Activation of enamido zirconium complexes for ethylene polymerization: Electrophilic addition versus electrophilic abstraction reaction

Article abstract of DOI:10.1021/om020949p

Deprotonation of the α-diimine compound {2,6-(CHMe₂)₂-C₆H₃}N=C(CH₃ )C(CH₃)=N{2,6(CHMe₂)₂-C₆H ₃} with excess KH in THF gives dipotassium N,N′-(1,2

Full text of DOI:10.1021/om020949p

Organometallics 2003, 22, 1503-1511
1503
Activa tion of En a m id o Zir con iu m Com p lexes for
Eth ylen e P olym er iza tion : Electr op h ilic Ad d ition ver su s
Electr op h ilic Abstr a ction Rea ction
Young Heui Kim,† Tae Ho Kim,† Na Young Kim,† Eun Sook Cho,†
Bun Yeoul Lee,*,† Dong Mok Shin,‡ and Young Keun Chung‡
Department of Molecular Science and Technology, Ajou University, Suwon, 442-749 Korea,
and Department of Chemistry and the Center for Molecular Catalysis, College of Natural
Sciences, Seoul National University, Seoul, 151-742 Korea
Received November 15, 2002
Deprotonation of the R-diimine compound {2,6-(CHMe2)2-C6H3}NdC(CH3)C(CH3)dN{2,6-
(CHMe2)2-C6H3} with excess KH in THF gives dipotassium N,N′-(1,2-dimethylene-1,2-
ethanediyl)bis(2,6-diisopropylanilide) (1) in 75% yield. Reaction of 1 with bis(2-picolyl)-
zirconium dichloride generated in situ by the reaction of ZrCl4 and 2 equiv of (2-
picolyl)potassium affords [N,N′-(1,2-dimethylene-1,2-ethanediyl)bis(2,6-diisopropylanilido)-
κ2N,N′]bis(2-picolyl)zirconium(IV) (2) in 35% yield. Similar reaction of 1 with LMCl3 (L )
Cp, Cp*; M ) Zr, Hf) gives the desired complexes {2,6-(CHMe2)2-C6H3}NCd(CH2)Cd(CH2)N-
{2,6-(CHMe2)2-C6H3}MLCl (L ) Cp*, M ) Zr, 4; L ) Cp*, M ) Hf, 5; L ) Cp, M ) Zr, 6) in
79%, 94% and 54% yields, respectively. Reaction of the chloride complexes with MeMgBr
affords the corresponding methyl complexes {2,6-(CHMe2)2-C6H3}NCd(CH2)Cd(CH2)N{2,6-
(CHMe2)2-C6H3}MLMe (L ) Cp*, M ) Zr, 7; L ) Cp*, M ) Hf, 8; L ) Cp, M ) Zr, 9) in 63%,
69% and 90% yields, respectively. The solid-state structure of 7 was determined. When 2, 7,
or 9 is treated with 1 equiv of B(C6F5)3, one observes formation of the picolyl- or methyl-
abstracted ion-paired complex in NMR spectra. When Al(C6F5)3 is added to 2, 8, or 9, the
aluminum atom is coordinated by the methylene functionality of the enamide ligand to form
zwitterionic complexes. The solid structure of a zwitterionic complex generated by the
addition of Al(C3F5)3 to 8 was determined and confirms the molecular connectivity. The
zwitterionic complexes are active to ethylene polymerization, while the ion-paired complexes
are sluggish. Complexes 2 and 6 are highly active to the ethylene polymerization when they
are activated with MAO.
In tr od u ction
by electrophilic abstraction reaction by Lewis acids (eq
1).4 The activated complex is an ion-paired complex
Homogeneous transition-metal complexes for olefin
polymerization are ongoing topics of research in both
academic and industrial fields.1,2 Polyolefins made from
ethylene and/or R-olefins including propylene are envi-
ronmentally benign and are expected to substitute
plastics derived from monomers, which are produced
with higher resource usage and are less ecologically
benign.3 The metal complexes are traditionally activated
† Ajou University.
‡ Seoul National University.
(1) Recent reviews: (a) Coates, G. W.; Hustad, P. D.; Reinartz, S.
Angew. Chem., Int. Ed. 2002, 41, 2236. (b) Matsui, S.; Fujita, T. Catal.
Today 2001, 66, 63. (c) Mecking, S.; Held, A.; Bauer, F. M. Angew.
Chem., Int. Ed. 2002, 41, 544. (d) Coates, G. W. J . Chem. Soc., Dalton
Trans. 2002, 467.
(2) (a) Bolig, A. D.; Chen, E. Y.-X. J . Am. Chem. Soc. 2002, 124,
5612. (b) Choo, T. C.; Waymouth, R. M. J . Am. Chem. Soc. 2002, 124,
4188. (c) Hustad, P. D.; Tian, J .; Coates, G. W. J . Am. Chem. Soc. 2002,
124, 3614. (d) Kunz, K.; Erker, G.; Kehr, G.; Fro¨hlich, R.; J acobsen,
H.; Berke, H.; Blacque, O. J . Am. Chem. Soc. 2002, 124, 3316. (e) Yoder,
J . C.; Bercaw, J . E. J . Am. Chem. Soc. 2002, 124, 2548. (f) Imuta, J .;
Kashiwa, N.; Toda, Y. J . Am. Chem. Soc. 2002, 124, 1176. (g) Landis,
C. R.; Rosaaen, K. A.; Uddin, J . J . Am. Chem. Soc. 2002, 124, 12062.
(h) Kang, M.; Sen, A.; Zakharov, L.; Rheingold, A. L. J . Am. Chem.
Soc. 2002, 124, 12080. (i) Hustad, P. D.; Coates, G. W. J . Am. Chem.
Soc. 2002, 124, 11578. (j) Keaton, R. J .; Sita, L. R. J . Am. Chem. Soc.
2002, 124, 9070.
consisting of a transition-metal cation and a bulky
noncoordinating anion, and the catalyst activity, life-
time, chain-transfer characteristics, and stereoregula-
tion are strongly dependent on the nature of the ion
pairs.5 The preactivated complex requires two alkyls or
halides. One of them is abstracted by the Lewis acid,
and the monomer inserts into the remaining metal-
(3) Eissen, M.; Metzger, J . O.; Schmidt, E.; Schneidewind, U. Angew.
Chem., Int. Ed. 2002, 41, 414.
(4) E. Y.-X. Chen, T. J . Marks, Chem. Rev. 2000, 100, 1391.
10.1021/om020949p CCC: $25.00 © 2003 American Chemical Society
Publication on Web 03/06/2003

1504 Organometallics, Vol. 22, No. 7, 2003
Kim et al.
alkyl bond. Recently, some different activation reactions
have been reported. Chen et al. have reported that
group 4 complexes bearing only one alkyl or halide can
serve as efficient catalysts for olefin polymerization.6
They proposed a bimetallic mechanism resembling that
originally proposed by Natta and Mazzanti (eq 2). Bazan
et al. and we have shown that nickel complexes contain-
ing carboxylato,7 carboxamidato,8 or enamido ligands9
can be activated by electrophilic addition reactions of
Lewis acids. In those cases, the Lewis acid is added to
the functional group to afford zwitterionic active com-
plexes (eq 3).10 Herein, we disclose that the novel
activation reaction can be expanded to group 4 transi-
tion-metal complexes.
a bis(2-picolyl)zirconium complex (eq 5), in which ni-
trogen atoms on the picolyl ligands are expected to
coordinate to the zirconium atom to block the interaction
with the electron-rich methylene carbons. 2-Picolyl-
lithium-2-picoline is obtained when 2.5 equiv of 2-pi-
coline is reacted with n-BuLi in cold ether (86%).
Addition of 1 to the bis(2-picolyl)zirconium dichloride,
which is generated in situ in THF by the reaction of 2.0
equiv of 2-picolyllithium with ZrCl4(THF)2, affords
successfully the desired complex [N,N′-(1,2-dimethylene-
1,2-ethanediyl)bis(2,6-diisopropylanilido)-κ2N,N′]bis(2-
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion . The dianionic
bis(enamido) ligand, dipotassium N,N′-(1,2-dimethyl-
ene-1,2-ethanediyl)bis(2,6-diisopropylanilide) (1) for group
4 metal complexes, which can serve as preactivated
complexes for the novel activation reaction, is synthe-
sized by the deprotonation of the R-diimine compound
{2,6-(CHMe2)2-C6H3}NdC(CH3)C(CH3)dN{2,6-(CHMe2)2-
C6H3} with excess KH in 75% yield (eq 4). The R-diimine
1
picolyl)zirconium(IV) (2). The H NMR spectrum of the
crude product shows that the reaction is fairly clean but
some side product signals (ca., 15%) are observed.
Isolation of the product by discarding the side product
was not successful. The analytically pure complex can
be obtained in 35% yield when 2-picolylpotassium is
used instead of 2-picolyllithium.
