Novel, highly active binuclear 2,5-disubstituted amino-p-benzoqumone-nickel(II) ethylene polymerization catalysts

Article abstract of DOI:10.1021/om030068y

The reaction of salts of the 2,5-distributed amino-p-benzoquinone bridging ligand with trans-bis(triphenylphosphane)phenylnickel(II) chloride was studied. High-molecular-weight, moderately branched polyether of broad molecular-weight distribution was obta

Full text of DOI:10.1021/om030068y

Organometallics 2003, 22, 2851-2854
2851
Novel, High ly Active Bin u clea r 2,5-Disu bstitu ted
Am in o-p-ben zoqu in on e-Nick el(II) Eth ylen e
P olym er iza tion Ca ta lysts†
Dao Zhang‡ and Guo-Xin J in*,‡,§
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied
Chemistry, Chinese Academy of Sciences, Changchun 130 022, China, and Department of
Chemistry, Fudan University, Shanghai 200 433, China
Received J anuary 29, 2003
Reaction of salts of the 2,5-disubstituted amino-p-benzoquinone bridging ligand (1a -e)
with trans-bis(triphenylphosphane)phenylnickel(II) chloride results in the binuclear com-
plexes 2a -e, which show high activities for ethylene polymerization without any cocatalysts.
High-molecular-weight, moderately branched polyethylene of broad molecular-weight
distribution was obtained.
Over the past decade, late-transition-metal catalysts
for olefin polymerization have received increasing at-
traction, for they are much less oxophilic and more
tolerant of polar functional groups than the catalysts
ordinarily used.1 Among the numerous catalysts, neu-
tral nickel catalysts play an important role and now are
considered to be very promising catalysts for olefin
polymerization and copolymerization.2-6 In the 1960s,
Keim et al. developed neutral nickel(II) complexes
bearing bidentate phosphoro keto-ylide P,O ligands
[(P∧O)NiIIR(L)], which are the basis for the Shell high
olefin process (SHOP) for ethylene oligomerization to
form linear R-olefins.2 Two years ago, Grubbs et al.
developed the neutral, single-component salicylaldi-
mine-based nickel(II) complexes [(N∧O)NiIIR(L)] cata-
lysts for polyolefin.5 More recently, a new neutral
nickel(II) complex reported by the Brookhart group,
[(N∧O)NiIIR(L)], based upon an anilinotropone ligand
has been shown to be a highly active ethylene polym-
erization catalyst.6 As expected, these single-component
catalysts can produce high-molecular-weight polyeth-
ylene. They also can polymerize functionalized olefins
and require no cocatalyst. In addition, such neutral
complexes can polymerize ethylene in an aqueous emul-
sion, affording stable polymer lattices with high molec-
ular mass.7
To date, the quest for novel polymerization catalysts
involves the search for new ligand structures. The well-
known late-transition-metal systems, such as catalysts
bearing P-O, N-O, and N-N ligands for ethylene
polymerizations affording high-molecular-weight poly-
mers with high activities, are based on variations in the
ligands. However, in the course of our studies on the
late-transition-metal catalysts,8 we found this search to
be empirical in nature; recent developments have
provided somewhat more comprehensive guidelines for
catalyst design. We report here ethylene polymerization
by a series of new, neutral binuclear nickel(II) complexes
of bridging ligands comprising 2,5-disubstituted amino-
p-benzoquinones without any cocatalysts and the prop-
erties of polymer obtained. To the best of our knowledge,
neutral, single-component binuclear nickel(II) com-
plexes for olefin polymerization have not been reported.9
The free ligands 1a -e were prepared from a substi-
tuted amine and 2,5-dihydroxy-p-benzoquinone by vi-
nylogous nucleophilic substitution in m-cresol.10 By
using trifuoroacetic acid as a catalyst, almost all ligands
were obtained in good yield. A single crystal of 1a
suitable for an X-ray structure determination was
obtained from acetic acid. The crystal structure of 1a
(Figure 1)11 shows a symmetrical framework and two
* To whom correspondence should be addressed at Fudan Univer-
sity. E-mail: gxjin@fudan.edu.cn. Fax: +86-21-65641740. Tel: +86-
21-65643776.
