Bimetallic phenylene-bridged Cp/amide titanium complexes and their olefin polymerization

Article abstract of DOI:10.1039/b710017e

Bimetallic dichlorotitanium complexes, {2,6-[η⁵-2,5-Me ₂C₅H₂]₂-4-R-C₆H ₂N-N}{Ti(iv)Cl₂}₂ (7, R = Me; 8, R = F) and 4,4′-A[{2-(η⁵-2,3,5-Me₃C₅H)C ₆H₃NC₆H₁₁-κN}Ti(iv)Cl ₂]₂ (18, A = CH₂; 19, A = O; 20, A = ortho-C₆H₄) are prepared via a key step of the Suzuki-coupling reaction of 2-dihydroxyboryl-3-methyl-2-cyclopenten-1-one (1) with dibromo-compounds. The solid state structure of 7 was determined by X-ray crystallography. Complexes 7 and 8 are not active for ethylene/1-hexene copolymerization. Meanwhile, the complexes 18-20 are highly active and their activities are higher than that of the mononuclear analogue, {2-(η⁵-2,3,5-Me₃C₅H)C₆H ₃NC₆H₁₁-κN}Ti(iv)Cl₂ (21). The molecular weights of the polymers obtained with the bimetallic complexes 18-20 are higher than that of the polymer obtained using 21. Slightly higher contents of long-chain-branching are observed for the copolymers obtained using the bimetallic system. The Royal Society of Chemistry.

Full text of DOI:10.1039/b710017e

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www.rsc.org/dalton | Dalton Transactions
Bimetallic phenylene-bridged Cp/amide titanium complexes and their
olefin polymerization†‡
Sang Hoon Lee,a Chun Ji Wu,a Ui Gab Joung,a Bun Yeoul Lee*a and Jinil Parkb
Received 2nd July 2007, Accepted 2nd August 2007
First published as an Advance Article on the web 20th August 2007
DOI: 10.1039/b710017e
5
Bimetallic dichlorotitanium complexes, {2,6-[g -2,5-Me2C5H2]2-4-R-C6H2N-lN}{Ti(IV)Cl2}2 (7, R =
5
Me; 8, R = F) and 4,4ꢀ-A[{2-(g -2,3,5-Me3C5H)C6H3NC6H11-jN}Ti(IV)Cl2]2 (18, A = CH2; 19, A = O;
20, A = ortho-C6H4) are prepared via a key step of the Suzuki-coupling reaction of 2-dihydroxyboryl-
3-methyl-2-cyclopenten-1-one (1) with dibromo-compounds. The solid state structure of 7 was
determined by X-ray crystallography. Complexes 7 and 8 are not active for ethylene/1-hexene
copolymerization. Meanwhile, the complexes 18–20 are highly active and their activities are higher than
5
that of the mononuclear analogue, {2-(g -2,3,5-Me3C5H)C6H3NC6H11-jN}Ti(IV)Cl2 (21). The
molecular weights of the polymers obtained with the bimetallic complexes 18–20 are higher than that of
the polymer obtained using 21. Slightly higher contents of long-chain-branching are observed for the
copolymers obtained using the bimetallic system.
Introduction
Bimetallic catalysis has been commonly observed in metalloen-
zymes and scientific activities have been devoted to mimicking its
advantageous characteristics by constructing bimetallic systems.1
Marks et al. have reported dinuclear homogeneous Ziegler–Natta
(1)
catalysts which showed some advantages over its mononuclear
counterpart in some olefin polymerizations.2 We also developed
bimetallic Zn complexes wherein high turnover numbers and
high molecular weights were achieved in CO2/(cyclohexene oxide)
copolymerization, as well as bimetallic salicylaldimine–nickel
catalysts which showed high polar monomer incorporation in
ethylene/(polar norbornene) copolymerizations via a cooperative
action between the two metal centers.3 To achieve the cooperative
action of the two metal centers as exhibited by the natural
metalloenzymes, they should be suitably arranged in space and
the construction of a well-designed ligand system is of impor-
tance.
The complexes exhibit a narrower Cp(cent)–Ti–N angle than
5
the standard constrained-geometry catalyst (CGC), [Me2Si(g -
Me4C5)(NtBu)]Ti(IV)Cl2 indicating a more “constrained feature”
5
in the o-phenylene-bridged complexes. While the silicon atom in
the CGC severely deviates from the cyclopentadienyl plane,6 the
elements constituting the chelation in the o-phenylene-bridged
complexes are not situated in a severely strained position. Some
complexes are superior to the CGC in ethylene/a-olefin copoly-
merization in terms of activity and a-olefin incorporation. Herein,
we report the construction of bimetallic titanium complexes based
on the o-phenylene-bridged Cp/amide ligand system and their
advantageous polymerization reactivity.
Recently, we disclosed
a novel preparation route for
o-phenylene-bridged (dimethyl or trimethylcyclopentadienyl)/
(amide, sulfonamide, carboxamide, or phosphinoamide) ligand
system.4 The Suzuki-coupling reaction of 2-bromoaniline deriva-
tives with 2-dihydroxyboryl-3,4-dimethyl-2-cyclopenten-1-one or
2-dihydroxyboryl-3-methyl-2-cyclopenten-1-one is a key step in
this novel route (eqn (1)).
