Synthesis and characterization of iron, cobalt, and nickel complexes bearing novel N,N-chelate ligands and their catalytic properties in ethylene oligomerization

Article abstract of DOI:10.1002/ejic.200700020

Treatment of o-ROC₆H₄NC (R = PhCH₂, iPr) with [Li{2-CH(SiMe₃)C₅H₄N}] afforded dimeric lithium complexes [Li{N(o-ROC₆H₄)C(SiMe ₃)CH(2-C₅H₄N)}]₂ (3, R = PhCH ₂; 4, R = iPr). Reaction of the hthium complexes with 1 equiv. of (dme)NiCl₂ gave nickel complexes [Ni{N(o-ROC₆H ₄)-C(SiMe₃)CH(2-C₅H₄N)} ₂] (5, R = PhCH₂; 6, R = iPr). The stoichiometric reaction of complexes 3 and 4 with Et₃NH⁺Cl^- formed 2-{o-ROC₆H₄NHC(SiMe₃)CH}C₅H ₄N (7, R = PhCH₂; 8, R = iPr) in quantitative yields. Reaction of 7 or 8 with metal halides, including (dme)NiCl₂, NiBr₂, FeCl₂·4H₂O, and CoCl₂ yielded complexes [MX₂{(o-ROC₆H₄)N=C(SiMe ₃)CH₂(2-C₅H₄N)}] (9, R = PhCH ₂, M = Ni, X = Cl; 10, R = iPr, M = Ni, X = Cl; 11, R = PhCH ₂, M = Ni, X = Br; 12, R = iPr, M = Ni, X = Br; 13, R = PhCH ₂, M = Fe, X = Cl; 14, R = iPr, M = Fe, X = Cl; 15, R = PhCH ₂, M = Co, X = Cl; 16, R = iPr, M = Co, X = Cl). For comparasion, nickel and cobalt complexes [MX₂{(o-MeC₆H ₄)N=C(SiMe₃)CH₂(2-C₅H ₄N)}] (M = Ni, X = Br, 18; M = Co, X = Cl, 19) were similarly synthesized through reaction of 2-{o-MeC₆H₄NHC(SiMe ₃)CH}C₅H₄N (17) with NiBr₂ and CoCl₂, respectively. These compounds were characterized by NMR (for 3, 4, 7, 8, and 17) and IR (for 5-19) spectroscopy, elemental analyses and HRMS (for 5, 6, and 9-19). The molecular structures of complexes 3, 6, 12, and 14 were characterized by single-crystal X-ray diffraction techniques. The catalytic behavior in ethylene oligomerization of complexes 5, 6, 9-16, 18, and 19 was investigated. Under optimal conditions, the complexes showed good catalytic activities upon activation with appropriate aluminum co-catalysts (8.72 × 10² to 18.2 × 10² kg/mol h atm for the nickel complexes upon activation with Et₂AlCl and 4.3 × 10² to 8.1 × 10² kg/mol h atm for the iron and cobalt complexes upon activation with MMAO). Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700020

FULL PAPER
DOI: 10.1002/ejic.200700020
Synthesis and Characterization of Iron, Cobalt, and Nickel Complexes Bearing
Novel N,N-Chelate Ligands and Their Catalytic Properties in Ethylene
Oligomerization
Li Wang,[a] Cheng Zhang,[a] and Zhong-Xia Wang*[a]
Keywords: Iron / Cobalt / Nickel / Catalysis / Ethylene / Oligomerization
Treatment of o-ROC6H4NC (R = PhCH2, iPr) with [Li{2-
CH(SiMe3)C5H4N}] afforded dimeric lithium complexes
[Li{N(o-ROC6H4)C(SiMe3)CH(2-C5H4N)}]2 (3, R = PhCH2; 4,
R = iPr). Reaction of the lithium complexes with 1 equiv. of
(dme)NiCl2 gave nickel complexes [Ni{N(o-ROC6H4)-
C(SiMe3)CH(2-C5H4N)}2] (5, R = PhCH2; 6, R = iPr). The stoi-
chiometric reaction of complexes 3 and 4 with Et3NH+Cl–
formed 2-{o-ROC6H4NHC(SiMe3)CH}C5H4N (7, R = PhCH2;
8, R = iPr) in quantitative yields. Reaction of 7 or 8 with metal
halides, including (dme)NiCl2, NiBr2, FeCl2·4H2O, and CoCl2
yielded complexes [MX2{(o-ROC6H4)N=C(SiMe3)CH2(2-
C5H4N)}] (9, R = PhCH2, M = Ni, X = Cl; 10, R = iPr, M = Ni,
X = Cl; 11, R = PhCH2, M = Ni, X = Br; 12, R = iPr, M = Ni,
X = Br; 13, R = PhCH2, M = Fe, X = Cl; 14, R = iPr, M = Fe,
X = Cl; 15, R = PhCH2, M = Co, X = Cl; 16, R = iPr, M =
Co, X = Cl). For comparasion, nickel and cobalt complexes
[MX2{(o-MeC6H4)N=C(SiMe3)CH2(2-C5H4N)}] (M = Ni, X =
Br, 18; M = Co, X = Cl, 19) were similarly synthesized
through reaction of 2-{o-MeC6H4NHC(SiMe3)CH}C5H4N
(17) with NiBr2 and CoCl2, respectively. These compounds
were characterized by NMR (for 3, 4, 7, 8, and 17) and IR (for
5–19) spectroscopy, elemental analyses and HRMS (for 5, 6,
and 9–19). The molecular structures of complexes 3, 6, 12,
and 14 were characterized by single-crystal X-ray diffraction
techniques. The catalytic behavior in ethylene oligomeriza-
tion of complexes 5, 6, 9–16, 18, and 19 was investigated.
Under optimal conditions, the complexes showed good cata-
lytic activities upon activation with appropriate aluminum
co-catalysts (8.72ϫ102 to 18.2ϫ102 kg/molhatm for the
nickel complexes upon activation with Et2AlCl and 4.3ϫ102
to 8.1ϫ102 kg/molhatm for the iron and cobalt complexes
upon activation with MMAO).
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
Introduction
N,N,P,[8] and N,N,N ligands.[9] A representative example are
bis(imino)pyridine ligands whose iron complexes showed
exceptionally high activities for ethylene polymerization
when activated with MAO.[10]
Late-transition-metal complexes with N,N-chelate li-
gands have attracted considerable attention due to their
catalytic actions, especially for developing non-metallocene
catalysts for the polymerization of ethylene and α-olefins.[1]
Following the pioneering studies of Keim and Fink,[1d,2]
Brookhart and co-workers reported on the discovery of the
α-diimine complexes of NiII and PdII catalysts for the poly-
merization of ethylene and α-olefins.[3] Subsequently, the
number of academic publications and patents for polyole-
fins and oligomers obtained with late-transition-metal com-
plexes increased remarkably.[1,4] A large number of struc-
tural variations of diimines have also been reported to ad-
just the steric and electronic properties of the N,N-chelate
ligands.[1,5] These include β-diimines and analogues whose
complexes of NiII and PdII, however, usually exhibit lower
catalytic activities than the α-diimine complexes.[1a,6] A fur-
ther modification is to append a donor sidearm, con-
structing tridentate chelating ligands such as N,N,O,[7]
Furthermore, late-transition-metal complexes could act
as better candidates for ethylene oligomerization because of
their facile β-H elimination.[11] Many neutral and cationic
late-transition-metal complexes with chelate ligands have
been successfully applied in the field of olefin oligomeriza-
tion.[12,13] The Shell Higher Olefin Process (SHOP) is an
excellent example. However, the demand for linear α-olefins
in the C4–C10 range is growing fast. Much effort is still de-
voted to the development of highly selective ethylene oligo-
merization catalysts, and identifying and fine-tuning the pa-
rameters that influence the activity and selectivity of suit-
able catalysts continues to represent a challenge.[13] Our cur-
rent efforts focus on the synthesis of new functional ligands
and their corresponding late-transition-metal complexes as
well as the catalytic behavior for ethylene oligomerization.
Herein, we report on the synthesis and characterization of
new ligands and their lithium and late-transition-metal
complexes, while their catalytic behavior for ethylene oligo-
merization was also investigated and discussed.
