2-Oxazoline/benzoxazole-1,10-phenanthrolinylmetal (iron, cobalt or nickel) dichloride: Synthesis, characterization and their catalytic reactivity for the ethylene oligomerization

Article abstract of DOI:10.1016/j.jorganchem.2008.09.046

Series of 2-benzoxazole-1,10-phenanthrolines (L1-L4) and 2-oxazoline-1,10-phenanthrolines (L5-L8) were synthesized and used as tridentate N^N^N ligands in coordinating with metal (nickel, cobalt or iron) chlorides. Their metal complexes, nickel(II) (Ni1-Ni8), cobalt(II) (Co1-Co8) and iron(II) (Fe1-Fe8), were characterized by elemental and IR spectroscopic analyses. The molecular structures of the ligand L2 and the complexes Ni3, Co1, Co3 and Fe2 have been determined by the single-crystal crystallography. The nickel complex Ni3 and iron complex Fe2 display an octahedral geometry, whereas cobalt complex Co1 is with a distorted bipyramidal geometry and Co3 as square pyramidal geometry. At 10 atm ethylene, all the complexes showed good activities in ethylene dimerization upon activation with appropriate aluminum cocatalysts; the nickel complexes gave the activity up to 3.11 × 10⁶ g mol^-1(Ni) h^-1 upon activation with diethylaluminum chloride (Et₂AlCl), meanwhile the cobalt and iron complexes showed activities up to 1.51 × 10⁶ g mol^-1(Co) h^-1 and 1.89 × 10⁶ g mol^-1(Fe) h^-1, individually, upon activation with modified methylaluminoxane (MMAO).

Full text of DOI:10.1016/j.jorganchem.2008.09.046

Journal of Organometallic Chemistry 693 (2008) 3867–3877
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
2-Oxazoline/benzoxazole-1,10-phenanthrolinylmetal (iron, cobalt or nickel)
dichloride: Synthesis, characterization and their catalytic reactivity for the
ethylene oligomerization
Min Zhang a, Rong Gao a, Xiang Hao a, Wen-Hua Sun a,b,
*
a Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
b State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Series of 2-benzoxazole-1,10-phenanthrolines (L1–L4) and 2-oxazoline-1,10-phenanthrolines (L5–L8)
were synthesized and used as tridentate N^N^N ligands in coordinating with metal (nickel, cobalt or iron)
chlorides. Their metal complexes, nickel(II) (Ni1–Ni8), cobalt(II) (Co1–Co8) and iron(II) (Fe1–Fe8), were
characterized by elemental and IR spectroscopic analyses. The molecular structures of the ligand L2 and
the complexes Ni3, Co1, Co3 and Fe2 have been determined by the single-crystal crystallography. The
nickel complex Ni3 and iron complex Fe2 display an octahedral geometry, whereas cobalt complex
Co1 is with a distorted bipyramidal geometry and Co3 as square pyramidal geometry. At 10 atm ethylene,
all the complexes showed good activities in ethylene dimerization upon activation with appropriate alu-
minum cocatalysts; the nickel complexes gave the activity up to 3.11 Â 106 g molÀ1(Ni) hÀ1 upon activa-
tion with diethylaluminum chloride (Et2AlCl), meanwhile the cobalt and iron complexes showed
activities up to 1.51 Â 106 g molÀ1(Co) hÀ1 and 1.89 Â 106 g molÀ1(Fe) hÀ1, individually, upon activation
with modified methylaluminoxane (MMAO).
Received 28 August 2008
Received in revised form 20 September
2008
Accepted 25 September 2008
Available online 2 October 2008
Keywords:
Ethylene oligomerization
2-Benzoxazole-1, 10-phenanthroline
2-Oxazoline-1, 10-phenanthroline
Nickel
Cobalt
Iron
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
to devise new tridentate ligands such as O^N^N [40], N^P^N [41],
P^N^N [42,43], and N^N^N [44–49] for their complexes as new
The major chemical industry of about 6 million tons of
a
-olefins
catalysts; promisingly some N^N^N tridentate complexes gave
good to high activities [50,51] with different models [52] in our
group. Especially those catalytic precursors include the iron, cobalt,
nickel and other metals, which are dependent of tridentate ligands
such as 2-imino-1,10-phenanthroline derivatives (A, Scheme 1)
[53–58], 2-(2-benzimidazolyl)-6-[1-(arylimino)ethyl] pyridines
[59–61], 2-quinoxalinyl-6-iminopyridines [62,63], and 2-methyl-
2,4-bis(6-iminopyridin-2-yl)-1H-1,5-benzodiazepines [64,65].
Altering its imino-group of model A into a N-cyclic group, late
transition metal complexes bearing 2-(benzimidazol-2-yl)-1,10-
phenanthrolines (B, Scheme 1) were synthesized and showed high
catalytic activities towards ethylene oligomerization [66,67]. Bian-
chini group reported that the cobalt complexes bearing 2-thio-
phen-2-yl-6-iminopyridines showed about 5 times higher active
provides basic feedstocks for detergents, lubricant, plasticizers and
also the comonomers in the copolymerization with ethylene for
the linear low-density polyethylene (LLDPE) [1–3]. Late transition
metal complexes have demonstrated the feature of importance in
ethylene oligomerization with the practicing catalyst represented
by the nickel complexes in the Shell higher olefin process (SHOP)
[4–9]. In the past decade, late-transition metal complexes in olefin
reactivity have been greatly attracted because of the initial works
of cationic
a-diimino nickel and palladium complexes by Brook-
hart group [10] and bis(imino)pyridinyl iron and cobalt complexes
by Brookhart [11] and Gibson groups [12], individually. Inspired
with SHOP process for ethylene oligomerization [4–9], bidentate
nickel dihalides bearing P^P [13–15], N^O [16–21], P^N [22–27],
N^N [28–37] and organonickel complexes [38,39] have been
widely studied for ethylene reactivities. Encouraged by the finding
of bis(imino)pyridyl iron and cobalt complexes as highly active cat-
alysts in ethylene reactivity [11,12], special efforts have been paid
in ethylene oligomerization with longer chain
a-olefins than their
analogues bearing 2-furanyl-6-iminopyridines (C, Scheme 1) [68–
70], which indicates the influence of the heteroatoms of ligands.
In our extensive research, the ligands could be expectably changed
with benzoxazole instead of benzimidazole, and the nickel com-
plexes ligated by benzoxazolyl substituent show higher activity
for ethylene dimerization than its benzimidazolyl analogue
[60,71,72]. Therefore 2-benzoxazole-1,10-phenanthroline deriva-
tives (D, Scheme 1) are synthesized. In addition of alternation of
* Corresponding author. Address: Key Laboratory of Engineering Plastics and
Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100190, China. Tel.: +86 10 62557955; fax: +86 10
62618239.
E-mail address: whsun@iccas.ac.cn (W.-H. Sun).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.09.046

3868
M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
R'''
N
R'
Ar
O
N
N
N
N
O
X
N
N
N
N
N
N
N
N
N
N
R1
R3
Ar
R1
R''
X = O, S
R3
R
R2
E
D
C
A
B
this work
Scheme 1. Ligands for model catalysts.
steric and electronic influences, 2-oxazoline-1,10-phenanthroline
derivatives are prepared (E, Scheme 1). Their metal (nickel, cobalt
or iron) complexes are easily formed and showed higher catalytic
activities in ethylene oligomerization than those analogues ligated
by 2-(benzimidazol-2-yl)-1,10-phenanthrolines (B) [66,67]. Herein
the syntheses and characterizations of 2-benzoxazole-1,10-phen-
anthrolines (D), 2-oxazoline-1,10-phenanthrolines (E) and their
metal (nickel, cobalt or iron) complexes are reported, and the cat-
alytic behaviors of the metal complexes in ethylene oligomeriza-
tion with different cocatalysts and reaction parameters are
investigated and discussed in detail.
1,10-phenanthrolines (L1–L4) in acceptable yields [76]. Forma-
tions of benzoxazole and oxazoline differ regarding the role of
fused-benzene derivatives, oxazoline-phenanthrolines could not
be obtained through direct reaction of its aldehyde with ethanol-
amines. The alternative synthetic procedure employs the interme-
diates of methoxyimidates. The aldehydes were converted into
corresponding oximes, which could be further dehydrated in acetic
anhydride to give the nitriles [74,75]. The methoxyimidates were
easily formed in the reaction of nitriles with methanol in the pres-
ence of base [77]. After neutralization with acetic acid and subse-
quent removal of the solvent, condensation of the relevant
methoxyimidates with aminoethanol or 2-amino-2-methyl
propan-1-ol gave the corresponding oxazoline-phenanthroline
derivatives (L5–L8) in acceptable yields [78]. All 2-benzoxazole-
1,10-phenanthrolines (L1–L4) and oxazoline-phenanthrolines
(L5–L8) are well characterized by IR, 1H, and 13C NMR spectroscopy
as well as the elemental analysis. Moreover, the molecular struc-
tures of ligand L2 in the solid state is confirmed by the single-crys-
tal X-ray diffraction.
The routine stoichiometric reactions of the ligands (L1–L8) with
metal chlorides gave their corresponding complexes in good yields
(Scheme 3) [66,67]. The nickel complexes (Ni1–Ni8) and cobalt
complexes (Co1–Co8) in green powders were synthesized by treat-
ing the corresponding ligands with an equimolar NiCl2 Á 6H2O or
CoCl2 in anhydrous ethanol. The iron complexes (Fe1–Fe8) in pur-
ple powders were readily prepared by mixing the corresponding li-
gands with one equivalent of FeCl2 Á 4H2O in anhydrous ethanol at
2. Results and discussion
2.1. Synthesis and characterization
The synthesis of 2-methyl-1,10-phenanthroline has been per-
formed without any problem on tens gram-scale by the reaction
of 8-aminoquinoline with crotonaldehyde according to the litera-
ture [73]. 2-Methyl-1,10-phenanthroline was treated with twofold
excess of phenyllithium to obtain 2-methyl-9-phenyl-1,10-phe-
nanthroline in 73% yield after the routine workup and separation
by column chromatography (Scheme 2).
