Synthesis, characterization, and ethylene polymerization activities of neutral nickel(II) complexes derived from anilino-substituted enone ligands bearing trifluoromethyl and trifluoroacetyl substituents

Article abstract of DOI:10.1021/om050931p

A series of neutral Ni(II) complexes derived from anilino-substituted enone ligands bearing electron-withdrawing trifluoromethyl and trifluoroacetyl groups have been synthesized and characterized: [η²-ArNC(R ₁)C=C(R₂)C(O)CF₃]Ni(PPh₃)Ph (3a, Ar = 3,5-i-Pr₂C₆H₃, R₁ = H, R ₂ = COCF₃; 3b, Ar = 3,5i-Pr₂C₆H ₃, Ri = Me, R₂ = COCF₃; 3c, Ar = 3,5-i-Pr ₂C₆H₃, R₁ = Me, R₂ = H; 3d, Ar = 3,5-Me₂C₆H₃, R₁ = Me, R₂ = COCF₃). When they are activated with either Ni(COD)₂ or B(C₆F₅)₃, these complexes are active for the polymerization of ethylene to branched polyethylenes. Complex 3a is especially active and long-lived, with a turnover frequency of 5 × 10⁵ at 60 °C and 200 psig of ethylene, a half-life exceeding 15 h at 35 °C, and a total turnover number exceeding 10⁶ at 35 °C and 200 psig. Molecular weights and degrees of branching of polyethylenes obtained from 3a are reported as a function of reaction temperature and ethylene pressure.

Full text of DOI:10.1021/om050931p

1868
Organometallics 2006, 25, 1868-1874
Synthesis, Characterization, and Ethylene Polymerization Activities
of Neutral Nickel(II) Complexes Derived from Anilino-Substituted
Enone Ligands Bearing Trifluoromethyl and Trifluoroacetyl
Substituents
Lei Zhang, Maurice Brookhart,* and Peter S. White
Department of Chemistry, UniVersity of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
ReceiVed October 28, 2005
A series of neutral Ni(II) complexes derived from anilino-substituted enone ligands bearing electron-
withdrawing trifluoromethyl and trifluoroacetyl groups have been synthesized and characterized: [η2-
ArNC(R1)CdC(R2)C(O)CF3]Ni(PPh3)Ph (3a, Ar ) 3,5-i-Pr2C6H3, R1 ) H, R2 ) COCF3; 3b, Ar ) 3,5-
i-Pr2C6H3, R1 ) Me, R2 ) COCF3; 3c, Ar ) 3,5-i-Pr2C6H3, R1 ) Me, R2 ) H; 3d, Ar ) 3,5-Me2C6H3,
R1 ) Me, R2 ) COCF3). When they are activated with either Ni(COD)2 or B(C6F5)3, these complexes
are active for the polymerization of ethylene to branched polyethylenes. Complex 3a is especially active
and long-lived, with a turnover frequency of 5 × 105 at 60 °C and 200 psig of ethylene, a half-life
exceeding 15 h at 35 °C, and a total turnover number exceeding 106 at 35 °C and 200 psig. Molecular
weights and degrees of branching of polyethylenes obtained from 3a are reported as a function of reaction
temperature and ethylene pressure.
A particular appeal of examining late-metal catalysts was the
potential to copolymerize ethylene and polar monomers such
as alkyl acrylates.22-24 While a limited set of polar monomers
were successful in copolymerizations using the diimine systems,
even the successful polar monomers exhibited reduced rates,
due to the substantial electrophilicity of the cationic metal center
and the propensity to form stable chelate structures following
polar monomer incorporation.8,11,25 In addition, these cationic
catalysts were sensitive to polar additives such as water and
alcohols. For these reasons, considerable attention turned to
developing neutral catalysts based on Ni(II) which should have
reduced electrophilicity and thus reduced sensitivity to polar
groups.
Introduction
In 1995 cationic Ni(II) and Pd(II) catalysts derived from bulky
aryl-substituted R-diimines were reported to convert ethylene
and R-olefins to high-molecular-weight polyolefins.1 These
materials exhibited unique microstructures due primarily to the
now well-established ability of the metal to migrate along the
polymer chain via â-hydride elimination/reinsertion reactions
without undergoing chain transfer.2-7 This discovery was
followed by intense collaborative activities between the UNC
and DuPont Versipol groups, and later by other groups, in
developing the catalytic chemistry and related mechanistic
understanding of the diimine systems and related catalysts.8-21
The first neutral Ni(II) catalysts for ethylene polymerizations
were reported in the 1980s.22,26-28 These catalysts were primarily
based on modifications of the SHOP systems and incorporated
anionic phosphino-enolate ligands. Such systems normally
provided low-molecular-weight linear polyethylene at modest
rates. Incorporation of bulky substituents29 or perfluoroalkyl
* To whom correspondence should be addressed. E-mail: mbrookhart@
unc.edu.
(1) Johnson, L. K.; Killian, C. M.; Brookhart, M. J. Am. Chem. Soc.
1995, 117, 6414.
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Chem. Phys. 1995, 196, 467.
(3) Svejda, S. A.; Johnson, L. K.; Brookhart, M. J. Am. Chem. Soc. 1999,
121, 10634.
(4) Tempel, D. J.; Johnson, L. K.; Huff, R. L.; White, P. S.; Brookhart,
M. J. Am. Chem. Soc. 2000, 122, 6686.
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Feldman, J.; McCord, E. F.; S. J. McLain; Kreutzer, K. A.; Nennet, A. M.
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10.1021/om050931p CCC: $33.50 © 2006 American Chemical Society
Publication on Web 03/11/2006

Neutral Ni(II) Complexes
Organometallics, Vol. 25, No. 8, 2006 1869
groups30 in the backbone of the P,O chelates greatly accelerated
the polymerization rates, but molecular weights of the linear
PE were modest. Claverie31 and Mecking32,33 have shown that
neutral P,O chelate Ni complexes bearing perfluoroalkyl or
hydrophilic groups can be used for emulsion polymerizations
of ethylene in water. Other interesting SHOP-type derivatives,
though mainly used for oligomerization, are zwitterionic Ni(II)
complexes developed recently by the Bazan group.34
backbone. Complex 3a shows especially high activity and long
lifetime when activated with B(C6F5)3 or Ni(COD)2.
