Polymerization and Oligomerization of Ethylene by Cationic Nickel (II) and Palladium(II) Complexes Containing Bidentate Phenacyldiarylphosphine Ligands

Article abstract of DOI:10.1021/om030388h

A series of Ni(II) and Pd(II) catalysts have been synthesized from the P,O chelating ligands phenacyl(aryl)₂phosphine. The (P,O)Ni-allyl ⁺B(Ar_f)₄^- [Ar_f = 3,5-(CF₃)₂C₆H₃] complexes 6a-c are active for polymerization of ethylene in the case of 6b (aryl = 2,4,6-(CH ₃)₃C₆H₂) and for dimerization of ethylene to butenes in the case of 6a (aryl = C₆H₅) and 6c (aryl = C₆H₅, 2,4,6-(C₆H₅) ₃C₆H₂). These catalysts are characterized by their high initial activity but relatively short catalytic lifetime and poor thermal stability. The palladium analogues (P,O)PdMe(NCMe)⁺B(Ar _f)₄^- are approximately an order of magnitude less active than the Ni analogues and generate butenes and hexenes. The barriers for migratory insertion in a series of methyl ethylene complexes [(p-XC₆H₄)₂PCH₂C(O)(p-YC ₆H₄)]Pd(CH₃)(C₂H₄) ⁺B(Ar_f)₄^- (X,Y = H, H; -OCH ₃, H; -CF₃, H; H, -OCH₃; H, -CF₃) were measured. Values of ΔG? ranged from 18.2 to 20.3 kcal/mol and, relative to the unsubstituted system, decreased for X,Y = -CF₃ and increased for X,Y = -OCH₃.

Full text of DOI:10.1021/om030388h

5324
Organometallics 2003, 22, 5324-5335
P olym er iza tion a n d Oligom er iza tion of Eth ylen e by
Ca tion ic Nick el(II) a n d P a lla d iu m (II) Com p lexes
Con ta in in g Bid en ta te P h en a cyld ia r ylp h osp h in e Liga n d s
J on M. Malinoski and Maurice Brookhart*
Department of Chemistry, University of North Carolina at Chapel Hill,
Chapel Hill, North Carolina 27599-3290
Received May 29, 2003
A series of Ni(II) and Pd(II) catalysts have been synthesized from the P,O chelating ligands
phenacyl(aryl)2phosphine. The (P,O)Ni-allyl+B(Arf)4- [Arf ) 3,5-(CF3)2C6H3] complexes 6a -c
are active for polymerization of ethylene in the case of 6b (aryl ) 2,4,6-(CH3)3C6H2) and for
dimerization of ethylene to butenes in the case of 6a (aryl ) C6H5) and 6c (aryl ) C6H5,
2,4,6-(C6H5)3C6H2). These catalysts are characterized by their high initial activity but
relatively short catalytic lifetime and poor thermal stability. The palladium analogues
-
(P,O)PdMe(NCMe)+B(Arf)4 are approximately an order of magnitude less active than the
Ni analogues and generate butenes and hexenes. The barriers for migratory insertion in a
-
series of methyl ethylene complexes [(p-XC6H4)2PCH2C(O)(p-YC6H4)]Pd(CH3)(C2H4)+B(Arf)4
(X,Y ) H, H; -OCH3, H; -CF3, H; H, -OCH3; H, -CF3) were measured. Values of ∆Gq
ranged from 18.2 to 20.3 kcal/mol and, relative to the unsubstituted system, decreased for
X,Y ) -CF3 and increased for X,Y ) -OCH3.
In tr od u ction
During 1995-1996 our group and the DuPont Versi-
pol group reported a series of highly active cationic d8
square-planar Ni(II) and Pd(II) olefin polymerization
catalysts based on aryl-substituted R-diimine ligands.1-3
The key structural feature of these systems is the
incorporation of bulky substituents at the ortho posi-
tions of the aryl rings, which project into the axial sites
and retard the rate of chain transfer, thereby generating
high molecular weight polymer. These catalysts poly-
merize ethylene and R-olefins to a wide range of linear
to highly branched polymers and have been shown to
copolymerize ethylene and polar comonomers such as
methyl acrylate and more recently vinyl alkoxysilanes.4-7
These results have sparked considerable interest in
developing new late metal olefin polymerization cata-
lysts based on both cationic and neutral metal centers
and incorporating a wide variety of heteroatom substit-
F igu r e 1. (P,O)Ni(II) and -Pd(II) Catalysts.
uents on the supporting ligands. Recent reviews cover
much of this work.8-11
We recently reported the synthesis of Ni(II) and Pd-
(II) complexes based on the bidentate P,O chelating
ligand phenacyldi-tert-butylphosphine (Figure 1).12,13
These catalysts are cationic analogues of the well-known
SHOP systems14-16 in which B(Arf)4- [Arf ) 3,5-(CF3)2-
C6H3] serves as a bulky, noncoordinating counteranion.
The Ni-allyl complex 1 is highly active (TOFs > 3 × 106
h-1) at high temperatures and ethylene pressures for
formation of linear polyethylene (Mw ) 5000-12 000,
(1) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem. Soc.
1995, 117, 6414.
(2) Brookhart, M. S.; J ohnson, L. K.; Killian, C. M.; Arthur, S. D.;
Feldman, J .; McCord, E. F.; McLain, S. J .; Kreutzer, K. A.; Bennett,
M. A.; Coughlin, E. B.; Ittel, S. D.; Parthasarathy, A.; Tempel, D. J .
WO 9623010, 1996.
(3) Gates, D. P.; Svejda, S. A.; On˜ate, E.; Killian, C. M.; J ohnson,
L. K.; White, P. S.; Brookhart, M. Macromolecules 2000, 33, 2320.
(4) J ohnson, L. K.; Mecking, S.; Brookhart, M. J . Am. Chem. Soc.
1996, 118, 267.
(5) Mecking, S.; J ohnson, L. K.; Wang, L.; Brookhart, M. J . Am.
Chem. Soc. 1998, 120, 888.
(6) J ohnson, L. K.; McLain, S. J .; Sweetman, K. J .; Wang, Y.;
Bennett, A. M. A.; Wang, L.; McCord, E. F.; Ionkin, A.; Ittel. S. D.;
Radzewich, C. E.; Schiffino, R. S. WO 200344066, 2003.
(7) J ohnson, L. K.; Bennett, A.; Butera, P.; Dobbs, K.; Drysdale, N.;
Hauptman, E.; Ionkin, A.; Ittel, S. D.; McCord, E. F.; McLain, S. J .;
Radzewich, C. E.; Rinehart, A.; Schiffino, R. S.; Sweetman, K. J .;
Uradnisheck, J .; Wang, L.; Wang, Y.; Yin, Z. Abstracts of Papers, 225th
ACS National Meeting, New Orleans, LA, American Chemical Soci-
ety: Washington, DC, 2003; POLY-356.
(8) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283.
(9) Ittel, S. D.; J ohnson, L. K.; Brookhart, M. Chem. Rev. 2000, 100,
1169.
(10) Boffa, L. S.; Novak, B. M. Chem. Rev. 2000, 100, 1479.
(11) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 429.
(12) Liu, W.; Malinoski, J . M.; Brookhart, M. Organometallics 2002,
21, 2836.
(13) Wang, L.; Brookhart, M.; J ohnson, L. K.; Ittel, S. D.; Wang, Y.;
Kunitsky, K.; Kreutzer, K. A.; Guan, Z.; Liu, W.; Malinoski, J . M. WO
0259165, 2002.
(14) Keim, W.; Kowalt, F. H.; Goddard, R.; Kru¨ger, C. Angew. Chem.,
Int. Ed. Engl. 1978, 17, 466.
(15) Klabunde, U.; Ittel, S. D. J . Mol. Catal. 1987, 41, 123.
(16) Starzewski, K. A. O.; Witte, J . Angew. Chem., Int. Ed. Engl.
1987, 26, 63.
10.1021/om030388h CCC: $25.00 © 2003 American Chemical Society
Publication on Web 11/08/2003

Polymerization and Oligomerization of Ethylene
Organometallics, Vol. 22, No. 25, 2003 5325
Sch em e 1. Syn th esis of P h en a cyld ia r ylp h osp h in e Liga n d s a n d Cor r esp on d in g Ca tion ic Ni-a llyl Ca ta lysts
6-8 branches/1000 carbons). In addition, catalyst 1
copolymerizes ethylene and methyl-10-undecenoate, a
polar-functionalized monomer, albeit with significantly
reduced yields and low comonomer incorporation. Pal-
ladium catalysts 2 and 3a were found to oligomerize
ethylene to an amorphous material (TOF ) 2 × 104 h-1
,
Mn ≈ 350) in which the degree of branching decreases
with increasing ethylene concentration. Despite its high
activity, Ni-allyl catalyst 1 displays very slow rates of
initiation, particularly at low temperatures and ethylene
pressures. In addition, the barrier for ethylene insertion
into the palladium methyl bond for complex 3b was
found to be ∆Gq ) 21.4 kcal/mol, which is over 4 kcal/
mol higher in energy than the barrier observed for
ethylene insertion in the palladium R-diimine systems.17
We report here the investigation of Ni(II) and Pd(II)
catalysts similar to 1-3 but which incorporate (P,O)
chelating ligands of the type (Ar)(Ar′)CH2C(O)C6H5 [Ar,
Ar′ ) C6H5, C6H5; 2,4,6-(CH3)3C6H2, 2,4,6-(CH3)3C6H2;
C6H5, 2,4,6-(C6H5)3C6H2]. Electronic effects on insertion
barriers in the palladium systems were probed by
incorporating p-CF3 and p-OCH3 substituents in the
aryl rings of both the phenacyl and (Ar)2P moieties.
F igu r e 2. Thermal ellipsoid plot of 6b. B(Arf)4- counterion
omitted for clarity. Selected bond distances (Å) and angles
(deg): Ni(1)-P(1) ) 2.169(3), Ni(1)-O(6) ) 1.908(7), Ni(1)-
C(1) ) 1.995(11), Ni(1)-C(2) ) 1.998(11), Ni(1)-C(3) )
2.024(11), C(1)-C(2) ) 1.373(22), C(2)-C(3) ) 1.314(24),
C(27)-Ni(1) ) 3.82(2), C(39)-Ni(1) ) 3.13(6), P(1)-Ni(1)-
O(6) ) 87.95(21), C(1)-Ni(1)-C(3) ) 72.94(6), C(21)-P(1)-
Ni(1) ) 111.7(8), C(31)-P(1)-Ni(1) ) 123.9(1), C(4)-C(5)-
C(11)-C(12) ) 11.30, C(22)-C(21)-P(1)-C(4) ) 38.79,
C(36)-C(31)-P(1)-C(4) ) 107.04.
Resu lts a n d Discu ssion
4c contains a phenyl group and a 2,4,6-triphenylaryl
group on the phosphine moiety. Cationic Ni-allyl cata-
lysts 6a -c were prepared using the same procedure for
synthesis of 1. Reaction of [(C3H5)NiCl]2 with 2 equiv
of 4a -c yields the neutral π-allyl complexes 5a -c, in
which the carbonyl oxygen of the ligand remains un-
complexed. Treatment of 5a -c with NaB(Arf)4 in diethyl
ether generates the cationic complexes 6a -c as stable
yellow powders. Complexes 6a -c are moderately air
sensitive but stable indefinitely in the solid state and
in solution under inert atmosphere.
X-ray quality crystals of 6b were grown from diethyl
ether/pentane at -35 °C under argon. An ORTEP
diagram of complex 6b is shown in Figure 2. The
coordination geometry around Ni is distorted square
planar [P(1)-Ni(1)-O(6) ) 87.95(21), C(1)-Ni(1)-C(3)
) 72.94(6)°] with the π-allyl group occupying two cis
coordination sites. The phenyl ring of the ligand ketone
is slightly twisted from coplanarity with C(4)-C(5)-
O(6) [torsion angle C(4)-C(5)-C(11)-C(12) ) 11.30°].
The tetrahedral geometry of the phosphorus atom
results in projection of one of the methyl substituents
of each mesityl group toward the axial sites above and
Syn th esis a n d Eth ylen e P olym er iza tion Activity
of (ph en acyldiar ylph osph in e)Ni-allyl+B(Ar f)4- Com -
p lexes. Phenacyldiarylphosphine ligands 4b and 4c
were prepared using a modification of the procedure
described for synthesis of the previously reported ligand
phenacyldiphenylphosphine 4a (Scheme 1).18 Depro-
tonation of acetophenone with LDA to generate the
lithium enolate followed by reaction with the corre-
sponding diarylchlorophosphine19,20 generates ligands
4a -c. Ligand 4a bears two phenyl groups on phospho-
rus, while 4b contains bulkier mesityl groups. Ligand
(17) The rate of insertion for ethylene into the Pd-Me bond for a
typical R-diimine Pd(II) complex at -30 °C has been found to be
kobs ) 1.9 × 10-3 s-1, ∆Gq ) 17.2 kcal/mol. See ref 12.
(18) (a) Bouaoud, S.-H.; Bransutein, P.; Grandjean, D.; Matt, D.;
Nobel, D. Inorg. Chem. 1986, 25, 3765. (b) Demerseman, B.; Guilbert,
B.; Renouard, C.; Gonzalez, M.; Dixneuf, P. H.; Masi, D.; Mealli, C.
Organometallics 1993, 12, 3906.
(19) Dimesitylchlorophosphine has been previously reported: Gold-
white, H.; Kaminski, C.; Millhauser, G.; Ortiz, J .; Vargas, M.; Vertal,
L.; Lappert, M. F.; Smith, S. J . J . Organomet. Chem. 1986, 310, 21.
(20) The previously unreported complex (2,4,6-triphenylaryl)chlo-
rophenylphosphine was prepared by treatment of 2,4,6-triphenylbro-
mobenzene with n-BuLi followed by reaction with dichlorophenylphos-
phine.

