Reactivity of methacrylates in insertion polymerization

Article abstract of DOI:10.1021/ja107538r

Polymerization of ethylene by complexes [{(P∧O)PdMe(L)}] (P∧O = κ²-(P,O)-2-(2-MeOC₆H₄)₂PC ₆H₄SO₃)) affords homopolyethylene free of any methyl methacrylate (MMA)-derived units, e

Full text of DOI:10.1021/ja107538r

Published on Web 11/02/2010
Reactivity of Methacrylates in Insertion Polymerization
Thomas Ru¨nzi, Damien Guironnet, Inigo Go¨ttker-Schnetmann, and Stefan Mecking*
Chair of Chemical Materials Science, Department of Chemistry, UniVersity of Konstanz,
78464 Konstanz, Germany
Received August 20, 2010; E-mail: stefan.mecking@uni-konstanz.de
Abstract: Polymerization of ethylene by complexes [{(P^O)PdMe(L)}] (P^O ) κ2-(P,O)-2-(2-MeOC6H4)2-
PC6H4SO3)) affords homopolyethylene free of any methyl methacrylate (MMA)-derived units, even in the
presence of substantial concentrations of MMA. In stoichiometric studies, reactive {(P^O)Pd(Me)L} fragments
generated by halide abstraction from [({(P^O)Pd(Me)Cl}µ-Na)2] insert MMA in a 1,2- as well as 2,1-mode.
The 1,2-insertion product forms a stable five-membered chelate by coordination of the carbonyl group.
Thermodynamic parameters for MMA insertion are ∆Hq ) 69.0(3.1) kJ mol-1 and ∆Sq ) -103(10) J mol-1
K-1 (total average for 1,2- and 2,1-insertion), in comparison to ∆Hq ) 48.5(3.0) kJ mol-1 and ∆Sq ) -138(7)
J mol-1 K-1 for methyl acrylate (MA) insertion. These data agree with an observed at least 102-fold preference
for MA incorporation vs MMA incorporation (not detected) under polymerization conditions. Copolymerization
of ethylene with a bifunctional acrylate-methacrylate monomer yields linear polyethylenes with intact
methacrylate substituents. Post-polymerization modification of the latter was exemplified by free-radical
thiol addition and by cross-metathesis.
Introduction
like vinyl acetate or vinyl chloride. ꢀ-X elimination (X )
acetate, chloride) is one significant decomposition route.5 While
Catalytic insertion polymerization of ethylene and propylene
is one of the most well-studied chemical reactions. In terms of
applications, it is employed for the production of more than 70
million tons of polyolefins annually.1 An insertion (co)polym-
erization of electron-deficient polar-substituted vinyl monomers
like acrylates remains a challenge, however.
the copolymers obtained with cationic Pd(II) diimine catalysts
are highly branched, with analogous Ni(II) complexes6 and
neutral Pd(II) phosphinesulfonato complexes, linear ethylene-
methyl acrylate (MA) copolymers are formed.7
It was not until the mid-1990s that cationic Pd(II) diimine
complexes were reported to catalyze the insertion copolymer-
ization of ethylene and 1-olefins with acrylates.2 These d8 metal
(late transition metal) complexes are less oxophilic than early
transition metal polymerization catalysts and, therefore, more
tolerant toward polar moieties.3 Due to “chain walking” of the
catalyst, the highly branched copolymers, which consist of
ethylene as the major component (g75 mol %), contain acrylate
units at the end of branches preferentially.2,4 The mechanism
of this branch formation is well understood from extensive
variable-temperature NMR studies. Such studies have also
provided an understanding of the problems associated with
monomers not amenable for polymerization with these catalysts,
The latter catalysts, studied as in situ mixtures of ligands and
metal sources (above, left)7,8 as well as well-defined single-
component catalyst precursors [(P^O)PdMe(L)] (L ) pyridine,
lutidine, PPh3, 1/2Me2NCH2CH2NMe2, dimethylsulfoxide),9-12
are compatible with a remarkably broad scope of vinyl mono-
mers.13 Ethylene copolymerization with vinyl amides,14 vinyl
ethers,15 vinyl fluoride,16 vinyl sulfones,17 and even acryloni-
trile18 and vinyl acetate19 has been reported. Multiple consecu-
tive acrylate insertions can occur during copolymerization and
(1) Mu¨lhaupt, R. Macromol. Chem. Phys. 2003, 204, 289–327.
(2) (a) Johnson, L. K.; Mecking, S.; Brookhart, M. J. Am. Chem. Soc.
1996, 118, 267–268. (b) Mecking, S.; Johnson, L. K.; Wang, L.;
Brookhart, M. J. Am. Chem. Soc. 1998, 120, 888–899.
(5) (a) Foley, S. R.; Stockland, R. A.; Shen, H.; Jordan, R. F. J. Am.
Chem. Soc. 2003, 125, 4350–4361. (b) Williams, B. S.; Leatherman,
M. D.; White, P. S.; Brookhart, M. J. Am. Chem. Soc. 2005, 127,
5132–5146.
(3) (a) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. ReV. 2000, 100,
1169–1203. (b) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003,
103, 283–316. (c) Mecking, S. Coord. Chem. ReV. 2000, 203, 325–
351. (d) Mecking, S. Angew. Chem., Int. Ed. 2001, 40, 534–540. (e)
Guan, Z. Chem. Eur. J. 2002, 8, 3086–3092. (f) Domski, G. J.; Rose,
J. M.; Coates, G. M.; Bolig, A. D.; Brookhart, M. Prog. Polym. Sci.
2007, 32, 30–92. (g) Chen, E. Y.-X. Chem. ReV. 2009, 109, 5157–
5214.
(6) (a) Johnson, L.; Bennett, A.; Dobbs, K.; Hauptman, E.; Ionkin, A.;
Ittel, S.; McCord, E.; McLain, S.; Radzewich, C.; Yin, Z.; Wang, L.;
Wang, Y.; Brookhart, M. Polym. Mater. Sci. Eng. 2002, 86, 319. (b)
Wang, L.; Hauptman, E.; Johnson, L. K.; Marshall, W. J.; McCord,
E. F.; Wang, Y.; Ittel, S. D.; Radzewich, C. E.; Kunitsky, K.; Ionkin,
A. S. Polym. Mater. Sci. Eng. 2002, 86, 322. (c) Johnson, L.; et al.
ACS Symp. Ser. 2003, 857, 131–142.