Neutral ligands based on bidentate anionic N,O ligands have
received considerable recent attention since incorporation of a
bulky ortho-substituted aryl-N functionality, modeled after the
diimine systems, results in substantial increases in polymer
molecular weights as well as incorporation of branching due to
chain walking.35-40 Early prominent examples were based on
salicylaldimines formed from ortho-disubstituted anilines and
first reported by the DuPont39 and Grubbs groups.40 These
systems were shown to copolymerize ethylene and norbornene
derivatives containing polar functionalities;40 Mecking demon-
strated that related Ni(II) catalysts were effective for the aqueous
emulsion polymerization of ethylene.32,41
Results and Discussion
Ligand Syntheses. Complexes 3a-d all share a common
five-membered N,O chelate backbone and differ only in the
substitution patterns along the backbone. As noted in the
Introduction, the rationale for preparing these complexes with
highly electron-withdrawing fluoroalkyl substituents was the
expectation, based on analogy to P,O chelates, that such
complexes may exhibit significantly enhanced activities in
ethylene polymerization. All of the complexes 3a-d are
prepared from the corresponding acyl-substituted enamine
ligands 4a-d. However, despite the similarities in structure,
different synthetic routes must be employed to access these
ligands.
This laboratory has reported the synthesis of anionic five-
membered N,O chelates derived from bulky anilinotropones35-37
and anilinoperinaphthenone42 for preparation of Ni(II) catalysts
of types 1 and 2. These systems proved to be compatible with
Ligand 4a is prepared by displacement of the Et2N- group
in
((diethylamino)methylene)-1,1,1,5,5,5-hexafluoroacetyl-
acetone (DAMFA) by 2,6-diisopropylaniline catalyzed by the
Lewis acid FeCl3 (eq 1), in analogy with the known chemistry
of DMAFA. Following chromatographic purification, 4a was
isolated in good yields and high purity.
polar solvents and highly active for formation of branched PEs.
Mechanistic studies established the nature of the catalyst resting
state(s) and the mechanisms of chain transfer and decomposi-
tion.37 DFT studies of both the salicylaldimine and anilino-
tropone systems have been reported.17,43
We report here our efforts to further enhance the activity of
neutral Ni(II) catalysts through synthesis and screening of a
series of catalysts 3a-d, which incorporate the strongly electron
withdrawing -CF3 and -C(O)CF3 groups in the ligand
Ligands 4b and 4d were prepared by the reaction of the
corresponding imidoyl chloride with silver cyclooctadiene
hexafluroacetylacetonate in toluene at 25 °C (eq 2). Crystal-
(29) Gibson, V. C.; Tomov, A.; White, A. J. P.; Williams, D. J. Chem.
Commun. 2001, 719.
(30) Soula, R.; Broyer, J. P.; Llauro, M. F.; Tomov, A.; Spitz, R.;
Claverie, J.; Drujon, X.; Malinge, J.; Saudemont, T. Macromolecules 2001,
34, 2438.
(31) Soula, R.; Novat, C.; Tomov, A.; Spitz, R.; Claverie, J.; Drujon,
X.; Malinge, J.; Staudemont, T. Macromolecules 2001, 34, 2022.
(32) Bauers, F. M.; Mecking, S. Macromolecules 2001, 34, 1165.
(33) Mecking, S.; Held, A.; Bauers, F. M. Angew. Chem., Int. Ed. 2002,
41, 544.
(34) Lee, B. Y.; Bazan, G. C.; Vela, J.; Komon, Z. J. A.; Bu, X. J. Am.
Chem. Soc. 2001, 123, 5352.
(35) Hicks, F. A.; Brookhart, M. Organometallics 2001, 20, 3217.
(36) Hicks, F. A.; Jenkins, J. C.; Brookhart, M. Organometallics 2003,
22, 3533.
(37) Jenkins, J. C.; Brookhart, M. J. Am. Chem. Soc. 2004, 126, 5827.
(38) Wang, C.; Friedrich, S.; Younkin, T. R.; Li, R. T.; Grubbs, R. H.;
Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149.
(39) Johnson, L. K.; Bennett, A. M. A.; Ittel, S. D.; Wang, L.;
Parthasarathy, A.; Hauptman, E.; Simpson, R. D.; Feldman, J.; Coughlin,
E. B. Vol. WO 98/30609, U.S., 1998.
(40) Younkin, T. R.; Connor, E. F.; Henderson, J. I.; Friedrich, S. K.;
Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460.
(41) Bauers, F. M.; Mecking, S. Angew. Chem., Int. Ed. 2001, 40, 3020.
(42) Jenkins, J. C.; Brookhart, M. Organometallics 2003, 22, 250.
(43) Michalak, A.; Ziegler, T. Organometallics 2003, 22, 2069.
lizations from CH2Cl2/hexane at lower temperature afford the
pure ligands in excellent yields. Use of the silver enolate is
required, since the lithium enolate results in substantial imi-
doylation at oxygen.
In analogy with the preparation of ligand 4a, ligand 4c was
prepared by displacement of the methoxy group from the enol

1870 Organometallics, Vol. 25, No. 8, 2006
Zhang et al.
Figure 2. ORTEP view of 4d. Selected interatomic distances (Å)
and angles (deg): C(6)-N(7) ) 1.4497(19), N(7)-C(8) )
1.3200(19), C(8)-C(9) ) 1.4231(20), C(9)-C(12) ) 1.4160(21),
C(12)-O(21) ) 1.2373(18), C(9)-C(10) ) 1.4862(20); C(5)-
Figure 1. ORTEP view of 4b. Selected interatomic distances (Å)
and angles (deg): C(6)-N(13) ) 1.4475(17), N(13)-C(14) )
1.3241(6), C(14)-C(16)
1.4170(19), C(16)-C(17)
)
1.4167(18), C(16)-C(23)
1.4957(18), C(23)-O(24)
)
)
C(6)-N(7)-C(8)
) -81.5(3), C(6)-N(7)-C(8)-C(16) )
)
-6.60(19), N(7)-C(8)-C(9)-C(12) ) 2.50(18), C(8)-C(9)-
C(12)-O(21) ) -2.88(17).
1.2415(16), C(17)-O(18) ) 1.2014(19); C(1)-C(6)-N(13)-C(14)
) 86.86(16), N(13)-C(14)-C(16)-C(23) ) -0.62(10), C(14)-
C(16)-C(23)-O(24) ) 1.51(9), C(6)-N(13)-C(14)-C(15) )
5.99(11).
Scheme 1
ether (4-methoxy-1,1,1-trifluoro-3-penten-2-one) by 2,6-diiso-
propylaniline (eq 3). High yields of pure product are obtained
in acetonitrile after 3 days at 25 °C.
sodium salts with (PPh3)2Ni(Ph)(Cl) at 25 °C generated the
desired Ni(II) complexes. Following filtration and removal of
THF, crystallization of the resulting crude mixtures from
toluene/pentane at -30 °C gave crystalline complexes suitable
for X-ray diffraction in 33-68% yield.
