Chain Transfer to Toluene in Styrene Coordination Polymerization

Article abstract of DOI:10.1002/anie.201914603

The chain-transfer reaction is rather important in coordination polymerization regarding catalytic efficiency, adjustment of molecular weight, and control of chain structure. To date, chain transfer to H₂ and Al, Mg, and Zn alkyl compounds and β-H elimination are the commonly encountered modes. Now a novel chain transfer to toluene is reported. By introducing fluorine atoms into the β-diketimine ligands, an inert catalytic system for styrene (St) coordination polymerization was transferred into the highly active one. The activity increased with an increase in the number of fluorines in the ligands. Surprisingly, the molecular weights of resultant polystyrenes are very low (M_n=2000–6600 Da) despite of St loadings, corresponding up to 121 chains per active species. The mechanisms were investigated by DFT simulation, MALDI-TOF MS, isotope tracing experiment and 2D NMR spectrum analyses, which revealed that the fluorine activated the polymerization and directed chain transfer to toluene.

Full text of DOI:10.1002/anie.201914603

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Chain Transfer to Toluene in Styrene Coordination
Polymerization
Authors: Fei Lin, zhaohe Liu, Meiyan Wang, Bo Liu, Shihui Li, and
Dongmei Cui
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201914603
Angew. Chem. 10.1002/ange.201914603
Link to VoR: http://dx.doi.org/10.1002/anie.201914603
http://dx.doi.org/10.1002/ange.201914603

10.1002/anie.201914603
Angewandte Chemie International Edition
COMMUNICATION
Chain Transfer to Toluene in Styrene Coordination
Polymerization
Fei Lin,a,b Zhaohe Liu,a,b Meiyan Wang,c Bo Liu,a Shihui Li*a and Dongmei Cui*a,b
Abstract: Chain transfer reaction is rather important in coordination
polymerization regarding to catalytic efficiency, adjustment of
molecular weight and control of chain structure. To date, chain
transfer to H2, Al-, Mg- and Zn alkyl compounds and β-H elimination
are the commonly encountered modes. We report herein a novel
chain transfer to toluene. By introducing fluorine atoms into the β-
diketimine ligands, an inert catalytic system for styrene (St)
coordination polymerization was transferred into the highly active
one. The activity increased with the increase of fluorine number in
the ligands. Surprisingly, the molecular weights of resultant
polystyrenes are very low (Mn = 2000 – 6600 Da) despite of St
loadings, corresponding up to 121 chains per active species. The
mechanisms were investigated by DFT simulation, MALDI-TOF MS,
isotope tracing experiment and 2D NMR spectrum analyses, which
revealed that the fluorine activated the polymerization and directed
chain transfer to toluene.
catalyst can be industrialized, since it is beneficial to the
precious metal-based catalysts by propagating more chains from
one metal center. Thus, chain transfer in coordination
polymerization has gathered an upsurge in research interest in
the past decades such as β-H elimination, or addition of H2 or Al-,
Mg- and Zn alkyl compounds for some properly designed
organometallic precursors.[10] However, chain transfer to toluene
is rather rare, because toluene is usually inert in
a
polymerization process and widely used as the reaction medium,
although toluene can be transferred to important industrial
chemicals via C-H activation by using the late transition metal
catalysts.[11] Recently, a progress had been made on developing
anisole as chain transfer agent in St coordination polymerization
by using the cationic half-sandwich rare-earth metal
complexes.[12] To date, the only chain transfer to toluene was
reported by Busico group in 2016 for propylene polymerization
using Cp-phosphinimide Ti catalysts.[13] The chain transfer
follows radical mechanism: homolysis of Ti-C bond arouses
polypropenyl radical to abstract benzylic proton; the obtained
benzyl radical combines with Ti cationic species to initiate
propylene coordination polymerization. Thus, chain transfer to
solvent in coordination polymerization is still an open research
area.
Herein, we report a series of newly designed rare-earth
complexes chelating to fluorine substituted β-diketimine ligands,
which, surprisingly, display high activity for St polymerization,
contrary to their completely inert analogues without fluorine
substituent. More strikingly, the unprecedented chain-transfer to
toluene has been achieved to afford very low molecular weight
PS that are important coatings and additives. This work provides
a new avenue of transferring inert systems to active ones and an
unprecedented method of fabricating oligomers via chain-
transfer to solvent, which refreshes the coordination chemistry.
