Intramolecular benzylation of an imino group of tridentate 2,5-Bis(N-aryliminomethyl)pyrrolyl ligands bound to zirconium and hafnium gives amido-pyrrolyl complexes that catalyze ethylene polymerization

Article abstract of DOI:10.1021/om049873i

Amido-pyrrolyl complexes of zirconium (3a-d) and hafnium (4a-f) were prepared by the reaction of tetrabenzyl-zirconium and -hafnium with 2,5-bis(N-aryliminomethyl)pyrrole ligands (2a-e), respectively. During the course of the reaction, one of two imino mo

Full text of DOI:10.1021/om049873i

Organometallics 2004, 23, 2797-2805
2797
In tr a m olecu la r Ben zyla tion of a n Im in o Gr ou p of
Tr id en ta te 2,5-Bis(N-a r ylim in om eth yl)p yr r olyl Liga n d s
Bou n d to Zir con iu m a n d Ha fn iu m Gives Am id o-P yr r olyl
Com p lexes Th a t Ca ta lyze Eth ylen e P olym er iza tion
Hayato Tsurugi, Yutaka Matsuo, Tsuneaki Yamagata, and Kazushi Mashima*
Department of Chemistry, Graduate School of Engineering Science, Osaka University,
Toyonaka, Osaka 560-8531, J apan
Received February 21, 2004
Amido-pyrrolyl complexes of zirconium (3a -d ) and hafnium (4a -f) were prepared by the
reaction of tetrabenzyl-zirconium and -hafnium with 2,5-bis(N-aryliminomethyl)pyrrole
ligands (2a -e), respectively. During the course of the reaction, one of two imino moieties of
the ligand was selectively benzylated to give unique dianionic tridentate ligands, which
stabilized dibenzyl complexes of zirconium and hafnium. The coordinative unsaturation
around the metal center was compensated by not only the donation of the imino moiety but
also by the η2-coordination of one of the two benzyl ligands, as confirmed by spectral data
together with X-ray analysis of 3b and 3c. The zirconium complexes 3b and 3c bearing
bulky substituents at the nitrogen atoms of the ligand exhibited high catalytic activities
(3b, 131 (kg PE)(mol cat)-1 h-1 at 60 °C; 3c, 458 (kg PE)(mol cat)-1 h-1 at 75 °C) upon
combining with 1000 equiv of MMAO. Lewis-base-free cationic alkyl complexes 5b, 5c, 6b,
and 6c were prepared by alkyl abstruction from the corresponding dibenzyl complexes of
zirconium 3b,c and hafnium 4b,c, and the resulting cationic complexes 5c and 6c were
found to catalyze the ethylene polymerization without MMAO.
In tr od u ction
(N-aryliminomethyl)pyridine,8 and R-diimine9 deriva-
tives, which serve the polymerization catalysts as
supporting ligands, have attracted particular interest
in terms of their advantageous feasibility and flexibility
in design to introduce sterically and electronically
demanding features on the ligand.10,11 Despite these
merits, the catalysts supported by these ligands have
been found to be occasionally deactivated by the alky-
lation of the CdN bond of the ligand. Scott et al. recently
reported that titanium and zirconium dibenzyl com-
plexes A having a bridged phenoxyimine ligand (R3 )
H) were decomposed by an intramolecular benzylation.
The migratory insertion of the benzyl group into the
CdN bond gave thermally unstable products B (eq 1),
Recent development of well-defined single site transi-
tion metal catalysts enables us to precisely control not
only catalytic activity for R-olefin polymerization but
also microstructure of polymers.1-3 The nitrogen-based
polydentate ligands such as phenoxyimine,4-7 2,6-bis-
* Corresponding author. E-mail: mashima@chem.es.osaka-u.ac.jp.
Fax: 81-6-6850-6296.
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Williams, D. J . Chem. Commun. 1998, 849. (c) Small, B. L.; Brookhart,
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J . P.; Williams, D. J . J . Am. Chem. Soc. 1999, 121, 8728. (e) Britovsek,
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10.1021/om049873i CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/29/2004

2798 Organometallics, Vol. 23, No. 11, 2004
Tsurugi et al.
resulting in no catalytic activity for ethylene polymer-
ization, whereas protection against ligand alkylation by
introducing the bulky substituents at R3 positions of the
ligand rendered complexes A stable, providing active
catalysts.12
activity for ethylene polymerization compared to the
corresponding bis(iminopyrrolyl) dichloro complexes of
zirconium.16a,b For understanding the polymerization
mechanism of 1 as a catalyst precursor, we tried to
isolate cationic derivatives of 1; however, we were not
able to detect any cationic species due to their thermal
instability.
We thus turned our attention to tridentate 2,5-bis-
(N-aryliminomethyl)pyrrole ligands (2a -e),17 which
were expected to be better supporting ligands of cationic
alkyl species owing to the presence of an additional
nitrogen donor moiety.
On the contrary, nitrogen-based ligands, in some
cases, have been alkylated to be anionic ligands that
support some alkyl complexes. A reaction of AlMe3 with
bis(imino)pyridine ligand afforded an aluminum com-
plex C.13 During the course of the reaction, one of two
imino moieties was selectively methylated. The same
methylated tridentate ligand was utilized for preparing
dialkyl complexes of lutetium (D).14 Furthermore, the
anionic tridentate ligand stabilized cationic alkyl com-
plexes of aluminum and lutetium, derived from the
reactions of C and D with B(C6F5)3, respectively. Ad-
ditionally, Gambarotta et al. reported that a tridentate
anionic ligand derived from the ring CdN bond methy-
lation of 2,6-bis[1-(N-arylimino)ethyl]pyridine was used
to prepare a vanadium complex E, which exhibited
catalytic activity for ethylene polymerization upon
activation with MAO.15
Here we report unique benzylation of one of two imino
groups of the tridentate bis(imino)pyrrolyl ligand, by the
reaction of 2 with M(CH2Ph)4 (M ) Zr, Hf), giving
complexes 3a -c and 4a -e, which were characterized
by spectral data along with X-ray analysis of 3b and
3c. We found that these zirconium and hafnium com-
plexes became catalyst precursors for ethylene polym-
erization. Moreover, cationic monobenzyl complexes 5b,
5c, 6b, and 6c were prepared by treating the corre-
sponding dibenzyl complexes of 3b, 3c, 4b, and 4c with
[Ph3C][B(C6F5)4], and 5c and 6c were found to catalyze
ethylene polymerization in the absence of Al-cocatalyst.
The alkylation of the CdN moiety of the nitrogen-
based ligand was thus anticipated to have the capability
to stabilize a cationic alkyl species that catalyzes
polymerization of ethylene. We already reported that
an intramolecular benzylation of the imino moiety of
bidentate iminopyrrolyl ligands afforded an amido-
pyrrolyl complex 1, and it exhibited better catalytic
(12) Knight, P. D.; Clarke, A. J .; Kimberley, B. S.; J ackson, R. A.;
Scott, P. Chem. Commun. 2002, 352.
Resu lts a n d Discu ssion
(13) Bruce, M.; Gibson, V. C.; Redshaw, C.; Solan, G. A.; White, A.
J . P.; Williams, D. J . Chem. Commun. 1998, 2523.
(14) Cameron, T. M.; Gordon, J . C.; Michalczyk, R.; Scott, B. L.
Chem. Commun. 2003, 2282.
(15) Reardon, D.; Conan, F.; Gambarotta, S.; Yap, G.; Wang, Q. J .
Am. Chem. Soc. 1999, 121, 9318.
Syn th esis a n d Ch a r a cter iza tion of Zir con iu m -
a n d Ha fn iu m -Ben zyl Com p lexes. The reaction of Zr-
(CH2Ph)4 with 1 equiv of tridentate 2,5-bis(N-arylimi-
nomethyl)pyrrolyl ligands 2a -c in toluene afforded the

Intramolecular Benzylation of an Imino Group
Organometallics, Vol. 23, No. 11, 2004 2799
corresponding dibenzyl complexes of zirconium (3a -c)
along with the release of 1 equiv of toluene (eq 2). In
contrast, reaction with 1 equiv of p-substituted pyrrolyl
ligands 2d and 2e resulted in a complicated mixture,
from which no products were isolated. Complexes 3a -c
were air- and moisture-sensitive and were characterized
by spectral data, and X-ray analysis of 3b and 3c (vide
infra).