1
Ligands 4a-d were fully characterized by H, 13C, and 19F
NMR spectroscopy. All exist in the enamine form rather than
the imine form and exhibit a broad N-H signal at ca. 12 ppm.
This low-field shift suggests that the preferred geometries are
U-shaped to accommodate H-bonding between N-H and the
carbonyl oxygen. Consistent with the enamine structure, com-
plexes 4a and 4c display vinylic resonances at 7.93 and 5.55
ppm, respectively.
Solid-state structures of ligands 4b and 4d have been
determined by single-crystal X-ray diffraction (Figures 1 and
2). As anticipated from 1H NMR data, both ligands exist in the
U form appropriate for intramolecular hydrogen bonding and
the five atoms of the chelate backbones of both ligands are in
the same plane, within a couple of degrees. The aryl rings lie
roughly perpendicular to the plane of these chelate backbones.
The slight difference between the dihedral angle C(1)-C(6)-
N(13)-C(14) of 4b, 86.9°, and C(5)-C(6)-N(7)-C(8) of 4d,
81.5°, can be attributed to the steric effect of the bulkier
isopropyl group in 4b. The isopropyl methyl groups of 4b (and
4c) exhibit two sets of resonances, indicating that rotation around
of the aryl ring is slow on the NMR time scale. Complex 4a,
which lacks a vinylic methyl group, shows a single resonance
for the isopropyl methyl group, indicating rapid rotation of the
aryl group on the NMR time scale.
1
These complexes were fully characterized by H, 13C, 19F,
and 31P NMR spectroscopy (see Experimental Section). For
complex 3a, the coordination of the ligand to the Ni(II) center
slows the rotation around the N-aryl bond and results in the
observation of two magnetically inequivalent isopropyl methyl
doublets in the 1H NMR spectrum. The methine signals in 3a-c
shift to lower fields by ca. 0.6 ppm (3.60 ppm for 3a, 3.34 ppm
for 3b, and 3.36 ppm for 3c) compared with the signals for the
corresponding free ligands 4a-c. The 13C resonances of the
coordinated carbonyl groups shift to higher fields upon com-
plexation; e.g., the 13C signal in 4b appears at 176.6 ppm and
shifts to 161.4 ppm in 3b.
Complex 3b was characterized by single-crystal X-ray
diffraction (Figure 3). The complex is square planar, with all
L-Ni-L bond angles very close to 90°. As expected on the basis
of electronic considerations, the PPh3 ligand is trans to the better
donor amido nitrogen. The diisopropyl-substituted aryl ring is
nearly perpendicular to the coordination square plane, as shown
by the Ni(1)-N(6)-C(18)-C(19) dihedral angle of -90.1°.
There is a slight twist in the ligand backbone to accommodate
the square-planar coordination, as illustrated by the C(3)-C(4)-
C(5)-N(6) dihedral angle of -28.2°. (Compare this to the
N(13)-C(14)-C(16)-C(23) dihedral angle of -0.62° in the
ligand 4b.)
Synthesis of Nickel Complexes 3a-d. Complexes 3a-d
were synthesized as shown in Scheme 1. The enamines 4a-d
were readily deprotonated with excess sodium hydride in THF
to yield the corresponding sodium salts. In situ reactions of these
The differing substitution patterns along the ligand backbone
significantly affects the steric and electronic properties of the

Neutral Ni(II) Complexes
Organometallics, Vol. 25, No. 8, 2006 1871
Table 1. Ethylene Polymerization Results Using Catalyst 3aa
en- cat.
cocat.
T
t
Brc/
try (µmol) (µmol) (°C) psig (h)
TONb
4 700
Mw
MWD 1000C
1d
3.9
1.5
1.5
1.5
1.5
1.2
1.5
1.2
1.2
1.2
1.2
1.2
0
70 100
70 200
60 200
60 400
50 200
70 200
60 200
1
1
1
1
1
1
1
2d
3.8
3.8
3.8
3.8
4.8
6.0
4.8
4.8
4.8
4.8
4.8
123 000 23 000 2.4
188 000 27 000 2.3
287 000 29 000 2.2
142 000 34 000 2.1
384 000 23 000 3.1
506 000 25 000 3.7
336 000 115 000 6.0
990 000 100 000 5.4
1 349 000
42
39
35
35
45
41
35
34
46
49
47
3d
4d
5d
6e
7e
8e
35 200 1.7
9e
35 200
35 200
60 200
60 200
5
9
1
1
10e
11e
12e
437 000
164 000
a All polymerization temperatures are well-controlled with variation less
than (2 °C. b In units of mol of C2H4 (mol of Ni)-1 c Branching numbers
.
were measured by 1H NMR spectroscopy in C6D5Br at 120 °C. d Polymer-
ization was carried out in 80 mL of toluene in a 300 mL reactor with 2.5
equiv of Ni(COD)2. e Polymerization was carried out in 200 mL of toluene
in a 1 L reactor with 4.0 equiv of B(C6F5)3.
Table 2. Ethylene Polymerization Results Using Catalysts
3b-da
cat.
T
t
Brc/
MWD 1000C
entry cat (µmol) (°C) psig (h) TONb
Mw
Figure 3. ORTEP view of 3b. Selected interatomic distances (Å)
and angles (deg): Ni(1)-N(6) ) 1.953(3), Ni(1)-O(2) )
1.907(2), Ni(1)-C(30) ) 1.900(3), Ni(1)-P(36) ) 2.1884(9),
C(3)-O(2) ) 1.269(4), C(3)-C(4) ) 1.388(5), C(4)-C(5) )
1.460(5), C(5)-N(6) ) 1.308(4); N(6)-Ni(1)-O(2) ) 90.42(11),
C(30)-Ni(1)-P(36) ) 86.97(10), Ni(1)-N(6)-C(18)-C(19) )
-90.1, C(3)-C(4)-C(5)-N(6) ) -28.2, Ni(1)-O(2)-C(3)-C(4)
) 23.9.