We reported previously CGC complexes (Py-CH2-
Polystyrene (PS), one of the most widely used plastics, can
be fabricated by radical, ionic or coordination polymerization. For
the past decades, in order to endow PS with versatile physical
properties, extensive investigations have been paid to innovate
organometallic catalysts to control PS microstructures,[1] such as
the groups
constrained-geometry-configuration(CGC)
3
and
4
metallocenes,[2] half-metallocenes[3]
complexes.[4]
Comparatively, complexes anchoring non-cyclopentadienyl
ligands are less promising. Except the highly active and specific
selective titanium catalysts attached to bis-phenolate ligands,[5]
those bearing acetylacetonate[6] and Schiff-base[7] ligands show
low activities. We reported very recently that the rare-earth metal
complexes attached to quinolyl aniline ligands exhibit low
activities[8] while those bearing -diimine ligands are completely
inert although they can be activated by polar ortho-
methoxystyrene monomers.[9] Therefore, to unveil the dilemma
of resembling η5-coordination mode of the non-Cp ligands is a
rather challenging topic.
On the other hand, chain transfer to monomer, initiator and
some solvents usually happen in free radical and cationic
polymerizations, which are less controllable and considered as
side reactions. On contrary, chain transfer in a coordination
polymerization displays various advantages over the single-
component catalytic systems, which is requisite regarding to
adjust molecular weight, functionalize chain end and form multi-
blocked or topological chain structures. From application
viewpoint, chain-transfer is a key factor to evaluate whether a
Flu)Ln(CH2SiMe3)2(THF)n
(co)polymerizations of styrene[14] and its derivatives.[15] Whilst
the non-Cp β-diketimine stabilized precursors
catalyze
highly
efficient
(BDI)Ln(CH2SiMe3)2(THF) (Ln = Sc, Y, Lu) are completely
inert.[9] Therefore, we designed a series of electron-withdrawing
β-diketimine ligands containing different fluorine substituents (a-
e) (Scheme 1). Straightforward metathesis reaction between
Sc(CH2SiMe3)3(THF)2 and a-e, respectively, afforded scandium
complexes 1-5. X-ray diffraction analyses revealed the overall
molecular structure of 1-5 is a THF solvated monomer (Figures
S1-S5 and Table S1). Noticeably, with the fluorine number
increasing, the methylene carbon resonances of CH2SiMe3 shift
obviously downfield from 41.71 to 45.18 ppm, in agreement with
the strong electron-withdrawing effect of fluorine atoms.
Surprisingly, all complexes 1-5 in combination with
[Ph3C][B(C6F5)4] were able to catalyze St polymerization in
toluene. Interestingly, with the increase of fluorine number in β-
diketiminato skeleton, the catalytic activity of the corresponding
complex became higher, reaching the highest (260.2 kg of
polymer/(molSc·h)) for complex 5 by converting 5000 equiv. of St
completely into polymer within 2 h (Table 1, entries 1-5).
[a]
F. Lin, Z. Liu, Dr. B. Liu, Dr. S. Li and Prof. D. Cui
State Key Laboratory of Polymer Physics and Chemistry
Changchun Institute of Applied Chemistry, Chinese Academy of
Sciences, Changchun 130022, China
E-mail: dmcui@ciac.ac.cn; shihui-li@ciac.ac.cn.
F. Lin, Z. Liu and Prof. D. Cui
University of Chinese Academy of Sciences, Changchun Branch
Changchun 130022, China;
University of Science and Technology of China, Hefei, Anhui, China
Dr. M. Wang
[b]
[c]
Institute of Theoretical Chemistry, Jilin University, Changchun
This article is protected by copyright. All rights reserved.

10.1002/anie.201914603
Angewandte Chemie International Edition
COMMUNICATION
Table 1. Styrene polymerization catalyzed by precursors 1-5.
[d]
Entry[a]
Precursor
[St]/[Sc]
t (h)
Conv. (%)
Activity[b]
Mn, calcd[c] (×103)
Mn, exp[d] (×103)
Mw/Mn
Chains/Sc
1
2
3
4
5
6
7
1
2
3
4
5
5
5
1000
1000
1000
1000
1000
2000
5000
2
2
2
2
1
1
2
4.5
13.1
42.1
70.0
100
100
100
2.3
6.8
4.7
6.6
5.7
4.6
3.5
2.4
2.9
4.3
1.52
1.64
1.70
1.79
2.30
2.21
2.11
0.7
2.4
13.6
21.9
36.4
104.1
208.2
260.2
43.8
9.5
72.8
20.8
43.4
71.8
121.1
104.1
208.2
520.8
[a] Polymerization conditions: Ln (10 μmol), 1:1 [catalyst]/[Ph3C][B(C6F5)4] mixture (molar ratio), toluene/monomer = 3/1 (v/v), Tp = 20°C, unless otherwise noted.
