Tridentate Aryloxy-Based Titanium Catalysts towards Ethylene Oligomerization and Polymerization

Article abstract of DOI:10.1002/ejic.201500721

A series of tridentate aryloxy-based ligands were synthesized and characterized for their coordination behaviour towards Ti^IV. Coordination studies revealed that the nature of the central atom (amine vs. ether) and the type of bridging spacer (aromatic vs. aliphatic) are important aryloxy ligand parameters and influence the ligand coordination mode and the formation of stable titanium complexes. This series of titanium complexes were evaluated in ethylene oligomerization and polymerization after activation with methylaluminoxane (MAO) and showed the preferential formation of polyethylene. In some cases, the formation of a small amount of 1-hexene suggests the existence of several catalytic centres in the reaction mixture.

Full text of DOI:10.1002/ejic.201500721

FULL PAPER
DOI:10.1002/ejic.201500721
Tridentate Aryloxy-Based Titanium Catalysts towards
Ethylene Oligomerization and Polymerization
Hugo Audouin,[a] Rosalba Bellini,[a] Lionel Magna,*[a]
Nicolas Mézailles,[b] and Hélène Olivier-Bourbigou[a]
Keywords: Titanium / Tridentate ligands / Homogeneous catalysis / Oligomerization / Polymerization
A series of tridentate aryloxy-based ligands were synthe-
sized and characterized for their coordination behaviour
towards TiIV. Coordination studies revealed that the nature
of the central atom (amine vs. ether) and the type of bridging
spacer (aromatic vs. aliphatic) are important aryloxy ligand
parameters and influence the ligand coordination mode and
the formation of stable titanium complexes. This series of ti-
tanium complexes were evaluated in ethylene oligomeriza-
tion and polymerization after activation with methylalumin-
oxane (MAO) and showed the preferential formation of poly-
ethylene. In some cases, the formation of a small amount of
1-hexene suggests the existence of several catalytic centres
in the reaction mixture.
ligands, Fujita and co-workers discovered that the introduc-
tion of an additional donor group can completely switch
the catalyst activity from polymerization to highly active
and selective trimerization.[5] On the basis of systematic in-
vestigations,[5c] several structural variations of these FI tri-
dentate ligands were proposed, and the additional pendant
2-methoxybiphenyl donor was identified as a critical feature
to induce 1-hexene selectivity (IIa; Figure 1). Along the
same lines, we and other groups have reported on the appli-
cation of bidentate aryloxy-based TiIV systems and contrib-
uted to the further development of this ligand family for
selective ethylene oligomerization.[6]
Introduction
Coordination chemistry and organometallic chemistry
are at the very heart of homogeneous transition-metal catal-
ysis. The identification and fine-tuning of catalyst param-
eters, in terms of activity and selectivity, continue to repre-
sent great challenges for ligand design, coordination chem-
istry and organometallic chemistry. Although the combina-
tion of the electronic and steric properties of the ligand has
been recognized as a powerful tool for catalyst optimiza-
tion, predictions remain very difficult. Therefore, to a large
extent, catalyst discovery still relies on a delicate interplay
between intuition, laboratory experience and, in many
cases, lucky breaks. A strategy that has emerged to acceler-
ate catalyst development is based on the evaluation of struc-
turally diverse and meaningful ligand libraries through
high-throughput screening techniques. This approach has
been remarkably valid in the field of olefin polymerization
catalysis, for which the screening of ligand libraries has en-
abled the fine-tuning of the physical properties of poly-
olefinic materials.[1] In this research area, ligands such as
phenoxyimines (FI) have attracted great interest owing to
their synthetic accessibility and easy structural diversifica-
tion (I; Figure 1), which makes this class of ligands very
attractive for lead identification and catalysis optimiza-
tion.[2–4] In the course of their investigations on this type of
[a] IFP Energies nouvelles,
Rond-Point de l’échangeur de Solaize, BP3, 69360 Solaize,
France
Figure 1. Titanium aryloxy complexes.
E-mail: lionel.magna@ifpen.fr
http://www.ifpenergiesnouvelles.fr/
Depending on the structure of the aryloxy ligand (steric
hindrance, nature of the heteroatom and nature of the
spacer group), mono-aryloxy or bis-aryloxy complexes can
be obtained (III and IV; Figure 1).[6a,6b] Upon activation
[b] Laboratoire Hétérochimie Fondamentale et Appliquée, CNRS,
Université Paul Sabatier
118, Route de Narbonne, 31062 Toulouse Cedex 9, France
http://lhfa.cnrs.fr/index.php/equipes/shen/accueil-shen
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1
with methylaluminoxane (MAO), catalysts derived from III yields.[11] All of the compounds were characterized by H
and IV are poorly active towards ethylene with a selectivity and 13C NMR spectroscopy and mass spectrometry.
oriented towards polymers (Ͼ95%).
The aryloxy ether ligands were obtained by following a
In light of this and the potential impact of a third coordi- second route, which is shown in Scheme 2. The first step is
nation donor of the aryloxy-based TiIV complexes, we de- the reduction of 3,5-di-tert-butylsalicylaldehyde to the cor-
cided to further study this ligand family through the evalu- responding alcohol[12] and the subsequent bromination to
ation of a small library of tridentate aryloxy-based ligands 3,5-di-tert-butyl-2-hydroxybenzyl bromide.[13] The repara-
(Figure 2) derived from the aryloxy amine and aryloxy tion of ligands 3a–3d was then readily achieved by reaction
ether ligands found in structures III and IV (Figure 1).[7] of this highly reactive intermediate with the corresponding
For both ligand families, special attention was devoted to deprotonated alcohol HO–(Y)–OMe. All of the compounds
1
the role of the spacer group between the nitrogen or oxygen were characterized by H and 13C NMR spectroscopy and
atom linked to the aryloxy group and the third donor group mass spectrometry.
(fixed as OMe in this study; Figure 2). By this means, we
wished to gain a better insight into the critical parameters
that influence the coordination mode of this class of ligand,
the stability of the resulting titanium complexes and their
reactivity as catalysts in ethylene oligomerization versus
polymerization.
Scheme 2. Synthetic route to tridentate aryloxy ether ligands.
In addition, crystals of ligand 3a were grown from a satu-
rated pentane solution, and the structure was determined
by X-ray crystallography (Figure 3). The solid-state struc-
ture shows intramolecular H-bond interactions between the
phenolic hydrogen atom and the ether and methoxy func-
tionalities. Similarities with the analogous tridentate aryl-
oxy amine ligand described by McGuinness et al. can be
observed.[9] The distance between O32 and H541 is compar-
able to that of the H bond between the NMe group and the
Figure 2. Ligand platforms used in this study.