(4) Related stoichiometric studies of acrylate insertion in Pd(II)
complexes: (a) Braunstein, P.; Frison, C.; Morise, X. Angew. Chem.,
Int. Ed. 2000, 39, 2867–9870. (b) Braunstein, P.; Agostinho, M. Chem.
Commun. 2007, 58–60.
(7) Drent, E.; van Dijk, R.; van Ginkel, R.; van Oort, B.; Pugh, R. I.
Chem. Commun. 2002, 744–745.
(8) Kochi, T.; Yoshimura, K.; Nozaki, K. Dalton Trans. 2006, 25–27.
9
10.1021/ja107538r  2010 American Chemical Society
J. AM. CHEM. SOC. 2010, 132, 16623–16630 16623

A R T I C L E S
Ru¨nzi et al.
in acrylate homooligomerization.12 Copolymerization of ethyl-
ene with CO can occur in a non-alternating fashion,20 and
alternating copolymers of CO with methyl acrylate and vinyl
acetate have been reported.21
Table 1. Polymerization of Ethylene in the Presence of Methyl
Methacrylate and Methyl Isobutyratea
concn of additive
[mol/L]
TOF [mol (C2H4)
mol (Pd)-1 h-1
entry
yield [g]
]
Mw/Mnb
Mnb[g mol-1
]
1-1
1-2
1-3
1-4
1-5
1-6
1-7
-
3.14
2.74
1.60
0.83
0.32
3.17
2.17
9.0 × 104
7.8 × 104
4.6 × 104
2.4 × 104
0.9 × 104
9.1 × 104
6.2 × 104
2.1
2.4
2.2
1.9
n.m.
2.1
2.1
1.8 × 104
1.5 × 104
1.6 × 104
1.8 × 104
n.m.
Curiously, in view of the aforementioned scope of vinyl
monomers studied, little information exists on the behavior of
methacrylatessone of the largest volume vinyl monomerssin
such insertion polymerizations. Stoichiometric reaction of a
cationic diimine complex with methyl methacrylate (MMA)
yielded the isolable cationic chelate complex resulting from 1,2-
insertion.22 Polymerization of ethylene by neutral phosphineeno-
lato Ni(II) catalysts in the presence of MMA resulted in chain
termination upon MMA insertion, to yield enolate-terminated
polyethylenes.23 The nature of the products of ethylene polym-
erization with neutral Ni(II) salicylaldiminato complexes in the
presence of MMA is a topic of current interest.24 Otherwise,
little has been reported on the reactivity or lack thereof of
methacrylates in insertion polymerization. We now give a full
0.10 MMA
0.25 MMA
0.50 MMA
1.00 MMA
0.10 MIB
0.50 MIB
1.8 × 104
1.8 × 104
a 100 mL total volume (toluene), 2.5 µmol of 1-dmso (stock solution
in CH2Cl2), 5 bar ethylene pressure, 80 °C reaction temperature, 0.5 h
reaction time; 50 mg of radical inhibitor (galvinoxyl) was added. MMA,
methyl methacrylate; MIB, methyl isobutyrate. b Determined by GPC in
1,2,4-trichlorobenzene at 160 °C vs PE standards, n.m., not measured.
account of the reactivity toward methacrylates in insertion
polymerization catalyzed by neutral phosphinesulfonato Pd(II)
complexes.
Results and Discussion
(9) Borkar, S.; Newsham, D. K.; Sen, A. Organometallics 2008, 27, 3331–
3334.
Polymerization in the Presence of Methyl Methacrylate. For
polymerization studies, the dimethylsulfoxide-substituted
1-dmso12 was employed as a catalyst precursor. Due to the
lability of the dmso ligand, this catalyst precursor enables
polymerizations at low ethylene concentrations, and conse-
quently relatively high [comonomer] vs [ethylene], which can
favor comonomer incorporation. However, polymerizations in
the presence of variable concentrations of MMA (Table 1)
yielded ethylene homopolymer exclusively, as evidenced by
high-temperature 1H NMR and IR spectroscopic analysis of the
polymer formed (Figures S1-S5, Supporting Information).
Concerning the experimental accuracy of polymer analysis, in
ethylene-MA copolymers with 0.1 mol % acrylate incorpora-
tion, the latter could be clearly observed by NMR and IR
spectroscopy (Figures S6 and S7, Supporting Information).
Taking into account the molecular weights of the polyethylenes
formed (Table 1), the detection limit is less than one methacry-
late unit per chain. That is, also MMA-derived end groups can
be excluded. Indeed, only ethylene-derived vinyl and internal
olefinic end groups are observed by 1H NMR spectroscopy. By
comparison to the ethylene homopolymerization essentially
occurring in the presence of methacrylate, polymerization in
the presence of acrylate (MA) under conditions similar to those
of entry 1-4 (95 °C and 0.6 M methyl acrylate) resulted in the
formation of a copolymer with a substantial acrylate incorpora-
tion of 9.4 mol %. This corresponds to a preference for acrylate
vs methacrylate incorporation of at least 102.
While no incorporation was observed, increasing amounts of
MMA in the reaction mixture resulted in decreased polymeri-
zation productivities (entries 1-1 to 1-5).25 By comparison to
ethylene polymerization in the absence of MMA, no enhanced
loss of polymerization activity with polymerization reaction time
is evident (Table S1, Supporting Information). This suggests
that MMA is not primarily involved in an irreversible deactiva-
tion process. In polymerizations in the presence of the saturated
analogue of MMA, methyl isobutyrate (MIB), a similar lowering
of productivity with increasing MIB concentrations is observed
(entries 1-6 and 1-7), albeit the effect is less pronounced than
with MMA itself. Likely, coordination of the ester moiety to
(10) Skupov, K. M.; Marella, P. R.; Simard, M.; Yap, G. P. A.; Allen, N.;
Conner, D.; Goodall, B. L.; Claverie, J. P. Macromol. Rapid Commun.
2007, 28, 2033–2038.
(11) Vela, J.; Lief, G. R.; Shen, Z.; Jordan, R. F. Organometallics 2007,
26, 6624–6635.
(12) (a) Guironnet, D.; Roesle, P.; Ru¨nzi, T.; Go¨ttker-Schnetmann, I.;
Mecking, S. J. Am. Chem. Soc. 2009, 131, 422–423. (b) Guironnet,
D.; Caporaso, L.; Neuwald, B.; Go¨ttker-Schnetmann, I.; Cavallo, L.;
Mecking, S. J. Am. Chem. Soc. 2010, 132, 4418–4426.
