Pyrazolyl-pyrimidine based ligands in palladium catalyzed copolymerization and terpolymerization of CO/olefins

Article abstract of DOI:10.1016/j.jorganchem.2008.01.022

Cationic palladium(II) complexes of the type [PdMe (NCMe) (N - N^′)] [BAr₄^′] containing bisnitrogen ligands with a pyrazole moiety were synthesized from the corresponding neutral derivatives [PdClMe(N-N′)]. Their characterization by ¹H and ¹³C NMR spectroscopy in solution evidences the presence of the Pd-Me group cis to the pyrazole ring. The catalytic behaviour of the cationic complexes in CO/4-tert-butylstyrene copolymerization and CO/ethylene/4-tert-butylstyrene terpolymerization was investigated. Productivity was greatly enhanced when the reaction was carried out in 2,2,2-trifluoroethanol (TFE). Molecular weights and polydispersity (M_w/M_n) of the obtained polyketones resulted among the best reported for C_s-bisnitrogen planar ligands.

Full text of DOI:10.1016/j.jorganchem.2008.01.022

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1269–1275
www.elsevier.com/locate/jorganchem
Pyrazolyl-pyrimidine based ligands in palladium
catalyzed copolymerization and terpolymerization of CO/olefins
a
a,
a,
b
*
*
´
Antonio F. Bella , Aurora Ruiz , Carmen Claver , Francisco Sepulveda ,
b
b
´
Felix A. Jalon , Blanca R. Manzano
a Universitat Rovira i Virgili, Facultat de Qu´ımica, C/Marcel.li Domingo s/n, 43007 Tarragona, Spain
b Universidad de Castilla-La Mancha, Facultad de Qu´ımicas, Avda, C. J. Cela, 10, 13071 Ciudad Real, Spain
Received 12 June 2007; received in revised form 11 January 2008; accepted 11 January 2008
Available online 19 January 2008
Dedicated to Dr. Antonio Abad for his contributions in organometallic chemistry.
Abstract
Cationic palladium(II) complexes of the type ½PdMeðNCMeÞðN–N0Þꢀ½BAr40 ꢀ containing bisnitrogen ligands with a pyrazole moiety
were synthesized from the corresponding neutral derivatives [PdClMe(N–N0)]. Their characterization by 1H and 13C NMR spectroscopy
in solution evidences the presence of the Pd–Me group cis to the pyrazole ring. The catalytic behaviour of the cationic complexes in CO/
4-tert-butylstyrene copolymerization and CO/ethylene/4-tert-butylstyrene terpolymerization was investigated. Productivity was greatly
enhanced when the reaction was carried out in 2,2,2-trifluoroethanol (TFE). Molecular weights and polydispersity (Mw/Mn) of the
obtained polyketones resulted among the best reported for Cs-bisnitrogen planar ligands.
Ó 2008 Published by Elsevier B.V.
Keywords: Palladium; Nitrogen ligands; Polyketone; Carbon monoxide; Copolymerization; Terpolymerization
1. Introduction
The research on polyketones prepared with late transi-
tion metal catalysts continues in academic and industrial
laboratories around the world. It has been comprehen-
sively reviewed [2–9]. The most thoroughly studied como-
nomers are ethene and propene, for which Pd complexes
based on bisphosphine ligands and non-coordinating coun-
terion have been by far the most widely used precatalysts
[2,10]. Alternating copolymerization of ethene or propene
with carbon monoxide has become an attractive option
due to the readily available and inexpensive starting mate-
rials. Moreover, the resulting polymer, poly(1,4-ketone),
has potential photo- and biodegradable properties owing
to the repeating carbonyl units [11], which lend themselves
to further chemical modifications [12]. Among the higher
olefins, vinylarenes have gained most attention as comono-
mers. Most of the results with styrene and derivatives have
been obtained with catalysts based on ligands developed for
the stereocontrolled co- and terpolymerization [13–25],
as for N–N [13–17], P–N [18,19], N–N0 [25] and P–O [23].
The search for new polymers with high content of het-
eroatom functionalities that can provide materials with
interesting engineering properties continues unabated ever
since the rise of polyolefin production and of the plastics
made from them for daily use. Whereas alternating eth-
ene/CO copolymers are white crystalline high-melting sol-
ids, only poorly soluble and difficult to process, the
corresponding terpolymers containing small amount of
propene/CO units (5–10%) show reduced melting transi-
tions and more favourable behaviour in blow-molding or
extrusion applications. This thermoplastic material was
commercialised by Shell under the trade name Carilon in
the 1990s [1].
*
Corresponding authors.
E-mail addresses: mariaaurora.ruiz@urv.cat (A. Ruiz), claver@quimica.
urv.es (C. Claver).