2-Methyl-1,10-phenanthroline and 2-methyl-9-phenyl-1,10-
phenanthroline were oxidized with selenium dioxide to form their
corresponding aldehydes, respectively [74,75]. The aldehydes re-
acted with 2-aminophenol derivatives to afford 2-benzoxazole-
NH2
OH
N
N
O
R2
SeO2
N
PhLi
N
N
N
N
I2, K2CO3
tBuOH
R1
CHO
R1
R2
L1 L2 L3 L4
N
N
R1
R2
H
H
H
H
Ph
H
NH2OH·HCl
Ph
Pyridine/EtOH
Me tBu
Ac2O
CH3ONa
OMe
NH
N
CN
N
N
CH3OH
N
N
N
N
OH
R1
R1
R3
R1
R3
Benzene
p-TsOH
OH
NH2
L5 L6 L7 L8
O
N
R1
R3
H
H
H
Ph Ph
Me
N
N
Me
H
R3
R3
R1
Scheme 2. Synthesis of 2-benzoxazole- or 2-oxazoline-1,10-phenanthrolines (L1–L8).

M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
3869
Similarly to the benzoimidazole analogue, the N3–C13 bond length
(1.293(3) Å) is relatively longer than the typical imino C@N bond.
Single crystals of complex Ni3 suitable for X-ray diffraction
analysis were grown by slowly laying of diethyl ether into their
methanol solutions. The asymmetric unit of complex Ni3 contains
the halves of two independent molecules, as shown in Fig. 2. The
two molecules have slightly different bond lengths and bond an-
gels, as shown in Table 1. Complex Ni3 demonstrates a distorted
octahedral coordination geometry of the Ni-center because of the
coordination of methanol. One chloride is replaced by one metha-
nol molecule and acts as a counterion. The nickel atom and the
mutually trans-disposed oxygen atoms are almost in one line
[174.40(2)o for (O30–Ni1–O40) in (a) and 174.94(2)o for O30’–
Ni1’–O40’ in (b)]. The Ni atom deviates slightly out of the coordina-
tion plane [0.0094 Å for (a) and 0.0282 Å for (b)]. It is notable that
the dihedral angle between phenanthroline plane and benzoxazole
plane [0.7o in (a) and 2.7o in (b)] is smaller than those of its benzo-
imidazole nickel analogues (5.8–7.9o) [66]. In both molecules, the
Ni–N(benzoxazole) are longer than the two Ni-N(phenanthroline)
bonds, which is different from the benzoimidazole nickel ana-
logues in which the Ni–N(benzoimidazole) are shorter than one
of the two Ni–N(phenanthroline) bonds [66].
O
O
MCl2
EtOH
N
N
N
H
N
R1
N
N
M
R1
R2
R2
Cl
H
H
Cl
R1
R2
H
Ph
H
Me tBu
Ni Ni1 Ni2 Ni3 Ni4
Co Co1 Co2 Co3 Co4
Fe Fe1 Fe2 Fe3 Fe4
MCl2
EtOH
O
O
N
N
R3
R3
R3
R3
N
R1
N
N
N
M
R1
Cl
Cl
Ph Ph
Me
R1
R3
H
H
H
Me
H
Ni Ni5 Ni6 Ni7 Ni8
Co Co5 Co6 Co7 Co8
Fe Fe5 Fe6 Fe7 Fe8
Scheme 3. Synthesis of metal complexes.
Single crystals of complexes Co1, Co3 and Fe2 suitable for X-ray
diffraction analysis were grown by diffusing diethyl ether into
their methanol solutions. Their structures were depicted in Figs.
3–5, respectively. Their selected bond lengths and angles are listed
in Table 2.
room temperature under nitrogen. All resultant complexes precip-
itated from the reaction solution, filtrated, washed with diethyl
ether and dried in vacuum.
All complexes were characterized by IR spectroscopy and ele-
mental analysis. The IR spectra of the complexes show the C@N
stretching vibrations of the iron, cobalt, and nickel complexes
shifted to lower wave number along with weaker intensities com-
paring with those of their corresponding ligands, thereby indicates
the presence of coordinative interactions between the nitrogen
atoms of benzoxazole/oxazoline and imino-groups with the central
metal. To confirm their real molecular structures in the solid state,
the structures of Ni3, Co1, Co3 and Fe2 are determined by single-
crystal X-ray diffraction analysis.
In the structure of Co1 (Fig. 3), the coordination geometry of the
cobalt center can be best described as distorted trigonal bipyrami-
dal with the phenanthroline nitrogen atom (N1) and the two chlo-
rines (Cl1 and Cl2) forming the equatorial plane. The cobalt atom
slightly deviates by 0.0041 Å from the plane with equatorial angles
range between 111.20(1)o and 132.51(1)o. The two axial Co–N
bonds subtend an angle of 149.85(2)o. The equatorial plane is
nearly perpendicular to the phenanthrolinyl plane, with a dihedral
angle of 89.2o. The dihedral angle between phenanthroline plane
and benzoxazole plane in Co1 is 0.9o. The Co1–N1 (phenanthro-
line) bond is about 0.2281 Å shorter than Co1–N3 (benzoxazole)
(2.301(5) Å) bond and 0.1641 Å shorter than Co1–N2 (phenanthro-
line) (2.237(5) Å) bond respectively.
2.2. X-ray crystallographic studies
Crystals of ligand L2 suitable for X-ray diffraction analysis were
grown from dichloromethane/hexane (1:8, v/v) solution at room
temperature over several days. Its molecular structure is shown
in Fig. 1. The dihedral angle between phenanthrolinyl plane and
benzoxazole plane is 9.4o, which is slightly larger than that of (1-
methyl-1H-benzimidazol-2-yl)-1,10-phenanthroline (7.6o) [66]
and indicates all the non-hydrogen atoms are almost coplanar.
Fig. 1. ORTEP drawing of L2 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles
(deg): C1–C13 1.471(3), C1–N1 1.330(3), C1–C2 1.406(3), C15–C16 1.388(3), C16–
C17 1.408(3); C13–C1–C2 119.52(2), N1–C1–C2 123.94(2), N3–C13–O1 115.37(2),
C15–C16–C17 119.96(2).
Fig. 2. ORTEP drawing of Ni3 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms have been omitted for clarity.

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M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
Table 1
Table 2
Selected bond lengths (Å) and bond angles (deg) for Ni3.
Selected bond lengths (Å) and bond angles (deg) for Co1, Co3 and Fe2.
Co1 Co3
2.073(4) 2.080(4)
Ni1–N1
2.027(5)
2.157(4)
2.215(4)
2.3184(2)
1.443(7)
77.61(2)
153.57(2)
75.96(2)
175.70(1)
98.12(1)
108.31(1)
Ni1’–N1’
2.024(4)
2.157(4)
2.199(4)
2.3164(2)
1.462(7)
77.55(2)
153.04(2)
75.51(2)
178.06(1)
100.84(1)
106.07(1)
Fe2
2.180(3)
2.234(3)
2.289(3)
2.3087(1)
2.4808(1)
1.454(5)
Ni1–N2
Ni1’–N2’
Bond lengths (Å)
M–N1
Ni1–N3
Ni1’–N3’
Ni1–Cl1
Ni1’–Cl1’
M–N2
M–N3
M–Cl1
M–Cl2
2.237(5)
2.301(5)
2.2529(2)
2.2723(2)
1.472(8)
2.199(4)
2.202(4)
2.2564(1)
2.2962(1)
1.451(7)
C1–C13
C1’–C13’
N1–Ni1–N2
N2–Ni1–N3
N1–Ni1–N3
N1–Ni1–Cl1
N2–Ni1–Cl1
N3–Ni1–Cl1
N1’–Ni1’–N2’
N2’–Ni1’–N3’
N1’–Ni1’–N3’
N1’–Ni1’–Cl1’
N2’–Ni1’–Cl1’
N3’–Ni1’–Cl1’
C1–C13
Bond angles (deg)
N1–M–N2
N2–M–N3
N1–M–N3
N1–M–Cl1
N1–M–Cl2
N2–M–Cl1
N2–M–Cl2
N3–M–Cl1
N3–M–Cl2
Cl1–M–Cl2
75.62(2)
149.85(2)
74.61(2)
132.51(1)
111.20(1)
97.73(1)
97.94(1)
98.76(1)
97.11(1)
116.29(7)
75.41(2)
146.30(1)
74.19(1)
152.14(1)
96.25(1)
100.10(1)
100.86(1)
99.95(1)
96.58(1)
111.55(5)
73.75(1)
144.75(1)
71.66(1)
169.68(8)
86.58(8)
114.48(8)
90.34(8)
99.26(8)
94.22(8)
99.23(5)
Unlike complex Co1, in the molecular structure of Co3, the co-
balt atom deviates by 0.3706 Å from the plane formed by N1, N2
and N3; meanwhile the chlorine atom Cl1 is almost in coplanar
manner with deviation of 0.3111 Å, and the other chlorine atom
Cl2 deviates 2.6595 Å from this plane in the opposite direction.
Based on this structural character, the coordination geometry of
complex Co3 can be best described as a distorted square pyramidal
with the basal plane composed by N1, N2, N3 and Cl1 (Fig. 4). The
similar structure of cobalt complex has been reported [61]. The ba-
sal plane is coplanar with the phenanthroline ring (6.9o) and the
benzoxazole ring (8.4o).
Fig. 3. ORTEP drawing of Co1 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms have been omitted for clarity.