(13) (a) Berkefeld, A.; Mecking, S. Angew. Chem., Int. Ed. 2008, 47, 2538–
2542. (b) Nakamura, A.; Ito, S.; Nozaki, K. Chem. ReV. 2009, 109,
5215–5244.
(14) Skupov, K. M.; Piche, L.; Claverie, J. P. Macromolecules 2008, 41,
2309–2310.
(15) Luo, S.; Vela, J.; Lief, G. R.; Jordan, R. F. J. Am. Chem. Soc. 2007,
129, 8946–8947.
(16) Weng, W.; Shen, Z.; Jordan, R. F. J. Am. Chem. Soc. 2007, 129,
15450–15451.
(17) Bouilhac, C.; Ru¨nzi, T; Mecking, S. Macromolecules 2010, 43, 3589–
3590.
(18) Kochi, T.; Noda, S.; Yoshimura, K.; Nozaki, K. J. Am. Chem. Soc.
2007, 129, 8948–8949.
(19) Ito, S.; Munakata, K.; Nakamura, A.; Nozaki, K. J. Am. Chem. Soc.
2009, 131, 14606–14607.
(20) (a) Drent, E.; van Dijk, R.; van Ginkel, R.; van Oort, B.; Pugh, R. I.
Chem. Commun. 2002, 964–965. (b) Hearley, A. K.; Nowack, R. J.;
Rieger, B. Organometallics 2005, 24, 2755–2763. (c) Haras, A.;
Michalak, A.; Rieger, B.; Ziegler, T. Organometallics 2006, 25, 946–
953.
(21) (a) Kochi, T.; Nakamura, A.; Ida, H.; Nozaki, K. J. Am. Chem. Soc.
2007, 129, 7770–7771. (b) Nakamura, A.; Munakata, K.; Kochi, T.;
Nozaki, K. J. Am. Chem. Soc. 2008, 130, 8128–8129.
(22) Borkar, S.; Yennawar, H.; Sen, A. Organometallics 2007, 26, 4711–
4714.
(23) Gibson, V. C.; Tomov, A. Chem. Commun. 2001, 1964–1965.
(24) The presence of methyl acrylate was reported to suppress any polymer
formation: (a) 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
2002, 40, 2842–2854. Other studies report formation of (co)polymer
in the presence of acrylates or methacrylates, respectively: (b) Johnson,
L. K.; Bennett, A. M. A.; Dobbs, K. D.; Ionkin, A. S.; Ittel, S. D.;
Wang, Y.; Radzewich, C. E.; Wang, L. Patent WO 01/92347, 2001.
(c) Wang, L.; Hauptman, E.; Johnson, L. K.; McCord, E. F.; Wang,
Y.; Ittel, S. D. Patent WO 01/92342, 2001. (d) Shen, H.; Goodall,
B. L. U.S. Patent 2006/0270811, 2006. (e) Rodriguez, B. A.; Delferro,
M.; Marks, T. J. J. Am. Chem. Soc. 2009, 131, 5902–5919. However,
the distinct 13C NMR resonances of the methylene carbons adjacent
to a carbonyl group resulting from random acrylate or methacrylate
incorporation-CbH2CaH2CR(COOMe)CaH2CbH2-were not observed;
e.g., for methyl acrylate (R ) H), δ 32.4 (R), 27.4 (ꢀ), ref 7. For 13
C
NMR data of an ethylene/methyl methacrylate copolymer from acyclic
diene metathesis, cf.: (f) Schwendeman, J. E.; Wagener, K. B.
Macromolecules 2004, 37, 4031–4037.
(25) It is assumed that the solubility of ethylene does not differ significantly
for variable concentrations of toluene solutions of methyl methacrylate
and methyl isobutyrate.
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16624 J. AM. CHEM. SOC. VOL. 132, NO. 46, 2010

Reactivity of Methacrylates in Insertion Polymerization
A R T I C L E S
Scheme 1. Synthesis of Complex 2
Table 2. Selected Bond Distances (Å) and Angles (°) for Complex
the active sites during polymerization reversibly blocks coor-
dination sites and contributes to retardation of polymerization
by methacrylate.
2
Pd1-C1
Pd1-P1
P1-O1
Pd1-Cl1
Pd1-Na1
Cl1-Na1
Na1-O1
2.025(3)
2.2191(7)
2.190(2)
2.3804(7)
3.6940(11)
2.7400(14)
2.402(2)
C1-Pd1-P1
C1-Pd1-O1
P1-Pd1-Cl1
O1-Pd1-Cl1
O1-Pd1-Na1
Pd1-Cl1-Na1
Pd1-O1-Na1
87.11(9)
176.51(10)
174.21(3)
86.20(6)
74.56(6)
92.07(3)
106.99(9)
Synthesis of Reactive Precursors. The aformentioned obser-
vations raise the question whether MMA can insert at all for
the catalyst studied. Prerequisite for insertion studies are reactive
precursors free of any other strongly coordinating ligands or
bases. While dmso complexes are relatively labile,12 dmso can
still compete with monomers for coordination to the metal center
and hamper preparative and stoichiometric insertion reactions.
Recently, base-free oligomeric complexes [{(P^O)Pd(Me)}n]
(1n) were obtained by abstraction of pyridine from [(P^O)Pd(Me)-
pyridine] with B(C6F5)3.11 The low solubility of these base-
free complexes is a key advantage in synthesis, as it allows
simple separation of unreacted starting material; however, for
mechanistic studies, a complete and immediate solubility of the
reactive [(P^O)Pd(Me)] fragment is desirable. An appropriate
precursor that fulfills these conditions was found in the new
dimeric compound [({(P^O)Pd(Me)Cl}µ-Na)2] (2), which is
available in quantitative yield by the reaction of the sodium
phosphinesulfonate, (P^O)Na, with [(COD)Pd(Me)Cl] in acetone
(Scheme 1). Crystals suitable for X-ray analysis were grown
directly from the reaction mixture. The solid-state structure
confirms a distorted square planar coordination geometry at the
Pd center, with the methyl and the phosphine mutually cis to
each other (Figure 1, Table 2). In addition, two Pd fragments
are bridged by a sodium atom coordinated by a sulfonato oxygen
atom of each fragment, a chloride atom, and two acetone
molecules.
solution results; no insoluble oligomeric [{(P^O)Pd(Me)}n]
species form. Presumably, under these conditions, the nascent
[(P^O)Pd(Me)] species are trapped to [(P^O)Pd(Me)(MMA)].