0022-328X/$ - see front matter Ó 2008 Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2008.01.022

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A.F. Bella et al. / Journal of Organometallic Chemistry 693 (2008) 1269–1275
Furthermore, it has been shown that catalytic tests per-
formed in 2,2,2-trifluoroethanol (TFE) as solvent, greatly
improved catalyst lifetime leading to higher productivities
and molecular weights [26].
2.2. Synthesis and characterization of cationic pal0ladium
catalyst precursors ½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr4ꢀ
(1b–3b)
We have previously shown that in the CO/tert-butylsty-
The
cationic
palladium
catalyst
precursors
rene/ethylene
terpolymerization
catalyzed
by
½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr04ꢀ (Scheme 2) were synthe-
sized by adding a CH2Cl2 solution of the neutral deriva-
tives (1a–3a) to an equimolar solution of NaBAr04 in
anhydrous MeCN. These palladium complexes were
obtained as yellow pale solids, which resulted to be com-
pletely soluble in chlorobenzene and dichloromethane, sol-
vents selected for copolymerization and terpolymerization,
respectively. No crystals suitable for structural determina-
tion were obtained for complexes 1b–3b. They were fully
identified by means of elemental analysis, 1H and 13C
{1H} NMR spectroscopy in solution. The resonances were
assigned on the basis of selective decoupling experiments
and on the multiplicity of the signals. The coordinated
methyl group appear upfield as a singlet in the range
between 1.2 and 1.3 ppm, showing irrelevant chemical shift
differences of this Pd–Me proton signal, moving from 1b to
3b. This indicates that there is not a clear electronic influ-
ence of the substituents (Y) in position 40 of the pyrazole
ring over these methyl groups.
½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr04ꢀ complexes [Ar0 = 3,5-
(CF3)2C6H3], where N–N0 = pyridine-imidazoline and pyr-
azolyl-pyrimidine ligands, the olefin preferentially inserted
in the terpolymer chain is strictly related to the nature of
the nitrogen ligand [27].
In this paper we extend this study to the synthesis and
characterization of complexes of general formula
½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr04ꢀ from their corresponding
chloro neutral complexes containing pyrazolyl-pyrimidine
ligands. The catalytic behaviour of the cationic complexes
in CO/4-tert-butylstyrene copolymerization and CO/ethyl-
ene/4-tert-butylstyrene terpolymerization has been studied.
Furthermore, catalytic experiments have been carried out
in 2,2,2-trifluoroethanol (TFE).
2. Results and discussion
2.1. Synthesis and characterization of neutral palladium
complexes [PdClMe(N–N0)] (1a–3a)
Irradiation of the methyl group at room temperature
produced a NOE difference signal on H03 of the pyrazole
ring. This reflects a trans-disposition with respect the
pyrimidine moiety of the ligand (Scheme 2).
New neutral complexes 2a and 3a were readily synthe-
sized similarly to a procedure reported in the literature
[28] for the synthesis of the neutral complex [PdClMe(1)],
(1a). Addition of 1 equiv. of the corresponding ligand to
a solution of [PdClMe(cod)] in toluene gave the neutral
complexes 2a and 3a (Scheme 1), which were fully charac-
terized by elemental analysis, 1H and 13C {1H} NMR spec-
troscopy in solution as well as by NOE and g-HSQC
experiments. 1H NMR shows the signals corresponding
to coordinated pyrazolyl-pyrimidine ligands and the r-
bonded palladium methyl group. Spectroscopic data also
suggested that H6 is sensitive to coordination being the
1H NMR signal considerably downfield shifted with
respect to the corresponding one in the free ligand [29].
This suggest that chloride is cis coordinated [30] to the
pyrimidine ring in all neutral complexes (1a–3a). This has
been confirmed by NOE experiments at room temperature,
that showed the interaction between the Pd–Me group and
H03 of the pyrazole ring.
The relative disposition of the ligands found in com-
plexes 1a–3a and 1b–3b is that expected considering elec-
tronic factors. The methyl group which has a higher trans
influence than the chloride or acetonitrile is situated trans
to the weaker donor heterocycle. Besides, on the basis of
steric factors the stereochemistry predicted would be the
same. The methyl in proximity of H6 of the six-membered
pyrimidine ring would give rise to a major steric repulsion
than in the proximity of H30 of the five-membered pyrazole
moiety. 1H NOESY NMR spectrum for cationic complexes
1b–3b recorded at room temperature did not show any
interionic contact. This is not surprising considering that
B(3,5-(CF3)2C6H3)4 is a weak coordinating anion [31].
