Synthesis, characterization and ethylene polymerization behavior of binuclear iron complexes bearing N,N′-bis(1-(6-(1-(arylimino)ethyl) pyridin-2-yl)ethylidene)benzidines

Article abstract of DOI:10.1039/c3ra42631a

A series of N,N′-bis(1-(6-(1-(arylimino)ethyl)pyridin-2-yl) ethylidene)benzidines and the bi-metallic iron complexes thereof have been synthesized and fully characterized. All iron complexes, when activated by MAO or MMAO, exhibited high activities of up to 1.3 × 10⁷ g mol^-1 (Fe) h^-1 for the polymerization of ethylene. On comparison with their mononuclear counterparts, such bi-metallic complexes not only retain a relatively high activity at elevated temperatures (up to 70 °C), but also exhibit increased lifetimes. The polyethylenes obtained were characterized by GPC, DSC and high temperature NMR spectroscopy, which indicated multimodal and highly linear features.

Full text of DOI:10.1039/c3ra42631a

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Synthesis, characterization and ethylene polymerization
behavior of binuclear iron complexes bearing
N,N0-bis(1-(6-(1-(arylimino)ethyl) pyridin-2-yl)-
ethylidene)benzidines†
Cite this: RSC Adv., 2013, 3, 26184
a
a
a
a
c
*
Qifeng Xing, Tong Zhao, Yusen Qiao, Lin Wang, Carl Redshaw
ab
*
and Wen-Hua Sun
A series of N,N0-bis(1-(6-(1-(arylimino)ethyl)pyridin-2-yl)ethylidene)benzidines and the bi-metallic iron
complexes thereof have been synthesized and fully characterized. All iron complexes, when activated by
MAO or MMAO, exhibited high activities of up to 1.3 ꢀ 107 g molꢁ1 (Fe) hꢁ1 for the polymerization of
ethylene. On comparison with their mononuclear counterparts, such bi-metallic complexes not only
retain a relatively high activity at elevated temperatures (up to 70 ꢂC), but also exhibit increased
lifetimes. The polyethylenes obtained were characterized by GPC, DSC and high temperature NMR
spectroscopy, which indicated multimodal and highly linear features.
Received 29th May 2013
Accepted 21st October 2013
DOI: 10.1039/c3ra42631a
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binuclear complexes9–11 as well as multi-nuclear complexes12
have been studied.
Introduction
Highly active ethylene polymerization complex pre-catalysts
based on 2,6-bis(imino)pyridyl metal complexes (metal ¼ iron
or cobalt),1 which were found to possess activities higher than
those observed for a-diimino-nickel (or palladium) complex
pre-catalysts,2 were a breakthrough in late transition metal-
based pre-catalysts for polyolen production. On comparison
with commercial Ziegler–Natta3 or metallocene4 catalytic
systems, late transition metal complex pre-catalysts display
signicant advantages5 such as ease of preparation, enhanced
stability as well as the ability to nely tune the properties of the
obtained polyethylene via simple modication of the ancillary
ligands or by controlling the parameters of the catalytic reac-
tion. The key in designing complex pre-catalysts is to develop
heterocyclic compounds as suitable ligands,5–8 in which the
bulky substituted bis(imino)pyridines enhance the catalytic
behavior of their metal (Fe or Co) complexes.8 Moreover,
synergistic effects have commonly been considered in multi-
nuclear complexes, and in our laboratory and elsewhere,
In the case of the most investigated complex pre-catalysts
bearing 2,6-bis(imino)pyridine derivatives, positive synergic
effects were observed for the bi-nuclear complex models A13a
and B13b and the multinuclear complex C,12a all of which dis-
played higher activity than did the corresponding mononuclear
complexes.1 In addition, binuclear complexes bearing hybrid
ligands of both bidentate and tridentate coordination, e.g. D13c
and E9a–c were capable of both ethylene oligomerization and
polymerization. In the course of pursuing binuclear complex
pre-catalysts,14 we found that the tetramethylbenzidine-based
metal complex pre-catalysts (F) produced polyethylene of high
molecular weight and narrow polydispersity,14a whilst the
methyl-bridged dianiline derived dinuclear nickel pre-catalysts
(G) generally provided both polyethylenes and oligomers.14b The
signicant catalytic behavior exhibited by nickel complex pre-
catalysts bearing ligands based on benzidines and methyl-
bridged anilines inspired us to revisit the binuclear complexes
bearing 2,6-bis(imino)pyridyl motifs connected via tetraalkyl-
benzidines H, which differ from the analog models A13a
and B.13b Various bulky benzidines were designed and were
used to synthesize complex pre-catalysts with better thermo-
stability. Fortunately, the newly designed bi-metallic iron(II)
complexes, when activated with MAO or MMAO, revealed high
activities toward ethylene polymerization when operating at
high temperatures of around 70 ꢂC. Herein, the synthesis
and characterization of the organic compounds and their
metal complexes are reported, and the ethylene polymerization
behavior is discussed.
aKey laboratory of Engineering Plastics and Beijing National Laboratory for Molecular
Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
E-mail: whsun@iccas.ac.cn; Fax: +86 10 62618239; Tel: +86 10 62557955
bState Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of
Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
cDepartment of Chemistry, University of Hull, Hull HU6 7RX, UK. E-mail: c.redshaw@
hull.ac.uk; Fax: +44 1482 466410; Tel: +44 1482 465219
† CCDC 938522. For crystallographic data in CIF or other electronic format see
DOI: 10.1039/c3ra42631a
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Results and discussion
Synthesis and characterization of the organic compounds and
their iron complexes
Benzidine derivatives15 and 2-acetyl-6-aryliminopyridine16 were
prepared according to the literature. The condensation reactions
of the two aforementioned substances were conducted in toluene
in the presence of a catalytic amount of 4-methylbenzenesulnic
acid to form the target compounds, N,N0-bis(1-(3-(1-arylimino-
ethyl)pyridin-2-yl)ethylidene)tetraalkylbenzidine derivatives (L1–
L11, Scheme 2). The newly synthesized compounds were reacted
with iron(II) dichloride in methanol to form the corresponding
binuclear iron complexes in good yields (Fe-1–Fe-11, Scheme 2).
All compounds were consistent with their elemental analyses.
The structures of the organic compounds were further conrmed
1
by H and 13C NMR spectroscopic measurements. The effective
coordination to iron was reected in the FT-IR spectra, where the
C]N stretching vibration bands appeared in the range of 1620–
1632 cmꢁ1 for iron complexes versus 1639–1650 cmꢁ1 for the
ligands as free compounds. In addition, the structures of the
iron complexes were also veried by MALDI-TOF measurements.
Our attempts to obtain single-crystals of the iron complexes
have thus far been unsuccessful; however the representative
compound L5 was re-crystallized from a saturated dichloro-
methane solution.
Scheme 2 Synthetic procedure.
Scheme 1 Representative models of multinuclear and target complexes.
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and N(1)–C(5) are hybrids between double and single bonds due
to the conjugated cyclic pyridine ring.
The molecular structure of L5 reveals the co-planar nature of
the two benzene rings within the tetraalkylbenzidine motif.