[b] Given in kg of polymer/(molSc·h). [c] Mn,calcd = [St]/[Sc]×104.1×conv (%). [d] Determined by GPC in THF at 40 oC against polystyrene standard.
Thus, up to 120 times of chain transfer took place in the
polymerization procedure, alternatively, one active metal center
grew 120 polymer chains. This arises a question: which type of
chain transfer reaction happens in this system?
The matrix assisted laser desorption/ionization time-of-flight
mass spectroscopy (MALDI-TOF MS) is a powerful method to
identify the polymer chain ends and ascertain the chain transfer
type. The MALDI-TOF MS spectrum of polystyrene isolated from
precursor 5 shows two sets of molecular ion peaks with the
same spacing of a St unit (m/z = 104.15) between the adjacent
peaks (Figure 1). The blue peaks with low responds are resulted
from polystyrene terminated by β-H elimination. The red peaks
with high responds correlate to polystyrene with H and Ph-CH2-
as both chain ends, which seem to be generated from the rare
Scheme 1. Synthesis of fluorine-containing β-diketiminate rare-earth metal
complexes 1-5.
These results meant, by tuning the substituents of ligands, we
successfully transformed inert catalysts into highly active ones.
To investigate the reason behind, the LUMO energies of the
active species based on these complexes (Figure S6 for
complex 1) were simulated by DFT. Obviously, the two phenyl
groups from the ligands bearing more fluorine atoms contribute
significantly to the active species by lowering the LUMO
energies from -0.16434 au for 1 to -0.18974 for 5 au (Figure S7
and Table S2). Thus, the energy gap (ΔE) between the HOMO
of St and the LUMO of the active species became narrower
varying from 0.06154 au to 0.03614 au, in agreement with the
enhancement of the catalytic activity from 2.3 kg/(mol·h) for 1 to
104.1 kg/(mol·h) for 5 (Table 1). Apparently, the electron-
withdrawing fluorine atoms dramatically increase the Lewis
acidity of the active metal center, which facilitates the
coordination of the vinyl group to accelerate St polymerization.
Under the St-to-Sc ratio of 1000:1, the molecular weights of
the polymers obtained from precursors 1-5 were different,
decreasing with the increase of fluorine number. However, this
difference can be completely ignored as compared to the huge
deviations of these measured molecular weights (Mn, exp) from
the theoretic ones (Mn, calcd), which are surprisingly low and with
slightly broadened distribution (Table 1, entries 1-5). Moreover,
increasing the ratio to 5000:1, a polymer with Mn, exp (4.3×103
Da) of 2 orders of magnitude lower than Mn, calcd (520.8×103 Da)
was still generated (Table 1, entries 6 and 7), indicating a strong
chain transfer reaction proceeded in this polymerization system.
chain transfer to toluene.
Figure 1. MALDI-TOF mass spectrum of polystyrene (Table 1, entry 5).
There are two possible chain transfer pathways due to the
different chemical nature of methyl-H (sp3-C-H) and phenyl-H
(sp2-C-H) in a toluene molecule as shown in Scheme 2. Path a:
This article is protected by copyright. All rights reserved.

10.1002/anie.201914603
Angewandte Chemie International Edition
COMMUNICATION
Scheme 2. Possible chain transfer reactions of styrene coordination polymerization in this study.
chain transfer reaction takes place between the active species A
and the sp3-C-H of toluene to afford the new scandium benzyl
active species B. 1,2- and 2,1-insertions of St to B lead to the
intermediates C and D, respectively. The second chain transfer
reactions proceed between C/toluene and D/toluene to recover
the active species B and give polymers I and II, respectively.
Path b: chain transfer reaction takes place between the active
species A and the sp2-C-H of toluene to afford the new active
species E. The following 1,2- and 2,1-insertions of St to E
afford polymer V or VI. As depicted in Scheme 2, the resultant
polymers I-VI possess chain ends of phenyl-α-H, phenyl-β-H and
phenyl-H in different ratios.