5326 Organometallics, Vol. 22, No. 25, 2003
Malinoski and Brookhart
Ta ble 1. Eth ylen e P olym er iza tion w ith
6b a t 1 a tm a
Ta ble 2. 200 p sig Eth ylen e P olym er iza tion
w ith 6ba
time temp yield TON
TOF
branches
Mn (/1000 C)c
time temp yield
entry (h) (°C)
TON
TOF
branches
)
Mn (/1000 C)c
b
b
entry (min) (°C) (g) (× 10-3) (× 10-3 h-1
)
(g) (× 10-5
)
(× 10-5 h-1
1
15
30
45
25 0.01
25 0.17
25 0.72
25 2.17
0.3
4.1
17
52
1.2
8.2
23
53
33
88
39
39
15
17
810
870
850
1060
770
800
960
930
910
1130
850
7
8
6
5
6
7
7
8
9
6
9
1
2
3
4
5
0.5
1
2
1
1
25
25
25
40
60
23.9
28.2
29.1
25.8
12.9
5.6
6.8
7.0
6.2
3.1
11
860
780
770
990
830
8
5
6
5
6
2
3
4
5
6
7
8
9
6.8
3.5
6.2
3.1
60
180
60
180
60
180
60
180
25 4.14 100
40 3.66 88
40 4.84 120
a
Polymerization conditions: 2.0 mg (1.48 µmol) of 6b; 200 mL
b
of toluene. Mn determined by 1H NMR in C6D5Br at 100 °C.
c Polymer branching per 1000 carbons; determined by 1H NMR in
C6D5Br at 100 °C.
60 1.63
60 1.87
80 0.72
80 1.08
39
45
17
26
10
11
9.0
40 °C (productivities up to 3.2 × 105 kg PE mol-1 h-1
)
a
Polymerization conditions: 2.0 mg (1.48 µmol) of 6b; 50 mL
with a significant drop in productivity at 60 °C. Fur-
thermore, the catalyst lifetimes at high ethylene pres-
sure are shorter than those recorded at low pressure.
At 25 °C and 1 atm ethylene pressure, turnover fre-
quencies for 6b decrease from 52 500 (1 h run) to 33 300
h-1 (3 h run; Table 1, entries 4, 5). At 25 °C and 200
psig ethylene pressure, however, the activity drops by
almost half from 30 to 60 min (polymer yield increases
from 23.9 to 28.2 g), indicating that the majority of
active catalyst has decomposed after 1 h. The shorter
catalyst lifetimes are likely due to exotherms during
polymerizations. Even at very low catalyst concentra-
tions of 7.4 × 10-6 M, polymerizations with 6b at 200
psig ethylene pressure generate a substantial reaction
exotherm (approximately 20-30 °C above starting tem-
perature) that cannot be completely controlled by the
internal cooling coils of the autoclave. Despite its short
catalytic lifetime, the turnover frequencies recorded
while 6b remains active for ethylene polymerization are
comparable to activities reported for well-known early
metal and Ni R-diimine systems.22
b
of toluene. Mn determined by 1H NMR in C6D5Br at 100 °C.
c Polymer branching per 1000 carbons; determined by 1H NMR in
C6D5Br at 100 °C.
below the square plane of the molecule [C(39)-Ni(1) )
3.13(6) Å, C(27)-Ni(1) ) 3.82(2) Å]. The mesityl groups
orient themselves nearly perpendicular to each other
in order to minimize steric interactions.
The results of 1 atm ethylene polymerization studies
with 6b are shown in Table 1. Unlike catalyst 1,
complex 6b is quite active at low temperatures and
pressures and generates low molecular weight polyeth-
ylene.21 The highest polymerization activities occur in
the temperature range from 25 to 40 °C; lower polymer
yields and catalyst lifetimes are observed at higher
temperatures. In addition, lower calculated turnover
frequencies reported for 3 h versus 1 h polymerizations
at 25 and 40 °C indicate that catalyst decomposition
occurs even at lower temperatures. Experiments run
over 15 min intervals at 25 °C (entries 1-4) indicate
that 6b does not initiate completely at the beginning of
polymerization. After 15 min only 10 mg of PE (TOF )
1.2 × 103 h-1) is formed; however, at 30 and 45 min
polyethylene yields increase to 170 and 720 mg, respec-
tively, with calculated TOFs of 8.2 × 103 and 2.3 × 104
h-1, suggesting that the number of active catalyst sites
in solution is increasing with time. This observation was
verified by NMR studies in which a large excess of
ethylene was purged through a solution of 6b in CD2-
Under either 1 atm or 200 psig ethylene pressure 6b
generates polyethylene that is isolated as a white
powder. Analysis of the product by 1H and 13C NMR
spectroscopy shows that the polymer is relatively low
molecular weight with Mn values from 750 to 1130,
which corresponds to an average of 26-40 ethylene
units per chain.23 The polymer chains are linear with
approximately 5-9 methyl branches per 1000 carbons,
which equates to about one branch on every other
polymer chain.24 In all cases the polymer end groups
were greater than 95% R-olefin, implying â-hydride
elimination as the predominant chain-transfer mecha-
nism. As shown in Tables 1 and 2 the polymer molecular
weight and branching do not significantly change with
varying reaction time, temperature, and ethylene con-
centration. The polymers displayed sharp Tm values
between 98 and 104 °C as measured by DSC.
1
Cl2 at 25 °C. The resulting H NMR spectrum showed
complete consumption of ethylene and formation of
polyethylene with no detectable decrease in the Ni-allyl
resonances. This suggests that only a very small amount
of 6b was initiated followed by rapid propagation and
consumption of ethylene. Despite the observed short
catalyst lifetimes and somewhat slow rate of initiation,
6b is still significantly more active for ethylene polym-
erization at 1 atm ethylene pressure than the parent
di-tert-butylphosphine-substituted Ni catalyst 1.
Similar ethylene polymerization behavior for catalyst
6b is observed at higher ethylene pressure. The results
of polymerization of ethylene under 200 psig pressure
are shown in Table 2. Catalyst 6b is approximately an
order of magnitude more active for ethylene polymeri-
zation at 200 psig (6.8 × 105 turnovers in 1 h at 25 °C
vs 5.3 × 104 turnovers at 1 atm). As in the 1 atm
ethylene experiments, the highest polymer yields for 200
psig ethylene polymerizations are recorded at 25 and
Catalysts 6a and 6c were found to be very active at
25 °C under high ethylene pressure for dimerization of
ethylene to butenes. The results of ethylene dimeriza-
tion experiments are shown in Table 3. The yields of
(22) In comparison, certain Ni(II) R-diimine catalysts exhibit eth-
ylene polymerization activities of up to 1.0 × 105 kg PE (mol Ni)-1
h-1. See ref 16.
(23) The low molecular weight of the polyethylene generated by 6b
did not allow for unambiguous polymer characterization by gel
permeation chromatography.
(24) Polymer branching values were determined from 1H NMR
spectra (C6D5Br solution at 100 °C) and corrected for methyl end
groups. For the formula used in this calculation see: (a) Daugulis, O.;
Brookhart, M. Organometallics 2002, 21, 5926. (b) Daugulis, O.;
Brookhart, M.; White, P. S. Organometallics 2002, 21, 5935.
(21) Catalyst 1 generates only a trace amount of polyethylene under
1 atm ethylene pressure at 25 °C. See ref 20.

Polymerization and Oligomerization of Ethylene
Organometallics, Vol. 22, No. 25, 2003 5327
Ta ble 3. Dim er iza tion of Eth ylen e w ith 6a a n d 6ca
Sch em e 2. Syn th esis of
-
(P h en a cyld ia r ylp h osp h in e)P d Me(L)+B(Ar f)4
time
(min)
yield
(g)b
TON
TOF
(×10-5
)
(× 10-5 h-1
)
(L ) NCMe, OEt2)
entry
catalyst
1
2
3
4
5
6a
6a
6c
6c
6c
15
30
30
60
120
12.7
13.2
20.1
26.0
28.1
3.4
3.5
5.4
6.9
7.5
13
7.0
11
6.9
3.8
a
Reaction conditions: 1.34 µmol of Ni catalyst; 200 psig
ethylene; 105 mL of toluene; 25 °C (reaction exotherm controlled
by ice bath). Yield determined by mass of final reaction mixture
b
vs mass of 105 mL of toluene (90.8 g).
oligomerization reactions were determined by subtract-
ing the mass of the starting toluene solution from the
mass of the reaction mixture following the dimerization
reaction. Control experiments show the ethylene re-
maining in the toluene solution following the protocol
used is not significant relative to the butene product.
The oligomerization products for 6a and 6c were
1
determined to be exclusively butenes by H NMR and
GC. Catalyst 6a generates 85% 1- vs 2-butene, while
catalyst 6c forms R-olefin with 98% selectivity. Despite
its high initial activity (TOF for 15 min experiment )
1.3 × 106 h-1), catalyst 6a is almost completely deacti-
vated after 15 min. Catalyst 6c displays longer catalytic
lifetimes as it remains active after 1 h, although the
catalyst productivity is substantially decreased. Due to
the difficulty in measuring the mass of volatile butene
products in hot toluene solution, oligomerization experi-
ments were not carried out at higher temperatures,
although significantly decreased catalyst lifetimes are
expected as observed with catalyst 6b.
The results of ethylene polymerization and dimeriza-
tion studies show that catalysts 6a -c are considerably
more active at low temperatures and ethylene pressures
than the parent complex 1, but generate lower molec-
ular weight material with shorter catalyst lifetimes. The
contrasting behaviors of 6b and 6a ,c show that steric
bulk on aryl groups positioned both above and below
the axial sites of the molecule as in 6b is required to
retard chain transfer and generate higher molecular
weight polyethylene. This result is consistent with
reported examples of (R-diimine)Ni and (pyridinedi-
imine)Fe catalysts, in which decreasing the steric bulk
on the imine aryl rings results in highly active olefin
oligomerization catalysts.25-28 It is conceivable that
bulkier aryl groups on the ligand phosphine may gener-
ate higher molecular weight polymer. However, the
competitive formation of P-O and P-P coupled prod-
ucts in the reaction of the diaryl phosphorus chlorides
with the enolate (as determined by 31P NMR) prevented
the synthesis of phenacyldiarylphosphine ligands with
any aryl groups larger than mesityl.29
methyl diethyl ether complexes 8a -c and 9a -c were
prepared using an analogous procedure as described for
catalysts 2 and 3 (Scheme 2).12 The neutral palladium
methyl chloride complexes 7a -c were generated by
treatment of (COD)PdMeCl (COD ) 1,5-cyclooctadiene)
with 1 equiv of the respective ligands 4a -c. Slow
addition of a CH2Cl2/ligand solution at -78 °C followed
by warming to room temperature prevented the com-
petitive formation of (bisphosphine)PdMeCl species.30
Abstraction of chloride by NaB(Arf)4 in the presence of
excess acetonitrile forms the cationic palladium methyl
complexes 8a -c, in which an acetonitrile ligand oc-
cupies the fourth coordination site. Catalysts 8a -c can
be isolated as air-sensitive yellow-white powders that
are stable for several hours in solution at room tem-
perature. Complexes 9a -c were generated by treatment
of 7a -c with NaB(Arf)4 in diethyl ether solvent. The
cationic methyl diethyl ether complexes 9a -c are
considerably less stable and decompose rapidly in solu-
tion at room temperature.
Due to the poor solution stability of the methyl diethyl
ether cations 9a -c, only the palladium methyl aceto-
nitrile complexes were used for large-scale reactions
with ethylene. The results of oligomerization experi-
ments with 8a -c under 200 psig ethylene pressure are
shown in Table 4. As was the case with the previously
reported phenacyldi-tert-butylphosphine-based cata-
lysts, the Pd analogues are about an order of magnitude
less active than their Ni counterparts.12 Complexes 8a
and 8c generate butenes, while 8b forms a mixture of
butenes and hexenes. The nature of the product from
ethylene oligomerization reactions was determined by
1H NMR spectroscopy and GC. In all cases the product
is >90% R-olefin. Catalysts 8a -c display rather short
lifetimes, as the majority of the catalyst is deactivated
after 1 h.
Syn th esis a n d Eth ylen e P olym er iza tion Activity
-
of (p h en a cyld ia r ylp h osp h in e)P d Me(L)+B(Ar f)4
Com p lexes. Cationic palladium methyl acetonitrile and
(25) Killian, C. M.; J ohnson, L. K.; Brookhart, M. Organometallics
1997, 16, 2005.
Mech a n ist ic St u d ies of E t h ylen e In ser t ion in -
(26) Svejda, S. A.; Brookhart, M. Organometallics 1999, 18, 65.
(27) Small, B. L.; Brookhart, M. Macromolecules 1999, 32, 2120.
(28) Britovsek, G. J . P.; Mastroianni, S.; Solan, G. A.; Baugh, S. P.
D.; Redshaw, C.; Gibson, V. C.; White, A. J . P.; Williams, D. J .;
Elsegood, M. R. J . Chem. Eur. J . 2000, 6, 2221.
to (p h en a cyld ia r ylp h osp h in e)P d Me(η2-C2H4)+B-
(30) The complex trans-(phenacyldiphenylphosphine)2PdMeCl was
independently generated by treatment of (COD)PdMeCl with 2 equiv
of 4a . This compound has been previously observed: Andrieu, J .;
Braunstein, P.; Naud, F.; Adams, R. D. J . Organomet. Chem. 2000,
601, 43.
(29) P-O coupling products appear as a singlet in 31P NMR spectra
between 90 and 140 ppm. P-P coupled products appear as doublets
from 100 to 130 and -30 to -60 ppm.