However, the pyridyl plane is almost perpendicular to the
phenyl plane of the benzidine with a dihedral angle of ca.
88.77ꢂ, whilst a similar dihedral angle between the pyridyl and
phenyl of the aniline is observed at ca. 86.71ꢂ.
Fig. 1 ORTEP drawing of L5 with thermal ellipsoids at 30% probability level.
Hydrogen atoms have been omitted for clarity.
Catalytic behavior towards ethylene
ꢂ
˚
Table 1 The selected bond lengths (A) and angles ( ) for complexes L5
According to previous publications,5 co-catalysts such as
methylaluminoxane (MAO) or modied methylaluminoxane
(MMAO) are commonly employed in combination with iron
complex pre-catalysts. Therefore, complex Fe-4 was used to
optimize the suitable catalytic parameters in the presence
of either methylaluminoxane (MAO) or modied methyl-
aluminoxane (MMAO).
˚
Bond length (A)
Bond angle (ꢂ)
N(2)–C(6)
N(2)–C(20)
N(1)–C(1)
N(1)–C(5)
N(3)–C(8)
N(3)–C(10)
1.267(5)
1.432(5)
1.327(5)
1.336(5)
1.268(6)
1.427(6)
C(6)–N(2)C(20)
C(1)–N(1)–C(5)
C(8)–N(3)–C(10)
N(1)–C(1)–C(2)
N(1)–C(1)–C(8)
N(2)–C(20)–C(21)
N(2)–C(25)–C(20)
N(1)–C(5)–C(4)
N(1)–C(5) –C(6)
121.3(4)
119.1(4)
122.2(4)
121.6(4)
117.7(4)
120.0(4)
119.2(4)
122.0(4)
116.1(4)
Optimizing polymerization parameters by complex Fe-4. The
catalytic behavior of complex Fe-4 was evaluated using different
molar ratios of Fe/Al, differing ethylene pressures and over
different reaction temperatures, in the presence of either MAO
(entries 1–14, Table 2) or MMAO (entries 15–22, Table 2).
With the Al/Fe molar ratio xed at 1000, the reaction
temperature was varied over the range 30 ꢂC–80 ꢂC (entries 1–6,
Table 2) and signicantly affected the catalytic activities; the
X-ray crystallographic studies
The molecular structure of L5 was conrmed by single crystal
X-ray diffraction and is shown in Fig. 1; selected bond lengths
and angles are collected in Table 1. It is clear that the bonds
N(2)–C(6) and N(3)–C(8) are shorter than the bonds N(2)–C(20)
and N(3)–C(10), each being consistent with double and single
bond features, respectively. In addition, the bonds N(1)–C(1)
ꢂ
optimum temperature was found to be ca. 60 C. Considering
the highly exothermic nature of the polymerization process, the
critical factor for late-transition metal complex pre-catalysts is
to maintain good activity at the operational temperature
employed in industry.17 The optimum observed temperature of
Table 2 Ethylene polymerization by Fe-4a
Entry
Co-cat.
Al/Fe
T/ꢂC
t/min
Activityb
Mwd/103 g molꢁ1
Mw/Mn
c
Tm /ꢂC
d
1
2
3
4
5
6
7
8
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
1000
1000
1000
1000
1000
1000
1500
2000
2500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1000
2000
2500
30
40
50
60
70
80
60
60
60
60
60
60
60
60
40
50
60
70
80
60
60
60
30
30
30
30
30
30
30
30
30
15
45
60
30
30
30
30
30
30
30
30
30
30
5.30
5.50
7.50
9.40
9.30
7.30
12.5
8.40
7.30
23.0
8.60
6.70
1.70
10.9
9.00
9.10
11.7
11.1
3.70
7.70
10.5
9.20
133.4
132.5
132.3
133.0
132.6
132.2
133.0
131.7
129.5
131.7
131.8
133.6
129.7
132.2
131.2
128.3
130.6
128.9
123.4
130.2
129.0
128.3
153
165
179
195
164
77.0
240
88.9
35.0
194
248
262
87.0
159
127
112
11.5
10.9
9.80
25.0
2.20
1.80
7.90
12.0
16.0
17.0
13.0
11.0
27.1
15.9
10.6
20.9
29.1
37.2
67.0
19.0
35.6
32.8
4.20
10.5
9.40
6.90
1.20
1.40
9
10
11
12
13e
14f
15
16
17
18
19
20
21
22
a
c
Conditions: 1.0 mmol of Fe-4; 10 atm of ethylene; total volume 100 mL. b Activity: 106 g PE molꢁ1 (Fe) hꢁ1
.
Determined by DSC. d Determined by
GPC. e 1 atm of ethylene. 5 atm of ethylene.
f
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around 60 C should be highlighted as an advantage of these
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ꢂ
Regarding the inuence of ethylene pressure (entries 7,
newly designed binuclear iron complex, particularly when 13,14, Table 2), the catalytic activity increased remarkably on
compared against pre-catalyst model A13a at around 20 C and increasing the ethylene pressure, whilst the GPC curves of the
ꢂ
B13b at around 30 ꢂC. Further increasing the temperature using obtained polyethylene (Fig. 4) possessed higher molecular
Fe-4 resulted partly in decomposition of the active species along weights and narrow polydispersity. Moreover, the catalytic
with a lower solubility of ethylene.18
system under higher pressure produced polyethylene possess-
The GPC measurements revealed wide polydispersities for ing close to unimodel features.
the obtained polyethylenes (Fig. 2), consistent with multi-site
On checking the lifetime of the active species for Fe-4/MAO
catalysis. According to the main peaks of the GPC curves, the (entry 7, entries 10–12, Table 2), the activity over 15 min reached
catalytic system at lower temperature generally preferred to as high as 2.3 ꢀ 107 g molꢁ1 (Fe) hꢁ1, and over 60 min, the
form polyethylenes with higher molecular weights; this is activity remained at 6.7 ꢀ 106 g molꢁ1 (Fe) hꢁ1. There was no
consistent with previous observations for iron complex pre- induction time for the catalytic system, and active species only
catalysts.8 Moreover, various Al/Fe molar ratios were screened, slowly deactivated. The obtained polyethylenes possessed
and the best activity was obtained at Al/Fe 1500 : 1 (entries 4, 7– higher molecular weights with wider polydispersity on pro-
9, Table 2); higher molar ratios of Al/Fe resulted in polyethylene longing the reaction time, during which the termination of
of lower molecular weight (Fig. 3), indicating that chain-transfer polymeric chains at different times was considered to produce
from the iron species to the aluminium was enhanced, resulting polyethylene with wide molecular polydispersity.19
in increased polymer chain termination on either increasing the
reaction temperature or the Al/Fe molar ratio.18
To elucidate the structural features of the resultant poly-
ethylene, 13C NMR spectroscopy was conducted in dichloro-
benzene and revealed (entry 9) only a single peak besides the
solvent d-1,2-dichlorobenzene (Fig. 5), indicating a highly linear
polyethylene.
Fig. 2 The GPC curves of polyethylenes obtained by Fe-4 at different temper-
atures (entries 1–6, Table 2).
Fig. 4 The GPC curves of the polyethylenes by Fe-4 under different pressure
(entries 7, 13, and 14, Table 2).