2.3. Catalytic CO/TBS copolymerization
The CO/4-tert-butylstyrene (TBS) copolymerization
reaction promoted by cationic palladium catalysts
H5´
N
H4
H6
Y
Y
N
N
N
toluene
rt
N
H5
+
N
N
N
H3´
Pd
Pd
Me
Cl
Me
Cl
Y=H 1, pzpm
Me 2, Mepzpm
Br 3, Brpzpm
Y=H 1a
Me 2a
Br 3a
Scheme 1. Synthesis and characterization of the neutral palladium derivatives [PdClMe(N–N0)] (1a–3a)

A.F. Bella et al. / Journal of Organometallic Chemistry 693 (2008) 1269–1275
1271
in the same position, respectively (Table 1, entries 1–3).
Surprisingly, for the catalytic system 3b in chlorobenzene,
when the TBS/Pd ratio was increased, higher molecular
weight and productivity were obtained. GPC in THF
revealed the formation of a mixture of copolymers with very
different magnitude of molecular weight values (Table 1,
entry 4). A polymeric fraction with Mn value in the order
of 106 was only present in a concentration of 10% weight
of the overall composition. 1H and 13C NMR spectra
showed no formation of TBS homopolymer. Decomposi-
tion to Pd(0) is observed for the catalytic system 3b after
24 h at room temperature, under 1bar CO pressure in chlo-
robenzene. The solution obtained with catalyst 1b and 2b in
the same conditions, however, are yellow after 24 h, indi-
cating the presence of Pd(II) species. Productivities were
reasonably improved when the copolymerization reactions
were carried out in 2,2,2-trifluoroethanol (entries 5 and 6).
This effect has previously been observed for CO/styrene
copolymerization using palladium systems containing bis-
oxazoline, bipyridine and related ligands [26c]. Also in
TFE when the TBS/Pd ratio was increased higher produc-
tivity was obtained (entries 7 and 8). Usually at room tem-
perature TFE and TBS are not miscible thus a double
phase system could be operating. An increase of the ratio
TFE/TBS leads to the formation of a more homogeneous
system that remarkably improves productivities (entries 8
and 9). Molecular weights for polyketones obtained in fluo-
rinated media depend on the catalyst employed. In partic-
ular, catalyst 2b gave higher Mn values in TFE (entries 2
and 5), while negligible solvent effects on Mn and polydis-
persity were observed for catalyst 3b (entries 3 and 6).
e
H5`
N
H4
H6
Y
CF3
N
N
b
c
a
H5
B
d
N
H3`
CF3
Pd
4
MeCN
Me
NOE effect
Y=H 1b
Me 2b
Br 3b
Scheme 2. trans-Disposition of the Me group with respect to the
pyrimidine moiety.
½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr04ꢀ (1b–3b) was investigated
(Table 1). All catalytic experiments were carried out at
1 bar of CO and room temperature. Catalysts 1b–3b were
active towards 4-tert-butylstyrene/CO copolymerization
leading in all cases to syndiotactic polyketones. The high
stereochemical control attributed to chain-end control is
due to the interaction of the growing chain with the incom-
ing styrene unit, which inserts exclusively in the 2,1 fashion
[20,22,32,33]. This trend is equivalent to what is generally
reported in the literature for ligands possessing Cs symme-
try. Analysis of the 13C{1H} spectra indicated high stereo-
regularity from the signals of the methylene carbon atoms.
The resonance at 43.2 ppm (100% relative content) was
assigned to the syndiotactic uu-triad by comparison with
literature values [18,34].
The productivity and molecular weight of the catalytic
systems for CO/TBS copolymerization carried out in chlo-
robenzene is influenced by the nature of the substituent in
position 40 of the ligands coordinated to palladium. Thus,
productivity and molecular weight for the cationic complex
2b bearing a methyl group was lower than that found for
complexes 1b and 3b containing hydrogen and bromide
2.4. Catalytic CO/TBS/E terpolymerization
Table 2 shows the results obtained in CO/4-tert-butyl-
styrene/ethylene terpolymerization using the cationic
Table 1
CO/TBS copolymerisationa
Table 2
Terpolymerization of 4-tert-butylstyrene (TBS) and ethene with CO using
½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr40 ꢀ (N–N0 = 1–3)a
Entry Catalyst
precursor
TBS/ Productivity [g
Pd
Mn(Mw/Mn)e
PK(gPdꢁ1 ꢁ1)]d
h
Entry Catalyst
TBS/ PCO/ Productivityc %Ed Mn(Mw/Mn)e
1
2
3
4
1b
2b
3b
3b
310
310
310
11.8
7.5
11.3
14.1
3.60 ꢂ 104 (1.3)
1.50 ꢂ 104 (1.7)
1.90 ꢂ 104 (1.3)
1.30 ꢂ 106 (1.1)
2.90 ꢂ 104 (1.4)
3.49 ꢂ 104 (1.6)
1.95 ꢂ 104 (1.4)
4.96 ꢂ 104 (1.8)
1.30 ꢂ 104 (1.7)
1.48 ꢂ 104 (1.6)
precursor Pd
E(1:1) [g PK(g
(atm) Pdꢁ1 hꢁ1)]
1
2
3
4
1b
2b
2b
3b
3b
2b
3b
2000 10
2000 10
620 10
2000 10
2000 15
2000 10
2000 10
31.2
37.5
38.3
43.8
54.6
28
24
30
22
29
32
28
6.1 ꢂ 104(1.3)
4.0 ꢂ 104 (1.3)
4.0 104(1.2)
3.8 ꢂ 104(1.2)
3.8 ꢂ 104 (1.3)
8.2 ꢂ 104 (1.1)
4.7 ꢂ 104 (1.1)
2000
5b
6b
7b
8b
9c
2b
3b
2b
3b
3b
310
310
24.6
16.9
5
2000
2000
2000
73.7
123.7
187.5
6b
7b
125
87.5
Effect of TFE as solvent.
