2-Arylimino-9-phenyl-1,10-phenanthrolinyl-iron, -cobalt and -nickel complexes: Synthesis, characterization and ethylene oligomerization behavior

FULL PAPER

DOI: 10.1002/ejic.200700690

2-Arylimino-9-phenyl-1,10-phenanthrolinyl-iron, -cobalt and -nickel Complexes:

Synthesis, Characterization and Ethylene Oligomerization Behavior

Suyun Jie,^[a]Shu Zhang,^[a]and Wen-Hua Sun*^[a]

Keywords: Nitrogen ligands / Late transition metals / Iron / Ethylene / Oligomerization

A series of 2-imino-9-phenyl-1,10-phenanthrolines 1–6 has

been prepared and investigated as new tridentate N3 ligands

in coordination with metal chlorides. Their iron(II) (1a–6a),

cobalt(II) (1b–6b), and nickel(II) (1c–6c) complexes have been

synthesized and characterized by elemental and spectro-

scopic analysis in conjunction with single-crystal X-ray dif-

ment with MAO or MMAO, while the cobalt complexes show

higher activities than their iron analogues and lead to the

formation of C₆and C₈oligomers. The nickel complexes dis-

play high catalytic activities toward ethylene oligomerization

in the presence of Et₂AlCl and an auxiliary ligand (PPh₃).

fraction studies. Some of the iron complexes show good ac- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,

tivities in the selective dimerization of ethylene upon treat-

Germany, 2007)

the catalytic activity and the resulting oligomerization or

polymerization products.^[4]Extensive research into alterna-

tive models of iron and cobalt complexes ligated with new

types of tridentate N₃ligands did not result in highly active

precursors for ethylene oligomerization or polymeriza-

tion.^[17]Nevertheless, tridentate N₃ligands are still of great

interest for the preparation of late transition metal com-

plexes as catalysts for ethylene oligomerization and polyme-

rization^{[10–15,17–20]}as the selective synthesis of short ethyl-

ene oligomers, particularly α-olefins, is of industrial impor-

tance.

The variation of catalyst models by designing new or-

ganic compounds that can be used as tridentate ligands has

been targeted by our group for the production of highly

active catalysts of iron and cobalt,^{[11,15,19,20]}as well as

nickel.^[11–14]Some of these complexes have shown promis-

ing catalytic activities toward ethylene oligomerization and

polymerization, such as highly active iron catalysts bearing

2-imino-1,10-phenanthrolines^[19]and 2-(2-benzimidazolyl)-

2-[1-(arylimino)ethyl]pyridines^[15b]along with bimetallic

iron complexes bearing 2-methyl-2,4-bis(6-iminopyridin-2-

yl)-1H-1,5-benzodiazepines;^[15a]their cobalt analogues also

showed good activities.^[15a,15b,20]Similarly to the bis(imino)-

pyridine catalytic systems,^[4]we found that the above iron-

based catalysts are generally more active than their cobalt

analogues, although the exceptional cobalt complexes lig-

ated by 2,9-bis(imino)-1,10-phenanthrolines showed better

activity than their iron analogues.^[11]Moreover, all the cor-

responding nickel complexes showed good catalytic activity

for ethylene oligomerization,^[11,12,14a]as did our more recent

nickel complexes bearing 2-(benzimidazol-2-yl)-1,10-phen-

anthrolines.^[13]

Introduction

Ethylene oligomerization is an important catalytic pro-

cess for the production of linear α-olefins as basic chemi-

cals.^[1]The catalysts currently used in industrial processes

include alkylaluminum compounds, a combination of alkyl-

aluminum compounds and early transition metal com-

plexes, nickel(II) complexes,^[1a]and monoanionic [P,O]

nickel-based catalysts (SHOP).^[2]In the past decade, re-

search on late transition metal complexes as catalysts for

ethylene oligomerization and polymerization has attracted

considerable attraction in both academic and industrial

circles due to the possibility of their forming highly active

and selective catalysts.^[3–5]This was stimulated by the pion-

eering work by Brookhart’s group,^[6]who discovered that

cationic α-diiminonickel complexes are effective catalysts

for ethylene oligomerization and polymerization. Since this

initial investigation of tetracoordinate nickel complexes,

more attention has been paid recently to pentacoordinate

complexes of nickel incorporating tridentate ligands such as

[7]

[8]

[9]

[9a]

∧ ∧

N P N,

∧ ∧

P N N,

∧ ∧

N N O,

P N P,

and

as well as their iron and cobalt analogues.

[10–15]

∧ ∧

N N N,

The discovery of highly active iron- and cobalt-based ole-

fin polymerization catalysts was made possible by the de-

sign of bis(imino)pyridines as tridentate ligands by the

Brookhart and Gibson groups,^[16]who carried out detailed

investigations of metal complexes bearing bis(imino)pyr-

idine ligands by modifying the substituents on the aryl ring

linked to the imino group and checking their influence on

[a] Key Laboratory of Engineering Plastics and Beijing National

Laboratory for Molecular Sciences, Institute of Chemistry,

Chinese Academy of Sciences,

Beijing 100080, China

Along with the decisive influence of the ligands, espe-

cially the steric and electronic effects of substituents, on the

Fax: +86-10-6261-8239

E-mail: whsun@iccas.ac.cn

5584

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Catalytic Ethylene Oligomerization

catalytic activities and products, the nature of the metal also

greatly affects catalytic behavior. Metal complexes contain-

ing 2-imino-1,10-phenanthrolines generally show good to

high catalytic activities for ethylene oligomerization and po-

lymerization.^[12,19,20]A high steric bulk of the ligands was

recognized to be critical for a high catalytic activity of di-

iminonickel complexes for ethylene polymerization,^[6]

whereas, in comparison with 2-imino-1,10-phenanthrolinyl

metal complexes,^[12,19,20]the additional imino group

in metal complexes bearing 2,9-diimino-1,10-phenan-

throlines^[11]has a negative effect as the additional imino

group is assumed to coordinate to the active species, which

results in a deactivated species. In order to check the effect

of steric hindrance, 2-imino-9-phenyl-1,10-phenanthroline

complexes have been targeted as precursors for ethylene

oligomerization.

Herein we report the synthesis of 2-acetyl- and 2-ben-

zoyl-9-phenyl-1,10-phenanthrolines and their subsequent

transformation into 2-imino-9-phenyl-1,10-phenanthrolines

for use as ligands. These compounds keep the same coordi-

native framework as 2-imino-1,10-phenanthrolines but with

an additional phenyl group at the 9-position. Their late

transition metal (Fe, Co, and Ni) complexes are synthesized

and characterized and the catalytic properties of these com-

plexes for ethylene oligomerization are evaluated under

various reaction conditions. The effects of ligand environ-

ment and reaction conditions on the activity and the distri-

bution of oligomers obtained are investigated systemati-

cally.

Scheme 1. Synthesis of ketone I.

2-Benzoyl-9-phenyl-1,10-phenanthroline (ketone II) was

prepared in a one-step reaction between 2-cyano-1,10-phen-

anthroline and three equivalents of phenyllithium

(Scheme 2). Thus, a solution of phenyllithium in diethyl

ether was added dropwise to a suspension of 2-cyano-1,10-

phenanthroline in toluene at –78 °C, then the mixture was

slowly warmed to room temperature and stirred overnight.

The reaction proceeds by initial addition of phenyllithium

to the nitrile group^[25]followed by a Ziegler alkylation.^[24]

Subsequent hydrolysis gave the benzoyl-substituted prod-

uct. The resultant mixture was extracted with dichloro-

methane and the organic phase was purified on a silica col-

umn. The desired compound (2-benzoyl-9-phenyl-1,10-

phenanthroline) was obtained as a slightly yellow solid in

acceptable yield.

Results and Discussion

Preparation of Ketones I and II

2-Cyano-1,10-phenanthroline and 2-acetyl-1,10-phen-

anthroline were prepared according to the literature

procedures.^[19a,21]

2-Acetyl-9-phenyl-1,10-phenanthroline

(ketone I) was synthesized by attaching a phenyl group at

the phenanthroline ring using 2-acetyl-1,10-phenanthroline

as the starting material (Scheme 1). The carbonyl group of

2-acetyl-1,10-phenanthroline was first protected with ethyl-

ene glycol and the 2-(2-methyl-1,3-dioxolan-2-yl)-1,10-

phenanthroline formed in this condensation reaction was

purified on an alumina column.^[22]A solution of 1.7 equiva-

lents of phenyllithium in diethyl ether was added dropwise

to a suspension of 2-(2-methyl-1,3-dioxolan-2-yl)-1,10-

phenanthroline in toluene under nitrogen at low tempera-

ture (0 °C) and the reaction mixture was maintained for an

additional 3 h at 0 °C.^[23]This procedure gave 2-(2-methyl-

1,3-dioxolan-2-yl)-9-phenyl-1,10-phenanthroline by elimi-

nation of lithium hydride.^[24]2-(2-Methyl-1,3-dioxolan-2-

yl)-9-phenyl-1,10-phenanthroline was purified as a yellow

oil on a silica column and then refluxed in acetone in the

presence of p-toluenesulfonic acid to cleave the 1,3-dioxol-

ane moiety. The desired product (2-acetyl-9-phenyl-1,10-

phenanthroline) precipitated from the solution and was ob-

tained by filtration as a pale-yellow solid.

Scheme 2. Synthesis of ketone II.

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S. Jie, S. Zhang, W.-H. Sun

FULL PAPER

Synthesis and Characterization of Ligands 1–6 and

Complexes 1a–6a, 1b–6b, and 1c–6c

2, iron complex 2a, cobalt complexes 1b, 4b, and 6b, and

nickel complexes 1c and 5c in the solid state were confirmed

by single-crystal X-ray diffraction analysis.

The 2-imino-9-phenyl-1,10-phenanthrolinyl ligands 1–6

were prepared by condensing ketones I or II with the corre-

sponding substituted anilines in the presence of p-tolu-

enesulfonic acid in toluene or tetraethyl silicate (Scheme 3).