Fig. 3 The GPC curves of polyethylenes obtained by Fe-4 with various Al/Fe
ratios (entries 4, 7–9, Table 2).
Fig. 5 The 13C-NMR spectrum of the polyethylene produced by Fe-4 (entry 9,
Table 2).
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In a similar manner, the co-catalyst modied methyl- lower activity than did the analog Fe-8; such an observation
aluminoxane (MMAO) was used to explore the catalytic behavior makes more sense if the net charge of metal ion is positively
of complex Fe-4 under various parameters (entries 1–22, Table 2). affecting its catalytic activity.19 In all cases, the binuclear iron
In all cases, high activity toward ethylene polymerization was complexes exhibited higher activity and better thermo-stability
observed. Typically, the catalytic system using MAO exhibited than did the mono-nuclear analogs1 and related binuclear
better activity than did the system with MMAO; it is noteworthy analogs.13
that better thermo-stability with MMAO was observed (entries
17–19, Table 2). Moreover, the quenched solutions aer
removing polyethylenes were analyzed and no oligomers were
observed. Compared to the binuclear iron-complex pre-catalysts
Conclusion
Binuclear iron complexes ligated by N,N0-bis(1-(3-(1-arylimi-
noethyl)pyridin-2-yl)ethylidene)tetraalkylbenzidine derivatives
have been synthesized, characterized and screened as ethylene
polymerization pre-catalysts. Upon activation with MAO or
MMAO, all the binuclear iron complex pre-catalysts exhibited
high activities towards ethylene polymerization. The resultant
polyethylenes revealed a wide polydispersity, though the poly-
ethylene was highly linear. As well as the high activity [up to
1.3 ꢀ 107 g molꢁ1 (Fe) hꢁ1], the current complex pre-catalysts
performed with better thermo-stability than did related mono-
metallic complexes1 and other binuclear analogs.13 The title
binuclear iron complex pre-catalysts are currently under further
investigation in our laboratory, in order that their behaviour can
more closely match that required for industrial consideration.
derived from bis(imino)pyridines, the current model system
showed better activity and higher thermo-stability than did those
of the analogs A13a and B.13b
Ethylene polymerization by various iron complexes Fe-n. All
the iron complexes were explored following activation by MAO
under the optimum conditions determined for Fe-4, and the
data are collected in Table 3.
These iron complexes can be divided into groups according
to the different benzidine-bridges present, and catalytic trends
can be observed due to the inuence of the substituents present
at the aniline moiety. According to the performances by Fe-1
through Fe-3 obtained using the tetramethylbenzidine-bridged
ligands (entries 1–3, Table 3), the iron complex Fe-2 derived
from 2,6-diethylaniline exhibited higher activities than the
analogs Fe-1 and Fe-3, which is consistent with previous
observations for bis(imino)pyridyl iron complex pre-catalysts
due to the optimum bulkiness of the ethyl substituent versus
both methyl and i-propyl.1 Regarding the groups, Fe-4 to Fe-6
from tetraethylbenzidine-bridged ligands (entries 4–6, Table 3)
and Fe-7 to Fe-9 from tetra(isopropyl)benzidine-bridged ligands
(entries 7–9, Table 3), the catalytic activities of the binuclear
iron complexes decreased when using bulkier substituents at
the aniline, indicating that the ethylene coordination and
insertion (catalytic activity) became slower when bulky-substit-
uents surrounded the metal.8f It is difficult to rationalize a
general trend for the catalytic performance in terms of the
inuence of the ligands. For Fe-10 with an additional methyl
substituent, higher activity was observed versus Fe-1, which is
probably caused by the better solubility of the complex.20
However, Fe-11 with an additional methyl-substituent showed
Experimental
General considerations
All manipulations of air and/or moisture sensitive compounds
were carried out under a nitrogen atmosphere using standard
Schlenk techniques. Toluene was reuxed over sodium-benzo-
phenone and distilled under nitrogen prior to use. Methyl-
aluminoxane (MAO, 1.46 M solution in toluene) and modied
methylaluminoxane (MMAO, 1.93 M in heptane, 3A) were
purchased from Akzo Nobel Corp. High-purity ethylene was
purchased from Beijing Yansan Petrochemical Co. and used as
received. Other reagents were purchased from Aldrich, Acros, or
local suppliers. NMR spectra were recorded on Bruker DMX
400 MHz instrument at ambient temperature using TMS as
an internal standard. High temperature NMR spectra were
recorded on Bruker DMX 300 MHz instrument at ambient
temperature using TMS as an internal standard and d-1,2-
dichlorobenzene as the solvent. FT-IR spectra were recorded on
a Perkin-Elmer System 2000 FT-IR spectrometer. Elemental
analysis was carried out using an HPMOD 1106 microanalyzer.
MALDI-TOF spectra were detected on autoex III Bruker, using
CCA as the substrate. Molecular weights (Mw) and molecular
weight distribution (Mw/Mn) of polyethylenes were determined
by a PL-GPC220 at 150 ꢂC with three PLgel 10 mm MIXED-B
columns, with 1,2,4-trichlorobenzene as the solvent. Melting
points of polyethylenes were obtained from the second scanning
run on Q2000 DSC-7 at a heating rate of 10 ꢂC minꢁ1 to 150 ꢂC.
Table 3 Ethylene polymerization by iron complexesa
c
c
d
Entry Cat.
PE (g) Activityb Mw (kg molꢁ1
)
Mw/Mn Tm (ꢂC)
1
2
3
4
5
6
7
8
Fe-1
Fe-2
Fe-3
Fe-4
Fe-5
Fe-6
Fe-7
Fe-8
Fe-9
8.50
13.1
8.00
12.5
11.9
7.40
12.6
9.30
8.10
8.50
13.1
8.00
12.5
11.9
7.40
12.6
9.30
8.10
11.4
5.37
88.7
66.1
51.6
11.1
9.50
7.00
27.1
18.6
16.4
30.6
24.4
18.6
131.9
132.5
134.3
133.0
133.1
133.6
132.6
133.2
133.3
132.8
131.8
240
232
225
283
181
174
Synthesis and characterization of N,N0-bis(1-(3-(1-arylimino-
ethyl)pyridin-2-yl)ethylidene)tetraalkylbenzidine derivatives
9
10
11
Fe-10 11.4
Fe-11 5.37
73.7
22.8
7.50
3.90
3,30,5,50-Tetraethylbenzidine derivatives were synthesized
according to the literature,15 meanwhile 2-acetyl-6-arylimino-
pyridine was prepared by our previously reported method.16
a
General conditions: 1.0 mmol of Fe; 1500 of Al/Fe; 100 mL toluene for 10
atm ethylene; 60 ꢂC; 30 min. 106 g molꢁ1 (Fe) hꢁ1
.
Determined by
b
c
GPC. d Determined by DSC.
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Further reaction of 3,30,5,50-tetraethylbenzidine with two 769 (s), 689 (w). Anal. calcd for C56H60N6 (792): N, 10.60; C,
equivalent of 2-acetyl-6-aryliminopyridine formed the desired 81.78; H, 7.63. Found: N, 10.69; C, 81.95; H, 7.39%.
