Vanadium(III) complexes containing phenoxy–imine–thiophene ligands: Synthesis, characterization and application to homo- and copolymerization of ethylene

Article abstract of DOI:10.1002/aoc.3678

A set of vanadium(III) complexes, namely {SNO}VCl₂(THF)₂ (2a, SNO?=?thiophene-(N═CH)-phenol; 2b, SNO?=?5-phenylthiophene-(N═CH)-phenol; 2c, SNO?=?5-phenylthiophene-(N═CH)-4-tert-butylphenol; 2d, SNO?=?5-methylthiophene-(N═CH)-phenol;

Full text of DOI:10.1002/aoc.3678

Received: 23 September 2016
DOI 10.1002/aoc.3678
Revised: 4 October 2016
Accepted: 7 October 2016
F U L L PA P E R
Vanadium(III) complexes containing phenoxy–imine–thiophene
ligands: Synthesis, characterization and application to homo‐ and
copolymerization of ethylene
Nayara T. do Prado1 | Ronny R. Ribeiro2 | Osvaldo L. Casagrande Jr1
1 Laboratory of Molecular Catalysis, Institute of
A set of vanadium(III) complexes, namely {SNO}VCl2(THF)2 (2a, SNO = thiop-
Chemistry, Universidade Federal do Rio Grande
do Sul, Av. Bento Gonçalves, 9500, Porto Alegre,
hene‐(N═CH)‐phenol; 2b, SNO
SNO = 5‐phenylthiophene‐(N═CH)‐4‐tert‐butylphenol; 2d, SNO = 5‐methyl-
thiophene‐(N═CH)‐phenol; 2e, SNO = 5‐methylthiophene‐(N═CH)‐4‐tert‐butyl-
= 5‐phenylthiophene‐(N═CH)‐phenol; 2c,
RS 91501‐970, Brazil
2 Departamento de Química, Universidade Federal
do Paraná, Centro Politécnico, 81530‐900
Curitiba, PR, Brazil
phenol; 2f, SNO
=
5‐methylthiophene‐(N═CH)‐2‐methylphenol; 2g,
SNO = 5‐methylthiophene‐(N═CH)‐4‐fluorophenol), were synthesized by reaction
of VCl3(THF)3 with phenoxy–imine–thiophene proligands (1a–g). All vanadium
(III) complexes were characterized using elemental analysis and infrared and elec-
tron paramagnetic resonance spectroscopies. Upon activation with
methylaluminoxane (MAO), vanadium precatalysts 2a–g proved active in the poly-
merization of ethylene (213.6–887.2 kg polyethylene (mol[V])−1⋅h−1), yielding
high‐density polyethylenes with melting temperatures in the range 133–136 °C
and crystallinities varying from 28 to 41%. The 2e/MAO catalyst system was able
to copolymerize ethylene with 1‐hexene affording poly(ethylene‐co‐1‐hexene)s
with melting temperatures varying from 126 to 102 °C and co‐monomer incorpora-
tion in the range 3.60–4.00%.
Correspondence
Osvaldo de L. Casagrande Jr, Laboratory of
Molecular Catalysis, Institute of Chemistry,
Universidade Federal do Rio Grande do Sul, Av.
Bento Gonçalves, 9500, Porto Alegre, RS,
91501‐970, Brazil.
Email: osvaldo.casagrande@ufrgs.br
KEYWORDS
ethylene polymerization, ethylene–1‐hexene copolymerization, phenoxyimine ligands,
vanadium(III) complexes
1
|
INTRODUCTION
available and their high performance in the production of
polyolefin products.[2] Among the variety of catalysts that
have been used for this purpose, vanadium‐based complexes
have been extensively investigated for the production of
high‐molecular‐weight polyethylene (PE) as well as
ethylene–α‐olefin with high co‐monomer incorporations.[3]
However, one deficiency associated with the use of vanadium
catalysts is the loss of activity at elevated temperatures due to
the reduction of catalytically active vanadium species to inac-
tive species (typically to V(II)).[3c,4] In order to overcome this
problem, several classes of neutral and anionic ligands have
been employed to generate more robust and thermally stable
vanadium catalysts. In particular, many well‐defined and
highly active homogeneous vanadium(III) catalysts with bi‐
Polyolefin materials are used in a wide variety of applications,
including grocery bags, containers, toys, adhesives, home
appliances, engineering plastics, automotive parts, medical
applications and prosthetic implants, and account for
about 60% of the global thermoplastic polymer market.[1]
Besides the homopolymers of ethylene and propylene,
copolymerization of ethylene with α‐olefins generates an
important class of commodity plastics (linear low‐density
polyethylene). In this context, the design and synthesis of
efficient non‐metallocene catalysts for olefin polymerization
have grown considerably over the past few decades largely
due to the remarkable variety of non‐cyclopentadienyl ligands
Appl Organometal Chem 2016; 1–10
wileyonlinelibrary.com/journal/aoc
Copyright © 2016 John Wiley & Sons, Ltd.
1

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DO PRADO ET AL.
and tridentate ligands have been described in the literature
and their polymerization activity investigated.[5] Selected
examples are presented in Chart 1. For instance, Gambarotta
and co‐workers found that bis(imino)pyridine vanadium(III)
complexes showed high catalytic activity towards ethylene
polymerization and produced bimodal molecular weight dis-
tribution PEs.[5a] In 2003, Fujita and co‐workers described a
highly active (65 100 kg of PE (mol[V])−1⋅h−1 at 75 °C)
and thermally robust vanadium catalyst bearing two
phenoxyimines for ethylene polymerization (Chart 1).[5b]
Li and co‐workers described the synthesis and charac-
evaluating the influence of some experimental parameters
on catalyst activity and polymer properties.
2
| EXPERIMENTAL
2.1 | General considerations
All manipulations involving air‐ and/or water‐sensitive
compounds were carried out in an MBraun glovebox or
under dry argon using standard Schlenk techniques. Tolu-
ene, tetrahydrofuran (THF), pentane and hexane (Et2O)
were dried using a Braun MB‐SPS‐800 solvent purifica-
tion system. Others solvents were dried using the appro-
priate drying agents under argon before use. VCl3(THF)3,
2,4‐di‐tert‐butylsalicylaldehyde, 2‐thiophenecarbaldehyde,
5‐phenylthiophene‐2‐carboxaldehyde, 2‐aminophenol, 2‐
amino‐4‐tert‐butylphenol and 2‐amino‐4‐fluorophenol were
purchased from Sigma‐Aldrich and used as received.
