Acyclic amines as ancillary ligands in Ru-based catalysts for ring-opening metathesis polymerization. Probing the electronic and steric aspects of cyclic and acyclic amines

Article abstract of DOI:10.1016/j.molcata.2006.06.041

The present paper reports the ROMP of norbornene with [RuCl₂(PPh₃)₂(L)_x], where L represents the acyclic amines diethanolamine, triethanolamine, triethylamine, phenylamine, diphenylamine or sec-butylamine. Previous representative results with cyclic amines are also cited to observe of the behavior of cyclic and acyclic amines as ancillary ligands. Three productive types of ligands were observed as a function of their electronic nature and steric hindrance: ligands with high cone angle and strong σ-donor character (NH₂^sBu, NEt₃ and piperidine), ligands with high cone angle and low σ-donor character (NH₂Ph and NHPh₂) and ligand with low cone angle and π-acceptor character (4-H₂NC(O)-pyridine). Ligands with low cone angle and strong σ-donor character can restrict the catalytic activity of the metal complex (imidazole, pyridine, 4-H₃C-pyridine and 4-H₂N-pyridine). Thus, latent complexes can be designed using different amines as ancillary ligands.

Full text of DOI:10.1016/j.molcata.2006.06.041

Journal of Molecular Catalysis A: Chemical 259 (2006) 286–291
Acyclic amines as ancillary ligands in Ru-based catalysts for
ring-opening metathesis polymerization
Probing the electronic and steric aspects of cyclic and acyclic amines
∗
´
Jose Milton E. Matos, Benedito S. Lima-Neto
Instituto de Qu´ımica de Sa˜o Carlos, Universidade de Sa˜o Paulo, CP 780, CEP 13560-970, Sa˜o Carlos, SP, Brazil
Received 7 February 2006; received in revised form 15 June 2006; accepted 23 June 2006
Available online 4 August 2006
Abstract
The present paper reports the ROMP of norbornene with [RuCl2(PPh3)2(L)x], where L represents the acyclic amines diethanolamine, tri-
ethanolamine, triethylamine, phenylamine, diphenylamine or sec-butylamine. Previous representative results with cyclic amines are also cited to
observe of the behavior of cyclic and acyclic amines as ancillary ligands. Three productive types of ligands were observed as a function of their
s
electronic nature and steric hindrance: ligands with high cone angle and strong ␴-donor character (NH2 Bu, NEt3 and piperidine), ligands with high
cone angle and low ␴-donor character (NH2Ph and NHPh2) and ligand with low cone angle and ␲-acceptor character (4-H2NC(O)-pyridine). Lig-
ands with low cone angle and strong ␴-donor character can restrict the catalytic activity of the metal complex (imidazole, pyridine, 4-H3C-pyridine
and 4-H2N-pyridine). Thus, latent complexes can be designed using different amines as ancillary ligands.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Olefin metathesis; ROMP; Norbornene; Ancillary ligands; Amines; Ruthenium; Ligand electronic nature
1. Introduction
Grubbs type complexes are, of course, one of the catalyst models
[1–4,7–16].
Ruthenium-based catalysts have been one of the most excit-
ing developments in the area of olefin metathesis [1–4]. The
greatest example is the second-generation Grubbs type catalysts
[RuCl2(NHC)(L)( CHR)], where NHC is an N-heterocyclic
carbeneandtypicallyL = PCy3 andR = Ph[1–4]. Thesecatalysts
can afford the syntheses of complex organic molecules via cross
and ring-closing metathesis and make it possible to obtain poly-
mers with low polydispersity indexes (Mw/Mn) via ring-opening
metathesis polymerization (ROMP), controlling the initiation
and propagation rates. Furthermore, the Ru-carbene complexes
are usually functional-group-tolerant catalysts and active in dif-
ferent media.
Although it is reasonable to assume that Grubbs type com-
plexes are powerful catalysts for olefin metathesis, new catalysts
must be formulated when the design of new materials through
catalysis is a continuous challenge [5,6]. In the interim, olefin
metathesis is a reaction that can provide different materials and
It is well known that an effective and versatile tool in the
design of novel catalysts is the properties of the ancillary lig-
ands that support the active metal centers [17–21]. Tuning the
electronic and steric effects it is possible to drive the catalyst
to achieve optimum activity and selectivity [6]. Many catalytic
processes have been improved using transition metal complexes
with different ligands [6,22], like in the case of the second-
generation Grubbs type catalysts [1–4].