To distinguish the chain ends, the polymerization was
performed in toluene-d8 with precursor 5 to give the deuterium-
2
incorporating polystyrene (Table 2, entry 1, vide infra). The H-
NMR spectrum reveals the integral intensity ratio of phenyl-D:
phenyl-α-D : phenyl-β-D to be 3.84:3:1 (Figure 2), corresponding
to the chain end style of polymer III, where St propagates into
polymer chain via 1,2-insertion mode and chain transfer to
toluene through ortho-sp2-C-H activation.[16] 1,2-Insertion is
unusual for most catalytic systems,[17] which becomes the main
mode here possibly because it is sterically favored than 2,1-
insertion, since the two C6F5 groups and the penultimate phenyl
ring of active polymeric species encounter mutual repulsion.[18]
provide the intermediates
F
and G, respectively. The
subsequent sp2-C-H bond activation (deprotonation) of toluene
in F and G yield polymers III and IV, respectively, by releasing
the scandium phenyl species E. With respect of the Sc-H active
species (H) arising from the β-H elimination, it is minor present
(Scheme 2, path c). Sc-H initiates 1,2- or 2,1-insertion of St to
This article is protected by copyright. All rights reserved.

10.1002/anie.201914603
Angewandte Chemie International Edition
COMMUNICATION
carbon from toluene was detected although the molecular
weights of the obtained polymers were rather low. This meant
the isolated polystyrenes are β-H elimination products. Possibly
the presence of halogen atom disturbs chain transfer to toluene.
These results allowed us to elucidate the mechanism for the
chain transfer to toluene (Scheme 3). The cationic scandium
polystyrenyl active species Sc-PS adopts a toluene molecule via
strong hydrogen-bond interaction between the fluorine atom and
a methyl proton of the lower pKa within toluene.[19] Meanwhile
the scandium methylene moiety Sc-CH2 catches ortho-phenyl-H
to form the transition state Sc-PS-Tol. Thus, chain-transfer
reaction, alternatively, deprotonation, take places to give
polymer III and a new scandium phenyl active species Sc-Tol. In
the process, methyl serves as the directing group and the
propagating polymer chain has the priority to abstract the ortho-
phenyl-H. Insertion-propagation of styrenes into Sc-Tol
regenerates the active species Sc-PS to complete
catalytic cycle.
a
Figure 2. 2H-NMR spectra of the deuterium-incorporating polystyrene (up)
(Table 2, entry 1) and toluene-d8 (down) (C2D2Cl4 as the internal standard,
CHCl3, 25oC).
To clarify the driven force of chain transfer to toluene, some
other solvents were employed as the polymerization medium.
When benzene-d6 was used, the molecular weight of the
obtained polystyrene was still very low (Table 2, entry 2),
however, no 2H resonance was observed, indicating that the
chain transfer to benzene didn’t occur in this polymerization
process. In addition, the MALDI-TOF MS spectrum shows only
one set of molecular ion peaks (Figure S16), which corresponds
to polystyrene terminated by β-H elimination. Thus, methyl group
in toluene plays a pivotal role. To confirm this, p-xylene was
used instead of toluene (Table 2, entry 3). As shown in Figures
S17 and S18, the peaks at 20.92 and 21.25 ppm are attributed
to the two methyl carbons C1 and C1’ of p-xylene, indicative of
chain transfer to p-xylene. When p-fluorotoluene, p-
chlorotoluene and p-bromotoluene were used as the solvent in
St polymerization, there were still no resonance of methyl
Scheme 3. Possible mechanism for chain transfer to toluene in styrene
coordination polymerization catalyzed by precursor 5.
Table 2. Styrene Polymerization Catalyzed by Precursor
5
in Different
Solvents.
In conclusion, we have developed a series of new scandium
complexes chelated by fluorine-containing β-diketiminate ligands,
which display increasing activities up to 260.2 kg
polymer/(molSc·h) for styrene polymerization with more fluorine
atoms anchored on the ligands under the activation of
[Ph3C][B(C6F5)4]. This is surprisingly contrary to their analogues
bearing β-diketiminate ligands without a fluorine substituent,
which are completely inert towards this polymerization. DFT
calculations suggest the more the fluorine atoms are in the
ligand, the lower the LUMO energy of the active species is,
leading to the narrower energy gap between the HOMO of
styrene and the LUMO of the active species and a higher activity.
