Influence of the operating conditions on the catalytic activity of [PdCl2(dapp)] in the CO-ethene copolymerization in the H 2O-CH3COOH as a solvent (dapp = 1,3-bis(di(2- methoxyphenyl)phosphino)propane)

Article abstract of DOI:10.1016/j.molcata.2010.09.012

The influence on the productivity of [PdCl₂(dapp)] in H ₂O-CH₃COOH in the CO-ethene copolymerization and on the LVN of the copolymer of the following reaction parameters has been studied: (i) composition of the H₂O-CH₃COOH reaction medium; (ii) temperature; (iii) CO/ethene ratio at a given total pressure; (iv) total pressure at fixed ratio CO/ethene = 1/1; (v) CO or ethene partial pressure at a given pressure of one monomer; (vi) reaction time. High molecular weight PKs are obtained under high pressure with the monomers in the ratio 1/1 at relatively low temperature and with a H₂O/CH₃COOH 40-50% with productivity ranging from 4 to 20 kg PK(g Pd h)^-1. The relation between productivity and LVN has been discussed in the light of the key steps of the catalytic cycle.

Full text of DOI:10.1016/j.molcata.2010.09.012

Journal of Molecular Catalysis A: Chemical 332 (2010) 158–164
Contents lists available at ScienceDirect
Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Influence of the operating conditions on the catalytic activity of [PdCl2(dapp)] in
the CO–ethene copolymerization in the H2O–CH3COOH as a solvent
(dapp = 1,3-bis(di(2-methoxyphenyl)phosphino)propane)
Andrea Vavasoria, Federico Dall’Acquaa, Gianni Cavinatob, Luigi Tonioloa,∗
a Department of Chemistry, University Ca’ Foscari of Venice, Consortium INSTM-RU of Venice, Dorsoduro 2137, 30123 Venezia, Italy
b Department of Chemical Science, University of Padova, Via Marzolo 1, 35131 Padova, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 July 2010
Received in revised form 8 September 2010
Accepted 8 September 2010
Available online 17 September 2010
The influence on the productivity of [PdCl2(dapp)] in H2O–CH3COOH in the CO–ethene copolymerization
and on the LVN of the copolymer of the following reaction parameters has been studied: (i) composition
of the H2O–CH3COOH reaction medium; (ii) temperature; (iii) CO/ethene ratio at a given total pressure;
(iv) total pressure at fixed ratio CO/ethene = 1/1; (v) CO or ethene partial pressure at a given pressure
of one monomer; (vi) reaction time. High molecular weight PKs are obtained under high pressure with
the monomers in the ratio 1/1 at relatively low temperature and with a H2O/CH3COOH 40–50% with
Keywords:
Palladium
Chloride
Dapp
Carbon monoxide–ethene
copolymerization
Water–acetic acid
productivity ranging from 4 to 20 kg PK(g Pd h)−1
.
The relation between productivity and LVN has been discussed in the light of the key steps of the
catalytic cycle.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
the main product is methyl propanoate (MP), which can
be considered the lightest product of the copolymerization
Cationic palladium–phosphine complexes catalyze the copoly-
merization of carbon monoxide with ethene (E) to yield a wide
spectrum of important products ranging from perfectly alternating
polyketones (PKs) to derivatives of low molecular weight products
such as diethyl ketone or propanoic acid and its esters [1–8].
In general, compared to monophosphine complexes, which may
present trans- and cis-coordination, diphosphine complexes that
maintain cis-coordination throughout the catalytic cycle, are far
superior because cis-coordination favours all the elementary steps
of the catalytic cycle [1,5], including the product-forming one [9].