1
2
3
4
5
6
7
8
9
3b
3b
3b
3b
3b
3b
3b
3c
3c
8
5
70 100
60 200
50 100
50 200
3
1
1
1
1 500d
78 000 17 000
52 000 19 000
106 000 27 000
79
4.9
3.6
3.3
3.5
3.2
3.0
3.0
2.3
3.7
2.8
1.5
65
54
58
56
53
55
56
41
34
2.5
2.3
3.9
3.2
1.7
5.0
5.0
3.5
11.3
12.5
50 200 0.5 48 000 20 000
50 300
40 200
60 200
50 200
50 300
25 200
60 200
1
1
1
1
1
3
1
87 000 24 000
32 000 21 000
37 000 13 000
32 000 17 000
48 000 18 000
3 000 59 000
30 000 3 000
Ni(II) centers and in turn their behavior as catalysts for ethylene
polymerizations, results of which are summarized below.
Ethylene Polymerizations Catalyzed by 3a-d. To initiate
polymerization, ethylene must replace PPh3 to yield a
Ni(phenyl)(ethylene) complex, which then undergoes migratory
insertion to yield a Ni-alkyl species that propagates through a
series of migratory insertion reactions. The propagating nickel
alkyl species can “rest” as a Ni(PPh3)(alkyl) complex, a
Ni(ethylene)(alkyl), complex or a Ni(alkyl) complex, which
would most likely exist as a â-agostic structure.37,44 For catalysts
of type 1 there exists an equilibrium between the (N,O)Ni(PPh3)-
alkyl and the (N,O)Ni(ethylene)alkyl complexes. At high
pressures the ethylene complex is the major species and the
turnover frequency becomes independent of ethylene pressure.
Polymerizations of ethylene catalyzed by 3a-d were gener-
ally carried out in 80 mL of toluene in a 300 mL reactor, except
for catalyst 3a, for which ethylene polymerizations, when using
B(C6F5)3 as activator, were conducted in 200 mL of toluene in
a 1 L reactor due to a mass transport problem of ethylene (vide
infra). Ethylene pressures varied between 100 and 400 psig;
temperatures varied between 25 and 80 °C. Low catalyst
loadings were employed so that reaction exotherms could be
controlled. Internal temperatures of the autoclaves did not vary
more than ca. (2 °C. Results for the ethylene polymerization
are summarized in Table 1 (for complex 3a) and Table 2 (for
complexes 3b-d). Turnover numbers as a function of time and
temperature are given in the tables and relate to productivities.
Since catalyst decay often occurs during polymerization runs,
the intrinsic activities are best judged by calculating turnover
frequencies at early times.
10 3c
11 3c
12 3d
a Polymerization was carried out in 80 mL of toluene in a 300 mL reactor
with 2.5 equiv of Ni(COD)2. The temperature is well-controlled with
variation less than (2 °C. b In units of mol of C2H4 (mol of Ni)-1
.
c Branching numbers were measured by 1H NMR spectroscopy in C6D5Br
at 120 °C. d Mn was measured by H NMR.
1
low productivities are observed for complexes 3a,b (see Table
1, entry 1 and Table 2, entry 1) and no polymer is obtained for
3c,d even at 200 psig of ethylene. This implies, in contrast to
catalysts of type 1, that the equilibria lie in favor of the PPh3
complexes even at high ethylene pressures. Subsequent ethylene
polymerizations were conducted using 2-4 equiv of phosphine
scavengers to activate these complexes.
For the most active catalyst studied, 3a, the productivity is
greatly enhanced from a TON of only ca. 4700 after 1 h and
100 psig at 70 °C without an activator to 1.23 × 105 at 200
psig with 2.5 equiv of Ni(COD)2 and 3.84 × 105 with 4 equiv
of B(C6F5)3 (compare entries 1, 2, and 6). The optimal
productivity for ethylene polymerization is reached at 60 °C
(compare entry 3 with entries 2 and 5 and compare entry 7 with
entries 6 and 8); the catalyst productivity increases as the
ethylene pressure increases (compare entries 3 and 4). BPh3 and
Rh(acac)2(C2H4)2 were also studied as activators. BPh3 appears
to be nearly as effective as B(C6F5)3 (compare entries 11 and
7; 4.37 × 105 TON versus 5.06 × 105 TON), but Rh(acac)-
(C2H4)2 is clearly much less effective (see entries 11 and 12 vs
entry 7). At 60 °C, complex 3a activated by Ni(COD)2 or
B(C6F5)3 forms a catalyst system with a short lifetime: t1/2
<
20min. However, experiments at 35 °C have shown the catalyst
is remarkably long-lived (entries 8-10). Between 1.7 and 5.0
h the TON increases linearly with time and shows a calculated
TOF of 2.0 × 105 at each time. The TON number at 9 h is less
than the extrapolated value (1.35 × 106 vs 1.8 × 106), but at
Without the addition of an activator to sequester PPh3 and
drive the equilibrium toward the Ni(ethylene)(alkyl) complex,
(44) Wiencko, H. L.; Kogut, E.; Warren, T. H. Inorg. Chim. Acta 2003,
345, 199.

1872 Organometallics, Vol. 25, No. 8, 2006
Zhang et al.
that time, the reactor is completely filled with solvent-swollen
polyethylene and ethylene uptake is clearly limited by mass
transfer. On the basis of these observations, conservatively the
catalyst half-life must be greater than 15 h and likely is much
more.
withdrawing trifluoromethyl and trifluoroacetyl groups have
been synthesized and characterized. These complexes are active
for ethylene polymerization in the presence of an activator
(Ni(COD)2 or B(C6F5)3) to sequester PPh3. Moderately branched
polyethylenes, generally in the range of 35-55 branches per
1000 carbons, are produced, consistent with expectations based
on the presence of ortho-disubstituted aryl groups on nitrogen.
The productivity ranking under standard conditions (200 psig,
60 °C, Ni(COD)2 activator) follows the order 3a > 3b > 3c ≈
3d. The spread in productivities is modest but significant
(188 000 TOs for 3a to 30 000 TOs for 3d). The rationale for
these productivity differences is not obvious. Variations could
result from not only differences in intrinsic turnover frequencies
but also variable lifetimes. We do note that 3a, the most
productive catalyst, is the only one which bears no methyl
substituent R to nitrogen. A notable feature of 3a, the catalyst
we investigated most thoroughly, is not only the excellent
productivity at 60 °C but also the very long lifetime at 35 °C.
Judging from entries 8-10 in Table 1, the half-life must exceed
many hours, since no decrease in activity after 5 h is seen, while
the productivity at 9 h was limited by reactor capacity. Further
studies of 3a are underway concerning the detailed mechanism
of chain propagation and transfer and the catalyst decay
pathway, as well as the use of 3a for copolymerizations of
ethylene and polar monomers.
