A highly efficient titanium catalyst for the synthesis of ultrahigh-molecular-weight polyethylene (UHMWPE)

Article abstract of DOI:10.1002/chem.201301176

Long chain running: The polymerization performance of guanidinato titanium(IV) olefin catalysts is tuned by monodentate ancillary ligands. Polymerization activities of up to 8800 kg_PE mol_cat. ^-1 h^-1 bar^-1

Full text of DOI:10.1002/chem.201301176

DOI: 10.1002/chem.201301176
A Highly Efficient Titanium Catalyst for the Synthesis of Ultrahigh-
Molecular-Weight Polyethylene (UHMWPE)
Isabelle Haas, Christian Hꢀbner, Winfried P. Kretschmer, and Rhett Kempe*[a]
Ultrahigh-molecular-weight polyethylene (UHMWPE) is
a unique polymer with outstanding physical and mechanical
properties and a molecular weight of 2–6ꢀ106 gmolÀ1. It is
known for its chemical inertness, lubricity, and impact and
abrasion resistance. Therefore, UHMWPE has a variety of
important commercial uses, including polymer components
in knee and hip replacements,[1] pickers for textile ma-
ACHTUNGTRENNUNGchinACHTUNGTRENNUNG
ery, microporous films for battery separators,[2] the
lining for coal chutes and dump trucks, runners for bottling
production lines, and bumpers and siding for ships and har-
bors.[3]
We are investigating Group 4 metal based polymerization
catalysts stabilized by very bulky monoanionic bidentate N
ligands.[4] Recently, our group discovered a guanidinato tita-
nium catalyst system that is able to polymerize ethylene by
coordinative chain-transfer polymerization.[5] It is highly
active in the presence of very high chain-transfer-agent to
catalyst ratios and undergoes polyethylene chain transfer to
triethylaluminum. These results encouraged us to develop a
new titanium-based polymerization catalyst class [Gua-
TiLCl2] (Gua=1,2-bis(2,6-diisopropylphenyl)-3,3-diethylgua-
nidinato; L=additional monoanionic ligand, for instance,
imidazolidine-2-imide, guanidide, phenoxide, or amide;
Scheme 1). The bulky guanidinato ligand (Gua) is mono-
Scheme 1. Monodentate ancillary ligands (top); synthesis of the com-
plexes 2–5 (bottom).
A
um 1,1,3,3-bis(pentamethylene)guanidide LiB was prepared
to alter the properties of the already highly active polymeri-
zation catalyst 1 (Scheme 1). Some of the additional ligands
L, such as aryloxides[6] and guanidinates[7] or closely related
ketimides[8] and phosphoraneimides,[9] are already docu-
mented in the olefin polymerization chemistry literature,
but were never combined with guanidinato ligands. Herein,
we report the synthesis and structure of dichloro titanium
complexes of the type [GuaTiLCl2] and their use in ethylene
polymerization. One of the catalysts introduced is able to
produce UHMWPE with a very high activity.
in situ by reaction of piperidyl lithium with 1-piperidinecar-
bonitrile,[11] whereas sterically protected 1,3-bis(2,6-di
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
corresponding 1,2-dianilinoethane and cyanogen bromide in
toluene according to literature procedures.[12] The two other
monoanionic monodentate ligands used are 2,6-diphenyl-
phenoxide (D) and dicyclohexylamide (A; Scheme 1), both
of which are prepared from their commercially available
protonated forms by deprotonation of the hydroxyl or
amine function, respectively. The guanidinato titanium di-
chloride complexes 2–5 were prepared by simple salt elimi-
nation reactions from the titanium precursor 1 and the Li
salts of the ligands (Scheme 1). All complexes were ana-
lyzed by NMR spectroscopy, elemental analysis, and single-
crystal structure analysis. Crystals suitable for X-ray analysis
were obtained by layering concentrated solutions in toluene
with hexane or by recrystallization from toluene. The molec-
ular structures of complexes 2–5 are presented in Figures 1
and 2. Selected bond lengths and angles are listed in
Table 1. Crystallographic details are available in the Sup-
porting Information (Table S1).