5328 Organometallics, Vol. 22, No. 25, 2003
Malinoski and Brookhart
Ta ble 4. Oligom er iza tion of Eth ylen e w ith 8a -ca
Ta ble 6. Ba r r ier s to Eth ylen e In ser tion for 10a
a n d 10d -g
entry catalyst time (min) yield (g)b TON (× 10-3
)
productc
catalyst
temp (°C)
kins
∆Gq (kcal/mol)
1
2
3
4
8a
8a
8b
8c
30
60
60
60
0.4
0.5
0.8
1.2
4.4
5.6
8.8
butenes
butenes
butenesd
butenes
10a
10d
10e
10f
10g
-20.0
-6.3
-27.7
-10.2
-27.7
1.27(3) × 10-4
1.68(9) × 10-4
9.6(2) × 10-5
6.7(1) × 10-5
2.9(1) × 10-4
19.2
20.2
18.7
20.3
18.2
13
a
Reaction conditions: 3.24 µmol of Pd catalyst; 200 psig
b
ethylene; 105 mL of toluene; 25 °C. Yield determined by mass of
final reaction mixture vs mass of 105 mL of toluene (90.8 g).
Electr on ic Effects on th e Ba r r ier to Migr a tor y
In ser tion . Substitution of aryl groups for aliphatic tert-
butyl groups on phosphorus has a significant impact on
the reactivity of the corresponding cationic Ni(II) and
Pd(II) catalysts, resulting in lower barriers to migratory
insertion and faster catalyst initiation at low temper-
atures and ethylene pressures. It is unlikely that this
is a result of the different steric influence of di-tert-
butylphosphine compared to aryl phosphines since
complexes 9a -c have very different steric environments
around the metal center yet very similar barriers to
ethylene insertion. Thus, the observed trends in reactiv-
ity are likely due to the influence of the more electron-
withdrawing aryl groups relative to the tert-butyl
groups. Since access to palladium methyl ethylene
complexes is relatively straightforward for these sys-
tems, we have investigated the electronic effects on the
barrier for migratory insertion by synthesizing phena-
cyldiarylphosphine ligands with electron-donating and
electron-withdrawing groups at the para position of the
aryl groups of the -PAr2 moiety and the ArCO- moiety
(Scheme 3). Ligands 4d -g were synthesized using the
same procedure as 4a -c with the appropriate methoxy-
or trifluoromethyl-substituted acetophenone and diaryl-
chlorophosphines. Ligands 4d and 4e contain methoxy
and trifluoromethyl groups, respectively, at the para
positions of the phenacyl group, while ligands 4f and
4g bear similar substitution at the para positions of the
diaryl substituents on phosphorus. Treatment of ligands
4d , 4f, and 4g with (COD)PdMeCl generates the pal-
ladium methyl chloride complexes 7d , 7f, and 7g, and
subsequent chloride abstraction with NaB(Arf)4 in di-
ethyl ether solvent forms the cationic palladium methyl
ether species 9d , 9f, and 9g. The palladium methyl
ethylene complex 10e was accessed directly via reaction
of NaB(Arf)4 with the product of 4e and (COD)PdMeCl
in the presence of excess ethylene.31
c Product determined by 1H NMR and GC. 1H NMR suggests the
d
presence of small quantities of higher R-olefins, presumably
primarily 1-hexene.
Ta ble 5. Eth ylen e In ser tion Ba r r ier s for 10a -c
catalyst
temp (°C)
k
ins (s-1
)
∆Gq (kcal/mol)
10a
10b
10c
-20.0
-20.0
-20.0
1.27(3) × 10-4
1.29(5) × 10-4
7.2(2) × 10-5
19.2
19.2
19.5
-
(Ar f)4 Com p lexes. Treatment of palladium methyl
ether complexes 9a -c with 10-15 equiv of ethylene in
CD2Cl2 at -78 °C cleanly generates the corresponding
palladium methyl ethylene species (eq 1). These alkyl-
olefin species serve as model complexes for the resting
state in ethylene dimerization for these systems. The
η2-ethylene ligand appears as a broad singlet resonance
at δ 5.40 in the 1H NMR spectrum at -40 °C due to
rapid exchange of free and bound ethylene on the NMR
time scale. Sharp resonances for free diethyl ether at δ
3.41 (quartet) and 1.13 (triplet) indicate clean displace-
ment of ether by ethylene. The kinetics of ethylene
insertion into the palladium methyl bond were mea-
sured by warming the sample to -20 °C and monitoring
the disappearance of the Pd-methyl resonance in the
1H NMR spectrum over time. The first-order rate
constants and corresponding free energies of activation
for ethylene insertion into the Pd-methyl bond for
10a -c are listed in Table 5. The insertion barriers for
complexes 10a -c are a full 2 kcal/mol lower than those
previously observed for the di-tert-butylphosphine ana-
logue 3.17 The significantly lower barrier to insertion
in these systems is consistent with the observation that
the phenacyldiarylphosphine catalysts display higher
activities at lower reaction temperatures for ethylene
polymerization and oligomerization than the analogous
di-tert-butylphosphine complexes 1-3. As was the case
for 8a -c, complexes 9a and 9c generate butenes and
9b forms a mixture of butenes and hexenes. Since
subsequent ethylene insertion and chain-transfer pro-
cesses occur at approximately the same rate as ethylene
insertion into the palladium-methyl bond, no palladium
propyl species was observed as a reaction intermediate.
After complete consumption of the Pd-methyl species a
reaction mixture generated from 9b was cooled to -90
The palladium methyl ethylene species 10d , 10f, and
10g were accessed by addition of 15 equiv of ethylene
to -78 °C solutions of 9d , 9f, and 9g in CD2Cl2
(-78 °C), and the barriers for ethylene insertion into
the palladium methyl bond for these complexes as well
as for 10e were determined via 1H NMR spectroscopy
by monitoring loss of the palladium methyl resonance
over time (Table 6). The addition of an electron-donating
p-methoxy group to the phenacyl moiety (10d ) raises
the barrier to ethylene insertion by 1.0 kcal/mol (com-
pared to unsubstituted complex 9a ), while an electron-
withdrawing trifluoromethyl group at the same position
(31) Reaction of 4e with (COD)PdMeCl in THF yields a clear yellow
solution. 31P NMR indicates one product at δ 30.59 which is consistent
with a κ2-(P, O)PdMeCl complex. Upon workup, an insoluble white solid
is isolated that is most likely a chloride-bridged dimeric complex.
Treatment of this material with NaBAr′4 in diethyl ether does not form
1
°C; however no agostic species were observed in the H
-
the (P,O)PdMe(OEt2)+BAr′4 complex but likely forms the cationic
NMR spectrum. This suggests the presence of an alkyl
olefin complex, but spectra at this stage are too complex
to make unambiguous assignments.
-
chloride-bridged dimer. Treatment of the product with NaBAr′4 in
the presence of excess ethylene in CD2Cl2 does in fact form the desired
(P,O)PdMe(η2-ethylene)+BAr′4 complex 10e.
-

Polymerization and Oligomerization of Ethylene
Organometallics, Vol. 22, No. 25, 2003 5329
Sch em e 3. Syn th esis of pa r a -Meth oxy- a n d pa r a -Tr iflu or om eth yl-Su bstitu ted Liga n d s a n d Cor r esp on d in g
P a lla d iu m Com p lexes
(10e) lowers the barrier by approximately 0.5 kcal/mol.
Similarly, p-methoxy group substitution on the phos-
phine phenyl groups (9f) results in a 1.1 kcal/mol larger
barrier, while trifluoromethyl group substitution de-
creases the barrier by 1.0 kcal/mol. Complexes 9d , 9f,
9g, and 10e all generate predominately 1-butene when
exposed to ethylene.
These findings are somewhat unexpected in view of
earlier experimental34 and theoretical35 results that
suggest that in d8 square-planar methyl ethylene com-
plexes containing unsymmetrical bidentate ligands
increasing the donor strength trans to the strong donor
methyl group should lower the migration barrier, while
decreasing the donor strength should raise the insertion
barrier. Further study of the effects of electronically
asymmetric ligands on insertion barriers is in progress.
There is strong evidence that, of the two possible
isomers, the methyl ethylene complexes 10a -g adopt
the structures shown in Figure 3. This general structure
is consistent with the expected ligand trans effects in
that the better donor methyl group is trans to the poorer
donor keto group and the weaker donor C2H4 is trans
to the better donor phosphine. In addition the X-ray
crystal structure in the close analogue [κ2-(t-Bu)2PCH2-
C(O)C6H5]PdMe(η2-C2H4)+B(Arf)4-, 11, exhibits this ge-
ometry.32 The substituent effects observed suggest that
decrease in the donor ability of either the diaryl phos-
phine ligand or the keto group decreases the barrier to
insertion, while increase in the donor ability of either
group increases the insertion barrier. This observation
is consistent with the general notion that increasing the
electrophilicity of the metal center should decrease the
insertion barrier. This trend is further reinforced by the
observation that the barrier to insertion in the di-tert-
butylphosphine complex 11 is higher than that of 10a -
g, and the barrier in the imine derivative 12 containing
the better imine N donor atom exceeds 24 kcal/mol,
although in both cases steric factors may play a role.33,34
Su m m a r y
In summary, a new series of cationic Ni(II) and Pd-
(II) catalysts bearing bidentate phenacyldiarylphos-
phine ligands are reported. Ni-allyl complexes 6a -c are
very active catalysts for polymerization and oligomer-
ization of ethylene. Complex 6b generates linear poly-
ethylene with Mn ) 770-1130, while 6a and 6c are
highly active for the dimerization of ethylene to pre-
dominantly 1-butene. These results indicate that ortho-
substitution on both phosphine aryl substituents is
required to sufficiently retard the rate of chain transfer
relative to propagation to generate polymeric materials.
(33) The palladium methyl ethylene complex 12 was stable (no
ethylene insertion) in CD2Cl2 solution at 25 °C for over 6 h. Assuming
a
minimum half-life of 24 h at this temperature, we calculate a
maximum kobs ) 8 × 10-6 s-1 and a minimum ∆Gq ) 24.5 kcal/mol.
Malinoski, J . M.; Brookhart, M. Unpublished results. For a general
procedure for synthesis of complexes of the type 12 see ref 34.
(34) Daugulis, O.; Brookhart, M. Organometallics 2002, 21, 5926.
(35) Chan, M. S. W.; Deng, L.; Ziegler, T. Organometallics 2000,
19, 2741.
(32) Malinoski, J . M.; Brookhart, M. Organometallics 2003, 22, 621.

