Synthesis, molecular structures, and norbornene polymerization of methallyl nickel (II) complexes of 2-(diphenylamino)benzoate

Article abstract of DOI:10.1021/om020134g

Reaction of 2-(diphenylamino)benzoic acid with bis(methallyl)nickel(II) results in the dinuclear complex bis(η³-methallyl)bis{μ-[(2-diphenylamino)benzoato-O:O′]} dinickel(II) (1), where the nitrogen atom does not coordinate to the nickel. Addit

Full text of DOI:10.1021/om020134g

Organometallics 2002, 21, 3481-3484
3481
Syn th esis, Molecu la r Str u ctu r es, a n d Nor bor n en e
P olym er iza tion of Meth a llyl Nick el(II) Com p lexes of
2-(Dip h en yla m in o)ben zoa te
Bun Yeoul Lee,*,† Young Heui Kim,† Hyeon J eong Shin,† and Choong Hoon Lee‡
Department of Molecular Science and Technology, Ajou University, Suwon 442-749 Korea, and
LG Chemical Ltd./ Research Park, 104-1, Moonji-dong, Yusung-gu, Taejon 305-380 Korea
Received February 19, 2002
Summary: Reaction of 2-(diphenylamino)benzoic acid
with bis(methallyl)nickel(II) results in the dinuclear
complex bis(η3-methallyl)bis{µ-[(2-diphenylamino)ben-
zoato-O:O′]}dinickel(II) (1), where the nitrogen atom does
not coordinate to the nickel. Addition of B(C6F5)3 to 1 in
benzene affords the nitrogen-coordinating complex [(2-
diphenylamino)benzoate tris(pentafluorophenyl)borate-
κ2N,O](η3-methallyl)nickel(II) (2). The structures of 1 and
2 are confirmed by X-ray crystallography. Complex 2
shows good activity for norbornene polymerization, while
complex 1 is inactive.
ligand frameworks containing carbonyl functionalities.
Herein, we report the syntheses of a nickel complex
derived from 2-(diphenylamino)benzoate and its activa-
tion by addition of B(C6F5)3 to the carbonyl for nor-
bornene polymerization.
Reaction of 2-(diphenylamino)benzoic acid6 with bis-
(methallyl)nickel(II) gives a clean complex with con-
comitant isobutylene byproduct. Only two methallyl-
CH2 signals are observed (2.36 and 1.71 ppm in C6D6)
in the 1H NMR spectrum. If the complex is a N,O-
chelated square planar structure frequently observed
in phosphine analogues,7 four methallyl-CH2 proton
signals should appear. Furthermore only one methallyl-
CH2 carbon signal is observed in the 13C NMR spectrum
(50.23 ppm). These observations suggest that the struc-
ture is different from the ones observed for phosphine
analogues. Broad signals are observed at 7.65 and 6.80
ppm from the protons attached to the 3 and 6 positions
in the benzoate ring. The X-ray crystallography reveals
that the complex is a dinuclear structure bridged by a
carboxylate with a square-planar arrangement of ligands
on nickel, as shown in Figure 1. The basic structure is
close to that of bis(η3-methallyl)bis(trifluoroacetato)-
dinickel.8 The nitrogen donor does not coordinate to
nickel, and each diphenylamino group is located eclipsed.
Four C-O bond lengths are almost the same (av
1.250(3) Å), and the four Ni-O bond lengths are also
almost in the same range (av 1.911(8) Å). Observation
of only one methally-CH2 carbon and only two methally-
Late transition metal catalysts for transforming ole-
fins to more valuable oligomers or polymers have
attracted considerable attention from both academic and
industrial field.1,2 Usually transition metal complexes
are activated by electrophilic abstraction of methyl or
hydride by Lewis acids.3 Recently, it has been reported
that nickel complexes containing carboxylato or car-
boxamidato ligands could be activated by electrophilic
addition of Lewis acids to the carbonyl.4,5 By the
addition, the neutral metal complexes become zwitte-
rionic and consequently the electron density of the metal
is reduced. The novel activation process was successfully
applied to the catalysts for the dimerization, oligomer-
ization, and polymerization of ethylene. The fact that a
little variation of the ligand structure may lead to
profound change in the catalytic reactivities prompts
us to synthesize nickel catalysts chelated by various
† Ajou University.
