Synthesis of palladium complexes with an anionic P～O chelate and their use in copolymerization of ethene with functionalized norbornene derivatives: Unusual functionality tolerance

Article abstract of DOI:10.1021/om0607402

A series of anionic P～O ligands and corresponding palladium - allyl complexes have been synthesized. The latter, along with palladium species formed in situ, were employed for the copolymerization of ethene with functionalized norbornene derivatives. The formed copolymers had high norbornene content (>40 mol %). The systems are highly tolerant of reactive functionalities, and the copolymerizations can even be carried out in the presence of water.

Full text of DOI:10.1021/om0607402

210
Organometallics 2007, 26, 210-216
Synthesis of Palladium Complexes with an Anionic P∼O Chelate
and Their Use in Copolymerization of Ethene with Functionalized
Norbornene Derivatives: Unusual Functionality Tolerance
Shengsheng Liu, Sachin Borkar, David Newsham, Hemant Yennawar, and Ayusman Sen*
Department of Chemistry, The PennsylVania State UniVersity, UniVersity Park, PennsylVania 16802
ReceiVed August 15, 2006
A series of anionic P∼O ligands and corresponding palladium-allyl complexes have been synthesized.
The latter, along with palladium species formed in situ, were employed for the copolymerization of
ethene with functionalized norbornene derivatives. The formed copolymers had high norbornene content
(>40 mol %). The systems are highly tolerant of reactive functionalities, and the copolymerizations can
even be carried out in the presence of water.
groups and resistant to â-hydrogen abstraction. We,3 Grubbs,4
Bazan,5 Mecking,6 and others2m have recently described nickel-
based systems for the copolymerization of ethene with func-
tionalized norbornenes. However, the extent of incorporation
of the norbornene monomer is low (<25 mol %). Herein, we
report on catalyst systems based on palladium complexes
incorporating anionic P∼O ligands. Two π-allyl complexes were
synthesized and crystallographically characterized. Copolymer-
izations carried out using these, along with complexes formed
in situ show unusual functionality tolerance from several
standpoints. First, they catalyze the copolymerization of ethene
with functionalized norbornene derivatives to form copolymers
with very high norbornene content (>40 mol %). Second, the
system is so highly tolerant of reactive functionalities that the
copolymerization can even be carried out in the presence of
water.
The catalytic systems are based on that reported by Drent,7
who also reported the copolymerization of ethene with nor-
bornene derivatives.7b Two related P∼O ligands, 2-[bis(2-
methoxyphenyl)phosphino]benzenesulfonicacid (1) and 2-[bis-
(2,6-dimethoxyphenyl)phosphino]benzenesulfonicacid (2), were
employed (Figure 1). The X-ray crystal structure of 2 was
determined and is shown in Figure 2. In one series of
experiments, the catalytic systems were formed in situ by
combining Pd(dibenzylideneacetone)2 [Pd(DBA)2] and one of
the ligands in a 1:1.2 molar ratio.
Introduction
Metal-catalyzed addition polymerization that leads to materi-
als incorporating relatively high amounts of functionalized vinyl
monomers is an area of great current interest in synthetic
polymer chemistry.1 The copolymers of ethene with norbornene
show such superior properties as excellent transparency, high
glass transition temperature, good solvent resistance, and high
thermal stability. The range of desirable properties is expected
to be further enhanced by the use of appropriately functionalized
norbornene derivatives. The inherent difficulty of polymerizing
functionalized vinyl monomers stems from the poisoning of the
catalyst center by coordination of the functionality. Late
transition metals are more tolerant of polar functionalities in
the monomer and the formed polymer. A number of nickel and
palladium compounds have been shown to catalyze the addition
polymerization of functionalized norbornenes.2 However, most
of them are ineffective for the copolymerization of ethene with
norbornene because the former act as a chain transfer agent
through â-hydrogen abstraction. Therefore, in order to achieve
the copolymerization of ethene with functionalized norbornenes,
it is necessary for the catalyst to be both tolerant of functional
* Corresponding author. E-mail: asen@psu.edu.
(1) (a) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 429. (b) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem.
ReV. 2000, 100, 1169. (c) Boffa, L. S.; Novak, B. M. Chem. ReV. 2000,
100, 1479.