Mixtures of complex 2 and MMA in CD2Cl2 remain totally
homogeneous after addition of AgBF4 and removal of AgCl
and NaBF4 by filtration, and this allows for a more concise
investigation of the MMA insertion into the [(P^O)Pd(Me)]
fragment under conditions where no reagents or ligands other
than MMA (and 2 equiv of acetone) are present.
Stoichiometric Methacrylate Insertion. Heating of a CD2Cl2
solution obtained by halide abstraction from 2 in the presence
of 60 equiv of MMA to 80 °C for 2 h resulted in the formation
of three new complexes, 4-6, as well as methyl tiglate (7), as
1
evidenced by H and 31P NMR spectroscopy (Scheme 2). The
major product (ca. 62%) is the 1,2-insertion product (4) of MMA
into the Pd-Me bond of [(P^O)Pd(Me)]. In addition, the
products of 1,2-insertion of MMA into a [(P^O)Pd(H)] fragment,
complex 5 (ca. 30%), and of 2,1-insertion of MMA into a
fragment [(P^O)Pd(H)], complex 6 (ca. 8%) were observed. (For
detailed characterization, see Figures S9-S13, Supporting
Information, and Experimental Section.) The intermediate
formation of [(P^O)Pd(H)] is further evidenced by the formation
Upon addition of AgBF4 to a CD2Cl2 solution of 2, instan-
taneous halide abstraction occurs, as evidenced by AgCl visibly
precipitating within seconds. In the presence of MMA, a clear
Figure 1. ORTEP plot of complex 2. Ellipsoids are shown with 50% probability. Hydrogen atoms are omitted for clarity.
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J. AM. CHEM. SOC. VOL. 132, NO. 46, 2010 16625

A R T I C L E S
Ru¨nzi et al.
Scheme 2. Products of MMA Insertion into the Palladium Methyl Bond of the [(P^O)PdMe] Fragment
of 7 (ca. 40%), identified by 1H and 1H,1H COSY experiments.
7 is the product of ꢀ-H-elimination from the product of 2,1-
insertion into the [(P^O)Pd(Me)] fragment, 3 (not directly
observed). Since a ꢀ-H elimination is not possible from complex
4, we conclude that the aforementioned [(P^O)Pd(H)] fragments
are formed along with 7 by ꢀ-H elimination from 3. The
conceivable 1,2-insertion of 7 into a Pd-H species, i.e., the
“rearrangement” product of 3, is not observed likely due to
hindered insertion of the bulky trisubstituted olefin. The overall
product distribution observed in this NMR experiment corre-
sponds to a ca. 3:2 ratio of 1,2- vs 2,1-insertion of MMA into
the palladium methyl bond. Upon workup of the reaction
mixture, complexes 5 and 6 decomposed, presumably via ꢀ-H-
elimination. This allowed for the isolation of complex 4 as the
only organometallic species in ca. 60% yield.
a detailed kinetic analysis of the disappearance of the Pd-Me
species formed after chloride abstraction under pseudo-first-
order conditions (20 equiv of monomer). Isothermal studies at
different temperatures in the range of 30-69 °C provided an
Eyring analysis (Figure 2), from which the average activation
enthalpy for the disappearance of complex 2 by 1,2- or 2,1-
insertion of MMA was determined to be ∆Hq ) 69.0(3.1) kJ
mol-1, while the respective activation entropy was determined
to be ∆Sq ) -103(10) J mol-1 K-1. At 25 °C, the average free
activation enthalpy ∆Gq(25 °C) is 99.8(4.2) kJ mol-1. The
corresponding experiment for the disappearance of the chloride-
free Pd-Me species in the presence of 20 equiv of MA (by
exclusive 2,1-insertion) was performed between -20 and 26
°C. This temperature range resulted from the much higher rates
of this reaction. Eyring analysis gave ∆Hq ) 48.5(3.0) kJ mol-1
A detailed analysis by H, 13C, H,1H gCOSY, H,{13C}
gHSQC, and gHMBC NMR experiments, FAB mass spectrom-
etry, and elemental analysis confirmed the identity of complex
4. Key 1H NMR spectroscopic features comprise a pal-
ladium-R-methylene doublet resonance at δ 1.09 ppm with a
3JPH ) 2.6 Hz and a ꢀ-methyl singlet resonance at δ 1.15 ppm.
A chelating coordination of the carbonyl group in 4 is evidenced
by the low-field-shifted resonance of the C(O)OMe group at δ
and ∆Sq ) -138(7) J mol-1 K-1. This corresponds to a free
1
1
1
26
activation enthalpy of ∆Gq(25 °C) ) 89.5(3.6) kJ mol-1
.
Comparison with the ∆Gq(25 °C) for MMA insertion yields a
preferential insertion of MA vs MMA by ∼102. A comparison
of MA vs MMA insertion at polymerization conditions, 80 °C,
requires extrapolation of the thermodynamic data to this
temperature. This introduces a larger error, due to the error in
the determined ∆Sq values, and includes the assumption that
the ratio of 1,2- vs 2,1-insertion of MMA is temperature
independent. Keeping this in mind, the thermodynamic data
correspond to a preference by 10-102 of acrylate vs methacrylate.
Reactivity of the Isolated Insertion Product. A prerequisite
for chain growth is a free coordination site for incoming
monomers. In the case of 4, this corresponds to an opening of
the (C,O)-chelate. As a model reaction, the strong donor PPh3
was found to displace the carbonyl group and open the chelate
of 4 in an equilibrium, as indicated by the appearance of a set
of doublets with a coupling constant of trans-2JPP ) 525 Hz,
followed by a cis-trans isomerization to a species bearing the
1
192.74 ppm (for H and 31P NMR spectra, see Figure S9,
Supporting Information). The identification of complexes 5 and
6 is based on a detailed NMR analysis of the reaction mixture
in the presence of MMA. While the indicative key resonance
of complex 6 is the low-field-shifted carbonyl resonance at 208
ppm, indicating a four-membered carbonyl chelate, complex 5
was identified by the characteristic ꢀ-methyl doublet coupling
3
to the methine multiplet with JHH ) 7.6 Hz (for additional
information, see Supporting Information).
The homogeneous nature of the reaction solution obtained
from 2 and silver tetrafluoroborate in CD2Cl2 also allowed for
Figure 2. Eyring plot of MMA insertion (left) and MA insertion (right) into the Pd-Me bond of [(P^O)Pd(Me)].