In tailoring transition metal complexes for catalysis, phos-
phines and phosphites were successfully introduced as ancillary
ligands [23–25]. However, many trivalent phosphorus ligands
may degrade under certain reaction conditions, as they are air-
and moisture-sensitive, hazardous to manipulate and usually
expensive. Therefore an option not very well explored in the
development of homogeneous catalysts is to arrange phosphines
and amines in the same metal center. Our particular interest and
approach is in dealing with both ␴-donor and steric hindrance
aspects using ligands that are easy to manipulate and econom-
ically viable. Many amines can substitute phosphines in these
aspects [26]. Amine-complexes are usually explored in catalysis
as bidentate amines or hemilabile P–N ligands [6,27–33].
∗
Corresponding author. Tel.: +55 16 3373 9953; fax: +55 16 3373 9976.
E-mail address: benedito@iqsc.usp.br (B.S. Lima-Neto).
1381-1169/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2006.06.041

J.M.E. Matos, B.S. Lima-Neto / Journal of Molecular Catalysis A: Chemical 259 (2006) 286–291
287
Having in mind that a variety of phosphines and amine has
individually promoted Ru(II) chemistry to applications in photo-
chemistry, bioinorganic and catalytic processes, previous studies
in our group have focused on the chemistry of complexes of
type [RuCl2(PPh3)2(amine)x] prepared from [RuCl2(PPh3)3]
[34,35]. It was observed that piperidine and some 4-X-pyridines
are effective as ancillary ligands for ROMP of norbornene and
2,5-norbornadiene. For example, quantitative polynorbornenes
were obtained with piperidine (x = 1) and isonicotinamide (4-
H2NC(O)-pyridine; x = 2) derivative complexes for less than
1 min at room temperature and for 5 min at 50 ◦C, respectively.
It is notorious to observe that these amines show different
electronic and steric characteristics. Isonicotinamide does not
behave as a typical ␴-donor ligand (pKa 3.61) as piperidine
does (pKa 11.2). Furthermore, piperidine is larger than ison-
icotinamide, where the cone angles (θ) are 121◦ and 100◦,
respectively [36,37]. In both cases there are evidences that the
propagating metal species is coordinated to one PPh3 molecule
and to one amine [34,35]. Thus, the effects from each amine
combined with the effects from the acid and sized PPh3 molecule
generated complexes that present very good activities with dif-
ferent induction periods. It is very important to observe the
induction period since it involves the in situ formation of the
catalyst itself and the initiation of the polymerization process
[7]. Consequently, polymers with different characteristics can
be obtained choosing certain complexes. In part, these different
behaviors come from the fact that the illustrated complexes have
different coordination numbers (x = 1 or 2), but this cannot be
generalized.
using a Bruker ESP 300C apparatus (X-band) equipped with
1
a TE102 cavity and HP 52152A frequency counter. H and
1
31P{ H} NMR spectra were obtained in CDCl3 solution at
25.0 0.1 ◦C using a Bruker AC-200 spectrometer equipped
with a probe operating at 200.13 and 81.015 MHz, respec-
tively. The chemical shifts obtained are reported in ppm rela-
tive to the high frequency of tetramethylsilane or 85% H3PO4.
Molecular weights (Mw, Mn) and molecular weight distribu-
tion (Mw/Mn) were obtained by gel permeation chromatography
analyses obtained using a Shimadzu 77251 spectrometer sys-
tem equipped with a PL gel column (5 ␮m MIXED-C: 30 cm,
Ø = 7.5 mm). The retention time was calibrated with respect to
standard monodispersed polystyrene using HPLC-grade CHCl3
as eluent.
2.3. Synthesis and characterization of the complexes
The complexes of type [RuCl2(PPh3)2(L)2], where
s
L = NH(EtOH)2, N(EtOH)3, NH2Ph or (NH2 Bu), were
prepared adding 1.23 mmol of the amines to the solutions of
[RuCl2(PPh3)3] (0.47 mmol; 450 mg) in acetone (50 mL). The
mixtures were stirred at room temperature for 2 h under argon
atmosphere. The complexes precipitated when the volumes
of the solutions were reduced (∼5 mL) under vacuum. The
solids were then filtered, washed with ethyl ether and dried in
a vacuum. The absence of signals in the EPR spectra of the
complexes suggests that the oxidation state of the ruthenium
is +2 in each case. The six-coordinated nature of the isolated
complexes is supported by the satisfactory analytical results.