Results and Discussion
(2) (a) Mehler, C.; Risse, W. Makromol. Chem., Rapid Commun. 1992,
13, 455. (b) Breunig, S.; Risse, W. Makromol. Chem. 1992, 193, 2915. (c)
Goodall, B. L.; McIntosh, L. H., III; Rhodes, L. F. Macromol. Symp. 1995,
89, 421. (d) Safir, A. L.; Novak, B. M. Macromolecules 1995, 28, 5396.
(e) Mathew, J. P.; Reinmuth, A.; Melia, J.; Swords, N.; Risse, W.
Macromolecules 1996, 29, 2755. (f) Heinz, B. S.; Heitz, W.; Kru¨gel, S.
A.; Raubacher, F.; Wendorff, J. H. Acta Polym. 1997, 48, 385. (g) Heinz,
B. S.; Alt, F. P.; Heitz, W. Macromol. Rapid Commun. 1998, 19, 251. (h)
Abu-Surrah, A.; Reiger, B. J. Mol. Catal. A 1998, 128, 239. (i) Janiak, C.;
Lassahn, P. J. Mol. Catal. A 2001, 166, 193. (j) Hennis, A. D.; Polley, J.
D.; Long, G. S.; Sen, A.; Yandulov, D.; Lipian, J.; Benedikt, G. M.; Rhodes,
L. F.; Huffman, J. Organometallics 2001, 20, 2802. (k) Lipian, J.; Mimna,
R. A.; Fondran, J. C.; Yandulov, D.; Shick, R. A.; Goodall, B. L.; Rhodes,
L. F.; Huffman, J. C. Macromolecules 2002, 35, 8969. (l) Barnes, D. A.;
Benedikt, G. M.; Goodall, B. L.; Huang, S. S.; Kalamarides, H. A.; Lenhard,
S.; McIntosh, L. H. Selvy, K. T.; Shick, R. A.; Rhodes, L. F. Macromol-
ecules 2003, 36, 2623. (m) Goodall, B. L. In Late Transition Metal
Polymerization Catalysis; Rieger, B., Baugh, L. S., Kacker, S., Striegler,
S., Eds.; Wiley-VCH: Weinheim, 2003; p 101. (n) Funk, J. K.; Andes, C.
E.; Sen, A. Organometallics 2004, 23, 1680.
Table 1 summarizes the results of copolymerization of ethene
with functionalized norbornenes. The polyethene obtained in
(3) Benedikt, G. M.; Elce, E.; Goodall, B. L.; Kalamarides, H. A.;
McIntosh, L. H., III; Rhodes, L. F.; Selvy, K. T.; Andes, C.; Oyler, K.;
Sen, A. Macromolecules 2002, 35, 8978.
(4) (a) Younkin, T. R.; Connor, E. F.; Henderson, J. I.; Friedrich, S. K.;
Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460. (b) Connor, E.
F.; Younkin, T. R.; Henderson, J. I.; Hwang, S.; Grubbs, R. H.; Roberts,
W. P.; Litzau, J. J. J. Polym. Sci. Part A, Polym. Chem. 2002, 40, 2842.
(5) (a) Diamanti, S. J.; Ghosh, P.; Shimizu, F.; Bazan, G. C. Macro-
molecules 2003, 36, 9731. (b) Diamanti, S. J.; Khanna, V.; Hotta, A.;
Yamakawa, D.; Shimizu, F.; Kramer, E. J.; Fredrickson, G. H.; Bazan, G.
C. J. Am. Chem. Soc. 2004, 126, 10528.
(6) Bauers, F. M.; Mecking, S. Macromolecules 2001, 34, 1165.
(7) (a) Drent, E.; van Dijk, R.; van Ginkel, R.; van Oort, B.; Pugh, R. I.
Chem. Commun. 2002, 744. (b) Drent, E.; Sjardijn, W.; Suykerbuyk, J.;
Wanninger, K. PCT Int. Appl. WO0006615, 2000.
10.1021/om0607402 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 11/24/2006

Palladium Complexes with an Anionic P∼O Chelate
Organometallics, Vol. 26, No. 1, 2007 211
carbons of the norbornene units in the polymer backbone. The
CH2 carbons from ethene and NB units appear at 29.8 and 30-
31.8 ppm, respectively.