In the structure of Fe2 (Fig. 5), the coordination geometry
around the iron center can be described as a distorted octahedron
because of the coordination of the solvent, which is essentially
similar to that of Ni3 and its benzoimidazole analogue [67]. As
expected, the iron center is coordinated to N1, N2 in the phenan-
throline ring and N3 in the benzoxazole ring, forming two fused
5-membered rings with acute N–Fe–N angles: 73.75(1)° (N1–
Fe1–N2) and 71.66(1)° (N1–Fe1–N3), in which the iron atom lies
ca. 0.1882 Å out of the coordinated plane. The benzoxazole plane
is nearly coplanar to the phenanthroline plane with a dihedral an-
gle of 4.5°. The bond lengths of Fe–N are significantly different: the
Fe1–N1 bond length (2.180(3) Å) is shorter than that of Fe1–N2
(2.234(3) Å) and Fe1–N3 (2.289(3) Å), in which the differences
were virtually identical to those seen in the 2,6-bis(imino)pyridyl
iron(II) complexes [11,12] and 2-imino-1,10-phenanthrolinyl iro-
n(II) complexes [54].
Fig. 4. ORTEP drawing of Co3 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms have been omitted for clarity.
2.3. Catalytic behavior towards ethylene reactivity
2.3.1. Catalytic behavior of nickel complexes
Complex Ni1 was typically investigated with various reaction
conditions, such as the cocatalysts, molar ratios of cocatalyst to
nickel, reaction temperature and ethylene pressure. With cocata-
Table 3
Selection of suitable cocatalyst based on Ni1.a
Cocat.
Al/Ni
Activityb
Oligomer distributionc (%)
a-C4(%)
P
P
C4/
C
C6/
C
MAO
MMAO
Et2AlCl
1000
1000
200
0.79
0.94
3.83
75.8
87.4
90.4
24.2
12.6
9.6
50.2
52.1
52.9
a
Conditions: 5
105 g molÀ1(Ni) hÀ1
Determined by GC and C signifies the total amounts of oligomers.
l
mol Ni1, 30 mL toluene, 1atm ethylene, 20 oC, 20 min.
b
c
.
Fig. 5. ORTEP drawing of Fe2 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms have been omitted for clarity.
P

M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
3871
lysts of Et2AlCl, MAO or MMAO, complex Ni1 showed moderate
activities in ethylene oligomerization for producing butenes and
hexenes at 1 atm (Table 3). Cocatalysts significantly affected its
catalytic behaviors and Et2AlCl was found to be more active and
selective for a-C4 than MMAO or MAO. Therefore, further catalytic
studies were performed with the activation of Et2AlCl.
vs. Entry 14 in Table 4). Such phenomenon is consistent to the
observation that the metal complexes bearing 2-iminophenanthr-
olines with an additional phenyl group on the 9-position were
slightly deactivated and caused by too bulky ligand for ethylene
to coordinate to active site [54,58]. Incorporating an electron-
t
donating alkyl group (R2 = Me or Bu, R3 = Me) on benzoxazole or
The amount of cocatalyst (Et2AlCl) greatly influenced the cata-
lytic performances. The enhancement of Al/Ni molar ratio from
100 to 200 resulted in an increase of catalytic activity up to
3.83 Â 105 g molÀ1(Ni) hÀ1 at the Al/Ni ratio of 200. A further in-
crease of the Al/Ni molar ratio showed negative effect from the
view of catalytic activity (Entries 1–3, Table 4). Meanwhile, the
oxazoline might push more electrons to the nickel atom, reduce
the net charge on the nickel center, and therefore resulted in lower
catalytic activity for ethylene oligomerization. This result agrees
with the theoretical calculated correlation between the activity
and the net charge of the metal center in late-transition metal
complexes [81–83] (such as Entries 8 and 9 vs. Entry 7; Entry 12
vs. Entry 11; and Entry 14 vs. Entry 13 in Table 4). Notably, com-
plexes bearing oxazolines display higher catalytic activities with
lower selectivities for 1-butene than analogues bearing benzoxaz-
oles (Entry 11 vs. Entry 7; Entry 12 vs. Entry 8; and Entry 13 vs. En-
try 10 in Table 4). That could be explained with steric effect of
fused benzene ring, moreover, oxazolines provide less electronic
donation to metal center than benzoxazoles could.
a-C4 selectivity decreased gradually with the increase of Al/Ni mo-
lar ratio. Therefore the Al/Ni molar ratio of 200 is selected in the
catalytic systems of other nickel complexes. Notably, compared
to its benzimidazole nickel analogue (optimized Al/Ni molar ratio
of 300) [66], less amount of Et2AlCl was used, which may indicates
that the benzoxazole substituted nickel complexes are easier to be
activated. As the exothermic reaction of oligomerization is con-
cerned, reaction temperature was found to have a remarkable
influence on the catalytic activity and the distribution of oligomers
obtained. The highest activity was achieved at 20 °C (Entry 2, Table
4), and a slightly lower activity was obtained along with a less
amount of butenes (85.6%) produced at lower temperature (0 °C;
Entry 4, Table 4). Elevating the reaction temperature from 20 oC
to 60 oC resulted in a sharp decrease of activity, which may be
attributed to the decomposition of the active catalytic sites and
lower ethylene solubility at higher temperature. Moreover, higher
reaction temperature resulted in an increased proportion of bu-
tenes, but a sharp decreased selectivity for 1-butene (Entries 2, 5
and 6, Table 4). The increase of ethylene pressure from 1 to
10 atm ethylene resulted in much higher activities due to an effect
of increased ethylene concentration in solution (Entries 2 and 7,
Table 4). The better selectivity for 1-butene was also observed at
higher pressure, which can be ascribed to the fact that the in-
creased dimerization in turn attenuated the effect of parallel isom-
erization of 1-butene into 2-butene [25,79,80].
2.3.2. Catalytic behavior of cobalt complexes
After selection of suitable cocatalyst, MMAO was found the most
active. The catalytic activity of cobalt complexes Co1–Co8 in ethyl-
ene oligomerization has been evaluated employing MMAO as
cocatalyst under 10 atm of ethylene. Compared to their nickel ana-
logues, all cobalt complexes exhibited lower activities for dimeriza-
tion and trimerization of ethylene, but with higher selectivities for
a-olefins. Similar to their nickel analogues, the additional Ph-group
on the 9-position of phenanthroline negatively affects on the cata-
Table 5
Oligomerization of ethylene with Co1–Co8/MMAO system.a
Entry
Complex
Activityb
Oligomer distributionc(%)
a-C4 (%)
P
P
C4/
C
C6/
C
1
2
3
4
5
6
7
8
Co1
Co2
Co3
Co4
Co5
Co6
Co7
Co8
15.1
7.88
6.32
0.57
1.92
1.58
0.77
0.68
82.5
80.1
78.9
74.5
92.8
95.3
83.7
85.1
17.5
19.9
21.1
25.5
7.2
75.6
77.3
84.3
90.9
58.2
62.1
76.4
78.1
On the base of optimum conditions on Ni1, all the nickel com-
plexes Ni1–Ni8 are investigated at 20 oC with Al/Ni ratio of 200
and 10 atm ethylene (Entries 7–14, Table 4). It can be observed that
ligand environment has considerable effect on the catalytic behav-
4.7
16.3
14.9
iors, such as activity and
phenyl group on the 9-position of the phenanthroline ring led to
a dramatic decrease in catalytic activity and an increase in -C4
a-C4 selectivity. The introduction of a
a
Conditions: 5 l
mol cobalt, 100 mL toluene, 20 oC, 10 atm ethylene, 20 min, Al/
Co = 1000.
b
105 g molÀ1(Co) hÀ1
.
a
P
c
Determined by GC and C signifies the total amounts of oligomers.
selectivity (Entry 7 vs. Entry 10; Entry 11 vs. Entry 13; Entry 12
Table 4
Ethylene oligomerization by Ni1–Ni8/Et2AlCl system.a
Entry
Complex
Al/Ni
T/oC
P/atm
Activityb
Oligomer distribution(%)c
a-C4(%)
P
P
C4/
C
C6/
C
1
2
3
4
5
6
7
8
Ni1
Ni1
Ni1
Ni1
Ni1
Ni1
Ni1
Ni2
Ni3
Ni4
Ni5
Ni6
Ni7
Ni8
100
200
300
200
200
200
200
200
200
200
200
200
200
200
20
20
20
0
1
1
1
1
1
1
10
10
10
10
10
10
10
10
1.80
3.83
1.36
1.94
0.53
0.07
25.7
21.9
18.1
10.3
31.1
27.4
14.5
10.9
94.8
90.4
89.1
85.6
97.2
98.1
92.0
93.2
91.5
90.1
95.8
97.1
85.1
80.9
5.2
55.7
52.9
48.1
65.0
41.3
22.3
63.9
65.7
70.3
84.1
44.2
45.1
60.1
61.3
9.6
10.9
14.4
2.8
1.9
8.0
6.8
8.5
9.9
4.2
40
60
20
20
20
20
20
20
20
20
9
10
11
12
13
14
2.9
14.9
19.1
a
Conditions: 5
lmol nickel, 20 min, 30 mL toluene for 1 atm ethylene; 100 mL toluene for 10 atm ethylene.
b
c
105 g molÀ1(Ni) hÀ1
.
P
Determined by GC and C signifies the total amounts of oligomers.

3872
M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
Table 6
Oligomerization of ethylene with Fe1–Fe8/MMAO system.a
Entry
Complex
Al/Fe
T/oC
P/atm
Activityb
Oligomer distributionc(%)
a-C4(%)
P
P
C4/
C
C6/
C
1
2
3
4
5
6
7
8
Fe1
Fe1
Fe1
Fe1
Fe1
Fe1
Fe1
Fe1
Fe2
Fe3
Fe4
Fe5
Fe6
Fe7
Fe8
500
800
1000
800
800
800
800
800
800
800
800
800
800
800
800
20
20
20
0
1
1
1
1
1
9.14
18.1
12.4
7.19
10.5
7.69
2.12
189.3
101.5
91.3
19.7
25.1
31.7
9.40
15.3
89.9
10.1
16.5
13.1
15.5
11.5
9.9
62.3
60.8
54.3
65.4
56.7
44.0
25.6
80.3
81.5
83.0
83.5
86.9
84.5
88.5
90.1
98.3
85.1
83.7
80.1
30
40
60
20
20
20
20
20
20
20
20
1
1
1.7
10
10
10
10
10
10
10
10
14.9
16.3
19.9
9
10
11
12
13
14
15
100
100
93.5
91.7
95.3
96.0
6.5
8.3
4.7
4.0
61.3
64.7
80.1
83.3
a
Conditions: 5
lmol iron, 30 mL toluene for 1 atm ethylene; 100 mL toluene for 10 atm ethylene; 20 min.
b
c
104 g molÀ1(Fe) hÀ1
.