Results and discussion
Synthesis and characterization
Dinuclear titanium complexes, where the two titanium metals
share one nitrogen donor, are prepared. Inthe complexes, theTi–Ti
separation is very short and does not vary with the conformational
changes of the molecule (Scheme 1). Thus, the Suzuki-coupling
reaction of two equivalents of 1 with 2,6-dibromo-4-R-aniline
(R = Me or F) under conventional conditions affords the
desired cyclopentenone compounds, which are transformed into
bis(dimethylcyclopentadiene) compounds 5 and 6 by the treatment
of methyllithium in the presence of CeCl3 and subsequent aqueous
acidic work-up. The reactions of 5 and 6 with two equivalents of
Ti(NMe2)4 at 80 ◦C for 1 d and subsequent treatment of Me2SiCl2
with the resulting bis(dimethylamido)titanium complexes afford
the desired dinuclear dichlorotitanium complexes 7 and 8.7 Only
aDepartment of Molecular Science and Technology, Suwon, 443-749, South
Korea
bSchool of Mechanical Engineering, Ajou University, Suwon, 443-749, South
Korea. E-mail: bunyeoul@ajou.ac.kr; Fax: +82-31-219-2394; Tel: +82-31-
219-1844
† CCDC reference number 652537. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b710017e
‡ Electronic supplementary information (ESI) available: Details of the
synthetic procedures and characterizations of 4, 6, 8, 10, 11, 13, 14, 16, 17,
19, and 20. See DOI: 10.1039/b710017e
4608 | Dalton Trans., 2007, 4608–4614
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four signals are observed at 2.21, 2.48, 6.69, and 7.05 ppm as
singlets in the 1H NMR spectrum of 7 (CDCl3). Three signals are
observed at 2.23 (singlet), 6.72 (singlet), and 7.01 ppm (doublet,
3JHF = 8 Hz) in the 1H NMR spectrum of 8 (CDCl3).
Scheme 1 i) 1, Na2CO3, Pd(PPh3)4 (1.6 mol%); ii) MeLi–CeCl3, then HCl
(2 N); iii) Ti(NMe2)4; iv) Me2SiCl2.
Fig. 1 Thermal ellipsoid plot (30% probability level) of 7.
Bimetallic titanium complexes where the Ti–Ti separation is
larger than those in 7 and 8 have been prepared (Scheme 2).
Thus, the dibromo-compounds 9–11 are prepared by the bromi-
nation reaction of the corresponding bis(aniline) compounds.
Cyclopentenone compounds 12–14 are obtained in excellent yields
(>90%) by the Suzuki-coupling reaction. A transformation of 12
to 15 is achieved in 51% yield by the conventional method—
CeCl3-mediated MeLi addition and then elimination reaction—
but the yields for the transformation of 13–14 into 16–17 are
not satisfactory under the same conditions. Changing the THF-
insoluble CeCl3 with THF-soluble La(OTf)3 provided 67% and
41% yields of the desired compounds 16–17, respectively.8 The
transformation of the cyclopentadienyl compounds 15–17 into
the dichlorotitanium complexes 18–20 are achieved without any
problems by the conventional method in high yields (>75%).
˚
˚
(2.069(5) A) is bigger than that of Ti(2)–N(1) (1.864(5) A), the
˚
Ti(1)–Cp(centroid) bond length (1.882 A) is shorter than that
˚
of the Ti(2)–Cp(centroid) (2.155 A). The five Ti(1)–C (on Cp)
distances are almost invariable and this is in agreement with the ob-
servations for other o-phenylene-bridged Cp/amido complexes.4
However, the distribution of the Ti(2)–C (on Cp) distances
is abnormal. In most of the constrained bridged-metallocene
complexes, the M–C (on Cp) bond distance increases by moving
from the bridgehead to the peripheral carbons,9 but the Ti(2)–C
(on Cp) distance in 7 is the shortest with the peripheral carbons
˚
˚
(d[Ti(2)–C(15)], 2.456(6) A; d[Ti(2)–C(16)], 2.460(7) A; d[Ti(2)–
˚
C(17), 2.398(7) A). The bond angles around Ti(1) (Cp(cent)–
Ti(1)–N(1), C(13)–N(1)–Ti(1), Cl(2)–Ti(1)–Cl(1), Cp(cent)–C(1)–
C(8), C(1)–Cp(cent)–Ti(1), C(13)–C(8)–C(1), and C(8)–C(13)–
N(1)) do not deviate from the corresponding angles observed for
5
the mononuclear o-phenylene-bridged Cp/amide complex [2-(g -
2,3,5-Me3C5H)C6H3NC6H11-jN]Ti(IV)Cl2,4 but the angles around
Ti(2) deviate severely. Overall, these metrical parameters indicate
that Ti(1) adopts a normal comfortable geometry while Ti(2)
deviates from the normal situation.