1
CH2 protons in the 13C and H NMR spectra can be well
‡ LG Chemical Ltd.
explained by the solid structure, which suggests that
the solution structure in benzene might be the same as
the solid structure. Broad signals of protons on the
benzoate ring might result from slow rotation of the
benzoate ring containing a bulky diphenylamino group
around the C(ipso)-CO2 axis on the NMR time scale.
(1) Review: (a) Mecking, S. Angew. Chem., Int. Ed. 2001, 40, 534.
(b) Ittel, S. D.; J ohnson, L. K.; Brookhart, M. Chem. Rev. 2000, 100,
1169. (c) Mecking, S. Coord. Chem. Rev. 2000, 203, 325.
(2) (a) Ikeda, S.; Ohhata, F.; Miyoshi, M.; Tanaka, R.; Minami, T.;
Ozawa, F.; Yoshifuji, M. Angew. Chem., Int. Ed. 2000, 39, 4512. (b)
Rieth, L. R.; Eaton, R. F.; Coates, G. W. Angew. Chem., Int. Ed. 2001,
40, 2153. (c) Bauers, F. M.; Mecking, S. Angew. Chem., Int. Ed. 2001,
40, 3020. (d) Hicks, F. A.; Brookhart, M. Organometallics 2001, 20,
3217. (e) Schmid, M.; Eberhardt, R.; Klinga, M.; Leskela¨, M.; Rieger,
B. Organometallics 2001, 20, 2321. (f) Small, B. L.; Marcucci, A. J .
Organometallics 2001, 20, 5738. (g) McCord, E. F.; McLain, S. J .;
Nelson, L. T. J .; Arthur, S. D.; Coughlin, E. B.; Ittel, S. D.; J ohnson,
L. K.; Tempel, D.; Killian, C. M.; Brookhart, M. Macromolecules 2001,
34, 362. (h) Gottfried, A. C.; Brookhart, M. Macromolecules 2001, 34,
1140. (i) Bauers, F. M.; Mecking, S. Macromolecules 2001, 34, 1165.
(j) Soula, R.; Novat, C.; Tomov, A.; Spitz, R.; Claverie, J .; Drujon, X.;
Malinge, J .; Saudemont, T. Macromolecules 2001, 34, 2022. (k) Soula,
R.; Broyer, J . P.; Llauro, M. F.; Tomov, A.; Spitz, R.; Claverie, J .;
Drujon, X.; Malinge, J .; Saudemont, T. Macromolecules 2001, 34, 2438.
(l) Leatherman, M. D.; Brookhart, M. Macromolecules 2001, 34, 2748.
(3) Chen, E. Y.-X.; Marks, T. J . Chem. Rev. 2000, 100, 1391.
(4) Komon, Z. J . A.; Bu, X.; Bazan, G. C. J . Am. Chem. Soc. 2000,
122, 1830.
Addition of an equimolar amount of B(C6F5)3 to the
dinuclear complex results in formation of a clean
(5) (a) Komon, Z. J . A.; Bu, X.; Bazan, G. C. J . Am. Chem. Soc. 2000,
122, 12379. (b) Lee, B. Y.; Bazan, G. C.; Vela, J .; Komon, Z. J . A.; Bu,
X. J . Am. Chem. Soc. 2001, 123, 5352. (c) Lee, B. Y.; Bu, X.; Bazan, G.
C. Organometallics 2001, 20, 5425.
(6) Goldberg, I. Ber. 1907, 40, 2448.
(7) Keim, W.; Schultz, R. J . Mol. Catal. 1994, 92, 21.
(8) Goddard, R.; Kru¨ger, C.; Mynott, R.; Neumann, M.; Wilke, G. J .
Organomet. Chem. 1993, 454, C20.
10.1021/om020134g CCC: $22.00 © 2002 American Chemical Society
Publication on Web 07/11/2002

3482 Organometallics, Vol. 21, No. 16, 2002
Notes
Ta ble 1. Nor bor n en e P olym er iza tion Resu ltsa
temp
(°C)
yield
(g)
activity
b
b
complex
(10-6 g/mol‚h)
Mw
Mw/Mn
1
r.t.
r.t.
r.t.