Effect
of
TFE
as
solvent.
Catalyst
precursor
a
½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr40 ꢀ (N–N0 = 1–3).
Reaction conditions: nPd = 0.0125 mmol; solvent: 15 mL of CH2Cl2;
a
24 h; room temperature.
Reaction conditions: nPd = 0.0125 mmol; PCO = 1 bar; solvent: 5 mL
b
Same conditions, except solvent: 15 mL of TFE.
Calculated from isolated polymer.
Calculated by relative integration of the 1H NMR signals of the
of chlorobenzene; 24 h; room temperature.
c
b
Same conditions, except solvent: 5 mL of TFE.
Same conditions, except solvent: 15 mL of TFE.
Calculated from isolated polymer.
Determined by SEC-MALLS in THF.
d
c
d
terpolymers.
e
e
Determined by SEC-MALLS in THF.

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A.F. Bella et al. / Journal of Organometallic Chemistry 693 (2008) 1269–1275
palladium catalytic precursors ½PdðMeÞðNCMeÞðN–N0Þꢀ
½BAr04ꢀ (1b–3b). When terpolymerization experiments were
carried out in dichloromethane, as reaction medium, the
productivities of all the complexes 1b–3b are modest and
do not exceed the value of 55 g PK/g Pd h, obtained with
complex 3b (Table 2, entries 1– 5). The effect of the nature
of the N–N ligand evidences increasing productivities going
from 1 (pzpm) to 2 (Mepzpm) and 3 (Brpzpm) containing
catalysts. On the other hand, Mn values significantly
decreased going from unsubstituted 1 (pzpm) to 2
(Mepzpm) and 3 (Brpzpm) (entries 1, 2 and 4). Variation
of the TBS/Pd ratio has not a significant influence on the
productivity and molecular weight values, in the case of
catalyst 2b (entries 2 and 3). An increment of the CO/E
pressure from 10 to 15 atm resulted in a better productivity
for the catalyst precursor 3b, indicating a positive depen-
dency on the CO/E pressure of the catalytic experiment
(entries 4 and 5), while almost no variation on the molecu-
lar weight and polydispersity was observed in this case.
Productivities were significantly affected by the nature of
the reaction medium as shown in Fig. 1. An increase in pro-
ductivity from 1.5 to 3 times was observed for the terpoly-
merization reaction in TFE, even though the reaction was
carried out in the absence of 1,4-benzoquinone as an oxi-
dant for the catalytic system [35]. The differences appear
reasonably pronounced, probably due to the high stability
of catalysts 1b–3b in TFE. These catalysts preserve their
activity for up to 24 h without decomposition in the
absence of an oxidant. Productivity as high as 125 g PK
(gPdꢁ1 hꢁ1) (Table 2, entry 6) was attained with the pre-
catalyst 2b. GPC analysis of the obtained terpolymers also
revealed differences on the molecular weights for the ter-
polymers obtained in fluorinated medium compared to
those in CH2Cl2. CO/ethylene/4-tert-butylstyrene terpoly-
mers with Mn values as high as 82,000 were obtained with
TFE (Table 2, entry 6). The enhancement of the length of
the polymeric chain indicates that the fluorinated alcohol
increase the ratio between the propagation and the termi-
nation rate which could give an evidence of a greater stabil-
ity of the active species in solution. The incorporation
degree of ethylene, [ethylene–CO] units, into the produced
terpolymers, was calculated by 1H NMR and resulted to be
much lower than the incorporation of 4-tert-butylstyrene,
[4-tert-butylstyrene–CO] units, due to a faster insertion of
the aromatic olefin than ethylene into the Pd–acyl bond.
