Synthesis of titanium(IV) and zirconium(IV) complexes with an [OSSO]-type bis(phenolate) ligand bearing a trans-cyclohexane-1,2-diyl ring and 1-hexene polymerization

Article abstract of DOI:10.1021/om101131k

The Ti(IV) and Zr(IV) complexes 9 and 11 with a new [OSSO]-type bis(phenolate) ligand bearing a trans-cyclohexane-1,2-diyl ring (6) were synthesized. The reaction of 6 with Ti(OiPr)₄ in toluene gave the two C₂-symmetric, diastereomer

Full text of DOI:10.1021/om101131k

ARTICLE
pubs.acs.org/Organometallics
Synthesis of Titanium(IV) and Zirconium(IV) Complexes
with an [OSSO]-Type Bis(phenolate) Ligand Bearing a
trans-Cyclohexane-1,2-diyl Ring and 1-Hexene
Polymerization
Akihiko Ishii,* Kanako Asajima, Tomoyuki Toda, and Norio Nakata
Department of Chemistry, Faculty of Science and Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo,
Sakura-ku, Saitama 338-8570, Japan
S Supporting Information
b
ABSTRACT:
The Ti(IV) and Zr(IV) complexes 9 and 11 with a new [OSSO]-type bis(phenolate) ligand bearing a trans-cyclohexane-1,2-diyl
ring (6) were synthesized. The reaction of 6 with Ti(OiPr)4 in toluene gave the two C2-symmetric, diastereomeric Ti complexes
(Λ*,S*,S*)-9 and (Δ*,S*,S*)-9, the latter of which was characterized by X-ray crystallography. The reaction of 6 with Zr(CH2Ph)4
also provided a mixture of the two C2-symmetric diastereomers (Λ*,S*,S*)-11 and (Δ*,S*,S*)-11. Polymerization of 1-hexene
employing 11 as the precatalyst yielded isotactic poly(1-hexene) with high activity. In relation to the activity, an NMR study was
carried out for the cationic zirconium complex 12þ[B(CH2Ph)(C6F5)3]ꢀ in comparison with the corresponding complex
13þ[B(CH2Ph)(C6F5)3]ꢀ, bearing a trans-cyclooctane-1,2-diyl ring in the ligand.
’ INTRODUCTION
1 and 5ꢀ5ꢀ5 for 2.3a These [OSSO]-type bis(phenolate)
ligands have also been employed for the synthesis of complexes
with transition metals in addition to group 4 elements.9
Development of homogeneous, single-site metallocene and
post-metallocene catalysts for olefin polymerization has been
drawing considerable attention1 since the reports by Sinn and
Kaminsky.2 Recently, group 4 metal complexes having [OSSO]-
type bis(phenolate) ligands have been extensively investigated
(Chart 1).3ꢀ7 Kol developed complexes 1, after their study on
complexes bearing [ONNO]-type tetradentate ligands,8 and
showed that 1 served as a precatalyst for the polymerization of
1-hexene with moderate activity to give atactic poly(1-hexene).3a
On the other hand, Okuda and co-workers prepared complexes
24 and 3.5 Polymerization of styrene with 2 (R1, R2 = tBu; ML2 =
TiCl2, Ti(OiPr)2, Zr(CH2Ph)2, Hf(CH2Ph)2) activated by
methylaluminoxane (MAO) gave isotactic polystyrenes,4a while
that of 1-hexene with 2 (R1, R2 = tBu, L = Me, CH2Ph) activated
by B(C6F5)3 gave oligo(1-hexene)s.4b Polymerization of styrene
with 1-hexene as a chain-transfer agent with enantiopure 3
(L = Cl) activated by MAO provided optically active, isotactic
polystyrenes with oligo(1-hexene) terminal groups.5 There is a
difference between 1 and 2 in the chelation ring sizes: 6ꢀ5ꢀ6 for
Recently we reported the first syntheses of trans-cyclooctane-
1,2-dithiol.10 Stimulated by the earlier studies mentioned above,
we prepared Zr complex 4 with a new [OSSO]-type ligand bear-
ing a trans-cyclooctane-1,2-diyl ring (5) (Chart 2).7 Complex 4
activated by B(C6F5)3 or (Ph3C)[B(C6F5)4] provided a highly
active and highly stereospecific catalytic system for the polym-
erization of 1-hexene to give isotactic poly(1-hexene)s. We
assumed two roles of the fused eight-membered ring: one is
the rigidity of the entire molecule to retain a favorable reaction
site for the isospecific polymerization, and the other is the partial
flexibility to follow fine structure changes of the complex during
the course of the polymerization reaction.7 An aim of the present
study is to clarify the influence of the fusion of cycloalkane rings
on [OSSO]-type bis(phenolate) tetradentate ligands. We report
Received: December 2, 2010
Published: May 11, 2011
r
2011 American Chemical Society
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Organometallics
ARTICLE
Chart 1. Group 4 Metal Complexes 1ꢀ3 with [OSSO]-Type
Scheme 1. Synthesis of Ligand 6 by the Reaction of 7 with 8
Ligands
Chart 2. Zirconium Complex 4 and the Ligand 5 with a trans-
Cyclooctane-1,2-diyl Ring
here the preparation of the [OSSO]-type tetradentate ligand 6,
having a trans-cyclohexane-1,2-diyl ring, the preparation of tita-
nium and zirconium complexes using 6, and the catalytic ability
of the zirconium complex to polymerize 1-hexene. We also
discuss the effect of fusion of a cycloalkane-1,2-diyl ring in
ligands 5 and 6.
Figure 1. ORTEP drawing of ligand 6 with 30% probability ellipsoids.
The C6H10(SCH2)2 part was disordered, and only the major set
(occupancy 78%) of this part is shown. Hydrogen atoms of tert-butyl
groups are omitted for clarity. Relevant bond lengths (Å) and a dihedral
angle (deg): S1ꢀC1 = 1.841(6), S2ꢀC2 = 1.842(5); S1ꢀC1ꢀC2ꢀS2
= 167.1(2).
’ RESULTS AND DISCUSSION
Ligand 6 was prepared by the reaction of trans-cyclohexane-
1,2-dithiol (7)11 with the 2-hydroxybenzyl bromide 812 in the
presence of triethylamine in 90% yield (Scheme 1). The structure
of 6 was supported by its spectroscopic data and finally deter-
mined by X-ray crystallography (Figure 1). The C6H10(SCH2)2
part was disordered, and Figure 1 shows only the major set
(occupancy 78%) of the part. Under such circumstances, 6 took a
diaxial conformation, which is in contrast with the diequatorial
conformation of 5.5b
Ti Complexes. Ligand 6 was treated with Ti(OiPr)4 in toluene
at room temperature for 3.5 h under an argon atmosphere
(Scheme 2). Whereas the 1H NMR spectrum measured at 303
K showed only broad signals, that measured at 253 K in C7D8
showed two well-resolved sets of signals, indicating C2 symmetry,
in an integral ratio of 3:2. Figure 2 shows the part of the NMR
spectrum for benzyl and isopropoxy methine protons. Benzyl
protons of the major species appeared at δ 3.39 and 4.01 ppm as
doublets (Jgem = 14 Hz), and those of the minor species were
observed at δ 3.37 and 3.63 ppm as doublets (Jgem = 14 Hz).