[a] Department of Chemistry, University of Science and Technol-
ogy of China,
Hefei, Anhui 230026, P. R. China
Eur. J. Inorg. Chem. 2007, 2477–2487
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2477

L. Wang, C. Zhang, Z.-X. Wang
FULL PAPER
Results and Discussion
Synthesis and Characterization
Compounds 1 and 2 were prepared according to a litera-
ture method.[14] Syntheses of 3–16 are summarized in
Scheme 1. Reaction of o-ROC6H4NC (R = PhCH2, iPr)
with [Li{2-CH(SiMe3)C5H4N}] afforded dimeric lithium
complexes [Li{N(o-ROC6H4)C(SiMe3)CH(2-C5H4N)}]2 (3,
R = PhCH2; 4, R = iPr) as yellow, air-sensitive solids. In
the reaction, a 1,2-SiMe3 migration from the α- to the β-
carbon atom took place. This type of reaction between an
isocyanide and (trimethylsilyl)methyllithium has been re-
ported.[15] Reaction of 3 and 4 with 1 equiv. of (dme)NiCl2
gave nickel complexes [Ni{N(o-ROC6H4)C(SiMe3)CH(2-
C5H4N)}2] (5, R = PhCH2; 6, R = iPr). Attempts to synthe-
size [NiCl{N(o-ROC6H4)C(SiMe3)CH(2-C5H4N)}] by reac-
tion of 3 or 4 with various amounts of (dme)NiCl2 were
unsuccessful. Complexes 3 and 4 were treated with 1 equiv.
of Et3NH+Cl– to afford 2-{o-ROC6H4NHC(SiMe3)-
CH}C5H4N (7, R = PhCH2; 8, R = iPr) as a pale yellow
solid (7) or a yellowish oil (8), each existing in an enamine
form. Reaction of 7 or 8 with metal halides, including
(dme)NiCl2, NiBr2, FeCl2·4H2O and CoCl2, yielded
[MX2{(o-ROC6H4)N=C(SiMe3)CH2(2-C5H4N)}] (9, R =
PhCH2, M = Ni, X = Cl; 10, R = iPr, M = Ni, X = Cl; 11,
R = PhCH2, M = Ni, X = Br; 12, R = iPr, M = Ni, X =
Br; 13, R = PhCH2, M = Fe, X = Cl; 14, R = iPr, M = Fe,
X = Cl; 15, R = PhCH2, M = Co, X = Cl; 16, R = iPr, M
= Co, X = Cl). Compound 17 was prepared with a similar
procedure as for 7 and 8 (Scheme 2). Thus, reaction of o-
MeC6H4NC with [Li{2-CH(SiMe3)C5H4N}] in Et2O gave
the lithium complex [Li{N(o-MeC6H4)C(SiMe3)CH(2-
C5H4N)}], which was hydrolyzed directly by treatment with
1 equiv. of water to afford neutral enamine 17. Complexes
18 and 19 were synthesized through reaction of 17 with
NiBr2 or CoCl2 in thf, just as for complexes 9–16.
Scheme 1. Synthesis of compounds 3–16. Reagents and conditions:
i: Et2O, –30 °C to room temperature, 15 h; ii: (dme)NiCl2, thf,
–80 °C to room temperature, 15 h; iii: Et3NH+Cl–, toluene, 0 °C to
room temperature, 20 h; iv: L1MX2 [L1MX2 = (dme)NiCl2, NiBr2,
FeCl2·4H2O, CoCl2], thf, 0 °C to room temperature, 15 h.
1
Complexes 3 and 4 were fully characterized by H and
13C NMR spectroscopy and elemental analyses. The data
are consistent with their respective structure. Complexes 5
and 6 are paramagnetic and were characterized by IR spec-
troscopy, elemental analyses, and high-resolution mass
spectrometry. Compounds 7 and 8 were characterized by
Scheme 2. Synthesis of compounds 17–19. Reagents and condi-
tions: i: Et2O, –30 °C to room temperature, 15 h, and then H2O,
thf, 0 °C to room temperature, 10 min.; ii: NiBr2 or CoCl2, thf, 0 °C
to room temperature, 15 h.
1H, 13C NMR, and IR spectroscopy and elemental analy- the coordinated ligands as imine forms in the complexes.
1
ses. The H NMR spectra of 7 and 8 exhibit NH proton This is also consistent with the single-crystal X-ray diffrac-
signals at δ = 11.77 and 11.58 ppm, respectively, and eth- tion results of complexes 12 and 14.
enyl proton signals at δ = 5.69 and 5.59 ppm, respectively.
Complexes 3, 6, 12, and 14 were further characterized by
Their 13C NMR spectra also show the existence of the C– single-crystal X-ray diffraction techniques. The structure of
C double bonds. These data prove the enamine forms of 7 complex 3 is presented in Figure 1 along with selected bond
and 8. The similar compound 17 also exists in an enamine lengths and bond angles. The structure shows that complex
form, being a mixture of (Z) and (E) isomers. It was charac- 3 is dimeric in the solid state, in which two lithium atoms
1
terized by H NMR and IR spectroscopy and high-resolu- are bridged by two enamine nitrogen atoms, forming a 1,3-
tion mass spectrometry. Complexes 9–16, 18, and 19 are Li2N2 four-membered ring. With the 1,3-Li2N2 ring as the
crystalline solids or powders and paramagnetic; the com- base, the NC3NLi and NC2OLi rings form the flaps of an
plexes are yellow (9, 13, and 14), purple (10 and 18), red “open-box”-like structural framework, in which each four-
(11 and 12), or blue (15, 16, and 19). They gave satisfactory coordinate lithium atom has a distorted tetrahedral geome-
elemental analyses and high-resolution mass spectra. The try. The Li–N distances from 1.967(8) to 2.108(8) Å are in
IR spectra show C=N double-bond absorptions, proving the normal range. For example, the Li–N distances in
2478
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Eur. J. Inorg. Chem. 2007, 2477–2487

Iron, Cobalt and Nickel Complexes with N,N-Chelate Ligands
FULL PAPER
[Li{N(SiMe3)C(R2)C(R1)(C5H4N-2)}]2 (R1 = H, R2 = tBu;
R1 = SiMe3, R2 = Ph) vary from 1.968(6) to 2.032(6) Å,
and in [Li{N(SiMe3)C(Ph)}2CH]2 from 1.952(10) to
2.095(2) Å.[16]
Figure 2. ORTEP drawing of complex 6 with 30% probability ther-
mal ellipsoids. Selected bond lengths [Å] and bond angles [°]:
Ni(1)–N(1) 2.045(3), Ni(1)–N(2) 1.968(3), Ni(1)–N(3) 2.043(4),
Ni(1)–N(4) 1.976(3), Ni(1)···O(1) 2.574, Ni(1)···O(2) 2.586, C(6)–
C(7) 1.377(6), C(25)–C(26) 1.371(6), N(2)–C(7) 1.377(5), N(4)–
C(26) 1.373(5); N(1)–Ni(1)–N(2) 90.42(14), N(1)–Ni(1)–N(3)
100.11(14),
100.77(14),
N(1)–Ni(1)–N(4)
N(2)–Ni(1)–N(4)
100.42(14),
163.29(13),
N(2)–Ni(1)–N(3)
N(3)–Ni(1)–N(4)
Figure 1. ORTEP drawing of complex 3 with 30% probability ther-
mal ellipsoids. Selected bond lengths [Å] and bond angles [°]: Li(1)–
N(1) 2.108(8), Li(1)–N(3) 1.990(8), Li(1)–N(4) 1.967(8), Li(1)–O(1)
2.055(8), Li(2)–N(1) 2.016(8), Li(2)–N(2) 1.982(8), Li(2)–N(3)
2.072(8), Li(2)–O(2) 2.037(8), Li(1)–Li(2) 2.495(10), N(1)–C(1)
1.403(5), C(1)–C(2) 1.363(5), N(3)–C(24) 1.394(5), C(24)–C(25)
1.363(5); N(1)–Li(1)–N(3) 103.8(3), N(1)–Li(1)–N(4) 119.0(4),
N(3)–Li(1)–N(4) 98.9(4), N(3)–Li(1)–O(1) 121.7(4), N(4)–Li(1)–
O(1) 130.7(4), N(1)–Li(1)–O(1) 79.8(3), N(1)–Li(2)–N(2) 98.4(3),
N(1)–Li(2)–N(3) 104.2(3), N(2)–Li(2)–N(3) 119.3(4), N(1)–Li(2)–
O(2) 122.2(4), N(2)–Li(2)–O(2) 129.2(4), N(3)–Li(2)–O(2) 81.3(3),
Li(1)–N(1)–Li(2) 74.4(3), Li(1)–N(3)–Li(2) 75.8(3).
89.88(14), O(1)–Ni(1)–N(1) 158.89, O(2)–Ni(1)–N(3) 158.58.
[CH2{C(Me)=NAr}2]NiBr2 [2.010(5) and 2.022(5) Å,
respectively].[6a] The Ni1–Br1 distance [2.3599(7) Å] is
longer than that of Ni1–Br2 [2.3419(7) Å], and both are
normal for four-coordinate NiII complexes.[19] The N2–C7
distance of 1.288(4) Å agrees with that of a C=N double
bond, indicating that the enamine tautomerizes to an imine
after coordination to NiII. The N1–Ni1–N2 bond angle of
91.76(12)° is close to that of [CH2{C(Me)=NAr}2]NiBr2
[93.7(2)°].[6a] However, the Br1–Ni1–Br2 bond angle of
124.78(3)° is wider than that of [CH2{C(Me)=NAr}2]NiBr2
[118.54(5)°].[6a]
The molecular structure of complex 6 is depicted in Fig-
ure 2 along with selected bond lengths and bond angles. In
the structure, a noteworthy feature is the distances between
the Ni atom and the oxygen atoms. The Ni···O distances
(2.574 and 2.586 Å, respectively) are longer than the sum
of the covalent radii, however, much shorter than the sum
of the van der Waals radii.[17] Hence, interactions between
the Ni atom and the O atoms should be present. In this
case, the coordination geometry of the Ni atom can be re-
garded as a distorted octahedron. The N1,N4,O1,N2 atoms
are approximately coplanar, the torsion angle of N1–N4–
O1–N2 being 0.7°, while the Ni atom is out of the plane.