Anal. Calc. for [RuCl2(PPh3)2(NH(EtOH)2)2] (wine; 63%
yield): C, 58.8; H, 5.8; N, 3.1; Found: C, 57.1; H, 5.6; N,
2.9. Anal. Calc. for [RuCl2(PPh3)2(N(EtOH)3)2] (wine; 65%
yield): C, 57.9; H, 6.1; N, 2.8; Found: C, 58.1; H, 5.9; N,
2.9. Anal. Calc. for [RuCl2(PPh3)2(NH2Ph)2] (brown; 63%
yield): C, 65.2; H, 5.0; N, 3.2; Found: C, 65.1; H, 5.3; N,
The present paper reports the ROMP of norbornene
with [RuCl2(PPh3)2(L)x] where L is an acyclic amine:
diethanolamine (NH(EtOH)2), triethanolamine (N(EtOH)3),
triethylamine (NEt3), phenylamine (NH2Ph), diphenylamine
s
(NHPh2) and sec-butylamine (NH2 Bu). The aim is to collect
more information about amines as ancillary ligands, as well as
about amine–phosphine systems, to discuss the representative
data from the studies with cyclic amines [34,35].
s
3.3. Anal. Calc. for [RuCl2(PPh3)2(NH2 Bu)2] (yellow pallid;
48% yield): C, 62.4; H, 6.2; N, 3.3; Found: C, 62.4; H, 6.5;
N, 3.0.
2. Experimental
Attempts to precipitate the complexes with either NHPh2 or
NEt3 from the respective mother liquor have failed so far. Other-
wise, these complexes are formed adding the amine (4.6 ␮mol)
to a solution of [RuCl2(PPh3)3] (2 ␮mol) in CHCl3 (2 mL).
2.1. General remarks
1
All manipulations were performed under argon atmosphere.
All the solvents used were analytical grade and were dis-
tilled from the appropriate drying agents immediately prior
to use. Other commercially available reagents were purified
by standard procedures or used without further purification.
RuCl3·xH2O from Stream, norbornene (NBE) from Across,
Following the reaction with NEt3 by H NMR in CDCl3, the
5–8 ppm downshifts in the amine aliphatic signals indicate that
NEt3 coordinates to ruthenium for 8 h. In the case of NHPh2,
after 10 min the spectrum in the aromatic region shows the pro-
ton signals of both PPh3 and NHPh2 molecules bonded to Ru
and those from the free phosphine, which was replaced by the
amine; the N–H proton is observed at 5.85 ppm. In both cases,
the 31P NMR spectra confirmed the presence of free phosphine
(−4.7 ppm) and the absence of signals from the dimeric specie
[Ru(␮-Cl)Cl(PPh3)2]2 typicalofthestartingcomplexinsolution
[38–40]. It indicates that one molecule of PPh3 is dissociated in
the presence of amine and the coordination of the amine pre-
vents the formation of binuclear complexes [38–40]. Thus, the
NMR data suggest that the complexes with NHPh2 and NEt3 are
formed in solution and exist as monomeric species.
s
NH(EtOH)2, N(EtOH)3, NH2Ph, NHPh2, NEt3 and NH2 Bu,
2,5-norbornadiene (NBdiene), ethyldiazoacetate (EDA) and
PPh3 from Aldrich were used as achieved. Room temperature
(RT) was 24 1 ◦C.
2.2. Instrumentation
Elemental analyses were performed using an EA 1110
CHNS-O Carlo Erba Instrument. EPR was carried out at RT

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J.M.E. Matos, B.S. Lima-Neto / Journal of Molecular Catalysis A: Chemical 259 (2006) 286–291
2.4. Polymerization reactions
Table 1 (entries 3, 4, 6, 8, 10, 13, 14, 15, 18). The table also
includes some previous results obtained with the complex with-
out amine (1) and derivative complexes with the unsaturated
cyclic amines (entries 2, 5, 7, 9, 11, 12, 16, 17) or piperidine
(19,20) [34,35,41], to discuss the representative data.
In a typical experiment using the isolated Ru(II) complexes
with the amines NH(EtOH)2, N(EtOH)3, NH2Ph or (NH2 Bu),
s
1.0 ␮mol of complex is dissolved in 2 mL of CHCl3 and 470 mg
of monomer is added so that the molar ratio [monomer]/[Ru] is
5000:1, after which 5 ␮L of ethyldiazoacetate (EDA) are added.