In all the structures of the mononuclear o-phenylene-bridged
Cp/(amide, sulfonamide, phosphinoamide) titanium complexes,
the cyclopentadienyl plane is situated perpendicular to the pheny-
lene plane and the titanium atom is situated on the phenylene
plane. In this dinuclear complex, the two cyclopentadienyl planes
are situated slightly tilted to the phenylene plane (79.64(21) and
78.94(25)◦). Consequently, the titanium atoms are situated slightly
˚
deviated from the phenylene plane. Ti(1) is situated 0.34(1) A above
˚
the phenylene plane while Ti(2) is 0.42(1) A below the plane. These
deviated situations of the cyclopentadienyl plane and the Ti atoms
result in a staggered conformation of the Cl(1) and Cl(2) atoms
with respect to the Cl(3) and Cl(4) atoms (dihedral angles: Cl(1)–
Ti(1)–Ti(2)–Cl(3), 38.7◦; Cl(1)–Ti(1)–Ti(2)–Cl(4), 64.2◦; Cl(2)–
Scheme 2 i) 2, Na2CO3, Pd(PPh3)4 (1 mol%); ii) MeLi–La(OTf)3, then
HCl (2 N); iii) Ti(NMe2)4; iv) Me2SiCl2.
◦
˚
Ti(1)–Ti(2)–Cl(3), 42.1 ). The closest Cl–Cl separation is 3.558 A.
X-Ray crystallographic studies
Polymerization studies
The molecular structure of 7 was confirmed by X-ray crystal-
lography (Fig. 1). The nitrogen atom adopts a perfectly trigonal
planar geometry (sum of the bond angles around the N(1),
360◦) and coordinates to the two titanium atoms. The Ti–
The newly prepared complexes were tested for ethylene/1-hexene
copolymerization after activation with (Ph3C)[B(C6F5)4] and
iBu3Al. The triisobutylaluminium is added both as a scavenger and
as an alkylating agent. The polymerization conditions and the re-
sults are summarized in Table 2. A related mononuclear complex,
˚
Ti separation is 3.3967(17) A. The bond distances and bond
angles around each titanium atom are significantly different
from each other (Table 1). While the Ti(1)–N(1) bond length
5
{2-(g -2,3,5-Me3C5H)C6H3NC6H11-jN}Ti(IV)Cl2 (21) was tested
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◦
˚
Table 1 Selected bond distances (A) and angles ( ) around Ti(1) and Ti(2) observed in 7 and the corresponding distances and angles observed in
5
[2-(g -2,3,5-Me3C5H)C6H3NC6H11-jN]Ti(IV)Cl2 (21)
Around Ti(1) in 7
Around Ti(2) in 7
21
Ti(1)–C(1)
Ti(1)–C(2)
Ti(1)–C(5)
Ti(1)–C(3)
Ti(1)–C(4)
Cp(cent)–Ti(1)
Ti(1)–Cl(1)
Ti(1)–Cl(2)
Ti(1)–N(1)
2.255(5)
2.236(6)
2.252(6)
2.277(6)
2.251(7)
1.882
2.2796(18)
2.242(2)
2.069(5)
Ti(2)–C(15)
Ti(2)–C(16)
Ti(2)–C(19)
Ti(2)–C(17)
Ti(2)–C(18)
Cp(cent)–Ti(2)
Ti(2)–Cl(3)
2.456(6)
2.460(7)
2.509(7)
2.398(7)
2.429(8)
2.155
2.2243(19)
2.287(2)
1.864(5)
2.3245(15)
2.3619(17)
2.3275(16)
2.3741(18)
2.3306(17)
2.008
2.2944(7)
2.2889(7)
1.9003(13)
Ti(2)–Cl(4)
Ti(2)–N(1)
Ti(1)–Ti(2)
N(1)–C(13)
3.3967(17)
1.424(6)
1.4092(19)
Cl(1)–Cl(3)
Cl(1)–Cl(4)
3.652
3.797
Cl(2)–Cl(3)
Cl(2)–Cl(4)
3.558
5.789
Cp(cent)–Ti(1)–N(1)
C(13)–N(1)–Ti(1)
Ti(2)–N(1)–Ti(1)
Cl(2)–Ti(1)–Cl(1)
Cp(cent)–C(1)–C(8)
C(1)–Cp(cent)–Ti(1)
C(13)–C(8)–C(1)
C(8)–C(13)–N(1)
104.67
125.7(4)
Cp(cent)–Ti(2)–N(1)
C(13)–N(1)–Ti(2)
119.4(2)
Cl(3)–Ti(2)–Cl(4)
Cp(cent)–C(15)–C(12)
C(15)–Cp(cent)–Ti(2)
C(15)–C(12)–C(13)
N(1)–C(13)–C(12)
106.59
114.9(4)
104.6
129.11(10)
106.39(8)
170.17
89.15
113.8(5)
113.2(6)
103.40(8)
165.70
91.50
112.9(5)
125.3(5)
105.52(2)
170.55
89.16
113.36(13)
113.18(13)
Table 2 Ethylene/1-hexene copolymerization resultsa
−1
e
Catalyst
Ab/106g molTi h−1
[Hex]c/mol%
Mw × 10−3
Mw/Mn
[g]sp at 0.20/g dL−1
[g]d/dL g−1
g0 × 10−5/P
LCBIf
18
19
20
21g
6.4
6.3
5.2
4.4
22
20
23
21
292
200
268
190
2.4
2.2
2.6
2.0
0.356
0.268
0.332
0.240
1.53
1.19
1.44
1.08
15
3.8
11
0.74
0.75
0.75
0.70
1.9
a Polymerization conditions: 240 mL toluene solution of 1-hexene (0.20 M), 4 lmol Ti, 16 lmol of (Ph3C)[B(C6F5)4], 1.6 mmol of iBu3Al, 60 psig ethylene,
10 min, temperature 90 ◦C. b Activity, averaged over 3 runs. c 1-Hexene content in the copolymer measured by 1H NMR spectroscopy. d Intrinsic viscosity
calculated from the measured specific viscosity at a single nominal concentration of 0.20 g dL−1 by using Martin’s equation of log([g]sp/c) = log[g] +
0.2138[g]c. e Zero-shear viscosity estimated using the Sabia equation fit of dynamic complex viscosity g* versus radian frequency. f Long-chain-branching
5
index calculated with the equation LCBI = g00.179/4.8[g] − 1. g Mononuclear complex, {2-(g -2,3,5-Me3C5H)C6H3NC6H11-jN}Ti(IV)Cl2.