† Dedicated to Prof. E. O. Fischer on the occasion of his 85th
birthday.
‡ Changchun Institute of Applied Chemistry, Chinese Academy of
Sciences.
(7) Bauers, F. M.; Mecking, S. Angew. Chem. 2001, 113, 3112-3115;
Angew. Chem., Int. Ed. 2001, 40, 3020-3022.
§ Fudan University.
(8) (a) Zhang, D.; J in, G. X.; Hu, N. H. Chem. Commun. 2002, 574-
575. (b) Zhang, D.; J in, G. X. Eur. J . Inorg. Chem. 2003, 1570-1576.
(c) Liu, C. K.; J in, G. X. New J . Chem. 2002, 1485-1489.
(9) Binuclear metallocenes for olefin polymerization have been
reported. For example: (a) Reddy, K. P.; Petersen, J . L. Organome-
tallics 1989, 8, 2107-2113. (b) J uling, S.; Muelhaupt, R.; Plenio, H. J .
Organomet. Chem. 1993, 460, 191-195. (c) Larkin, S. A.; Golden, J .
T.; Shapiro, P. J .; Yap, G. P. A.; Foo, D. M. J .; Rheingold, A. L.
Organometallics 1996, 15, 2393-2398. (d) Segerer, U.; Blaurock, S.;
Sieler, J .; Hey-Hawkins, E. Organometallics 1999, 18, 2838-2842.
(10) Ueda, M.; Sakai, N.; Imai, Y. Macromol. Chem. 1979, 180,
2813-2818.
(1) Recent reviews: (a) Britovsek, G. J . P.; Gibson, V. C.; Wass, D.
F. Angew. Chem. 1999, 111, 448-468; Angew. Chem., Int. Ed. 1999,
38, 428-447. (b) Mecking, S. Coord. Chem. Rev. 2000, 203, 325-351.
(c) Ittel, S. D.; J ohnson, L. K.; Brookhart, M. Chem. Rev. 2000, 100,
1169-1204. (d) Mecking, S. Angew. Chem. 2001, 113, 550-557; Angew.
Chem., Int. Ed. 2001, 40, 534-540.
(2) Peuckert, M.; Keim, W. Organometallics 1983, 2, 594-597.
(3) Klabunde, U.; Ittel, S. D. J . Mol. Catal. 1987, 41, 123-134.
(4) Ostoja-Starzewski, K. A.; Witte, J . Angew. Chem. 1987, 99, 76-
77; Angew. Chem., Int. Ed. Engl. 1987, 26, 63-64.
(5) (a) Younkin, T. R.; Connor, E. F.; Henderson, J . I.; Friedrich, S.
K.; Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460-462. (b)
Wang, C.; Friedrich, S.; Younkin, T. R.; Li, R. T.; Grubbs, R. H.;
Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149-3151.
(6) Hicks, F. A.; Brookhart, M. Organometallics 2001, 20, 3217-
3219.
(11) Crystal data for 1a : triclinic, P1h, a ) 8.417(3) Å, b ) 8.827(3)
Å, c ) 12.86(4) Å, R ) 75.3(3)°, â ) 80.48(3)°, γ ) 67.92(3)°, V ) 854.6-
(5) Å3, Z ) 1. The structure was solved by direct methods and refined
by full-matrix least-squares procedures: R1 ) 0.0497 and wR2 )
0.0493 for 3339 independent reflections.