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Reactivity of Methacrylates in Insertion Polymerization
A R T I C L E S
Table 3. Polymerization of Ethylene with 4 and 1-dmsoa
catalyst
entry precursor
p(ethylene)
[bar]
TOF [mol (C2H4)
yield PE [g] mol (Pd)-1 h-1
Mnb
[g mol-1
]
]
Mw/Mnb
3-1
3-2
3-3
4
4
4
30
20
10
10
5
5.82
5.36
2.20
5.04
4.92
8.0 × 104
7.7 × 104
3.1 × 104
1.0 × 105
1.0 × 105
2.0
1.9
2.0
1.9
2.2
2.3 × 104
2.5 × 104
1.3 × 104
1.3 × 104
1.3 × 104
3-4 1-dmso
3-5 1-dmso
a Reaction conditions: 100 mL of toluene, 80 °C, entry 3-1 to 3-3
with 2.5 µmol of Pd(II), entries 3-4 and 3-5 with 3.5 µmol of Pd(II).12
b Determined by GPC at 160 °C vs linear PE.
possibility of introducing intact methacrylate units in polyeth-
ylenes. Copolymerization of ethylene with 8 results in polymers
bearing unsaturated methacrylate groups in the side chain; e.g.,
for a 0.33 M toluene solution of 8 and 5 bar ethylene pressure,
poly(ethylene-co-8) was obtained with 3.9 mol % of 8 incor-
porated.28 13C NMR (Figure 3) confirms that the acrylate units
are incorporated in the linear polyethylene chain, while the
methacrylate units remain unreacted in the side chain.
phosphine ligands cis to each other (cis-2JPP ) 11 Hz) (Figures
S18 and S19, Supporting Information). At low temperature (-80
°C), which favors chelate opening by reducing the entropic
contribution to the equilibrium position, opening was also
observed with 3 equiv of pyridine (Figure S20, Supporting
Information). With ethylene (∼20:1 ratio ethylene:Pd) as a
weaker ligand in NMR experiments in the temperature range
of -80 to 25 °C, no opening was observed. Exposure of 4 to
ethylene under polymerization conditions resulted in polyeth-
ylene formation, however (Table 3). Activation requires an initial
opening of the chelate by coordination of ethylene, but once
insertion has occurred for a given catalyst precursor molecule,
coordination of the carbonyl groups no longer appears relevant
due to the increasingly large, unfavorable chelate ring sizes.
Polymerization activities with 4 are independent of ethylene
concentration at p g 20 bar (entries 3-1 to 3-3). By comparison,
with 1-dmso as a catalyst, precursor activities are independent
of ethylene pressure at p g 5 bar (entries 3-4 and 3-5 and ref
12). This again suggests a quite strong coordination of the
methacrylate-derived ester group to the Pd center in the five-
membered chelate 4.
The intact methacrylate moieties in the linear polyethylene
lend themselves to post-polymerization reactions, which can
provide otherwise inaccessible polymers. Free-radical-initiated
addition of thiols, namely 3-mercaptopropionic acid, occurred
virtually quantitatively (>95%), as confirmed by elemental
analysis. Consumption of the methacrylic moieties was con-
1
firmed by H NMR (Scheme 3 and Figure S22, Supporting
Information). The polymer remains soluble upon modification.
This demonstrates that no radical cross-linking has occurred
under these conditions. By this reaction of thiocarboxylic acid,
both thiol and carboxylic acid groups were introduced. Such
functional groups are known to be problematic for most
polymerization catalysts, hindering introduction by direct
polymerization.
As another example of post-polymerization modification of
the methacrylate-substituted polyethylene, cross-metathesis was
studied preliminarily. Methacrylates are convertible via cross-
metathesis with other 1-olefins by Grubbs second-generation
catalyst.29 Exposure of the terpolymer poly(ethylene-co-8-co-
APEG) (APEG ) oligoglycol monoacrylate) to Grubbs second-
generation alkylidene and an excess of 4-phenylbutene in
C2H2Cl4 at 70 °C resulted in cross-metathesis degrees of up to
15% (Scheme 3 and Figure S23, Supporting Information).
Comparison of gel permeation chromatography (GPC) traces
before and after modification revealed that metathesis proceeds
exclusively between methacrylates and the added olefins (Figure
S24, Supporting Information). No substantial increase in mo-
lecular weight, as would be expected for interchain homomet-
athesis of methacrylates (or metathesis with the olefinic end
groups of the polymer), was observed.
Methacrylate-Functionalized Polyethylene. The large differ-
ences in reactivity observed in the above polymerizations and
mechanistic studies for acrylate and methacrylate correspond
to an orthogonal reactivity in insertion polymerizations with the
catalyst studied. An acrylate and a methacrylate moiety are
combined in the bifunctional ethylene glycol ester 8.27 As
anticipated, 8 reacts exclusively with the acrylate moiety (eq
1). In an NMR tube, 13 equiv of 8 were added to a CD2Cl2
solution of 1-dmso. The tube was kept at room temperature,
1
and H NMR spectra were acquired periodically (Figure S16,
Supporting Information). Complete conversion of the starting
compound occurred within 150 min. The first-order rate constant
for the consumption of 1-dmso, monitored by the disappearance
of the Pd-Me 1H NMR resonance, is kobs ) 2.80 × 10-4 s-1 at
25 °C (Figure S17, Supporting Information). Simultaneously,
a triplet at 0.25 ppm, resulting from 2,1-insertion of the acrylate
moiety, increases. No signals corresponding to an insertion of
methacrylate were observed. The insertion product (9) was
isolated after removing the excess of 8 by washing the complex
with ether. One equivalent of dmso, resonating at δ ) 2.76 ppm
Summary and Conclusions
Even in the presence of substantial concentrations of MMA,
polymerization of ethylene by the catalyst studied provides linear
ethylene homopolymer without any detectable incorporation of
methacrylate. The detection limit amounts to less than one
methacrylate unit per chain. By comparison to MA, which is
incorporated to a substantial degree under identical polymeri-
1
in the H NMR spectrum, is evidence for 9 occurring in the
nonchelated form, as depicted in eq 1 (δ ) 2.54 ppm for free
dmso in CD2Cl2). The inertness of methacrylates in olefin
insertion polymerization (Vide supra) and the remarkably
different reactivity versus acrylates in this respect offer the
(28) Copolymerization conditions and results: 0.33 M toluene solution of
8 (50 mL total volume), 5 bar ethylene pressure, 20 µmol of 1-dmso,
90 °C polymerization temperature, 1 h polymerization time, 200 mg
of BHT (free radical inhibitor); TOF C2H4 [mol(C2H4) mol Pd-1
h-1], 2400; TOF 8 [mol(8) mol Pd-1 h-1]: 100; 3.9 mol % of 8
(determined from the glycol resonances in ratio to the aliphatic protons
by 1H NMR); Mn ) 6500, Mw/Mn ) 1.88 (determined by GPC at 160
°C vs linear PE).
