacement factors of the host carbon
atoms. All calculations were performed using the SHELXTL crystallographic
software packages. [19]
3. Results and discussion
3.1. Synthesis and characterization of the Cu(II) complexes
The ligands LaH, LbH, LcH, and LfH were synthesized according to the literature and
identified with NMR spectroscopy and elemental analyses. LdH and LeH were
synthesized in
a
similar procedure via nucleophilic substitution of
ortho-C6H4F(CH=NAr) with the corresponding aniline lithium salt. The NMR spectra

LdH and LeH showed the characteristic resonance at 11.56 ppm and 10.92 ppm
respectively assignable to the amine hydrogen atoms which attached to the imino
nitrogen atom by a hydrogen bond. The diagnostic resonances around 165.6 ppm
assignable to the carbon atoms in imino fragments are also comparable to the
corresponding ones in other anilido-imine ligands.[14]
Ar
Ar'
Ar
Ar'
NH N
nBuLi THF
N
Cl
Cl
nBuLi THF
CuCl2
N
N
N
N
N
N
Cu
Cu
Cu
CuCl2
Cl
Ar'
Ar
Ar
nBuLi
THF
1f, Ar = 2,6-iPr2C6H3
1a, Ar = Ar'=2,6-Me2C6H3
1b, Ar =Ar'= 2,6-Et2C6H3
1d, Ar = 2,6-iPr2C6H3,
Ar'= 3,5-(CF3)2C6H3
CuCl2
Ar'
N
1e, Ar = 2,6-iPr2C6H3,
Ar'= p-OMeC6H4
Cu Cl
N
Ar
1c, Ar =Ar'= 2,6-iPr2C6H3
Scheme 1. Synthesis of anilido-imino Cu(II) complexes
The lithium salt of anilido-imine ligands LaLi~LeLi were prepared in situ by
n
treating the corresponding ligands with BuLi in THF at low temperature. Reactions
of these lithium salts of anilindo-imine ligands with CuCl2 afford the brown solution.
Evaporating the solution to dryness and extracting the residue with toluene afford the
anilido-imino copper complexes 1a~1e in moderate to high yields as brown powder.
These complexes were well identified by elemental analyses and IR spectroscopy. The
molecular structure of 1c was previously reported to be a monomer and the copper
atom was in a trigonal-planar geometry.[18] The formation of the 15e tri-coordinated
Cu(II) chloride may be ascribed to the stronger steric repulsion between the bulky
substitutes on the two ligands. The crystals of 1a and 1d suitable for X-ray diffraction

analysis were grown from THF/hexane mixed solution. The molecular structures of
1a and 1d were established by X-ray diffraction analyses and their molecular
structures are shown in Figure 1 and Figure 2 respectively with the selected bond
lengths and angles in the captions. The crystallographic data in CIF format is shown
in the supporting information. There are two metrically identical molecules in the
unsymetric unit of 1d and only one molecule was dipicted in Figure 2. In contrast to
1c, both of 1a and 1d are dimmer consisted of two LCu (L = La or Ld) units linked
with each other by two chlorine bridges. In each molecular, the two copper atoms and
two chloride atoms are coplanar forming a perfect square Cu2Cl2 core and the dihedral
angles between the Cu2Cl2 square and the two coordinated ligand-planes are
50.68(21)° and 53.16(20)° for 1a, and 55.676(87)° and 57.741(76)° for 1d
respectively (63.676(73)° and 54.735(84)° in the other molecule in 1d). In each LCu
unit the copper center is basically coplanar with its parental ligand and the geometry
at each copper center could be described as a warped square-planar i.e., intermediate
between tetrahedral and square planar. The geometry parameter τ4 for the Cu center is
0.29(av) for 1a and 0.31(av) for 1d. Considering that the τ4 value 1 for the tetrahedron
and 0 for square-planar geometry, the copper centers in 1a and 1d are more closer to
square-planar.[20] The two parent coordination planes in same molecular are oriented
orthogonally to each other to minimize the compulsion between the ortho substitutes
on the aryl ring. The Cu–Cl bond lengths (2.305(3)–2.320(2) Å in 1a and
2.2854(12)–2.3522(12) Å in 1d) are slightly longer than those of Cu–Cl
(2.1997(13)–2.2001(13) Å) in CuCl2(Dipp-BIAN) [10a] as well as that of 2.1290(8) Å

in 1c. In both complexes, the bond lengths of Cu–Namino are shorter than the
corresponding value for Cu–Nimino and their metric parameters are slightly longer than
the corresponding one in 1c respectively.
Figure 1. Perspective view of complex 1a with thermal ellipsoids drawn at 30%
probability level. Uncoordinated solvents and hydrogens are omitted for clarity. The
selected bond lengths (Å) and angles (deg.): Cu(1)–N(1) 1.913(9), Cu(1)–N(2)
1.931(7), Cu(2)–N(3) 1.904(8), Cu(2)–N(4) 1.946(8), Cu(1)–Cl(1) 2.305(3),
Cu(1)–Cl(2) 2.320(2), Cu(2)–Cl(1) 2.315(2), Cu(2)–Cl(2) 2.313(3), N(1)–Cu(1)–Cl(1)
174.96(5), N(3)–Cu(1)–N(2) 175.49(7), N(1)–Cu(1)–N(3) 92.36(7).