P
Determined by GC and C signifies the total amounts of oligomers.
lytic activities while causing positive effect on the selectivities for
-olefins (showing with 1-butene in Entry 4 vs. Entry 1; Entry 7
try 12; Entry 15 with Entry 14, Table 6) resulted in higher activities
and selectivities for 1-butene. Both the catalytic activities and
selectivities of these iron complexes bearing benzoxazoles (except
Fe4) were found much higher than those of complexes containing
oxazolines, such as examples of Fe5 with Fe1 (Entry 12 vs. Entry 8,
Table 6) and Fe7 with Fe4 (Entry 14 vs. Entry 11, Table 6). All iron
complexes exhibited slightly higher activities than those of their
cobalt analogues, which commonly observed in tridentate metal
(Fe and Co) catalysts in ethylene reactivity [11,12,86].
a
vs. Entry 5; Entry 8 vs. Entry 6, Table 5). A similar tend was observed
in complexes bearing ligands with additional alkyl substituents, R2
(Me or tBu, Entries 2 and 3 vs Entry 1, Table 5) or R3 (Me, Entry 6 vs.
Entry 5; Entry 8 vs Entry 7, Table 5). The 2-oxazoline-1,10-phen-
anthrolinyl cobalt chloride (Co5) (Entry 5, Table 5) displayed much
lower activity than that of 2-benzoxazole-1,10-phenanthrolinyl co-
balt chloride (Co1) (Entry 1, Table 5).
Compared with 2-benzimidazolylphenanthrolines nickel, iron
and cobalt dichloride [66,67], complexes containing a 2-benzoxaz-
ole substituent generally showed slightly higher catalytic activity
than their 2-benzimidazole analogues. In comparison with benz-
imidazole analogue, the benzoxazoles which posses stronger elec-
tron-withdrawing ability, made more net charge on the nickel
center, thus having more positive impact on the catalytic activity
than its benzimidazole counterparts. This result is consistent with
the computational conclusion related to the relationship between
catalytic activity and the net charge of the metal center in late-
transition metal complexes [81–83].
2.3.3. Catalytic behavior of iron complexes
After selection of suitable cocatalyst, MMAO was found the
most active. Complex Fe1 was first investigated by employing
MMAO as cocatalyst with various ratios at 1 atm of ethylene and
then changing reaction temperature. Both cocatalysts activate the
iron complex in ethylene oligomerization (Table 6). The amount
of cocatalyst has great influence on the catalytic performance.
The enhancement of Al/Fe molar ratio from 500 to 800 resulted
of increasing catalytic activities in ethylene oligomerization (En-
tries 1 and 2, Table 6), and the catalytic activity of Fe1 peaked at
1.81 Â 105 g molÀ1(Fe) hÀ1 at an Al/Fe molar ratio of 800. Further
higher loading of MMAO resulted in decreased activity (Entry 3, Ta-
ble 6), which could be caused due to unnecessary scavenger and
also the isobutyl group from MMAO hindering the insertion reac-
3. Conclusions
tion of ethylene [84,85]. Similar as its nickel analogue, the
selectivity of Fe1 gradually decreased with the increase of the Al/
Fe molar ratio.
a-C4
Metal (nickel, cobalt and iron) complexes ligated by 2-oxazo-
line- or 2-benzoxadozole-1,10-phenanthrolines have been synthe-
sized, characterized and evaluated as catalyst precursors in
ethylene oligomerization. On treatment with Et2AlCl, nickel com-
plexes oligomerized ethylene with high activities (Ni5/Et2AlCl:
3.11 Â 106 g molÀ1(Ni) hÀ1). Upon activation with MMAO, cobalt
and iron complexes showed nice catalytic activities (Co1/MMAO:
The reaction temperature affects the catalytic performance. The
optimum temperature was 20 oC at 1 atm ethylene (Entry 2, Table
6). The random selectivities of dimer or trimer were observed in
changing reaction temperature (Entries 2, 4–7, Table 6). The higher
temperature reaction used, the lower selectivity 1-butene ob-
served. A similar influence of temperature on the oligomer distri-
bution produced by iron-based systems has been reported [59].
Based on the above results, the reaction parameters are fixed as
20 oC and an Al/Fe molar ratio of 800. At 10 atm ethylene, the re-
sults by all iron complexes in ethylene oligomerization are listed
in Table 6 (Entries 8–15). Similarly to the above nickel and cobalt
analogues, the phenyl group on the 9-position of phenanthroline
ring caused lower activities and higher selectivities for 1-butene
(compare Entry 11 vs. Entry 8; Entry 14 vs. Entry 12; Entry 15
vs. Entry 13, Table 6). Moreover, adding other alkyl groups such
1.51 Â 106 g molÀ1(Co) hÀ1
;
Fe1/MMAO: 1.89 Â 106 g molÀ1(Fe)
h
À1). Higher activity and better selectivity for 1-butene could be
obtained under higher ethylene pressure and ambient temperature.
The variation of oxygen-containing group (benzoxazole or oxazo-
line) on the 2-position of the phenanthroline ring shows great influ-
ence on the catalytic performance of those metal complexes.
4. Experimental
4.1. General considerations
t
as R2 (Me or Bu, compare Entries 9 and 10 with Entry 8, Table 6)
also led to lower activities and higher selectivities for 1-butene.
All air- or moisture-sensitive manipulations were carried out
under nitrogen using standard Schlenk techniques. Melting points
However, the additional R3 groups (Me, compare Entry 13 with En-

M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
3873
were determined with a digital electrothermal apparatus without
calibration. IR spectra were obtained with a Perkin–Elmer FTIR
2000 spectrophotometer by using KBr disks in the range of
4000–400 cmÀ1. NMR spectra were recorded with a Bruker DMX-
300 or Bruker ARX 400 spectrometer with TMS as the internal stan-
dard. Elemental analyses were performed with a Flash EA 1112
microanalyzer. GC was performed with a VARIAN CP-3800 gas
chromatograph equipped with a flame ionization detector and a
J = 8.4 Hz, 1H, phen), 7.97 (d, J = 8.8 Hz, 1 H, phen), 7.86 (d,
J = 8.8 Hz,
1 H, phen), 7.59 (t, J = 7.2 Hz, 2 H, Ph), 7.51 (t,
J = 7.2 Hz, 1 H, Ph) ppm. 13C NMR (100 MHz, CDCl3): d = 193.8,
157.7, 151.8, 145.8, 145.6, 138.9, 137.1, 136.8, 131.1, 129.5,
128.9, 128.6, 127.6, 125.5, 120.7, 119.2 ppm. C19H12N2O (284.31):
Calc. C 80.27, H 4.25, N 9.85. Found C 80.54, H 4.15, N 10.11%.
4.2.4. 2-(Benzoxazol-2-yl)-1,10-phenanthroline (L1)
30-m (0.2 mm i.d., 0.25
l
m film thickness) CP-Sil 5 CB column. Tol-
To a solution of 1,10-phenanthroline-2-carbaldehyde (2.08 g,
10 mmol) in tert-butyl alcohol (30 ml) was added 2-aminophenol
(1.20 g, 11.0 mmol). The mixture was stirred at room temperature
under nitrogen atmosphere for 30 min, and then K2CO3 (4.15 g,
30 mmol) and I2 (5.08 g, 20 mmol) were added to the mixture
and stirred at 70 oC for 18 h. The reaction was quenched with sat-
urated aqueous Na2SO3 until the iodine color almost disappeared
and was extracted with Et2O. The organic layer was washed with
brine and dried over Na2SO4. After filtration, the solvent was re-
moved in vacuo. The residual was chromatographed on silica
gel (AcOEt) to give 0.68 g of the product as white solid in 23%
yield. M.p. = 172–174 °C. FT-IR (KBr disc, cmÀ1): 3059(m),
uene was refluxed in the presence of sodium/benzophenone and
distilled under nitrogen prior to use. The polymerization-grade
ethylene was supplied by Beijing Yansan Petrochemical Co. Et2AlCl
(1.90 M) solution in toluene and triethylaluminum (diluted to 2 M
in toluene for usage) were purchased from Acros Chemicals, while
methylaluminoxane (MAO, 1.46 M in toluene) and modified meth-
ylaluminoxane (MMAO, 1.93 M in heptane, 3A) were purchased
from Akzo Nobel Corp. All other commercial chemicals were used
without further purification.
4.2. Synthesis of ligands (L1–L8)
1613(m,
tC@N), 1586(m), 1549(m), 1501(s), 1489(s), 1449(s),
4.2.1. 2-Methyl-9-phenyl-1,10-phenanthroline
1400(m), 1289(s), 1246(m), 1126(m), 1113(s), 1065(s), 877(s),
858(s), 764(m), 744(m), 718(s). 1H NMR (400 MHz, CDCl3):
d = 9.32 (dd, J1 = 1.7 Hz, J2 = 4.3 Hz, 1 H, phen), 8.74 (d, 1 H,
J = 8.3 Hz, phen), 8.45 (d, J = 8.4 Hz, 1 H, phen), 8.30 (dd, J1 =
1.6 Hz, J2 = 8.1 Hz, 1 H, phen), 7.92–7.86 (m, 3 H, 1 H-phen, 2
H- benzoxazole), 7.79 (dd, J1 = 1.4 Hz, J2 = 6.8 Hz, 1 H, phen),
7.70 (dd, J1 = 4.4 Hz, J2 = 8.0 Hz, 1 H, phen), 7.48–7.42 (m, 2 H,
benzoxazole), ppm. 13C NMR (100 MHz, CDCl3): d = 160.9, 150.4,
149.8, 145.1, 145.0, 144.5, 141.0, 136.3, 135.4, 128.6, 128.2,
127.4, 125.5, 125.3, 124.2, 122.7, 121.4, 119.9, 110.8 ppm.