The effect of solvent on copolymerization of ethene with
bicyclo[2.2.1]hept-5-enyl-2-methyl acetate is presented in Table
2. Good activity was observed in aromatic solvent and even in
relatively coordinating 1,2-dimethoxyethane (DME), although
the incorporation of the functionalized monomer was much
lower in the latter. On the other hand, no polymer was obtained
when the reaction was carried out in acetonitrile, suggesting
stronger coordination of acetonitrile to the metal center. This
is supported by the qualitative observation that a purple toluene
solution of Pd(DBA)2 and ligand 1 immediately turned bright
yellow when a small amount of acetonitrile was added. It is
noteworthy that the molecular weights of the copolymers of
ethene with bicyclo[2.2.1]hept-5-enyl-2-methyl acetate are much
higher than that of copolymers of ethene with acrylates,7
presumably because the inaccessibility of â-hydrogens in
norbornenes prevents chain termination/transfer. The single-site
characteristic of the catalyst is supported by the relatively narrow
molecular weight distribution of the obtained copolymers (Mw/
Mn < 2).
Figure 1. Chemical structures of ligands 1 and 2.
Gas chromatography was employed to investigate the relative
uptake of the exo versus endo isomer of bicyclo[2.2.1]hept-5-
enyl-2-methyl acetate in the copolymerization reaction. As is
clear from Figure 4, there is a high preference for the
incorporation of the exo isomer in the growing polymer chain.
This is in agreement with earlier reports.2b,e,g,j,n
A very unusual feature of the present catalytic system is that
while it tolerates coordinating functionalities present in nor-
bornene derivatives and in acrylates,7 allowing the copolymer-
ization of these classes of monomers with ethene, simple
1-alkenes such as propene, 1-hexene, and styrene cannot be
polymerized. Analysis of products from attempted copolymer-
ization with ethene reveals no detectable comonomer incorpora-
tion into polyethene chains. Furthermore, the rate of polyethene
formation in the presence of these monomers is almost an order
of magnitude slower. To our knowledge this is the only known
alkene polymerization system that shows such a selectivity. We
had earlier reported that the rate of insertion of vinyl monomers
(CH2dCHR) into palladium-alkyl bonds in cationic complexes
decreases with increasing donor ability of the substituent (R )
CO2R > H > alkyl).8 An alkene with an electron-withdrawing
substituent coordinates less strongly to the electrophilic metal
(i.e., σ-donation is more important than π-back-donation).9 Thus,
a weaker metal-alkene bond has to be broken for the insertion
to proceed (i.e., the destabilization of the alkene complex leads
to a lower insertion barrier).9 Therefore, both the failure of
1-alkenes to be incorporated in the present system and the
attenuation of polymerization activity in their presence can be
ascribed to stronger binding but slower insertion rate for
1-alkenes.
Figure 2. ORTEP diagram of ligand 2. The hydrogens and
methylene chloride are omitted for clarity.
run 1 is predominantly linear, as evidenced by a single dominant
13C NMR resonance at 28 ppm and a melting point (DSC) of
127.8 °C. As shown in Table 1, the activity for ethene
copolymerization with norbornene or bicyclo[2.2.1]hept-5-enyl-
2-methyl acetate is comparable or even higher than that of ethene
homopolymerization (run 1 vs 2, 3). In particular, the high
copolymerization rate with bicyclo[2.2.1]hept-5-enyl-2-methyl
acetate is remarkable. Lowering the ethene pressure from 500
to 150 psi lowers the copolymerization activity but leads to very
high incorporation of functional norbornenes (e.g., runs 4, 5).
Both the copolymerization activity and the level of function-
alized norbornene incorporation into the resultant copolymer
appear to be a sensitive function of the ligand. For example,
under the same conditions, the Pd(DBA)2/ligand 1 catalyst
produced copolymers with 37.7 mol % of bicyclo[2.2.1]hept-
5-enyl-2-methyl acetate (run 4) and 22.6 mol % of bicyclo-
[2.2.1]hept-5-en-2-ol acetate (run 6), while the Pd(DBA)2/ligand
2 catalyst generated only copolymers with 31.2 mol % of
bicyclo[2.2.1]hept-5-enyl-2-methyl acetate (run 8) and 13.3 mol
% of bicyclo[2.2.1]hept-5-en-2-ol acetate (run 10). On the other
hand, there is little effect on copolymer molecular weight (e.g.,
run 6: Mn, 47 000; Mw/Mn, 2.1; run 10: Mn, 49 700; Mw/Mn,
1.8).
The structures of the obtained copolymers were analyzed by
1H and 13C NMR spectroscopy (see Figure 3). The relative
simplicity of the latter suggests structures with isolated nor-
bornene units. Presumably the size of the norbornene monomer
precludes its consecutive insertion. Thus only EEE, NEE, and
ENE triads are present (E ) ethene, N ) norbornene monomer).
