Synthesis and ethylene polymerization activity of a series of 2-anilinotropone-based neutral nickel(II) catalysts

Article abstract of DOI:10.1021/om030142c

A method for the synthesis of bulky 2-anilinotropones has been developed, utilizing palladium-catalyzed cross-coupling techniques. Deprotonation of these anilinotropones followed by reaction with (PPh₃)₂Ni(Ph)Cl produces ethylene polymerization catalysts of the general formula [[(2-R-6-R′C₆H₃)NC₇H ₅O]Ni(Ph)(PPh₃)] C3a-j: R, R′ = Me, Me (a), ⁱPr, ⁱPr (b), ^tBu, H (c), ^tBu, Me (d), Ph, Ph (e), Cl, Cl (f), Br, Br (g), 2,3,4,5,6-F₅ (h), Me, H (j), Me, CF₃ (k)). Ethylene polymerizations with 3a-j have been explored under a variety of reaction conditions. The complex [[(2)6-ⁱPr ₂C₆H₃)NC₇H ₄O(7-aryl)]Ni(Ph)(PPh₃)] (14: aryl = phenyl (a), 1-naphthyl (b)), possessing steric bulk at the 7-position, have been prepared and are both long-lived and active ethylene polymerization catalysts. At low temperatures 14a,b produce polyethylene with narrow molecular weight distributions (MWD ca. 1.2). The polymerization results suggest that chain transfer occurs via a β-hydride elimination pathway and that catalyst decomposition proceeds through reductive elimination of the free ligand from a nickel-hydride intermediate.

Full text of DOI:10.1021/om030142c

Organometallics 2003, 22, 3533-3545
3533
Syn th esis a n d Eth ylen e P olym er iza tion Activity of a
Ser ies of 2-An ilin otr op on e-Ba sed Neu tr a l Nick el(II)
Ca ta lysts
Frederick A. Hicks, J ason C. J enkins, and Maurice Brookhart*
Department of Chemistry, University of North Carolina at Chapel Hill,
Chapel Hill, North Carolina 27599
Received February 28, 2003
A method for the synthesis of bulky 2-anilinotropones has been developed, utilizing
palladium-catalyzed cross-coupling techniques. Deprotonation of these anilinotropones
followed by reaction with (PPh3)2Ni(Ph)Cl produces ethylene polymerization catalysts of the
i
i
general formula [[(2-R-6-R′C6H3)NC7H5O]Ni(Ph)(PPh3)] (3a -j: R, R′ ) Me, Me (a ), Pr, Pr
t
t
(b), Bu, H (c), Bu, Me (d ), Ph, Ph (e), Cl, Cl (f), Br, Br (g), 2,3,4,5,6-F5 (h ), Me, H (j), Me,
CF3 (k )). Ethylene polymerizations with 3a -j have been explored under a variety of reaction
conditions. The complex [[(2,6-iPr2C6H3)NC7H4O(7-aryl)]Ni(Ph)(PPh3)] (14: aryl ) phenyl
(a ), 1-naphthyl (b)), possessing steric bulk at the 7-position, have been prepared and are
both long-lived and active ethylene polymerization catalysts. At low temperatures 14a ,b
produce polyethylene with narrow molecular weight distributions (MWD ca. 1.2). The
polymerization results suggest that chain transfer occurs via a â-hydride elimination pathway
and that catalyst decomposition proceeds through reductive elimination of the free ligand
from a nickel-hydride intermediate.
In tr od u ction
polymer chain via a series of â-elimination and reinser-
tion reactions which can occur at rates competitive with
or faster than olefin insertion. This process results in
formation of branched polymers from ethylene and
“chain-straightened” polymers from R-olefins.5,9 (2) Cer-
tain monomers such as trans-2-butene, which cannot
be polymerized by early-metal systems, can be success-
fully polymerized with late-metal systems.12 (3) Many
late-metal catalysts are compatible with protic solvents
and nucleophilic impurities. Water compatibility has led
to successful emulsion polymerization of ethylene.13-16
(4) Expanded functional group tolerance has permitted
the copolymerization of alkyl acrylates (polar monomers)
with ethylene and R-olefins (nonpolar monomers).17-20
Much of our effort has focused on cationic systems of
the general type 1 based on R-diimine ligands as well
as catalysts incorporating closely related neutral
Olefin polymerization catalysts based on early-metal
metallocene complexes were introduced nearly two
decades ago and are seeing increasing commercial
utilization.1-3 Their single-site nature makes them
attractive for ligand tailoring, and as a result these
catalysts have been modified in innumerable ways to
enhance polymerization activity, improve catalyst life-
time, increase the R-olefin/ethylene reactivity ratio in
copolymerizations, and control microstructures of polypro-
pylene and other poly-R-olefins.1-3 A drawback of met-
allocene and classical Ziegler catalysts is the extreme
oxophilicity of the early-metal center. This oxophilicity
renders metallocenes inactive toward most functional-
ized monomers and highly sensitive to polar solvents
and impurities. The sensitivity of metallocenes to polar
substituents is largely responsible for an increase in
interest in late-transition-metal complexes as olefin
polymerization catalysts over the past several years.4-7
Late-metal catalysts complement early-metal catalysts
in several ways. (1) Polymers exhibiting quite different
microstructures are frequently obtained.5,8-11 This arises
from the ability of the metal to walk along the growing
(10) Guan, Z.; Cotts, P. M.; McCord, E. F.; McLain, S. J . Science
1999, 283, 2059.
(11) Killian, C. M.; Tempel, D. J .; J ohnson, L. K.; Brookhart, M. J .
Am. Chem. Soc. 1996, 118, 11664.
(12) Leatherman, M. D.; Brookhart, M. Macromolecules 2001, 34,
2748.
(13) Mecking, S.; Held, A.; Bauers, F. M. Angew. Chem., Int. Ed.
2002, 41, 545.
(14) Bauers, F. M.; Mecking, S. Macromolecules 2001, 34, 1165.
(15) Soula, R.; Saillard, B.; Spitz, R.; Claverie, J .; Llaurro, M. F.;
Monnet, C. Macromolecules 2002, 35, 1513.
(16) Soula, R.; Broyer, J . P.; Llauro, M. F.; Tomov, A.; Spitz, R.;
Claverie, J .; Drujon, X.; Malinge, J .; Saudemont, T. Macromolecules
2001, 34, 2438.
(1) Alt, H. G.; Koppl, A. Chem. Rev. 2000, 100, 1205.
(2) Coates, G. W. Chem. Rev. 2000, 100, 1223.
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100, 1253.
(4) Boffa, L. S.; Novak, B. M. Chem. Rev. 2000, 100, 1479.
(5) Ittel, S. D.; J ohnson, L. K.; Brookhart, M. Chem. Rev. 2000, 100,
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1996, 118, 267.
(6) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428.
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(8) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem. Soc.
1995, 117, 6414.
(9) Gates, D. P.; Svejda, S. A.; Onate, E.; Killian, C. M.; J ohnson,
L. K.; White, P. S.; Brookhart, M. Macromolecules 2000, 33, 2320.
(18) Mecking, S.; J ohnson, L. K.; Wang, L.; Brookhart, M. J . Am.
Chem. Soc. 1998, 120, 888.
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1985, 24, 599.
(20) J ohnson, L.; Bennett, A.; Dobbs, K.; Hauptman, E.; Ionkin, A.;
Ittel, S.; McCord, E.; McLain, S.; Radzewich, C.; Yin, Z.; Wang, L.;
Wang, Y.; Brookhart, M. Polym. Mater. Sci. Eng. 2002, 86, 319.
10.1021/om030142c CCC: $25.00 © 2003 American Chemical Society
Publication on Web 07/17/2003

3534 Organometallics, Vol. 22, No. 17, 2003
Hicks et al.
ligands.8,9,11,12,17,18,21,22 The R-diimine Ni complexes are
F igu r e 1. Ethylene oligomerization with SHOP-type
catalysts.
105 mol of PE ((mol of Ni) h)-1 and lifetimes in excess
of 6 h have been observed at 45-50 °C.28
We have recently reported catalysts of type 3 and 4
based on anilinotropone and anilinoperinaphthenone
ligands, respectively.29,30 High activities have been
observed for the unsubstituted anilinotropone catalyst
(6 × 104 mol of PE ((mol of Ni) h)-1), and in a direct
comparison with the parent, unsubstituted salicylaldi-
mine catalyst, 2a (3400 mol of PE ((mol of Ni) h-1), the
anilinotropone systems appear to be more reactive.27,29
Clearly a major difference between these two systems
is that the salicylaldimine catalysts contain a six-
membered chelate, while the anilinotropone catalysts
contain a five-membered chelate. It is not clear if chelate
size is responsible for the difference in activities, but
Keim has shown with SHOP-type catalysts that a
decrease in activity is observed with expansion of
chelate size (Figure 1).31
The goal of this work was to fully explore the ethylene
polymerization properties of the anilinotropone-based
system. Reported herein is the synthesis of several
2-anilinotropone ligands and the corresponding Ni(II)
complexes as well as extensive ethylene polymerization
results using these catalysts. Also reported are catalysts
derived from hindered 2-anilino-7-aryltropone ligands
and their activity toward ethylene. Preliminary reports
of parts of this work have appeared in the literature.29,32
very reactive toward ethylene and R-olefins and, as
noted above, produce polymers with unique microstruc-
tures. The cationic Ni catalysts are electrophilic and
sensitive to protic solvents. Functional group compat-
ibility is diminished relative to Pd analogues; however,
it should be noted that copolymerization of ethylene and
alkyl acrylates has been achieved at high ethylene
pressures (>500 psig) and temperatures above 80
°C.20,23
In view of the high sensitivity of the cationic Ni and
Pd catalysts, there has been substantial interest in
developing neutral Ni catalysts to overcome these
limitations. Several early examples of neutral Ni cata-
lysts based on SHOP-type ligands have been reported,
although productivities and molecular weights are often
low.16,19,24,25 More recently, neutral Ni catalysts modeled
after 1, containing a bulky ortho-disubstituted aryl
imine functionality, have been reported. Catalysts of
type 2, based on salicylaldimines, have been described
Resu lts a n d Discu ssion
Liga n d Syn th esis. Initial attempts to prepare anili-
notropones were based on literature reports of nucleo-
philic substitution of 2-(tosyloxy)tropone by isopropyl-
amine.33-35 However, nucleophilic substitution with a
variety of anilines was unsuccessful. In addition to trace
amounts of the desired product 5b , the predominant
product obtained was the benzenoid rearrangement
product, 6, derived from attack of the aniline at the
3-position (Scheme 1).36 On the basis of the work of
Buchwald and Hartwig on the palladium-catalyzed
cross-coupling of amines with aryl halides and triflates,
the possibility of a palladium-catalyzed cross-coupling
of aniline with a 2-halo- or 2-triflatotropone was
considered.37-40 Buchwald has demonstrated the utility
by both the DuPont26 and the Grubbs groups.27,28 The
most active systems contain either electron-withdrawing
nitro substituents in the aromatic ring26 or bulky
substituents at C-3, with a 9-anthracenyl group being
most effective.27,28 In the latter case, activities of 1.3 ×
(29) Hicks, F. A.; Brookhart, M. Organometallics 2001, 20, 3217.
(30) J enkins, J . C.; Brookhart, M. Organometallics 2003, 22, 250.
(31) Keim, W.; Schulz, R. P. J . Mol. Catal. A 1994, 92, 21.
(32) Hicks, F. A.; Brookhart, M. Org. Lett. 2000, 2, 219.
(33) Ito, S.; Tsunetsuga, J .; Kanno, T.; Sugiyama, H.; Takeshita, H.
Tetrahedron Lett. 1965, 3659.
(21) Small, B. L.; Brookhart, M. J . Am. Chem. Soc. 1998, 1210, 7143.
(22) Small, B. L.; Brookhart, M. J . Am. Chem. Soc. 1998, 120, 4049.
(23) McLain, S. J .; Sweetman, K. J .; J ohnson, L. K.; McCord, E.
Polym. Mater. Sci. Eng. 2002, 86, 320.
(34) Biggi, G.; Cima, F. D.; Pietra, F. J . Am. Chem. Soc. 1973, 95,
7101.
(24) Peuckert, M.; Keim, W. Organometallics 1983, 2, 594.
(25) Hirose, K.; Keim, W. J . Mol. Catal. 1992, 73, 271.
(26) J ohnson, L. K.; Bennett, A. M. A.; Ittel, S. D.; Wang, L.;
Parthasarathy, A.; Hauptman, E.; Simpson, R. D.; Feldman, J .;
Coughlin, E. B. WO 98/30609, 1998.
(35) Biggi, G.; de Hoog, A. J .; Cima, F. D.; Pietra, F. J . Am. Chem.
Soc. 1973, 95, 7108.
(36) Mukai, T. Bull. Chem. Soc. J pn. 1959, 32, 272.
(37) Wolfe, J . P.; Wagaw, S.; Marcoux, J .-F.; Buchwald, S. L. Acc.
Chem. Res. 1998, 31, 805.
(27) Wang, C.; Friedrich, S.; Younkin, T. R.; Li, R. T.; Grubbs, R.
H.; Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149.
(28) Younkin, T. R.; Connor, E. F.; Henderson, J . I.; Friedrich, S.
K.; Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460.
(38) Yang, B. H.; Buchwald, S. L. J . Organomet. Chem. 1999, 576,
125.
(39) Hartwig, J . F. Angew. Chem., Int. Ed. Engl. 1998, 37, 2046.
(40) Hartwig, J . F. Acc. Chem. Res. 1998, 31, 852.