The selectivity mainly depends on the nature of the lig-
and. C3-bridged diarylphosphines, such as dppp or dapp
(dppp = 1,3-bis(diphenylphosphino)propane; dapp = 1,3-bis(di(2-
methoxyphenyl)phosphino)propane), are highly active in the
copolymerization process [8]. Upon increasing steric bulk, the
chain-growing process becomes more and more inhibited, whereas
the chain-transfer termination step is favoured [9]. This is
well illustrated by substitution of the aryl groups with butyl
groups, in which case both the productivity and molecu-
lar weight decrease to the point that with t-Bu2(CH2)3Bu2-t
process (97.4% selectivity, TOF 25,000 h−1 at 120 ◦C, 40 bar,
CO/ethene = 2/1, MeOH as a solvent) [10]. A even higher selectivity
is achieved using a dtbpx-based catalyst (dtbpx = 1,2-bis[di-t-
butyl)phosphinomethyl]benzene; 99.98%, TOF = 50,000 h−1, 80 ◦C,
10 bar, CO/ethene = 1/1 [11]. In this case, the wider bite angle of
dtppx magnifies the steric bulk of the t-Bu groups, which may
account for the exceptionally high selectivity to MP.
Other factors that influence the activity and selectivity are: the
nature of the counter anion, the solvent, the operating conditions
and added promoting agents, protic acids, organic oxidant and
water [12–14].
The nature of the solvent may exert a dramatic influence on
the performance of the catalyst. It was reported, first by us, that the
neutral precursors [PdX2(dppp)] (X = AcO, Cl), inactive in MeOH, the
solvent of most common use, turn into highly active systems when
used in H2O/AcOH as a solvent [13,15]. In spite of the lower sol-
ubility of the monomers in H2O–CH3COOH, with respect to those
in MeOH, the productivity of the [PdX2(dppp)]/(H2O–CH3COOH)
system is much higher than that of the corresponding cationic com-
plex (X = TsO) in MeOH (27 kg PK(g Pd h)−1 versus 6 kg PK(g Pd h)−1
.
These studies have been extended to the use of [PdCl2(dppf)]
(dppf = 1,1ꢀ-bis(diphenylphosphino)ferrocene), which is also inac-
tive in MeOH. It has been found that in H2O/AcOH it is highly active
to give PKs of moderately high molecular weight [16]. Instead, the
∗
Corresponding author. Tel.: +39 041 243 8553; fax: +39 041 234 8517.
E-mail address: toniolo@unive.it (L. Toniolo).
1381-1169/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2010.09.012

A. Vavasori et al. / Journal of Molecular Catalysis A: Chemical 332 (2010) 158–164
159
analogous cationic precursors having TsO− as counter anion used
in MeOH yields co-oligomers and other molecules of even lower
molecular weight, such as dimethyl 4-oxoheptanoate, methyl 4-
oxohexanoate, dimethyl succinate and MP [17].
solvent and catalyst were contained in a ca. 150 mL Pyrex bottle,
placed inside the autoclave.
The monomers were supplied to the autoclave in the ratio 1/1
from a gas reservoir connected to the autoclave through a constant
pressure regulator.
Subsequently, the catalytic activity of other [PdCl2(P–P)] com-
plexes
(P–P = 1,2-bis(di(2-methyoxyphenyl)phosphino)ethane,
In
a
typical experiment, 0.60 mg of [PdCl2(dapp)]
dapp and dapp with substituents in the C3-bridging chain in
H2O/AcOH has been briefly reported [18,19].
(8.88 × 10−4 mmol) was added to 80 mL of solvent (CH3COOH–H2O,
H2O = 55% (mol/mol) contained in the bottle placed in the auto-
clave. The autoclave was washed by pressurising with a 1/1 mixture
of CO/C2H4 (ca. 0.5 MPa) and then depressurising to atmospheric
pressure (this cycle was repeated 5 times, at room temperature
with stirring). The autoclave was then pressurised with 0.5 MPa
of the gas mixture and then heated to 90 ◦C in ca. 10 min without
stirring. The pressure was then adjusted to the desired value and,
while stirring (700 rpm), maintained constant throughout the
experiment by continuously supplying the monomers from the
reservoir. At the end of the experiment the autoclave was quickly
cooled and carefully depressurised. The slurry product was filtered,
washed with water and acetone and dried under vacuum at 70 ◦C.
The dried polymer was weighted and the productivity was cal-
culated as g PK(g Pd h)−1; the reproducibility was within ca. 5%.
