Neutral and cationic dendritic palladium(II) complexes containing N,N′-iminopyridine chelating ligands. synthesis and their use for the syndiospecific copolymerization of CO/4-tert-butylstyrene

Article abstract of DOI:10.1021/om0601044

Series of neutral and cationic palladium carbosilane dendritic compounds of the general formula Gn-ONNMe_m[Pd(X)Y] (X, Y = Cl; X = Me, Y = Cl; X = Me, Y = MeCN), containing 4 (n = 1), 8 (n = 2) or 16 (n = 3) terminal pyridylimine complexes, substituted with m methyl groups (m = 0, 2, 3), along with the corresponding monometallic counterparts (n = 0), have been synthesized. Monometallic or dendritic chloro methyl or cationic methyl palladium compounds consist of a cis/trans mixture of diastereoisomers, with compositions according to their electronic and steric features. The cationic compounds Gn-ONNMe _m[PdMe(MeCN)]⁺ are found to be active catalysts for the alternating copolymerization of CO and 4-tert-butylstyrene, producing mainly syndiotactic polyketones due to a chain-end stereocontrolled mechanism. Modification of the pyridylimine ligand framework by methyl substituents has a decisive influence on the activities of the palladium compounds. Some of them are found to retain some activity after several days of catalytic reaction. Also, the size (i.e., generation n) of the dendritic precursor affects the catalyst performance and the microstructure of the copolymerization products. Thus, higher generation catalysts show superior activities and produce shorter and less stereoregular copolymer chains.

Full text of DOI:10.1021/om0601044

Organometallics 2006, 25, 3045-3055
3045
Neutral and Cationic Dendritic Palladium(II) Complexes Containing
N,N′-Iminopyridine Chelating Ligands. Synthesis and Their Use for
the Syndiospecific Copolymerization of CO/4-tert-Butylstyrene†
Jose´ M. Benito, Ernesto de Jesu´s,* F. Javier de la Mata, Juan C. Flores,* and Rafael Go´mez
Departamento de Qu´ımica Inorga´nica, UniVersidad de Alcala´, Campus UniVersitario,
28871 Alcala´ de Henares, Madrid, Spain
ReceiVed February 2, 2006
Series of neutral and cationic palladium carbosilane dendritic compounds of the general formula Gn-
ONNMem[Pd(X)Y] (X, Y ) Cl; X ) Me, Y ) Cl; X ) Me, Y ) MeCN), containing 4 (n ) 1), 8 (n )
2) or 16 (n ) 3) terminal pyridylimine complexes, substituted with m methyl groups (m ) 0, 2, 3), along
with the corresponding monometallic counterparts (n ) 0), have been synthesized. Monometallic or
dendritic chloro methyl or cationic methyl palladium compounds consist of a cis/trans mixture of
diastereoisomers, with compositions according to their electronic and steric features. The cationic
compounds Gn-ONNMem[PdMe(MeCN)]+ are found to be active catalysts for the alternating copolym-
erization of CO and 4-tert-butylstyrene, producing mainly syndiotactic polyketones due to a chain-end
stereocontrolled mechanism. Modification of the pyridylimine ligand framework by methyl substituents
has a decisive influence on the activities of the palladium compounds. Some of them are found to retain
some activity after several days of catalytic reaction. Also, the size (i.e., generation n) of the dendritic
precursor affects the catalyst performance and the microstructure of the copolymerization products. Thus,
higher generation catalysts show superior activities and produce shorter and less stereoregular copolymer
chains.
show the best performance in CO/aromatic olefin copolymeriza-
tion.5-9 The polyketones obtained are characterized by chemo-
regularity, in the sense that their propagation occurs by perfect
alternation of olefin and CO comonomers. The process is also
regioregular in copolymerization reactions involving styrenes,
because the secondary migratory insertion of Pd-acyl into the
aromatic olefin produces electronically stabilized benzylic
intermediates. Besides, the polymer stereoregularity can be tuned
by the choice of the ligand. Planar achiral precursors (C2V or Cs
Introduction
Sen1 established in 1982 that the use of cationic complexes
with weakly coordinating anions and phosphine ligands im-
proved the stability and activity of palladium catalysts in ethene/
CO copolymerization. Afterward, the studies carried out by
Drent2 on cationic palladium complexes containing chelating
bidentate diphosphine ligands made the commercial production
of aliphatic polyketones economically attractive. The work of
Drent, together with the contributions of Brookhart and others,3
highlighted the role of late-transition-metal catalysts based on
cationic complexes with multidentate ligands in olefin homo-
and copolymerization. For example, such catalysts can be highly
active in novel copolymerization reactions, such as those of
olefins with functionalized polar comonomers (e.g., acrylates),4
or in perfect alternating copolymerization of carbon monoxide
and olefins to give high-molecular-weight polyketones.5,6
Whereas palladium(II) catalysts with bidentate phosphorus-
donor chelating ligands are efficient in CO/aliphatic olefin
copolymerization, those with bidentate nitrogen-donor chelates
(5) (a) van Leeuwen, P. W. N. M. Homogeneous Catalysis. Understand-
ing the Art; Kluwer Academic: Dordrecht, The Netherlands, 2004; p 239.
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and Cooligomers; Kluwer Academic: Dordrecht, The Netherlands, 2003.
(c) Drent, E.; van Broekhoven, J. A. M.; Budzelaar, P. H. M. In Applied
Homogeneous Catalysis with Organometallic Compounds; Cornils, B.,
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* To whom correspondence should be addressed. E-mail:
ernesto.dejesus@uah.es (E.d.J.); juanc.flores@uah.es (J.C.F.). Tel.: +34
91 885 4603 (E.d.J.); +34 91 885 4607 (J.C.F.). Fax: +34 91 885 4683.
† Dedicated to Prof. Jose´ Antonio Abad on the occasion of his retirement.
(1) (a) Sen, A.; Lai, T.-W. J. Am. Chem. Soc. 1982, 104, 3520. (b) Sen,
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10.1021/om0601044 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 05/10/2006

3046 Organometallics, Vol. 25, No. 12, 2006
Benito et al.
Chart 1
symmetry) give highly syndiotactic polyketones due to chain-
end control produced by the interaction of the growing chain
with the incoming styrene comonomer,7,8 while C2-symmetric
chiral catalysts provide an enantiomorphic site-controlled
propagation and give isotactic microstructures.9 Additionally,
chiral C1-symmetric active compounds, containing N,N′-unsym-
metrical ligands, yield syndiotactic or isotactic copolymers, since
the influences of chain-end and site controls are in a sensitive
equilibrium.8 Even though P,N8b or P,O10 chelates have been
applied successfully to copolymerize styrenes, most of the
reported catalysts contain N,N-symmetrical or N,N′-unsym-
metrical related donor ligands, such as bipyridine, phenanthro-
line, pyridine-pyrazole, pyridine-oxazoline, and pyridine-
imidazoline.
Unsymmetrical N,N′-pyridylimine-type compounds have been
used as catalysts in ethylene polymerization reactions with group
10 metals11 or applied in solid-phase organometallic synthesis
and radical polymerization with molybdenum and copper
complexes,12 respectively. On the other hand, there are in the
literature a few reports describing CO/styrene copolymerization
reactions using N,N′-alkylpyridylimine palladium(II) com-
pounds.13
lane dendrimers containing early-transition-metal complexes
bonded to the dendritic periphery or focal point, usually through
O- or N-donor anchoring ligands.17,18 In our study of the
catalytic performance in ethylene polymerization of nickel(II)
complexes coordinated to carbosilane dendrimers through the
pyridylimine ligands Ia-c (Chart 1), we found that the
microstructure and oligomer/polymer product distribution are
significantly affected by the size of the dendritic precursor.19
Since dendritic moieties bring about distinctive catalytic envi-
ronments, and the CO/styrene copolymerization reaction is
sensitive to the active site surroundings, we decided to extend
and explore the capacity of metallodendrimer chemistry into
this type of process. This paper describes the synthesis,
characterization, and performance, as catalyst precursors for CO/
4-tert-butylstyrene copolymerization, of different neutral and
cationic palladium-pyridylimine-ended carbosilane dendrimers,
as well as monometallic model complexes. The influence of
the dendrimer generation on the catalytic results has been
analyzed. Dendrimers containing PdCl2 or PdClMe substituents
anchored at their periphery by bidentate chelate ligands have
been previously reported.20
Metallodendrimer research has been steadily gaining ground
during the past few years, and a considerable number of
dendritic macromolecules containing transition metals at their
core, branches, or periphery14 have been prepared for use in
metal-based catalysis,15 including oligomerization and polym-
erization.16,17 We have contributed to the chemistry of carbosi-
Results and Discussion
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Palladium Dendrimers Copolymerizing CO/Styrene
Organometallics, Vol. 25, No. 12, 2006 3047
Scheme 1
soluble in toluene and ethers, and insoluble in alkanes, whereas
1a is only partially soluble in dichloromethane. Compounds 2
are fairly soluble in ethers and aromatic or chlorinated solvents,
although slow conversion to compounds 1 together with
decomposition to black Pd(0) was observed in the last class of
solvents.21 Attempts to prepare complexes 2 by methylation of
1 with 1 equiv of LiMe or SnMe4 led to impure chloro methyl
compounds 2 with the formation of much metallic palladium.
The cationic methyl acetonitrile complexes 3 were readily
obtained in acetonitrile by the abstraction of the chloro ligand
in 2 with Na[BArf4] (BArf4 ) 3,5-(CF3)2C6H3) (Scheme 1).
These cationic compounds are air-stable, hygroscopic orange-
yellow solids, soluble in common organic solvents but not in
alkanes.