Ethylene (White Martins Co.) and argon were deoxygen-
ated and dried through BTS columns (BASF) and acti-
vated molecular sieves prior to use. MAO (Witco,
5.21 wt% Al solution in toluene, 20% TMA) was used
as received. Infrared (IR) spectra were obtained with a
Bruker FT‐IR Alpha spectrometer. NMR spectra were
recorded with a Varian Inova 300 spectrometer. 1H and
13C chemical shifts are reported in ppm versus SiMe4
and were determined by reference to the residual solvent
peaks. 13C NMR spectra of the copolymers were recorded
with a Varian Inova 300 NMR spectrometer at 125 °C
with C6D6–o‐C6H4Cl2 as the solvent. Electron paramag-
netic resonance (EPR) experiments were performed at
X‐band using a Bruker EMX micro‐X spectrometer. Ele-
mental analysis was performed by the Analytical Central
Service of the Institute of Chemistry‐USP (Brazil) and is
the average of two independent determinations. Melting
temperatures were determined using differential scanning
calorimetry (DSC) with a TA Instruments DSC‐Q20 at a
heating rate of 10 °C min−1 after twice previous heating
terization
of
vanadium(III)
complexes
bearing
salicylaldiminato ligands. In the presence of Et2AlCl, these
salicyladiminato vanadium complexes were highly active
catalysts for ethylene polymerization at 25 °C (up to 22
300 kg of PE (mol[V])−1⋅h−1⋅bar−1), and afforded high‐
molecular‐weight polymers (Mw > 100 kg mol−1) with
unimodal molecular weight distributions.[5c] More recently,
Golisz and Bercaw reported that a vanadium(III) complex
containing bis(phenoxy)pyridine ligand showed remarkable
catalytic activity for propylene polymerization in the pres-
ence of methylaluminoxane (MAO) (803 kg of polypropyl-
ene (mol[V])−1⋅h−1
)
affording high‐molecular‐weight
polypropylene with uniform molecular weight distribution
(Mw = 1.17 × 106 g mol−1; Mw/Mn = 2.03).[5d]
As part of our investigation of tridentate chelating
ligands in oligomerization and polymerization catalysis,[6]
we have been interested in preparing a new set of
vanadium(III) complexes containing phenoxyimine ligands
with pendant thiophene group. Herein, we report the syn-
thesis and characterization of a series of vanadium(III)
complexes supported by phenoxy–imine–thiophene ligands
and investigate the catalytic performance in polymerization
of ethylene and copolymerization of ethylene with 1‐hexene
using MAO as co‐catalyst. We anticipated that the nature
of the ligand would significantly affect polymerization
behavior as well as polymer properties. Furthermore, we
discuss the performance of these vanadium precatalysts,
to 180 °C and cooling to 40 °C at 10 °C min−1
.
2.2 | Synthesis of phenoxy–imine–thiophene ligands
2.2.1
|
Thiophene‐(N═CH)‐phenol (1a)[7]
To a stirred solution of 2‐thiophenecarbaldehyde (0.4486 g,
4.00 mmol) in ethanol, 2‐aminophenol (0.4365 g, 4.00 mmol)
and formic acid (3 drops) were added. The reaction mixture
was stirred for 72 h at 35 °C. The final reaction mixture
was evaporated to dryness, and recrystallized from THF–hex-
ane to give 1a as yellow crystals (0.5500 g, 68%); m.p.
79.0 °C. 1H NMR (300 MHz, CDCl3, δ, ppm): 8.79 (s, 1H),
7.52 (2H, m), 7.28 (1H, m), 7.16 (3H, m), 7.00 (1H, dd),
6.89 (1H, td). 13C NMR (100 MHz, CDCl3, δ, ppm):
115.00; 115.74, 120.01, 127.96, 128.72, 130.64, 132.45,
135.02, 142.81, 149.62, 152.19. IR (ATR, cm−1): 3337 (w),
1608 (s), 1591 (s), 1577 (s), 1480 (s), 1417 (m), 1376 (m),
CHART 1 Selected examples of vanadium(III) complexes successfully
applied in homo‐ and copolymerization of ethylene with α‐olefins

DO PRADO ET AL.
3
1354(m), 1295 (m), 1255 (s), 1218 (s), 1176 (s), 1149 (m),
1101 (m), 1048 (m), 1036 (m), 969 (m), 925 (w), 880 (w),
864 (w), 813 (s), 743 (s), 734 (s), 717 (s), 578 (m), 499
(m). Anal. Calcd for C11H9NOS (%): C, 65.00; H, 4.46; N,
6.89. Found (%): C, 65.12; H, 4.53; N, 7.16.
(300 MHz, CDCl3, δ, ppm): 8.67 (1H, s), 7.35 (1H, m),
7.24 (1H, d), 7.16 (1H, td), 6.99 (1H, dd), 6.88 (1H, td),
6.82 (1H, d), 2.56 (3H, s). 13C NMR (100 MHz, CDCl3, δ,
ppm): 16.23, 115.08, 115.72, 120.18, 126.60, 128.68,
133.33, 135.47, 140.85, 146.77, 149.92, 152.20. IR (ATR,
cm−1): 3341 (w), 3064 (w), 3039 (w), 2910 (w), 1615 (s),
1586 (s), 1490 (w), 1461 (s), 1366 (s), 1286 (w), 1250 (s),
1230 (s), 1145 (m), 1046 (m), 1025 (m), 953 (m), 927 (m),
810 (m), 790 (s), 739 (s), 606 (s), 575 (m), 507 (s), 478
(m), 424 (m). Anal. Calcd for C12H11NOS (%): C, 66.13;
H, 5.10; N, 6.45. Found (%): C, 65.89; H, 5.07; N, 6.37.
2.2.2
| 5‐Phenylthiophene‐(N═CH)‐phenol (1b)
Ligand 1b was prepared as described above for 1a, starting
from 5‐phenylthiophene‐2‐carboxaldehyde (0.1883 g,
1.00 mmol) and 2‐aminophenol (0.1091 g, 1.00 mmol). The
reaction mixture was stirred for 24 h at 35 °C. Ligand 1b
was obtained as a yellow solid after recrystallization from
THF–hexane (0.2400 g, 87%); m.p. 133.9 °C. 1H NMR
(300 MHz, CDCl3, δ, ppm): 8.75 (1H, s), 7.69 (2H, m),
7.36 (5H, m), 7.19 (2H, m), 7.01 (1H, dd), 6.90 (1H, td).
13C NMR (100 MHz, CDCl3, δ, ppm): 115.13, 115.81,
120.22, 123.96, 126.29, 128.81, 128.93, 129.25, 133.74,
133.78, 135.23, 142.07, 149.65, 149.72, 152.48. IR (ATR,
cm−1): 3410 (w), 1605 (w), 1583 (m), 1571 (m), 1495 (w),
1482 (m), 1453 (m), 1438 (m), 1361 (w), 1349 (w), 1319
(w), 1292 (w), 1250 (m), 1203 (m), 1172 (m), 1146 (m),
1057 (m), 1033 (m), 958 (m), 907 (w), 812 (s), 750 (s), 686
(s), 579 (s), 539 (m), 483 (s), 437 (m). Anal. Calcd for
C17H13NOS (%): C, 73.09; H, 4.69; N, 5.01. Found (%): C,
72.76; H, 4.50; N, 4.60.
2.2.5
| 5‐Methylthiophene‐(N═CH)‐4‐tert‐butyl‐phenol (1e)
Ligand 1e was prepared as described above for 1a, starting
from 5‐methylthiophene‐2‐carboxaldehyde (0.5047 g,
4.00 mmol) and 2‐amino‐4‐tert‐butylphenol (0.6609 g,
4.00 mmol). The reaction mixture was stirred for 72 h at
35 °C. Ligand 1e was obtained as a yellow solid after recrys-
tallization from THF–hexane (0.7500 g, 69%); m.p. 99.3 °C.
1H NMR (300 MHz, CDCl3, δ, ppm): 8.58 (1H, s), 7.15 (2H,
m), 7.10 (1H, m), 6.83 (1H, d), 6.72 (1H, d), 2.46 (3H, s),
1.23 (9H, s). 13C NMR (100 MHz, CDCl3, δ, ppm): 16.20,
31.72, 34.53, 112.61, 114.42, 125.64, 126.61, 133.09,
134.60, 143.07, 149.54, 149.83. IR (ATR, cm−1): 3419 (m),
2953 (m), 2862 (w), 1611 (m), 1588 (s), 1499 (m), 1466
(s), 1440 (m), 1363 (m), 1276 (m), 1219 (s), 1167 (m),
1053 (m), 966 (m), 929 (m), 876 (m), 813 (s), 749 (w), 705
(w), 638 (m), 584 (s), 570 (s), 559 (s), 509 (s), 420 (m). Anal.