as a comparison catalyst. Complexes 7 and 8 do not show any
activity for ethylene and ethylene/1-hexene copolymerization. In
contrast, the bimetallic complexes 18–20 show a higher activity
than the mononuclear analogue 21. The highest activity is
observed with the methylene-bridged complex 18, which is about
1.5 times higher in activity than the mononuclear analogue.
A trend of higher activity has also been observed in some
other dinuclear systems.10 The molecular weights of the polymers
obtained with the bimetallic complexes 18–20 are higher than that
of the polymer obtained with the mononuclear analogue 21. The
highest molecular-weight polymer is obtained with complex 18
which gives the highest activity. The molecular weight distributions
are narrow (Mw/Mn = 2.0–2.6) in all cases but slightly broader
molecular weight distributions are observed with the bimetallic
complexes. The 1-hexene contents in the copolymers are almost
invariable not only when changing the mononuclear system to a
dinuclear system but also when the bridge in the dinuclear system
is varied.
made by CGC technology under certain process conditions con-
tain a certain amount of LCB. Through the presence of LCB, the
CGC technology polymer shows the rheological properties of high
melt fracture resistance and shear-thinning behavior. The unique
molecular structure and rheological properties of the polymers
containing LCB allow one to design new polyethylene products
with excellent processability for applications such as blown film,
cast film, injection molding, blow molding, thermoforming, etc.
The reinsertion of a vinyl-terminated chain into the chain-
growth metal center has been proposed and accepted as the
most probable LCB mechanism.12 If the mechanism is to be
accepted, then one can expect a higher incorporation of long-
chain-branching through the employment of the bimetallic system
as illustrated in Scheme 3. Positioning two metal centers in close
proximity might provide a higher probability for coordination
of a vinyl-terminated polymer chain being generated on the
neighboring titanium center by chain transfer reactions. A method
to quantitatively assess the LCB was introduced by Shroff and
Mavridis.13 In addition, the quantitative index of the long-chain-
branching is given by the relation: long-chain-branching index
(LCBI) = g00.179/4.8[g] − 1, where go (P) is the zero shear viscosity at
Long-chain branching (LCB) is one of the unique characteristic
features of the ethylene homopolymers and ethylene/a-olefin
copolymers made by CGC.11 Homopolymers and copolymers
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Experimental
General remarks
All manipulations were performed under an inert atmosphere
using standard glovebox and Schlenk techniques. Toluene, pen-
tane, THF, and C6D6 were distilled from benzophenone ketyl.
Me2SiCl2 was dried over CaH2 and transferred under vacuum to a
reservoir. NMR spectra were recorded on a Varian Mercury plus
400. Elemental analyses were carried out at the Inter-University
Center Natural Science Facilities, Seoul National University. Gel
permeation chromatograms (GPC) were obtained at 140 ◦C in
trichlorobenzene using Waters Model 150-C+ GPC and the data
were analyzed using a polystyrene analyzing curve. Details of
synthetic procedures and characterizations of 4, 6, 8, 10–11, 13–14,
16–17, and 19–20 are available as ESI.‡
Scheme 3 Plausible mechanism for incorporation of long-chain branch-
ing by a bimetallic catalyst.