The new compounds have been characterized by NMR, IR,
MS, and elemental analysis (see Experimental Section). Com-
plexes 2a and 3a,b consisted of a mixture of diastereoisomers,
designated cis or trans with regard to the relative positions of
the methyl and imine groups on the square-planar palladium
environment (Figure 1). The assignment of NMR resonances
is favored for 2c and 3c because of the steric hindrance caused
by the methyl substituent in the ortho position of the pyridine
ring.24
The proton and carbon atom signals of the pyridylimine
groups undergo large shifts in the NMR spectra of compounds
1-3 in comparison with the NMR data observed for ligands I
(see Supporting Information).19 The general remark is that proton
and carbon resonances shift to lower field on complexation, as
might be expected for a lowering in electron density of the N,N
ligands.25 The most affected chemical shifts are those due to
the imine group and the pyridine ring, in a phenomenon termed
the CIS effect (CIS ) coordination-induced shift).24 The
remarkable negative CIS effect observed for H9 (∆δ = -0.4)
and H7 (∆δ = -0.3) (the numbering scheme for the py-
ridylimine fragment is given in Chart 1) is explained by the
fact that the transoid conformation of the free ligands I in
solution12a changes to cisoid by coordination to the metal center
(Scheme 1).11b,24 Conversely, in compounds 1 and cis-2 (Figure
1), H12 (or CH315) shows the largest coordination shifts (∆δ =
+0.6), owing to the strong deshielding effect of the chloro ligand
cis to the pyridyl ring. On the other hand, the chemical shifts
of the Pd-Me, H12, and the imine proton (H7) are at δ 1.2,
8.63, and 8.31, respectively, for trans-2a, whereas they are at
δ 0.77, 9.10, and 8.35, respectively, for cis-2a with the Pd-
Me group closer to the shielding aromatic ring and with the
electron-withdrawing and deshielding chloro ligand trans to the
1
imine group. The H, 13C, and 19F NMR data of the [BArf4]-
counterion are invariable for compounds 3, in correspondence
with a noncoordinating anion. The proton NMR spectra of these
cationic complexes in CD3CN show free acetonitrile resonances,
indicating exchange between the free and coordinated solvent.
Figure 1. Diatereoisomeric composition for compounds 2 and 3.
Mass spectra (EI/MS) for compounds 1-3 show the corre-
sponding bidentate ligand ion peak I. The positive ion electro-
spray mass spectra (ESI+/MS) of compounds 1 and 2, carried
out in acetonitrile solutions, exhibit the fragments after the loss
of a chloride anion and coordination of an acetonitrile molecule
[M - Cl + MeCN]+ and peaks due to dimetallic species formed
by chloro bridges [M2 - Cl]+ (i.e., [{PdX(I)}2(µ-Cl)], X ) Cl,
Me). The formation of both types of species has been reported
to each isomer is based on the nuclear Overhauser effect
measured between the 1H resonances of the Pd-Me group and
the pyridylimine protons. The integration of those methyl
resonances, at ca. 1 ppm, also was used for the determination
of the cis/trans composition shown in Figure 1. The different
diastereoisomer ratios observed in solution can be rationalized
by a combination of steric and electronic arguments. Thus, cis
isomers are favored for chloro complexes 2, following Pearson’s
maximum hardness principle,22 according to which the hardest
part of the pyridylimine ligand, i.e., the imine group, is placed
preferably trans to the softest ligand, i.e., the methyl group in
3 and the chloro group in 2.23 On the other hand, the cis isomer
(23) (a) Meneghetti, S. P.; Lutz, P. J.; Kress, J. Organometallics 1999,
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(22) Pearson, R. G. J. Chem. Educ. 1999, 76, 267.

3048 Organometallics, Vol. 25, No. 12, 2006
Benito et al.
Scheme 2
to occur in related nickel and palladium complexes.26 The cation
parent ion peak [M - BR4]+ is observed for compounds 3 by
ESI+/MS.
yellow to orange diamagnetic air-stable solids. Subsequent
addition of Na[BArf4] to the chloro(methyl)palladium dendri-
mers 5b-7b in acetonitrile gave Gn-ONNMe2[PdMe(MeCN)]
(n ) 1, 8b; n ) 2, 9b; n ) 3, 10b), obtained as air-stable orange
solids that become sticky oily solids in the presence of moisture
or vapors of organic solvents.
The IR spectra of compounds 1 and 2 show a single medium
to strong absorption at ca. 1589-1596 cm-1, together with a
much weaker band, instead of the group of three intense
absorptions observed in the range 1565-1627 cm-1 for the
imine and pyridine groups in the free ligands I.19 The disap-
pearance or shift of CdN vibrations in the IR spectra of related
complexes is explained as a result of the bonding of the
pyridylimine ligand to the metal center, reducing the electron
density in the CdN bond and, consequently, leading to a lower
An important issue related with metallodendrimers is their
solubility. Peripheral polymetallic dendrimers are often less
soluble as the number of metal centers increases, and this feature
habitually renders impracticable the preparation of high-
generation derivatives wholly metalated at their terminal
functional groups. Compounds 4-10 are more soluble when
the dendrimer generation is lower, the pyridylimine group bears
more methyl substituents, the palladium metal is methylated,
or the complex is cationic. Accordingly, the dichloro derivatives
4a,b precipitate out from the CH2Cl2 solution during their
preparation and are found to be only moderately soluble in very
polar organic solvents such as DMSO. A similar behavior has
been described for an alkylpyridylimine palladium derivative
based on a first-generation poly(propyleneimine) dendrimer
(DAB).27 This lack of solubility explains why the dichloropal-
ladium dendrimers were prepared only in the first generation.
Surprisingly, attempts to synthesize compound 4c failed, giving
a mixture of inseparable products.
ν
CdN value.11b A single absorption appears at 1610 cm-1 in the
cationic compounds 3, probably due to the presence of the harder
donor character of acetonitrile compared to that of the chloro
ligand.
Synthesis and Characterization of Dendrimers. The py-
ridylimine ligands described above have been used to link
carbosilane dendrimers and metal complexes by procedures
similar to those applied in the preparation of complexes 1-3.
Thus, neutral and cationic polymetallic dendrimers of first to
third generations containing 4, 8, or 16 dichloro, chloro methyl,
or methyl acetonitrile palladium complexes at their periphery
were prepared from the dendritic pyridylimine ligands G1-
ONNMem (II), G2-ONNMem (III), and G3-ONNMem (IV)
(Scheme 2 and Figure 2). The neutral dendrimers G1-ONNMem-
[PdCl2] (4a,b) and Gn-ONNMem[PdClMe] (n ) 1, 5b,c; n )
2, 6b,c; n ) 3, 7b,c) were obtained by reaction of II-IV and
[PdCl2(COD)] or [PdClMe(COD)] in CH2Cl2, and isolated as
The solubility of these systems is significantly enhanced when
methyl groups are present on the pyridylimine ligands and on
each palladium center and when an acetonitrile molecule is
coordinated to cationic metal centers. Thus, neutral chloro-
(methyl)- and cationic methyl(acetonitrile)palladium dendrimers,
which are soluble in dichloromethane, THF, or acetonitrile and
(26) (a) Wilson, S. R.; Wu, Y. Organometallics 1993, 12, 1478. (b) Sen,
H.; Jordan, R. F. Organometallics 2003, 22, 1878. (c) Foley, S. R.; Sen,
H.; Qadeer, U. A.; Jordan, R. F. Organometallics 2004, 23, 600.
(27) Smith, G.; Chen, R.; Mapolie, S. J. Organomet. Chem. 2003, 673,
111.

Palladium Dendrimers Copolymerizing CO/Styrene
Organometallics, Vol. 25, No. 12, 2006 3049
Figure 2. Metallodendrimers 7b and 9b.
slightly soluble in diethyl ether or toluene were readily
synthesized not only in the first generation (5 and 8) but also
in the second (6 and 9) and third generations (7 and 10). As
pointed out for the monometallic complexes, solutions of these
compounds in chlorinated solvents slowly decompose by Pd-
Me/Pd-Cl exchange, and black Pd(0) becomes visible after
about 24 h.
increasing the generation28 is favored in the cationic dendrimers
by the positive charge that repels the metal centers from each
other in a radial-spherical mode, contributing to restrict the
mobility of the dendrimer arms. In fact, very complex and
inscrutable 13C NMR spectra were registered for the second-
and third-generation derivatives 9 and 10.
The IR spectra of all metallodendrimers 4-10 are also
consistent with coordination of the pyridylimine groups, showing
a strong absorption at ca. 1589-1596 cm-1 for neutral
compounds 4-7 and at ca. 1610 cm-1 for the cationic
dendrimers 8-10, instead of the group of three intense absorp-
tions observed in the range 1565-1627 cm-1 for the corre-
sponding free dendritic ligands II-IV.19
CO/4-tert-Butylstyrene Catalyses using (Pyridylimine)-
palladium Compounds. Compounds 3 and polycationic den-
drimers 8b-10b were used as single-component catalysts for
the copolymerization of carbon monoxide and 4-tert-butylsty-
rene (TBS), under the same mild conditions using the same
concentration of palladium centers; the results are summarized
in Table 1. Alternatively, cationic active species were generated
in situ from the chloro(methyl)palladium compounds 2 and 5c
using Na[BArf4] in the presence of acetonitrile.
