Bimetallic (iron or cobalt) complexes bearing 2-methyl-2,4-bis(6- immopyridin-2-yl)-1H-1,5-benzodiazepines for ethylene reactivity

Article abstract of DOI:10.1021/om070062z

A series of bimetallic (ferrous and cobaltous) complexes ligated by 3,3-dihydro-2-methyl-2,4-bis(6-iminopyridin-2-yl)-lH-1,5-benzodiazepines were synthesized and evaluated as catalysts for ethylene oligomerization and polymerization with high activity and a-olefm selectivity in the presence of modified methylaluminoxane (MMAO).

Full text of DOI:10.1021/om070062z

2456
Organometallics 2007, 26, 2456-2460
Bimetallic (Iron or Cobalt) Complexes Bearing
2-Methyl-2,4-bis(6-iminopyridin-2-yl)-1H-1,5-benzodiazepines for
Ethylene Reactivity
Shu Zhang, Igor Vystorop, Zhenghua Tang, and Wen-Hua Sun*
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute
of Chemistry, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China
ReceiVed January 21, 2007
A series of bimetallic (ferrous and cobaltous) complexes ligated by 3,3-dihydro-2-methyl-2,4-bis(6-
iminopyridin-2-yl)-1H-1,5-benzodiazepines were synthesized and evaluated as catalysts for ethylene
oligomerization and polymerization with high activity and R-olefin selectivity in the presence of modified
methylaluminoxane (MMAO).
Chart 1. Concept of the Bimetallic Catalyst
Introduction
Combined catalytic systems have recently drawn more
attention in general chemical processes, and extensive investiga-
tions have also covered their use in ethylene reactivity.1 With
polyolefin materials as the target, linear low-density polyeth-
ylene (LLDPE) was produced by two combined characteristic
metallic complex systems which individually catalyzed ethylene
oligomerization and polymerization. The technical combination
of late-transition-metal complexes and metallocene with a
cocatalyst of methylaluminoxane (MAO) indeed produced
branched polyethylenes;2 however, it was difficult to maintain
the microstructural polyethylenes with the combined catalytic
system when changing reaction parameters due to the different
catalytic (dynamics and thermal stability) behaviors. It would
be interesting to design bimetallic complexes in which two
catalytic sites were held in close proximity to perform under
the same conditions when reaction parameters are changed. A
successful example of early-late heterobimetallic complexes
for ethylene polymerization has been reported recently.3 With
the focus on iron and cobalt catalysts for use in ethylene
reactivity, the most effective model was the N∧N∧N tridentate
(bis(imino)pyridyl)metal (iron or cobalt) complexes (A)4 as well
as the recent (2-imino-1,10-phenanthrolinyl)iron and -cobalt
complexes.5 However, (mono(imino)pyridyl)metal complexes
are promising, having moderate catalytic activity at this moment
(B).6 The fused framework of models A and B could be
envisaged as a conceptual model of bimetallic complexes as
catalysts for ethylene reactivity, as shown in Chart 1. To
transform this model into reality, the two coordination pockets
would be kept with some necessary adaptations through
alternating atoms, forming a cyclic core between two active sites.
Herein we report the synthesis of bimetallic complexes and their
catalytic behavior for ethylene oligomerization and polymeri-
zation.
Results and Discussion
1. Synthesis and Characterization of the Ligands and
Complexes. The reaction of o-phenylenediamine with acetyl-
arenes has been investigated, with a detailed consideration of
the reaction mechanism.7 In the first step, reaction of o-
phenylenediamine with diacetylpyridine produced a novel
compound, 3,3-dihydro-2-methyl-2,4-bis(6-acetylpyridin-2-yl)-
1H-1,5-benzodiazepine, in considerable yield, which further
reacted with aniline derivatives to form 3,3-dihydro-2-methyl-
2,4-bis(6-iminopyridin-2-yl)-1H-1,5-benzodiazepines. The title
bimetallic complexes were easily formed in high yield by the
(5) (a) Sun, W.-H.; Jie, S.; Zhang, S.; Zhang, W.; Song, Y.; Ma, H.;
Chen, J.; Wedeking, K.; Fro¨hlich, R. Organometallics 2006, 25, 666. (b)
Jie, S.; Zhang, S.; Wedeking, K.; Zhang, W.; Ma, H.; Lu, X.; Deng, Y.;
Sun, W.-H. C. R. Chim. 2006, 9, 1500. (c) Pelletier, J. D. A.; Champouret,
Y. D. M.; Cadarso, J.; Clowes, L.; Gan˜ete, M.; Singh, K.; Thanarajasingham,
V.; Solan, G. A. J. Organomet. Chem. 2006, 691, 4114. (d) Sun, W.-H.;
Zhang, S.; Jie, S.; Zhang, W.; Li, Y.; Ma, H.; Chen, J.; Wedeking, K.;
Fro¨hlich, R. J. Organomet. Chem. 2006, 691, 4196. (e) Jie, S.; Zhang, S.;
Sun, W.-H.; Kuang, X.; Liu, T.; Guo, J. J. Mol. Catal. A: Chem. 2007,
269, 85.