2-Anilinotropone-Based Nickel(II) Catalysts
Organometallics, Vol. 22, No. 17, 2003 3535
a
Sch em e 1
a
H2NAr ) 2,6-diisopropylaniline.
Sch em e 2
F igu r e 2. ORTEP view of 5b showing important atom
labels. Selected interatomic distances (Å): C(2)-O(1) )
1.2519(24), C(8)-N(9) ) 1.3546(24). Torsion angle (deg):
C(8)-N(9)-C(10)-C(11) ) 88.4(3).
Ta ble 1. Cr ysta llogr a p h ic Da ta for 5b
formula
mol wt
C19H23NO
327.46
color
yellow
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
C2/c
15.5935(6)
14.1245(5)
19.3648(7)
90
113.759(1)
90
3903.63(25)
1.114
R (deg)
â (deg)
γ (deg)
V (Å3)
Dcalcd (Mg/m3)
wavelength (Å)
0.710 73
0.07
µ (mm-1
)
cryst dimens (mm)
temp (°C)
mode
2θ range (deg)
no. of rflns
0.35 × 0.20 × 0.25
-100
ω
4.00-50.00
18 103
no. of indep rflns
R(F)
Rw(F)
3325
0.073
0.079
of this methodology for coupling two sterically hindered
substrates.37
hkl range
-18 to +16, 0-16, 0-23
Bruker SMART
SADABS
Mo KR
graphite
8
Initial attempts at aniline-tropolone cross-coupling
were carried out with the commercially available 2-(to-
syloxy)tropone. The results were a significant improve-
ment over the nucleophilic route employed previously,
but even with catalyst loadings of 5 mol %, yields were
only ca. 30%. Upon switching to 2-triflatotropone, cross-
coupling yields were significantly higher, even with 1
mol % catalyst loading (Scheme 2).32 Yields of 5a -i were
previously reported32 and range from 36 to 90%. Low
yields are obtained for highly sterically encumbered
anilines (36% for 5d and 37% for 5e), but remarkably,
coupling products from electron-deficient anilines are
formed in good to excellent yields (5f, 75%; 5i, 89%).
Anilinotropones 5j-l, reported here for the first time,
are produced in yields of 88-89%.
Crystals of 2-(2,6-diisopropylanilino)tropone (5b) suit-
able for X-ray diffraction were prepared by slow diffu-
sion of hexamethylsiloxane into a concentrated solution
of 5b in toluene at room temperature. Crystallographic
data for 5b are summarized in Table 1, and an ORTEP
diagram is shown in Figure 2. The C-O and C-N bond
lengths (1.2519(24) and 1.3546(24) Å, respectively) are
type of diffractometer
abs cor method
radiation for intensity measmts
monochromator
Z
of intermediate value for single and double bonds,
indicating some degree of delocalization on the order of
an amide group. Also of note is the near 90° angle at
which the N-aryl ring sits relative to the plane of the
seven-membered tropone ring. Finally, the N-H hydro-
gen was found and determined to be hydrogen-bonded
to the carbonyl oxygen, O1.
Ca ta lyst Syn th esis. Deprotonation of 2-anilino-
tropones proceeds readily in THF with a slight excess
of sodium hydride. The sodium salts of the anili-
notropones were isolated as THF adducts, usually with
1 equiv of THF coordinated. In all cases the salt was
isolated prior to reaction with the nickel precursor. An
X-ray crystal structure of the sodium salt of 2-(2,6-
diisopropylanilino)tropone was obtained (see the Sup-
porting Information). As with the free ligand the N-aryl
ring is perpendicular to the plane of the tropone ring.

3536 Organometallics, Vol. 22, No. 17, 2003
Hicks et al.
Ta ble 2. Eth ylen e P olym er iza tion w ith 3b,
[(2,6-iP r 2C6H3)NC7H5O]Ni(P h )(P P h 3)a
Sch em e 3
cat.
(10-6
entry mol) (°C) (psig)
T
ethylene yield
(g)
branches/
TON 10-3Mn PDI 1000 C
1
2
3
4
5
6
7
8
14.8 60b 400
13.7 33 000
1.2 8 200 204
6.8 31 900 292
11.4 53 600 119
4.0 19 000
0.15 980
4.0 27 000
6.3 42 500
9.2 62 100
7.6 52 400
7.1 47 800 104
2.6 17 500 120
7.5 51 500
10.9 74 500 108
8.8 60 400 111
57
2.8
2.8
2.0
1.8
1.9
64
8
7.6
7.6
7.6
40 400
60 400
80 400
27
49
67
113
90
76
61
61
45
41
66
48
43
7.6 100 400
61
6.7 2.0
50
63
90
92
5.2
5.2
5.2
5.2
5.2
5.2
5.2
5.2
5.2
5.2
80 1 atm
80 50
1.7
1.9
1.8
1.8
2.0
2.0
1.9
1.9
2.0
80 100
80 200
80 200
80 400
80 600
80 200
80 400
80 600
9
10c
11
12
13c,d
14c,d
15c,d
The C-N and C-O bond lengths are 1.292(8) and 1.298-
(9) Å, respectively: thus, relative to the neutral ligand
the C-N bond has contracted and the C-O bond has
lengthened. Note also that the sodium ion has taken
the place of the hydrogen-bonded N-H proton.
78
a
Reactions run in 200 mL of toluene for 1 h unless otherwise
noted. Exotherm from 60 to 103 °C. c Reaction time 10 min.
Research Plus grade ethylene.
b
d
Neutral nickel complexes of 5 were first synthesized
by combining the sodium salt of the appropriate anili-
notropone with bis(triphenylphosphine)nickel phenyl
chloride in toluene for ca. 18 h. Sodium chloride was
separated by filtration, and the product was isolated by
recrystallization from toluene/pentane. While effective
for some of the more bulky anilinotropones, this method
was inefficient for the less sterically hindered ones. Due
to the low to moderate solubility of (PPh3)2Ni(Ph)Cl in
toluene, a significant amount of bis(anilinotropone)-
nickel(II) complex (see below) was formed during the
course of the reaction. Removal of this impurity required
multiple recrystallizations. To eliminate formation of
this bis-ligand complex, the reaction was run in THF
at room temperature for 1 h (Scheme 3). THF was
chosen because of its ability to dissolve (PPh3)2Ni(Ph)-
Cl. Upon filtration and standard workup (see the
Experimental Section for details) the desired (anili-
notropone)nickel(II) complex was obtained free of bis-
ligand complex. A previously reported X-ray structure
of 3b29 confirms the geometry depicted in Scheme 3 with
PPh3 trans to nitrogen and the phenyl group trans to
oxygen. Also of note is the lack of change of the C-N
and C-O bond lengths from those in 5b, indicating that
the negative charge lies predominantly on the nitrogen
atom.
first variable investigated was reaction temperature
(entries 2-5, Table 2). Ethylene pressure was held
constant at 400 psig. With the exception of the run at
40 °C, the Mn value of the resultant polymers decreases
with increasing temperature. The degree of branching,
determined by 1H NMR spectroscopy, steadily increases
from 40 to 100 °C (8-67 branches per 1000 carbon
atoms). The molecular weight distributions for entries
2-5 are clearly monomodal with all polydispersities ca.
2.0, indicating that the number-average molecular
weights are the chain-transfer-limited values. This
implies that the lower molecular weights obtained at
higher temperatures are the result of an increase in the
ratio of the chain transfer rate relative to the chain
propagation rate, a normal feature of such polymeriza-
tions. The catalyst TON is at a maximum at 80 °C.
The effects of ethylene pressure variation on the
polymerization activity of 3b were also studied (entries
6-12, Table 2) with several trends evident. As seen in
entries 6-12 (80 °C data), polymer molecular weights
steadily increase and branching numbers decrease from
113 to 41 branches per 1000 carbon atoms as pressure
increases from 1 atm to 600 psig of ethylene. A 13C NMR
spectrum of the polymer of entry 7 (90 branches/1000
C), run using a protocol reported by Cotts,42 indicated
the presence of methyl, ethyl, propyl, and higher
branches in a ratio of ca. 14:2:1:1. No signals were
observed that corresponded to hyperbranched material
(branches on branches). All of the resultant polymers
have molecular weight distributions at or near 2.0,
again indicating that the number-average molecular
weights are the chain-transfer-limited values. Maxi-
mum turnover numbers were obtained at 200 psig of
ethylene. Comparison of entries 11 (60 min run) and
12 (10 min run) shows that only ca. 20% more polymer
is generated after 10 min, indicating that the catalyst
lifetime at 80 °C and 200 psig is relatively short. Using
the 10 min data, an initial turnover frequency is
calculated to be 3.1 × 105 mol of ethylene ((mol of Ni)
h)-1. The actual initial TOF will be higher, since a
Eth ylen e P olym er iza tion Stu d ies: P olym er iza -
tion s Em p loyin g 3b. Catalyst 3b is a highly active
ethylene polymerization catalyst. Table 2 summarizes
polymerizations conducted in toluene. To accurately
compare activities and lifetimes under various reaction
conditions, it is critical to avoid reaction exotherms
which are common with such highly active catalysts.
For example, even with temperature control via water-
cooled coils in a 1 L autoclave, a concentration of 74 µM
of 3b in 200 mL of toluene under 400 psig of ethylene
leads to an uncontrollable exotherm from a starting
reaction temperature of 60 °C to a peak temperature of
103 °C (entry 1). Various catalyst loadings were inves-
tigated to determine the optimal range for both tem-
perature control and high activity. A concentration of
ca. 25-40 µM was determined to be optimal under the
chosen conditions for obtaining reliable temperature
control and maximum catalyst turnover numbers.41
(41) At concentrations of 15 µM and lower, turnover numbers are
significantly reduced likely due to quenching of some catalyst by trace
impurities.
(42) Cotts, P. M.; Guan, Z.; McCord, E.; McLain, S. Macromolecules
2000, 33, 6945.
The ethylene polymerization activity of catalyst 3b
was screened under a wide variety of conditions. The