The molecular structure of complex 12 is depicted in Fig-
ure 3 along with selected bond lengths and bond angles.
The crystalline complex 12 is monomeric and the Ni center
is in a distorted tetrahedral environment. The Ni···O dis-
tance of 3.781 Å shows no interactions between the atoms.
The six-membered metallacycle exhibits a boat conforma-
tion. This is very similar to that of [CH2{C(Me)=NAr}2]-
NiBr2 (Ar = 2,6-iPr2C6H3).[6a] The C5,N1,N2,C7 atoms are
approximately coplanar, the torsion angle being 1.5°. The
distance of Ni1–N1 [1.986(3) Å] is slightly shorter than that
of Ni1–N2 [1.993(3) Å], and both are close to those found
Figure 3. ORTEP drawing of complex 12 with 30% probability
thermal ellipsoids. Selected bond lengths [Å] and bond angles [°]:
Ni(1)–N(1) 1.986(3), Ni(1)–N(2) 1.993(3), Ni(1)–Br(1) 2.3599(7),
Ni(1)–Br(2) 2.3419(7), Ni(1)···O(1) 3.781, C(5)–C(6) 1.501(6),
C(6)–C(7) 1.527(5), N(2)–C(7) 1.288(4); N(1)–Ni(1)–N(2)
91.76(12), N(1)–Ni(1)–Br(1) 109.96(9), N(1)–Ni(1)–Br(2) 106.84(9),
N(2)–Ni(1)–Br(1) 104.81(9), N(2)–Ni(1)–Br(2) 113.73(9), Br(1)–
in
[2-{Ph2P=N(2Ј,6Ј-Me2C6H3)}-6-Me3SiC5H3N]NiBr2
[1.996(8) Å] and [2-(Ph3P=NCH2)-6-MeC5H3N]NiBr2
[1.983(3) Å],[18] and slightly shorter than those of Ni(1)–Br(2) 124.78(3).
Eur. J. Inorg. Chem. 2007, 2477–2487
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2479

L. Wang, C. Zhang, Z.-X. Wang
FULL PAPER
The structure of complex 14 is presented in Figure 4 ity.[5f,20] We determined the catalytic activity for ethylene
along with selected bond lengths and bond angles. The polymerization or oligomerization of complexes 5 and 6
crystalline 14 is monomeric and has a skeletal structure sim- upon activation with MAO or MMAO and the results are
ilar to that of 12, including tetrahedral metal coordination listed in Table 1. All catalytic reactions shown in Table 1
geometry and the boat conformation of the six-membered were carried out at 20 °C and 1 atm ethylene pressure for
metallacycle. The Fe1–N1 distance of 2.103(2) Å is slightly 0.5 h. When MMAO was used as the co-catalyst, the Al/Ni
shorter than that of Fe1–N2 [2.115(2) Å], and both are ratio of 800:1 revealed very low catalytic activity for com-
within the normal range for this class of four-coordinate plexes 5 and 6. Complex 5 exhibited the highest catalytic
iron complexes. The Fe1–Cl1 distance of 2.2405(11) Å is activity upon activation with 1000 equiv. of MMAO, while
longer than that of Fe1–Cl2 [2.2264(10) Å]. They are close complex 6 reached its best activity in the presence of
to those in [2-{Ph2P=N(2Ј,6Ј-RЈ2C6H3)}-6-RC5H3N]FeCl2 1500 equiv. of MMAO (Entries 2 and 6 in Table 1). When
(R
=
Ph, SiMe3; RЈ
=
Me, iPr) [2.2451(11)– MAO was used as the co-catalyst, the Al/Ni ratio of 800:1
2.2754(15) Å].[18] The Fe···O distance of 3.812 Å is beyond gave the best catalytic activities for both complexes 5 and 6
the distance of bonding interaction. The N2–C7 distance of (Entries 1 and 4 in Table 1). Higher or lower Al/Ni ratios
1.287(3) Å is almost the same as that of complex 12, show- resulted in a decline of the catalytic activities. The catalytic
ing the ligand also to exist in an imine form.
reactions predominantly formed dimers of ethylene in the
presence of either MAO or MMAO, and the content of α-
olefin is from 24.9 to 77.8%.
It was reported that in the catalytic reaction of bis(chel-
ate)nickel complexes the active species was in situ generated
by treatment of the nickel complexes with the organoalumi-
num compound under ethylene.[20c–20e,21] In our catalytic
systems, the bis(chelate)nickel complexes 5 and 6 may go
through a similar reaction in the presence of MAO and eth-
ylene as shown in Figure 5. Thus, active species I was gener-
ated by reaction of 5 or 6 with MAO and ethylene. The
active intermediate may be stabilized by a weak coordina-
tion of the RO group to the nickel center. Subsequently, the
ethylene molecule coordinates to the nickel center to carry
out the further reactions.
The nickel complexes 9–12 can catalyze ethylene dimer-
ization and trimerization in the presence of MAO, MMAO,
or Et2AlCl. However, using Et2AlCl as the co-catalyst re-
vealed higher activity. Therefore, a systematic investigation
of the catalytic behavior of complexes 9–12 was performed
using Et2AlCl as the co-catalyst (Table 2). In each case the
polymerization reaction gave a mixture of C4 and C6 spe-
cies. At 20 °C and 1 atm ethylene pressure for 0.5 h, the Al/
Ni molar ratio of 200:1 afforded the highest catalytic ac-
tivity for complexes 9–12 (9, 1.2ϫ103; 10, 1.21ϫ103; 11,
1.82ϫ103; and 12, 1.25ϫ103 kg/molh, respectively, En-
tries 2, 5, 8, and 17 in Table 2). Longer reaction times re-
sulted in decline of both turnover frequency and the pro-
Figure 4. ORTEP drawing of complex 14 with 30% probability
thermal ellipsoids. Selected bond lengths [Å] and bond angles [°]:
Fe(1)–N(1) 2.103(2), Fe(1)–N(2) 2.115(2), Fe(1)–Cl(1) 2.2405(11),
Fe(1)–Cl(2) 2.2264(10), Fe(1)···O(1) 3.812, N(2)–C(7) 1.287(3);
N(1)–Fe(1)–N(2) 86.08(9), N(1)–Fe(1)–Cl(1) 112.84(7), N(1)–
Fe(1)–Cl(2) 108.80(7), N(2)–Fe(1)–Cl(1) 108.49(7), N(2)–Fe(1)–
Cl(2) 113.78(7), Cl(1)–Fe(1)–Cl(2) 121.39(4).
Catalytic Properties of Complexes 5, 6, 9–16, 18, and 19
for Ethylene Oligomerization
It has been reported that bis(chelate)nickel complexes portion of C4 components (Entries 15 and 18 in Table 2).
can catalyze vinylic polymerization of norbornene, polyme- The decrease of the activity can be attributed to the deacti-
rization or oligomerization of ethylene or α-olefins in the vation of the active species during a longer reaction period.
presence of appropriate organoaluminum co-catalysts. In the reaction catalyzed by 9/Et2AlCl, augmentation of the
Some showed high catalytic activity and good selectiv- Al/Ni ratio resulted in enhancement of the proportion of
Table 1. Ethylene oligomerization with complexes 5 and 6.[a]
Activity[b]
C4 [%][c]
α-C4
C6 [%][c]
α-C6
[c]
[c]
Entry
Complex
Co-catalyst
Al/M
1
2
3
4
5
6
5
5
5
6
6
6
MAO
MMAO
MMAO
MAO
MMAO
MMAO
800
1000
1500
800
1000
1500
78
395
177
71
52
224
Ͼ99
Ͼ99
Ͼ99
97.4
Ͼ99
Ͼ99
24.9
77.8
65.7
51.5
67.8
58.6
2.6
35.7
[a] Conditions: 5 µmol of pre-catalyst, 30 mL of toluene, 1 atm ethylene, 0.5 h. [b] kg/molh. [c] Weight percent determined by GC analysis.
2480 Eur. J. Inorg. Chem. 2007, 2477–2487
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Iron, Cobalt and Nickel Complexes with N,N-Chelate Ligands
FULL PAPER
Figure 5. Possible mechanism for ethylene oligomerization catalyzed by 5 and 6/MAO.