The structure of 2 can be confirmed by NMR spectra
and elemental analysis. An attempt to obtain single
crystals suitable for X-ray crystallography was not
successful. Observation of two dCH2 signals at 4.82 and
compound serves well as a ligand for the late-transition-
metal catalyst.11 Metalations of the ligand by reaction
with ZrCl4(THF)2, TiCl4(THF)2, or HfCl4(THF)2 were not
successful. Fairly successful syntheses of bis(amido)
complexes of group 4 have been reported.12 We at-
tributed the synthetic failure to the incompatibility of
the electron-deficient metal center and the electron-rich
methylene carbons on the enamido ligand. Instead of
the zirconium dichloride complex, we tried to synthesize
1
3.49 ppm as singlets (C6D6) in the H NMR spectrum
(Figure 3A) suggests an enamido ligand structure as
depicted in eq 5. Only one CHMe2 signal, a septet (J )
6.8 Hz) at 4.02 ppm, and two CH(CH3) signals, doublets
at 1.45 and 1.17 ppm, are observed, due to the symmetry
of the complex. A set of ring protons on the picolyl ligand
are observed at 6.88 (doublet), 6.41 (triplet), 6.04
(doublet), and 5.96 ppm (triplet), and methylene protons
on picolyl are observed as a singlet at 2.03 ppm. The
signal observed at 82.19 ppm in the 13C{1H} NMR
spectrum is assigned unambiguously by DEPT experi-
ments to the methylene carbon (CH2dCN) in the ena-
mido ligand. Coordination of the nitrogen atom on the
picolyl ligand to the zirconium cannot be confirmed by
(5) (a) Chen, M.-C.; Marks, T. J . J . Am. Chem. Soc. 2001, 123, 11803.
(b) Metz, M. V.; Schwartz, D. J .; Stern, C. L.; Marks, T. J . Organo-
metallics 2002, 21, 4159. (c) Metz, M. V.; Sun, Y.; Stern, C. L.; Marks,
T. J . Organometallics 2002, 21, 3691. (d) Schaper, F.; Geyer, A.;
Brintzinger, H. H. Organometallics 2002, 21, 473. (e) Beck, S.; Lieber,
S.; Schaper, F.; Geyer, A.; Brintzinger, H.-H. J . Am. Chem. Soc. 2001,
123, 1483.
(6) (a) J in, J .; Wilson, D. R.; Chen, E. Y.-X. Chem. Commun. 2002,
708. (b) Cano, J .; Royo, P.; Lanfranchi, M.; Pellinghelli, M. A.;
Tiripicchio, A. Angew. Chem., Int. Ed. 2001, 40, 2495.
(7) (a) Komon, Z. J . A.; Bu, X.; Bazan, G. C. J . Am. Chem. Soc. 2000,
122, 1830 (b) Komon, Z. J . A.; Bu, X.; Bazan, G. C. J . Am. Chem. Soc.
2000, 122, 12379. (c) Lee, B. Y.; Kim, Y. H.; Shin, H. J .; Lee, C. H.
Organometallics 2002, 21, 3481.
(8) (a) Lee, B. Y.; Bazan, G. C.; Vela, J .; Komon, Z. J . A.; Bu, X. J .
Am. Chem. Soc. 2001, 123, 5352. (b) Lee, B. Y.; Bu, X.; Bazan, G. C.
Organometallics 2001, 20, 5425.
1
the H or 13C{1H} NMR spectra. Coordination of nitro-
gen to zirconium was reported in a similar complex, bis-
(cyclopentadienyl)bis[(6-methyl-2-pyridinyl)methyl]zir-
conium(IV).13
The side product observed when 2-picolyllithium is
used is very crystalline, and single crystals suitable for
X-ray crystallography were obtained from a pentane
(9) Kim, Y. H.; Kim, T. H.; Lee, B. Y.; Woodmansee, D.; Bu, X.;
Bazan, G. C. Organometallics 2002, 21, 3082.
(12) (a) Scollard, J . D.; McConville, D. H. J . Am. Chem. Soc. 1996,
118, 10008. (b) Scollard, J . D.; McConville, D. H.; Payne, N. C.; Vittal,
J . J . Macromolecules 1996, 29, 5241. (c) O’Shaughnessy, P. N.;
Gillespie, K. M.; Morton, C.; Westmoreland, I.; Scott, P. Organome-
tallics 2002, 21, 4496. (d) Lee, C. H.; La, Y.-H.; Park, J . W. Organo-
metallics 2000, 19, 344. (e) Liang, L.-C.; Schrock, R. R.; Davis, W. M.
Organometallics 2000, 19, 2526. (f) J eon, Y.-M.; Heo, J .; Lee, W. M.;
Chang, T.; Kim, K. Organometallics 1999, 18, 4107.
(10) Recently, other types of zwitterionic active complexes have been
reported; see: (a) Lu, C. C.; Peters, J . C. J . Am. Chem. Soc. 2002, 124,
5272. (b) Thomas, J . C.; Peters, J . C. J . Am. Chem. Soc. 2001, 123,
5100. (c) Cook, K. S.; Piers, W. E.; McDonald, R. J . Am. Chem. Soc.
2002, 124, 5411. (d) Strauch, J . W.; Erker, G.; Kehr, G.; Fro¨hlich, R.
Angew. Chem., Int. Ed. 2002, 41, 2543.
(11) (a) Ittel, S. D.; J ohnson, L. K.; Brookhart, M. Chem. Rev. 2000,
100, 1169. (b) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am.
Chem. Soc. 1995, 117, 6414.
(13) Beshouri, S. M. Fanwick, P. E.; Rothwell, I. P.; Huffman, J . C.
Organometallics 1987, 6, 891.

Activation of Enamido Zirconium Complexes
Organometallics, Vol. 22, No. 7, 2003 1505
composition, the C(29)-C(31) and C(30)-C(32) bond
lengths change to be in the range of C-C single-bond
lengths (1.446(8) and 1.424(8) Å, respectively) and those
of C(29)-N(3) and C(30)-N(4) change to be in the range
of C-N double-bond lengths (1.302(7) and 1.301(7) Å,
respectively). The zirconium atom is placed slightly out
of the N(1)-C(1)-C(2)-N(2) plane made by the enamido
ligand. The dihedral angles of Zr(1)-N(1)-C(1)-C(2)
and Zr(1)-N(2)-C(2)-C(1) are -14.5 and 5.1°, respec-
tively. The zirconium is placed much more out of the
C(31)-C(29)-C(30)-C(32) plane made by the dialkyl
ligand and the dihedral angles of Zr(1)-C(31)-C(29)-
C(30) and Zr(1)-C(32)-C(30)-C(29) are respectively
-30.0 and 42.3°. In the 2-picolyl ligand, the N(5)-
C(57)-C(62) angle shrinks to 110.5(6)° by the coordina-
tion of a nitrogen atom and the Zr(1)-N(5)-C(57) angle
is 94.4(4)°.
F igu r e 1. ORTEP view of 3, showing the atom-numbering
scheme. Thermal ellipsoids are shown at the 30% prob-
ability level. Hydrogen atoms have been omitted for clarity.
Selected bond distances (Å) and angles (deg): Zr(1)-N(1),
2.126(5); Zr(1)-N(2), 2.126(5); Zr(1)-N(5), 2.285(5); Zr(1)-
C(31), 2.354(6); Zr(1)-C(32), 2.463(6); Zr(1)-C(62), 2.318-
(6); N(1)-C(1), 1.407(8); N(2)-C(2), 1.425(8); C(1)-C(2),
1.485(9); C(1)-C(3), 1.332(9); C(2)-C(4), 1.351(9); C(57)-
C(62), 1.444(9); N(5)-C(57), 1.352(8); C(29)-C(31), 1.446-
(8); C(29)-C(30), 1.520(8); C(30)-C(32), 1.424(8); N(3)-
C(29), 1.302(7); N(4)-C(30), 1.301(7); Li(1)-N(3), 1.996(13);
Li(1)-N(4), 1.948(12); Li(1)-N(6), 2.087(13); N(1)-Zr(1)-
N(2), 74.5(2); N(5)-Zr(1)-C(62), 59.9(2); C(31)-Zr(1)-
C(32), 69.1(2); Zr(1)-C(62)-C(57), 90.6(4); N(5)-C(57)-
C(62), 110.5(6); Zr(1)-N(5)-C(57), 94.4(4).
In contrast to the reactions with ZrCl4 and HfCl4,
reactions of 1 with Cp*ZrCl3, Cp*HfCl3, and CpZrCl3
give cleanly the desired bis(enamido) complexes with
79%, 94% and 54% yields, respectively (eq 6). The
reaction with the corresponding titanium complex is not
clean. The characteristic methylene (CH2d) signals are
1
observed in H NMR spectra (C6D6) as a pair of singlets
at 4.7-4.8 and 3.6-3.7 ppm, conforming the ligand acts
as an enamido species. The addition of MeMgBr (THF
solution) in diethyl ether gives cleanly the methyl
complexes 7-9 (63%, 69% and 90% yields, respectively).