40
50
70
0
0
0.15
0.13
0.16
0.16
0
0
3.6
3.1
3.8
3.8
B(C6F5)3
2
2
2
2
633 000
592 000
448 000
358 000
2.1
2.2
2.0
1.9
a
Polymerization conditions: 10 g norbornene solution in toluene
b
(50 wt %), 0.5 µmol of complex, 5 min. Determined by GPC in
1,2,4-trichlorobenzene at 140 °C based on polystyrene standards.
(1.229(4) or 1.234(4) Å) is characteristic of a C-O double
bond, while the C-OB distance (1.297(4) or 1.288(4) Å)
is more indicative of a single bond. These measurements
support the zwitterionic resonance structure 2. The
N-C distance for 2 (av 1.482(7) Å) is longer than that
observed for 1 (av 1.424(11) Å). For 1, delocalization of
nonbonding electrons on nitrogen to the benzene ring
makes the N-C bonds shorter. If the solid structure is
preserved in solution, four distinct proton signals and
two carbon signals should be observed from the meth-
allyl-CH2 fragment in the NMR spectra, but only one
broad carbon and proton signal is observed. These
observations indicate that the complex is under some
fluxional motion in benzene.
F igu r e 1. ORTEP view of 1, showing the atom-numbering
scheme. Thermal ellipsoids are shown at 30% probability
level. Hydrogen atoms have been omitted for clarity.
Selected bond distances (Å): Ni(1)-O(2), 1.915(2); Ni(1)-
O(4), 1.919(2); Ni(2)-O(1), 1.905(2); Ni(2)-O(3), 1.903(2);
C(1)-O(1), 1.253(4); C(1)-O(2), 1.246(4); C(2)-O(3), 1.252(4);
C(2)-O(4), 1.250(4); Ni(1)-C(81), 1.986(4); Ni(1)-C(83),
1.974(4); Ni(2)-C(71), 1.987(4); Ni(2)-C(73), 1.991(4); N(1)-
C(21), 1.411(4); N(1)-C(11), 1.426(4); N(1)-C(31), 1.437(4).
When ethylene gas is added to a C6D6 solution of 2,
the signals in the 1H NMR spectrum are broadened
immediately and a mixture of 1-butene and 2-butene is
formed slowly. The rate is so slow that it takes more
than 1 day to transform all gaseous ethylene to butene
(turnover frequency, 0.5 h-1). In the case of [(C6H5)2-
PC6H4C(OB(C6F5)3)O-κ2P,O]Ni(η3-CH2CMeCH2), the eth-
ylene gas was disappeared immediately.4 However,
when norbornene is added to the solution, the solution
becomes viscous immediately, implying the complex is
active for norbornene polymerization.9,10 The detailed
norbornene polymerization results are summarized in
Table 1. Neither complex 1 nor B(C6F5)3 alone shows
any activity for the norbornene polymerization, but
complex 2 is highly active. The activity reaches 3.6 ×
106 g/mol‚h at room temperature, and the value is
F igu r e 2. ORTEP view of 2, showing the atom-numbering
scheme. Thermal ellipsoids are shown at 30% probability
level. Hydrogen atoms have been omitted for clarity.
Selected bond distances (Å): Ni(1)-O(1), 1.899(3); Ni(1)-
N(1), 2.0593; Ni(1)-C(71), 1.986(5); Ni(1)-C(73), 1.989(5);
C(1)-O(1), 1.229(4); C(1)-O(2), 1.297(4); B(1)-O(2), 1.546(5);
N(1)-C(21), 1.487(4); N(1)-C(11), 1.486(4); N(1)-C(31),
1.474(4).