N,N0-bis(1-(3-(1-aryliminoethyl)pyridin-2-yl)ethylidene)tetra-
N,N0-Bis(1-(3-(1-(2,6-diisopropylphenylimino)ethyl)pyridin-2-
yl)ethylidene)tetramethylbenzidine (L3)
alkylbenzidine derivatives. As a typical example, the synthesis of
N,N0-bis(1-(3-(1-(2,6-diethylphenylimino)ethyl)pyridin-2-yl)
ethylidene)tetraethylbenzidine (L5) was conducted as follows:
2-acetyl-6-(1-((2,6-diethylphenyl)imino)ethyl)pyridine (0.75 g,
2.5 mmol) and 3,30,5,50-tetraethylbenzidine (0.28 g, 1.25 mmol)
were mixed in 100 mL toluene in the presence of a catalytic
amount 4-methylbenzenesulnic acid. The mixture was
reuxed for 24 h, then cooled to room temperature. The solu-
tion was evaporated at reduced pressure, the residue was then
separated by a column chromatography to collect the product,
N,N0-bis(1-(3-(1-(2,6-diethylphenylimino)ethyl)pyridin-2-yl)-
ethylidene)tetra-ethylbenzidine (L5) in 0.24 g as a yellow solid,
yield 22.6% (mp: 272 ꢂC). 1H NMR (400 MHz, CDCl3, ppm): 8.51
(d, J ¼ 8.0 Hz, 4H, Py–H), 7.95 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.13 (d,
J ¼ 7.6 Hz, 4H, Ph–H), 7.05 (t, J ¼ 8.0 Hz, 2H, Ph–H), 6.29 (s, 4H,
Ph–H), 2.40–2.53 (m, 8H, 4 ꢀ CH2), 2.24 (s, 6H, 2 ꢀ CH3), 2.10 (s,
6H, 2 ꢀ CH3), 1.14 (t, J ¼ 7.6 Hz, 12H, 4 ꢀ CH3). 13C NMR: (100
MHz, CDCl3, ppm): 167.5, 166.9, 155.2, 155.0, 147.9, 136.9,
136.0, 131.2, 126.4, 126.0, 125.8, 123.4, 122.3, 24.7, 18.2, 16.9,
Prepared as a yellow solid, yield 0.28 g, 26.8% (mp: 245 ꢂC). 1H
NMR (400 MHz, CDCl3, ppm): 8.56 (d, J ¼ 8.0 Hz, 4H, Py–H),
7.96 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.36 (s, 4H, Ph–H), 7.19 (d, J ¼ 7.6
Hz, 4H, Ph–H), 7.11 (t, J ¼ 8.0 Hz, 2H, Ph–H), 2.71–2.83 (m, 4H, 2
ꢀ CH2), 2.31 (s, 6H, 2 ꢀ CH3), 2.29 (s, 6H, 2 ꢀ CH3), 2.14 (s, 12H,
4 ꢀ CH3), 1.18 (d, 12H, J ¼ 2.0 Hz, 4 ꢀ CH3), 1.16 (d, 12H, J ¼ 2.0
Hz, 4 ꢀ CH3). 13C NMR (100 MHz, CDCl3, ppm): 167.5, 166.5,
155.3, 155.2, 152.6, 137.4, 136.4, 131.2, 126.9, 126.0, 125.7,
124.5, 123.2, 122.1, 28.4, 25.6, 23.3, 23.0, 18.2, 17.9. FT-IR
(cmꢁ1): 2957 (m), 2015 (w), 1641 (nC]N, s), 1570 (w), 1460 (m),
1361 (s), 1322 (w), 1243 (m), 1204 (s), 1117 (m), 859 (w), 824 (m),
766 (s), 692 (w). Anal. calcd for C58H68N6 (848): N, 9.90; C, 82.03;
H, 8.07. Found: N, 9.55; C, 81.86; H, 8.15%.
N,N0-Bis(1-(3-(1-(2,6-dimethylphenylimino)ethyl)pyridin-2-yl)-
ethylidene)tetraethylbenzidine (L4)
16.7, 13.8. FT-IR (cmꢁ1): 2964 (m), 1637 (nC]N, s), 1567 (m), 1450 Prepared as a yellow solid, yield 0.43 g, 43.6% (mp: 283 ꢂC). 1H
(s), 1362 (s), 1321 (w), 1296 (w), 1243 (m), 1200 (s), 1119 (m), NMR (400 MHz, CDCl3, ppm): 8.51 (d, J ¼ 8.0 Hz, 4H, Py–H),
1098 (m), 857 (w), 828 (m), 769 (m), 689 (w). Anal. calcd for 7.95 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.13 (d, J ¼ 7.6 Hz, 4H, Ph–H), 7.05
C
58H68N6 (848): N, 9.90; C, 82.03; H, 8.07. Found: N, 9.65; C, (t, J ¼ 8.0 Hz, 2H, Ph–H), 6.29 (s, 4H, Ph–H), 2.29–2.43 (m, 8H, 4
81.96; H, 8.12%.
ꢀ CH2), 2.24 (s, 6H, 2 ꢀ CH3), 2.10 (s, 6H, 2 ꢀ CH3), 1.14 (t, J ¼
7.6 Hz, 12H, 4 ꢀ CH3). 13C NMR (100 MHz, CDCl3, ppm): 167.5,
166.9, 155.2, 155.0, 147.9, 136.9, 136.0, 131.2, 126.4, 126.0,
125.8, 123.4, 122.3, 24.7, 18.2, 16.9, 16.7, 13.8. FT-IR (cmꢁ1):
2964 (m), 1637 (nC]N, s), 1567 (w), 1450 (m), 1362 (s), 1321 (w),
1296 (w), 1243 (m), 1200 (s), 1119 (s), 1098 (m), 857 (m), 828 (m),
769 (s), 689 (w). Anal. calcd for C54H60N6 (792): N, 10.60; C,
81.78; H, 7.63. Found: N, 10.65; C, 81.95; H, 7.39%.
