Monocyclopentadienyl bis(phenoxo-imino) zirconium complexes as precatalyst species for olefin polymerization. Stereospecific methylation of an imino group with formation of a zirconium - Amido bond

Article abstract of DOI:10.1021/om049596f

The Schiff base N,N′-o-phenylenebis(3,5-di-tert-butyl- salicylideneimine) (1; _tBu₄salophenH₂) reacts with 1 equiv of Zr(η⁵-C₅H₅)Cl ₃·DME in the presence of 2.2 equiv of NEts in pentane to give the monocyclopentadienyl bis(phenoxo-imino) monochloro zirconium derivative Zr(η⁵-C₅H₅)[C₆H ₄-1,2-{N=CH(3,5-^tBu₂C₆H ₂-2-O)}₂]Cl (2). Moreover, 2 equiv of the monolithiated reagent derived from 3-tert-butyl-N-ethylsalicylaldimine by reaction with LiⁿBu in hexane reacts at -78°C with 1 equiv of Zr(η⁵-C₅H₅)Cl₃·DME in THF to yield the corresponding monocyclopentadienyl bis(phenoxo-imino) monochloro zirconium complex Zr(η⁵-C₅H₅)[CH ₃-CH₂N=CH{(3-^tBuC₆H ₃-2-O)}]₂Cl (5) after elimination of LiCl. Methylation of 2 with MgClMe in pentane or toluene at -78°C affords Zr(η⁵- C₅H₅)[1,2-C₆H₄{N=CH(3,5- ^tBu₂C₆H₂-2-O)}{NCH(Me)(3,5- ^tBu₂C₆H₂-2-O)}] (3) as a result of the reduction of one of the C=N bonds of the coligand. The hydrolysis of 3 gives the new organic compound [C₆H₄{N=CH(3,5- ^tBu₂C₆H₂-2-OH)}{NCH(Me)(3,5- ^tBu₂C₆H₂-2-OH)}] (4), which was also quantitatively isolated by reaction of 1 with MgClMe followed by treatment with a saturated solution of NH₄Cl in water. All of the reported compounds were characterized by the usual analytical and spectroscopic methods, and the molecular structure of 5 was determined by X-ray diffraction analysis from suitable single crystals. The catalytic activities of 2, 3, and 5 for ethylene polymerization using MAO as cocatalyst were determined.

Full text of DOI:10.1021/om049596f

5324
Organometallics 2004, 23, 5324-5331
Mon ocyclop en ta d ien yl Bis(p h en oxo-im in o) Zir con iu m
Com p lexes a s P r eca ta lyst Sp ecies for Olefin
P olym er iza tion . Ster eosp ecific Meth yla tion of a n Im in o
Gr ou p w ith F or m a tion of a Zir con iu m -a m id o Bon d
Martial Sanz and Toma´s Cuenca*,†
Departamento de Quı´mica Inorga´nica, Universidad de Alcala´, Campus Universitario,
28871-Alcala´ de Henares, Spain
Mikhail Galakhov
NMR Spectroscopy Center, Universidad de Alcala´, Campus Universitario,
28871-Alcala´ de Henares, Spain
Alfonso Grassi
Dipartamento di Chimica, Universita` di Salerno, via S. Allende, 84081 Baronissi, Italy
Robyn K. J . Bott, David L. Hughes, Simon J . Lancaster, and
Manfred Bochmann*
Wolfson Materials Centre, School of Chemical Sciences, University of East Anglia,
Norwich NR4 7TJ , U.K.