F igu r e 1. Molecular structure of complex 3b. All hydrogen
atoms are omitted for clarity.
1
The H NMR spectra of 3a -c essentially displayed
the same pattern, clearly indicating that one of two
imino groups was selectively benzylated. The most
informative spectral data were three sets of benzyl
signals: methylene protons of a benzyl group attached
to the carbon adjacent to the nitrogen group appeared
as an ABX pattern, while those of the other two benzyl
groups bound to the zirconium atom were observed as
an ABq pattern. In the 13C NMR spectra, two carbon
resonances due to two ZrCH2Ph groups were displayed
around δ 70, while a signal due to CH2Ph of the ligand
appeared at higher field (around δ 42). It is noteworthy
that one of two methylene carbons bound to the zirco-
nium atom had a large J C-H value (132-136 Hz for 3a -
c), which was compatible with that (132 Hz) of the η2-
benzyl complexes [Cp2Zr(η2-CH2Ph)][B(C6F5)4]. On the
other hand, the J C-H value (120-122 Hz for 3a -c) of
another ZrCH2Ph was comparable to that (J C-H ) 119
Hz) reported for a typical η1-bonding mode of zir-
conocene dibenzyl complexes.18
The pyrrolyl ring protons were observed in the olefinic
region, indicating that the pyrrolyl anion was attached
in an η1-N-coordination mode to the zirconium atom.
The resonance of the imine proton of 3a -c was shifted
to higher field and the imine carbon signal appeared in
lower field compared to those of the corresponding free
ligand, suggesting that the imino nitrogen atom was
also coordinated to the zirconium atom.
F igu r e 2. Molecular structure of complex 3c. All hydrogen
atoms are omitted for clarity.
Ta ble 1. Selected Bon d Dista n ces a n d An gles in
Com p lexes 3b a n d 3c
3b
3c
Bond Distances (Å)
2.1408(11)
2.0867(12)
2.3932(12)
2.2860(14)
2.6588(13)
2.2916(15)
1.4904(17)
1.3189(18)
Zr-N1
Zr-N2
Zr-N3
Zr-C41
Zr-C42
Zr-C51
N2-C5
N3-C6
2.1317(12)
2.0827(12)
2.4228(13)
2.2691(17)
2.7806(17)
2.2900(16)
1.4854(18)
1.312(2)
Bond Angles (deg)
71.22(4)
N1-Zr-N2
N1-Zr-N3
N2-Zr-N3
Zr-C41-C42
Zr-C51-C52
N2-C5-C1
N3-C6-C4
71.26(5)
67.46(5)
67.43(4)
138.12(4)
87.18(9)
113.19(10)
106.06(11)
116.64(12)
(16) (a) Matsuo, Y.; Mashima, K.; Tani, K. Chem. Lett. 2000, 1114.
(b) Tsurugi, H.; Yamagata, T.; Tani, K.; Mashima, K. Chem. Lett. 2003,
32, 756. For other complexes having bis(iminopyrrolyl) ligands see:
Use of Cr: (c) Gibson, V. C.; Maddox, P. J .; Newton, C.; Redshaw, C.;
Solan, G. A.; White, A. J . P.; Williams, D. J . Chem. Commun. 1998,
1651. (d) Gibson, V. C.; Newton, C.; Redshaw, C.; Solan, G. A.; White,
A. J . P.; Williams, D. J . J . Chem. Soc., Dalton Trans. 2002, 4017. Use
of Ti: (e) Yoshida, Y.; Matsui, S.; Takagi, Y.; Mitani, M.; Nitabaru,
M.; Nakano, T.; Tanaka, H.; Fujita, T. Chem. Lett. 2000, 1270. (f)
Yoshida, Y.; Matsui, S.; Takagi, Y.; Mitani, M.; Nakano, T.; Tanaka,
H.; Kashiwa, N.; Fujita, T. Organometallics 2001, 20, 4793. (g) Yoshida,
Y.; Saito, J .; Mitani, M.; Takagi, Y.; Matsui, S.; Ishii, S.; Nakano, T.;
Kashiwa, N.; Fujita, T. Chem. Commun. 2002, 1298. Use of Hf: (h)
Matsui, S.; Spaniol, T. P.; Takagi, Y.; Yoshida, Y.; Okuda, J . J . Chem.
Soc., Dalton Trans. 2002, 24, 4529.
138.15(5)
93.78(11)
112.62(10)
105.97(11)
117.49(14)
Figures 1 and 2 show crystal structures of 3b and 3c,
respectively, and their selected bond distances and
angles are summarized in Table 1. The zirconium atom
of 3b adopts a distorted trigonal bipyramidal geometry,
where an amido nitrogen atom (N(2)) and an imine
nitrogen atom (N(3)) occupy the axial positions, and two
benzyl groups and the nitrogen atom (N(1)) of the
pyrrolyl moiety are placed at equatorial positions. In
complex 3b, the distance (2.1408(11) Å) of Zr-N(1) is
(17) (a) Dawson, D. M.; Walker, D. A.; Thornton-Pett, M.; Bochmann,
M. J . Chem. Soc., Dalton Trans. 2000, 459. (b) Matsuo, Y.; Mashima,
K.; Tani, K. Organometallics 2001, 20, 3510.
(18) Bochmann, M.; Lancaster, S. J . Organometallics 1993, 12, 633.

2800 Organometallics, Vol. 23, No. 11, 2004
Tsurugi et al.
comparable to that (2.14-2.35 Å)16a,b,17,19 found for
zirconium-pyrrolyl complexes. The distance (2.0867(12)
Å) of Zr-N(2) is much shorter than that of Zr-N(1) and
is comparable to that of metal-amido complexes.20
Although the distance (2.3932(12) Å) of Zr-N(3) is
longer than others, it is short enough to interact with
the metal center. The angle (138.12(4)°) of N(2)-Zr-
N(3) significantly deviates from 180°, but is reasonable
as a complex with a meridional tridentate ligand.21 The
short distance (2.6588(13) Å) of Zr-C(42) and the acute
angle (87.18(9)°) of Zr-C(41)-C(42) clearly show the η2-
coordination of the benzyl ligand, consistent with the
structure depicted by NMR spectral data. The coordi-
natively unsaturation around the metal center in 3b is
thus compensated by not only the coordination of the
imino group but also the coordination of the ipso carbon
of the benzyl group. The other benzyl moiety is normal:
the Zr-C(52) distance is 3.187 Å and the Zr-C(51)-
C(52) angle is 113.19(10)°. The structural features of
3c are essentially the same as 3b. A notable difference
is that complex 3c has a longer distance (2.7806(17) Å)
of Zr-C(42) and larger angle (93.78(11)°) of Zr-C(41)-
C(42) than those of 3b owing to bulky ortho-diisopropyl
substituents on the phenyl groups of 3c.
Ta ble 2. Eth ylen e P olym er iza tion Ca ta lyzed by
Zir con iu m (3a -d ) a n d Ha fn iu m Com p lexes (4a -f)a
amount of cat.
yield PE
(mg)
activity (kg PE)
(mol cat.)-1 h-1
cat.
(µmol)
3a
3b
3c
4a
4b
4c
4d
4e
9.6
7.6
2.1
8.6
3.5
8.7
17.0
4.9
134
395
103
11
22
50
14
52
49
1.3
6.4
5.7
0.1
0.1
1.7
0.5
a
Conditions: cocatalyst ) 1000 equiv of MMAO, ethylene
pressure 1 atm, reaction 2 h at rt, [cat.] ) 1.0-1.3 mM in toluene.
Hz for 4e), although a sterically less demanding envi-
ronment of 4d and 4e might be expected to require the
contribution of the η2-mode of the benzyl group. Thus,
it is likely assumed that the less hindered substituent
on the ligand increased the donation of the imino moiety
to the metal center.