The ligands were obtained in high yield and were charac-

Crystal Structures

Single crystals of ligand 2 suitable for X-ray diffraction

analysis were grown by recrystallization from a dichloro-

methane/hexane (1:5, v/v) solution. The molecular structure

is shown in Figure 1. The imino nitrogen atom is disposed

trans to the phenanthroline nitrogen atoms with a typical

C=N double bond length of 1.270(2) Å. The phenyl ring on

C1 is nearly coplanar with the plane of the phenanthroline

moiety (dihedral angle: 6.2°), whereas the aryl ring on the

imino nitrogen atom is approximately perpendicular to the

plane of the phenanthroline moiety and the phenyl plane

on C1 (dihedral angles: 92.1 and 89.6°, respectively).

1

terized by IR, H, and ¹³C NMR spectroscopy as well as

elemental analysis. The iron complexes 1a–6a were readily

prepared by mixing the corresponding ligand with one

equivalent of FeCl₂·4H₂O in thf at room temperature under

nitrogen (Scheme 3). The resulting complexes precipitated

from the reaction solution and were separated as air-stable

green or brown solids. Similarly, the cobalt complexes 1b–

6b and nickel complexes 1c–6c were synthesized by treating

the corresponding ligand with one equivalent of CoCl₂or

NiCl₂·6H₂O in anhydrous ethanol at room temperature.

The methyl ketimine cobalt complexes 1b–3b were obtained

as green powders, whereas the phenyl ketimine complexes

4b–6b were red-brown. The corresponding nickel complexes

1c–6c were obtained as orange or yellow powders. All com-

plexes were well characterized by FT-IR spectroscopy and

elemental analysis. A comparison of the IR spectra of the

complexes and their corresponding ligands shows that the

C=N stretching vibrations of the iron, cobalt, and nickel

complexes are shifted to lower wavenumber and their peak

intensities greatly reduced, thereby indicating a coordinative

interaction between the imino nitrogen atom and the cen-

tral metal. Some samples for elemental analysis were pre-

pared as crystals, therefore the analytical results show the

incorporation of solvent molecules. The structures of ligand

Figure 1. Molecular structure of ligand 2 with all hydrogen atoms

omitted for clarity. Selected bond lengths [Å] and bond angles [°]:

N1–C1 1.330(2), N1–C12 1.355(3), N2–C11 1.356(3), N2–C10

1.327(2), N3–C19 1.270(2), N3–C21 1.422(3); C19–N3–C21

121.62(2), N3–C19–C10 117.6(2), N3–C19–C20 125.0(2).

Single crystals of complex 2a suitable for X-ray diffrac-

tion analysis were obtained by slow diffusion of diethyl

ether into its methanol solution under nitrogen. The asym-

metric unit of complex 2a contains the halves of two inde-

pendent molecules, as shown in Figure 2. The coordination

geometry around the iron center can be described as a dis-

torted trigonal bipyramid in which N2 of the phenan-

throline group and two chlorides form the equatorial plane.

The two independent molecules have slightly different bond

lengths and bond angles, as shown in Table 1. The iron cen-

ter deviates slightly (0.0469 Å) from the equatorial plane in

both molecules, and the phenyl ring on C1 or C1A and the

plane of the phenanthroline moiety make the same dihedral

angle (53.5°), which is very different from that in the corre-

sponding ligand 2 (6.2°). The plane of the phenanthroline

moiety is nearly perpendicular to the equatorial plane [86.8°

in (a) and 88.4° in (b)]. The dihedral angles between the

phenyl ring on C1 or C1A and the equatorial plane are also

the same (139.1°) for the two molecules, while the angles

between the aryl ring on the imino nitrogen atom and the

Scheme 3. Synthesis of ligands 1–6 and complexes 1a–6a, 1b–6b,

and 1c–6c.

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Eur. J. Inorg. Chem. 2007, 5584–5598

Catalytic Ethylene Oligomerization

equatorial plane are very different [56.8° in (a) and 78.9° in Table 1. Selected bond lengths [Å] and angles [°] for complex 2a.

(b)]. The Fe–N bond in the equatorial plane in each mole-

Fe–N1

Fe–N2

Fe–N3

Fe–Cl1

Fe–Cl2

N3–C19

N2–Fe–N1

N2–Fe–N3

N1–Fe–N3

N1–Fe–Cl1

N2–Fe–Cl1

N3–Fe–Cl1

N1–Fe–Cl2

N2–Fe–Cl2

N3–Fe–Cl2

Cl1–Fe–Cl2

2.391(3)

2.101(3)

2.298(3)

2.3405(1)

2.2492(1)

1.293(5)

73.77(1)

73.18(1)

145.86(1)

93.70(8)

98.23(9)

99.19(8)

104.73(9)

141.53(9)

95.87(9)

120.09(5)

FeA–N1A

FeA–N2A

FeA–N3A

FeA–Cl1A

2.393(3)

2.104(3)

2.283(3)

2.3456(1)

2.2469(1)

1.271(5)

73.18(1)

72.89(1)

cule is clearly shorter than the two axial Fe–N bonds, and

the axial Fe–N(phenanthroline) bond is about 0.1 Å longer

than the Fe–N(imino) bond. The phenyl group on C1 re-

sults in a longer Fe–N1 bond length [av. 2.392(3) Å] than

that of a related 2-acetyl-1,10-phenanthroline complex

[2.271(3) Å].^[19a]The two Fe–Cl bond lengths differ by

about 0.1 Å. Although the two imino C=N bonds are

slightly different [1.293(5) Å in (a) and 1.271(5) Å in (b)],

they are both typical of an imino C=N double bond. The

C=N bond length in molecule (b) is almost identical to that

in ligand 2 [1.270(2) Å].

FeA–Cl2A

N3A–C19A

N2A–FeA–N1A

N2A–FeA–N3A

N1A–FeA–N3A 144.89(1)

N1A–FeA–Cl1A

N2A–FeA–Cl1A

N3A–FeA–Cl1A

N1A–FeA–Cl2A 105.71(9)

N2A–FeA–Cl2A 143.73(9)

N3A–FeA–Cl2A

Cl1A–FeA–Cl2A 117.38(5)

94.32(8)

98.71(9)

99.43(9)

96.35(9)

The cobalt atom in complex 1b deviates slightly

(–0.0517 Å) from the equatorial plane composed by N2,

Cl1, and Cl2 and the axial Co–N bonds form an angle of

149.22(1)° (N1–Co–N3). The phenyl ring on C1 and the

plane of the phenanthroline moiety form a dihedral angle

of 41.0°, and the plane of the phenanthroline moiety is al-

most perpendicular to the equatorial plane (dihedral angle:

93.2°). The dihedral angles between the phenyl ring on C1

and the equatorial plane and the aryl ring on the imino

nitrogen atom and the equatorial plane are 134.0° and

133.7°, respectively. The two axial Co–N distances [2.313(4)

and 2.279(4) Å] are much longer than the Co–N bond

[2.035(4) Å] in the equatorial plane and the two Co–Cl link-

ages differ by 0.06 Å. The imino N3–C19 bond length is

1.289(6) Å, which is typical of a C=N double bond.

Figure 2. Molecular structure of complex 2a showing the two crys-

tallographically independent molecules of the asymmetric unit.

Water molecules and all hydrogen atoms have been omitted for

clarity.

Figure 3. Molecular structure of complex 1b. Water molecules and

all hydrogen atoms have been omitted for clarity.

Single crystals of cobalt complexes 1b, 4b, and 6b were

grown by slow diffusion of hexane into their solutions in

dichloromethane. Their molecular structures are shown in

The central cobalt atom in the phenyl ketimine complex

Figures 3, 4, and 5, respectively, and selected bond lengths 4b also deviates slightly (0.0196 Å) from the equatorial

and angles are collected in Table 2. The coordination geom- plane containing N2, Cl1, and Cl2. The bond lengths and

etry around the cobalt center in these complexes can be angles around the cobalt center are very similar to those in

described as a distorted trigonal bipyramid with N2 of the 1b, although the phenyl ring on C1 and the plane of the

phenanthrolinyl group and two chlorides forming the equa- phenanthroline moiety make a dihedral angle (16.4°) that is

torial plane.

very different from that in 1b (41.0°). The phenyl ring on

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5587

S. Jie, S. Zhang, W.-H. Sun

FULL PAPER

The central cobalt atom in the phenyl ketimine complex

6b, which contains bulkier isopropyl groups at the ortho po-

sitions of the aryl ring at the imino nitrogen atom, deviates

slightly more (0.1829 Å) from the equatorial plane contain-

ing N2, Cl1, and Cl2 than in the other complexes. This

complex also has a smaller N2–Co–Cl1 bond angle

[97.27(8)°] and larger N2–Co–Cl2 bond angle [140.69(8)°].

The two axial Co–N bonds also make a slightly smaller

angle of 143.99(9)° (N1–Co–N3). In contrast to the other

complexes, the phenyl ring on C1 is nearly coplanar to the

plane of the phenanthroline moiety, with a dihedral angle

of 3.3° that is much smaller than in other analogues and

even smaller than in ligand 2 (6.2°). The dihedral angles

between the phenyl ring on C1, the plane of the phenan-

throline moiety, the phenyl ring on the imino carbon, and

the aryl ring on the imino nitrogen and the equatorial plane

[82.8°, 80.4°, 88.9°, and 89.2°, respectively] are similar to

those in 4b. The axial Co–N1(phenanthroline) bond in 6b

is 0.19 Å shorter than the Co–N3(imino) bond, which is

very different from the situation in other cobalt analogues

(about 0.04 Å in 1b and 4b). One possible reason for this is

that the bulkier isopropyl groups at the ortho positions of

the aryl ring bound to the imino nitrogen take up more

space and lead to a shortening of the Co–N1 bond

[2.180(2) Å] and a lengthening of the Co–N3 bond

[2.372(2) Å]. This steric effect also leads to a shortening of

the imino N3–C19 bond [1.255(4) Å].

Figure 4. Molecular structure of complex 4b showing one CH₂Cl₂

molecule. All hydrogen atoms have been omitted for clarity.

Single crystals of nickel complexes 1c and 5c were ob-

tained by layering hexane on their corresponding dichloro-

methane solutions. X-ray diffraction analysis revealed that

they display a distorted trigonal bipyramidal geometry in

which the central nickel atom is coordinated to three nitro-

gen atoms from the ligand and two halides. Similar to their

iron and cobalt analogues, one nitrogen atom (N2) of the

phenanthrolinyl group and two chlorides compose the

equatorial plane; the imino nitrogen (N3) and another ni-

trogen (N1) of the phenanthrolinyl group occupy the two

axial coordination sites. Their molecular structures are

shown in Figures 6 and 7, respectively, and selected bond

lengths and angles are collected in Table 2.