The methylene signals are still observed as a pair of
singlets in almost the same region observed for the
chloride complexes, and methyl signals are observed as
1
a singlet at 0.6-0.7 ppm in the H NMR spectra.
solution. The molecular structure and selected bond
lengths and angles for the side product 3 are shown in
The molecular structure of 7 was confirmed by X-ray
crystallography. The structure and selected bond lengths
and angles are shown in Figure 2. Three independent
molecules are present in a unit cell. It has a three-legged
piano-stool structure. The zirconium atom is situated
out of the N-C-C-N plane, and the dihedral angles
Zr(1)-N(1)-C(35)-C(36) and Zr(1)-N(2)-C(36)-C(35)
are 32.7 and -16.6°, respectively. The CH2dC bond
distance (average 1.330(13) Å) and C-NAr′ distance
(average 1.426(8) Å) strongly support the enamido
structure drawn in eq 6. The averaged Zr-N distance
is 2.085(12) Å, which is shorter than that of the ate
complex 3 (2.126(5) Å).
Figure 1. The complex is a distorted-octahedral ate
complex bonded by a chelated picolyl ligand and two
ligands derived from 1, one of which acts as a bis-
(enamido) ligand while the other acts as a dialkyl ligand.
A lithium ion is coordinated by the remaining nitrogens
on the dialkyl ligand and by nitrogen on 2-picoline. The
distances between zirconium and the two nitrogens of
the enamido ligand are identical (2.126(5) Å). The bond
lengths of N(1)-C(1) and N(2)-C(2) (1.407(8) and 1.425-
(8) Å, respectively) are within the range of C-N single-
bond lengths, and those of C(1)-C3 and C(2)-C(4)
(1.332(9) and 1.351(9) Å, respectively) are within the
range of C-C double-bond lengths. The two bond
lengths between zirconium and carbons on the dialkyl
ligand are not identical (2.354(6) and 2.463(6) Å), and
both of them are longer than that of zirconium and
carbon on the picolyl ligand (2.318(6) Å). When the
enamido ligand acts as a dialkyl ligand with the same
Activa tion Rea ction . Activation studies were car-
ried out by adding B(C6F5)3 or Al(C6F5)314 to the enamido
complexes 2 and 7-9 with NMR spectroscopy. Figure
1
3 shows the selected region of the H NMR spectra for
2 itself and the complexes obtained by adding B(C6F5)3
and Al(C6F5)3 to 2. The NMR spectra strongly support
that the picolyl-abstracted ion-paired complex 10 is
(14) Chen, E. Y.-X.; Kruper, W. J .; Roof, G.; Wilson, D. R. J . Am.
Chem. Soc. 2001, 123, 745.

1506 Organometallics, Vol. 22, No. 7, 2003
Kim et al.
methylene signals on the enamide shift severely to 5.33
and 3.98 ppm, with reduction of the intensity by half,
and a broad singlet signal is observed at 3.21 ppm,
which can be assigned to the protons on methylene
bonded to Al. Only one set of picolyl ring protons is
observed without reduction of intensity at 5.8-6.5 ppm,
implying that both picolyl ligands are still bonded
symmetrically to the zirconium. Two septet CHMe2
signals are observed at 3.61 and 3.17 ppm. A strange
feature of the spectrum is the observation of picolyl CH2
signals at 1.97 and 1.76 ppm. The signals are rather
broad, but the splitting pattern can be analyzed as that
observed for an AB spin system. The broad nature of
the peaks implies that the picolyl ligand is under
fluxional motion, presumably coordination-decoordi-
nation and/or change of coordination site of the nitro-
gens. Observation of the AB spin system signals can be
interpreted by the coordination of the nitrogen atoms
on the picolyl ligand. Once the nitrogen atom coordi-
nates to the zirconium, two CH2 protons on the picolyl
ligand are diastereotopic with each other, as depicted
in eq 8, and each proton signal will appear separately
with coupling to each other to appear as a doublet. A
signal is observed severely downfield shifted at 197.41
ppm in the 13C NMR spectrum, which can be assigned
to the carbon on AlCH2CdN. The shift might be at-
tributed to the change from an enamido to an imine
functionality by the coordination of alane. Both acti-
vated complexes are so stable that any decomposition
is not observed in C6D6 solution for several days.
However, purification by recrystallization to analytically
pure compounds or single crystals for X-ray crystal-
lography failed, due to the lack of crystallinity of the
complexes.
F igu r e 2. ORTEP view of 7, showing the atom-numbering
scheme. Thermal ellipsoids are shown at the 30% prob-
ability level. Hydrogen atoms have been omitted for clarity.
Selected bond distances (Å) and angles (deg): Zr(1)-N(1),
2.071(5); Zr(1)-N(2), 2.077(5); Zr(1)-C(39), 2.317(6); N(1)-
C(35), 1.437(7); N(2)-C(36), 1.423(8); C(35)-C(37), 1.342-
(9); C(36)-C(38), 1.346(8); C(35)-C(36), 1.514(9); N(1)-
C(11), 1.449(8); N(1)-Zr(1)-N(2), 85.1(2); N(1)-Zr(1)-
C(39), 103.5(2); N(1)-C(35)-C(37), 121.8(7); C(37)-C(35)-
C(36), 121.3(6).
F igu r e 3. 1H NMR spectra (C6D6) of 2 (A), 2 + B(C6F5)3
(B), and 2 + Al(C6F5)3 (C).
formed by B(C6F5)3 (eq 7) while the alane-added zwit-
terionic complex 11 is formed by Al(C6F5)3 (eq 8). In
Figure 3B for the product of addition of B(C6F5)3, one
observes appearance of a broad singlet at 2.52 ppm,
which is assigned to methylene protons on picolyl
bonded to B(C6F5)3, and the intensity of methylene
protons (1.93 ppm) on the picolyl ligand bonded to
zirconium is reduced by half. Two sets of picolyl ring
protons are observed at 5.8-6.8 and 8.45 ppm. Signals
of methylene protons on the enamido ligand are ob-
served at 4.65 and 3.75 ppm as singlets without reduc-
tion of the intensity. A pair of rather broad septet
CHMe2 signals (J ) 6.8 Hz) is observed at 3.49 and 2.81
ppm due to the destroyed symmetry. However, in Figure
3C, for the product obtained by the addition of Al(C6F5)3,
one observes totally different patterns. In this case, the
When an equimolar amount of B(C6F5)3 is added to 7
in C6D6 solution, the H NMR spectrum indicates that
1
a methyl-abstracted ion-paired complex is formed (eq
9). The signal for the methyl protons is shifted from 0.63
to 1.67 ppm, and all methylene (CH2dCN) signals (4.84
and 3.67 ppm) are still observed without reduction of
intensity. The complex is so unstable in C6D6 solution

Activation of Enamido Zirconium Complexes
Organometallics, Vol. 22, No. 7, 2003 1507
that it decomposes at room temperature overnight to
give oily precipitates. Addition of Al(C6F5)3 gives a more
complex 1H NMR spectrum, but careful inspection leads
to a tentative interpretation of the formation of a
mixture of a methyl-abstracted ion-paired complex and
an alane-added zwitterionic complex (ratio 1/2). The
ratio of the two complexes is dependent on solvent. In
CD2Cl2, a ratio favoring the more zwitterionic complex
is observed (1/6), but the ratio returns to the original
value by changing the solvent to benzene. To elucidate
the formation of the zwitterionic complex unambigu-
ously, we tried to grow single crystals for X-ray crystal-
lography, but these attempts failed.
F igu r e 4. ORTEP view of 14, showing the atom-number-
ing scheme. Thermal ellipsoids are shown at the 30%
probability level. Hydrogen atoms have been omitted for
clarity. Selected bond distances (Å) and angles (deg): Hf-
N(1), 2.044(3); Hf-N(2), 2.184(3); Hf-C(11), 2.205(3);
N(1)-C(37), 1.432(4); N(2)-C(36), 1.326(4); C(37)-C(39),
1.326(5); C(37)-C(36), 1.486(5); C(36)-C(38), 1.466(4);
C(38)-Al, 2.065(3); N(1)-Hf-N(2), 79.80(11); N(1)-C(37)-
C(39), 122.6(4); C(39)-C(37)-C(36), 120.0(4); N(2)-C(36)-
C(38), 123.5(4); C(37)-C(36)-C(38), 120.8(4); C(36)-C(38)-
Al, 124.9(2).
However, addition of Al(C6F5)3 to the hafnium com-
plex 8 affords a single clean complex which can be
interpreted as an alane-added zwitterionic complex (eq
10). The intensity of signals of the methylene protons
of B(C6F5)3 to the cyclopentadienyl zirconium complex
9 while addition of Al(C6F5)3 affords the zwitterionic
complex 15. However, both complexes decompose in
C6D6 over several hours.