Table 2. Ethylene oligomerization with complexes 9–12.[a]
Entry
Complex
Al/Ni
P [atm]
Time [h]
T [°C]
Activity[b]
C4 [%][c]
C6 [%][c]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
9
50
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
10
1
1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1
20
20
20
20
20
20
20
20
20
20
20
0
40
60
20
20
20
20
20
5.4
12
76.2
76.4
97.2
95.0
60.2
83.8
86.3
72.3
89.4
91.4
82.0
88.2
59.0
6.7
23.8
23.6
2.8
9
200
400
600
200
50
9
9
2.45
2.21
12.1
7.78
8.47
18.2
4.83
4.3
2.72
5.65
4.27
3.28
12.8
92
5.0
10
11
11
11
11
11
11
11
11
11
11
11
12
12
12
39.8
16.2
13.7
27.7
10.6
8.6
18.0
11.8
41.0
93.3
53.8
22.0
33.8
40.2
24.2
100
200
300
400
500
200
200
200
200
200
200
200
200
46.2
78.0
66.2
59.8
75.8
0.5
0.5
1
12.5
8.72
8.63
10
0.5
[a] Conditions: 5 µmol of pre-catalyst, Et2AlCl as co-catalyst, 30 mL of toluene (120 mL of toluene when determined under 10 atm
ethylene). [b] 102 kg/molh. [c] Weight percent determined by GC analysis.
C4 component in the products. While in the reaction cata- to the chelate ring size.[6] In our catalytic systems each of
lyzed by the 11/Et2AlCl system, the Al/Ni ratio of 400:1 the complexes 9–12 exhibited good catalytic activity under
gave the highest proportion of C4 component. A change the optimal conditions. Single-crystal X-ray diffraction re-
in the reaction temperature also dramatically affected the sults show that complex 12 has a similar skeletal structure
distribution of the polymerization products. We tested the and bond lengths and angles to that of the (β-diimine)nickel
catalytic reaction of the 11/Et2AlCl system with a 200:1 Al/ complex
[CH2{C(Me)=NAr}2]NiBr2
(Ar
=
2,6-
Ni ratio under 1 atm ethylene pressure at 0 °C, 20 °C, 40 °C, iPr2C6H3).[6a] Therefore, the relatively high catalytic activity
and 60 °C, respectively, and found that the proportion of C6 of 9–12 is most likely the result of the existence of the o-
component increased as the reaction temperature increased
(Entries 8 and 12–14 in Table 2). In addition, it was also
noted that an increase in ethylene pressure did not enhance
the catalytic activity of the catalysts in terms of unit pres-
sure (Entries 16 and 19 in Table 2).
It has been reported that (β-diimine)nickel and (8-quinol-
ylimine)nickel catalysts (Scheme 3) showed very low cata-
lytic activity for ethylene polymerization compared with (α-
diimine)nickel complexes and the difference was attributed Scheme 3.
Eur. J. Inorg. Chem. 2007, 2477–2487
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2481

L. Wang, C. Zhang, Z.-X. Wang
FULL PAPER
OR substituent on the phenylene ring of the ligands. The plex 15 (Entries 4 and 11 in Table 3). When MAO was used
oxygen atom of the OR group may stabilize the active inter- as co-catalyst, the Al/Co ratio of 800:1 resulted in the high-
mediate through coordination to the metal center during est catalytic activity for complex 15 (Entry 14 in Table 3),
the reaction (see below).
higher or lower Al/Co ratios leading to decrease of the cata-
The nature of aluminum co-catalysts greatly affected the lytic activity.
catalytic activities of the pre-catalysts and the distribution
of the products. The cobalt and iron complexes 13–16 were
inactive for ethylene oligomerization when Et2AlCl was
used as the co-catalyst. However, these cobalt and iron
complexes exhibited catalytic activities for ethylene oligo-
merization in the presence of MMAO or MAO (Table 3).
When MMAO was used as the co-catalyst, the complexes
revealed high catalytic activity (up to 8.01ϫ102 kg/molh,
Entry 12 in Table 3) and the polymerization products were
almost solely C4 species in most cases. When MAO was
used as the co-catalyst, complexes 13 and 14 showed very
low catalytic activity, while 15 and 16 exhibited moderate
activity (up to 24.6 kg/molh, Entry 14 in Table 3) and the
major polymerization products were C6 species. We also ex-
amined the effect of Al/M ratio for complexes 13 and 15,
respectively. When MMAO was used as co-catalyst, the
catalytic activity increased with the enhancement of Al/M
molar ratio until 1500:1 for complex 13 and 2000:1 for com-
It is very rare to see that iron and cobalt complexes with
a six-membered N,N-chelate ring exhibit high catalytic ac-
tivity for ethylene polymerization or oligomerization. Good
activity shown by complexes 13–16 upon activation with
MMAO is also attributed to the existence of o-OR substitu-
ents on the phenylene ring of the ligands.
The proportion of terminal olefins in the dimers or tri-
mers was also determined for the reactions catalyzed by
complexes 9–16 under representative reaction conditions
(Table 4). At 20 °C and 1 atm ethylene pressure for 0.5 h,
the reactions catalyzed by the 9–12/Et2AlCl (1:200) systems
gave relatively low α-butene and α-hexene proportions.
When activated with MMAO, each of the complexes 13–16
led to relatively high α-butene proportions, from 84.5 to
90.7%.
In order to understand the role of o-OR substituents on
the phenylene ring of the ligands in complexes 9–16, we
investigated the catalytic behavior of complex 18 whose li-
gand does not contain an extra donor group on the phenyl-
ene ring. The results are shown in Table 5. Compared with
complexes 11 and 12 under the same polymerization condi-
tions, complex 18 exhibited lower catalytic activity. Hence,
we think that the existence of o-RO substituents on the
phenylene ring in the nickel complexes may stabilize the
active intermediate through a weak coordination of the
oxygen atom to the metal center, which leads to the rise in
their catalytic activities (Scheme 4). Although the stabiliz-
ing action of the aluminum activator to the active interme-
diate is usually important, the intramolecular coordination
may provide extra stabilization in our catalytic systems. Bi-
anchini and co-workers also observed that complex IX exhi-
bits higher catalytic activity than complex X in ethylene
oligomerization upon activation with MAO and they
thought that the sulfur atom of the former may play an
active role (Scheme 5).[22] In addition, the activity of com-
plex 19 is also lower than that of complexes 15 or 16
whether MAO or MMAO was used as the co-catalyst. This
is possibly due to the existence of the same stabilization in
the 15 or 16/activator system.
Table 3. Ethylene oligomerization with complexes 13–16.[a]
Entry Complex Co-catalyst Al/M Activity[b] C4 [%][c] C6 [%][c]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
13
13
13
13
13
14
15
15
15
15
15
16
15
15
15
15
16
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MMAO
MAO
500
800
121
195
233
550
518
430
174
340
426
470
623
801
8.5
98.4
98.7
98.9
92.8
99.3
99.4
96.0
99.3
99.4
99.5
99.8
99.6
3.0
1.6
1.3
1.1
7.2
0.7
0.6
4.0
0.7
0.6
0.5
0.2
0.4
97.0
80.2
89.5
95.1
79.0
1000
1500
2000
1500
500
800
1000
1500
2000
2000
500
MAO
MAO
MAO
MAO
800
24.6
12.8
6
19.8
10.5
4.9
1000
1200
800
11
21.0
[a] Conditions: 5 µmol of pre-catalyst, 30 mL of toluene, 1 atm eth-
ylene, 20 °C, 0.5 h. [b] kg/molh. [c] Weight percent determined by
GC analysis.
Table 4. Oligomer composition catalyzed by pre-catalysts 9–16[a]
.
Entry
Complex
Co-catalyst
Al/Ni
T [°C]
Activity[b]
C4 [%][c]
α-C4 [%][c]
C6 [%][c]
α-C6 [%][c]
1
2
3
4
5
6
7
8
9
9
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
MMAO
MMAO
MMAO
MMAO
200
200
200
200
200
1500
1500
2000
2000
20
20
20
0
20
20
20
20
20
10.8
11.2
17.1
5.77
11.5
5.75
4.14
6.72
8.28
79.8
66.0
78.0
85.6
69.4
97.7
Ͼ99
Ͼ99
Ͼ99
26.4
18.6
29.7
36.6
32.0
90.7
86.4
84.5
90.0
20.2
34
22.0
14.4
30.6
2.3
32.4
29.5
44.3
38.2
26.4
28
10
11
11
12
13
14
15
16
[a] Conditions: 5 µmol of pre-catalyst, 30 mL of toluene, 1 atm ethylene, 0.5 h. [b] 102 kg/molh. [c] Weight percent determined by GC
analysis.