More excitingly, despite of monomer loading, the complexes
give very low molecular weight polystyrenes due to the
unprecedented chain transfer to toluene. The driving force for
the chain-transfer is arising from the hydrogen bonding
C−F···H−C between the fluorine and the methyl proton in
toluene, which directs the active propagating polymer chain to
[b]
[b]
Entry[a]
Solvent
[St]/[Sc]
t
Conv.
(%)
Mn.exp
Mw/Mn
(h)
(×103)
1
2
3
4
5
6
toluene-d8
benzene-d6
500
500
500
500
500
500
4
2
4
4
4
4
85.6
6.2
5.8
2.8
7.0
6.1
6.7
1.91
2.08
1.61
2.03
2.33
2.17
>99.9
>99.9
>99.9
>99.9
>99.9
p-xylene
p-fluorotoluene
p-chlorotoluene
p-bromotoluene[c]
[a] Polymerization con
μmol), 1:1 [Sc]/[Ph3C][B(C6F5)4] mixture
(molar ratio), solvent/monomer = 3/1 (v/v), Tp = 20°C, unless otherwise noted.
[b] Determined by GPC in THF at 40 oC against polystyrene standard. [c] The
mixed solvents of 4-bromotoluene and hexane were used (4-
bromotoluene/hexane = 2:1) because 4-bromotoluene is solid at the room
temperature.
This article is protected by copyright. All rights reserved.

10.1002/anie.201914603
Angewandte Chemie International Edition
COMMUNICATION
[10] a) Z. B. Jian, D. M. Cui, Z. M. Hou, X. F. Li, Chem. Commun. 2010, 46,
3022-3024; b) I. German, W. Kelhifi, S. Norsic, C. Boisson, F. D'Agosto,
Angew. Chem. Int. Ed. 2013, 52, 3438-3441; c) I. Göttker-Schnetmann,
P. Kenyon, S. Mecking, Angew. Chem. Int. Ed. 2019, 58, 17777-17781.
[11] a) B. Butschke, H. Schwarz, Organometallics 2011, 30, 1588-1598; b) L.
Johansson, O. B. Ryan, C. Romming, M. Tilset, J. Am. Chem. Soc.
2001, 123, 6579-6590.
abstract the ortho-H of toluene. This work sheds new lights on
organometallic chemistry about how to design highly active
catalysts and widens polymer science about chain transfer
mechanism. It also paves a new avenue to access very low
molecular weight polystyrene in the most convenient and
cheapest method.
[12] A. Yamamoto, M. Nishiura, J. Oyamada, H. Koshino, Z. Hou,
Macromolecules 2016, 49, 2458-2466.
[13] C. Ehm, R. Cipullo, M. Passaro, F. Zaccaria, P. H. M. Budzelaar, V.
Busico, Acs Catal. 2016, 6, 7989-7993.
Acknowledgements
[14] a) Y. Pan, W. Rong, Z. Jian, D. Cui, Macromolecules 2012, 45, 1248-
1253; b) B. Liu, D. Cui, T. Tang, Angew. Chem. Int. Ed. 2016, 55,
11975-11978.
This work was supported by the NSF China for Projects Nos.
21634007, 21574125, 51773193 and 51673184.
[15] D. Liu, R. Wang, M. Wang, C. Wu, Z. Wang, C. Yao, B. Liu, X. Wan, D.
Cui, Chem. Commun.2015, 51, 4685-4688.
Keywords: C-H activation •chain transfer• coordination
polymerization • styrene polymerization •rare earths
[16] The ortho-sp2-C-H activation by active species E was confirmed by 1H
(Figure S8), 13C (Figure S9), HSQC (Figures S10-11) and HMBC
(Figures S12-15) NMR analyses of an oligomeric polystyrene sample
(Table 1, entry 5, Mn = 2400, Mw/Mn = 2.30). In the 13C NMR spectra,
the strong multi peaks within 144.5-146.5 ppm are related to the ipso-
carbon Cc of the atactic polystyrene main chain; while the resonance at
[1]
a) A. Zambelli, P. Longo, C. Pellecchia, A. Grassi, Macromolecules
1987, 20, 2035-2037; b) N. Ishihara, T. Seimiya, M. Kuramoto, M. Uoi,
Macromolecules 1986, 19, 2464-2465; c) A. A. El-Shehawy, H.
Yokoyama, K. Sugiyama, A. Hirao, Macromolecules 2005, 38, 8285-
8299.