As shown in Table 1, all the catalysts produced polyketone,
with the exception of precursors with a methyl group on the
12-position of the pyridine ring (2c and 5c activated with Na-
[BArf4]/MeCN and 3c). According to earlier findings with
related complexes, the presence of a methyl substituent ortho
to the coordinating N atom of the pyridine causes enough
hindrance to encumber either the CO insertion or the coordina-
tion-insertion of the substrate.7c,8 Also, an interference effect
attributable to an excess of competing acetonitrile must be
responsible for lower activities when the cationic species are
prepared in situ, in comparison to the observed behavior for
the isolated cationic compounds (entries 1 and 2 vs entries 4
and 5). The productivities of the active catalysts ((0.3-2.6) ×
103 g of copolymer (mol of Pd)-1 h-1) are comparable to those
found for other precursors containing different N,N ligands.8,9
Additionally, the productivity increases in reactions carried out
in neat TBS, in the absence of CH2Cl2 (compare entries 5 vs 7
or 9-11 vs 12-14), in agreement with the generally accepted
copolymerization mechanism with styrene insertion as the rate-
determining step.6,7e Degradation of the catalysts is evident in
Palladium dendrimers have been characterized by NMR and
IR spectroscopy. However, mass spectrometric techniques,
including MALDI-TOF, were not informative. Elemental analy-
ses were satisfactory for the metallic dendrimers, with the
exception of those for the third-generation neutral complexes
7b,c and polycationic compounds 9b and 10b, which are slightly
low in the percent of C, most likely due to persistent trapping
of some impurities in the dendritic matrix. The broad charac-
teristics of the 1H and 13C{1H} NMR spectra of the carbosilane
framework in dendrimers 4-10 are almost identical with those
described for the metal-free dendrimers,19 whereas chemical
shifts of the terminal pyridylimine groups are comparable with
those found for the model complexes 1-3 and, therefore, CIS
effects are parallel to those described above for mononuclear
complexes. Accordingly, in general the most affected protons
are H12 (∆δ = +0.3 for dichloropalladium dendrimers 4a,b and
15
chloro(methyl)palladium dendrimers 5b-7b) and CH3 (∆δ
= +0.4 for dendrimers 5c-7c), due to the presence of a chloro
ligand cis to the pyridyl ring, and the H12 CIS effect becomes
negative for the cationic dendrimers 8b-10b, with acetonitrile
instead of chloro ligands (∆δ = -0.4). Again, H9 and H7 shift
to higher field (∆δ ranging from -0.1 to -0.5 ppm) in all
metallodendrimers because the free ligands rotate to a cisoid
conformation to coordinate to a metal center.
The isomer composition (cis:trans ratio) in dendrimers 5-10
also follows a behavior parallel to that observed for the related
mononuclear complexes. Thus, only the cis isomer is observed
by NMR for the chloro(methyl)palladium dendrimers 5b,c, 6b,c,
and 7b,c, as was observed for the monometallic complexes 2b,c.
Diastereoisomer ratios for cationic dendrimers 8b-10b are
difficult to discern, because their spectra show broad and
overlapped resonances of the isomers. Nevertheless, we estimate
a cis:trans ratio of about 40:60, as judged by the result described
for the reference cationic complex 3b and by the relative integral
of H12, which appears clearly defined for each isomer in the
NMR spectra of polycationic dendrimers. The typical broadened
and unstructured NMR resonances observed for dendrimers on
(28) Lorenz, K.; Mu¨lhaupt, R.; Frey, H.; Rapp, U.; Mayer-Posner, F. J.
Macromolecules 1995, 28, 6657.

3050 Organometallics, Vol. 25, No. 12, 2006
Benito et al.
Table 1. CO/TBS Copolymerization Catalyzed by Complexes 2 and 3 and Pd Dendrimers 5c and 8b-10ba
h
entry
precursor
CP yield (g)d
activitye
% conversnf
% s-CPg
g of CP/mol of Pd
Mw
PDIh
1
2
3
4
5
2ab
2bb
2cb
3a
0.095
0.130
0.31
0.43
6.6
8.9
64
70
7 600
10 400
n.d.i
n.d.i
n.d.i
n.d.i
0.130
0.243
0.43
0.81
8.9
16.7
66
71
10 400
19 440
4633
18 293
1.70
2.12
3b
6
7
3c
3bc
0.543
1.81
20.9
60
43 440
79 733
2.87
8
9
5cb (G1-ONNMe3[Pd(Cl)Me])
8b (G1-ONNMe2[Pd(L)Me]+)
9b (G2-ONNMe2[Pd(L)Me]+)
10b (G3-ONNMe2[Pd(L)Me]+)
8bc (G1-ONNMe2[Pd(L)Me]+)
9bc (G2-ONNMe2[Pd(L)Me]+)
10bc (G3-ONNMe2[Pd(L)Me]+)
3bc,j
0.100
0.099
0.164
0.729
0.750
0.792
0.720
1.005
0.33
0.33
0.54
2.43
2.50
2.64
0.60
0.84
6.8
6.8
70
67
66
66
64
63
60
60
8 000
7 920
22 282
11 320
20 741
53 937
43 583
38 775
82 951
42 702
1.80
1.56
2.70
2.79
3.00
3.64
2.77
3.45
10
11
12
13
14
15
16
11.2
28.1
28.9
30.6
28.5
39.1
51 200
58 320
60 000
63 360
57 600
80 400
9bc,j (G1-ONNMe2[Pd(L)Me]+)
a Copolymerization conditions: 5 mL of dichloromethane; n(Pd) ) 12.5 µmol; V(TBS) ) 1.4 mL; n(TBS)/n(Pd) ) 620; tp ) 24 h; Tp ) 20 °C; PCO
1 atm. b Activated in situ by addition of 1 equiv of Na[BArf4] in a CH2Cl2/MeCN mixture. c Same conditions but in neat TBS: V(TBS) ) 2.5 mL; n(TBS)/
)
n(Pd) ) 1100. d CP ) copolymer. e In untis of kg of CP (mol of Pd)-1 h-1 f TBS conversion calculated from the CP weight. g Percent of syndiotactic triads
.
(uu) determined from 13C NMR intensities of ipso carbon atom resonances. h Determined by GPC in THF at 40 °C. i Not determined. j tp ) 96 h.
Figure 4. Effect of time on yield of copolymer produced by
compounds Gn-ONNMe2[Pd(L)Me]+ in neat TBS.
transfer process is accompanied, in most cases, by decomposi-
tion of the active centers (e.g., reduction of unstable Pd(II)
hydride species formed by â-H elimination).6 Some workers
overcame this problem by including quinones, combined with
a protic solvent, in the catalytic system.8 Metallic palladium(0)
appeared in suspension after 24 h of reaction time with
compounds 2-10, although for compounds “b” the initial color
Figure 3. (a) Activities for Gn-ONNMe2[Pd(MeCN)Me+] and (b)
copolymer Mw values obtained using neat TBS as a solvent.
of their solutions (yellow-orange) remains very intense, as a
sign of catalyst endurance. More copious precipitation of black
particles was observed in the reactions carried out in CH2Cl2
as compared to those in neat TBS. Faster deactivation of the
catalysts induced by the solvent, through Pd-C/Pd-Cl bond
exchange and Pd(0) formation, might help in the above-noted
decrease of productivity in CH2Cl2.21 Analyses of the evolution
of yields over a 96 h period in neat TBS (Figure 4) or CH2Cl2
using monometallic complex 3b and dendrimers 8b-10b show
apparently that the dendritic supports have no noticeable effect
on the lifetime of the active species. Therefore, the reverse
activity shown by monometallic versus dendritic catalysts in
neat TBS and CH2Cl2 is more likely to be caused by the different
rates of the insertion steps than by catalyst degradation. It is
well-known that adaptation of the dendritic conformation to the
polarity of the solvent can lead to changes in the catalytic
behavior.29 On the other hand, it is remarkable that activities
seem to stabilize after 24 h, and their values are, 4 days later,
all of the polymerizations, by the appearance of some metallic
palladium over the course of the reaction, and solutions become
very viscous in neat aromatic monomer as a solvent.
Among the mononuclear compounds, the most active precur-
sors are those containing methyl substituents on the aryl ring
(compounds “b”, entry 1 vs 2 or entry 4 vs 5). A parallel result
was found in ethylene polymerization reactions with analogous
nickel compounds activated with MAO.19b In CH2Cl2, the
cationic dendrimers are less active than the corresponding
monometallic derivative (entries 5 and 9-11), but the opposite
trend is observed in neat TBS, where a slight increase of the
productivity is additionally observed with the generation of the
dendrimer, giving the third-generation dendrimer 10b the highest
conversion (Table 1, Figure 3a).
An important aspect of these types of catalysts is their stability
or durability under catalytic conditions, because the chain

Palladium Dendrimers Copolymerizing CO/Styrene
Organometallics, Vol. 25, No. 12, 2006 3051
about 10% of those registered during the first day. In a longer
run with compound 3b the CP yield (815 mg) still rises after 8
days.
generation could be the result of the increased size of the
dendritic precursor, which diminishes the effectiveness of the
chain-end control, in a way similar to that in which the
stereoregularity of styrene/CO copolymers produced by alky-
lpyridylimine derivatives is affected by the bulkiness of the alkyl
group of the ligand.13 Finally, syndiotacticities are insignificantly
affected by the polymerization time (compare entry 7 vs 15 or
13 vs 16).
The observed molecular weights of the polyketones produced
(up to Mw ) 80 000) are within the upper range reported for
other bis-nitrogen systems, while showing wider molecular
weight distributions (PDI ) Mw/Mn ) 1.5-3.5), in particular
those obtained from neat TBS.7-9,13 The ratio of mass of
polymer produced per mole of palladium to Mw, which indicates
the number of chains produced by the Pd center, is in most
cases close to 1 (Table 1). All these data point to a mechanism
in which the polymer chain grows until the active complex
decomposes. Catalysts with a greater stability in relation to the
rate of chain growth should give higher molecular weights and
polydispersities, as observed for cationic monometallic com-
pound “b”, whose improved stability was mentioned above
(entry 4 vs 5), or in the absence of solvent (entries 5, 9, 10, and
11 vs 7, 12, 13, and 14). On the other hand, no linear correlation
is observed between Mw and the monomer conversion, while
molecular weights, and polydispersities, are insignificantly
affected by the polymerization time (entry 7 vs 15, or 13 vs
16). Moreover, the ratio of mass of polymer produced per mole
of palladium to Mw is in several cases close to but appreciably
greater than 1 (entries 4, 11, 14, and 16). This clearly means
that chain transfer processes must be accompanied by decom-
position of the active centers in most instances, but some of
them should be able to restart the polymerization cycle.