Calcd for C16H19NOS (%): C, 70.29; H, 7.00; N, 5.12. Found
(%): C, 69.64; H, 6.57; N, 5.06.
2.2.3
| 5‐Phenylthiophene‐(N═CH)‐4‐tert‐butyl‐phenol (1c)
Ligand 1c was prepared as described above for 1a, starting
from 5‐phenylthiophene‐2‐carboxaldehyde (0.1883 g,
1.00 mmol) and 2‐amino‐4‐tert‐butylphenol (0.1652 g,
1.00 mmol). The reaction mixture was stirred for 72 h at
35 °C. Ligand 1c was obtained as a yellow solid after recrys-
tallization from THF–hexane (0.2600 g, 78%); m.p. 120.9 °C.
1H NMR (300 MHz, CDCl3, δ, ppm): 8.76 (1H, s), 7.69 (2H,
m), 7.48 (1H, d), 7.43 (2H, m), 7.36 (2H, m), 7.29 (1H, d),
7.23 (1H, dd), 7.04 (1H, s), 6.94 (1H, d), 1.34 (9H, s). 13C
NMR (100 MHz, CDCl3, δ, ppm): 31.61, 34.47, 112.45,
114.49, 123.81, 125.92, 126.16, 128.62, 129.10, 133.30,
133.71, 134.33, 142.07, 143.00, 148.99, 149.30, 149.91. IR
(ATR, cm−1): 3453 (w), 2955 (m), 2861 (w), 1610 (m),
1584 (s), 1501 (m), 1455 (s), 1440 (m), 1362 (m), 1342
(w), 1280 (m), 1245 (m), 1214 (s), 1168 (m), 1095 (w),
1060 (m), 1025 (w), 958 (m), 927 (m), 877 (m), 821 (s),
807 (m), 754 (s), 687 (s), 634 (m), 588 (m), 529 (s), 479
(s), 427 (m). Anal. Calcd for C21H21NOS (%): C, 75.19; H,
6.31; N, 4.18. Found (%): C, 74.82; H, 6.42; N, 4.04.
2.2.6
| 5‐Methylthiophene‐(N═CH)‐2‐methylphenol (1f)
Ligand 1f was prepared as described above for 1a, starting
from 5‐methylthiophene‐2‐carboxaldehyde (0.5047 g,
4.00 mmol) and 2‐amino‐2‐methylphenol (0.4926 g,
4.00 mmol). The reaction mixture was stirred for 72 h at
35 °C. Ligand 1f was obtained as a yellow solid after recrys-
tallization from THF–hexane (0.7500 g, 69%); m.p. 82.0 °C.
1H NMR (300 MHz, CDCl3, δ, ppm): 8.66 (1H, s), 7.29 (1H,
d), 7.09 (1H, d), 7.01 (1H, d), 6.79 (2H, m), 2.55 (3H, s),
2.29 (3H, s). 13C NMR (100 MHz, CDCl3, δ, ppm): 15.69,
16.05, 112.99, 119.22, 124.28, 126.45, 129.59, 132.90,
134.66, 140.92, 146.30, 149.52, 150.45. IR (ATR, cm−1):
3332 (m), 2908 (w), 2844 (w), 1620 (m), 1595 (s), 1456
(s), 1360 (m), 1314 (m), 1281 (w), 1248 (s), 1210 (s), 1158
(s), 1083 (m), 1043 (m), 1010 (m), 965 (m), 940 (w), 830
(m), 802 (s), 788 (s), 711 (s), 734 (s), 695 (w), 634 (s), 559
(m), 506 (m), 490 (s), 435 (m). Anal. Calcd for C13H13NOS
(%): C, 67.50; H, 5.66; N, 6.06. Found (%): C, 67.22; H,
5.52; N, 6.02.
2.2.4
|
5‐Methylthiophene‐(N═CH)‐phenol (1d)[8]
Ligand 1d was prepared as described above for 1a, starting
from 5‐methylthiophene‐2‐carboxaldehyde (0.5047 g,
4.00 mmol) and 2‐aminophenol (0.4365 g, 4.00 mmol). The
reaction mixture was stirred for 48 h at 35 °C. Ligand 1d
was obtained as a yellow solid after recrystallization from
THF–hexane (0.6400 g, 74%); m.p. 70.5 °C. 1H NMR
2.2.7
| 5‐Methylthiophene‐(N═CH)‐4‐fluorophenol (1g)
Ligand 1g was prepared as described above for 1a, starting
from 5‐methylthiophene‐2‐carboxaldehyde (0.5047 g,

4
DO PRADO ET AL.
4.00 mmol) and 2‐amino‐4‐fluorophenol (0.5085 g,
4.00 mmol). The reaction mixture was stirred for 96 h at
35 °C. Ligand 1 g was obtained as yellow crystals after
recrystallization from THF–hexane (0.6800 g, 72%); m.p.
72.7 °C. Crystals suitable for X‐ray diffraction analysis were
(w), 1637 (s), 1596 (m), 1499 (m), 1434 (s), 1362 (m),
1322 (w), 1265 (s), 1189 (m), 1126 (m), 1072 (m), 999
(m), 828 (s), 757 (s), 684 (s), 525 (m), 474 (m). Anal. Calcd
for C29H36Cl2NO3SV (%): C: 58.00, H: 6.04, N: 2.33. Found
(%): C: 57.67, H: 5.78, N: 2.21.
1
obtained from this batch. H NMR (300 MHz, CDCl3, δ,
ppm): 8.61(1H, s), 7.35 (1H, d), 6.98 (1H, dd), 6.89 (2H,
m), 6.82 (1H, m), 2.56 (3H, s). 13C NMR (100 MHz, CDCl3,
δ, ppm): 15.58, 111.23, 115.12, 118.43, 126.04, 127.11,
138.33, 139.08, 142.07, 147.22, 152.24, 156.81. IR (ATR,
cm−1): 3347 (m), 3066 (w), 2969 (w), 2919 (w), 2857 (w),
1625 (m), 1595 (s), 1535 (m), 1494 (s), 1464 (s), 1371 (m),
1250 (s), 1226 (s), 1132 (s), 1093 (m), 1051 (m), 970 (m),
957 (m), 856 (s), 817 (m), 793 (s), 764 (m), 732 (m), 705
(w), 626 (w), 596 (w), 567 (m), 529 (m), 502 (s), 453 (m),
425 (m). Anal. Calcd for C13H13NOS (%): C, 61.26; H,
4.28; N, 5.95. Found (%): C, 61.21; H, 4.11; N, 5.94.
2.3.4
(2d)
| [V{5‐methylthiophene‐(N═CH)‐OC6H4}(THF)2Cl2]
This complex was prepared as described above for 2a,
starting from 1d (0.0406 g, 0.187 mmol) and VCl3(THF)3
(0.070 g, 0.187 mmol) in THF (10 ml) to give 2d as an
orange solid (0.0700 g, 78%). IR (ATR, cm−1): 1638 (s),
1590 (m), 1485 (m), 1445 (s), 1357 (m), 1317 (m), 1225
(s), 1163 (m), 1105 (w), 1062 (m), 998 (m), 867 (m), 807
(m), 758 (F), 578 (m), 502 (m), 481 (m), 434 (m). Anal.