complex. Very sharp signals are observed from the
(diphenylamino)benzoate ligand fragment in the 1H and
13C NMR spectra, but the methallyl-CH2 protons are
very broad at 1.1-1.7 ppm. Only one broad methallyl-
CH2 carbon signal at 56.75 ppm and one broad meth-
allyl-CCH3 carbon signal at 149.0 ppm are observed in
the 13C NMR spectrum. The 11B NMR and 19F NMR
spectra are similar to those observed for [(C6H5)2-
PC6H4C(OB(C6F5)3)O-κ2P,O]Ni(η3-CH2CMeCH2).4 Single
crystals were grown by vapor phase addition of pentane
to a benzene solution at room temperature. The solid
structure is very similar to that of [(C6H5)2PC6H4C(OB-
(C6F5)3)O-κ2P,O]Ni(η3-CH2CMeCH2) in terms of molec-
ular connectivity and bond lengths (Figure 2). There are
two independent molecules, two benzene molecules and
a pentane molecule in the unit cell. The C-ONi distance
1
sustained up to 80 °C. The H NMR spectra in C2D2Cl4
confirm that the polymers are obtained exclusively
by the vinyl-type polymerization. The 13C-CPMAS
spectrum of the soluble polynorbornene produced by
Ni(acac)2/MAO is different from that of the insoluble
polymer produced by Pd(acac)2/MAO. The latter has
more signals than the former. The increase of the
number of signals was interpreted in terms of cross-
(9) Review: J aniak, C.; Lassahn, P. G. Macromol. Rapid Commun.
2001, 22, 479.
(10) (a) Hennis, A. D.; Polley, J . D.; Long, G. S.; Sen, A.; Yandulov,
D.; Lipian, J .; Benedikt, G. M.; Rhodes, L. F.; Huffman, J . Organo-
metallics 2001, 20, 2808. (b) Groux, L. F.; Zargarian, D. Organome-
tallics 2001, 20, 3811. (c) Zhao, C.; Ribeiro, M. R.; Portela, M. F.;
Pereira, S.; Nunes, T. Eur. Polym. J . 2001, 37, 45.

Notes
Organometallics, Vol. 21, No. 16, 2002 3483
Ta ble 2. Cr ysta llogr a p h ic P a r a m eter sa
1
2
formula
fw
a, Å
b, Å
c, Å
C
46H42N2Ni2O4
C49.5H33 BF15NNiO2
1028.29
15.847(4)
17.263(5)
18.737(5)
109.329(5)
103.015(5)
102.690(5)
4465(2)
P-1
1.530
4
0.540
39 636
15 660
1288
5.08
804.24
16.921(2)
8.7318(12)
27.104(4)
90
106.550(2)
90
3838.8(9)
P2(1)/c
1.392
R, deg
â, deg
γ, deg
V, Å3
space group
d(calc), g cm-1
Z
F igu r e 3. 13C-CPMAS spectrum of polynorbornene.
4
µ, mm-1
no. of data collected
no. of unique data
no. of variables
R (%)
1.028
32 626
6754
521
4.87
linking.11 The 13C-CPMAS spectrum of the polynor-
bornene produced by 2 at room temperature looks like
a combination of both spectra (Figure 3). Even though
the determinations of the actual molecular weights are
limited,12 we can measure the molecular weights rou-
tinely by using a GPC instrument based on polystyrene
standard and compare the data with previously reported
ones. The molecular weight of the polymer obtained by
2 at room temperature (Mw ) 633 000) is substantially
lower than the one obtained by Ni(acac)2/MAO catalyst
under similar conditions (Mw ) 3 800 000).11 Narrow
molecular distribution (MWD ) 1.9-2.2) indicates the
presence of a single active species in the polymerization
solution. The dependency of the molecular weight on
polymerization temperature follows a general trend of
the metallocene catalysts: the higher the temperature,
the lower the molecular weight.
Rw (%)
goodness of fit
11.9
1.004
7.01
0.820
a
All data collected at 150 K with Mo KR radiation, R(F) ) ∑||Fo|
- |Fc||/∑|Fo| with Fo > 4.0σ(F), Rw ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo)2]2]1/2
with Fo > 4.0σ(F).