10.1021/om030068y CCC: $25.00 © 2003 American Chemical Society
Publication on Web 05/20/2003

2852 Organometallics, Vol. 22, No. 14, 2003
Zhang and J in
Ta ble 1. P olym er iza tion of Eth ylen e by Com p lexes
2a -ea
reacn conditions
results
entry catalyst T, amt of
no. (amt, µmol) (°C) PE (g) activityb Mw
Mwc/
c
d
Mn
Tm
1
2
3
4
5
6e
7
8
2a (27)
2a (22)
2a (22)
2a (22)
2b (41)
2c (15)
2d (41)
2e (131)
40
60
80
100
80
80
2.82
3.31
3.81
2.97
2.60
0.24
0.04
104
148
170
133
64
43.1
41.2
6.7
1.7
53.5
3.5 128.8
5.0 125.8
3.7 121.1, 70.0
3.2 103.9, 71.1
8.2 125.6
23
1
6.0 48.2 123.7
80
n.d.f n.d.f n.d.f
80 trace
a
Conditions: ethylene pressure, 0.4 Mpa; polymerization time,
1 h; total volume of toluene, 120 mL; 800 rpm; PE ) polyethylene.
b
In units of 103 g of PE (mol of Ni)-1 h-1
.
c Mw (×10-4) and Mw/
F igu r e 1. Crystal structure of 1a (with acetic acid solvent
molecules omitted). Selected distances (Å) and angles
(deg): O(1)-C(15) ) 1.236(2), C(14)-C(15) ) 1.420(3),
C(13)-C(14) ) 1.359(3), N(1)-C(1) ) 1.451(3), N(1)-C(13)
) 1.340(2), C(1)-C(2) ) 1.385(3), C(1)-C(6) ) 1.403(3);
O(1)-C(15)-C(14) ) 123.4(2), C(13)-C(14)-C(15) ) 120.9-
(2), N(1)-C(13)-C(14) ) 125.2(2), C(1)-N(1)-C(13) )
124.5(2), N(1)-C(1)-C(2) ) 118.7(2).
d
Mn values were determined by GPC. Tm values were determined
by DSC with second heat curves. e Polymerization time: 40 min.
f Not determined.
olefin polymerization. Its activity was comparable to
that of the Grubbs catalyst ([3-phenyl phenolate-2′,6′-
diisopropylphenylimine](triphenylphosphine)phenyl-
nickel(II))5a under the same conditions. A reduction in
steric bulk resulted in a marked decrease from 1.7 ×
105 g of PE (mol of Ni)-1 h-1 for 2a to 6.4 × 104 g of PE
(mol of Ni)-1 h-1 for 2b (R ) 2,6-Me2-C6H5). For
complexes 2c (R ) naphthyl) and 2d (R ) phenyl),
activities decreased to 2.3 × 104 and 1.0 × 103 g of
polymer/(mol of cat)-1 h-1, respectively. However, the
replacement of the aryl at the R position with cyclohexyl
afforded only traces of polymer with complex 2e. This
different catalytic behavior clearly suggests that the
change of bulky substituents at the R position influences
the polymerization activity, as in other late-transition-
metal catalyst systems.
Sch em e 1. Syn th esis of Bin u clea r Nick el
Com p lexes 2a -e
In a series of ethylene polymerization experiments,
reaction temperatures have some effect on the activities
of catalysts. For complex 2a , 80 °C represents the
optimum (entry 3). At a lower or higher temperature,
the catalytic performance decreased.
GPC analysis of polyethylene obtained employing
complexes 2a -c revealed molecular weights of typically
Mw ) 4.31 × 105, 5.35 × 105, and 6.03 × 104, respec-
tively. The relatively wide molecular weight distribu-
tions of 3.21-48.24 were quite different from those of
well-behaved single-site catalysts.12 The mononuclear
nickel catalyst with an anilinotropone ligand reported
by Brookhart afforded polyethylene with a narrower
molecular weight distribution of 1.68-2.81. Figure 2
shows the evidence for a bimodal distribution of poly-
ethylene obtained by catalyst 2a (Table 1, entry 2). The
observed effects on very wide molecular weight distribu-
tion can also be explained on the basis of electronic
effects and cooperative interactions of the two adjacent
nickel centers in binuclear complexes. These two metal
centers are electronically coupled through the ligand
bridge. When one of the centers was activated by
removing phosphane at a given time, it had an electron-
withdrawing effect on another center. The interaction
between two metals made it possible to create more than
one kind of active species during the polymerization.