Calcd for C20H26Cl2NO3SV (%): C: 49.80, H: 5.43, N:
2.90. Found (%): C: 49.11, H: 4.87, N: 2.23.
2.3 | Synthesis of vanadium(III) complexes
2.3.5
(THF)2Cl2] (2e)
| [V{5‐methylthiophene‐(N═CH)‐4‐tert‐butyl‐(OC6H3)}
2.3.1
| [V{thiophene‐(N═CH)‐OC6H4}(THF)2Cl2] (2a)
A solution of 1a (0.0381 g, 0.187 mmol) in THF (10 ml) was
added dropwise to a stirring solution of [V(THF)3Cl3]
(0.070 g, 0.187 mmol) in THF (15 ml), and the resulting solu-
tion was allowed to stir for 24 h at 35 °C. The solvent was
removed until about one‐third remained and 10 ml of pentane
added to complete the precipitation. The product was col-
lected by filtration, washed with pentane (3 × 10 ml) and
dried in vacuo. Complex 2a was obtained as an orange solid
(0.0500 g, 57%). IR (ATR, cm−1): 1638 (s), 1589 (m), 1480
(s), 1409 (s), 1350 (m), 1318 (m), 1253 (s), 1184 (w), 1155
(w), 1103 (w), 1058 (m), 1040 (m), 997 (s), 861 (F), 823
(m), 749 (s), 564 (m), 516 (w), 469 (w). Anal. Calcd for
C19H24Cl2NO3SV (%): C: 48.73, H: 5.17, N: 2.99. Found
(%): C: 47.04, H: 4.88, N: 2.66.
This complex was prepared as described above for 2a,
starting from 1e (0.0511 g, 0.187 mmol) and VCl3(THF)3
(0.070 g, 0.187 mmol) in THF (10 ml) to give 2e as an orange
solid (0.0700 g, 70%). IR (ATR, cm−1): 2959 (m), 2869 (f),
1640 (F), 1599 (m), 1496 (m), 1445 (F), 1362 (m), 1266
(F), 1163 (f), 1129 (m), 1063 (f), 1005 (f), 830 (F), 735 (f),
684 (f), 626 (f), 499 (F). Anal. Calcd for C24H34Cl2NO3SV
(%): C: 53.54, H: 6.36, N: 2.60. Found (%): C: 52.77, H:
5.88, N: 2.44.
2.3.6
(THF)2Cl2] (2f)
| [V{5‐methylthiophene‐(N═CH)‐2‐methyl‐(OC6H3)}
This complex was prepared as described above for 2a,
starting from 1f (0.0433 g, 0.187 mmol) and VCl3(THF)3
(0.070 g, 0.187 mmol) in THF (10 ml) to give 2f as an orange
solid (0.0600 g, 65%). IR (ATR, cm−1): 1636 (s), 1593 (m),
1476 (m), 1441 (s), 1357 (m), 1312 (m), 1274 (m), 1209
(m), 1161 (m), 1099 (w), 1060 (w), 999 (m), 923 (w), 850
(s), 805 (m), 743 (s), 487 (s), 432 (m). Anal. Calcd for
C21H28Cl2NO3SV (%): C: 50.81, H: 5.69, N: 2.82. Found
(%): C: 50.04, H: 5.43, N: 2.67.
2.3.2
(2b)
| [V{5‐phenylthiophene‐(N═CH)‐OC6H4}(THF)2Cl2]
This complex was prepared as described above for 2a,
starting from 1b (0.0523 g, 0.187 mmol) and VCl3(THF)3
(0.070 g, 0.187 mmol) in THF (10 ml) to give 2b as a red
solid (0.0600 g, 59%). IR (ATR, cm−1): 1635 (s), 1588 (m),
1491 (m), 1480 (m), 1434 (s), 1359 (m), 1325 (w), 1256
(s), 1187 (m), 1156 (w), 1106 (w), 1073 (m), 1000 (m),
869 (m), 809 (m), 755 (s), 687 (m), 599 (w), 572 (w), 463
(m), 441 (m). Anal. Calcd for C25H28Cl2NO3SV (%): C:
55.15, H: 5.18, N: 2.57. Found (%): C: 54.67, H: 4.56,
N: 2.44.
2.3.7
(THF)2Cl2] (2g)
| [V{5‐methylthiophene‐(N═CH)‐4‐fluoro‐(OC6H3)}
This complex was prepared as described above for 2a,
starting from 1g (0.0440 g, 0.187 mmol) and VCl3(THF)3
(0.070 g, 0.187 mmol) in THF (10 ml) to give 2g as an orange
solid (0.0640 g, 69%). IR (ATR, cm−1): 1640 (s), 1598 (s),
1491 (s), 1445 (s), 1358 (m), 1310 (m), 1259 (s), 1199 (s),
1167 (m), 1144 (m), 1097 (w), 1065 (m), 1004 (m), 972
(m), 852 (s), 815 (s), 724 (m), 494 (s), 447 (m), 429 (m).
Anal. Calcd for C20H25Cl2NO3SV (%): C: 48.01, H: 5.04,
N: 2.80. Found (%): C: 47.65, H: 4.56, N: 2.55.
2.3.3
(THF)2Cl2] (2c)
| [V{5‐phenylthiophene‐(N═CH)‐4‐tert‐butyl‐(OC6H3)}
This complex was prepared as described above for 2a,
starting from 1c (0.0627 g, 0.187 mmol) and VCl3(THF)3
(0.070 g, 0.187 mmol) in THF (10 ml) to give 2c as a red
solid (0.0800 g, 71%). IR (ATR, cm−1): 2956 (w), 2868

DO PRADO ET AL.
5
2.4 | EPR spectroscopy
Solid samples of the vanadium complexes were dissolved in
THF for solution studies at 25 and −78 °C. Signal channel
field modulation amplitude was adjusted to less than 10%
of the smallest line width to safely improve signal‐to‐noise
ratio, while signal channel time constant was set to less than
10% of the conversion time to avoid distortion effects. Micro-
wave power was set below saturation.
2.5 | Procedures for polymerization of ethylene and
copolymerization of ethylene with 1‐hexene
FIGURE 1 Molecular structure of 1g (thermal ellipsoids drawn at 30%
probability level)
All ethylene oligomerization tests were performed in a
100 ml double‐walled stainless Parr reactor equipped with
mechanical stirring, internal temperature control and continu-
ous feed of ethylene. The Parr reactor was dried in an oven at
120 °C for 5 h prior to each run, and then placed under vac-
uum for 30 min. In a typical reaction, toluene (with 1‐hexene)
and MAO solution were canulla‐transferred into the reactor
under an ethylene atmosphere. After complete thermal equil-
ibration (20 min), the toluene catalyst solution was injected
into the reactor under a stream of ethylene and then the reac-
tor was immediately pressurized, and stirred at 500 rpm for
15 min. The total pressure (5 bar) was kept constant by a con-
tinuous feed of ethylene. Afterwards, the reactor was
depressurized and cooled to 25 °C. The polymer was
precipitated using 20 ml of ethanol acidified with hydrochlo-
ric acid, under stirring for 30 min. After filtration and wash-
ing with small portions of acidic ethanol, then ethanol and
water, the resulting polymeric material was dried in a vacuum
oven at 60 °C for 12 h.
torsion angle of 179.7(3)°. The N(7)─C(7) (1.278 Å) and
N(7)─C(8) (1.408 Å) bond distances are comparable to those
found in similar Schiff base ligands bearing thiophene
group.[9]
The reaction of 1a–1g with 1 equiv. of VCl3(THF)3 in
THF at 35 °C yielded the corresponding vanadium com-
plexes (2a–2g) as orange or red moisture‐sensitive solids in
moderate to good yields (57–78%) (Scheme 1). The identity
of 2a–2g was established on the basis of elemental analysis
and IR and EPR spectroscopies. Due to the high sensitivity
of these vanadium complexes to air and moisture, all manip-
ulations were performed either using standard Schlenk‐line
techniques or in a glovebox under an inert atmosphere of
argon. Elemental analyses of 2a–2g are in agreement with
the formation of vanadium complexes of general formula
{SNO}VCl2(THF)2 having two molecules of THF coordi-
nated to the vanadium metal center. These complexes are
1
paramagnetic and show very broad peaks in the H NMR
spectra. All attempts to recrystallize the precatalysts 2a–2g
using various crystallization procedures failed resulting in
amorphous materials, unfortunately not suitable for a sin-
gle‐crystal X‐ray diffraction analysis.