2-Anilinotropone-Based Nickel(II) Catalysts
Organometallics, Vol. 22, No. 17, 2003 3537
Ta ble 3. Eth ylen e P olym er iza tion w ith 3b p lu s
P h osp h in e Sca ven ger sa
Ta ble 5. Eth ylen e P olym er iza tion w ith 3b p lu s
P ola r Ad d itives
additive
branches/
branches/
1000 C
entry solvent (amt (mL)) yield (g) TON 10-3Mn PDI 1000 C
entry initiator yield (g) TON
10-3Mn PDI
1
2
3
4
5
6
7
8
toluene none
THF none
hexane none
PhCl none
2.8
3.3
2.6
4.8
0.34
2.3
1.4
1.5
1.1
2.7
3.8
0.85
0.16
0.72
19 000
22 500
17 400
32 200
2 290
15 700
9 600
10 200
7 700
18 800
26 200
5 800
1 100
5 000
189
146
163
182
66
192
128
135
131
146
163
86
1.8
1.8
1.8
1.9
4.0
1.8
1.9
1.9
1.9
2.0
1.9
2.3
2.4
1.5
37
39
35
46
33
36
38
39
37
38
43
41
48
37
1
2
3
4
none
7.6
6.7
8.5
7.9
51 300
45 300
57 000
53 300
91
84
79
87
1.8
1.9
2.0
1.8
61
58
60
61
B(C6F5)3
B(C6H5)3
Ni(COD)2
EtOAc none
a
toluene EtOAc (1)
toluene H2O (1)
hexane H2O (1)
toluene EtOH (1)
toluene NEt3 (1)
toluene EtOAc (20)
toluene H2O (20)
toluene EtOH (20)
toluene NEt3 (20)
Reactions run in 200 mL of toluene at 80 °C and 200 psig of
ethylene for 10 min with 5.2 µmol of catalyst.
a
9
Ta ble 4. P olym er iza tion w ith 3b p lu s P P h 3
10
11
12
13
14
entry
PPh3 (equiv)
time (min)
tield (g)
TON
1
2
3
4
5
6
0
5
0
5
50
50
10
10
30
30
15
60
7.5
6.3
8.8
8.7
1.2
3.4
51 500
43 400
60 400
60 000
5 600
21
87
the presence of added PPh3.27,28 In contrast, for 3b at
80 °C and 200 psig of ethylene no significant changes
in TON, Mn, PDI, or branching numbers are observed
with 2.4 equiv of added B(C6F5)3, BPh3, or Ni(COD)2.
(Similar results were obtained at 40 °C; see the Sup-
porting Information.)
Data in Table 4 show that when the polymerization
is carried out in the presence of 5 equiv of PPh3 (80 °C,
200 psig), a small decrease in TON is observed after a
polymerization time of 10 min, while virtually no change
in TON is noted after a polymerization of 30 min. These
results suggest that added PPh3 might slightly inhibit
the turnover frequency but at the same time increase
catalyst lifetime. Entries 5 and 6 demonstrate that at
a significantly higher PPh3 loading (50 equiv) activity
is inhibited while catalyst lifetime is substantially
increased.
The observation that scavengers do not increase
turnover numbers suggests that under the reaction
conditions PPh3 is essentially fully dissociated from the
active nickel catalyst. Furthermore, addition of 5 equiv
of PPh3 appears insufficient to shift the equilibrium
significantly back toward a PPh3 complex. In contrast,
50 equiv of PPh3 substantially retards the TOF and
suggests that a large fraction of the catalyst rests as a
PPh3 complex.
Solvent effects on ethylene polymerization using 3b
(60 °C, 200 psig) were also investigated (Table 5, entries
1-6). THF, hexane, chlorobenzene, and ethyl acetate
were all investigated in addition to toluene. Polymeri-
zation in ethyl acetate leads to a significant drop in TON
and broadening of the molecular weight distribution.
With the exception of ethyl acetate, however, activities
in all other solvents are comparable to or somewhat
greater than the activity in toluene. A significant
increase in TON and polymer branching is observed in
chlorobenzene at 60 °C.
16 400
a
Reactions run at 200 psi Research Plus grade ethylene, 80 °C,
in 200 mL of toluene with 5.2 µmol of catalyst.
significant amount of catalyst decays during the 10 min
run. When salicylaldimine catalyst 2a was subjected to
the same reaction conditions, it was found to be more
than an order of magnitude less reactive with a TOF of
0.24 × 105 mol of ethylene ((mol of Ni) h)-1. Additionally,
3b produces polyethylene with a substantially higher
Mn value when compared with 2b (89 600 vs 2800).
Catalyst 3b has an initial activity comparable to that
of the anthracenyl-substituted salicylaldimine catalyst
(reported TON ) 1.32 × 105 mol of ethylene ((mol of
Ni) h)-1);28 however, 2b is reported to have a signifi-
cantly longer lifetime relative to 3b. This remarkable
aryl effect prompted us to investigate the analogous
7-aryl-substituted versions of the anilinotropone-based
catalyst. These studies are reported in a subsequent
section.
The observed drop in catalyst activity above 200 psig
of ethylene may in part be due to impurities in the
monomer feed. To test this possibility, several polym-
erization reactions were conducted with a significantly
more pure ethylene feed (99.9996%, see Experimental
Section). Polymerization with more pure ethylene affects
the productivity of 3b at higher ethylene pressures
(Table 2, entries 13-15). Polymerization at 400 psig of
ethylene (entry 14) with the high-purity ethylene is
more active than polymerization at 200 psig with either
ethylene source (entries 10 and 13). The activity at 600
psig of ethylene (entry 15) drops off only slightly from
the observed activity at 400 psig (entry 14) with the
hyperpure ethylene, but in comparison with standard
grade ethylene polymerization at 600 psig (entry 12),
the TON value increases by almost 400%. These data
suggest that impurities in the ethylene feed can inhibit
polymerization at higher ethylene pressures, conditions
where greater quantities of impurity will be present. It
is unclear which impurities in the monomer feed are
responsible for the observed drop in catalyst turnover
number. Experiments are ongoing to determine the
specific nature of the impurity.
Neutral, late-metal catalysts are attractive due to
their purported polar group tolerance.4 To test the limits
of this tolerance, several polymerizations were carried
out in the presence of polar additives (Table 5, entries
7-15). When run in neat THF or with added ethyl
acetate (∼10 vol % in toluene) polymerizations with 3b
proceed with a small increase in catalyst turnover
number. Reactions run with added H2O or NEt3 led to
3.5- and 4-fold decreases in activity, respectively. The
use of ethanol proved more problematic, leading to a
20-fold decrease in TON. The increased solubility of
ethanol in toluene, in comparison with water, is likely
Catalyst 3b was also screened in the presence of both
phosphine scavenging cocatalysts (Table 3) and added
triphenylphosphine (Table 4). The activity of salicyla-
ldimine catalyst 2b is reported to increase in the
presence of added scavengers and greatly decrease in

3538 Organometallics, Vol. 22, No. 17, 2003
Hicks et al.
Ta ble 6. 1-Hexen e Oligom er iza tion a
substituted catalyst 3d . There is not, however, a cor-
relation between steric bulk and catalyst activity.
Catalyst 3a is less reactive than catalyst 3b, as ex-
pected, but further addition of steric bulk, i.e., the
2-methyl-6-tert-butyl-substituted catalyst 3d , causes a
decrease in catalyst activity. The monosubstituted
catalysts 3c (2-tert-butyl) and 3j (2-methyl) are both
very poor catalysts (entries 15 and 16). Substitution of
a trifluoromethyl group for a methyl group in the
2-trifluoromethyl-6-methyl-substituted catalyst (3k , en-
tries 12 and 13) causes a slight increase in catalyst
turnover number when compared with the dimethyl-
substituted catalyst 3a (41 200 and 32 600, respectively)
and a substantial increase in polymer molecular weight
(88 000 and 42 000, respectively). While electronic dif-
ferences are certainly evident, steric factors cannot be
ignored, as a trifluoromethyl group is larger than a
methyl group. The dichloro- and dibromo-substituted
catalysts 3f,g exhibit comparable turnover numbers and
are somewhat less reactive than the dimethyl-substi-
tuted catalyst 3a (entries 8-11). These trends are
consistent with steric effects, as judged by A values for
these groups. The A values for -Cl and -Br substitu-
ents are quite similar, as the larger size of -Br relative
to -Cl is offset by a longer C-Br bond. The A value of
-CH3 is significantly larger than those of -Cl or -Br.
Finally, the pentafluoro-substituted catalyst 3h pro-
duces low-molecular-weight polymer with low activity
(entry 14). With the exception of catalyst 3h , all polymer
molecular weight distributions are monomodal and near
the chain-transfer-limited value of 2. Polymer branching
numbers are between 49 and 73 branches per 1000
carbon atoms for all polymerizations. Finally, none of
the modifications to the aryl ring lead to an increase in
catalyst lifetime (Table 7, entries 1-13).
entry
T (°C)
yield (mg)
TON
DP
branches/1000 C
1
2
40
60
84
127
130
200
21
16
147
152
a
Conditions: 50 vol % 1-hexene in toluene, 3 h, total volume 2
mL.
Ta ble 7. Eth ylen e P olym er iza tion w ith 3a -h ,j,k
t
yield
(g)
branches/
TON 10-3Mn PDI
1000 C
entry
Ar
(min)
1
2
3
4
5
6
7
8
2,6-Me2
2,6-Me2
2,6-iPr2
2,6-iPr2
2,6-Ph2
2-tBu-6-CH3
2-tBu-6-CH3
2,6-Cl2
2,6-Cl2
2,6-Br2
2,6-Br2
2-Me-6-CF3
2-Me-6-CF3
F5
10
30
10
30
10
10
30
10
30
10
30
10
30
10
10
10
4.7
6.3
7.6
8.8
32 600
43 100
52 400
60 400
59 800
43
92
95
1.7
1.8
61
61
8.7
1.8
2.0
53
73
0.88
0.88
3.4
3.5
3.6
3.8
6.0
6.8
1.0
6 000 115
6 000
23 400
24200
23800
26400
41200
46700
7000
10
22
88
2.0
1.9
1.9
53
56
59
9
10
11
12
13
14
15
16
1.6b 3.03
4.7b 2.4
18
49
57
72
2-Me
0.81
Trace
5600
2-tBu
2.1
a
Reactions run in 200 mL of toluene, 80 °C, 200 psig of ethylene
b
with ∼5.2 µmol of catalyst. Determined by 1H NMR.
partially responsible for the more dramatic decrease in
TON. Branching numbers vary relatively little with
solvent or additive, and under these conditions all are
in the range of 35-45 branches per 1000 carbon atoms.
Polar solvents and additives appear to slightly increase
branching, but no clear trend is evident.
Several neutral nickel ethylene polymerization cata-
lysts have been reported to oligomerize R-olefins.16,43 To
date, none have been reported to be active R-olefin
polymerization catalysts. Similar results are observed
with 3b (Table 6). Oligomerization of 1-hexene at 40 and
60 °C leads to low yields of oligomers with degrees of
polymerization of 21 and 16, respectively. Branching
numbers are 147 and 152 branches per 1000 carbon
atoms (slightly less than the expected 166 branches per
1000 carbons atoms), indicating a very minor amount
of chain straightening via a 2,1-insertion and chain-
walking.10
Ar yl Su bstitu en t Effects on Eth ylen e P olym er -
iza tion . A series of anilinotropone ligands and corre-
sponding nickel complexes (3a -h ,j,k ) were synthesized
in an effort to determine the effects of varying the o-aryl
substituents on ethylene polymerization. The results are
summarized in Table 7. All catalysts were screened at
80 °C and 200 psig of ethylene. Catalyst 3e, with a 2,6-
diphenyl-substituted aryl ring, has a slightly higher
polymerization activity than the standard 2,6-diisopro-
pyl-substituted catalyst 3b (entries 3 and 5). Similar
results were observed with analogues of the R-diimine
nickel system.44 With the exception of the 2,6-diphenyl-
substituted catalyst, all polymerization catalysts are
less active than the standard 2,6-diisopropyl-substituted
catalyst. Entries 1-7 show that, as the steric bulk is
increased, the Mn values of the polymers produced
increase from 42 K with the 2,6-dimethyl-substituted
catalyst 3a to 115 K with the 2-methyl-6-tert-butyl-
The melt transition temperatures of several of the
polymers were measured. Branching numbers ranged
from 8 branches per 1000 carbon atoms (entry 2, Table
2) to 73 branches per 1000 carbon atoms (entry 6, Table
7). Generally, as expected, the more branched polymers
have lower Tm’s than those with fewer branches. Poly-
mers with 73, 53, 27, and 8 branches per 1000 carbon
atoms (entries 6 and 5, Table 7, and entries 3 and 2,
Table 2, respectively) have Tm’s of 51, 73, 104, and 122
°C, respectively.
2-An ilin o-7-Ar yltr op on e-Der ived Ca ta lysts. As
noted earlier, Grubbs reported that substitution of the
salicylaldimine catalyst 2a in the 6-position with a
9-anthracenyl group greatly increases catalyst perfor-
mance, leading to much longer lifetimes, higher activi-
ties, and higher molecular weight polymers.27,28 In view
of these results, we chose to apply a similar strategy to
the anilinotropone system. The synthetic route to 2-anili-
no-7-aryltropone is relatively straightforward and is
depicted in Scheme 4. Tropolone was converted to
2-methoxytropone by reaction with iodomethane in the
presence of base. Then 2-methoxytropone, 8, was bro-
minated using N-bromosuccinimide and purified by
column chromatography. Both phenylboronic acid and
1-naphthylboronic acid were coupled with 2-methoxy-
7-bromotropone using standard Suzuki coupling reac-
tion conditions to yield 10a ,b, which were then deme-
thylated with hydrochloric acid to yield 7-aryltropolones
11a ,b. Conversion to the triflates was performed using
(43) Keim, W.; Hoffman, B.; Lodewick, R.; Peiukert, M.; Schmitt,
G. J . Mol. Catal. 1979, 6, 79.
(44) Moody, L. S. et al. WO0222694, 2002.