The reaction of tetrabenzyl hafnium with 1 equiv of
2a -e gave the corresponding hafnium complexes 4a -e
as air- and moisture-sensitive yellow solids (eq 3). In
contrast to the reaction of tetrabenzyl zirconium, reac-
tions with less bulky p-substituted pyrrolyl ligands 2d
and 2e afforded 4d and 4e, respectively, presumably due
to the general tendency that hafnium alkyl complexes
are more stable toward an insertion of the imine into
the Hf-carbon bond than the corresponding zirconium
alkyl complexes.22 Complexes 4a -e have the same
structure as 3a -c. The 1H NMR spectra of 4a -e
displayed three sets of benzyl signals (one ABX signal
and two ABq signals). The 13C NMR spectrum of the
complexes 4a -c showed that one of two methylene
carbons, HfCH2Ph, has a large J C-H value (134-138
Hz), suggesting that one benzyl group coordinated in
an η2-mode to the hafnium atom, while the other with
a small J C-H value (117-119 Hz) adopts an η1-benzyl
coordination mode. Complexes 4d and 4e have two
benzyl groups coordinating in an η1-fashion to the
hafnium atom as judged by the J C-H values of benzyl
methylene carbons (124 and 126 Hz for 4d ; 118 and 125
Ca ta lytic P er for m a n ce of th e Ben zyl Com p lexes
for Eth ylen e P olym er iza tion . The zirconium and
hafnium pyrrolyl complexes 3a -c and 4a -e were used
as catalyst precursors for ethylene polymerization under
atomspheric pressure of ethylene in the presence of
excess amounts of MMAO (1000 equiv), and the results
are summarized in Table 2. Zirconium complexes are
superior in activity to the corresponding hafnium com-
plexes. The higher catalytic activities were achieved
when zirconium complexes 3b and 3c, bulky 2,6-
dialkylphenyl derivatives, were used as catalyst precur-
sors. Temperature dependence of the polymerization
activity for complexes 3b and 3c was further investi-
gated (Table 3). In the case of the complex 3c, the
highest polymerization activity was obtained at 75 °C,
whose activity was 10 times higher than that operated
at room temperature, indicating that at room temper-
ature the insertion of ethylene into the metal-carbon
bond of catalytically active cationic species was pre-
vented, to some extent, by steric bulkiness of the imino
and amido moieties. Similarly, complex 3b showed the
highest activity of the polymerization at 60 °C. The
polyethylenes obtained by using 3b and 3c at various
temperature have rather broad Mw/Mn values (26.7-
51.4 for 3b; 17.5-43.2 for 3c), due to the thermal
instability of the catalytically active species under the
polymerization condition. These observations imply that
the coordination of the imino group as the third N-donor
was required to stabilize an active cationic spicies, but
lowered the catalytic activity at room temperature.
F or m a tion of Ca tion ic Ben zyl Com p lexes a n d
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metallics 2000, 19, 2944.
(22) Martin, A.; Uhrhammer, R.; Gardner, T. G.; J ordan, R. F.;
Rogers, R. D. Organometallics 1998, 17, 382.

Intramolecular Benzylation of an Imino Group
Organometallics, Vol. 23, No. 11, 2004 2801
Ta ble 3. Tem p er a tu r e Effect on th e P er for m a n ce
of Eth ylen e P olym er iza tion Ca ta lyzed by 3a a n d
3ba
5c, 6b, and 6c were prepared by treatment of complexes
3b, 3c, 4b, and 4c with [Ph3C][B(C6F5)4], respectively
(eq 4). Monitoring the reaction of 3c and [Ph3C]-
[B(C6F5)4] in bromobenzene-d5 by 1H NMR spectroscopy
showed the quantitative formation of a cationic complex
5c and Ph3CCH2Ph. The 1H NMR spectrum of 5c
displayed an ABq signal attributed to ZrCHaHbPh (δ
2.31 and 2.95 with a coupling constant of 9.1 Hz). In
the 13C NMR spectrum of complex 5c, the carbon signal
of ZrCH2Ph was observed at δ 83.5 with a large J C-H
value (140 Hz), indicating the large contribution of the
η2-coordination of the benzyl moiety, due to a stronger
Lewis acidic nature and coordinative unsaturation of
the cationic zirconium center. The other three complexes
5b, 6b, and 6c have almost the same spectral pattern.
activity (kg PE)
entry
cat.
time (min)
temp (°C)
(mol cat)-1 h-1
1
2
3
4
5
6
7
8
3a
3a
3a
3a
3a
3a
3b
3b
3b
3b
3b
3b
360
90
60
90
30
90
600
60
30
20
20
60
0
r.t.
45
60
75
90
0
r.t.
45
60
75
90
1.2
28
71
131
68
50
1.5
57
88
258
447
75
9
10
11
12
1
a
The H NMR spectra of 5b, 5c, 6b, and 6c additionally
Conditions: cocatalyst ) 1000 equiv of MMAO, ethylene
pressure 1 atm, [cat.] ) 0.25 mM in toluene.
showed temperature-dependence. The ortho-protons of
the benzyl phenyl group bound to the zirconium atom
of 5c were observed as two doublets (δ 5.14 and 5.44)
at -25 °C, which became one broad signal at room
temperature. This process can be rationalized by the
restricted rotation of the MCH2-Ph bond through the
η1-coordination mode,23 the ∆Gqvalue being estimated
to be 14.7 kcal/mol (coalesced at 32.5 °C). For the other
three complexes, the ∆Gq value was found to be 13.4
kcal/mol for 5b (coalesced at 10 °C), 13.7 kcal/mol for
6b (coalesced at 10 °C), and 14.3 kcal/mol for 6c
(coalesced at 20 °C).
We observed that complexes 5b and 6b with the 2,6-
xylyl-substituted ligand gradually decomposed within
a few hours, probably through the C-H activation of
an ortho-methyl group of the ligand.24 The characteriza-
tion of the decomposed products was hampered by their
poor solubility in organic solvents such as toluene and
bromobenzene.
the catalyst systems involve cationic alkyl complexes
as key intermediates in ethylene polymerization.
We further examined the reactions of 5c and 6c with
1-hexene in C6D5Br, and the reactions were monitored
1
by 1H NMR spectroscopy. The H NMR spectrum of the
mixture of 5c and 1-hexene displayed no signal due to
ZrCH2Ph of 5c, indicating that 1-hexene inserted into
the Zr-benzyl bond. The reaction solution was then
quenched by adding 1 N HCl. The resulting organic
product was collected and analyzed by using GC-MS
to be CH3CH(nBu)CH2Ph, which is a product of insertion
of one molecule of 1-hexene into the metal-benzyl bond.
No oligomer or polymer of 1-hexene was obtained. The
insertion of 1 equiv of 1-hexene stabilized the cationic
species and prevented further insertion of the monomer,
presumably due to the interaction between the phenyl
ring of the hydrocarbyl group bound to the metal and
the cationic metal center via an η6-coordination. This
was supported by the observation that the phenyl
protons of the benzyl group shifted to higher field
compared with complexes 5c and 6c. Such an insertion
of only 1 equiv of R-olefin into the metal-benzyl bond
has been revealed by the η6-coordination of the phenyl
ring at the chain end to the cationic center, as evident
from the shift of the phenyl protons to lower field after
the reaction.21f,25
Con clu sion
We have demonstrated that the reactions of 2,5-bis-
(N-aryliminomethyl)pyrrole (2) with tetrabenzyl-zirco-
nium and -hafnium afforded the corresponding amido-
pyrrolyl complexes by the unique intramolecular benzyla-
tion of one of two imino moieties of the tridentate
ligands. The resulting dianionic ligands not only stabi-
lized dibenzyl complexes of zirconium and hafnium but
also enhanced the catalytic activity. The high unsat-
uration around the metal center was found to be
compensated by contributions through the donation of
the imino nitrogen atom and the η2-coordination of one
of two benzyl groups bound to the metal center. These
complexes upon activation by excess amounts of MMAO
Cationic complexes are catalytically active for ethyl-
ene polymerization without aluminum cocatalyst. A
solution of 5c or 6c in C6H5Br was exposed to atmo-
spheric pressure of ethylene at room temperature for 1
h to give trace amounts of polyethylene, suggesting that
(25) (a) Pellecchia, C.; Grassi, A.; Zambelli, A. J . Chem. Soc., Chem.
Commun. 1993, 947. (b) Pellecchia, C.; Grassi, A.; Zambelli, A.
Organometallics 1994, 13, 298. (c) Pellecchia, C.; Grassi, A.; Zambelli,
A. J . Organomet. Chem. 1994, C9. (d) Horton, A. D.; de With, J .
Organometallics 1997, 16, 5424. (e) Thorn, M. G.; Etheridge, Z. C.;
Franwick, P. E.; Rothwell, I. P. Organometallics 1998, 17, 3636.