The 13C NMR assignments are based on our previous report;3
the resonance at 33.2 ppm can be assigned to the apical carbon
of the norbornene. The resonances between 41.6-42.4 and
47.4-48.2 ppm are due to the bridgehead CH and the CH
As discussed above, the catalyst system is remarkably tolerant
of coordinating functionalities present either in the monomer
or in the reaction solvent. To further underscore this, we carried
out the emulsion copolymerization of ethene with bicyclo[2.2.1]-
hept-5-enyl-2-methyl acetate in a 9:1 (v/v) mixture of water
and toluene (the latter was required to dissolve the catalyst and
the monomer) (Conditions: Pd(DBA)2, 13.5 µmol; ligand 1,
16.2 µmol; sodium dodecylsulfate, 0.9 g; ethene, 500 psi;
(8) Kang, M.; Sen, A.; Zakharov, L.; Rheingold, A. L. J. Am. Chem.
Soc. 2002, 124, 12080.
(9) von Schenck, H.; Stro¨mberg, S.; Zetterberg, K.; Ludwig, M.;
Åkermark, B.; Svensson, M. Organometallics 2001, 20, 2813.

212 Organometallics, Vol. 26, No. 1, 2007
Table 1. Ethene/Functional Norbornene Copolymerization
Liu et al.
b
a Conditions: [Ligand]/[Pd] ) 1.2 (molar ratio); toluene, 10 mL; 95 °C. Conditions: [B(C6F5)3]/Pd ) 2; toluene, 10 mL; 95 °C.

Palladium Complexes with an Anionic P∼O Chelate
Organometallics, Vol. 26, No. 1, 2007 213
Figure 3. 13C NMR (C2D2Cl4) spectrum of copolymer of ethene with norbornene (15.2 mol %).
Figure 5. ORTEP of complexes 3a and 3b. Hydrogen atoms in
3a and hydrogen atoms and chloroform molecule in 3b are omitted
for clarity.
Table 3. Selected Bond Distances (Å) and Angles (deg) of
Complexes 3a and 3b
Figure 4. Plot of endo/exo isomers present in unreacted bicyclo-
[2.2.1]hept-5-enyl-2-methyl acetate as a function of time in its
copolymerization with ethene. (Reaction conditions: ethene, 250
psi; bicyclo[2.2.1]hept-5-enyl-2-methyl acetate, 2 g; Pd(DBA)2, 4.5
µmol; ligand 1, 5.4 µmol; toluene, 10 mL; 1,1,2,2-tetrachloroethane,
50 µL; 95 °C.)
3a
3b
Pd(1)-O(2) ) 2.117(2)
Pd(1)-O(3) ) 2.154 (4)
Pd(1)-P(1) ) 2.3028(8)
Pd(1)-C(21) ) 2.223(3)
Pd(1)-C(22) ) 2.109(3)
Pd(1)-C(23) ) 2.087(3)
P(1)-C(1) ) 1.837(3)
Pd(1)-P(5) ) 2.3048 (14)
Pd(1)-C(21) ) 2.100(6)
Pd(1)-C(22) ) 2.136(7)
Pd(1)-C(23) ) 2.251(8)
P(5)-C(1) ) 1.835(5)
Table 2. Solvent Effecta
S(1)-C(6) ) 1.788(3)
S(1)-C(6) ) 1.786(5)
yield activity (kg/ NB incorp
O(2)-Pd(1)-P(1) ) 94.00(7)
C(7)-P(1)-Pd(1) ) 114.69(11)
S(1)-O(2)-Pd(1) ) 124.66(13)
C(14)-P(1)-Pd(1) ) 117.29(10)
O(3)-Pd(1)-P(5) ) 94.78(10)
C(7)-P(5)-Pd(1) ) 115.30(18)
S(1)-O(3)-Pd(1) ) 118.1(2)
C(14)-P(5)-Pd(1) ) 119.82(19)
b
b
run
solvent
(g)
mol[Pd]‚h)
(mol %)
Mn
Mw/Mn
1
2
3
4
5
6
acetonitrile
DME
ethanol
anisole
toluene
n.r.
