Influence of steric and electronic perturbations on the polymerization activities of α-iminocarboxamide nickel complexes

Article abstract of DOI:10.1021/om8000263

A series of N,O-bound, neutral nickel complexes containing α-iminocarboxamide, η¹-CH₂Ph, and PMe ₃ ligands were synthesized to examine the effect of steric and electronic variations at the site adjacent to the imine functionality. These complexes were subsequently activated with Ni(COD)₂ for use in ethylene homopolymerization and ethylene/norbornene acetate (NBA) copolymerization reactions. As the bulk of the substituents is increased, one observes a progressive decrease in the rate of ring rotation, a more crowded coordination sphere around nickel, increased monomer consumption activity, and higher molecular weights of the products. Copolymerization reactions showed that the increased crowding around nickel decreases the reactivity of NBA relative to ethylene. As electron density is removed from the metal center, the catalytic species become more active toward ethylene and are more prone to interact with the functionality on NBA.

Full text of DOI:10.1021/om8000263

Organometallics 2008, 27, 2273–2280
2273
Influence of Steric and Electronic Perturbations on the
Polymerization Activities of r-Iminocarboxamide Nickel Complexes
Jason D. Azoulay, Koji Itigaki, Guang Wu, and Guillermo C. Bazan*
Mitsubishi Chemical Center for AdVanced Materials, Institute for Polymer and Organic Solids,
Departments of Chemistry & Biochemistry and Materials, UniVersity of California,
Santa Barbara, California 93106
ReceiVed January 10, 2008
A series of N,O-bound, neutral nickel complexes containing R-iminocarboxamide, η1-CH2Ph, and PMe3
ligands were synthesized to examine the effect of steric and electronic variations at the site adjacent to
the imine functionality. These complexes were subsequently activated with Ni(COD)2 for use in ethylene
homopolymerization and ethylene/norbornene acetate (NBA) copolymerization reactions. As the bulk of
the substituents is increased, one observes a progressive decrease in the rate of ring rotation, a more
crowded coordination sphere around nickel, increased monomer consumption activity, and higher molecular
weights of the products. Copolymerization reactions showed that the increased crowding around nickel
decreases the reactivity of NBA relative to ethylene. As electron density is removed from the metal
center, the catalytic species become more active toward ethylene and are more prone to interact with the
functionality on NBA.
Introduction
Polyolefins are commodity materials with major economic
implications. Metal-mediated polymerizations that serve in this
context continue to be an active research area in academic and
industrial laboratories.1 Late transition metal initiators for olefin
polymerization and oligomerization are of particular interest due
to their lower oxophilicity and greater functional group toler-
Figure 1. General structure of R-iminocarboxamidate ligands.
ance, relative to their early transition metal counterparts.2 Nickel-
based catalysts have been shown to participate in chain walking
reactions,3 tolerate polar functionalities,4 and have even been
used in water.5 These catalytic properties are significant for
developing materials with unique properties.1
narrow molecular weight distributions (PDIs) have allowed for
the preparation of complex polymeric architectures. Block
copolymers containing segments of random sequences of
ethylene and NBA with different molar compositions7 show
microphase separation and have the potential to reduce the
interfacial energy between polyolefins and polar plastics. More
recently, tapered tetrablock copolymers,8 composed of alternat-
ing amorphous and semicrystalline block segments, have been
synthesized and possess elastomeric properties.The basic struc-
tural framework of R-iminocarboxamide ligands is shown in
Figure 1. Variations studied thus far incorporate a methyl group
adjacent to the imine functionality. Changes in Ar1 and Ar2
modify the binding preferences to the [Ni(CH2Ph)PMe3] frag-
ment. When the combined steric bulk in Ar1 and Ar2 is
sufficiently large, the N,O-binding mode is observed. Reduction
Activation of [N-(2,6-diisopropylphenyl)-2-(2,6-diisopropy-
lphenylimino)propanimidato-κ2N,O]Ni(η1-CH2Ph)(PMe3), 1, by
Ni(COD)2 generates an active site capable of copolymerizing
ethylene and 5-norbornen-2-yl acetate (NBA) in a quasi-living
fashion.6 The time-dependent growth of Mn and relatively
* Corresponding author. Fax: +1 805 893 4120. Tel: +1 805 893 5538.
E-mail: bazan@chem.ucsb.edu.
(1) (a) Rieger, B.; Baugh, L.; Striegler, S.; Kacker, S. Late Transition
Metal Polymerization Catalysis; John Wiley & Sons: New York, 2003. (b)
Blom, R.; Follestad, A.; Rytter, E.; Tilset, M.; Ystenes, M. Organometallic
Catalysts and Olefin Polymerization: Catalysts for a New Millennium;
Springer-Verlag: Berlin, Germany, 2001. (c) Galli, P.; Vecellio, G. J. Polym.
Sci. Part A: Polym. Chem. 2004, 42, 396. (d) Keim, W.; Kowalt, F. H.;
Goddard, R.; Kruger, C. Angew. Chem., Int. Ed. 1978, 17, 466. (e) Bonnet,
M. C.; Dahan, F.; Ecke, A.; Keim, W.; Schultz, R. P.; Tkatchenko, I. Chem.
Commun. 1994, 615 For relevant reviews see: (f) Ittel, S. D.; Johnson, L. K.;
Brookhart, M. Chem. ReV. 2000, 100, 1169. (g) Boffa, L. S.; Novak, B. M.
Chem. ReV. 2000, 100, 1479. (h) Yanjarappa, M. J.; Sivaram, S. Prog.
Polym. Sci. 2002, 27, 1347. (i) Mecking, S.; Held, A.; Bauers, F. M. Angew.
Chem., Int. Ed. 2002, 41, 544. (j) Gibson, V. C.; Spitzmesser, S. K. Chem.
ReV. 2003, 103, 283. (k) Mecking, S. Coord. Chem. ReV. 2000, 203, 325.
(l) Domski, G. J.; Rose, J. M.; Goates, G. W.; Bolig, A. D.; Brookhart, M.
Prog. Polym. Sci. 2007, 32, 30.
(4) (a) Younkin, T. R.; Conor, E. F.; Henderson, J. I.; Friedrich, S. K.;
Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460. (b) Connor, E. F.;
Younkin, T. R.; Henderson, J. I.; Hwang, S.; Grubbs, R. H.; Roberts, W. P.;
Litzau, J. J. J. Polym. Sci.: Part A: Polym. Chem. 2002, 40, 2842.
(5) (a) Held, A.; Bauers, F. M.; Mecking, S.; Friedrich, S. K Chem.
Commun. 2000, 301. (b) Bauers, F. M.; Mecking, S. Macromolecules 2001,
34, 1165. (c) Korthals, B.; Schnetmann, I. G.; Mecking, S. Organometallics
2007, 26, 1311.
(6) Diamanti, S. J.; Ghosh, P.; Shimizu, F.; Bazan, G. C. Macromolecules
2003, 36, 9731.
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F.; Kramer, E. J.; Fredrickson, G. H.; Bazan, G. C. J. Am. Chem. Soc.