C19H11N3O (297.31): Calc. C 76.76, H 3.73, N 14.13. Found C
76.50, H 4.03, N 14.50%.
A phenyllithium solution was prepared through the slow addi-
tion of bromobenzene (2.31 mL, 22.0 mmol) solution in diethyl
ether (20 mL) to two equivalents of lithium (313 mg, 45.0 mmol)
in diethyl ether (30 mL) at room temperature under nitrogen.
Phenyllithium solution was thereafter added dropwise to a suspen-
sion of 2-methyl-1,10-phenanthroline (1.94 g, 10.00 mmol) in tol-
uene (40 mL) at À78 °C and then the mixture was slowly warmed
to room temperature and stirred overnight. The reaction was
quenched by slow addition of water (100 mL). The brown organic
layer was separated and the aqueous layer was extracted several
times with CH2Cl2. The organic phases was combined and dried
with anhydrous sodium sulfate. After the evaporation of solvent,
the residue was purified on a silica column (8/1 petroleum ether/
triethylamine) and the pure product was obtained as ivory white
solid in 73% yield (1.97 g). M.p. = 194–196 °C. FT-IR (KBr disc, cmÀ1):
4.2.5. 2-(5-Methylbenzoxazol-2-yl)-1,10-phenanthroline (L2)
In a similar manner to that described for L1, L2 was obtained as
white solid in 28% yield. M.p. = 198–200 °C FT-IR (KBr disc, cmÀ1):
3059(m), 3042(m), 1651(m), 1608(m,
t
C@N), 1501(s), 1489(s),
3030(m), 1734(m), 1619(m, tC@N), 1585(m), 1549(m), 1502(s),
1449(s), 1400(m), 1289(m), 1246(m), 1126(m), 1114(m),
1071(w), 858(s), 744(s), 718(s). 1H NMR (400 MHz, CDCl3):
d = 8.41 (d, J = 7.5 Hz, 2 H, Ph), 8.33 (d, J = 8.4 Hz, 1 H, phen), 8.17
(d, J = 8.2 Hz, 1H, phen), 8.14 (d, J = 8.4 Hz, 1 H, phen), 7.78 (s, 2
H, phen), 7.60–7.48 (m, 4 H, 3 H-Ph, 1 H-phen) ppm. 13C NMR
(100 MHz, CDCl3): d 159.6, 157.1, 145.8, 139.7, 137.0, 136.3,
129.5, 128.8, 128.0, 127.8, 127.1, 126.3, 123.7, 120.2, 26.0 ppm.
C19H14N2 (270.33): calcd. C 84.42, H 5.22, N 10.36. Found C
84.74, H 5.15, N 10.11%.
1482(s), 1443(s), 1418(m), 1402(m), 1352(m), 1311(w), 1263(s),
1192(m), 1108(s), 1080(m), 1069(s), 948(m), 874(s), 853(s),
807(s). 1H NMR (400 MHz, CDCl3): d = 9.32 (d, J = 4.3 Hz, 1 H, phen),
8.73 (d, 1 H, J = 8.3 Hz, phen), 8.46 (d, J = 8.4 Hz, 1 H, phen), 8.31 (d,
J = 8.1 Hz, 1 H, phen), 7.92 (d, J = 8.9 Hz, 1 H, phen), 7.89 (d,
J = 8.9 Hz, 1 H, phen), 7.71 (dd, J1 = 4.3 Hz, J2 = 8.0 Hz, 1 H, phen),
7.67–7.64 (m, 2 H, benzoxazole), 7.25 (d, J = 6.5 Hz, 1 H, benzoxaz-
ole), 2.52 (s, 3 H, CH3) ppm. 13C NMR (100 MHz, CDCl3): d = 161.6,
150.7, 149.4, 145.8, 145.7, 145.6, 141.9, 136.8, 135.8, 134.5, 129.1,
128.8, 127.9, 127.2, 125.8, 123.1, 122.1, 120.1, 110.1, 21.3 ppm.
C20H13N3O (311.34): Calc. C 77.16, H 4.21, N 13.50. Found C
77.40, H 4.03, N 13.77%.
4.2.2. 1,10-Phenanthroline-2-carbaldehyde
Selenium dioxide (3.42 g, 30.8 mmol) was added to a solution of
2-methyl-1,10-phenanthroline (3.00 g, 15.4 mmol) in dioxane
(50 ml). The mixture was heated under reflux for 2 h and then fil-
tered through Celite. Evaporation of the solvent afforded a yellow
solid. Some more product was obtained by washing the Celite with
CH2Cl2 (3.59 g, 12.6 mmol, 82%). M.p. = 153–155 °C ([lit. 54,
[87]]152–154 °C).
4.2.6. 2-(5-Tert-butylbenzoxazol-2-yl)-1,10-phenanthroline(L3)
In a similar manner to that described for L1, L3 was obtained as
white solid in 47% yield. M.p. = 114–116 °C. FT-IR (KBr disc, cmÀ1):
3050(m), 2959(s), 2867(m), 1618(m,
tC@N), 1586(m), 1544(m),
1503(s), 1481(s), 1442(s), 1419(m), 1269(s), 1108(s), 1080(m),
1064(s), 945(m), 876(m), 856(s), 833(m). 1H NMR (400 MHz,
CDCl3): d = 9.32 (d, J = 4.3 Hz, 1 H, phen), 8.74 (d, 1 H, J = 8.3 Hz,
phen), 8.45 (d, J = 8.4 Hz, 1 H, phen), 8.30 (d, J = 8.0 Hz, 1 H, phen),
7.92–7.87 (m, 3 H, 2 H-phen, 1 H-benzoxazole), 7.72-7.67 (m, 2 H,
1 H-phen, 1 H- benzoxazole), 7.51 (d, J = 8.6 Hz, 1 H, benzoxazole),
1.43 (s, 9 H, tBu) ppm. 13C NMR (100 MHz, CDCl3): d = 161.7, 150.8,
149.2, 148.1, 145.9, 145.7, 141.6, 136.9, 135.8, 129.1, 128.8, 127.9,
125.9, 123.9, 123.1, 122.1, 116.6, 110.7, 34.7, 31.5 ppm. C23H19N3O
(353.42): Calc. C 78.16, H 5.42, N 11.89. Found C 78.40, H 5.03, N
11.77%.
4.2.3. 9-Phenyl-1,10-phenanthroline-2-carbaldehyde
In a similar manner to that described for 1,10-phenanthroline-
2-carbaldehyde,
was obtained as yellow solid in 79% yield. M.p. = 228–230 °C. FT-
IR (KBr disc, cmÀ1): 3060(m), 2823(s), 1705(s,
C„N), 1614(m,
9-phenyl-1,10-phenanthroline-2-carbaldehyde
t
t
C@N), 1602(m), 1578(m), 1546(m), 1487(s), 1370(m), 1280(m),
1260(s), 1098(m), 1090(m), 884(s), 797(s), 739(s), 692(s). 1H
NMR (400 MHz, CDCl3): d = 10.56 (s, 1 H, CHO), 8.43–8.36 (m, 4
H, 2 H-phen, 2 H-Ph), 8.30 (d, J = 8.2 Hz, 1 H, phen), 8.20 (d,

3874
M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
4.2.7. 2-(Benzoxazol-2-yl)-9-phenyl-1,10-phenanthroline (L4)
In a similar manner to that described for L1, L4 was obtained as
white solid in 21% yield using 9-phenyl-1,10-phenanthroline-2-
carbaldehyde as the starting material. M.p. = 214–216 °C. FT-IR
(KBr disc, cmÀ1): 3061(m), 3035(m), 2843(m), 1952(m), 1621(m,
2233(m), 1960(w), 1616(m, tC@N), 1601(m), 1576(m), 1542(m),
1504(m), 1485(s), 1420(m), 1404(m), 1364(m), 1299(m),
1280(m), 1206(m), 1148(m), 1100(m), 1023(m), 911(m), 863(s).
1H NMR (400 MHz, CDCl3): d = 8.40-8.35 (m, 4 H, 2 H-phen, 2
H-Ph), 8.21 (d, J = 8.4 Hz, 1 H, phen), 8.01–7.96 (m, 2 H, phen),
7.82 (d, J = 8.8 Hz, 1 H, phen), 7.59 (t, J = 7.4 Hz, 2 H, Ph), 7.51
tC@N), 1603(m), 1587(m), 1579(m), 1546(m), 1487(s), 1450(s),
1422(m), 1368(m), 1245(s), 1115(m), 1102(s), 1063(s), 929(m),
898(m), 886(m), 860(s), 806(m). 1H NMR (400 MHz, CDCl3):
d = 8.75 (d, J = 8.3 Hz, 1 H, phen), 8.50–8.46 (m, 3 H, 2H-Ph, 1 H-
phen), 8.37 (d, J = 8.4 Hz, 1 H, phen), 8.21 (d, J = 8.4 Hz, 1 H, phen),
7.94 (d, J = 8.8 Hz, 1 H, phen), 7.88 (m, 2 H, benzoxazole), 7.81 (d,
(t, J = 7.1 Hz, 1
H, Ph) ppm. 13C NMR (100 MHz, CDCl3):
d = 158.3, 146.9, 145.3, 139.0, 137.4, 137.2, 133.4, 130.3, 129.8,
129.1, 128.1, 128.0, 126.1, 125.5, 121.5, 118.0 ppm. C19H11N3
(281.31): Calc. C 81.12, H 3.94, N 14.94. Found C 81.48, H
3.63, N 14.89%.