0
118
32
133
167
104
0
1.59
0.43
1.80
2.25
5.62
38.2
34.6
31.4
29.0
66 900
1.82
61 100
73 000
60 100
1.79
1.91
1.73
In an attempt to better define the catalysts, π-allyl (3a) and
π-1-methallyl (3b) complexes incorporating the P∼O ligand 1
were synthesized by the reaction of the chloro-bridged allyl/π-
1-methallyl dimer with the sodium salt of 1 in dichloromethane
at -20 °C.10 The crystal structures of complexes 3a and 3b are
depicted in Figure 5, and bond length and bond angles are given
in Table 3. In view of the expected significantly stronger trans
effect of the phosphine ligand, it is not surprising that the Pd-C
chlorobenzene 1.40
a Conditions: solvent, 10 mL; bicyclo[2.2.1]hept-5-enyl-2-methyl acetate,
2 g; ethene, 150 psi; Pd(DBA)2, 4.5 µmol; ligand 1, 5.4 µmol; 95 °C; 3 h.
bDetermined by SEC relative to polystyrene standards.
bicyclo[2.2.1]hept-5-enyl-2-methyl acetate, 3 g; toluene, 10 mL;
water, 90 mL; 95 °C, 3 h. Yield, 7.1 g; activity, 175 kg/mol-
[Pd]‚h; norbornene, 13.4 mol % Mn, 42 000; Mw/Mn, 1.9). The
lower activity is expected due to significantly reduced solubility
of ethene in water.
(10) Hearley, A. K.; Nowack, R. J.; Rieger, B. Organometallics 2005,
24, 2755-2763.

214 Organometallics, Vol. 26, No. 1, 2007
Liu et al.
Scheme 1. Outline of Ligand Synthesis
used as solvent. The chemical shifts are referenced relative to the
solvent. Molecular weights and molecular weight distributions were
measured on a Shimadzu size exclusion chromatograph (SEC) using
a flow rate of 1 mL/min and a three-column bed (Styragel HR 7.8
× 300 mm columns with 5 mm bead size: 100-10 000, 500-
30 000, and 5000-6 000 000 D), a Shimadzu RID 10A differential
refractometer, and SPD-10A UV-vis detector. SEC samples were
run in CHCl3 at ambient temperature and calibrated to polystyrene
standards obtained from Aldrich. GC data were obtained on a
Hewlett-Packard 5890 Series II instrument fitted with an Alltech
EC-5 column and a FID detector using 1,1,2,2-tetrachloroethane
as an internal standard.
Synthesis of Ligand. All manipulations were performed under
an inert atmosphere using standard glovebox and Schlenk tech-
niques. Solvents were degassed in 20 L reservoirs and passed
through two sequential purification columns. Oxygen was removed
by a copper catalyst, and water was removed by activated alumina.
2-[Bis(2-methoxyphenyl)phosphino]benzenesulfonic Acid
(ligand 1). This ligand was synthesized by two different procedures
(Scheme 1). Procedure I is the same as the literature procedure7
except that n-butyllithium was used in the last step. In procedure
II, bis(2-methoxyphenyl)methoxyphosphine was converted to bis-
(2-methoxyphenyl)chlorophosphine as follows before reacting with
the lithium salt of benzenesulfonic acid. To a solution of bis(2-
methoxyphenyl)methoxyphosphine (1.89 g, 6.85 mmol) in THF (10
mL) was added dropwise a solution of PCl3 (4.71 g, 34.3 mmol)
in THF (10 mL) at 0 °C. The reaction was then allowed to stand
for 5 h at room temperature. The unreacted PCl3 was removed under
vacuum. The bis(2-methoxyphenyl)chlorophosphine solution in
THF was added slowly to the lithium salt of benzenesulfonic acid
at -40 °C. The reaction was allowed to stand at room temperature
for 16 h. Water (40 mL) was then added, followed by the removal
of THF in vacuum. The aqueous solution was acidified to pH ) 1
by adding concentrated HCl (37%). The precipitate was filtered
off, and the filtrate was washed with tert-butyl methyl ether (15
mL). After extracting with CH2Cl2 (20 mL × 3), the crude product
was dried over anhydrous MgSO4. Solvent was removed under
vacuum to afford a white powder (1.05 g, 38.2%). 1H NMR (CD2-
Cl2, ppm): 9.1 (1H, P-H), 6.8-8.4 (m, 12H, phenyl), 3.8 (s, 6H,
OCH3). 31P NMR (CDCl3): -9.6 ppm.
bond of the allyl group trans to it is significantly longer than
the one trans to the sulfonate group (3a, 2.22 versus 2.09 Å;
3b, 2.25 versus 2.10 Å).