Results and Discussion
The aryloxy amine ligands 2a–2d were prepared by the phenolic hydrogen atom reported previously (2.004/
procedure displayed in Scheme 1. It should be noted that a 2.028 Å). In both structures, the distortion angles between
potentially noninnocent NH group was chosen in the struc- the phenol and ether (or NMe) moieties are also similar
ture. Indeed, such NH moieties are deprotonated upon [107.9(4)/112.31(9)°].
MAO activation,[8] which leads to an overall dianionic li-
With these eight new ligands in hand, the synthesis of
gand, unlike the recently evaluated NMe analogues.[9] This the respective titanium(IV) complexes was studied. The syn-
deprotonation proved to be of special interest for R2P–NH– thesis relies on a classical procedure in which ligands 2a–2d
PR2/CrIII systems in the selective trimerization of ethylene or 3a–3d are treated with 1.1 equiv. of TiCl4 in toluene at
to 1-hexene.[10] The Schiff base condensation of the com- –78 °C. Quite surprisingly, however, this procedure, which
mercial 3,5-di(tert-butyl)salicylaldehyde with the appropri- is efficient for 1a and 1b, failed to deliver the corresponding
ate amine provided the corresponding aryloxy imine ligands complexes cleanly with the saturated ligands 2a and 2b or
1a–1d.[5a] These intermediates were then reduced by NaBH4 with ligands 3a and 3b. Alternative synthetic strategies were
to the desired aryloxy amine ligands 2a–2d in excellent followed, such as reactions with less acidic titanium precur-
Scheme 1. Synthetic route to tridentate aryloxy amine ligands.
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Scheme 4. Synthesis of 6 and 7.
Figure 3. ORTEP diagram of the molecular structure of ligand 3a
(CCDC-1405437). The thermal ellipsoids are shown at the 50%
probability level. Hydrogen atoms are omitted for clarity except for
the phenolic hydrogen atom. Selected bond length [Å] and angles
[°]: C53–O54 1.392(6), C47–O32 1.467(6), O54–H541 0.855(3),
O32–H541 2.004(3), O37–H541 2.284(4); C48–C53–O54 122.0(4),
C48–C47–O32 107.9(4), C53–O54–H541 103.8(3).
sors such TiCl4(THF)2 (THF = tetrahydrofuran) or the use
of a silylated phenol derivative before the reaction with the
titanium precursor [TiCl4 or TiCl4(THF)2], but none of
these reactions were successful. We were not able to identify
1
the decomposition products precisely, but H NMR spec-
troscopy of the bulk product showed the disappearance of
the methylene group. The stability of the methylene group
linked to the phenol moiety has been reported to be poor
in some instances, especially if highly acidic compounds
such as TiCl4 are used and, thus, can be evoked to explain
these disappointing results.[14]
Figure 4. ORTEP diagram of the molecular structure of 4 (CCDC-
1405434). The thermal ellipsoids are shown at the 50% probability
level. Hydrogen atoms are omitted for clarity except for that of
the amine group. Selected bond length [Å] and angles [°]: Ti–Cl2
2.3112(6), Ti–Cl3 2.2700(5), Ti–Cl5 2.3675(6), Ti–O7 1.7617(12),
Ti–N23 2.1943(14), Ti–O26 2.1715(13); Cl2–Ti–Cl3 95.19(2), Cl2–
On the other hand, the classical synthesis proved success- Ti–Cl5 166.37(2), Cl3–Ti–Cl5 92.18(2), O7–Ti–N23 83.41(5), O7–
Ti–O26 158.75(5), N23–Ti–O26 75.36(5), Ti–O7–C8 144.40(11).
ful with ligands 2c–2d (Scheme 3) and 3c–3d (Scheme 4).
With ligand 2c, the hexacoordinate complex 4 was ob-
tained. Crystals of 4 were grown by slow diffusion of hept-
Interestingly, under similar conditions, the reaction of li-
ane into a dichloromethane solution of the complex (Fig- gand 2d with TiCl4 led to a mixture of two complexes, 5(A)
1
ure 4). Interestingly, 4 adopts a distorted octahedral geome- and 5(B), in a 73:27 ratio (Scheme 3). The H NMR spec-
try with the ligand arranged in a meridional fashion. The trum of 5(A) is characterized by the signal of a methoxy
five-membered N(23)–O(26) chelate ring of 4 adopts a dis- group at δ = 4.23 ppm, which is in accordance with a triden-
torted folded conformation, which results in an inclination tate chelation to the titanium centre, as depicted in
1
of this ring of ca. 40° to the equatorial plane [Ti, O(7), C(8), Scheme 3. In contrast, the H NMR spectrum of 5(B) dis-
C(9), C(22)].
plays a broad singlet at δ = 7.85 ppm for the NH group,
Scheme 3. Synthesis of complexes 4 and 5.
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whereas the pendant methoxy group exhibits a singlet at δ
= 3.40 ppm, identical to the chemical shift of this group in
the free ligand. Moreover, the absence of signals corre-
sponding to diastereotopic protons, typical for an ABX sys-
tem, further confirmed the ligand arrangement in 5(B) de-
picted in Scheme 3.
From this mixture, crystals of 5(A) suitable for X-ray dif-
fraction were grown by the diffusion of heptane into a
dichloromethane solution of the bulk product. The solid-
state analysis revealed an octahedral geometry at the tita-
nium centre, which possesses meridional chlorido ligands
(Figure 5).
Figure 6. ORTEP diagram of the molecular structure of 6 (CCDC-
1405436). The thermal ellipsoids are shown at the 50% probability
level. Hydrogen atoms are omitted for clarity. Selected bond length
[Å] and angles [°]: Ti–O14 1.765(2), Ti–O5 2.151(3), Ti–O8
2.146(2), Ti–Cl3 2.259(1), Ti–Cl2 2.312(2), Ti–Cl4 2.336(2); Cl2–
Ti–Cl3 94.05(5), Cl2–Ti–Cl4 167.03(5), Cl3–Ti–Cl4 93.25(5), O8–
Ti–O5 74.7(1), O8–Ti–O14 157.6(1), O5–Ti–O14 83.9(1), Ti–O14–
C13 143.4(2).
To summarize, the coordination studies revealed that the
nature of the spacer group X or Y (aryl vs. alkyl) has a
major influence on the stability of the ligands in the coordi-
nation sphere of the metal centre. Ligands bearing biphenyl
and aryl spacers such as 2a–2b and 3a–3b led to decomposi-
tion, whereas ligands 2c–2d and 3c–3d provided the ex-
pected Ti complexes.