N,N0-Bis(1-(3-(1-(2,6-dimethylphenylimino)ethyl)pyridin-2-yl)-
ethylidene)tetramethylbenzidine (L1)
Using a similar procedure to L5, L1 was also prepared as a
yellow solid, yield 0.45 g, 49.3% (mp: 235 ꢂC). 1H NMR: (400
MHz, CDCl3, ppm): 8.53 (d, J ¼ 8.0 Hz, 2H, Py–H), 7.96 (t, J ¼ 8.0
Hz, 1H, Py–H), 7.37 (d, J ¼ 8.0 Hz, 2H, Ph–H), 7.09 (t, J ¼ 8.0 Hz,
1H, Ph–H), 6.96 (s, 2H, Ph–H), 2.31 (s, 3H, CH3), 2.26 (s, 3H,
CH3), 2.14 (s, 6H, 2 ꢀ CH3), 2.07 (s, 6H, 2 ꢀ CH3). 13C NMR (100
MHz, CDCl3, ppm): 167.5, 167.3, 155.2, 155.1, 148.8, 148.7,
N,N0-Bis(1-(3-(1-(2,6-diisopropylphenylimino)ethyl)pyridin-2-
yl)ethylidene)tetraethylbenzidine (L6)
136.9, 136.0, 128.0, 126.4, 125.8, 125.5, 123.1, 122.4, 18.2, 18.0, Prepared as a yellow solid, yield 0.34 g, 30.5% (mp: 270 ꢂC). 1H
16.7, 16.5. FT-IR (cmꢁ1): 2913 (m), 1639 (nC]N, s), 1569 (m), 1461 NMR (400 MHz, CDCl3, ppm): 8.53 (d, J ¼ 8.0 Hz, 4H, Py–H),
(s), 1429 (s), 1362 (s), 1324 (w), 1296 (w), 1247 (m), 1200 (s), 1120 7.96 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.40 (s, 4H, Ph–H), 7.17 (d, J ¼ 7.6
(m), 1083 (m), 857 (m), 814 (m), 769 (s), 689 (w). Anal. calcd for Hz, 4H, Ph–H), 7.11 (t, J ¼ 8.0 Hz, 2H, Ph–H), 2.78–2.91 (m, 4H, 4
C
50H52N6 (736): N, 11.40; C, 81.49; H, 7.11. Found: N, 10.99; C, ꢀ CH), 2.34–2.51 (m, 8H, 4 ꢀ CH2), 2.29 (s, 6H, 2 ꢀ CH3), 2.26 (s,
81.36; H, 6.92%.
6H, 2 ꢀ CH3), 1.22 (t, 12H, J ¼ 7.6 Hz, 4 ꢀ CH3), 1.16 (d, 24H, J ¼
5.6 Hz, 8 ꢀ CH3). 13C NMR (100 MHz, CDCl3, ppm): 167.2, 167.0,
155.3, 155.2, 146.8, 146.6, 136.9, 136.6, 135.9, 131.7, 124.7,
123.6, 123.1, 122.3, 28.4, 25.0, 23.3, 23.0, 17.2, 17.0, 14.0. FT IR
(cmꢁ1): 2962 (m), 1635 (nC]N, s), 1569 (w), 1454 (m), 1362 (s),
1322 (w), 1241 (m), 1196 (s), 1120 (s), 1103 (m), 869 (w), 824 (m),
766 (s), 692 (m). Anal. calcd for C62H76N6 (904): N, 9.28; C, 82.26;
H, 8.46. Found: N, 8.89; C, 81.95; H, 8.43%.
N,N0-Bis(1-(3-(1-(2,6-diethylphenylimino)ethyl)pyridin-2-yl)-
ethylidene)tetramethylbenzidine (L2)
Prepared as a yellow solid, yield 0.41 g, 42.6% (mp: 238 ꢂC). 1H
NMR (400 MHz, CDCl3, ppm): 8.51 (d, J ¼ 8.0 Hz, 4H, Py–H),
7.95 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.13 (d, J ¼ 7.6 Hz, 4H, Ph–H), 7.05
(t, J ¼ 8.0 Hz, 2H, Ph–H), 6.29 (s, 4H, Ph–H), 2.29–2.44 (m, 8H, 4
ꢀ CH2), 2.24 (s, 6H, 2 ꢀ CH3), 2.10 (s, 6H, 2 ꢀ CH3), 1.14 (t, J ¼
7.6 Hz, 12H, 4 ꢀ CH3). 13C NMR (100 MHz, CDCl3, ppm): 167.5,
166.9, 155.2, 155.0, 147.9, 136.9, 136.0, 131.2, 126.4, 126.0,
N,N0-Bis(1-(3-(1-(2,6-dimethylphenylimino)ethyl)pyridin-2-yl)-
ethylidene)tetraisopropylbenzidine (L7)
125.8, 123.4, 122.3, 24.7, 18.2, 16.9, 16.7, 13.8. FT-IR (cmꢁ1): Prepared as a yellow solid, yield 0.36 g, 34.4% (mp: 279 ꢂC). 1H
2964 (m), 1637 (nC]N, s), 1567 (s), 1450 (m), 1362 (s), 1321 (w), NMR (400 MHz, CDCl3, ppm): 8.57 (d, J ¼ 8.0 Hz, 4H, Py–H),
1296 (w), 1243 (s), 1200 (m), 1119 (m), 1098 (w), 857 (w), 828 (m), 7.97 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.42 (s, 4H, Ph–H), 7.10 (d, J ¼ 7.6
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N,N0-Bis(1-(3-(1-(2,6-diethyl-4-methylphenyl)imino)ethyl)-
pyridin-2-yl)ethylidene tetraisopropylbenzidine (L11)
Hz, 4H, Ph–H), 6.97 (t, J ¼ 7.6 Hz, 2H, Ph–H), 2.79–2.90 (m, 4H, 4
ꢀ CH), 2.35 (s, 6H, 2 ꢀ CH3), 2.28 (s, 6H, 2 ꢀ CH3), 2.10 (s, 12H,
4 ꢀ CH3), 1.41 (d, J ¼ 7.2 Hz, 24H, 8 ꢀ CH3). 13C NMR (100 MHz,
CDCl3, ppm): 167.3, 167.2, 155.2, 155.0, 148.8, 137.3, 137.0,
136.1, 128.0, 125.5, 123.1, 122.4, 122.3, 121.8, 28.6, 23.4, 23.0,
18.1, 17.4, 16.6. FT-IR (cmꢁ1): 2958 (m), 1636 (nC]N, s), 1569 (w),
1460 (m), 1362 (s), 1321 (w), 1244 (w), 1200 (m), 1117 (s), 868 (w),
822 (m), 760 (m). Anal. calcd for C58H68N6 (848): N, 9.90; C,
82.03; H, 8.07. Found: N, 9.59; C, 81.93; H, 8.05%.
Prepared on 0.25 g scale as a yellow solid, yield 22.1% (mp:
265 ꢂC). 1H NMR (400 MHz, CDCl3, ppm): 8.50 (d, J ¼ 7.6 Hz, 2H,
Py–H), 7.94 (t, J ¼ 8.0 Hz, 1H, Py–H), 7.41 (s, 1H, Ph–H), 7.27 (s,
1H, Ph–H), 6.94 (s, 2H, Ph–H), 2.78–2.87 (m, 2H, 2 ꢀ CH), 2.36–
2.43 (m, 4H, 2 ꢀ CH2), 2.35 (s, 3H, CH3), 2.27 (s, 3H, CH3), 1.26
(d, J ¼ 1.6 Hz, 12H, 4 ꢀ CH3), 1.15 (t, J ¼ 7.6 Hz, 6H, 2 ꢀ CH3).
13C NMR: (100 MHz, CDCl3, ppm): 167.2, 155.4, 155.2, 145.6,
145.4, 137.3, 136.9, 136.1, 132.5, 131.2, 126.8, 122.3, 121.9,
121.8, 28.6, 24.7, 23.4, 23.4, 23.1, 23.0, 21.1, 17.3, 16.8, 13.9. FT-
IR (cmꢁ1): 2964 (m), 1643 (nC]N, m), 1577 (m), 1456 (s), 1365 (s),
1325 (w), 1254 (m), 1195 (s), 1121 (w), 857 (m), 814 (m), 779 (w),
694 (w). Anal. calcd for C64H80N6 (932): N, 9.00; C, 82.36; H, 8.64.