Methine protons of isopropoxy groups in the major and minor
species resonated at δ 4.97 and 5.20, respectively, as septets. For
aromatic protons, nonequivalent protons of the major species
were observed at δ 6.76 and 7.58 ppm as doublets (J = 3 Hz) and
those of the minor species appeared at δ 6.69 and 7.50 ppm as
doublets (J = 3 Hz). Thus, each species has magnetically
equivalent C6H2(t-Bu)2CH2 and isopropoxy groups, indicating
that they have C2-symmetric, cis-R structures in solution. Thus,
we assigned the two complexes as diastereomers (Λ*)-9 and
(Δ*)-9, having an identical configuration of the cyclohexane-1,2-
1
diyl-fusing moiety. Variable-temperature H NMR experiments
of 9 in C7D8 in the range 273ꢀ323 K gave the free energy of
activation for the interconversion as ΔGq = 65 ( 2 kJ molꢀ1
(ΔHq = 88 ( 2 kJ molꢀ1, ΔSq = 76 ( 5 J Kꢀ1 molꢀ1, Tc = 303 K)
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Scheme 2. Synthesis of Titanium Complexes 9 by the Reac-
from the line shape analysis of isopropyl methine protons (Figure 3).
tion of 6 with Ti(OiPr)4
This fluxional behavior is similar to that of complex 1 (M = Ti;
L = OiPr; ΔGq = 48 ( 1 kJ mol
)
ꢀ1 3a having the same 6ꢀ5ꢀ6
cheleting ring size system, where 9 has a larger ΔGq value owing
to the fusion of a cyclohexane ring. With regard to complexes
having the 5ꢀ5ꢀ5 cheletion system, their fluxionality is largely
dependent on the bulkiness of substituents on the phenolato
rings. Complexes 2 (M = Ti; L = OiPr) having H and/or Me groups
as the substituents show fluxional behavior (R1, R2 = H, ΔGq =
56.5 ( 1 kJ molꢀ1; R1 = H, R2 = Me, ΔGq = 56.2 ( 1 kJ molꢀ1
;
R1, R2 = Me, ΔGq = 58.6 ( 2 kJ molꢀ1),4c and in contrast, those
having bulky CMe2Ph or tBu groups as the substituents are not
fluxional.4c Complexes 3 (L = Cl, OiPr),5 which undergo fusion
of a cyclohexane ring, also exist as their respective single stereo-
isomers in solution. In comparison, among the three diisopropoxy
titanium complexes having tBu groups 9, 2 (M = Ti; L = OiPr, R1,
R2 = tBu), and 3 (L = OiPr), the 6ꢀ5ꢀ6 chelation system of 9 is
more flexible than the 5ꢀ5ꢀ5 cheletion system for titanium(IV)
complexes, regardless of the presence of a fused cyclohexane ring.
Recrystallization of a mixture of 9 gave yellow crystals, and an
X-ray diffraction analysis showed the structure of (Δ*,S*,S*)-9.
There are two independent molecules in the unit cell, and one of
them is shown in Figure 4. The structures of the two independent
molecules are almost similar, except for the conformation about
an OꢀiPr bond. (Δ*,S*,S*)-9 takes a distorted-octahedral struc-
ture: the two sulfur atoms, two oxygen atoms of isopropoxy
groups, and Ti atom reside on the same plane. The averaged
values of apical O1ꢀTi1ꢀO2 bond angles and S1ꢀC1ꢀC2ꢀS2
Figure 2. 1H NMR spectrum (δ 3.2ꢀ5.3 ppm) of a mixture of (Λ*,S*,
S*)-9 and (Δ*,S*,S*)-9 measured at 253 K in C7D8.
1
Figure 3. Experimental H NMR spectra for isopropoxy methine protons of a mixture of (Λ*,S*,S*)-9 and (Δ*,S*,S*)-9 in the range 273ꢀ323 K
(Tc = 303 K) in C7D8 (left) and simulated spectra computed with the specific rate constant k (right).
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Chart 3. Respective Model Complexes (Λ,S,S)-10 and
(Δ,S,S)-10 for (Λ,S,S)-9 and (Δ,S,S)-9
Figure 4. ORTEP drawing of one of two independent molecules of
(Δ*,S*,S*)-9 with 30% probability ellipsoids. Hydrogen atoms and a
solvated molecule (hexane) are omitted for clarity. Selected bond
lengths (Å), angles (deg), and a dihedral angle (deg): Ti1ꢀO3 =
1.8161(14), Ti1ꢀO4 = 1.8081(14), Ti1ꢀO1 = 1.8867(14), Ti1ꢀO2
=
1.9045(14), Ti1ꢀS1
=
2.6941(6), Ti1ꢀS2
= 2.7188(6);
O4ꢀTi1ꢀO3 = 107.08(7), O1ꢀTi1ꢀO2 = 160.23(6), S1ꢀTi1ꢀS2
= 76.019(17), S1ꢀTi1ꢀO3 = 89.04(5), S2ꢀTi1ꢀO4 = 87.87(5),
S2ꢀTi1ꢀO3 = 165.05(5), S1ꢀTi1ꢀO4 = 163.82(5), O3ꢀTi1ꢀO1
= 94.86(6), O2ꢀTi1ꢀO4 = 94.48(6), O2ꢀTi1ꢀO3 = 96.50(6),
O4ꢀTi1ꢀO1 = 97.58(6), S1ꢀTi1ꢀO1 = 82.09(4), S2ꢀTi1ꢀO2 =
81.92(4), S2ꢀTi1ꢀO1
=
82.93(4), S1ꢀTi1ꢀO2
= 81.98(4);
S1ꢀC1ꢀC2ꢀS2 =44.68(18).
dihedral angles were 159.4 and 44.8°, respectively. For reference,
although the chelation ring sizes and ligands (L) are different,
the corresponding values in complexes having the same rela-
tive configuration are reportedly 158.50(19) and 53.8(5)° for
(Λ,R,R)-3 (L = Cl) and 159.6(1) and 48.3(3)° for (Λ*,R*,R*)-3
(L = CH2Ph, where the tBu group para to phenoxido oxygens is
replaced by a Me group).5 While the apical OꢀTiꢀO bond
angles are almost similar, the SꢀCꢀCꢀS dihedral angle in (Δ*,
S*,S*)-9 is substantially smaller than those in the reference
complexes. Thus, an influence of the difference in chelation ring
sizes, 6ꢀ5ꢀ6 for 9 and 5ꢀ5ꢀ5 for 3, was observed in the
SꢀCꢀCꢀS dihedral angles.