Figure 5. Molecular structure of complex 6b showing one CH₂Cl₂

molecule. All hydrogen atoms have been omitted for clarity.

C1, the plane of the phenanthroline moiety, the phenyl ring

on the imino carbon atom, and the aryl ring on the imino

nitrogen atom are all approximately perpendicular to the

equatorial plane, with dihedral angles of 80.1°, 88.9°, 91.5°,

and 86.0°, respectively.

Table 2. Selected bond lengths [Å] and bond angles [°] in complexes 1b, 1c, 4b, 5c, and 6b.

1b (M = Co)

1c (M = Ni)

4b (M = Co)

5c (M = Ni)

6b (M = Co)

M–N1

M–N2

M–N3

M–Cl1

M–Cl2

N3–C19

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

2.313(4)

2.035(4)

2.279(4)

2.300(7)

1.962(6)

2.238(6)

2.274(3)

2.217(3)

1.275(9)

78.4(3)

2.299(3)

2.034(3)

2.257(3)

2.2745(1)

2.2404(1)

1.278(4)

76.64(12)

74.01(1)

149.77(1)

94.07(8)

96.22(8)

100.88(8)

131.09(8)

98.37(8)

97.55(8)

128.01(5)

2.219(3)

1.970(4)

2.220(3)

2.2988(1)

2.2234(1)

1.276(5)

78.32(1)

75.40(1)

152.86(1)

91.79(1)

98.16(1)

99.41(1)

129.52(1)

99.04(1)

93.33(1)

131.07(6)

2.180(2)

2.012(2)

2.372(2)

2.2192(1)

2.1917(9)

1.255(4)

77.62(1)

70.50(9)

143.99(9)

103.79(7)

103.95(7)

97.27(8)

140.69(8)

96.55(7)

90.89(7)

119.62(4)

2.2923(2)

2.2357(2)

1.289(6)

76.16(15)

74.00(15)

149.22(1)

97.95(11)

99.72(1)

104.94(1)

133.77(1)

96.80(1)

95.48(1)

121.12(6)

76.0(3)

154.1(2)

95.46(2)

92.28(2)

101.4(2)

120.9(2)

93.11(2)

97.66(2)

137.71(1)

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Catalytic Ethylene Oligomerization

[110.62(4)° and 153.12(8)°, respectively, in the related nickel

complex].^[12]

Despite several similarities with 1c, complex 5c also has

its own structural characteristics due to the presence of a

phenyl group at the imino carbon instead of a methyl group.

Thus, the central nickel atom deviates 0.0102 Å from the

equatorial plane containing N2, Cl1, and Cl2, and the in-

troduced phenyl group forms a dihedral angle of 5.7° with

the plane of the phenanthroline moiety and is almost per-

pendicular to the equatorial plane (dihedral angle of 82.2°).

The equatorial plane is still almost perpendicular to the

plane of the phenanthroline moiety (dihedral angle of

87.5°), whereas the dihedral angle between the plane of the

phenyl group on the imino nitrogen and the plane of the

phenanthroline moiety decreases significantly to 7.2°. The

plane of the pendant phenyl group on C1 makes a de-

creased dihedral angle of 8.0° with the plane of the phenan-

throline moiety and an increased dihedral angle of 79.9°

with the equatorial plane. All bond lengths and angles in

5c are similar to those in 1c.

Figure 6. Molecular structure of complex 1c showing one CH₂Cl₂

molecule. All hydrogen atoms have been omitted for clarity.

Ethylene Oligomerization

Ethylene Oligomerization with Iron Complexes 1a–6a

The iron(II) complexes 1a–6a were first investigated as

ethylene oligomerization catalysts at 1 atm of ethylene pres-

sure (Table 3), although the results were not satisfactory as

almost no absorption of ethylene was observed with dieth-

ylaluminum chloride as co-catalyst. Activation with methyl-

aluminoxane (MAO) gave a low catalytic activity for

methyl-substituted complexes 1a and 4a, although ethyl-

substituted complexes 2a and 5a were found to be less

active and isopropyl-substituted complexes 3a and 6a com-

pletely inactive. Modified methylaluminoxane (MMAO)

was found to be a more effective co-catalyst than MAO

with a similar effect of the ligand environment on the cata-

Figure 7. Molecular structure of complex 6b showing two CH₂Cl₂

molecules. All hydrogen atoms have been omitted for clarity.

The central nickel atom in 1c deviates by 0.0128 Å from lytic activity. Thus, for complexes bearing the same substit-

the equatorial plane containing N2, Cl1, and Cl2 and the uents on the aryl ring of the imino nitrogen, phenyl ket-

two axial Ni–Cl bonds make an axial angle (N1–Ni–N3) of imine (R = Ph) complexes 4a–6a showed a relatively higher

154.1(2)°. Both the equatorial plane and the plane of the catalytic activity than the corresponding methyl ketimine

phenyl group on the imino nitrogen are almost perpendicu- (R = Me) complexes 1a–3a. Complex 4a exhibited the high-

lar to the plane of the phenanthroline moiety (dihedral est activity of 2.64ϫ10⁵gmol^–1(Fe)h^–1, with 1-butene as

angles of 84.8° and 87.8°, respectively). The plane of the the main product. Under the same reaction conditions, the

pendant phenyl group on C1 makes a dihedral angle of variation of R¹on the aryl ring of the imino nitrogen was

33.6° with the plane of the phenanthroline moiety and 51.2° found to have a strong influence on the catalytic activity.

with the equatorial plane. Similarly to a related phenan- Thus, increasing the bulkiness of R¹in both methyl and

throlinylnickel complex, the Ni–N bond in the equatorial phenyl ketimine complexes caused the catalytic activity to

plane is clearly shorter than the axial Ni–N bonds, although decrease dramatically (methyl Ͼ ethyl Ͼ isopropyl), and in

the presence of a phenyl group on C1 leads to an elongation all cases essentially only dimerization was achieved, with a

of the Ni–N1 bond [2.300(7) Å vs. 2.157(3) Å];^[12]the two high selectivity for 1-butene.

Ni–Cl bond lengths are essentially identical. Despite show-

The iron(II) complexes 1a–6a were studied for ethylene

ing typical character of a C=N double bond, the imino N3– oligomerization at 10 atm of ethylene pressure in the pres-

C19 bond [1.275(9) Å] is slightly shorter than that in a re- ence of MAO or MMAO; much higher catalytic activities

lated phenanthrolinylnickel complex [1.284(4) Å],^[12]were observed than those obtained at 1 atm (Table 3). With

whereas much larger Cl1–Ni–Cl2 [137.71(1)°] and smaller MAO as

a

co-catalyst the highest activity of

N2–Ni–Cl1 [120.9(2)°] bond angles are observed after ad- 1.94ϫ10⁶gmol^–1(Fe)h^–1was obtained with complex 4a. In

dition of a phenyl group at the 9-position of phenanthroline general, however, under similar conditions, these complexes

Eur. J. Inorg. Chem. 2007, 5584–5598

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5589

S. Jie, S. Zhang, W.-H. Sun

FULL PAPER

Table 3. Ethylene oligomerization with complexes 1a–6a.^[a]

Entry

Cat.

Co-cat.

P [atm]^[b]

T [°C]^[c]

Activity^[d]

% Oligomer distribution^[e]

% Selectivity for

[e]

C₄/ΣC

C₆/ΣC

1-C₄

1

2

3

4

5

6

7

8

1a

2a

3a

4a

5a

6a

1a

2a

3a

4a

5a

6a

1a

2a

3a

4a

5a

6a

1a

2a

3a

4a

5a

6a

MAO

1

20

40

0.259

0.059

–

0.295

0.052

–

4.78

1.63

0.199

100

–

100

–

100

99.2

98.7

100

–

96.1

100

–

100

–

MAO

MMAO

MAO

100

99.8

100

99.9

100

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

1

26.4

5.13

0.275

–

10

40.8

29.1

0.621

194

51.6

0.409

269

47.9

1.90

211

54.3

0.465

0.8

1.3

–

0.8

1.4

–

0.6

–

99.2

98.6

MAO

100

99.4

100

99.1

98.7

100

MMAO

0.9

1.3

–

[a] General conditions: cat.: 5 μmol; Al/Fe: 500; solvent (toluene): 30 mL for 1 atm and 100 mL for 10 atm; reaction time: 30 min. [b]

Ethylene pressure. [c] Reaction temperature. [d] 10⁴gmol^–1(Fe)h^–1. [e] Weight percentage determined by GC.

were found to be much less active than the corresponding sequent investigations at 1 and 10 atm of ethylene pressure.

2-imino-1,10-phenanthrolinyliron complexes,^[19]probably The 5b/MAO system showed the lowest activity, with a but-

due to the presence of a phenyl group at the 9-position of ene content in the oligomeric products of more than 90%,

the 1,10-phenanthroline ligand, which hinders the insertion at an Al/Co molar ratio of 100 (entry 2, Table 4). Increasing

of ethylene. MMAO was found to be more effective than the Al/Co molar ratio in the range 200–2000 led to an in-

MAO at 10 atm of ethylene pressure, and the methyl-substi- crease in the activity to 6.42ϫ10⁵gmol^–1(Co)h^–1at a Al/

tuted complexes 1a [2.69ϫ10⁶gmol^–1(Fe)h^–1] and 4a Co molar ratio of 500 and then a gradual decrease. The

[2.11ϫ10⁶gmol^–1(Fe)h^–1] displayed the highest activity. distribution of oligomers and the selectivity for 1-butene

The isopropyl-substituted complexes 3a and 6a always hardly changed.

showed lower catalytic activity, probably because the bulk-

ier isopropyl groups at the ortho positions of the aryl ring

at the imino nitrogen affect the active species by preventing

the coordination of an ethylene molecule at the metal cen-

ter. A similar trend to that obtained at 1 atm as regards the

effect of ligand environment on the catalytic activities and

catalytic products was obtained for both the MAO and

MMAO catalytic systems.