Moreover, with an increase in temperature the effect
hydrogen-bonded acetic acid molecules. A band at 1720
cm-1 in the IR spectrum is also indicative of 1a .
Binuclear nickel(II) complexes 2a -e were obtained
1
by the reaction of trans-[Ni(PPh3)2(Ph)Cl] with /2 equiv
of the lithium salts of the free ligands, which were
obtained via deprotonation (Scheme 1). Most of the
complexes were isolated as blue powders. To date, we
have not obtained crystals suitable for an X-ray struc-
ture determination. However, the high activities for
ethylene polymerization and spectral characterizations
of 2a -e suggest that they have a square-planar struc-
ture, as in other comparable nickel(II) [N,O] com-
plexes.5-8
Complexes 2a -e were catalytically active in ethylene
polymerization (Table 1). Complex 2a , comprising a
bulky substituted aryl group bound to the anilino
function (R ) 2,6-iPr2-C6H5), has a high potential for
(12) For metallocenes, a similar phenomenon was observed. The
molecular weight distributions of polyethylene produced by binuclear
group IV metallocene-MAO catalysts are usually broad compared with
those of polyethylene produced by mononuclear compounds.9

Novel Binuclear Ethylene Polymerization Catalysts
Organometallics, Vol. 22, No. 14, 2003 2853
hydroquinone, 2,6-diisopropylaniline, 2,6-dimethylaniline, naph-
thylamine, aniline, and cyclohexanylamine, were used as
purchased from Acros Co. m-Cresol was purified by vacuum
distillation and stored over 4 Å molecular sieves. 2,5-Dihy-
droxy-p-benzoquinone14 and trans-[Ni(PPh3)2PhCl]15 were pre-
pared according to the analogous methods reported. For
compounds 1a -e and complexes 2a -e, 1H NMR spectra were
recorded on a Unity-400 spectrometer; ESI-MS spectra were
recorded on a Finigan MAT 8500 spectrometer (70 eV), and
elemental analysis was performed on a Perkin-Elmer Series
II CHN/O analyzer 2400. For polyethylene, 13C NMR spectra
were obtained using o-dichlorobenzene as a solvent on an FX-
100 NMR spectrometer at 130 °C. Molecular weight distribu-
tion (Mw/Mn) values of polyethylene were determined using a
PL GPC-220 gel permeation chromatograph at 150 °C using
narrow standards calibration and equipped with three PL gel
columns (sets of PL gel 10 µm MIXED-B LS); 1,2,4-trichlo-
robenzene was employed as a solvent at a flow rate of 1.00
mL min-1
.
[µ-p-Ben zoqu in on e-2,5-bis(2,6-d iisop r op yla n ilin o)]bis-
[(tr ip h en ylp h osp h a n e)p h en yln ick el(II)] (2a ). (a ) F r ee
Liga n d Syn th esis.10 A 1.4 g (10 mmol) amount of 2,5-
dihydroxy-p-benzoquinone were added to a stirred solution of
2,6-diisopropylaniline (3.85 g, 20 mmol) in m-cresol (40 mL).
After 0.40 g (3.2 mmol) of trifuoroacetic acid as a catalyst was
charged into the reaction mixture, the mixture was heated
with stirring at 100 °C for 1.5 h under an argon atmosphere.
The resulting reaction mixture was poured into 5% aqueous
sodium hydroxide (1.2 L). The precipitate was collected by
filtration, washed with water, and dried in vacuo at 80 °C for
F igu r e 2. GPC spectra of polyethylene produced by
catalyst 1a (Table 1, entry 2). The spectral components of
the pattern (curves A and B) were obtained by deconvolu-
tion of the observed spectrum. Curve C represents the sum
of the components.
of molecular weight declining became remarkable be-
cause of the higher rate of â-hydrogen elimination.