Figure 5. Structures of two conformers for both (Λ,S,S)-10 and
(Δ,S,S)-10 optimized by DFT calculations with the LANL2DZ basis
set for Ti and the 6-31þG(d) basis sets for other elements.
as a common part of model (10) and real (9) compounds
(Table 1). The calculated chemical shifts of benzyl protons with
reference to the TMS standard were δ 4.29 and 3.47 ppm
(Δδ = 0.82 ppm) for (Λ,S,S)-10a and δ 3.77 and 3.46 ppm
(Δδ = 0.31 ppm) for (Δ,S,S)-10a. In the case of conformers 10b,
exo hydrogens (Hexo) undergo a high-field shift, δ 3.90 ppm for
(Λ,S,S)-10b and δ 3.54 ppm for (Δ,S,S)-10b, leading to smaller
Δδ values, 0.41 ppm for (Λ,S,S)-10b and 0.06 ppm for (Δ,S,S)-
10b. These trends of chemical shifts and Δδ values for (Λ,S,S)-
10 and (Δ,S,S)-10 are in good agreement with those of two
doublets for the major diastereomer of 9 (δ 3.99 and 3.38 ppm,
Δδ = 0.61 ppm) and those for the minor species (δ 3.60 and 3.36
ppm, Δδ = 0.24 ppm), respectively (see Figure 2). The remark-
able downfield shift of Hexo in (Λ,S,S)-10a is considered to be
due to its proximity to a TiꢀOe bond. Figure 6 shows the relevant
moieties of (Λ,S,S)-10a and (Δ,S,S)-10a. The interatomic
While the structure of the other diastereomer is essentially
assigned to be (Λ*,S*,S*)-9, to obtain some information on the
1
assignment of H NMR data of (Δ*,S*,S*)-9 and (Λ*,S*,S*)-9,
DFT calculations were performed for their model compounds
(Λ,S,S)-10 and (Δ,S,S)-10 (Chart 3).13 Structure optimizations
were carried out on two conformers (10a,b) about TiꢀOMe
bonds for each and their C2 symmetry was retained during the
calculations. The optimized structures are exhibited in Figure 5.
Confomers with suffix b have conformations similar to that of
(Δ*,S*,S*)-9 in the crystalline state.
NMR shielding constants were calculated for (Λ,S,S)-10 and
(Δ,S,S)-10 by the GIAO method,14 and chemical shifts of benzyl
protons (Hendo and Hexo) and their difference (Δδ) were compared
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Table 1. Calculated Chemical Shifts (δ, ppm) of Benzyl
Protons (Hexo and Hendo) in (Λ,S,S)-10 and (Δ,S,S)-10
and the Corresponding Values of (Λ*,S*,S*)-9 (Major)
and (Δ*,S*,S*)-9 (Minor)
Scheme 3. Synthesis of Zirconium Complexes 11 by the
Reaction of 6 with Zr(CH2Ph)4
(Λ,S,S)- (Λ,S,S)- (Δ,S,S)- (Δ,S,S)- (Λ*,S*,S*)-9b (Δ*,S*,S*)-9b
10aa
10ba
10aa
10ba
(major)
(minor)
δ(Hexo
)
4.29
3.47
0.82
3.90
3.49
0.41
3.77
3.46
0.33
3.54
3.48
0.06
3.99
3.38
0.61
3.60
3.36
0.24
δ(Hendo
Δδ
)
a Basis sets B3LYP/LANL2DZ (Ti) and 6-31þG(d) (C, H, O, S). b In
C6D6.
corresponding titanium complexes, where these phenomena
were explained in terms of the strong soft-S/soft-Zr interaction
compared to the soft-S/hard-Ti interaction.3a This is also the
present case, and broadening of signals was not observed at room
temperature, unlike the case for titanium complex 9, indicating
that the ΔꢀΛ interconversion of 11 is slow enough at room
temperature on the NMR time scale.16 We could not obtain
single crystals suitable for X-ray crystallography from the mixture
of (Λ*,S*,S*)-11 and (Δ*,S*,S*)-11 and used the mixture for
further studies.
1-Hexene Polymerization. Polymerization of 1-hexene was
examined with zirconium complex 11, which was used as a mix-
ture of diastereomers, and B(C6F5)3 or (Ph3C)[B(C6F5)4] as the
activators (Scheme 4). The results are summarized in Table 2.
The polymerization carried out at room temperature for 15 min
gave poly(1-hexene) with high isotacticity (mmmm = 93%) and
an Mw value of 40 500 for B(C6F5)3 (run 1) or 44 000 for
(Ph3C)[B(C6F5)4] (run 2). The reaction carried out at 0 °C with
(Ph3C)[B(C6F5)4] yielded poly(1-hexene) with higher isotacti-
city (mmmm = 97%) and a larger Mw value (66 000) (run 3).
Thus, the dependence of isotacticity and Mw on the two
activators was small, and polydispersity indexes (PDI) were 1.9
in the three runs.
Figure 6. Relevant moieties of (Λ,S,S)-10a (a) and (Δ,S,S)-10a (b)
with Hexo O and Hexo Ti distances (Å) and calculated 1H NMR
3 3 3
3 3 3
chemical shifts (ppm) at the B3LYP/LANL2DZ (Ti) and 6-31þG(d)
(C, H, O, S) levels.
distances Hexo Oe and Hexo Ti in (Λ,S,S)-10a are 2.826
3 3 3
3 3 3
and 3.325 Å, respectively, which are remarkably smaller than
the corresponding distances of 3.297 and 3.555 Å in
(Δ,S,S)-10a. Thus, we assigned the major diastereomer of 9 in
solution to (Λ*,S*,S*)-9 and the minor one to (Δ*,S*,S*)-9, the
structure of which was determined by X-ray diffraction.
Zr Complexes. Next, ligand 6 was treated with Zr(CH2Ph)4 in
toluene at room temperature to give again a mixture of two
diastereomers 11 in 40% combined yield, similarly to the case for
titanium complex 9 (Scheme 3). Figure 7 shows the region
(δ 1.7ꢀ3.7 ppm) of benzyl protons in the 1H NMR spectrum of
the mixture measured at room temperature, which indicates the
formation of two C2-symmetric diastereomers in a ratio of 3:2.