The IR spectra of the vanadium complexes show the char-
acteristic absorption bands related to the phenoxy–imine–
thiophene ligands. Particularly, the IR spectra of 2a–2g show
the absence of O─H stretching bands in the range
3332–3453 cm−1 indicating the coordination of the phenoxy
3
| RESULTS AND DISCUSSION
3.1 | Synthesis and characterization of V(III)
complexes bearing phenoxy–imine–thiophene ligands
The phenoxy–imine–thiophene proligands (1a–1g) were
readily synthesized by Schiff base condensations between
the 2‐thiophenecarbaldehyde and the corresponding
phenolamine. The identity of this class of ligands was
established using elemental analysis, IR and NMR spectros-
1
copies, and an X‐ray diffraction study for 1g. The H NMR
spectra of 1a–1g in CDCl3 at room temperature exhibit reso-
nances in the region 8.79–8.58 ppm assigned to the imine
proton (HC═N), with the corresponding 13C NMR reso-
nances for the carbons of the imine moieties at ca 149 ppm.
Single crystals of 1g suitable for crystal X‐ray diffraction
analysis were obtained by slow evaporation from pentane
solution. The molecular geometry and atom‐labeling scheme
are shown in Figure 1.
The molecular structure of 1g shows that the geometry
around the C═N bond is essentially co‐planar, with phenoxy
group trans to the thiophene unit, and C(8)–N(7)–C(6)–C(5)
SCHEME 1 Synthesis of {SNO}VCl2(THF)2 complexes

6
DO PRADO ET AL.
group to the vanadium metal center. Furthermore, the IR
spectra of the these complexes show absorption bands at
1592–1619 cm−1 corresponding to the coordinated HC═N
unit of the ligands (1a–1g).[10,11]
Powdered solids and THF solutions of 2a, 2c, 2d, 2e and
2g in nitrogen atmosphere were analyzed using EPR spec-
troscopy at 77 K before and after air exposure. EPR spectra
are very consistent among all samples and the typical
responses are illustrated for sample 2e in Figure 2. The results
are consistent with an EPR‐silent vanadium(III) species being
oxidized to a detectable vanadium(IV) species.[12]
Before exposure to air, powder and solution samples
already show a low‐intensity vanadium(IV) spectrum due to
some degree of oxidation during sample preparation and/or
manipulation (Figure 2, black). However, after air exposure,
the signal intensity greatly increases, indicating the oxidation
of the vanadium(III) (Figure 2, red). Moreover, the great
increase in the signal indicates the majority of vanadium spe-
cies in the solid and solution samples being in the +3 oxida-
tion state before air exposure.
3.2 | Ethylene polymerization
The performance of vanadium complexes 2a–2g was
explored in homopolymerization of ethylene in toluene and
using MAO as co‐catalyst. The typical results are collected in
Table 1. Initial studies carried out at 30 °C show that these
catalyst systems are able to produce high‐density PE with
melting temperatures (Tm) in the range 133–136 °C, and crys-
tallinities varying from 28 to 41%. The resulting PEs are
insoluble for ordinary gel permeation chromatography analy-
sis (in o‐dichlororbenzene at 140 °C) probably due to their
ultrahigh molecular weights.[13]
As shown in Figure 3, the presence of substituents
t
(Me, Bu) on the phenoxy unit promotes higher activities in
comparison with the unsubstituted catalysts. For instance,
the precatalysts 2c and 2e containing p‐tBu group are ca 2.0
times more active than 2b and 2d (compare runs 2 versus 3
and 4 versus 5). In this case, we assume that the introduction
of these electron‐donating group at the R2 position in the
phenoxy moiety strengthens the vanadium–oxygen bond,
improving the stability of the active species as already
reported for zirconium complexes bearing phenoxy–imine
chelate ligands.[14] On the other hand, the presence of substit-
uents (Me, Ph) on the thiophene unit show less of an influ-
ence on the activity as result of no interaction of this
pendant group with the vanadium metal center; however,
we cannot rule out the beneficial role of thiophene moiety
for stabilizing catalytically active species, and thus improving
the catalyst performance.[15]
The replacement of p‐tBu group by a fluorine atom as in
precatalyst 2 g leads to a higher activity (887.2 kg of PE
(mol[V])−1⋅h−1) as compared to the counterpart 2e (664.8 kg
of PE (mol[V])−1⋅h−1). In this case, we speculate that the intro-
duction of electron‐withdrawing group into a phenoxy moiety
decreases the electron density on oxygen atom, which
decreases the electron density of the vanadium metal center.
Accordingly, it will make ethylene monomer coordination to
the vanadium much easier and enhance catalytic activity. A
similar effect has been reported for titanium complexes con-
taining β‐enaminoketonato and phenoxyimine ligands.[16,17]
To gain a more detailed understanding of ethylene poly-
merization behavior of this class of precatalysts, we decided
to explore the effect of reaction parameters such as tempera-
ture, MAO loading and reaction time using some selected
vanadium complexes. As presented in Figure 4, increasing
the polymerization temperature from 30 to 50 °C does not
significantly affect the catalytic activity of 2d and 2e, which
are comparable considering an average error of 10%. How-
ever, on further increasing the temperature (80 °C), the cata-
lytic activity dropped substantially suggesting the thermal
deactivation of the catalyst probably associated with the
reduction of the catalytically active vanadium species to
low‐valent, less active or inactive species.[2b,5q,18] Further-
more, the comparable polymerization performance of 2d
and 2e at 80 °C (219.2 kg of PE (mol[V])−1⋅h−1 (2d);
FIGURE 2 EPR spectra (77 K) of 2e before and after air exposure.
(a) Powdered solid and (b) frozen THF solution. The solid‐state spectrum is
broad due to magnetic interactions among paramagnetic vanadium(IV)
centers

DO PRADO ET AL.
7
TABLE 1 Ethylene polymerization reactions using 2a–2ga
Run
Catalyst
[Al]/[V]
Temp. (°C)
mpol (g)
Activityb
Tm (°C)
χ (%)c
1
2
2a
2b
2c
2d
2d
2d
2e
2f
500
500
500
500
500
500
500
500
500
500
500
500
500
100
250
1000
2000
4000
30
30
30
30
50
80
30
30
30
30
30
50
80
30
30
30
30
30
0.267
0.320
0.678
0.450
0.543
0.274
0.831
0.508
1.109
0.617
1.219
0.733
0.330
0.314
0.829
0.776
0.931
0.941
213.6
256.0
542.4
360.0
434.4
219.2
664.8
406.4
887.2
1486.7
487.6
586.4
264.0
251.2
663.2
620.8
744.8
752.8
135
134
133
134
133
134
136
135
134
133
131
137
137
136
135
136
135
135
34
30
31
30
21
33
41
28
40
46
42
50
43
31
35
37
33
34
3
4
5
6
7
8
9
2g
2g
2g
2e
2e
2e
2e
2e
2e
2e
10d
11e
12
13
14
15
16
17
18
aReaction conditions unless specified otherwise: toluene =100 ml, [V] = 5 μμmol, polymerization time = 15 min, P(ethylene) = 5 bar (kept constant), MAO as co‐catlyst.