Among the reactions carried out in CH2Cl2, the trend observed
with the dendrimer generation is unclear. In neat TBS, however,
the increase in generation results in a decrease in Mw (Figure
3b) and in broader molecular weight distributions (Table 1,
entries 7 and 12-14). These results might be related to our
previous work with nickel complexes for ethylene polymeri-
zation in which the changes in the oligomer/polymer distribution
by the generation of the dendritic precursor were interpreted as
a consequence of the steric pressure that bulkier dendrimers
caused on the growing chains, enhancing chain transfer pro-
cesses and favoring the formation of an assortment of shorter
polymers.19
Conclusion
In summary, a series of neutral and cationic palladium
coordination compounds with a set of versatile monochelating
or carbosilane-dendritic pyridylimine ligands has been synthe-
sized and characterized. The cationic compounds are found to
be active catalysts for alternating syndiospecific copolymeri-
zation of carbon monoxide and 4-tert-butylstyrene, and their
catalytic performance is definitely sensitive to the dendrimer
generation. Several dendritic effects on activity or selectivity
have been reported to date.16d,19,32 In this paper, we have shown
an example in which the presence of the dendrimer is almost
irrelevant in terms of stability of the active species, but the
dendritic support affects the activity of the active center, and
the molecular weight and weight distribution, as well as the
stereoregularity of the polyketones produced from CO/4-tert-
butylstytrene.
Experimental Section
Reagents and General Techniques. All operations were per-
formed under an argon atmosphere using Schlenk or drybox
techniques. Unless otherwise stated, reagents were obtained from
commercial sources and used as received. [PdCl2(COD)],33 [PdClMe-
(COD)],24b Na[BArf4] (Arf ) 3,5-(CF3)2C6H3),34 pyridylimine
ligands I,12a,19 and carbosilane-pyridylimine dendritic ligands
GnONNMem II (n ) 1), III (n ) 2), and IV (n ) 3)19 were prepared
according to literature procedures. Solvents were dried prior to use
and distilled under argon as described elsewhere.35 NMR spectra
were recorded on Varian Unity 500+, Varian Unity VR-300, and
Varian Unity 200 NMR spectrometers. Chemical shifts δ are
1
reported in ppm referenced to SiMe4 for H, 13C, and 29Si, and
As far as the microstructure of the produced polyketone is
concerned, quantitative examination of the 13C{1H} NMR
spectra shows that all active catalytic systems afford a regio-
regular copolymer with a degree of syndiotacticity above 60%
(uu triad proportion, Table 1), indicating that the processes
proceed mainly by a chain-end stereocontrolled mecha-
nism.7,8,30,31 The syndiotactic component is slightly higher in
copolymer produced by compounds “b” (e.g., compare entries
1 and 2) and in the presence of CH2Cl2 (e.g., entry 5 vs 7) and
slightly decreases at higher metallodendrimer generation (e.g.,
compare entries 5 and 9-11). At this point, it is worth recalling
that the catalytic mixture becomes very viscous in reactions
carried out without solvent and, therefore, the lower syndio-
tacticity in neat TBS might be ascribed to a stalled motion of
the reactants and the growing chain, in combination with an
easier displacement of the coordinated carbonyl group of the
polymer chain by an augmented concentration of comonomer.8b
The lowering in uu triad portions with increasing dendrimer
assignments for the pyridylimine ligands are according to the
numbering of the positions depicted in Chart 1. IR spectra were
recorded on a Perkin-Elmer FT-IR Spectrum-2000 spectrophotom-
eter. Elemental analyses and mass spectra were performed by the
Microanalytical Laboratories of the University of Alcala´ (MLUAH)
on a Heraeus CHN-O-Rapid microanalyzer and on Hewlett-Packard
5988A Quadruplo (EI) and Thermo Quest Finningan Automass
Multi (ESI) mass spectrometers. Polyketone molecular weight
determinations were made by the MLUAH on Waters GPCV 2000
equipment operating at 40 °C with THF solvent and polystyrene
calibration standards.
(32) (a) See ref 20c. (b) Kleij, A. W.; Gossage, R. A.; Jastrzebski, J. T.
B. H.; Boersma, J.; van Koten, G. Angew. Chem., Int. Ed. 2000, 39, 176.
(c) Breinbauer, R.; Jacobsen, E. N. Angew. Chem., Int. Ed. 2000, 39, 3604.
(d) Kleij, A. W.; Gossage, R. A.; Gebbink, R. J. M. K.; Brinkmann, N.;
Reijerse, E. J.; Kragl, U.; Lutz, M.; Spek, A. L.; van Koten, G. J. Am.
Chem. Soc. 2000, 122, 12112. (e) Ropartz, L.; Morris, R. E.; Foster, D. F.;
Cole-Hamilton, D. J. Chem. Commun. 2001, 361. (f) Dahan, A.; Portnoy,
M. Chem. Commun. 2002, 2700. (g) Drake, M. D.; Bright, F. V.; Detty,
M. R. J. Am. Chem. Soc. 2003, 125, 12558. (h) Delort, E.; Darbre, T.;
Reymond, J.-L. J. Am. Chem. Soc. 2004, 126, 15642. (i) Fujihara, T.; Obora,
Y.; Tokunaga, M.; Sato, H.; Tsuji, Y. Chem. Commun. 2005, 4526.
(33) Drew, D.; Doyle J. R. In Inorganic Syntheses; Cotton, F. A., Ed.;
McGraw-Hill: New York, 1972; Vol. 13, p 47.
(29) (a) Twyman, L. J.; King, A. S. H.; Martin, I. K. Chem. Soc. ReV.
2002, 31, 69. (b) Reek, J. N. H.; de Groot, D.; Oosterom, G. E.; Kamer, P.
C. J.; van Leeuwen, P. W. N. M. C. R. Chim. 2003, 6, 1061.
(30) (a) Nozaki, K.; Hijama, T. J. Organomet. Chem. 1999, 576, 248.
(b) Sen, A.; Jiang, Z. Macromolecules 1993, 26, 911.
(31) (a) Bastini, A.; Consiglio, G.; Suter, U. W. Angew. Chem., Int. Ed.
Engl. 1992, 31, 303. (b) Corradini, P.; DeRosa, A.; Panunzi, A.; Pino, P.
Chimia 1990, 44, 52.
(34) Brookhart, M.; Grant, B.; Volpe, A. F., Jr. Organometallics 1992,
11, 3920.
(35) Perrin, D. P.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, U.K., 1988.

3052 Organometallics, Vol. 25, No. 12, 2006
Benito et al.
Preparation of Dichloropalladium Complexes 1. The synthesis
of the dichloropalladium compounds 1a-c is exemplified by the
preparation of 1a.
9.10 (d, 1H, JH,H ) 4.6 Hz, H12). 13C{1H} NMR (CDCl3): δ 0.3
(SiMe3), 1.7 (PdMe), 120.2 (C3,5), 123.7 (C2,6), 126.3 (C9), 128.3
(C11), 138.5 (C10), 142.2 (C1), 149.6 (C12), 151.6 (C8), 155.3 (C4),
165.9 (C7). NMR data for the minor isomer are as follows. 1H NMR
(CDCl3): δ 0.23 (s, 9H, SiMe3), 1.20 (s, 3H, PdMe), 6.81 (AA′
part of an AA′BB′ spin system, 2H, H3,5), 7.47 (BB′ part of an
AA′BB′ spin system, 2H, H2,6), 7.57 (pt, 1H, H11), 7.74 (d partially
obscured by the major isomer, 1H, H9), 8.02 (pt, 1H, H10), 8.31 (s,
1H, H7), 8.63 (d, 1H, JH,H ) 5.3 Hz, H12). IR (KBr): ν 1614 (w),
1598 cm-1 (m, CdN). MS (70 eV, EI): m/z 270 [Ia]+. MS (ESI+
in CH3CN): m/z 819 [M2 - Cl]+, 432 [M - Cl + CH3CN]+.
PdCl2(Me3SiO-4-Ph-NdCH-2-Py) (1a). [PdCl2(COD)] (266
mg, 0.94 mmol) was added to ligand Ia (254 mg, 0.94 mmol) in
dichloromethane (50 mL), and the resulting solution was stirred at
room temperature overnight. Removal of the solvent, followed by
washings of the residue with pentane (4 × 15 mL), gave compound
1a as a yellow solid. Yield: 370 mg (88%). Anal. Calcd for
C15H18N2OSiCl2Pd (447.73): C, 40.24; H, 4.05; N, 6.26. Found:
1
C, 39.86; H, 3.71; N, 6.31. H NMR (CDCl3): δ 0.28 (s, 9H,
SiMe3), 6.77 (AA′ part of an AA′BB′ spin system, 2H, H3,5), 7.37
(BB′ part of an AA′BB′ spin system, 2H, H2,6), 7.61 (pt, 1H, H11),
7.88 (d, 1H, JH,H ) 7.2 Hz, H9), 8.10 (pt, 1H, H10), 8.17 (s, 1H,
H7), 9.27 (d, 1H, JH,H ) 5.6 Hz, H12). 13C{1H} NMR (CDCl3): δ
0.4 (SiMe3), 119.5 (C3,5), 125.6 (C2,6), 128.0 (C9), 128.2 (C11), 140.3
(C10), 140.5 (C1), 151.0 (C12), 155.4 (C4), 156.5 (C8), 166.8 (C7).