2-Anilinotropone-Based Nickel(II) Catalysts
Organometallics, Vol. 22, No. 17, 2003 3539
Sch em e 4
Ta ble 8. Eth ylen e P olym er iza tion w ith 14a ,ba
Sch em e 5
T
t
yield
10-3
Mn PDI 1000 C
×
branches/
entry
R
(°C) (min) (g)
TON
1
2
3
4
5
6
7
8
Ph
Ph
Ph
Ph
Ph
Ph
Ph
25
25
25
40
40
80
80
10
30
60
10
60
10 11.9
60 15.2
10
60
0.47
1.5
2.5
2.0
8.8
2 500
74
1.2
1.4
1.5
1.3
6.4
10
20
19
34
19
76
63
22
9
8 100 199
13 200 280
9 600 251
47 400 581
64 300
87 700
11 200 250
50 600 831
88
2.1
1.3
3.8
trifluoromethanesulfonic anhydride with pyridine as
solvent. The coupling conditions used for the synthesis
of the unsubstituted anilinotropone ligands were modi-
fied slightly. Catalyst loading was increased from 1.0
to 5.0 mol %, and the reaction temperature was in-
creased from 80 to 90 °C. The more forcing conditions
were necessary to compensate for the added steric bulk
of the aryl-substituted triflate. In the case of the
naphthyl-substituted triflatotropone 12b the yields of
coupled product were significantly reduced (see the
Experimental Section).
The synthesis of (2-anilino-7-aryltropone)nickel(II)
complexes 14a ,b was modified slightly from the proce-
dure described for unhindered anilinotropones 5a -j
(Scheme 5). The 2-anilino-7-aryltropones 13a ,b were
deprotonated in THF in the presence of a 5-fold excess
of sodium hydride. One equivalent of (PPh3)2Ni(Ph)Cl
was added to the reaction mixture in solid form. Sodium
hydride and sodium chloride were removed by filtration,
and the product was isolated by recrystallization from
toluene/pentane.
The polymerization activity of 14a ,b was screened at
both 40 and 80 °C at 200 psig of ethylene (entries 4-12,
Table 8). Polymerization at 80 °C produces polyethylene
with 10 min turnover numbers somewhat higher than
those with the unsubstituted catalyst (e.g. 64 300 for
14a vs 52 400 for 3b). The percentage increase in TON
from 10 to 60 min for 14a (64 300 to 87 700) is somewhat
greater than that for 3b (52 400 to 62 100) but still
rather small and indicative of a catalyst half-life on the
order of 8-10 min. A substantially different set of
results is obtained at 40 °C. Entries 8-10 (Table 8) show
that for naphthyl-substituted catalyst 14b TON in-
creases almost linearly between 10 and 180 min, sug-
gesting a catalyst half-life well in excess of 3 h at 40
°C. Equally significant is the dramatic increase in
polymer molecular weight from 10 to 60 min (250 000
to 831 000). The polymer produced in 180 min is too high
naphthyl 40
naphthyl 40
naphthyl 40
naphthyl 80
naphthyl 80
1.9
8.8
9
10
11
12
180 30.7 177 000
10 10.9
60 16.0
11
70
62
51 900
76 200
56
56
2.2
2.7
a
Reactions run in 200 mL of toluene at 200 psig of ethylene
with 6.5 µmol of catalyst.
in molecular weight to be analyzed by GPC. The
observed increase in molecular weight combined with
the low polydispersity observed for entry 8 suggests that
very little chain transfer occurs under these conditions.
The high polydispersity obtained for entry 9 is likely
due to the exceptionally high molecular weight of the
polymer and the viscous nature of the sample used for
GPC analysis. Similar results were obtained for the
phenyl-substituted anilinotropone catalyst (entries 4-7,
Table 8). The low polydispersity obtained at 40 °C (10
min) suggests that lowering the reaction temperature
further may result in a further decrease in PDI and a
living polymerization. Polymerization at 25 °C shows
that, while not truly living, the catalyst produces
polyethylene with polydispersities well below 2.0 and a
continually increasing Mn value with reaction time
(entries 1-3).
Catalysts 14a ,b exhibit higher turnover numbers
relative to the unsubstituted catalyst 3b at 40 °C. The
reason for this increase in activity is not clear. The
intrinsic barrier to ethylene insertion may be lowered,
or the equilibrium ratio of the PPh3 complex to the
required ethylene complex may be shifted in favor of
the ethylene complex. These mechanistic aspects are
currently under investigation. The combination of high
turnover frequencies and long catalyst lifetime at 40 °C
results in high total productivities for these aryl-
substituted catalysts, as illustrated by entry 10 where
2 × 105 turnovers are achieved in 3 h. The increased
steric bulk of a naphthyl group relative to a phenyl
group has little effect on overall catalyst performance

3540 Organometallics, Vol. 22, No. 17, 2003
Hicks et al.
Sch em e 6
Sch em e 7
Sch em e 8
or polymer properties. The branching numbers for both
of the aryl-substituted catalysts are similar to those
obtained for 3b under similar reaction conditions.
Finally, the initial activity obtained at 80 °C with 14a ,b
is higher than that obtained at 40 °C with other reaction
conditions held constant; however, in terms of produc-
tivity the decreased activity at 40 °C is more than
compensated for by the dramatically increased catalyst
lifetime.
The variable-temperature and -pressure experiments
with 3b suggest the branching mechanism depicted in
Scheme 6, which mirrors the mechanism suggested for
branching in the diimine catalyst system 2.8,9 A branch
in the polymer is introduced first by â-hydride elimina-
tion of a growing polymer chain, followed by olefin
rotation and reinsertion with opposite regiochemistry.
This process may occur many times prior to ethylene
insertion and therefore lead to methyl as well as higher
branches. As the ethylene pressure is increased, mono-
mer coordination and insertion becomes more favorable
and therefore the unimolecular branching pathway is
less favored. Conversely, as temperature is increased,
the unimolecular branching pathway is entropically
favored over ethylene coordination and insertion and,
therefore, more branching is observed.
The fact that the molecular weight significantly
increases with ethylene pressure (e.g. Mn ) 50 000, 50
psig, 80 °C; 90 000, 200 psig, 80 °C; entries 9 and 11,
Table 2) suggests that chain transfer to monomer is not
the major chain transfer mechanism. Theoretical cal-
culations have suggested that for similar systems the
alkyl olefin intermediate in the polymerization may
partition as shown in eq 5 (Scheme 7).45-47 Pathway a
represents insertion and propagation, while pathway b
represents chain transfer to monomer. If chain transfer
to monomer is the sole chain transfer mechanism, then
the ratio of kct/kp should be independent of ethylene
concentration and thus the chain-transfer-limited mo-
lecular weight should be independent of ethylene con-
centration. Since this is not observed, a chain transfer
process which is not dependent on ethylene concentra-
tion seems more likely. This is best rationalized by the
conventional â-hydride elimination mechanism shown
in eq 6. Of course, given the qualitative Mn values and
the substantial error in these determinations, it is
possible that some chain transfer occurs via the chain
transfer to monomer pathway.
Ca ta lyst Dea ctiva tion Stu d ies. The fate of the
catalyst upon deactivation was investigated. Upon
precipitation of the polymer in methanol, the filtrate
was separated and the decomposition product was
isolated. The decomposition product was determined by
1H NMR spectroscopy to be the bis(anilinotropone)-
nickel(II) complex 15. The identity of this complex was
confirmed through independent synthesis by combining
(DME)NiBr2 with 2 equiv of the sodium salt 7b (Scheme
8). Crystals of 15 suitable for an X-ray diffraction study
were grown from a concentrated solution of toluene
layered with pentane at -30 °C. The crystallographic
(45) Deng, L.; Margl, P.; Ziegler, T. J . Am. Chem. Soc. 1997, 119,
1094.
(46) Deng, L.; Woo, T. K.; Cavallo, L.; Margl, P. M.; Ziegler, T. J .
Am. Chem. Soc. 1997, 119, 6177.
(47) Chan, M. S. W.; Deng, L.; Ziegler, T. Organometallics 2000,
19, 2741.

2-Anilinotropone-Based Nickel(II) Catalysts
Organometallics, Vol. 22, No. 17, 2003 3541
tropones has been demonstrated. Reaction of the sodium
salts of the anilinotropones with (PPh3)2Ni(Ph)(Cl)
provides a convenient route to catalysts of the type [[(2-
R-6-R′C6H3)NC7H5O]Ni(Ph)(PPh3)], active for ethylene
polymerization. Catalysts incorporating alkyl substit-
uents at the 2- and 6-positions of the N-aryl ring
generate high-molecular-weight polyethylenes with mono-
modal molecular weight distributions of ca. 2 (or less
at low temperatures). Total turnover numbers of ca.
60 000 are observed in 10 min at 80 °C, but catalyst
lifetimes are short at this temperature. Branching
increases with increasing temperature and decreasing
pressure, consistent with earlier observations using
aryl-substituted diimine catalysts. Replacement of the
standard 2,6-diisopropyl substituents on the aryl group
with 2,6-dimethyl, 2,6-dichloro, 2,6-dibromo, and 2-meth-
yl-6-trifluoromethyl substituents has little effect on
productivity. A slight increase in TON is observed for
the 2,6-diphenyl-substituted catalyst. Significant reduc-
tion in TON is observed for the 2-methyl-6-tert-butyl-,
2-methyl-, 2-tert-butyl-, and 2,3,4,5,6-pentafluoro-sub-
stituted catalysts. Molecular weights generally increase
with increasing steric bulk of the ortho substituents. As
expected, these neutral catalysts have a high tolerance
for polar additives.
F igu r e 3. ORTEP view of 15.
Ta ble 9. Cr ysta llogr a p h ic Da ta for 15
formula
mol wt
color
NiC38H44N2O2
619.46
orange
Substitution of the 2-(2,6-diisopropylanilino)tropone
ligand in the 7-position with either phenyl or naphthyl
groups results in a small increase in productivities and
lifetimes at 80 °C and 200 psig. However, at 40 °C these
catalysts exhibit much longer lifetimes (t1/2 > 1 h) and
higher total turnover numbers can be achieved relative
to 80 °C polymerizations.
Molecular weights of the polyethylenes increase with
pressure, which suggest chain transfer at least in part
occurs through classical â-hydride elimination rather
than chain transfer to monomer. The catalyst decay
product is the Ni(II) bis-ligand complex, whose forma-
tion must be initiated by reductive elimination of the
ligand from a Ni(II) species. Utilization of these cata-
lysts in copolymerizations and mechanistic studies of
chain propagation and catalyst decay are in progress.
cryst syst
space group
a (Å)
b (Å)
c (Å)
triclinic
P1h
18.4952(3)
11.5835(4)
34.7657(13)
82.197(1)
87.842(1)
83.726(1)
3368.21(21)
1.222
R (deg)
â (deg)
γ (deg)
V (Å3)
D
calcd (Mg/m3)
wavelength (Å)
0.71073
0.61
µ (mm-1
)
cryst dimens (mm)
temp (°C)
0.30 × 0.10 × 0.10
-100
mode
2θ range (deg)
no. of rflns
no. of indep rflns
R(F)
Rw(F)
ω
5.00-55.00
37 225
14 719
0.057
0.060
hkl range
type of diffractometer
abs cor method
-10 to +11, 0-15, -44 to +45
Bruker SMART
SADABS
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Argon was purified by passage
through columns of BASF R3-11 catalyst (Chemalog) and 4 Å
molecular sieves. Toluene and pentane were deoxygenated and
dried over a column of activated alumina. THF was distilled
under a nitrogen atmosphere from sodium benzophenone ketyl
prior to use. Ethyl acetate, triethylamine, and ethanol were
degassed, dried over 4 Å molecular sieves, and stored under
argon. Water was degassed and stored under argon. CP grade
ethylene was used as received from National Welders Supply.
Some studies were conducted utilizing Research Plus grade
ethylene obtained from Matheson; the purity level is 99.9996%.
The anilinotropones,32 (PPh3)2Ni(Ph)(Cl),50 salicylaldiminato
Ni complex 2,27 2-methoxytropone,51 2-methoxy-7-bromo-
tropone,52 2-methoxy-7-phenyltropone,53 2-methoxy-7-naphth-
yltropone,53 7-phenyltropolone,53 7-naphthyltropolone,53 and
radiation for intensity measmts Mo KR
monochromator
graphite
4
Z
data are summarized in Table 9, and an ORTEP
diagram of 15 is shown in Figure 3. The structure
confirmed that the N atoms are trans to each other in
the bis-ligand complex, thereby minimizing steric repul-
sion of the two bulky N-aryl rings. These results are
similar to those reported for the salicylaldimine cata-
lysts and SHOP catalysts.28,48,49 Formation of the bis-
ligand complex is best explained by reductive elimina-
tion from a nickel-hydride intermediate to form free
ligand followed by attack of the free ligand on a Ni(II)
species present in the catalytic cycle.
54
(DME)NiBr2 were prepared according to literature proce-
dures.
Su m m a r y
(50) Hiodai, M.; Kashiwaga, T.; Ikeuchi, T.; Uchida, Y. J . Organomet.
Chem. 1971, 30, 279.
(51) Tamburlin-Thumin, I.; Crozet, M. P.; Barriere, J . C. Synthesis
1999, 1149.
The utility of palladium cross-coupling as an effective
method for the synthesis of a variety of 2-anilino-
(48) Klabunde, U.; Ittel, S. D. J . Mol. Catal. 1987, 41, 123.
(49) Klabunde, U.; Tulip, T. H.; Roe, D. C.; Ittel, S. D. J . Organomet.
Chem. 1987, 334, 141.
(52) Takeshita, H. M. Synthesis 1986, 578.
(53) Piettre, S. R. et al. J . Med. Chem. 1997, 40, 4208.
(54) Ward, L. G. L. Inorg. Synth. 1973, 13, 154.