P olym er iza tion Stu d ies. The complexes 10-15
were tested for ethylene polymerization by adding
ethylene gas into an NMR cell containing a C6D6
solution. In the case of the alane-added zwitterionic
complex 11, rather fast ethylene consumption is ob-
served. Added ethylene gas under atmospheric pressure
disappears completely over 3 h in the 1H NMR spectrum
with the concomitant formation of polyethylene par-
on the enamido ligand is reduced by half and broad new
signals appear at 3.52 and 3.24 ppm, which can be
assigned as Al-CH2 signals. Two signals are observed
because the two protons on a methylene carbon are
diastereotopic with each other due to the chiral center
on the zirconium atom. The other methylene signals
shift severely from 4.92 and 3.66 ppm to 5.67 and 4.29
ppm. The complex is fairly stable. No decomposition is
observed in C6D6 solution for several days. Addition of
B(C6F5)3 does not afford a clean complex.
Single crystals suitable for X-ray crystallography were
obtained by vapor-phase addition of pentane to a toluene
solution at room temperature overnight. The molecular
structure with selected bond lengths and angles is
shown in Figure 4. A disordered toluene molecule was
found for one molecule of 14 in the crystal lattice.
Measurements of bond lengths are consistent with the
zwitterionic structure shown in eq 10. The AlCC-N
distance (1.326(4) Å) is characteristic of a C-N double
bond, while the AlC-C distance (1.466(4) Å) is indica-
tive of a single bond. The Al-C distance (2.065(3) Å) is
almost same as that observed for the nickel complex
(2.053(4) Å).9 The N-Hf distance on the aluminum-
added side is substantially longer that that observed for
the other side (2.184(3) and 2.044(3) Å, respectively).
1H NMR studies strongly support that the methyl-
abstracted ion-paired complex 13 is formed by addition
1
ticles. The original H NMR spectrum obtained before
the addition of ethylene is not changed, which implies
that a very small fraction of the dissolved complex acts
as a catalyst. It can be postulated that it takes some
time for the ethylene to coordinate and insert into the
Zr-picolyl bond, because the picolyl ligand is bonded
rather strongly to the zirconium by the chelation. Once
it is initiated, it can act as a highly active catalyst.
Similar results have been observed, with the nickel
catalyst having the methallyl ligand as a leaving
group.7,8 In the case of the ion-paired complex 10, very
slow consumption of ethylene gas is observed. The
intensity of the ethylene peak is reduced by about half
overnight. The original spectrum of the complex was
preserved in this case as well.
Complexes derived from the pentamethylcyclopenta-
dienyl (Cp*) ligand, 12 and 14, do not show any activity,
which may be attributed to the absence of any vacant
site by steric congestion. The ion-paired cyclopentadi-
enyl (Cp) complex 13 shows negligible activity as well.
However, rapid ethylene consumption and formation of
polyethylene precipitates are observed with the zwit-
terionic cyclopentadienyl complex 15. Polymerization
with carefully dried ethylene gas at room temperature

1508 Organometallics, Vol. 22, No. 7, 2003
Kim et al.
Ta ble 1. Eth ylen e P olym er iza tion Resu ltsa
diethyl ether, and C6D6 were distilled from benzophenone
ketyl. Toluene used for the polymerization reaction was
purchased from Aldrich (anhydrous grade) and purified further
over Na/K alloy. Ethylene was purchased from Conley Gas
(99.9%) and purified by contact with molecular sieves and
copper overnight under 150 psig pressure. NMR spectra were
recorded on a Varian Mercury Plus 400 or Bruker Advance
DRX-500 spectrometer. 19F NMR spectra were calibrated and
reported downfield from external CCl3F (Bruker DRX-500) or
R,R,R-trifluorotoluene (Varian Mercury 400). 11B NMR spectra
were calibrated and reported downfield from external BF3‚
OEt2. Elemental analyses were carried out on a Fisons EA1108
microanalyzer. Gel permeation chromatograms (GPC) were
obtained at 140 °C in trichlorobenzene using a Waters Model
150-C+ GPC, and the data were analyzed using a polystyrene
analyzing curve. Methylaluminoxane (MAO) was purchased
as a solution in toluene from Akzo (7.6 wt % of Al, MMAO
temp time
entry complex (°C) (min) (kg/(mol‚h))
activity
b
b
Mw
Mw/Mn
1
2
2
2
2
2
6
6
9
25
50
80
80
25
80
25
25
20
12
20
20
3
6
10
4
12 000
33 000
10 000
8800
30 000
24 000
250
134 000
16 800
8000
18e
1.8
2.1
1.7
2.9
11e
3
4c
5
7200
129 000
504 000
insoluble
6
7d
8
Cp2ZrCl2
23 000
a
Polymerization conditions: 30 mL of toluene, 0.5 µmol of
b
catalyst, Al/Zr ) 5000, 60 psig of ethylene. Determined by GPC
in 1,2,4-trichlorobenzene at 140 °C against polystyrene standards.
d
c Hexane diluent instead of toluene. A 5.0 µmol portion of the
complex and Al(C6F5)3 (17.5 µmol) were used without adding MAO
under 100 psig of ethylene. e Bimodal distribution.
type
4).
{2,6-(CHMe2)2-C6H3}NdC(CH3)C(CH3)dN{2,6-
(CHMe2)2-C6H3}16 and Al(C6F5)3‚(toluene)14 were prepared
according to the literature methods.
and 100 psig pressure gives 250 kg/(mol h) activity
(entry 7 in Table 1).
MAO is also a Lewis acid,15 and activation by either
electrophilic addition or abstraction reactions are ex-
pected for 2 and the monochloride complexes 4-6.
Pentamethylcyclopentadienyl (Cp*) complexes 4 and 5
also do not show any activities in these cases, but
complex 2 and the cyclopentadienyl complex 6 are
highly active when they are activated with MAO. The
activities are comparable with that of Cp2ZrCl2 (entry
8). In the case of 2, maximum activity is observed at 50
°C. Interestingly, at low temperature (25 °C), a bimodal
molecular weight distribution (Mw/Mn ) 18) is observed
with rather high molecular weight (Mw ) 134 000), but
at high temperature (50 and 80 °C) narrow molecular
weight distributions are observed (Mw/Mn ) 1.8 and 2.1,
respectively) with low molecular weight (Mw ) 16 800
and 8000, respectively). In the case of 6, the trend of
molecular weight and molecular weight distribution is
reversed: at low temperature (25 °C) narrow molecular
weight distribution (Mw/Mn ) 2.9) and low molecular
weight (Mw ) 129 000) are observed (entry 5), while at
high temperature (80 °C) broad molecular weight dis-
tributions (Mw/Mn ) 11) with the appearance of a
shoulder on the high molecular weight portion is
observed (entry 6).
Dip ot a ssiu m N,N′-(1,2-Dim et h ylen e-1,2-et h a n ed iyl)-
b is(2,6-d iisop r op yla n ilid e) (1). {2,6-(CHMe2)2-C6H3}Nd
C(CH3)C(CH3)dN{2,6-(CHMe2)2-C6H3} (7.00 g, 17.3 mmol) and
KH (3.47 g, 86.5 mmol) were stirred in THF (50 mL) under
argon for 1 week at room temperature (ca, 25 °C). The evolved
hydrogen gas was vented through a mercury bubbler. The
excess KH was removed by filtration over Celite. The solvent
was removed to leave a volume of about 10 mL. When the
solution was stored in a freezer (-30 °C) overnight, a white
crystalline solid was deposited. The solvent was decanted
rapidly at -30 °C, and the obtained solid was dried by
evacuation. The solid was triturated with pentane (50 mL) for
2 h and filtered and washed three times with pentane (20 mL).
A yellow solid was obtained (6.74 g, 75%). The 1H NMR
spectrum indicates that a half-molecule of THF was incorpo-
rated for each dipotassium salt. 1H NMR (400 MHz, C6D6/THF-
d8 (10:1)): δ 7.22 (d, J ) 7.6 Hz, 4 H, Ph H3), 6.95 (t, J ) 7.6
Hz, 2 H, Ph H4), 3.92 (septet, J ) 6.7 Hz, 4 H, CHMe2), 3.09
(d, J ) 3.7 Hz, 2 H, CdCH2), 2.49 (d, J ) 3.5 Hz, 2 H, Cd
CH2), 1.48 (d, J ) 6.7 Hz, 12 H, CH(CH3)2), 1.31 (d, J ) 6.7
Hz, 12 H, CH(CH3)2). 13C{1H} NMR (100 MHz, C6D6/THF-d8
(10:1)): δ 170.65 (CH2CN), 156.20 (Ph C1), 142.49 (Ph C3),
122.71 (Ph C4) 118.12 (Ph C2), 67.77 (CH2dC), 27.75 (CH-
(CH3)2), 25.78 (CH(CH3)2), 25.11 (CH(CH3)2).