The titanium precursor complex 1 (Scheme 1) was easily
prepared by reaction of diethylamido titanium trichloride[10]
with N,N’-bis(2,6-diisopropyl)carbodiimide through meth-
ACHTUNGTRENNUNG
anediimine insertion into the titanium–amide bond.[5] Lithi-
[a] I. Haas, C. Hꢁbner, Dr. W. P. Kretschmer, Prof. Dr. R. Kempe
Lehrstuhl Anorganische Chemie II, Universitꢂt Bayreuth
Universitꢂtsstraße 30, NW I, 95440 Bayreuth (Germany)
Fax : (+49)921552157
E-mail: kempe@uni-bayreuth.de
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201301176.
9132
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 9132 – 9136

COMMUNICATION
Figure 2. Molecular structures of 4 (top) and 5 (bottom). Complex 4 crys-
tallized with two independent molecules per asymmetric unit. Carbon-
bonded hydrogen atoms are omitted for clarity.
Figure 1. Molecular structures of 2 (top) and 3 (bottom). Carbon-bonded
hydrogen atoms and one toluene molecule in the asymmetric unit of
complex 3 are omitted for clarity.
the guanidinate central atom are distorted because of coor-
dination to the titanium center. The N-C-N angle between
the ligating nitrogen atoms is considerably smaller than 1208
(106–1108), whereas the remaining angles are greater than
1208 (124–1288). However, the sum of the angles around the
central carbon atom in each chelating guanidinate ligand is
3608 indicating no deviation from planarity.[13] Complex 5
Complexes 2 and 3 crystallize in the monoclinic space
group P21/n, complex 4 in the monoclinic space group C2/c
and complex 5 in the monoclinic space group P21. The ge-
ometry around the titanium centers in all four complexes is
roughly trigonal bipyramidal including the guanidinate
ligand, an ancillary ligand, and two chloro ligands. The
equatorial positions are occupied by Cl1, Cl2, and one of
the guanidinate nitrogen donors (N1 in complex 2, 3, and 5
and N3 in complex 4). The axial positions are occupied by
the second nitrogen donor of the guanidinate ligand and the
ancillary ligand donor atom. The distortion of the trigonal
bipyramid results from the very small bite angle of the che-
lating guanidinate (range 62–648), caused by the high steric
demand of the 2,6-diisopropyl moieties. The angles around
À
shows the same bond length of 1.353(4) ꢄ for all three C N
bonds; they are therefore indistinguishable, indicating con-
siderable delocalization of the uncoordinated nitrogen atom
lone pair into the ligand p system.[14] This is in contrast to
the crystallographic data of complexes 2, 3, and 4 in which
À
the C N bond to the uncoordinated nitrogen atom
(1.359(2)–1.376(5) ꢄ) is slightly longer than those to the co-
ordinated nitrogen atoms (1.337(5)–1.3533(19) ꢄ).
Chem. Eur. J. 2013, 19, 9132 – 9136
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9133

R. Kempe et al.
Table 1. Selected bond lengths [ꢄ] and angles [8].
(1.493(2) ꢄ) in the amide complex 2 are significantly longer
3
[15]
À
than C
(sp ) N single bonds,
but the sum of the bond
complex
2
3
4
5
À
angles around N4 is 359.988 and the Ti1 N4 bond length is
1.8663(13) ꢄ , which clearly confirms the sp2 hybridization
of N4.
À
Ti1 Cl1
2.2851(5)
2.3232(5)
2.0839(13)
2.1011(13)
1.8663(13)
–
1.3431(19)
1.368(2)
1.3533(19)
–
2.3462(5)
2.3035(5)
2.0787(13)
2.1239(13)
1.7662(14)
–
1.348(2)
1.359(2)
1.350(2)
1.327(2)
1.355(2)
1.367(2)
–
2.2788(13)
2.3216(14)
2.150(3)
2.097(4)
1.765(3)
–
1.337(5)
1.376(5)
1.336(5)
1.326(5)
1.353(5)
1.360(5)
–
2.2185(9)
2.2824(10)
2.047(3)
2.055(2)
À
Ti1 Cl2
À
Ti1 N1
À
Ti1 N3
To compare their efficiencies in ethylene polymerization,
all of the synthesized complexes were activated with methyl-
alumoxane (MAO; Table 2, entries 1–6). Complex 1, without
any ancillary ligand, was used as the reference system for
the polymerization performances of the new catalysts 2–5.
