Direct observation of a cationic ruthenium complex for ethylene insertion polymerization

Article abstract of DOI:10.1039/c3sc50676b

We report here the first direct observation of a cationic ruthenium complex catalyzing ethylene insertion polymerization. An arene-tethered ruthenium complex (η⁶-C₆H₅(CH₂) ₃SCH₃RuCl₂) (3) was synthesized and shown to be able to catalyze ethylene polymerization upon activation with AlMe ₂Cl. For mechanistic studies, we synthesized the homologous dimethylated η⁶-C₆H₅(CH₂) ₃SCH₃Ru(CH₃)₂ (4) complex, which upon activation with the Brookhart acid ([H(Et₂O)₂] ⁺ [BAr′₄]^-) was also active for ethylene insertion polymerization. ¹H-NMR and mass spectrometry (MS) studies provide direct evidence for a ruthenium cationic [η⁶-C ₆H₅(CH₂)₃SCH₃Ru(oligomer) ]⁺ complex as the active species during polymerization. This has unambiguously shown for the first time a ruthenium complex as the active species for catalyzing olefin insertion polymerization.

Full text of DOI:10.1039/c3sc50676b

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Direct observation of a cationic ruthenium complex for
ethylene insertion polymerization†
Cite this: Chem. Sci., 2013, 4, 2902
*
Miguel A. Camacho-Fernandez, Max Yen, Joseph W. Ziller and Zhibin Guan
We report here the first direct observation of a cationic ruthenium complex catalyzing ethylene insertion
polymerization. An arene-tethered ruthenium complex (h6-C6H5(CH2)3SCH3RuCl2) (3) was synthesized and
shown to be able to catalyze ethylene polymerization upon activation with AlMe2Cl. For mechanistic
studies, we synthesized the homologous dimethylated h6-C6H5(CH2)3SCH3Ru(CH3)2 (4) complex, which
upon activation with the Brookhart acid ([H(Et2O)2]+ [BAr04]ꢀ) was also active for ethylene insertion
polymerization. 1H-NMR and mass spectrometry (MS) studies provide direct evidence for a ruthenium
cationic [h6-C6H5(CH2)3SCH3Ru(oligomer)]+ complex as the active species during polymerization. This has
unambiguously shown for the first time a ruthenium complex as the active species for catalyzing olefin
insertion polymerization.
Received 11th March 2013
Accepted 2nd May 2013
DOI: 10.1039/c3sc50676b
www.rsc.org/chemicalscience
offer the possibility of combining such good attributes. In
particular, ruthenium complexes have proven to be very versa-
Introduction
The polyolen industry continues to grow steadily because of
continuous discoveries of new catalysts, processes, and poly-
olen materials with new properties. While early transition
metal catalysts generally have high activity for olen polymeri-
zation, their oxophilicity has largely prevented their use for
incorporation of polar olens.1 During the last two decades,
signicant advances have been made in the development of
late-transition-metal polymerization catalysts. A few notable
examples include the Ni(II)- and Pd(II)-a-diimine systems
discovered by Brookhart and coworkers2 and the Pd(II)-ortho-
phosphino-arenesulfonate system initially introduced by Drent
and coworkers.3 Excitingly, some of the late transition metal
catalysts are able to copolymerize functional olens such as
methyl acrylate (MA).2a,3,4 Following these pioneering studies, a
number of groups have made important contributions to this
area both in new catalyst design and new polymer synthesis.5
Despite their promising attributes, late transition metal cata-
lysts are generally less active than early transition metal cata-
lysts, warranting the search for other transition metal
complexes for olen polymerization.
tile in various types of catalytic reactions and show excellent
functional group tolerance.6 Although best known for metath-
esis polymerization,6c ruthenium has also been sporadically
investigated for olen insertion polymerization.7 In early 1970's,
hydrido-ruthenium species – HRuCl(PPh3)3 or (H)2Ru(PPh3)4 –
were reported for insertion polymerization of ethylene or polar
olens.7a,b Later, Nomura et al.7c,d reported a ruthenium–pybox
complex (1) (Chart 1), which in combination with MAO could
polymerize ethylene. However, in a detailed study by Brookhart
and coworkers,7e a similar Ru–diiminopyridine complex (2) was
shown to be completely inactive despite the fact that analogous
Fe(II)–diiminopyridine complexes showed excellent activity
toward ethylene insertion polymerization.8 The authors attrib-
uted the inactivity to the coordination geometry of the Ru
complex. The distorted square pyramidal coordination of Ru
complex 2 results in non-degenerate coordination sites of olen
and alkyl groups relative to the tridentate ligand, resulting in a
prohibitively high energetic barrier for migratory insertion.