The solution is maintained at room temperature or at 50 1 ◦C
in silicone oil bath under magnetic stirring for the desired time.
At room temperature, 5 mL of methanol are added and the pre-
cipitated polymer is filtered, washed with methanol and dried in
a vacuum before being weighed.
Polymerization runs using the in situ generated complexes
with the amines NHPh2 or NEt3 were performed using a solu-
tion of [RuCl2(PPh3)3] (1 ␮mol) in CHCl3 (2 mL) previously
stirred in presence of the amine (2.3 ␮mol) for 2 h at room tem-
perature, then following the addition of monomer (470 mg) and
EDA (5 ␮L) to the resulting solution. The polymerization pro-
cedure is the same as described above.
Observing the results obtained with the ex situ generated
complexes, the cases with NH(EtOH)2 and N(EtOH)3 showed
the lowest catalytic activity among the acyclic amines (3, 4).
The yield was roughly 20% better in relation to the precursor
(L = PPh3; 1) when the amine was NH2Ph (10). An unusual
s
catalytic activity was observed using the NH2 Bu derivative
complex when 85% of polynorbornene had been obtained at
RT for 5 min (13). This value was roughly the same at 50 ◦C
for 5 min (92%; 15), considering 5–10% of experimental error
and the fact that at elevated temperature the attached polymer
catalyst becomes less crowed by the polymer chain allowing a
better consumption of monomer.
The solution of [RuCl2(PPh3)3] with amines NHPh2 and
NEt3 showed reactivity at RT for 5 min with yields of 65% (6)
and 67% (8), respectively. Runs at 50 ◦C for 5 min yielded 90%
(14) and 98% (18) of polymers. These results support the for-
mation of amine complexes since they are very different from
that complex in the absence of amine, where the precursor com-
plex is not active at RT for 5 min and yields ∼1/3 less polymers
at 50 ◦C for 5 min (1). Furthermore, it is also considered that
3. Results and discussion
All the studied complexes were effective to ROMP of nor-
bornene at most for 5 min at 50 ◦C. The data of the isolated
polynorbornenes obtained from the reactions are summarized in
Table 1
Data for the ROMP of norbornene with [RuCl2(PPh3)2(L)x] in increasing order of the yield values
Entry
Ancillary ligand
L
Temperature (◦C)
Time (min)
Yield (%)
Mn (104)
Mw/Mn
a
pKa
θb (◦)
145
82.9
125f
x
c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
PPh3
2.73
6.95
8.96
7.76
9.17
0.78
5.23
1
2
2
2
2
NI
2
NI
2
2
2
2
2
NI
2
2
2
NI
1
1
50
50
50
50
50
RT
50
RT
50
50
50
50
RT
50
50
50
50
50
RT
RT
5
5e
5
5
5e
5
5
5
5
5
120
120
5
5
5
5
120
5
<1
<1
63
19
30
36
63
65
67
67
70
78
82
83
85
90
92
94
94
98
99
99
190
3.0
89
23
19
54
4.2
64
4.3
9.4
74
80
73
62
62
17
83
69
120
220
1.40
6.30
1.57
2.43
1.80
2.10
1.32
2.00
1.46
1.62
1.75
1.72
1.46
1.90
1.37
1.45
1.20
1.70
1.90
1.14
Imidazoled
NH(EtOH)2
N(EtOH)3
4-H2N-pyh
NHPh2
150g
91.9
136
91.9
150
91.9
111
91.9
91.9
113
136
113
91.9
91.9
150
121
121
Pyh,i
NEt3
10.8
4-H3C-pyh,i
NH2Ph
5.98
4.60
5.23
5.98
10.6
0.78
10.6
3.61
3.61
10.8
Pyh,i
4-H3C-pyh,i
NH2sBu
NHPh2
NH2sBu
4-H2NC(O)-pyh
4-H2NC(O)-pyh
NEt3
Piperidinec
Piperidinec,j
11.2
11.2
[Ru] = 1 ␮mol, [monomer]/[Ru] = 5000, 5 ␮L EDA in CHCl3. Py, pyridine; RT, room temperature; NI, complex was not isolated.
a
Ref. [47].
Ref. [36,37].
Ref. [34].
Ref. [41].
b
c
d
e
Similar result for 120 min.
f
θ ≈ NEt3.
g
θ ≈ NHEt2.
h
Ref. [35].
i
[NBE]/[Ru] = 3000.