It is worth noting that the activity (370 g mmolꢀ1 hꢀ1) of the
11/B(C6F5)3 system is lower by 1 order of magnitude than the
4/B(C6F5)3 system (activity 2500 g mmolꢀ1 hꢀ1, Mw = 59 000,
PDI = 1.7, mmmm >95%)7 but still 4.5 times higher than the
system of 1 (ML2 = Zr(CH2Ph)2)/B(C6F5)3 reported by Kol
(activity 80 g mmolꢀ1 ꢀ1, Mw = 7400, PDI = 1.6) that gave
h
1
regioregular and stereoirregular (atactic) poly(1-hexene).3a Kol
described the possibility that the lack of stereocontrol by 1
(ML2 = Zr(CH2Ph)2)/B(C6F5)3 could be ascribed to the
reduced directing power of the phenolate substituents rather
than a fluxional catalyst behavior.3a The present results show that
the o-tert-butyl groups in 11 are enough to provide isospecificity.
Observation of Zr Cation. To obtain some insights into the
difference in activity between 4/B(C6F5)37 and 11/B(C6F5)3 in
1-hexene polymerization, we measured 1H, 13C, and 19F NMR of
the zirconium cation 12þ[B(CH2Ph)(C6F5)3]ꢀ generated from
11, which is the starting species for the coordination polymer-
ization of 1-olefins,17 and compared them with those of the corre-
sponding zirconium cation 13þ[B(CH2Ph)(C6F5)3]ꢀ (Chart 4)
On the basis of the similarity of H NMR data for the benzyl
protons to those of the zirconium complex (Λ*,S*,S*)-6 (δ 2.16
(d, J = 10 Hz) and 2.78 (d, J = 10 Hz) ppm for ZrCH2Ph protons
and δ 3.16 (d, J = 14 Hz) and 3.50 (d, J = 14 Hz) ppm for
SCH2Ar protons),7,15 the minor diastereomer was assigned to
(Λ*,S*,S*)-11 (denoted with b in Figure 7: δ 2.17 (d, J = 10 Hz)
and 2.79 (d, J = 10 Hz) ppm for ZrCH2Ph protons and δ 3.23
(d, J = 14 Hz) and 3.52 (d, J = 14 Hz) ppm for SCH2Ar protons).
The other set of signals (denoted O in Figure 7) was essentially
assigned to those of (Δ*,S*,S*)-11. Kol reported that 1 (ML2 =
Zr(OtBu)2, Zr(CH2Ph)2) existed as the respective single iso-
mers and the ΔꢀΛ interconversion was slow in solution at
room temperature, in contrast with the fluxional nature of the
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Figure 7. Part of the 1H NMR spectrum (500 MHz, 298 K, C6D6) of a mixture of (Λ*,S*,S*)-11 (b, minor) and (Δ*,S*,S*)-11 (O, major).
1
Scheme 4. Polymerization of 1-Hexene with Zirconium
Complex 11 as the Precatalyst
In a comparison between the H NMR spectra of 12þ[B-
(CH2Ph)(C6F5)3]ꢀ and 13þ[B(CH2Ph)(C6F5)3]ꢀ,19 we ob-
serve a difference in the chemical shifts of methyne protons
(ꢀCHSꢀ). Thus, the two inequivalent protons appeared at
δ 1.85 and 2.34 ppm for 12þ and δ 2.03 and 2.92 ppm for 13þ.
One of these protons in 13þ is shifted remarkably downfield, and
Δδ values are 0.89 ppm for 13þ and 0.49 ppm for 12þ. In
addition, the chemical shift differences of the corresponding
methine carbons (ꢀCHSꢀ) were 2.8 ppm for 12þ (δ 52.1 and
54.9 ppm) and 6.4 ppm for 13þ (δ 51.6 and 58.0 ppm), where
the downfield shift of one of the methine carbons (δ 58.0 ppm)
in 13þ is remarkable. These observations suggest that there is
some difference in the strength of coordination of sulfur atoms in
12þ and 13þ to the respective cationic Zr centers. We consider
that one of the sulfur atoms in 13þ can coordinate the cationic Zr
center more strongly than the other, accompanying a structural
change provided by the flexible nature of the cyclooctane part, to
afford additional stability to 13þ. This effect would present a
reason for the activity of 4/B(C6F5)3 being higher than that of
11/B(C6F5)3 in 1-hexene polymerization. Morokuma and co-
workers reported a theoretical study on ethylene polymerization
reactions catalyzed by zirconium and titanium chelating alkoxide
complexes 14aꢀc (Chart 5)21 based on the Cossee mech-
anism.17 They showed that in the case of 14a the stabilization
effect by the coordination of sulfur to the metal center in the
initial complex was initially lost in the formation of the π
complex, which resulted in a relatively small energy gain of this
step compared with the cases of 14b,c, and then came back in the
transition state to the final insertion product. This behavior
lowers the activation energy for 14a to explain well the higher
activity of 14a compared with that of 14b,c. This would be the
case for zirconium cations 12þ and 13þ, the latter of which
undergoes stronger stabilization by a sulfur atom to show a
higher reactivity in the polymerization of 1-hexene.
from 4. Thus, a mixture of (Λ*,S*,S*)-11 and (Δ*,S*,S*)-11 was
treated with B(C6F5)3 in C6D6 at room temperature. In the
19F{1H} NMR, three inequivalent 19F nuclei in the counteranion
([B(CH2Ph)(C6F5)3]ꢀ) were observed at δ ꢀ166.5 (m-F), ꢀ
163.7 (p-F), and ꢀ130.2 (o-F) ppm. The Δδ (|δm-F ꢀ δp-F|)
value was 2.8 ppm, which indicates weak coordination between
[B(CH2Ph)(C6F5)3]ꢀ and the zirconium cation center,18 as
observed in 13þ[B(CH2Ph)(C6F5)3]ꢀ.7,19 Interestingly, the
1H NMR spectrum indicated a clean formation of a single zirconium
cation with C1 symmetry (12þ[B(CH2Ph)(C6F5)3]ꢀ). Thus, four
singlets due to t-Bu groups were observed at δ 1.28, 1.32, 1.53,
and 1.61 ppm (Figure 8a) and three pairs of two doublets due to
three benzyl groups were observed at δ 2.51 (d, J = 9.3 Hz,
ZrCH2Ph), 2.83 (d, J = 9.3 Hz, ZrCH2Ph), 3.30 (d, J = 11.5 Hz,
SCH2Ar), 3.40 (d, J = 12.3 Hz, SCH2Ar), 3.50 (d, 12.3 Hz,
SCH2Ar), and 3.55 (d, J = 11.5 Hz, SCH2Ar) (Figure 8b). A
singlet at δ 3.44 is due to BCH2Ph protons of the counteranion.20
We assume that 12þ has a Λ*,S*,S* configuration, as shown in
Scheme 5, because the 1H NMR spectrum of 12þ[B(CH2Ph)-
(C6F5)3]ꢀ bears a close resemblance to that of Zr cation 13þ: for
instance, for t-Bu groups δ 1.23, 1.31, 1.53, 1.60; for benzyl
groups δ 2.55 (d, J = 9.6 Hz, ZrCH2Ph), 2.77 (d, J = 9.6 Hz,
ZrCH2Ph), 3.40 (d, J = 12.4 Hz, SCH2Ar), 3.47 (d, J = 11.4 Hz,
SCH2Ar), 3.54 (d, 11.4 Hz, SCH2Ar), and 3.59 (d, J = 12.4 Hz,
SCH2Ar) ppm.19
In 12þ and 13þ, benzyl ligands would have η2 coordination to
the zirconium cation center, similar to that in reported group 4
’ CONCLUSION
We synthesized hexacoordinated titanium(IV) (9) and
zirconium(IV) (11) complexes with a new [OSSO]-type tetra-
dentate ligand bearing a trans-cyclohexane-1,2-diyl ring (6).