In the liquid phase, analysed by CG, no propanoic acid or other
low molecular weight products were found.
The cationic dapp-based system in MeOH has been devel-
oped by Schell for industrial application for producing PKs. It
gives a satisfactory balance between productivity and molecu-
lar weight, better than the analogous dppp-based system (with
Pd(AcO)2/(P–P)/(TFAH) = 1/0.5/2 (TFAH = trifluoroacetic acid; pro-
ductivity 12,700 g PK(g Pd h)−1 versus 7100 g PK(g Pd h)−1
, LVN
1.58 dL/g versus 1.05 dL/g under 50 atm (CO/E = 1/1), at 90 ◦C for 1 h
[8]).
Recently, several industries have shown a renewed keen inter-
est in high molecular weight PKs for applications in the field of
fibers [20,21]. This prompted us to take into consideration the
use of [PdCl2(dapp)] in H2O/AcOH with the aim of obtaining high
molecular weight PKs with high productivity. Here, we present an
extensive study on the influence of the operating conditions on the
catalytic activity on the CO–ethene copolymerization catalyzed by
this system.
The CO2 evolution during the reaction was monitored by sam-
pling with a micro-syringe the gas phase of the reactor which was
then analysed by a gas-chromatograph, following the same proce-
dure already reported [13].
2. Experimental
2.1. Reagents
2.4. Limiting viscosity number (LVN) measurement and average
viscosity molecular weight calculation
Acetic acid (100%, glacial), solvents, triethylamine, m-cresol,
CDCl3, were purchased from Aldrich; palladium(II) chloride
was purchased from Chimet S.p.A.; 1,1,1,1,3,3,3-hexafluoro-2-
propanol (99%) was purchased from Riedel De Haen. The complex
[PdCl2(PhCN)2] was prepared as reported in literature [22]. The
complex [PdCl2(dapp)] was prepared from [PdCl2(PhCN)2] and
The LVN of a dilute polyketone solution was determined by
using the Huggins relationship between the viscosity number and
the polymer concentration by extrapolation to zero concentration
[23]. The polyketone solution was prepared in m-cresol as a sol-
vent and the viscosity was measured by using a Cannon-Fenske
type capillary viscosimeter, thermostated at 25 ◦C.
The average molecular weight of the polyketone can be calcu-
lated from the LVN using the following Mark–Houwink equation
[24]:
dapp (1/1) in CH2Cl2/EtOH (31P{ H} NMR 16.30 ppm at r.t. in
1
CD2Cl2). Dapp was provided by Hyosung Corporation. Carbon
monoxide and ethene were supplied by SIAD Company (‘research
grade’, purity > 99.9%).
[ꢀ]m-cresol,25 = 1.01 × 10−4M0w.85
2.2. Equipment
◦
C
The catalyst precursor was weighted on a Sartorious Micro bal-
ance (precision 0.001 mg). Gas-chromatographic analysis of the liq-
uid phase was performed on a Hewlett Packard Model 5890, Series
II chromatograph fitted with a HP1, 30 m × 0.35 ␮m × 0.53 ␮m col-
umn (detector: FID; carrier gas: N2, 0.2 mL/min; oven: 50 ◦C (2 min)
to 200 ◦C at 15 ◦C/min). Gas-chromatographic analysis of the gas
phase was performed on a Hewlett Packard Model 5890, Series II
chromatograph fitted with a 18 ft × 1/8 SS Silica Gel, 60/80 packed
column (detector: TCD; carrier gas: helium, 30 mL/min; oven: 40 ◦C
(2 min) to 100 ◦C at 15 ◦C/min).
3. Results and discussion
The influence on the productivity of the catalyst and on the LVN
of the copolymer of the following reaction parameters has been
studied: (i) composition of the H2O–CH3COOH reaction medium;
(ii) temperature; (iii) CO/ethene ratio at a given total pressure; (iv)
total pressure at fixed ratio CO/ethene = 1/1; (v) CO and ethene par-
tial pressures at a given pressure of one monomer; (vi) reaction
time.