3542 Organometallics, Vol. 22, No. 17, 2003
Hicks et al.
Yields refer to isolated yields of compounds of greater than
Gen er a l P r oced u r e for th e Syn th esis of Na Sa lts of
2-An ilin otr op on es. To a sidearm flask in a glovebox was
added NaH (1.2 equiv). The flask was removed from the
glovebox and placed on a vacuum line under argon. THF (5-
10 mL) was added to the flask, and the flask was cooled with
an ice-water bath. Slow addition of 2-anilinotropone (1 equiv)
as a solution in THF (3 mL) resulted in vigorous evolution of
hydrogen. When gas evolution ceased, the flask was removed
from the ice-water bath and warmed to room temperature.
After 2 h, the solution was cannula-filtered away from the
remaining NaH, and the residual NaH was washed with THF
(3 mL). The THF was removed in vacuo to produce essentially
a quantitative yield of the desired salt as its THF adduct. The
amount of THF incorporated varied with different salts and
1
95% purity, as estimated by H NMR analysis and elemental
1
analysis. All H NMR spectra are reported in δ units in parts
per million (ppm) downfield from tetramethylsilane. All 13C
NMR spectra are reported in ppm relative to residual 13C in
solvent. All 31P NMR data are reported relative to H3PO4
external standard. 1H NMR spectra of polyethylenes were
recorded in C6D5Br at 120 °C. The formula used to calculate
branching was (CH3/3)/[(CH + CH2 + CH3)/2] × 1000 )
branches per 1000 carbons. CH3, CH2, and CH refer to the
integration obtained for the methyl, methylene, and methine
resonances, respectively. 13C NMR spectra of polyethylenes
were recorded in a 0.05 M Cr(acac)3 solution in bromobenzene-
d5 with 15 wt % polymer. Peaks were assigned as described
by Cotts.42 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
equipped with Shodex columns. A calibration curve was
established with polystyrene standards, and universal calibra-
tion was applied using Mark-Houwink constants for polyeth-
ylene (k ) 4.34 × 10-4; R ) 0.724). Mn for low-molecular-weight
polymer samples was determined by 1H NMR end group
analysis. Elemental analyses were performed by Atlantic
Microlab Inc. of Norcross, GA.
1
was determined by H NMR.
Na Sa lt of 2-(2,6-Dim eth yla n ilin o)tr op on e (7a ). The
general procedure was employed with 405 mg (1.8 mmol) of
anilinotropone and 50 mg (2 mmol) of NaH. The salt was
isolated with 2.18 equiv of THF. 1H NMR (400 MHz, C6D6): δ
7.05 (m, 2 H), 6.92 (m, 1 H), 6.58-6.33 (m, 4 H), 6.05 (m, 1
H), 3.40 (THF), 1.94 (s, 6 H), 1.31 (THF).
Na Sa lt of 2-(2,6-Diisop r op yla n ilin o)tr op on e (7b). The
general procedure was employed with 1.28 g (4.5 mmol) of
anilinotropone and 120 mg (5 mmol) of NaH. The salt was
isolated with 1 equiv of THF. 1H NMR (250 MHz, C6D6): δ
7.18-7.04 (m, 3 H), 6.6-6.4 (m, 3 H), 6.32 (dd, J ) 8.0, 12.2
Hz, 1 H), 6.02 (dt, J ) 3.2, 7.8 Hz, 1 H), 3.36 (THF), 2.94 (m,
2 H), 1.26 (THF), 1.14 (d, j ) 7.0 Hz, 6 H), 1.00 (d, J ) 7 Hz,
1 H). 13C NMR (100 MHz, C6D6): δ 177.6, 165.8, 148.7, 139.0,
134.4, 133.5, 124.2, 123.5, 121.2, 118.4, 117.9, 68.0, 28.2, 25.6,
24.9, 23.9.
Gen er a l P r oced u r e for th e P r ep a r a tion of An ilin o-
tr op on es. A flame-dried Schlenk tube was charged with
2-triflatotropone (1.0 equiv), Cs2CO3 (1.4 equiv), Pd2dba3 (0.5
mol %), and racemic 2,2′-bis(diphenylphosphino)-1,1′-binaph-
thyl (1 mol %) under argon. Toluene (5 mL) and the appropri-
ate aniline (1.2 equiv) were added, and the reaction mixture
was heated to 80 °C and stirred for the duration noted below.
The reaction mixture was cooled to room temperature, diluted
with diethyl ether, and filtered through Celite. The filtrate was
concentrated and purified by flash chromatography on silica
gel using 15% ethyl acetate in hexanes as the eluent.
Na Sa lt of 2-(2-ter t-Bu tyla n ilin o)tr op on e (7c). The
general procedure was employed with 462 mg (1.8 mmol) of
anilinotropone and 50 mg (5 mmol) of NaH. The salt was
1
isolated with 1.5 equiv of THF. H NMR (250 MHz, C6D6): δ
7.42 (d, J ) 8.0 Hz, 1 H), 6.98 (m, 1 H), 6.66 (m, 2 H), 6.45 (m,
3 H), 6.04 (at, J ) 9.0 Hz, 1 H), 3.44 (THF), 1.37 (THF), 1.29
(s, 9 H).
Na Salt of 2-(2-ter t-Bu tyl-6-m eth ylan ilin o)tr opon e (7d).
The general procedure was employed with 303 mg (1.14 mmol)
of anilinotropone and 31 mg (1.3 mmol) of NaH. The salt was
isolated with 1.16 equiv of THF. 1H NMR (400 MHz, C6D6): δ
7.33 (d, J ) 7.6 Hz, 1 H), 7.07 (d, J ) 7.6 Hz, 1 H), 6.94 (at, J
) 7.6 Hz, 1 H), 6.52 (m, 2 H), 6.39 (m, 2 H), 6.04 (m, 1 H),
3.40 (THF), 1.97 (s, 3 H), 1.30 (s, 9 H + THF).
Na Sa lt of 2-(2,6-Dip h en yla n ilin o)tr op on e (7e). The
general procedure was employed with 352 mg (1.0 mmol) of
anilinotropone and 28 mg (1.2 mmol) of NaH. The salt was
isolated with 0.55 equiv of THF. 1H NMR (400 MHz, C6D6): δ
7.28 (d, J ) 7.6 Hz, 2 H), 7.19 (d, J ) 6.8 Hz, 2 H), 7.04 (t, J
) 7.6 Hz, 1 H), 6.81 (m, 6 H), 6.63 (d, J ) 11.6 Hz, 1 H), 6.44
(m, 2 H), 6.08 (at, J ) 9.0 Hz, 1 H), 6.00 (d, J ) 10.4 Hz, 1 H),
3.52 (THF), 1.39 (THF).
Syn th esis of 2-(2-Meth yla n ilin o)tr op on e (5j). Following
the general procedure, 762 mg (3.0 mmol) of triflatotropone
and 384 µL (3,6 mmol) of 2-methylaniline were converted to
the anilinotropone in 14.5 h (561 mg, 89%). 1H NMR (400 MHz,
CDCl3): δ 8.57 (bs, 1 H), 7.40-7.30 (m, 3 H), 7.30-7.21 (m, 3
H), 7.12 (dd, J ) 10, 10.4 Hz, 1 H), 6.77 (m, 1 H), 6.71 (d, J )
10.4 Hz, 1 H), 2.21 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ
176.5, 154.5, 137.5, 136.5, 136.2, 134.6, 131.4, 130.2, 127.1,
126.1, 124.2, 110.6, 17.8. Anal. Calcd for C14H13NO: C, 79.59;
H, 6.20; N, 6.63. Found: C, 79.62; H, 6.17; N, 6.62.
Syn t h esis of 2-(2-Met h yl-6-t r iflu or om et h yla n ilin o)-
tr op on e (5k ). Following the general procedure, 762 mg (3.0
mmol) of triflatotropone and 630 mg (3,6 mmol) of 2-methyl-
6-(trifluoromethyl)aniline were converted to the anilinotropone
1
in 14.5 h (781 mg, 93%). H NMR (400 MHz, CDCl3): δ 8.50
(bs, 1 H), 7.64 (d, J ) 7.8 Hz, 1 H), 7.55 (d, J ) 7.6 Hz, 1 H),
7.41 (at, J ) 7.8 Hz, 1 H), 7.33 (m, 2 H), 7.07 (at, J ) 10.2 Hz,
1 H), 6.77 (m, 1 H), 6.14 (d, J ) 10.1 Hz, 1 H), 2.17 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ 176.8, 154.2, 138.6, 137.4,
135.8, 134.9, 134.5, 131.1, 128.4 (q, J ) 29.6 Hz), 127.6, 124.8
(q, J ) 5.2 Hz), 124.4, 123.3 (q, J ) 272 Hz), 110.5, 17.7. 19F
NMR (377 MHz, C6D6): δ -62.2. Anal. Calcd for C15H12NOF3:
C, 64.51; H, 4.33; N, 5.02. Found: C, 64.23; H, 4.24; N, 4.87.
Na Sa lt of 2-(2,6-Dich lor oa n ilin o)tr op on e (7f). The
general procedure was employed with 658 mg (2.5 mmol) of
anilinotropone and 71 mg (2.95 mmol) of NaH. The salt was
1
isolated with 1.6 equiv of THF. H NMR (400 MHz, C6D6): δ
7.08 (d, J ) 8.0 Hz, 2 H), 6.73 (d, J ) 10.4 Hz, 1 H), 6.59 (at,
J ) 10.2 Hz, 1 H), 6.51 (m, 1 H), 6.39 (m, 2 H), 6.11 (at, J )
9.2 Hz, 1 H), 3.50 (THF), 1.35 (THF).
Na Sa lt of 2-(2,6-Dibr om oa n ilin o)tr op on e (7g). The
general procedure was employed with 721 mg (2.0 mmol) of
anilinotropone and 58 mg (2.44 mmol) of NaH. The salt was
isolated with 1 equiv of THF. 1H NMR (400 MHz, C6D6): δ
7.26 (m, 2 H), 6.74 (m, 1 H), 6.61 (m, 1 H), 6.50 (m, 1 H), 6.35
(d, J ) 11.2 Hz, 1 H), 6.23 (m, 1 H), 6.14 (m, 1 H), 3.51 (THF),
1.33 (THF).
Syn th esis of 2-(2,6-Diflu or oa n ilin o)tr op on e (5l). Fol-
lowing the general procedure, 254 mg (1.0 mmol) of triflato-
tropone and 129 µL (1.2 mmol) of 2,6-difluoroaniline were
converted to the anilinotropone in 16 h (219 mg, 94%). 1H NMR
(400 MHz, CDCl3): δ 8.30 (bs, 1H), 7.35 (m, 2H), 7.25 (m, 1H),
7.16 (t, J ) 10.2 Hz), 1H), 7.05 (m, 2H), 6.55 (dt, J ) 2.5, 10.2
Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 177.0, 159.0 (d, J )
4.6 Hz, 1C), 156.5 (d, J ) 4.6, 1C). 137.3, 135.5, 131.6, 127.3
(t, J ) 9.6 Hz, 1C), 125.2, 115.5, (t, J ) 15.6 Hz, 1C), 112.1,
111.4. 19F NMR (376 MHz, CDCl3): δ -116.6 (s). Anal. Calcd
for C13H8NOF2: C, 66.93; H, 3.89; N, 6.01. Found: C, 66.66;
H, 3.90; N, 5.97.
Na Sa lt of 2-(2,3,4,5,6-P en ta flu or oa n ilin o)tr op on e (7h ).
The general procedure was employed with 581 mg (1.9 mmol)
of anilinotropone and 100 mg (4.2 mmol) of NaH. The salt was
isolated with no excess THF. 1H NMR (400 MHz, d6-acetone):