2-P icolyllith iu m -2-P icolin e. n-BuLi (72.4 mmol) was
added dropwise to a stirred solution of dry 2-picoline (16.85 g,
181 mmol, 2.5 equiv), purified by distillation over CaH2, in
cold ether (50 mL, -20 °C). Orange crystals precipitated
immediately. The mixture was stirred for 1 h. Ether was
removed by evaporation. The solid was washed with pentane
Su m m a r y
Enamido zirconium and hafnium complexes have
been synthesized which have electron-rich methylene
carbons in the ligand frame. Addition of Al(C6F5)3 to the
complexes gives mainly zwitterionic complexes by elec-
trophilic addition to the methylene carbon, while addi-
tion of B(C6F5)3 gives exclusively ion-paired complexes
by electrophilic abstraction of the methyl or picolyl
group. The ion-paired complex is sluggish for ethylene
polymerization, but the zwitterionic complexes show
good activity. The enamido complexes show activities
comparable with that of Cp2ZrCl2 for ethylene polym-
erization when they are activated with MAO.
1
(50 mL) and dried under vacuum (12 g, 86%). H NMR (400
MHz, C6D6): δ 8.53 (dd, J ) 4.2, 0.9 Hz, 1 H, picoline H3,6),
7.51 (d, J ) 6.0 Hz, 1 H, picolyl H3,6), 6.78 (td J ) 7.6, 1.7 Hz,
1 H), 6.60-6,41 (m, 2 H), 6.40-6.24 (m, 2 H), 5.49 (td, J )
6.0, 1.1 Hz, picolyl H4,5), 3.38 (s, 2 H, picolyl CH2), 2.41 (s, 3
H, picoline CH3). 13C{1H} NMR (100 MHz, C6D6): δ 162.84
(picolyl C2), 158.91 (picoline), 149.69 (picoline), 148.34, 136.96
(picoline), 132.98, 129.26, 129.23, 129.13, 127.37, 123.70
(picoline), 121.02 (picoline), 117.47, 100.40, 57.45 (picolyl CH2),
23.78 (picoline).
2-P icolylp ota ssiu m . KOtBu (7.89 g, 70.3 mmol), which had
been purified by sublimation twice, was dissolved in dried
2-picoline (65 g), and n-BuLi (70.3 mmol) was added dropwise
to the solution. An orange solid precipitated, which was filtered
and washed with pentane (10 mL). The powder was dried
under vacuum (7.3 g, 78%). 1H NMR (400 MHz, THF-d8): δ
6.95 (d, J ) 5.0 Hz, 1 H, H3,6), 5.97 (ddd, J ) 9.0, 6.0, 2.0 Hz,
1 H, H4,5), 5.53 (d, J ) 9.0 Hz, 1 H, H3,6), 4.73 (t, J ) 5.0 Hz,
Exp er im en ta l Section
Gen er a l Rem a r k s. All manipulations were performed
under an inert atmosphere using standard glovebox and
Schlenk techniques. Toluene, pentane, cyclohexane, THF,
(15) Harlan, C. J .; Bott, S. G.; Barron, A. R. J . Am. Chem. Soc. 1995,
117, 6465.
(16) Gonioukh, A.; Popham, N. WO Patent Application 0050474 to
BASF.

Activation of Enamido Zirconium Complexes
Organometallics, Vol. 22, No. 7, 2003 1509
1
1 H, H4,5), 2.51 (s, 2 H, CH2). 13C{1H} NMR (100 MHz, THF-
d8): δ 162.78 (C2), 149.66, 131.45, 113.86, 95.45, 58.88 (CH2).
[N,N′-(1,2-Dim et h ylen e-1,2-et h a n ed iyl)b is(2,6-d iiso-
p r op yla n ilid o)-K2N,N′]b is(2-p icolyl)zir con iu m (IV) (2).
ZrCl4(THF)2 (0.377 g, 1.00 mmol) was dissolved in cold THF
(7.0 mL, -20 °C), and 2-picolylpotassium (0.262 g, 2.00 mmol)
was added to the solution. The mixture was stirred for 2 h at
room temperature. The dipotassium salt 1 (0.480 g, 1.00 mmol)
was added at room temperature to the mixture. The solution
was stirred overnight. Solvent was removed under reduced
pressure. The compound was extracted with cyclohexane (ca,
20 mL). The solvent was removed, and the solid was triturated
with hexane (ca. 5 mL). A brownish red powder was obtained
solution in a freezer (-30 °C) overnight. H NMR (400 MHz,
C6D6): δ 7.3-7.1 (m, 6 H, Ph H3-5), 4.83 (s, 2 H, CdCH2), 3.72
(s, 2 H, CdCH2), 3.39 (septet, J ) 6.8 Hz, 2 H, CH(CH3)2),
3.20 (septet, J ) 6.8 Hz, 2 H, CH(CH3)2), 1.66 (s, 15 H, Cp*
CH3), 1.39 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.34 (d, J ) 6.8 Hz,
6 H, CH(CH3)2), 1.33 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.31 (d,
J ) 6.8 Hz, 6 H, CH(CH3)2). 13C{1H} NMR (100 MHz, C6D6):
δ 150.58, 145.59, 144.56, 143.61, 126.36, 124.88, 124.52,
123.68, 93.75 (CH2dC), 30.44, 28.24 (CH(CH3)2), 26.85, 26.09,
25.21, 24.06 (CH(CH3)2), 11.19 (Cp* CH3). Anal. Calcd for
C
38H53ClN2Zr: C, 68.7; H, 8.04; N, 4.22. Found: C, 68.5; H,
8.15; N, 4.65.
Ch lor o[N,N′-(1,2-d im et h ylen e-1,2-et h a n ed iyl)b is(2,6-
d iisop r op yla n ilid o)- K2N,N′](p en ta m eth ylcyclop en ta d i-
en yl)h a fn iu m (IV) (5). The dipotassium salt 1 (0.508 g, 0.983
mmol) and Cp*HfCl3 (0.413 g, 0.983 mmol) were weighed in a
vial inside a glovebox. Cold THF (15 mL, -30 °C) was added,
and the resulting solution was stirred overnight at room
temperature. The solvent was removed under vacuum. Pen-
tane (12 mL) and toluene (4 mL) were added to the residue,
and the solution was filtered over Celite. The solvent was
removed under vacuum to give a dark yellow solid (0.700 g,
1
(0.344 g, 51%), which is quite pure as indicated by its H NMR
spectrum. Further purification to give an analytically pure
compound was carried out by dissolving the powder in cyclo-
hexane and hexane (60 mL, 1/1 v/v) and filtration. The solvent
was removed under reduced pressure, and the powder was
triturated again with hexane (0.234 g, 35%). 1H NMR (400
MHz, C6D6): 7.24 (s, 6 H, Ph H3-5), 6.88 (d, J ) 5.6 Hz, 2 H,
picolyl H3,6), 6.41 (t, J ) 7.4 Hz, 2 H, picolyl H4,5), 6.04 (d, J )
7.4 Hz, 2 H, picolyl H3,6), 5.96 (t, J ) 6.0 Hz, 2 H, picolyl H4,5),
4.82 (s, 2 H, enamido CH2), 4.02 (septet, J ) 6.8 Hz, 4 H,
CH(CH3)2), 3.49 (s, 2 H, enamido CH2), 2.03 (s, 4 H, picolyl
CH2), 1.45 (d, J ) 6.8 Hz, 12 H, CH(CH3)2), 1.17 (d, J ) 6.8
Hz, 12 H, CH(CH3)2). 13C{1H} NMR (100 MHz, C6D6, DEPT):
δ 161.35 (picolyl ipso-C or Ph ipso-C), 158.69 (picolyl ipso-C
or Ph ipso-C), 145.89 (CH), 145.53 (CH2dCN), 138.70 (CH),
125.61 (CH), 123.86 (CH), 123.21 (CH), 116.24 (CH), 82.19
(CH2dCN), 47.19 (picolyl CH2), 29.07 (CH(CH3)2), 27.83 (CH-
(CH3)2), 24.30 (CH(CH3)2). Anal. Calcd for C40H50N4Zr: C, 70.9;
H, 7.43; N, 8.26. Found: C, 71.2; H, 7.36; N, 7.93.
Ate Com p lex 3. The complex was isolated when synthesis
of 2 was tried with 2-picolyllithium-2-picoline instead of
2-picolylpotassium. Thus, ZrCl4(THF)2, picolyllithium-2-pi-
coline, and 1 were reacted according to the same procedure.