All the NMR spectra were recorded on a Bruker Avance 300 spec-
trometer. The 1H NMR and 13C NMR spectra of the polyketone were
recorded in 1,1,1,3,3,3-hexafluoroisopropanol/CDCl3 (10/1) using
the Inverse 1H-Gated Decoupling Technique. The 31P NMR spec-
tra of the complex [PdCl2(dapp)] were recorded in CD2Cl2, external
85% H3PO4.
1H and 13C NMR analyses show that the monomers are per-
fectly alternating in the PK chains even when one monomer is used
in large excess with respect to the other. Moreover, the chains end
exclusively with keto groups [12]. In addition, during catalysis there
is CO2 evolution. This is consistent with the mechanism in which
the catalysis is initiated by a Pd–H+ species and is terminated by
a protonolysis step with H2O [13,15], which gives the PK and a
Pd–OH+ species, which regenerates the Pd–H+ after insertion of
CO and evolution of CO2. The mechanism of the catalytic copoly-
merization has been extensively studied [1,3]. Scheme 1 shows a
simplified catalytic cycle.
2.3. Carbon monoxide–ethene copolymerization
The copolymerization reactions were carried out by using a
Hastelloy C autoclave of ca. 250 mL provided with a four-blade
self-aspirating turbine. In order to avoid contamination by metallic
species due to corrosion of the internal surface of the autoclave,
Apart the CO2 that is formed for the activation of the starting
precursor to give the Pd–H+ species, the overall copolymerization

160
A. Vavasori et al. / Journal of Molecular Catalysis A: Chemical 332 (2010) 158–164
Cl
Cl
+
CO, H2O, L
-HCl, -Cl-, -CO2
H
L
[Pd]° + H+
*Pd
*Pd
CO2
CO
+
+
OH
L
L
*Pd
*Pd
O
n CO
n
+
L
O
*Pd
O
n-1
H2O
O
n-1
*Pd = Pd(dapp); L = H2O, CO,
.
Scheme 1. Catalytic cycle for the CO–E copolymerization.
species of the type [(dapp)(␮-H)(␮-CO)Pd(dapp)]2+ or [(dapp)(␮-
CO)2Pd(dapp)]2+, which ultimately may lead to the formation of
inactive Pd(0) [1,3]. In addition, the acid may destabilize the ␤-
and ␥-chelate rings through protonation at the oxygen atoms of
the rings which have been proposed to be resting states in the
incorporation of the monomers into the growing chain [26].
Protonation at the oxygen atm of the ␤-chelate intermediate in
the synthesis of diethyl ketone (DEK) by carbonylation of ethene
catalyzed by a Pd(AcO)2/dtbpe/TfOH system (dtbpe = 1,2-bis(di-
␤-butylphosphino)ethane, TfOH = trifluoromethansulfonic acid)
has been proposed to explain the significant increasing of
oligomers/copolymers formation upon increasing the TfOH/Pd
ratio [10]. A promoting effect of an acid on the copolymerization
process has been observed also in the case of the carbonyla-
tion of ethene using Pd(AcO)2 in combination with an excess
of PPh3 or with its monosulfonated derivative PPh2PhSO3H, in
AcOH and in the presence of TsOH (Pd/P/TsOH = 1/8/80–800, 90 ◦C,
0.10–0.50 MPa). The reaction switches from monocarbonylation
with formation of propanoic acid to oligocarbonylation products
reaction is:
cat
nCO + nCH2CH2 + H2O−→ − [CH2CH2C(O)]n−+CO2
(1)
It is well known that H2O, CO and E are capable of interacting with
Pd(II). This interaction may cause the displacement of a Cl− ligand,
which may be favoured also by the solvation with H2O and the high
dielectric constant of the reaction medium. In this way the precur-
sor becomes more available toward coordination. The initial Pd–H+
species may form through the interaction of H2O and CO with the
cationic centre, by a reaction closely related to the WGSR [7,25]. The
high pressure of the monomers and the high concentration of H2O
may favour also the dissociation of the other Pd–Cl bond, giving
rise to a cationic coordinatively-unsaturated Pd–H+ species hav-
ing easily available coordination sites similar to the one generated
from a cationic precursor with weakly coordinating anions which
is active in MeOH. This may explain why the [PdCl2(dapp)], hav-
ing strongly coordinating Cl− anions, inactive in MeOH, turns into
a highly active catalyst when used in H2O/CH3COOH as a solvent
[13,15,16].