(6) (a) Sun, W.-H.; Tang, X.; Gao, T.; Wu, B.; Zhang, W.; Ma, H.
Organometallics 2004, 23, 5037. (b) Bluhm, M. E.; Folli, C.; Do¨ring, M.
J. Mol. Catal. A: Chem. 2004, 212, 13. (c) Kaul, F. A. R.; Puchta, G. T.;
Frey, G. D.; Herdtweck, D.; Herrmann, W. A. Organometallics 2007, 26,
988. (d) Tang, X.; Sun, W.-H.; Gao, T.; Hou, J.; Chen, J.; Chen, W. J.
Organomet. Chem. 2005, 690, 1570. (e) Zhang, W.; Sun, W.-H.; Tang, X.;
Gao, T.; Zhang, S.; Hao, P.; Chen, J. J. Mol. Catal. A: Chem. 2007, 265,
159.
* To whom correspondence should be addressed. E-mail:
whsun@iccas.ac.cn. Tel: +86 10 62557955. Fax: +86 10 62618239.
(1) Wasilke, J.-C.; Obrey, S. J.; Baker, R. T.; Bazan, G. C. Chem. ReV.
2005, 105, 1001 and references therein.
(2) (a) Cui, Y.; Shao, C.; Sun, W.-H. Central Eur. J. Chem. 2003, 1,
325. (b) Li, Z.; Zhu, N.; Sun, W.-H.; Shao, C.; Ke, Y.; Hu Y.; He, J. Polym.
Int. 2001, 50, 1275. (c) Mecking, S. Macromol. Rapid Commun. 1999, 20,
139. (d) Souza, R. F. D.; Casagrande, O. L. Macromol. Rapid Commun.
2001, 22, 1293. (e) Mota, F. F.; Mauler, R. S.; Souza, R. F. D.; Casagrande,
O. L. Macromol. Chem. Phys. 2001, 201, 1016. (f) Kunrath, F. A.; Souza,
R. F.; Casagrande, O. L. Macromol. Rapid Commun. 2000, 21, 277. (g)
Wang, H.; Ma, Z.; Ke, Y.; Hu, Y. Polym. Int. 2003, 52, 1546. (h) Frediani,
M.; Bianchini, C.; Kaminsky, W. Kinet. Catal. 2006, 47, 207.
(3) Kuwabara, J.; Takeuchi, D.; Osakada, K. Chem. Commun. 2006, 3815.
(4) (a) Small, B. L.; Brookhart, M.; Bennett, A. M. A. J. Am. Chem.
Soc. 1998, 120, 4049. (b) Britovsek, G. J. P.; Gibson, V. C.; McTavish, S.
J.; Solan, G. A.; White, A. J. P.; Williams, D. J.; Kimberley, B. S.; Maddox,
P. J. Chem. Commun. 1998, 849.
(7) (a) Tang, X.; Cui, Y.; Sun, W.-H.; Miao, Z.; Yan, S. Polym. Int.
2004, 53, 2155. (b) Cui, Y.; Tang, X.; Shao, C.; Li, J.; Sun, W.-H. Chin.
J. Chem. 2005, 23, 589.
10.1021/om070062z CCC: $37.00 © 2007 American Chemical Society
Publication on Web 03/29/2007

Bimetallic Complexes for Ethylene ReactiVity
Organometallics, Vol. 26, No. 9, 2007 2457
Scheme 1. Synthetic Procedure
Figure 1. Molecular structure of L2 with thermal ellipsoids at the
30% probability level. Hydrogen atoms have been omitted for
clarity. Selected bond lengths (Å) and angles (deg): C2-N1 )
1.282(5), C8-N3 ) 1.477(5), C15-N4 ) 1.289(5), C23-N6 )
1.287(5); C2-N1-C25 ) 120.5(4), C8-N3-C9 ) 120.1(4),
C14-N4-C15 ) 118.2(4), C23-N6-C31 ) 121.6(4).
reaction of iron or cobalt chloride with the ligands (Scheme 1).