Indeed, a recent computational study calculated that the
An ideal catalyst system should combine the functional
group tolerance of late transition metals with the high activities
of early transition metals. Group 8 metals, located right in the
center of the transition metal block in the periodic table, may
Department of Chemistry, University of California, 1102 Natural Sciences 2, Irvine,
California 92697-2025, USA. E-mail: zguan@uci.edu; Fax: +1 949-824-2210; Tel: +1
949-824-5172
Chart 1 Reported complexes 1 and 2, and our complex 3. Both 1 and 2 have
non-equivalent coordination sites for the putative olefin and alkyl groups of the
active growing species. The designed complex 3 has two equivalent cis coordi-
nation sites.
† Electronic supplementary information (ESI) available: Experimental procedures,
synthesis, and characterization of compounds. Detailed 1H-NMR and ESI-MS
studies on active polymerization species. Polymerization studies and X-ray
structures. See DOI: 10.1039/c3sc50676b
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barriers for migratory insertion of the coordinated olen into
the Ru alkyl bond in 1 and 2 are larger than 25 kcal molꢀ1, too
high for olen insertion polymerization.9 Very recently, Claverie
et al. reported a Ru–di(phosphine-arenesulfonato) complex that
surprisingly made crosslinked polyethylene.10 Notably, none of
the aforementioned studies have elucidated the active species
responsible for olen insertion polymerization.
Scheme 1 Synthesis of complex 3.
On the basis of these previous studies, we hypothesized that
it would be possible to achieve active Ru(II) complexes for
insertion polymerization if they are designed in such a manner ruthenium in solution as evidenced by the diastereotopic arene
that the alkyl and olen occupy equivalent coordination sites in and tethered arm protons observed in the 1H-NMR spectra (ESI
cis geometry for the active intermediates. To test this hypoth- Fig. S1–S7†). On the basis of variable temperature NMR data,
esis, herein we designed a Ru(II) h6-arene complex containing a the inversion barrier on sulfur was estimated to be 14.4 ꢂ
tethered sulfur ligand (3, Chart 1). As shown in the X-ray 0.1 kcal molꢀ1 (see ESI for details†), which is close to the
structure (Fig. 1), the complex adopts a “piano stool” type of inversion barrier for a tetramethylcyclopentadienyl-S-tethered
coordination geometry, which upon activation should generate cobalt complex reported previously.14
two equivalent coordination sites for active migratory insertion.
Complex 3 was tested for ethylene polymerization using
In this study, we focus on the investigation of active species of AlMe2Cl as the co-catalyst (Table 1). Encouragingly, upon acti-
this complex for ethylene insertion polymerization. To the best vation complex 3 exhibited moderate activity for producing
of our knowledge, this is the rst direct observation of a cationic linear polyethylene.
Ru complex responsible for olen insertion polymerization.
The polymerization result is reproducible (entries 1 and 2 in
Table 1). Increasing ethylene pressure resulted in an increase in
molecular weight and a decrease in branching density (entry 3).
The polyethylene samples obtained are semicrystalline with
melting temperatures (Tm) around 130 ꢁC. Gel permeation
chromatography (GPC) revealed bimodal molecular weight
distribution with a high molecular weight fraction (Mn > 2 ꢃ
105 g molꢀ1) and a signicantly lower molecular weight fraction
(Mn ꢄ 600–850 g molꢀ1), suggesting the presence of two
different active species. As a negative control, a blank poly-
merization with only AlMe2Cl co-catalyst did not produce any
polyethylene (entry 4), indicating that the ruthenium complex is
critical for active polymerization.