2482
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 2477–2487

Iron, Cobalt and Nickel Complexes with N,N-Chelate Ligands
Table 5. Ethylene oligomerization with complexes 18 and 19.[a]
FULL PAPER
Entry
Complex
Co-catalyst
Al/M
Activity[b]
C4 [%][c]
α-C4 [%][c]
C6 [%][c]
α-C6 [%][c]
1
2
3
4
5
6
7
18
18
18
19
19
19
19
Et2AlCl
Et2AlCl
Et2AlCl
MMAO
MMAO
MAO
100
200
500
800
2000
800
126
159
220
142
129
4
43.8
98.2
45.5
98.4
Ͼ99
81.6
37.8
11.6
58.5
29.5
65.7
98
56.2
1.8
54.5
1.6
23.7
14.5
12.3
56.4
18.4
62.2
MAO
2000
1.2
[a] Conditions: 5 µmol of pre-catalyst, 30 mL of toluene, 1 atm ethylene, 0.5 h. [b] kg/molh. [c] Weight percent determined by GC analysis.
vents were distilled under N2 from sodium/benzophenone (toluene,
n-hexane, thf, and Et2O) or CaH2 (CH2Cl2) and degassed prior to
use. NMR spectra were recorded with a Bruker av300 spectrometer
1
at ambient temperature. The chemical shifts of H and 13C NMR
spectra are referenced to internal solvent resonances. IR spectra
were recorded with a Bruker VECTOR-22 spectrometer. HRMS
data were determined with an Agilent6890/Micromass GCT-MS
spectrometer. Elemental analyses were performed by the Analytical
Center of the University of Science and Technology of China. The
magnetic moments of the paramagnetic complexes were determined
Scheme 4. Possible active intermediates of 9–12/Et2AlCl systems.
by the Evans NMR method.[23] Gas chromatographic analyses were
performed with a Carlo Erba Strumentazione gas chromatograph
equipped with a flame-ionization detector and a 30 m (0.25 mm
i.d., 0.25-µm film thickness) DM-1 silica capillary column or with
an HP5890 gas chromatograph equipped with a flame-ionization
detector and a 30 m (0.25 mm i.d., 0.25-µm film thickness) CAT-
7221 silica capillary column. High-purity ethylene was purchased
from Beijing Yanshan Petrochemical Co. and used as received.
Methylaluminoxane (MAO, 1.46  in toluene) and modified meth-
ylaluminoxane (MMAO, 1.93  in heptane) were purchased from
Akzo Nobel Corp. Et2AlCl was purchased from Fluka as a 1.90 
Scheme 5.
solution in hexane.
Preparations
Conclusions
o-PhCH2OC6H4NC (1): Compound 1 was prepared according to a
literature method.[12] 1H NMR (CDCl3): δ = 5.20 (s, 2 H, CH2),
6.91–7.01 (m, 2 H, Ph, C6H4), 7.26–7.49 (m, 7 H, Ph, C6H4) ppm.
We have synthesized novel anionic and neutral N,N-che-
late ligands and their iron, cobalt, and nickel complexes.
Single-crystal X-ray diffraction revealed that in bis(chelate)-
nickel complex 6 there are relatively weak bonding interac-
tions between the O atoms and the Ni atoms. Investigation
of catalytic behavior for ethylene oligomerization showed
that complexes 5 and 6 could catalyze ethylene oligomeriza-
tion with good activity in the presence of MAO or MMAO,
giving mainly C4 species. The nickel complexes with neutral
ligands exhibited high catalytic activity upon activation
with Et2AlCl. This relatively high activity compared with
previously reported (β-diimine)nickel complexes and ana-
IR (KBr): ν = 3072 (w), 3034 (w), 2947 (w), 2936 (w), 2876 (w),
˜
2127 (vs), 1593 (s), 1492 (vs), 1469 (m), 1454 (s), 1382 (m), 1301
(m), 1287 (vs), 1251 (vs), 1162 (m), 1109 (s), 1080 (w), 1040 (w),
1001 (s), 932 (w), 917 (m), 857 (m), 760 (m), 744 (vs), 695 (s), 617
(w) cm–1.
o-iPrOC6H4NC (2): Compound 2 was prepared according to the
same method as for 1 as a colorless oil, b.p. 100 °C/2 Torr. 1H
NMR (CDCl3): δ = 1.33 (d, J = 6.1 Hz, 6 H, iPr), 4.55 (sept, J =
6 Hz, 1 H, CH), 6.80–6.91 (m, 2 H, C6H4), 7.21–7.27 (m, 2 H,
C H ) ppm. IR (liquid film): ν = 3076 (w), 2981 (s), 2935 (m), 2125
˜
6
4
logues is attributed to the stabilizing action of the o-OR (vs), 1596 (s), 1492 (vs), 1455 (m), 1386 (m), 1376 (m), 1286 (s),
1260 (s), 1176 (w), 1162 (m), 1139 (m), 1117 (s), 1043 (m), 952 (s),
group on the phenylene ring of the ligands to the active
species through coordination of the oxygen atom to the
metal center. The iron and cobalt complexes bearing neutral
ligands also exhibited good catalytic activity upon acti-
867 (w), 752 (s) cm–1.
[LiN(o-PhCH2OC6H4){C(SiMe3)CHC5H4N-2}]2 (3): To a stirred
solution
of
[Li(TMEDA){2-CH(SiMe3)C5H4N}]
(3.84 g,
vation with MMAO. However, when MAO was used as the 13.38 mmol) in diethyl ether (20 mL) was added compound 1
(2.80 g, 13.40 mmol) at –30 °C. The resultant solution was warmed
to room temperature and stirred overnight. The mixture was fil-
tered and the precipitate was washed with diethyl ether (2ϫ5 mL).
The solid was dried in vacuo to give a yellow powder of 3 (4.21 g,
82.7%), m.p. 181–182 °C. 1H NMR (C6D6): δ = 0.48 (s, 9 H,
SiMe3), 4.42 (d, J = 11.7 Hz, 1 H, CH2), 4.58 (d, J = 11.4 Hz, 1
H, CH2), 5.62 (s, 1 H, CH), 6.48–6.53 (m, 1 H, Ar), 6.57 (d, J =
8.4 Hz, 1 H, Ar), 6.66 (d, J = 7.8 Hz, 1 H, Ar), 6.92–7.22 (m, 6 H,
co-catalyst, the iron and cobalt complexes showed relatively
low activities.
Experimental Section
General Procedure: All air-sensitive manipulations were performed
under N2 using standard Schlenk and vacuum-line techniques. Sol-
Eur. J. Inorg. Chem. 2007, 2477–2487
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2483

L. Wang, C. Zhang, Z.-X. Wang
FULL PAPER
Ar), 7.42 (d, J = 7.8 Hz, 1 H, Ar), 7.98–8.01 (m, 1 H, Ar) ppm.
13C NMR (C6D6): δ = 2.60, 70.17, 110.49, 110.88, 114.93, 119.02,
121.95, 122.38, 125.24, 128.22, 128.57, 128.81, 135.52, 136.35,
1.01, 70.29, 109.88, 112.66, 118.26, 120.78, 122.16, 122.32, 122.65,
127.22, 127.72, 128.53, 134.31, 135.63, 137.55, 147.37, 150.62,
152.84, 159.30 ppm. IR (liquid film): ν = 3064 (w), 3036 (w), 2953
˜
147.24, 148.87, 151.64, 157.50, 168.08 ppm. C23H25LiN2OSi (w), 2897 (vw), 1590 (s), 1577 (vs), 1540 (vs), 1507 (m), 1463 (m),
(380.484): calcd. C 72.60, H 6.62, N 7.36; found C 71.92, H 6.62,
N 7.30.
1450 (m), 1411 (w), 1360 (m), 1301 (w), 1259 (s), 1217 (s), 1158
(w), 1109 (w), 1046, 1024 (w), 911 (vw), 847 (s), 804 (m), 738 (s),
694 (m) cm–1. C23H26N2OSi (374.551): calcd. C 73.76, H 7.00, N
7.48; found C 73.46, H 7.10, N 7.40.
[LiN(o-iPrOC6H4){C(SiMe3)CHC5H4N-2}]2 (4): Complex 4 was
prepared according to the same method as for 3. To a solution of
[Li(TMEDA){2-CH(SiMe3)C5H4N}] (3.55 g, 12.37 mmol) in di-
ethyl ether (20 mL) was added compound 2 (2.00 g, 12.42 mmol) at
–30 °C. The mixture was warmed to room temperature and stirred
overnight. The resultant precipitate was washed with diethyl ether
and dried in vacuo to afford a yellow powder of 4 (3.85 g, 93.5%),
o-iPrOC6H4NHC(SiMe3)CHC5H4N-2 (8): Compound 8 was pre-
pared according to a procedure similar to that of 7. Treatment of
4 (1.412 g, 4.25 mmol) with Et3NH+Cl– (0.60 g, 4.36 mmol) in tolu-
ene afforded, after workup, compound 8 (1.386 g, 100%) as a yel-
1
lowish oil. H NMR (CDCl3): δ = 0.13 (s, 9 H, SiMe3), 1.31 (d, J
1
m.p. 242–243 °C. H NMR (C6D6): δ = 0.46 (s, 9 H, SiMe3), 0.97
= 6 Hz, 6 H, iPr), 4.47 (sept, J = 6 Hz, 1 H, iPr), 5.59 (s, 1 H, CH),
6.74–6.85 (m, 4 H, Ar), 6.92–6.98 (m, 2 H, Ar), 7.40–7.46 (m, 1 H,
Ar), 8.32–8.34 (m, 1 H, Ar), 11.58 (s, 1, NH) ppm. 13C NMR
(CDCl3): δ = 1.04, 22.39, 71.36, 109.77, 115.16, 118.19, 120.66,
121.50, 122.22, 122.26, 135.33, 135.58, 147.19, 149.33, 152.39,
(d, J = 6 Hz, 3 H, iPr), 1.35 (d, J = 6 Hz, 3 H, iPr), 4.36 (heptet,
J = 6 Hz, 1 H, iPr), 5.81 (s, 1 H, CH), 6.68–6.75 (m, 2 H, Ar), 6.84
(d, J = 8.4 Hz, 1 H, Ar), 7.01–7.06 (m, 1 H, Ar), 7.14–7.17 (m, 2
H, Ar), 7.21–7.27 (m, 1 H, Ar), 8.40 (dd, J = 1.2, 5.1 Hz, 1 H, Ar)
ppm. 13C NMR (C6D6): δ = 2.40, 20.43, 22.01, 70.29, 110.85,
110.93, 115.39, 119.21, 121.71, 123.20, 125.70, 135.86, 147.17,
149.42, 150.43, 157.97, 169.99 ppm. C19H25LiN2OSi (332.441):
calcd. C 68.64, H 7.58, N 8.43; found C 68.21, H 7.57, N 8.26.