All of the organic compounds were characterized by FT-IR,
1H NMR, and 13C NMR spectra and elemental analyses, while
the complexes were characterized by elemental analyses and
FT-IR spectra. The elemental analyses of the iron complexes
were consistent with the composition LFe2Cl4. However, the
cobalt complexes possess the molecular formula LCo2Cl4‚EtOH.
The molecular structures of L2 and C2 were determined by
X-ray diffraction analysis.
Figure 2. Molecular structure of C2 with thermal ellipsoids at
the 30% probability level. Hydrogen atoms and solvent have been
omitted for clarity. Selected bond lengths (Å) and angles (deg):
Co1-N1 ) 2.165(5), Co1-N2 ) 2.092(5), Co1-N3 ) 2.340(6),
Co1-Cl1 ) 2.421(2), Co1-Cl2 ) 2.431(2), Co1-O ) 2.082(5),
Co2-N4 ) 2.214(5), Co2-N5 ) 2.051(5), Co2-N6 ) 2.224(5),
Co2-Cl3 ) 2.325(2), Co2-Cl4 ) 2.2541(2); N1-Co1-N2 )
75.5(2), N2-Co1-N3 ) 71.9(2), N1-Co1-N3 ) 140.3(2), N1-
Co1-Cl1 ) 87.29(2), N2-Co1-Cl1 ) 104.53(2), N3-Co1-Cl1
) 79.62(2), N1-Co1-Cl2 ) 95.88(2), N2-Co1-Cl2 ) 85.11(2),
N3-Co1-Cl2 ) 103.25(2), Cl1-Co1-Cl2 ) 170.34(7), N4-
Co2-N5 ) 75.14(2), N5-Co2-N6 ) 75.15(2), N4-Co2-N6 )
149.96(2), N4-Co2-Cl3 ) 94.06(1), N5-Co2-Cl3 ) 102.98(1),
N6-Co2-Cl3 ) 96.80(1), N4-Co2-Cl4 ) 99.02(1), N5-Co2-
Cl4 ) 148.33(2), N6-Co2-Cl4 ) 103.88(1), Cl3-Co2-Cl4 )
108.51(7).
2. Crystal Structures. The molecular structures of L2 and
C2 are shown in Figures 1 and 2, respectively, along with
selected bond lengths and angles. Two imino groups of L2 in
the solid state are in the E conformation with the typical imino
CdN double-bond lengths of 1.282(5) and 1.287(5) Å. The aryl
rings on the imine are approximately perpendicular to the
pyridine rings, and their dihedral angles are 98.8° (C3-C7, N2)
and 87.5° (C18-C22, N4), respectively. The crystals of cobalt
complex C2, with one incorporated ethanol molecule in the solid
state, were obtained from the solvent mixture of dichloromethane
and ethanol. The structure consists of one ligand molecule, two
cobalt(II) cations, and four chlorides. One of the cobalt (Co1)
atoms is six-coordinated with an additional ethanol molecule,
while the second cobalt (Co2) atom is five-coordinated. The
six-coordinated structure consists of a metal atom surrounded
by three nitrogen atoms from the ligand, two chlorides, and one
ethanol molecule linked by the oxygen atom, in a distorted-
octahedral geometry. The Co1-N3 (2.340(6) Å) bond length
is much longer than those of Co1-N1 (2.165(5) Å) and Co1-
N2 (2.092(5) Å), which can be attributed to the sp3 N3. The
three nitrogen atoms and the oxygen atom occupied the
equatorial plane, whereas the axial position is occupied by two
chlorides. The geometry of the five-coordinated structure around
Co2 can be described as a distorted trigonal bipyramid. The
nitrogen (N5) of the pyridine and the two chlorides form an
equatorial plane, while the axial plane consists of the other two
nitrogen atoms (N4 and N6) and the cobalt core with a bond
angle of 149.96(2)° for N4-Co2-N6. The cobalt atom deviates
by 0.0491 Å from the equatorial plane. The Co2-N5(pyridine)
bond (2.051(5) Å) is shorter by about 0.17 Å than the Co2-
N4(benzodiazepine) bond (2.214(5) Å) and Co2-N6(imino)
bond (2.224(5) Å), which is similar to the case for the (2,6-
bis(imino)pyridyl)cobalt(II) complexes.4 The two Co2-Cl bond
lengths are slightly different: Co2-Cl3 ) 2.325(2) Å and Co2-
Cl4 ) 2.2541(2) Å). The N4-C15 bond length in the benzo-
diazepine and the N6-C23 bond length are 1.283(7) and
1.278(8) Å, respectively, with the typical character for a CdN
double bond. All the atoms of the pyridine ring (N5, C18, C19,
C20, C21, C22) and N4, C15, N6, and C23 as well as the Co2
atom make an almost perfect plane, with the largest deviation
from the plane being 0.1024 Å at Co2. The 2,6-diisopropyl-
phenyl group C25-C26-C27-C28-C29-C30 is oriented to
the basal coordination plane N4-C15-C18-N5-C22-C23-
N6-Co2, with a dihedral angle of 79.9°. An inspection of the
intermetallic distance (4.979 Å) reveals that there is no direct
Co‚‚‚Co interaction between the two metal centers.