Complexes 9 and 11 were found to be mixtures of Λ*,S*,S*
and Δ*,S*,S* diastereomers, and the structures were elucidated
by NMR, X-ray diffraction, DFT calculations, and comparison
with a corresponding complex having an analogous ligand
bearing a trans-cyclooctane-1,2-diyl ring (5). In 1-hexene
polymerization, the catalytic system consisting of dibenzyl zirco-
nium complex 11 and an activator features high isospecificity
with high activity, indicating that ligand 6 is rigid enough to retain
the C2 symmetry during polymerization. In comparison between
1
metal, cationic complexes, on the basis of the JCꢀH value
(143 Hz) for the benzyl carbon (δ 72.3) of 12þ.18,20 Okuda
and co-workers observed a zirconium cation generated from 3
(L = CH2Ph) by treatment with B(C6F5)3 in C6D5Br, albeit not
1
in a clean form, where the H NMR spectrum showed an
apparent C2-symmetric species above 10 °C.5b Incidentally, they
succeeded in the X-ray structure analysis of a cationic zirconium
complex prepared from 2 (M = Ti; R1, R2 = tBu; L = Me) and
B(C6F5)3 in the presence of Me2PCH2CH2PMe2 (DMPE),
which underwent coordination of two phosphorus atoms of
the dmpe and took a pentagonal-bipyramidal structure.4b
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Table 2. Polymerization of 1-Hexene with Zirconium Complex 11 (0.056 mmol %) and B(C6F5)3 or (Ph3C)[B(C6F5)4] as the
Activators
run
amt of 11 (mmol)a
activator (amt (mmol))
temp (°C)
yield (g)
activity (g mmolꢀ1 hꢀ1
)
Mw
PDI
amt of mmmm (%)
1
2
3
0.020
0.020
0.020
B(C6F5)3 (0.020)a
Ph3Cþb (0.020)a
Ph3Cþb (0.020)a
room temp
room temp
0
1.8
1.8
1.0
370
370
190
40 500
44 000
66 000
1.9
1.9
1.9
93
93
97
a 0.056 mmol % to 1-hexene (3.0 g). b (Ph3C)[B(C6F5)4].
Chart 4. Cationic Zirconium Complex 13þ[B(CH2Ph)-
(C6F5)3]ꢀ Generated from 4 with B(C6F5)3.
Scheme 5. Generation of the Cationic Zirconium Complex
12þ[B(CH2Ph)(C6F5)3]ꢀ from 11 with B(C6F5)3
Chart 5. Zirconium and Titanium Chelating Alkoxide Com-
plexes 14
difference in reactivity is attributable to the difference in the ability to
stabilize zirconium cations between ligands in 12þ and 13þ.
’ EXPERIMENTAL SECTION
General Considerations. The melting points were determined on
a Mel-Temp capillary tube apparatus and are uncorrected. 1H, 19F, and
13C spectra were obtained with Bruker DRX400, AVANCE300, and
AVANCE500 spectrometers. In the case of 19F NMR, R,R,R-trifluor-
otoluene (δ ꢀ64) was used as the external standard. X-ray crystal-
lography was performed with Bruker AXS SMART and Rigaku Saturn724
diffractometers. Elemental analyses were performed at the Molecular
Analysis and Life Science Center of Saitama University. Molecular
weights and molecular weight distributions of poly(1-hexene)s were
determined against a polystyrene standard by gel permeation chroma-
tography on a HLC-8220 GPC apparatus (Tosoh Corp.) of the
laboratory of Dr. Zhaomin Hou (Organometallic Chemistry Laboratory,
RIKEN Advanced Science Institute).
Preparation of trans-1,2-bis(3,5-di-tert-butyl-2-hydroxyben-
zylsulfanyl)cyclohexane (6). A mixture of thiol 7 (1.08 g, 7.3 mmol)
and 3,5-di-tert-butyl-2-hydroxybenzyl bromide (8; 4.58 g, 15.3 mmol) was
dissolved in THF (90 mL) under argon. To the solution cooled at 0 °C was
added triethylamine (2.1 mL, 1.5 mg, 15.3 mmol), and the mixture was
stirred for 1 h at 0 °C and overnight at room temperature. The precip-
itates formed were removed by filtration, and the filtrate was con-
centrated under reduced pressure. The oily yellow residue was dissolved
in ether and aqueous ammonium chloride was added. The organic layer was
washed with water, dried over anhydrous magnesium sulfate, and evapo-
rated to dryness under reduced pressure. The residue was subjected
Figure 8. Portions of the 1H NMR spectrum (500 MHz, 298 K) for tert-
butyl and cyclohexane-methylene protons (a) and benzyl protons (b) in
the cationic complex 12þ[B(CH2Ph)(C6F5)3]ꢀ in C6D6.
ligands 6 bearing a trans-cyclohexane-1,2-diyl and 5 bearing a
trans-cyclooctane-1,2-diyl, the catalytic system of complex 11
bearing 6 is less active than the catalytic system of 4 bearing 5. In
the 1H and 13C NMR observations of the corresponding cationic
zirconium complexes 12þ[B(CH2Ph)(C6F5)3]ꢀ and 13þ[B-
(CH2Ph)(C6F5)3]ꢀ, we obtained a result suggesting that the
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to column chromatography (silica gel, hexane/dichloromethane 1/1) to
give 6 (3.86 g, 90%).