Received J une 4, 2004
The Schiff base N,N′-o-phenylenebis(3,5-di-tert-butyl-salicylideneimine) (1; tBu4salophenH2)
reacts with 1 equiv of Zr(η5-C5H5)Cl3‚DME in the presence of 2.2 equiv of NEt3 in pentane
to give the monocyclopentadienyl bis(phenoxo-imino) monochloro zirconium derivative Zr-
(η5-C5H5)[C6H4-1,2-{NdCH(3,5-tBu2C6H2-2-O)}2]Cl (2). Moreover, 2 equiv of the monolithiated
reagent derived from 3-tert-butyl-N-ethylsalicylaldimine by reaction with LinBu in hexane
reacts at -78 °C with 1 equiv of Zr(η5-C5H5)Cl3‚DME in THF to yield the corresponding
monocyclopentadienyl bis(phenoxo-imino) monochloro zirconium complex Zr(η5-C5H5)[CH3-
CH2NdCH{(3-tBuC6H3-2-O)}]2Cl (5) after elimination of LiCl. Methylation of 2 with MgClMe
in pentane or toluene at -78 °C affords Zr(η5-C5H5)[1,2-C6H4{NdCH(3,5-tBu2C6H2-2-O)}-
{NCH(Me)(3,5-tBu2C6H2-2-O)}] (3) as a result of the reduction of one of the CdN bonds of
the coligand. The hydrolysis of 3 gives the new organic compound [C6H4{NdCH(3,5-tBu2C6H2-
2-OH)}{NCH(Me)(3,5-tBu2C6H2-2-OH)}] (4), which was also quantitatively isolated by
reaction of 1 with MgClMe followed by treatment with a saturated solution of NH4Cl in
water. All of the reported compounds were characterized by the usual analytical and
spectroscopic methods, and the molecular structure of 5 was determined by X-ray diffraction
analysis from suitable single crystals. The catalytic activities of 2, 3, and 5 for ethylene
polymerization using MAO as cocatalyst were determined.
In tr od u ction
gated.2 Chelating bidentate monoanionic ligands based
on alkoxo-pyridino groups,3 tridentate dianionic ligands
based on dialkoxo-amino groups,4 and tetradentate lig-
ands based on dialkoxo-diamino5 and dialkoxo-diimino
groups6 have received increasing attention for cyclo-
pentadienyl-free halide or alkyl group 4 catalyst precur-
The quest for new olefin polymerization catalysts
displaying high activities similar to those of the group
4 metallocene complexes MCp2X2 is a highly topical
research challenge. In this context, ligands with oxygen
and nitrogen donors have been extensively investi-
1
(2) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
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Munslow, I. J .; Clarke, A. J .; Deeth, R. J .; Westmoreland, I.; Scott, P.
Chem. Commun. 2002, 1868.
† Tel: +34-918854655. Fax: +34-918854683. E-mail: tomas.cuenca@
uah.es.
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H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth, R. M. Angew.
Chem., Int. Ed. Engl. 1995, 34, 1143. (d) Bochmann, M. J . Chem. Soc.,
Dalton Trans. 1996, 255. (e) Hlatky, G. G. Coord. Chem. Rev. 1999,
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10.1021/om049596f CCC: $27.50 © 2004 American Chemical Society
Publication on Web 09/30/2004

Cyclopentadienyl Bis(phenoxo-imino) Zr Complexes
Organometallics, Vol. 23, No. 22, 2004 5325
sors M(N,O-)2X2, M(N,O-,O-)X2, and M(N,N,O-,O-)X2,
which have proved to be active in olefin polymerizations
upon activation with suitable activators. Monocyclopen-
tadienyl dihalide or dialkyl group 4 metal complexes
MCp(N,O-)X2 containing a bidentate N,O- monoanionic
chelate ligand have been also reported,7 producing high-
molecular-weight polyethylene7d when activated with
methylaluminoxane (MAO). The polymerization process
using these complexes can be rationalized by the ac-
cepted Ziegler-Natta model,1 since two coordination
sites in cis positions are available.