2458 Organometallics, Vol. 26, No. 9, 2007
Zhang et al.
Table 1. Ethylene Oligomerization and Polymerization
Initiated by Bimetallic Complexesa
oligomer
Tb
R-Od polymer
(%) activitye (wt %)f
PE
entry cat. Al/M (°C) activityc
K
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
F1
F1
F1
F1
F1
F1
F1
F2
C1
C1 1000
C1 1500
C1 2000
C1 2500
C1 1500
C1 1500
C2 1000
500
1000
1500
2000
2500
1500
1500
1000
500
30
30
30
30
30
40
60
30
30
30
30
30
30
40
60
30
0.12
2.06
1.30
1.33
1.31
0.38
0.15
0.15
0.03
0.61
0.91
0.74
0.29
1.20
2.46
0.24
0.43 >99 trace
0.71 >99 1.38
0.72 >99 3.00
0.66 >99 3.37
0.69 >99 3.40
0.66 >99 0.46
0.66 >99 trace
0.59 >99 0.10
>99 trace
0.64 >99 0.45
0.64 >99 1.20
0.59 >99 1.49
0.57 >99 0.47
0.70 >99 2.50
0.80 >99 7.37
0.53 >99 0.15
40.2
69.8
71.7
72.2
54.6
39.5
42.6
57.0
66.7
62.3
67.6
75.0
38.1
Figure 3. Oligomer distribution obtained in entries 1-5 in Table
1.
a General conditions: cat., 2.5 µmol; cocat., MMAO; reaction time, 30
min; ethylene pressure, 30 atm; solvent, toluene (100 mL). b Reaction
very small amounts of oligomers and polymer were produced
(entry 9 in Table 1). When the Al/Co molar ratio was further
increased, the catalytic activity improved. At an Al/Co molar
ratio of 1500, the catalytic system displayed the highest
oligomerization activity of 0.91 × 105 g (mol of cat.)-1 h-1
atm-1 (entry 11 in Table 1). However, the highest polymeri-
zation activity of 1.49 × 105 g (mol of cat.)-1 h-1 atm-1 and
the largest polymer percentage of 66.7% were obtained with
an Al/Co molar ratio of 2000 (entry 12 in Table 1). In addition,
the distribution of oligomers was also greatly influenced by the
Al/Co molar ratio. The K value peaked at 0.64 with Al/Co molar
ratios of 1000 and 1500. Elevating the reaction temperature of
the C1/MMAO system from 30 to 60 °C resulted in a sharp
increase in productivity and polymer percentage (entries 11, 14,
and 15 in Table 1), suggesting that C1 is thermally stable (under
the experimental conditions) with a considerable lifetime.
However, the activity of F1 decreased sharply at higher reaction
temperature, which could be attributed to the lower stability of
iron active species.
In most cases, some polyethylene waxes as higher oligomers
were obtained, in addition to lower oligomers. The waxes were
confirmed to be mainly linear R-olefins from the characteristic
vibrations of CdC and various C-H bonds. 1H and 13C NMR
spectra (Figure 4) of the waxes produced with complex F1 were
recorded in 1,2-dichlorobenzene-d4 using TMS as an internal
standard. The 13C NMR spectra further demonstrated that linear
R-olefins absolutely predominated in the waxes; also, the single
peaks at δ 139 and 114 ppm showed the properties of a vinyl-
unsaturated chain end. On the basis of 1H NMR measurements,
the average molecular weight indicated that the carbon number
of the waxes obtained was about 60.
temperature. c Oligomerization activity: 105 g (mol of cat.)-1 h-1 atm-1
.
d Percent R-olefin content determined by GC and GC-MS. e Polymerization
.
activity: 105 g (mol of cat.)-1 h-1 atm-1 f The percentage of polyethylene
waxes.
3. Catalytic Behavior toward Ethylene Reactivity. The iron
and cobalt complexes were studied for their catalytic activities
with various alkylaluminums as cocatalysts. The catalytic system
with modified methylaluminoxane (MMAO) showed high
catalytic activities for ethylene oligomerization and polymeri-
zation with very high selectivity for R-olefin. The detailed results
are summarized in Table 1. The distribution of oligomers
obtained in all cases follows Schulz-Flory rules, which is
characteristic of the constant K, where K represents the
probability of chain propagation (K ) (rate of propagation)/
((rate of propagation) + (rate of chain transfer)) ) (moles of
C
n+2)/(moles of Cn). The K values are determined by the molar
ratio of C12 and C14 fractions.