[NBE]/[Ru] = 2000.
j

J.M.E. Matos, B.S. Lima-Neto / Journal of Molecular Catalysis A: Chemical 259 (2006) 286–291
289
catalysis occurs with the amine–phosphine complexes since all
the reactions were performed after the necessary times for the
formation of the complexes, as accompanied by 1H NMR (see
Section 2). The in situ formation of highly active mononuclear
ruthenium complexes was also observed with [RuCl2(PPh3)3]
or [RuCl2(PPh3)2(triazol-5-ylidene)] in the presence of amine
ligands when catalysis experiments were conducted for living
radical polymerization of methyl methacrylate [42,43].
differ from that result with 4-H2NC(O)-py (17) that produces
polymer with low Mw/Mn for 120 min. Besides, the case with
imidazole shows monomodal weight distribution with a high
Mw/Mn value. Thus, it can be concluded that the large disper-
sion in the molecular weight is due to the electronic effects that
generate complexes affording different initiation and propaga-
tion ROMP processes, since these type of ligands show similar
and small cone angles.
The catalytic activities at RT characterize fast initiation reac-
tions in the cases with NEt3 (8), NHPh2 (6) and NH2 Bu
The simple fact that the results are different from each other
and from that obtained with L = PPh3 suggests that the interme-
diate complexes are bonded to the respective amines and shows
that these amines are capable of acting as ancillary ligands. The
presence of the amines avoids forming binuclear complexes in
solution, which is the behavior of the parent [RuCl2(PPh3)3]
complex, as previously discussed in the case with piperidine
[34]. Therefore, the high activity of the catalysts is attributed to
the retention of the mononuclear character.
s
(13), increasing the number of Ru species able to promote the
propagation reaction, which could afford narrow polydispersity
indexes. However, although the Mn values are in the same order
of magnitude, the Mw/Mn values are relatively high, suggest-
ing that a chain transfer occurred during the polymerization
[44].
In general, the complexes with acyclic amines show bet-
ter yields than those with cyclic amines, except in the case
of 4-H2NC(O)-py, which showed quantitative reaction at 50 ◦C
for 5 min (16). Piperidine can be observed as a type of hybrid
between acyclic and saturated cyclic ligands, which resembles
NHEt2 (pKa 10.9; θ = 125◦), providing very good results when
the run is carried out at RT (19, 20).
Acyclic amines with very low ␴-donor and large θ (such as
NHPh2) can afford good metal complex reactivity, as well as
s
good ␴-donor with large θ amines (such as piperidine, NH2 Bu
and NEt3). These ligands provide high reactivity at RT, there-
fore one can conclude that the steric hindrance is really a very
important factor independently of the ␴-donor character of the
ligand.
Observing all the cases, the high cone angle values seem to
be the main beneficial effect since the largest amines afforded
complexes to react under the lowest temperature for less reaction
time.
Good catalytic behaviors could be expected from the com-
plexes with NH(EtOH)2 and N(EtOH)3 (3, 4), since they are
␴-donors and the cone angles are probable ∼125◦ and ∼150◦,
which are the values of the ligands NHEt2 and NEt3 [36], respec-
tively. However, these results can be attributed to the presence
of the OH group in the ligands. Such group which can coor-
dinate to the metal center competing with either the formation
of the carbene active species or the incoming olefin substrate
for the vacant coordination site; this will be like a hemilabile
ligand. A poisoning of the active species by the OH group
was observed when complexes [RuCl2(PPh3)2(piperidine)] and
[RuCl2(PPh3)2(imidazole)2] were in the presence of 2-propanol
used as additive [41]. A similar case could explain the behavior
of the [RuHCl(CO)(PiPr3)2] complex, which is ∼4 times more
active in the ROMP of norbornene in presence of toluene instead
of 2-propanol [45].