159.22 ppm. IR (liquid film): ν = 3065 (w), 3007 (w), 2975 (m),
˜
2904 (w), 1590 (vs), 1578 (vs), 1540 (vs), 1505 (m), 1463 (m), 1411
(w), 1361 (m), 1301 (w), 1258 (vs), 1218 (s), 1160 (w), 1150 (w),
1118 (m), 1044 (vw), 956 (vw), 912 (vw), 848 (s), 802 (m), 739 (m),
687 (w) cm–1. C19H26N2OSi (326.508): calcd. C 69.89, H 8.03, N
8.58; found C 69.72, H 8.13, N 8.46.
Ni[N(o-PhCH2OC6H4){C(SiMe3)CHC5H4N-2}]2 (5): To a stirred
suspension of (dme)NiCl2 (0.15 g, 0.684 mmol) in thf (5 mL) was
added compound 3 (0.26 g, 0.684 mmol) at about –80 °C. The re-
sultant mixture was warmed to room temperature and stirred over-
night. Volatiles were removed in vacuo and the residue was ex-
tracted with Et2O. The diethyl ether solution was filtered and the
filtrate concentrated in vacuo to form dark red-brown crystals of 5
[NiCl2{N(o-PhCH2OC6H4)=C(SiMe3)CH2C5H4N-2}] (9): To
a
stirred suspension of (dme)NiCl2 (0.35 g, 1.59 mmol) in thf (5 mL)
was added 7 (0.60 g, 1.60 mmol) in thf (10 mL) at 0 °C. The mix-
ture was warmed to room temperature and stirred overnight. Vola-
tiles were removed in vacuo and the yellow solids were washed with
Et2O (2ϫ2 mL). The solid was dissolved in CH2Cl2 and filtered
(0.25 g, 91%), m.p. 169–170 °C. IR (KBr): ν = 3088 (vw), 3053 (w),
˜
3024 (w), 2951 (w), 2894 (vw), 1600 (m), 1572 (w), 1557 (w), 1501 through Celite. Toluene (10 mL) was added to the filtrate. Concen-
(m), 1481 (s), 1469 (vs), 1453 (m), 1418 (m), 1384 (vs), 1314 (w), tration of the solution in vacuo gave yellow-green crystals of com-
1277 (m), 1260 (m), 1246 (m), 1208 (m), 1189 (m), 1153 (m), 1113 plex 9 (0.59 g, 74.2%), m.p. 192–194 °C. IR (KBr): ν = 3057 (s),
˜
(w), 1102 (vw), 1022 (w), 1004 (w), 847 (m), 783 (w), 751 (w), 732 3036 (m), 2951 (m), 2897 (vw), 2875 (m), 1603 (s), 1590 (m), 1579
(m), 693 (w) cm–1. C46H50N4NiO2Si2 (805.779): calcd. C 68.57, H
6.25, N 6.95; found C 68.77, H 6.43, N 6.90. HRMS (EI): calcd. for
(m), 1488 (vs), 1452 (s), 1442 (s), 1397 (w), 1377 (w), 1347 (w),
1320 (m), 1288 (m), 1267 (m), 1254 (s), 1235 (s), 1207 (m), 1195
C46H50N4NiO2Si2 [M]+ 804.2826; found 804.2820. µeff = 3.77 BM. (m), 1161 (m), 1115 (m), 1063 (m), 1045 (m), 1018 (s), 897 (w), 871
(s), 846 (vs), 791 (w), 758 (vs), 736 (s), 725 (s), 692 (m), 651 (w),
Ni[N(o-iPrOC6H4){C(SiMe3)CHC5H4N-2}]2 (6): Complex 6 was
prepared according to a procedure similar to that of 5. Reaction
of (dme)NiCl2 (0.195 g, 0.886 mmol) with 4 (0.30 g, 0.904 mmol)
in thf gave, after workup, dark red-brown crystals of 6 (0.295 g,
634 (w) cm–1. C23H26Cl2N2NiOSi (504.15): calcd. C 54.80, H 5.20,
N5.56; found C 55.01, H 5.27, N 5.45. HRMS (EI): calcd. for
C23H26ClN2NiOSi [M – Cl]+ 467.0856; found 467.1482. µeff
=
3.82 BM.
92%), m.p. 180–182 °C. IR (KBr): ν = 3052 (vw), 2974 (w), 2948
˜
(w), 2894 (w), 1599 (m), 1572 (w), 1558 (w), 1503 (m), 1480, 1469
(vs), 1420 (s), 1369 (vs), 1309 (w), 1289 (s), 1265 (s), 1244 (m), 1207
[NiCl2{N(o-iPrOC6H4)=C(SiMe3)CH2C5H4N-2}] (10): Complex 10
was prepared according to a procedure similar to that for 9. Treat-
(m), 1154 (m), 1138 (m), 1117 (m), 1048 (w), 1005 (w), 948 (w), ment of (dme)NiCl2 (0.27 g, 1.23 mmol) with 8 (0.40 g, 1.23 mmol)
846 (s), 786 (s), 740 (s), 684 (vw), 621 (vw) cm–1. C38H50N4NiO2Si2
(709.694): calcd. C 64.31, H 7.10, N 7.89; found C 64.39, H 7.03,
in thf formed, after similar workup, purple crystals of 10 (0.42 g,
75.1%), m.p. 182–184 °C. IR (KBr): ν = 3104 (vw), 3068 (w), 3029
˜
N 8.01. HRMS (EI): calcd. for C38H50N4NiO2Si2 [M]+ 708.2826; (w), 2977 (m), 2931 (w), 2896 (w), 1605 (m), 1592 (s), 1569 (w),
found 708.2823. µeff = 3.70 BM.
1485 (vs), 1446 (s), 1417 (w), 1372 (w), 1358 (w), 1283 (vw), 1250
(s), 1203 (w), 1176 (w), 1159 (w), 1139 (w), 1120 (w), 1095 (m),
1067 (w), 1030 (w), 955 (w), 933 (w), 924 (w), 853 (vs), 803 (w), 765
(vs), 700 (w), 680 (vw) cm–1. C19H26Cl2N2NiOSi (456.107): calcd. C
50.03, H 5.75, N 6.14; found C 49.93, H 5.74, N 6.14. HRMS (EI):
calcd. for C19H26ClN2NiOSi [M – Cl]+ 419.0856; found 419.0849.
µeff = 3.88 BM.
o-PhCH2OC6H4NHC(SiMe3)CHC5H4N-2 (7): To a stirred solu-
tion of 3 (1.488 g, 3.92 mmol) in toluene (20 mL) was added
Et3NH+Cl– (0.54 g, 3.93 mmol) at 0 °C. The resultant mixture was
warmed to room temperature and stirred for 20 h. The solution
was filtered and volatiles were removed from the filtrate in vacuo
to afford 7 as a yellowish oil (1.464 g, 100%). The oil was dissolved
in hexane and cooled to –30 °C to form a pale yellow precipitate.
[NiBr2{N(o-PhCH2OC6H4)=C(SiMe3)CH2C5H4N-2}] (11): To a
The precipitate was filtered at –30 °C and then dried in vacuo to
afford a pale yellow solid, m.p. 81–83 °C. H NMR (CDCl3): δ = added 7 (0.25 g 0.67 mmol) in thf (10 mL) at 0 °C. The resultant
0.20 (s, 9 H, SiMe3), 5.17 (s, 2 H, CH2), 5.69 (s, 1 H, CH), 6.84– mixture was warmed to room temperature and stirred overnight.
stirred suspension of NiBr2 (0.14 g, 0.64 mmol) in thf (5 mL) was
1
6.95 (m, 4 H, Ar), 7.02 (d, J = 8.1 Hz, 1 H, Ar), 7.10 (d, J = 7.5 Hz,
1 H, Ar), 7.29–7.37 (m, 3 H, Ar), 7.48–7.55 (m, 3 H, Ar), 8.23–
The color of the solution changed from straw-yellow to red. Vola-
tiles were removed in vacuo and the red solid residue was dissolved
8.25 (m, 1 H, Ar), 11.77 (s, 1 H, NH) ppm. 13C NMR (CDCl3): δ = in CH2Cl2. After filtration through Celite, the solvent was removed
2484
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Iron, Cobalt and Nickel Complexes with N,N-Chelate Ligands
FULL PAPER
from the filtrate and the solid was washed with diethyl ether
(2ϫ2 mL) to give red crystalline 11 (0.302 g, 77.4%), m.p. 189–
calcd. C 54.77, H 5.20, N 5.55; found C 54.99, H 5.28, N 5.65.