Sch em e 1
Very recently, new types of cyclopentadienyl-amido8
and monocyclopentadienyl-alkoxo9 monochloro or mono-
alkyl group 4 complexes have been reported. The double-
silylamido-bridged cyclopentadienyl zirconium benzyl
complex Zr[η5-C5H3(SiMe2-η1-NtBu)2]Bz reacts with
B(C6F5)3 to give the isolated ion pair {Zr[η5-C5H3(SiMe2-
η1-NtBu)2]}+[PhCH2B(C6F5)3]-, which is active in eth-
ylene polymerizations, even though it does not appar-
ently contain a Zr-alkyl ligand.8c
The use of tetradentate Schiff bases H2L to synthesize
group 4 metal coordination compounds has been studied
in order to explore their reactivity with ammonium
salts10 or trimethylaluminum11 to generate cationic
species, considered as the active species in the olefin
polymerization processes. Compounds of the type M(L)-
Cl2 (M ) Ti, Zr, Hf; L ) N,N,O-,O--donor Schiff base)
have been described in which the “MCl2” fragment
exhibits a cis or trans geometry, depending on the
nature of the metal and the ligand (L).12 In this context,
we have focused our efforts on the preparation of
monocyclopentadienyl monochloro and monoalkyl group
4 metal complexes of the type MCp(L)X (X ) halo and
alkyl ligands), incorporating one tetradentate or two
bidentate Schiff base ancillary ligands, and we were
interested in exploring the reactivity of such complexes
toward aluminum alkyls and B(C6F5)3. Herein we report
the synthesis and characterization of some monocyclo-
pentadienyl phenoxo-imino monochloro zirconium com-
pounds, the results of alkylation reactions involving a
ligand CdN bond, and the application of these com-
plexes in ethylene polymerizations in the presence of
MAO.
(5) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M. J . Am. Chem. Soc. 2000,
122, 10706. (b) Balsells, J .; Caroll, P. J .; Walsh, P. J . Inorg. Chem.
2001, 40, 5568. (c) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt,
Z. Organometallics 2001, 20, 3017.
(6) (a) Woodman, P. R.; Munslow, I. J .; Hitchcock, P. B.; Scott, P. J .
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M.; Mori, J .-I.; Yoshida, Y.; Saito, J .; Ishii, S.; Tsuru, K.; Matsui, S.;
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Kashiwa, N.; Fujita, T. J . Am. Chem. Soc. 2002, 124, 3327. (d)
Lamberti, M.; Pappalardo, D.; Zambelli, A.; Pellecchia, C. Macromol-
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Chiesi-Villa, A.; Guastini, C. J . Chem. Soc., Dalton Trans. 1990, 1345.
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P. R.; Alcock, N. W.; Munslow, I. J .; Sanders, C. J .; Scott, P. Dalton
2000, 3340. (i) Tian, J .; Coates, G. W. Angew. Chem., Int. Ed. 2000,
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Y. J . Organomet. Chem. 2001, 620, 1. (k) Bradley, D. C.; Hursthouse,
M. B.; Rendall, I. F. J . Chem. Soc. D 1969, 672. (l) Bradley, D. C.;
Hursthouse, M. B.; Rendall, I. F. J . Chem. Soc. D 1970, 368.
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(b) Matthews, J . D.; Singer, N.; Swallow, A. G. J . Chem. Soc. A 1970,
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Resu lts a n d Discu ssion
1. Mon ocyclop en ta d ien yl Der iva tives Con ta in -
in g a Bis(p h en oxo-im in o) Tetr a d en ta te Liga n d .
The tetradentate Schiff base 1 (Scheme 1) was prepared
in high yield from 1,2-diaminobenzene and 3,5-di-tert-
butyl-salicylaldehyde in cold methanol following a modi-
fied literature procedure.13 NMR data of 1 are in accord
with a C2v-symmetric molecule.