The results shown are representative of at least duplicated experiments, yielding reproducible results within 10%.
bkg of PE (mol[V])−1⋅h−1
.
cCrystallinity calculated as (ΔHf/ΔHfα) × 100, ΔHfα = 286.6 J g−1
dReaction time = 5 min.
.
eReaction time = 30 min.
FIGURE 3 Influence of nature of vanadium complex on activity (30 °C,
5 μmol of catalyst, PC2H4 = 5 bar, molar ratio [Al]/[V] = 500)
FIGURE 4 Influence of temperature on activity using the precatalysts 2d
and 2e (30 °C, 15 min, 5 μmol of catalyst, PC2H4 = 5 bar, molar ratio [Al]/
[V] = 500)
264.0 kg of PE (mol[V])−1⋅h−1 (2e)) suggests the formation
of similar active species, which the presence of tert‐butyl
group in 2e did not induce any additional thermal stability
as compared with 2d.
To examine the role of the MAO loading in the poly-
merization, we carried out several runs using 2e in which
the [Al]/[V] molar ratio was systematically varied from
100 to 4000 equiv. Upon activation with 100 equiv. of
MAO, the precatalyst 2e shows moderate activity of
251.2 kg of PE (mol[V])−1⋅h−1 which is increased 2.6
times upon using 250 equiv. (663.2 kg of PE (mol[V])
−1⋅h−1). However, further increase of the [Al]/[V] molar
ratio from 500 to 4000 shows only slight variations in the
activity attaining values in the range 664.8–752.8 kg of
PE (mol[V])−1⋅h−1. Thus, the [Al]/[V] molar ratio of 250
appears as a good tradeoff between activity and cost of
co‐catalyst.

8
DO PRADO ET AL.
FIGURE 6 Effect of 1‐hexene concentration on activity and Tm using
precatalyst 2e (30 °C, 5 μmol of catalyst, PC2H4 = 5 bar, molar ratio [Al]/
[V] = 500)
FIGURE 5 Lifetime graph of ethylene polymerization for precatalyst 2g
(30 °C, 5 μmol of catalyst, PC2H4 = 5 bar, molar ratio [Al]/[V] = 500)
Lifetime study of the 2g/MAO catalytic system was con-
ducted for 5, 15 and 30 min at 30 °C in order to verify the
deactivation process (runs 9–11 in Table 1). As can be seen in
Figure 5, the relationship between reaction time and polymer
yield indicates that 2g undergoes almost complete deactiva-
tion after 15 min. At 30 min a net 67% of catalytic activity
is reduced in contrast with that at 5 min.
shown in Figure 6, the catalytic activity reaches the minimum
value with a 1‐hexene feed concentration of 0.64 mol l−1. A
greater loading of 1‐hexene (1.61 mol l−1) leads to an improve-
ment in the activity (762.4 kg of PE (mol[V])−1⋅h−1) that can
be tentatively associated with the hexene homopolymerization
process that occurs in parallel with the ethylene–hexene copo-
lymerization reaction.[19a]
The DSC curves of ethylene–1‐hexene copolymer pro-
duced at different co‐monomer concentrations are presented
in Figure 7. The ethylene–1‐hexene copolymers produced
using 2e/MAO are found to exhibit Tm between 102 and
123 °C with crystallinities varying from 12 to 24%. As can
be seen in Figure 7, the melting temperatures of the resulting
copolymers decrease with an increase of 1‐hexene feed as
result of higher co‐monomer incorporation into the main
polymer chain.
3.3 | Copolymerization of ethylene with 1‐hexene
The ethylene–1‐hexene copolymerization reactions were per-
formed using complex 2e as precatalyst at 30 °C, in toluene–
1‐hexene mixture with an overpressure of ethylene (5 bar),
and using MAO as co‐catalyst ([Al]/[V] =500). Representa-
tive copolymerization results are summarized in Table 2.
The catalytic activities and Tm of the ethylene–1‐hexene
copolymers are substantially influenced by 1‐hexene concen-
tration. Thus, it is found that the activity decreases on increas-
ing the 1‐hexene concentration from 0.32 to 0.97 mol l−1 as
result of a ‘negative co‐monomer effect’.[19] In this case, the
chain propagation rate (Rp) of the ethylene–hexene copoly-
The microstructure of ethylene–1‐hexene copolymers
produced using the 2e/MAO catalyst system was analyzed
merization is smaller
than that for ethylene
homopolymerization (compare run 1 with runs 2–5). As
TABLE 2 Copolymerization of ethylene with 1‐hexene using 2e/MAO
catalytic systema
Run
[1‐hexene] (mol l−1
)
mpol (g)
Activityb
Tm (°C)
χ (%)c
1
2
3
4
5
6
0.00
0.32
0.64
0.97
1.29
1.61
0.831
0.574
0.496
0.664
0.772
0.953
664.8
459.0
397.0
531.2
617.6
762.4
136
123
117
115
113
102
41
19
12
24
18
18
aReaction conditions: toluene =100 ml, [V]
= 5 μmol, polymerization
time = 15 min, P(ethylene) = 5 bar (kept constant), T = 30 °C, MAO as cocatalyst
([Al][V] = 500). The results shown are representative of at least duplicated exper-
iments yielding reproducible results within 15%.
FIGURE 7 DSC thermograms of PE and ethylene–1‐hexene copolymers
produced using the 2e/MAO system (30 °C, 5 μmol of catalyst, PC2H4 = 5 bar,
molar ratio [Al]/[V] = 500)
bkg of PE (mol[V])−1⋅h−1
cCrystallinity calculated as (ΔHf/ΔHfα) × 100, ΔHfα = 286.6 J g−1
.
.

DO PRADO ET AL.
9
TABLE 3 Monomer sequence distributions for poly(ethylene‐co‐1‐hexene)s obtained with 2e/MAO catalyst systema
Sequence distribution (%)b
1‐
Hexene
content
(mol%)c
Run
[HHH]
[EHH]
[EHE]
[EEE]
[HEH]
[HEE]
5
6
0.0
0.0
0.5
0.0
3.1
4.0
89.5
87.5
0.7
0.4
6.3
8.0
3.6
4.0
aPolymerization conditions: see Table 2.
bCalculated by analysis of 13C NMR spectra.
c1‐Hexene content estimated on the basis of 13C NMR spectra.
4
| CONCLUSIONS
A new set of vanadium(III) complexes bearing phenoxyimine
ligands with pendant thiophene group has been prepared and
evaluated for homo‐ and copolymerization of ethylene under
MAO activation. EPR results indicate that the vast majority
of vanadium species in the solid and solution samples were
in the +3 oxidation state before air exposure. Upon activation
with MAO, these vanadium(III) precatalysts showed moderate
catalytic activity for ethylene polymerization producing high‐
density PE. The impossibility of dissolving these PEs in a
common solvent for gel permeation chromatography analysis
suggests that such polymers might present very high molecu-
lar weights. The presence of electron‐donating group (Me,
tBu) at the para position in the phenoxy moiety strengthens
the vanadium–oxygen bond, improving the stability and
activity of the active species as compared with the
unsubstituted moiety. However, much higher activity was
obtained using phenoxyimine bearing an electron‐withdraw-
ing group (fluorine) in 2g that can be tentatively associated
with easier coordination of ethylene monomer to the vana-
dium metal center. As expected, the presence of substitu-
ents (Me, Ph) on the thiophene unit showed less of an
influence on the activity; however, we cannot rule out the
beneficial role of thiophene moiety for stabilizing catalyti-
cally active species. The optimization results showed that
2e/MAO operates with good activity at low MAO loading
(250 equiv.) and moderate polymerization temperature
(50 °C). Lifetime study of the 2g/MAO catalytic system
showed that polymerization activity progressively decreased
when the reaction time was prolonged from 5 to 30 min. In this
case, the relationship between reaction time and polymer yield
indicates that 2 g undergoes almost complete deactivation
after 15 min. Precatalyst 2e was able to copolymerize ethylene
with 1‐hexene producing ethylene–1‐hexene copolymers with
low co‐monomer incorporation. Furthermore, this catalyst
system showed lower activities as compared with the ethylene
homopolymerization results that might be attributed to the
steric and electronic effects of the ligand on the metal center.