(23) Bei, X.; Swenson, D. C.; J ordan, R. F. Organometallics 1997,
16, 3282.
(24) (a) Schrock, R. R.; Bonitatebus, J . P. J .; Schrodi, Y. Organo-
metallics 2001, 20, 1056. (b) Schrodi, Y.; Schrock, R. R.; Bonitatebus,
J . P. J . Organometallics 2001, 20, 3560.

2802 Organometallics, Vol. 23, No. 11, 2004
Tsurugi et al.
29.1 (CH(CH3)2), 29.2 (2C,CH(CH3)2), 29.6 (CH(CH3)2), 42.2 (t,
showed catalytic activity for ethylene polymerization,
and complexes 3b and 3c with the bulky substituents
on the ligand were found to be better catalyst precursors
among them. The Lewis-base-free cationic alkyl species
5b, 5c, 6b, and 6c were respectively prepared by
reaction of 3b, 3c, 4b, and 4c with [Ph3C][B(C6F5)4], and
5c and 6c were tested as catalysts for ethylene polym-
erization without the aluminum cocatalyst. We also
found that 1 equiv of 1-hexene inserted into the metal-
benzyl bond of the cationic complexes 5c and 6c, but
the successive insertion was prevented by the coordi-
native interaction of the phenyl moiety of the chain end
to the cationic metal center.
1
1J C-H ) 130 Hz, CHCH2Ph), 68.1 (t, J C-H ) 120 Hz, ZrCH2-
1
1
Ph), 73.1 (t, J C-H ) 132 Hz, ZrCH2Ph), 78.0 (d, J C-H ) 137
1
Hz, CHCH2Ph), 111.4 (d, J C-H ) 173 Hz, pyrrole ring), 122.0
1
1
(d, J C-H ) 169 Hz, pyrrole ring), 164.7 (d, J C-H ) 166 Hz,
NdCH), 122-163 (aromatic carbons). Anal. Calcd for C51H59N3-
Zr1: C, 76.07; H, 7.38; N, 5.22. Found: C, 76.05; H, 7.58; N,
4.82.
Similarily, zirconium complexes 3a and 3b were prepared.
{(o-TOL)2-p yr -CH2P h }Zr (CH2P h )2 (3a ): 96% yield, mp
145-160 °C (dec). 1H NMR (300 MHz, C6D6, 35 °C): δ 1.54
and 1.60 (ABq, 2J H-H ) 12.1 Hz, 2H, ZrCHHPh), 1.96 and 2.23
2
(ABq, J H-H ) 8.7 Hz, 2H, ZrCHHPh), 1.97 (s, 3H, CH3), 2.06
2
3
(dd, J H-H ) 12.8 Hz, J H-H ) 10.9 Hz, 1H, CHCHHPh), 2.34
2
3
(s, 3H, CH3), 2.78 (dd, J H-H ) 12.8 Hz, J H-H ) 4.7 Hz, 1H,
CHCHHPh), 5.27 (dd, J H-H ) 10.9 and 4.7 Hz, 1H, CH-N),
3
Exp er im a n ta l Section
3
3
5.38 (d, J H-H ) 7.2 Hz, 2H, o-Ph of ZrCH2Ph), 5.43 (d, J H-H
) 3.5 Hz, 1H, pyrrole ring), 6.56 (d, 3J H-H ) 3.5 Hz, 1H, pyrrole
ring), 6.8-7.3 (m, 19H, aromatic protons and NdCH). 13C
Gen er a l P r oced u r es. All manipulations involving air- and
moisture-sensitive organometallic compounds were performed
using standard Schlenk techniques under argon. Complexes
Zr(CH2Ph)4 and Hf(CH2Ph)4 were prepared according to the
literature.26,27 Tridentate ligands 2a -e were prepared accord-
ing to the literature.17b [Ph3C][B(C6F5)4] was prepared accord-
ing to the literature.28 Hexane, THF, toluene, and ether were
dried and deoxygenated by distillation over sodium benzophe-
none ketyl under argon. Benzene-d6 and THF-d8 were distilled
from P2O5 and thoroughly degassed by trap-to-trap distillation
before use. Bromobenzene and bromobenzene-d5 were distilled
over CaH2 and then degassed. Methylalminoxane (MMAO-3A,
Tosoh-finechem) was used as received. Ethylene (Sumitomo
Seika Chemicals Co.) was dried by passing through a dry-
column (Nikka Seiko Co., DC-3A) and a gas-clean column
1
NMR (75 MHz, C6D6, 35 °C): δ 18.7 (q, J C-H ) 126 Hz, 2C,
CH3), 42.2 (t, 1J C-H ) 131 Hz, CHCH2Ph), 65.6 (t, 1J C-H ) 122
1
Hz, ZrCH2Ph), 66.8 (t, J C-H ) 136 Hz, ZrCH2Ph), 73.6 (d,
1J C-H ) 138 Hz, CHCH2Ph), 111.2 (d, 1J C-H ) 172 Hz, pyrrole
1
1
ring), 122.7 (d, J C-H ) 169 Hz, pyrrole ring), 164.8 (d, J C-H
) 168 Hz, NdCH), 122-163 (aromatic carbones).
(XYL2-p yr -CH2P h )Zr (CH2P h )2 (3b): 92% yield, mp 151-
156 °C (dec). 1H NMR (300 MHz, C6D6, 35 °C): δ 1.00 and
2
1.64 (ABq, J H-H ) 12.4 Hz, 2H, ZrCHHPh), 1.97 (s, 2H,
2
3
ZrCH2Ph), 2.09 (s, 3H, CH3), 2.09 (dd, J H-H ) 12.4 Hz, J H-H
) 11.5 Hz, 1H, CHCHHPh), 2.21 (s, 3H, CH3), 2.32 (s, 3H,
2
3
CH3), 2.48 (s, 3H, CH3), 2.71 (dd, J H-H ) 12.4 Hz, J H-H
)
3
4.8 Hz, 1H, CHCHHPh), 5.04 (dd, J H-H ) 11.5 and 4.8 Hz,
3
1
1H, CH-N), 5.33 (d, J H-H ) 3.6 Hz, 1H, pyrrole ring), 5.68
(Nikka Seiko Co., GC-RX) before use. The H (300 MHz) and
(d, 3J H-H ) 6.6 Hz, 2H, o-Ph of ZrCH2Ph), 6.58 (d, 3J H-H ) 3.6
13C (75 Hz) NMR spectra were measured on a Varian-Unity-
Inova-300 spectrometer. The elemental analyses were recorded
by using a Perkin-Elmer 2400 at the Faculty of Engineering
Science, Osaka University. All melting points were measured
in sealed tubes under argon atmosphere.
Hz, 1H, pyrrole ring), 6.8-7.3 (m, 19H, aromatic protons and
NdCH). 13C NMR (75 MHz, C6D6, 35 °C): δ 19.5 (q, J C-H
)
)
)
1
1
1
127 Hz, CH3), 19.7 (q, J C-H ) 126 Hz, CH3), 20.1 (q, J C-H
1
1
127 Hz, CH3), 21.4 (q, J C-H ) 124 Hz, CH3), 42.4 (t, J C-H
1
132 Hz, CHCH2Ph), 68.9 (t, J C-H ) 120 Hz, ZrCH2Ph), 69.7
(DIP 2-p yr -CH2P h )Zr (CH2P h )2 (3c). In a Schlenk tube, Zr-
(CH2Ph)4 (525 mg, 1.15 mmol) and 1c (494 mg, 1.12 mmol)
were placed, and then toluene (40 mL) was added at -78 °C.
The reaction mixture was allowed to warm to room temper-
ature and stirred overnight. All volatiles were removed under
reduced pressure. The resulting yellow oil was dissolved in a
small amount of hexane and stored at room temperature. The
yellow crystals were formed and then dried under vacuum to
give 3c as yellow crystals (857 mg, 95% yield), mp 155-162
(t, 1J C-H ) 136 Hz, ZrCH2Ph), 77.4 (d, 1J C-H ) 136 Hz, CHCH2-
1
Ph), 111.4 (pyrrole ring), 122.0 (pyrrole ring), 165.5 (d, J C-H
) 167 Hz, NdCH), 122-163 (aromatic carbones). Anal. Calcd
for C43H43N3Zr1: C, 74.52; H, 6.25; N, 6.06. Found: C, 73.98;
H, 6.26; N, 6.15.