The polymerization data for complex 1 activated with MAO
showed a high activity of 1670 kgmolÀ1 hÀ1 barÀ1, a polydis-
persity index (PDI) of 2.5 and a molecular weight of
21000 gmolÀ1. Complex 2 did not show any polymerization
activity after activation with MAO, whereas the control ex-
periment with (N,N-dicyclohexylamido)titanium trichloride
gave some polymerization activity. Comparison of the poly-
merization results of complexes 3 and 1, both activated with
MAO, showed nearly identical data. Molecular weights of
about 20000 gmolÀ1 and PDIs of 2.5 were obtained
(Figure 3).
À
Ti1 N4
–
À
Ti1 O1
1.8100(19)
1.353(4)
1.353(4)
1.353(4)
–
–
–
–
À
C1 N1
À
C1 N2
À
C1 N3
À
C11 N4
À
C11 N5
–
–
À
C11 N6
À
N4 C30
1.483(2)
1.493(2)
110.05(13)
63.73(5)
–
95.108(18)
359.99
–
À
N4 C36
–
–
–
N1-C1-N3
N1-Ti1-N3
Ti1-N4-C11
Cl1-Ti1-Cl2
ꢀ<(C1)
109.21(13)
63.10(5)
168.05(12)
95.867(18)
359.99
110.2(4)
62.15(13)
170.5(3)
94.86(5)
360.0
106.6(3)
63.85(10)
–
101.10(4)
360.0
–
–
ꢀ<(C11)
ꢀ<(N4)
359.99
–
359.8
–
359.98
Table 2. Ethylene homopolymerization with complexes 1–5 (Ti complex (2 mmol ), toluene (150 mL), ethylene
Closer examination of the an-
cillary monodentate ligand
shows that the sum of the bond
angles around C11 is 359.998
(for complex 3) and 359.88 (for
complex 4), which confirms that
the carbon atoms are sp2 hybri-
dized. An advantage of the
monodentate guanidide ligands
is that they can donate more
than two electrons to the titani-
um center because of the pres-
ence of lone pairs and C=N
double bonds. The additional p
(2 bar), 508C, 15 min run time).[a]
[b]
Cat.
Co-cat.
n
A
G
m
[g]
N
Activity
Mw
[gmolÀ1
]
Mw/Mn
[b]
[kgmolÀ1 hÀ1 barÀ1
]
U
1
2
3
4
5
1
MAO
MAO
MAO
MAO
MAO
1300
1300
1300
1300
1300
1.67
0.18
–
0.45
0.97
1670
180
–
450
970
21000
417000
–
19000
1259000
2.5
14.5
–
2.5
93.3
[c]
2
3
4
(2385000)
188000
6
5
MAO
1300
1.35
1350
20.8
AHCTUNGTRENN(GUN 412000)
7
8
9
10
11
12
13
1
d-MAO
d-MAO
d-MAO
d-MAO
d-MAO
d-MAO
d-MAO
1000
1000
1000
1000
1000
1000
1000
1.36
0.36
–
2.10
5.56
0.88
0.76
1360
360
–
2100
5560
8800
760
172000
1465000
–
280000
1546000
2488000
369000
3.3
123.3
–
20.9
3.8
[c]
2
3
4
À
bonds increase the Ti N bond
4[d]
5
3.4
1.8
order and strength, and simulta-
neously decrease the electron
deficiency of the titanium
center, thereby enhancing the
stability of the complex. Fur-
[a] Numbers in brackets display the high-molecular-weight fraction of bimodal distributions. [b] Determined
by HT-GPC analysis. [c] (N,N-Dicyclohexylamido)titanium trichloride. [d] 0.2 mmol Ti complex.