3.1. Influence of the composition of the reaction medium
8000
Fig. 1 shows the influence of the composition of the solvent car-
rying out the copolymerization for 4 h at 60 ◦C under 45 atm of total
pressure (CO/E = 1/1).
7000
6
The productivity increases upon increasing the concentration
of H2O up to a maximum of 7000 g PK(g Pd h)−1 at 55% (mol/mol).
The beneficial effect of H2O has been outlined above. In addition
labile coordination of H2O may stabilize the coordinatively unsatu-
rated Pd(II) species, for example of the type [(dapp)Pd(OH)]+ which
is formed in the protonolysis chain-transfer termination step (cfr.
Scheme 1), against their tendency to dimerize to achieve the usual
four-coordination of Pd(II). In general dimeric species are less active
[1,3]. On the other hand, upon increasing the H2O concentration
the solubility of the two monomers decreases [13] and hence the
copolymerization rate (see later). Concerning the acid, not only the
solubility of the monomers increases with increasing its concentra-
tion, but also a higher concentration of active Pd–H+ species may
be accomplished because the acid may prevent the deprotonation
of the hydride with formation of hydride-deficient formally-Pd(I)
6000
5000
4000
4
productivity
LVN
3000
2000
30
40
50
60
70
H2O, % (mol/mol)
Fig. 1. Influence of H2O on the productivity and on the LVN. Run condi-
tions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: H2O–CH3COOH; V: 80 mL; 45 atm
(CO/ethene = 1/1); 60 ◦C; 4 h; 700 rpm.

A. Vavasori et al. / Journal of Molecular Catalysis A: Chemical 332 (2010) 158–164
161
20000
18000
16000
14000
12000
10000
8000
2,0
1,9
1,8
1,7
1,6
1,5
1,4
1,3
1,2
1,1
1,0
0,9
0,8
0,7
0,6
0,5
6000
Fig. 2. ␤ and ␥ chelate.
4000
2000
0
productivity
LVN
and to polyketones as the pressure and concentration of TsOH
increase; the yield in polyketones also increases upon increasing
the acidity [27,28].
0
5
10
15
20
25
30
35
40
45
50
pCO (Ptot. = 45 atm), atm
In the present case, Fig. 1 shows that as far as the productiv-
ity is concerned the best compromise between the favourable and
unfavourable influences of H2O and AcOH seems to be achieved
when they are in the ratios 55–70/45–30. The trend shown in Fig. 1
has been observed also in the CO–E copolymerization catalyzed by
[PdCl2(dppf)] in H2O–CH3COOH [16].
Differently, LVN increases regularly with lowering the H2O con-
centration. This fact suggests that the chain-transfer termination
step occurs via protonolysis mainly by H2O even in the presence of
relatively large amounts of CH3COOH. Concurrently, the increasing
of acid concentration increases the solubility of the monomers and
easies the destabilization of the ␤- and ␥-chelates, which favour
also the formation of higher molecular weight polymers. There-
fore, particularly high LVNs are achievable at the expenses of the
productivity. It is interesting to point out that the trend of LVN
shown in Fig. 1 is the opposite of that found using [PdCl2(dppf)]
in H2O–CH3COOH, in which case LVN increases (slightly) upon
decreasing H2O concentration [16] (see Fig. 2).
Fig. 4. Influence of CO partial pressure under constant CO–E total pressure on the
productivity and on the LVN. Run conditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; sol-
vent: H2O–CH3COOH, H2O: 55%; V: 80 mL; 45 atm (CO + ethene); 90 ◦C; 1 h; 700 rpm.