5330 Organometallics, Vol. 22, No. 25, 2003
Malinoski and Brookhart
withdrawing trifluoromethyl groups at the para position
of the phenacyl group and phosphine aryl groups.
Measurement of the barrier for ethylene insertion in the
palladium methyl ethylene complexes derived from
these ligands showed that the electron-withdrawing
-CF3 group on either the phenacyl group or the aryl-
phosphine substituents lowered the activation barrier
by 0.5-1.0 kcal/mol, while the electron-donating -OCH3
group in these positions raised the barrier to insertion
by approximately 1.0 kcal/mol. These results suggest
that the magnitude of the insertion barrier for these
systems is governed by the overall electrophilic nature
of the metal and not the donor properties of the
phosphine or ketone binding sites alone.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations of compounds
were performed using standard high-vacuum or Schlenk
techniques. Argon was purified by passage through columns
of BASF R3-11 catalyst (Chemalog) and 4 Å molecular sieves.
Solid organometallic compounds were transferred in an argon-
filled MBraun drybox. NMR spectra were acquired with
1
Bruker AMX300 or DRX400 spectrometers. H and 13C chemi-
cal shifts are reported in ppm downfield of TMS and were
referenced to residual 1H NMR signals and to the 13C NMR
signals of the deuterated solvents, respectively. 31P NMR
chemical shifts are reported relative to H3PO4. Coupling
constant J values are reported in Hz. All spectra were acquired
at room temperature unless otherwise noted.
Ma ter ia ls. Hexanes, diethyl ether, pentane, methylene
chloride, toluene, and acetonitrile were deoxygenated and dried
via passage over a column of activated alumina.36 Tetrahy-
drofuran was distilled from sodium/benzophenone under ni-
trogen. Chloroform-d, methylene chloride-d2, and bromobenzene-
d5 were purchased from Cambridge Isotope Laboratories and
dried over 4 Å molecular sieves. Polymer grade ethylene was
purchased from Matheson and used without further purifica-
tion for both the bulk polymerizations and the NMR experi-
ments. Diisopropylamine was distilled and stored over molec-
ular sieves. Acetophenone, n-C4H9Li (1.6 M in hexanes),
chlorodiphenylphosphine, dichlorophenylphosphine, 4′-meth-
oxyacetophenone, and 4′-trifluoroacetophenone were pur-
chased from Aldrich and used without further purification.
NaB(Arf)4 was purchased from Boulder Scientific Company and
used without further purification. Phenacyldiphenylphos-
phine18 (4a ), dimesitylchlorophosphine,19 2,4,6-triphenylbro-
mobenzene,37 bis (4-methoxyphenyl)chlorophosphine,37 bis[4-
(trifluoromethyl)phenyl]chlorophosphine,38 [(C3H5)NiCl]2,39 and
(COD)PdMeCl40 were prepared according to literature proce-
dures.
F igu r e 3. (P,O)Pd methyl ethylene complexes.
Ta ble 7. Su m m a r y of Cr ysta l Da ta , Da ta
Collection , a n d Str u ctu r e Refin em en t P a r a m eter s
for Com p lex 6b
formula
fw
temp (K)
space group
a (Å)
C65H56O2BF24PNi
1425.60
173
P1h
12.7745(9)
14.2552(11)
17.9429(14)
3225.0(4)
2
b (Å)
c (Å)
V, Å3
Z
µ(Mo KR) (Å)
0.71073
1.468
Fcalcd (mg m-3
)
cryst size (mm)
2θ range (deg)
total no. of reflns
no. of unique data, I ) 3.0σ(I)
Rmerge
0.30 × 0.25 × 0.05
5.00-45.00
28031
4133
0.047
no. of params
R1
847
0.062
Sp ectr a l Da ta for th e B(Ar f)4 Cou n ter ion . The following
1H and 13C spectroscopic assignments of the BAr′4- counterion
in CD2Cl2 were invariant for different complexes and temper-
atures and are not reported in the spectroscopic data for each
of the cationic complexes.
wR2
0.064
goodness of fit
2.3211
Catalysts 6a -c are characterized by their high activities
at lower reaction temperatures but poor thermal stabil-
ity and short catalyst lifetimes. Cationic palladium
methyl acetonitrile complexes 8a -c showed modest
activity for oligomerization of ethylene to butenes and
hexenes at high ethylene pressure but also displayed
short catalyst lifetimes. The barrier to migratory inser-
tion of ethylene in the palladium methyl ethylene
complexes in these systems was found to be 19.2-19.5
kcal/mol, which is about 2 kcal/mol lower than that
previously measured for the analogous phenacyldi-tert-
butylphosphine complex. Electronic effects on the eth-
ylene barrier were investigated by synthesis of ligands
4d -g bearing electron-donating methoxy and electron-
-
1
B[3,5-C6H3-(CF 3)2]4 [B(Ar f)4). H NMR (CD2Cl2): δ 7.74
(s, 8H, Ho), 7.57 (s, 4H, Hp). 13C{1H} NMR (CD2Cl2): δ 162.2
(q, J CB ) 37.4 Hz, Cipso), 135.2 (Co), 129.3 (q, J CF ) 31.3 Hz,
Cm), 125.0 (q, J CF ) 272.5 Hz, CF3), 117.9 (Cp).
(36) Pangborn, A. B.; Ghirardelli, M. A.; Grubbs, R. H.; Rosen, R.
K.; Timers, F. J . Organometallics 1996, 15, 1518-1520.
(37) Olmstead, M. M.; Power, P. P. J . Organomet. Chem. 1991, 119,
1460.
(38) Casalnuovo, A. L.; Rajanbabu, T. V.; Ayers, T. A.; Warren, T.
H. J . Am. Chem. Soc. 1994, 116, 9869.
(39) Wilke, G.; Bogdanovic, B.; Herdt, P.; Heimbach, P.; Keim, W.;
Kro¨ner, M.; Oberkirch, W.; Tanaka, K.; Steinru¨cke, E.; Walter, D.;
Zimmerman, H. Angew. Chem., Int. Ed. Engl. 1966, 5, 151.
(40) Rulke, R. W.; Ernsting, J . M.; Spek, A. L.; Elsevier, C. J .; van
Leeuwen, P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769.