To further probe the active species for the polymerization, we
synthesized dimethylated complex 4 via direct methylation of 3
with MeLi (Scheme 2). Complex 4 was fully characterized using
1H and 13C-NMR including COSY, HMQC and NOE experi-
ments, ESI-MS, and X-ray crystallography (Fig. 2 and ESI
Fig. S8–S13†). Similar to 3, complex 4 exists as a mixture of two
enantiomers in the unit cell (ESI Fig. S14†). The sulde arm
remains coordinated to ruthenium in solution as evidenced by
the diastereotopic arene and tethered arm protons in the
1H-NMR spectra (ESI Fig. S8†).
Results and discussion
For this purpose, complex 3 was synthesized by following
similar procedures reported in literature.11 First, methyl
3-phenylpropyl sulde was prepared using a literature proce-
dure,12a followed by Birch reduction12b to afford ligand 3a. For
complexation, RuCl3(hydrate) and 3a were heated to reux in
ethanol to form 3 as an orange powder (Scheme 1). Complex 3
was fully characterized using 1H and 13C-NMR including COSY
and NOE experiments, electrospray ionization mass spectrom-
etry (ESI-MS), elemental analysis, and X-ray crystallography (see
ESI, Fig. S1–S7†). An analogous dialkylruthenium(II) h6-arene
complex with a tethered phosphine ligand was reported previ-
ously, which was inactive for ethylene polymerization.13
A single crystal of complex 3 suitable for X-ray diffraction was
obtained by slow diffusion of hexanes into a solution of 3 in
dichloromethane (DCM) at 4 ꢁC. The X-ray structure of 3 in
ORTEP is shown in Fig. 1. Due to the chirality of the sulfur atom,
complex 3 exists as a mixture of two enantiomers in the unit
cell (ESI Fig. S7†). The sulde arm remains coordinated to
Complex 4 can be mono-demethylated by treating it with a
stoichiometric amount of a strong acid to generate the
proposed cationic active species. In our study, we used 1 eq. of
the Brookhart oxonium acid,2a [H(Et2O)2]+ [BAr04]ꢀ (where Ar0 ¼
3,5-(CF3)2C6H3), to protonate complex 4 and remove one methyl
group. Upon exposure to ethylene, the mono-demethylated
complex exhibited activity for polymerizing ethylene. Similar to
polymerization with the 3/AlMe2Cl system, higher ethylene
pressure resulted in higher activity and lower brancꢀhing
density. As a control, exposure of only ([H(Et2O)2]+ [BAr04] ) to
ethylene in the absence of complex 4 did not yield any polymer
(entry 8), proving again that the ruthenium complex is the active
species responsible for ethylene polymerization. The strꢀucture
of the polymer obtained with 4/([H(Et2O)2]+ [BAr04] ) was
Fig. 1 X-ray crystal structure of complex 3. ORTEP drawing, ellipsoids at 60%
probability radius, hydrogens omitted for clarity. Selected interatomic distances
ꢁ
˚
(A) and angles ( ): Cl(1)–Ru(1) ¼ 2.4032(1), Cl(2)–Ru(1) ¼ 2.4228(1), S(1)–Ru(1) ¼
2.3670(1), Cl(1)–Ru(1)–Cl(2) ¼ 86.88(0).
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Table 1 Ethylene polymerization resultsa
Entry
Cat.
Co-cat.
Timeb (h)
Pressurec (psi)
Mn
PDIe
Branchingg (Me/1000C)
TOFh (hꢀ1
)
d
f
Tm (ꢁC)
1i
2i
3i
4
3
3
3
—
4
4
4
—
AlMe2Cl
AlMe2Cl
AlMe2Cl
AlMe2Cl
HBArFl
HBArFl
HBArFl
HBArFl
4
4
12
4
12
12
12
12
400
400
800
400
400
800
800
800
198 000/638 j
2.03/1.27 j
3.01/1.06 j
3.03/1.15 j
n/a
1.19
1.23
129
130
131
n/a
61
75
69
n/a
18
20
8
n/a
36
27
26
n/a
22.3
25.3
46.1
0
1.5
3.0
2.8
0
214 000/646 j
262 000/848 j
n/a
610
656
657
n/a
5k
6k
7k
8
1.17
n/a
a
General conditions: all polymerizations run in a 600 mL Parr reactor with 100 mL of dichloromethane (DCM) as the solvent. Temperature was kept
45–50 ꢁC. b Hours. c Ethylene pressure. d Determined using GPC in 1,2,4-trichlorobenzene vs. polyethylene standards. e PDI ¼ Mw/Mn. f Determine
using DSC in ꢁC. g Determined using 1H-NMR and expressed as the number of Me's per 1000 carbons. h TOF calculated assuming all Ru is active.