3.3. Influence of the pressure of the monomers
The results shown in Fig. 5 refer to experiments carried out at
a constant total pressure (45 atm) and different CO/E ratios. The
highest productivity and LVN are obtained when the monomers
are approximately in the ratio 1/1. A similar trend has been also
observed using the cationic precursor [Pd(TsO)(H2O)(dppp)](TsO)
in MeOH as a solvent [14].
Fig. 5 shows the influence of the pressure of E keeping the
pressure of CO constant. The productivity increases on increas-
ing the pressure of E up to 50 atm, then it decreases whereas LVN
increases also above 50 atm. Similar trends have been observed on
increasing the pressure of CO keeping constant that of the other
monomer (Fig. 6). The fact that the productivity passes through a
maximum on increasing the pressure of one monomer and keep-
ing the pressure of the other monomer constant at a relatively low
value, suggests that the two monomers compete for the coordi-
nation to the metal centre, so that at a relatively high pressure of
one monomer the coordination of the other is disfavoured. This
picture is in agreement with the trend of productivity shown in
Fig. 7, where the productivity regularly increases upon increasing
the pressure of both monomers used in the ratio 1/1. The same trend
was observed using the precursor [Pd(TsO)(H2O)(dppp)](TsO) in
3.2. Influence of the temperature
The influence of the temperature on productivity and LVN has
been studied under the conditions of Fig. 3. On increasing the tem-
perature the productivity increases but the LVN decreases. This
result suggests that the chain growing process presents an acti-
vation energy lower than the one of the chain-transfer termination
step. This is not surprisingly because only after a relatively large
number of monomer insertion steps only one termination step
occurs.
15000
14000
13000
12000
11000
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
10
8
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
8
6
4
2
0
productivity
LVN
6
4
2
productivity
LVN
0
0
10
20
30
40
50
60
70
80
40
50
60
70
80
90
p E, atm
T, °C
Fig. 3. Influence of temperature on the productivity and on the LVN. Run con-
ditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: H2O–CH3COOH, H2O: 55%; V:
80 mL; 45 atm (CO/ethene = 1/1); 1 h; 700 rpm.
Fig. 5. Influence of E partial pressure on the productivity and on the LVN. Run con-
ditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: CH3COOH + H2O, H2O: 55%; V:
80 mL; pCO: 15 atm, 90 ◦C, 1 h, 700 rpm.

162
A. Vavasori et al. / Journal of Molecular Catalysis A: Chemical 332 (2010) 158–164
5
5,0
4,5
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
24000
16000
14000
12000
10000
8000
6000
4000
2000
0
22000
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
4
3
2
1
0
productivity
LVN
productivity
LVN
0
10
20
30
40
50
60
70
80
90 100 110 120
0
10
20
30
40
50
60
ptotal, atm (CO/E 1/1)
p CO, atm
Fig. 7. Influence of total pressure (CO/E = 1/1) on the productivity and on the LVN.
Run conditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: CH3COOH + H2O, H2O:
55%; V: 80 mL; 90 ◦C, 1 h, 700 rpm.
Fig. 6. Influence of CO partial pressure on the productivity and on the LVN. Run
conditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: CH3COOH + H2O, H2O: 55%;
V: 80 mL; pE: 15 atm, 90 ◦C, 1 h, 700 rpm.
12
24000
MeOH [14]. These results show that in order to reach both high
productivity and LVN the monomers must be balanced.
11
22000
10
Going back to Figs. 5 and 6, whereas the productivity decreases
at a relatively high pressure of one monomer, LVN increases regu-
larly. This fact suggests that, even though the reaction rate slows
down the polymer chain growing process goes on, i.e. the ter-
mination chain transfer step is inhibited. This may be explained
taking into account the mechanism of the termination step, which
involves a pre-equilibrium of a ␤-chelate species with its enolate
isomer by a ␤-H elimination/hydride migration and protonation
to the more nucleophilic oxygen atom to give an enol [29,30],
which rearranges to the ketone with concomitant formation of
a [Pd–OH]+ species (Scheme 2), which is converted to active
Pd–H+ via a partial water gas-shift reaction (cfr. Scheme 1). It was
found that the enolate formation is much slower than protonol-
ysis [29,30]. Since enolate formation requires the availability of
another coordination it may be inhibited under a relatively high
pressure of one monomer, so that the chain growing process can
proceed further, even though at a lower rate because the two
monomers are a unbalanced ratio (cfr. Fig. 4). Under the con-
ditions of Fig. 7 both productivity and LVN increase regularly
also at relatively high pressures because the two monomers are
used in the ratio 1/1, so that the process of chain growing may
go on without being accompanied by a declining of the reaction
rate.