The reactivity of the Ti complexes 4–7 was evaluated
towards ethylene poly- and oligomerization with MAO as
a cocatalyst (Table 1). As a benchmark in this study, we
used IIb [featuring a tBu moiety instead of the adamantyl
(Ad) moiety in IIa; Figure 1], which was synthesized by fol-
lowing the procedure described previously.[5a] Complex IIb
exhibited high activity [294 kg(C2H4)/g(Ti)/h] and selectiv-
ity towards 1-hexene (86% C6, Ͼ99.5% C6=1). The main
byproduct was a C10 olefin mixture, which can be explained
Figure 5. ORTEP diagram of the molecular structure of 5(A)
(CCDC-1405435). The thermal ellipsoids are shown at the 50%
probability level. Hydrogen atoms are omitted for clarity except for
that of the amine group. Selected bond length [Å] and angles [°]:
Ti–Cl2 2.3727(6), Ti–Cl3 2.2781(6), Ti–Cl4 2.3184(6), Ti–O5
2.1541(14), Ti–N9 2.2314(16), Ti–O17 1.7703(13); Cl2–Ti–Cl3
94.56(2), Cl2–Ti–Cl4 165.11(2), Cl3–Ti–Cl4 95.62(2), O5–Ti–N9
87.85(6), O5–Ti–O17 171.10(6), N9–Ti–O17 84.30(6), C16–O17–Ti
143.24(12), N9–Ti–Cl3 177.45(5).
Complexes 6 and 7 were obtained in turn from ligands by the co-trimerization of 1-hexene with two ethylene mol-
3c and 3d, respectively (Scheme 4).
ecules.[5a,9,15] Low amounts of butenes, octenes and C14 ole-
Complex 6 appeared as a dark red powder that is highly fins were also detected in the liquid phase (less than 0.5%).
soluble in CH2Cl2. Crystals suitable for X-ray analysis were After drying, 2% of polyethylene (PE) can be isolated from
obtained by slow diffusion of pentane into a CH2Cl2 solu- the reaction mixture. The activity as well as the selectivity
tion of 6. Similarly to the amine analogue 4, complex 6 with complex IIb appeared similar to those of the original
adopts a distorted octahedral geometry with the ligand ar- system IIa, developed by Fujita et al.[5a] Nevertheless, a
ranged in a meridional fashion (Figure 6). The Ti–N23 small decrease of 1-hexene selectivity was observed. The
bond in 4 is slightly longer [2.1943(14) Å] than the Ti–O5 steric impact of the adamantyl group in IIa (vs. tBu for IIb)
bond in 6 [2.151(3) Å]. This bond lengthening can be ex- can be evoked to explain this result. Some of the PE proper-
plained by the weaker titanium–amine interaction in 4 com- ties were obtained from differential scanning calorimetry
pared with the titanium–ether interaction in 6. The other (DSC) analysis. This material melts/softens at ca. 126 °C.
Ti–O and Ti–Cl bonds in 4 and 6 are very similar.
By following the method described by Tait and co-
Contrary to ligand 2d, ligand 3d led to the formation of workers,[16] the crystallinity of this PE was estimated to be
a single complex (7) in solution; complex 7 was also isolated ca. 29%. The microstructure was accessible through 13C
as a dark red solid. Despite several attempts, we were not NMR spectroscopy analysis. The material formed was an
able to isolate crystals of 7 for X-ray diffraction analysis. ethylene/1-hexene copolymer with the incorporation of ca.
1
However, the H NMR spectroscopic data are consistent 1% of 1-hexene in the polymeric chain. This analysis
with the effective formation of a κ3-(OOO)-titanium che- showed good agreement with the DSC thermal analysis.
lated system, as proved by the chemical shift of the OMe Moreover, the absence of a signal corresponding to the ex-
signal at δ = 4.25 ppm, significantly downfield from that of tremity of the polymeric chain suggests an elevated molec-
the free ligand.
ular weight.
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Table 1. Ethylene oligo-/polymerization for IIb and 4–7.[a]
Entry Catalyst Activity[b] C6 [%] (1-C6)[c,d] C10 [%][c,d] PE [%][e]
Experimental Section
General: Unless stated otherwise, reactions were performed under
argon by standard Schlenk techniques. Anhydrous CH2Cl2, toluene
and pentane were purified with a solvent purification system (SPS-
M-Braun). NMR spectra (1H, 31P and 13C) were recorded with a
Bruker AV 300 MHz spectrometer at 303 K unless stated otherwise.
NMR spectra of polymers (13C) were recorded with a Bruker DRX
400 MHz spectrometer equipped with a PSEX 10 mm probe. Deu-
terated solvents were purchased from Sigma–Aldrich or Eurisotop.
CD2Cl2 was used as a solvent, if not further specified. GC analyses
were performed with an Agilent 6850 series II device equipped with
an autosampler and fitted with PONA columns. GC–MS analyses
were conducted with an Agilent 6890 N apparatus equipped with
a PONA or HP-5-MS column and an Agilent 5975B inert XL EI/
CI MSD mass spectrometer. With exception of the compounds
given below, all reagents were purchased from commercial suppliers
and used without further purification. DSC analyses were per-
formed with a TA Instruments Q100 analyzer. MAO was supplied
by Chemtura as a 10% solution in toluene. 3-tert-Butyl-5-methyl-
salicylaldehyde,[18] 2-(2Ј-methoxyphenyl)aniline,[19] 2,4-di-tert-
butyl-6-(hydroxymethyl)phenol,[12] 2,4-di-tert-butyl-6-(bromometh-
yl)phenol[13] and 2-hydroxy-2Ј-methoxybiphenyl[20] were prepared
according to literature methods. CCDC-1405437 (for 3a), -1405434
(for 4), -1405435 [for 5(A)] and -1405436 (for 6) contain the supple-
mentary crystallographic 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.
1[f,g]
2
3
4
5
IIb
4
5
6
7
294
4
4
7
8
86 (99+)
–
12
–
–
Ͻ1
Ͻ1
2
99+
99+
93
–
4 (92)
3 (88)
94
[a] Catalyst (5 μmol), MAO (500 equiv.), toluene (10 mL), 30 bar,
30 °C, 1 h. [b] In kg(C2H4)/g(Ti)/h. For catalysts producing essen-
tially PE, the activities in kg(PE)/mol(Ti)/bar/h are 6 (Entries 2 and
3), 11 (Entry 4) and 12 (Entry 5). [c] In wt.-%. [d] Traces of C4, C8
and C10+ olefins. [e] In wt.-% (calculated from isolated solid). [f]
2 μmol catalyst. [g] Reaction time 30 min.[17]
Under identical conditions, the amine-based TiIV com-
plexes 4 and 5 (Table 1, Entries 2–3) produce solely polyeth-
ylene. Under these reaction conditions, the swelling of the
polyethylene in contact with the solvent in the reactor pre-
vents the recovery of sufficient liquid phase for analysis.