Figure 2. Perspective view of complex 1d with thermal ellipsoids drawn at 30%
probability level. Uncoordinated solvents and hydrogens are omitted for clarity. The
selected bond lengths (Å) and angles (deg.): Cu(1)–N(1) 1.902(3), Cu(1)–N(2)
1.942(3), Cu(2)–N(3) 1.914(3), Cu(2)–N(4) 1.943(3), Cu(1)–Cl(1) 2.3522(12),
Cu(1)–Cl(2) 2.2885(12), Cu(2)–Cl(1) 2.2854(12), Cu(2)–Cl(2) 2.3418(12),
N(1)–Cu(1)–N(2) 95.24(14), N(3)–Cu(2)–N(4) 94.45(15), Cl(1)–Cu(1)–Cl(2)
87.65(4), Cl(1)–Cu(2)–Cl(2) 87.98(4).
Similarly, reaction of the tridentate ligand LfH with BuLi and subsequent addition of
CuCl2, after appropriate work up, gave the complex 1f in moderate yield. Complex 1f
was also characterized with IR and elemental analysis. The crystals of 1f that are
suitable for X-ray diffraction were grown from hexane solution. The molecular
structure of 1f is shown in Figure 3 with the selected bond lengths and angles in the
caption. Complex 1f is monomer with copper atom coordinated by the N,N,N

tridentate ligands and one chlorine atom, and the geometry around Cu center could be
described as distorted square plane (the two large angles in the N3CuCl are 157.85
and 154.88° which are greatly larger than 109°.28' for an ideal tetrahedron, τ4 = 0.19).
The Cu atoms is essentially coplanar with the quinolinyl plane but stay out of the
anilido-imino coordination plane with the deviation of 0.6830(38) Å. The whole
ligand is greatly twisted with the dihedral angle between the quinolinyl ring and
anilido-imino parent plane of 32.14(9)°. The Cu–Cl bond lengths of 2.2326(10) Å is
slightly shorter than those in 1a and 1d. The Nquino–Cu bond lengths (1.997(3) Å) is
longer than the Nquino–Cu (1.967(3) Å) and the Namino–Cu (1.939(3) Å), but these
value are all comparable with those of 1.9873(3)–2.158(3)
2-imino-1,10-phenanthroline copper complexes.[18]
Å
in the
Figure 3. Perspective view of complex 1f with thermal ellipsoids drawn at 30%
probability level. Uncoordinated solvents and hydrogens are omitted for clarity. The
selected bond lengths (Å) and angles (deg.): Cu(1)–N(1) 1.939(3), Cu(1)–N(2)
1.967(3), Cu(1)–N(3) 1.997(3), Cu(1)–Cl(1) 2.2326(10), C(1)–N(1) 1.369(4);

N(1)–Cu(1)–N(3) 83.00(12), N(3)–Cu(1)–N(2) 154.88(12), N(1)–Cu(1)–N(3)
91.86(12), N(1)–Cu(1)–Cl(1) 157.84(10), N(2)–Cu(1)–Cl(1) 96.52(9).
Table 1. Summary of crystallographic data for complexes 1a, 1d, and 1f.
1a
C46H46Cl2Cu2N4
852.85
Monoclinic
P32
11.3648(10)
11.3678(10)
27.666(5)
90
1d
C57H57Cl2Cu2F12N4
1224.09
Triclinic
P-1
1f
C28H28ClCuN3
505.52
Monoclinic
P2(1)/n
8.4380(14)
21.048(4)
14.177(2)
90
106.726(3)
90
2411.4(7)
4
Formula
Fw
cryst syst
space group
a (Å)
12.7809(10)
21.0161(17)
23.0108(19)
107.848(1)
97.755(1)
96.852(1)
5744.3(8)
4
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
90
120
3094.6(7)
3
1.373
v (Å3)
Z
Dcalcd(gcm-3)
µ (mm-1)
F(000)
1.4153
0.912
2513
1.392
1.038
1052
1.197
1326
26.02
16392
7928
0.0648
0.974
θmax(deg)
collected reflns
Uniq reflns
Rint
26.02
21949
14056
0.0327
28.30
14234
5695
0.0529
1.005
GOF
1.0223
R1
wR2
0.0527
0.1048
0.0620
0.1034
0.0579
0.1370
Largest diff peak,
hole (e A^-3)
0.517, –0.295
0.9831, –0.7667
1.068, –0.323
3.2. ATRP polymerization of styrene with copper complexes
All the copper complexes were tested as catalysts for ATRP of styrene. The
polymerizations were performed in toluene at 60–100ºC with 1a–1f as catalysts and
AIBN as initiator. The polymerization results are summarized in Table 1. Initially,
with 0.5 equivalent AIBN (1 equivalent initiator, Cu:[I] = 1 : 1), these complexes
exhibit moderate activities and the conversions of 52.5%–59.3% are obtained (entry
1–6). The molecular weight of the resulted polymer are slightly larger than the
calculated values with narrow PDI (from 1.47–1.58). However, with the increase of
the ratio of Cu:[I] from 1:1 to 1:10, the conversions are gradually increased and up to