190 ◦C, and [g] (dL g−1) is the intrinsic viscosity in trichlorobenzene
at 135 ◦C. The intrinsic viscosity, [g], is calculated from the specific
viscosity, [g]sp, measured at a single nominal concentration of
◦
0.20 g dL−1 in 1,2,4 trichlorobenzene (TCB) at 135 C using an
Ubbelohde viscometer. The calculation is performed iteratively
using Martin’s equation of log([g]sp/c) = log[g] + km[g]c, where
Martin’s constant km = 0.2138.14 The zero-shear viscosity g0 is
estimated using the Sabia equation15 fit of dynamic complex
viscosity g* versus radian frequency, log(g*/g0) = (g*/g0 − A)
log[1 + (x/x0)B] where AB = 0.72. The curve of dynamic complex
viscosity g* versus radian frequency is obtained on a Rheometrics
dynamic analyzer at 190 ◦C. Fig. 2 shows the real and fitted
plots of complex viscosity g* versus radian frequency x for the
polymers prepared using 18–21. The LCBI measured on the
polymer obtained with the mononuclear catalyst is 0.70 while
the LCBI of the polymers obtained with the bimetallic catalysts
18–20 is ∼0.75. Even though the improvement for the long-
chain-branching incorporation is not significant by employing the
bimetallic system, a trend of slightly higher long-chain-branching
content is observed in the copolymers obtained with the bimetallic
system.
Compound 3
Compound 1 (2.27 g, 16.2 mmol), Na2CO3 (2.06 g, 19.4 mmol),
Pd(PPh3)4 (0.30 g, 0.26 mmol), and 2,6-dibromo-4-methylaniline
(1.72 g, 6.49 mmol) were added to a Schlenk flask inside a glove-
box. The flask was brought out from the glovebox and degassed
DME (20 mL) and degassed water (5 mL) were successively added
with a syringe. The mixture was stirred for 2 d at 95 ◦C. It was then
transferred to a separating funnel containing ethyl acetate (50 mL)
after the solution was cooled to room temperature. Afterwards,
water (50 mL) was added and the organic phase was collected. The
water phase was extracted with additional ethyl acetate (20 mL ×
2). The organic phases were combined and dried over anhydrous
MgSO4. Next, solvent was removed with a rotary evaporator to
give a residue which was purified by column chromatography on
silica gel eluting with methylene chloride and ethyl acetate (v/v, 1 :
1). A white solid was obtained (1.27 g, 66%); mp 200 ◦C. IR (neat):
−1
1
=
3434 and 3354 (N–H), 1696 (C O) cm . H NMR (CDCl3): d 2.12
(s, 6H, CH3), 2.26 (s, 3H, Ph–CH3), 2.58 (br t, J = 4.4 Hz, 4H,
CH2), 2.72 (br t, J = 4.4 Hz, 4H, CH2), 3.52 (br s, 2H, NH), 6.73
(s, 2H, C6H2) ppm. 13C{ H} NMR (CDCl3): d 18.69, 20.46, 32.01,
1
34.88, 118.88, 126.99, 130.82, 139.43, 140.18, 174.56, 207.63 ppm.
Anal. calc. (C19H21NO2): C, 77.26; H, 7.17; N, 4.74%. Found: C,
77.20; H, 7.00; N, 4.74%.
Compound 5
Anhydrous CeCl3 (1.17 g, 4.76 mmol) and THF (15 mL) were
added to a Schlenk flask inside a glovebox. The flask was brought
out and the solution was cooled to −78 ◦C. MeLi (3 mL,
5.90 mmol, 1.6 M solution in diethyl ether) was added using a
syringe. The mixture was stirred for 1 h at −78 ◦C. Compound 3
(0.358 g, 1.18 mmol) was added as a solid under a weak N2 flow.
It was transferred to a separating funnel containing H2O (20 mL)
and ethyl acetate (20 mL), after the mixture was stirred for 2 h at
−78 ◦C. The organic phase was collected and the water phase was
extracted further with additional ethyl acetate (10 mL × 2). The
combined organic phases were shaken vigorously with aqueous
HCl (2 N, 10 mL) for 2 min. Aqueous saturated NaHCO3 (15 mL)
was added carefully to neutralize the solution. Afterwards, the
collected organic phase was dried over anhydrous MgSO4 and
the solvent was removed with a rotary evaporator to give a residue
which was purified by column chromatography on silica gel eluting
Fig. 2 Complex viscosity (g*) at 190 ◦C versus radian frequency for the
polymers obtained with 18–21. The points are real data and the lines are
the ones fitted to the Sabia equation.
Conclusion
Bimetallic titanium complexes (18–20) based on an o-phenylene-
bridged Cp/amide ligand system are prepared by using a key
step of the Suzuki-coupling reaction of 2-dihydroxyboryl-3,4-
dimethyl-2-cyclopenten-1-one (2) with bis(bromoaniline) deriva-
tives. The bimetallic complexes show higher activities, higher
molecular weights, and slightly higher long-chain-branching con-
tent in the ethylene/1-hexene copolymerization than the mononu-
clear analogue.
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with toluene and hexane (v/v, 5 : 1). A yellow solid was obtained
4,4ꢀ-Methylenebis(2-bromo-N-cyclohexylaniline) (9)
1
(0.27 g, 80%). IR (neat): 3456 and 3448 (N–H) cm−1. H NMR
4,4ꢀ-Methylenebis(N-cyclohexylaniline) (8.75 g, 24.1 mmol) was
dissolved in methylene chloride (80 mL) and a solution of Br2
(7.72◦g, 48.29 mmol) in methylene chloride (10 mL) was added
at 0 C over 30 min. The solution was stirred for a further 2 h.