IR (KBr): ν 1617 (w), 1596 cm-1 (s, CdN). MS (70 eV, EI): m/z
270 [Ia]+. MS (ESI+ in CH3CN): m/z 861 [M2 - Cl]+, 489 [M +
CH3CN]+, 454 [M - Cl + CH3CN]+.
PdClMe[Me3SiO-4-(2,5-Me2Ph)-NdCH-2-Py] (2b). Yellow
solid. Yield: 66%. Anal. Calcd for C18H25N2OSiClPd (455.37): C,
1
47.48; H, 5.53; N, 6.15. Found: C, 47.14; H, 5.47; N, 6.14. H
NMR (CDCl3): δ 0.27 (s, 9H, SiMe3), 0.68 (s, 3H, PdMe), 2.14
(s, 3H, Me14), 2.24 (s, 3H, Me13), 6.62 (s, 1H, H3), 6.72 (s, 1H,
H6), 7.71 (m, 2H, H9 and H11), 8.00 (pt, 1H, H10), 8.35 (s, 1H, H7),
9.14 (d, 1H, JH,H ) 4.4 Hz, H12). 13C{1H} NMR (CDCl3): δ 0.5
(SiMe3), 0.7 (PdMe), 16.2 and 17.9 (Me13,14), 120.6 (C3), 123.8
(C6), 126.1 (C9), 127.2 (C5), 128.3 (C2), 128.4 (C11), 138.5 (C10),
141.0 (C1), 149.7 (C12), 151.3 (C8), 152.9 (C4), 166.6 (C7). IR
(KBr): ν 1616 (w), 1586 cm-1 (s, CdN). MS (70 eV, EI): m/z
298 [Ib]+. MS (ESI+ in CH3CN): m/z 875 [M2 - Cl]+, 460 [M
- Cl + CH3CN]+.
PdCl2[Me3SiO-4-(2,5-Me2Ph)-NdCH-2-Py] (1b). Yellow solid.
Yield: 64%. Anal. Calcd for C17H22N2OSiCl2Pd (475.79): C, 42.92;
1
H, 4.66; N, 5.89. Found: C, 43.31; H, 4.69; N, 6.07. H NMR
(CDCl3): δ 0.26 (s, 9H, SiMe3), 2.10 (s, 3H, Me14), 2.45 (s, 3H,
Me13), 6.56 (s, 1H, H3), 6.88 (s, 1H, H6), 7.71 (pt, 1H, H11), 7.87
(d, 1H, JH,H ) 7.3 Hz, H9), 8.15 (pt and s overlapping, 2H, H10
and H7), 9.36 (d, 1H, JH,H ) 5.9 Hz, H12). 13C{1H} NMR (CDCl3):
δ 0.6 (SiMe3), 16.1 and 19.1 (Me13,14), 120.5 (C3), 124.7 (C6), 127.0
(C5), 127.6 (C9), 128.5 (C11), 130.1 (C2), 140.1 (C10), 140.4 (C1),
151.5 (C12), 154.1 (C4), 154.8 (C8), 167.9 (C7). IR (KBr): ν 1615
(w), 1594 cm-1 (m, CdN). MS (70 eV, EI): m/z 298 [Ib]+. MS
(ESI+ in CH3CN): m/z 917 [M2 - Cl]+, 482 [M - Cl + CH3-
CN]+.
PdClMe[Me3SiO-4-(2,5-Me2Ph)-NdCH-2-(6-MePy)] (2c). Yel-
low solid. Yield: 81%. Anal. Calcd for C19H27N2OSiClPd
(469.39): C, 48.62; H, 5.80; N, 5.97. Found: C, 48.29; H, 5.62;
1
N, 6.11. H NMR (CDCl3): δ 0.26 (s, 9H, SiMe3), 0.83 (s, 3H,
PdMe), 2.14 (s, 3H, Me14), 2.24 (s, 3H, Me13), 3.08 (s, 3H, Me15),
6.60 (s, 1H, H3), 6.71 (s, 1H, H6), 7.47 (d, 1H, JH,H ) 8.0 Hz,
H11), 7.49 (d, 1H, JH,H ) 7.5 Hz, H9), 7.82 (pt, 1H, H10), 8.33 (s,
1H, H7). 13C{1H} NMR (CDCl3): δ 0.6 (SiMe3), 4.6 (PdMe), 16.2
and 17.9 (Me13,14), 25.8 (Me15), 120.6 (C3), 124.1 (C6), 124.6 (C9),
127.2 (C5), 128.5 (C2), 130.2 (C11), 137.9 (C10), 141.1 (C1), 151.1
(C8), 152.7 (C4), 164.5 (C12), 167.7 (C7). IR (KBr): ν 1625 cm-1
(w), 1591 cm-1 (s, CdN). MS (70 eV, EI): m/z 312 [Ic]+. MS
(ESI+ in CH3CN): m/z 903 [M2 - Cl]+, 474 [M - Cl + CH3-
CN]+.
PdCl2[Me3SiO-4-(2,5-Me2Ph)-NdCH-2-(6-MePy)] (1c). Yel-
low solid. Yield: 72%. Anal. Calcd for C18H24N2OSiCl2Pd
(489.81): C, 44.14; H, 4.94; N, 5.72. Found: C, 43.89; H, 4.86;
1
N, 5.90. H NMR (CDCl3): δ 0.26 (s, 9H, SiMe3), 2.12 (s, 3H,
Me14), 2.44 (s, 3H, Me13), 3.16 (s, 3H, Me15), 6.56 (s, 1H, H3),
6.86 (s, 1H, H6), 7.47 (d, 1H, JH,H ) 7.8 Hz, H11), 7.66 (d, 1H,
JH,H ) 7.0 Hz, H9), 7.94 (pt, 1H, H10), 8.10 (s, 1H, H7). 13C{1H}
NMR (CDCl3): δ 0.8 (SiMe3), 16.3 and 19.2 (Me13,14), 27.8 (Me15),
120.3 (C3), 124.2 (C6), 125.4 (C9), 126.8 (C5), 130.8 (C11), (C2 not
observed), 138.8 (C10), 140.4 (C1), 154.0 (C4), 154.7 (C8), 167.3
(C12), 167.6 (C7). IR (KBr): ν 1622 (w), 1594 cm-1 (m, CdN).
MS (ESI+ and APCI in CH3CN): m/z 945 [M2 - Cl]+, 496 [M -
Cl + CH3CN]+, 312 [Ic]+.
Preparation of Cationic Methylpalladium Complexes 3. The
synthesis of the cationic compounds 3a-c is exemplified by the
preparation of 3a.
[PdMe(MeCN)(Ia)]+[BArf4]- (3a). Compound 2a (75 mg, 0,-
175 mmol) and Na[BArf4] (Arf ) 3,5-(CF3)2C6H3; 155.5 mg, 0.175
mmol) were combined in a Schlenk tube and stirred in acetonitrile
(10 mL) at room temperature overnight. The greenish yellow
suspension was evaporated to dryness, the residue was dissolved
in dichloromethane (2 × 10 mL), and the resulting yellow solution
was filtered. Removal of the solvent under reduced pressure gave
3a as an orange-yellow oily solid, consisting of a mixture of 20%
cis and 80% trans isomers, according to the relative position of the
methyl ligand with regard to the position of the imine nitrogen.
The compound can be purified by redissolution in CH2Cl2, followed
by filtration and precipitation by addition of pentane, isolating 3a
as a yellow solid. Yield: 130 mg (57%). Anal. Calcd for C50H36N3-
OSiPdBF24 (1296.14): C, 46.33; H, 2.80; N, 3.24. Found: C, 46.20;
H, 2.74; N, 3.31. NMR data for the major isomer are as follows.
1H NMR (CDCl3): δ 0.27 (s, 9H, SiMe3), 1.12 (s, 3H, PdMe),
2.17 (s, 3H, CH3CN), 6.91 (AA′ part of an AA′BB′ spin system,
2H, H3,5), 7.15 (BB′ part of an AA′BB′ spin system, 2H, H2,6),
7.49 (broad s, 4H, Arf Hp), 7.57 (pt, 1H, H11), 7.68 (broad s, 9H,
H9 and Arf Ho overlapping), 7.96 (pt, 1H, H10), 8.25 (s, 1H, H7),
8.43 (d, 1H, JH,H ) 5.3 Hz, H12). 13C{1H} NMR (CDCl3): δ 0.1
(SiMe3), 3.0 (PdMe), 4.9 (CH3CN), 117.4 (Arf Cp), 120.9 (C3,5),
123.0 (C2,6), 124.4 (q, JC,F ) 272.1 Hz, CF3), 128.4 (C9 and C11),
128.8 (q, JC,F ) 29.0 Hz, Arf Cm), 134.7 (Arf Co), 140.3 (C1), 140.6
(C10), 149.2 (C12), 155.7 (C8), 157.2 (C4), 159.5 (C7), 161.6 (q,
JC,B ) 49.5 Hz, Arf Cipso). NMR data for the minor isomer are as
Preparation of Chloro(methyl)palladium Complexes 2. The
synthesis of the chloro(methyl)palladium compounds 2a-c is
exemplified by the preparation of 2a.
PdClMe(Me3SiO-4-Ph-NdCH-2-Py) (2a). [PdClMe(COD)]
(145 mg, 0.55 mmol) was added to Ia (148 mg, 0.55 mmol) in
diethyl ether or dichloromethane (10 mL), and the resulting orange
solution was stirred at room temperature for 2 h. The solvent was
removed under vacuum, and the residue was washed with pentane
(2 × 20 mL) and cold diethyl ether (2 × 10 mL) to give compound
2a as a yellow solid, consisting of a mixture of 76% cis and 24%
trans isomers, according to the relative position of the methyl ligand
with regard to the position of the imine nitrogen. When needed,
purer samples were obtained by repetition of the operations:
redissolution in CH2Cl2, followed by filtration and precipitation by
adding pentane. Yield: 170 mg (73%). Anal. Calcd for C16H21N2-
OSiClPd (427.31): C, 44.97; H, 4.95; N, 6.56. Found: C, 45.09;
H, 4.96; N, 6.66. NMR data for the major isomer are as follows.