The reaction temperature was found to have a remark-

able influence on the catalytic activity and the distribution

of oligomers. The highest activity was achieved at 20 °C and

a slightly lower activity was obtained, although with a

higher amount of butene produced (91.0%), at lower tem-

perature (0 °C; entry 8, Table 4). An elevated reaction tem-

perature also resulted in a decrease of the catalytic activity

and butene content; for instance, 5b/MAO showed an ac-

tivity of 8.74ϫ10⁴gmol^–1(Co)h^–1with a 72.5% butene

content at 80 °C (entry 11, Table 4). No significant differ-

Ethylene Oligomerization with Cobalt Complexes 1b–6b

Complex 5b was studied as a model for ethylene oligo- ence was observed between methyl- and ethyl-substituted

merization under varying conditions at 1 atm of ethylene complexes for both methyl and phenyl ketimine complexes.

pressure (Table 4). No catalytic activity was observed with However, the isopropyl-substituted complexes 3b and 6b

diethylaluminum chloride (Al/Co = 100 or 200) as co-cata- displayed lower catalytic activities and gave a smaller

lyst at 20 °C, whereas in the presence of MAO or MMAO amount of butene and higher amount of hexene than the

(Al/Co = 500) the catalytic activity increased remarkable corresponding methyl- or ethyl-substituted complexes. In

and the products mainly consisted of butene and hexene, contrast to bis(imino)pyridine,^[4]2-benzimidazolyl-6-imino-

with a high selectivity for 1-butene (Ͼ96%). The catalytic pyridine,^[15b]2-quinoxalinyl-6-iminopyridine,^[15c]and 2-

system 5b/MAO showed a higher activity than 5b/MMAO, imino-1,10-phenanthroline systems,^[19,20]these cobalt com-

although both gave a similar distribution of oligomers and plexes display much higher catalytic activities than their

a similar selectivity for 1-butene (entries 1 and 4, Table 4). corresponding iron analogues under similar reaction condi-

MAO was therefore chosen as a co-catalyst during the sub- tions.

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Eur. J. Inorg. Chem. 2007, 5584–5598

Catalytic Ethylene Oligomerization

Table 4. Ethylene oligomerization with complexes 1b–6b.^[a]

Entry

Cat.

P [atm]^[b]

Al/Co

T [°C]^[c]

Activity^[d]

% Oligomer distribution^[e]

% Selectivity for

[e]

C₄/ΣC

C₆/ΣC

Ն C₈/ΣC

1-C₄

1^[f]

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

5b

1b

2b

3b

4b

6b

1b

2b

3b

4b

5b

6b

1

500

100

200

500

1000

1500

2000

500

20

0

40

60

80

20

30

5.93

0.76

2.33

6.42

5.70

5.42

4.31

3.64

5.05

1.41

0.874

6.85

6.71

5.23

5.58

2.85

43.2

40.6

65.2

49.0

73.3

28.0

77.1

90.7

86.3

78.5

77.8

76.0

82.2

91.0

81.1

72.4

72.5

94.3

91.9

80.0

84.4

55.2

92.1

95.7

75.7

84.5

80.5

46.7

16.2

5.9

6.7

3.4

3.1

6.3

7.1

7.3

3.0

1.4

2.9

8.4

10.9

–

2.7

3.5

0.8

16.7

0.3

1.3

2.1

2.7

19.3

96.1

98.0

97.0

96.7

97.4

96.1

98.2

98.4

95.9

97.2

96.3

97.0

97.9

95.4

96.4

94.3

99.8

99.7

99.8

99.7

100

10.6

15.2

15.1

16.7

14.8

7.6

16.0

19.2

16.6

5.7

5.4

16.5

14.8

28.1

7.6

10

4.0

23.0

13.4

16.8

34.0

[a] General conditions: cat.: 5 μmol; co-cat.: MAO; solvent (toluene): 30 mL for 1 atm and 100 mL for 10 atm; reaction time: 30 min. [b]

Ethylene pressure. [c] Reaction temperature. [d] 10⁵gmol^–1(Co)h^–1. [e] Weight percentage determined by GC. [f] Co-cat.: MMAO.

When the ethylene pressure was increased from 1 to with a selectivity of 78.5% for 1-butene, at 1 atm of ethylene

10 atm the catalytic activity of each complex increased pressure (entry 5, Table 5).

greatly, with a very high selectivity for 1-butene. Complex

The addition of PPh₃as an auxiliary ligand to nickel-

5b was found to have the highest activity based catalytic systems has been demonstrated to improve

[7.33ϫ10⁶gmol^–1(Co)h^–1; entry 21, Table 4]. For methyl catalytic activity and prolong catalyst lifetime,^[7a,12,26]al-

ketimine complexes, methyl-substituted 1b and ethyl-substi- though the mechanism is still not clear. However, in the

tuted 2b showed comparable catalytic activities and a sim- presence of MAO, the addition of PPh₃had no effect and

ilar distribution of oligomers, whereas isopropyl-substituted the system still had no activity. For the catalytic system 5c/

3b showed a higher activity and gave a larger amount of MMAO, the addition of 10 equiv. of PPh₃resulted in an

hexene than 1b or 2b. A slightly higher amount of hexene increase in catalytic activity but a drastic decrease in the

was obtained for the corresponding phenyl ketimine com- selectivity for 1-butene (entry 4, Table 5).

plexes than with the methyl ketimine complexes. Complex

6b, which contains bulkier isopropyl groups on the aryl ring

of the imino nitrogen, was found to be slightly less active

and produce a wider distribution of oligomers (C₄to C₂₂,

along with a small amount of polyethylene waxes) than 4b

or 5b (entry 22, Table 4).

The effect of varying the amount of PPh₃added on the

catalytic activity and the selectivity for 1-butene was investi-

gated with the catalytic system 5c/Et₂AlCl at 1 atm of ethyl-

ene pressure. Addition of two equivalents of PPh₃improved

the catalytic activity to 9.63ϫ10⁴gmol^–1(Ni)h^–1, with a

small amount of hexene generated, whereas the selectivity

for 1-butene decreased from 78.5% to 27.1% (entry 6,

Table 5). Increasing the amount of PPh₃(Յ20) led to a fur-

ther enhancement of catalytic activity and a further de-

crease of selectivity for 1-butene. The addition of 20 equiv-

Ethylene Oligomerization with Nickel Complexes 1c–6c

Complex 5c was investigated for ethylene oligomerization

in the presence of different co-catalysts at 1 atm of ethylene

pressure. Unlike the nickel complexes ligated by other 1,10-

phenanthroline derivatives,^[11–13]almost no catalytic activity

was observed with 5c in the presence of MAO. When

MMAO was used as a co-catalyst, however, slightly better

activity was obtained and only butene was generated, with

alents

of

PPh₃

gave

the

highest

activity

[6.82ϫ10⁵gmol^–1(Ni)h^–1] and the lowest selectivity (8.5%;

entry 10, Table 5). Further increasing the amount of PPh₃

to 30 equivalents reduced the catalytic activity and in-

creased the selectivity for 1-butene.

The effect of reaction temperature on the catalytic ac-

a high selectivity for 1-butene (entry 3, Table 5). However, tivity was also studied in the presence of 10 equivalents of

Et₂AlCl was found to be more effective as a co-catalyst for PPh₃. When keeping the other conditions constant, the op-

nickel complexes, although the selectivity for 1-butene was timum catalytic activity was obtained at 20 °C; both in-

slightly lower. For example, at an Al/Ni molar ratio of 300, creasing and decreasing the reaction temperature led to a

5c/Et₂AlCl showed an activity of 1.43ϫ10⁴gmol^–1(Ni)h^–1, lower catalytic activity and higher selectivity for 1-butene.

Eur. J. Inorg. Chem. 2007, 5584–5598

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5591

S. Jie, S. Zhang, W.-H. Sun

FULL PAPER

Table 5. Ethylene oligomerization with complexes1c–6c.^[a]

Equiv. of

PPh₃

Entry

Cat.

P [atm]^[c]

T [°C]^[d]

t [min]^[e]

Activity^[f]

% Oligomer distribution^[g]% Selectivity for

[b]

[g]

C₄/ΣC

C₆/ΣC

1-C₄

1^[h]

2^[h]

3^[i]

4^[i]

5

6

7

8

9

5c

1c

2c

3c

4c

6c

5c

1c

2c

3c

4c

6c

–

10

–

10

–

2

1

10

20

0

30

60

30

60

30

60

30

60

30

60

30

60

30

60

30

–

0.048

0.128

0.143

0.963

2.29

3.31

3.71

6.82

2.75

1.14

1.91

2.36

1.58

3.74

3.49

3.29

4.67

3.33

3.68

3.47

4.71

5.88

3.89

2.26

5.87

100

–

92.8

41.6

78.5

27.1

24.0

15.9

3.5

97.8

2.2

1.9

3.5

2.3

1.2

0.8

1.6

2.8

4.6

2.0

3.3

2.7

3.0

2.5

3.9

2.2

4.3

2.5

3.6

1.1

–

5

98.1

96.5

97.7

98.8

99.2

98.4

97.2

95.4

98.0

96.7

97.3

97.0

97.5

96.1

97.8

95.7

97.5

96.4

98.9

10

20

30

10

–

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

8.5

27.2

34.6

16.3

22.7

20.2

17.5

4.3

15.9

5.8

14.0

3.2

15.2

2.8

10.6

6.6

97.1

93.0

36.5

36.2

50.2

63.4

38.9

34.9

0

40

60

20

30

10

20

100

51.7

97.5

98.1

98.7

98.9

98.1

98.4

2.5

1.9

1.3

1.1

1.9

1.6

36.8

61.5

39.6

39.1

57.7

[a] General conditions: cat.: 5 μmol; co-cat.: Et₂AlCl; Al/Ni: 300; solvent (toluene): 30 mL for 1 atm and 100 mL for 10 atm. [b] PPh₃

was added as an auxiliary ligand. [c] Ethylene pressure. [d] Reaction temperature. [e] Reaction time. [f] 10⁵gmol^–1(Ni)h^–1. [g] Weight

percentage determined by GC. [h] Co-cat.: MAO; Al/Ni: 500. [i] Co-cat.: MMAO; Al/Ni: 500.