(26) Similar activation energies were reported for the cationic diimine Pd
complex (refs 2 and 22). In our experiments with MA, further insertion
into the monoinserted complex was observed. For details cf. ref 12b.
(27) Schmider, M.; Mu¨h, E.; Klee, J. E.; Mu¨lhaupt, R. Macromolecules
2005, 38, 9548–9555.
(29) Chatterjee, K.; Choi, T.; Sanders, D. P.; Grubbs, R. H. J. Am. Chem.
Soc. 2003, 125, 11360–11370.
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A R T I C L E S
Ru¨nzi et al.
Figure 3. 13C{1H}NMR spectrum of poly(ethylene-co-8) in C2D2Cl4 at 130 °C.
Scheme 3. Post-polymerizaton Modification of Poly(ethylene-co-8) and Poly(ethylene-co-8-co-APEG)a
a Reaction conditions: (i) 100 mg of polymer, 10 mL of C2H2Cl4, 40 equiv of thiol, 0.4 equiv of AIBN, 9 h, 80 °C. (ii) 100 mg of polymer, 10 mL of
C2H2Cl4, 10 equiv of 4-phenylbutene, 0.1 equiv of Ru-alkylidene complex, 12 h, 70 °C.
zation conditions, MMA is at least 102-fold less amenable to
incorporation under polymerization conditions.
concentration already at p(ethylene) g 5 bar, and the chelate is
completely opened by equiv of pyridine at room
1
Detailed mechanistic studies with an appropriate precursor
providing the reactive [(P^O)PdMe] fragment in solution reveal
that methacrylate insertion into the Pd-Me bond is possible in
principle. Insertion occurs in both 1,2- and 2,1-fashion, with a
slight preference for the former. While the 1,2-insertion product,
which lacks ꢀ-H atoms, could be isolated, the 2,1-insertion
products are subject to facile ꢀ-H elimination under the reaction
conditions of this insertion. In the 1,2-insertion product (4), the
carbonyl unit of the inserted MMA binds to the metal center to
form a five-membered chelate. This chelate is very stable, and
opening requires harsher conditions than for the corresponding
six-membered chelate formed by two consecutive 2,1-insertions
of MA into the Pd-Me bond (ethylene polymerizations with
the latter as a catalyst precursor are independent of ethylene
temperature).12b Eyring analysis yielded thermodynamic pa-
rameters ∆Hq ) 69.0(3.1) kJ mol-1 and ∆Sq ) -103(10) J
mol-1 K-1 as the total average for 1,2- and 2,1-insertion of
methacrylate. By comparison, for MA insertion, ∆Hq amounts
to 48.5(3.0) kJ mol-1 and ∆Sq ) -138(7) J mol-1 K-1. These
thermodynamic parameters are also in qualitative agreement with
the lack of observation of any methacrylate incorporation in
ethylene polymerization.
The huge difference in reactivity of acrylate vs methacrylate,
and essential inertness of the latter under polymerization
conditions, enables the generation of linear polyethylenes with
intact methacrylate substituents by copolymerization with a
mixed bifunctional acrylate-methacrylate (8). These polymers
are attractive for post-polymerization reactions to materials
9
16628 J. AM. CHEM. SOC. VOL. 132, NO. 46, 2010

Reactivity of Methacrylates in Insertion Polymerization
A R T I C L E S
Ethylene Polymerization. Ethylene polymerization was carried
out in a 250 mL stainless steel mechanically stirred (1000 rpm)
pressure reactor equipped with a heating/cooling jacket supplied
with a thermostat controlled by a thermocouple dipping into the
polymerization mixture. A valve controlled by a pressure transducer
allowed for applying and keeping constant ethylene pressure. Prior
to a polymerization experiment, the reactor was heated under
vacuum to the desired temperature for 60 min and then filled with
argon. A stock solution of the catalyst precursor in methylene
chloride was prepared. The required amount of complex was filled
into a syringe. The reactor was vented, and in a slight argon/ethylene
stream, the solvent and catalyst solution was transferred via cannula.
The reactor was closed, and a constant ethylene pressure was
applied. After the desired reaction time, the reactor was rapidly
vented and cooled to room temperature. The reaction mixture was
filled into a flask, and the solvent was removed in vacuum. The
remaining polymer was dried in vacuum at 30 mbar and 50 °C for
48 h.
Polymerization of Ethylene in the Presence of Methyl
Methacrylate and Methyl Isobuyrate, Respectively. A procedure
identical to that for ethylene homopolymerization was applied. A
mixture of toluene and MMA or MIB, respectively, with a total
volume of 50 mL was transferred into the reactor under an argon
counter stream. The catalyst precursor 1-dmso was dissolved in 1
mL of dichloromethane and introduced by a syringe to the reactor.
After the desired reaction time, the reactor was rapidly vented and
cooled to room temperature. The reaction mixture was stirred with
an excess volume of methanol. The polymer was isolated by
filtration, washed several times with methanol, and dried in vacuo
at 50 °C and 23 mbar for at least 48 h.
otherwise difficult to access. This was exemplified by thiol
addition to provide a thiol and carboxylic acid-substituted
polyethylene and by cross-metathesis.
Experimental Section
Materials and General Considerations. Unless noted otherwise,
all manipulations of complexes were carried out under an inert
atmosphere using standard Schlenk techniques. All glassware was
dried at 80 °C for at least 48 h. Toluene was distilled from sodium
and diethyl ether, THF, and dioxane were distilled from sodium/
benzophenone ketyl under argon. Methylene chloride, chloroform,
and pentane were distilled from CaH2. Dimethylsulfoxide p.a.,
acetone p.a., and methanol p.a. were degassed and used without
further purification. Ethylene (3.5 grade) was supplied by Praxair.