The cyclic amines present small cone angles (<100◦) and
seem to act as a function of the electronic balance in the
Ru center. The strongest ␴-donor amines poison the catalyst
as they strongly bind the metal center throughout a phos-
phine ← Ru ← amine synergism effect, providing inert starting
complexes. This is the case with imidazole (2) and 4-H2N-py
(5), which showed similar results for 120 min. A moderate ␴-
donor with a possibility to make some degree of amine ← Ru(II)
␲-back-bonding, such as pyridine (7) and 4-H3C-py (9), can
afford more polymer as a function of time when the yields
increased for 120 min, where there exists a ␲-electron compe-
tition between PPh3 and amine molecules. Thus, the different
results among these cyclic amines can be attributed to the dis-
sociation of the ligands, which are difficult to occur in the
cases with imidazole (2) and 4-H2N-py (5). It can be ratio-
nalized that ␲-acceptors improve the yields since ␲-electron
competition will tune the dissociation of ligands to generate
complexes with lower coordination numbers. This is the case
with the weak ␴-donor and moderate ␲-acceptor 4-H2NC(O)-py
(16), which produces quite quantitative polynorbornene under
typical conditions. Thus, decreasing the ␴-donor character and
increasing the ␲-acceptor ability of the ligands, the complexes
become more effective and the following order can be written
characterizing different latent complexes: imidazole < 4-H2N-
py ꢀ pyridine ∼ 4-H3C-py ꢀ 4-H2NC(O)-py. This order is also
an ancillary ligand order considering that the yields, molecular
weights and polydispersity indexes are, in general, different;
that is, the results suggest that the propagating species are elec-
tronically different. For example, the cases with pyridine and
4-H3C-py show similar results for 120 min (11, 12), but they
Similarly what occurs with the complex with piperidine [34],
s
the activity of the complex with NH2 Bu was sensitive to the
amount of the monomer in the medium (Fig. 1). When a fresh
feed of monomer was added to the reaction mixture up to a
point where nearly all monomer of the previous batch had
been consumed (5 min), the values of the Mn increased up to
5000. After 25 min (five batches), the isolated polymer presented
monomodal weight distribution with low polydispersity index
(Mw/Mn = 1.47), therefore it is possible to say that this complex
shows living nature in the catalytic process.
s
The complex with NH2 Bu showed activity for ROMP
of 2,5-norbornadiene with yield of 80% at 50 ◦C for 5 min
(Table 2). This result is much better than those obtained with
[RuCl2(PPh3)3] and complex with piperidine, where both are
five-coordinated. Unfortunately, the obtained polynorbornadi-
ene was insoluble in CHCl3 and was not characterized at this
time.

290
J.M.E. Matos, B.S. Lima-Neto / Journal of Molecular Catalysis A: Chemical 259 (2006) 286–291
Therefore, this can be used to control the lability of complexes.
Five-coordinated complexes can obviously provide faster reac-
tions as in the case with piperidine.
It can be concluded that amines as ancillary ligands can
be a valuable contribution to fundamental and practical cata-
lyst research and can constitute a promising approach towards
achieving certain goals in molecular catalytic chemistry. They
can be used to design latent catalysts that can be switchable on
by a certain event. Thus, a very interesting perspective could
be predicted using cyclic and acyclic amines substituted with
carbene function, instead of substituted pyridine, as used by dif-
ferent authors [46].
Research with this type of catalytic system can combine the
advantage of a satisfactory steric control of the coordination
mode of the substrate with a good electronic catalytical activity.
Tests with ␴-donor phosphines replacing PPh3 in [RuCl2
(PPh3)2(amine)2] are currently ongoing in our laboratory and
will be soon reported.
Fig. 1. Values of Mn and Mw/Mn recorded by GPC during the ROMP of
norbornene as a function of [NBE]/[Ru] molar ratio using [RuCl2(PPh3)2
(NH2sBu)2] in CHCl3 at RT; [Ru] = 1 ␮mol, 5 ␮L of EDA.
Table 2
Data for the ROMP of 2,5-norbornadiene with [RuCl2(PPh3)2(L)x]
Acknowledgements
L
x
Temperature Time
Yield
(%)
Mn
(104)
Mw/Mn
(◦C)
(min)
The authors are indebted to the Brazilian financial sup-
port from FAPESP (Proc. 00/11443-0), CNPq and CAPES for
research grants and fellowships, Professor Douglas Wagner
Franco (IQSC/USP) for the permission to use his GPC equip-
ment and Angela Cristina Pregnolato Giannpedro for reading
this manuscript.
a
PPh3
1
1
2
50
RT
50
5
5
5
6
48
80
0.34
3.53
Piperidinea
NH2sBu
0.53
3.40
b
b
[Ru] = 1 ␮mol, [monomer]/[Ru] = 5000, 5 ␮L EDA in CHCl3.
a
Ref. [34].
Polymer was insoluble.
b
References
1H NMR made it possible to observe the formation of a
copolymer with norbornene and 2,5-norbornadiene using the
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s
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