δ
20.89 ppm is assigned to methyl C1 of the chain-end, which
correlates to the methyl protons at δ 2.22 ppm in the HSQC spectrum.
The resonance at δ 3.46 ppm can be assigned to the methine proton
H8 connecting to the ortho-phenyl carbon C7, which correlates with C8
at 47.87 ppm (Figures S12, S15). These evidences suggested that the
active polystyrene chain transfers to the ortho-H of toluene,
alternatively, the ortho-sp2-C-H is prone to be abstracted.
[2]
[3]
[4]
a) P. Longo, A. Proto, A. Zambelli, Macromol. Chem. Phys. 1995, 196,
3015-3029; b) E. Kirillov, C. W. Lehmann, A. Razavi, J. F. Carpentier, J.
Am. Chem. Soc. 2004, 126, 12240-12241.
a) T. E. Ready, R. O. Day, J. C. W. Chien, M. D. Rausch,
Macromolecules 1993, 26, 5822-5823; b) Y. J. Luo, J. Baldamus, Z. M.
Hou, J. Am. Chem. Soc. 2004, 126, 13910-13911.
[17] a) D. J. Byun, A. Fudo, A. Tanaka, M. Fujiki, K. Nomura,
Macromolecules 2004, 37, 5520-5530; b) L. Caporaso, M. Loria, M.
Mazzeo, K. Michiue, T. Nakano, T. Fujita, L. Cavallo, Macromolecules
2012, 45, 8588-8597; c) A. Zambelli, P. Longo, C. Pellecchia, A. Grassi,
Macromolecules 1987, 20, 2035-2037; d) L. Perrin, E. Kirillov, J. F.
Carpentier, L. Maron, Macromolecules 2010, 43, 6330-6336.
a) Z. B. Jian, S. J. Tang, D. M. Cui, Chem. Eur. J. 2010, 16, 14007-
14015; b) N. Guo, C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 2008,
130, 2246-2261.
[5]
[6]
[7]
C. Capacchione, A. Proto, H. Ebeling, R. Mulhaupt, K. Moller, T. P.
Spaniol, J. Okuda, J. Am. Chem. Soc. 2003, 125, 4964-4965.
A. Zambelli, L. Oliva, C. Pellecchia, Macromolecules 1989, 22, 2129-
2130.
[18] L. Caporaso, L. Izzo, I. Sisti, L. Oliva, Macromolecules 2002, 35, 4866-
4870.
a) L. Yong, J. L. Huang, B. Lian, Y. L. Qian, Chinese J. Chem. 2001, 19,
429-432; b) K. Michiue, M. Onda, H. Tanaka, H. Makio, M. Mitani, T.
Fujita, Macromolecules 2008, 41, 6289-6291.
[19] a) M. Mitani, J.-i. Mohri, Y. Yoshida, J. Saito, S. Ishii, K. Tsuru, S.
Matsui, R. Furuyama, T. Nakano, H. Tanaka, S.-i. Kojoh, T. Matsugi, N.
Kashiwa, T. Fujita, J. Am. Chem. Soc. 2002, 124, 3327-3336; b) M. P.
Weberski, C. L. Chen, M. Delferro, C. Zuccaccia, A. Macchioni, T. J.
Marks, Organometallics 2012, 31, 3773-3789.
[8]
[9]
D. T. Liu, Y. J. Luo, W. Gao, D. M. Cui, Organometallics 2010, 29,
1916-1923.
D. T. Liu, C. G. Yao, R. Wang, M. Y. Wang, Z. C. Wang, C. J. Wu, F.
Lin, S. H. Li, X. H. Wan, D. M. Cui, Angew. Chem., Int. Ed. 2015, 54,
5205-5209.
This article is protected by copyright. All rights reserved.

10.1002/anie.201914603
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
COMMUNICATION
Fei Lin, Zhaohe Liu, Meiyan Wang, Bo
Liu, Shihui Li* and Dongmei Cui*
Page 1 – Page 5
Chain Transfer to Toluene in Styrene
Coordination Polymerization
The highly efficient chain transfer to toluene has been achieved for the first time in
styrene coordination polymerization by using rare-earth metal precursors. The
higher polymerization activity is attributed to the fluorine substitutents on the ß-
diiminato ligands by lowering the LUMO energy of active metal center, which also
direct the chain transfer to ortho-proton of toluene.
This article is protected by copyright. All rights reserved.