Polymerization and Oligomerization of Ethylene
Organometallics, Vol. 22, No. 25, 2003 5331
1
(P h en a cyld ip h en ylp h osp h in e)Ni-a llyl(Cl) (5a ). To a
mixture of [(C3H5)NiCl]2 (0.075 g, 0.28 mmol) and 4a (0.175
g, 0.58 mmol) was added 15 mL of hexanes. The resulting
orange suspension was stirred for 3 h. The orange solid
precipitate was isolated by filtration, washed with 10 mL of
pentane, and dried under high vacuum. Yield: 0.196 g (82%).
1H NMR (300 MHz, CD2Cl2): δ 7.93 (d, 2H, J ) 7.2, H-Aro),
7.66 (m, 3H, HAr), 7.56 (m, 2H, HAr), 7.42 (m, 8H, HAr), 5.44
(m, 1H, allyl -CH-), 4.21 (d, 2H, J PH ) 9.3, -CH2-), 3.36 (br
s, 2H, allyl H2C-), 2.51 (br s, 2H, allyl H2C-). 13C{1H} NMR
(100.62 MHz, CD2Cl2): δ 196.1 (d, J CP ) 2), 137.4 (d, J CP ) 2),
solid powder. Yield: 0.063 g (43%). H NMR (300 MHz, CD2-
Cl2, 258 K): δ 7.96 (d, 2H, J ) 7.5, H-Aro), 7.60 (m, 9H, HAr),
7.46 (m, 4H, HAr), 4.40 (d, 2H, J PH ) 11, -CH2-), 3.91 (m,
4H, OCH2CH3), 1.58 (m, 6H, OCH2CH3), 0.97 (s, 3H, Pd-Me).
13C{1H} NMR (75.48 MHz, CD2Cl2, 258 K): δ 205.3, 137.6,
133.3, 130.7, 130.1, 130.0, 129.9, 126.6, 47.0 (d, J CP ) 37), 22.8,
16.4, -0.1. 31P{1H} NMR (121.49 MHz, CD2Cl2, 258 K):
δ
37.51. This compound was not sufficiently stable for elemental
analysis.
P h en a cyld im esitylp h osp h in e (4b). To a -78 °C solution
of diisopropylamine (0.34 mL, 2.41 mmol) in 10 mL of THF
was added n-C4H9Li (1.5 mL, 2.41 mmol, 1.6 M solution in
hexanes). The LDA solution was stirred for 30 min and added
via cannula to a -78 °C solution of acetophenone (0.28 mL,
2.41 mmol) in 10 mL of THF. The solution was stirred for 2 h
and added via cannula to a -78 °C solution of dimesitylchlo-
rophosphine (0.700 g, 2.30 mmol) in 20 mL of THF. The
resulting yellow solution was warmed to room temperature
and stirred for 2 h. The reaction mixture was concentrated to
ca. 5 mL in vacuo, and 20 mL of toluene was added to fully
precipitate the white solid LiCl. The solution was filtered
through Celite, and the solvent was removed in vacuo to yield
a yellow oil. The residue was stirred in 20 mL of pentane at 0
°C for 1 h to yield a white precipitate. The solid was isolated
via filtration and washed with 10 mL of cold pentane to yield
a white powder. Yield: 0.485 g (54%). 1H NMR (400 MHz,
CDCl3): δ 7.79 (d, 2H, J ) 7.6, Ar-Ho), 7.47 (t, 1H, J ) 7.2,
Ar-Hp), 7.34 (t, 2H, J ) 7.6, Ar-Hm), 6.70 (d, 4H, J ) 3, ArMes),
4.12 (d, 2H, J PH ) 1.6, -CH2-), 2.18 (s, 6H, Mes-Mep), 2.16
133.8, 133.6 (d, J CP ) 12), 132.9 (d, J CP ) 40), 130.7 (d, J CP
)
1.6), 129.0, 128.9, 128.9, 128.8, 111.3. 31P{1H} NMR (121.49
MHz, CD2Cl2): δ 17.15. Anal. Calcd for C23H17ClOPNi: C,
62.84; H, 3.90. Found: C, 62.90; H, 4.70.
(P h en a cyld ip h en ylp h osp h in e)Ni-a llyl+B(Ar f)4- (6a ). To
a mixture of 5a (0.050 g, 0.11 mmol) and NaB(Arf)4 (0.102 g,
0.12 mmol) at -78 °C was added 10 mL of diethyl ether. The
resulting yellow suspension was warmed to room temperature
and stirred for 2 h. The solution was isolated via filtration,
and the solvent was removed in vacuo. The resulting yellow-
orange oil was coevaporated with 2 × 5 mL of pentane, and
the residual brittle foam was dried under high vacuum to form
a yellow powder. Yield: 0.097 g (67%). 1H NMR (400 MHz,
CD2Cl2): δ 8.11 (d, 2H, J ) 8.6, H-Aro), 7.87 (t, 1H, J ) 7.6,
H-Arp), 7.60 (m, 12H, HAr), 5.94 (m, 1H, allyl -CH-), 4.33
(br s, 2H, -CH2-), 3.55 (br s, 2H, allyl CH2-), 2.35 (br s, 2H,
allyl CH2-). 13C{1H} NMR (75.48 MHz, CD2Cl2): δ 212.4,
138.6, 133.0, 132.7, 132.5, 131.6, 130.3, 130.2, 130.1, 119.4,
44.8. 31P{1H} NMR (161.96 MHz, CD2Cl2): δ 28.63. Anal. Calcd
for C55H29BF24OPNi: C, 52.13; H, 2.31. Found: C, 52.34; H,
2.89.
(s, 12H, Mes-Meo). 13C{1H} NMR (75.48 MHz, CD2Cl2):
197.4 (d, J CP ) 9.9), 141.9 (d, J CP ) 14.7), 138.3, 138.2, 133.0,
132.0 (d, J CP ) 24.4), 130.1 (d, J CP ) 3), 128.7 (d, J CP ) 3),
128.5, 39.4 (d, J CP ) 25), 22.9 (d, J CP ) 13.8), 20.7. 31P{1H}
NMR (161.87 MHz, CDCl3): δ -24.73. Anal. Calcd for C26H29
OP: C, 80.38; H, 7.52. Found: C, 79.41; H, 7.47.
δ
(P h en a cyld ip h en ylp h osp h in e)P d Me(Cl) (7a ). To a solu-
tion of (COD)PdMeCl (0.158 g, 0.60 mmol) in 10 mL of CH2-
Cl2 at -78 °C was added a solution of 4a (0.181 g, 0.59 mmol)
in 10 mL of CH2Cl2. The resulting solution was warmed to
room temperature and stirred for 1 h. The solvent was removed
in vacuo, and the resulting white solid residue was washed
with 2 × 10 mL of pentane and dried under high vacuum.
-
(P h en a cyld im esitylp h osp h in e)Ni-a llyl(Cl) (5b). To a
mixture of [(C3H5)NiCl]2 (0.051 g, 0.19 mmol) and 4b (0.150
g, 0.39 mmol) was added 15 mL of hexanes. The resulting
orange suspension was stirred for 3 h. The orange solid
precipitate was isolated by filtration, washed with 10 mL of
pentane, and dried under high vacuum. Yield: 0.119 g (60%).
1H NMR (400 MHz, CD2Cl2): δ 7.68 (m, 2H, Ar-Ho), 7.46 (t,
1H, J ) 6.4, Ar-Hp), 7.32 (m, 2H, Ar-Hm), 6.79 (s, 4H, Ar-
Hm), 5.44 (m, 1H, allyl -CH-), 4.41 (m, 2H, -CH2-), 3.34 (br
s, 2H, allyl CH2-), 2.55 (s, 6H, Mes-Mep), 2.37 (br s, 2H, allyl
CH2-), 2.22 (s, 12H, Mes-Meo). 13C{1H} NMR (75.47 MHz,
CD2Cl2): δ 196.6, 141.6 (d, J CP ) 9.5), 140.0, 138.3, 133.2,
131.1, 131.0, 128.7, 128.5. 109.8, 39.7 (d, J CP ) 19.7), 25.2,
21.0. 31P{1H} NMR (161.87 MHz, CD2Cl2): δ -0.59. Anal.
Calcd for C29H34ClOPNi: C, 66.51; H, 6.54. Found: C, 65.55;
H, 6.48.
1
Yield: 0.162 g (59%). H NMR (400 MHz, CDCl3): δ 7.75 (m,
4H, HAr), 7.67 (m, 1H, HAr), 7.35 (m, 8H, HAr), 7.21 (m, 2H,
H
Ar), 4.18 (d, 2H, J PH ) 10, -CH2-), 0.60 (s, 3H, Pd-Me). 13C-
{1H} NMR (75.48 MHz, CD2Cl2): δ 204.5, 134.1. 134.0, 133.5,
131.0 (d, J CP ) 2), 130.7, 130.0, 128,6 (d, J CP ) 2), 128.5, 38.8,
5.1. 31P{1H} NMR (161.87 MHz, CDCl3): δ 31.69. Anal. Calcd
for C21H20ClOPPd: C, 54.69; H, 4.37. Found: C, 55.09; H, 4.57.
(P h en a cyld ip h en ylp h osp h in e)P d Me(NCMe)+B(Ar f)4
-
(8a ). To a mixture of 7a (0.050 g, 0.11 mmol) and NaB(Arf)4
(0.097 g, 0.110 mmol) at -78 °C were added 8 mL of diethyl
ether and acetonitrile (0.20 mL, 2.82 mmol). The resulting pale
yellow suspension was warmed to 0 °C and stirred for 1 h.
The solution was isolated via filtration and the solvent
removed in vacuo. The yellow oil residue was coevaporated
with 2 × 5 mL of pentane at 0 °C, and the resulting brittle
foam was dried under high vacuum to form a white-yellow
(P h en a cyld im esit ylp h osp h in e)Ni-a llyl+B(Ar f)4 (6b ).
-
To a mixture of 5b (0.090 g, 0.17 mmol) and NaB(Arf)4- (0.152
g, 0.17 mmol) at -78 °C was added 10 mL of diethyl ether.
The resulting yellow suspension was warmed to room tem-
perature and stirred for 2 h. The solution was isolated via
filtration, and the solvent was removed in vacuo. The resulting
yellow-orange oil was coevaporated with 2 × 5 mL of pentane,
and the residual brittle foam was dried under high vacuum
1
solid powder. Yield: 0.061 g (42%). H NMR (400 MHz, CD2-
Cl2, 258 K): δ 8.02 (d, 2H, J ) 8.2, H-Aro) 7.75 (m, 1H, H-Arp)
7.62 (m, 8H, HAr), 7.51 (m, 4H, HAr), 4.41 (d, 2H, J PH ) 11.2,
-CH2-), 2.36 (s, 3H, Pd-NCMe), 0.84 (s, 3H, Pd-Me). 13C-
{1H} NMR (100.62 MHz, CD2Cl2, 258 K): δ 197.2, 137.2, 133.4,
133.2, 132.9, 130.6, 130.0, 129.9, 129.8, 129.7, 128.7, 34.4, 3.4.
31P{1H} NMR (161.96 MHz, CD2Cl2, 258 K): δ 37.02. This
compound was not sufficiently stable for elemental analysis.
(P h en acyldiph en ylph osph in e)P dMe(OEt2)+B(Ar f)4- (9a).
To a mixture of 7a (0.050 g, 0.11 mmol) and NaB(Arf)4 (0.097
g, 0.110 mmol) at -78 °C was added 10 mL of diethyl ether.
The resulting pale yellow suspension was warmed to 0 °C and
stirred for 1 h. The solution was isolated via filtration and the
solvent removed in vacuo. The yellow oil residue was coevapo-
rated with 2 × 5 mL of pentane at 0 °C, and the resulting
brittle foam was dried under high vacuum to form a pale white
1
to form a yellow powder. Yield: 0.169 g (73%). H NMR (400
MHz, CD2Cl2): δ 8.02 (d, 2H, J ) 8, Ar-Ho), 7.82 (t, 1H, J )
7, Ar-Hp), 7.58 (m, 2H, Ar-Hm), 6.98 (s, 4H, Ar-Hm), 5.86
(m, 1H, allyl -CH-), 4.81 (m, 2H, -CH2-), 4.17 (m, 1H, allyl
CHH′-), 3.70 (m, 1H, allyl CHH′-), 3.06 (br s, 1H, allyl
-HH′C), 2.42 (d, 12H, J ) 6, Mes-Meo), 2.28 (d, 6H, J ) 3.6,
Mes-Mep), 1.95 (d, 1H, J ) 13, allyl -CHH′). 13C{1H} NMR
(75.48 MHz, CD2Cl2): δ 204.2, 138.7, 133.2, 132.3 (d, J CP
)
8.4), 131.9 (d, J CP ) 9), 131.7, 130.4, 126.9, 123.3, 119.7, 117.4,
51.3, 48.2 (d, J CP ) 28.7), 24.8, 21.2. 31P{1H} NMR (161.87
MHz, CD2Cl2): δ 5.64. Anal. Calcd for C61H46BF24OPNi: C,
54.23; H, 3.43. Found: C, 53.61; H, 3.45.