After an aqueous KOH solution (1 N, 200 mL) was added, the
product was extracted with methylene chloride (300 mL × 2).
The combined organic layers were dried over anhydrous MgSO4
and the solvent was removed with a rotary evaporator to give a
residue which was purified by column chromatography on silica
gel eluting with hexane and ethyl acetate (30 : 1). A white solid was
obtained (9.58 g, 52%); mp 97 ◦C, IR (neat): 3401 (N–H) cm−1. 1H
NMR (C6D6): d 0.93–1.17 (m, 10H, Cy), 1.38–1.42 (m, 2H, Cy),
1.52–1.57 (m, 4H, Cy), 1.79–1.82 (m, 4H, Cy), 3.01–3.07 (m, 2H,
N–CH), 3.54 (s, 2H, bridged-CH2), 4.22 (d, J = 8.0 Hz, 2H, NH),
6.45 (d, J = 8.0 Hz, 2H, C6H3), 6.89 (dd, J = 8.0 Hz, 1.6 Hz,
(C6D6): d 1.90 (s, 3H, CH3), 1.91 (s, 3H, CH3), 1.98 (d, J = 1.6 Hz,
3H, CH3), 2.00 (d, J = 2.0 Hz, 3H, CH3), 2.24 (s, 3H, Ph-CH3),
2.84 (t, J = 1.6 Hz, 2H, CH2), 3.37 (br d, J = 2.8 Hz, 2H, NH2),
1
5.98 (d, J = 1.6 Hz, 2H, Cp-H), 6.87 (s, 2H, C6H2) ppm. 13C{ H}
NMR (C6D6): d 14.94, 14.98, 15.01, 15.10, 20.09, 44.64, 122.24,
122.31, 124.59, 124.64, 126.03, 126.12, 130.01, 130.09, 140.64,
140.69, 140.83, 140.86, 140.95, 144.20, 144.34 ppm. Anal. calc.
(C21H25N): C, 86.55; H, 8.65; N, 4.81%. Found: C, 86.42; H, 8.42;
N, 4.71%.
Complex 7
Compound 5 (0.224 g, 0.77 mmol), Ti(NMe2)4 (0.345 g,
1.54 mmol), and toluene (10 mL) were added to a Schlenk flask.
The solution was stirred for 1 d at 80 ◦C. Removal of the solvent
1
2H, C6H3), 7.34 (d, 2H, J = 1.2 Hz, C6H3) ppm. 13C{ H} NMR
1
gave a red oil found to be pure through a H NMR spectrum
(C6D6): d 25.16, 26.24, 33.29, 39.78, 51.80, 110.28, 112.30, 129.15,
130.88, 133.07, 142.75 ppm. Anal. calc. (C25H32Br2N2): C, 57.71;
H, 6.20; N, 5.38%. Found: C, 58.09; H, 6.48; N, 5.52%.
analysis. 1H NMR (C6D6): d 2.02 (s, 12H, CH3), 2.31 (s, 3H, Ph-
CH3), 3.11 (s, 24H, N–CH3), 5.72 (s, 4H, Cp-H), 6.93 (s, 2H,
C6H2) ppm. Me2SiCl2 (0.600 g, 4.65 mmol) was added to a flask
containing the resulting bis(dimethylamido)titanium complex in
toluene (10 mL). After the solution was stirred for 12 h at room
temperature, all volatiles were removed under vacuum to give
dark red crystals which were triturated with pentane (10 mL)
(0.321 g, 80%). Analytically pure crystals of 7 were obtained from
Compound 12
The compound was synthesized using the same conditions and
procedure as for 3 using 9 (4.15 g, 7.98 mmol). It was purified by
column chromatography on silica gel eluting with hexane and ethyl
acetate (3 : 1). A white solid was obtained (4.18 g, 91%). Owing to
the presence of two chiral centers, it was obtained as a mixture of
two diastereomers and some signals are split in the NMR spectra;
◦
1
the toluene solution at −30 C. H NMR (CDCl3): d 2.21 (s,
12H, CH3), 2.48 (s, 3H, Ph-CH3), 6.69 (s, 4H, Cp-H), 7.05 (s,
1
2H, C6H2) ppm. 13C{ H} NMR (CDCl3): d 15.46, 21.09, 118.95,
122.68, 128.78, 135.09, 140.05, 143.03, 174.02 ppm. Anal. calc.
(C21H21Cl4NTi2): C, 48.05; H, 4.03; N, 2.67%. Found: C, 47.90; H,
3.95; N, 2.62%.