i
6 mmol of complex 3 and 1000 equivalents of AlMe2Cl (1.0 M solution in hexanes) as co-catalyst. j Bimodal distribution. k 55 mmol of complex 4 and
([H(Et2O)2]+ [BAr04]ꢀ) (1 eq.) as co-catalyst. l HBArF ¼ ([H(Et2O)2]+ [BAr04]ꢀ) entries 4 and 8 are negative control polymerizations with only AlMe2Cl
and ([H(Et2O)2]+ [BAr04]ꢀ) respectively.
discrepancies between activity and molecular weight were also
observed in early transition metal polymerization catalysts
between well-dened cationic species and aluminium alkyl
activated systems. For example, in Jordan's seminal work on a
well-dened Cp2ZrMe(THF)+ system for ethylene polymeriza-
tion, the activity was ꢄ430 turnovers per hour and the Mn was
ꢄ7130 g molꢀ1
,
15 both of which are orders of magnitude lower
Scheme 2 Synthesis of complex 4.
than for Cp2ZrCl2/aluminum alkyl activated polymerization.16
Other studies have also shown that both polymerization activity
and polyolen molecular weight depend signicantly on the co-
catalyst used.17 One possibility for our 3/AlMe2Cl system is the
formation of a small amount of highly active Cl-bridged or
clustered species contributing to the formation of high molec-
ular weight polyethylene. Similar halogen-bridged species of
this type have been previously reported.18
To further investigate the active species contributing to
ethylene polymerization, we monitored the initial ethylene
binding and subsequent migratory insertion to the in situ
generated cationic Ru species using low temperature 1H-NMR .
For this purpose, dimethylated complex 4 was added to
Fig. 2 X-Ray crystal structure of 4. ORTEP drawing, ellipsoids at 60% probability
˚
radius, hydrogens omitted for clarity. Selected interatomic distances (A) and
ꢁ
angles (ꢁ): C(12)–Ru(1)
¼
2.204(1), S(1)–Ru(1)
¼
2.3187(4), C(11)–Ru(1)
¼
ethylene-saturated CD2Cl2 solution at ꢀ78 C. Addition of one
equivalent of [H(Et2O)2]+ [BAr04]ꢀ (Scheme 3) cleaves one methyl
group to generate the active cationic species, complex 5. Low
temperature 1H-NMR (from ꢀ90 to 25 ꢁC, ESI Fig. S15–S27†)
shows that complex 5 exists as two different diastereomers (5A
major and 5B minor, Scheme 3) due to the chirality of the sulfur
atom. Based on the NMR integrations, the two species are
present in a 4 : 1 ratio at ꢀ90 ꢁC. Density function theory (DFT)
calculations conrm that complex 5A is the major species
because it has less steric repulsion between the S–CH3 methyl
2.141(2).
identied as polyethylene through 1H-NMR analysꢀis. GPC traces
of polymers made with the 4/([H(Et2O)2]+ [BAr04] ) system are
monomodal with molecular weights and PDIs very similar to
the low molecular weight fraction of polyethylene obtained
with the 3/AlMe2Cl system (ESI, Fig. S40 and S41†), suggesting
that the low molecular weight polyethylene could be produced
by the same active species for both the 3/AlMe2Cl and 4/
([H(Et2O)2]+ [BAr04]ꢀ) systems. The relatively low molecular
weight of polyethylene could be due to the low activity and facile
chain transfer of catalysts 3 and 4 which lack steric bulkiness. In
the case of polymerizations with the 3/AlMe2Cl system, a much
high molecular weight polyethylene was also formed, presum-
ably by a different active species with an unknown structure.
The elucidation of the active species in such aluminium alkyl
activated systems remains an unsolved challenge in the coor-
dination polymerization eld. Similar to our observation, large Scheme 3 In situ activation and initial ethylene binding to the Ru complex 4.