thermore, because electron donation is maximized for a
This agreement indicates an immediate transfer of the an-
cillary guanidinate ligand of complex 3 to the alkyl alumi-
num that is usually present in small amounts in MAO. Acti-
vation of complex 4 with MAO leads to a bimodal distribu-
tion (Table 2, entry 5). This indicates that two active sites
are operating during the polymerization process. The lower
À
linear Ti N=C arrangement, the angles in complexes 3 and
4 are found to be around 1708 (170.58 for 4 and 168.18 for
3). Complex 5 also shows the linear Ti-O-C arrangement
with an angle of 170.7(2)8. Moreover, the zwitterionic reso-
nance structures of the two monoanionic guanidides in com-
plexes 3 and 4 suggest increased negative charge on the
metal-binding nitrogen atom. The bond lengths in the ancil-
lary ligand and at the metal center confirm this. Whereas
the titanium–nitrogen bond lengths are 1.765(3) and
1.7662(14) ꢄ in the two guanidide complexes 4 and 3, re-
spectively, the titanium-oxygen bond length is significantly
larger (1.8100(19) ꢄ) in the aryloxide complex 5 and the ti-
tanium–amide bond length is 1.8663(13) ꢄ in complex 2.
À
À
À
The N C bond lengths N4 C30 (1.483(2) ꢄ) and N4 C36
Figure 3. Mw distribution plots of polymers (Table 2, entries 1 and 4).
9134
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 9132 – 9136

Titanium Catalyzed Synthesis of Ultrahigh-Molecular-Weight Polyethylene
COMMUNICATION
In summary, the reaction of the lithiated amine, guani-
dine, imidazolidin-2-imine, or phenol with [GuaTiCl3] (1) se-
lectively led to the desired nonbridged titanium dichlorides.
The “addition” of a second anionic ligand drastically alters
the polymerization behavior of the precursor complex 1 .
Some complexes are completely inactive and others show
about one order of magnitude higher activity than the al-
ready highly active precursor 1. Furthermore, drastically dif-
ferent polymer products can be obtained, for instance
UHMWPE. The many bulky monoanionic non-cyclopenta-
dienyl ligands developed in recent years might be useful
candidates to further develop nonbridged, mixed ligand
Group 4 metal complexes combining high polymerization
activity and unusual selectivity patterns.
Figure 4. Mw distribution plots of polymers (Table 2, entries 1, 5, and 11).
molecular-weight fraction is identical to that observed for
precatalyst 1/MAO (Table 2, entry 1, Figure 4). The very
high-molecular-weight fraction indicates the potential of the
catalyst to produce UHMWPE.
The gel permeation chromatography (GPC) data provide
explicit evidence for ligand transfer of the imidazolidin-2-
imido ligand to the alkyl aluminum. In comparison to the
catalyst system 3/MAO, for which immediate ligand transfer
is observed, the catalyst system 4/MAO showed gradual
ligand transfer to aluminum alkyls during the 15 min poly-
merization run. The slower transfer may be due to the
higher steric demand of the imidazolidin-2-imido ligand
compared to the ancillary guanidinate ligand in catalyst
system 3.
Acknowledgements
Financial support from the German National Academic Foundation is
gratefully acknowledged.
Keywords: mixed ligand complexes
polymerization · titanium · polyethylene
·
N
ligands
·
After activation with MAO, catalyst precursor 5 also gave
a polymer with a bimodal distribution of chain lengths. The
GPC spectra are consistent with those obtained by using
catalyst precursor 4 and indicate that after activation with
MAO the low-molecular-weight fraction obtained is similar
to the one obtained with 1/MAO (Table 2, entry 1) and the
high-molecular-weight fraction is similar to that obtained
with 5/dry methylalumoxane (d-MAO; Table 2, entry 13,
Figure S1 in the Supporting Information). Even the small
amounts of free TMA in MAO suffice to transfer the ancil-
lary aryloxide to aluminum. To completely inhibit the ligand
transfer described above, all catalyst precursors were tested
with d-MAO as the activator, from which free TMA was re-
moved (Table 2, entries 7–13). Under these conditions, com-
plex 1 gave a higher molecular-weight fraction together with
a broader PDI because efficient chain transfer to aluminum
was suppressed. Complex 2 showed no polymerization activ-
[1] M. C. Sobieraj, C. M. Rimnac, J. Mech. Behav. Biomed. 2009, 2,
433–443.