2-Anilinotropone-Based Nickel(II) Catalysts
Organometallics, Vol. 22, No. 17, 2003 3543
δ 6.85 (at, H ) 10.2 Hz, 1 H), 6.73 (d, J ) 10 Hz, 1 H), 6.69 (at
J ) 11.4 Hz, 1 H), 6.19 (d, J ) 11.2 Hz, 1 H), 6.14 (at, J ) 9.2
Hz, 1 H).
Na Sa lt of 2-(2-Meth yla n ilin o)tr op on e (7j). The general
procedure was employed with 508 mg (2.4 mmol) of anilino-
tropone and 69 mg (2.9 mmol) of NaH. The salt was isolated
with 0.89 equiv of THF. 1H NMR (400 MHz, C6D6): δ 7.11 (m,
2 H), 6.93 (m, 1 H), 6.64-6.45 (m, 4 H), 6.41 (dd, J ) 8.6, 11.4
Hz, 1 H), 6.08 (at, J ) 9.0 Hz, 1 H), 3.46 (THF), 1.89 (s, 3 H),
1.32 (THF).
Na Sa lt of 2-(2-Met h yl-6-(t r iflu or om et h yl)a n ilin o)-
tr op on e (7k ). The general procedure was employed with 688
mg (2.5 mmol) of anilinotropone and 71 mg (2.95 mmol) of
NaH. The salt was isolated with 1 equiv of THF. 1H NMR (400
MHz, C6D6): δ 7.39 (d, J ) 7.6 Hz, 1 H), 7.06 (d, J ) 7.6 Hz,
1 H), 6.70 (at, J ) 7.6 Hz, 1 H), 6.57 (m, 2 H), 6.45 (dd, J )
8.2, 11.6 Hz, 1 H), 6.28 (d, J ) 11.6 Hz, 1 H), 6.08 (at, J ) 8.8
Hz, 1 H), 3.46 (THF), 1.88 (s, 3 H), 1.33 (THF).
to afford 195 mg (57%) of the desired complex as a yellow-
orange solid. 1H NMR (400 MHz, CD2Cl2): δ 7.47 (m, 6 H),
7.38 (m, 3 H), 7.28 (m, 6 H), 7.18 (dd, J ) 1.4, 8 Hz, 1 H), 7.11
(bs, 1 H), 6.95 (at, J ) 10.2 Hz, 1 H), 6.81 (m, 2 H), 6.72 (m,
1 H), 6.55 (M, 2 H), 6.46 (d, J ) 9.4 Hz, 1 H), 6.42 (dd, J )
1.6, 7.7 Hz, 1 H), 6.23 (m, 2 H), 6.07 (bs, 1 H), 1.51 (s, 9 H).
13C NMR (100 MHz, CD2Cl2): δ 179.9 (d, J ) 7.5 Hz), 169.1,
151.3 (d, J ) 45 Hz), 146.9, 142.3, 138.4 (broad), 137.8 (broad),
134.8, 134.6 (d, J ) 10.5 Hz), 133.7, 131.9, 131.5, 130.1 (d, J
) 1.9 Hz), 128.9, 128.8, 128.2 (d, J ) 9.7 Hz), 126.3, 125.1
(broad), 124.2, 121.6, 120.9, 120.7, 120.5, 36.4, 32.8..31P NMR
(162 MHz, CD2Cl2): δ 29.34. Anal. Calcd for C41H38NOPNi:
C, 75.71; H, 5.89; N, 2.15. Found: C, 75.76; H, 5.92; N, 2.19.
2-(2-ter t-Bu t yl-6-m et h yla n ilin o)t r op on e Ni Com p lex
3d . The general procedure was employed with 219 mg (0.59
mmol) of the sodium salt and 409 mg (0.59 mmol) of (Ph3P)2-
Ni(Ph)(Cl) to afford 185 mg (47%) of the desired complex as a
1
yellow-orange solid. H NMR (400 MHz, C6D6): δ 7.63 (m, 6
H), 7.23 (bs, 1 H), 7.15 (m, 1 H), 6.98 (m, 10 H), 6.81 (m, 2 H),
6.75 (d, J ) 10.4 Hz, 1 H), 6.58 (at, J ) 10 Hz, 1 H), 6.48 (m,
2 H), 6.41 (m, 3 H), 6.11 (at, J ) 9.0 Hz, 1 H), 2.46 (s, 3 H),
1.69 (s, 9 H). 13C NMR (100 MHz, CD2Cl2): δ 179.8 (d, J ) 7.3
Hz), 168.1, 149.3 (d, J ) 45.3 Hz), 145.6, 142.1, 138.3 (broad),
137.2 (broad), 134.7, 134.5 (d, J ) 10.5 Hz), 133.9, 133.1, 131.9,
131.4, 130.1, 128.2 (d, J ) 9.9 Hz), 128.1, 127.1, 124.9 (broad),
124.4, 121.7, 121.1, 120.4, 119.7, 36.9, 33.3, 19.6..31P NMR (162
MHz, CD2Cl2): δ 29.02. Anal. Calcd for C42H40NOPNi: C,
75.92; H, 6.07; N, 2.11. Found: C, 75.75; H, 6.11; N, 2.15.
2-(2,6-Dip h en yla n ilin o)tr op on e Ni Com p lex 3e. The
general procedure was employed with 225 mg (0.55 mmol) of
the sodium salt and 380 mg (0.55 mmol) of (Ph3P)2Ni(Ph)(Cl)
to afford 220 mg (54%) of the desired complex as a yellow-
orange solid. The compound was isolated with 0.33 equiv of
Gen er a l P r oced u r e for t h e Syn t h esis of 2-An ili-
n otr op on e Nick el Com p lexes (3). In a flame-dried Schlenk
flask in a glovebox were added the sodium salt of 2-anili-
notropone-THF (1.0 equiv) and (Ph3P)2Ni(Ph)(Cl) (1.0 equiv).
The flask was removed from the glovebox, placed on a vacuum
line under Ar, and cooled to -30 °C in a dry ice/acetone bath.
THF (∼15 mL) was added to the flask, which was warmed to
room temperature for 1 h. The reaction mixture was stirred
at ambient temperature for 1 h. THF was removed in vacuo,
and the crude reaction mixture was dissolved in toluene (∼15
mL). Cannula transfer onto a pad of Celite was followed by
filtration under argon. The Celite pad was washed with toluene
(3 × 5 mL), and the solvent volume was reduced to 3-5 mL.
Pentane (50 mL) was added, and the Schlenk flask was placed
in a -30 °C freezer overnight. Solvent was removed from the
precipitate via cannula filtration, and the residual solid was
washed with pentane (3 × 10 mL). Drying in vacuo produces
the desired nickel complex.
2-(2,6-Dim eth yla n ilin o)tr op on e Ni Com p lex 3a . The
general procedure was employed with 172 mg (0.54 mmol) of
the sodium salt and 372 mg (0.54 mmol) of (Ph3P)2Ni(Ph)(Cl)
to afford 190 mg (57%) of the desired complex as a yellow-
orange solid. 1H NMR (400 MHz, CD2Cl2): δ 7.54 (m, 6 H),
7.39 (m, 3 H), 7.28 (m, 6 H), 7.21 (d, J ) 8 Hz, 2 H), 7.09 (dd,
J ) 10, 10.6 Hz, 1 H), 6.99 (m, 2 H), 6.94 (d, J ) 10.6 Hz, 1
H), 6.71 (d, J ) 10.7 Hz, 1 H), 6.63 (at, J ) 9.5 Hz, 1 H), 6.56
(t, J ) 8 Hz, 1 H), 6.22 (m, 2 H), 6.14 (m, 2 H), 2.21 (s, 6 H).
13C NMR (100 MHz, CD2Cl2): δ 179.9 (d, J ) 7.2 Hz), 167.7,
150.3 (d, J ) 44.5 Hz), 146.4, 136.9 (d, J ) 1.8 Hz), 134.7,
134.6 (d, J ) 10.7 Hz), 134.3, 131.8 (d, J ) 1.9 Hz), 131.4,
130.1, 128.2 (d, J ) 9.7 Hz), 127.7, 124.8 (d, J ) 2.6 Hz), 124.3,
122.0, 121.1, 120.5, 117.7, 18.3.31P NMR (162 MHz, C6D6): δ
29.03. Anal. Calcd for C39H34NOPNi: C, 75.26; H, 5.51; N, 2.25.
Found: C, 75.49; H, 5.57; N, 2.38.
1
toluene. H NMR (400 MHz, C6D6): δ 7.95 (d, J ) 7.6 Hz, 4
H), 7.49 (m, 6 H), 7.20 (m, 6 H), 7.13 (m, 6 H), 6.98 (8 H +
toluene), 6.77 (d, J ) 11.6 Hz, 1 H), 6.55 (m, 2 H), 6.4 (m, 4
H), 6.02 (m, 1 H), 2.09 (toluene). 13C NMR (100 MHz, CD2-
Cl2): δ 179.6 (d, J ) 7.5 Hz), 168.9, 148.0 (d, J ) 45.1 Hz),
144.6, 140.8, 138.3 (d, J ) 2.7 Hz), 137.0, 134.8, 134.5 (d, J )
10.6 Hz), 133.8, 131.8, 131.3, 130.5, 130.2, 130.0 (d, J ) 1.9
Hz), 129.3, 128.5, 128.1 (d, J ) 9.8 Hz), 127.7, 127.0, 125.6,
125.2, 124.9 (d, 1.9 Hz), 122.0, 121.2, 121.1, 120.5, 21.5..31
P
NMR (162 MHz, C6D6): δ 29.03. Anal. Calcd for C49H38NOPNi‚
0.33(toluene): C, 79.3; H, 5.27; N, 1.80. Found: C, 79.24; H,
5.37; N, 1.77.
2-(2,6-Dich lor oa n ilin o)tr op on e Ni Com p lex 3f. The
general procedure was employed with 200 mg (0.50 mmol) of
the sodium salt and 344 mg (0.50 mmol) of (Ph3P)2Ni(Ph)(Cl)
to afford 250 mg (75%) of the desired complex as a yellow-
1
orange solid. H NMR (400 MHz, C6D6): δ 7.54 (m, 6 H), 7.39
(m, 3 H), 7.29 (m, 6 H), 7.09 (dt, J ) 1.0, 10.2 Hz, 1 H), 6.96
(m, 5 H), 6.72 (d, J ) 10.8 Hz, 1 H), 6.70 (d, J ) 8.1 Hz, 1 H),
6.63 (at, J ) 9.5 Hz, 1 H), 6.23 (at, J ) 9.5 Hz, 1 H), 6.23 (m,
2 H), 6.14 (m, 2 H). 13C NMR (100 MHz, CD2Cl2): δ 180.2 (d,
J ) 6.8 Hz), 167.7, 149.9 (d, J ) 45.3 Hz), 144.2, 137.1 (d, J )
1.7 Hz), 135.5, 134.8, 134.7 (d, J ) 10.6 Hz), 131.7, 131.3, 130.2
(d, J ) 2 Hz), 128.2 (d, J ) 9.7 Hz), 128.1, 125.6, 124.9 (d, J
) 2.1 Hz), 123.2, 122.9, 121.4, 117.8. 31P NMR (162 MHz, CD2-
Cl2): δ 29.13. Anal. Calcd for C37H28NOPNiCl2: C, 67.00; H,
4.26; N, 2.11. Found: C, 66.95; H, 4.37; N, 2.15.
2-(2,6-Dibr om oa n ilin o)tr op on e Ni Com p lex 3g. The
general procedure was employed with 220 mg (0.49 mmol) of
the sodium salt and 341 mg (0.49 mmol) of (Ph3P)2Ni(Ph)(Cl)
to afford 315 mg (85%) of the desired complex as a yellow-
orange solid. 1H NMR (400 MHz, CD2Cl2): δ 7.54 (m, 6 H),
7.39 (m, 3 H), 7.28 (m, 6 H), 7.21 (d, J ) 8.0 Hz, 2 H), 7.09 (m,
1 H), 7.00 (m, 2 H), 6.94 (d, J ) 10.4 Hz, 1 H), 6.72 (d, J )
10.8 Hz, 1 H), 6.63 (at, J ) 9.4 Hz, 1 H), 6.56 (t, J ) 8.0 Hz,
1 H), 6.22 (m, 2 H), 6.14 (t, J ) 7.2 Hz, 2 H). 13C NMR (100
MHz, CD2Cl2): δ 180.2 (d, J ) 6.8 Hz), 167.3, 149.6 (d, J )
45.7 Hz), 146.5, 137.4, 135.5, 134.8, 134.7 (d, J ) 10.6 Hz),
2-(2,6-Diisop r op yla n ilin o)tr op on e Ni Com p lex 3b. The
general procedure was employed with 201 mg (0.54 mmol) of
the sodium salt and 372 mg (0.54 mmol) of (Ph3P)2Ni(Ph)(Cl)
to afford 241 mg (67%) of the desired complex as a yellow-
1
orange solid. H NMR (400 MHz, C6D6): δ 7.63 (m, 6 H), 7.08
(d, J ) 7.0 Hz, 2 H), 6.98 (m, 12 H), 6.76 (d, J ) 10.4 Hz, 1 H),
6.58 (at, J ) 9.9 Hz, 1 H). 6.53 (d, J ) 11.5 Hz, 1 H), 6.45-
6.33 (m, 4 H), 6.13 (at, J ) 9.4 Hz, 1 H), 3.82 (sept, J ) 6.8
Hz, 2 H), 1.32 (d, J ) 6.8 Hz, 6 H), 1.09 (d, J ) 6.8 Hz, 6 H).
13C NMR (100 MHz, C6D6): δ 180.2 (d, J ) 7.6 Hz), 169.6,
148.9 (d, J ) 45 Hz), 144.4, 142.3, 138.1 (d, J ) 2.2 Hz), 134.6
(d, J ) 10.5 Hz), 133.1, 132.0, 131.6, 129.9 (d, J ) 1.9 Hz),
125.9, 125.5 (d, J ) 2 Hz), 123.7, 122.2, 121.7, 121.3, 121.1,
29.0, 25.9, 23.9. 31P NMR (162 MHz, C6D6): δ 28.9. Anal. Calcd
for C43H42NOPNi: C, 76.12; H, 6.24; N, 2.06. Found: C, 75.83;
H, 6.24; N, 1.98.
2-(2-ter t-Bu t yla n ilin o)t r op on e Ni Com p lex 3c. The
general procedure was employed with 201 mg (0.53 mmol) of
the sodium salt and 372 mg (0.54 mmol) of (Ph3P)2Ni(Ph)(Cl)