In general, an induction time of 10–20 min is observed after 5.88ϫ10⁵gmol^–1(Ni)h^–1after 30 min and methyl-

the addition of PPh₃, and a lower temperature led to a substituted 4c showed the highest activity of

longer induction time and catalyst lifetime. For instance, 4.71ϫ10⁵gmol^–1(Ni)h^–1after 60 min (entry 23 and 24,

the catalytic activity of 5c at 0 or 20 °C after 60 min was Table 5).

found to be higher than that after 30 min, although a lower

The catalytic activity and selectivity for 1-butene of 5c

selectivity for 1-butene was obtained with a slightly larger increased to 2.26ϫ10⁵gmol^–1(Ni)h^–1and 97.1%, respec-

amount of hexene produced after 60 min, which indicates tively (entry 26, Table 5) at 10 atm of ethylene pressure

that the isomerization reaction of 1-butene to 2-butene without PPh₃, whereas at 1 atm the catalytic activity and

takes place at the same time as the oligomerization reaction. the selectivity for 1-butene did not change greatly when

Generally, phenyl ketimine complexes display slightly 10 equivalents of PPh₃was introduced into the catalytic sys-

higher activities than methyl ketimine complexes bearing tem (entry 27, Table 5), which means that both the PPh₃/Ni

the same substituents on the aryl ring of the imino nitrogen. molar ratio and the concentration of PPh₃in the reaction

The catalytic properties of methyl ketimine complexes after solution affect the catalytic properties. When the amount of

30 min were found to be not greatly affected by the substit- PPh₃was increased to 20 equivalents the catalytic activity

uents on the aryl ring of the imino nitrogen, and complexes of 5c increased to 5.17ϫ10⁶gmol^–1(Ni) h^–1, with a lower

1c–3c showed comparable catalytic activity and similar selectivity for 1-butene (36.5%; entry 28, Table 5). Five

selectivity for 1-butene. However, when the reaction time other nickel complexes were therefore also investigated in

was prolonged to 60 min a higher catalytic activity and the presence of 20 equivalents of PPh₃at 10 atm of ethylene

slightly higher selectivity for 1-butene were achieved with pressure. A higher catalytic activity and selectivity for 1-

ethyl-substituted 2c than with methyl-substituted 1c and butene was obtained for each complex than at 1 atm, and

isopropyl-substituted 3c. For phenyl ketimine complexes, the highest activity of 6.15ϫ10⁶gmol^–1(Ni)h^–1was

isopropyl-substituted 6c showed the highest activity of achieved with 2c, with a selectivity of 50.2% for 1-butene.

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Eur. J. Inorg. Chem. 2007, 5584–5598

Catalytic Ethylene Oligomerization

52.4 mmol) and p-toluenesulfonic acid (206 mg) was refluxed in tol-

uene (100 mL) for 18 h until no further formation of water was

observed in a Dean–Stark trap. The solvent was then removed un-

der reduced pressure and the residue was eluted with petroleum

ether/ethyl acetate (1:2, v/v) on an alumina column. The second

eluting fraction was collected and concentrated to give a slightly

yellow solid in 50.0% yield (1.333 g). M.p. 119–121 °C. FT-IR

In general, the selectivity for 1-butene increases with in-

creasing ethylene pressure, probably due to a competition

between chain transfer and chain isomerization, and a

higher ethylene concentration thus favors the formation of

1-butene due to rapid chain transfer rather than chain isom-

erization.^[27]

(KBr disc): ν = 3054, 2993, 2980, 2938, 2900, 1619, 1589, 1552,

˜

1505, 1490, 1476, 1445, 1391, 1376, 1256, 1232, 1204, 1147, 1129,

1106, 1029, 1009, 953, 855, 789, 752, 675 cm^–1. ¹H NMR

(400 MHz, CDCl₃): δ = 9.24 (d, J = 4.4 Hz, 1 H, phen), 8.25 (d, J

= 8.4 Hz, 1 H, phen), 8.22 (d, J = 8.4 Hz, 1 H, phen), 7.93 (d, J =

8.4 Hz, 1 H, phen), 7.77 (s, 2 H, phen), 7.61 (dd, J₁= 8.0 Hz, J₂=

4.4 Hz, 1 H, phen), 4.18 (t, J = 6.4 Hz, 2 H, CH₂), 4.01 (t, J =

6.4 Hz, 2 H, CH₂), 1.98 (s, 3 H, CH₃) ppm. ¹³C NMR (100 MHz,

CDCl₃): δ = 161.5, 150.5, 146.4, 145.8, 136.8, 136.0, 129.0, 128.1,

126.7, 126.3, 122.9, 119.5, 109.2, 65.2, 25.6 ppm. C₁₆H₁₄N₂O₂

(266.29): calcd. C 72.16, H 5.30, N 10.52; found C 72.18, H 5.23,

N 11.00.

Conclusions

A series of iron, cobalt, and nickel complexes bearing 2-

imino-9-phenyl-1,10-phenanthroline ligands have been syn-

thesized, characterized, and evaluated as catalyst precursors

in ethylene oligomerization. Some iron complexes show

good catalytic activities, with high selectivity for ethylene

oligomerization [1a/MMAO: 2.69ϫ10⁶gmol^–1(Fe)h^–1],

upon treatment with MAO or MMAO. Unexpectedly, in

contrast to previous results with other tridentate N₃cata-

lytic systems, the cobalt complexes generally show much

higher activities and broader oligomer distributions than

the corresponding iron analogues. The ligand environment

and the reaction parameters play an important role in influ-

2-Acetyl-9-phenyl-1,10-phenanthroline (I): A phenyllithium solution

was prepared by slowly adding a solution of bromobenzene

(0.9 mL, 8.50 mmol) in diethyl ether (20 mL) to two equiv. of lith-

ium (118 mg, 17.0 mmol) in diethyl ether (30 mL) at room tempera-

encing both the catalytic activity and the oligomer distribu- ture under nitrogen. The phenyllithium solution was then added

dropwise to a suspension of 2-(2-methyl-1,3-dioxolan-2-yl)-1,10-

phenanthroline (1.333 g, 5.00 mmol) in toluene (40 mL) at 0 °C and

the initial yellow suspension turned dark brown. The resultant

solution was stirred under nitrogen at 0 °C for an additional 3 h,

then the reaction was quenched by slow addition of water (100 mL)

and the mixture stirred. The yellow organic layer was separated

and the aqueous layer was extracted several times with CH₂Cl₂.

The organic phases were combined and dried with anhydrous so-

dium sulfate. After evaporation of the solvent the residue was puri-

fied on a silica column to give the pure product as a yellow oil.

This oil was dissolved in 50 mL of acetone containing p-toluenesul-

fonic acid (170 mg) as a catalyst and refluxed for 15 h. The desired

product was precipitated from the solution and collected by fil-

tration as a pale-yellow solid in 47.5% yield (710 mg). M.p. 184–

tions for iron and cobalt complexes. The highest activity of

up to 7.33ϫ10⁶gmol^–1(Co)h^–1for ethylene oligomeriza-

tion has been obtained with the catalytic system 5b/MAO

at 10 atm of ethylene pressure. Et₂AlCl is a more effective

co-catalyst for nickel complexes, and the addition of PPh₃

significantly improves the catalytic activity and prolong the

catalyst lifetime. The addition of 20 equiv. of PPh₃leads to

higher catalytic activities at 10 atm of ethylene pressure.

Experimental Section

General: All manipulations of air- and moisture-sensitive com-

pounds were carried out under an atmosphere of nitrogen using

standard Schlenk techniques. Melting points were measured with a

digital electrothermal apparatus without calibration. IR spectra

were recorded with a Perkin–Elmer FT-IR 2000 spectrometer for

186 °C. FT-IR (KBr disc): ν = 3103, 3026, 2916, 1694, 1633, 1620,

˜

1597, 1565, 1537, 1495, 1367, 1285, 1219, 1190, 1120, 1034, 1011,

1

888, 817, 766, 741, 678, 566 cm^–1. H NMR (300 MHz, CDCl₃): δ

= 8.44 (d, J = 7.2 Hz, 2 H, Ph), 8.34 (d, J = 3.0 Hz, 2 H, phen),

8.30 (d, J = 8.4 Hz, 1 H, phen), 8.17 (d, J = 8.4 Hz, 1 H, phen),

7.88 (d, J = 8.7 Hz, 1 H, phen), 7.78 (d, J = 8.7 Hz, 1 H, phen),

7.59 (t, J = 7.2 Hz, 2 H, Ph), 7.50 (t, J = 7.2 Hz, 1 H, Ph), 3.14 (s,

3 H, COCH₃) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 200.3, 156.6,

152.3, 145.4, 144.8, 138.5, 136.5, 130.4, 129.3, 128.4, 128.1, 127.3,

127.0, 125.3, 119.7, 119.6, 25.2 ppm. C₂₀H₁₄N₂O (298.34): calcd. C

80.52, H 4.73, N 9.39; found C 80.00, H 4.77, N 9.36.

1

KBr discs in the range 4000–400 cm^–1. H and ¹³C NMR spectra

were recorded with a Bruker DMX-300 or DMX-400 instrument

with TMS as the internal standard. Elemental analyses were per-

formed with a Flash EA1112 microanalyzer. GC analyses were per-

formed 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 capillary column. The yield of oligomers

was calculated by referencing to the mass of solvent on the basis

of the prerequisite that the mass of each fraction is approximately

proportional to its integrated area in the GC trace.

Synthesis of 2-Benzoyl-9-phenyl-1,10-phenanthroline (II): A phen-

yllithium solution was prepared by slowly adding a solution of bro-

mobenzene (3.2 mL, 30.5 mmol) in diethyl ether (20 mL) to two

equiv. of lithium (439 mg, 63.2 mmol) in diethyl ether (30 mL) at

room temperature under nitrogen. This phenyllithium solution was

then added dropwise to a suspension of 2-cyano-1,10-phenan-

throline (2.053 g, 10.0 mmol) in toluene (50 mL) at –78 °C and the

mixture was slowly warmed to room temperature. After stirring for

12 h at room temperature, the reaction was quenched by slow ad-

dition of water (100 mL) and the mixture stirred. The red organic

layer was separated and the aqueous layer was extracted several

times with CH₂Cl₂. The organic phases were combined and dried

Toluene, diethyl ether and thf were refluxed over sodium-benzo-

phenone and distilled under nitrogen prior to use. Diethylalumi-

num chloride was purchased from Acros Chemicals. Methylalumin-

oxane (MAO, 1.46 m in toluene) and modified methylaluminoxane

(MMAO-3A, 7% aluminum in heptane solution) were purchased

from Akzo Corp (USA). All other chemicals were obtained com-

mercially and used without further purification unless otherwise

stated.