P r ep a r a tion of (DIP 2-p yr -CH2P h )Hf(CH2P h )2 (4c). To
a solution of Hf(CH2Ph)4 (110 mg, 0.20 mmol) and 1c (90 mg,
0.20 mmol) at -78 °C was added toluene (30 mL). The reaction
mixture was allowed to warm to room temperature. After
stirring for 1 h at 50 °C, all volatiles were removed under
reduced pressure. The resulting yellow-brown oil was dissolved
in toluene to give yellow crystals of 4c: (174 mg, 97% yield),
mp 165-176 °C (dec). 1H NMR (300 MHz, C6D6, 35 °C): δ 1.03
(d, 3J H-H ) 6.8 Hz, 3H, CH3), 1.14 (d, 3J H-H ) 6.8 Hz, 3H, CH3),
1
3
°C (dec). H NMR (300 MHz, C6D6, 35 °C): δ 1.03 (d, J H-H
)
3
6.8 Hz, 3H, CH3), 1.12 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.20 (d,
3J H-H ) 6.8 Hz, 3H, CH3), 1.25 (d, J H-H ) 6.8 Hz, 3H, CH3),
3
3
3
1.26 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.32 (d, J H-H ) 6.8 Hz,
3
3
3H, CH3), 1.38 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.49 (d, J H-H
)
)
2
6.8 Hz, 3H, CH3), 1.83 (s, 2H, ZrCH2Ph), 1.89 (dd, J H-H
12.5 Hz, 3J H-H ) 11.5 Hz, 1H, CHCHHPh), 2.09 and 2.18 (ABq,
1.23 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.27 (d, J H-H ) 6.8 Hz,
3
3
2
3
3
3
J H-H ) 10.1 Hz, 2H, ZrCHHPh), 2.92 (dd, J H-H ) 12.5 Hz,
3H, CH3), 1.28 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.33 (d, J H-H )
3
3J H-H ) 4.7 Hz, 1H, CHCHHPh), 3.40 (sep, J H-H ) 6.8 Hz,
6.8 Hz, 3H, CH3), 1.40 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.48 (d,
2 3
3
1H, CH(CH3)2), 3.64 (sep, 3J H-H ) 6.8 Hz, 1H, CH(CH3)2), 3.69
3J H-H ) 6.8 Hz, 3H, CH3), 1.79 (dd, J H-H ) 12.5 Hz, J H-H
)
3
3
2
(sep, J H-H ) 6.8 Hz, 1H, CH(CH3)2), 3.74 (sep, J H-H ) 6.8
11.7 Hz, 1H, CHCHHPh), 1.83 and 1.94 (ABq, J H-H ) 13.9
3
Hz, 1H, CH(CH3)2), 5.11 (dd, J H-H ) 11.5 and 4.7 Hz, 1H,
Hz, 2H, HfCHHPh), 1.94 and 2.06 (ABq, 2J H-H ) 10.9 Hz, 2H,
3
2
3
CH-N), 5.29 (d, J H-H ) 3.5 Hz, 1H, pyrrole ring), 5.97 (d,
HfCHHPh), 2.94 (dd, J H-H ) 12.6 Hz, J H-H ) 4.6 Hz, 1H,
3J H-H ) 6.9 Hz, 2H, o-Ph of ZrCH2Ph), 6.59 (d, J H-H ) 3.5
CHCHHPh), 3.45 (sep, J H-H ) 6.8 Hz, 1H, CH(CH3)2), 3.65
3
3
3
3
Hz, 1H, pyrrole ring), 6.9-7.4 (m, 19H, aromatic protons), 7.81
(s, 1H, NdCH). 13C NMR (75 MHz, C6D6, 35 °C): δ 22.4 (CH-
(CH3)2), 22.7 (CH(CH3)2), 24.2 (CH(CH3)2), 26.2(CH(CH3)2), 26.7
(CH(CH3)2), 27.2 (CH(CH3)2), 27.6 (CH(CH3)2), 28.1 (CH(CH3)2),
(sep, J H-H ) 6.8 Hz, 1H, CH(CH3)2), 3.76 (sep, J H-H ) 6.8
Hz, 1H, CH(CH3)2), 3.87 (sep, 3J H-H ) 6.8 Hz, 1H, CH(CH3)2),
3
3
5.24 (dd, J H-H ) 11.7 and 4.6 Hz, 1H, CH-N), 5.27 (d, J H-H
3
) 3.5 Hz, 1H, pyrrole ring), 6.01 (d, J H-H ) 6.9 Hz, 2H, o-Ph
3
of HfCH2Ph), 6.55 (d, J H-H ) 3.5 Hz, 1H, pyrrole ring), 6.8-
(26) Zucchini, U.; Albizzati, E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357.
(27) Felten, J . J .; Anderson, W. P. J . Organomet. Chem. 1972, 36,
7.4 (m, 19H, aromatic protons), 8.00 (s, 1H, NdCH). 13C NMR
(75 MHz, C6D6, 35 °C): δ 22.5 (CH(CH3)2), 22.7 (CH(CH3)2),
24.5 (CH(CH3)2), 26.5 (CH(CH3)2), 26.7 (CH(CH3)2), 27.3 (CH-
(CH3)2), 27.6 (CH(CH3)2), 27.7 (CH(CH3)2), 28.9 (CH(CH3)2),
29.1 (CH(CH3)2), 29.1 (CH(CH3)2), 29.8 (CH(CH3)2), 42.6 (t,
87.
(28) Chien, J . C. W.; Tsai, W. M.; Rausch, M. D. J . Am. Chem. Soc.
1991, 113, 8570.

Intramolecular Benzylation of an Imino Group
Organometallics, Vol. 23, No. 11, 2004 2803
1
1
1
1J C-H ) 132 Hz, CHCH2Ph), 76.0 (t, J C-H ) 117 Hz, HfCH2-
ring), 123.8 (d, J C-H ) 170 Hz, pyrrole ring), 159.7 (d, J C-H
) 167 Hz, NdCH), 119-162 (aromatic carbones). Anal. Calcd
for C41H39N3O2Hf1: C, 65.46; H, 5.23; N, 5.59. Found: C, 64.71;
H, 5.22; N, 5.73.
1
1
Ph), 77.2 (t, J C-H ) 138 Hz, HfCH2Ph), 82.1 (d, J C-H ) 126
Hz, CHCH2Ph), 112.1 (d, J C-H ) 173 Hz, pyrrole ring), 123.1
1
1
1
(d, J C-H ) 169 Hz, pyrrole ring), 165.3 (d, J C-H ) 168 Hz,
NdCH), 122-163 (aromatic carbons). Anal. Calcd for C51H59N3-
Hf1: C, 68.63; H, 6.66; N, 4.71. Found: C, 68.39; H, 6.83; N,
4.74.
Similarily, hafnium complexes 4a , 4b, 4d , and 4e were
prepared.
F or m a tion of [(DIP 2-p yr -CH2P h )Zr (CH2P h )][B(C6F 5)4]
(5c). A solution of 3c (39.2 mg, 49 µmol) and [Ph3C][B(C6F5)4]
(46.4 mg, 50 µmol) in C6D5Br (0.60 mL) was sealed in a NMR
tube. The color of the solution gradually turned red-brown at
room temperature. The 1H NMR spectrum of the solution at
35 °C revealed the quantitative formation of [(DIP2-pyr-CH2-
Ph)Zr(CH2Ph)][B(C6F5)4] and Ph3CCH2Ph (CH2 at 3.84 ppm).