Found: N, 8.71; C, 82.03; H, 8.59%.
N,N0-Bis(1-(3-(1-(2,6-diethylphenylimino)ethyl)pyridin-2-yl)-
ethylidene)tetraisopropylbenzidine (L8)
Prepared as a yellow solid, yield 0.36 g, 31.9% (mp: 276 ꢂC). 1H
NMR (400 MHz, CDCl3, ppm): 8.53 (d, J ¼ 8.0 Hz, 4H, Py–H),
7.96 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.42 (s, 4H, Ph–H), 7.13 (d, J ¼ 7.6
Hz, 4H, Ph–H), 7.05 (d, J ¼ 8.0 Hz, 2H, Ph–H), 2.73–2.81 (m, 4H,
4 ꢀ CH), 2.40–2.54 (m, 8H, 4 ꢀ CH2), 2.36 (s, 6H, 2 ꢀ CH3), 2.28
(s, 6H, 2 ꢀ CH3), 1.24 (d, J ¼ 7.2 Hz, 24H, 8 ꢀ CH3), 1.16 (t, J ¼
7.6 Hz, 12H, 4 ꢀ CH3). 13C NMR (100 MHz, CDCl3, ppm): 167.5,
167.0, 155.3, 155.0, 145.6, 139.3, 137.3, 136.1, 131.3, 128.3,
126.0, 123.4, 122.4, 121.8, 28.6, 24.7, 23.4, 23.0, 16.9, 13.8. FT-IR
(cmꢁ1): 2960 (m), 2015 (w), 1636 (nC]N, s), 1582 (w), 1444 (m),
1362 (s), 1322 (w), 1240 (m), 1196 (w), 1117 (s), 868 (m), 823 (m),
783 (m), 762 (s). Anal. calcd for C62H76N6 (904): N, 9.28; C, 82.26;
H, 8.46. Found: N, 8.97; C, 82.03; H, 8.43%.
Synthesis and characterization of binuclear iron complexes
The formation of the iron complexes is illustrated by the
procedure for complex Fe-1 as follows: N,N0-Bis(1-(3-(1-(2,
6-dimethylphenylimino)ethyl)pyridin-2-yl)ethylidene)tetra-
methyl benzidine (L1) (0.074 g, 0.10 mmol) and FeCl2$4H2O
(0.040 g, 0.20 mmol) were mixed in CH2Cl2 (5 mL) and EtOH (5
mL) for 8 h at room temperature. The precipitate was collected
by ltration and washed with diethyl ether (3 ꢀ 5 mL), then
dried under vacuum to afford Fe-1 as a blue solid (0.050 g,
67.7% yield). FT-IR (cmꢁ1): 2908 (w), 1624 (nC]N, m), 1591 (m),
1498 (w), 1466 (s), 1365 (m), 1265 (s), 1224 (s), 1095 (s), 858 (m),
823 (s), 775 (m), 738 (m), 689 (w). Anal. calcd for C50H52N6Fe2Cl4
(990): N, 8.48; C, 60.63; H, 5.29. Found: N, 8.80; C, 60.43; H,
5.37%. MS (MALDI-TOF, m/z): 990.17. Found: m/z 981.2 [M ꢁ
FeCl4 + CCA]+, 837.1 [M ꢁ FeCl3]+, 747.1 [M ꢁ Fe2Cl4]+.
Fe-2. A mixture of N,N0-bis(1-(3-(1-(2,6-diethylphenylimino)
ethyl)pyridin-2-yl)ethylidene)tetramethylbenzidine (L2) (0.079
g, 0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in CH2Cl2 (5
mL) and EtOH (5 mL) was stirred for 8 h at room temperature.
The precipitate was collected by ltration and washed with
diethyl ether (3 ꢀ 5 mL), then dried under vacuum to afford Fe-2
as a blue solid (0.026 g, 33.6% yield). FT-IR (cmꢁ1): 2966 (s),
1619 (nC]N, w), 1584 (m), 1465 (s), 1370 (s), 1263 (s), 1209 (m),
1104 (m), 1033 (m), 865 (s), 806 (m), 766 (m), 738 (w). Anal. calcd
for C56H60N6Fe2Cl4 (1046): N, 7.62; C, 63.17; H, 6.22. Found: N,
7.49; C, 63.48; H, 6.07%. MS (MALDI-TOF, m/z): 1046.23. Found:
m/z 1037.1 [M ꢁ FeCl4 + CCA]+, 884.0 [M ꢁ FeCl3]+, 794.0 [M ꢁ
Fe2Cl4]+.
N,N0-Bis(1-(3-(1-(2,6-diisopropylphenylimino)ethyl)pyridin-2-
yl)ethylidene)tetraisopropylbenzidine (L9)
Prepared on 0.42 g scale as a yellow solid, yield 35.0% (mp:
202 ꢂC). 1H NMR (400 MHz, CDCl3, ppm): 8.60 (d, J ¼ 8.0 Hz, 4H,
Py–H), 7.99 (t, J ¼ 8.0 Hz, 2H, Py–H), 7.43 (s, 4H, Ph–H), 7.17 (d, J
¼ 7.6 Hz, 4H, Ph–H), 7.12 (t, J ¼ 8.0 Hz, 2H, Ph–H), 2.71–2.89 (m,
8H, 4 ꢀ CH2), 2.30 (s, 6H, 2 ꢀ CH3), 2.27 (s, 6H, 2 ꢀ CH3), 1.25
(d, J ¼ 5.6 Hz, 24H, 8 ꢀ CH3), 1.19 (d, J ¼ 5.6 Hz, 24H, 8 ꢀ CH3).
13C NMR (100 MHz, CDCl3, ppm): 167.2, 167.0, 155.2, 155.1,
146.6, 146.3, 145.6, 137.4, 137.3, 136.9, 136.1, 135.8, 135.7,
124.6, 123.8, 123.6, 123.1, 123.1, 122.6, 122.3, 121.8, 28.6, 28.4,
23.4, 23.3, 23.3, 23.0, 22.9, 17.3, 17.2, 17.1. FT-IR (cmꢁ1): 2960
(m), 2158 (w), 2015 (w), 1639 (nC]N, s), 1570 (m), 1455 (s), 1361
(s), 1323 (w), 1239 (m), 1194 (s), 1117 (m), 961 (w), 868 (m), 823
(m), 763 (s), 691 (m). Anal. calcd for C66H84N6 (960): N, 8.74; C,
82.45; H, 8.81. Found: N, 8.59; C, 82.15; H, 8.66%.