Synthesis of 2-Acetyl-9-phenyl-1,10-phenanthroline (I)

2-(2-Methyl-1,3-dioxolan-2-yl)-1,10-phenanthroline: A mixture of 2- with anhydrous sodium sulfate. After evaporation of the solvent

acetyl-1,10-phenanthroline (2.230 g, 10.0 mmol), glycol (3.254 g, the residue was purified on a silica column to give the pure product

Eur. J. Inorg. Chem. 2007, 5584–5598

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5593

S. Jie, S. Zhang, W.-H. Sun

FULL PAPER

as a yellow solid in 21.3% yield (1.245 g). M.p. 162–164 °C. FT-IR

(sept, J = 6.8 Hz, 2 H, 2 iPr), 2.66 (s, 3 H, COCH₃), 1.19 (d, J =

6.6 Hz, 6 H, iPr), 1.17 (d, J = 6.5 Hz, 6 H, iPr) ppm. ¹³C NMR

(75 MHz, CDCl₃): δ = 167.7, 156.9, 155.8, 146.7, 146.0, 145.2,

(KBr disc): ν = 3060, 3034, 1645, 1616, 1595, 1575, 1545, 1505,

˜

1486, 1446, 1420, 1364, 1319, 1288, 1183, 1152, 1093, 1023, 944,

878, 865, 768, 716, 692 cm^–1. ¹H NMR (300 MHz, CDCl₃): δ = 139.2, 137.1, 136.5, 135.8, 129.9, 129.7, 129.0, 127.8, 127.5, 127.3,

8.93 (d, J = 7.2 Hz, 2 H, Ph), 8.55–8.39 (m, 4 H), 8.30 (d, J = 126.1, 123.7, 123.1, 120.6, 119.9, 28.3, 23.3, 23.0, 17.3 ppm.

8.4 Hz, 1 H, phen), 8.16 (d, J = 8.4 Hz, 1 H, phen), 7.89 (d, J =

C₃₂H₃₁N₃(457.61): calcd. C 83.99, H 6.83, N 9.18; found C 84.00,

8.7 Hz, 1 H, phen), 7.81 (d, J = 8.7 Hz, 1 H, phen), 7.72–7.62 (m, H 6.84, N 8.98.

3 H, Ph), 7.56–7.49 (m, 3 H, Ph) ppm. ¹³C NMR (100 MHz,

Synthesis of Ligand 4: 2-Benzoyl-9-phenyl-1,10-phenanthroline

CDCl₃): δ = 191.4, 156.5, 153.4, 145.9, 144.6, 138.8, 136.7, 136.6,

132.7, 132.5, 129.8, 129.6, 128.6, 128.3, 127.8, 127.5, 127.3, 125.4,

122.6, 119.6 ppm. C₂₅H₁₆N₂O (360.41): calcd. C 83.31, H 4.47, N

7.77; found C 82.94, H 4.45, N 7.73.

(760 mg, 2.10 mmol), 2,6-dimethylaniline (585 mg, 4.80 mmol), and

p-toluenesulfonic acid (100 mg) were combined with tetraethyl sili-

cate (5 mL) in a flask. The flask was equipped with a condenser

and a Dean–Stark trap and the mixture was heated at about 130 °C

for 36 h under N₂. Tetraethyl silicate was then removed under re-

duced pressure and the residue was eluted with petroleum ether/

ethyl acetate (6:1, v/v) on an alumina column. The second fraction

was collected and concentrated to give a yellow solid in 38.4% yield

Synthesis of Ligand 1: A mixture of 2-acetyl-9-phenyl-1,10-phenan-

throline (225 mg, 0.75 mmol), 2,6-dimethylaniline (184 mg,

1.50 mmol), and p-toluenesulfonic acid (80 mg) in toluene (20 mL)

was refluxed for 24 h under N₂. The solvent was then evaporated

under reduced pressure and the residue was eluted with petroleum

ether/ethyl acetate (20:1, v/v) on an alumina column. The second

fraction was collected and concentrated to give a yellow solid in

(376 mg). M.p. 142–144 °C. FT-IR (KBr disc): ν = 3055, 2943,

˜

1616, 1589, 1577, 1544, 1505, 1484, 1441, 1368, 1319, 1290, 1207,

1088, 1024, 969, 858, 773, 765, 740, 716, 694 cm^–1. ¹H NMR

(400 MHz, CDCl₃): δ = 8.87 (d, J = 8.4 Hz, 1 H, phen), 8.37 (d, J

= 8.4 Hz, 1 H, phen), 8.26–8.24 (m, 3 H), 8.11 (d, J = 8.4 Hz, 1 H,

phen), 7.82 (s, 2 H, phen), 7.57 (d, J = 8.0 Hz, 2 H, Ph), 7.46 (m,

4 H, Ph), 7.38 (t, J = 7.2 Hz, 2 H, Ph), 6.96 (d, J = 7.2 Hz, 2 H,

Ar), 6.86 (t, J = 7.2 Hz, 1 H, Ar), 2.12 (s, 6 H, 2 Me) ppm. ¹³C

NMR (100 MHz, CDCl₃): δ = 166.1, 155.9, 155.7, 148.2, 145.7,

144.7, 138.5, 136.3, 136.0, 135.4, 129.6, 129.2, 129.1, 128.9, 128.3,

127.9, 127.3, 127.0, 126.8, 126.7, 125.5, 125.2, 122.7, 121.7, 118.9,

18.2 ppm. C₃₃H₂₅N₃(463.57): calcd. C 85.50, H 5.44, N 9.06; found

C 85.14, H 5.47, N 8.94.

34.6% yield (105 mg). M.p. 190–192 °C. FT-IR (KBr disc): ν =

˜

3041, 3018, 2914, 1635, 1605, 1590, 1546, 1506, 1485, 1467, 1362,

1293, 1204, 1118, 1091, 855, 761, 739, 687 cm^–1. ¹H NMR

(300 MHz, CDCl₃): δ = 8.80 (d, J = 8.4 Hz, 1 H, phen), 8.45 (d, J

= 7.5 Hz, 2 H, Ph), 8.34 (d, J = 8.7 Hz, 2 H, phen), 8.18 (d, J =

8.4 Hz, 1 H, phen), 7.85 (d, J = 3.9 Hz, 2 H, phen), 7.56 (t, J =

7.5 Hz, 2 H, Ph), 7.47 (t, J = 7.5 Hz, 1 H, Ph), 7.11 (d, J = 7.5 Hz,

2 H, Ar), 6.97 (t, J = 7.5 Hz, 1 H, Ar), 2.62 (s, 3 H, COCH₃), 2.09

(s, 6 H, 2 Me) ppm. ¹³C NMR (75 MHz, CDCl₃): δ = 168.0, 156.9,

155.8, 149.0, 146.0, 145.1, 139.2, 137.1, 136.5, 129.8, 129.6, 128.9,

127.9, 127.8, 127.5, 127.3, 126.1, 125.3, 123.1, 120.6, 119.9, 18.0,

16.7 ppm. C₂₈H₂₃N₃(401.50): calcd. C 83.76, H 5.77, N 10.47;

found C 83.69, H 5.76, N 10.40.

Synthesis of Ligand 5: Ligand 5 was prepared from 2-benzoyl-9-

phenyl-1,10-phenanthroline (570 mg, 1.58 mmol) and 2,6-dieth-

ylaniline (498 mg, 3.27 mmol) as a yellow solid in 72.8% yield

(556 mg) in a similar manner to that described for ligand 4. M.p.

Synthesis of Ligand 2: Ligand 2 was prepared from 2-acetyl-9-

phenyl-1,10-phenanthroline (446 mg, 1.50 mmol) and 2,6-dieth-

ylaniline (491 mg, 3.20 mmol) as a yellow solid in 44.2% yield

(284 mg) in a similar manner to that described for ligand 1. M.p.

187–189 °C. FT-IR (KBr disc): ν = 3060, 3034, 2962, 2918, 1618,

˜

1586, 1542, 1504, 1485, 1440, 1363, 1294, 1200, 1090, 965, 869, 763,

1

697 cm^–1. H NMR (400 MHz, CDCl₃): δ = 8.85 (d, J = 8.0 Hz, 1

H, phen), 8.37–8.22 (m, 4 H), 8.09 (d, J = 8.0 Hz, 1 H, phen), 7.80

(s, 2 H, phen), 7.58 (s, 2 H, Ph), 7.45–7.36 (m, 6 H, Ph), 7.01–6.97

(m, 3 H, Ar), 2.61 (q, J = 7.2 Hz, 2 H, Et), 2.34 (q, J = 7.2 Hz, 2

H, Et), 1.16 (t, J = 7.2 Hz, 6 H, 2 Et) ppm. ¹³C NMR (100 MHz,

CDCl₃): δ = 165.7, 156.2, 156.1, 147.6, 146.1, 145.1, 138.9, 136.7,

136.4, 135.4, 131.1, 130.3, 129.6, 129.2, 128.7, 128.5, 127.7, 127.5,

127.3, 127.2, 125.8, 125.5, 123.4, 122.1, 119.2, 24.5, 13.5 ppm.

C₃₅H₂₉N₃(491.62): calcd. C 85.51, H 5.95, N 8.55; found C 85.03,

H 5.94, N 8.48.

181–183 °C. FT-IR (KBr disc): ν = 3060, 3037, 2960, 2929, 2868,

˜

1639, 1608, 1589, 1546, 1507, 1486, 1452, 1418, 1369, 1296, 1258,

1194, 1119, 1099, 862, 828, 762, 740, 686 cm^–1. ¹H NMR

(300 MHz, CDCl₃): δ = 8.80 (d, J = 8.4 Hz, 1 H, phen), 8.45 (d, J

= 7.5 Hz, 2 H, Ph), 8.33 (d, J = 8.4 Hz, 2 H, phen), 8.17 (d, J =

8.4 Hz, 1 H, phen), 7.80 (d, J = 3.9 Hz, 2 H, phen), 7.56 (t, J =

7.5 Hz, 2 H, Ph), 7.47 (t, J = 7.5 Hz, 1 H, Ph), 7.16 (d, J = 7.2 Hz,

2 H, Ar), 7.07 (t, J = 7.2 Hz, 1 H, Ar), 2.64 (s, 3 H, COCH₃), 2.42

(q, J = 7.2 Hz, 4 H, 2 Et), 1.16 (t, J = 7.2 Hz, 6 H, 2 Et) ppm. ¹³C

NMR (75 MHz, CDCl₃): δ = 167.7, 156.9, 155.9, 148.0, 146.0,

145.1, 139.2, 137.1, 136.5, 131.1, 129.8, 129.6, 128.9, 127.8, 127.5,

127.3, 126.1, 126.0, 123.4, 120.5, 119.8, 24.7, 17.0, 13.8 ppm.