For catalysts 2b,c, polymer crystallinity amounts to
ca. 47% and 42% and the melt peaks occur at ca. 126
and 124 °C. From the DSC curves of polymers produced
by catalyst 2a at different temperatures something
different could be found. When the polymerization
temperature was increased to 80 °C, a bimodal distribu-
tion of DSC appeared (for figures giving DSC curves,
see the Supporting Information). The results showed
that the interaction between two metals created more
than one kind of active species during the polymeriza-
tion. Another reason for this was that, at higher reaction
temperatures, branching polyethylene increases and the
polymer molecular weight and melting point decrease.1c
High-temperature 13C NMR spectra showed that the
polymers are moderately branched (see Supporting
Information).13 Methyl branches predominate with ca.
10 methyl branches per 1000 carbon atoms. Additional
weak signals suggested that higher branches, such as
butyl, are also present. The polymer microstructure is
similar to that obtained with other single-component
nickel(II) complexes.
1
3
8 h. Yield: 3.88 g (84.8%). H NMR (CDCl3): δ 1.17 (d, J )
3
6.8 Hz, 12H, CH3(iPr)), 1.25 (d, J ) 6.8 Hz, 12H, CH3(iPr)),
2.97 (septet, 3J ) 6.8 Hz, CH(iPr)), 5.05 (s, 2H, H(p-benzo-
quinone)), 7.24 (d, 4H, H(arom)), 7.36 (t, 2H, H(arom)), 7.64
(s, 1H, NH). IR (KBr): 3245 (vs; N-H), 1570 cm-1 (vs; CdO).
Anal. Calcd for C30H38N2O2 (458.64): C, 78.56; H, 8.35; N, 6.11.
Found: C, 78.54; H, 8.30; N, 6.15. EI-MS (m/e (relative
abundance, %)): 458 (M+, 24). The 2,5-bis(2,6-diisopropyl-
aniline)-p-benzoquinone (1a ) obtained was crystallized from
acetic acid to afford red single crystals suitable for X-ray
determination. IR (KBr): 3245 (vs; N-H), 1720 (vs; CdO(acetic
acid)), 1570 cm-1 (vs; CdO).
(b) Com p lex Syn th esis. Complex 2a was synthesized by
a similar method reported by Brookhart6 and Grubbs.5 The
sodium salt of 1a was obtained by treating 1a with 2 equiv of
NaH or BuLi in THF solution. trans-Bis(triphenylphosphane)-
phenylnickel(II) chloride (1.5 mmol) reacted with 1/2 equiv of
the lithium salt of 1a (0.72 mmol) in toluene to afford the dark
blue binuclear nickel(II) complex 2a . Yield: 0.47 g (52.5%).
1H NMR (C6D6CD3): δ 1.00 (d, 3J ) 6.8 Hz, 12H, CH3(iPr)),
1.25 (d, 3J ) 6.8 Hz, 12H, CH3(iPr)), 3.38 (m, 3J ) 6.4 Hz,
CH(iPr)), 5.31 (s, 2H, H(p-benzoquinone)), 6.45-7.86 (m, 46H,
H(arom)). Anal. Calcd for C78H76N2Ni2O2P2 (1252.80): C, 74.78;
H, 6.11; N, 2.24. Found: C, 74.54; H, 6.08; N, 2.32. EI-MS (m/e
(relative abundance, %)): 651 (M+ - 2PPh3 - Ph, 5), 574 (M+
- 2PPh3 - 2Ph, 17).