{(o-TOL)2-p yr -CH2P h }Hf(CH2P h )2 (4a ): 93% yield, mp
145-156 °C (dec). 1H NMR (300 MHz, C6D6, 35 °C): δ 1.51 (s,
1H NMR (300 MHz, C6D5Br, 35 °C): δ 0.85 (d, J H-H ) 6.4
3
2
2H, HfCH2Ph), 1.78 and 2.15 (ABq, J H-H ) 10.2 Hz, 2H,
Hz, 3H, CH3), 0.88 (d, 3J H-H ) 6.4 Hz, 3H, CH3), 0.94 (d, 3J H-H
) 6.8 Hz, 3H, CH3), 0.98 (d, 3J H-H ) 6.7 Hz, 3H, CH3), 1.15 (d,
HfCHHPh), 2.00 (s, 3H, CH3), 2.06 (dd, 2J H-H ) 12.7 Hz, 3J H-H
) 11.2 Hz, 1H, CHCHHPh), 2.38 (s, 3H, CH3), 2.84 (dd, 2J H-H
3J H-H ) 6.8 Hz, 3H, CH3), 1.20 (d, J H-H ) 6.3 Hz, 3H, CH3),
3
3
3
) 12.7 Hz, J H-H ) 4.4 Hz, 1H, CHCHHPh), 5.40 (d, J H-H
)
3
3
3
1.22 (d, J H-H ) 6.7 Hz, 3H, CH3), 1.35 (d, J H-H ) 6.3 Hz,
3H, CH3), 1.58 (br t, J H-H ) 11.9 Hz, 1H, CHCHHPh), 2.31
3.6 Hz, 1H, pyrrole ring), 5.44 (dd, J H-H ) 11.2 and 4.4 Hz,
3
1H, CH-N), 5.50 (d, J H-H ) 7.4 Hz, 2H, o-Ph of HfCH2Ph),
2
3
and 2.95 (ABq, J H-H ) 9.1 Hz, 2H, ZrCHHPh), 2.49 (m, 1H,
6.50 (d, J H-H ) 3.6 Hz, 1H, pyrrole ring), 6.8-7.3 (m, 22H,
2
3
aromatic protons and NdCH). 13C NMR (75 MHz, C6D6, 35
CH(CH3)2), 2.57 (dd, J H-H ) 12.5 Hz, J H-H ) 4.2 Hz, 1H,
CHCHHPh), 2.88 (m, 1H, CH(CH3)2), 3.10 (m, 1H, CH(CH3)2),
1
1
°C): δ 18.6 (q, J C-H ) 126 Hz, 2C, CH3), 42.5 (t, J C-H ) 130
3
1
3.45 (m, 1H, CH(CH3)2), 5.05 (d, J H-H ) 3.5 Hz, 1H, pyrrole
Hz, CHCH2Ph), 72.4 (t, J C-H ) 119 Hz, HfCH2Ph), 72.8 (t,
1
1J C-H ) 138 Hz, HfCH2Ph), 74.7 (d, J C-H ) 131 Hz, CHCH2-
ring), 5.20 (br, 2H, o-Ph of ZrCH2Ph), 5.60 (br d, J H-H ) 7.7
3
1
Hz, 1H, CH-N), 6.57 (d, J H-H ) 3.5 Hz, 1H, pyrrole ring),
Ph), 111.9 (pyrrole ring), 123.3 (pyrrole ring), 165.2 (d, J C-H
) 168 Hz, NdCH), 122-163 (aromatic carbons).
6.7-7.4 (aromatic protons), 7.87 (s, 1H, NdCH). 13C NMR (75
MHz, C6D5Br, 23 °C): δ 21.9 (CH(CH3)2), 21.9 (CH(CH3)2), 22.2
(CH(CH3)2), 23.1 (CH(CH3)2), 24.2 (CH(CH3)2), 24.9 (CH(CH3)2),
25.9 (CH(CH3)2), 26.9 (CH(CH3)2), 27.9 (CH(CH3)2), 29.4 (CH-
(CH3)2), 29.4 (CH(CH3)2), 29.4 (CH(CH3)2), 41.1 (t, 1J C-H ) 132
(XYL2-p yr -CH2P h )Hf(CH2P h )2 (4b): 87% yield, mp 168-
184 °C (dec). 1H NMR (300 MHz, C6D6, 35 °C): δ 0.98 and
2
1.49 (ABq, J H-H ) 13.5 Hz, 2H, HfCHHPh), 1.77 and 1.92
(ABq, 2J H-H ) 10.3 Hz, 2H, HfCHHPh), 2.00 (dd, 2J H-H ) 12.6
1
3
Hz, CHCH2Ph), 77.7 (d, J C-H ) 142 Hz, CHCH2Ph), 83.5 (t,
Hz, J H-H ) 11.3 Hz, 1H, CHCHHPh), 2.13 (s, 3H, CH3), 2.25
1J C-H ) 140 Hz, ZrCH2Ph), 112.1 (d, J C-H ) 180 Hz, pyrrole
1
(s, 3H, CH3), 2.40 (s, 3H, CH3), 2.51 (s, 3H, CH3), 2.75 (dd,
1
2J H-H ) 12.6 Hz, J H-H ) 4.9 Hz, 1H, CHCHHPh), 5.19 (dd,
3
ring), 166.1 (d, J C-H ) 170 Hz, NdCH), 122-163 (aromatic
3J H-H ) 11.3 and 4.9 Hz, 1H, CH-N), 5.30 (d, 3J H-H ) 3.3 Hz,
and pyrrolyl carbones).
3
Similarly, [(XYL2-pyr-CH2Ph)Zr(CH2Ph)][B(C6F5)4] (5b) was
generated in situ and characterized by its H NMR spectrum.
Stirring a solution of 5b at room temperature for a few hours
afforded microcrystals, which did not dissolve in toluene and
C6H5Br. H NMR (300 MHz, C6D5Br, 25 °C): δ 1.32 (br, 1H,
CHCHHPh), 1.77 (s, 3H, CH3), 2.11 (s, 6H, CH3), 2.15 (over-
rapped with other resonances, 1H, ZrCHHPh), 2.25 (m, 1H,
1H, pyrrole ring), 5.76 (d, J H-H ) 7.1 Hz, 2H, o-Ph of HfCH2-
1
3
Ph), 6.54 (d, J H-H ) 3.3 Hz, 1H, pyrrole ring), 6.9-7.5 (m,
aromatic protons and NdCH). 13C NMR (75 MHz, C6D6, 35
°C): δ 19.5 (CH3), 19.7 (CH3), 20.1 (CH3), 21.4 (CH3), 42.9 (t,
1
1
1J C-H ) 131 Hz, CHCH2Ph), 74.5 (t, J C-H ) 119 Hz, HfCH2-
1
1
Ph), 76.4 (d, J C-H ) 138 Hz, CHCH2Ph), 76.9 (t, J C-H ) 134
Hz, HfCH2Ph), 112.0 (d, J C-H ) 173 Hz, pyrrole ring), 123.0
(d, J C-H ) 169 Hz, pyrrole ring), 165.9 (d, J C-H ) 168 Hz,
NdCH), 122-163 (aromatic carbons).
1
2
1
1
CHCHHPh), 2.54 (d, J H-H ) 8.8 Hz, 1H, ZrCHHPh), 5.06 (d,
3J H-H ) 3.7 Hz, 1H, pyrrole ring), 5.12 (br, 2H, o-Ph of ZrCH2-
3
Ph), 5.22 (dd, J H-H ) 4.1 and 11.5 Hz, 1H, CH-N), 6.54 (d,
{(p-ANI)2-p yr -CH2P h }Hf(CH2P h )2 (4d ): 90% yield, mp
129-140 °C (dec). 1H NMR (300 MHz, C6D6, 35 °C): δ 1.91
and 2.20 (ABq, 2J H-H ) 11.5 Hz, 2H, HfCHHPh), 2.05 and 2.32
(ABq, 2J H-H ) 12.2 Hz, 2H, HfCHHPh), 2.53 (dd, 2J H-H ) 13.3
3J H-H ) 3.7 Hz, 1H, pyrrole ring), 6.6-7.2 (aromatic protons
and NdCH).
Cationic hafnium complexes 6b and 6c were prepared in a
similar procedure.
[(XYL2-p yr -CH2P h )Hf(CH2P h )][B(C6F 5)4] (6b): 1H NMR
(300 MHz, C6D5Br, 25 °C): δ 1.15 (t, J H-H ) 12.0 Hz, 1H,
CHCHHPh), 1.77 (s, 3H, CH3), 1.85 and 2.41 (ABq, J H-H
3
2
Hz, J H-H ) 9.8 Hz, 1H, CHCHHPh), 3.08 (dd, J H-H ) 13.3
Hz, 3J H-H ) 4.1 Hz, 1H, CHCHHPh), 3.38 (s, 3H, OCH3), 3.50
3
(s, 3H, OCH3), 5.54 (d, J H-H ) 3.5 Hz, 1H, pyrrole ring), 5.61
3
3
2
(dd, J H-H ) 9.8 and 4.1 Hz, 1H, CH-N), 6.39 (d, J H-H ) 7.1
Hz, 2H, o-Ph of HfCH2Ph), 6.45 (d, 3J H-H ) 3.5 Hz, 1H, pyrrole
ring), 6.7-7.3 (m, 19H, aromatic protons), 7.43 (s, 1H, NdCH).