The ligands greatly affected the catalytic behavior of their
complexes. Under the same reaction conditions, noticeably
reduced catalytic activities were observed for the sterically
bulkier catalyst systems. This could be exemplified by compar-
ing the 2,6-diisopropyl-substituted F2 or C2 with 2,6-dimethyl-
substituted F1 or C1 (entries 2 vs 8 and 10 vs 16 in Table 1).
The bulkiness at the ortho positions of the imino-N aryl ring
may prevent the insertion of ethylene at the active center in the
catalytic system, therefore resulting in decreased catalytic
activity. When the Al/Fe molar ratio was increased from 500
to 1000, both oligomerization and polymerization activities of
F1 increased sharply (entries 1 and 2 in Table 1). A further
increase of the Al/Fe molar ratio to 1500 resulted in decreased
oligomerization activity and increased polymerization activity.
Increasing the Al/Fe molar ratio from 1500 to 2500 led to almost
constant production for both oligomers and polymers (entries
3-5 in Table 1). In addition, a higher Al/Fe molar ratio led to
a higher proportion of polyethylene wax. With an Al/Fe molar
ratio of 2500, the proportion of polyethylene wax peaked at
72.2%. Furthermore, the Al/Fe molar ratio had an obvious
influence on oligomer distribution, as revealed by the different
K values when the Al/Fe molar ratio was increased from 500
to 2500. The oligomer distributions obtained at different Al/Fe
molar ratio with F1 are shown in Figure 3. The K value peaked
at 0.72 at an Al/Fe molar ratio of 1500. The effect of the Al/Co
molar ratio on ethylene reactivity was also investigated using
the cobalt complex C1. At an Al/Co molar ratio of 500, only
Conclusion
A series of new ligands with two different binding sites were
synthesized and fully characterized. The reaction of these ligands
with metal chlorides afforded bimetallic complexes. An X-ray
crystallographic study revealed that one ligand coordinated with
two metal cations with two different coordination geometries.
Upon treatment with MMAO, the iron(II) complexes showed
high catalytic activities of up to 3.40 × 105 g (mol of cat.)-1
h-1 atm-1 for polymerization and 2.06 × 105 g (mol of cat.)-1
h-1 atm-1 for oligomerization with high R-olefin selectivity.
The cobalt complexes showed lower activity than their iron
analogues under the same conditions. However, when the

Bimetallic Complexes for Ethylene ReactiVity
Organometallics, Vol. 26, No. 9, 2007 2459
1
Figure 4. NMR spectra of the waxes obtained in entry 2 in Table 1: (a) 13C NMR; (b) H NMR.
J ) 7.8 Hz, 1H, Py Hp); 7.73 (d, 2H, Py Hm); 7.35 (d, J ) 7.1 Hz,
reaction temperature increased to 60 °C, cobalt complexes
displayed a higher polymerization activity of 7.37 × 105 g (mol
of cat.)-1 h-1 atm-1 and oligomerization activity of 2.46 × 105
g (mol of cat.)-1 h-1 atm-1 with high R-olefin selectivity. The
two metallic catalytic centers influenced each other during the
ethylene oligomerization and polymerization. The investigation
of their mononuclear analogues and cooperative effects of
bimetallic complexes is in progress.
1H, Ar H); 7.10 (t, J ) 7.3 Hz, 1H, Ar H); 7.04 (t, J ) 7.5 Hz,
1H, Ar H); 6.92 (t, J ) 7.5 Hz, 1H, Ar H); 4.93 (s, 1H); 3.87 (d,
1H, J ) 12.7 Hz); 3.47 (d, 1H, J ) 12.7 Hz); 2.72 (s, 3H); 2.71 (s,
3H); 1.71 (s, 3H). 13C NMR (75 MHz, CDCl3): δ 199.3, 199.2,
165.7, 164.7, 155.3, 151.9, 151.8, 138.6, 138.3, 137.2, 136.9, 129.0,
126.9, 124.2, 122.8, 121.7, 121.0, 119.3, 73.1, 37.5, 30.8, 25.2.
Anal. Calcd for C24H22N4O2 (398.46): C, 72.34; H, 5.57; N, 14.06.
Found: C, 72.03; H, 5.66; N, 13.81.