Similarly, the ether-based TiIV complexes 6 and 7 also pre-
dominantly produce polyethylene (93 and 94%, respec-
tively). Interestingly, for both 6 and 7, small but significant
amounts of 1-hexene were produced (Table 1, Entries 4 and
5); therefore, several active species compete in the reaction
media. The physical properties of the polymers produced
with 6 and 7 seem to be different to those obtained with
IIb. They melt/soften at 136–138 °C, which is significantly
higher than the value for the PE produced with IIb.
Furthermore, the crystallinity of these materials appeared
to be ca. 41–45%, which is once again significantly higher
than the value for IIb. The microstructures, Mn values and
Mw values of theses polyethylenes were not accessible owing
to the insolubility of the material even at high temperature;
this suggests that linear polyethylene with an ultrahigh mo-
lecular weight is formed.
Ligand 1e Used in IIb: To a solution of 3-tert-butyl-5-methylsalicyl-
aldehyde (0.786 g, 3.95 mmol) in MeOH (15 mL) was added a solu-
tion of 2-(2Ј-methoxyphenyl)aniline (0.759 g, 3.95 mmol) in MeOH
(5 mL) and a few drops of acetic acid. The reaction mixture was
stirred at room temperature overnight. The product precipitated
from the reaction solution as orange solid and was isolated by fil-
tration (0.959 g, yield 65%). MS (EI+): m/z = 373 [M]+. H NMR
1
(300 MHz, CD2Cl2): δ = 13.32 (s, 1 H, OH), 8.51 (s, 1 H, N=CH),
7.51–7.30 (m, 4 H, Ar-H), 7.27–7.19 (m, 2 H, Ar-H), 7.15 (d, J =
2.1 Hz, 1 H, Ar-H), 7.06–6.92 (m, 3 H, Ar-H) 3.72 (s, 3 H, OCH3),
2.27 (s, 3 H, Ar-CH3), 1.35 [s, 9 H, Ar-C(CH3)3] ppm. 13C{1H}
NMR (75 MHz): δ = 163.5 (CH), 158.6 (C), 157.0 (C), 147.8 (C),
137.5 (C), 134.6 (C), 131.7 (CH), 131.7 (CH), 131.4 (CH), 130.6
(CH), 129.4 (CH), 129.0 (CH), 128.9 (CH), 127.2 (C), 126.8 (CH),
120.7 (CH), 119.2 (C), 118.4 (CH), 111.0 (CH), 55.5 (CH3), 35.0
(C), 29.4 (CH3), 20.7 (CH3) ppm.
Conclusions
General Procedure for the Synthesis of Ligands 1a–1d: Ligands 1a–
1d were synthesized by condensation reactions of 3,5-di-tert-butyl-
salicylaldehyde (1.0 equiv.) with the corresponding amine
(1.0 equiv.) in MeOH (0.6 m). The reaction mixture was stirred at
room temperature overnight. Compounds 1a and 1b precipitated
from their reaction solutions and were isolated by filtration. Li-
gands 1c and 1d were isolated as oils after concentration under
high vacuum.
We have reported the synthesis and characterization of a
library of aryloxy-based titanium complexes. Coordination
studies revealed that both the nature of the central hetero-
element (amine vs. ether) and the type of bridging spacer
(aromatic vs. aliphatic) are crucial ligand features for the
formation of stable titanium complexes. For the tridentate
aryloxy–TiIV complexes studied, decomposition occurs if
aromatic spacers are used. If aliphatic spacer groups are
used, the complexes obtained adopt distorted octahedral
geometries with the ligand arranged in a meridional fash-
ion. Furthermore, when activated with MAO, these TiIV
precatalysts produced polyethylene in 93–99%. Only with
the Ti complexes bearing the “O,O,O” ligand could a sig-
nificant amount of 1-hexene be detected. Further investi-
gations are currently in progress to identify the specific fea-
ture of the tridentate aryloxyimine–TiIV complexes respon-
sible for the selective production of 1-hexene.
Ligand 1a: Yield 84% (orange solid). MS (EI+): m/z = 415 [M]+.
1H NMR (300 MHz, CD2Cl2): δ = 13.38 (br. s, 1 H, OH), 8.61 (s,
1 H, N=CH), 7.51–7.45 (m, 1 H, Ar-H), 7.42–7.36 (m, 4 H, Ar-
H), 7.29–7.21 (m, 3 H, Ar-H), 7.07–6.98 (m, 2 H, Ar-H), 3.76 (s, 3
H, OCH3), 1.39 [s, 9 H, Ar-C(CH3)3], 1.33 [s, 9 H, Ar-C(CH3)3]
ppm. 13C{1H} NMR (75 MHz): δ = 163.8 (CH), 158.5 (C), 157.1
(C), 147.9 (C), 140.7 (C), 136.9 (C), 134.6 (C), 131.7 (CH), 131.4
(CH), 129.4 (CH), 129.0 (CH), 128.9 (C), 128.1 (CH), 127.1 (CH),
126.7 (CH), 120.7 (CH), 118.8 (C), 118.3 (CH), 110.9 (CH), 55.5
(CH3), 35.3 (C), 34.4 (C), 31.6 (CH3), 29.4 (CH3) ppm.
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Ligand 1b: Yield 95% (yellow solid). MS (EI+): m/z = 339 [M]+.
(CH2), 58.9 (CH3), 53.8 (CH2), 48.3 (CH2), 35.2 (C), 34.4 (C), 31.8
1H NMR (300 MHz, CD2Cl2): δ = 8.72 (s, 1 H, N=CH), 7.47 (d, (CH3), 29.7 (CH3) ppm.
J = 2.5 Hz, 1 H, Ar-H), 7.29–7.18 (m, 3 H, Ar-H), 7.06–6.97 (m,
Ligand 2d: Yield 99% (colourless oil). MS (EI+): m/z = 461 [M]+.
2 H, Ar-H), 3.92 (s, 3 H, OCH3), 1.49 [s, 9 H, Ar-C(CH3)3], 1.35
[s, 9 H, Ar-C(CH3)3] ppm. 13C{1H} NMR (75 MHz): δ = 164.3
(CH), 158.9 (C), 153.4 (C), 140.9 (C), 138.1 (C), 137.3 (C), 128.3
(CH), 128.0 (CH), 127.2 (CH), 121.4 (CH), 120.3 (CH), 119.0 (C),
112.4 (CH), 56.3 (CH3), 35.5 (C), 34.5 (C), 31.7 (CH3), 29.7 (CH3)
ppm.