After the solvent was removed, the residue was extracted with
toluene. The toluene was removed, and the solid was triturated
with hexane. Orange cubic crystals were deposited from the
filtrate when it was stored at room temperature overnight. 1H
NMR (400 MHz, C6D6): δ 7.47 (d, J ) 4.4 Hz, 1 H), 7.25-7.00
(m, 13 H), 6.84 (t, J ) 7.6 Hz, 1 H), 6.83 (d, J ) 4.0 Hz, 1 H),
6.53 (t, 7.6 Hz, 1 H), 6.35 (t, J ) 6.4 Hz, 1 H), 6.08 (d, J ) 7.6
Hz, 1 H), 6.05 (t, J ) 6.4 Hz, 1 H), 4.74 (s, 2 H, CdCH2), 3.97
(septet, J ) 6.8 Hz, 2 H, CHMe2), 3.77 (septet, J ) 6.8 Hz, 2
H, CHMe2), 3.37 (s, 2 H, CdCH2), 3.01 (br septet, J ) 6.8 Hz,
2 H, CHMe2), 2.61 (br-septet, J ) 6.8 Hz, 2 H, CHMe2), 2.54
(br s, 2 H, picolyl CH2), 2.39 (s, 2 H, CH2CdN), 1.64 (s, 2 H,
CH2CdN), 1.53 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.36 (d, J )
6.8 Hz, 6 H, CH(CH3)2), 1.35 (d, J ) 6.8 Hz, 6 H, CH(CH3)2),
0.90 (br d, 12 H, CH(CH3)2), 1.28 (br, 12 H, CH(CH3)2), 0.87
(d, J ) 6.8 Hz, 6 H, CH(CH3)2). 13C{1H} NMR (100 MHz,
C6D6): δ 178.43, 165.89, 160.18, 158.15 (picoline), 148.96
(picoline), 148.61, 147.14, 145.72, 145.28, 144.07, 139.32,
138.72, 137.78, 137.60 (picoline), 125.95, 125.04, 124.37,
124.13, 124.11, 123.70 (picoline), 122.74, 121.28 (picoline),
117.30, 82.25 (CdCH2), 67.01 (br, Zr-CH2CdN), 44.52 (picolyl
CH2), 28.84, 28.42 (br), 27.93, 27.82, 24.82, 24.68 (br), 24.45
(br), 23.86, 23.86 (br), 23.71 (br), 23.28 (br). Anal. Calcd for
1
94%), which is quite pure, as shown by its H NMR spectrum.
Analytically pure compound was obtained by recrystallization
in pentane solution in a freezer (-30 °C) overnight. H NMR
1
(400 MHz, C6D6): δ 7.25-7.12 (m, 6 H, Ph H3-5), 4.86 (s, 2 H,
CdCH2), 3.65 (s, 2 H, CdCH2), 3.45 (septet, J ) 6.8 Hz, 2 H,
CH(CH3)2), 3.27 (septet, J ) 6.8 Hz, 2 H, CH(CH3)2), 1.69 (s,
15 H, Cp* CH3), 1.41 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.34 (d,
J ) 6.8 Hz, 12 H, CH(CH3)2), 1.31 (d, J ) 6.8 Hz, 6 H, CH-
(CH3)2). 13C{1H} NMR (100 MHz, C6D6): δ 149.71, 145.56,
144.96, 144.45, 126.37, 124.89, 123.61, 123.21, 93.11 (CH2d
C), 30.19, 28.14 (CH(CH3)2), 26.88, 26.20, 25.28, 24.05 (CH-
(CH3)2), 10.99 (Cp* CH3). Anal. Calcd for C38H53ClHfN2: C,
60.7; H, 7.10; 3.73. Found: C, 60.4; H, 7.35; N, 3.98.
Ch lor o(cyclop en t a d ien yl)[N,N′-(1,2-d im et h ylen e-1,2-
eth a n ed iyl)bis(2,6-d iisopr op yla n ilido)-K2N,N′]zir con iu m -
(IV) (6). The dipotassium salt 1 (0.283 g, 0.588 mmol) and
CpZrCl3 (0.155 g. 0.588 mmol) were weighed in a vial inside a
glovebox, and cold THF (7 mL, -30 °C) was added. The
mixture was stirred at room temperature overnight. The
resulting solution was filtered over Celite, and the solvent was
removed under vacuum. The residue was dissolved in pentane,
and the solution was stored overnight at -30 °C. Red micro-
1
crystalline solid was deposited (0.190 g, 54%). H NMR (400
MHz, C6D6): δ 7.3-7.6 (m, 6 H, Ph H3-5), 5.95 (s, 5 H, Cp),
4.69 (s, 2 H, CdCH2), 3.62 (s, 2 H, CdCH2), 3.51 (septet, J )
6.8 Hz, 2 H, CH(CH3)2), 3.46 (septet, J ) 6.8 Hz, 2 H,
CH(CH3)2), 1.38 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.29 (d, J )
6.8 Hz, 6 H, CH(CH3)2), 1.29 (d, J ) 6.8 Hz, 6 H, CH(CH3)2),
1.25 (d, J ) 6.8 Hz, 6 H, CH(CH3)2). 13C{1H} NMR (100 MHz,
C6D6): δ 151.89 (CH2CN), 145.57, 144.28, 142.72 (Ph C1,3,5),
126.99, 124.92, 124.16 (Ph C2,4,6), 116.28 (Cp), 92.20 (CH2d
C), 28.90, 28.57 (CH(CH3)2), 26.25, 25.94, 25.49, 24.73 (CH-
(CH3)2). Anal. Calcd for C33H43ClN2Zr: C, 66.7; H, 7.29; N, 4.71.
Found: C, 67.0; H, 7.18; N, 5.05.
Met h yl[N,N′-(1,2-d im et h ylen e-1,2-et h a n ed iyl)b is(2,6-
d iisop r op yla n ilid o)- K2N,N′](p en ta m eth ylcyclop en ta d i-
en yl)zir con iu m (IV) (7). Compound 4 (0.150 g, 0.226 mmol)
was dissolved in diethyl ether (5.0 g), and 1.0 equiv of MeMgCl
in THF was added at room temperature. The color changed
from red to dark yellow upon addition. After the solution was
stirred at room temperature for 2 h, all volatiles were removed
under vacuum. The compound was extracted with pentane
(10.0 g). Red single crystals, which are suitable for X-ray
crystallography and elemental analysis, were grown from the
solution at -30 °C overnight. The yield was 0.091 g (63%). 1H
NMR (400 MHz, C6D6): δ 7.3-7.1 (m, 6 H, Ph H3-5), 4.88 (s,
2 H, CdCH2), 3.70 (s, 2 H, CdCH2), 3.51 (septet, J ) 6.8 Hz,
2 H, CH(CH3)2), 3.03 (septet, J ) 6.8 Hz, 2 H, CH(CH3)2), 1.60
(s, 15 H, Cp* CH3), 1.42 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.39
C
68H89LiN6Zr: C, 75.0; H, 8.24; N, 7.72. Found: C, 75.3; H,
8.17; N, 7.31.
Ch lor o[N,N′-(1,2-d im et h ylen e-1,2-et h a n ed iyl)b is(2,6-
d iisop r op yla n ilid o)-K2 N,N′](p en ta m eth ylcyclop en ta d i-
en yl)zir con iu m (IV) (4). The dipotassium salt 1 (0.166 g,
0.345 mmol) and Cp*ZrCl3 (0.115 g, 0.345 mmol) were weighed
in a vial inside a glovebox. Toluene (5 mL) was added, and
the resulting solution was stirred overnight at room temper-
ature. The solution was filtered over Celite. The solvent was
removed under vacuum to give a red solid (0.180 g, 79%), which
1
is quite pure, as shown by its H NMR spectrum. Analytically
pure compound was obtained by recrystallization in pentane

1510 Organometallics, Vol. 22, No. 7, 2003
Kim et al.
(d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.28 (d, J ) 6.8 Hz, 6 H, CH-
(CH3)2), 1.27 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 0.63 (s, 3 H, Zr-
CH3). 13C{1H} NMR (100 MHz, C6D6): δ 152.91, 145.72, 144.60,
144.27, 126.42, 125.27, 123.94, 122.29, 91.73 (CH2dC), 34.96
(Zr-CH3), 30.10, 28.75 (CH(CH3)2), 26.93, 26.81, 25.57, 24.75
(CH(CH3)2), 11.25 (Cp* CH3). Anal. Calcd for C39H56N2Zr: C,
72.7; H, 8.76; N, 4.35. Found: C, 72.9; H, 8.84; N, 4.50.
Met h yl[N,N′-(1,2-d im et h ylen e-1,2-et h a n ed iyl)b is(2,6-
d iisop r op yla n ilid o)- K2N,N′](p en ta m eth ylcyclop en ta d i-
en yl)h a fn iu m (IV) (8). Compound 5 (0.695 g, 0.924 mmol) was
dissolved in diethyl ether (10.0 g), and 1.0 equiv of MeMgCl
in THF was added at room temperature. The color changed
from red to dark green upon addition. After the solution was
stirred at room temperature for 2 days, all volatiles were
removed under vacuum. The compound was extracted with
pentane (30.0 g). Yellow-green crystals were obtained from the
solution at -30 °C overnight. The yield was 0.468 g (69%). 1H
NMR (400 MHz, C6D6): δ 7.3-7.1 (m, 6 H, Ph H3-5), 4.92 (s,
2 H, CdCH2), 3.66 (s, 2 H, CdCH2), 3.55 (septet, J ) 6.8 Hz,
2 H, CH(CH3)2), 3.07 (septet, J ) 6.8 Hz, 2 H, CH(CH3)2), 1.62
(s, 15 H, Cp* CH3), 1.42 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.41
(d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.28 (d, J ) 6.8 Hz, 6 H, CH-
(CH3)2), 1.27 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 0.53 (s, 3 H, Hf-
6.8 Hz, 2 H, CHMe2), 1.97 (br d, J ) 11 Hz, 2 H), 1.76 (br d,
J ) 11 Hz, 2 H), 1.18 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.14 (d,
J ) 6.8 Hz, 6 H, CH(CH3)2), 0.94 (d, J ) 6.8 Hz, 6 H, CH-
(CH3)2), 0.77 (d, J ) 6.8 Hz, 6 H, CH(CH3)2). 13C{1H} NMR
(100 MHz, C6D6): δ 197.41 (AlCH2C), 159.27, 157.12, 150.4
1
(dm, J CF ) 230 Hz), 145.79, 144.85, 142.14, 142.07, 141.36,
1
1
140.45, 140.04, 139.1 (dm, J CF ) 240 Hz), 137.0 (dm, J CF
)
240 Hz), 127.30, 125.04, 124.68, 124.56, 118.32, 100.42 (NCd
CH2), 51.99 (ZrCH2), 29.73, 29.04, 27.70, 25.94, 24.35, 23.62.