FIGURE
8
Typical 13C{1H} NMR spectrum (o‐C6D4Cl2, 408 K) of
poly(ethylene‐co‐1‐hexene) produced with 2e/MAO ([V] = 5 μmol; toluene
=100 ml; MAO as co‐catalyst; [Al]/[V] = 500; T = 30 °C; PC2H4 = 5 bar;
[1‐hexene] = 1.61 mol l−1; time = 15 min)
by 13C NMR in o‐C6D4Cl2 at 135 °C. Table 3 summarizes
the 13C NMR analysis results for ethylene–1‐hexene copoly-
mers produced using 1‐hexene concentrations of 1.29 and
1.61 mol l−1. A typical 13C NMR spectrum for resultant
poly(ethylene‐co‐1‐hexene) is shown in Figure 8. The
absence of resonances in the range 40–42 ppm in the 13C
NMR spectrum related to α,α‐carbon in the HH dyad
sequence[20] indicates that 1‐hexene units are essentially iso-
lated by ethylene units in the polymer chains. In addition, no
[EHH] or [HHH] sequences are observed.
The co‐monomer content of the ethylene–1‐hexene copol-
ymers was calculated based on 13C NMR analysis,[20] and the
results are given in Table 3. It is observed that on varying the
1‐hexene concentration from 1.20 to 1.61 mol l−1 the
co‐monomer content remains almost unchanged indicating
the low co‐monomer incorporation ability of precatalyst 2e.
This result can be associated with the steric hindrance and
electron effect of the phenoxy–imine–thiophene ligand
hampering the coordination of the co‐monomer to the
vanadium metal center.
The highest 1‐hexene incorporation (4.0%) is found for
copolymerization reaction carried out using 1.61 mol l−1
(run 6) which is much lower as compared with other
similar vanadium(III) complexes having phenoxy bidentate
ligands.[5n,5p]
ACKNOWLEDGMENTS
This research was financially supported by Petrobras S/A.
N. T. do Prado gratefully acknowledge CNPq for a fellow-
ship. We thank R. P. das Chagas (Instituto de Química,

10
DO PRADO ET AL.
Hessen, J. H. Teuben, Eur. J. Inorg. Chem. 1867, 1998; s) R. Schmidta,
M. B. Welcha, R. D. Knudsenb, S. Gottfriedc, H. G. Alt, J. Mol. Catal.
A 2004, 222, 17; t) D. Reardon, F. Conan, S. Gambarotta, G. Yap, Q.‐Y.
Wang, J. Am. Chem. Soc. 1999, 121, 9318.
Universidade Federal de Goiás) for the X‐ray diffraction
analysis of 1g.
REFERENCES
[6] a) A. L. Bergamo, H. K. Da Cas, R. S. Rambo, C. S. Schwalm, A. C. A.
Casagrande, R. Stieler, O. L. Casagrande Jr., Catal. Commun. 2016, 86,
77; b) A. C. Pinheiro, A. H. Virgilli, E. Kirillov, T. Roisnel, J.‐F. Carpentier,
O. L. Casagrande Jr., RSC Adv. 2015, 5, 91524; c) A. C. Pinheiro, E. Kirillov,
T. Roisnel, J.‐F. Carpentier, O. L. Casagrande Jr., Dalton Trans. 2015, 44,
16073; d) F. S. Gomes, A. L. Bergamo, O. L. Casagrande Jr., Macromol.
Chem. Phys. 2014, 215, 1735.
[1] a) N. Desmangles, S. Gambarotta, C. Bensirmon, S. Davis, H. Zahalka,
J. Organometal. Chem. 1998, 562, 53; b) M. Motevalli, D. Shah, S. A. A.
Shah, A. C. Sullivan, Organometallics 1994, 13, 4109; c) M. P. Coles, C.
I. Dalby, V. C. Gibson, I. R. Little, E. L. Marshall, M. H. Ribeiro da Costa,
S. Mastroianni, J. Organometal. Chem. 1999, 591, 78; d) K. Nomura, B.
Kitiyanan, Adv. Org. Synth. 2013, 3, 174; e) T. Xiao, W. Zhang, J. Lai,
W.‐H. Sun, C. R. Chim. 2011, 14, 851; f) W. Zhang, W.‐H. Sun, C. Redshaw,
Dalton Trans. 2013, 42, 8988; g) J. Ma, C. Feng, S. Wang, K.‐Q. Zhao, W.‐
H. Sun, C. Redshaw, G. A. Solan, Inorg. Chem. Front. 2014, 1, 14; h) R.
Gao, W.‐H. Sun, C. Redshaw, Catal. Sci. Technol. 2013, 3, 1172; i) S. Wang,
W.‐H. Sun, C. Redshaw, J. Organometal. Chem. 2014, 751, 717.
[7] I. Kaya, A. Aydın, J. Appl. Polym. Sci. 2011, 121, 3028.
[8] W.‐S. Hwang, J.‐H. Lai, D.‐L. Wag, M. Y. Chiang, J. Chin. Chem. Soc.
1999, 46, 529.
[9] a) A. Cuin, G. A. Pereira, A. J. Bortoluzzi, A. C. Massabni, P. P. Corbi,
J. Struct. Chem. 2013, 54, 269; b) C. Kazak, M. Aygün, G. Turgut, M.
Odabasoglu, S. Özbey, O. Büyükgüngöra, Acta Crystallogr. C 2000, 56,
1044.
[2] a) T. Matsugi, T. Fujita, Chem. Soc. Rev. 2008, 37, 1264; b) D. Takeuchi,
Dalton Trans. 2010, 39, 311; c) K. Nomura, S. Zhang, Chem. Rev. 2011,
111, 2342; d) J. Q. Wu, Y. S. Li., Coord. Chem. Rev. 2011, 255, 2303;
e) C. Redshaw, Y. Tang, Chem. Soc. Rev. 2012, 41, 4484; f) V. C. Gibson,
S. K. Spitzmesser, Chem. Rev. 2003, 103, 283; g) S. D. Ittel, L. K. Johnson,
M. Brookhart, Chem. Rev. 2000, 100, 1169; h) W.‐H. Sun, H. Yang, Z. Li,
Y. Li, Organometallics 2003, 22, 3678; i) M. Mitani, R. Furuyama, J.
Mohri, J. Saito, S. Ishii, H. Terao, N. Kashiwa, T. Fujita, J. Am. Chem.
Soc. 2002, 124, 7888; j) C. Capacchione, A. Proto, H. Ebeling, R.
Mülhaupt, T. P. Spaniol, K. Müller, J. Okuda, J. Am. Chem. Soc. 2003,
125, 4964.
[10] M. Bialek, E. Bisz, J. Polym. Resarch 2013, 20, 164.
[11] D. J. Curran, S. Siggia, in The Chemistry of the Carbon‐Nitrogen Double
Bond, (Ed: S. Patai), Wiley‐Interscience, New York 1970 149.