◦
−1
1
=
mp 164–166 C. IR (neat): 3456 (N–H), 1631 (C O) cm . H
NMR (C6D6): d 0.74 (d, J = 6.8 Hz, 6H, CH3), 1.17–1.20 (m, 10H,
Cy), 1.42–1.45 (m, 2H, Cy), 1.57–1.62 (m, 4H, Cy), 1.66 (s, 6H,
CH3), 1.82 (dd, J = 18.4, 2.0 Hz, 2H, CH2), 1.92–2.07 (m, 4H, Cy),
2.16–2.19 (m, 2H, CH), 2.41 (dd, J = 18.4, 6.4 Hz, 2H, CH2), 3.18
(br s, 2H, N–CH), 3.98 (s, 2H, bridged-CH2), 6.74 (d, J = 8.0 Hz,
2H, C6H3), 6.98 (d, J = 2.4 Hz, 2H, C6H3) 7.21 (dd, J = 8.0, 2.4 Hz,
4,4ꢀ-Methylenebis(N-cyclohexylaniline)
4,4ꢀ-Methylenebis(aniline) (10.0 g, 50.44 mmol) and cyclohex-
anone (39.6 g, 0.404 mol) were dissolved in toluene (80 mL) and
then molecular sieves (15.0 g) were added. The flask was sealed
with a screw-cap and heated at 100 ◦C for 4 d. After the molecular
sieves◦were filtered off, all volatiles were removed under vacuum
at 60 C to give a crude imine compound. The imine compound
was dissolved in degassed methanol (200 mL) and THF (50 mL).
Sodium borohydride (11.5 g, 0.303 mol) was added slowly under a
weak stream of nitrogen gas and the mixture was stirred at room
temperature for 5 h. Aqueous 1 N KOH (200 mL) was added and
the product was extracted with methylene chloride (250 mL × 2).
The combined organic layers were dried over anhydrous MgSO4
and solvent was removed with a rotary evaporator to give a residue
which was purified by recrystallization from hexane and ethyl
acetate (10 : 1). A light yellow solid was obtained (9.58 g, 52%);
2H, C6H3) ppm. 13C{ H} NMR (C6D6): d 16.29, 19.38, 25.27,
1
26.53, 33.74, 37.74, 40.78, 43.73, 51.99, 112.51, 119.22, 129.97,
130.15, 131.53, 132.00, 132.32, 132.41, 144.58, 177.01, 205.33 ppm.
Anal. calc. (C39H50N2O2): C, 80.93; H, 8.71; N, 4.84%. Found: C,
81.15; H, 8.94; N, 5.03%.
Compound 15
La(OTf)3 (1.823 g, 3.11 mmol) and THF (15 mL) were added to
a Schlenk flask inside a glovebox. The flask was brought out and
the solution was cooled to −78 ◦C. MeLi (3.11 mmol) was added
using a syringe. The solution was warmed to room temperature
◦
and stirred for 1 h. After the solution was cooled to −78 C, 12
(0.300 g, 0.52 mmol) dissolved in THF (1.0 mL) was added. The
◦
◦
1
mp 116 C. H NMR (C6D6): d 0.84–0.94 (m, 4H, Cy), 1.02–
1.20 (m, 6H, Cy), 1.46–1.58 (m, 6H, Cy), 1.89–1.92 (m, 4H, Cy),
3.04–3.10 (m, 2H, N–CH), 3.05 (d, J = 6.4 Hz, 2H, NH), 3.91 (s,
2H, bridged-CH2), 6.47 (d, J = 8.0 Hz, 4H, C6H4), 7.13 (d, J =
mixture was stirred for 2 h at −78 C. After an aqueous NaOH
solution (20 mL, 1 M) was added, the organic phase was extracted
with ethyl acetate (20 mL × 2). The combined organic phases
were washed with water (40 mL) and were shaken vigorously with
aqueous HCl solution (2 N, 10 mL) for 3 min. Aqueous saturated
NaHCO3 (20 mL) was added carefully to neutralize the solution.
The collected organic phase was dried over anhydrous MgSO4
and the solvent was removed with a rotary evaporator to give a
1
8.0 Hz, 4H, C6H4) ppm. 13C{ H} NMR (C6D6): d 25.48, 26.50,
33.81, 41.00, 51.96, 113.73, 130.03, 130.84, 145.91 ppm. Anal. calc.
(C25H34N2): C, 82.82; H, 9.45; N, 7.73%. Found: C, 83.03; H, 9.38;
N, 7.62%.