85.2% conversion is obtained (entry 6–9). Meanwhile the molecular weight
distributions maintained almost intact. The control experiment shows that without the
catalyst only 49.1% of monomer is consumed in 20 hours affording the polymer with
broadened PDI (entry 10). At 80 °C and with 10 equivalent of initiator, complexes 1a,
1b also show high activities giving the conversion of 82.5–85.2% in 20 hours with the
molecular weight ranging from 12500–13300. Complex 1c with bulky ligands show
relatively higher activity than that of 1b and 1c under the same conditions. Moreover,
1d, 1e without ortho substitutes on imino group show lower activities affording the
conversion from 77.3 to 78.2%. This phenomenon presumably due to that the bulky
groups around the metal center may make the complexes more stable and less
decomposition. Notably, complex 1f with tridentate ligand shows 76.2% conversion
in 20 h at 80 °C, which is lower than the corresponding bidentated analogous with
ortho substitutes (1a, 1b, and 1c). The molecular structures suggests that the "blade"
coordination of quinolinyl group does not give a full protection to the metal center.
The polymerization temperature shows significant influence on the activity (entry 9,
16, 17). The conversion increased from 58.2% to 85.2% when the temperature goes
from 60 °C to 80 °C, and then dropped to 71.2% when the temperature reached to
100 °C. The lower activity at 60 °C might due to the lower radical generating rate,
while at 100 °C the lower activity probably due to the fast decomposition rate of the
AIBN at high temperature. We suspect that the increasing viscosity of the reaction
mixture causes a heterogeneity in the overall styrene concentration in solution which
broad the distribution. To further investigate the living character of this catalytic

system, the dynamic of the polymerization was carried out. As shown in Figure 4, the
Mn; GPC values of the polymers increased linearly with the increase of monomer
conversion. However the molecular weight distribution (Mw/Mn) was kept in narrow
range suggesting the controllable nature of the polymerization.
Table 1. Polymerization of styrene with copper(II) complexes.
Entry
Cat
[Cu]:[I]:[Sty]
Convertion
(%)b
Mn(expt.)c
× 104
Mn(calc.)
× 104
PDI
1
2
3
4
5
6
7
8
1a
1b
1d
1e
1f
1:1:200
56.8
59.3
54.7
54.1
52.5
61.4
63.4
64.9
85.2
49.1
82.5
84.1
77.5
77.3
76.2
58.2
71.2
83.8
86.5
85.7
1.45
1.41
1.39
1.32
1.30
1.53
2.97
1.47
1.33
1.34
1.25
1.32
1.34
1.25
1.30
0.82
0.97
0.72
2.10
2.16
1.18
1.23
1.14
1.13
1.09
1.28
3.30
1.35
0.88
0.51
0.86
0.87
0.81
0.80
0.79
0.61
0.74
0.44
1.35
1.78
1.54
1.55
1.47
1.50
1.48
1.58
1.47
1.58
1.57
2.50
1.55
1.59
1.44
1.42
1.45
1.54
1.67
1.48
1.60
1.63
1:1:200
1:1:200
1:1:200
1:1:200
1c
1c
1c
1c
1c
1a
1b
1d
1e
1f
1:1:200
1:2:1000
1:5:1000
1:10:1000
0:10:1000
1:10:1000
1:10:1000
1:10:1000
1:10:1000
1:10:1000
1:10:1000
1:10:1000
1:10:500
1:10:1500
1:10:2000
9
10
11
12
13
14
15
16d
17e
18
19
20
1c
1c
1c
1c
1c
aPolymerization conditions: Cat. = 10 µmol based on Cu(II), toluene (5 mL), T = 80 °C, 20 h;
bIsolated yield. cDetermined by GPC relative to polystyrene standards. dT = 60 °C. eT = 100 °C
Figure 4. Plot of average-number molecular weight (Mn, GPC) and molecular weight

distribution (Mw/Mn) versus the conversion. Polymerization condition: [Cu]:[I]:[Sty]
= 1:10:1000 at 80 °C.
4. Conclusions
Several copper complexes based on bidentate anilido-aldimino ligands and
N,N,N,-tridentate quinolinyl anilido-aldimino ligand have been synthesized and used
in reverse ATRP of styrene. These complexes show moderate to high activities and
controllable characters. The ortho groups on imino moieties show great influence on
the activities.
Acknowledgements
The authors would like to thank the National Natural Science Foundation of China
(21574052, U1462111, and 51673078) and Jilin University (J1103302).
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Graphical abstract
Several copper complexes supported by bidentated and tridentated anilido-imine
ligands were synthesized and used as catalysts for reverse ATRP of styrene.