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group and the ethylene bound to Ru. In the minor complex (5B),
ethylene coordinates on the same side as the methyl group,
resulting in higher steric repulsion. A number of NMR tech-
niques, including COSY, HMQC, and NOE experiments, were
employed to investigate the active species (ESI Fig. S15–S27†).
The ethylene coordinated to the cationic Ru species in complex
ꢁ
5 was observed at ꢀ90 C with no free rotation, affording four
proton signals from 4.0 ppm to 1.5 ppm. At ꢀ10 ꢁC, the two
diastereomers re-equilibrated to a ratio of 5A : 5B ꢄ 2 : 1. Upon
further warming, the ethylene proton signals coalesced to give
two doublets centered at 2.9 ppm. At 25 ꢁC, the two sets of peaks
from the two diastereomers coalesced into one set of broad
peaks due to dynamic exchange, precluding detailed structural
analysis. At 45 ꢁC, the Ru–Me peaks started to disappear and the
1H-NMR spectrum became more complex (see ESI, Fig. S28†).
The initial migratory insertion barrier was determined by
monitoring Ru–Me peak disappearance.2c The rst insertion
was observed at 288 K at a very slow rate (ESI Fig. S33†). As
mentioned above, complex 5 exists in two diastereomers, 5a and
5b. The Ru–Me peak for the major isomer, 5a, signicantly
overlaps with those of the growing oligomers, precluding
quantitative integration of the signal (ESI Fig. S34†). Therefore,
the Ru–Me peak of the minor isomer, 5b, was chosen for kinetic
analysis. We determined the initial migratory insertion barrier
by monitoring Ru–Me rst-order disappearance for 5b at 301 K
for a period of 6 h. The initial migratory insertion barrier was
calculated to be 22.8 ꢂ 0.1 kcal molꢀ1 at 301 K (ESI Fig. S35†),
which is signicantly lower than the calculated barriers for
complexes 1 and 2.9 Free ethylene consumption was also
monitored, which correlates well with Ru–Me disappearance
(ESI Fig. S36 and S37†). Monitoring the growth of oligomers was
complicated by rapid b-hydrogen elimination and chain trans-
fer as well as by peak overlaps.
The same solution used for these aforementioned NMR
studies was heated to 45 ꢁC (318.15 K) for 15 minutes and then
subjected to electrospray mass spectrometry (ESI-MS) analysis
of species existing in the solution (Fig. 3). The ESI-MS spec-
trum unambiguously conrmed that migratory insertion
indeed occurred on cationic ruthenium species 5. Two series
of growing oligomers were observed in the spectrum with
increasing numbers of ethylene insertion. In one series of
peaks, the number of carbons in the alkyl chain is odd (n ¼ 1,
3, 5, 7, Fig. 3, blue dots), which resulted from primary ethylene
insertion to complex 5. In another series of peaks, the number
of carbons in the alkyl chain is even (n ¼ 0, 2, 4, 6, Fig. 3, red
dots), which presumably formed by ethylene insertion aer
chain transfer to the Ru center occurred (see ESI Fig. S29–S31
for detailed analysis†). The isotopic pattern for each peak
agrees well with the molecular formula for each oligomeric
species. Interestingly, an almost identical ESI-MS spectrum
was obtained when the 3/AlMe2Cl system was exposed to
ethylene (1 atm at 45 ꢁC for ve minutes, in ESI Fig. S32†),
conrming that at least one of the active species (low molec-
ular weight fraction) in the 3/AlMe2Cl system is the same as in
the 4/[H(Et2O)2]+ system. Both our NMR and ESI-MS data
conrm that the ruthenium is the active centre where the
polymer chain grows.
Fig. 3 ESI-MS spectrum of the in situ polymerization sample. Several growing
oligomeric species were identified due to successive ethylene insertion to the
cationic Ru center. Blue circles indicate oligomers resulting from primary ethylene
insertion to complex 5. Red circles indicate oligomers formed from ethylene
insertion to Ru(H)+ species generated from chain transfer. Detailed analysis and
comparison with simulated isotopic patterns are available in the ESI.†
Conclusions
In conclusion, we have designed and synthesized a novel
ruthenium h6-arene complex with a tethered sulfur ligand that
is capable of catalyzing ethylene insertion polymerization. The
structures of the Ru complexes were fully characterized using
NMR, ESI-MS, elemental analysis, and X-ray crystallography.