19F NMR (C6D6, 376 MHz): δ -27.60 (d, 3J FF ) 19 Hz), -63.01
3
(t, J FF ) 19 Hz), -70.05 (s).
B(C6F 5)3 + 7 (12). Compound 7 (16.1 mg, 25 µmol) and
B(C6F5)3 (12.8 mg, 25 µmol) were dissolved in C6D6 in an NMR
tube at room temperature. The complex is so unstable in C6D6
solution that it decomposes overnight to give oily precipitates.
1H NMR (500 MHz, C6D6): δ 7.06 (m, 4 H, Ph H3,5), 6.94 (m,
2 H, Ph H4), 4.84 (s, 2 H, CdCH2), 3.67 (s, 2 H, CdCH2), 2.82
(septet, J ) 6.8 Hz, 2 H, CH(CH3)2), 2.40 (septet, J ) 6.8 Hz,
2 H, CH(CH3)2), 1.67 (s, 3 H, BCH3), 1.49 (s, 15 H, Cp* CH3),
1.23 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.22 (d, J ) 6.8 Hz, 6 H,
CH(CH3)2), 1.06 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 0.65 (d, J )
6.8 Hz, 6 H, CH(CH3)2). 19F NMR (470 MHz, C6D6): δ -133.34
(d, J ) 21 Hz, o-F), -161.53 (dd, J ) 21 Hz, p-F), -166.59
(dd, J ) 21 Hz, 6, m-F).
CH ). 13C{1H} NMR (100 MHz, C6D6): δ 151.20, 145.43, 144.50,
3
144.40, 126.04, 124.78, 123.43, 120.92, 91.11 (CH2dC), 39.42
(Hf-CH3), 29.44, 28.21 (CH(CH3)2), 26.58, 26.42, 25.16, 24.22
(CH(CH3)2), 10.63 (Cp* CH3). Anal. Calcd for C39H56HfN2: C,
64.0; H, 7.71; N, 3.83. Found: C, 63.8; H, 7.80, N; 3.95.
(Cyclop en ta d ien yl)(Meth yl)[N,N′-(1,2-d im eth ylen e-1,2-
eth a n ediyl)bis(2,6-d iisopr op yla n ilido)-K2N,N′]zir con iu m -
(IV) (9). The complex was prepared according to the same
method and conditions as for 7. A red glassy solid was
obtained, which was shown to be quite pure by its NMR
spectra (90%). Purification by recrystallization to give an
analytically pure complex failed. 1H NMR (400 MHz, C6D6):
δ 7.3-7.1 (m, 6 H, Ph H3,4,5), 5.85 (s, 5 H, Cp), 4.73 (s, 2 H,
CH2dC), 3.58 (s, 2 H, CH2dC), 3.58 (septet, J ) 6.8 Hz, 2 H,
CH(CH3)2), 3.33 (septet, J ) 6.8 Hz, 2 H, CH(CH3)2), 1.38 (d,
J ) 6.8 Hz, 6 H, CH(CH3)2), 1.34 (d, J ) 6.8 Hz, 6 H, CH-
(CH3)2), 1.35 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.19 (d, J ) 6.8
Hz, 6 H, CH(CH3)2), 0.67 (s, Zr-CH3). 13C{1H} NMR (100 MHz,
C6D6): δ 153.49 (CH2C-N), 145.14, 143.67, 143.21 (Ph C1,3,5),
126.56, 124.77, 123.91 (Ph C2,4,6), 114.72 (Cp), 89.64 (CH2d
C), 30.54 (Zr-CH3), 28.68, 28.37 (CH(CH3)2), 26.16, 26.04,
25.60, 24.56 (CH(CH3)2).
B(C6F 5)3 + 9 (13). Compound 9 (17.3 mg, 30 µmol) and
B(C6F5)3 (15.4 mg, 30 µmol) were dissolved in C6D6 in an NMR
cell at room temperature. The complex decomposed in C6D6
solution over several hours. 1H NMR (400 MHz, C6D6): δ 7.01-
(m, 4 H, Ph H3,5), 6.90 (m, 2 H, Ph H4), 5.91 (s, 5 H, Cp), 4.63
(s, 2 H, CH2dC), 3.67 (s, 2 H, CH2dC), 2.93 (septet, J ) 6.8
Hz, 2 H, CH(CH3)2), 2.24 (septet, J ) 6.8 Hz, 2 H, CH(CH3)2),
1.71 (br, 3 H, BCH3), 1.19 (d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.04
(d, J ) 6.8 Hz, 6 H, CH(CH3)2), 1.03 (d, J ) 6.8 Hz, 6 H, CH-
(CH3)2), 0.80 (d, J ) 6.8 Hz, 6 H, CH(CH3)2).
Al(C6F 5)3 + 8 (14). Compound 8 (60 mg, 82 µmol) and Al-
(C6F5)3‚(toluene) (51 mg, 82 µmol) were dissolved in toluene
(2 mL) in a vial inside a glovebox. After it was stirred for 3
min at room temperature, the solution was filtered over Celite.
The filtrate was evacuated under vacuum to remove the
solvent. Trituration with pentane gave a yellow powder (77
mg, 77%). Single crystals suitable for X-ray crystallography
were obtained by vapor-phase addition of pentane to a toluene
solution at room temperature overnight. 13C{1H} NMR data
could not be obtained due to the compound’s low solubility in
C6D6 and decomposition in polar solvents such as CDCl3 and
CD2Cl2. 1H NMR (500 MHz, C6D6): δ 7.2-6.8 (m, 6 H, Ph
H3-5), 5.67 (s, 1 H, CdCH2), 4.29 (s, 1 H, CdCH2), 3.52 (d, J )
6.5 Hz, 1 H, CCH2Al), 3.24 (d, J ) 6.5 Hz, 1 H, CCH2Al), 2.90
(septet, J ) 6.8 Hz, 1 H, CH(CH3)2), 2.78 (septet, J ) 6.8 Hz,
1 H, CH(CH3)2), 2.38 (septet, J ) 6.8 Hz, 1 H, CH(CH3)2), 1.88
(septet, J ) 6.8 Hz, 1 H, CH(CH3)2), 1.39 (d, J ) 6.8 Hz, 3 H,
CH(CH3)2), 1.38 (s, 15 H, Cp* CH3), 1.21 (d, J ) 6.8 Hz, 3 H,
CH(CH3)2), 1.13 (d, J ) 6.8 Hz, 3 H, CH(CH3)2), 1.08 (d, J )
6.8 Hz, 3 H, CH(CH3)2), 1.05 (d, J ) 6.8 Hz, 3 H, CH(CH3)2),
0.85 (d, J ) 6.8 Hz, 3 H, CH(CH3)2), 0.84 (d, J ) 6.8 Hz, 3 H,
CH(CH3)2), 0.61 (d, J ) 6.8 Hz, 3 H, CH(CH3)2), 0.58 (s, 3 H,
Hf-CH3). 19F NMR (470 MHz, C6D6): δ -123.12, -157.20,
-164.22.