J = 7.4 Hz,
1 H, phen), 7.62 (t, J = 7.3 Hz, 2 H, Ph), 7.53 (t,
J = 7.2 Hz, 1 H, Ph), 7.50–7.42 (m, 2 H, benzoxazole) ppm. 13C
NMR (100 MHz, CDCl3): d = 162.1, 157.8, 151.5, 148.8, 147.8,
146.3, 145.9, 145.1, 142.1, 139.3, 137.4, 137.1, 129.8, 129.0,
128.3, 128.0, 125.9, 125.0, 121.6, 120.9, 120.7, 116.3, 111.9 ppm.
C25H15N3O (373.41): Calc. C 80.41, H 4.05, N 11.25. Found C
80.18, H 4.23, N 11.59%.
4.2.12. 2-(4,5-Dihydrooxazol-2-yl)-1,10-phenanthroline (L5)
1,10-Phenanthroline-2-carbonitrile was converted into the
corresponding methyl carboxyimidate following a reported meth-
od [77]. A solution of methyl carboxyimidate (1.90 g, 8 mmol) in
anhydrous benzene containing the appropriate aminoalcohol
(488 mg, 8 mmol) and a few milligrams of p-toluenesulfonic acid
was slowly distilled under nitrogen atmosphere until all the sub-
strate was reacted (1–2 h). The solvent was removed and the
residual was purified through silica (acetone as eluent) to give
0.58 g of the product as white solid in 29% yield. M.p. = 88–
90 oC. FT-IR (KBr disc, cmÀ1): 3058(m), 2933(m), 2879(w),
4.2.8. 1,10-Phenanthroline-2-carboaldoxime
A
solution of 1,10-phenanthroline-2-carbaldehyde (0.5 g,
2.40 mmol), hydroxylamine hydrochloride (0.5 g, 7.20 mmol) and
pyridine (1 ml) in ethanol (30 ml) was heated under reflux for
2 h. The resulting green precipitate was recrystallized from ethanol
to give the product in 92% yield. M.p. = 224–226 °C. FT-IR (KBr disc,
1652(m,
tC@N), 1617(m), 1559(m), 1508(m), 1493(m), 1401(s),
1356(m), 1260(w), 1151(m), 1136(s), 1114(m), 1081(s), 949(s),
857(s), 719(s), 704(s). 1H NMR (400 MHz, CDCl3): d = 9.13 (d, 1
H, J = 8.0 Hz, phen), 8.24 (s, 2 H, phen), 8.17 (d, 1 H, J = 8.0 Hz,
phen), 7.73–7.71 (m, 2 H, phen), 7.59–7.56 (m, 1 H, phen), 4.57
(t, J = 9.5 Hz, 2 H, CH2), 4.15 (t, J = 9.7 Hz, 2 H, CH2). 13C NMR
(100 MHz, CDCl3): d = 164.4, 150.5, 146.2, 145.9, 145.6, 136.8,
136.3, 129.5, 129.0, 128.2, 126.2, 123.5, 122.7, 80.0, 68.5, 55.1.
C15H11N3O (249.27): Calc. C 72.28, H 4.45, N 16.86. Found C
72.18, H 4.33, N 17.19%.
cmÀ1): 3600–2800(s), 1615(m,
tC@N), 1596(s), 1531(s), 1461(s),
1402(s), 1349(m), 1288(s), 1228(s), 1190(s), 1139(s), 1100(m),
990(s), 961(m), 941(s), 884(m), 867(s), 825(s), 818(m), 729(s). 1H
NMR (400 MHz, DMSO): d = 12.0 (s, OH), 8.65–8.61 (m, 2 H, phen),
8.55 (s, 1 H, CH=NOH), 8.46–8.42 (m, 3 H, phen), 8.24 (d, J = 8.5 Hz,
1 H, phen), 8.08–8.06 (m, 2 H, Ph), 7.63–7.56 (m, 3 H, Ph) ppm. 13C
NMR (100 MHz, DMSO): d = 153.4, 148.9, 144.5, 140.2, 138.5,
130.1, 129.7, 129.1, 127.9, 126.8, 125.4, 122.0 ppm. C13H9N3O
(223.23): Calc. C 69.95, H 4.06, N 18.82. Found C 69.78, H 4.23, N
18.59%.
4.2.13. 2-(4,5-Dihydro-4,4-dimethyloxazol-2-yl)-1,10-phenanthroline
(L6)
4.2.9. 9-Phenyl-1,10-phenanthroline-2-carboaldoxime
In a similar manner to that described for L5, the product L6 was
obtained as white solid in 31% yield. M.p. = 78–80 oC FT-IR (KBr
disc, cmÀ1): 3057(m), 2967(m), 2931(m), 2900(m), 2867(w),
In a similar manner to that described for 1,10-phenanthroline-
2-carboaldoxime, 9-phenyl-1,10-phenanthroline-2-carboaldoxime
was obtained as green solid in 87% yield. M.p. = 360–362 °C. FT-
1690(m), 1645(m,
tC@N), 1618(m), 1586(m), 1559(m), 1506(m),
IR (KBr disc, cmÀ1): 3600–2800(s), 1895(m), 1628(m,
t
C@N),
1492(s), 1464(m), 1400(s), 1369(m), 1357(m), 1308(s), 1200(m),
1175(m), 1128(s), 1077(s), 963(s), 861(s), 712(s). 1H NMR
(400 MHz, CDCl3): d = 9.22 (d, 1 H, J = 4.4 Hz, phen), 8.40 (d, 1 H,
J = 8.4 Hz, phen), 8.31 (d, 1 H, J = 8.3 Hz, phen), 8.26 (d, 1H,
J = 8.1Hz, phen), 7.85 (d, 1 H, J = 8.8 Hz, phen), 7.81 (d, 1 H,
J = 8.8 Hz, phen), 7.66 (dd, 1H, J = 4.4, 8.0 Hz, phen), 4.32 (s, 2H,
CH2), 1.47 (s, 6H, CH3) ppm. 13C NMR (100 MHz, CDCl3): d =
161.8, 150.5, 146.5, 146.0, 145.6, 136.8, 136.4, 129.5, 129.0,
128.1, 126.2, 123.5, 122.8, 80.0, 68.2, 28.6 ppm. C17H15N3O
(277.32): Calc. C 73.63, H 5.45, N 15.15. Found C 73.28, H 5.53, N
15.49%.
1577(s), 1557(s), 1531(s), 1507(m), 1479(s), 1442(m), 1418(m),
1332(m), 1308(s), 1193(s), 1161(s), 1013(s), 999(s), 883(m),
868(s), 856(s), 773(m), 765(m), 753(m), 729(s), 688(s), 672(m).
1H NMR (400 MHz, DMSO): d = 12.0 (s, OH), 8.65–8.61 (m, 2 H,
phen), 8.55 (s, I H, CH@NOH), 8.46–8.42 (m, 3 H, phen), 8.24 (d,
J = 8.5 Hz, 1 H, phen), 8.17 (d, J = 8.7 Hz, 1 H, Ph), 8.05 (d,
J = 8.8 Hz, 1 H, Ph) 7.63–7.52 (m, 3 H, Ph) ppm. 13C NMR
(100 MHz, DMSO): d = 152.3, 149.0, 144.5, 141.0, 138.7, 137.3,
130.5, 129.9, 129.4, 128.7, 127.0, 126.5, 125.4, 122.3, 119.6 ppm.
C19H13N3O (299.33): Calc. C 76.24, H 4.38, N 14.04. Found C
76.58, H 4.33, N 13.79%.
4.2.14. 2-(4,5-Dihydrooxazol-2-yl)-9-phenyl-1,10-phenanthroline
(L7)
4.2.10. 1,10-phenanthroline-2-carbonitrile
A
solution of 1,10-phenanthroline-2-carboaldoxime (0.5 g,
In a similar manner to that described for L5, the product L7 was
2.24 mmol) in acetic anhydride (10 ml) was heated under reflux
for 2 h. After dilution with water (20 mL) and neutralization by
NaHCO3, the aqueous phase was extracted by CH2Cl2 and purified
by silica gel column (1/2 EtOAc/Petroleum ether) to give the prod-
uct as white solid in 54% yield. M.p. = 231–233 °C. ([lit. 54, [88]]
233–234 °C].
obtained as white solid in 34% yield. M.p. = 108–110 oC FT-IR (KBr
disc, cmÀ1): 2924(m), 1632(m,
tC@N), 1615(m), 1605(m), 1585(m),
1543(m), 1498(s), 1484(m), 1371(m), 1356(m), 1307(s), 1276(m),
1114(s), 1098(m), 1070(m), 949(s), 857(s), 772(s), 733(s), 698(s).
1H NMR (400 MHz, CDCl3): d = 8.41–8.31 (m, 5 H), 8.14 (d, 1 H,
J = 8.4 Hz, Phen), 7.88 (d, 1 H, J = 8.7 Hz, phen), 7.80 (d, 1 H,
J = 8.2 Hz, phen), 7.56 (t,
2 H, J = 7.3 Hz, Ph), 7.48 (t, 1 H,
4.2.11. 9-Phenyl-1,10-phenanthroline-2-carbonitrile
J = 7.2 Hz, Ph). 13C NMR (100 MHz, CDCl3): d = 164.7, 158.0, 146.5,
146.0, 145.8, 139.3, 137.1, 137.0, 130.1, 129.7, 128.9, 128.2,
128.0, 125.8, 122.7, 121.1, 68.4, 55.3. C21H15N3O (325.36): Calc. C
77.52, H 4.65, N 12.91. Found C 77.18, H 5.03, N 12.59%.