3544 Organometallics, Vol. 22, No. 17, 2003
Hicks et al.
132.0, 131.7, 131.3, 130.2 (d, J ) 1.6 Hz), 128.2 (d, J ) 9.8
Hz), 126.4, 124.9 (d, J ) 2 Hz), 123.2, 123.0, 122.3, 121.4,
118.0. 31P NMR (162 MHz, CD2Cl2): δ 29.03. Anal. Calcd for
6H), 7.25 (m, 1H), 7.0 (t, J ) 14 Hz, 1H). 19F NMR (CDCl3,
376 MHz): δ -74.9.
2-Tr ifla to-7-n a p h th yltr op on e (12b). Yield: 1.09 g, 34%.
1H NMR (CDCl3, 300 MHz): δ 7.9 (m, 1H), 7.65 (m, 2H), 7.5
(m, 7H), 7.15 (m, 1H). 19F NMR (CDCl3, 282 MHz): δ -75.0.
Gen er a l P r oced u r e for th e P r ep a r a tion of 7-Ar yl-2-
a n ilin otr op on es. A flame-dried Schlenk tube was charged
with 7-aryl-2-triflatotropone (1.0 equiv), ground cesium car-
bonate (1.4 equiv), Pd2(dba)3 (2.5 mol %), and racemic BINAP
(5 mol %) under an atmosphere of argon. Toluene (5 mL) and
2,6-diisopropylaniline were added sequentially, and the reac-
tion mixture was stirred at 90 °C under argon. After sufficient
reaction time, the reaction mixture was cooled to room
temperature, diluted with CH2Cl2, and filtered through a pad
of Celite. The solution was concentrated, and the residue was
chromatographed on silica gel with 15% ethyl acetate in
hexanes as the eluent.
7-P h en yl-2-(2,6-diisopr opyl)an ilin otr opon e (13a). A 1.03
g (3.12 mmol) portion of 2-triflato-7-phenyltropone and 706
µL (3.74 mmol) of 2,6-diisopropylaniline were converted to
anilinotropone in 20 h (550 mg, 49%). 1H NMR (CDCl3, 400
MHz): δ 8.7 (bs, 1H), 7.55 (m, 3H), 7.4 (m, 4H), 7.3 (m, 2H),
7.1 (t, J ) 10 Hz, 1H), 6.75 (t, J ) 10 Hz, 1H), 6.3 (d, J ) 10
Hz, 1H), 2.9 (sept, J ) 7 Hz, 2H), 1.16 (d, J ) 7 Hz, 6H), 1.14
(d, J ) 7 Hz, 6H). 13C NMR (CDCl3, 100 MHz): δ 174.4, 157.5,
147.2, 143.2, 141.3, 139.3, 135.6, 133.2, 130.1, 129.0, 128.1,
127.5, 124.6, 122.7, 110.5, 28.9, 24.6, 23.4. Anal. Calcd for
C25H27NO: C, 84.10; H, 7.50; N, 3.92. Found: C, 83.47; H, 7.79;
N, 3.62.
C
37H28NOPNiBr2: C, 59.08; H, 3.75; N, 1.86. Found: C, 59.35;
H, 3.82; N, 1.90.
2-(2,3,4,5,6-P en t a flu or oa n ilin o)t r op on e Ni Com p lex
3h . The general procedure was employed with 136 mg (0.44
mmol) of the sodium salt and 308 mg (0.44 mmol) of (Ph3P)2-
Ni(Ph)(Cl) to afford 169 mg (57%) of the desired complex as a
1
yellow-orange solid. H NMR (400 MHz, CD2Cl2): δ 7.52 (m,
6 H), 7.39 (m, 3 H), 7.30 (m, 6 H), 7.18 (dt, J ) 0.9, 10.25 Hz,
1 H), 7.06 (m, 1 H), 6.87 (d, J ) 7.2 Hz, 2 H), 6.80 (d, J ) 10.8
Hz, 1 H), 6.74 (at, J ) 9.6 Hz, 1 H), 6.50 (d, J ) 11.2 Hz, 1 H),
6.36 (t, J ) 7.15 Hz, 1 H), 6.28 (m, 2 H). 13C NMR (100 MHz,
CD2Cl2; spectrum hard to interpret due to extensive F cou-
pling): δ 180.8 (d, J ) 6.5 Hz), 169.1, 152.2 (d, J ) 45.5 Hz),
136.8, 136.2, 135.4, 134.6 (d, J ) 10.7 Hz), 132.3 (m), 131.4,
131.0, 130.3 (d, J ) 1.9 Hz), 128.9 (m), 128.3 (d, J ) 9.8 Hz),
125.5 (d, J ) 2.5 Hz), 124.5, 124.3, 122.0, 118.0. 31P NMR (162
MHz, CD2Cl2): δ 29.71. 19F NMR (377 MHz, CD2Cl2):
δ
-147.73 (m), -163.75 (t, J ) 22.6 Hz), -166.52 (m). Anal.
Calcd for C37H25NOPNiF5: C, 64.94; H, 3.68; N, 2.05. Found:
C, 64.45; H, 3.90; N, 2.31.
2-(2-Meth yla n ilin o)tr op on e Ni Com p lex 3j. The general
procedure was employed with 100 mg (0.34 mmol) of the
sodium salt and 234 mg (0.34 mmol) of (Ph3P)2Ni(Ph)(Cl) to
afford 105 mg (51%) of the desired complex as a yellow-orange
1
solid. H NMR (400 MHz, CD2Cl2): δ 7.50 (m, 6 H), 7.39 (m,
3 H), 7.28 (m, 6 H), 6.98 (dt, J ) 1.0, 10.2 Hz, 1 H), 6.87-6.67
(m, 6 H), 6.59 (d, J ) 10.4 Hz, 1 H), 6.53 (dd, J ) 1.3, 7.6 Hz,
1 H), 6.49 (at, J ) 9.5 Hz, 1 H), 6.27 (d, J ) 11.6 Hz, 1 H),
6.18 (m, 2 H), 6.06 (bs, 1 H), 2.19 (s, 3 H). 13C NMR (100 MHz,
CD2Cl2): δ 179.9 (d, J ) 7.5 Hz), 168.5, 151.6 (d, J ) 44.4
Hz), 147.8, 138.0 (broad), 137.1 (broad), 134.7, 134.6 (d, J )
10.6 Hz), 134.1, 132.1, 131.9, 131.5, 130.1 (d, J ) 2.3 Hz),
130.0, 128.2 (d, J ) 9.7 Hz), 126.3, 126.2, 125.0 (broad), 124.2,
122.0, 121.0, 120.8, 118.6, 17.9. 31P NMR (162 MHz, CD2Cl2):
δ 29.43. Anal. Calcd for C38H32NOPNi: C, 75.02; H, 5.30; N,
2.30. Found: C, 74.12; H, 5.33; N, 2.31.
2-(2-Meth yl-6-(tr iflu or om eth yl)an ilin o)tr opon e Ni Com -
p lex 3k . The general procedure was employed with 192 mg
(0.51 mmol) of the sodium salt and 357 mg (0.51 mmol) of
(Ph3P)2Ni(Ph)(Cl) to afford 205 mg (59%) of the desired
complex as a yellow-orange solid. 1H NMR (400 MHz, CD2-
Cl2): δ 7.49 (m, 6 H), 7.37 (m, 3 H), 7.27 (m, 7 H), 7.04 (d, J
) 9.9 Hz, 1 H), 6.96 (m, 2 H), 6.86 (m, 2 H), 6.63 (d, J ) 10.6
Hz, 1 H), 6.55 (m, 2 H), 6.17 (m, 3 H), 6.05 (m, 1 H), 2.17 (s,
3 H). 13C NMR (100 MHz, CD2Cl2; spectrum is hard to
interpret due to extensive F coupling): δ 180.1 (d, J ) 7.3 Hz),
168.0, 149.4 (d, J ) 46.0 Hz), 146.4, 138.1, 136.8, 135.2, 134.8,
134.6 (d, J ) 10.6 Hz), 134.4, 134.0, 131.8, 131.3, 130.1 (d, J
) 2.5 Hz), 128.2 (d, J ) 9.7 Hz), 126.2, 125.1 (broad), 124.8,
124.7 (broad), 124.5 (q, J ) 5.6 Hz), 124.3, 123.5, 122.4, 121.9,
121.1, 118.9, 18.2. 31P NMR (162 MHz, CD2Cl2): δ 29.37. Anal.
Calcd for C39H31NOPNiF3: C, 69.25; H, 4.62; N, 2.07. Found:
C, 69.15; H, 4.57; N, 2.10.
2-Tr ifla to-7-Ar yltr op on e. Both triflatotropones were pre-
pared according to literature procedures.55 7-Aryltropolone (1
equiv) was dissolved in pyridine (10 mL) and cooled to 0 °C.
Triflic anhydride was added dropwise, and the reaction
mixture was warmed to room temperature and stirred over-
night. The reaction mixture was diluted with water (100 mL)
and extracted with diethyl ether (4 × 75 mL). The organic
phase was washed with water (1 × 50 mL), 1 N HCl (2 × 50
mL), water (1 × 50 mL), and brine (1 × 50 mL) and dried over
Na2SO4. The solvent was removed to yield the desired product.
2-Tr ifla to-7-p h en yltr op on e (12a ). Yield: 1.03 g, 63%. 1H
NMR (CDCl3, 400 MHz): δ 7.6 (d, J ) 14 Hz, 1H), 7.45 (m,
7-(1-Naph th yl)-2-(2,6-diisopr opyl)an ilin otr opon e (13b).
A 350 mg (0.92 mmol) portion of 2-triflato-7-(1-naphthyl)-
tropone and 210 µL (1.10 mmol) of 2,6-diisopropylaniline were
1
converted to anilinotropone in 42 h (200 mg, 53%). H NMR
(CDCl3, 400 MHz): δ 8.7 (bs, 1H), 7.9 (m, 2H), 7.6 (m, 3H),
7.4 (m, 5H), 7.3 (m, 2H), 6.8 (t, J ) 9.5 Hz, 1H), 6.4 (d, J ) 9.5
Hz, 1H), 3.0 (sept, J ) 7 Hz, 1H), 2.9 (sept, J ) 7 Hz, 1H),
1.21 (d, J ) 7 Hz, 3H), 1.17 (d, J ) 7 Hz, 3H), 1.16 (d, J ) 7
Hz, 3H), 1.13 (d, J ) 7 Hz, 3H). 13C NMR (CDCl3, 100 MHz):
δ 174.8, 156.9, 147.2, 147.1, 141.1, 140.9, 140.3, 136.4, 134.1,
133.0, 132.0, 129.5, 129.4, 129.1, 128.8, 128.3, 127.1, 126.5,
126.1, 126.0, 124.7, 122.9, 111.1, 29.0, 28.9, 25.0, 23.8, 23.7.
Anal. Calcd for C29H29NO: C, 85.47; H, 7.17; N, 3.44. Found:
C, 85.44; H, 7.07; N, 2.72.
Mod ified P r oced u r e for th e P r ep a r a tion of 2-An ilin o-
7-a r yltr op on e Ni Com p lexes. A flame-dried Schlenk tube
was charged with the appropriate anilinotropone (1.0 equiv)
and sodium hydride (5.0 equiv) under an atmosphere of argon.
THF (∼30 mL) was added, and the reaction mixture was
stirred for 18 h. Then (PPh3)2Ni(Ph)Cl (1.0 equiv) was added
as a solid and the reaction mixture was stirred for 1 h and
then filtered through a pad of Celite. The solvent was removed
in vacuo, and the residue was recrystallized from toluene and
pentane.
7-P h en yl-2-(2,6-d iisop r op yl)a n ilin otr op on e Ni Com -
p lex 14a . A 65 mg (0.18 mmol) portion of the anilinotropone
and 127 mg (0.18 mmol) of (PPh3)2Ni(Ph)Cl were converted to
the desired product (65 mg, 48%). 1H NMR (CD2Cl2, 400
MHz): δ 7.3 (m, 9H), 7.1 (m. 7H), 6.95 (m, 8H), 6.8 (m, 3H),
6.5 (t. J ) 10 Hz, 1H), 6.35 (d. J ) 10 Hz, 1H), 6.25 (m, 1H),
6.15 (m, 2H), 3.55 (sept, J ) 7 Hz, 2H), 1.2 (d, J ) 7 Hz, 6H),
1.0 (d, J ) 7 Hz, 6H). 13C NMR (CD2Cl2, 100 MHz): δ 176.5,
169.8, 149.5, 143.3, 142.4, 137.7, 137.6, 134.4, 134.3, 132.1,
131.7, 129.9, 129.8, 128.2, 128.0, 127.7, 126.2, 125.3, 125.1,
123.5, 121.1, 28.8, 25.7, 23.8. 31P NMR (CD2Cl2, 162 MHz): δ
26.5. Anal. Calcd for C49H46NiNOP: C, 78.00; H, 6.14; N, 1.86.
Found: C, 77.73; H, 6.15, N, 1.81.
7-Na p h th yl-2-(2,6-d iisop r op yla n ilin o)tr op on e Ni Com -
p lex 14b. A 200 mg (0.49 mmol) portion of the anilinotropone
and 340 mg (0.49 mmol) of (PPh3)2Ni(Ph)Cl were converted to
the desired product (90 mg, 23%). 1H NMR (CD2Cl2, 400
MHz): δ 7.7 (d, J ) 8 Hz, 1H), 7.6 (d, J ) 8 Hz, 1H), 7.5 (d, J
(55) Echavarren, A. M.; Stille, J . K. J . Am. Chem. Soc. 1988, 110,
1557.