Polymers produced using either Ni(COD)2 or B(C6F5)3 as the
activator are quite similar. Monomodal GPC traces are observed
with molecular weight distributions (MWD) generally in the
range of 2-4, indicating a single-site catalytic species is
involved for ethylene polymerization. (MWD values above 2
occur in cases exhibiting high total TOs. As noted above, under
these conditions the autoclave is filled with solvent-swollen
polymer and mass transfer effects likely result in an increase
of the MWD value above 2.) Mn values are limited by chain
transfer to the monomer, as is supported by entries 3 and 4,
showing that an increase of ethylene pressure does not result
in a significant increase of PE molecular weight. Mw values lie
in the range of 23-100 K and decrease as expected at higher
1
temperatures. Total branching numbers, as measured by H
NMR spectroscopy,45 fall between 35 and 45 branches per 1000
carbons. Higher temperatures (60-70 °C) produce polymers
with branching numbers in the high end of this range, while
lower temperatures (35-50 °C) show branching numbers in the
low end of the range. (Compare entries 2 and 6 with entries 8
and 9.) The degree of branching of PE produced by complex
3a with Ni(COD)2 or B(C6F5)3 as activator is higher than that
from catalysts of type 1 or type 2, where generally 10 branches
per 1000 C are observed for type 1 and 17-34 branches for
type 2. The 9 h run at 35 °C produces PE with an unusually
high branching number, in comparison to the number for runs
at shorter time (entry 10). We ascribe the high branching to the
fact that the reactor was filled with solvent-swollen polyethylene,
causing slow mass transport of ethylene to the Ni center and
thus a reduced polymerization rate vs the polymer chain
â-hydride elimination/reinsertion rate responsible for branching.
While standard runs were carried out at 200 psig, a 400 psig
experiment (entry 4, Table 1) shows that branching is decreased
at higher pressures. Both the increase in branching with an
increase in temperature and the decrease in branching at higher
pressures are consistent with behavior noted previously for the
diimine and related systems.4,12,36,37 A detailed mechanistic
explanation of these effects has been advanced.12,13
Experimental Section
General Considerations. All manipulations of air- and/or water-
sensitive 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 drybox and, unless stated otherwise, were stored at
1
room temperature. The H, 13C, 19F, and 31P NMR spectra were
acquired using Bruker 300 and 400 MHz spectrometers. Chemical
shifts were reported in δ units as parts per million (ppm) and
referenced against residual deuterated solvent peaks (1H, 13C) or
the external standards CF3COOH (19F) and H3PO4 (31P). Flash
chromatography was performed using 60 Å silica gel (SAI). High-
temperature gel permeation chromatography (GPC) was performed
by DuPont (Wilmington, DE) in 1,2,4-trichlorobenzene at 135 °C
using a Waters HPLC 150C chromatograph equipped with Shodex
columns. All calibration curves were established with polystyrene
standards, and universal calibration was applied using Mark-
Houwink constants for polyethylene (k ) 4.34 × 10-4; R ) 0.724).
Elemental analyses were performed by Altantic Microlab Inc. of
Norcross, GA.
Materials. Anhydrous solvents were used in the reactions.
Solvents were distilled from drying agents or passed through
alumina columns under an argon or nitrogen atmosphere. NMR
solvents were vacuum-transferred from CaH2, degassed by repeated
freeze-pump-thaw cycles, and stored over 4 Å molecular sieves.
2,6-Diisopropylaniline, FeCl3, NaH, and Ni(COD)2 were used as
received. Polymer-grade ethylene was used as received for bulk
polymerizations and NMR experiments. The following starting
materials were prepared according to literature procedures: (PPh3)2-
Ni(Ph)(Cl),46 N-(2,6-diisopropylphenyl)acetimidoyl chloride,47 N-(2,6-
dimethylphenyl)acetimidoyl chloride,47 Ag(COD)(hfacac),48
((diethylamino)methylene)-1,1,1,5,5,5-hexafluoroacetylacetone
(DAMFA),49 and 4-methoxy-1,1,1-trifluoro-3-penten-2-one.50 Yields
Complexes 3b-d are active ethylene polymerization catalysts
in the presence of 2.5 equiv of Ni(COD)2 as activator, but all
are less productive than 3a (Table 2). Polyethylenes produced
by 3b-d have lower molecular weights and are more highly
branched when compared to polymers produced by 3a under
similar conditions (200 psig of ethylene, 60 °C; compare entries
2, 8, and 12 of Table 2 with entry 3 of Table 1). As seen from
entries 2 and 12, decreasing the steric bulk around Ni(II) by
replacing ortho isopropyl groups with methyl groups has
dramatically decreased the polymer molecular weight and
catalyst productivity from Mw ) 17 000, TON ) 78 000 for
3b to Mw ) 3000, TON ) 30 000 for 3d. Entries 4 and 5 show
the lifetime of catalytic species generated from 3b/Ni(COD)2
is long, with t1/2 > 60min at 50 °C. The polymerization results
follow the trend observed with complex 3a (vide supra).
Conclusions
(46) Hiodai, M.; Kashiwaga, T.; Ikeuchi, T.; Uchida, Y. J. Organomet.
Chem. 1971, 30, 279.
(47) Johnson, L. K. In WO 00/66638; U.S., 2000.
A series of new neutral (N,O) chelated Ni(II) complexes
derived from anilino-substituted enone ligands bearing electron-
(48) Doyle, G.; Van Engen, D.,Organometallics 1985, 4, 830-835.
(49) Schreiber, S. L. Tetrahedron Lett. 1980, 21, 1027-1030.
(50) Okada, E.; Hojo, M.; Inoue, R. Synthesis 1992, 533.
(45) Daugulis, O.; Brookhart, M.; White, P. S. Organometallics 2002,
21, 5935.

Neutral Ni(II) Complexes
Organometallics, Vol. 25, No. 8, 2006 1873
refer to isolated yields of compounds of greater than 95% purity,
mL of toluene. Yield: 3.310 g (96%). 1H NMR (400 MHz,
CDCl3): δ 13.07 (br s, 1H, NH), 7.39 (t, J ) 7.6 Hz, 1H, Ar p-H),
7.25 (d, J ) 7.6 Hz, 2H, Ar m-H), 2.78 (septet, J ) 6.8 Hz, 2H,
iPr CH), 1.87 (s, 3H, vinylic CH3), 1.16 (d, J ) 6.8 Hz, 6H, iPr
CH3), 1.21 (d, J ) 6.8 Hz, 6H, iPr CH3). 13C NMR (100 MHz,
CDCl3): δ 184.8 (br s, CO), 176.6 (br s, CO), 171.6 (vinylic CCH3),
144.9 (Ar C-N), 130.9, 130.0, 124.4 (Ar C), 116.5 (br q, J ) 300
Hz, 2CF3), 100.4 (vinylic CdCCH3), 28.9 (iPr CH3), 22.5 (iPr CH3),
24.3 (iPr CH), 17.8 (vinylic CCH3). 19F NMR (376 MHz, CDCl3):
δ -75.38, -71.57. Anal. Calcd (C19H21F6NO2): C, 55.7; H, 5.17;
N, 3.42. Found: C, 55.6; H, 5.02; N, 3.38.