1H NMR (300 MHz, CD2Cl2): δ = 7.19 (d, J = 2.5 Hz, 1 H, Ar-
H), 6.88 (d, J = 2.5 Hz, 1 H, Ar-H), 3.94 (s, 2 H, Ar-CH2N), 3.45
(t, J = 6.1 Hz, 2 H, NHCH2CH2), 3.30 (s, 3 H, OCH3), 2.76 (t, J
= 6.7 Hz, 2 H, CH2CH2OCH3), 1.79 (m, 2 H, CH2CH2CH2), 1.41
[s, 9 H, Ar-C(CH3)3], 1.28 [s, 9 H, Ar-C(CH3)3] ppm. 13C{1H}
NMR (75 MHz): δ = 155.3 (C), 140.7 (C), 135.9 (C), 123.6 (CH),
123.0 (CH), 122.8 (C), 71.5 (CH2), 58.8 (CH3), 53.9 (CH2) 46.8
(CH2), 35.2 (C), 34.4 (C), 31.8 (CH3), 29.8 (CH2), 29.6 (CH3) ppm.
1
Ligand 1c: Yield 73% (yellow oil). MS (EI+): m/z = 291 [M]+. H
NMR (300 MHz, CD2Cl2): δ = 13.77 (br s, 1 H, OH), 8.37 (s, 1 H,
N=CH), 7.38 (d, J = 2.4 Hz, 1 H, Ar-H), 7.12 (d, J = 2.4 Hz, 1 H,
Ar-H), 3.75 (m, 2 H, CH=NCH2), 3.67 (m, 2 H, CH3OCH2), 3.36
(s, 3 H, OCH3), 1.43 [s, 9 H, Ar-C(CH3)3], 1.31 [s, 9 H, Ar-C(CH3)
3] ppm. 13C{1H} NMR (75 MHz): δ = 167.9 (CH), 158.4 (C), 140.5
(C), 136.9 (C), 127.3 (CH), 126.5 (CH), 118.4 (C), 72.4 (CH2), 59.4
(CH3), 59.0 (CH2), 35.3 (C), 34.5 (C), 31.7 (CH3), 29.6 (CH3) ppm.
Ligand 3a: To a solution of 2-(2Ј-methoxyphenyl)phenol (1.379 g,
6.89 mmol) in pentane (20 mL) and Et2O (10 mL) in a Schlenk
flask was added dropwise tetramethylethylenediamine (TMEDA;
0.800 g, 6.89 mmol). After 10 min, nBuLi was added (1.33 m in hex-
ane, 5.30 mL, 7.05 mmol) at –78 °C. The mixture was stirred at
room temperature for 4 h. A solution of 6-(bromomethyl)-2,4-di-
tert-butylphenol (2.06 g, 6.89 mmol) in Et2O (3 mL) was added.
The mixture was stirred overnight. The volatiles were removed,
water (20 mL) and dichloromethane (20 mL) were added, and the
organic phase was separated and washed with aqueous 1 m HCl
(10 mL) and water (20 mL). The organic phase was then dried with
MgSO4 and filtered, and the volatiles were removed in vacuo to
give a yellow oil. The residue was precipitated in pentane to give
the ligand 3a (0.669 g, yield 23%) as a white solid. MS (EI+): m/z
= 418 [M]+. 1H NMR (300 MHz, CD2Cl2): δ = 7.48–6.93 (m, 11
H, Ar-H and OH), 5.08 (s, 2 H, Ar-CH2O), 3.82 (s, 3 H, OCH3),
1.37 [s, 9 H, Ar-C(CH3)3], 1.26 [s, 9 H, Ar-C(CH3)3] ppm. 13C{1H}
NMR (75 MHz): δ = 156.9 (C), 155.6 (C), 152.9 (C), 142.1 (C),
136.9 (C), 131.6 (CH), 131.3 (CH), 129.2 (CH), 129.1 (CH), 128.8
(C), 127.9 (C), 124.6 (CH), 124.0 (CH), 121.9 (C), 121.6 (CH),
121.1 (CH), 111.6 (CH), 111.1 (CH), 70.5 (CH2), 56.1 (CH3), 35.1
(C), 34.3 (C), 31.5 (CH3), 29.7 (CH3) ppm.
1
Ligand 1d: Yield 96% (yellow oil). MS (EI+): m/z = 305 [M]+. H
NMR (300 MHz, CD2Cl2): δ = 13.86 (br s, 1 H, OH), 8.41 (s, 1 H,
N=CH), 7.37 (d, J = 2.5 Hz, 1 H, Ar-H), 7.11 (d, J = 2.5 Hz, 1 H,
Ar-H), 3.66 (td, J = 6.8, J = 1.2 Hz, 2 H, CH=NCH2), 3.46 (t, J
= 6.1 Hz, 2 H, CH3OCH2), 3.32 (s, 3 H, OCH3), 1.95 (quin, J =
6.6 Hz, 2 H, CH2CH2CH2), 1.43 [s, 9 H, Ar-C(CH3)3], 1.31 [s, 9 H,
Ar-C(CH3)3] ppm. 13C{1H} NMR (75 MHz): δ = 166.7 (CH), 158.5
(C), 140.5 (C), 136.9 (C), 127.1 (CH), 126.3 (CH), 118.4 (C), 70.4
(CH2), 58.7 (CH3), 56.6 (CH2), 35.3 (C), 34.5 (C), 31.7 (CH3), 31.3
(CH2), 29.6 (CH3) ppm.
General Procedure for the Synthesis of Ligands 2a–2d: To a solution
of 1a–1d (1 equiv.) in MeOH (0.5 m) at 0 °C was added NaBH4
(3 equiv.) in one portion. The reaction mixture was warmed to
room temperature and stirred for 16 h. The solvent was removed
with a rotary evaporator, and the solid obtained was dissolved in
Et2O (20 mL), washed with a saturated NaHCO3 solution (3ϫ
10 mL), dried with MgSO4, which was removed by filtration, and
the filtrate concentrated.
Ligand 3b: To a solution of 2-methoxyphenol (0.415 g, 0.33 mmol)
in pentane (10 mL) and Et2O (5 mL) in a Schlenk flask, TMEDA
(0.388 g, 0.33 mmol) was added dropwise. After 10 min, nBuLi
(1.7 m in hexane, 1.97 mL, 0.33 mmol) was added at –78 °C. The
mixture was stirred at room temperature for 4 h. A solution of 6-
(bromomethyl)-2,4-di-tert-butylphenol (1.00 g, 0.33 mmol) in Et2O
(2 mL) was added. The mixture was stirred overnight. The volatiles
were removed, water (20 mL) and dichloromethane (20 mL) were
added, and the organic phase was separated and washed with aque-
ous 1 m HCl (10 mL) and water (20 mL). The organic phase was
then dried with MgSO4 and filtered, and the volatiles were removed
in vacuo to give a yellow oil. The residue was precipitated in cold
pentane to give the ligand 3b (0.351 g, yield 31%) as a white solid.