3,3-Dihydro-2-methyl-2,4-bis((((2,6-dimethylphenyl)imino)-
ethyl)pyridin-2-yl)-1H-1,5-benzodiazepine (L1). A solution of 3,3-
dihydro-2-methyl-2,4-bis(6-acetylpyridin-2-yl)-1H-1,5-benzodiaz-
epine (1.20 g, 3.01 mmol), 2,6-dimethylaniline (1.06 g, 8.73 mmol),
and a catalytic amount of p-toluenesulfonic acid and silica-alumina
catalyst in ethanol (25 mL) were refluxed for 24 h, and 4 Å
molecular sieves (2 g) were added to remove water. After filtration
and solvent evaporation, the crude product was purified by column
chromatography on alumina with petroleum ether/ethyl acetate (20/
1) as eluent. The second part to elute was collected and concentrated
to give a yellow solid. The third and the fourth parts to elute were
collected, and the reaction was repeated with the first part to elute.
This process was carried out four times to obtain the products (L1)
in 27% yield (0.50 g). Mp: 103-105 °C. FT-IR (KBr disk, cm-1):
3342 (νN-H), 3016, 2920, 1645 (νCdN), 1572, 1469, 1362, 1308,
Experimental Section
1. General Considerations. All manipulations of air- and/or
moisture-sensitive compounds were carried out under a nitrogen
atmosphere using standard Schlenk techniques. NMR spectra were
recorded on a Bruker DMX-300 spectrometer, with TMS as the
internal standard. IR spectra were recorded on a Perkin-Elmer FT-
IR 2000 spectrometer using KBr disks in the range of 4000-400
cm-1. Elemental analyses were performed on a Flash EA 1112
microanalyzer. GC analyses were performed with a Varian CP-
3800 gas chromatograph equipped with a flame ionization detector
and a 30 m (0.2 mm i.d., 0.25 µm film thickness) CP-Sil 5 CB
column. The yields of oligomers were calculated by referencing to
the mass of the solvent, on the basis of the prerequisite that the
mass of each fraction is approximately proportional to its integrated
areas in the GC trace. GC-MS analysis was performed with HP
1
1243, 1206, 821, 759. H NMR (300 MHz, CDCl3): δ 8.47 (d, J
1
) 7.7 Hz, 1H, Py Hm); 8.41 (d, J ) 7.7 Hz, 1H, Py Hm); 8.20 (d,
J ) 7.8 Hz, 1H, Py Hm); 7.90 (t, J ) 7.6 Hz, 1H, Py Hp); 7.74 (t,
J ) 7.6 Hz, 1H, Py Hp); 7.60 (d, J ) 7.7 Hz, 1H, Py Hm); 7.37 (d,
J ) 7.5 Hz, 1H, Ar H); 7.07-6.88 (m, 9H, Ar H); 5.17 (s, 1H);
4.05 (d, J ) 12.3 Hz, 1H); 3.35 (d, J ) 12.6 Hz, 1H); 2.19 (s, 3H);
2.16 (s, 3H); 2.07-2.02 (m, 12H, PhCH3); 1.74 (s, 3H). 13C NMR
(75 MHz, CDCl3): δ 166.6, 166.5, 164.1, 155.1, 154.4, 148.2,
138.8, 138.6, 136.8, 136.5, 128.9, 127.5, 126.6, 124.9, 122.6, 122.0,
121.3, 121.0, 120.7, 120.3, 118.8, 73.1, 37.5, 31.0, 17.5, 16.1. Anal.
Calcd for C40H40N6 (604.79): C, 79.44; H, 6.67; N, 13.90. Found:
C, 79.69; H, 6.72; N, 13.62.
5890 Series II and HP 5971 Series mass detectors. H NMR and
13C NMR spectra of the polymer samples were recorded on a Bruker
DMS-300 instrument at 110 °C in 1,2-dichlorobenzene-d4 using
TMS as an internal standard. Solvents were dried by the appropriate
drying reagents and distilled under nitrogen prior to use. Silica-
alumina catalyst (support, grade 135) was purchased from Aldrich
Chemicals. Modified methylaluminoxane (MMAO, 1.93 M in
heptane, 3A) was purchased from Akzo Corp. All other chemicals
were obtained commercially and used without further purification
unless otherwise stated.
2. Synthesis and Characterization. 3,3-Dihydro-2-methyl-2,4-
bis(6-iminopyridin-2-yl)-1H-1,5-benzodiazepines. A mixture of
2,6-diacetylpyridine (4.750 g, 29.1 mmol) and silicon-aluminum
catalyst (2 g) was heated to 80 °C under a nitrogen atmosphere.