Alkene insertion is the rate-determining step in the CO/
alkene polymerization reaction [2,36,37] and the preferred
coordination of the olefinic double bond is likely to depend
on the steric characteristics of the alkene [38] together with
the steric influence of the ligand coordinated to the palla-
dium centre. Bulkier ligands could increase activation ener-
gies of the olefin double bond coordination step, making
incorporation of small olefins particularly facile. The
higher incorporation of 4-tert-butylstyrene over ethylene
found for the cationic catalysts 1b–3b, could therefore be
ascribed to the modest steric hindrance offered from this
class of Cs symmetrical ligands. Additional analysis by
means of 13C NMR of the CO/TBS/E terpolymers showed
the signal of alternating CO/TBS copolymers together with
two added signals at 36.3 and 35.3 ppm corresponding to
the presence of CO/E units. Methylene carbons of tert-
butylstyrene give two signals at 43.2 and 45.4 ppm. The
former signal was attributed to the syndiotactic uu-triad
by comparison with literature values [17,18,34,39] which
indicates complete stereoregularity. The signal at
45.4 ppm was attributed to isolated CO/TBS units [19].
3. Conclusions
Cationic palladium(II) complexes of general formula
½PdMeðNCMeÞðN–N0Þꢀ½BAr40 ꢀ
containing
bisnitrogen
ligands of Cs-symmetry effectively promote CO/4-tert-
butylstyrene copolymerization and CO/ethylene/4-tert-butyl-
styrene terpolymerization. The corresponding polyketones
are obtained in high yield with a molecular weight up to
82,000 and polydispersities ranging between 1.3 and 1.7,
which are in the order of the best ones reported for Cs-bis-
nitrogen planar ligands using styrene derivatives [9]. Syn-
diotactic microstructure of CO/vinyl arene polyketones
was produced. High yields as well as enhanced growth of
the polymeric chain are observed when the reaction is
carried out in trifluoroethanol.
CH2Cl2
140
TFE
120
100
80
60
40
20
0
4. Experimental
4.1. General remarks
Chemicals and solvents were purchased from commer-
cial sources and were used as received unless otherwise sta-
ted. Reactions were carried out under inert atmosphere
(nitrogen), using standard Schlenk techniques. Solvents
were purified prior to use by conventional methods [40].
The ligands 1–3 [29,41], the palladium complexes
[28,30,42] and the NaBAr04 [43] salt were prepared accord-
CO/TBS/E 2b
CO/TBS/E 3b
Fig. 1. CO/styrene/ethene terpolymerization: effect of the catalyst pre-
cursor ½PdðMeÞðNCMeÞðN–N0Þꢀ½BAr04ꢀ, 2b and 3b, and of the solvent on
the productivity.

A.F. Bella et al. / Journal of Organometallic Chemistry 693 (2008) 1269–1275
1273
0
0
0
ing to reported methods. Carbon monoxide (CP grade
99.99%) was supplied by Air Liquide. The methylene chlo-
ride and chlorobenzene were used without further purifica-
tion for the copolymerization and terpolymerization
142.7 ðC3 Þ, 130.3 ðC5 Þ, 120.9 (C5), 99.3 ðC4 Þ, ꢁ5.1 (Pd–
CH3).
4.3. Synthesis of ½PdðMeÞðNCCH3Þð1–3Þꢀ½BAr0 ꢀ (1b–3b)
4
1
reactions. One and two-dimensional H, 13C {1H} NMR
spectra were recorded on a 300 MHz Varian Gemini spec-
trometer and on a Varian Mercury VX 400 MHz spectrom-
eter. Referencing is relative to TMS (1H and 13C). Samples
were prepared dissolving about 20 mg of compound in
0.5 mL of the deuterated solvent. The following abbrevia-
tions are used: s, singlet; d, doublet; t, triplet; q, quartet,
m, multiplet and br, broad. Unless specified the 13C reso-
nances are singlets. Chemical shifts are in ppm and cou-
pling constants (J) in Hz. Some assignments in NMR
4.3.1. ½PdðMeÞðNCCH3Þð1Þꢀ½BAr0 ꢀ (1b)
4
To a stirred solution of NaBAr04 (Ar0 = 3,5-(CF3)2C6H3)
(0.133 g, 0.15 mmol) in 3 mL of MeCN was added 3 mL of
a
previously prepared CH2Cl2 solution containing
[PdClMe(1)] (1a) (0.045 g, 0.15 mmol). The light yellow
solution obtained was stirred for 1 h and filtered through
celite to remove NaCl. The solvent was evaporated under
reduced pressure to leave an oil which was then extensively
washed with hexane, dissolved in a minimum amount of
dry dichloromethane and the solvent evaporated under
vacuum furnishing a yellow solid identified as the cationic
complex 1b, (0.150 g, 85%). Anal. Calc. for
C42H24BF24N5Pd: C, 43.05; H, 2.06; N, 5.98. Found: C,
1
spectra were determined by two-dimensional H-NOESY
techniques. 1H–13C g-HSQC spectra: standard pulse
sequence with an acquisition time of 0.1 s, pulse width
11 ms, relaxation delay 1 s, number of scans 8, number of
increments 256. Fourier Transform Infrared (FT IR) spec-
tra were recorded as Nujol mulls. Absorptions are reported
in wavenumbers (cmꢁ1). Elemental analyses were carried
out on a Carlo Erba Microanalyser EA 1108. The molecu-
lar weight and molecular weight distributions of the
obtained copolymers and terpolymers, were determined
by gel-permeation chromatography (GPC-MALLS).