MS (EI+): m/z = 342 [M]+. 1H NMR (300 MHz, CD2Cl2): δ = 7.65
(s, 1 H, OH), 7.32 (d, J = 2.6 Hz, 1 H, Ar-H), 7.18–6.90 (m, 5 H,
Ar-H), 5.06 (s, 2 H, Ar-CH2O), 3.92 (s, 3 H, OCH3), 1.45 [s, 9
H, Ar-C(CH3)3], 1.30 [s, 9 H, Ar-C(CH3)3] ppm. 13C{1H} NMR
(75 MHz): δ = 153.5 (C), 151.4 (C), 147.6 (C), 142.0 (C), 136.9 (C),
124.9 (CH), 124.4 (CH), 124.2 (CH), 122.1 (C), 121.5 (CH), 118.7
(CH), 112.3 (CH), 74.2 (CH2), 56.2 (CH3), 35.3 (C), 34.5 (C), 31.7
(CH3), 29.8 (CH3) ppm.
Ligand 2a: Yield 90% (white foam). MS (EI+): m/z = 417 [M]+. 1H
NMR (300 MHz, CD2Cl2): δ = 8.88 (br s, 1 H, OH or NH), 7.41–
7.31 (m, 2 H, Ar-H), 7.25–7.22 (m, 2 H, Ar-H), 7.16–6.98 (m, 6 H,
Ar-H), 4.34 (m, 2 H, Ar-CH2N), 3.83 (s, 3 H, OCH3), 1.37 [s, 9
H, Ar-C(CH3)3], 1.27 [s, 9 H, Ar-C(CH3)3] ppm. 13C{1H} NMR
(75 MHz): δ = 157.2 (C), 154.0 (C), 145.5 (C), 141.7 (C), 136.4 (C),
132.1 (CH), 131.1 (CH), 129.9 (CH), 129.0 (CH), 128.6 (C), 127.6
(C), 123.9 (C), 123.6 (CH), 122.8 (CH), 121.4 (CH), 120.4 (CH),
113.8 (CH), 111.2 (CH), 55.9 (CH3), 49.6 (CH2), 35.2 (C), 34.5 (C),
31.7 (CH3), 29.8 (CH3) ppm.
Ligand 2b: Yield 99% (white solid). MS (EI+): m/z = 341 [M]+. 1H
NMR (300 MHz, CD2Cl2): δ = 8.71 (br s, 1 H, OH or NH), 7.32
(d, J = 2.4 Hz, 1 H, Ar-H), 7.31 (d, J = 2.4 Hz, 1 H, Ar-H), 7.09–
6.88 (m, 4 H, Ar-H), 4.55 (br s, 1 H, OH or NH), 4.37 (s, 2 H, Ar-
CH2N), 3.84 (s, 3 H, OCH3), 1.42 [s, 9 H, Ar-C(CH3)3], 1.31 [s, 9
H Ar-C(CH3)3] ppm. 13C{1H} NMR (75 MHz): δ = 154.0 (C),
149.2 (C), 141.9 (C), 137.7 (C), 136.5 (C), 124.1 (CH), 123.7 (CH),
123.3 (CH), 121.5 (CH), 120.6 (CH), 114.4 (CH), 110.4 (CH), 55.9
(CH3), 49.8 (CH2), 35.3 (C), 34.6 (C), 31.8 (CH3), 29.9 (CH3) ppm.
Ligand 3c: To a suspension of NaH (5.20 g, 130.3 mmol) in THF
Ligand 2c: Yield 99% (colourless oil). MS (EI+): m/z = 447 [M]+. (60 mL) in a Schlenk flask, 2-methoxyethanol (7.63 g, 100.2 mmol)
1H NMR (300 MHz, CD2Cl2): δ = 7.19 (d, J = 2.4 Hz, 1 H, Ar- was added dropwise at room temperature. The mixture was stirred
H), 6.87 (d, J = 2.4 Hz, 1 H, Ar-H), 3.95 (s, 2 H, Ar-CH2N), 3.51
for 4 h. A solution of 6-(bromomethyl)-2,4-di-tert-butylphenol
(t, J = 5.1 Hz, 2 H, NHCH2CH2), 3.34 (s, 3 H, OCH3), 2.82 (t, J (10.0 g, 33.4 mmol) in THF (60 mL) was added. The mixture was
= 5.1 Hz, 2 H, CH2CH2OCH3), 1.43 [s, 9 H, Ar-C(CH3)3], 1.30 [s, heated under reflux overnight. Upon cooling, water (50 mL) was
9 H, Ar-C(CH3)3] ppm. 13C{1H} NMR (75 MHz): δ = 155.2 (C), added, and the organic phase was separated, washed with aqueous
140.7 (C), 135.9 (C), 123.7 (CH), 123.1 (CH), 122.6 (C), 71.4 1 m HCl (30 mL) and water (50 mL). The organic phase was then
Eur. J. Inorg. Chem. 2015, 5272–5280
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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FULL PAPER
1
dried with MgSO4 and filtered, and the volatiles were removed in
vacuo to give the ligand 3c (8.70 g, yield 88%) as a yellow oil. H
of 4 in dichloromethane. H NMR (300 MHz, CD2Cl2): δ = 7.36
(d, J = 2.0 Hz, 1 H, Ar-H), 7.11 (d, J = 2.0 Hz, 1 H, Ar-H), 4.58
1
NMR (300 MHz, CDCl3): δ = 7.61–7.50 (br. s, 1 H, OH), 7.27 (d, (m, 1 H, CH2), 4.36 (m, 1 H, CH2), 4.26 (s, 3 H, OCH3), 4.17 (m,
J = 2.4 Hz, 1 H, Ar-H), 6.90 (d, J = 2.4 Hz, 1 H, Ar-H), 4.71 (s, 2 1 H, CH2), 3.86 (m, 1 H, CH2), 3.64 (m, 1 H, CH2), 3.182 (m, 1
H, Ar-CH2O), 3.74–3.69 (m, 2 H, CH3OCH2), 3.62–3.57 (m, 2 H, H, CH2), 1.54 [s, 9 H, C(CH3)3], 1.31 [s, 9 H, C(CH3)3] ppm.
CH2OCH2), 3.41 (s, 3 H, OCH3), 1.43 [s, 9 H, Ar-C(CH3)3], 1.29 13C{1H} NMR (75 MHz): δ = 161.2 (C), 148.5 (C), 135.9 (C), 128.9
[s, 9 H, Ar-C(CH3)3] ppm. 13C{1H} NMR (75 MHz): δ = 153.2
(C), 124.8 (CH), 124.3 (CH), 75.3 (CH2), 67.0 (CH3), 55.6 (CH2),
(C), 141.5 (C), 136.4 (C), 124.2 (CH), 123.4 (CH), 122.0 (C), 73.7 50.5 (CH2), 35.8 (C), 35.1 (C), 31.5 (CH3), 30.5 (CH3) ppm.