(1 mL) and hexane (5 mL) at room temperature. After the mixtue was
stirred for 5 min at room temperature, a solution of 1-hexene (3.0 g) was
added. This mixture was stirred for 15 min at this temperature. The
reaction was quenched by addition of methanol, and volatile materials
were removed in vacuo at 70 °C overnight to leave poly(1-hexene) (1.8 g).
Reaction of [OSSO]Zr(CH2Ph)2 (11) with B(C6F5)3. To an
NMR tube equipped with a PTFE valve (J. Young Ltd.) were added 11
(17.1 mg, 0.020 mmol), benzene-d6 (0.5 mL), and B(C6F5)3 (10.2 mg,
0.020 mmol) in that order. The mixture immediately turned yellow and
separated into two phases: 19F NMR (470.6 MHz, C6D6) δ ꢀ166.5 (t, 2J
= 20 Hz, 6 F, m-F), ꢀ163.7 (pseudo t, 2J = 21 Hz, 3 F, p-F), ꢀ130.2 (d, 2J
= 22 Hz, 6 F, o-F); 1H NMR (500 MHz, C6D6) δ 0.85ꢀ1.0 (m, 6H),
1.2ꢀ1.7 [m, 38 H {1.27 (s, t-Bu), 1.32 (s, t-Bu), 1.53 (s, t-Bu), 1.61 (s, t-
Bu)}], 1.81ꢀ1.89 (m, 1 H, CHS), 1.89ꢀ1.96 (m, 1 H), 2.31ꢀ2.38 (m, 1
H, CHS), 2.51 (d, J = 9.3 Hz, ZrCH2Ph), 2.83 (d, J = 9.3 Hz, ZrCH2Ph),
3.30 (d, J = 11.5 Hz, SCH2Ar), 3.40 (d, J = 12.3 Hz, SCH2Ar), 3.44 (br s,
2 H, BCH2Ph), 3.50 (d, 12.3 Hz, SCH2Ar), and 3.55 (d, J = 11.5 Hz,
SCH2Ar), 6.20 (br s, 2 H, o-H of BCH2Ph), 6.7ꢀ6.82 [m, 3 H {1H of p-
H of ZrCH2Ph (δ 6.78, t, J = 7 Hz) and 2 H of m-H of BCH2Ph}], 6.85
(t, J = 7 Hz, 1 H, p-H of BCH2Ph), 6.92 (t, J = 8 Hz, 2 H, m-H of
ZrCH2Ph), 7.15 (Ar-H, overlapped with signals due to residual protons
of the solvent and detemined by the HꢀH COSY experiment), 7.18 (d, J
= 7.5 Hz, 2 H, o-H of ZrCH2Ph), 7.34 (d, J = 2 Hz, Ar-H), 7.51 (d, J = 2
Hz, Ar-H), 7.60 (d, J = 2 Hz, Ar-H); 13C{1H} NMR (100.7 MHz, C6D6)
δ 24.6 (CH2, c-C6H10S2), 25.5 (CH2, c-C6H10S2), 30.4 (CH3, CMe3),
30.5 (CH3, CMe3), 31.2 (CH2, ArCH2), 31.34 (CH3, CMe3), 31.37
(CH3, CMe3), 31.5 (CH2, c-C6H10S2), 32.6 (CH2, br s, BCH2Ph), 34.6
(C, CMe3), 34.7 (C, CMe3), 35.4 (CH2 and C, c-C6H10S2 and CMe3,
respectively), 35.5 (C, CMe3), 38.4 (CH2, ArCH2), 52.1 (CH, CHS),
54.9 (CH, CHS), 72.3 (CH2, ZrCH2Ph), 120.2 (C, ipso-C of BCH2Ph or
ZrCH2Ph), 121.1 (C, ipso-C of BCH2Ph or ZrCH2Ph), 123.2 (CH, p-C
of ZrCH2Ph), 125.7 (2CH, Ar), 126.0 (CH, Ar), 126.2 (CH, Ar), 127.5
(CH, m-C of ZrCH2Ph), 129.3 (2CH, o-C and p-C of BCH2Ph), 129.4
(CH, o-C of ZrCH2Ph), 133.1 (C, Ar), 136.7 (C, Ar), 136.9 (C, Ar),
137.1 (dm, 1JCꢀF = 249 Hz, o- or m-C of BC6F5), 137.7 (dm, 1JCꢀF = 249
Hz, p-C of BC6F5), 139.4 (m, ipso-C of BC6F5), 145.7 (C, Ar), 145.9
(C, Ar), 149.0 (C, Ar), 149.1 (dm, 1JCꢀF = 237 Hz, o- or m-C of BC6F5),
157.3 (C, Ar), 157.9 (C, Ar) (m-C of BCH2Ph was observed as a broad
singlet centered at δ 128.0 ppm in the CꢀH COSY spectrum).
13C NMR data for 13þ[B(CH2Ph)(C6F5)3]ꢀ (125.7 MHz, C6D6):
δ 22.2 (CH2), 24.3 (CH2), 26.2 (CH2), 27.1 (CH2), 28.9 (CH2), 30.4
(CH3), 30.5 (CH3), 31.2 (CH2), 31.3 (CH3), 31.4 (CH3), 31.7 (CH2),
32.5 (CH2, br s, BCH2Ph), 34.6 (C), 34.7 (C), 35.4 (C), 35.5 (C), 38.8
(CH2), 51.6 (CH, CHS), 58.0 (CH, CHS), 72.0 (CH2, ZrCH2Ph, JCꢀH
= 143 Hz), 120.5 (C), 121.4 (C), 123.2 (CH, p-C of ZrCH2Ph), 125.7
(2CH, Ar), 126.0 (CH, Ar), 126.1 (CH, Ar), 127.5 (CH, m-C of
ZrCH2Ph), 129.1 (CH, p-C of BCH2Ph), 129.2 (CH, o-C of ZrCH2Ph),
132.9 (C, Ar), 136.9 (C, Ar), 137.2 (dm, JCꢀF = 251 Hz), 138.2
(dm, JCꢀF = 242 Hz), 145.8 (C, Ar), 146.0 (C, Ar), 149.0 (C, Ar),
149.1 (dm, JCꢀF = 240 Hz), 157.4 (C, Ar), 157.8 (C, Ar). One of the
quaternary sp2 carbons (Ar) and o- and m-C of BCH2Ph were not
assigned because of overlapping and broadening, respectively.