2004, 126, 10528. (b) Diamanti, S. J.; Khanna, V.; Hotta, A.; Coffin, R. C.;
Yamakawa, D.; Kramer, E. J.; Fredrickson, G. H.; Bazan, G. C. Macro-
molecules 2006, 39, 3270.
(2) (a) Johnson, L. K.; Mecking, S.; Brookhart, M. J. Am. Chem. Soc.
1996, 118, 267. (b) Mecking, S.; Johnson, L. K.; Wang, L.; Brookhart, M.
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10.1021/om8000263 CCC: $40.75
2008 American Chemical Society
Publication on Web 04/16/2008

2274 Organometallics, Vol. 27, No. 10, 2008
Azoulay et al.
Scheme 1. Synthetic Approach to Substituted r-Iminocar-
of the steric interference gives rise to complexes that take
advantage of the electronically preferred N,N-binding geometry.
Only N,O-bound complexes give rise to useful catalytic species
in the presence of Ni(COD)2 or to single-component catalysts.9
The preference of “catalytic species” over “initiating species”
has been discussed previously.1l
boxamide Ligandsa
In this contribution, we provide an improved synthetic route
to R-iminocarboxamide ligands, which allows for the incorpora-
tion of substituents that were designed to probe steric and
electronic perturbations at the site adjacent to the imine group,
i.e., replacement of Me in Figure 1. More significantly, we
demonstrate that the resulting complexes provide catalysts with
improved performance in terms of elevated activities and
narrower molecular weight distributions. These reaction features
allow for better control over the final polymer product in both
homopolymerization and copolymerization reactions
a
(a) Triethylamine, toluene (0 °C to RT); (b) 2,6-diisopropylaniline,
triethylamine, toluene, RT; (c) 2,6-diisopropylaniline, TiCl4, triethy-
lamine, toluene, 0-85 °C (depending on substrate).
Results and Discussion
the range δ ) -7.85 to -8.06 ppm for all products, it is possible
to determine that the R-iminocarboxamide fragment is coordi-
nated in an N,O-fashion.13 For comparison, N,N-bound com-
plexes exhibit 31P NMR signals ranging from -20.0 to -25.0
ppm, depending on the ligand framework. These data are
consistent with the formation of [N-(2,6-diisopropylphenyl)-
2-(2,6-diisopropylphenylimino)butanamidato-κ2N,O](η1-CH2Ph)-
(PMe3)nickel (2, R ) Et), [N-(2,6-diisopropylphenyl)-2-(2,6-
diisopropylphenylimino)-4-methylpentanamidato-κ2N,O](η1-
CH2Ph)(PMe3)nickel (3, R ) CH2CHMe2), [N-(2,6-diisopro-
pylphenyl)-2-(2,6-diisopropylphenylimino)-3-methylbutanami-
dato-κ2N,O](η1-CH2Ph)(PMe3)nickel (4, R ) CHMe2), [N-(2,6-
diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-2-phenyle-
thanamidato-κ2N,O](η1-CH2Ph)(PMe3)nickel (5, R ) Ph),
[N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-2-(4-(triflu-
oromethyl)phenyl)ethanamidato-κ2N,O](η1-CH2Ph)(PMe3)-
nickel(6,R)p-CF3-Ph),and[N-(2,6-diisopropylphenyl)-2-(2,6-diiso-
propylphenylimino)-2-(4-methoxyphenyl)ethanamidato-
κ2N,O](η1-CH2Ph)(PMe3)nickel (7, R ) p-OCH3-Ph). The
presence of a trifluoromethyl substituent in compound 6 was
verified by a singlet (δ ) -0.26 ppm) in the 19F NMR spectrum.
The compositions of 2–7 were verified by elemental analysis.
Figure 2 highlights the 1H NMR spectra at room temperature
of compounds 1–4 in the 0.4 to 1.8 ppm range. This series can
be used to probe steric effects on the properties of the
complexes. Of particular interest in Figure 2 are the methyl
signals arising from the isopropyl groups on the aryl ring bound
to the carboxamide nitrogen, i.e., Ar1 in Figure 1.9,13 For all
spectra, the isopropyl groups on Ar2 provide for two doublets;
they do not average by rotation of the aryl ring within the time
scale of the NMR experiment. In the case of 1, a broad doublet
is observed, centered around δ ) 1.58 ppm. For 2, the signal
broadens, and in the case of 3, two broad signals at δ )
1.77–1.62 ppm and δ ) 1.62–1.54 ppm are observed. The
spectrum of 4 shows two resolved doublets at δ )1.73 ppm
and δ ) 1.63 ppm. These data are consistent with a progressive
decrease in the rate of ring rotation with increasing size at the
R position. This trend also implies that CHMe2 is bulkier than
CH2CHMe2. For completeness, we point out that compounds
5–7, which incorporate differences in both the steric and
Synthesis and Characterization of r-Iminocarboxamide
Nickel Complexes. The synthesis of R-iminocarboxamide
ligands typically begins by the reaction of pyruvic acid, or the
corresponding sodium salt, with oxalyl chloride, to generate the
acid chloride in situ. Reaction with anilines at the acid chloride
site is promoted by the addition of an equivalent of triethy-
lamine. 2,6-Diisopropylaryl substituents were of interest due
to their known stabilization of reactive nickel centers and
tendency to increase the molecular weight of the polyethylene
product.10 The condensation of a second equivalent of 2,6-
diisopropylaniline typically takes place by heating in the
presence of catalytic acid. Using this approach, one obtains
conversions of >95% and ∼70% when R ) Et and CH2CHMe2,
respectively, and fails in the presence of other, more hindered
substrates. A new synthetic procedure thus had to be established
to systematically evaluate variations in the backbone size.
An improved method for the condensation of anilines with
11
pyruvamides was found that utilizes TiCl4 and triethylamine
in toluene and provides the desired R-iminocarboxamide ligands
in >90% conversion. In this reaction, a solution of TiCl4 is
added to a solution of 2,6-diisopropylaniline and excess tri-
ethylamine at low temperature. The pyruvamide is subsequently
added and the reaction mixture is allowed to stir and warm to
room temperature. Reaction times are substrate dependent. The
overall process is illustrated in Scheme 1. Conversions of >95%
were obtained when R ) Et, CH2CHMe2, Ph, p-CF3-Ph, and
p-OCH3-Ph. For the bulkiest substrate, R ) CHMe2, the reaction
mixture required heating to 85 °C, and approximately 90% of
the substrate was converted to the desired product.
Deprotonation using KH in THF provided the potassium salts
of the ligands, which were subsequently reacted with Ni(η1-
CH2Ph)Cl(PMe3)2 in toluene at room temperature for 2.5 h.12
The products of these reactions contain nickel ligated by
R-iminocarboxamide, η1-CH2Ph, and PMe3 ligands as deter-
mined by 1H and 13C NMR spectroscopies. A single isomer is
observed in all cases with respect to the PMe3 orientation relative
to the imine nitrogen. From the 31P NMR signals, which fall in
(9) (a) Rojas, R. S.; Wasilke, J. C.; Wu, G.; Ziller, J. W.; Bazan, G. C.