(CH2), 71.6 (CH2), 69.4 (CH2), 59.1 (CH3), 35.1 (C), 34.3 (C), 31.7 C18H30Cl3NO2Ti (446.70): calcd. C 48.40, H 6.77, N 3.14; found
(CH3), 29.8 (CH3) ppm.
C 48.35, H 6.79, N 3.05.
Ligand 3d: To a suspension of NaH (0.239 g, 9.96 mmol) in THF
Complex 5: The general procedure was applied with TiCl4 (0.209 g,
1.1 mmol) and 2d (0.307 g, 1.0 mmol) in toluene (10 mL). The re-
moval of the volatiles gave 5 as a red solid (0.322 g, yield 70%).
The analysis of the complex by NMR spectroscopy showed the
formation of two complexes 5(A)/5(B) in a 73:23 ratio. Single crys-
tals of 5(A) were grown by slow diffusion of heptane into a di-
chloromethane solution. C19H32Cl3NO2Ti (460.73): calcd. C 49.54,
(20 mL) in
a Schlenk flask, 3-methoxypropan-1-ol (0.464 g,
5.15 mmol) was added dropwise at room temperature. The mixture
was stirred for 4 h. A solution of 6-(bromomethyl)-2,4-di-tert-but-
ylphenol (1.009 g, 3.37 mmol) in THF (10 mL) was added. The
mixture was heated under reflux overnight. Upon cooling, water
(20 mL) was added, and the organic phase was separated and
washed with aqueous 1 m HCl (10 mL) and water (20 mL). The H 7.00, N 3.04; found C 49.37, H 7.08, N 2.94.
organic phase was then dried with MgSO4 and filtered, and the
Compound 5(A): 1H NMR (300 MHz, CD2Cl2): δ = 7.34 (d, J =
volatiles were removed in vacuo to give a yellow residue. Column
chromatography (EtOAc/heptane, 1:10, v/v) gave the ligand 3d
(0.220 g, yield 21%) as a colourless oil. 1H NMR (300 MHz,
CDCl3): δ = 7.69 (s, 1 H, OH), 7.26 (d, J = 2.6 Hz, 1 H, Ar-H),
6.88 (d, J = 2.6 Hz, 1 H, Ar-H), 4.66 (s, 2 H, Ar-CH2O), 3.66 (t, J
= 6.1 Hz, 2 H, CH2OCH2), 3.49 (t, J = 6.1 Hz, 2 H, CH3OCH2),
3.35 (s, 3 H, OCH3), 1.91 (quint, J = 6.1 Hz, 2 H, CH2CH2CH2),
1.42 [s, 9 H, Ar-C(CH3)3], 1.28 [s, 9 H, Ar-C(CH3)3] ppm. 13C{1H}
NMR (75 MHz): δ = 153.1 (C), 141.5 (C), 136.4 (C), 124.1 (CH),
123.1 (CH), 122.1 (C), 73.6 (CH2), 69.9 (CH2), 68.2 (CH2), 58.9
(CH3), 35.1 (C), 34.3 (C), 31.8 (CH3), 29.8 (CH2), 29.8 (CH3) ppm.
2.3 Hz, 1 H, Ar-H), 7.11 (d, J = 2.1 Hz, 1 H, Ar-H), 4.86 (td, J =
11.6, J = 2.1 Hz, 1 H, CH2), 4.54 (t, J = 12.8 Hz, 1 H, CH2), 4.23
(s, 3 H, OCH3), 4.08 (dt, J = 11.7, J = 3.4 Hz, 1 H, CH2), 3.57
(dd, J = 13.8, J = 2.1 Hz, 1 H, CH2), 3.23 (td, J = 12.0, J = 2.1 Hz,
1 H, CH2), 3.13 (m, 1 H, CH2), 2.35 (m, 1 H, CH2), 1.96 (m, 1 H,
CH2), 1.54 [s, 9 H, C(CH3)3], 1.31 [s, 9 H, C(CH3)3] ppm. 13C{1H}
NMR (75 MHz): δ = 163.2 (C), 148.2 (C), 135.8 (C), 130.0 (C),
124.7 (CH), 124.3 (CH), 78.5 (CH2), 69.4 (CH3), 57.2 (CH2), 52.4
(CH2), 35.7 (C), 35.1 (C), 31.5 (CH3), 30.4 (CH3), 26.9 (CH2) ppm.
Compound 5(B): 1H NMR (300 MHz, CD2Cl2): δ = 7.91 (br. s, 1
H, NH), 7.51 (d, J = 2.0 Hz, 1 H, Ar-H), 7.16 (d, J = 2.0 Hz, 1 H,
Ar-H), 4.51 (br. s, 2 H, CH2), 3.75 (m, 2 H, CH2), 3.52 (br. s, 2 H,
CH2), 3.40 (s, 3 H, OCH3), 2.11 (m, 2 H, CH2), 1.57 [s, 9 H,
C(CH3)3], 1.32 [s, 9 H, C(CH3)3] ppm. 13C{1H} NMR (75 MHz):
δ = 148.7 (C), 140.4 (C), 127.1 (CH), 126.6 (CH), 123.1 (C), 73.5
(CH2), 59.9 (CH3), 50.1 (CH2), 48.8 (CH2), 36.1 (C), 35.2 (C), 31.4
(CH3), 31.2 (CH3), 25.1 (CH2) ppm.
Complex IIb: To a solution of freshly distilled TiCl4 (0.355 g,
1.87 mmol) in toluene at –78 °C in a Schlenk flask, a solution of
ligand 1e (0.636 g, 1.70 mmol) in toluene was added dropwise. The
mixture was allowed to return to room temperature and then
stirred overnight. The volatiles were removed under reduced pres-
sure, and pentane was added to precipitate the complex. The solid
was isolated by filtration with a cannula, washed twice with pent-
ane and dried under vacuum. Complex IIb was obtained as a dark
General Procedure for the Preparation of the Titanium Complexes 6
and 7: To a solution of freshly distilled TiCl4 (1.1 equiv.) in toluene
at –78 °C in a Schlenk flask, a solution of the ligand (1.0 equiv.) in
toluene was added dropwise. The mixture was allowed to return to
room temperature and stirred overnight. The solution was concen-
trated, and pentane was added to precipitate the complex. The solid
was isolated by filtration with a cannula, washed three times with
pentane and dried under vacuum.