Neither complex 3a nor 3b showed significant activity toward
the copolymerization of ethene and norbornene, presumably
because the η3-allyl group occupies two coordination positions,
thereby preventing the coordination of the incoming monomer.
However, the polymerization activity was restored when 1-2
molar equiv of B(C6F5)3 was added (Table 1). Under these
conditions, the polymerization activity of 3b was similar to that
observed when the catalytic system was formed in situ. The
activity of 3a was somewhat lower possibly because the smaller
allyl group binds more tightly to the metal than the 1-methallyl
group. The specific role played by B(C6F5)3 in activating 3a
and 3b is currently under investigation.
In conclusion, we have described catalyst systems based on
palladium complexes incorporating anionic P∼O ligands. Two
new π-allyl complexes were synthesized and crystallographically
characterized. Copolymerizations carried out using these, along
with complexes formed in situ, show functionality tolerance that
was unusual from several standpoints. First, they catalyze the
copolymerization of ethene with functionalized norbornene
derivatives to form copolymers with very high norbornene
content (>40 mol %). Second, the system is so highly tolerant
of reactive functionalities that the copolymerization can even
be carried out in the presence of water.
Experimental Section
Materials. All chemicals were purchased from Aldrich except
as stated otherwise. The functionalized norbornene monomers used
in this work are a mixture of endo and exo isomers. Bicyclo[2.2.1]-
hept-5-ene-2-carboxylic acid ethyl ester (97%), bicyclo[2.2.1]hept-
5-en-2-ol acetate (97%), and bicyclo[2.2.1]hept-5-enyl-2-methyl
acetate (97%) were generously donated by the BF Goodrich
Company. Palladium(II)acetate and bis(dibenzylideneacetone)-
palladium(0) [Pd(DBA)2] were obtained from Johnson Matthey
Company. Allylpalladium chloride dimer, 1-methallylpalladium
chloride dimer, and tris(pentafluorophenyl)borane were purchased
from Strem Chemicals and used without further purification. CP
grade ethene was supplied by the Matheson Company and used
without further purification.
2-[Bis(2,6-dimethoxyphenyl)phosphino]benzenesulfonic Acid
(ligand 2). To a solution of benzenesulfonic acid (1.08 g, 6.84
mmol) in THF (15 mL) was added dropwise n-butyllithium (15
mmol, 2.5 M in hexane) at 0 °C. After stirring at room temperature
for 18 h a solution of bis(2,6-dimethoxyphenyl)methoxyphosphine
(2.30 g, 6.86 mmol) in THF (50 mL) was added at -40 °C, and
Characterization. NMR spectra were recorded at 125 °C on a
1
Bruker DPX-300 spectrometer at 300.15 MHz for H NMR and
75.4 MHz for 13C NMR spectra. 1,1,2,2-Tetrachloroethane-d2 was

Palladium Complexes with an Anionic P∼O Chelate
Organometallics, Vol. 26, No. 1, 2007 215
Table 4. Crystal Data for Ligand 2 and Complexes 3a and 3b
2‚CH2Cl2
C23H25Cl2O7PS
3a
3b‚2CHCl3
empirical formula
fw
C23H23O5PPdS
547.84
C26H25Cl6O5PPdS
799.59
547.36
temperature
wavelength (Mo KR)
cryst size
cryst habit
cryst syst
98(2) K
0.71073 Å
108(2) K
0.71073 Å
0.20 × 0.14 × 0.11 mm
yellow cuboidal
monoclinic
298(2) K
0.71073 Å
0.38 × 0.36 × 0.24 mm
yellow cubical
orthorhombic
Pna2(1)
0.43 × 0.39 × 0.36 mm
clear brick
monoclinic
P2(1)/c
space group
unit cell dimens
P2(1)/n
a ) 13.979(2) Å
b ) 11.9196(17) Å
c ) 15.071(2) Å
2475.2(6) Å3
4
a ) 10.8667(11) Å
b ) 17.0383(18) Å
c ) 11.8080(13) Å
2176.7(4) Å3
4
a ) 14.9431(19) Å
b ) 10.2521(13) Å
c ) 21.630(3) Å
3313.7(7) Å3
4
volume
Z
density(calcd)
absorp coeff
F(000)
1.469 g/cm3
0.453 mm-1
1136
1.672 g/cm3
1.055 mm-1
1108
1.603 g/cm3
1.189 mm-1
1600
R1
3.72%
4.03%
5.35%
wR2
10.36%
11.34%
12.86%
diffractometer
data collection method
θ range for data collection
index ranges
CCD area detector
phi and omega scans
2.19-28.31°
-18 e h e 18,
-15 e k e 10,
-20 e l e 19
CCD area detector
phi and omega scans
2.10-28.30°
-14 e h e 13,
-22 e k e 21,
-11 e l e 15
CCD area detector
phi and omega scans
1.88-28.35°
-19 e h e 13,
-12 e k e 13,
-28 e l e 28
the reaction was allowed to stand for a further 12 h. Water (40
mL) was then added, followed by the removal of THF in vacuum.