5332 Organometallics, Vol. 22, No. 25, 2003
Malinoski and Brookhart
1
(P h en a cyld im esitylp h osp h in e)P d Me(Cl) (7b). To a sus-
pension of (COD)PdMeCl (0.105 g, 0.40 mmol) in 10 mL of
diethyl ether was added a solution of 4b (0.185 g, 0.48 mmol)
in 10 mL of diethyl ether. The resulting yellow solution was
stirred for 2 h, during which time a white precipitate formed.
The solid was isolated via filtration, washed with 2 × 10 mL
of pentane, and dried under high vacuum to yield a white-
yellow solid. Yield: 0.120 g (56%). 1H NMR (400 MHz, CD2-
Cl2): δ 7.92 (d, 2H, J ) 8.6, Ar-Ho), 7.67 (t, 1H, J ) 9, Ar-
Hp), 7.47 (t, 2H, J ) 8, Ar-Hm), 6.91 (d, 4H, J ) 3.6, Ar-Hm),
4.51 (d, 2H, J PH ) 10, -CH2-), 2.48 (s, 12H, Mes-Meo), 2.26
(s, 6H, Mes-Mep), 0.86 (d, 3H, J PH ) 3.6, Pd-Me). 13C{1H}
NMR (75.48 MHz, CD2Cl2): δ 204.7 (d, J CP ) 4.9), 141.5, (d,
J CP ) 2.3), 136.1, 135.1 (d, J CP ) 4.9), 131.8 (d, J CP ) 8.5),
1.153 g (50%). H NMR (300 MHz, CDCl3): δ 7.64 (d, 2H, J )
7, Ar-Ho), 7.51 (d, 6H, J ) 2.4, Ar-H0), 7.38 (m, 8H, HAr),
7.00 (m, 4H, HAr), 6.89 (m, 2H, HAr). 13C{1H} NMR (75.48 MHz,
CDCl3): δ 151.5 (d, J CP ) 30), 143.3, 141.9 (d, J CP ) 8), 139.6,
138.6 (d, J CP ) 35), 136.4 (d, J CP ) 45), 134.3 (d, J CP ) 45),
130.1 (d, J CP ) 3), 129.2, 129.1, 128.9, 128.5, 127.9 (d, J CP
)
5), 127.7, 127.5, 127.3. 31P{1H} NMR (121.49 MHz, CDCl3): δ
79.15. Anal. Calcd for C30H22ClP: C, 80.26; H, 4.94. Found:
C, 80.06; H, 5.03.
P h en a cyl(2,4,6-t r ip h en yla r yl)p h en ylp h osp h in e (4c).
To a -78 °C solution of diisopropylamine (0.31 mL, 2.23 mmol)
in 10 mL of THF was added n-C4H9Li (1.4 mL, 2.23 mmol, 1.6
M solution in hexanes). The LDA solution was stirred for 30
min and added via cannula to a -78 °C solution of acetophe-
none (0.26 mL, 2.23 mmol) in 10 mL of THF. The solution was
stirred for 2 h and added via cannula to a -78 °C solution of
(2,4,6-triphenylaryl)chlorophenylphosphine (1.00 g, 2.23 mmol)
in 20 mL of THF. The resulting yellow solution was warmed
to room temperature and stirred for 2 h. The reaction mixture
was concentrated to ca. 5 mL in vacuo and 20 mL of toluene
was added to fully precipitate the white solid LiCl. The solution
was filtered through Celite, and the solvent was removed in
vacuo to yield a yellow oil. The residue was stirred in 20 mL
of pentane at 0 °C for 1 h to yield a white precipitate. The
solid was isolated via filtration and washed with 10 mL of cold
pentane to yield a white powder. Yield: 0.584 g (49%). 1H NMR
(400 MHz, CD2Cl2): δ 7.65 (m, 5H, HAr), 7.53 (m, 3H, HAr),
7.42 (m, 8H, HAr), 7.17 (m, 7H, HAr), 6.97 (m, 4H, HAr), 3.13
(m, 2H, -CH2-). 13C{1H} NMR (75.48 MHz, CD2Cl2): δ 197.6
(d, J CP ) 11), 150.5 (d, J CP ) 16), 143.1 (d, J CP ) 4.8), 141.2,
141.1, 139.8, 137.0, 133.1, 132.9, 130.8 (d, J CP ) 17), 129.9 (d,
J CP ) 2), 129.1, 129.0 (d, J CP ) 2.7), 128.6 (d, J CP ) 3), 128.5,
128.4, 128.2, 128.1, 127.8, 127.5, 127.2 (d, J CP ) 4.5), 39.2 (d,
J CP ) 22). 31P{1H} NMR (161.86 MHz, CD2Cl2): δ -20.79.
Anal. Calcd for C38H29BOP: C, 85.69; H, 5.49. Found: C, 83.29;
H, 5.52.
130.3, 129.63, 127.1, 126.4, 48.4 (d, J CP ) 30.5), 24.9 (d, J CP
)
8.7), 21.1, -1.3. 31P{1H} NMR (161.87 MHz, CD2Cl2): δ 9.32.
Anal. Calcd for C27H32ClOPPd: C, 59.46; H, 5.92. Found: C,
58.32; H, 5.99.
(P h e n a c y ld i m e s i t y lp h o s p h i n e )P d M e (N C M e )+B -
-
(Ar f)4 (8b). To a mixture of 7b (0.040 g, 0.073 mmol) and
NaB(Arf)4 (0.066 g, 0.074 mmol) at -78 °C was added 10 mL
of diethyl ether and acetonitrile (0.50 mL, 9.6 mmol). The
resulting pale yellow suspension was warmed to 0 °C and
stirred for 1 h. The solution was isolated via filtration and the
solvent removed in vacuo. The yellow oil residue was coevapo-
rated with 2 × 5 mL of pentane at 0 °C, and the resulting
brittle foam was dried under high vacuum to form a white-
yellow solid powder. Yield: 0.043 g (41%). 1H NMR (300 MHz,
CD2Cl2, 268 K): δ 7.93 (d, 2H, J ) 7.5, Ar-Ho), 7.70 (m, 1H,
Ar-Hp), 7.50 (t, 2H, Ar-Hm), 6.94 (d, 4H, J ) 4, Ar-Hm), 4.55
(d, 2H, J PH ) 10, -CH2-), 2.43 (s, 12H, Mes-Meo), 2.36 (s,
3H, Pd-NCMe), 2.26 (s, 6H, Mes-Mep), 0.76 (d, 3H, J PH ) 2,
Pd-Me). 13C{1H} NMR (75.48 MHz, CD2Cl2, 268 K): δ 206.7,
142.5, 140.7 (d, J CP ) 9.6), 137.2, 133.8 (d, J CP ) 5.8), 132.0
(d, J CP ) 9.0), 130.5, 129.8, 124.7, 124.0, 49.5 (d, J CP ) 41),
25.0 (d, J CP ) 8.6), 22.8, 21.1, 3.5. 31P{1H} NMR (121.49 MHz,
CD2Cl2, 268 K): δ 7.63. This compound was not sufficiently
stable for elemental analysis.
[P h en a cyl(2,4,6-tr ip h en yla r yl)p h en ylp h osp h in e]Ni-a l-
lyl(Cl) (5c). To a mixture of [(C3H5)NiCl]2 (0.044 g, 0.16 mmol)
and 4c (0.091 g, 0.17 mmol) was added 15 mL of hexanes. The
resulting orange suspension was stirred for 3 h. The orange
solid precipitate was isolated by filtration, washed with 10 mL
of pentane, and dried under high vacuum. Yield: 0.170 g
(78%). 1H NMR (400 MHz, CDCl3): δ 7.68 (d, 2H, J ) 7.6,
Ar-Ho), 7.57 (m, 5H, HAr), 7.42 (m, 10H, HAr), 7.39 (m, 6H,
(P h en a cyld im esit ylp h osp h in e)P d Me(OE t 2)+B(Ar f)4
-
(9b). To a mixture of 7b (0.040 g, 0.073 mmol) and NaB(Arf)4
(0.066 g, 0.074 mmol) at -78 °C was added 10 mL of diethyl
ether. The resulting pale yellow suspension was warmed to 0
°C and stirred for 1 h. The solution was isolated via filtration
and the solvent removed in vacuo. The yellow oil residue was
coevaporated with 2 × 5 mL of pentane at 0 °C, and the
resulting brittle foam was dried under high vacuum to form a
H
Ar), 6.95 (m, 4H, HAr), 5.18 (m, 1H, allyl -CH-), 3.98 (m,
2H, -CH2-), 2.65 (m, 2H, allyl H2C-), 1.91 (m, 2H, allyl
-CH2). 13C{1H} NMR (75.48 MHz, CD2Cl2): δ 198.0, 149.8 (d,
J CP ) 15), 147.6, 143.8 (d, J CP ) 7), 142.7, 139.6, 139.2, 137.9,
132.0, 131.9, 130.9 (d, J CP ) 11.3), 129.7, 129.5, 128.9, 128.8,
128.3, 127.8, 111.3, 41.6 (m). 31P{1H} NMR (161.87 MHz,
CDCl3): δ 10.98. Anal. Calcd for C41H34ClOPNi: C, 73.74; H,
5.13. Found: C, 71.78; H, 5.34.
1
pale white solid powder. Yield: 0.050 g (48%). H NMR (300
MHz, CD2Cl2, 258 K): δ 7.88 (d, 2H, J ) 7.8, Ar-Ho), 7.68 (m,
1H, Ar-Hp), 7.41 (t, 2H, J ) 7.5, Ar-Hm), 6.91 (d, 4H, J ) 4,
Ar-Hm), 4.58 (d, 2H, J PH ) 10, -CH2-), 3.85 (q, 4H, J ) 7,
OCH2CH3), 2.41 (s, 12H, Mes-Meo), 2.25 (s, 6H, Mes-Mep),
1.47 (t, 6H, OCH2CH3), 0.85 (s, 3H, Pd-Me). 13C{1H} NMR
(75.48 MHz, CD2Cl2, 258 K): δ 206.1, 142.4, 140.4 (d, J CP
)
[P h en a cyl(2,4,6-t r ip h en yla r yl)p h en ylp h osp h in e]Ni-
a llyl+B(Ar f)4 (6c). To a mixture of 5c (0.085 g, 0.13 mmol)
-
9.6), 132.0 (d, J CP ) 9.1), 130.4, 129.8, 126.6, 123.0, 119.4, 50.2
(d, J CP ) 38), 34.5, 24.9 (d, J CP ) 8.8), 21.0, 15.9, 2.8. 31P{1H}
NMR (121.49 MHz, CD2Cl2, 258 K): δ 6.91. This compound
was not sufficiently stable for elemental analysis.
and NaB(Arf)4 (0.113 g, 0.13 mmol) at -78 °C was added 15
mL of diethyl ether. The resulting yellow suspension was
warmed to room temperature and stirred for 2 h. The solution
was isolated via filtration, and the solvent was removed in
vacuo. The resulting yellow-orange oil was coevaporated with
2 × 5 mL of pentane, and the residual brittle foam was dried
under high vacuum to form an orange powder. Yield: 0.123 g
(65%). 1H NMR (400 MHz, CDCl3): δ 7.95 (d, 2H, J ) 7.6,
Ar-Ho), 7.76 (t, 1H, J ) 7.6, Ar-Hp), 7.65 (m, 8H, HAr), 7.47
(m, 7H, HAr), 7.28 (m, 1H, Ar-Hp), 7.18 (m, 2H, HAr), 6.74 (m,
2H, HAr), 4.75 (m, 1H, allyl -CH-), 4.25 (m, 1H, allyl HH′C-),
3.49 (m, 2H, -CH2-), 3.07 (br s, 1H, allyl HH′C-), 2.50 (br s,
1H, allyl -CHH′), 1.95 (br s, 1H, allyl -CHH′). 13C{1H} NMR
(2,4,6-Tr ip h en yla r yl)ch lor op h en ylp h osp h in e. A -78 °C
solution of 2,4,6-triphenylbromobenzene (2.00 g, 5.2 mmol) and
20 mL of THF was charged with n-C4H9Li (3.3 mL, 5.2 mmol,
1.6 M solution in hexanes). The resulting white suspension
was stirred for 1 h, then added via cannula to a -78 °C solution
of dichlorophenylphosphine (0.70 mL, 5.2 mmol) in 15 mL of
THF. The reaction mixture was warmed to room temperature
and stirred for 2 h. The solvent was removed in vacuo, and 15
mL of toluene was added to precipitate LiCl. The suspension
was filtered through Celite and the solvent removed in vacuo
to yield a pale yellow oil. The residue was stirred in 15 mL of
hexanes for 2 h, during which time a white precipitate formed.
The solid was isolated via filtration, washed with 10 mL of
pentane, and dried in vacuo to yield a white powder. Yield:
(100.62 MHz, CD2Cl2): δ 210.8 (d, J CP ) 20), 150.6 (d, J CP
)
11), 145.6, 142.3 (d, J CP ) 5.4), 138.8, 138.6, 133.4, 131.6, 130.9,
130.7 (d, J CP ) 7.3), 130.4, 130.0, 129.9, 129.8, 129.7, 129.3,
129.2, 128.9, 127.8, 123.7 (d, J CP ) 40), 117.2, 53.3, 44.0 (d,