[µ-p -Ben zoq u in on e-2,5-b is(2,6-d im et h yla n ilin o)]b is-
[(tr ip h en ylp h osp h a n e)p h en yln ick el(II)] (2b). 2,5-Bis(2,6-
dimethylaniline)-p-benzoquinone (1b) was obtained as a pale
pink solid in 91% yield. 1H NMR (CDCl3): δ 2.22 (s, 12H, CH3),
5.03 (s, 2H, H(p-benzoquinone)), 7.14 (d, 4H, H(arom)), 7.21
(t, 2H, H(arom)), 7.65 (s, 2H, NH). IR (KBr): 3253 (vs; N-H),
1563 cm-1 (vs; CdO). Anal. Calcd for C22H22N2O2 (346.43): C,
76.28; H, 6.40; N, 8.09. Found: C, 76.28; H, 6.38; N, 8.12. EI-
MS (m/e (relative abundance, %)): 346 (M+, 40). 2b was
obtained as a blue powder. Yield: 0.54 g (65.7%). Anal. Calcd
In conclusion, binuclear nickel(II) 2,5-disubstituted
amino-p-benzoquinone complexes represent new types
of homogeneous neutral, single-component catalysts
containing two catalytically active or dormant sites.
High-molecular-weight, moderately branched polymers
are accessible at reasonable rates by employing bulky
substituted ligands.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were per-
formed under an argon atmosphere using standard Schlenk
techniques. Toluene, benzene, hexane, and tetrahydrofuran
were dried by refluxing these solvents with appropriate drying
agents (sodium/benzophenone) and distillation under argon
prior to use. Commercial reagents, namely n-BuLi (1.6 M),
(14) J ones, R. G.; Shonle, H. A. J . Am. Chem. Soc. 1945, 67, 1034-
1035.
(15) (a) Sehun, P. A. Inorg. Synth. 1972, 13, 124-127. (b) Hidai,
M.; Kashiwagi, T.; Ikeuchi, T.; Uchida, Y. J . Organomet. Chem. 1971,
30, 279-282.
(13) Branching structure assigned according to: (a) Randall, J . C.
J . Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201-317.
(b) Axelson, D. E.; Levy, G. C.; Mandelkern, L. Macromolecules 1979,
12, 41-52.

2854 Organometallics, Vol. 22, No. 14, 2003
Zhang and J in
for C70H60N2Ni2O2P2 (1140.58): C, 73.71; H, 5.30; N, 2.46.
Found: C, 73.38; H, 5.12; N, 2.76. EI-MS (m/e (relative
abundance, %)): 538 (M+ - 2PPh3 - Ph, 18). No satisfying
1H NMR data for the complexes were obtained due to their
insolubility.
10H, CH2(cyclohexanylamine)), 1.63-1.67 (m, 2H, CH2(cyclo-
hexanylamine)), 1.76-1.81 (m, 4H, CH2(cyclohexanylamine)),
1.96-1.99 (m, 10H, CH2(cyclohexanylamine)), 3.27(m, 2H, CH-
(cyclohexanylamine)), 5.33 (s, 2H, H(p-benzoquinone)), 6.58 (d,
3J ) 6.8 Hz, 2H, NH). IR (KBr): 3272 (vs; N-H), 1562 cm-1
(vs; CdO). Anal. Calcd for C18H26N2O2 (302.42): C, 71.49; H,
8.66; N, 9.26. Found: C, 71.49; H, 8.67; N, 9.27. EI-MS (m/e
(relative abundance, %)): 302 (M+, 100). 2e was obtained as
a yellowish powder. Yield: 0.64 g (80.6%). Anal. Calcd for
[µ-p -Ben zoq u in on e-2,5-b is(n a p h t h yla m in o)]b is[(t r i-
p h en ylp h osp h a n e)p h en yln ick el(II)] (2c). 2,5-Bis(naph-
thylamino)-p-benzoquinone (1c) was obtained as a brown
powder in 94% yield. 1H NMR (CDCl3): δ 5.77 (s, 2H, H(p-
benzoquinone)), 7.50-7.58 (m, 8H, H(naphthylene)), 7.83 (d,
2H, H(naphthylene)), 7.90-7.94 (m, 4H, H(naphthylene)), 8.36
(s, 2H, NH). IR (KBr): 3284 (vs; N-H), 1594, 1573 cm-1 (vs;
CdO). Anal. Calcd for C26H18N2O2 (390.44): C, 79.98; H, 4.65;
N, 7.18. Found: C, 80.01; H, 4.63; N, 7.20. EI-MS (m/e (relative
abundance, %)): 390 (M+, 100). 2c was obtained as a blue
powder. Yield: 0.48 g (56.3%). Anal. Calcd for C74H56N2Ni2O2P2
(1184.60): C, 75.03; H, 4.76; N, 2.36. Found: C, 74.31; H, 4.85;
C
66H64N2Ni2O2P2 (1096.57): C, 73.29; H, 5.88; N, 2.55.