1
43.17; H, 2.24; N, 6.09%. H NMR (400 MHz, CDCl3,
3
4
RT): dH 8.74 (dd, J = 4.8 Hz, J = 2.4Hz, 1H, H6), 8.57
(dd, 3J = 3.2 Hz, 4J = 0.8 Hz, 1H, H5 ), 8.33 (dd,
0
3J = 5.2 Hz, J = 2.4 Hz, 1H, H4), 7.84 (dd, J = 2.4 Hz,
4
3
4
0
J = 0.8 Hz, 1H, H3 ), 7.71 (s, 8H, Hb), 7.52 (s, 4H, Hd),
7.15 (t, 3J = 5.2 Hz, 1H, H5), 6.76 (dd, 3J = 3.2 Hz,
4
0
J = 2.4 Hz, 1H, H4 ), 2.32 (s, 3H, Pd–NCCH3), 1.3 (s,
3H, Pd–CH3). 13C {1H} NMR (100.5 MHz, CDCl3, RT)
4.2. Synthesis of [PdClMe(2–3)] (2a,3a)
dC 161.9 (q, JCB = 49.8 Hz, Ca), 161.6 (C6), 156.3 (C4),
0
0
156.0 (C2), 143.8 ðC3 Þ, 135.0 (Cb), 132.3 ðC5 Þ, 129.2 (m,
In a 25 mL Schlenk flask, 0.5 mmol of the correspond-
ing ligand 2–3, were dissolved in 10 mL of distilled and
degassed toluene, under a nitrogen atmosphere. To this
solution were added 5 mL of a previously prepared toluene
solution containing [PdClMe(cod)] (0.133 g, 0.5 mmol),
[ligand]/[Pd] = 1. The solution was stirred at room temper-
ature for 1 h. The yellow solid was filtered off, extensively
washed with diethylether and dried under vacuum to con-
stant weight.
Cc), 124.7 (q, JC–F = 272 Hz, Ce), 123.3 (Pd–NCCH3),
0
120.8 (C5), 117.7 (Cd), 111.2 ðC4 Þ, 3.2 (Pd–NCCH3),
ꢁ0.1 (Pd–CH3).
4.3.2. ½PdðMeÞðNCMeÞð2Þꢀ½BAr04ꢀ (2b)
Compound 2b was obtained in a similar way as
described for compound 1b as a yellow solid, (0.158g,
89%). Anal. Calc. for C43H26BF24N5Pd: C, 43.55; H,
2.21; N, 5.91. Found: C, 43.52; H, 2.24; N, 5.42%. 1H
3
NMR (400 MHz, CDCl3, RT): dH 8.69 (dd, J = 4.8 Hz,
4.2.1. [PdClMe(2)] (2a)
Yield: (0.152 g, 96%). Anal. Calc. for C9H11ClN4Pd: C,
34.09; H, 3.50; N, 17.67. Found: C, 33.82; H, 3.76; N,
4J = 2.4Hz, 1H, H6), 8.34 (dd, 3J = 5.6 Hz, 4J = 2.4 Hz,
0
0
H4), 8.31 (s, 1H, H5 ), 7.71 (s, 8H, Hb) 7.65 (s, 1H, H3 ),
7.53 (s, 4H, Hd), 7.15 (t, 3J = 5.2 Hz, 1H, H5) 2.28 (s,
3H, Pd–NCCH3), 2.18 (s, 3H, CH3-pz), 1.23 (s, 3H,
Pd–CH3). 13C {1H} NMR (100.5 MHz, CDCl3, RT) dC
161.9 (q, JCꢁB = 49.4 Hz, Ca), 161.5 (C6), 156.3 (C4),
1
17.08%. H NMR (400 MHz, CD2Cl2, RT): dH 8.93 (dd,
4
3
3J = 5.2 Hz, J = 2.4 Hz, 1H, H6), 8.77 (dd, J = 4.8 Hz,
4
0
0
J = 2.4 Hz, H4), 8.31 (s, 1H, H5 ), 7.66 (s, 1H, H3 ), 7.38
(t, 3J = 5.2 Hz, 1H, H5), 2.19 (s, 3H, CH3-pz), 0.99 (s,
3H, Pd–CH3).13C {1H} NMR (100.5 MHz, CD2Cl2) dC
0
0
155.9 (C2), 144.5 ðC3 Þ, 135.0 (Cb), 130.2 ðC5 Þ, 129.2 (m,
Cc), 124.7 (q, JC–F = 272 Hz, Ce), 122.4 (Pd–NCCH3),
0
0
0
160.3 (C6), 157.3 (C4), 143.4 ðC3 Þ, 128.8 ðC5 Þ, 121.8
121.0 ðC4 Þ 120.3 (C5), 117.8 (Cd), 9.2 (CH3-pz), 3.0
0
ðC4 Þ, 120.3 (C5), 9.5 (CH3-pz), ꢁ7.0 (Pd–CH3).