[2] H. Yoneda, Y. Nishimura, Y. Doi, M. Fukuda, M. Kohno, Polym. J.
2010, 42, 425–437.
[3] S. M. Kurtz, The UHMWPE Handbook - Ultra-High Molecular
Weight Polyethylene in Total Join Replacement, Elsevier Academic
Press, San Diego, 2004, pp. 1–5.
[4] a) J. Obenauf, W. P. Kretschmer, T. Bauer, R. Kempe, Eur. J. Inorg.
Chem. 2013, 537–544; b) A. Noor, W. P. Kretschmer, G. Glatz, R.
Kempe, Inorg. Chem. 2011, 50, 4598–4606; c) Ch. Dçring, W. P.
Kretschmer, R. Kempe, Eur. J. Inorg. Chem. 2010, 2853–2860;
d) W. P. Kretschmer, T. Bauer, B. Hessen, R. Kempe, Dalton Trans.
2010, 39, 6847–6852; e) Ch. Dçring, W. P. Kretschmer, T. Bauer, R.
Kempe, Eur. J. Inorg. Chem. 2009, 4255–4264; f) Ch. Dçring, R.
Kempe, Eur. J. Inorg. Chem. 2009, 412–418; g) A. Noor, W. P.
Kretschmer, G. Glatz, A. Meetsma, R. Kempe, Eur. J. Inorg. Chem.
2008, 5088–5098; h) W. P. Kretschmer, B. Hessen, A. Noor, N. M.
Scott, R. Kempe, J. Organomet. Chem. 2007, 692, 4569–4579;
i) W. P. Kretschmer, A. Meetsma, B. Hessen, T. Schmalz, S. Qayyum,
R. Kempe, Chem. Eur. J. 2006, 12, 8969–8978; j) N. M. Scott, R.
Kempe, Eur. J. Inorg. Chem. 2005, 1319–1324.
ity, whereas the control experiment with (N,N-dicyclohex
ACHTUNGERTNyNUNG l-
[5] S. K. T. Pillai, W. P. Kretschmer, M. Trebbin, S. Fçrster, R. Kempe,
Chem. Eur. J. 2012, 18, 13974–13978.
ACHTUNGTRENNUNG
ular weight and an extremely broad polydispersity. The ac-
tivity of catalyst system 3 significantly increased with the
use of d-MAO as the activator, as did the molecular weight
[6] a) K. Nomura, K. Oya, Y. Imanishi, J. Mol. Catal. A Chem. 2001,
174, 127–140; b) K. Nomura, K. Itagaki, Macromolecules 2005, 38,
8121–8123; c) F. Z. Khan, K. Kakinuki, K. Nomura, Macromole-
cules 2009, 42, 3767–3773; d) K. Nomura, T. Komatsu, Y. Imanishi,
Macromolecules 2000, 33, 8122–8124; e) K. Nomura, K. Kakinuki,
M. Fujiki, K. Itagaki, Macromolecules 2008, 41, 8974–8976; f) K.
Kakinuki, M. Fujiki, K. Nomura, Macromolecules 2009, 42, 4585–
4595; g) K. Itagaki, M. Fujiki, K. Nomura, Macromolecules 2007, 40,
6489–6499; h) K. Nomura, S. Pracha, K. Phomphrai, S. Katao, D.-H.