4612 | Dalton Trans., 2007, 4608–4614
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©

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Table 3 Crystallographic parameters of 7a
residue which was purified by column chromatography on silica
gel eluting with hexane and ethyl◦acetate (20 : 1). A white solid was
obtained (0.170 g, 57%); mp 120 C. 1H NMR (C6D6): d 0.90–1.02
(m, 6H, Cy), 1.09–1.17 (m, 4H, Cy), 1.40–1.53 (m, 6H, Cy), 1.81
(s, 6H, CH3), 1.87 (s, 6H, CH3), 1.89 (s, 6H, CH3), 1.92–1.96 (m,
4H, Cy), 2.68 (AB, J = 22.8 Hz, 2H, CH2), 2.78 (AB, J = 22.8 Hz,
2H, CH2), 3.17–3.19 (m, 2H, N–CH), 3.70 (d, J = 7.6 Hz, 2H,
NH), 4.00 (s, 2H, bridged-CH2), 6.71 (d, J = 8.0 Hz, 2H, C6H3),
7.09 (d, J = 2.0 Hz, 2H, C6H3), 7.23 (dd, J = 8.4, 2.0 Hz, 2H,
Formula
M
Color
C21H21Cl4NTi2·C6H6
603.10
Dark red
Size/mm
0.2 × 0.2 × 0.15
12.3965(7)
11.8196(7)
19.4218(8)
93.877(3)
2839.2(3)
Monoclinic
P21/n
˚
a/A
˚
b/A
˚
c/A
b/◦
V/A
3
˚
1
C6H3) ppm. 13C{ H} NMR (C6D6): d 12.25, 13.89, 14.80, 25.46,
Crystal system
Space group
D(calc)/g cm−1
Z
26.41, 33.97, 41.19, 49.04, 51.88, 111.13, 123.13, 128.96, 130.11,
131.13, 133.01, 136.52, 136.59, 141.14, 143.63 ppm. Anal. calc.
(C41H54N2): C, 85.66; H, 9.47; N, 4.87%. Found: C, 85.43; H, 9.75;
N, 4.94%.
1.411
4
l/mm−1
0.955
No. of data collected
No. of unique data
No. of variables
R
15378
5352 [R(int) = 0.1417]
312
0.0692
0.1331
1.013
Complex 18
Rw
Goodness of fit
It was synthesized using the same conditions and procedure as for
7 using 15 (0.160 g, 0.28 mmol). It was purified by trituration in
pentane. Overall yield from 15 was 87% (0.195 g). The 1H NMR
(C6D6) data for the intermediate bis(dimethylamido)titanium
complex: d 0.89–0.99 (m, 2H, Cy), 1.13–1.26 (m, 4H, Cy), 1.36–
1.49 (m, 6H, Cy), 1.63–1.74 (m, 4H, Cy), 1.80 (s, 6H, CH3), 1.89 (s,
6H, CH3), 1.97 (s, 6H, CH3), 2.02–2.16 (m, 4H, Cy), 2.91 (s, 12H,
NCH3), 3.09 (br s, 12H, NCH3), 4.08 (s, 2H, bridged-CH2), 5.66
(br s, 2H, Cp-H), 6.75 (br s, 2H, C6H3), 7.20 (s, 2H, C6H3), 7.23 (d,
J = 8.0 Hz, 2H, C6H3) ppm. The analytical data for 18: 1H NMR
(C6D6): d 1.43–1.50 (m, 6H, Cy), 1.68–1.75 (m, 4H, Cy), 1.69 (s,
3H, CH3), 1.70 (s, 3H, CH3), 1.81 (s, 3H, CH3), 1.82 (s, 3H, CH3),
1.88–1.96 (m, 6H, Cy), 2.05–2.17 (m, 4H, Cy), 2.12 (s, 6H, CH3),
3.95 (s, 2H, bridged-CH2), 5.52–5.59 (m, 2H, N–CH), 6.09 (s, 2H,
Cp-H), 6.68 (d, J = 8.4 Hz, 2H, C6H3), 7.04 (s, 2H, C6H3), 7.09
a
˚
Data collected at 293(2) K with Mo-Ka radiation (k(Ka) = 0.7107 A),
ꢀ
ꢀ
ꢀ
2
R(F) = ꢁFo| − |Fcꢁ/ |Fo| with Fo >2.0r(I), Rw = [ [w(Fo
−
ꢀ
Fc2)2]/ [w(Fo)2]2]1/2 with Fo >2.0r(I).
X-Ray crystallography
A crystal of 7 coated with grease (Apiezon N) was mounted inside
a thin glass tube with epoxy glue and placed on an Enraf-Nonius
CCD single crystal X-ray diffractometer. The structure was solved
by direct methods using the SHELX-96 program and least-squares
refinement using the SHELXL-Plus (5.1) software package. All
non-hydrogen atoms were refined anisotropically. All hydrogen
atoms were included in calculated positions. The crystal data and
refinement results are summarized in Table 3.
CCDC reference number 652537.
1
(d, J = 8.4 Hz, 2H, C6H3) ppm. 13C{ H} NMR (C6D6): d 12.80,
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b710017e
14.94, 15.23, 26.11, 27.43, 27.76, 27.85, 37.38, 40.94, 59.71, 110.91,
118.48, 129.02, 129.58, 131.45, 132.61, 136.71, 142.02, 142.69,
143.15, 162.20 ppm. Anal. calc. (C41H50Cl4N2Ti2): C, 60.92; H,
6.23; N, 3.47%. Found: C, 61.14; H, 6.31; N, 3.34%.
Acknowledgements
This work was supported by grant No. R01-2006-000-10271-
0 from the Basic Research Program of the Korea Science &
Engineering Foundation.
Polymerization
To a glass reactor (500 mL) were added 240 mL of a toluene
solution of 1-hexene (0.20 M). After the solution was heated to
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4614 | Dalton Trans., 2007, 4608–4614
This journal is
The Royal Society of Chemistry 2007
©