The aqueous solution was acidified to pH ) 1 by adding
concentrated HCl (37%). The precipitate was filtered off, and the
filtrate was washed with tert-butyl methyl ether (15 mL). After
extracting with CH2Cl2 (20 mL × 3), the crude product was dried
over anhydrous MgSO4. Solvent was removed under vacuum to
afford a white powder (1.25 g, 39.6%). The crystal for X-ray
analysis was obtained at -10 °C from a mixture of CH2Cl2 and
then placed in an oil-bath at 95 °C for 3 h. Following the reaction,
the reactor was cooled to room temperature. The contents of the
reactor were then poured into 500 mL of HCl-acidified methanol.
The precipitated polymer was washed and dried under vacuum.
Composition of the copolymer was determined from the integration
of the resonances at 3.60-4.20 ppm for the CH2OCO unit of
bicyclo[2.2.1]hept-5-enyl-2-methyl acetate and 1.2 ppm for the CH2
unit of ethene. Yield: 2.98 g, bicyclo[2.2.1]hept-5-enyl-2-methyl
acetate, 37.7 mol %.
1
hexane. H NMR (CD2Cl2, ppm): 10.3 (1H, P-H), 6.6-8.4 (m,
Determination of the Relative Uptake of endo versus exo
Isomer of Bicyclo[2.2.1]hept-5-enyl-2-methyl Acetate. In a N2-
filled glovebox, a 300 mL glass-lined stainless steel autoclave
equipped with a magnetic stir bar was charged toluene (10 mL),
Pd(DBA)2 (4.5 µmol), ligand 1 in toluene (5.4 µmol in 1 mL of
toluene), and bicyclo[2.2.1]hept-5-enyl-2-methyl acetate (2.0 g, 12
mmol), and 50 µL of 1,1,2,2-tetrachloroethane as internal reference.
The autoclave was charged with 250 psi of ethene and then placed
in an oil-bath at 95 °C. The amount of unreacted exo and endo
isomer present during the course of the reaction was determined
by GC analysis of samples taken at set intervals.
10H, phenyl), 3.6 (s, 12H, OCH3). 31P NMR (CDCl3): -29.3 ppm.
Synthesis of Complex 3a. Sodium carbonate (Na2CO3) (0.315
g, 2.97 mmol) was added to a flask containing ligand 1 (1 g, 2.48
mmol) and 15 mL of dichloromethane. The solution was stirred
until it formed a white precipitate (ca. 4 h). To this was added a
dichloromethane solution of allylpalladium chloride dimer (0.45
g, 1.24 mmol) at -20 °C, and stirring continued overnight. The
reaction mixture was filtered, and the filtrate was recrystallized using
pentane as a nonsolvent. Yield: 1.09 g (80%). 1H NMR (CD2Cl2,
ppm): 8.19 (1H, m, arom), 7.53 (2H, m, arom), 7.39 (1H, m, arom),
6.9-7.2 (8H, m, arom), 5.66 (1H, m, CH), 4.74 (1H, m, HCH),
3.80 (1H, m, HCH), 3.14 (1H, m, HCH), 2.65 (1H, d, HCH), 3.80
(6H, m, OCH3). 31P NMR (CD2Cl2, ppm): -2.9 (s). Because of
the general instability of this class of palladium compounds,
elemental analysis was not attempted. However, 3a was judged pure
by NMR spectroscopy (see Supporting Information). Its structure
was further established by X-ray crystallography.