B(C6F 5)3 + 2 (10). Complex 2 (20.3 mg, 0.030 mmol) was
dissolved in C6D6, and B(C6F5)3 (15.4 mg, 0.030 mmol) was
added to the solution. NMR studies were carried out with the
1
solution. H NMR (400 MHz, C6D6): δ 8.46 (d, J ) 5.2 Hz, 1
H), 7.30-6.90 (m, 7 H), 6.70 (t, J ) 7.4 Hz, 1 H), 6.54 (t, 7.2
Hz, 1 H), 6.51 (d, J ) 5.2 Hz, 1 H), 6.38 (d, J ) 7.6 Hz, 1 H),
6.06 (t, J ) 6.2 Hz, 1 H), 5.96 (t, J ) 6.4 Hz, 1 H), 4.65 (s, 2 H,
CH2dC), 3.49 (br s, 2 H, CHMe2), 3.48 (s, 2 H, CH2dC), 2.81
(br septet, J ) 6.8 Hz, 2 H, CHMe2), 2.52 (br s, 2 H, BCH2),
1.93 (s, 2 H, Zr-CH2), 1.28 (br d, 6 H, CH(CH3)2), 1.10 (br d,
12 H, CH(CH3)2), 0.51 (br d, 6 H, CH(CH3)2). 13C{1H} NMR
(100 MHz, C6D6): δ 167.79, 162.48, 165.8 (br), 155.8 (br, NCd
1
CH2), 148.6 (dm, J CF ) 240 Hz), 146.29, 144.97 (br), 144.62
1
(br), 144.31, 141.85, 140.44, 139.0 (dm, J CF ) 250 Hz), 137.1
1
(dm, J CF ) 250 Hz), 127.56, 127.34, 125.54, 123.99, 124 (br,
Al(C6F 5)3 + 9 (15). Compound 9 (17.3 mg, 30 µmol) and
Al(C6F5)3‚(toluene) (18.6 mg, 30 µmol) were dissolved in C6D6
in a NMR tube. The complex decomposed in C6D6 solution over
ipso-C in C6F5), 87.8 (br, NCdCH2), 50.76 (ZrCH2), 29.71,
29.54, 27.25, 25.43, 24.98, 23.6 (br, CH2B). 19F NMR (C6D6,
3
1
376 MHz): δ -39.21 (br s), -67.34 (t, J FF ) 20 Hz), -71.493
several hours. H NMR (400 MHz, C6D6): δ 7.2-6.6 (m, 6 H,
(t, 3J FF ) 20 Hz) ppm. 11B{1H} NMR (C6D6, 128 MHz): δ -14.4.
Al(C6F 5)3 + 2 (11). A C6D6 solution for NMR studies was
Ph H3-5), 5.58 (s, 5 H, Cp), 5.06 (m, 2 H, CH2dC), 3.82 (m, 2
H, CH2dC), 3.25 (br, 2 H, CCH2Al), 2.98 (septet, J ) 6.8 Hz,
1 H, CH(CH3)2), 2.83 (septet, J ) 6.8 Hz, 1 H, CH(CH3)2), 2.80
(septet, J ) 6.8 Hz, 1 H, CH(CH3)2), 1.72 (septet, J ) 6.8 Hz,
1 H, CH(CH3)2), 1.37 (d, J ) 6.8 Hz, 3 H, CH(CH3)2), 1.23 (d,
J ) 6.8 Hz, 3 H, CH(CH3)2), 1.06-0.84 (m, 12 H, CH(CH3)2),
0.87 (s, 3 H, Zr-CH3), 0.58 (d, J ) 6.8 Hz, 3 H, CH(CH3)2),
0.48 (d, J ) 6.8 Hz, 3 H, CH(CH3)2).
1
prepared according to the same procedure as for 10. H NMR
(400 MHz, C6D6): δ 7.3-6.8 (m, 6 H), 6.45 (d, J ) 5.2 Hz, 2 H,
picolyl H3,6), 6.40 (t, J ) 7.6 Hz, 2 H, picolyl H4,5), 5.94 (d, J )
8.4 Hz, 2 H, picolyl H3,6), 5.90 (t, J ) 7.6 Hz, 2 H, picolyl H4,5),
5.33 (s, 1 H, CH2dC), 3.98 (s, 1 H, CH2dC), 3.61 (septet, J )
6.8 Hz, 2 H, CHMe2), 3.21 (s, 2 H, Al-CH2), 3.17 (septet, J )

Activation of Enamido Zirconium Complexes
Organometallics, Vol. 22, No. 7, 2003 1511
Ta ble 2. Cr ysta llogr a p h ic P a r a m eter sa
Al(C6F 5)3 + 7. Compound 7 (19.3 mg, 30 µmol) and Al-
(C6F5)3‚(toluene) (18.6 mg, 30 µmol) were dissolved in C6D6 in
an NMR tube at room temperature. The 1H NMR spectrum
can be tentatively interpreted as a mixture of a methyl-
abstracted ion-paired complex and alane-added zwitterionic
complex (ratio 1/2). Signals assigned to the zwitterionic
complex are given in italics. 1H NMR (500 MHz, C6D6): δ
7.13-6.77 (m, 6 H, Ph H3-5), 5.60 (s, 1 H, CdCH2), 4.84 (s, 2
H, CdCH2), 4.32 (s, 1 H, CdCH2), 3.68 (s, 2 H, CdCH2), 3.43
(d, J ) 6.9 Hz, 1 H, CCH2Al), 3.19 (d, J ) 6.9 Hz, 1 H, CCH2Al),
2.90 (septet, J ) 6.8 Hz, 1 H, CH(CH3)2), 2.88 (septet, J ) 6.8
Hz, 2 H, CH(CH3)2), 2.78 (septet, J ) 6.8 Hz, 1 H, CH(CH3)2),
2.35 (septet, J ) 6.8 Hz, 1 H, CH(CH3)2), 2.34 (septet, J ) 6.8
Hz, 2 H, CH(CH3)2), 1.62 (septet, J ) 6.8 Hz, 1 H, CH(CH3)2),
1.48 (s, 15 H, Cp* CH3), 1.39 (d, J ) 6.8 Hz, 3 H, CH(CH3)2),
1.38 (s, 3 H, Zr-CH3), 1.31 (s, 15 H, Cp* CH3), 1.23 (d, J )
6.8 Hz, 3 H, CH(CH3)2), 1.21 (d, J ) 6.8 Hz, 12 H, CH(CH3)2),
1.10 (d, J ) 6.8 Hz, 3 H, CH(CH3)2), 1.09 (d, J ) 6.8 Hz, 12 H,
CH(CH3)2), 1.04 (d, J ) 6.8 Hz, 3 H, CH(CH3)2), 0.86 (d, J )
6.8 Hz, 3 H, CH(CH3)2), 0.79 (s, 3 H, Zr-CH3), 0.75 (d, J )
6.8 Hz, 3 H, CH(CH3)2), 0.73 (d, J ) 6.8 Hz, 3 H, CH(CH3)2),
0.60 (d, J ) 6.8 Hz, 3 H, CH(CH3)2). 19F NMR (470 MHz,
C6D6): δ -123.20, -156.21, -157.32, -163.92, -164.24.
Eth ylen e P olym er iza tion . In a drybox, in a dried 70 mL
glass reactor was added 30 mL of toluene. Activated complex
prepared by mixing a complex (0.5 µmol) and MAO (0.89 g,
Al/Zr ) 5000) in the reactor. The reactor was assembled and
brought out from the drybox. The reactor was immersed in
an oil bath whose temperature had been set to a given value,
and the mixture was stirred for 15 min. Ethylene was fed
under 60 psig pressure. After the polymerization reaction was
conducted for a given time, the reaction was quenched by
venting ethylene gas and pouring the mixture into acetone.
White precipitates were collected by filtration and dried under
vacuum. Table 1 summarizes the polymerization results.
Cr ysta llogr a p h ic Stu d ies. Crystals coated with grease
(Apiezon N) were mounted inside a thin glass tube with epoxy
glue and placed on an Enraf-Nonius CCD single-crystal X-ray
diffractometer using graphite-monochromated Mo KR radia-
tion (λ ) 0.710 73 Å). The structures were solved by direct
methods (SHELXS-97)17 and refined against all F2 data
(SHELXS-97). All non-hydrogen atoms were refined with
anisotropic thermal parameters. The hydrogen atoms were
3
7
14
formula
C
68H89Li-
N6Zr
C117H168
N6Zr3
-
C64H64Al-
F
15HfN2
fw
a, Å
b, Å
c, Å
1088.61
12.8688(4)
24.2011(7)
21.0004(9)
90
1932.23
1351.64
17.3514(3)
12.5037(2)
29.1875(6)
90
19.3649(2)
17.9860(3)
31.4958(4)
90
R, deg
â, deg
97.2330(10)
90
97.6226(9)
90
101.0644(6)
90
γ, deg
V, Å3
6488.3(4)
P21/n
1.114
10873.0(3)
P21/c
1.180
6214.72(19)
P21/n
1.445
space group
D(calcd), g cm-3
Z
4
4
4
µ, mm-1
no. of data collected
no. of unique data
no. of variables
R (%)
0.211
17376
9284
0.330
1.777
24002
13840
763
0.0366
0.0438
0.698
38409
23350
1177
0.0654
0.1566
0.918
702
0.0567
0.1347
0.961
R
w (%)
goodness of fit
a
All data collected at 293(2) K with Mo KR radiation. R(F) )
2
∑||Fo| - |Fc||/∑|Fo| with Fo > 2.0σ(I); Rw ) [∑[w(Fo - Fc2)2]/
∑[w(Fo)2]2]1/2 with Fo > 2.0σ(I).
treated as idealized contributions. The crystal data and
refinement results are summarized in Table 2.
Ack n ow led gm en t. This work was supported by
Grant No. (R05-2002-000155-0) 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
the crystallographic studies of 3, 7 and 14. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM020949P
(17) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany,
1997.