HRMS (EI): calcd. for C23H26Cl2CoN2OSi [M]+ 503.0523; found
503.0515. µeff = 6.46 BM.
191 °C. IR (KBr): ν = 3056 (m), 2953 (m), 2860 (m), 1604 (m),
˜
1593 (m), 1574 (w), 1486 (s), 1444 (s), 1407 (w), 1372 (w), 1348 (w),
1315 (w), 1285 (w), 1253 (s), 1239 (m), 1205 (w), 1161 (w), 1112
(m), 1067 (w), 1040 (w), 1020 (m), 942 (vw), 921 (vw), 904 (vw),
851 (vs), 801 (w), 766 (s), 735 (s), 695 (m), 655 (vw), 632 (w), 613
(vw) cm–1. C23H26Br2N2NiOSi (593.052): calcd. C 46.58, H 4.42,
N 4.72; found C 46.66, H 4.39, N 4.70. HRMS (EI): calcd. for
[CoCl2{N(o-iPrOC6H4)=C(SiMe3)CH2C5H4N-2}] (16): Complex
16 was prepared according to a procedure similar to that for 15.
Treatment of CoCl2 (0.208 g, 1.6 mmol) with
8 (0.532 g,
1.63 mmol) in thf afforded, after workup, complex 16 (0.72 g, 99%)
as blue crystals, m.p. 199–201 °C. IR (KBr): ν = 3072 (w), 3027
˜
(m), 2978 (m), 2941 (w), 2897 (w), 1605 (m), 1592 (s), 1572 (w),
1488 (vs), 1445 (s), 1379 (m), 1346 (w), 1300 (w), 1280 (w), 1250
(vs), 1207 (w), 1175 (w), 1158 (w), 1142 (w), 1118 (s), 1067 (vw),
C23H26Br2N2NiOSi [M]+ 589.9535; found 589.9540. µeff
=
3.86 BM.
[NiBr2{N(o-iPrOC6H4)=C(SiMe3)CH2C5H4N-2}] (12): Complex 12 1039 (w), 1028 (w), 956 (m), 937 (w), 845 (vs), 774 (s), 760 (vs), 736
was prepared according to the same route as for 11. Thus, reaction
of NiBr2 (0.15 g, 0.68 mmol) with 8 (0.23 g, 0.70 mmol) in thf gave,
after similar workup, complex 12 (0.30 g, 78.9%) as red crystals,
(w), 651 (w), 643 (w) cm–1. C19H26Cl2CoN2OSi (456.347): calcd. C
50.01, H 5.74, N 6.14; found C 49.99, H 5.58, N 6.13. HRMS (EI):
calcd. for C19H26Cl2CoN2OSi [M]+ 455.0523; found 455.0523. µeff
m.p. 209–211 °C. IR (KBr): ν = 3103 (w), 3070 (w), 3028 (w), 2974 = 6.54 BM.
˜
(m), 2934 (w), 2903 (w), 1595 (s), 1569 (vw), 1488 (vs), 1445 (s),
o-MeC6H4NHC(SiMe3)CHC5H4N-2 (17): To a solution of [Li-
1422 (w), 1384 (m), 1375 (m), 1351 (w), 1301 (m), 1280 (m), 1252
(vs), 1207 (w), 1174 (w), 1158 (w), 1141 (w), 1118 (s), 1071 (vw),
1039 (w), 1031 (w), 956 (m), 846 (vs), 772 (s), 758 (s), 705 (vw), 677
(vw), 643 (w) cm–1. C19H26Br2N2NiOSi (545.01): calcd. C 41.87, H
4.81, N 5.14; found C 41.97, H 4.80, N 5.16. HRMS (EI): calcd.
(TMEDA)][2-CH(SiMe3)C5H4N] (1.07 g, 3.73 mmol) in diethyl
ether (15 mL) was added 2-methylphenyl isocyanide (0.44 g
3.76 mmol) at –30 °C. The resultant mixture was warmed to room
temperature and stirred overnight to give a dark red solution. Vola-
tiles were removed in vacuo and thf (10 mL) was added. To the
solution H2O (0.068 g) was added at 0 °C and the mixture stirred
for 10 min to give a greenish-yellow solution. The solvent was re-
moved in vacuo and n-hexane was added. The mixture was filtered
and the solvent was removed from the filtrate in vacuo. The residue
was distilled under reduced pressure to give a pale yellow oil
(0.80 g, 76%) as a mixture of (Z) and (E) isomers [(Z)/(E) = 1:3.4],
b.p. 130 °C/0.1 Torr. 1H NMR (C6D6, 300 MHz): (E) isomer: δ =
0.24 (s, 9 H, SiMe3), 2.51 (s, 3 H, Me), 5.75 (s, 1 H, =CH), 6.55
(d, J = 9.9 Hz, 1 H, C6H4), 6.99–7.33 (m, 5 H, C6H4, C5H4N),
for C19H26Br2N2NiOSi [M]+ 541.9535; found 541.9536. µeff
=
4.20 BM.
[FeCl2{N(o-PhCH2OC6H4)=C(SiMe3)CH2C5H4N-2}] (13): Com-
plex 13 was prepared according to a procedure similar to that for
11. Treatment of FeCl2·4H2O (0.188 g, 0.945 mmol) with
7
(0.358 g, 0.957 mmol) in thf afforded, after similar workup, a yel-
low crystalline complex (0.3 g, 63%) as yellow crystals, m.p.189–
191 °C. IR (KBr): ν = 3065 (m), 3030 (m), 2956 (m), 1593 (s), 1569
˜
(w), 1491 (s), 1484 (m), 1445 (s), 1381 (w), 1344 (w), 1280 (w), 1253
(vs), 1203 (w), 1162 (w), 1115 (m), 1063 (w), 1022 (m), 850 (vs), 7.62–7.68 (m, 1 H, C5H4N), 8.49–8.51 (m, 1 H, C5H4N), 11.76 (s,
809 (w), 773 (s), 761 (vs), 730 (m), 692 (m), 675 (w), 639 (w), 615 1 H, NH) ppm. (Z) isomer: δ = 0.34 (s, 9 H, SiMe3), 2.16 (s, 3 H,
(w) cm–1. C23H26Cl2FeN2OSi (501.301): calcd. C 55.11, H 5.23, N
5.59; found C 54.89, H 5.10, N 5.54. HRMS (EI): calcd. for
C23H26Cl2FeN2OSi [M]+ 500.0541; found 500.0550. µeff = 7.00 BM.
Me), 5.52 (d, J = 10.2 Hz, 1 H, =CH) ppm, aromatic ring region
overlaps that of (E) isomer. IR (liquid film): ν = 3006 (w), 2953
˜
(m), 2897 (w), 1643 (m), 1622 (s), 1584 (vs), 1539 (s), 1496 (m),
1469 (s), 1410 (m), 1352 (s), 1303 (m), 1250 (s), 1217 (s), 1149 (s),
1110 (w), 1076 (w), 1045 (w), 993 (w), 934 (vw), 912 (w), 848 (vs),
801 (m), 758 (s), 729 (m) cm–1. HRMS (EI): calcd. for C17H22N2Si
[M]+ 282.1552; found 282.1546.
[FeCl2{N(o-iPrOC6H4)=C(SiMe3)CH2C5H4N-2}] (14): Complex 14
was prepared according to a procedure similar to that for 11. Treat-
ment of FeCl2·4H2O (0.191 g, 0.96 mmol) with
8 (0.302 g,
0.926 mmol) in thf formed, after similar workup, yellow crystalline
complex 14 (0.296 g, 71.4%) as yellow crystals, m.p.178–180 °C. IR
[NiBr2{N(o-MeC6H4)=C(SiMe3)CH2C5H4N-2}] (18): To a suspen-
(KBr): ν = 3102 (m), 3067 (m), 3027 (m), 2979 (s), 2899 (m), 1604 sion of NiBr2 (0.195 g, 0.89 mmol) in thf (5 mL) was added a solu-
˜
(m), 1585 (m), 1568 (w), 1484 (vs), 1444 (s), 1382 (w), 1374 (w), tion of 17 (0.25 g 0.89 mmol) in thf (10 mL) at 0 °C. The resultant
1348 (w), 1279 (w), 1249 (s), 1201 (w), 1157 (w), 1141 (w), 1118
(m), 1063 (w), 1037 (w), 1022 (w), 953 (w), 934 (w), 854 (vs), 772
mixture was warmed to room temperature and stirred overnight.