Complexes 3 and 4 adopt a “piano stool” type of coordination
geometry, which upon activation generates two equivalent
coordination sites for active migratory insertion. The active
catalytic species was investigated using low temperature 1H-
NMR and mass spectrometry. Our results have unambiguously
established that the cationic ruthenium is the active species for
ethylene insertion polymerization. The initial migratory inser-
tion barrier was determined to be ꢄ22.8 ꢂ 0.1 kcal molꢀ1 at 301
K, a barrier signicantly higher than that of the nickel- and
palladium-a-diimine system2,4c but lower than the calculated
barriers for previous ruthenium complexes 1 and 2.9 To the best
of our knowledge, this is rst direct observation of a cationic Ru
complex responsible for olen insertion polymerization. A
number of other Ru complexes are currently under investiga-
tion in our laboratory for both ethylene homopolymerization
and copolymerization with polar olens.
Acknowledgements
This work was supported by the US National Science Founda-
tion (CHE-1012422).
Notes and references
1 (a) Topics in Organometallic Chemistry, ed. Z. Guan, Springer,
Berlin/Heidelberg, 2009, vol. 26; (b) Organometallic Catalysts
and Olen Polymerization: Catalysts for a New Millennium, ed.
R. Blom, A. Follestad, E. Rytter, M. Tilset and M. Ystenes,
Springer, Berlin, 2009.
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2 (a) L. K. Johnson, C. M. Killian and M. Brookhart, J. Am.
Chem. Soc., 1995, 117, 6414; (b) L. K. Johnson, S. Mecking
and M. Brookhart, J. Am. Chem. Soc., 1996, 118, 267; (c)
S. A. Svejda, L. K. Johnson and M. Brookhart, J. Am. Chem.
Soc., 1999, 121, 10634–10635.
7 (a) B. R. James and L. D. Markham, J. Catal., 1972, 27, 442–
451; (b) S. Komiya, A. Yamamoto and S. Ikeda, Bull. Chem.
Soc. Jpn., 1975, 48, 101–107; (c) K. Nomura, S. Warit and
Y. Imanishi, Macromolecules, 1999, 32, 4732–4734; (d)
K. Nomura, W. Sidokmai and Y. Imanishi, Bull. Chem. Soc.
Jpn., 2000, 73, 599–605; (e) E. L. Dias, M. Brookhart and
P. S. White, Organometallics, 2000, 19, 4995–5004.
3 E. Drent, R. van Dijk, R. van Ginkel, B. van Oort and
R. I. Pugh, Chem. Commun., 2002, 744–745.
4 (a) A. Nakamura, S. Ito and K. Nozaki, Chem. Rev., 2009, 109,
5215–5244; (b) L. S. Boffa and B. M. Novak, Chem. Rev., 2000,
100, 1479–1493; (c) S. D. Ittel, L. K. Johnson and
M. Brookhart, Chem. Rev., 2000, 100, 1169–1203.
8 (a) B. L. Small, M. Brookhart and A. M. A. Bennett, J. Am.
Chem. Soc., 1998, 120, 4049–4050; (b) G. J. P. Britovsek,
M. Bruce, V. C. Gibson, B. S. Kimberley, P. J. Maddox,
S. Mastroianni, S. J. McTavish, C. Redshaw, G. A. Solan,
¨
5 (a) J. M. Rose, A. E. Cherian and G. W. Coates, J. Am. Chem.
Soc., 2006, 128, 4186–4187; (b) A. Berkefeld, M. Drexler,
S. Stromberg, A. J. P. White and D. J. Williams, J. Am.
Chem. Soc., 1999, 121, 8728–8740.