Found: C, 73.28; H, 5.87; N, 2.59. EI-MS (m/e (relative
abundance, %)): 495 (M+ - 2PPh3 - Ph, 7).
Eth ylen e P olym er iza tion . A 500 mL autoclave was
charged with 100 mL of toluene under an atmosphere of argon.
The catalyst was weighed and added to the polymerization
system. After three cycles of ethylene gas exchange, the
ethylene pressure was raised to the specified value and
maintained for a certain time. The polymerization was termi-
nated by the addition of methanol and dilute HCl (10%). The
solid polyethylene was filtered, washed with methanol, and
dried at 40 °C for 10 h under vacuum.
N, 2.49. EI-MS (m/e (relative abundance, %)): 583 (M+
2PPh3 - Ph, 3%).
-
[µ-p-Ben zoqu in on e-2,5-bis(an ilin o)]bis[(tr iph en ylph os-
p h a n e)p h en yln ick el(II)] (2d ). The ligand 2,5-bis(anilino)-
p-benzoquinone (1d ) was obtained as a pale pink solid in 98%
yield. 1H NMR (CDCl3): δ 5.03 (s, 2H, H(p-benzoquinone)),
7.14 (d, 4H, H(arom)), 7.21 (t, 2H, H(arom)), 7.65(s, 2H, NH).
IR (KBr): 3230 (vs; N-H), 1566 cm-1 (vs; CdO). Anal. Calcd
for C18H14N2O2 (290.32): C, 74.47; H, 4.86; N, 9.65. Found:
C, 74.49; H, 4.84; N, 9.67. EI-MS (m/e (relative abundance,
%)): 290 (M+, 100%). 2d was obtained as a pale blue powder.
Ack n ow led gm en t. We are grateful to the National
Nature Science Foundation of China (Grant Nos.
20274008, 29925101) and the Special Funds for Major
State Basic Research Projects (Grant No. 1999064800)
for financial support.
Yield: 0.57 g (72.3%). Anal. Calcd for
C66H52N2Ni2O2P2
(1084.48): C, 73.10; H, 4.83; N, 2.58. Found: C, 72.41; H, 4.75;
Su p p or tin g In for m a tion Ava ila ble: Figures giving three
DSC curves and 13C NMR spectra of polyethylene prepared
and tables and figures giving complete details of the crystal-
lographic study of 1a . This material is available free of charge
via the Internet at http://pubs.acs.org.
N, 2.73. EI-MS (m/e (relative abundance, %)): 560 (M+
2PPh3, 11%), 483 (M+ - 2PPh3 - Ph, 6%).
-
[µ-p -Ben zoq u in on e-2,5-b is(cycloh exa n yla m in o)]b is-
[(tr ip h en ylp h osp h a n e)p h en yln ick el(II)] (2e). 2,5-Bis(cy-
clohexanylamino)-p-benzoquinone (1e) was prepared as a pale
pink solid in 99% yield. 1H NMR (CDCl3): δ 1.23-1.41 (m,
OM030068Y