Kim, H. J. Kim, N. Suzuki, J. Mol. Catal. A Chem. 2012, 365, 136–
145; i) K. Nomura, K. Oya, T. Komatsu, Y. Imanishi, Macromole-
cules 2000, 33, 3187–3189; j) K. Nomura, H. Okumura, T. Komatsu,
N. Naga, Macromolecules 2002, 35, 5388–5395; k) K. Nomura, M.
Tsubota, M. Fujiki, Macromolecules 2003, 36, 3797–3799; l) W.
Wang, T. Tanaka, M. Tsubota, M. Fujiki, S. Yamanaka, K. Nomura,
of the polyACHTUNGTRENNUNGmer obtained. Complexes 4 and 5 yielded mono-
modal molecular-weight distributions after activation with
d-MAO. The GPC spectrum of 5/d-MAO showed a PDI of
1.8, the narrowest observed for all of the systems tested.
Furthermore, the activity of catalyst system 4/d-MAO in-
creased dramatically, as did the molecular weight of the
polyACHTUNGTRENNUNGmer obtained. By lowering the amount of active catalyst
from 2 to 0.2 mmol, to avoid diffusion control, the activity
and molecular weight can be further enhanced, reaching
8800 kgmolÀ1 hÀ1 barÀ1 and UHMWPE of 2500 kgmolÀ1.
Chem. Eur. J. 2013, 19, 9132 – 9136
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9135

R. Kempe et al.
Adv. Synth. Catal. 2005, 347, 433–446; m) K. Nomura, N. Naga, M.
Miki, K. Yanagi, Macromolecules 1998, 31, 7588–7597; n) K.
Nomura, N. Naga, M. Miki, K. Yanagi, A. Imai, Organometallics
1998, 17, 2152–2154; o) K. Nomura, Dalton Trans. 2009, 8811–8823;
p) Y. Takii, P. M. Gurubasavaraj, S. Katao, K. Nomura, Organome-
tallics 2012, 31, 8237–8248; q) I. Korobkov, S. Gambarotta, Organo-
metallics 2009, 28, 4009–4019; r) P. M. Gurubasavaraj, K. Nomura,
Inorg. Chem. 2009, 48, 9491–9500; s) M. G. Thorn, Z. C. Etheridge,
P. E. Fanwick, I. P. Rothwell, J. Organomet. Chem. 1999, 591, 148–
162; t) W. Wang, M. Fujiki, K. Nomura, J. Am. Chem. Soc. 2005,
127, 4582–4583; u) D. J. Byun, A. Fudo, A. Tanaka, M. Fujiki, K.
Nomura, Macromolecules 2004, 37, 5520–5530; v) K. Nomura, Y.
Hatanaka, H. Okumura, M. Fujiki, K. Hasegawa, Macromolecules
2004, 37, 1693–1695; w) K. Nomura, A. Fudo, Catal. Commun.
2003, 4, 269–274; x) K. Nomura, H. Okumura, T. Komatsu, N.
Naga, Y. Imanishi, J. Mol. Catal. A Chem. 2002, 190, 225–234; y) K.
Nomura, T. Komatsu, Y. Imanishi, J. Mol. Catal. A Chem. 2000, 159,
127–137.
Am. Chem. Soc. 2000, 122, 5499–5509; i) E. G. Ijpeij, M. A. Zuide-
veld, H. J. Arts, F. van der Burgt, G. H. J. van Doremaele (DSM,
Linz), WO2007031295, 2007; j) E. G. Ijpeij, P. J. H. Windmuller, H. J.
Arts, F. van der Burgt, G. H. J. van Doremaele, M. A. Zuideveld
(DSM, Linz), WO2005090418, 2005; k) E. G. Ijpeij, B. Coussens,
M. A. Zuideveld, G. H. J. van Doremaele, P. Mountford, M. Lutz,
A. L. Spek, Chem. Commun. 2010, 46, 3339–3341; l) J. Liu, K.
Nomura, Adv. Synth. Catal. 2007, 349, 2235–2240; m) I. A. Latham,
G. J. Leigh, G. Huttner, I. Jibril, J. Chem. Soc. Dalton Trans. 1986,
377–383.
[9] a) D. W. Stephan, J. C. Stewart, F. Guꢅrin, R. E. v. H. Spence, W.