20000
9
18000
8
16000
7
14000
6
12000
productivity
LVN
5
10000
8000
6000
4000
2000
0
4
3
2
1
0
45 atm
110 atm
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
T, °C
Fig. 8. Influence of temperature on the productivity and on the LVN. Run con-
ditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: CH3COOH + H2O, H2O: 55%; V:
80 mL; 45 atm (dotted line), 110 atm (solid line); CO/ethene = 1/1; 1 h; 700 rpm.
ity (2500 g PK(g Pd h)−1). At ca. 75 ◦C both productivity and LVN are
relatively high (ca. 15,000 g PK(g Pd h)−1 and ca. 7 dL/g).
3.5. Influence of the composition of the solvent under high
pressure
It is interesting to compare the trends of the productivity shown
in Figs. 5 and 6 with those observed when using the cationic dapp-
Pd(II)/TFAH catalytic system in MeOH. It was found that keeping
constant the pressure of CO or that of E (25 atm in both cases) the
productivity increases linearly upon increasing the pressure of E
up to 25 atm, whereas in the other case the productivity passes
through a maximum at pCO = ca. 15 atm and declines at higher pres-
sure. It was suggested that CO impedes coordination of E [31].
In general, the results above discussed are encouraging in order
to achieve both high productivity and LVN. We have seen that
the composition of the solvent has a strong influence on them.
Therefore, we carried out some experiments under constant high
pressure and at relatively low temperature (110 atm, 70 ◦C), using
a solvent of variable composition. Fig. 9 shows that LVN increases
regularly with lowering the concentration of H2O as found at lower
pressure (cfr. Fig. 1), whereas the highest productivity is achieved
at lower H2O concentration (40–50% versus 55–65%). A reasonable
explanation may be the following. In order to achieve high activity
it is necessary that the Cl− anion remains uncoordinated during the
catalysis, which is favoured under high pressure of the monomers,
which can be achieved at lower concentration of H2O.
3.4. Influence of the temperature and of the total pressure with
the monomers in the ratio 1/1
The previous experiments have shown that high LVN can
be achieved under high total pressure and at low temperature,
whereas in order to achieve a high productivity it is necessary to
increase the temperature. Fig. 8 gives a picture of the influence of
both temperature and pressure on productivity and LVN. At 90 ◦C
under 110 atm a productivity as high as 22,800 g PK(g Pd h)−1 is
achieved with LVN = 3.8 dL/g, whereas at 60 ◦C a much higher LVN
is achievable (11.2 dL/g), though at the expenses of the productiv-
3.6. Influence of reaction time
Figs. 10 and 11 show that when the reaction is carried out
for longer reaction times the productivity decreases, whereas LVN
increases. The productivity depends on the rate of chain growing

A. Vavasori et al. / Journal of Molecular Catalysis A: Chemical 332 (2010) 158–164
163
7000
6000
5000
4000
3000
2000
1000
0
11
8000
10
9
7000
6000
5000
4000
3000
2000
1000
0
8
O = H2O 45%
7
Δ = H2O 31%
6
productivity
LVN
5
4
30
35
40
45
50
55
60
65
70
H2O, % (mol/mol)
0
1
2
3
4
5
6
time, h
Fig. 9. Influence of H2O on the productivity and on the LVN. Run conditions:
[PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: CH3COOH + H2O, V: 80 mL; 110 atm;
CO/ethene = 1/1; 70 ◦C; 4 h; 700 rpm.