Volatiles were removed in vacuo and the residual solid was dis-
(s), 730 (m), 696 (w), 676 (vw), 640 (w), 607 (w) cm–1. solved in CH2Cl2 and filtered. The solvent was removed in vacuo
C19H26Cl2FeN2OSi (453.259): calcd. C 50.35, H 5.78, N 6.18;
from the filtrate and the residue washed with thf (3ϫ2 mL) to af-
ford purple-red crystals of 18 (0.27 g, 61%), m.p. 274–276 °C. IR
found
C 50.29, H 5.70, N 6.08. HRMS (EI): calcd. for
C19H26Cl2FeN2OSi [M]+ 452.0541; found 452.0527. µeff = 6.93 BM.
(KBr): ν = 3102 (w), 3047 (w), 2956 (w), 2917 (w), 1599 (s), 1567
˜
(w), 1482 (s), 1443 (s), 1411 (m), 1359 (w), 1286 (w), 1254 (s), 1191
(w), 1113 (m), 1070 (w), 1041 (w), 1029 (w), 849 (vs), 796 (w), 766
(vs), 718 (w), 703 (w) cm–1. C17H22Br2N2NiSi (500.957): calcd. C
40.76, H 4.43, N 5.59; found C 40.87, H 4.49, N 5.78. HRMS (EI):
[CoCl2{N(o-PhCH2OC6H4)=C(SiMe3)CH2C5H4N-2}] (15): To a
solution of CoCl2 (0.067 g, 0.515 mmol) in thf (5 mL) was added 7
(0.196 g, 0.524 mmol) in thf (10 mL) at 0 °C while stirring. The
mixture was warmed to room temperature and stirred overnight.
The color of the solution changed to blue. Volatiles were removed
in vacuo and the residue was washed with diethyl ether (2ϫ2 mL).
The solid was dissolved in CH2Cl2 and then filtered. Toluene was
added to the solution and then concentrated to afford 15 (0.16 g,
calcd. for C17H22Br2N2NiSi [M]+ 497.9272; found 497.9263. µeff
=
3.95 BM.
[CoCl2{N(o-MeC6H4)=C(SiMe3)CH2C5H4N-2}] (19): To a suspen-
sion of CoCl2 (0.092 g, 0.71 mmol) in thf (5 mL) was added a solu-
tion of 17 (0.2 g 0.71 mmol) in thf (10 mL) at 0 °C. The resultant
mixture was warmed to room temperature and stirred overnight.
Volatiles were removed in vacuo and the residue was dissolved in
CH2Cl2 and filtered. The solvent was removed in vacuo from the
60.8%) as blue crystals, m.p. 196–198 °C. IR (KBr): ν = 3072 (w),
˜
3028 (m), 2953 (m), 2897 (w), 1596 (s), 1568 (w), 1492 (s), 1446 (s),
1381 (w), 1347 (w), 1279 (w), 1254 (vs), 1205 (w), 1163 (w), 1116
(w), 1067 (vw), 1039 (w), 1026 (m), 933 (vw), 850 (vs), 774 (s), 763
(vs), 730 (w), 692 (w), 643 (vw) cm–1. C23H26Cl2CoN2OSi (504.39): filtrate and the residue washed with thf (2 mLϫ3) to give a blue
Eur. J. Inorg. Chem. 2007, 2477–2487
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2485

L. Wang, C. Zhang, Z.-X. Wang
FULL PAPER
Table 6. Details of the X-ray structure determinations of compounds 3, 6, 12, and 14.
3
6
12
14
Empirical formula
Formula mass
Crystal system
Space group
a [Å]
C46H50Li2N4O2Si2
760.96
monoclinic
P21/c
11.1979(19)
23.748(4)
17.346(3)
107.884(3)
4389.9(13)
4
C38H50N4NiO2Si2
709.71
monoclinic
P21/n
19.736(3)
11.1103(15)
19.857(3)
116.108(2)
3909.8(9)
4
C19H26Br2N2NiOSi
545.04
monoclinic
P2(1)/c
9.1529(9)
10.9906(11)
23.504(2)
95.151(2)
2354.9(4)
4
C19H26Cl2FeN2OSi
453.26
monoclinic
P2(1)/c
9.1215(12)
10.8936(16)
23.224(3)
94.339(2)
2301.1(5)
4
b [Å]
c [Å]
β [°]
V [Å3]
Z
Dcalcd. [g/cm3]
F(000)
1.151
1616
0.121
1.206
1512
0.594
1.537
1096
4.278
1.308
944
0.950
µ [mm–1
]
θ range for data collection [°]
No. of reflections collected
No. of independent reflections
1.50 to 25.00
18479
1.94 to 26.39
21552
1.74 to 26.46
12793
2.07 to 26.40
12689
7713 (Rint = 0.0942)
7978 (Rint = 0.0771)
4847 (Rint = 0.0336)
4711 (Rint = 0.0355)
(Rint
)
No. of data/restraints/parameters 7713/0/511
7978/0/434
0.988
4847/6/240
0.997
4711/6/240
1.004
Goodness of fit on F2
0.995
R1 = 0.0673; wR2 =
0.1324
R1 = 0.0542; wR2 =
0.1290
R1 = 0.0377; wR2 =
0.0758
R1 = 0.0409; wR2 =
0.0876
Final R indices[a] [IϾ2σ(I)]
R1 = 0.1926; wR2 =
0.1842
R1 = 0.1481; wR2 =
0.1688
R1 = 0.0764; wR2 =
0.0896
R1 = 0.0787; wR2 =
0.1038
R indices (all data)
Largest difference peak/hole
0.356/–0.423
1.056/–0.389
0.811/–0.690
0.338/–0.251
[eÅ–3
]
2
2
[a] Σ||Fo| – |Fc||/Σ|Fo|; wR2 = [Σw(Fo – Fc /Σw(Fo4)]1/2
.
powder of 19 (0.19 g, 65%), m.p. 255–260 °C. IR (KBr): ν = 3100
at constant pressure. Toluene (120 mL) containing the pre-catalyst
was transferred into the fully dried reactor under N2. The required
amount of co-catalyst was injected into the reactor through a sy-
ringe. As the desired temperature was reached, the reactor was pres-
surized to 10 atm. After stirring for 30 min, the reactor was cooled
˜
(w), 3071 (w), 3026 (w), 2979 (w), 2952 (w), 1604 (m), 1587 (s),
1477 (m), 1442 (s), 1346 (w), 1255 (m), 1157 (w), 1112 (w), 1061
(w), 1027 (w), 849 (vs), 796 (w), 774 (s), 762 (s), 719 (w) cm–1.
C17H22Cl2CoN2Si (412.294): calcd. C 49.52, H 5.38, N 6.79; found
C 49.23, H 5.48, N 6.75. HRMS (EI): calcd. for C17H22Cl2CoN2Si to about –10 °C and depressurized. The contents were transferred
[M]+ 411.0261; found 411.0266. µeff = 6.48 BM.
into a cooled flask and then 10% HCl solution (30 mL) was added.
The mixture was worked up and analyzed using the same procedure
as described above for the 1 atm reaction.
Crystal Structure Determination: Crystals were mounted in Linde-
mann capillaries under N2. Diffraction data were collected with a
Siemens CCD area-detector at 294(2) K with graphite-monochro-
mated Mo-Kα radiation (λ = 0.71073 Å). A semi-empirical absorp-
tion correction was applied to the data. The structures were solved
by direct methods using SHELXS-97[24] and refined against F2 by
full-matrix least squares using SHELXL-97.[25] Crystal data and
experimental details of the structure determinations are listed in
Table 6. CCDC-632191 to -632194 contain the supplementary crys-
tallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgments
We thank the National Natural Science Foundation of China
(Grant No. 20272056) for support. We are also grateful to Pro-
fessor W.-H. Sun of the Institute of Chemistry, The Chinese Acad-
emy of Sciences, for his kind help in determining the catalytic ethyl-
ene oligomerization activities of the complexes and Professors H.-
B. Song and H.-G. Wang of Nankai University for single-crystal
X-ray structure determinations.
Catalytic Oligomerization of Ethylene: The oligomerization with
1 atm ethylene was carried out in a Schlenk tube. In a dried Schlenk
tube was placed the pre-catalyst (5 µmol) and then the Schlenk tube
was back-filled three times with N2 and twice with ethylene. Tolu-
ene (30 mL) was added to the Schlenk tube and then the appropri-
ate co-catalyst solution was added through a syringe. The reaction
mixture was vigorously stirred at the given temperature under
1 atm ethylene. After the desired period of time (30 min or 60 min),
the reaction was terminated by cooling the system to about –10 °C
and then adding 10% HCl solution (30 mL). About 1 mL of the
organic layer was dried with anhydrous Na2SO4 in a sealed Schlenk
tube at about –10 °C for gas chromatographic analysis. To the re-
maining solution was added ethanol (100 mL), no polymer was ob-
served. The oligomerization with 10 atm ethylene was carried out
in a stainless steel autoclave (0.25 L capacity) equipped with gas
ballast through a solenoid valve for continuous feeding of ethylene
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Iron, Cobalt and Nickel Complexes with N,N-Chelate Ligands
FULL PAPER
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