Polymerization and Oligomerization of Ethylene
Organometallics, Vol. 22, No. 25, 2003 5333
J CP ) 27). 31P{1H} NMR (161.87 MHz, CDCl3): δ 16.91. Anal.
Calcd for C73H46BF24OPNi: C, 58.63; H, 3.10. Found: C, 58.17;
H, 3.16.
The solution was filtered through Celite, and the solvent was
removed in vacuo to yield a yellow oil. The residue was stirred
in 20 mL of pentane at 0 °C for 1 h to yield a white precipitate.
The solid was isolated via filtration and washed with 10 mL
of cold pentane to yield a white powder. Yield: 1.045 g (46%).
1H NMR (300 MHz, CD2Cl2): δ 7.92 (d, 2H, J ) 8.7, Ar-Ho),
7.44 (m, 4H, HAr), 7.35 (m, 6H, HAr), 6.92 (d, 2H, J ) 9, Ar-
Hp), 3.86 (s, 3H, -OMe), 3.76 (s, 2H, -CH2-). 13C{1H} NMR
(75.48 MHz, CD2Cl2): δ 195.8 (d, J CP ) 8.5), 164.2, 138.4 (d,
J CP ) 15), 133.3 (d, J CP ) 20), 131.5 (d, J CP ) 2), 130.4, 129.4,
129.0 (d, J CP ) 6.5), 114.2, 56.1, 40.6 (d, J CP ) 20). 31P{1H}
NMR (121.49 MHz, CD2Cl2): δ -17.48. Anal. Calcd for
[P h en acyl(2,4,6-tr iph en ylar yl)ph en ylph osph in e]P dMe-
(Cl) (7c). To a suspension of (COD)PdMeCl (0.091 g, 0.34
mmol) in 10 mL of diethyl ether was added a solution of 4c
(0.200 g, 0.37 mmol) in 10 mL of diethyl ether. The resulting
yellow solution was stirred for 2 h, during which time a white
precipitate formed. The solid was isolated via filtration,
washed with 2 × 10 mL of pentane, and dried under high
vacuum to yield a white-yellow solid. Yield: 0.173 g (74%). 1H
NMR (300 MHz, CD2Cl2): δ 7.77 (br s, 2H, HAr), 7.60 (m, 6H,
C
21H20O2P: C, 75.21; H, 6.01. Found: C, 75.25; H, 5.74.
H
Ar), 7.41 (m, 9H, HAr), 7.32 (m, 5H, HAr), 7.22 (m, 5H, HAr),
3.54 (m, 2H, -CH2-), 0.62 (s, 3H, Pd-Me). 13C{1H} NMR
(75.48 MHz, CD2Cl2): δ 195., 149.1, 143.2, 139.4, 137.0, 134.3,
134.2, 133.5, 130.6 (d, J CP ) 8), 130.4, 129.5, 129.2, 128.9,
127.7, 39.9, 6.5. 31P{1H} NMR (121.49 MHz, CD2Cl2): δ 20.20.
Anal. Calcd for C39H32ClOPPd: C, 67.93; H, 4.68. Found: C,
66.27; H, 4.79.
[(p a r a -Met h oxy)p h en a cyld ip h en ylp h osp h in e]P d Me-
(Cl) (7d ). To a solution of (COD)PdMeCl (0.158 g, 0.60 mmol)
in 10 mL of CH2Cl2 at -78 °C was added a solution of 4d (0.200
g, 0.59 mmol) in 10 mL of CH2Cl2. The resulting solution was
warmed to room temperature and stirred for 1 h. The solvent
was removed in vacuo, and the resulting white solid residue
was washed with 2 × 10 mL of pentane and dried under high
vacuum. Yield: 0.198 g (67%). 1H NMR (400 MHz, CD2Cl2): δ
7.75 (m, 6H, HAr), 7.41 (m, 6H, HAr), 6.76 (d, 2H, J ) 8.8, Ar-
Ho), 4.11 (d, 2H, J PH ) 10.4, -CH2-), 3.77 (s, 3H, -OMe), 0.54
(s, 3H, Pd-Me). 13C{1H} NMR (100.61 MHz, CD2Cl2): δ 193.1,
164.3, 134.5 (d, J CP ) 11.8), 131.4, 131.3, 131.0, 130.5, 128.8
(d, J CP ) 10.9), 114.1, 56.0, 39.0, 5.4. 31P{1H} NMR (161.87
MHz, CD2Cl2): δ 30.77. Anal. Calcd for C22H23ClO2PPd: C,
53.68; H, 4.71. Found: C, 54.40; H, 4.70.
[(p a r a -Met h oxy)p h en a cyld ip h en ylp h osp h in e]P d Me-
(OEt2)+B(Ar f)4- (9d ). To a mixture of 7d (0.050 g, 0.102 mmol)
and NaB(Arf)4 (0.092 g, 0.104 mmol) at -78 °C was added 10
mL of diethyl ether. The resulting pale yellow suspension was
warmed to 0 °C and stirred for 1 h. The solution was isolated
via filtration and the solvent removed in vacuo. The yellow
oil residue was coevaporated with 2 × 5 mL of pentane at
0 °C, and the resulting brittle foam was dried under high
vacuum to form a yellow-white solid powder. Yield: 0.067 g
(47%). 1H NMR (300 MHz, CD2Cl2, 258 K): δ 7.96 (d, 2H, J )
8.7, Ar-Ho), 7.57 (m, 10H, HAr), 6.92 (m, 2H, Ar-Hp), 4.36 (d,
2H, J PH ) 11.4, -CH2-), 3.86 (s, 3H, -OMe), 3.80 (m, 4H,
-OCH2CH3), 1.52 (m, 6H, -OCH2CH3), 0.83 (s, 3H, Pd-Me).
13C{1H} NMR (75.48 MHz, CD2Cl2, 258 K): δ 202.5, 167.1,
[P h en acyl(2,4,6-tr iph en ylar yl)ph en ylph osph in e]P dMe-
-
(NCMe)+B(Ar f)4 (8c). To a mixture of 7c (0.025 g, 0.036
mmol) and NaB(Arf)4 (0.033 g, 0.036 mmol) at -78 °C was
added 8 mL of diethyl ether and acetonitrile (0.10 mL, 1.9
mmol). The resulting pale yellow suspension was warmed to
0 °C and stirred for 1 h. The solution was isolated via filtration
and the solvent removed in vacuo. The yellow oil residue was
coevaporated with 2 × 5 mL of pentane at 0 °C, and the
resulting brittle foam was dried under high vacuum to form a
white-yellow solid powder. Yield: 0.025 g (46%). 1H NMR (300
MHz, CD2Cl2, 268 K): δ 7.87 (d, 2H, J ) 7.2, Ar-Ho), 7.56 (m,
6H, HAr), 7.41 (m, 8H, HAr), 7.31 (t, 2H, J ) 7.2, Ar-Hm), 7.13
(m, 2H, HAr), 6.90 (d, 2H, J ) 6.6, Ar-Ho), 3.78 (m, 2H,
-CH2-), 2.10 (s, 3H, -NCMe), 0.61 (d, 3H, J PH ) 3, Pd-Me).
13C{1H} NMR (75.48 MHz, CD2Cl2, 268 K): δ 194.4, 148.4
(d, J CP ) 11.2), 144.9, 138.4, 137.4, 137.4, 135.8 (d, J CP ) 3),
135.3, 132.1, 131.5 (d, J CP ) 2), 131.3, 131.1, 130.8, 130.7 (d,
J CP ) 9.4), 130.3, 130.1, 129.4, 127.6, 125.4, 124.1, 119.5, 36.6
(d, J CP ) 30), 29.5 (d, J CP ) 20), 22.8, 11.1. 31P{1H} NMR
(121.49 MHz, CD2Cl2, 268 K): δ 20.85. This compound was
not sufficiently stable for elemental analysis.
[P h en acyl(2,4,6-tr iph en ylar yl)ph en ylph osph in e]P dMe-
(OEt2)+B(Ar f)4- (9c). To a mixture of 7c (0.100 g, 0.145 mmol)
and NaB(Arf)4 (0.128 g, 0.145 mmol) at -78 °C was added 15
mL of diethyl ether. The resulting pale yellow suspension was
warmed to 0 °C and stirred for 1 h. The solution was isolated
via filtration and the solvent removed in vacuo. The yellow
oil residue was coevaporated with 2 × 5 mL of pentane at
0 °C, and the resulting brittle foam was dried under high
vacuum to form a yellow-white solid powder. Yield: 0.108 g
(47%). 1H NMR (300 MHz, CD2Cl2, 258 K): δ 7.85 (s, 2H, Ar-
Ho), 7.63 (m, 4H, HAr), 7.44 (m, 8H, HAr), 7.26 (m, 4H, HAr),
7.08 (s, 2H, HAr), 6.95 (s, 2H, HAr), 3.98 (m, 2H, -CH2-), 3.48
(q, 4H, J ) 7, -OCH2CH3), 1.15 (t, 6H, J ) 7, -OCH2CH3),
0.63 (s, 3H, Pd-Me). 13C{1H} NMR (75.48 MHz, CD2Cl2, 258
K): δ 197.5, 149.0 (d, J CP ) 10), 144.6, 138.8, 138.4, 135.9,
131.4, 131.0, 130.8, 130.7, 130.3, 130.1, 128.9 (d, J CP ) 2),
127.5, 126.9, 67.9, 41.0, 15.3, 14.3. 31P{1H} NMR (121.49 MHz,
CD2Cl2, 258 K): δ 24.55. This compound was not sufficiently
stable for elemental analysis.
133.7, 133.3, 133.1, 130.0 (d, J CP ) 12), 127.3, 126.2 (d, J CP
)
5.4), 115.1, 70.5, 56.4, 46.8 (d, J CP ) 35.5), 16.3, -0.5. 31P{1H}
NMR (121.49 MHz, CD2Cl2, 258 K): δ 38.04. This compound
was not sufficiently stable for elemental analysis.
(p a r a -Tr iflu or om et h yl)p h en a cyld ip h en ylp h osp h in e
(4e). To a -78 °C solution of diisopropylamine (1.5 mL, 10.6
mmol) in 10 mL of THF was added n-C4H9Li (6.7 mL, 10.6
mmol, 1.6 M solution in hexanes). The LDA solution was
stirred for 30 min and added via cannula to a -78 °C solution
of 4′-trifluoromethylacetophenone (2.00 g, 10.6 mmol) in 10
mL of THF. The solution was stirred for 2 h and added via
cannula to a -78 °C solution of chlorodiphenylphosphine (1.91
mL, 10.6 mmol) in 20 mL of THF. The resulting yellow solution
was warmed to room temperature and stirred for 2 h. The
reaction mixture was concentrated to ca. 5 mL in vacuo, and
20 mL of toluene was added to fully precipitate the white solid
LiCl. The solution was filtered through Celite, and the solvent
was removed in vacuo to yield a yellow oil. The residue was
stirred in 20 mL of pentane at 0 °C for 1 h to yield a white
precipitate. The solid was isolated via filtration and washed
with 10 mL of cold pentane to yield a white powder. Yield:
(pa r a -Meth oxy)p h en a cyld ip h en ylp h osp h in e (4d ). To
a -78 °C solution of diisopropylamine (0.94 mL, 6.66 mmol)
in 10 mL of THF was added n-C4H9Li (4.2 mL, 6.66 mmol, 1.6
M solution in hexanes). The LDA solution was stirred for 30
min and added via cannula to a -78 °C solution of 4′-
methoxyacetophenone (1.00 g, 6.66 mmol) in 10 mL of THF.
The solution was stirred for 2 h and added via cannula to a
-78 °C solution of chlorodiphenylphosphine (1.2 mL, 6.66
mmol) in 20 mL of THF. The resulting yellow solution was
warmed to room temperature and stirred for 2 h. The reaction
mixture was concentrated to ca. 5 mL in vacuo, and 20 mL of
toluene was added to fully precipitate the white solid LiCl.
1
1.800 g (46%). H NMR (400 MHz, CDCl3): δ 7.99 (d, 2H, J )
8.4, Ar-Ho), 7.65 (d, 2H, J ) 8.4, Ar-Ho), 7.43 (m, 5H, HAr),
7.33 (m, 5H, HAr), 3.79 (s, 2H, -CH2-). 13C{1H} NMR (75.48
MHz, CD2Cl2): δ 196.7 (d, J CP ) 8.4), 140.2, 137.8, 137.6, 133.2
(d, J CP ) 20), 132.3 (q, J CF ) 312), 129.7, 129.5 (d, J CP ) 2),
129.2 (d, J CP ) 6.8), 126.1 (q, J CF ) 4), 41.2 (d, J CP ) 22). 31P-
{1H} NMR (161.87 MHz, CDCl3): δ -15.16. Anal. Calcd for
C
21H16F3OP: C, 67.75; H, 4.33. Found: C, 67.55; H, 4.39.