Fig. 10. Influence of reaction time on the productivity. Run conditions:
[PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: CH3COOH + H2O; V: 80 mL; 110 atm
(CO/ethene 1/1); 70 ◦C; 1 h; 700 rpm.
and on their concentration, the latter is related to the concentra-
tion of the Pd–H+ species that starts the catalysis. LVN depends on
the rate of chain growing relative to the rate of the chain termina-
tion process. The fact that the lowering of productivity occurs with
concomitant increasing of LVN suggests that the after the chain-
transfer termination step the regeneration of active Pd–H+ species
becomes less efficient and/or that the copolymer inhibits the inser-
tion of the monomers more than the protonolysis chain transfer
process. The lowering of the productivity may be caused also by
the difficulty of maintaining efficient the stirring of the PK/solvent
slurry as the amount of PK, since this presents a relatively low
apparent density and conglobates a relatively large fraction of the
Scheme 2. Termination step for the CO–E copolymerization.
12,0
11,5
11,0
10,5
10,0
9,5
H2O = 45 %
H2O = 31 %
9,0
8,5
8,0
7,5
7,0
6,5
6,0
5,5
5,0
1
2
3
4
5
6
reaction time, h
Fig. 11. Influence of reaction time on the LVN. Run conditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; solvent: CH3COOH + H2O; V: 80 mL; 110 atm (CO/ethene 1/1); 70 ◦C; 1 h;
700 rpm.

164
A. Vavasori et al. / Journal of Molecular Catalysis A: Chemical 332 (2010) 158–164
Table 1
[9] P.W.N.M. van Leeuwen, M.A. Zuideveld, B.H.G. Swennenhuis, Z. Freixa, P.C.J.
Kamer, K. Goubitz, J. Fraanje, M. Lutz, A.L. Spek, J. Am. Chem. Soc. 125 (2003)
5523.
Influence of temperature. Run conditions: [PdCl2(dapp)]: 8.88 × 10−4 mmol; sol-
vent: CH3COOH + H2O, H2O: 40%; V: 80 mL.
[10] R.I. Pugh, E. Drent, Adv. Synth. Catal. 344 (2002) 837.
[11] W. Clegg, G.R. Eastham, M.R.J. Elsegood, R.P. Tooze, X.L. Wang, K. Whiston, J.
Chem. Soc. Chem. Commun. (1999) 1877.
Total pressure (atm)
T (◦C)
Reaction
time (h)
Productivity
(g/g Pd h)
LVN (dL/g)
[12] E. Drent, J.A.M. van Broekhoven, M.J. Doyle, J. Organomet. Chem. 417 (1991)
235.
[13] A. Vavasori, L. Toniolo, G. Cavinato, F. Visentin, J. Mol. Catal. A: Chem. 204–205
(2003) 295.
[14] A. Fabrello, A. Vavasori, F. Dall’Acqua, L. Toniolo, J. Mol. Catal. A: Chem. 276
(2007) 211.
110
110
110
110
60
70
80
90
4
4
2
2
4000
6100
10,500
20,300
11.1
10.3
8.5
4.5
[15] A. Vavasori, L. Toniolo, G. Cavinato, J. Mol. Catal. A: Chem. 215 (2004) 63.
[16] A. Vavasori, A. Bellieni, L. Ronchin, F. Dall’Acqua, L. Toniolo, G. Cavinato, J. Mol.
Catal. A: Chem. 263 (2007) 9.
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Freixa, P.J. Kamer, A.L. Spek, O.V. Gusev, M. Kal’sin, Organometallics 22 (2003)
2409.
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hauser, E.J. Garcia Suarez, J. Chem. Soc. Dalton Trans. (2006) 1877.
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solvent to the point that after 4 h of reaction most of the solvent
appears to be absorbed into the copolymer.
In conclusion, high LVN can be achieved under high pressure at
relatively low temperature and H2O concentration, though at the
expenses of the productivity. This may be improved upon increas-
ing the temperature as shown in Table 1.
[20] R. Taniguchi, J. Kato, T. Komatsu, Patent US 7666975 B2 by Asahi Kasei Fibers
Corp., Japan (2010).
Acknowledgement
[21] http://ep.espacenet.com/.
Hyosung Corporation (Korea) is gratefully acknowledged for
financial support.
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