1
as estimated by H NMR analysis and elemental analysis.
1
Analysis of Polymer Branching by H NMR Spectroscopy.
1H NMR spectra were recorded in either CDCl3 at room temperature
or in C6D5Br at 120 °C. Assignment of peaks and calculation of
polymer branching were carried out by following the previously
published method.51
General Polymerization Procedure. Polymerizations were
carried out in a mechanically stirred 300 mL Parr reactor equipped
with an electric heating mantle controlled by a thermocouple dipping
into the reaction mixture. The reactor was heated under vacuum at
120 °C for 1-2 h and then back-filled with Ar, cooled to the desired
reaction temperature. A 70 mL portion of toluene was injected,
and the reactor was purged with ethylene (3 × 100 psig). A solution
of the catalyst in 10 mL of toluene was added to the vented reactor
via cannula. The reactor was sealed and pressurized with ethylene
to the desired pressure, and the stirring motor was engaged. When
the reaction time was reached, the ethylene pressure was released,
and the reaction was quenched with 120 mL of MeOH. Polymer
was collected and weighed after removing the volatiles in vacuo
and dried in a vacuum oven overnight at 80 °C.
A 1 L Parr reactor with external heating and cooling control
was also used for polymerizations. A procedure similar to that for
the 300 mL Parr reactor was used, but 190 mL of toluene was
injected before ethylene purging and the reaction was quenched
with 250 mL of MeOH instead.
For cocatalyst studies, the catalyst solution was prepared by
dissolving both catalyst and cocatalyst in 10 mL of toluene at room
temperature, except for Ni(COD)2, where the catalyst solution was
prepared at -20 °C.
(c) Synthesis of 4d. This compound was prepared from Ag-
(COD)(hfacac) (2.328, 1.1 mmol) in 25 mL of toluene and N-(2,6-
dimethylphenyl)acetimidoyl chloride (1.000 g, 1.1 mmol) in 25 mL
1
of toluene. Yield: 1.543 g (79%). H NMR (400 MHz, CD2Cl2):
δ 12.98 (br s, 1H, NH), 7.26 (t, J ) 7.6 Hz, 1H, Ar p-H), 7.20 (d,
J ) 7.6 Hz, 2H, Ar m-H), 2.20 (s, 6H, Ar 2,6-o-CH3), 1.89 (s, 3H,
vinylic CH3). 13C{1H} NMR (100 MHz, CDCl3): δ 183.8 (br s,
CO), 177.2 (br s, 2CO), 171.2 (vinylic CCH3), 134.6, 133.8, 129.2,
129.0 (Ar C), 116.3 (q, J ) 288 Hz, 2CF3), 100.4 (vinylic
CdCCH3), 18.0 (Ar 2,6-o-CH3), 17.2 (vinylic CH3). 19F NMR (376
MHz, CD2Cl2): δ -77.2, -73.6. Anal. Calcd (C19H21F6NO2): C,
51.0; H, 3.71; N, 3.96. Found: C, 51.0; H, 3.62; N, 3.75.
4-((2,6-Diisopropylphenyl)amino)-1,1,1-trifluoro-pent-3-en-2-
one (4c). A solution of 2,6-diisopropylaniline (1.63 mL, 8.7 mmol)
and 4-methoxy-1,1,1-trifluoro-3-penten-2-one (1.746 g, 10.4 mmol)
in MeCN (8 mL) was stirred at room temperature for a prolonged
time (monitored by silica TLC, about 3 days). The solvent was
removed under reduced pressure after the completion of reaction
as judged by TLC. The crude product was redissolved in Et2O (20
mL) and was washed with 1 N HCl and then saturated aqueous
NaHCO3. After drying over Na2SO4, Et2O was removed to provide
3-[((2,6-Diisopropylphenyl)amino)methylene]-1,1,1,5,5,5-hexa-
fluoropentane-2,4-dione (4a). A Schlenk tube flame-dried under
vacuum was charged with ((diethylamino)methylene)-1,1,1,5,5,5-
hexafluoroacetylacetone (DAMFA; 3.577 g, 12.3 mmol) and FeCl3
(0.1982 g, 1.2 mmol) under argon. Dry toluene (10 mL) was added,
followed by 2,6-diisopropylaniline (2.8 mL 14.8 mmol). After it
was refluxed for 3 days, the mixture was cooled to room
temperature, quenched with 1 N HCl (10 mL), extracted with ether
(3 × 10 mL), and washed with saturated NaHCO3 (50 mL) and
brine (50 mL). After drying over Mg2SO4, volatiles were removed
under reduced pressure and pure product was obtained by silica
gel chromatography with ethyl acetate-hexane (1:16 v:v) as eluent.
1
2.537 g of pure product (93%). H NMR (400 MHz, CDCl3): δ
12.17 (br s, 1H, NH), 7.34 (t, J ) 7.6 Hz, 1H, Ar p-H), 7.20 (d, J
) 7.6 Hz, 2H, Ar m-H), 5.55 (s, 1H, vinylic H), 2.91 (septet, J )
6.8 Hz, 2H, iPr CH), 1.80 (s, 3H, vinylic CH3), 1.21 (d, J ) 6.8
Hz, 6H, iPr CH3), 1.14 (d, J ) 6.8 Hz, 6H, iPr CH3). 13C{1H}
NMR (100 MHz, CDCl3): δ 176.7 (q, J ) 33 Hz, CdO), 170.4
(vinylic CCH3), 145.5 (Ar C-N), 132.1, 129.2, 124.0 (Ar C), 117.6
(q, J ) 287 Hz, CF3), 89.5 (vinylic CH), 28.6 (iPr CH3), 22.6 (iPr
CH3), 24.5 (iPr CH), 19.7 (vinylic CH3). 19F NMR (376 MHz,
CDCl3): δ -75.35. Anal. Calcd (C17H22F3NO): C, 65.2; H, 7.08;
N, 4.47. Found: C, 64.6; H, 6.94; N, 4.27.