C₃₀H₂₇N₃(429.56): calcd. C 83.88, H 6.34, N 9.78; found C 83.66,

H 6.40, N 9.60.

Synthesis of Ligand 6: Ligand 6 was prepared from 2-benzoyl-9-

phenyl-1,10-phenanthroline (394 mg, 1.09 mmol) and 2,6-diisopro-

pylaniline (433 mg, 2.44 mmol) as a yellow solid in 74.0% yield

(420 mg) in a similar manner to that described for ligand 4. M.p.

170–171 °C. FT-IR (KBr disc): ν = 3063, 2958, 2860, 1611, 1588,

˜

1544, 1506, 1487, 1463, 1430, 1358, 1291, 1194, 1091, 966, 858,

1

777, 757, 701 cm^–1. H NMR (300 MHz, CDCl₃): δ = 8.84 (d, J =

Synthesis of Ligand 3: Ligand 3 was prepared from 2-acetyl-9-

phenyl-1,10-phenanthroline (298 mg, 1.00 mmol) and 2,6-diisopro-

pylaniline (448 mg, 2.50 mmol) as a yellow solid in 53.1% yield

(243 mg) in a similar manner to that described for ligand 1. M.p.

8.4 Hz, 1 H, phen), 8.38–8.24 (m, 4 H), 8.11 (d, J = 8.4 Hz, 1 H,

phen), 7.82 (s, 2 H, phen), 7.62 (m, 2 H, Ph), 7.49–7.39 (m, 6 H,

Ph), 7.04 (m, 3 H, Ar), 3.00 (sept, J = 6.8 Hz, 2 H, 2 iPr), 1.19 (d,

J = 6.8 Hz, 6 H, iPr), 0.97 (d, J = 6.8 Hz, 6 H, iPr) ppm. ¹³C NMR

(100 MHz, CDCl₃): δ = 164.9, 155.9, 145.7, 144.6, 138.5, 136.3,

136.0, 135.2, 134.5, 130.3, 129.1, 128.7, 128.4, 128.2, 128.1, 127.2,

127.1, 126.9, 126.7, 125.4, 123.2, 122.4, 121.8, 111.8, 28.1, 23.7,

21.6 ppm. C₃₇H₃₃N₃(519.68): calcd. C 85.51, H 6.40, N 8.09; found

C 84.91, H 6.36, N 7.84.

256–258 °C. FT-IR (KBr disc): ν = 3061, 2962, 2924, 2865, 1635,

˜

1607, 1589, 1579, 1546, 1507, 1486, 1462, 1436, 1420, 1381, 1366,

1294, 1247, 1189, 1117, 1097, 860, 780, 761, 741, 685 cm^–1. ¹H

NMR (400 MHz, CDCl₃): δ = 8.82 (d, J = 8.4 Hz, 1 H, phen), 8.45

(d, J = 7.6 Hz, 2 H, Ph), 8.33 (dd, J₁= 8.4 Hz, J₂= 4.7 Hz, 2 H,

phen), 8.17 (d, J = 8.4 Hz, 1 H, phen), 7.88 (d, J = 4.0 Hz, 2 H,

phen), 7.56 (t, J = 7.6 Hz, 2 H, Ph), 7.47 (t, J = 7.6 Hz, 1 H, Ph),

Synthesis of Iron Complexes 1a–6a. General Procedure: The ligand

7.21 (d, J = 7.6 Hz, 2 H, Ar), 7.13 (t, J = 7.6 Hz, 1 H, Ar), 2.86 (0.20 mmol) and one equiv. of FeCl₂·4H₂O (0.20 mmol) were

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Catalytic Ethylene Oligomerization

placed in a Schlenk tube, which was purged three times with nitro-

gen and then charged with thf. The reaction mixture was then

1445, 1371, 1317, 1289, 1213, 999, 863, 774, 748, 721, 703 cm^–1.

C₃₃H₂₅Cl₂CoN₃·CH₂Cl₂(678.34): calcd. C 60.20, H 4.01, N 6.19;

stirred at room temperature for 9 h. The resulting precipitate was found C 60.25, H 4.02, N 6.28.

filtered, washed with diethyl ether, and dried in vacuo. All the

Complex 5b: Isolated as a red-brown powder in 77.6% yield

iron(II) complexes were isolated in high yield.

(84 mg). FT-IR (KBr disc): ν = 3063, 2963, 2934, 2875, 1613, 1596,

˜

1552, 1498, 1490, 1442, 1371, 1319, 1288, 1108, 995, 872, 782, 751,

720, 701 cm^–1. C₃₅H₂₉Cl₂CoN₃·CH₂Cl₂(706.40): calcd. C 61.21, H

4.42, N 5.95; found C 60.68, H 4.28, N 5.63.

Complex 1a: Isolated as a green powder in 98.4% yield (104 mg).

FT-IR (KBr disc): ν = 3059, 2953, 2918, 2867, 1615, 1590, 1555,

˜

1504, 1491, 1468, 1451, 1435, 1374, 1299, 1205, 865, 792, 772, 745,

702 cm^–1. C₂₈H₂₃Cl₂FeN₃·1/2CH₂Cl₂(570.72): calcd. C 59.98, H

4.24, N 7.36; found C 59.61, H 4.34, N 7.28.

Complex 6b: Isolated as a red-brown powder in 78.4% yield

(103 mg). FT-IR (KBr disc): ν = 3058, 3032, 2959, 2924, 2865,

˜

1619, 1599, 1552, 1489, 1437, 1370, 1319, 1274, 1207, 1100, 995,

873, 850, 759, 718, 652 cm^–1. C₃₇H₃₃Cl₂CoN₃·CH₂Cl₂(734.45):

calcd. C 62.14, H 4.80, N 5.72; found C 62.17, H 4.82, N 5.54.

Complex 2a: Isolated as a green powder in 95.9% yield (107 mg).

FT-IR (KBr disc): ν = 3063, 2966, 2929, 2872, 1617, 1584, 1558,

˜

1504, 1490, 1442, 1374, 1289, 1243, 1205, 1193, 1152, 1141, 1060,

859, 786, 759, 744, 701 cm^–1. C₃₀H₂₇Cl₂FeN₃(556.31): calcd. C

64.77, H 4.89, N 7.55; found C 64.26, H 4.59, N 7.50.

Complex 1c: Isolated as an orange powder in 89.3% yield (95 mg).

FT-IR (KBr disc): ν = 3445, 3056, 1611, 1587, 1556, 1503, 1489,

˜

1453, 1376, 1294, 1204, 1148, 862, 793, 773, 745, 702 cm^–1.

C₂₈H₂₃Cl₂N₃Ni·1/2CH₂Cl₂(573.57): calcd. C 59.68, H 4.22, N

7.33; found C 59.89, H 4.44, N 7.20.

Complex 3a: Isolated as a green powder in 66.2% yield (78 mg).

FT-IR (KBr disc): ν = 3062, 2969, 2926, 2865, 1611, 1590, 1557,

˜

1501, 1490, 1463, 1440, 1374, 1330, 1286, 1247, 1185, 1152, 1138,

870, 786, 748, 701 cm^–1. C₃₂H₃₁Cl₂FeN₃(584.36): calcd. C 65.77,

H 5.35, N 7.19; found C 65.15, H 5.32, N 6.95.

Complex 2c: Isolated as an orange powder in 89.7% yield (100 mg).

FT-IR (KBr disc): ν = 3442, 3062, 2958, 2871, 1616, 1584, 1559,

˜

1502, 1489, 1442, 1377, 1302, 1292, 1192, 1060, 859, 787, 762, 744,

701 cm^–1. C₃₀H₂₇Cl₂N₃Ni·1/2CH₂Cl₂(601.62): calcd. C 60.89, H

4.69, N 6.98; found C 60.46, H 4.96, N 6.67.

Complex 4a: Isolated as a gray-green powder in 86.9% yield

(103 mg). FT-IR (KBr disc): ν = 3056, 2922, 1620, 1588, 1549,

˜

1489, 1445, 1368, 1300, 1212, 1155, 1001, 863, 774, 744, 703 cm^–1.

C₃₃H₂₅Cl₂FeN₃·H₂O (608.34): calcd. C 65.15, H 4.47, N 6.91;

found C 65.12, H 4.11, N 6.85.

Complex 3c: Isolated as an orange powder in 76.5% yield (90 mg).

FT-IR (KBr disc): ν = 3426, 3060, 2967, 2865, 1609, 1586, 1558,

˜

1489, 1443, 1378, 1330, 1293, 1185, 1151, 869, 787, 761, 749,

702 cm^–1. C₃₂H₃₁Cl₂N₃Ni·CH₂Cl₂(672.14): calcd. C 58.97, H 4.95,

N 6.25; found C 58.44, H 5.02, N 6.20.

Complex 5a: Isolated as a brown powder in 79.8% yield (99 mg).

FT-IR (KBr disc): ν = 3061, 2966, 2874, 1594, 1553, 1490, 1444,

˜

1368, 1291, 1261, 1107, 1059, 1000, 868, 781, 702 cm^–1.

C₃₅H₂₉Cl₂FeN₃(618.38): calcd. C 67.98, H 4.73, N 6.80; found C

67.94, H 4.78, N 6.57.

Complex 4c: Isolated as a yellow powder in 96.0% yield (114 mg).

FT-IR (KBr disc): ν = 3388, 1618, 1592, 1554, 1486, 1445, 1378,

˜

1290, 1212, 1057, 1038, 1004, 868, 778, 754, 723, 703 cm^–1.

C₃₃H₂₅Cl₂N₃Ni·H₂O (611.19): calcd. C 64.85, H 4.45, N 6.88;

found C 65.09, H 4.16, N 6.82.

Complex 6a: Isolated as a green powder in 86.6% yield (112 mg).

FT-IR (KBr disc): ν = 3031, 2959, 2866, 1620, 1587, 1550, 1488,

˜

1459, 1436, 1364, 1319, 1274, 1206, 995, 872, 850, 704 cm^–1.