1H NMR (CDCl3): δ 0.24 (s, 9H, SiMe3), 0.77 (s, 3H, PdMe),
6.83 (AA′ part of an AA′BB′ spin system, 2H, H3,5), 7.03 (BB′
part of an AA′BB′ spin system, 2H, H2,6), 7.64 (pt, 1H, H11), 7.70
(d, 1H, JH,H ) 7.5 Hz, H9), 7.96 (pt, 1H, H10), 8.35 (s, 1H, H7),

Palladium Dendrimers Copolymerizing CO/Styrene
Organometallics, Vol. 25, No. 12, 2006 3053
1
follows. H NMR (CDCl3): δ 0.28 (s, 9H, SiMe3), 0.84 (s, 3H,
(40 mL), and the resulting yellow suspension was stirred at room
temperature for 48 h. Removal of the solvent, followed by washings
of the residue with pentane (4 × 5 mL), gave compound 4a as a
yellow solid, soluble in DMSO and insoluble in alkanes and
aromatic and chlorinated solvents. Yield: 300 mg (89%). Anal.
Calcd for C68H84N8O4Si5Cl8Pd4 (1927.20): C, 42.38; H, 4.39; N,
5.81. Found: C, 42.05; H, 4.57; N, 5.25. 1H NMR (DMSO-d6): δ
0.22 (s, 6H, SiMe2), 0.60 (m, 2H, SiCH2), 0.81 (m, 2H, CH2SiMe2),
1.39 (m, 2H, CH2CH2CH2), 6.81 (AA′ part of an AA′BB′ spin
system, 2H, H3,5), 7.34 (BB′ part of an AA′BB′ spin system, 2H,
H2,6), 7.88 (m, 1H, H11), 8.16 (m, 1H, H9), 8.35 (m, 1H, H10), 8.66
(s, 1H, H7), 8.98 (m 1H, H12). 13C{1H} NMR (DMSO-d6): δ -1.8
(SiMe2), 15.9 (CH2), 16.9 (CH2), 20.2 (CH2), 118.4 (C3,5), 125.2
(C2,6), 128.1 (C9), 128.8 (C11), 140.4 (C1), 140.7 (C10), 149.4 (C12),
154.7 (C4), 155.3 (C8), 170.9 (C7). IR (KBr): ν 1615 (vw), 1595-1
(s, CdN).
PdMe), 2.30 (s, 3H, CH3CN), 6.84 (AA′ part of an AA′BB′ spin
system, 2H, H3,5), 7.13 (BB′ part of an AA′BB′ spin system, 2H,
H2,6), 7.42 (pt, 1H, H11), 7.49 (broad s, 4H, Arf Hp), 7.68 (broad s,
9H, H9 and Arf Ho overlapping), 7.88 (pt, 1H, H10), 8.22 (s, 1H,
H7), 8.31 (d, 1H, JH,H ) 5.1 Hz, H12). 19F{1H} NMR (CDCl3): δ
-106.3 (s, CF3). IR (KBr): ν 1610 cm-1 (m, CdN). MS (ESI+ in
CH3CN): m/z 432 [M - BArf4]+, 270 [Ia]+. MS (ESI- in CH3-
CN): m/z 863 [BArf4]-.
[PdMe(MeCN)(Ib)]+[BArf4]- (3b). Orange-yellow solid. Mix-
ture of 44% cis and 56% trans isomers. Yield: 69%. Anal. Calcd
for C52H40N3OSiPdBF24 (1324.19): C, 47.17; H, 3.04; N, 3.17.
Found: C, 46.80; H, 2.94; N, 3.17. NMR data for the major isomer
1
are as follows. H NMR (CDCl3): δ 0.27 (s, 9H, SiMe3), 1.08 (s,
3H, PdMe), 2.04 (s, 3H, Me14), 2.15 (s, 3H, CH3CN), 2.31 (s, 3H,
Me13), 6.66 (s, 1H, H3), 6.74 (s, 1H, H6), 7.49 (broad s, 4H, Arf
Hp), 7.58 (pt, 1H, H11), 7.68 (broad s, 9H, H9 and Arf Ho
overlapping), 8.00 (pt, 1H, H10), 8.20 (s, 1H, H7), 8.42 (d, 1H, JH,H
) 5.0 Hz, H12). 13C{1H} NMR (CDCl3): δ 0.6 (SiMe3), 2.9 (PdMe),
4.6 (CH3CN), 16.3 and 18.2 (Me13,14), 117.3 (Arf Cp), 120.9 (C3),
123.0 (C6), 124.3 (q, JC,F ) 271.7 Hz, CF3), (C2 and C5 not
assigned), 128.3 (C9), 128.5 (C11), 128.7 (q, JC,F ) 28.1 Hz, Arf
Cm), 134.5 (Arf Co), 139.7 (C1), 140.4 (C10), 149.2 (C12), 154.1
(C8), 155.3 (C4), 161.3 (q, JC,B ) 49.6 Hz, Arf Cipso), 161.4 (C7).
NMR data for the minor isomer are as follows. 1H NMR (CDCl3):
δ 0.28 (s, 9H, SiMe3), 0.72 (s, 3H, PdMe), 2.14 (s, 3H, Me14),
2.17 (s, 3H, Me13), 2.30 (s, 3H, CH3CN), 6.64 (s, 1H, H3), 6.69 (s,
1H, H6), 7.40 (pt, 1H, H11), 7.49 (broad s, 4H, Arf Hp), 7.68 (broad
s, 9H, H9 and Arf Hp overlapping), 7.85 (pt, 1H, H10), 8.27 (s, 1H,
H7), 8.31 (d, 1H, JH,H ) 5.0 Hz, H12). 13C{1H} NMR (CDCl3): δ
0.7 (SiMe3), 3.3 (PdMe), 6.4 (CH3CN), 16.4 and 17.8 (Me13,14),
117.3 (Arf Cp), 120.8 (C3), 123.5 (C6), 124.3 (q, JC,F ) 271.7 Hz,
CF3), (C1, C2, and C5 not assigned), 127.7 (C9), 129.4 (C11), 128.7
(q, JC,F ) 28.1 Hz, Arf Cm), 134.5 (Arf Co), 140.0 (C10), 148.6 (C12),
150.2 (C8), 153.6 (C4), 161.3 (q, JC,B ) 49.6 Hz, Arf Cipso), 169.9
(C7). 19F{1H} NMR (CDCl3): δ -106.3 (s, CF3). IR (KBr): ν 1611
cm-1 (m, CdN). MS (ESI+ in CH3CN): m/z 460 [M - BArf4]+,
298 [Ib]+. MS (ESI- in CH3CN): m/z 863 [BArf4]-.
G1-ONNMe2[PdCl2] (4b). Orange solid slightly soluble in polar
solvents and insoluble in alkanes and halogenated solvents. Yield:
80%. Anal. Calcd for C76H100N8O4Si5Cl8Pd4 (2039.41): C, 44.76;
1
H, 4.94; N, 5.49. Found: C, 45.57; H, 5.44; N, 5.19. H NMR
(DMSO-d6): δ 0.21 (s, 6H, SiMe2), 0.63 (m, 2H, SiCH2), 0.81 (m,
2H, CH2SiMe2), 1.47 (m, 2H, CH2CH2CH2), 2.28 (s, 3H, Me14),
2.31 (s, 3H, Me13), 6.61 (AA′ part of an AA′BB′ spin system, 2H,
H3,5), 7.03 (BB′ part of an AA′BB′ spin system, 2H, H2,6), 7.89
(m, 1H, H11), 8.13 (m, 1H, H9), 8.36 (m, 1H, H10), 8.61 (s, 1H,
H7), 8.92 (m 1H, H12). IR (KBr): ν 1615 (vw), 1594 cm-1 (m,
CdN).
Preparation of G1-pyridylimine-Pd(Cl)Me Dendritic Com-
plexes 5. Compounds 5b,c were synthesized as described above
for 2 by starting from the corresponding G1-pyridylimine dendritic
ligands G1-ONNMem (IIb,c). The preparation of 5c is reported as
an example.
G1-ONNMe2[Pd(Cl)Me] (5b). Yellow solid. Yield: 86%. Anal.
Calcd for C80H112N8O4Si5Cl4Pd4 (1957.74): C, 49.08; H, 5.77; N,
1
5.72. Found: C, 49.13; H, 5.95; N, 5.38. H NMR (CDCl3): δ
0.22 (s, 6H, SiMe2), 0.64 (m, 2H, SiCH2), 0.60 (s, 3H, PdMe),
0.81 (m, 2H, CH2SiMe2), 1.50 (m, 2H, CH2CH2CH2), 2.06 (s, 3H,
Me14), 2.21 (s, 3H, Me13), 6.58 (s, 1H, H3), 6.71 (s, 1H, H6), 7.62
(m, 1H, H11), 7.88 (m, 1H, H9), 7.99 (pt, 1H, H10), 8.42 (s, 1H,
H7), 8.97 (m, 1H, H12). 13C{1H} NMR (CDCl3): δ -0.9 (SiMe2),
0.5 (PdMe), 16.1 and 17.8 (Me13,14), 17.1 (CH2), 17.9 (CH2), 21.7
(CH2), 120.4 (C3), 124.0 (C6), 126.8 (C9), 127.1 (C5), 128.3 (C2),
128.4 (C11), 138.6 (C10), 141.0 (C1), 149.3 (C12), 151.6 (C8), 152.9.3
(C4), 167.3 (C7). IR (KBr): ν 1615 cm-1 (w), 1586 cm-1 (m, Cd
N), 1565 cm-1 (w).