1
Yield: 2.230 g (46%). H NMR (400 MHz, CDCl3): δ 12.01 (br
s, 1H, NH), 7.93 (br s, 1H, vinylic H), 7.41 (t, J ) 7.6 Hz, 1H, Ar
p-H), 7.26 (d, J ) 7.6 Hz, 2H, Ar m-H), 2.97 (septet, J ) 6.8 Hz,
2H, iPr CH), 1.23 (d, J ) 6.8 Hz, 12H, iPr CH3). 13C{1H} NMR
(100 MHz, CDCl3): δ 181.4 (q, J ) 37.6 Hz, CO), 175.1 (q, J )
34.4 Hz, CO), 162.5 (vinylic CdCH), 143.9 (Ar C-N), 133.5,
130.0, 124.6 (Ar C), 116.8 (q, J ) 292.4 Hz, CF3), 116.4(q, J )
287.6 Hz, CF3), 101.6 (vinylic CdCH), 28.6 (iPr CH), 23.6 (iPr
CH3). 19F NMR (376 MHz, CDCl3): δ -72.68, -68.88. Anal.
Calcd (C18H19NO2F6): C, 54.7; H, 4.84; N, 3.54. Found: C, 55.8;
H, 5.04; N, 3.69.
3-[1-((2,6-Diisopropylphenyl)amino)ethylidene]-1,1,1,5,5,5-
hexafluoropentane-2,4-dione (4b) and 3-[1-((2,6-Dimethyl-
phenyl)amino)ethylidene]-1,1,1,5,5,5-hexafluoropentane-2,4-dione
(4d). (a) General Procedure. A toluene solution of Ag(COD)-
(hfacac) was added to imidoyl chloride in toluene via cannula at
room temperature. AgCl rapidly precipitated from the solution. The
mixture was further stirred for 2 h at room temperature and then
filtered through a pad of Celite and washed two times with toluene.
After removal of solvent in vacuo, products were recrystallized from
toluene and pentane to yield clear crystals.
Synthesis of Complexes 3a-d. (a) General Procedure. A
Schlenk tube flame-dried under vacuum was charged with ligands
4a-d and NaH (3 equiv) under argon. THF was added, and the
mixture was stirred at room temperature for 3 h. This solution
containing deprotonated ligand was transferred via cannula to
another flame-dried Schlenk flask containing (PPh3)2Ni(Ph)(Cl).
After 1 h of reaction, the mixture was filtered through a pad of dry
Celite and solvent was removed under vacuum. Crystals suitable
for single-crystal X-ray diffraction were obtained by slow diffusion
of pentane into a toluene solution (1:10 v:v) in the freezer (∼-30
°C).
(b) Synthesis of 3a. This compound was prepared from ligand
4a (0.218 g, 0.55 mmol) and NaH (39.8 mg, 1.66 mmol) in 10 mL
of THF and (PPh3)2Ni(Ph)(Cl) (0.384 g, 0.56 mmol). Yield: 0.133
1
g (33%). H NMR (400 MHz, CDCl3): δ 7.97 (d, J ) 8 Hz, 1H,
vinylic CH), 7.39-7.23 (m, 15H, PPh3), 6.91 (t, J ) 7.6 Hz, 1H,
Ar p-H), 6.80 (d, J ) 7.6 Hz, 2H, Ar m-H), 6.52 (d, J ) 7.6 Hz,
2H, Ni-Ph o-H), 6.25 (t, J ) 7.6 Hz, 1H, Ni-Ph p-H), 6.12 (t, J
) 7.6 Hz, 2H, Ni-Ph m-H), 3.60 (septet, J ) 6.8 Hz, 2H, iPr
CH), 1.13 (d, J ) 6.8 Hz, 6H, iPr CH3), 1.01 (d, J ) 6.8 Hz, 6H,
iPr CH3). 13C{1H} NMR (100 MHz, CDCl3): δ 177.9 (q, J ) 34.4
Hz, CdO), 161.6 (vinylic CH), 148.4, 142.5, 140.4, 136.6, 133.8,
130.2, 129.5, 128.2, 125.9, 122.7, 121.8 (Ar C), 118.0 (q, J ) 300
Hz, CF3), 116.5 (q, J ) 300 Hz, CF3), 105.4 (vinylic CdCH), 28.6
(b) Synthesis of 4b. This compound was prepared from Ag-
(COD)(hfacac) (3.568 g, 8.4 mmol) in 50 mL of toluene and N-(2,6-
diisopropylphenyl)acetimidoyl chloride (2.000 g, 8.4 mmol) in 30
(51) Daugulis, O.; Brookhart, M. Organometallics 2004, 23, 527-534.

1874 Organometallics, Vol. 25, No. 8, 2006
Zhang et al.
Table 3. Crystallographic Data Collection Parameters for 4b,d and 3b
4b 4d
3b
formula
mol wt
cryst syst
space group
a (Å)
C19H21F6NO2
409.37
triclinic
P1h
9.5817(4)
10.9073(5)
10.9450(5)
111.170(3)
108.944(3)
97.324(3)
969.28
C15H13F6NO2
353.26
triclinic
P1h
7.7190(12)
9.4574(15)
11.3047(17)
75.083(6)
78.299(6)
81.459(7)
776.82(21)
1.510
C43H40F6NNiO2P
806.47
monoclinic
P21/n
13.7411(7)
15.0842(8)
18.7681(13)
90
93.375(3)
90
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
3883.4(4)
1.38
D
calcd (Mg/m3)
1.403
scan mode
ω-ψ
ω
æ-ω
µ (mm-1
)
0.13
0.15
0.607
cryst dimens (mm)
2θ range (deg)
no. of rflns
no. of unique rflns
no. of obsd data (I > 2.5σ(I))
no. of refined params
hkl range
RF, %
Rw, %
GOF
Z
0.30 × 0.30 × 0.25
0.30 × 0.30 × 0.25
0.20 × 0.20 × 0.10
5.00-56.00
5.00-56.00
3-25
22 578
9345
4530
487
25 391
17 608
4647
3773
338
3371
2833
269
-12 to +12, 0-14, -14 to +13
-9 to +10, 0-12, -14 to +14
-17 to +18, -19 to +16, -24 to +18
0.043
0.051
2.8941
2
0.041
0.050
2.3672
2
0.046
0.049
1.134
4
(iPr CH), 25.3 (iPr CH3), 22.5 (iPr CH3). 19F NMR (376 MHz,
CDCl3): δ -71.59, -71.21. 31P{1H} NMR (162 MHz, CDCl3): δ
27.26. Anal. Calcd (C42H38NO2F6PNi): C, 63.7; H, 4.83; N, 1.77.
Found: C, 63.9; H, 4.86; N, 1.79.