Xu, D. G. Harrison, Organometallics 1999, 18, 1116–1118; b) R. S.
Schiffino, D. J. Crowther (Exxon, Darien), US5625016, 1997;
c) D. W. Stephan, J. C. Stewart, S. J. Brown, J. W. Swabey, Q. Wang
(Nova Chemicals, Calgary), US6063879, 1997; d) D. W. Stephan, Or-
ganometallics 2005, 24, 2548–2560; e) D. W. Stephan, J. C. Stewart,
F. Guꢅrin, S. Courtenay, J. Kickham, E. Hollink, C. Beddie, A.
Hoskin, T. Graham, P. Wie, R. E. v. H. Spence, W. Xu, L. Koch, X.
Gao, D. G. Harrison, Organometallics 2003, 22, 1937–1947;
f) N. L. S. Yue, D. W. Stephan, Organometallics 2001, 20, 2303–2308;
g) D. W. Stephan, J. C. Stewart, R. E. v. H. Spence, L. Koch, X. Gao,
S. J. Brown, J. W. Swabey, Q. Wang, W. Xu, P. Zoricak, D. G. Harri-
son, Organometallics 1999, 18, 2046–2048.
[10] E. Benzing, W. Kornicker, Chem. Ber. 1961, 94, 2263–2267.
[11] W. Clegg, R. Snaith, H. M. M. Shearer, K. Wade, G. Whitehead, J.
Chem. Soc. Dalton Trans. 1983, 1309–1317.
[12] L. Toldy, M. Kꢁrti, Z. Zubovics, I. Schꢂfer (Egypt Gyo. Gyar.),
DE2916140, 1979.
[13] P. J. Bailey, K. J. Grant, L. A. Mitchell, S. Pace, A. Parkin, S. Par-
sons, J. Chem. Soc. Dalton Trans. 2000, 1887–1891.
[14] P. J. Bailey, Coord. Chem. Rev. 2001, 214, 91–141.
[7] a) W. P. Kretschmer, C. Dijkhuis, A. Meetsma, B. Hessen, J. H.
Teuben, Chem. Commun. 2002, 608–609; b) W. Apisuk, A. G. Tram-
bitas, B. Kitiyanan, M. Tamm, K. Nomura, J. Polym. Sci. A: Polym.
Chem. 2013, 51, 2575–2580.; c) S. H. Stelzig, M. Tamm, R. M. Way-
mouth, J. Polym. Sci. Part A 2008, 46, 6064–6070; d) M. Tamm, S.
Randoll, E. Herdtweck, N. Kleigrewe, G. Kehr, G. Erker, B. Rieger,
Dalton Trans. 2006, 459–467.
[8] a) J. McMeeking, X. Gao, R. E. v. H. Spence, S. J. Brown, D. Jeremic
(Nova Chemicals, Calgary), US6114481, 2000; b) J. McMeeking, X.
Gao, R. E. v. H. Spence, S. J. Brown, D. D. Jeremic (Nova Chemi-
cals, Calgary), WO9914250, 1999; c) K. Nomura, K. Fujita, M.
Fujiki, J. Mol. Catal. A Chem. 2004, 220, 133–144; d) H. Zhang, K.
Nomura, J. Am. Chem. Soc. 2005, 127, 9364–9365; e) H. Zhang, K.
Nomura, Macromolecules 2006, 39, 5266–5274; f) K. Nomura, W.
Wang, M. Fujiki, J. Liu, Chem. Commun. 2006, 2659–2661; g) A. R.
Dias, M. T. Duarte, A. C. Fernandes, S. Fernandes, M. M. Marques,
A. M. Martins, J. F. da Silva, S. S. Rodrigues, J. Organomet. Chem.
2004, 689, 203–213; h) S. Zhang, W. E. Piers, X. Gao, M. Parvez, J.
[15] F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen,
R. Taylor, J. Chem. Soc. Perkin Trans. 1987, S1–S19.
Received: March 27, 2013
Published online: May 28, 2013
9136
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 9132 – 9136