N,N0-Bis(1-(3-(1-mesityliminoethyl)pyridin-2-yl)ethylidene)-
tetramethylbenzidine (L10)
Prepared on 0.30 g scale as a yellow solid, yield 32% (mp:
Fe-3. A mixture of N,N0-bis(1-(3-(1-(2,6-diisopropylphenyli-
228 ꢂC). 1H NMR (400 MHz, CDCl3, ppm): 8.49 (d, J ¼ 7.6 Hz, 2H, mino)ethyl)pyridin-2-yl)ethylidene)tetramethylbenzidine (L3)
Py–H), 7.93 (t, J ¼ 8.0 Hz, 1H, Py–H), 7.36 (s, 2H, Ph–H), 6.91 (0.084 g, 0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in
(s, 2H, Ph–H), 2.31 (s, 6H, 2 ꢀ CH3), 2.29 (s, 3H, CH3), 2.27 (s, CH2Cl2 (5 mL) and EtOH (5 mL) was stirred for 8 h at room
6H, 2 ꢀ CH3), 2.10 (s, 6H, 2 ꢀ CH3). 13C NMR: (100 MHz, CDCl3, temperature. The precipitate was collected by ltration and
ppm): 167.5, 167.3, 155.3, 148.8, 147.8, 137.0, 136.0, 131.1, washed with diethyl ether (3 ꢀ 5 mL), then dried under vacuum
128.0, 126.5, 126.3, 125.8, 125.5, 122.5, 18.2, 18.0, 16.7, 16.5. FT- to afford Fe-3 as a blue solid (0.079 g, 94.0% yield). FT-IR (cmꢁ1):
IR (cmꢁ1): 2964 (m), 2030 (w), 1643 (nC]N, s), 1574 (m), 1454 (s), 2963 (s), 2018 (w), 1616 (nC]N, w), 1584 (m), 1466 (s), 1372 (s),
1362 (s), 1322 (w), 1205 (s), 1150 (w), 1120 (m), 859 (m), 817 (m), 1324 (m), 1263 (s), 1210 (m), 1103 (m), 867 (m), 804 (s), 762 (w),
741 (w), 694 (w). Anal. calcd for C53H58N6 (764): N, 10.79; C, 734 (w), 692 (w). Anal. calcd for C58H68N6Fe2Cl4 (1102): N, 7.62;
81.71; H, 7.50. Found: N, 10.59; C, 82.15; H, 7.66%.
C, 63.17; H, 6.22. Found: N, 7.92; C, 63.09; H, 5.97%. MS
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(MALDI-TOF, m/z): 1102.29. Found: m/z 1093.2 [M ꢁ FeCl4
CCA]+, 940.1 [M ꢁ FeCl3]+, 850.1 [M ꢁ Fe2Cl4]+.
+
CH2Cl2 (5 mL) and EtOH (5 mL) was stirred for 8 h at room
temperature. The precipitate was collected by ltration and
Fe-4. A mixture of N,N0-bis(1-(3-(1-(2,6-dimethylphenylimino) washed with diethyl ether (3 ꢀ 5 mL), then dried under vacuum
ethyl)pyridin-2-yl)ethylidene)tetraethylbenzidine (L4) (0.079 g, to afford Fe-8 as a blue solid (0.080 g, 69.2% yield). FT-IR (cmꢁ1):
0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in CH2Cl2 2965 (s), 2107 (w), 1627 (nC]N, w), 1587 (s), 1441 (m), 1372 (s),
(5 mL) and EtOH (5 mL) was stirred for 8 h at room temperature. 1322 (m), 1258 (s), 1207 (m), 1107 (m), 869 (w), 810 (s), 763 (s),
The precipitate was collected by ltration and washed with 696 (s). Anal. calcd for C62H76N6Fe2Cl4 (1158): N, 7.25; C, 64.26;
diethyl ether (3 ꢀ 5 mL), then dried under vacuum to afford Fe-4 H 6.61. Found: N, 6.97; C, 64.65; H, 6.45%. MS (MALDI-TOF,
as a blue solid (0.091 g, 87.5% yield). FT-IR (cmꢁ1): 2968 (s), m/z): 1158.36. Found: m/z 1149.4 [M ꢁ FeCl4 + CCA]+, 996.3 [M ꢁ
1616 (nC]N, m), 1585 (s), 1448 (s), 1367 (s), 1266 (s), 1212 (s), FeCl3]+, 906.3 [M ꢁ Fe2Cl4]+.
1161 (w), 1096 (m), 871 (m), 831 (s), 748 (w), 699 (w). Anal. calcd
Fe-9. A mixture of N,N0-bis(1-(3-(1-(2,6-diisopropylphenyl-
for C54H60N6Fe2Cl4 (1046): N, 8.03; C, 61.97; H, 5.78. Found: N, imino)ethyl)pyridin-2-yl)ethylidene)tetraisopropylbenzidine
8.24; C, 62.06; H, 5.50%. MS (MALDI-TOF, m/z): 1046.23. Found: (L9) (0.096 g, 0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol)
m/z 1037.1 [M ꢁ FeCl4 + CCA]+, 884.0 [M ꢁ FeCl3]+, 794.0 [M ꢁ in CH2Cl2 (5 mL) and EtOH (5 mL) was stirred for 8 h at room
Fe2Cl4]+.
temperature. The precipitate was collected by ltration and
Fe-5. A mixture of N,N0-bis(1-(3-(1-(2,6-diethylphenylimino) washed with diethyl ether (3 ꢀ 5 mL), then dried under vacuum
ethyl)pyridin-2-yl)ethylidene)tetraethylbenzidine (L5) (0.084 g, to afford Fe-9 as a blue solid (0.056 g, 45.8% yield). FT-IR (cmꢁ1):
0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in CH2Cl2 2962 (s), 2162 (w), 2017 (w), 1618 (nC]N, w), 1586 (s), 1461 (s),
(5 mL) and EtOH (5 mL) was stirred for 8 h at room temperature. 1368 (s), 1264 (s), 1208 (s), 1101 (m), 1028 (m), 941 (w), 836 (s),
The precipitate was collected by ltration and washed with 804 (s), 764 (w). Anal. calcd for C66H84N6Fe2Cl4 (1214): N, 6.92;
diethyl ether (3 ꢀ 5 mL), then dried under vacuum to afford Fe-5 C, 65.25; H, 6.97. Found: N, 6.87; C, 65.17; H, 7.07%. MS
as a blue solid (0.070 g, 64.3% yield). FT-IR (cmꢁ1): 2964 (s), (MALDI-TOF, m/z): 1214.42. Found: m/z 1205.5 [M ꢁ FeCl4
2166 (w), 1621 (nC]N, m), 1584 (m), 1447 (s), 1368 (s), 1325 (m), CCA]+, 1052.4 [M ꢁ FeCl3]+, 962.4 [M ꢁ Fe2Cl4]+.
+
1296 (s), 1206 (s), 1107 (m), 868 (s), 805 (s), 765 (w), 698 (w).
Fe-10. A mixture of N,N0-bis(1-(3-(1-mesityliminoethyl)pyr-
Anal. calcd for C58H68N6Fe2Cl4 (1102): N, 7.62; C, 63.17; H, 6.22. idin-2-yl)ethylidene)tetramethylbenzidine (L10) (0.076 g,
Found: N, 7.68; C, 63.35; H, 6.07. MS (MALDI-TOF, m/z): 0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in CH2Cl2
1102.29. Found: m/z 1093.2 [M ꢁ FeCl4 + CCA]+, 850.1 [M ꢁ (5 mL) and EtOH (5 mL) was stirred for 8 h at room temperature.
Fe2Cl4]+.