¨
H. M. Moller and S. Mecking, J. Am. Chem. Soc., 2009,
9 W. Heyndrickx, G. Occhipinti, Y. Minenkov and V. R. Jensen,
J. Mol. Catal. A: Chem., 2010, 324, 64–74.
131, 12613–12622; (c) D. Guironnet, L. Caporaso,
¨
B. Neuwald, I. Gottker-Schnetmann, L. Cavallo and 10 L. Piche, J. C. Daigle and J. P. Claverie, Chem. Commun.,
S. Mecking, J. Am. Chem. Soc., 2010, 132, 4418–4426; (d) 2011, 47, 7836–7838.
A. Berkefeld and S. Mecking, Angew. Chem., Int. Ed., 2008, 11 B. Therrien, Coord. Chem. Rev., 2009, 253, 493–519.
47, 2538–2542; (e) B. P. Carrow and K. Nozaki, J. Am. 12 (a) N. E. Shevchenko, V. G. Nenajdenko and E. S. Balenkova,
Chem. Soc., 2012, 134, 8802–8805; (f) S. Ito, M. Kanazawa,
K. Munakata, J. I. Kuroda, Y. Okumura and K. Nozaki,
Synthesis, 2003, 1191–1200; (b) A. J. Birch, J. Chem. Soc., 1944,
430–436.
J. Am. Chem. Soc., 2011, 133, 1232–1235; (g) T. Kochi, 13 (a) K. Umezawa-Vizzini, Y. Ilse, I. Y. Guzman-Jimenez,
S. Noda, K. Yoshimura and K. Nozaki, J. Am. Chem. Soc.,
2007, 129, 8948–8949; (h) S. Luo, J. Vela, G. R. Lief and
R. F. Jordan, J. Am. Chem. Soc., 2007, 129, 8946–8947; (i)
K. H. Whitmire and T. R. Lee, Organometallics, 2003, 22,
3059–3065; (b) A. Abele, R. Wursche, M. Klinga and
B. Rieger, J. Mol. Catal. A: Chem., 2000, 160, 23–33.
W. Weng, Z. Shen and R. F. Jordan, J. Am. Chem. Soc., 14 O. Daugulis, M. Brookhart and P. S. White, Organometallics,
2007, 129, 15450–15451; (j) F. Wu, S. R. Foley, C. T. Burns 2003, 22, 4699–4704.
and R. F. Jordan, J. Am. Chem. Soc., 2005, 127, 1841–1853; 15 R. F. Jordan, C. S. Bajgur, R. Willet and B. Scott, J. Am. Chem.
(k) T. M. J. Anselment, C. Wichmann, C. E. Anderson, Soc., 1986, 108, 7410–7411.
E. Herdtweck and B. Rieger, Organometallics, 2011, 30, 16 Polymeric Materials Encyclopedia, ed. J. C. Salamone, Taylor &
6602–6611; (l) D. H. Camacho, E. V. Salo, J. W. Ziller and Francis, 1996, vol. 6, p. 4172.
Z. Guan, Angew. Chem., Int. Ed., 2004, 43, 1821–1825; (m) 17 E. Y.-X. Chen and T. J. Marks, Chem. Rev., 2000, 100, 1391–
D. H. Leung, J. W. Ziller and Z. Guan, J. Am. Chem. Soc.,
2008, 130, 7538–7539.
1434.
18 (a) J. M. Corker and J. Evans, J. Chem. Soc., Chem. Commun.,
1991, 1104–1106; (b) R. Fernando de Souza, L. C. Simon and
M. d. C. M. Alves, J. Catal., 2003, 214, 165–168; (c)
K. P. Bryliakov, E. P. Talsi, N. V. Semikolenova and
V. A. Zakharov, Organometallics, 2009, 28, 3225–3232; (d)
W. J. Evans, T. M. Champagne, D. G. Giarikos and
J. W. Ziller, Organometallics, 2005, 24, 570–579.
6 (a) R. Noyori and H. Takaya, Acc. Chem. Res., 1990, 23, 345–
350; (b) R. H. Grubbs, S. J. Miller and G. C. Fu, Acc. Chem.
Res., 1995, 28, 446–452; (c) T. M. Trnka and R. H. Grubbs,
Acc. Chem. Res., 2001, 34, 18–29; (d) J. Ueda,
M. Matsuyama, M. Kamigaito and M. Sawamoto,
Macromolecules, 1998, 31, 557–562.
2906 | Chem. Sci., 2013, 4, 2902–2906
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