[12] P. J. Alonso, J. Forniés, M. A. G. Monforte, M. Martín, B. Menjón, Chem.
Eur. J. 2005, 11, 4713.
[13] a) A. C. A. Casagrande, T. T. R. Tavares, M. C. A. Kuhn, O. L. Casagrande
Jr., J. H. Z. dos Santos, T. Teranishi, J. Mol. Catal. A 2004, 212, 267; b) P.
Smith, H. D. Chanzy, B. P. Rotzinger, Polymer 1989, 30, 1814.
[3] a) S. Gambarotta, Coord. Chem. Rev. 2003, 237, 229; b) K. Nomura, S.
Zhang, Chem. Rev. 2011, 111, 2342; c) H. Hagen, J. Boersma, G. van Koten,
Chem. Soc. Rev. 2002, 31, 357; d) L. S. Boffa, B. M. Novak, Chem. Rev.
2000, 100, 1479; e) C. Redshaw, Dalton Trans. 2010, 39, 5595; f) A. K.
Tomov, V. C. Gibson, D. Zaher, M. R. J. Elsegood, S. H. Dale, Chem.
Commun. 1956, 2004; g) G. Liu, D. J. Beetstra, A. Meetsma, B. Hessen,
Organometallics 2004, 23, 3914; h) H. R. Bigmore, M. A. Zuideveld, R.
M. Kowalczyk, A. R. Cowley, M. Kranenburg, E. J. L. Mclnnes, P.
Mountford, Inorg. Chem. 2006, 45, 6411; i) A. Jabri, I. Korobkov, S.
Gambarotta, R. Duchateau, Angew. Chem Int. Ed. 2007, 46, 6119; j) G.‐M.
Meppelder, T. S. Halbach, T. P. Spaniol, R. Mülhaupt, J. Okuda,
J. Organometal. Chem. 2009, 694, 1235; k) C. Redshaw, L. Warford, S. H.
Dale, M. R. J. Elsegood, Chem. Commun. 1954, 2004; l) C. Redshaw, M.
A. Rowan, D. M. Homden, S. H. Dale, M. R. J. Elsegood, S. Matsui, S.
Matsuura, Chem. Commun. 2006, 3329; m) D. Homden, C. Redshaw, J. A.
Wright, D. L. Hughes, M. R. J. Elsegood, Inorg. Chem. 2008, 47, 5799.
[14] N. Matsukawa, S. Matsui, M. Mitani, J. Saito, K. Tsuru, N. Kashiwa, T.
Fujita, J. Mol. Catal. A 2001, 169, 99.
[15] a) J.‐B. Wang, L.‐P. Lu, J.‐Y. Liu, Y.‐S. Li, Dalton Trans. 2014, 43, 12926;
b) L. Porri, A. Ripa, P. Colombo, E. Miano, S. Capelli, S. V. Meille,
J. Organometal. Chem. 1996, 514, 213; c) F. G. Sernetz, R. Mülhaupt, S.
Fokken, J. Okuda, Macromolecules 1997, 30, 1562; d) R. D. J. Froese,
D. G. Musaev, T. Natsubara, K. Morokuma, J. Am. Chem. Soc. 1997,
119, 7190; e) R. D. J. Froese, D. G. Musaev, K. Morokuma, Organometal-
lics 1999, 18, 373.
[16] W.‐P. Ye, J. Zhan, L. Pan, N.‐H. Hu, Y.‐S. Li, Organometallics 2008, 27,
3642.
[17] S. Ishii, J. Saito, M. Mitani, J. Mohri, N. Matsukawa, Y. Tohi, S. Matsui, N.
Kashiwa, T. Fujita, J. Mol. Catal. A 2002, 179, 11.
[18] Q. Yan, Z. Sun, W. Zhang, K. Nomura, W.‐H. Sun, Macromol. Chem. Phys.
2014, 215, 1744.
[4] G. Natta, A. Zambelli, G. Lanzi, I. Pasquon, E. R. Mognaschi, A. L. Segre, P.
Centola, Makromol. Chem. 1965, 81, 161.
[19] a) J. C. W. Chien, T. Nozaki, J. Polym. Sci. A: Polym. Chem. 1993, 31, 227;
b) M. Białek, K. Czaja, A. Pietruszka, Polym. Bull. 2013, 70, 1499; c) J.‐S.
Yoon, D.‐H. Lee, E. S. Park, I.‐M. Lee, D. K. Park, S. O. Jung, J Appl Polym
Sci. 2000, 75, 928.
[5] a) D. Reardon, F. Conan, S. Gambarotta, G. Yap, Q. Y. Wang, J. Am.
Chem. Soc. 1999, 121, 9318; b) Y. Nakayama, H. Bando, Y. Sonobe, Y.
Suzuki, T. Fujita, Chem. Lett. 2003, 766; c) J.‐Q. Wu, L. Pan, N.‐H. Hu,
Y.‐S. Li, Organometallics 2008, 27, 3840; d) S. Golisz, R. J. E. Bercaw,
Macromolecules 2009, 42, 8751; e) L.‐M. Tang, J.‐Q. Wu, Y.‐Q. Duan,
L. Pan, Y.‐G. Li, Y.‐S. Li, J. Polym. Sci. A: Polym. Chem. 2008, 46,
2038; f) J.‐Q. Wu, B.‐X. Li, S.‐W. Zhang, Y.‐S. Li, J. Polym. Sci. A: Polym.
Chem. 2010, 48, 3062; g) J.‐Q. Wu, L. Pan, Y.‐G. Li, S.‐R. Liu, Y.‐S. Li,
Organometallics 2009, 28, 1817; h) J.‐S. Mu, J.‐Y. Liu, S.‐R. Liu, Y. S.
Li, Polymer 2009, 50, 5059; i) J.‐Q. Wu, L. Pan, S.‐R. Liu, L.‐P. He,
Y.‐S. Li, J. Polym. Sci. A: Polym. Chem. 2009, 47, 3573; j) I. E. Soshnikov,
N. V. Semikolenova, A. A. Antonov, K. P. Bryliakov, V. A. Zakharov, E. P.
Talsi, Organometallics 2014, 33, 2583; k) S. Milione, G. Cavallo, C.
Tedesco, A. Grassi, J. Chem. Soc. Dalton Trans. 2002, 1839; l) J. Romero,
F. Carrillo‐Hermosilla, A. Antinolo, A. Otero, J. Mol. Catal. A 2009, 304,
180; m) L. Clowes, M. Walton, C. Redshaw, Y. Chao, A. Walton, P. Elo, V.
Sumerin, D. L. Hughes, Catal. Sci. Technol. 2013, 3, 152; n) S.‐W. Zhang,
L.‐P. Lu, B.‐X. Li, Y.‐S. Li, J. Polym. Sci. A: Polym. Chem. 2012, 50, 4721;
o) J.‐S. Mu, X.‐C. Shi, Y.‐S. Li, J. Polym. Sci. A: Polym. Chem. 2011, 49,
2700; p) J.‐S. Mu, Y.‐X. Wang, B.‐X. Li, Y.‐S. Li, Dalton Trans. 2011, 40,
3490; q) B.‐C. Xu, T. Hu, J.‐Q. Wu, N.‐H. Hua, Y.‐S. Li, Dalton Trans.
2009, 8854; r) M. J. R. Brandsma, E. A. C. Brussee, A. Meetsma, B.
[20] J. C. Randall, J. Macromol. Sci. Rev. Macromol. Chem. Phys. 1989,
C29, 201.
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complexes containing phenoxy–imine–thiophene
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