The precipitate was collected by ltration and washed with
Fe-6. A mixture of N,N0-bis(1-(3-(1-(2,6-diisopropylylphenyl- diethyl ether (3 ꢀ 5 mL), then dried under vacuum to afford Fe-
imino)ethyl)pyridin-2-yl)ethylidene)tetraethylbenzidine
(L6) 10 as a blue solid (0.078 g, 76.6% yield). FT-IR (cmꢁ1): 2964 (m),
(0.090 g, 0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in 1638 (nC]N, w), 1569 (m), 1454 (m), 1364 (s), 1322 (w), 1247 (w),
CH2Cl2 (5 mL) and EtOH (5 mL) was stirred for 8 h at room 1206 (s), 1119 (s), 852 (s), 816 (s), 790 (m), 762 (w), 692 (w). Anal.
temperature. The precipitate was collected by ltration and calcd for C52H56 N6 Fe2Cl4 (1018): N, 8.25; C, 61.32; H, 5.54.
washed with diethyl ether (3 ꢀ 5 mL), then dried under vacuum Found: N, 8.09; C, 61.17; H, 5.34%. MS (MALDI-TOF, m/z):
to afford Fe-6 as a blue solid (0.065 g, 56.3% yield). FT-IR (cmꢁ1): 1018.2. Found: m/z 1009.3 [M ꢁ FeCl4 + CCA]+, 856.1 [M ꢁ
2963 (s), 1621 (nC]N, m), 1584 (s), 1447 (m), 1367 (s), 1321 (m), FeCl3]+, 766.1 [M ꢁ Fe2Cl4]+.
1262 (s), 1206 (m), 1103 (m), 866 (w), 833 (s), 798 (s), 764 (w).
Anal. calcd for C62H76N6Fe2Cl4 (1158): N, 7.25; C, 64.26; H, 6.61. phenyl)imino)ethyl)pyridin-2-yl)ethylidene
Fe-11. A mixture of N,N0-bis(1-(3-(1-(2,6-diethyl-4-methyl-
tetraisopropyl-
Found: N, 7.45; C, 64.19; H, 6.58%. MS (MALDI-TOF, m/z): benzidine (L11) (0.092 g, 0.10 mmol) and FeCl2$4H2O (0.040 g,
1158.36. Found: m/z 1149.3 [M ꢁ FeCl4 + CCA]+, 996.1 [M ꢁ 0.20 mmol) in CH2Cl2 (5 mL) and EtOH (5 mL) was stirred for 8
FeCl3]+, 906.2 [M ꢁ Fe2Cl4]+.
h at room temperature. The precipitate was collected by ltra-
Fe-7. A mixture of N,N0-bis(1-(3-(1-(2,6-dimethylphenylimino) tion and washed with diethyl ether (3 ꢀ 5 mL), then dried under
ethyl)pyridin-2-yl)ethylidene)tetraisopropylbenzidine
(L7) vacuum to afford Fe-11 as a blue solid (0.070 g, 59.0% yield):
(0.084 g, 0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in FT-IR (cmꢁ1): 2962 (m), 2017 (w), 1618 (nC]N, w), 1586 (m), 1464
CH2Cl2 (5 mL) and EtOH (5 mL) was stirred for 8 h at room (m), 1368 (s), 1322 (w), 1264 (s), 1208 (m), 1101 (w), 836 (s), 804
temperature. The precipitate was collected by ltration and (s), 764 (w), 696 (w). Anal. calcd for C64H80N6Fe2Cl4 (1186): N,
washed with diethyl ether (3 ꢀ 5 mL), then dried under vacuum 7.08; C: 64.77, H: 6.79. Found: N, 6.68; C, 65.15; H, 6.62%. MS
to afford Fe-7 as a blue solid (0.030 g, 27.3% yield). FT-IR (cmꢁ1): (MALDI-TOF, m/z): 1186.39. Found: m/z 1177.5 [M ꢁ FeCl4
2962 (s), 1621 (nC]N, w), 1587 (m), 1465 (s), 1368 (s), 323 (m), CCA]+, 932.4 [M ꢁ Fe2Cl4]+.
1263 (s), 1213 (m), 1098 (m), 868 (w), 815 (s), 770 (w). Anal. calcd
+
for C58H68N6Fe2Cl4 (1102): N, 7.62; C, 63.17; H, 6.22. Found: N,
X-ray crystallographic studies
7.43; C, 63.60; H, 6.01. MS (MALDI-TOF, m/z): 1102.29. Found:
m/z 1093.2 [M ꢁ FeCl4 + CCA]+, 940.1 [M ꢁ FeCl3]+, 850.1 [M ꢁ The X-ray diffraction study was conducted using graphite–
Fe2Cl4]+.
monochromatic Mo-Ka radiation (l ¼ 0.71073 A) at 173(2) K.
˚
Fe-8. A mixture of N,N0-bis(1-(3-(1-(2,6-diethylphenylimino) Cell parameters were obtained by global renement of the
ethyl)pyridin-2-yl)ethylidene)tetraisopropylbenzidine (L8) positions of all collected reections. Intensities were corrected
(0.090 g, 0.10 mmol) and FeCl2$4H2O (0.040 g, 0.20 mmol) in for Lorentz and polarization effects and empirical absorption.
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Table 4 Crystal data and structure refinement details for L5
required amount of co-catalyst was added by a syringe. Aer the
reaction was carried out for the required period, the reaction
was immediately terminated by the addition of 10% aqueous
hydrogen chloride. The precipitated polymer was collected,
washed with water and ethanol, and nally dried.
CCDC
Empirical formula
FW
938522
C58H68N6
849.18
T (K)
Wavelength (A)
173(2)
˚
0.71073
Triclinic
ꢀ
P1
8.2594(17)
12.235(2)
13.770(3)
Crystal system
Space group
Acknowledgements
˚
a (A)
This work was supported by National Natural Science Founda-
tion of China (no. 20904059). The EPSRC are thanked for the
award of a travel grant (to CR).
˚
b (A)
˚
c (A)
a (deg)
b (deg)
g (deg)
74.30(3)
81.22(3)
73.35(3)
1279.1(4)
3
˚
Notes and references
V (A )
Z
1
Dcalcd (mg mꢁ3
)
1.102
0.065
458
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m (mmꢁ1
F(000)
)
Crystal size (mm)
q range (deg)
0.27 ꢀ 0.15 ꢀ 0.08
1.54–27.49
Limiting indices
ꢁ10 # h # 10, ꢁ15 # k # 15,
ꢁ17 # l # 17
11 474
5816 (0.0509)
99.0%
No. of reections collected
No. unique reections [R(int)]
Completeness to q (%)
Goodness of t on F2
1.152
Final R indices [I > 2s(I)]
R indices (all data)
Largest diff. peak and hole (A
R1 ¼ 0.1360, wR2 ¼ 0.3521
R1 ¼ 0.2238, wR2 ¼ 0.4188
0.343 and ꢁ0.186
ꢁ3
˚
)
No. of reections collected
The structure was solved by direct methods and rened by full-
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structure determinations and renements are provided in
Table 4.
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at ambient pressure.
Ethylene polymerization under 1 atm ethylene
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RSC Adv., 2013, 3, 26184–26193 | 26193