Organometallics 2005, 24, 5644. (b) Rojas, R. S.; Galland, G. B.; Wu, G.;
Bazan, G. C. Organometallics 2007, 26, 5339.
1
electronic properties of the ligand, exhibit H NMR spectra
similar to the spectrum of compound 2.
Crystallization from pentane at -35 °C provided single
crystals suitable for X-ray diffraction studies of compounds 2–5.
(10) (a) Johnsohn, L. K.; Killian, C. M.; Brookhart, M. J. Am. Chem.
Soc. 1995, 117, 6414. (b) Svedja, S. A.; Johnsohn, L. K.; Brookhart, M.
J. Am. Chem. Soc. 1999, 121, 10634.
(11) Carlson, R.; Larsson, U.; Hansson, L. Acta Chem. Scand. 1992,
46, 1211.
(12) Carmona, E.; Paneque, M.; Poveda, M. L. Polyhedron 1989, 8,
285.
(13) Lee, B. Y.; Bazan, G. C.; Vela, J.; Komon, Z. J.; Bu, X. J. Am.
Chem. Soc. 2001, 123, 5352.

R-Iminocarboxamide Nickel Complexes
Organometallics, Vol. 27, No. 10, 2008 2275
Scheme 2. Synthesis of 2–7 (reactions were carried out in toluene at RT for 2.5 h)
Figure 2. 1H NMR spectra of 1–4 in the 0.4–1.8 ppm range at 25
°C illustrating a progressive decrease in the rate of ring rotation
with increasing size at the R position.
Figure 4. ORTEP drawing of 3 (R ) CH2CHMe2) at the 50%
probability level. Hydrogen atoms are omitted for clarity.
Figure 3. ORTEP drawing of 2 (R ) Et) at the 50% probability
level. Hydrogen atoms are omitted for clarity.
Figure 5. ORTEP drawing of 4 (R ) CHMe2) at the 50%
probability level. Hydrogen atoms are omitted for clarity.
Repeated efforts to obtain suitable crystals were not successful
for 6 and 7. Results from these studies, provided in Figures
3–6, confirm the structures of compounds 2–5 as shown in
Scheme 2. Table 1 provides a summary of the metrical data,
together with previously attained data for compound 1 for
comparison purposes.13 As a result of the increased bulk, the
coordination sphere around nickel is more crowded in 2, 3, and
4, relative to 1. Larger distortions from square-planar geometry
are evident, as shown by the angle between the N(2)-Ni(1)-O(1)
and C(4)-Ni(1)-P(1) planes of 15.8° for 2, 14.5° for 3, and
14.8° for 4, versus 4.3° for 1. Examination of Table 1 shows
other variations in metrical parameters without obvious trends.
The additional steric bulk of the ligand backbone in compound
4 is transmitted throughout the structure in a way that hinders
the rotation of the aryl ring bound to the carboxamide nitrogen
and forces the ring to be more perpendicular relative to the
coordination plane. This structural feature leads to a more
effective blocking of the top and bottom of the square plane
(pseudoaxial sites) by the ortho substituents.14

2276 Organometallics, Vol. 27, No. 10, 2008
Azoulay et al.
Table 1. Selected Bond Distances (Å) and Angles (deg)
1
2
3
4
5
Ni(1)-N(2)
Ni(1)-O(1)
Ni(1)-C(4)
Ni(1)-P(1)
1.975(2)
1.910(2)
1.926(2)
2.1483(8)
1.975(3)
1.929(2)
1.958(3)
2.1535(10)
1.974(3)
1.903(2)
1.946(4)
2.1521(12)
1.984(2)
1.9016(18)
1.951(3)
1.972(3)
1.905(3)
1.945(4)
2.1513(12)
2.1395(10)
N(2)-Ni(1)-P(1)
O(1)-Ni(1)-C(4)
O(1)-Ni(1)-P(1)
N(2)-Ni(1)-O(1)
N(2)-Ni(1)-C(4)
C(4)-Ni(1)-P(1)
C(3)-N(1)-C(1)
C(4)-Ni(1)-P(1)a
169.9(6)
175.53(0)
87.35(5)
82.63(7)
96.27(10)
93.79(8)
116.4(2)
4.3
167.10(9)
168.71(13)
90.43(7)
83.24(10)
96.38(13)
92.01(11)
121.4(3)
166.01(9)
169.21(14)
87.98(8)
82.43(11)
97.55(14)
93.77(12)
116.3(3)
165.01(6)
172.07(11)
89.40(6)
82.56(8)
97.61(10)
92.10(9)
117.6(2)
14.77(15)
170.05(11)
175.45(16)
87.95(9)
82.79(13)
96.75(15)
92.76(12)
118.4(3)
15.78(18)
14.45(20)
5.89(0.21)
a Relative to N(2)-Ni(1)-O(1) plane.
Comparison of entries 1–5 (Table 2) reveals an increase in
monomer consumption activity as the bulk on the ligand
framework increases, i.e., 1 < 2 ∼ 5 < 3 < 4. A greater than
2-fold increase in activity is observed when the isopropyl
derivative 4 is compared to the parent methyl species 1. The
Mn of the polymer products also increases proportionally with
the increase in activity. Compound 4 exhibits the lowest
molecular weight distribution (PDI ∼1.2) when compared to
the other alkyl variants. The melting point of the polyethylene
obtained is similar in all cases.
In the case of 5, the activity and molecular weight observed
are higher than those obtained with the parent species 1. As
shown in entries 5–7 of Table 2, the molecular weight and
activity are higher for compound 6 and lower for 7 relative to
5. This trend suggests that as electron density is removed from
the metal center, the catalytic species becomes more active in
ethylene polymerization reactions (i.e., reactivity: 6 > 5 > 7).
Polyethylene made with compounds 5–7 exhibit the narrowest
polydispersities, between 1.1 and 1.2 in all cases. No discernible
differences in the melting points of the polymer products were
observed for compounds 5-7.
Figure 6. ORTEP drawing of 5 (R ) Ph) at the 50% probability
level showing both orientations of the phenyl ring on the benzyl
ligand. Hydrogen atoms are omitted for clarity.
Copolymerizations of ethylene and NBA were carried out
using 20 µmoL of catalyst precursor and 50 µmoL of Ni(COD)2
in a 0.15 M solution of NBA in 30 mL of toluene, as shown in
Scheme 4. Ethylene was introduced and maintained at 100 psi
and the reaction temperature was held at 20 °C. Examination
of the products by 1H NMR spectroscopy shows 1–13% molar
NBA incorporation within the polyethylene backbone.
The ORTEP drawing of 5 is shown in Figure 6. Refined
occupancy indicates that the disordered phenyl ring of the benzyl
ligand is equally located in two orientations (49.7(3)%:
50.3(3)%). Compound 5 exhibits a smaller distortion from
square-planar geometry with an N(2)-Ni(1)-P(1) angle of
170.05(11)° and an O(1)-Ni(1)-C(4) angle of 175.45(16)°.
Bond angles and distances are in close agreement with those
of 1. The position of the phenyl substituent on the ligand
backbone results in a less perpendicular arrangement between
the square plane on Ni and the imine and carboxamide aryl
rings. The result is that the ortho substituents are rotated away
from the pseudoaxial sites, at least in the solid state.
Reactivity in Homopolymerization and Copolymeriza-
tion Reactions. A series of ethylene homopolymerization and
copolymerization reactions were carried out with the intent of
examining how structural and electronic variations influence
reactivity, and the results are summarized in Table 2. Ethylene
homopolymerization reactions were performed using 10 µmoL
of 1–7 and 25 µmoL of Ni(COD)2 activator,15 as illustrated in
Scheme 3. Polymerizations were carried out using a 100 mL
autoclave reactor in 30 mL of toluene at an ethylene pressure
of 100 psi. The temperature was maintained at 20 °C over the
course of the reaction.
Focusing on compounds 1–5 (entries 8–13 in Table 2), one
observes a trend in the rate of polymer production similar to
that previously discussed for ethylene homopolymerizations.
Compounds 1 and 2 exhibit roughly the same reactivity in
copolymerization reactions in terms of activity and comonomer
incorporation. Compound 3 stands out, as it leads to simulta-
neous high levels of activity and NBA enchainment with slightly
broadened molecular weight distributions (entries 10 and 11).
When compared to the parent compound 1, similar copolymers
are obtained in approximately half the time when using 3 (entry
10). Entry 11 shows that increasing the reaction time yields
polymers with higher molecular weights and a decrease in the
total comonomer content. The latter feature was previously used
for the synthesis of tapered copolymer structures and reflects
the fact that the monomer concentration is depleted as it becomes
incorporated into the growing polymer chain.7 When using 4
(entry 12), the NBA incorporation is substantially reduced
compared to the other initiators. It is likely that the increased
crowding around nickel substantially decreases the reactivity
of the bulkier NBA, relative to ethylene.16
(14) Schleis, T.; Spaniol, T.; Okuda, J.; Heinemann, J.; Mulhaupt, R. J.
Organomet. Chem. 1998, 569, 159.
Copolymers made with 5 exhibit lower levels of incorporation
than 1–3; however, the molecular weight distribution remains
(15) See ref 6; the [Ni(COD)2/[Ni-R-iminocarboxamide] ratio of 2.5 was
determined in a previous study.

R-Iminocarboxamide Nickel Complexes
Organometallics, Vol. 27, No. 10, 2008 2277
Table 2. Summary of Polymerization Reactions with 1–7
activity
[kg P/(mol Ni)(h)]
entry
precursor
comonomer
time [min]
Mn [×103]
PDI
% inc.
Tm [°C]
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
1
2
3
3
4
5
6
7
20
20
20
20
20
20
20
30
30
15
30
30
30
30
30
220
255
420
534
259
280
180
109
105
177
176
243
141
104
157
80
86
1.3
1.3
1.4
1.2
1.2
1.1
1.2
1.4
1.3
1.5
1.6
1.3
1.2
1.3
1.3
127
127
129
128
127
127
126
62
57
76
96
118
68
121
182
102
113
91
68
65
63
97
NBA
NBA
NBA
NBA
NBA
NBA
NBA
NBA
13
13
12
7
1
7
9
10
11
12
13
14
15
186
92
75
7
5
68
72
83
Scheme 3. Polymerization of Ethylene Using 1–7 and
Ni(COD)2 as the Activator
quasi-living polymerization characteristics facilitates the syn-
thesis of polymers with unique properties and allows for the
synthesis of more complex architectures. R-Iminocarboxamide
ligands with sterically demanding alkyl substituents or aryl
groups with different electronic properties at the site adjacent
to the imine nitrogen can now be generated in a straightforward
manner from the corresponding pyruvic acids via a method that
utilizes TiCl4. This methodology affords previously unattainable
R-iminocarboxamide ligands that allow for an evaluation of how
steric and electronic perturbations at the site adjacent to the
imine functionality influence polymerization reactions.
Ethylene homopolymerization reactions show that as the bulk
on the ligand framework increases, so does the monomer
consumption activity and the molecular weight of the products,
i.e., 1 < 2 < 3 < 4. Additionally, as electron density is removed
from the metal center, the catalytic species becomes more active
in ethylene polymerization reactions. Copolymerizations with
NBA illustrate that as the bulk on the backbone is increased,
the reactivity of NBA relative to ethylene decreases. Compound
3, however, exhibits high levels of activity and NBA enchain-
ment, while compound 5 exhibits the most narrow molecular
weight distribution in copolymerization reactions.
Scheme 4. Copolymerization of Ethylene and NBA Using 1–
7 and Ni(COD)2 as the Activator
Experimental Section
General Remarks. All manipulations were performed under an
inert atmosphere using standard glovebox and Schlenk-line tech-
niques. Toluene and THF were distilled from sodium benzophenone
ketyl, and pentane was distilled from Na/K alloy. The toluene for
reactions with ethylene use was purchased from Aldrich (anhydrous
grade) and further dried over Na/K alloy. 5-Norbornen-2-yl acetate
was vacuum-distilled before use. Ethylene (99.99%) was purchased
from Matheson Trigas and purified by passing through Agilent
moisture and oxygen traps. Reagents, unless otherwise specified,
were purchased from Aldrich and used without further purification.
2-Oxo-2-(4-(trifluoromethyl)phenyl)acetic acid and 2-(4-methox-
yphenyl)-2-oxoacetic acid were purchased from Hansa Fine Chemi-
cals and used as received. NMR spectra were obtained using Varian
400 and 500 spectrometers. 1H and 13C NMR spectra were
calibrated using signals from the solvent. 31P NMR and 19F NMR
spectra were calibrated and reported downfield from an external
H3PO4 standard and R,R,R-trifluorotoluene in [d6]-benzene respec-
tively. Polymerization activities were calculated from the mass of
the product obtained. Polymers were characterized by GPC analysis,
relative to polystyrene standards, at 135 °C in o-dichlorobenzene
(in a Polymer Laboratories, high-temperature chromatograph, Pl-
GPC 200). Polymer melting points were measured on a TA
Instruments differential scanning calorimeter (model DSC 2920)
at a rate of 10 °C/min for three cycles using a temperature range
low over the course of the reaction (PDI ∼1.2). Compound 6
exhibits the lowest overall activity in copolymerization reactions.
When compared to 5, this suggests that the more electron-
deficient metal center interacts with the acetate functionality,
potentially along the endo face of the comonomer, making
enchainment less facile.17 Compound 7 exhibits the highest
activity relative to 5 and 6; however, monomer incorporation
is reduced.
Conclusions
The ability of R-iminocarboxamide nickel complexes to
copolymerize functionalized norbornenes with ethylene under
(16) Benedikt, G. M.; Elce, E.; Goodall, B. L.; Kalamarides, H. A.;
McIntosh, L. H.; Rhodes, L. F.; Selvy, K. T.; Andes, C.; Oyler, K.; Sen,
A. Macromolecules 2002, 35, 8978.
(17) Hennis, A. D.; Polly, J. D.; Long, G. S.; Sen, A.; Yandulov, D.;
Lipian, D.; Benedikt, G. M.; Rhodes, L. F.; Huffman, J. Organometallics
2001, 20, 2802.

2278 Organometallics, Vol. 27, No. 10, 2008
Azoulay et al.
Table 3. Crystal Data and Structure Refinement for Compounds 2–5
2
3
4
5
empirical formula
fw
C38 H55 N2 NiOP
645.52
C40 H59 N2NiOP
673.57
C39 H57 N2NiOP
659.55
C42H55 N2 NiOP
693.56
temp (K)
150(2)
140(2)
150(2)
150(2)
wavelength (Å)
cryst syst
space group
unit-cell dimens (Å, deg)
0.71073
monoclinic
P21/n
a ) 10.1616(14)
b )36.813(5)
c ) 20.361(3)
R ) 90
0.71073
monoclinic
P21/c
a ) 10.2237(16)
b ) 21.053(3)
c ) 18.063(3)
R ) 90
0.71073
monoclinic
P21/c
a ) 9.716(3)
b ) 20.040(7)
c ) 19.496(6)
R ) 90
0.71073
monoclinic
P21/n
a ) 9.9429(7)
b ) 25.4501(19)
c ) 15.2227(11)
R ) 90
ꢀ ) 92.918(2)
γ ) 90
7606.6(18)
8
1.127
0.581
ꢀ ) 96.135(3)
γ ) 90
3865.7(11)
4
1.157
0.574
ꢀ )100.578(5)
γ ) 90
ꢀ ) 93.662(2)
γ ) 90
volume (Å3)
3732(2)
3844.2(5)
Z
4
4
density (calcd) Mg/m3
1.174
0.593
1424
0.3x 0.2 × 0.2
1.47 to 27.54
-11 e h e 12
-25 e k e 24
-25 e l e 25
28 366
1.198
0.579
1488
0.2x 0.15x 0.15
2.09 to 26.37
-12 e h e 12
-31 e k e 31
-19 e l e 19
31 209
absorp coeff (mm-1
F(000)
)
2784
1456
cryst size (mm3)
θ range (deg)
index ranges
0.35 × 0.3 × 0.1
1.11 to 26.67
-12 e h e 12
-45 e k e 46
-25 e l e 24
60 496
0.2x 0.16x 0.08
1.49 to 26.43
-12 e h e 11
-26 e k e 26
-22 e l e 22
30 577
no. of reflns collected
no. of indep reflns
15 412 [R(int) ) 0.0754]
7787 [R(int) ) 0.1071]
7841 [R(int) ) 0.0506]
7759 [R(int) ) 0.0695]
completeness to the respective θ
no. of data/restraints/params
goodness-of-fit on F2
96.0
97.8
91.1
98.6
15 412/ 6/831
0.897
7787/5/439
0.832
7841/0/430
0.871
7759/12/435
1.451
final R indices [I > 2σ(I)]a
R indices (all data)
R1 ) 0.0586, wR2 ) 0.1296 R1 ) 0.0548, wR2 ) 0.1066 R1 ) 0.0492, wR2 ) 0.1120 R1 ) 0.0682, wR2 ) 0.1465
R1 ) 0.1153, wR2 ) 0.1551 R1 ) 0.1340, wR2 ) 0.1277 R1 ) 0.0810, wR2 ) 0.1194 R1 ) 0.1315, wR2 ) 0.1573
largest diff peak and hole (e Å-3
)
1.019 and -0.475
0.511 and -0.331
1.233 and -0.268
1.057 and -0.360
2
2 2
2
2 2
a Definitions: R1 ) ∑|Fo| - |Fc|]/∑|Fo|, wR2 ) [∑(Fo - Fc ) ]/∑[w(Fo2)2]]1/2, GOF ) [∑[w(Fo - Fc ) ]/(n - p)]1/2, where n is the number of
reflections and p is the total number of refined parameters. * min./max.
1
of 0–180 °C. H NMR spectra of the polymers were obtained in
1,1,2,2-tetrachloroethane-d2 at 115 °C. Elemental analyses were
performed by Analytic Laboratory, Marine Science Institute,
University of California, Santa Barbara. Gas chromatography/mass
spectroscopy was carried out on a Shimadzu GC-17A gas chro-
matograph and Shimadzu GCMS-QP5000 gas chromatograph–mass
spectrometer.
dropwise over a period of 5 min to give a deep red solution, which
was allowed to stir for an additional 10 min. A chilled solution of
N-(2,6-diisopropylphenyl)-2-oxo-2-phenylethanamide in 10 mL of
toluene (1.00 g, 3.23 mmol) was added at once. The solution was
vigorously stirred, allowed to warm to room temperature, and stirred
overnight. Subsequently, 250 mL of diethyl ether was added, and
the resulting suspension was stirred overnight open to air. The
suspension was filtered through a silica plug, and removal of the
solvent gave 1.39 g (2.97 mmol) of the desired product (92.0%).
1H NMR (399.95 MHz, [d1]-chloroform, 298 K): δ 9.22 (br, 1 H,
N-H), 7.35 (t, 3JHH ) 7.1 Hz, 1 H, ph-H), 7.30–7.21 (m, 7 H, ph-
X-ray Crystallography. The monocrystal was mounted on a
glass fiber and transferred to a Bruker CCD platform diffractometer.
The SMART18 program package was used to determine the unit-
cell parameters and for data collection (25 s/frame scan time for a
sphere of diffraction data). The raw frame data were processed
using SAINT19 and SADABS20 to yield the reflection data file.
Subsequent calculations were carried out using the SHELXTL21
program. The structure was solved by direct methods and refined
on F2 by full-matrix least-squares techniques. Analytical scat-
tering factors for neutral atoms were used throughout the
analysis.22 Hydrogen atoms were located from a difference
Fourier map and refined (x,y,z and Uiso).23 Single crystals of
2–5 suitable for X-ray diffraction studies were obtained by slow
crystallization from pentane. The crystal data and refinement
are summarized in Table 3.
Synthesis and Characterization of Compounds. Typical
Reaction Using TiCl4. Included here are representative procedures.
Complete details are available in the Supporting Information.
N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
2-phenylethanamide. In the glovebox, a dry solution of 2,6-
diisopropylaniline (572 mg, 3.23 mmol) and triethylamine (2.94 g,
29.1 mmol) in toluene (90 mL) was chilled to -35 °C. Titanium
tetrachloride (673 mg, 3.55 mmol) in 10 mL of toluene was added
3
H), 7.10 (m, 3 H, ph-H), 3.26 (septet, JHH ) 6.8 Hz, 2 H, iPr-
3
3
CH), 2.80 (septet, JHH ) 6.8 Hz, 2 H, iPr-CH), 1.30 (d, JHH
)
3
6.8 Hz, 12 H, iPr-CH3), 1.18 (d, JHH ) 6.8 Hz, 6 H, iPr-CH3),
0.93 (d, JHH ) 6.8 Hz, 6 H, iPr-CH3). 13C NMR (125.7 MHz,
3
[d1]-chloroform, 298 K): 162.64, 159.94 (carbonyl and imine),
145.95, 143.67, 135.24, 131.38, 130.14, 129.84, 128.29, 127.68,
124.80, 123.49, 123.19 (ph-C), 29.19, 28.67 (iPr-CH), 23.70, 23.52,
21.82 (iPr-CH3). Anal. Calcd (C32H40N2O): C, 82.01; H, 8.60; N,
5.98. Found: C, 81.83; H, 8.55; N, 5.97.
N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
3-methylbutanamide. In the glovebox, a dry solution of 2,6-
diisopropylaniline (964 mg, 5.45 mmol) and triethylamine (4.95 g,
49.0 mmol) in toluene (100 mL) was chilled to -35 °C. Titanium
tetrachloride (1.03 g, 5.45 mmol) in 10 mL of toluene was added
dropwise over a period of 5 min to give a deep red solution, which
was allowed to stir for an additional 10 min. A chilled solution of
N-(2,6-diisopropylphenyl)-3-methyl-2-oxo-2-butanamide in 25 mL
of toluene (1.5 g, 5.45 mmol) was added at once. The solution was
heated, under nitrogen, to 85 °C and allowed to stir overnight. The
solution was opened to the atmosphere, allowed to cool, and added
to 250 mL of diethyl ether. Stirring overnight gave a yellow
suspension. Filtration through Celite followed by column chroma-
tography on silica gel using hexane and ether (v/v, 4:1) gave 1.68 g
(18) SMART Software Users Guide, Version 5.1; Bruker Analytical
X-Ray Systems, Inc.; Madison, WI1999.
(19) SAINT Software Users Guide, Version 6.0; Bruker Analytical X-Ray
Systems, Inc.: Madison, WI, 1999.
(20) Sheldrick, G. M. SADABS, Version 2.05; Bruker Analytical X-Ray
Systems, Inc.: Madison, WI, 2001.
(21) Sheldrick, G. M. SHELXTL Version 6.12; Bruker Analytical X-Ray
Systems, Inc.: Madison, WI, 2001.
(22) International Tables for X-Ray Crystallography; Kluwer Academic
Publishers: Dordrecht, 1992; Vol. C.
(23) Flack, H. D. Acta Crystallogr. 1983, A39, 876.

R-Iminocarboxamide Nickel Complexes
Organometallics, Vol. 27, No. 10, 2008 2279
1
of the product (71.0%). H NMR (399.95 MHz, [d1]-chloroform,
[N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
3-methylbutanamidato-K2N,O](η1-CH2Ph)(PMe3)nickel (4). Po-
tassium N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
3-methylbutanamidate (100 mg, 0.211 mmol) in toluene was added
to Ni(η1-CH2Ph)Cl(PMe3)2 (71.2 mg, 0.211 mmol), and the mixture
was stirred for 2.5 h at room temperature. The suspension was
filtered, and all volatiles were removed under vacuum to give a
red solid. Successive recrystallizations from pentane at -35 °C
overnight gave the product as an orange solid (114.2 mg, 0.182
mmol, 86.0% yield). Single crystals for X-ray crystallography were
grown by slow recrystallization from pentane at -35 °C. 1H NMR
(399.95 MHz, [d6]-benzene, 298 K): δ 7.74 – 7.68 (m, 2 H, ph-H),
7.41 (d, 3JHH ) 7.7 Hz, 2 H, ph-H), 7.31–7.27 (m, 3JHH ) 8.0 Hz,
2 H, ph-H), 7.14–7.06 (m, 5 H, ph-H), 3.66 – 3.56 (m, 4 H, iPr-
3
298 K): δ 8.90 (br, 1 H, N-H), 7.30 (t, JHH ) 8.0 Hz, 1 H, ph-
H4), 7.26 (d, JHH ) 8.6 Hz, 2 H, ph-H3,5), 7.20–7.09 (m, 3 H,
3
3
ph-H), 3.13 (septet, JHH ) 6.8 Hz, 2 H, iPr-CH), 2.72 (septet,
3JHH ) 6.8 Hz, 2 H, iPr-CH), 2.63 (septet, JHH ) 6.8 Hz, 1 H,
3
3
3
iPr-CH), 1.29 (d, JHH ) 6.8 Hz, 6 H, iPr-CH3), 1.28 (d, JHH
)
5.5 Hz, 6 H, iPr-CH3), 1.24 (d, 3JHH ) 6.8 Hz, 6 H, iPr-CH3), 1.15
3
3
(d, JHH ) 6.8 Hz, 6 H, iPr-CH3), 1.10 (t, JHH ) 7.7 Hz, 3 H
CH3). 13C NMR (125.7 MHz, [d1]-chloroform, 298 K): δ 169.16,
161.82 (carbonyl and imine), 145.86 (amide-ph-C), 143.70 (imine-
ph-C), 134.99 (imine-ph-C), 131.23 (amide-ph-C), 128.10 (amide-
ph-C), 124.34 (imine-ph-C), 123.40, 122.92 (ph-C), 31.34, 29.10,
28.34 (iPr-CH), 23.55, 23.42, 21.94, 18.90 (iPr-CH3). Anal. Calcd
(C28H40N2O): C, 80.13; H, 9.74; N, 6.44. Found: C, 79.88; H, 9.80;
N, 6.47.
3
CH), 2.87 (septet, J ) 6.8 Hz, 1 H, iPr-CH), 1.73 (d, JHH ) 6.8,
6H, iPr-CH3), 1.63 (d, 3JHH ) 7.1 Hz, 6 H, iPr-CH3), 1.57 (d, 3JHH
[N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
butanamidato-K2N,O](η1-CH2Ph) (PMe3)nickel (2). Potassium
N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)butana-
midate (100 mg, 0.218 mmol) in toluene was added to Ni(η1-
CH2Ph)Cl(PMe3)2 (73.6 mg, 0.218 mmol), and the mixture was
stirred for 2.5 h at room temperature. The suspension was filtered,
and all volatiles were removed under vacuum to give a red solid.
Crystallization from pentane at -35 °C overnight gave the product
as a dark orange solid (115.5 mg, 0.179 mmol, 82.1% yield). Single
crystals for X-ray crystallography were grown by slow recrystal-
) 6.8 Hz, 6 H, iPr-CH3), 1.54 (d, 3JHH ) 7.06 Hz, 6 H, iPr-CH3),
3
1.37 (d, JHH ) 6.8 Hz, 6 H, iPr-CH3), 1.06 (br s, 2 H, benzyl-
2
CH2), 0.53 (d, JHP ) 10.4, 9 H, PCH3). 13C NMR (125.7 MHz,
[d6]-benzene, 298 K): δ 186.18 (carbonyl), 163.70, 150.95, 147.56,
141.28, 140.09, 138.12, 129.84, 127.20, 124.16, 123.49, 122.43,
122.34 (imine and ph-C), 33.32, 29.34, 28.40 (iPr-CH), 24.85,
1
24.30, 23.91, 23.76, 20.57 (iPr-CH3), 11.84 (d, JCP ) 27 Hz,
2
PCH3), 9.92 (d, JCP ) 31 Hz, CH2Ph). 31P NMR (161.19 MHz,
[d6]-benzene, 298 K, H3PO4): δ -8.00 ppm. Anal. Calcd
(C38H55N2NiOP): C, 71.02; H, 8.71; N, 4.25. Found: C, 70.97; H,
8.59; N, 4.24.
lization from pentane at -35 °C. 1H NMR (399.95 MHz, [d6]-
3
benzene, 298 K): δ 7.69 – 7.67 (m, 2 H, ph-H), 7.42 (d, JHH
)
7.7 Hz, 2 H, ph-H), 7.35 (t, 3JHH ) 8.0 Hz, 1 H, ph-H), 7.19–7.05
[N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
2-phenylethanamidato-K2N,O](η1-CH2Ph)(PMe3)nickel (5). Po-
tassium N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
2-phenylethanamideate (272 mg, 0.537 mmol) was added to Ni(η1-
CH2Ph)Cl(PMe3)2 (178.6 mg, 0.529 mmol), and the mixture was
stirred for 2.5 h at room temperature. The suspension was filtered,
and all volatiles were removed under vacuum to give a red solid.
Crystallization from pentane at -35 °C overnight gave the product
(227.5 mg, 0.328 mmol) as a dark red crystalline solid in 61.1%
yield. Single crystals for X-ray crystallography were grown by slow
recrystallization from pentane at -35 °C. 1H NMR (399.95 MHz,
3
(m, 6 H, ph-H), 3.72 (septet, JHH ) 6.8 Hz, 2 H, iPr-CH), 3.64
3
3
(septet, JHH ) 6.8 Hz, 2 H, iPr-CH), 2.67 (quartet, JHH ) 7.4
Hz, 2 H, Et-CH2), 1.60 (br, 12 H, iPr-CH3), 1.50 (d, 3JHH ) 7.4, 3
3
3
H, CH3), 1.48 (d, JHH ) 6.5 Hz, 6 H, iPr-CH3), 1.30 (d, JHH
)
7.1 Hz, 6 H, iPr-CH3), 1.14 (br s, 2 H, benzyl-CH2), 0.55 (d, 2JHP
) 10.4, 9 H, PCH3). 13C NMR (125.7 MHz, [d6]-benzene, 298 K):
δ 184.79 (carbonyl), 163.94, 150.80, 147.37, 141.03, 140.30,
138.30, 129.81, 127.29, 124.04, 123.53, 122.55, 122.40 (imine and
ph-C), 29.43, 28.64 (iPr-CH), 26.67, 24.37, 24.12 (iPr-CH3), 23.79
1
2
(Et-CH2), 11.94 (d, JCP ) 27 Hz, PCH3) 9.41 (d, JCP ) 31 Hz,
CH2Ph). 31P NMR (161.19 MHz, [d6]-benzene, 298 K, H3PO4): δ
-8.01 ppm. Anal. Calcd (C38H55N2NiOP): C, 70.70; H, 8.59; N,
4.34. Found: C, 70.60; H, 8.54; N, 4.32.
3
[d6]-benzene, 298 K): δ 7.80– 7.75 (m, 4 H, ph-H), 7.43 (d, JHH
) 7.4 Hz, 2 H, ph-H), 7.33–7.30 (m, 2 H, ph-H), 7.23–7.02 (m, 8
H, ph-H), 4.19 (septet, 3JHH ) 6.8 Hz, 2 H, iPr-CH), 3.59 (septet,
3JHH ) 6.8 Hz, 2 H, iPr-CH), 1.74–1.53 (br, 12 H, iPr-CH3), 1.49
(d, 3JHH ) 6.8, 6 H, CH3), 1.25 (s, 2 H, benzyl-CH2), 1.10 (d, 3JHH
[N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
4-methylpentanamidato-K2N,O](η1-CH2Ph)(PMe3)nickel (3). Po-
tassium N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
4-methylpentanamidate (180.7 mg, 0.371 mmol) was added to
Ni(η1-CH2Ph)Cl(PMe3)2 (125.2 mg, 0.371 mol), and the mixture
was stirred for 2.5 h at room temperature. The suspension was
filtered, and all volatiles were removed under vacuum to give a
red solid. Crystallization from pentane at -35 °C overnight gave
the product as a dark orange solid (225.7 mg, 0.335 mmol) in 90.3%
yield. Single crystals for X-ray crystallography were grown by slow
crystallization from pentane. 1H NMR (399.95 MHz, [d6]-benzene,
298 K): δ 7.77–7.75 (m, 2 H, ph-H), 7.42 (d, 3JHH ) 7.4 Hz, 2 H,
ph-H), 7.31–7.05 (m, 7 H, ph-H), 3.78–3.64 (m, 4 H, iPr-CH),
2.92–2.82 (m, 3 H, iBut-CH), 1.77–1.62 (br s, 6H,iPr-CH3),
2
) 6.8 Hz, 6 H, iPr-CH3), 0.64 (d, JHP ) 10.1 Hz, 9 H, PCH3).
13C NMR (125.7 MHz, [d6]-benzene, 298 K): δ 176.44 (carbonyl),
165.46, 150.71, 147.80, 141.06, 140.34, 137.79, 134.08, 130.69,
129.86, 129.78, 127.89, 127.50, 127.23, 124.10, 123.53, 122.49,
122.37 (imine and ph-C), 29.43, 29.10 (iPr-CH), 24.58, 23.73, 23.49
(iPr-CH3), 11.94 (d, 1JCP ) 27 Hz, PCH3), 10.03 (d, 2JCP ) 27 Hz,
CH2Ph). 31P NMR (161.19 MHz, [d6]-benzene, 298 K, H3PO4): δ
-8.03 ppm. Anal. Calcd (C42H55N2NiOP): C, 72.73; H, 7.99; N,
4.04. Found: C 72.56; H, 7.90; N, 3.99.
[N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
2-(4-(trifluoromethyl)phenyl)acetamidato-K2N,O](η1-CH2Ph)-
(PMe3)nickel (6). Potassium N-(2,6-diisopropylphenyl)-2-(2,6-
diisopropylphenylimino)-2-(4-(trifluoromethyl)phenyl)acetami-
date (100 mg, 0.174 mmol) was added to Ni(η1-CH2Ph)Cl(PMe3)2
(58.7 mg, 0.174 mmol), and the mixture was stirred for 2.5 h at
room temperature. The suspension was filtered, and all volatiles
were removed under vacuum to give a red solid. Crystallization
from pentane at -35 °C overnight gave the product (109 mg, 0.143
mmol) as a dark red crystalline solid in 82.2% yield. 1H NMR
(399.95 MHz, [d6]-benzene, 298 K): δ 7.62– 7.60 (m, 4 H, ph-H),
3
1.62–1.54 (br s, 6 H, iPr-CH3), 1.53 (d, JHH ) 6.8 Hz, 6 H, iPr-
3
3
CH3), 1.41 (d, JHH ) 6.8, 6 H, iPr-CH3), 1.10 (br d, JHH ) 3.4
3
Hz, 2 H, benzyl-CH2), 1.06 (d, JHH ) 6.5, 6 H, iBut-CH3), 0.52
(d, 2JHP ) 10.1, 9 H, PCH3). 13C NMR (125.7 MHz, [d6]-benzene,
298 K): δ 184.24 (carbonyl), 164.97, 150.65, 147.47, 140.94,
140.30, 138.39, 129.96, 127.47, 124.22, 123.62, 122.55, 122.43,
41.57 (imine and ph-C), 29.46, 28.61 (iPr-CH), 27.22, 25.15, 24.06
(iPr-CH3), 23.79, 23.182 (iBut-CH2 and CH3), 11.82 (d, 1JCP ) 27
Hz, PCH3) 9.65 (d, 2JCP ) 31 Hz, CH2Ph). 31P NMR (161.19 MHz,
[d6]-benzene, 298 K, H3PO4): δ -7.85 ppm. Anal. Calcd
(C40H59N2NiOP): C, 71.32; H, 8.83; N, 4.16. Found: C, 71.15; H,
8.63; N, 4.15.
3
7.27 (d, JHH ) 7.4 Hz, 2 H, ph-H), 7.18–7.13 (m, 3 H, ph-H),
3
7.04–6.93 (m, 6 H, ph-H), 3.95 (septet, JHH ) 6.8 Hz, 2 H, iPr-
CH), 3.38 (septet, 3JHH ) 7.1 Hz, 2 H, iPr-CH), 1.60–1.36 (br, 12
H, iPr-CH3), 1.31 (d, 3JHH ) 6.8, 6 H, CH3), 1.08 (s, 2 H, benzyl-

2280 Organometallics, Vol. 27, No. 10, 2008
Azoulay et al.
CH2), 0.88 (d, 3JHH ) 7.1 Hz, 6 H, iPr-CH3), 0.48 (d, 2JHP ) 10.4
Hz, 9 H, PCH3). 13C NMR (125.7 MHz, [d6]-benzene, 298 K): δ
175.08 (carbonyl), 165.12, 150.29, 147.34, 140.52, 140.12, 137.73,
137.36, 130.87, 129.72, 127.89, 124.25, 123.71, 122.77, 122.46
(imine and ph-C), 29.46, 29.04 (iPr-CH), 24.55, 23.70, 23.27 (iPr-
CH3), 11.89 (d, JCP ) 24 Hz, PCH3), 10.03 (d, JCP ) 27 Hz,
CH2Ph). 31P NMR (161.19 MHz, [d6]-benzene, 298 K, H3PO4): δ
-8.05 ppm. 19F NMR (161.19 MHz, [d6]-benzene, 298 K, R,R,R-
trifluorotoluene): δ -0.26 ppm. Anal. Calcd (C43H54F3N2NiOP):
C, 67.82; H, 7.15; N, 3.68. Found: C, 67.38; H, 7.09; N, 3.69.
Calcd (C43H57N2NiOP): C, 71.37; H, 7.94; N, 3.87. Found: C, 70.80;
H, 7.82; N, 3.87.
Typical Reaction with Ethylene. Polymerizations were con-
ducted in the following manner using the initiators 1–7. An
autoclave reactor (100 mL) was loaded inside a glovebox with an
appropriate amount (10 µmol) of the R-iminocarboxamide complex
and (25 µmol) Ni(COD)2 and toluene, such that the final volume
of the toluene solution was 30 mL. The reactor was sealed inside
the glovebox and attached to an ethylene line. Ethylene was fed
into the reactor continuously at 100 psi, and the pressurized reaction
mixture was stirred at 20 °C. Ethylene was vented after 20 min,
and acetone was added to quench the polymerization. The precipi-
tated polymer was collected by filtration and dried under high
vacuum overnight.
Typical Reaction with Ethylene and 5-Norbornen-2-yl
acetate (NBA). An autoclave reactor (100 mL) was loaded inside
a glovebox with an R-iminocarboxamide complex (20 µmol) and
Ni(COD)2 (50 µmol), 5-norbornen-2-yl acetate (4.50 mmol), and
toluene, such that the final volume of the toluene solution was 30
mL. The reactor was sealed inside the glovebox and attached to an
ethylene line. Ethylene was fed into the reactor continuously at
100 psi, and the pressurized reaction mixture was stirred at 20 °C.
Ethylene was vented after a specified amount of time, and acetone
added to quench the polymerization. The precipitated polymer was
collected by filtration and dried under high vacuum overnight.
1
2
N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-
2-(4-(methoxyphenyl)acetamidato-K2N,O](η1-CH2Ph)-
(PMe3)nickel (7). Potassium N-(2,6-diisopropylphenyl)-2-(2,6-
diisopropylphenylimino)-2-(4-(methoxyphenyl)acetamidate (100 mg,
0.186 mmol) was added to Ni(η1-CH2Ph)Cl(PMe3)2 (62.8 mg, 0.186
mmol), and the mixture was stirred for 2.5 h at room temperature.
The suspension was filtered, and all volatiles were removed under
vacuum to give a red solid. Crystallization from pentane at -35
°C over the course of two days gave the product (106 mg, 0.146
mmol) as a dark red solid in 78.8% yield. 1H NMR (399.95 MHz,
3
[d6]-benzene, 298 K): δ 7.78 (d, JHH ) 8.9 Hz, 2 H, ph-H), 7.72
(d, 3JHH ) 7.7 Hz, 2 H, ph-H), 7.40 (d, 3JHH ) 7.7 Hz, 2 H, ph-H),
7.30–7.26 (m, 2 H, ph-H), 7.22–7.05 (m, 5 H, ph-H), 6.68 (d, 3JHH
3
) 8.9 Hz, 2 H, ph-H), 4.18 (septet, JHH ) 6.8 Hz, 2 H, iPr-CH),
3
3.60 (septet, JHH ) 6.8 Hz, 2 H, iPr-CH), 1.72–1.57 (br, 6 H,
3
Acknowledgment. This work was funded through the
Mitsubishi Chemical Center for Advanced Materials and the
Department of Energy. The authors are grateful to Prof. Rene
S. Rojas and Dr. Jacek Brzezinski for useful discussions.
iPr-CH3), 1.46 (d, JHH ) 6.8, 12 H, CH3), 1.21 (s, 2 H, benzyl-
CH2), 1.12 (d, 3JHH ) 7.1 Hz, 6 H, iPr-CH3), 0.61 (d, 2JHP ) 10.4
Hz, 9 H, PCH3). 13C NMR (125.7 MHz, [d6]-benzene, 298 K): δ
175.65 (carbonyl), 165.73, 161.27, 150.92, 148.01, 141.55, 140.43,
137.87, 133.20, 129.86, 129.81, 129.78, 127.37, 126.98, 126.29,
124.22, 123.46, 122.40, 122.37, 112.78 (imine and ph-C), 54.59,
29.43, 29.10 (iPr-CH), 24.49, 23.82, 23.64, 14.26 (iPr-CH3), 12.00
(d, J ) 27 Hz, PCH3), 10.12 (d, 2JCP ) 34 Hz, CH2Ph). 31P NMR
(161.19 MHz, [d6]-benzene, 298 K, H3PO4): δ -8.06 ppm. Anal.
Supporting Information Available: Complete details for the
synthesis and characterization of all compounds. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM8000263