Data for 6: colorless crystals, mp 104ꢀ106 °C dec (EtOH); 1H NMR
(400 MHz, CDCl3) δ 1.19ꢀ1.43 (m, 44 H), 2.09ꢀ2.15 (m, 2 H),
2.58ꢀ2.61 (m, 2 H), 3.79 (s, 4 H), 6.75 (s, 2 H), 6.93 (d, J = 2 Hz, 2 H),
7.25 (d, J = 2 Hz, 2 H); 13C NMR (100 MHz, CDCl3) δ 24.7, 29.7, 31.6,
32.6, 33.9, 34.2, 35.0, 48.1, 121.6, 123.7, 125.2, 137.3, 142.2, 152.0. Anal.
Calcd for C36H54O2S2: C, 73.92; H, 9.34. Found: C, 74.17; H, 9.31.
Preparation of [OSSO]Ti(OiPr)2 (9). A solution of 6 (206.6 mg,
0.336 mmol) in toluene (10 mL) was added to a solution of Ti(OiPr)4
(153.2 mg, 0.336 mmol) in toluene (10 mL) at room temperature. The
mixture was stirred for 5 h at room temperature, and the solvent was
removed under reduced pressure. The residue was washed with hexane
(2 mL) and dried to give 9 (215.7 mg, 76%).
Data for 9 (a mixture of (Λ*,S*,S*)-9 (major) and (Δ*,S*,S*)-11
(minor)): yellow crystals; mp 110 °C dec; 1H NMR (500 MHz, C7D8,
253 K) δ 0.50ꢀ1.12 (m, 8 H, major, minor), 1.27 (d, 3J = 6 Hz, 6 H,
major), 1.33 (s, 18 H, major, minor), 1.38 (d, J = 6 Hz, 6 H, minor), 1.50
(d, J = 6 Hz, 6 H, major), 1.59ꢀ1.67 (m, 2 H, major), 1.63 (d, J = 6 Hz, 6
H, minor), 1.92 (s, 18 H, major, minor), 2.01ꢀ2.07 (m, 2 H, minor),
3.37 (d, J = 13 Hz, 2 H, minor), 3.39 (d, J = 14 Hz, 2 H, major), 3.63
(d, J = 14 Hz, 2 H, minor), 4.01 (d, J = 14 Hz, 2 H, major), 4.97 (sep, J = 6
Hz, 2 H, major), 5.20 (sep, J = 6 Hz, 2 H, minor), 6.69 (d, J = 2 Hz, 2 H,
minor), 6.76 (d, J = 3 Hz, 2 H, major), 7.50 (d, J = 3 Hz, 2 H, minor), 7.58
(d, 4J = 3 Hz, 2 H, major). Anal. Calcd for C42H68O4S2Ti: C, 67.35; H,
9.15. Found: C, 67.51; H, 9.37.
Preparation of [OSSO]Zr(CH2Ph)2 (11). In the glovebox, a
solution of 6 (300 mg, 0.513 mmol) in toluene (5 mL) was added to
a solution of Zr(CH2Ph)4 (234 mg, 0.513 mmol) in toluene (5 mL) at
room temperature. The mixture was stirred for 2 h at room temperature,
and the solvent was removed under reduced pressure. The residue was
washed with pentane (2 mL) and dried to give 11 (176 mg, 40%). 11 was
extremely unstable to air and moisture, so that we could not carry out
elemental analysis and HRMS measurements.
Data for 11 (a mixture of (Λ*,S*,S*)-11 (minor) and (Δ*,S*,S*)-11
(major)): 1H NMR (500.0 MHz, C6D6) δ 0.42ꢀ1.08 (m, 8 H, major,
minor), 1.22 (s, 18 H, major), 1.24 (s, 18 H, minor), 1.57ꢀ1.61 (m, 2 H,
major), 1.77 (s, 18 H, major), 1.80 (s, 18 H, minor), 1.84 (d, J = 9 Hz, 2
H, major), 1.96ꢀ2.02 (m, 2 H, minor), 2.16 (d, J = 10 Hz, 2 H, minor),
2.64 (d, J = 9 Hz, 2 H, major), 2.79 (d, J = 10 Hz, 2 H, minor), 2.94
(d, J = 12 Hz, 2 H, major), 3.22 (d, J = 15 Hz, 2 H, major), 3.23 (d, J = 15
Hz, 2 H, minor), 3.52 (d, J = 15 Hz, 2 H, minor), 6.57 (d, J = 2 Hz, 2 H,
major), 6.63 (d, J = 2 Hz, 2 H, minor), 6.90ꢀ7.27 (m, 10 H, major,
minor), 7.42 (d, J = 2 Hz, 2 H, major), 7.52 (d, J = 2 Hz, 2 H, minor);
13C{1H} NMR (100.7 MHz, C6D6) δ 24.9 (CH2, minor), 26.4 (CH2,
major), 30.6 (CH3, CMe3, minor), 31.0 (CH3, CMe3, major), 31.5 (CH2,
ZrCH2Ph, major), 31.7 (CH3, CMe3, minor), 31.8 (CH3, C, major), 31.8
(CH2, major or minor). 33.9 (CH2, major or minor), 34.1 (C, CMe3,
major), 34.2 (C, CMe3, minor), 34.66 (CH2, ZrCH2Ph, minor), 35.6
(C, CMe3, major), 35.6 (C, CMe3, minor), 47.5 (CH, CHS, minor), 52.9
(CH, CHS, major), 59.3 (CH2, SCH2Ar, major), 63.2 (CH2, SCH2Ar,
minor), 122.2 (C, ipso-C of ZrCH2Ph, minor), 123.2 (CH, ZrCH2Ph,
major or minor), 123.4 (CH, ZrCH2Ph, major or minor), 123.7 (CH, Ar,
major), 124.3 (CH, Ar, minor), 124.8 (C, ipso-C of ZrCH2Ph, major),
125.5 (CH, Ar, major), 125.6 (CH, Ar, minor), 129.6 (CH, ZrCH2Ph,
minor), 130.1 (CH, ZrCH2Ph, major), 137.96 (C, Ar, minor), 137.99
(C, Ar, major), 140.8 (C, Ar, major), 140.9 (C, Ar, minor), 145.4 (C, Ar,
major), 145.7 (C, Ar, minor), 158.0 (C, Ar, minor), 158.7 (C, Ar, major).
The assignment of “major” and “minor” in 13C NMR is based on peak
height and CꢀH COSY experiments. Not all of the CH carbons of
ZrCH2Ph in the major and minor diastereomers could be assigned).
Polymerization of 1-Hexene with 11/(Ph3C)[B(C6F5)4]
(Table 2, Run 2). In a glovebox, (Ph3C)[B(C6F5)4] (18.4 mg, 0.020
mmol) was added to a solution of 11 (17.1 mg, 0.020 mmol) in toluene
X-ray Crystallographic Analysis of 6 and (Δ*,S*,S*)-9.