[PdMe(MeCN)(Ic)]+[BArf4]- (3c). Orange-yellow solid. Yield:
93%. Anal. Calcd for C53H42N3OSiPdBF24 (1338.21): C, 47.57;
H, 3.16; N, 3.14. Found: C, 47.12; H, 3.08; N, 2.88. H NMR
1
(CDCl3): δ 0.27 (s, 9H, SiMe3), 0.79 (s, 3H, PdMe), 2.14 (s, 3H,
Me14), 2.16 (s, 3H, Me13), 2.25 (s, 3H, CH3CN), 2.53 (s, 3H, Me15),
6.63 (s, 1H, H3), 6.67 (s, 1H, H6), 7.35 (d, 1H, JH,H ) 7.8 Hz,
H11), 7.49 (broad s, 5H, H9 and Arf Hp overlapping), 7.67 (broad s,
8H, Arf Ho), 7.76 (pt, 1H, H10), 8.25 (s, 1H, H7). H NMR (CD2-
1
G1-ONNMe3[Pd(Cl)Me] (5c). [PdClMe(COD)] (59 mg, 0.22
mmol) was added to IIc (77 mg, 0.055 mmol) in dichloromethane
(15 mL), and the resulting yellow solution was stirred at room
temperature for 24 h. The solvent was removed under vacuum, and
the residue was washed with pentane (2 × 25 mL) and diethyl
ether (4 × 25 mL) to give compound 5c as an orange solid.
Analytically pure samples were obtained by operations of dissolu-
tion in CH2Cl2, filtration, and precipitation by adding pentane.
Yield: 50 mg (45%). Anal. Calcd for C84H120N8O4Si5Cl4Pd4
(2013.85): C, 50.10; H, 6.01; N, 5.56. Found: C, 49.74; H, 5.87;
Cl2): δ 0.28 (s, 9H, SiMe3), 0.81 (s, 3H, PdMe), 2.17 (s, 3H, Me14),
2.20 (s, 3H, Me13), 2.37 (s, 3H, CH3CN), 2.70 (s, 3H, Me15), 6.68
(s, 1H, H3), 6.70 (s, 1H, H6), 7.55 (broad s, 4H, Arf Hp), 7.60 (d,
1H, JH,H ) 8.0 Hz, H11), 7.66 (d, 1H, JH,H ) 7.7 Hz, H9), 7.71
(broad s, 8H, Arf Ho), 7.98 (pt, 1H, H10), 8.33 (s, 1H, H7). DEPT
experiments were useful for the assignation of 13C{1H} NMR
(CDCl3): δ 0.5 (SiMe3), 3.2 (PdMe), 8.7 (CH3CN), 16.3 and 17.7
(Me13,14), 25.1 (Me15), 117.4 (Arf Cp), 120.8 (C3), 123.7 (C6), 124.4
(q, JC,F ) 270.0 Hz, CF3), 126.0 (C9), 128.0 (C5), 128.1 (C2), 128.8
(q, JC,F ) 31.1 Hz, Arf Cm), 130.5 (C11), 134.6 (Arf Co), 139.4 (C1),-
1
N, 5.49. H NMR (CDCl3): δ 0.22 (s, 6H, SiMe2), 0.66 (m, 2H,
139.6 (C10), 150.6 (C8), 153.6 (C4), 161.4 (C12), 161.5 (q, JC,B
)
SiCH2), 0.78 (s, 3H, PdMe), 0.80 (m, 2H, CH2SiMe2), 1.50 (m,
2H, CH2CH2CH2), 2.09 (s, 3H, Me14), 2.23 (s, 3H, Me13), 3.03 (s,
3H, Me15), 6.58 (s, 1H, H3), 6.70 (s, 1H, H6), 7.42 (m, 1H, H11),
7.63 (m, 1H, H9), 7.82 (pt, 1H, H10), 8.40 (s, 1H, H7). 13C{1H}
NMR (CDCl3): δ -1.0 (SiMe2), 4.4 (PdMe), 16.2 and 17.9
(Me13,14), 17.2 (CH2), 17.9 (CH2 overlapping), 21.9 (CH2), 25.7
(Me15), 120.4 (C3), 124.2 (C6), 125.3 (C9), 127.1 (C5), 128.7 (C2),
130.1 (C11), 138.1 (C10), 141.2 (C1), 151.3 (C8), 152.8 (C4), 164.3
(C12), 168.2 (C7). IR (KBr): ν 1621 (m), 1590 cm-1 (s, CdN).
49.7 Hz, Arf Cipso), 171.0 (C7). 19F{1H} NMR (CDCl3): δ -106.3
(s, CF3). IR (KBr): ν 1611 cm-1 (m, CdN). MS (ESI+ in CH3-
CN): m/z 474 [M - BArf4]+, 312 [Ic]+. MS (ESI- in CH3CN):
m/z 863 [BArf4]-.
Preparation of G1-pyridylimine-PdCl2 Dendritic Complexes
4. Compounds 4a,b were synthesized as described above for 1 by
starting from the corresponding pyridylimine dendritic ligands G1-
ONNMem (IIa,b). The preparation of 4a is reported as an example.
G1-ONN[PdCl2] (4a). [PdCl2(COD)] (200 mg, 0.70 mmol) was
added to G1-ONN (IIa; 213 mg, 0.175 mmol) in dichloromethane
Preparation of G2-pyridylimine-Pd(Cl)Me Dendritic Com-
plexes 6. Compounds 6b,c were synthesized as described above

3054 Organometallics, Vol. 25, No. 12, 2006
Benito et al.
for 2, starting from the corresponding G2-pyridylimine dendritic
ligands G2-ONNMem (IIIb,c).
the 1H NMR resonances for the minor isomer (cis-Me-Pd-Nimine
)
are obscured by the signals corresponding to the major isomer.
G2-ONNMe2[Pd(Cl)Me] (6b). Yellow solid. Yield: 79%. Anal.
Calcd for C176H260N16O8Si13Cl8Pd8 (4228.20): C, 50.00; H, 6.20;
N, 5.30. Found: C, 49.66; H, 6.34; N, 4.98. 1H NMR (CDCl3): δ
-0.06 (s, 3H, SiMe), 0.21 (s, 12H, SiMe2), 0.57 (m, 8H, SiCH2),
0.60 (s, 6H, PdMe), 0.81 (m, 4H, CH2SiMe2), 1.31 (m, 2H,
CH2CH2CH2), 1.45 (m, 4H, CH2CH2CH2), 2.07 (s, 6H, Me14), 2.19
(s, 6H, Me13), 6.56 (s, 2H, H3), 6.71 (s, 2H, H6), 7.64 (m, 2H,
H11), 7.91 (m, 2H, H9), 8.00 (pt, 2H, H10), 8.44 (s, 2H, H7), 8.98
(s, 2H, H12). 13C{1H} NMR (CDCl3): δ -4.9 (SiMe), -0.9 (SiMe2),
0.4 (PdMe), 16.2 and 17.8 (Me13,14), 17.9, 18.5, 18.7, 19.1, and
21.8 (CH2), 120.4 (C3), 123.9 (C6), 126.9 (C5,9), 128.5 (C2,11), 138.7
(C10), 140.9 (C1), 149.0 (C12), 151.4 (C8), 152.7 (C4), 167.5 (C7).
IR (KBr): ν 1615 (w), 1586 (s, CdN), 1566 cm-1 (w).
G2-ONNMe3[Pd(Cl)Me] (6c). Yellow solid. Yield: 53%. Anal.
Calcd for C184H276N16O8Si13Cl8Pd8 (4340.41): C, 50.92; H, 6.41;
N, 5.16. Found: C, 50.45; H, 6.48; N, 4.97. 1H NMR (CDCl3): δ
-0.06 (s, 3H, SiMe), 0.22 (s, 12H, SiMe2), 0.60 (m, 8H, SiCH2),
0.75 (s, 6H, PdMe), 0.85 (m, 4H, CH2SiMe2), 1.23 (m, 2H,
CH2CH2CH2), 1.50 (m, 4H, CH2CH2CH2), 2.09 (s, 6H, Me14), 2.21
(s, 6H, Me13), 3.03 (s, 6H, Me15), 6.56 (s, 2H, H3), 6.69 (s, 2H,
H6), 7.43 (m, 2H, H11), 7.64 (m, 2H, H9), 7.82 (pt, 2H, H10), 8.41
(s, 2H, H7). 13C{1H} NMR (CDCl3): δ -4.9 (SiMe), -0.8 (SiMe2),
4.5 (PdMe), 16.3 and 18.0 (Me13,14), 17.8, 18.5, 18.7, 19.1 and 21.8
(CH2), 25.7 (Me15), 120.4 (C3), 124.2 (C6), 125.3 (C9), 127.0 (C5),
128.6 (C2), 130.1 (C11), 138.0 (C10), 141.0 (C1), 151.2 (C8), 152.7
(C4), 164.0 (C12), 168.2 (C7). IR (KBr): ν 1621 (m), 1590 cm-1
(s, CdN).