(Pd–NCCH3), ꢁ0.51 (Pd–CH3).
4.2.2. [PdClMe(3)] (3a)
Yield: (0.175 g, 92%). Anal. Calc. for C8H8BrClN4Pd:
C, 25.16; H, 2.11; N, 14.67. Found: C, 25.78; H, 2.24; N,
4.3.3. ½PdðMeÞðNCMeÞð3Þꢀ½BAr04ꢀ (3b)
Compound 3b was obtained in a similar way as
described for compound 1b as a brownish solid, (0.156 g,
83%). 1H NMR (400 MHz, CDCl3, RT): dH 8.71 (dd,
1
14.13%. H NMR (400 MHz, CDCl3, RT): dH 9.11 (dd,
3J = 5.2 Hz, 4J = 2.4Hz, 1H, H6), 8.85 (dd, 3J = 4.8 Hz,
J = 4.8 Hz, J = 2.4Hz, 1H, H6), 8.61 (s, 1H, H5 ), 8.36
3
4
0
4
3
4
0
0
0
J = 2.4 Hz, H4), 8.63 (s, 1H, H5 ), 7.85 (s, 1H, H3 ), 7.50
(t, 3J = 4.8 Hz, 1H, H5), 1.21 (3H, Pd–CH3).13C {1H}
NMR (100.5 MHz, CDCl3) dC 160.0 (C6), 157.5 (C4),
(dd, J = 5.2 Hz, J = 2.4 Hz, H4), 7.82 (s, 1H, H3 ), 7.70
(s, 8H, Hb) 7.52 (s, 4H, Hd), 7.19 (t, J = 5.2 Hz, 1H, H5)
3
2.28 (s, 3H Pd–NCCH3), 1.29 (s, 3H, Pd–CH3). 13C {1H}

1274
A.F. Bella et al. / Journal of Organometallic Chemistry 693 (2008) 1269–1275
NMR (100.5 MHz, CDCl3, RT) dC 161.9 (q,
JCꢁB = 49.7 Hz, Ca), 161.7 (C6), 156.6 (C4), 156.1 (C2),
stirrer, heating mantle and temperature controller. After
treating a solution of ½PdðMeÞðNCMeÞð1–3Þꢀ½BAr04ꢀ in
CH2Cl2 (15 mL) with bubbling CO (1 atm), 4-tert-butylsty-
rene was added, and the mixture immediately transferred
into a 100 mL stainless steel Berghoff autoclave previously
purged with a CO/E mixture. The reaction mixture was
then pressurized at the desired level and stirred for 24 h
before releasing unreacted gases. The resulting mixture
was filtered through Kieselghur and successively added
into 100 mL of rapidly stirred methanol to precipitate
poly{ethylene; 4-tert-butylstyrene)-alt-CO}.
0
0
144.3 ðC3 Þ, 135.0 (Cb), 132.1 ðC5 Þ, 129.1 (m, Cc), 124.7
(q, JC–F = 272.1 Hz, Ce), 122.3 (s, Pd–NCCH3), 121.24
0
(C5), 117.8 (Cd), 100.2 ðC4 Þ, 3.1 (Pd–NCCH3), 0.53 (s,
Pd–CH3).