In a similar manner to that described for 1,10-phenanthro-
line-2-carbonitrile, the product was obtained as yellow solid in
48% yield. M.p. = 264–266 °C. FT-IR (KBr disc, cmÀ1): 3054(m),

M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
3875
4.2.15. 2-(4,5-Dihydro-4,4-dimethyloxazol-2-yl)-9-phenyl-1,10-
phenanthroline (L8)
(483.02): C, 57.19; H, 3.96; N, 8.70. Found: C, 57.52; H, 3.60; N,
8.40%.
In a similar manner to that described for L5, the product L8 was
Cobalt complexes (Co1–Co8). Co1: Green powder in 89% yield.
obtained as white solid in 27% yield. M.p. = 100–102 oC FT-IR (KBr
IR (KBr disk, cmÀ1): 3060(m), 1624(m), 1602(m), 1578(m,
tC@N),
disc, cmÀ1): 3057(m), 2965(m), 2927(m), 1637(m,
tC@N), 1618(m),
1550(m), 1500(m), 1413(s), 1154(s), 861(s), 768(m), 750(s),
710(s). Anal. Calc. for C19H11N3CoCl2O (427.15): C, 53.42; H, 2.60;
N, 9.84. Found: C, 53.66; H, 2.55; N, 9.48%. Co2: Green powder in
1605(m), 1588(m), 1506(m), 1499(m), 1487(m), 1425(m),
1364(m), 1304(s), 1188(m), 1131(s), 1110(m), 1069(m), 967(s),
863(s), 770(s), 723(s), 696(s). 1H NMR (400 MHz, CDCl3): d = 8.45
(d, 1 H, J = 8.3 Hz, phen), 8.40 (d, 2 H, J = 7.5 Hz, Ph), 8.42 (d, 2 H,
J = 8.2 Hz, phen), 7.89 (d, 1 H, J = 8.7 Hz, phen), 7.81 (d, 1 H,
79% yield. IR (KBr disk, cmÀ1): 3056(m), 1625(m), 1580(m,
tC@N),
1549(m), 1500(m), 1412(s), 1163(s), 885(m), 862(s), 808(s),
748(s), 710(s). Anal. Calc. for C20H13N3CoCl2O (441.18): C, 54.45;
H, 2.97; N, 9.52. Found: C, 54.80; H, 3.19; N, 9.19. Co3: Green pow-
der in 80% yield. IR (KBr disk, cmÀ1): 3059(m), 2964(m), 1625(m),
J = 8.7 Hz, phen), 7.56 (t,
J = 7.1 Hz, Ph), 4.35 (s,
2
H, J = 7.1 Hz, Ph), 7.48 (t,
1 H,
2
H), 1.48 (s,
6
H, CH3). 13C NMR
(100 MHz, CDCl3): d = 162.1, 157.8, 146.9, 146.0, 145.8, 139.3,
137.0, 136.8, 130.0, 129.6, 128.9, 128.1, 128.0, 127.9, 125.8,
122.9, 120.9, 79.8, 68.2, 28.7. C23H19N3O (353.42): Calc. C 78.16,
H 5.42, N 11.89. Found C 78.48, H 5.13, N 11.69%.
1578(m, tC@N)), 1546(m), 1497(m), 1411(s), 1361(m), 1156(s),
887(m), 872(s), 821(s), 712(s). Anal. Calc. for C23H19N3Co-
Cl2O(483.26): C, 57.16; H, 3.96; N, 8.70. Found: C, 57.51; H, 3.60;
N, 8.31%. Co4: Green powder in 84% yield. IR (KBr disk, cmÀ1):
3055(m), 1625(m), 1582(m,
tC@N), 1538(m), 1507(m), 1487(m),
4.3. Synthesis ofnickel complexes Ni1–Ni8 andcobalt complexes Co1–
Co8
1456(m), 1382(m), 1364(m), 1159(s), 869(s). Anal. Calc. for
C25H15N3CoCl2O (503.25): C, 59.67; H, 3.00; N, 8.35. Found: C,
59.59; H, 3.32; N, 8.27%. Co5: Green powder in 77% yield. IR (KBr
4.3.1. General considerations
disk, cmÀ1): 3057(m), 1621(m,
tC@N), 1583(m), 1482(m),
To a solution of 0.20 mmol of NiCl2Á6H2O or CoCl2 in 10 mL of
anhydrous ethanol was added 0.20 mmol of ligand (suspended in
10 mL of ethanol). The suspension was heated for 30 min at
80 oC, and afterward the solution was stirred overnight at room
temperature. Diethyl ether (30 mL) was added to precipitate the
product, which was subsequently collected with filtration, washed
with diethyl ether and dried in vacuum. All the nickel or cobalt
complexes were obtained as green powders in high yields.
Nickel complexes (Ni1–Ni8). Ni1: Green powder in 89% yield. IR
1449(m), 1337(m), 1155(s), 866(s), 752(s). Anal. Calc. for
C15H11N3CoCl2O (379.11): C, 47.52; H, 2.92; N, 11.08. Found: C,
47.18; H, 3.25; N, 11.38%. Co6: Green powder in 73% yield. IR
(KBr disk, cmÀ1): 3042(m), 1641(m), 1616(m,
tC@N), 1604(m),
1514(m), 1462(m), 1414(m), 1374(m), 1338(m), 1302(m),
1161(s), 932(s), 864(s), 707(s). Anal. Calc. for C17H15N3CoCl2O
(407.16): C, 50.15; H, 3.71; N, 10.32. Found: C, 50.00; H, 3.91; N,
10.68%. Co7: Green powder in 70% yield. IR (KBr disk, cmÀ1):
3050(m), 1641(m), 1618(m,
tC@N), 1607(m, tC@N), 1563(m),
(KBr disk, cmÀ1): 3055(m), 1625(m), 1605(m), 1585(m,
t
C@N),
1490(m), 1395(m), 1279(m), 1173(s), 866(s), 704(s). Anal. Calc.
for C21H15N3CoCl2O (455.2): C, 55.41; H, 3.32; N, 9.23. Found: C,
55.20; H, 3.51; N, 9.58. Co8: Green powder in 72% yield. IR (KBr
1549(m), 1451(s), 1436(s), 1419(s), 1366(m), 1347(m), 1304(m),
1150(m), 885(s), 865(s), 810(s), 766(m), 754(m), 711(s). Anal. Calc.
for C19H11N3NiCl2O(426.91): C, 53.45; H, 2.60; N, 9.84. Found: C,
53.66; H, 2.55; N, 9.48%. Ni2: Green powder in 79% yield. IR (KBr
disk, cmÀ1): 3050(m), 1627(m,
tC@N), 1585(m), 1475(m),
1450(m), 1388(m), 1163(s), 865(s), 699(s). Anal. Calc. for
C23H19N3CoCl2O (483.26): C, 57.16; H, 3.96; N, 8.70. Found: C,
57.20; H, 3.81; N, 9.0%8.
disk, cmÀ1): 3060(m), 1625(m), 1582(m,
tC@N), 1546(m),
1500(m), 1457(s), 1417(s), 1364(m), 1348(m), 1167(m), 1136(m),
887(s), 862(s), 814(s), 711(s). Anal. Calc. for C20H13N3NiCl2O
(440.94): C, 54.48; H, 2.97; N, 9.53. Found: C, 54.13; H, 3.19; N,
9.69%. Ni3: Green powder in 84% yield. IR (KBr disk, cmÀ1):
4.4. Synthesis of iron complexes Fe1–Fe8
3061(m), 2948(m), 1624(m), 1582(m,
t
C@N), 1523(m), 1497(m),
4.4.1. General considerations
1480(m), 1457(s), 1416(s), 1365(m), 1350(m), 1159(m), 888(s),
868(s), 823(s), 784(s), 760(m), 713(s). Anal. Calc. for C23H19N3Ni-
Cl2O (483.02): C, 57.19; H, 3.96; N, 8.70. Found: C, 56.81; H, 3.70;
N, 8.99%. Ni4: Green powder in 88% yield. IR (KBr disk, cm–1):
The ligand (0.20 mmol) and 1 equiv. of FeCl2 Á 4H2O
(0.20 mmol) were placed in a Schlenk tube, which was then purged
three times with nitrogen and then charged with 10 mL of ethanol.
The reaction mixture was then stirred at room temperature for 9 h.
The resulting precipitate was filtered, washed with diethyl ether
and dried in vacuo to give the corresponding iron complex. All
the iron(II) complexes were isolated as purple powders in high
yields.
3062(m), 2970(m), 1636(m), 1606(m), 1576(m,
tC@N), 1499(m),
1462(s), 1418(s), 1391(m), 1378(m), 1332(m), 1304(m), 1201(m),
1162(m), 1145(m), 937(s), 866(s), 708(s). Anal. Calc. for
C25H15N3NiCl2O (503.01): C, 59.69; H, 3.01; N, 8.35. Found: C,
59.49; H, 3.32; N, 8.27%. Ni5: Green powder in 85% yield. IR (KBr
Iron complexes (Fe1–Fe8). Fe1: Purple powder in 81% yield. IR
disk, cmÀ1): 3034(m), 2929(m), 1641(m), 1614(m,
t
C@N),
(KBr disk, cmÀ1): 3052(m), 1622(m), 1580(m,
tC@N), 1547(m),
1605(m), 1583(m), 1574(m), 1498(m), 1422(s), 1390(m),
1276(m), 1170(m), 1141(m), 869(s), 698(s). Anal. Calc. for
C15H11N3NiCl2O (378.87): C, 47.55; H, 2.93; N, 11.09. Found: C,
47.52; H, 3.15; N, 10.88%. Ni6: Green powder in 77% yield. IR
1499(m), 1411(m), 1362(m), 1144(s), 1042(s), 883(m), 859(s),
791(s), 749(s), 711(s). Anal. Calc. for C19H11N3FeCl2O (424.06): C,
53.81; H, 2.61; N, 9.91. Found: C, 53.59; H, 2.42; N, 10.25%. Fe2:
Purple powder in 73% yield. IR (KBr disk, cmÀ1): 3049(m),
(KBr disk, cmÀ1): 2970(m), 1644(m), 1607(m,
tC@N), 1463(m),
1623(m), 1585(m, tC@N), 1484(m), 857(s), 741(s). Anal. Calc. for
1418(s), 1201(m), 1161(m), 937(s), 866(s), 707(s). Anal. Calc. for
C17H15N3NiCl2O (406.92): C, 50.18; H, 3.72; N, 10.33. Found: C,
50.22; H, 3.51; N, 10.48%. Ni7: Green powder in 79% yield. IR
C20H13N3FeCl2O (438.09): C, 54.83; H, 2.99; N, 9.59. Found: C,
54.61; H, 2.64; N, 9.87%. Fe3: Purple powder in 66% yield. IR (KBr
disk, cmÀ1): 3052(m), 1623(m), 1579(m,
tC@N), 1549(m),
(KBr disk, cmÀ1): 1643(m), 1618(m,
tC@N), 1562(m), 1491(m),
1500(m), 1479(m), 1410(m), 1360(m), 1155(s), 1141(s), 1120(s),
1038(s), 938(s), 886(m), 860(s), 835(s), 817(s), 753(s), 713(s). Anal.