G1-ONNMe2[PdMe(MeCN)] (8b). Orange-yellow solid. Yield:
69%. Anal. Calcd for C216H172N12O4Si5Pd4B4F96 (5433.02): C,
47.75; H, 3.19; N, 3.09. Found: C, 47.29; H, 2.97; N, 2.66. NMR
data for the major isomer (60% trans-Me-Pd-Nimine) are as
1
follows. H NMR (CDCl3): δ 0.20 (s, 6H, SiMe2), 0.65 (m, 2H,
SiCH2), 0.83 (m, 2H, CH2SiMe2), 0.86 (s, 3H, PdMe), 1.50 (m,
2H, CH2CH2CH2), 2.10 (bs, 3H, Me14), 2.20 (bs, 6H, CH3CN and
Me13 overlapping), 6.63 (bs, 1H, H3), 6.74 (bs, 1H, H6), 7.45 (bs,
4H, Arf Hp), 7.55 (m, 1H, H11), 7.65 (m, 1H, H9), 7.66 (bs, 8H, Arf
Ho), 7.92 (m, 1H, H10), 8.18 (s, 1H, H7), 8.25 (m, 1H, H12). 13C-
{1H} NMR (CDCl3): δ -1.4 (SiMe2), 2.6 (PdMe), 4.4 (CH3CN),
15.2 and 17.8 (Me13,14 and CH2), 17.5 (CH2), 21.8 (CH2), 117.4
(Arf Cp), 120.7 (C3), 123.2 (C6), 124.3 (q, JC,F ) 272 Hz, CF3),
(C2 and C5 not assigned), 128.4 (C9), 128.5 (C11), 128.8 (q, JC,F
)
28 Hz, Arf Cm), 134.6 (Arf Co), 139.5 (C1), 140.6 (C10), 149.2 (C12),
154.4 (C8), 155.5 (C4), 161.6 (q, JC,B ) 50 Hz, Arf Cipso), 161.6
(C7). IR (KBr): ν 1610 cm-1 (m, CdN).
G2-ONNMe2[PdMe(MeCN)] (9b). Orange-yellow solid. Yield:
74%. Anal. Calcd for C448H380N24O8Si13Pd8B8F192 (11 178.76): C,
48.14; H, 3.42; N, 3.01. Found: C, 47.48; H, 3.25, N, 2.80. NMR
data for the major isomer (60% trans-Me-P-Nimine) are as follows.
1H NMR (CDCl3): δ -0.07 (s, 3H, SiMe), 0.16 (s, 12H, SiMe2),
0.62 (m, 8H, SiCH2), 0.83 (m, 4H, CH2SiMe2), 0.84 (s, 6H, PdMe),
1.40 (bm, 6H, CH2CH2CH2), 2.07 (bs, 6H, Me14), 2.20 (bs, 12H,
CH3CN and Me13 overlapping), 6.60 (bs, 4H, H3,6), 7.42 (bs, 8H,
Arf Hp), 7.50-7.78 (m, 20H, H9,11 and Arf Ho), 7.97 (m, 2H, H10),
8.16 (s, 2H, H7), 8.27 (m, 2H, H12). IR (KBr): ν 1611 cm-1 (m,
CdN).
Preparation of G3-pyridylimine-Pd(Cl)Me Dendritic Com-
plexes 7. Compounds 7b,c were synthesized as described above
for 2 by starting from the corresponding G3-pyridylimine dendritic
ligands G3-ONNMem (IVb,c).
G3-ONNMe2[PdMe(MeCN)] (10b). Orange-yellow solid. Yield:
87%. Anal. Calcd for C928H828N48O16Si29Pd16B16F384 (22894.66):
C, 48.68; H, 3.65; N, 2.94. Found: C, 47.50; H, 3.68; N, 2.55.
NMR data for the major isomer (55% trans-Me-P-Nimine) are as
follows. 1H NMR (CDCl3): δ -0.08 (s, 9H, SiMe), 0.16 (s, 24H,
SiMe2), 0.62 (m, 20H, SiCH2), 0.83 (m, 8H, CH2SiMe2), 0.84 (s,
12H, PdMe), 1.40 (bm, 14H, CH2CH2CH2), 2.07 (s, 12H, Me14),
2.20 (bs, 24H, CH3CN and Me13 overlapping), 6.50-6.80 (bs, 8H,
H3,6), 7.42 (bs, 16H, Arf Hp), 7.66 (bm, 40H, H9,11 and Arf Ho),
8.00 (m, 4H, H10), 8.16 (s, 4H, H7), 8.27 (m, 4H, H12). IR (KBr):
ν 1611 cm-1 (m, CdN).
G3-ONNMe2[Pd(Cl)Me] (7b). Yellow-orange solid. Yield:
71%. Anal. Calcd for C368H556N32O16Si29Cl16Pd16 (8769.11): C,
1
50.40; H, 6.39; N, 5.11. Found: C, 49.18; H, 6.34; N, 4.50. H
NMR (CDCl3): δ -0.07 (s, 9H, SiMe), 0.21 (s, 24H, SiMe2), 0.57
(m, 20H, SiCH2), 0.65 (s, 12H, PdMe), 0.81 (m, 8H, CH2SiMe2),
1.31 (m, 6H, CH2CH2CH2), 1.44 (m, 8H, CH2CH2CH2), 2.07 (s,
12H, Me14), 2.18 (s, 12H, Me13), 6.55 (s, 4H, H3), 6.71 (s, 4H,
H6), 7.63 (m, 4H, H11), 7.90 (m, 4H, H9), 7.99 (pt, 4H, H10), 8.44
(s, 4H, H7), 8.97 (s, 4H, H12). 13C{1H} NMR (CDCl3): δ -4.8
(SiMe, only one peak can be distinguished), -0.8 (SiMe2), 0.5
(PdMe), 16.3 and 17.9 (Me13,14), 17.8, 18.5, 18.6, and 21.8 (CH2),
120.4 (C3), 123.9 (C6), 127.0 (C5,9), 128.3 (C2,11), 138.7 (C10), 140.9
(C1), 149.2 (C12), 151.5 (C8), 152.6 (C4), 167.4 (C7). IR (KBr): ν
1615 (m), 1585 (s, CdN), 1565 cm-1 (w).
General Procedure for CO/4-tert-Butylstyrene Copolymeri-
zation Reactions. Prior to use, 4-tert-butylstyrene (TBS) was passed
through neutral alumina (70-230 mesh) to remove the stabilizer.
All runs were made under the same catalytic conditions, at room
temperature, PCO ) 1 atm, in CH2Cl2 (TBS/Pd ) 620) or neat TBS
(TBS/Pd ) 1100). The corresponding catalyst precursor was
weighed (8-16 mg, 12.5 µmol of Pd), and when necessary, the
cocatalyst Na[BArf4] (10-15 mg) was also introduced into 30 mL
screw-capped glass pressure reactors (Schlenk) equipped with a
magnetic stirrer. The reactor was capped and sealed with a septum,
purged by repeated argon/vacuum operations, and, if used, purified
CH2Cl2 (5 mL) was charged, and flushed with CO gas. Copolym-
erization was initiated by the addition of 1.4 mL (reaction in CH2-
Cl2) or 2.5 mL (neat styrene) of TBS with vigorous stirring, under
1 atm of CO. After a desired time interval the CO feeding was
stopped, and CH2Cl2 (25 mL) was added in the case of viscous
mixtures. Palladium metal particles were removed by filtration
through a Celite column, and the solvent was removed under
reduced pressure. The polyketones were coagulated by vigorous
stirring in methanol and purified by reprecipitation with methanol
from a CH2Cl2 solution (5 mL). Finally the product was dried in
an oven at 80 °C to constant weight. The characterization of these
G3-ONNMe3[Pd(Cl)Me] (7c). Dark orange solid. Yield: 70%.
Anal. Calcd for C384H588N32O16Si29Cl16Pd16(8993.54): C, 51.28; H,
6.59; N, 4.98. Found: C, 50.32; H, 6.76; N, 4.56. 1H NMR
(CDCl3): δ -0.07 (s, 9H, SiMe), 0.20 (s, 24H, SiMe2), 0.57 (m,
20H, SiCH2), 0.73 (s, 12H, PdMe), 0.80 (m, 8H, CH2SiMe2), 1.31
and 1.45 (2 × m, 14H, CH2CH2CH2), 2.08 (s, 12H, Me14), 2.20 (s,
12H, Me13), 3.01 (s, 12H, Me15), 6.55 (s, 4H, H3), 6.68 (s, 4H,
H6), 7.42 (m, 4H, H11), 7.67 (m, 4H, H9), 7.82 (pt, 4H, H10), 8.42
(s, 4H, H7). 13C{1H} NMR (CDCl3): δ -4.8 (SiMe, only one peak
can be distinguished), -0.8 (SiMe2), 4.5 (PdMe), 16.3 and 17.9
(Me13,14), 17.8, 18.5, 18.6, 19.1, and 21.8 (CH2), 25.7 (Me15), 120.4
(C3), 124.2 (C6), 125.4 (C9), 127.0 (C5), 128.6 (C2), 130.1 (C11),
138.1 (C10), 141.0 (C1), 151.2 (C8), 152.6 (C4), 163.9 (C12), 168.6
(C7). IR (KBr): ν 1621 (m), 1590 cm-1 (s, CdN).
Preparation of Cationic Gn-pyridylimine-[Pd(MeCN)Me]+
Dendritic Complexes (8b-10b). Compounds 8b-10b were syn-
thesized as described above for 3, starting from the corresponding
chloro(methyl)palladium dendritic complex Gn-ONNMe2Pd(Cl)-
Me(5b, n ) 1; 6b, n ) 3; 7b, n ) 3). In each case, most parts of

Palladium Dendrimers Copolymerizing CO/Styrene
Organometallics, Vol. 25, No. 12, 2006 3055
materials was carried out by 1H and 13C{1H} NMR (room
temperature, CDCl3), IR, and GPC.
(Universitat Rovira i Virgili, Tarragona, Spain) for their valuable
assistance with the discussion and training on copolymerization
techniques.
Supporting Information Available: Table S1, summarizing
coordination-induced shift values observed by NMR for compounds
1-3. This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. We gratefully acknowledge financial
support from the DGI-Ministerio de Ciencia y Tecnolog´ıa
(Project BQU2001-1160) and Comunidad de Madrid (Project
GR/MAT/0733/2004). In addition, we express our gratitude to
Dr. Amaia Bastero, Dr. Aurora Ruiz, and Prof. Carmen Claver
OM0601044