)
9.9 Hz, 1H, HfCHHPh), 2.11 (s, 3H, CH3), 2.14 (s, 3H, CH3),
2
3
2.29 (dd, J H-H ) 12.9 Hz, J H-H ) 4.1 Hz, 1H, CHCHHPh),
13C NMR (75 MHz, C6D6, 35 °C): δ 42.0 (t, J C-H ) 130 Hz,
2.47 (s, 3H, CH3), 5.07 (d, J H-H ) 3.6 Hz, 1H, pyrrole ring),
1
3
CHCH2Ph), 55.7 (q, 1J C-H ) 143 Hz, 2C, OCH3), 73.0 (d, 1J C-H
) 138 Hz, CHCH2Ph), 76.8 (t, 1J C-H ) 124 Hz, HfCH2Ph), 78.5
(t, 1J C-H ) 126 Hz, HfCH2Ph), 111.6 (d, 1J C-H ) 172 Hz, pyrrole
5.10 (br, 2H, o-Ph of HfCH2Ph), 5.56 (dd, 3J H-H ) 4.1 and 11.3
3
Hz, 1H, CH-N), 6.54 (d, J H-H ) 3.6 Hz, 1H, pyrrole ring),
6.8-7.3 (aromatic protons), 7.53 (s, 1H, NdCH).
1
1
[(DIP 2-p yr -CH2P h )Hf(CH2P h )][B(C6F 5)4] (6c): 1H NMR
(300 MHz, C6D5Br, 25 °C): δ 0.87 (d, 3J H-H ) 6.3 Hz, 3H, CH3),
ring), 123.2 (d, J C-H ) 175 Hz, pyrrole ring), 160.8 (d, J C-H
) 168 Hz, NdCH), 115-163 (aromatic carbones).
{(p-TOL)2-p yr -CH2P h }Hf(CH2P h )2 (4e): 92% yield, mp
3
0.95 (m, 9H, CH3), 0.98 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.16 (d,
1
3
82-98 °C. H NMR (300 MHz, C6D6, 35 °C): δ 1.98 and 2.18
3J H-H ) 6.8 Hz, 3H, CH3), 1.21 (d, J H-H ) 6.8 Hz, 3H, CH3),
(ABq, 2J H-H ) 12.0 Hz, 2H, HfCHHPh), 2.16 (s, 3H, CH3), 2.22
1.26 (d, J H-H ) 6.8 Hz, 3H, CH3), 1.31 (t, J ) 12.1 Hz, 1H,
3
2
3
and 2.48 (ABq, J H-H ) 12.1 Hz, 2H, HfCHHPh), 2.32 (s, 3H,
CHCHHPh), 1.47 (d, J H-H ) 6.8 Hz, 3H, CH3), 2.07 and 2.86
2
3
CH3), 2.58 (dd, J H-H ) 13.2 Hz, J H-H ) 9.3 Hz, 1H,
(ABq, 2J H-H ) 10.2 Hz, 2H, HfCHHPh), 2.52 (sep, 3J H-H ) 6.3
2
3
2
3
CHCHHPh), 3.09 (dd, J H-H ) 13.2 Hz, J H-H ) 4.1 Hz, 1H,
Hz, 1H, CH(CH3)2), 2.55 (dd, J H-H ) 12.8 Hz, J H-H ) 4.1
3
CHCHHPh), 5.55 (d, J H-H ) 3.6 Hz, 1H, pyrrole ring), 5.66
Hz, 1H, CHCHHPh), 2.97 (sep, 3J H-H ) 6.8 Hz, 1H, CH(CH3)2),
3
3
3
3
(dd, J H-H ) 9.3 and 4.1 Hz, 1H, CH-N), 6.42 (d, J H-H ) 3.6
3.20 (sep, J H-H ) 6.8 Hz, 1H, CH(CH3)2), 3.51 (sep, J H-H )
3
3
Hz, 1H, pyrrole ring), 6.51 (d, J H-H ) 7.1 Hz, 2H, o-Ph of
6.8 Hz, 1H, CH(CH3)2), 5.06 (d, J H-H ) 3.6 Hz, 1H, pyrrole
3
HfCH2Ph), 6.7-7.4 (m, aromatic protons), 7.47 (s, 1H, NdCH).
ring), 5.45 (br, 2H, o-Ph of HfCH2Ph), 5.92 (dd, J H-H ) 4.1
13C NMR (75 MHz, C6D6, 35 °C): δ 21.3 (q, J C-H ) 126 Hz,
and 11.8 Hz, 1H, CH-N), 6.58 (d, 3J H-H ) 3.6 Hz, 1H, pyrrole
ring), 6.7-7.3 (aromatic protons), 8.13 (s, 1H, NdCH). 13C
NMR (75 MHz, C6D5Br, 25 °C): δ 21.4 (CH(CH3)2), 21.7 (CH-
(CH3)2), 23.0 (CH(CH3)2), 24.4 (CH(CH3)2), 25.5 (CH(CH3)2),
1
1
1
2C, CH3), 41.5 (t, J C-H ) 128 Hz, CHCH2Ph), 70.5 (d, J C-H
) 138 Hz, CHCH2Ph), 79.0 (t, 1J C-H ) 118 Hz, HfCH2Ph), 80.6
(t, 1J C-H ) 125 Hz, HfCH2Ph), 111.9 (d, 1J C-H ) 171 Hz, pyrrole

2804 Organometallics, Vol. 23, No. 11, 2004
Tsurugi et al.
Ta ble 4. Cr ysta l Da ta a n d Da ta Collection
26.4 (CH(CH3)2), 26.5 (CH(CH3)2), 27.2 (CH(CH3)2), 28.6 (CH-
1
P a r a m eter s of 3b a n d 3c
(CH3)2), 28.8 (2C, CH(CH3)2), 29.4 (CH(CH3)2), 41.4 (t, J C-H
1
) 129 Hz, CHCH2Ph), 75.1 (d, J C-H ) 139 Hz, CHCH2Ph),
3b
3c
1
1
82.4 (t, J C-H ) 138 Hz, HfCH2Ph), 112.2 (d, J C-H ) 177 Hz,
formula
fw
C
43H43N3Zr
C51H59N3Zr
805.27
1
pyrrole ring), 166.2 (d, J C-H ) 172 Hz, NdCH), 122-163
693.05
(aromatic and pyrrolyl carbons).
cryst syst
space group
a, Å
triclinic
monoclinic
P21/c (No. 14)
15.3212(3)
13.2839(3)
22.0592(4)
90.0
98.9295(4)
90.0
4435.2(2)
F or m a t ion
of [(DIP 2-p yr -CH2P h )Zr (CH2CH (n Bu )-
P1h (No. 2)
11.3951(11)
12.6564(11)
14.1142(11)
83.967(3)
71.381(4)
69.055(3)
1801.5(3)
CH2P h )][B(C6F 5)4] (7c). To a solution of 3c (10.7 mg, 15.1
µmol) in C6D5Br (0.20 mL) was added a solution of [Ph3C]-
[B(C6F5)4] (14.2 mg, 15.3 µmol) and 1-hexene (23.5 µmol) in
C6D5Br (0.30 mL) at -30 °C, and then it was sealed in a NMR
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
1
tube. The H NMR spectrum of the solution at 35 °C revealed
the quantitative formation of [(DIP2-pyr-CH2Ph)Zr(CH2CH(n-
Bu)Ph)][B(C6F5)4] and Ph3CCH2Ph (CH2 at 3.84 ppm). 1H NMR
(300 MHz, C6D5Br, 35 °C): δ 0.14 (t, J H-H ) 12.4 Hz, 1H,
ZrCHH), 0.8-1.3 (aliphatic), 1.36 (d, 3J H-H ) 6.6 Hz, 3H, CH-
no. of reflns for cell 57 686 (3.06-30.54°) 90 209 (2.05-27.50°)
determ (θ range)
Z, Dcalcd, g/cm-3
F(000)
2, 1.278
724
0.339
R-AXIS RAPID
153(1)
4, 1.206
1704
0.284
R-AXIS RAPID
3
(CH3)2), 1.48 (d, J H-H ) 5.8 Hz, 3H, CH(CH3)2), 2.2-3.6
µ[Mo KR], mm-1
diffractometer
T, K
3
(aliphatic), 5.05 (d, J H-H ) 3.6 Hz, 1H, pyrrole ring), 5.51 (t,
3J H-H ) 7.7 Hz, 1H, m-Ph of ZrCH2CH(nBu)CH2Ph), 6.07 (dd,
153(1)
3
3J H-H ) 4.4 and 12.4 Hz 1H, CH-N), 6.21 (t, J H-H ) 7.4 Hz,
cryst size, mm
no. of images
total oscillation
angles, deg
0.46 × 0.43 × 0.31
0.61 × 0.59 × 0.34
3
1H, m-Ph of HfCH2CH(nBu)CH2Ph), 6.41 (d, J H-H ) 3.6 Hz,
180
120
360
1H, pyrrole ring), 6.65 (overlapping with Ph3CCH2Ph reso-
540.0
nance, 1H, o-Ph of ZrCH2CH(nBu)CH2Ph), 6.8-7.3 (aromatic
3
protons), 7.35 (t, J H-H ) 7.1 Hz, 1H, p-Ph of ZrCH2CH(nBu)-
exposure time,
min per deg
2.00
0.83
CH2Ph), 7.46 (s, 1H, NdCH).