C₃₇H₃₃Cl₂FeN₃(646.43): calcd. C 68.75, H 5.15, N 6.50; found C

68.42, H 5.23, N 6.59.

Complex 5c: Isolated as a orange powder in 90.6% yield (113 mg).

FT-IR (KBr disc): ν = 3061, 2963, 1597, 1558, 1489, 1443, 1377,

˜

1291, 1209, 1148, 1108, 1065, 1040, 1004, 867, 784, 706 cm^–1.

C₃₅H₂₉Cl₂N₃Ni·1/2CH₂Cl₂(663.69): calcd. C 64.24, H 4.56, N

6.33; found C 64.50, H 4.75, N 6.60.

Synthesis of Cobalt Complexes 1b–6b and Nickel Complexes 1c–6c.

General Procedure: The ligand (0.20 mmol) and one equiv. of CoCl₂

or NiCl₂·6H₂O (0.20 mmol) were placed in a Schlenk tube along

with anhydrous 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. All the complexes

were isolated in high yield.

Complex 6c: Isolated as an orange powder in 75.1% yield (98 mg).

FT-IR (KBr disc): ν = 3440, 3057, 2962, 2866, 1621, 1595, 1554,

˜

1490, 1439, 1377, 1322, 1293, 1207, 1151, 1101, 1024, 872, 784,

763, 707 cm^–1. C₃₇H₃₃Cl₂N₃Ni·1/2CH₂Cl₂(691.75): calcd. C 65.11,

H 4.95, N 6.07; found C 65.01, H 5.04, N 5.85.

Complex 1b: Isolated as a green powder in 65.6% yield (70 mg).

General Procedure for Ethylene Oligomerization at 1 atm of Ethyl-

ene Pressure: A flame-dried, three-necked flask was loaded with

the catalyst precursor and purged three times with nitrogen. Ethyl-

ene was then charged in the flask along with freshly distilled tolu-

ene and the mixture stirred for 10 min under 1 atm of ethylene pres-

sure. The reaction temperature was controlled with a water bath

and the required amount of co-catalyst was then injected with a

syringe. The reaction mixture was stirred for the required time and

then the reaction was quenched by addition of 5% aqueous hydro-

gen chloride. The contents and distributions of oligomers were de-

termined by GC.

FT-IR (KBr disc): ν = 3063, 2945, 2914, 1619, 1585, 1557, 1504,

˜

1490, 1451, 1437, 1374, 1290, 1256, 1206, 1142, 989, 919, 865, 791,

772, 745, 700, 653, 609 cm^–1. C₂₈H₂₃Cl₂CoN₃·H₂O (549.36): calcd.

C 61.22, H 4.59, N 7.65; found C 61.46, H 4.34, N 7.24.

Complex 2b: Isolated as a green powder in 80.3% yield (91 mg).

FT-IR (KBr disc): ν = 3061, 2969, 2924, 2865, 1613, 1582, 1557,

˜

1501, 1489, 1463, 1441, 1375, 1330, 1288, 1185, 1153, 869, 786,

749, 700 cm^–1. C₃₀H₂₇Cl₂CoN₃(559.39): calcd. C 64.41, H 4.86, N

7.51; found C 64.25, H 4.92, N 7.27.

Complex 3b: Isolated as a green powder in 85.6% yield (103 mg).

FT-IR (KBr disc): ν = 3450, 3062, 2964, 2932, 2875, 1618, 1585,

˜

General Procedure for Ethylene Oligomerization at 10 Atm of Ethyl-

ene Pressure: A 250-mL stainless steel reactor equipped with a me-

chanical stirrer and a temperature controller was heated in vacuo

for at least 2 h at above 80 °C, then cooled to the required reaction

temperature under ethylene atmosphere and charged with toluene,

the desired amount of co-catalyst, and a toluene solution of the

1558, 1504, 1490, 1441, 1375, 1290, 1193, 859, 787, 760, 745,

701 cm^–1. C₃₂H₃₁Cl₂CoN₃(587.45): calcd. C 65.43, H 5.32, N 7.15;

found C 64.48, H 5.55, N 6.61.

Complex 4b: Isolated as a red-brown powder in 80.2% yield

(95 mg). FT-IR (KBr disc): ν = 3057, 2919, 1612, 1597, 1555, 1490,

˜

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Table 6. Crystal data and structure refinement for 1b, 2, 2a, and 4b.

1b

2

2a

4b

CCDC number

Formula

650187

C₂₈H₂₃Cl₂CoN₃O

547.32

293(2)

0.71073

monoclinic

C2/c

25.9027(8)

16.9116(6)

16.5805(5)

90

128.031(2)

90

5721.0(3)

8

650185

C₃₀H₂₇N₃

429.55

650186

C₃₀H₂₇C_l2FeN₃O_0.5

564.30

293(2)

0.71073

650188

C₃₃H₂₅Cl₂CoN₃·CH₂Cl₂

678.32

294(2)

Formula weight

Temperature [K]

Wavelength [Å]

Crystal system

Space group

a [Å]

b [Å]

c [Å]

α [°]

β [°]

294(2)

0.71073

triclinic

0.71073

triclinic

¯

P1

7.869(2)

11.840(3)

13.547(4)

105.675(5)

94.203(5)

99.069(5)

1191.1(6)

2

13.3880(6)

14.0560(6)

14.9754(6)

83.065(3)

86.114(3)

78.191(3)

2735.6(2)

4

8.6610(14)

9.5741(15)

19.014(3)

81.376(2)

88.499(3)

86.065(3)

1555.0(4)

2

γ [°]

V [Å³]

Z

D_calcd.[gcm^–3]

1.271

0.810

1.198

0.071

1.370

0.772

1.449

0.925

μ [mm^–1]

F(000)

2248

456

1168

694

Crystal size [mm]

θ range [°]

Limiting indices

0.26ϫ0.20ϫ0.15

2.46–28.32

–34ՅhՅ34

–22ՅkՅ22

–21ՅlՅ22

99.1 (θ = 28.32°)

empirical

334

0.24ϫ0.15ϫ0.12

1.82–26.49

–9ՅhՅ5

–14ՅkՅ14

–16ՅlՅ15

97.7 (θ = 26.49°)

empirical

302

0.20ϫ0.14ϫ0.12

1.37–28.36

–17ՅhՅ17

–18ՅkՅ18

–19ՅlՅ19

98.8 (θ = 28.36°)

empirical

667

0.25ϫ0.12ϫ0.08

1.08–26.45

–10ՅhՅ7

–10ՅkՅ11

–23ՅlՅ19

97.7 (θ = 26.45°)

empirical

379

% Completeness to θ

Absorption correction

No. of parameters

Goodness-of-fit on F²

R1 [I Ͼ 2σ(I)]

0.931

0.0672

0.981

0.0538

0.734

0.0494

1.018

0.0522

wR2

0.1895

0.915/–0.349

0.1183

0.121/–0.171

0.1191

0.381/–0.374

0.1208

0.491/–0.499

Largest diff. peak/hole [eÅ^–3]

Table 7. Crystal data and structure refinement for 1c, 5c, and 6b.

1c

5c

6b

650189

CCDC number

Formula

650190

650191

C₂₈H₂₃Cl₂N₃Ni·CH₂Cl₂

C₃₅H₂₉Cl₂N₃Ni·2CH₂Cl₂

791.07

293(2)

C₃₇H₃₃Cl₂CoN₃·CH₂Cl₂

734.42

293(2)

Formula weight

Temperature [K]

Wavelength [Å]

Crystal system

Space group

a [Å]

b [Å]

c [Å]

α [°]

β [°]

616.03

293(2)

0.71073

triclinic

0.71073

triclinic

monoclinic

P2₁/c

18.870(4)

9.7077(19)

15.550(3)

90

96.26(3)

90

2831.6(10)

4

¯

P1

9.2599(4)

9.6246(4)

20.9828(9)

97.054(2)

95.194(2)

98.629(2)

1823.54(13)

2

9.2300(18)

10.254(2)

17.912(4)

96.51(3)

90.33(3)

92.04(3)

1683.2(6)

2

γ [°]

V [Å³]

Z

D_calcd.[gcm^–3]

1.445

1.086

1.441

1.003

1.449

0.860

μ [mm^–1]

F(000)

1264

812

758

Crystal size [mm]

θ range [°]

Limiting indices

0.26ϫ0.19ϫ0.11

2.17–25.01

–19ՅhՅ22

–11ՅkՅ1

–18ՅlՅ18

100.0 (θ = 25.01°)

empirical

334

0.31ϫ0.22ϫ0.20

0.98–28.35

–12ՅhՅ12

–10ՅkՅ12

–27ՅlՅ27

98.7 (θ = 28.35°)

empirical

424

0.30ϫ0.18ϫ0.12

1.14–26.47

–11ՅhՅ11

–12ՅkՅ10

–17ՅlՅ22

97.4 (θ = 26.47°)

empirical

415

% Completeness to θ

Absorption correction

No. of parameters

Goodness-of-fit on F²

R1 [I Ͼ 2σ(I)]

1.00

0.0917

0.87

0.0614

1.038

0.0452

wR2

0.1527

0.360/–0.407

0.1661

0.540/–0.531

0.1048

0.697/–0.629

Largest diff. peak/hole [eÅ^–3]

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Eur. J. Inorg. Chem. 2007, 5584–5598

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sealed and pressurized to 10 atm of ethylene pressure at the re-

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tained with a feed of ethylene. After the required time the pressure

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X-ray Crystallography: Single-crystal X-ray diffraction studies for

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293(2) K. Intensity data for crystals of 2, 4b and 6b were collected

with a Bruker SMART 1000 CCD diffractometer with graphite-

monochromated Mo-K_αradiation (λ = 0.71073 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 di-

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non-hydrogen atoms were refined anisotropically. All hydrogen

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Acknowledgments

This project was supported by the National Natural Science Foun-

dation of China (grant nos. 20473099 and 20674089). We thank

Mr. Saliu Alao Amolegbe (a CAS-TWAS Postgraduate Fellow

from Nigeria) for English corrections.

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Received: July 2, 2007

Published Online: October 24, 2007

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Article Doi

2-Arylimino-9-phenyl-1,10-phenanthrolinyl-iron, -cobalt and -nickel complexes: Synthesis, characterization and ethylene oligomerization behavior

DOI: 10.1002/ejic.200700690

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Article abstract of DOI:10.1002/ejic.200700690

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