(8) (a) Amor, F.; Go´mez-Sal, P.; Royo, P.; Okuda, J . Organometallics
2000, 19, 5168. (b) Scholz, J .; Hadi, G. A.; Thiele, K.-H.; Go¨rls, H.;
Weimann, R.; Schumann, H.; Sieler, J . J . Organomet. Chem. 2001,
626, 243. (c) Cano, J .; Royo, P.; Lanfranchi, M.; Pellinghelli, M. A.;
Tiripicchio, A. Angew. Chem., Int. Ed. 2001, 40, 2495. (d) J in, J .;
Wilson, D. R.; Chen, E. Y.-X. Chem. Commun. 2002, 708.
(9) Kim, Y.; Han, Y.; Do, Y. J . Organomet. Chem. 2001, 634, 19.
(10) Tjaden, E. B.; Swenson, D. C.; J ordan, R. F.; Petersen, J . L.
Organometallics 1995, 14, 371.
Compound 1 reacts with 1 equiv of Zr(η5-C5H5)Cl3‚
DME14 (DME ) 1,2-dimethoxyethane) in the presence
of 2.2 equiv of NEt3 in pentane under reflux to form the
monocyclopentadienyl bis(phenoxo-imino) monochloro
complex Zr(η5-C5H5)[C6H4-1,2-{NdCH(3,5-tBu2C6H2-2-
O)}2]Cl (2). The reaction of 2 with methylmagnesium
chloride (3 M solution in THF) in pentane or toluene at
-78 °C does not give a zirconium methyl species but
results in alkylation of one of the CdN bonds, with
(11) Corden, J . P.; Errington, W.; Moore, P.; Wallbridge, M. G. H.
Chem. Commun. 1999, 323.
(12) (a) Floriani, C.; Solari, E.; Corazza, F.; Chiesi-Villa, A.; Agust´ın,
C. Angew. Chem., Int. Ed. Engl. 1989, 28, 64. (b) Mazzanti, M.; Rosset,
J .-M.; Floriani, C.; Chiesi-Villa, A.; Agust´ın, C. J . Chem. Soc., Dalton
Trans. 1989, 953. (c) Corazza, F.; Solari, E.; Floriani, C.; Chiesi-Villa,
A.; Agust´ın, C. J . Chem. Soc., Dalton Trans. 1990, 1335. (d) Woodman,
P.; Hitchcok, P. B.; Scott, P. J . Chem. Soc., Chem. Commun. 1996,
2735.
(13) (a) Pfeiffer, P. T. H. J . Prakt. Chem. 1937, 149, 242. (b)
Woltinger, J .; Ba¨ckvall, J . E.; Zsigmond, A. Chem. Eur. J . 1999, 5,
1460.
(14) Lund, E. C.; Livinghouse, T. Organometallics 1990, 9, 2426.

5326 Organometallics, Vol. 23, No. 22, 2004
Sanz et al.
Sch em e 2
identical chemical shifts are observed for compounds 2
and 3 (δ 164.2 and 159.3, respectively), which suggests
that in solution the imino N atom is not coordinated or
interacts only very weakly with the metal center, with
coordination being disfavored in compound 3 due to
folding of the diphenoxo-imino-amido ligand. Compari-
son of the chemical shifts for the carbon atoms in
compounds 3 and 4 shows that in 3 there is a very slight
π-interaction between the amido nitrogen free electron
pair and the metal atom (δNCHMe 58.2 and 57.7 for 3 and
4, respectively; ∆δNCHMe ) 0.5 ppm). This effect con-
tributes to the conjugation of the amido nitrogen free
electron pair with the phenylene ring system, as indi-
cated by the shielding of the ipso-C(phenylene)-N(sp3)
resonance in 3 (δ 134.9) with respect to that in 4 (δ
138.8; ∆δ ) 4 ppm). The small deshielding of the CO
resonances in compounds 2 and 3 compared with the
signal for 1 (δ 158.3) indicates σ + π coordination of
alkoxo ligands in the zirconium complexes. Taking into
account the nature of the alkoxo group as three-electron
(σ + π) and the amido as one-electron (σ) donor ligands,
a 16-electron metal environment for these zirconium
compounds can be achieved by coordination of the
cyclopentadienyl, the two alkoxo, and the chloro (or
amido) ligands.
formation of the diphenoxo-imino-amido zirconium com-
plex [Zr(η5-C5H5)[C6H4-1,2-{NdCH(3,5-tBu2C6H2-2-O)}-
{NCHCH3(3,5-tBu2C6H2-2-O)}] 3 (Scheme 1).