5334 Organometallics, Vol. 22, No. 25, 2003
Malinoski and Brookhart
[(pa r a -Tr iflu or om eth yl)p h en a cyld ip h en ylp h osp h in e]-
J ) 7, -OCH2CH3), 0.79 (s, 3H, Pd-Me). 13C{1H} NMR (75.48
MHz, CD2Cl2, 258 K): δ 205.7, 137.4, 135.1, 134.9, 130.7, 130.2,
129.8, 115.5 (d, J CP ) 13.3), 70.3, 56.0, 47.9 (d, J CP ) 30), 22.8,
14.3 (d, J CP ) 10), -0.2. 31P{1H} NMR (121.49 MHz, CD2Cl2,
258 K): δ 36.17. This compound was not sufficiently stable
for elemental analysis.
P d Me(η2-C2H4)+B(Ar f)4 (10e). To a solution of (COD)-
-
PdMeCl (0.053 g, 0.20 mmol) in 10 mL of THF at -78 °C was
added a solution of 4e (0.075 g, 0.20 mmol) in 10 mL of THF.
The resulting solution was warmed to room temperature and
stirred for 1 h. 31P{1H} NMR of the crude reaction mixture
shows a single resonance at δ 30.59 ppm. The solvent was
removed in vacuo, and the resulting white solid residue was
washed with 2 × 10 mL of pentane and dried under high
vacuum. Yield: 0.053 g (50%). Product not soluble for 1H, 13C
NMR analysis. 31P{1H} NMR (121.49 MHz, CD2Cl2): δ 30.59
(in THF solution). Anal. Calcd for C22H19ClF3OPPd: C, 49.93;
H, 3.62. Found: C, 50.18; H, 3.73. An NMR tube was charged
with white solid product (4.0 mg, 7.6 µmol) and NaB(Arf)4 (6.7
mg, 7.6 µmol) under argon. The NMR tube was fitted with a
rubber septum, cooled to -78 °C, and charged with ethylene
(1.0 mL, 40.6 µmol) and 0.8 mL of dry CD2Cl2. The resulting
pale yellow solution (very little NaCl precipitate) was used for
NMR characterization and ethylene insertion kinetics studies.
1H NMR (300 MHz, CD2Cl2, 243 K): δ 8.14 (d, 2H, J ) 7.8,
Ar-Ho), 7.81 (d, 2H, J ) 7.5, Ar-Hm), 7.62 (m, 4H, HAr), 7.56
(m, 6H, HAr), 5.41 (br s, Pd-[η2-C2H4]), 4.51 (d, 2H, J PH ) 12,
-CH2-), 0.94 (s, 3H, Pd-Me). 31P{1H} NMR (121.49 MHz,
CD2Cl2, 243 K): δ 29.28. This compound was not sufficiently
stable for elemental analysis.
P h en a cylbis(pa r a -tr iflu or om eth ylp h en yl)p h osp h in e
(4g). To a -78 °C solution of diisopropylamine (0.78 mL, 5.53
mmol) in 10 mL of THF was added n-C4H9Li (3.4 mL, 5.59
mmol, 1.6 M solution in hexanes). The LDA solution was
stirred for 30 min and added via cannula to a -78 °C solution
of acetophenone (0.65 mL, 5.53 mmol) in 10 mL of THF. The
solution was stirred for 2 h and added via cannula to a -78
°C solution of bis[4-(trifluoromethyl)phenyl]chlorophosphine
(1.972 g, 5.53 mmol) in 20 mL of THF. The resulting yellow
solution was warmed to room temperature and stirred for 2
h. The reaction mixture was concentrated to ca. 5 mL in vacuo,
and 20 mL of toluene was added to fully precipitate the white
solid LiCl. The solution was filtered through Celite, and the
solvent was removed in vacuo to yield a yellow oil. The residue
was stirred in 20 mL of pentane at 0 °C for 1 h to yield a white
precipitate. The solid was isolated via filtration and washed
with 10 mL of cold pentane to yield a white powder. Yield:
0.886 g (36%). 1H NMR (300 MHz, CDCl3): δ 7.93 (m, 2H, HAr),
7.59 (m, 9H, HAr), 7.46 (m, 2H, HAr), 3.85 (s, 2H, -CH2-). 13C-
{1H} NMR (75.48 MHz, CD2Cl2): δ 196.8 (d, J CP ) 8), 142.7
(d, J CP ) 17.8), 137.1, 134.1, 133.7 (d, J CP ) 15), 131.5 (d,
J CP ) 32), 129.2, 129.1 (d, J CP ) 2), 125.9, 124.6 (q, J CF ) 273),
40.2 (d, J CP ) 18.8). 31P{1H} NMR (121.49 MHz, CDCl3): δ
[P h en a cylbis(pa r a -m eth oxyp h en yl)p h osp h in e]P d Me-
(Cl) (7f). To a -78 °C solution of diisopropylamine (0.59 mL,
4.2 mmol) in 10 mL of THF was added n-C4H9Li (2.6 mL, 4.2
mmol, 1.6 M solution in hexanes). The LDA solution was
stirred for 30 min and added via cannula to a -78 °C solution
of acetophenone (0.49 mL, 4.2 mmol) in 10 mL of THF. The
solution was stirred for 2 h and added via cannula to a -78
°C solution of bis(4-methoxyphenyl)chlorophosphine (1.14 g,
4.2 mmol) in 20 mL of THF. The resulting yellow solution was
warmed to room temperature and stirred for 2 h. 31P{1H} NMR
of the crude reaction mixture displays the major resonance
(>85% of phosphorus-containing products) at δ -18.41 ppm.
The reaction mixture was concentrated to ca. 5 mL in vacuo,
and 20 mL of toluene was added to fully precipitate the white
solid LiCl. The solution was filtered through Celite, and the
solvent was removed in vacuo to yield 1.36 g of crude yellow
oil 4f. 31P{1H} NMR (161.87 MHz, CD2Cl2): δ -18.41 (major
peak). The product was dissolved in 10 mL of CH2Cl2 and
added via cannula to a -78 °C solution of (COD)PdMeCl (0.084
g, 0.32 mmol) in 10 mL of CH2Cl2. The resulting solution was
warmed to room temperature and stirred for 1 h. 31P{1H} NMR
of the crude reaction mixture shows a single resonance at δ
28.65 ppm. The solvent was removed in vacuo, and the
resulting white solid residue was washed with 2 × 10 mL of
pentane and dried under high vacuum. Yield: 0.105 g (63%).
1H NMR (400 MHz, CD2Cl2): δ 7.67 (m, 6H, HAr), 7.46 (m,
1H, HAr), 7.28 (m, 2H, HAr), 6.89 (m, 4H, HAr), 4.12 (d, 2H,
J PH ) 12, -CH2-), 3.81 (s, 6H, -OMe), 0.53 (s, 3H, Pd-Me).
13C{1H} NMR (75.48 MHz, CD2Cl2): δ 195.1 (d, J CP ) 5), 162.2,
137.7, 136.1 (d, J CP ) 13.4), 133.7, 129.0, 128.9, 121.4 (d,
J CP ) 56), 114.4 (d, J CP ) 12), 55.9, 39.7 (d, J CP ) 30), 5.5.
31P{1H} NMR (161.87 MHz, CD2Cl2): δ 28.64. Anal. Calcd for
C23H26ClO3PPd: C, 52.79; H, 5.01. Found: C, 52.95; H, 4.85.
-18.68. Anal. Calcd for
Found: C, 59.72; H, 3.47.
C22H15F6OP: C, 60.01; H, 3.43.
[P h en a cylbis(pa r a -tr iflu or om eth ylp h en yl)p h osp h in e]-
P d Me(Cl) (7g). To a solution of (COD)PdMeCl (0.090 g, 0.34
mmol) in 10 mL of CH2Cl2 at -78 °C was added a solution of
4g (0.150 g, 0.34 mmol) in 10 mL of CH2Cl2. The resulting
solution was warmed to room temperature and stirred for 1
h. The solvent was removed in vacuo, and the resulting white
solid residue was washed with 2 × 10 mL of pentane and dried
under high vacuum. Yield: 0.095 g (47%). 1H NMR (300 MHz,
CD2Cl2): δ 7.88 (m, 4H, HAr), 7.75 (d, 2H, J ) 13, Ar-Ho),
7.67 (d, 4H, J ) 7.2, Ar-Ho), 7.51 (m, 1H, Ar-Hp), 7.34 (m,
2H, Ar-Hm), 4.19 (d, 2H, J PH ) 10, -CH2-), 0.58 (d, 3H,
J PH ) 3, Pd-Me). 13C{1H} NMR (75.48 MHz, CD2Cl2): δ 194.3
(d, J CP ) 4.5), 137.1 (d, J CP ) 3), 135.4, 134.8 (d, J CP ) 12.5),
134.3, 133.2 (q, J CF ) 33), 129.2, 128.9, 125.9, 122.4, 39.1 (d,
J CP ) 30.5), 5.9. 31P{1H} NMR (121.49 MHz, CD2Cl2): δ 29.92.
Anal. Calcd for C23H18ClF6OPPd: C, 46.26; H, 3.04. Found:
C, 45.96; H, 3.00.
[P h en a cylbis(pa r a -tr iflu or om eth ylp h en yl)p h osp h in e]-
P d Me(OEt2)+B(Ar f)4- (9g). To a mixture of 7g (0.150 g, 0.251
mmol) and NaB(Arf)4 (0.222 g, 0.251 mmol) at -78 °C was
added 15 mL of diethyl ether. The resulting pale yellow
suspension was warmed to 0 °C and stirred for 1 h. The
solution was isolated via filtration and the solvent removed
in vacuo. The yellow oil residue was coevaporated with 2 × 5
mL of pentane at 0 °C, and the resulting brittle foam was dried
under high vacuum to form a yellow-white solid powder.
1
Yield: 0.218 g (58%). H NMR (300 MHz, CD2Cl2, 258 K): δ
8.01 (d, 2H, J ) 7.5, Ar-Ho), 7.86 (m, 5H, HAr), 7.76 (m, 4H,
[P h en a cylbis(pa r a -m eth oxyp h en yl)p h osp h in e]P d Me-
(OEt2)+B(Ar f)4- (9f). To a mixture of 7f (0.030 g, 0.057 mmol)
and NaB(Arf)4 (0.052 g, 0.058 mmol) at -78 °C was added 10
mL of diethyl ether. The resulting pale yellow suspension was
warmed to 0 °C and stirred for 1 h. The solution was isolated
via filtration and the solvent removed in vacuo. The yellow
oil residue was coevaporated with 2 × 5 mL of pentane at
0 °C, and the resulting brittle foam was dried under high
vacuum to form a yellow-white solid powder. Yield: 0.035 g
(43%). 1H NMR (300 MHz, CD2Cl2, 258 K): δ 7.98 (m, 2H, Ar-
Ho), 7.75 (t, 1H, J ) 7.8, Ar-Hp), 7.50 (m, 6H, HAr), 7.00 (d,
4H, J ) 7.2, Ar-Ho), 4.38 (d, 2H, J PH ) 10.8, -CH2-), 3.87
(q, 4H, J ) 7, -OCH2CH3), 3.81 (s, 6H, -OMe), 1.56 (t, 6H,
H
Ar), 7.50 (m, 2H, HAr), 4.52 (d, 2H, J PH ) 11.4, -CH2-), 3.78
(m, 4H, -OCH2CH3), 1.44 (m, 6H, -OCH2CH3), 0.85 (s, 3H,
Pd-Me). 13C{1H} NMR (75.48 MHz, CD2Cl2, 258 K): δ 204.9,
138.1, 133.8 (d, J CP ) 13.4), 133.1 (d, J CP ) 5.7), 131.2, 130.9,
130.0, 127.2 (m), 125.3, 121.6, 69.6, 46.7 (d, J CP ) 34.6), 16.1,
1.0. 31P{1H} NMR (121.49 MHz, CD2Cl2, 258 K): δ 37.54. This
compound was not sufficiently stable for elemental analysis.
P r oced u r e for 1 a tm Eth ylen e P olym er iza tion s w ith
6b. Complex 6b (2.0 mg, 1.48 µmol) was added to a Schlenk
flask under argon. The flask was back-filled three times with
1 atm ethylene, charged with 50 mL of toluene, and placed in
an oil bath at the appropriate reaction temperature. The

Polymerization and Oligomerization of Ethylene
Organometallics, Vol. 22, No. 25, 2003 5335
reaction solution was vigorously stirred under 1 atm ethylene
for the desired reaction time. The polymerization was quenched
by addition of 10 mL of acetone, and the reaction mixture was
poured into 300 mL of stirring methanol to precipitate the
polymer. The product was isolated via filtration, washed with
acetone, and dried overnight in a vacuum oven at 80 °C.
P r oced u r e for 200 p sig Eth ylen e P olym er iza tion s
w ith 6b. A 1000 mL Parr autoclave was heated under vacuum
at 100 °C for 4 h, cooled to room temperature, and back-filled
with ethylene. The reaction solvent (190 mL of toluene) was
added, and the reactor was warmed to the desired reaction
temperature under 200 psig ethylene pressure. The reactor
was vented, and a solution of 6b (2.0 mg, 1.48 µmol) in 10 mL
of toluene was added via cannula under argon pressure. The
reactor was pressurized to 200 psig ethylene and stirred for
the desired reaction time. The polymerization was quenched
by venting the autoclave followed by addition of acetone. The
reaction mixture was poured into a stirring solution of 750
mL of methanol and ca. 5 mL of HCl to precipitate the polymer.
The polymer product was isolated by filtration, washed with
acetone, and dried in vacuo.
P r oced u r e for 200 p sig Eth ylen e Oligom er iza tion w ith
6a a n d 6c. A 300 mL Parr autoclave was heated under
vacuum at 100 °C for 4 h, cooled to room temperature, and
back-filled with ethylene. The reaction solvent (95 mL of
toluene) was added, and the reactor was pressurized under
200 psig ethylene. The reactor was vented, and a solution of
1.34 µmol of catalyst and 10 mL of toluene was added via
cannula under argon pressure. The reactor was pressurized
to 200 psig ethylene and stirred at 25 °C for the desired
reaction time. The reaction temperature was maintained using
an external ice bath to control the reaction exotherm. The
reactor was vented to ambient pressure, and the contents were
poured into a pre-tared 500 mL flask and weighed. This
procedure was performed as quickly as possible to minimize
the potential evolution of butene products; however, we cannot
rule out a small loss of volatile products during workup. The
reaction yield was determined from the final mass of reaction
mixture versus the control mass of 105 mL of toluene after
ethylene pressurization and decompression (see below). An
aliquot (approximately 0.5 mL) of the reaction mixture was
transferred to a NMR tube containing 1 mL of CD2Cl2 and
promptly sealed. The products were analyzed by 1H NMR
spectroscopy and GC. The 1-butene was identified by 1H NMR
resonances at δ 5.78 (dCHR), 4.95 (dCH2), 2.0 (-CH2-), and
1.0 (-CH3). Resonances for the 2-butenes appear at δ 5.55
(dCHR) and 1.95-1.85 (-CH3). To determine the mass of the
control reaction solution (reaction mixture with no catalyst or
butene product), 105 mL of toluene was added to the autoclave
and stirred under 200 psig ethylene at 25 °C for 30 min. The
reactor was vented to ambient pressure, and the contents were
quickly poured into a 500 mL flask and weighed. Mass of
control reaction mixture ) 90.8 g.
P r oced u r e for 200 p sig Eth ylen e Oligom er iza tion w ith
8a -c. The same procedure and product analysis were followed
as described above using 3.24 µmol of catalysts 8a -c and 105
mL of toluene.
1H NMR An a lysis for P olyet h ylen e Olefin ic E n d
Gr ou p s. The olefinic end groups were determined from 1H
NMR spectra. R-Olefin: δ 5.85 (m, 1H, H2CdCH-), δ 5.0-4.9
(m, 2H, H2CdCH-). Internal olefin: δ 5.39 (m, 2H, trans
isomer), δ 5.34 (m, 2H, cis isomer). Vinylidene: δ 4.7 (br s,
2H). Trisubstituted olefin: δ 5.18 (m or br t, 1H).
P r oced u r e for in Situ Gen er a tion of (P ,O)P d Me(η2-
C2H4) Com p lexes (10a -d , 10f,g) for Mea su r em en t of Eth -
ylen e In ser tion Kin etics. The appropriate (P,O)PdMe(O-
Et2)+B(Arf)4 complex 9a -d and 9f,g (3.0 µmol) was added
-
to an NMR tube under argon. The tube was sealed with a
septum, cooled to -78 °C, and charged with 0.8 mL of CD2Cl2
and 1.0 mL (40.6 µmol) of ethylene. The kinetics of ethylene
insertion were measured via 1H NMR by monitoring the loss
of the palladium methyl resonance. See above for preparation
of 9e.
Ack n ow led gm en t. We thank the NSF (Grant CHE-
0107810) and the DuPont Corporation for financial
support of this work and Dr. Peter White (UNC) for
X-ray analysis of 6b.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic data for 6b and kinetics plots for ethylene migratory
insertion in selected complexes. This material is available free
of charge via the Internet at http://pubs.acs.org.
OM030388H