solution at room temperature for 2 days (0.600 g, 92%). 1H
NMR (400 MHz, C6D6): δ 7.65 (br d, J ) 6 Hz, 1 H, H3or6),
7.12 (d, J ) 7.6 Hz, 4 H, o-ph), 7.06-7.00 (m, 4 H, m-ph), 6.97-
6.90 (m, 2 H, p-ph), 6.80 (br, 1 H, H3or6), 6.77 (tt, J ) 7.2, 1.2
Hz, 2 H, H4
5), 2.36 (br s, 2 H, methallyl-CH2), 2.33 (br s, 3
and
H, methallyl-CH3), 1.71 (br s, 2 H, methallyl-CH2) ppm. 13C-
{1H} NMR (100 MHz, C6D6): δ 178.19 (carbonyl), 148.84,
145.39, 136.66, 131.69, 131.61, 131.46, 129.44, 125.83, 123.36,
122.82, 121.83, 50.23 (methallyl-CH2), 23.39 (methallyl-CH3)
ppm. Anal. Calcd for C46H42N2Ni2O4: C, 68.7; H, 5.3. Found:
C, 68.9; H, 5.6.
Exp er im en ta l Section
[(2-Dip h en yla m in o)ben zoa te tr is(p en ta flu or op h en yl)-
bor a te-K2N,O](η3-m eth a llyl)n ick el(II) (2). Bis(η3-methallyl)-
bis{µ-[(2-diphenylamino)benzoato-O:O′]}dinickel(II) (1) (0.100
g, 0.124 mmol) and B(C6F5)3 (0.127 g, 0.248 mmol) were
weighed in a flask inside a glovebox. Toluene (10 g) was added,
and the solution was stirred overnight. Removal of solvent
gave quantitatively a greenish yellow powder, which is quite
pure by 1H NMR. Single crystals for X-ray crystallography and
elemental analysis were grown by vapor phase addition of
pentane to a benzene solution at room temperature overnight.
One benzene and a half pentane molecule are incorporated
Gen er a l Con sid er a tion s. All manipulations were per-
formed under an inert atmosphere using standard glovebox
and Schlenk techniques. Toluene, pentane, and benzene were
distilled from benzophenone ketyl. Norbornene for polymeri-
zation was purchased from Aldrich and dissolved in toluene
(Aldrich anhydrous grade) to make a 50 wt % solution. The
solution was stirred for 3 days over Na/K alloy at room
temperature and vacuum-transferred. NMR spectra were
recorded on a Varian Unity 400 or 500 spectrometer. 11B NMR
and 19F NMR spectra were calibrated and reported downfield
from external BF3‚OEt2 and R,R,R-trifluorotoluene, respec-
tively.
2-(Dip h en yla m in o)ben zoic Acid . The compound was
synthesized according to the literature method.6 The NMR
data are not given in the literature. 1H NMR (400 MHz,
CDCl3): δ 8.03 (dd, J ) 8.0, 1.6 Hz, 1 H, H3or6), 7.53 (ddd, J )
8.0, 7.2, 1.6 Hz, 1 H, H4or5), 7.31 (ddd, J ) 7.6, 7.2, 1.2 Hz, 1
H, H4or5), 7.27-7.19 (m, 5 H), 7.05-6.96 (m, 6 H) ppm. 13C-
{1H} NMR (100 MHz, CDCl3): δ 169.75 (carbonyl), 147.75,
147.61, 134.03, 132.54, 130.07, 129.35, 127.67, 125.52, 123.19
ppm.
Bis(η3-m eth a llyl)bis{µ-[(2-d ip h en yla m in o)ben zoa to-O:
O′]}d in ick el(II) (1). Bis(methallyl)nickel(II) (0.300 g, 1.82
mmol) and 2-(diphenylamino)benzoic acid (0.474 g, 1.63 mmol)
were weighed in a vial inside a glovebox. Cold toluene (20 mL,
-30 °C) was added, and the solution was stirred overnight.