2-Anilinotropone-Based Nickel(II) Catalysts
Organometallics, Vol. 22, No. 17, 2003 3545
) 8 Hz, 1H), 7.4 (m, 3H), 7.2 (td, J ) 7.5, 1.3 Hz, 3H), 6.9 (m,
18H), 6.4 (m, 2H), 6.1 (m, 3H), 3.7 (sept, J ) 7 Hz, 1H), 3.5
(sept, J ) 7 Hz, 1H), 1.3 (d, J ) 7 Hz, 3H), 1.1 (d, J ) 7 Hz,
3H), 1.05 (t, J ) 8 Hz, 6H). 13C NMR (CD2Cl2, 100 MHz): δ
169.6, 169.5, 144.78, 141.3, 138.1, 134.1, 134.0, 133.9, 132.0,
131.8, 131.3, 129.6, 129.5, 127.9, 127.8, 127.1, 126.3, 125.7,
125.3, 123.5, 123.4, 1221.0, 120.7, 28.9, 28.8, 24.9, 23.7, 23.6.
in time, temperature, ethylene pressure, and solvent. For the
additive studies, 170 mL of toluene and 20 mL of the respective
additive were used in place of the 190 mL of toluene mentioned
above. For cocatalyst studies, the autoclave was charged with
180 mL of toluene. The catalyst was added in 10 mL of toluene
followed by the cocatalyst in 10 mL of toluene. For the studies
with excess PPh3, both the catalyst and PPh3 were added in
the same 10 mL of toluene. Polymerizations run at 60 and 80
°C produced a homogeneous, viscous solution of polymer and
solvent (i.e. no precipitate).
31P NMR (CD2Cl2, 162 MHz): δ 26.3. Anal. Calcd for C53H48
-
NiNOP: C, 79.11; H, 6.01; N, 1.74. Found: C, 78.72; H, 6.13,
N, 1.70.
L2Ni fr om 2-(2,6-Diisop r op yla n ilin o)tr op on e Ni Com -
p lex 15. To a flame-dried Schlenk flask in a glovebox were
added the sodium salt of a 2-anilinotropone-THF (377 mg,
0.90 mmol)) and (DME)NiBr2 (139 mg, 0.45 mmol). The flask
was removed from the glovebox and placed on a vacuum line
under Ar. Et2O (20 mL) was added to the flask, and the
reaction mixture was stirred at room temperature for 15 h.
The crude reaction mixture was filtered through filter paper
and condensed to produce 240 mg (88%) of a red-brown solid.
X-ray-quality crystals were grown by slow diffusion of pentane
into a concentrated toluene solution of 15 at -30 °C. 1H NMR
(400 MHz, C6D6): δ 7.29-7.21 (m, 6 H), 6.26-6.18 (m, 8 H),
5.92 (m, 2 H), 4.18 (sept, J ) 6.8 Hz, 4 H), 1.74 (d, J ) 6.8 Hz,
12 H), 1.19 (d, J ) 6.8 Hz, 12 H). 13C NMR (100 MHz, C6D6):
δ 180.4, 168.9, 143.6, 141.1, 134.6, 133.8, 126.7, 124.0, 122.8,
120.7, 119.3, 29.2, 24.5, 24.1. Anal. Calcd for C38H42N2O2Ni:
C, 73.67; H, 7.16; N, 4.50. Found: C, 74.10; H, 7.25; N, 4.39.
Gen er a l P r oced u r e for High -P r essu r e Eth ylen e P o-
lym er iza tion s. A 1000 mL Parr autoclave was heated under
vacuum to 110 °C and then was cooled to the desired reaction
temperature and back-filled with ethylene. The autoclave was
charged with toluene (190 mL), degassed with ethylene (2 ×
200 psig), and pressurized with ethylene to 200 psig. The
stirring motor was engaged, and the reactor was allowed to
equilibrate at the desired temperature for approximately 10
min. In a glovebox, a sidearm flask was charged with the
catalyst. The flask was removed from the glovebox and placed
on a vacuum line under Ar. The catalyst was dissolved in 10
mL of toluene and cannula-transferred into the vented auto-
clave with the stirring motor off. The autoclave was sealed
and pressurized to the desired level, and the stirring motor
was reengaged. After the prescribed reaction time, the stirring
motor was stopped, the reactor was vented, and the polymer
was isolated via precipitation from methanol and dried in a
vacuum oven. This procedure was employed with modifications
P r oced u r e for Eth ylen e P olym er iza tion a t 1 a tm . In a
glovebox, a sidearm flask was charged with 2 (5 mg, 7.6 µmol).
The flask was removed from the glovebox and placed on a
vacuum line under argon. Toluene (40 mL) was added to the
flask, and the flask was then placed in an 80 °C oil bath. After
10 min, the flask was evacuated and back-filled with ethylene
three times and left open to ethylene for the duration of the
polymerization. After 2 h, the reaction mixture was cooled to
room temperature and poured into 200 mL of stirred MeOH.
After the mixture was stirred for 12 h, an oil had separated
out on the bottom. The solvent was decanted and the residual
oil dissolved in hexane. This solution was filtered through a
pad of silica gel with additional hexane, and the solvent was
removed in vacuo to yield polymer.
P r oced u r e for 1-Hexen e Oligom er iza tion . A flame-dried
Schlenk tube was charged with 1 mL of degassed 1-hexene
and 0.5 mL of toluene under argon and heated to the desired
temperature. A solution of catalyst (7.4 µmol) in toluene (0.5
mL) at the same temperature was added to the 1-hexene/
toluene solution via cannula, and the reaction mixture was
stirred for 3 h. The product was isolated by rotary evaporation
and dried overnight on a vacuum line.
Ack n ow led gm en t. We thank the National Science
Foundation (Grant No. CHE0107810) and DuPont for
support of this work. J .C.J . thanks the University of
North Carolina for a Venable Fellowship.
Su p p or tin g In for m a tion Ava ila ble: A table of polym-
erization data with 3b at 40 °C in the presence of phosphine-
scavenging cocatalysts and tables giving X-ray structure and
crystallographic data for the sodium salt 7b. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM030142C