Methyl methacrylate and methyl acrylate, supplied by Sigma
Aldrich (99%, GC), were degassed using freeze-pump-thaw
cycles and stored at 4 °C. [2-di(2-methoxyphenyl)phosphino]ben-
zenesulfonic acid,7 2-(acryloyloxy)ethyl methacrylate (8),27 [(COD)-
Pd(Me)Cl],30 [(tmeda)PdMe2],31 1-dmso,12 and 1n,11 were prepared
by known procedures. All deuterated solvents were supplied by
Eurisotop. Galvinoxyl, purchased from ABCR, was stored at
-28 °C.
NMR spectra were recorded on a Varian Unity INOVA 400 or
a Bruker Avance DRX 600 spectrometer equipped with a cryoprobe
1
head. H and 13C NMR chemical shifts were referenced to the
solvent signal. Multiplicities are given as follows (or combinations
thereof): s, singlet; d, doublet; t, triplet; vt, virtual triplet; m,
multiplet. Coupling constants are given in hertz (Hz). The identity
1
and purity of metal complexes were established by H, 13C, and
31P NMR and elemental analysis. NMR assignments were confirmed
by 1H,1H gCOSY, 1H,13C gHSQC, and 1H,13C gHMBC experiments.
NMR probe temperatures were measured using an external anhy-
drous methanol standard for temperatures <25 °C or anhydrous
ethylene glycol standard for temperatures >25 °C. Errors in ∆Hq
and ∆Sq were calculated according to the derivation of Girolami et
al.,32 with the estimated error in the temperature calibration
measurement of (1 K and a deviation of 5% for the pseudo-first-
order rate constants k. High-temperature NMR measurements of
polyethylenes were performed in 1,1,2,2-tetrachloroethane-d2 at 130
°C. GPC measurements were carried out in 1,2,4-trichlorobenzene
at 160 °C at a flow rate of 1 mL min-1 on a Polymer Laboratories
220 instrument equipped with Olexis columns with differential
refractive index, viscosity, and light-scattering (15° and 90°)
detectors. Data reported were determined directly against PE
standards. FAB mass spectra were obtained with a double-focusing
Finnagan MAT 8200 mass spectrometer equipped with an ION
TECH (Teddington, UK) FAB ion source. About 1 µL of the sample
solution (CH2Cl2) and 1 µL of 3-nitrobenzyl alcohol (NBA) (and
NaI if necessary) were mixed on the tip of the sample holder. X-ray
analysis was performed at 100 K on a STOE IPDS-II diffractometer
equipped with a graphite-monochromated radiation source (λ )
0.71073 Å) and an image plate detection system. A crystal mounted
on a fine glass fiber with silicon grease was employed. The
selection, integration, and averaging procedure of the measured
reflex intensities, the determination of the unit cell dimensions by
a least-squares fit of the 2Θ values, data reduction, LP correction,
and space group determination were performed using the X-Area
software package delivered with the diffractometer. A semiempirical
absorption correction was performed. The structure was solved by
direct methods (SHELXS-97), completed with difference Fourier
syntheses, and refined with full-matrix least-squares using SHELXL-
Sodium [2-(2-Methoxyphenyl)phosphino]benzenesulfonate
((P^O)Na). 500 mg (1.2 mmol) of [2-di(2-methoxyphenyl)phos-
phino]benzenesulfonic acid and 33.6 mg (1.4 mmol) of sodium
hydride were dispersed in 20 mL of THF for 24 h. The solvent
was removed in vacuum. Adding 20 mL of methylene chloride and
20 mg of phenol (for scavenging excess sodium hydride) afforded
a dispersion. The solid was isolated by filtration, washed with ether,
and dried in vacuum to yield 480 mg (1.13 mmol, 94%) of a white
powder still containing one-sixth of Et2O.
4
4
1H NMR (400 MHz, CD3OD) δ ) 8.06 (ddd, JHH ) 1.2, JPH
) 4.0, 3JHH ) 7.8, 1H, 6-H), 7.37 (dt, 4JHH ) 1.2, 3JHH ) 7.7, 1H,
4
3
5-H), 7.27 (vt, J ) 7.8, 2H, 11-H), 7.21 (dt, JHH ) 1.2, JHH
)
4
3
3
7.5, 1H, 4-H), 6.96 (ddd, JHH ) 1.2, JPH ) 3.4, JHH ) 7.6, 1H,
3
3
3-H), 6.91 (dd, JPH ) 4.8, JHH ) 8.1, 2H, 12-H), 6.77 (vt, J )
7.4, 2H, 10-H), 6.57 (d, 4JPH ) 3.7, 2H, 9-H), 3.65 (s, 6H, OMe);
13C NMR (101 MHz, CD3OD) δ ) 162.66 (d, JPC ) 16.3, C8),
2
151.22 (d, 2JPC ) 27.6, C1), 136.96 (d, 2JPC ) 1.7, C3), 136.72 (d,
1JPC ) 22.7, C2), 135.04 (C9), 131.07 (C11), 130.90 (C4), 129.60
3
1
(s, C5), 128.71 (d, JPC ) 4.9, C6), 127.68 (d, JPC ) 14.6, C7),
122.00 (C10), 111.59 (C12), 56.11 (OMe); 31P NMR (161 MHz,
CD3OD) δ ) -29.88 (s). Anal. Calcd for (C20H18NaO5PS·1/6Et2O):
C, 56.84; H, 4.54; S, 7.34. Found: C, 56.35; H, 4.57; S, 7.08.
[{((P^O)Pd(Me)Cl)-µ-Na}2 ·4acetone] (P^O ) K2-(P,O)-2-(2-
MeOC6H4)2PC6H4SO3)) (2). 100 mg (0.33 mmol) of [(COD)-
Pd(Me)Cl] and 177.6 mg (0.42 mmol, 1.3 equiv) of sodium[2-di(2-
methoxyphenyl)phosphino]benzenesulfonate were added to 30 mL
of acetone, and the mixture was shaken until the dispersion became
clear. The solution was filtered right after the mixture became clear.
97 minimizing w(Fo - Fc2)2. Weighted R factor (wR) and the
2
goodness of fit (GooF) are based on F2.
(30) Salo, E. V.; Guan, Z. Organometallics 2003, 22, 5033–5046.
(31) De Graaf, W.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; van Koten,
G. Organometallics 1989, 8, 2907–2917.
(32) Morse, P. M.; Spencer, M. D.; Wilson, S. R.; Girolami, G. S.
Organometallics 1994, 13, 1646–1655.