All volatiles were removed by vacuum, and the residue was
dissolved in benzene. Deep yellow single crystals, which were
analytically pure and suitable for X-ray crystallography, were
obtained by vapor phase addition of pentane to a benzene
1
per each molecule in the single crystals. H NMR (400 MHz,
C6D6): δ 8.69 (dd, J ) 7.6, 1.6 Hz, 1 H, H3or6), 6.85 (t, J ) 7.2
Hz, 2 H, p-ph), 6.82 (td, J ) 7.6, 1.2 Hz, 1 H, H4or5), 6.76 (t, J
) 8.4 Hz, 4 H, m-ph), 6.68 (ddd, J ) 8.0, 7.6, 1.2 Hz, 1 H,
H4or5), 6.66 (d, J ) 7.6 Hz, 4 H, o-ph), 6.18 (dd, J ) 8.0 Hz, 1.2
Hz, 1 H, H3or6), 1.82 (s, 3 H, methallyl-CH3) 1.1-1.7 (br, 4 H,
methallyl-CH2) ppm. 13C{1H} NMR (100 MHz, C6D6): δ 172.52
1
(carbonyl), 148.8 (dm, J CF ) 240 Hz, p-CF), 149.0 (br,
1
methallyl-CCH3), 148.34, 140.0 (dm, J CF ) 250 Hz, o-CF),
1
137.5 (dm, J CF ) 250 Hz, m-CF), 134.91, 134.11, 129.31,
129.30, 128.76, 127.65, 127.12, 126.84, 124.87, 56.73 (br,
methallyl-CH2), 21.73 (methallyl-CH3) ppm. 19F NMR (376
3
MHz, C6D6): δ -77.0 (d, J FF ) 19 Hz, ortho-F), -102.30 (t,
3
3J FF ) 20 Hz, para-F), -107.76 (br t, J FF ) 18 Hz, meta-F)
ppm. 11B NMR (C6D6, 128 MHz): δ -3.1 ppm. Anal. Calcd for
C
41H21BF15NNiO2‚C6H6‚1/2(C5H12): C, 57.8; H, 3.24. Found:
C, 57.6; H, 3.10.
Nor bor n en e P olym er iza tion . The vial containing 10 g of
norbornene solution in toluene (50 wt %) was immersed in an
oil bath whose temperature had been set to a given value
inside a glovebox, and the solution was stirred for 15 min. The
catalyst in toluene (0.50 µmol) was added. The solution was
stirred vigorously for 5 min. The viscous solution was brought
out from the drybox and poured into a flask containing acetone.
The white precipitates were collected by filtration and dried
(11) Arndt, M.; Gosmann, M. Polym. Bull. 1998, 41, 433.
(12) In the case of the rigid polymers as polythiophenes, the GPC
determinations using polystyrene standards overestimate the molec-
ular weights severely. See: Feast, W. J .; Tsibouklis, J .; Pouwer, K. L.;
Groenendaal, L.; Meijer, E. W. Polymer 1996, 37, 5017.

3484 Organometallics, Vol. 21, No. 16, 2002
Notes
under vacuum overnight. 1H NMR spectra were obtained at
100 °C in C2D2Cl4. The 13C-CPMAS spectrum was measured
at 100 °C, pulse angle 90°, relaxation delay 3 s using a Bruker
MSL 300.
calculated at idealized positions and their atomic positions
were refined as riding atoms of their parent carbon atoms. The
crystal data and refinement results are summarized in
Table 2.
Cr ysta llogr a p h ic Stu d ies. Crystals were mounted onto
a thin glass fiber with paratone-8277 and immediately placed
in a cold nitrogen stream at 150 K on a Bruker SMART CCD
diffractometer equipped with a normal focus, 2.4 kW sealed
tube X-ray source (Mo KR radiation). A full sphere of intensity
data was collected in 2252 frames with ω scans (width of 0.30°
and exposure time of 30 s per frame). The numbers of
reflections used for the least-squares refinement of unit cell
parameters (at 150 K) were 8192 and 4838 for 1 and 2,
respectively. The empirical absorption corrections based on the
equivalent reflections were performed using the program
SADABS. The structures were solved by direct methods
followed by successive difference Fourier methods. All calcula-
tions were performed using SHELXTL (version 5.0.3). Full-
matrix refinements were against F2. Hydrogen atoms were
Ack n ow led gm en t. The authors are grateful to Prof.
G. C. Bazan at U.C. Santa Barbara for helping to
publish this result and Dr. X. Bu for the single-crystal
diffraction studies. This work was supported by grant
No. R05-2002-000-00155-0 from the Basic Research
Program of the Korea Science & Engineering Founda-
tion.
Su p p or tin g In for m a tion Ava ila ble: Complete details for
crystallographic studies of 1 and 2. The material is available
free of charge via the Internet at http://pubs.acs.org.
OM020134G