CDCl3): δ 22.50. Anal. Calcd (C41H41NOF3PNi): C, 69.3; H, 5.82;
N, 1.97. Found: C, 69.5; H, 5.88; N, 2.13.
(e) Synthesis of 3d. This compound was prepared from ligand
4d (0.300 g, 0.85 mmol) with NaH (61.2 g, 2.55 mmol) in 50 mL
of THF and (PPh3)2Ni(Ph)(Cl) (0.591 g, 0.85 mmol). Yield: 0.430
(c) Synthesis of 3b. This compound was prepared from ligand
4b (0.300 g, 0.73 mmol) with NaH (52.8 mg, 2.2 mmol) in 60 mL
in THF and (PPh3)2Ni(Ph)(Cl) (0.510 g, 0.73 mmol). Yield: 0.263
1
g (68%). H NMR (400 MHz, CDCl3): δ 7.36-7.20 (m, 15H,
PPh3), 6.62 (br s, 3H, Ar H), 6.53 (d, J ) 7.6 Hz, 2H, Ni-Ph
o-H), 6.24 (t, J ) 7.6 Hz, 1H, Ni-Ph p-H), 6.05 (t, J ) 7.6 Hz,
2H, Ni-Ph m-H), 2.18 (s, 6H, CH3), 1.54 (s, 3H, vinylic CH3).
13C{1H} NMR (100 MHz, CDCl3): δ 185.7 (q, J ) 35.2 Hz, CO),
165.7 (vinylic CCH3), 161.9 (q, J ) 34.4 Hz, CO), 147.7 (Ar C-N)
144.5, 136.5, 130.0, 129.9, 128.9, 127.9, 127.8, 125.0, 124.9, 121.4
(Ar C), 118.4 (q, J ) 283 Hz, CF3), 116.0 (q, J ) 293 Hz, CF3),
105.6 (vinylic CdCCH3), 21.8 (vinylic CH3), 18.9 (Ar CH3). 19F
NMR (376 MHz, CDCl3): δ -76.7, -70.2. 31P{1H} NMR (162
MHz, CDCl3): δ 27.6. Anal. Calcd (C39H32NO2F6PNi): C, 62.4;
H, 4.30; N, 1.87. Found: C, 64.0; H, 4.95; N, 1.76.
1
g (49%). H NMR (400 MHz, CDCl3): δ 7.35-7.19 (m, 15H,
PPh3), 6.97 (t, J ) 7.6 Hz, 1H, Ar p-H), 6.87 (d, J ) 7.6 Hz, 2H,
Ar m-H), 6.37 (d, J ) 7.6 Hz, 2H, Ni-Ph o-H), 6.29 (t, J ) 7.6
Hz, 1H, Ni-Ph p-H), 6.11 (t, J ) 7.6 Hz, 2H, Ni-Ph m-H), 3.34
(septet, J ) 6.8 Hz, 2H, iPr CH), 1.68 (s, 3H, vinylic CH3), 1.05
(d, J ) 6.8 Hz, 6H, iPr CH3), 0.99(d, J ) 6.8 Hz, 12H, iPr CH3).
13C{1H} NMR (100 MHz, CDCl3): δ 185.8 (q, J ) 34 Hz, CdO),
161.4 (q, J ) 34 Hz, CdO), 166.4 (vinylic CCH3), 145.2, 141.4,
139.6, 137.0, 133.8, 130.0, 129.5, 127.9, 126.0, 125.3, 123.4, 121.6
(Ar C), 118.7 (q, J ) 300 Hz, 2CF3), 105.6 (vinylic CdCCH3),
28.6 (iPr CH), 24.0 (allylic CH3), 24.3 (iPr CH3), 23.9 (iPr CH3).
19F NMR (376 MHz, CDCl3): δ -76.57, -70.27. 31P{1H} NMR
(162 MHz, CDCl3): δ 24.11. Anal. Calcd (C43H40NO2F6PNi): C,
64.0; H, 5.00; N, 1.74. Found: C, 63.8; H, 4.70; N, 1.86.
X-ray Crystal Structures. Diffraction data were collected on a
Bruker SMART 1K diffractometer, at -100 °C. Refinement was
carried out with the full-matrix least-squares method based on F
(NCRVAX) with anisotropic thermal parameters for all non-
hydrogen atoms. Hydrogen atoms were inserted in calculated
positions and refined riding with the corresponding atom. Complete
details of X-ray data collection for 4a,d and 3b are given in Table
3.
(d) Synthesis of 3c. This compound was prepared from ligand
4c (0.200 g, 0.64 mmol) with NaH (46.0 mg, 1.92 mmol) in 40
mL of THF and (PPh3)2Ni(Ph)(Cl) (0.444 g, 0.64 mmol). Yield:
1
0.222 g (50%). H NMR (400 MHz, CDCl3): δ 7.33-7.16 (m,
15H, PPh3), 6.92 (t, J ) 7.6 Hz, 1H, Ar p-H), 6.80 (d, J ) 7.6 Hz,
2H, Ar m-H), 6.43 (d, J ) 7.6 Hz, 2H, Ni-Ph o-H), 6.25 (t, J )
7.6 Hz, 1H, Ni-Ph p-H), 6.07 (t, J ) 7.6 Hz, 2H, Ni-Ph m-H),
5.49 (s, 1H, vinylic CH), 3.36 (septet, J ) 6.8 Hz, 2H, iPr CH),
1.67 (s, 3H, vinylic CH3), 1.07 (d, J ) 6.8 Hz, 6H, iPr CH3), 0.99
(d, J ) 6.8 Hz, 6H, iPr CH3). 13C{1H} NMR (100 MHz, CDCl3):
δ 168.5 (vinylic CCH3), 158.8 (q, J ) 30.4 Hz, CO), 146.6, 143.0,
140.0, 137.0, 133.9, 130.8, 129.5, 127.6, 125.2, 124.8, 122.9, 121.0
(Ar C), 119.0(q, J ) 286 Hz, CF3), 94.6 (vinylic CH), 28.3 (iPr
CH), 25.8 (vinylic CH3), 24.38 (iPr CH3), 23.80 (iPr CH3). 19F NMR
(376 MHz, CDCl3): δ -75.01 (CF3). 31P{1H} NMR (162 MHz,
Acknowledgment. We thank the National Science Founda-
tion (Grant No. CHE0107810) and DuPont for support of this
work and DuPont Analytical Division for help with analyzing
the PE molecular weight by high-temperature GPC.
Supporting Information Available: CIF files giving crystal-
lographic data for 4b,d and 3b. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM050931P