Benzene-1,2-diamine (1.794 g, 16.6 mmol) was then added to the
melting 2,6-diacetylpyridine. After 2 min, the mixture was cooled
and eluted on an alumina column. The second part to elute was
collected and concentrated to give a yellow solid in 41% yield.
Mp: 126-128 °C. FT-IR (KBr disk, cm-1): 3304 (νN-H), 3004,
3,3-Dihydro-2-methyl-2,4-bis((((2,6-diisopropylphenyl)imino)-
ethyl)pyridin-2-yl)-1H-1,5-benzodiazepine (L2). In a manner
similar to that described for L1, L2 was also prepared in 39% yield.
Mp: 202-204 °C. FT-IR (KBr disk, cm-1): 3307 (νN-H), 3056,
2961, 1645 (νCdN), 1570, 1455, 1363, 1312, 1235, 1122, 1109, 815,
771. 1H NMR (300 MHz, CDCl3): δ 8.49 (d, J ) 7.8 Hz, 1H, Py
Hm); 8.41 (d, J ) 7.6 Hz, 1H, Py Hm); 8.19 (d, J ) 7.6 Hz, 1H, Py
Hm); 7.86 (t, J ) 7.8 Hz, 1H, Py Hp); 7.71 (t, J ) 7.8 Hz, 1H, Py
Hp); 7.58 (d, J ) 7.6 Hz, 1H, Py Hm); 7.38 (d, J ) 6.6 Hz, 1H, Ar
H); 7.04 (m, 9H, Ar H); 5.28 (s, 1H); 4.08 (d, 1H, J ) 12.7 Hz);
3.40 (d, 1H, J ) 12.6 Hz); 2.68 (m, 4H, CH(CH3)2); 2.25 (s, 3H);
1
2972, 1696 (νCdO), 1621, 1581, 1475, 1360, 1254, 771. H NMR
(300 MHz, CDCl3): δ 8.54 (d, J ) 7.8 Hz, 1H, Py Hm); 8.04 (d,
J ) 7.4 Hz, 1H, Py Hm); 7.87 (t, J ) 7.8 Hz, 1H, Py Hp); 7.84 (t,

2460 Organometallics, Vol. 26, No. 9, 2007
Zhang et al.
2.17 (s, 3H); 1.74 (s, 3H); 1.14 (m, 24H, CH(CH3)2). 13C NMR
(75 MHz, CDCl3): δ 166.29, 166.17, 164.06, 155.15, 154.54,
145.98, 138.68, 138.56, 136.88, 136.49, 135.26, 129.10, 126.59,
123.17, 122.56, 121.88, 121.33, 120.92, 120.52, 120.11, 118.83,
72.43, 37.55, 31.28, 27.85, 22.73, 22.47. Anal. Calcd for C48H56N6
(717.00): C, 80.41; H, 7.87; N, 11.72. Found: C, 80.27; H, 7.86;
N, 11.39.
Table 2. Crystal Data and Structure Refinement Details for
L2 and C2
L2
C48H56N6
C2‚EtOH‚2CH2Cl2
formula
C50H61Cl4Co2N6O‚
2CH2Cl2
1191.56
formula wt
T (K)
716.99
293(2)
293(2)
wavelength (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.710 73
triclinic
P1h
0.710 73
triclinic
P1h
11.198(2)
16.308(3)
16.371(3)
103.77(3)
91.89(3)
96.22(3)
2881.2(1)
2
1.373
0.988
F1. Ligand L1 (0.1210 g, 0.20 mmol) and 2.1 equiv of FeCl2‚
4H2O (0.084 g, 0.42 mmol) were added together in a Schlenk which
was purged three times with nitrogen and then charged with freshly
distilled ethanol. The reaction mixture was stirred at room tem-
perature for 6 h, and absolute diethyl ether was added to precipitate
the complex. The resulting precipitate was filtered, washed with
diethyl ether, and dried under vacuum to furnish the product F1
(0.163 g, 0.19 mmol) as a green powder in 95% yield. FT-IR (KBr
disk, cm-1): 3246 (νN-H), 3071, 2971, 1620 (νCdN), 1590, 1469,
1371, 1258, 1208, 814, 776. Anal. Calcd for C40H40Cl4Fe2N6
(858.29): C, 55.98; H, 4.70; N, 9.79. Found: C, 55.79; H, 4.56;
N, 9.58. Complexes F2, C1, and C2 were also prepared by this
manner.