1
red solid (0.770 g, yield 88%). H NMR (300 MHz, CD2Cl2): δ =
8.14 (s, 1 H, N=CH), 7.56–7.45 (m, 3 H, Ar-H), 7.42–7.27 (m, 5
H, Ar-H), 7.20–7.11 (m, 2 H, Ar-H), 4.34 (s, 3 H, OCH3), 2.34
(s, 3 H, Ar-CH3), 1.50 [s, 9 H, Ar-C(CH3)3] ppm. 13C{1H} NMR
(75 MHz): δ = 169.3 (CH), 162.0 (C), 158.5 (C), 152.0 (C), 136.6
(C), 136.1 (CH), 134.6 (C), 133.1 (CH), 131.7 (2 C, CH), 131.1 (C),
130.5 (C), 130.2 (CH), 129.5 (CH), 128.2 (CH), 127.8 (CH), 127.6
(C), 126.2 (CH), 123.5 (CH), 72.5 (CH3), 35.4 (C), 30.0 (CH3), 21.1
(CH3) ppm. C25H26Cl3NO2Ti (526.74): calcd. C 57.01, H 4.98, N
2.66; found C 56.87, H 5.09, N 2.65.
Complex 6: The general procedure was applied with TiCl4 (0.188 g,
0.99 mmol) and 3c (0.264 g, 0.90 mmol) in toluene (10 mL). The
removal of the volatiles gave 6 (0.300 g, yield 74%) as a dark red
solid. Single crystals were grown by slow diffusion of pentane into
a solution of 6 in dichloromethane. 1H NMR (300 MHz, CD2Cl2):
δ = 7.39 (d, J = 2.3 Hz, 1 H, Ar-H), 7.08 (d, J = 2.3 Hz, 1 H,
Ar-H), 5.10 (s, 2 H, Ar-CH2O), 4.35 (br. s, 4 H, CH3OCH2 and
CH2OCH2), 4.26 (s, 3 H, OCH3), 1.54 [s, 9 H, Ar-C(CH3)3], 1.31
[s, 9 H, Ar-C(CH3)3] ppm. 13C{1H} NMR (75 MHz): δ = 161.4
(C), 148.8 (C), 135.6 (C), 126.4 (C), 125.0 (CH), 123.6 (CH), 78.5
(CH2), 73.7 (CH2), 73.3 (CH2), 67.4 (CH3), 35.8 (C), 35.2 (C), 31.5
(CH3), 30.5 (CH3) ppm. C18H29Cl3O3Ti (447.68): calcd. C 48.30,
H 6.53; found C 48.16, H 6.65.
General Procedure for the Preparation of the Titanium Complexes 4
and 5: To a solution of freshly distilled TiCl4 (1.1 equiv.) in toluene
at –78 °C in a Schlenk flask, a solution of the ligand (1.0 equiv.) in
toluene was added dropwise. The mixture was allowed to return to
room temperature and then warmed to 50 °C for 3 h as a stream
of argon was bubbled through to facilitate the release of HCl. After
the reaction mixture had cooled to room temperature, the volatiles
were removed under reduced pressure, and pentane was added to
precipitate the complex. The solid was isolated by filtration with a
cannula and dried under vacuum.
Complex 4: The general procedure was applied with TiCl4 (0.100 g,
0.53 mmol) and 2c (0.141 g, 0.48 mmol) in toluene (10 mL). The
removal of the volatiles gave 4 (0.180 g, yield 75%). Single crystals
were grown by slow diffusion of heptane into a saturated solution
Complex 7: The general procedure was applied with TiCl4 (0.144 g,
0.76 mmol) and 3d (0.215 g, 0.69 mmol) in toluene (10 mL). The
removal of the volatiles gave 7 (0.174 g, yield 55%) as a dark red
1
solid. H NMR (300 MHz, CD2Cl2): δ = 7.39 (d, J = 2.3 Hz, 1 H,
Eur. J. Inorg. Chem. 2015, 5272–5280
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Ar-H), 7.08 (d, J = 2.3 Hz, 1 H, Ar-H), 5.15 (s, 2 H, Ar-CH2O),
4.42 (t, J = 5.5 Hz, 2 H, CH2OCH2), 4.29 (t, J = 5.2 Hz, 2 H,
CH3OCH2), 4.25 (s, 3 H, OCH3), 2.41 (quint, J = 5.5 Hz, 2 H,
CH2CH2CH2), 1.54 [s, 9 H, Ar-C(CH3)3], 1.31 [s, 9 H, Ar-C-
(CH3)3] ppm. 13C{1H} NMR (75 MHz): δ = 162.7 (C), 148.6 (C),
135.5 (C), 127.5 (C), 124.9 (CH), 123.5 (CH), 80.5 (CH2), 78.1
(CH2), 77.5 (CH2), 69.3 (CH3), 35.7 (C), 35.2 (C), 31.5 (CH3), 30.5
(CH3), 27.9 (CH2) ppm. C19H31Cl3O3Ti (461.71): calcd. C 49.43,
H 6.77; found C 49.35, H 6.63.
Oligomerization Procedure: The catalytic experiments were per-
formed in a 35 mL stainless-steel autoclave equipped with a me-
chanical stirrer. In a typical procedure, the autoclave was preheated
to 100 °C and flushed with nitrogen. After cooling to room tem-
perature, the autoclave was filled with MAO (500 equiv.) in toluene.
After 5 min, the titanium precatalyst in toluene was added to the
reactor (total solvent volume 10 mL). The reactor was then pressur-
ized with ethylene and heated at 30 °C. During the reaction, the
pressure was maintained with a replenishing flow of ethylene. After
1 h, the reaction was stopped, and the autoclave was cooled to
10 °C and depressurized. The residual MAO was quenched with
acidified methanol. The organic phase was recovered and weighed
after separation from a solution (5 mL) of H2SO4 (10%). The com-
position of the organic phase was then determined by GC analysis.
If solid polyethylene formed, it was recovered from the reaction
mixture by filtration, dried at 100 °C for 16 h and weighed. The
thermal analysis of the polymers was conducted with a DSC Q100
analyzer (TA Instruments). The samples (Ͻ 10 mg) were heated to
150 °C and subsequently cooled to 0 or –70 °C at a rate of 10 °C/
min. A second heating cycle to 180 °C was used for data analysis.
The NMR spectra of the polymer were recorded with the samples
in a mixture of deuterated and nondeuterated o-dichlorobenzene
as the solvent at 393 K.
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Acknowledgments
We thank IFP Energies nouvelles (IFPEN) for the financial sup-
port of this work. We are grateful to Erwann Jeanneau (Centre
National de la Recherche Scientifique de Lyon), Pierre Braunstein
(University Louis Pasteur, Strasbourg) for the crystal structure
analysis and Christophe Boisson (University Claude Bernard,
Lyon) for NMR analysis of the polymers. David Proriol (IFPEN)
and Stéphane Harry (IFPEN) are also thanked for technical sup-
port.
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Received: July 2, 2015
Published Online: October 16, 2015
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim