The formation and polymerization behavior of Ni(II) α-diimine complexes using various aluminum activators

Article abstract of DOI:10.1016/S0022-328X(01)01340-7

Several Ni(II) α-diimine complexes have been synthesized and examined for ethylene and propylene polymerization in combination with different aluminum co-catalysts. The precatalysts used in the study were [ArN=C(Nap)-C(Nap)-C(Nap)=NAr]NiBr₂ (Nap = 1,8-naphthdiyl) (1, Ar = 2,4,6-trimethylphenyl; 2, Ar = 2-^tBu phenyl; 3, Ar = 2-ⁱPr phenyl). These complexes were synthesized via a one-pot reaction where the ligand is formed via an acid catalyzed condensation followed by direct addition of nickel(II) bromide. The complexes were also prepared by a two-step procedure where the ligand was first formed by condensation between the appropriate aniline and acenapthoquinone, and the resulting ligand was then allowed to react with (1,2-dimethoxyethane) nickel(II) dibromide. X-ray structural studies of complexes 1 and 2 have been carried out. Diethylaluminum chloride (DEAC), and 1,3-dichloro-1,3-diisobutyldialuminoxane (DCDAO) show higher activities for ethylene and propylene polymerizations in combination with these Ni(II) α-diimine complexes than does polymethylaluminoxane (MAO). The molecular weight of the resulting polymers as well as their respective polydispersities and T_ms are also presented. The polypropylenes obtained with 1/DEAC and 2/DEAC at 0 °C show similar rr triad percentage as previously reported for polypropylenes generated by MAO activated Ni(II) α-diimine complexes.

Full text of DOI:10.1016/S0022-328X(01)01340-7

Journal of Organometallic Chemistry 645 (2002) 158–167
www.elsevier.com/locate/jorganchem
The formation and polymerization behavior of Ni(II) a-diimine
complexes using various aluminum activators
Richard J. Maldanis, John S. Wood, A. Chandrasekaran, Marvin D. Rausch *,
James C.W. Chien *
Department of Chemistry, Lederle Graduate Research Center, Uni6ersity of Massachusetts, Amherst, MA 01003-4510, USA
Received 9 August 2001; received in revised form 26 September 2001; accepted 1 October 2001
Abstract
Several Ni(II) a-diimine complexes have been synthesized and examined for ethylene and propylene polymerization in
combination with different aluminum co-catalysts. The precatalysts used in the study were [ArNꢀC(Nap)ꢁC(Nap)ꢀNAr]NiBr2
(Nap=1,8-naphthdiyl) (1, Ar=2,4,6-trimethylphenyl; 2, Ar=2-tBu phenyl; 3, Ar=2-iPr phenyl). These complexes were
synthesized via a one-pot reaction where the ligand is formed via an acid catalyzed condensation followed by direct addition of
nickel(II) bromide. The complexes were also prepared by a two-step procedure where the ligand was first formed by condensation
between the appropriate aniline and acenaphthoquinone, and the resulting ligand was then allowed to react with (1,2-
dimethoxyethane) nickel(II) dibromide. X-ray structural studies of complexes 1 and 2 have been carried out. Diethylaluminum
chloride (DEAC), and 1,3-dichloro-1,3-diisobutyldialuminoxane (DCDAO) show higher activities for ethylene and propylene
polymerizations in combination with these Ni(II) a-diimine complexes than does polymethylaluminoxane (MAO). The molecular
weight of the resulting polymers as well as their respective polydispersities and Tms are also presented. The polypropylenes
obtained with 1/DEAC and 2/DEAC at 0 °C show similar rr triad percentage as previously reported for polypropylenes generated
by MAO activated Ni(II) a-diimine complexes. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Nickel; Polypropylene; Polyethylene; Diimine
ride (DEAC) can be used in activating these systems to
promote ethylene polymerizations [5]. Brookhart and
coworkers have demonstrated that DEAC can be used
in combination with these nickel catalyst systems to
promote oligomerization of ethylene with longer chain
lengths than was obtained with MAO [4a]. It was also
shown that trialkylaluminum compounds in combina-
tion with these complexes could polymerize ethylene [6].
However, the uses of late transition metal complexes
for propylene polymerizations are deficient in the litera-
ture [2,7]. Brookhart and coworkers discovered that
living polymerization of propylene could be achieved
when complex 2 was activated with MAO under opti-
mal conditions [4d]. Pellecchia and coworkers have
shown that a Ni(II) a-diimine complex in contact with
MAO can promote syndiospecific propylene polymer-
izations at sub-ambient temperatures [8]. In addition,
McCord et al. have published a detailed study on the
microstructure of the polypropylenes produced with
these nickel systems when activated by MAO [9]. Re-
1. Introduction
Recently, late transition metal complexes have been
shown to be useful in the field of Ziegler–Natta cataly-
sis [1]. In particular, over the past decade cationic
Ni(II) a-diimine complexes have gained considerable
attention in this field [2]. These complexes have been
shown to be primarily useful for ethylene polymeriza-
tions but are also known to promote homo- and co-
polymerizations of polar monomers [3]. Depending on
the steric bulk of the nickel catalyst used, polymers
with various microstructures have been produced [4].
It has also been shown that these Ni(II) a-diimine
complexes can be activated via non-traditional poly-
methylaluminoxane (MAO) type co-catalysts. Kumar
and Sivaram have shown that diethylaluminum chlo-
* Corresponding authors. Tel.: +1-413-545-2291; fax: +1-413-
545-4490.
E-mail address: rausch@chem.umass.edu (M.D. Rausch).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01340-7

R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
159
search continues to explore cationic Ni(II) a-diimine
complexes in an attempt to mimic the dominance
Group IV catalyst systems have shown in the field of
Ziegler–Natta chemistry.
Herein, we report the synthesis and crystal structures
of several Ni(II) a-diimine complexes (1–3). The syn-
thesis of these complexes can be carried out via two
procedures and these are detailed. The complexes have
been examined as catalyst precursors for ethylene and
propylene polymerizations in combination with various
aluminum co-catalysts.
slow layering of the subsequent solution with diethyl
ether. Repeated layering techniques led to dark purple
needles of complexes 1 and 2 suitable for X-ray studies.
Due to the paramagnetic nature of these a-diimine
1
Ni(II) complexes, H-NMR studies were not feasible.
Elemental analysis of complex 2 fits the structure ob-
tained by X-ray structural studies. We were not able to
obtain elemental analysis for the solvated species of
complex 1. However, we were able to achieve an analyt-
ical sample for the anhydrous form of complex 1 by
repeated Et2O–CH2Cl2 recrystallizations, followed by
drying in vacuo for several days. We were also able to
obtain mass spectral data on 1 for the parent ion after
bromine loss. This fragmentation pattern has been
shown to occur for similar nickel systems [4c,8a]. X-ray
structural analysis was not obtainable for complex 3
possibly due to the relative ease of solvent loss and its
open nickel center relative to 1 and 2.
Complexes 1–3 are all air stable complexes but do
require moisture-free solvents during handling. How-
ever, the use of wet glacial acetic acid does not interfere
with the formation of the nickel complex. This suggests
that the resulting complexes are acid-stabilized with
respect to decomposition.
2. Results and discussion
2.1. Synthesis of catalyst precursors
2.1.1. Synthesis of Ni(II) h-diimine complexes 6ia
one-pot reaction
The Ni(II) a-diimine complexes 1–3 investigated in
this study were synthesized via a modification of a
procedure described by Matei and Lixandru [10]. Ace-
naphthoquinone and the respective aniline were heated
at reflux in glacial acetic acid for 4 h followed by
addition of nickel(II) bromide, and the reflux was con-
tinued overnight (Eq. (1)).
After removal of the glacial acetic acid in vacuo,
compounds 1–3 were washed with diethyl ether to
remove any remaining acetic acid and unreacted ligand.
Further purification was also carried out by dissolving
the nickel complex in methylene chloride, followed by
2.1.2. Synthesis of Ni(II) h-diimine complexes 6ia
(DME)NiBr2 route
Complexes 1–3 can also be prepared by a similar
method previously described [4a,d,11] in which the

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R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
respective ligand (4–6) was first formed via an acid
catalyzed condensation between the aniline and the
diketone (Eq. (2)), followed by subsequent displacement
of 1,2-dimethoxyethane from (1,2-dimethoxyethane)
nickel(II) bromide [(DME)NiBr2] [12] (Eq. (3)).
desired complexes 1–3. The nickel complexes prepared
by this route showed identical chemical characteristics
and polymerization results as found for the complexes
made via Eq. (1). The complexes are sparingly soluble
in diethyl ether and hydrocarbons, are moderately solu-
ble in toluene, and are soluble in methylene chloride
and chloroform.
2.2. Crystal and molecular structures of complexes 1
and 2
Figs. 1 and 2 show ORTEP plots [13] and atom
labeling for the structures of complexes 1 and 2, while
Table 1 gives details of the bond distances and angles
for the geometry about the nickel atoms in each of the
complexes. As can be seen, complex 2 contains five-
Compounds 4–6 were recrystallized from diethyl
ether to afford elementally pure ligands. These com-
pounds were characterized by 1H-NMR and were
found to be free from impurities. Subsequent treatment
of these ligands with (DME)NiBr2 also produced the
coordinate nickel centers and is dimeric, the two halves
of the dimer being related by a crystallographic inver-
sion center, while complex 1 on the other hand, pos-
sesses crystallographic two-fold symmetry, the C2 axis
bisecting the a-diimine ligand.

R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
161
Table 1
,
Selected bond lengths (A) and bond angles (°) for compounds 1 and
2
Compound 1
Bond lengths
NiꢁN
2.021(3)
NiꢁBr
2.318(1)
Bond angles
NꢁNiꢁN a
NꢁNiꢁBr
82.6(2)
114.4(1)
BrꢁNiꢁBr a
NꢁNiꢁBr a
117.94(5)
111.3(1)
Compound 2
Bond lengths
NiꢁN(1)
2.058(4)
2.380(1)
2.551(1)
NiꢁN(2)
NiꢁBr(2)
2.106(4)
2.505(1)
NiꢁBr(1)
NiꢁBr(2) b
Bond angles
N(1)ꢁNiꢁBr(1)
Br(1)ꢁNiꢁBr(2)
N(2)ꢁNiꢁN(1)
N(2)ꢁNiꢁBr(1)
N(2)ꢁNiꢁBr(2)
129.5(1)
136.36(3)
80.4(2)
94.1(1)
89.2(1)
N(1)ꢁNiꢁBr(2)
N(2)ꢁNiꢁBr(2) b
N(1)ꢁNiꢁBr(2) b
Br(1)ꢁNiꢁBr(2) b
Br(2)ꢁNiꢁBr(2) b
94.1(1)
173.0(1)
95.2(1)
92.91(3)
85.79(2)
a Two-fold related atoms.
b Inversion related atoms.
Fig. 1. ORTEP diagram of 1 with 40% ellipsoids. H atoms have been
removed in drawings.
The compound 4d differs from 1 principally by hav-
ing the bulky pentafluorophenyl groups rather than
methyl groups in one of the ortho-positions of the
phenyl rings attached to the imine nitrogens. The crys-
tallographically imposed two-fold symmetries for both
of the two independent molecules in the unit cell of 4d
results in the pentafluorophenyl rings having an anti-
conformation above and below the nickel imine coordi-
nation plane. With the more symmetrically substituted
phenyl groups present in 1, there is no such conforma-
tional difference, and both the diimine ligand, and the
The pseudo-tetrahedral geometry about the nickel
atom in 1 is very similar to that reported recently by
Brookhart and coworkers [4c], for compound 4d in
their paper, namely, the complex bis(2-pentafluoro-
phenyl-6-methylphenyl-imino)acenaphthene nickel di-
bromide. Thus the NiꢁBr and NiꢁN distances in 1, of
2.318(1) and 2.021(3), compare closely with the aver-
ages of 2.306(1) and 2.024(3) reported for 4d, and the
bond angles at the nickel atom are likewise very similar.
Fig. 2. ORTEP diagram of 2 with 40% ellipsoids. H atoms have been removed in drawings.

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R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
complete complex approximate C26 symmetry quite
closely. The bis(imino)acenaphthene moiety is planar to
within the estimated S.D.s and the dihedral angle it
makes with the nitrogen bonded mesityl groups is
88.8(3)°, while the dihedral angle between the NiBr2
unit and the nickel–nitrogen plane is 88.1(2)°.
The geometries for the nickel atoms in the two
inversion related halves of the dimer in complex 2, may
be described as being basically trigonal bipyramidal,
two such bipyramids sharing an apical edge. However,
although the atoms defining the equatorial plane,
namely Ni, N(1), Br(1) and Br(2), are planar to within
the estimated S.D.s, the angles within the plane are far
from 120°. The terminal NiꢁBr(1) and the nickel–nitro-
gen distances are slightly longer than those in 1, and
there is a small, but significant difference between the
‘axial’ and ‘equatorial’ nickel–nitrogen and the nickel–
bromine bond lengths, perhaps supporting the trigonal-
bipyramidal description.
mer compared to the other nickel systems. This may be
due to the less bulky isopropyl moiety, thus causing
oligomerization processes possibly to occur.
The molecular weights of the resulting polymers as
well as their respective polydispersities are also reported
in Table 2. In general, the polydispersities are relatively
high and the Tms are lower compared to single site,
linear polyethylene obtained with metallocene catalyst
systems. It is apparent from the table that these
polyethylenes are more branched and have lower
molecular weights compared to those reported by
Brookhart and coworkers [4] possibly due to the lower
steric hindrance of the aniline moiety in our study. It is
well known that Ni(II) diimine complexes that lack
bulky diisopropylaniline moieties generally favor chain
transfer relative to chain propagation and thus produce
lower molecular weight polymers [2].
It is seen from the table that the polydispersities are
higher and the Tms are lower with the use of trialkylalu-
minum activators (TMA and TIBA) than are obtained
with the other co-catalyst systems (MAO, DEAC and
DCDAO) in combination with 1–3. This could result
from the higher affinity of TMA and TIBA to undergo
easier chain transfer processes due to a closer ion pair
relative to the cationic species. Also, bridging alkyls
would provide a closer ion pair relative to the Ni
center, thus causing chain transfer processes to occur
more readily. The melting points of the polymers ob-
tained with TMA and TIBA in combination with 1 are
much lower than those obtained with the other co-cata-
lyst systems. It is likely that catalyst 1 would provide a
more distant ion pair relative to 2 and 3 due to the
increased steric bulk of the trimethylaniline moiety. The
polydispersities are higher and the Tms are lower for the
resulting polymer obtained with 2 and 3 compared to 1.
Propylene polymerizations were also carried out with
the use of 1–3 in combination with DEAC, DCDAO
and MAO and the results are tabulated in Table 3.
Table 3 shows that both DEAC and DCDAO can
activate a-diimine nickel complexes to produce a signifi-
cant amount of polypropylene. In our study, the
1/DEAC system gave the highest amount of
polypropylene compared to the other systems. DCDAO
was also shown to promote a higher degree of propyl-
ene polymerization compared to MAO. Catalyst pre-
cursor 2 gave a polymer with a slightly higher Mw
compared to the polymers obtained with different co-
catalyst systems. In general, the molecular weights of
the polymers decrease as the polymerization tempera-
ture increases. Also, the polydispersities increase as the
temperature increases. It is interesting to note that the
Mw of the obtained polymers are fairly constant with
respect to the co-catalyst used. The polypropylenes
obtained with 1 and 2 were isolated as amorphous
solids that showed no true melting point by DSC.
In contrast to other structurally confirmed examples,
both of free a-diimine ligands [8a] and of their nickel
and palladium complexes [4c,11a], the tert-butyl substi-
tuted phenyl rings in 2 take on the syn-conformation,
so that both tert-butyl groups are on the same side of
the coordination plane. In this instance the conforma-
tion is presumably dictated by the steric requirements
arising from the dimerization of the complex to give a
five-coordinate geometry for the nickel. In all other
instances where asymmetrically substituted aryl rings
are employed, and monomeric complexes are formed,
the substituents on the ligand take up an anti-confor-
mation with respect to the acenaphthene plane. How-
ever, in common with the other characterized examples,
the phenyl rings are nearly perpendicular to the plane
formed by the nickel and nitrogen atoms, the dihedral
angles being 99.5° for the ring bonded to N(1), and
84.1° for that bonded to N(2).
2.3. Polymerization results
Polymerizations of ethylene were carried out using
nickel systems 1–3 at 20 °C with MAO, DEAC, 1,3-
dichloro-1,3-diisobutyldialuminoxane
(DCDAO),
trimethylaluminum (TMA), and triisobutylaluminum
(TIBA). The results are reported in Table 2.
It is apparent from Table 2 that 1/DEAC produces
the highest amount of polyethylene compared to the
other catalyst systems investigated. In our study,
DEAC appears to be the best co-catalyst even when
compared to MAO in generating the most poly-
ethylene. This is in agreement with the previous studies
by Marques et al. [14]. The trialkylaluminum activators
(TMA and TIBA) in combination with 1, 2 and 3
produce a factor of ten times lower amount of polymer
when compared to DEAC, DCDAO and MAO. Cata-
lyst precursor 3 generated the lowest amount of poly-

R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
163
Table 2
Ethylene polymerizations a using nickel precursors 1, 2 and 3 activated by various aluminum co-catalysts
b
c
c
c
d
Catalyst
Co-catalyst
P.E. (g)
A
(×10−6
)
Mw (×10−4
)
Mn (×10−4
)
Mw/Mn
Tm (°C)
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
TMA e
0.49
0.52
0.43
0.47
3.29
3.21
2.70
2.69
3.02
3.08
0.21
0.17
0.22
0.22
2.71
2.65
2.10
2.14
2.31
2.29
Trace
Trace
Trace
Trace
1.62
1.68
0.61
0.55
1.35
1.30
0.53
0.56
0.46
0.51
3.55
3.46
2.91
2.90
3.26
3.32
0.23
0.18
0.24
0.24
2.92
2.86
2.26
2.31
2.49
2.47
–
–
–
–
1.75
1.81
0.66
0.59
1.46
1.40
4.32
–
4.71
–
4.87
–
5.45
–
4.18
–
3.43
–
3.97
–
3.16
–
5.42
–
4.47
–
–
–
–
–
3.98
–
4.49
–
0.65
–
0.77
–
1.50
–
1.73
–
1.08
–
0.65
–
0.76
–
0.53
–
1.32
–
1.88
–
–
–
–
–
0.66
–
0.45
–
6.6
–
6.1
–
3.2
–
3.1
–
3.9
–
6.3
–
5.2
–
6.0
–
4.0
–
3.8
–
–
–
–
–
6.0
–
9.9
–
115
–
117
–
127
–
130
–
125
–
115
–
118
–
122
–
125
–
125
–
–
–
–
–
110
–
105
–
TMA e
TIBA f
TIBA f
DEAC g
DEAC g
MAO h
MAO h
DCDAO i
DCDAO i
TMA e
TMA e
TIBA f
TIBA f
DEAC g
DEAC g
MAO h
MAO h
DCDAO i
DCDAO i
TMA e
TMA e
TIBA f
TIBA f
DEAC g
DEAC g
MAO h
MAO h
DCDAO i
DCDAO i
3.18
–
0.54
–
6.0
–
108
–
a Polymerization conditions: [Ni], 50 mM in toluene; time of polymerization=1 h, Tp=20 °C, 15 PSIG ethylene.
b A (activity)=[g polymer/(mol Ni×conc. monomer×h)].
c Mw, Mn and Mw/Mn determined by GPC at 135 °C in 1,2,4-trichlorobenzene.
d Tm determined by DSC.
e TMA/Ni=100:1.
f TIBA/Ni=100:1.
g DEAC/Ni=250:1.
h MAO/Ni=500:1.
i DCDAO=300:1.
Compound 3 in combination with DEAC and DCDAO
gave polypropylene that was isolated as an oil which
indicates that oligomerization processes were possibly
occurring during the polymerization. Polymerizations
were also attempted for propylene with the use of
trialkylaluminum activators (TMA and TIBA) in con-
tact with 1–3. However, no polymer was obtained with
any of these systems.
Triad analyses were performed on the polypropylenes
obtained at 0 °C with 1/DEAC and 2/DEAC. The
NMR spectra showed that polymers derived from 1/
DEAC gave the higher percentage syndiotacticity with
a rr triad analysis of 87% while 2/DEAC produced a
syndiotacticity of 77%. Attempts to perform pentad
analysis on the resulting polypropylenes were unsuc-
cessful due to the poor resolution of the spectra as a
result of high regioirregular content of the polymer (see
Ref. [8a]).
In this study, we have outlined two different detailed
routes for the synthesis of several Ni(II) a-diimine
complexes. It was shown that these complexes could be
activated by several aluminum activators to promote
olefin polymerization. DEAC and DCDAO in combi-
nation with the Ni(II) a-diimine complexes were shown
to be more effective towards ethylene and propylene
polymerizations than MAO. Further modification of
the co-catalyst used with these types of complexes could
possibly lead to polypropylenes that resemble charac-
teristics of those obtained with Group IV metallocene
catalysts.

164
R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
Table 3
Propylene polymerizations with nickel precursors 1, 2 and 3 in combination with various aluminum activators at different temperatures
a
b
c
c
c
Catalyst
Co-catalyst
Tp
P.P. (g)
A
(×10−5
)
Mw (×10−4
)
Mn (×10−4
)
Mw/Mn (×10−4
)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
MAO d
−20
−20
0
0
20
0.41
0.44
0.55
0.58
0.63
0.67
0.52
0.49
0.68
0.68
0.74
0.75
0.72
0.70
0.74
0.71
0.85
0.81
0.05
0.07
0.09
0.12
0.16
0.14
0.21
0.24
0.35
0.39
0.45
0.44
0.29
0.29
0.41
0.39
0.55
0.49
Trace
Trace
Trace
Trace
Trace
Trace
0.38
0.36
0.42
0.41
0.55
0.51
0.42
0.38
0.55
0.50
0.61
0.65
1.42
1.53
2.42
2.55
3.80
4.03
1.81
1.70
2.99
2.99
4.45
4.51
2.51
2.43
3.25
3.12
5.11
4.87
0.17
0.24
0.39
0.53
0.96
0.84
0.73
0.83
1.54
1.71
2.71
2.65
1.00
1.00
1.80
1.71
3.31
2.95
–
4.49
–
4.11
–
3.93
–
3.81
–
3.77
–
3.64
–
4.42
–
4.41
–
3.65
–
4.13
–
3.88
–
3.54
–
4.54
–
4.10
–
3.77
–
6.34
–
5.85
–
4.90
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1.32
–
0.99
–
0.905
–
1.47
–
1.10
–
0.881
–
1.16
–
1.07
–
0.763
–
0.983
–
0.87
–
0.65
–
1.69
–
1.43
–
1.20
–
1.55
–
1.38
–
1.0
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
3.40
–
4.15
–
4.35
–
2.60
–
3.42
–
4.13
–
3.80
–
4.10
–
4.78
–
4.20
–
4.45
–
5.44
–
2.68
–
2.9
–
3.1
–
4.09
–
4.25
–
4.90
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
MAO d
MAO d
MAO d
MAO d
MAO d
20
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DEAC f
DEAC f
DEAC f
DEAC f
DEAC f
DEAC f
MAO d
−20
−20
0
0
20
20
−20
−20
0
0
20
20
−20
−20
0
0
20
MAO d
MAO d
MAO d
MAO d
MAO d
20
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DEAC f
DEAC f
DEAC f
DEAC f
DEAC f
DEAC f
MAO d
−20
−20
0
0
20
20
−20
−20
0
0
20
20
−20
−20
0
0
20
d
MAO
–
–
–
–
MAO d
MAO d
MAO d
MAO d
20
–
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DCDAO e
DEAC f
DEAC f
DEAC f
DEAC f
DEAC f
DEAC f
−20
−20
0
0
20
1.32
1.25
1.85
1.80
3.31
3.10
1.45
1.32
2.42
2.20
3.67
3.91
20
−20
−20
0
0
20
–
–
–
–
–
–
–
–
20
–
a Polymerization conditions: [Ni], 50 mM in toluene; time of polymerization=1 h, 15 PSIG propylene.
b A (Activity)=[g polymer/(mol Ni×conc. monomer×h)].
c Mw, Mn and Mw/Mn determined by GPC at 135 °C in 1,2,4-trichlorobenzene.
d MAO/Ni=500:1.
e DCDAO/Ni=250:1.
f DEAC/Ni=250:1.

R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
165
3. Experimental
crystals were washed with a small amount of Et2O (5
ml) and were used immediately for X-ray analysis.
Compound 1 (2.82 g, 4.45 mmol, 81%) was obtained
as a red solid after Et2O washings and drying in vacuo.
EIMS; m/z (%): 558, 557, 556, 555, 554, 553 [12, 36, 35,
100, 24, 71 M+−Br]]. Anal. Calc. for C30H28N2NiBr2:
C, 56.74; H, 4.44; N, 4.41. Found: C, 56.44; H, 4.58; N,
4.22%.
Compound 2 (2.80 g, 4.23 mmol, 77%) was obtained
as a orange solid after CH2Cl2 extraction and Et2O
washings. Anal. Calc. for C32H32N2NiBr2·CH2Cl2 sol-
vate: C, 52.98; H, 4.58; N, 3.74. Found: C, 52.70; H,
4.38; N, 3.62%.
All operations were carried out under Ar atmosphere
using standard Schlenk techniques unless otherwise
noted. Methylene chloride and 1,2-dimethoxyethane
were distilled under Ar from CaH2. Toluene, hexane,
and Et2O were each distilled under Ar from sodium–
potassium alloy. Anhydrous NiBr2, 2,4,6-trimethylani-
line, 2-isopropylaniline, 2-tert-butylaniline and bromine
were purchased from Aldrich and used without further
purification. MAO was purchased from Akzo Nobel.
DEAC, TIBA, DCDAO and TMA were purchased
from Aldrich and used without further purification.
(DME)NiBr2 was synthesized via a literature procedure
Compound 3 (2.51 g, 3.96 mmol, 72%) was obtained
as a yellow solid after CH2Cl2 extraction and Et2O
washings. Attempts to prepare a sample of elemental
analytical purity were not successful.
1
[12]. H-NMR spectra were recorded on a Bruker-200
spectrometer. EIMS were obtained on a JMS-700
MStation high-resolution two-sector mass spectrometer
using direct insertion. Molecular weights were deter-
mined by GPC in 1,2,4-trichlorobenzene. A calibration
curve was established with polystyrene standards and
universal calibration was applied using Mark–
Houwink constants for polyethylene and polypropy-
lene. Elemental analyses were performed by the
Microanalytical Laboratory, University of Massachu-
setts, Amherst, MA. 13C-NMR triad analyses on the
polypropylenes were performed for 2 h periods on a
Bruker-500 MHz instrument at 80 °C with benzene-d6/
1,2,4-trichlorobenzene as the solvent.
3.2. Synthesis of h-diimine ligands 4–6
Acenaphthoquinone (1.00 g, 5.55 mmol), 100 ml of
MeOH and a slight excess of the respective aniline (13
mmol) were placed in a 250 ml beaker and allowed to
stir for 3 days in the presence of formic acid (1 ml).
Methylene chloride and water were added and the
layers were separated. The resulting organic layer was
dried with MgSO4, filtered and the solvent was removed
to give the crude ligands as red oils. The impure ligands
were recrystallized from Et2O to give 4–6 in high yield.
Compound 4 (2.01 g, 4.83 mmol, 88%) was obtained
as red crystals (melting point (m.p.) 170 °C) after re-
crystallization from Et2O. 1H-NMR (200 MHz,
CDCl3): l=2.09 (s, 12H), 2.38 (s, 6H), 6.75 (d, 2H),
6.97 (s, 4H), 7.44 (t, 2H), 7.91 (d, 2H). Anal. Calc. for
C30H28N2: C, 86.50; H, 6.77; N, 6.73. Found: C, 86.35;
H, 6.84; N, 6.57%.
3.1. Synthesis of Ni(II) h-diimine complexes 1–3
6ia one-pot reaction
Acenaphthoquinone (1.00 g, 5.55 mmol) was placed
in a Schlenk tube followed by 100 ml glacial AcOH.
The resulting suspension was allowed to warm to 50 °C
and then a slight excess of the respective aniline (13
mmol) was introduced, forming a burgundy–red solu-
tion within minutes. This mixture was warmed to
120 °C and allowed to reflux for 4 h. Anhydrous NiBr2
(1.20 g, 5.55 mmol) was added as a solid to the subse-
quent mixture and the reaction was allowed to reflux
overnight. The solvent was removed in vacuo and the
resulting solid was washed with Et2O (20 ml×3). Alter-
natively, the solid can also be conveniently washed with
Et2O via Soxhlet extraction. The residue was extracted
with CH2Cl2 and the resulting deep red solution was
filtered via a cannula to another Schlenk tube. This
process was repeated twice and the solvent was re-
moved in vacuo to give 1–3 that were suitable for
polymerization use. Crystals of complexes 1 and 2
suitable for X-ray studies were obtained by dissolving a
small amount of the compound in CH2Cl2 (100 ml),
followed by slow addition of Et2O (20 ml), forming two
layers. The mixture was allowed to sit undisturbed
overnight. Resulting crystals formed at the sides of the
tube and the filtrate was decanted via a cannula. The
Compound 5 (2.07 g, 4.67 mmol, 85%) was obtained
as orange crystals (m.p. 175 °C) after recrystallization
1
from Et2O. H-NMR (200 MHz, CDCl3): l=1.39 (s,
18H), 6.84 (d, 2H), 6.96 (d, 2H), 7.51–7.20 (m, 8H),
7.89 (d, 2H). Anal. Calc. for C32H32N2: C, 86.45; H,
7.25; N, 6.30. Found: C, 86.30; H, 7.30; N, 6.20%.
Compound 6 (1.90 g, 4.56 mmol, 83%) was obtained
as orange crystals (m.p. 170 °C) after recrystallization
1
from Et2O. H-NMR (200 MHz, CDCl3): l=1.26 (m,
12H), 3.18 (m, 2H), 6.84 (m, 4H), 7.20 (m, 4H), 7.44 (t,
2H), 7.91 (m, 2H), 8.20 (m, 2H). Anal. Calc. for
C30H28N2: C, 86.50; H, 6.77; N, 6.73. Found: C, 86.35;
H, 6.81; N, 6.57%.
3.3. Synthesis of nickel complexes 1–3 6ia
(DME)NiBr2 reaction
(DME)NiBr2 (1.00 g, 3.25 mmol), the respective lig-
ands 4–6 (3.3 mmol) and CH2Cl2 (50 ml) were com-
bined in
a Schlenk flask and stirred at room

166
R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
Table 4
temperature (r.t.) for 16 h. The resulting suspension
was filtered and the filtrate was collected in another
Schlenk flask. The solvent was removed and the residue
was washed with Et2O (3×20 ml) to give complexes
1–3 in high yields.
Compound 1 (1.81 g, 3.05 mmol, 94%) was obtained
as dark-red microcrystals after CH2Cl2 extraction and
Et2O washings.
Compound 2 (2.02 g, 3.05 mmol, 94%) was obtained
as an orange powder after CH2Cl2 extraction and Et2O
washings.
Compound 3 (1.74 g, 3.05 mmol, 90%) was obtained
as an yellow powder after CH2Cl2 extraction and Et2O
washings.
Crystal data and structure refinement parameters for compounds 1
and 2
Compound
1
2
Empirical formula
C30H28Br2N2Ni·
0.25(C2H5)2O
653.6
Orthorhombic
Pcca (no. 54)
C
64H64Br4N4Ni2·
2CH2Cl2
1496.1
Monoclinic
P21/n (no. 14)
Formula weight
Crystal system
Space group
Unit cell dimensions
,
a (A)
16.6977(5)
11.4432(3)
17.6565(6)
–
3373.7(2)
4
1.287
29.6
0.50×0.25×0.20
2960
12.3065(2)
22.0991(4)
12.3293(2)
100.28(1)
3299.3(1)
2
1.506
32.0
0.75×0.18×0.15
5747
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
3.4. Crystal structure determination
v (Mo–Ka) (cm−1
Crystal size (mm)
Total independent
reflections
)
The X-ray crystallographic studies of compounds 1
and 2 were carried out on an Enraf–Nonius Kappa
CCD diffractometer using graphite monochromated
Reflections with
I\2|(I)
2119
4419
,
Mo–Ka radiation (u=0.71073 A). Data were collected
R(Fo) a
0.0545
0.136
1.14
0.048
0.114
1.05
at 296(2) K for a range in q up to 25°. For compound
2, this gave a total of 10 228 reflections, yielding 5747
independent values (Rint=0.026), and for compound 1,
5469 reflections yielding 2960 independent values
(Rint=0.029). The structures were solved by direct
methods and difference Fourier techniques and were
refined by full-matrix least-squares. Refinements were
based on F2 and were carried out using all the indepen-
dent data. All of the non-hydrogen atoms, apart from
those of the solvent molecules of crystallization, were
refined anisotropically. The hydrogen atoms were in-
cluded in the refinements as isotropic scatterers, riding
Rw(F2o) b
Goodness-of-fit on Fo2
a R(Fo)=ꢀꢁ ꢁFoꢁ−ꢁFcꢁ ꢁ/ꢀꢁFoꢁ.
b Rw(F2o)=[ꢀw(Fo2−F2c)2/ꢀwFo4]1/2
.
factors for non-hydrogen atoms were taken from Inter-
national Tables [17], and anomalous dispersion correc-
tions were included [18]. The hydrogen atom scattering
factor used is that tabulated by Stewart et al. [19].
3.5. Procedure of polymerizations
,
in either idealized positions (CꢁH=1.05 A), or in the
case of the methyl hydrogens, with torsional refinement
on the respective bonded atoms. Pertinent crystallo-
graphic data are summarized in Table 4, the final
agreement factors listed being based on reflections for
which I\2|(I).
Polymerizations of ethylene and propylene were car-
ried out in a flame dried 250 ml crown capped pressure
bottle sealed under Ar atmosphere. After drying the
polymerization bottle under an inert atmosphere, 50 ml
of dry toluene was added to the polymerization bottle.
The resulting solvent was then saturated with 15 PSIG
monomer pressure and maintained through the course
of the polymerization. The desired co-catalyst was then
added in the proper Al–Ni ratio to the polymerization
bottle via a syringe. If the amount of co-catalyst was
too small to be measured out neatly by a syringe, a 10
ml toluene solution of the co-catalyst was made, and
then 1 ml of the subsequent solution was added to the
polymerization bottle. At this time, the solutions were
brought to the desired temperatures and allowed to
equilibrate for 15 min. Subsequently, 1 ml of a 50 mM
toluene solution of the Ni catalyst was added to the
polymerization reactors. The polymerizations were ter-
minated after 1 h by quenching the mixture with 100 ml
of a 2% HCl–MeOH solution. The obtained polymers
were then filtered, washed with several 50 ml portions
of 2% HCl–MeOH solution and dried in vacuo at
Both compounds 1 and 2 possess crystallographic
symmetry, an inversion center in the case of 2 and a
two-fold axis in the case of 1, so that in each instance,
only one-half of a molecule comprises the asymmetric
unit. The crystals of both complexes also contain sol-
vent molecules of crystallization: CH2Cl2, to the extent
of four molecules per unit cell for compound 2, and, as
indicated by the best refinement model, one-quarter of
a molecule of Et2O per molecule of complex (or one
complete molecule per cell), in the case of 1. The
CH2Cl2 molecules are positionally disordered, and the
chlorine atoms were refined in a total of five partially
occupied positions, while the Et2O molecule in 1, is
located on a two-fold axis.
The computations involved were carried out using
SHELXS-86 [15] for the structure solution and SHELXL
97 for the refinement [16]. Neutral atom scattering
-

R.J. Maldanis et al. / Journal of Organometallic Chemistry 645 (2002) 158–167
167
(d) S.D. Arthur, A.M.A. Bennett, M.S. Brookhart, E.B. Cough-
lin, J. Feldman, S.D. Ittel, L.K. Johnson, C.M. Killian, K.A.
Kreutzer, US Patent Appl. 5,886,224, to DuPont, 1999.
[3] (a) L.K. Johnson, C.M. Killian, M. Brookhart, J. Am. Chem.
Soc. 117 (1995) 6414;
45 °C for several hours. After quenching, if the poly-
mers remained in solution, the mixture was extracted
with several portions of hexane, and the organic layers
were collected, dried with MgSO4 and filtered. After
rotary evaporation of the solvent and drying in vacuo
at 45 °C, an oily polymer was obtained.
(b) A.S. Abu-Surrah, B. Reiger, Angew. Chem. Int. Ed. Engl. 35
(1996) 2475;
(c) R.S. Mauler, R.F. De Souza, D.V.V. Vesccia, L.C. Simon,
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(d) S.G. Correia, M.M. Marques, J.R. Ascenso, A.F.G. Riberio,
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(f) S.D. Arthur, M.S. Brookhart, L.K. Johnson, C.M. Killian,
E.F. McCord, S.J. McLain, US Patent 5,891,963, to DuPont,
1999.
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 171422 and 171423 for com-
pounds 1 and 2, respectively. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
[4] (a) S.A. Svejda, M. Brookhart, Organometallics 18 (1999) 65;
(b) C.M. Killian, L.K. Johnson, M. Brookhart, Organometallics
16 (1997) 2005;
(c) D.P. Gates, S.A. Svejda, E. Onate, C.M. Killian, L.K.
Johnson, P.S. White, M. Brookhart, Macromolecules 33 (2000)
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Acknowledgements
(d) C.M. Killian, D.J. Tempel, L.K. Johnson, M. Brookhart, J.
Am. Chem. Soc. 118 (1996) 11664.
[5] K.R. Kumar, S. Sivaram, Marcromol. Chem. Phys. 201 (2000)
1513.
[6] L.C. Simon, R.S. Mauler, R.F. De Souza, J. Polym. Sci. Part A:
Polym. Chem. 37 (1999) 4656.
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We wish to thank Dr L.C. Dickinson for assistance
in acquiring 13C-NMR data, Dr G. Dabkowski for
performing elemental analyses, and Dr S. Eyles for help
in acquiring mass spectra data. We would like to thank
Dr M. Blais for previous studies in Ni(II) a-diimine
chemistry. We are also grateful to Solvay Polyolefins
Europe—Belgium for financial support of this research
program.
[10] T. Matei, T. Lixandru, Bul. Inst. Politeh. Iasi 13 (1967) 245;
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