11.5337(5)
12.2438(6)
15.7362(7)
98.347(3)
90.241(3)
104.096(2)
2130.65(2)
2
Z
D
calcd (Mg m-3
)
1.118
0.066
772
µ (mm-1
F(000)
)
1234
cryst size (mm)
θ range (deg)
0.19 × 0.17 × 0.11
1.31-25.01
-13 e h e 13,
-14 e k e 14,
-18 e l e 18
37 180
0.22 × 0.15 × 0.10
1.28-25.01
0 e h e 13,
-19 e k e 19,
-19 e l e 19
9464
F2. Yield: 97%. FT-IR (KBr disk, cm-1): 3258 (νN-H), 3063,
2964, 1616 (νCdN), 1588, 1467, 1370, 1257, 1200, 815, 770. Anal.
Calcd for C48H56Cl4Fe2N6 (970.50): C, 59.40; H, 5.82; N, 8.66.
Found: C, 59.45; H, 5.70; N, 8.50.
limiting indices
no. of rflns collected
no. of unique rflns
Rint
C1. Yield: 96%. FT-IR (KBr disk, cm-1): 3246 (νN-H), 3071,
2916, 1621 (νCdN), 1589, 1470, 1371, 1259, 1218, 816, 750. Anal.
Calcd for C40H40Cl4Co2N6‚C2H5OH (910.53): C, 55.40; H, 5.09;
N, 9.23. Found: C, 55.12; H, 4.88; N, 9.20.
7504
0.0914
5716
0.0610
completeness to θ (%)
99.8
empirical
0.971
R1 ) 0.0825,
wR2 ) 0.2360
R1 ) 0.1849,
wR2 ) 0.2872
0.637, -0.322
93.0
empirical
1.010
R1 ) 0.0726,
wR2 ) 0.1891
R1 ) 0.1286,
wR2 ) 0.2216
0.967, -1.010
abs cor
goodness of fit on F2
final R indices (I > 2σ(I))
C2. Yield: 83%. FT-IR (KBr disk, cm-1): 3217 (νN-H), 3069,
2965, 1620 (νCdN), 1587, 1467, 1369, 1258, 1202, 817, 770. Anal.
Calcd for C48H56Cl4Co2N6‚C2H5OH (1022.75): C, 58.72; H, 6.11;
N, 8.22. Found: C, 58.64; H, 5.79; N, 8.21.
R indices (all data)
largest diff peak,
3. General Procedure for Ethylene Oligomerization and
Polymerization. Ethylene oligomerization and polymerization was
carried out in a 500 mL autoclave stainless steel reactor equipped
with a mechanical stirrer and a temperature controller. Briefly,
toluene, the desired amount of cocatalyst, and a toluene solution
of the catalytic precursor (the total volume was 100 mL) were added
to the reactor in this order under an ethylene atmosphere. When
the desired reaction temperature was reached, ethylene at 30 atm
pressure was introduced to start the reaction, and the ethylene
pressure was maintained by constant feeding of ethylene. After 30
min, the reaction was stopped. A small amount of the reaction
solution was collected, the reaction was terminated by the addition
of 5% aqueous hydrogen chloride, and then this mixture was
analyzed by gas chromatography (GC) to determine the distribution
of oligomers obtained. The remaining solution was quenched with
HCl-acidified ethanol (5%), and the precipitated polyethylene was
filtered, washed with ethanol, and dried under vacuum at 60 °C to
constant weight.
hole (e Å-3
)
Intensity data for a crystal of C2 were collected on a Rigaku RAXIS
Rapid IP diffractometer with graphite-monochromated Mo KR
radiation (λ ) 0.710 73 Å). Cell parameters were obtained by global
refinement of the positions of all collected reflections. Intensities
were corrected for Lorentz and polarization effects and empirical
absorption. The structures were solved by direct methods and
refined by full-matrix least squares on F2. All non-hydrogen atoms
were refined anisotropically. Structure solution and refinement were
performed by using the SHELXL-97 package.8 Crystal data and
processing parameters are summarized in Table 2.
Acknowledgment. This work was supported by NSFC Grant
No. 20674089 and MOST Grant No. 2006AA03Z553. We thank
Mr. Sheriff Adewuyi (a CAS-TWAS Postgraduate Fellow from
Nigeria) for the English corrections.
4. Crystal Structure Determination. Single crystals of L2
suitable for X-ray diffraction analysis were obtained by slow
evaporation of its ethyl acetate solution. Crystals of C2 suitable
for single-crystal X-ray diffraction analysis were obtained by
layering diethyl ether on a dichloromethane/ethanol (1/1 v/v)
solution at room temperature. Single-crystal X-ray diffraction
studies for L2 were carried out on a Bruker P4 diffractometer with
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å).
Supporting Information Available: CIF files giving crystal-
lographic data for L2 and C2. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM070062Z
(8) Sheldrick, G. M. SHELXTL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany, 1997.