9
J. AM. CHEM. SOC. VOL. 132, NO. 46, 2010 16629

A R T I C L E S
Ru¨nzi et al.
Remaining solids were washed repetitively with acetone. After
removal of the solvent from the collected filtrates in vacuum, the
residual solid was washed with ether and dried under reduced
pressure to yield 87% of a white powder.
g mol-1 [M - C6H12O2]+. Anal. Calcd for (C26H29O7PPdS): C,
50.13; H, 4.69; S, 5.15. Found: C, 50.09; H, 4.76; S, 4.79
Key NMR Resonances of Complexes 5 and 6. 5: 1H NMR (in
parentheses: correlated 13C resonance identified by a gHSQC
experiment) (600 MHz, CD2Cl2) δ ) 3.92 (55.60) (s, 3H, OMe),
3.04 (45.64) (m, 1H, 2-H), 1.44, 1.24 (26.51) (m, 2H, 1-H), 1.09
3
(d, JHH ) 7.6 Hz, 3H, 4-H); 13C NMR (150 MHz, CD2Cl2) δ )
191.0 (CdO), 55.60 (OMe), 45.64 (C2), 26.51 (C1), 18.24 (C4);
31P NMR (161 MHz, CD2Cl2): δ ) 20.04 (s).
1H NMR (400 MHz, acetone-d6) δ ) 7.96 (m, 1H, 6-H), 7.73
(br, 2H, 12-H), 7.54 (vt, J ) 7.8, 2H, 10-H), 7.45 (m, 1H, 5-H),
7.37 (m, 2H, 4-H and 3-H), 7.02 (m, 4H, 9-H, 11-H), 3.62 (s, 6H,
Ar-OMe), 0.20 (d, JHP ) 3, 3H, Pd-Me). Anal. Calcd for
(C42H42Cl2Na2O10P2Pd2S2): C, 43.39; H, 3.64; S, 5.52. Found: C,
43.85; H, 4.09; S, 5.06.
6: 1H NMR (600 MHz, CD2Cl2) δ )3.85 or 3.78 (s, 3H, OMe),
2.13 (s, 6H, 2-H); 13C NMR (150 MHz CD2Cl2) δ ) (208.26)
(CdO), 55.73 or 55.41 (OMe), 31.47 (C2), C1 n.d.; 31P NMR (161
MHz, CD2Cl2) δ ) 24.88 (s).
[{(P^O)Pd{C(Et)HC(O)OCH2CH2OC(O)C(Me)CH2}(dmso)] (9).
1-dmso (22 mg, 0.0366 mmol) was dissolved in 0.6 mL of CH2Cl2.
After addition of 80 mg of 8 (0.48 mmol, 13 equiv), the solution
was kept for 2.5 h at room temperature. The solvent was then
removed in vacuum, and the complex was washed thrice with 7
mL of ether. After drying in vacuum, a yellow powder was obtained
(25.8 mg, 0.033 mmol, 90%).
3
[{(P^O)Pd{CH2CMe2COOMe}] (P^O ) K2-(P,O)-2-(2-MeO-
C6H4)2PC6H4SO3)) (4). 40 mg (0.077 mmol) of 1n was dispersed
in 7 mL of chloroform. After addition of 50 mg of methyl
methacrylate, the dispersion was heated to 90 °C for 2.5 h. The
resulting yellow dispersion was filtered, and the solvent was
removed. The resulting yellow powder was dissolved in 10 mL of
methanol. After evaporation and repetitive washing with ether, a
yellow powder was obtained. Yield 28.8 mg (0.046 mmol, 60%).
1H NMR (400 MHz, CD2Cl2) δ ) 8.74 (br, 1H), 7.97 (m, 1H),
7.55 (m, 2H), 7.44 (m, 2H), 7.29 (m, 2H), 7.14 (m, 1H), 6.99 (m,
2H), 6.87 (m, 1H), 6.11 (s, 1H, Hf′), 5.57 (s, 1H, Hf), 4.31 (m, 4H,
Hd and He), 3.50 and 3.64 (s, 6H, ArOCH3), 2.76 (s, 6H, dmso),
1.91 (s, 3H, Hg), 1.70 (vt, J ) 8.8, 1H, Hc), 1.38 and 0.74 (2 × m,
1H NMR (400 MHz, CD2Cl2) δ ) 8.07 (m, 1H, 6-H), 7.61 (br,
2H, 12-H), 7.54 (vt, J ) 7.7, 2H, 10-H), 7.46 (m, 1H, 5-H), (m,
2H, 4-H and 3-H), 7.03 (vt, J ) 7.5, 2H, 11-H), 6.95 (m, 2H, 9-H),
3.94 (s, 3H, 18-H), 3.62 (s, 6H, Ar-OMe), 1.15 (s, 6H, 15-H and
3
1H each, Hb, Hb′), 0.24 (t, JHH ) 7.2, 3H, Ha); 31P NMR (161
MHz, CD2Cl2) δ ) 25.10 (s).
Acknowledgment. Financial support by the DFG (grant Me1388/
10-1) is gratefully acknowledged. S.M. is indebted to the Fonds
der Chemischen Industrie.
3
16-H), 1.09 (d, JPH ) 2.6, 2H, 13-H); 13C NMR (101 MHz,
CD2Cl2) δ ) 192.74 (C17), 160.85 (d, 2JPC ) 2.0, C8), 149.21 (d,
2JPC )15.5, C1), 138.06 (C12), 134.70 (d, 3JPC ) 2.8, C4), 134.08
(C10), 130.88 (d, 4JPC ) 2.4, C5), 128.83 (d, 2JPC ) 7.5, C3), 128.10
Supporting Information Available: Additional experimental
procedures, analytical data, and CIF file for complex 2. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(d, 3JPC ) 8.8, C6), 127.45 (d, 1JPC ) 54.5, C2), 121.04 (d, 3JPC
)
1
3
12.4, C11), 116.35 (d, JPC ) 59.6, C7), 111.81 (d, JPC ) 4.8,
C9), 55.67 (ArOCH3), 55.61 (C18), 49.93 (C14) 32.50 (C13), 28.22
(C15 and C16); 31P NMR (161 MHz, CD2Cl2) δ ) 23.57 (s); FAB-
MS: calcd 622.96 g mol-1, found 622.4 g mol-1 [M + H]+, 506.4
JA107538R
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16630 J. AM. CHEM. SOC. VOL. 132, NO. 46, 2010