Calc. for C23H19N3FeCl2O (480.17): C, 57.53; H, 3.99; N, 8.75.
Found: C, 57.55; H, 3.71; N, 8.91%. Fe4: Purple powder in 71% yield.
1460(m), 1396(m), 1280(m), 1176(m), 1059(m), 1022(m), 872(s),
755(s), 720(s). Anal. Calc. for C21H15N3NiCl2O (454.96): C, 55.44;
H, 3.32; N, 9.24. Found: C, 55.22; H, 3.59; N, 9.48%. Ni8: Green
powder in 86% yield. IR (KBr disk, cm-1): 2970(m), 1617(m,
t
C@N),
IR (KBr disk, cmÀ1): 3057(m), 1624(m), 1583(m,
tC@N), 1540(m),
1503(m), 1461(m), 1400(m), 1316(m), 1180(m), 942(m), 879(s),
1455(m), 1366(m), 1314(m), 1149(s), 864(s). Anal. Calc. for
784(s), 757(s), 709(s), 663(s). Anal. Calc. for C23H19N3NiCl2O
C25H15N3FeCl2O (500.16): C, 60.03; H, 3.02; N, 8.40. Found: C,

3876
M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
Table 7
Crystal data and structure refinement for L2, Ni3, Co1, Co3 and Fe2.
L2
Ni3
Co1
Co3
Fe2
Formula
fw
C20H13N3O Á CH2Cl2
396.26
C23H19Cl2NiN3O Á 5/2CH3OH
563.13
C19H11Cl2CoN3O
427.14
C23H19Cl2CoN3O
483.24
C20H13Cl2FeN3O Á CH3OH
470.13
Temperature(K)
Wavelength(Å)
Cryst syst
Space group
a(Å)
173(2)
173(2)
0.71073
293(2)
173(2)
0.71069
173(2)
0.71073
Triclinic
P1
6.7650(1)
10.756(2)
14.665(3)
107.28(3)
95.76(3)
104.11(3)
970.8(3)
2
0.71073
Orthorhombic
Pbca
7.1956(1)
14.399(3)
35.157(7)
90
90
90
3642.7(1)
8
1.445
0.71073
Monoclinic
P2(1)/n
7.8120(2)
13.132(3)
16.798(3)
90
96.04(3)
90
1713.7(6)
4
Monoclinic
P2(1)/c
14.530(3)
20.637(4)
17.546(4)
90
100.57(3)
90
5172.1(2)
8
Monoclinic
P2(1)/c
12.494(3)
10.200(2)
16.825(3)
90
90.73(3)
90
2143.9(7)
4
b(Å)
c(Å)
a
(deg)
b(deg)
c
(deg)
Volume(Å3)
Z
Dcalc(g mÀ3
)
1.446
0.991
2344
1.656
1.326
860
1.497
1.070
988
1.608
1.076
480
l
(mmÀ1
F(000)
)
0.373
1632
Crystal size (mm)
h range (deg)
Limiting indicates
0.25 Â 0.15 Â 0.08
1.16–27.33
À9 6 h 6 9
À18 6 k 6 18
À45 6 l 6 45
7668
0.35 Â 0.25 Â 0.15
1.54–25.00
À16 6 h 6 17
À24 6 k 6 24
À20 6 l 6 20
29216
0.35 Â 0.30 Â 0.20
1.97–25.01
À9 6 h 6 9
À15 6 k 6 15
À19 6 l 6 19
5808
0.27 Â 0.20 Â 0.05
2.33–25.50
À15 6 h 6 15
À12 6 k 6 12
À20 6 l 6 20
7639
0.58 Â 0.35 Â 0.07
1.48–27.48
À8 6 h 6 8
À13 6 k 6 13
À19 6 l 6 18
7875
No. of reflections collected
No. of unique reflections
Rint
Completeness to h (%)
Absorp corr
4113
9114
3018
3990
0.0556
4426
0.0318
0.0173
99.9% (h = 27.33
Empirical
0.0824
100.0 (h = 25.00
Empirical
0.0509
100.0 (h = 25.01
Empirical
o
o
o
)
)
)
99.9 (h = 25.50o)
Empirical
300
99.6 (h = 27.48o)
Empirical
266
no. of params
245
1.057
643
1.332
235
1.196
Goodness-of-fit on F2
1.216
1.290
Final R indices (I > 2
r
(I))
R1 = 0.0474
wR2 = 0.1160
R1 = 0.0726
wR2 = 0.1253
0.503, À0.586
R1 = 0.0908
wR2 = 0.1465
R1 = 0.1174,
wR2 = 0.1554
0.653, À0.552
R1 = 0.0733
wR2 = 0.1278
R1 = 0.1179
wR2 = 0.1488
0.587, À0.483
R1 = 0.0746
wR2 = 0.1278
R1 = 0.1049
wR2 = 0.1371
0.471, À0.530
R1 = 0.0565
wR2 = 0.1244
R1 = 0.0751
wR2 = 0.1374
0.665, À0.546
R indices (all data)
Largest difference peak, hole(e ÅÀ3
)
60.29; H, 3.15; N, 8.29%. Fe5: Purple powder in 69% yield. IR (KBr
disk, cmÀ1): 3052(m), 1639(m), 1606(m,
C@N), 1577(m),
for determining the composition and mass distribution of oligo-
mers obtained.
t
1510(m), 1440(m), 1299(m), 1061(s), 867(s), 708(s). Anal. Calc.
for C15H11N3FeCl2O (376.02): C, 47.91; H, 2.95; N, 11.18. Found:
C, 47.72; H, 2.59; N, 11.52%. Fe6: Purple powder in 71% yield. IR
4.6. X-ray crystallographic studies
(KBr disk, cmÀ1): 3058(m), 2974(m), 1643(m), 1606(m,
t
C@N),
Single-crystal X-ray diffraction studies for ligand L2 and com-
plexes Ni3, Co1, Co3 and Fe2 were carried out on a Rigaku RAXIS
Rapid IP diffractometer with graphite-monochromated Mo K
radiation (k = 0.71073 Å). Cell parameters were obtained by glo-
bal refinement of the positions of all collected reflections. Inten-
sities were corrected for Lorentz and polarization effects and
empirical absorption. The structures were solved by direct meth-
ods and refined by full-matrix least squares of F2. All non-hydro-
1578(m), 1515(m), 1421(m), 1334(m), 1304(m), 1168(s), 1046(s),
943(s), 869(s), 837(s), 708(s). Anal. Calc. for C17H15N3Fe-
Cl2O(404.07): C, 50.53; H, 3.74; N, 10.40. Found: C, 50.66; H,
3.49; N, 10.61%. Fe7: purple powder in 74% yield. IR (KBr disk,
a
cmÀ1): 3056(m), 2961(m), 1626(m,
tC@N), 1580(m), 1479(m),
1460(m), 1385(m), 1162(s), 864(s). Anal. Calc. for C21H15N3Fe-
Cl2O(452.11): C, 55.79; H, 3.34; N, 9.29. Found: C, 55.66; H, 3.49;
N, 9.61%. Fe8: purple powder in 70% yield. IR (KBr disk, cmÀ1):
3053(m), 1630(m, VC@N), 1583(m), 1479(m), 1452(m), 1384(m),
1165(s), 868(s), 697(s). Anal. Calc. for C23H19N3FeCl2O(480.17): C,
57.53; H, 3.99; N, 8.75. Found: C, 57.76; H, 3.79; N, 8.61%.
t
gen atoms were refined anisotropically. The Bu group in Co3 is
partly disordered. Structure solution and refinement were per-
formed using the SHELXL-97 package [89]. Crystal data and pro-
cessing parameters for L2, Ni3, Co1, Co3 and Fe2 are
summarized in Table 7.
4.5. General procedure for ethylene oligomerization
Acknowledgement
A 250-mL stainless steel autoclave equipped with a mechanical
stirrer and a temperature controller was heated in vacuo at 80 °C
for 2 h. It was cooled to the required reaction temperature under
ethylene, and charged with toluene, the desired amount of cocata-
lyst, and toluene solution of catalytic precursor; the total volume
was 100 mL. The reactor was sealed and pressurized to the desired
ethylene pressure, and the ethylene pressure was maintained with
feeding of ethylene. After the reaction was carried out for the re-
quired period, the pressure was released. A small amount of the
reaction solution was collected, the reaction in this small sample
was terminated by the addition of 5% aqueous hydrogen chloride,
and the organic layer was analyzed by gas chromatography (GC)
This work was supported by NSFC No. 20674089.
Appendix A. Supplementary material
CCDC 699431, 699432, 699433, 699434 and 699435 contains
the supplementary crystallographic data for L2, Ni3, Co1, Co3
and Fe2, respectively. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2008.09.046.

M. Zhang et al. / Journal of Organometallic Chemistry 693 (2008) 3867–3877
3877
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