Synthesis of Complex 3b. Complex 3b was synthesized by using
methallylpalladium chloride dimer by following the above proce-
dure. Yield: 1.1 g (78%). 1H NMR (CD2Cl2, ppm): 6.9-8.4 (12H,
m, arom), 5.45 (1H, m, CHdCHCH3), 4.62 (1H, m, CHdCHCH3),
3.74 (6H, s, OCH3), 3.10 (1H, br, HCH-CHdCH), 2.51 (1H, br,
HCH-CHdCH), 1.76 (3H, m, CHdCHCH3). 31P NMR (CD2Cl2,
ppm): -4.87 (s). 3b was judged pure by NMR spectroscopy (see
Supporting Information). Its structure was further established by
X-ray crystallography.
Emulsion Copolymerization of Ethene with Functionalized
Norbornene. In a N2-filled glovebox, a 600 mL glass-lined stainless
steel autoclave equipped with a mechanical stir bar was charged
with toluene (7 mL), Pd(DBA)2 (13.5 µmol), ligand 1 in toluene
(16.2 µmol in 3 mL toluene), and bicyclo[2.2.1]hept-5-enyl-2-
methyl acetate (3.0 g, 18.1 mmol). The autoclave was then taken
out of the glovebox, and sodium dodecylsulfate in water (0.9 g in
90 mL of degassed water) was added using a syringe. After
pressurizing with 500 psi of ethene, the reactor was placed in an
oil-bath at 95 °C for 3 h. Following the reaction, the reactor was
cooled to room temperature. The contents of the reactor were then
poured into 500 mL of HCl-acidified methanol, and the polymer
was recovered by filtration. Yield: 7.1 g; bicyclo[2.2.1]hept-5-enyl-
2-methyl acetate, 13.4 mol %, Mn, 42 000; Mw/Mn, 1.9.
Copolymerization with Norbornene Derivatives Using 3a or
3b. In a typical copolymerization experiment, a 300 mL glass-lined
stainless steel autoclave equipped with a magnetic stir bar was
charged with toluene (10 mL), 3a or 3b (4.5 µmol), tris-
(pentafluorophenyl)borane (9 µmol), and norbornene (1.1 g, 11.7
mmol) inside the nitrogen-filled glovebox. The autoclave was
charged with 500 psi of ethene and immersed in an oil-bath
preheated at 95 °C. After the desired time period the autoclave
Copolymerization of Ethene and Functionalized Norbornene.
In a typical experiment (Table 1, run 4), in a N2-filled glovebox a
300 mL glass-lined stainless steel autoclave equipped with a
magnetic stir bar was charged with toluene (10 mL), Pd(DBA)2
(4.5 µmol), ligand 1 in toluene (5.4 µmol in 1 mL of toluene), and
bicyclo[2.2.1]hept-5-enyl-2-methyl acetate (3.0 g, 18.1 mmol). The
autoclave was charged with 150 psi of ethene (single charge) and

216 Organometallics, Vol. 26, No. 1, 2007
Liu et al.
was allowed to cool to room temperature and the polymer was
precipitated in acidified methanol and dried under vacuum.
X-ray Structure Determination. Crystal data for ligand 2 and
complexes 3a and 3b are given in Table 4. See Supporting
Information for more details. The X-ray intensity data were
measured at 98(2) K for 2, 108(2) K for 3a, cooled by Rigaku-
MSC X-Stream 2000, and 298(2) K for 3b, on a Bruker SMART
APEX CCD area detector system equipped with a graphite
monochromator and a Mo KR fine-focus sealed tube (λ ) 0.71073
Å) operated at 1600 W power (50 kV, 32 mA). The detector was
placed at a distance of 5.8 cm from the crystal.
1997); software used to prepare material for publication: SHELX-
TL.11
Acknowledgment. This research was supported by the
National Science Foundation and the Rohm & Haas Company.
We acknowledge the NSF grant CHE-0131112 for the purchase
of a Bruker-AXS single-crystal X-ray diffractometer.
Supporting Information Available: Crystal structure data for
2, 3a, and 3b and 1H NMR spectra of 3a and 3b are available free
of charge via the Internet at http://pubs.acs.org.
Data Collection. SMART (Bruker, 1997); cell refinement: SAINT
(Bruker, 1997); data reduction: SAINT; program(s) used to solve
structure: SHELXTL (Sheldrick, 1997); program(s) used to refine
structure: SHELXTL; molecular graphics: ORTEP-3.2 (Farrugia,
OM0607402
(11) (a) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565. (b) Sheldrick,
G. M. SHELXTL; Bruker AXS Inc.: Madison, WI, 1997.