Colorless single crystals of 6 were obtained by recrystallization from
ethanol, and yellow single crystals of (Δ*,S*,S*)-9 were obtained by
recrystallization from pentane. The intensity data were collected at
103 K for 6 on a Bruker AXS SMART diffractometer and at 100 K for
(Δ*,S*,S*)-9 on a Rigaku AFC10 diffractometer equipped with a
Saturn724þ CCD detector using graphite-monochromated Mo KR
radiation (λ = 0.710 73 Å). The structures were solved by direct
methods and refined by full-matrix least-squares procedures on F2 for
all reflections (SHELX-97).22
Crystallographic data and details of refinement for 6: C36H56O2S2,
MW = 584.93, monoclinic, space group P21/n, a = 9.9252(7) Å,
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ARTICLE
b = 33.704(2) Å, c = 11.0361(7) Å, β = 109.3670(10)°, V = 3482.9(4) Å3,
Z = 4, Dcalcd = 1.116 g cmꢀ3, R1 (I > 2σ(I)) = 0.0661 and wR2 (all data)
= 0.1864 for 6478 reflections and 446 parameters, GOF = 1.094.
Crystallographic data and details of refinement for (Δ*,S*,S*)-9:
A.; Tuzi, A.; Spaniol, T. P.; Okuda, J. Organometallics 2005,
24, 2971–2982. (d) Meppelder, G.-J. M.; Spaniol, T. P.; Okuda, J.
J. Organomet. Chem. 2006, 691, 3206–3211. (e) Gall, B. T.; Pelascini, F.;
Ebeling, H.; Beckerle, K.; Okuda, J.; M€ulhaupt, R. Macromolecules 2008,
41, 1627–1633. (f) Proto, A.; Capacchione, C.; Venditto, V.; Okuda, J.
Macromolecules 2003, 36, 9249–9251. (g) Capacchione, C.; Proto, A.;
Ebeling, H.; M€ulhaupt, R.; Okuda, J. J. Polym. Sci., Part A: Polym. Chem.
2006, 44, 1908–1913. (h) Capacchione, C.; DeCarlo, F.; Zannoni, C.;
Okuda, J.; Proto, A. Macromolecules 2004, 37, 8919–8922. (i) Lian, B.;
Spaniol, T. P.; Okuda, J. Organometallics 2007, 26, 6653–6660.
(5) (a) Beckerle, K.; Manivannan, R.; Lian, B.; Meppelder, G.-J. M.;
Raabe, G.; Spaniol, T. P.; Ebeling, H.; Pelascini, F.; M€ulhaupt, R.; Okuda,
J. Angew. Chem., Int. Ed. 2007, 46, 4790–4793. (b) Meppelder, G.-J. M.;
Beckerle, K.; Manivannan, R.; Lian, B.; Raabe, G.; Spaniol, T. P.; Okuda,
J. Chem. Asian J. 2008, 3, 1312–1323.
C87H143O8S4Ti2 ((C42H68O4S2Ti)2 0.5C6H14), MW = 1541.05,
3
monoclinic, space group P21/n, a = 19.3273(17) Å, b = 13.9791(11)
Å, c = 34.816(3) Å, β = 104.7800(10)°, V = 9095.3(13) Å3, Z = 4, Dcalcd
= 1.125 g cmꢀ3, R1 (I > 2σ(I)) = 0.0452 and wR2 (all data) = 0.1073 for
16 868 reflections and 943 parameters, GOF = 1.094.
’ ASSOCIATED CONTENT
S
Supporting Information.
CIF files giving crystallo-
b
graphic data for 6 and (Δ*,S*,S*)-9 and figures and tables giving
NMR spectra of 9, 11, and 12þ[B(CH2Ph)(C6F5)3]ꢀ, line-
shape analysis of VT-1H NMR of 9, optimized coordinates of 10,
and 13C NMR spectra of poly(1-hexene)s. This material is
available free of charge via the Internet at http://pubs.acs.org.
(6) (a) Capacchione, C.; Avagliano, A.; Proto, A. Macromolecules
2008, 41, 4573–4575. (b) Milione, S.; Cuomo, C.; Capacchione,
C.; Zannoni, C.; Grassi, A.; Proto, A. Macromolecules 2007, 40,
5638–5643.
(7) Ishii, A.; Toda, T.; Nakata, N.; Matsuo, T. J. Am. Chem. Soc. 2009,
131, 13566–13567.
’ AUTHOR INFORMATION
(8) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2000,
122, 10706–10707. (b) Segal, S.; Goldberg, I.; Kol, M. Organometallics
2005, 24, 200–202. (c) Yeori, A.; Groysman, S.; Goldberg, I.; Kol, M.
Inorg. Chem. 2005, 44, 4466–4468. (d) Groysman, S.; Sergeeva, E.;
Goldberg, I.; Kol, M. Inorg. Chem. 2005, 44, 8188–8190. (e) Yeori, A.;
Goldberg, I.; Shuster, M.; Kol, M. J. Am. Chem. Soc. 2006, 128,
13062–13063. See also: (f) Gendler, S.; Zelikoff, A. L.; Kopiliv, J.;
Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2008, 130, 2144–2145. (g)
Cohen, A.; Kopilov, J.; Lamberti, M.; Venditto, V.; Kol, M. Macro-
molecules 2010, 43, 1689–1691. (h) Sergeeva, E.; Kopilov, J.; Goldberg,
I.; Kol, M. Inorg. Chem. 2010, 49, 3977–3979.
(9) (a) Peckermann, I.; Kapelski, A.; Spaniol, T. P.; Okuda, J. Inorg.
Chem. 2009, 48, 5526–5534. (b) Konkol, M.; Kondracka, M.; Voth, P.;
Spaniol, T. P.; Okuda, J. Organometallics 2008, 27, 3774–3784.
(10) (a) Ishii, A.; Suzuki, M.; Sone, T.; Nakata, N. Phosphorus, Sulfur
Silicon Relat. Elem. 2009, 184, 1184–1205. (b) Ishii, A.; Ono, A.; Nakata,
N. J. Sulfur Chem. 2009, 30, 236–244.
Corresponding Author
*Fax: (þ81) 48-858-3394. E-mail: ishiiaki@chem.saitama-u.ac.jp.
’ ACKNOWLEDGMENT
We thank Dr. Masayoshi Nishiura and Dr. Zhaomin Hou
(Organometallic Chemistry Laboratory, RIKEN Advanced
Science Institute) for measurement of molecular weight and
distributions of poly(1-hexene)s. We are grateful to Dr. Tsukasa
Matsuo and Dr. Kohei Tamao (RIKEN Advanced Science
Institute) for their kind discussions. T.T. acknowledges a JSPS
fellowship for young scientists. N.N. thanks the Mitsubishi
Chemical Corporation Fund.
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