2θmax, deg
no. of reflns measd
no. of unique data
61.0
53 865
10 842 (0.0429)
55.0
65 053
10 168 (0.0562)
Reaction of 1-hexene with cationic hafnium complex 6c was
carried out in a similar procedure.
[(DIP 2-p yr -CH 2P h )H f(CH 2CH (n Bu )CH 2P h )][B(C6F 5)4]
(8c): 1H NMR (300 MHz, C6D5Br, 35 °C): δ 0.03 (t, J H-H
(Rint
)
completeness to
θ ) 30.43, %
no. of observations
max. and min.
transmn
99.2
99.9
)
12.9 Hz, 1H, HfCHH), 2.24, 2.80, and 3.17 (m, 4H, R, â, and γ
9125
8806
protons of HfCH2CH(nBu)CH2Ph), 0.86 (m, 3H, CH3 of nBu),
0.953840, 0.909887 0.9728, 0.9446
3
3
0.94 (d, J H-H ) 6.9 Hz, 3H, CH3), 0.97 (d, J H-H ) 6.6 Hz,
3H, CH3), 1.16 (d, 3J H-H ) 6.6 Hz, 3H, CH3), 1.20 (m, 6H, CH2
of nBu), 1.27 (d, 3J H-H ) 6.6 Hz, 3H, CH3), 1.33 (d, 3J H-H ) 6.6
Hz, 6H, CH3), 1.37 (d, 3J H-H ) 6.9 Hz, 3H, CH3), 1.48 (d, 3J H-H
no. of variables
R1, wR2 (all data)
596
496
0.0463, 0.0756
0.0398, 0.0810
0.0321, 0.0768
1.064
R1, wR2 (I > 2.0σ(I)) 0.0335, 0.0726
GOF on F2
∆F, e Å-3
1.024
0.474, -0.557
) 6.6 Hz, 3H, CH3), 2.45 (sep, 3J H-H ) 6.6 Hz, 1H, CH(CH3)2),
0.532, -0.335
2
2.46 (t, J H-H ) 12.9 Hz, 1H, NCHCHHPh), 2.64 (dd, J H-H
)
3
3
13.4 Hz, J H-H ) 4.4 Hz, 1H, NCHCHHPh), 2.80 (sep, J H-H
3
) 6.9 Hz, 1H, CH(CH3)2), 3.13 (sep, J H-H ) 6.6 Hz, 1H,
related absorption correction using the program ABSCOR was
applied. The data were corrected for Lorentz and polarization
effects.
3
CH(CH3)2), 3.23 (sep, J H-H ) 6.6 Hz, 1H, CH(CH3)2), 5.04 (d,
3J H-H ) 3.6 Hz, 1H, pyrrole ring), 5.70 (m, 1H, m-Ph of HfCH2-
CH(nBu)CH2Ph), 6.25 (m, 2H, CH-N and m-Ph of HfCH2CH-
The structures were solved by direct methods (SIR97)29 and
refined on F2 by full-matrix least-squares methods, using
SHELXL-97.30 The non-hydrogen atoms were refined aniso-
tropically by the full-matrix least-squares method. All hydro-
gen atoms of 3b were isotropically refined, and those of 3c
were included in the refinement on calculated positions riding
3
(nBu)CH2Ph), 6.40 (d, J H-H ) 3.6 Hz, 1H, pyrrole ring), 6.65
(overlapping with Ph3CCH2Ph resonance, 1H, o-Ph of HfCH2-
CH(nBu)CH2Ph), 6.8-7.3 (aromatic protons), 7.38 (t, J H-H
)
3
7.4 Hz, 1H, p-Ph of HfCH2CH(nBu)CH2Ph), 7.66 (s, 1H, Nd
CH).
2
on their carrier atoms. The function minimized was [∑w(Fo
Eth ylen e P olym er iza tion . In a typical experiment, to a
solution of 3c (1.7 mg, 2.1 µmol) in toluene (0.4 mL) was added
a toluene solution of MMAO (1.66 mol/L, 1.3 mL, 1000 equiv)
under ethylene atmosphere. The solution was stirred for 1 h,
and then the polymerization reaction was quenched with acidic
methanol. The solid polymer was collected and washed with
HCl (1.2 M) and MeOH. The polymer was dried in vacuo for a
few days to give constant weight polyethylene.
- Fc2)2] (w ) 1/[σ2(Fo2) + (aP)2 + bP]), where P ) (Max(Fo2,0)
+ 2Fc2)/3 with σ2(Fo2) from counting statistics. The functions
R1 and wR2 were (∑||Fo| - |Fc||)/∑|Fo| and [∑w(Fo - Fc2)2/
2
∑(wFo4)]1/2. All calculations of least-squares refinements were
performed with SHELXL-97 programs on a Silicon Graphics
Inc. Origin 3400 computer at the Research Center for Struc-
tural Biology Institute for Protein Research, Osaka University.
Structural parameters and X-ray structure analyses for 3b and
3c are summarized in Table 4. Crystallographic data have
been deposited at the CCDC, 12 Union Road, Cambridge CB2
1EZ, UK, and copies can be obtained on request, free of charge,
by quoting the publication citation and the deposition numbers
CCDC 230760 for 3b and CCDC 230759 for 3c.
Al-Coca ta lyst-F r ee Eth ylen e P olyem r iza tion . Lewis-
base-free cationic alkyl complexes 5c and 6c were generated
from the reaction of the dibenzyl complexes 3c and 4c with
[Ph3C][B(C6F5)4], respectively. The solution was then degassed,
and ethylene gas was introduced. The solution was stirred for
1 h, and the polymer was formed.
Cr ysta llogr a p h ic Da ta Collection a n d Str u ctu r e De-
ter m in a tion of 3b a n d 3c. Crystals of 3b and 3c suitable
for the X-ray diffraction study were mounted on glass fibers.
All measurements were made on a Rigaku R-AXIS-RAPID
imaging plate diffractometer with graphite-monochromated
Mo KR radiation (λ ) 0.71069). Indexing was performed from
two oscillations. The camera radius was 127.40 mm. Readout
was performed in the 0.100 mm pixel mode. A symmetry-
Ack n ow led gm en t. This work was supported by a
Grant-in Aid for Scientific Research on Priority Area
(29) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J . Appl. Crystallogr. 1999, 32, 115.
(30) Sheldrick, G. M. SHELXL-97; Program for the Solution of
Crystal Structures; University of Go¨ttingen: Go¨ttingen, Germany,
1997.

Intramolecular Benzylation of an Imino Group
Organometallics, Vol. 23, No. 11, 2004 2805
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data for complexes 3b and 3c, and 1H NMR spectra for
complexes 3a , 4a , 4b, and 4d are given. This material is
available free of charge via the Internet at http://pubs.acs.org.
(A) “Exploitation of Multi-Element Cyclic Molecules”
from the Ministry of Education, Culture, Sports, Sci-
ence, and Technology, J apan. H.T. was financially
supported by the center of excellence (21COE) program
“Creation of Integrated EcoChemistry of Osaka Uni-
versity”.
OM049873I