4.4. Copolymerization of 4-tert-butylstyrene with carbon
monoxide
The 4-tert-butylstyrene was passed through a small col-
umn of Al2O3 prior to use. Chlorobenzene or TFE were
used as purchased from Aldrich. The cationic precursors
1b–3b (0.0125 mmol) were dissolved in 5 mL of chloroben-
zene or TFE in a previously flushed Schlenk and the N2
atmosphere replaced with CO, bubbling through the solu-
tion (5 min), 4-tert-butylstyrene was then introduced and
the reaction was allowed to take place at r.t. and 1 bar of
CO. Reaction time was 24 h. Work-up included filtration
of the reaction mixture through Kieselghur and precipita-
tion of the polymeric material by adding the reaction solu-
tion dropwise into 100 mL of rapidly stirring methanol.
The off-white powder was collected by filtration, washed
with methanol and dried in vacuum overnight. Productivi-
ties were calculated from the weight of the isolated poly-
meric material.
4.7. Terpolymer characterization (obtained by using
½PdðMeÞðNCMeÞð3Þꢀ½BAr04ꢀ (3b) precatalyst)
1H NMR (400 MHz, CDCl3, RT): dH 7.41–7.15 (aro-
matic), 4.20 [bs, –CH(Ar)–CH2–C(O)–], 3.10 [bs,
–
CH(Ar)CHH–C(O)–], 2.51 [–CH(Ar)CHH–C(O)– and –
CHH–CHH–C(O)–], 1.27 [bs, C(CH3)3]; 13C{1H} NMR
(100.5 MHz, CDCl3, RT) dC 206.9 (–CO–), 149.8 (Cd),
134.6–134.2 (Ca), 128.2–127.5 (Cc), 125.6–124.8 (Cb), 52.9
(CH), 45.3–43.3 (–CH(Ar)–CH2–C(O)–], 36.2 (CH2–CH2–
C(O)–E), 35.4[–CH2-CH2C(O)–TBS], 34.6 (C(CH3) 31.5
(C(CH3). IR (nujol, cmꢁ1): 1705(C@O), 1459, 1375.
O
*
m
n
H
O
4.5. Copolymer characterization (obtained by using
½PdðMeÞðNCMeÞð3Þꢀ½BAr04ꢀ (3b) precatalyst)
1H NMR (400 MHz, CDCl3, RT): dH 2.92 (d,
3
3J = 7.68 Hz, 2H, Hb or Hc), 6.50 (d, J = 7.68 Hz, 2H,
2
3
Hc or Hb), 4.03 (m, 1H, CH) 2.92 (dd, J = 18.3, J = 7.3
4.8. Molecular weight measurement
2
3
H, 1H, CH2), 2.54 (dd, J = 18.3, J = 7.3 H, 1H, CH2),
1.14 (s, 9H, C(CH3). 13C {1H} NMR (100.5 MHz, CDCl3,
RT) dC 206.9 (–CO–), 149.8 (Cd), 134.3 (Ca), 128.2(Cc),
125.6 (Cb), 52.9 (CH), 43.2 (CH2), 34.5 (C(CH3)), 31.5
(C(CH3).
Before measuring the molecular weight, the CO/styrene
polyketones were treated as follows: The copolymer
(1.00 g) was stirred in ethyl acetate (50 mL) for 4 h. After
filtration it was stirred with diethyl ether (25 mL) for 2 h.
The solid was filtered and vacuum-dried. The copolymers’
molecular weights (Mw) and molecular weight distributions
(Mw/Mn) were determined by gel permeation chromatogra-
phy vs. polystyrene standards. The analyses were per-
formed by gel-permeation chromatography (GPC-
MALLS), measurements made in THF on a Waters 515
gel-permeation chromatography device using a lineal
Waters Ultrastyragel column with a Waters 2410 refractive
index detector vs. polystyrene standards. The CO/styrene
copolymers were dissolved as follows: 42 mg of each sam-
ple were solubilized in 5 mL of THF.
O
*
*
α
δ
n
β
γ
4.6. Terpolymerization of 4-tert-butylstyrene/ethylene/
carbon monoxide
Acknowledgements
The 4-tert-butylstyrene was passed through a small col-
umn of Al2O3 prior to use. Distilled dichloromethane or
TFE, as purchased from Aldrich, were used as the solvent.
The reactions were carried out in a stainless steel Berghoff
autoclave (150 mL), equipped with a teflon liner, magnetic
Thanks are due to the European Network ‘‘PALLA-
DIUM” 5th Framework Program (Contract No.HPRN-
CT-2002-00196) for financial support and for grant. The

A.F. Bella et al. / Journal of Organometallic Chemistry 693 (2008) 1269–1275
1275
(c) A. Bastero, A. Ruiz, C. Claver, S. Castillon, E. Daura, C. Bo, E.
Zangrando, Chem. Eur. J. 21 (2004) 3747.
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COST D-17 Action and the Spanish DGES/MCyT
(CTQ2005-01430/BQU) project are acknowledged.
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