The reaction of 3 with an excess of SiClMe3 followed
by treatment with a 3 M solution of NnBu4F in THF
resulted in the hydrolysis of the zirconium complex and
liberation of the new imine-amine substance 4. Alter-
natively, 4 can be also synthesized in quantitative yield
by reaction of 1 with 3.2 equiv of MgClMe followed by
treatment with a saturated aqueous solution of NH4Cl
(Scheme 2).
Compounds 2 and 3 are obtained as yellow and red
solids, respectively, which are soluble in aromatic,
aliphatic, and chlorinated hydrocarbon solvents. They
can be stored for months under an inert atmosphere
without decomposition and remain air stable for some
weeks in the solid state. The analytical composition fits
The formation of 3 can be explained by two possible
pathways (Scheme 3). In pathway A, compound 2 reacts
with MgClMe to give a zirconium methyl intermediate
which may undergo a stereospecific migration of the
methyl ligand to an imino moiety. Alternatively, the
Grignard reagent may react directly with the CdN
bond, a sequence that may be favored by the coordina-
tion of magnesium to the chloro ligand (pathway B). The
formation of the zirconium-amido bond in 3 is favored
by the “class a” (hard acid) character of the zirconium
atom.15
When the reaction of 2 with MgClMe/THF (1:1.2 ratio)
in rigorously dried toluene-d8 solution was monitored
by NMR spectroscopy at low temperatures, the forma-
tion of an asymmetric species was detected at -50 °C,
which was converted to 3 at room temperature. How-
ever, the formation of an intermediate zirconium methyl
complex (A) was never observed. It seems likely, there-
fore, that the formation of 3 takes place through direct
methylation of the imino function. We have also studied
this reaction under the same conditions on a preparative
scale, varying the molar ratio of 2 to MgClMe. When 2
is allowed to react with 0.8 equiv of MgClMe, we
observed in the final product the presence of starting
material and 3 as the major product. Treatment of 2
with an excess of the Grignard reagent (4 equiv) leads
exclusively and cleanly to 3; there is no alkylation of
zirconium or attack on the second imino function.
Reduction of an phenoxo-imino functionality to give
a phenoxo-amido group has been shown during the
olefin polymerization process catalyzed by a family of
zirconium complexes containing two phenoxo-imino
chelate ligands16 using Ph3CB(C6F5)4/AliBu3 as activa-
tor. Kinetic studies demonstrating similar behavior of
cyclopentadienyl-free Schiff-base dibenzyl complexes of
1
well the proposed formulations. The H NMR spectra
(CDCl3, 25 °C) of 1 and 2 show, respectively, singlets
assignable to the NdCH protons, AA′BB′ spin systems
for the phenylene ring, AB spin systems for the phenoxo
protons, and two signals for the tert-butyl groups. A
singlet for the cyclopentadienyl ring protons in the
expected region of the spectrum for compound 2 and one
singlet due to OH resonances in the spectrum of 1 are
1
also observed. The H NMR spectra (CDCl3, 25 °C) of
compounds 3 and 4 exhibit four singlets for the non-
equivalent tert-butyl groups, ABCD spin systems for the
phenylene rings, and two AB spin systems for the
phenoxo protons. The spectrum of 3 also shows the
typical resonances at δ 5.0 (q, 1H) and δ 1.18 (d, 3H)
with the coupling constant 3J ) 6.3 Hz for the NCH-
(CH3) fragment, while for 4 the characteristic signals
for the NHCH(CH3) group are observed at δ 4.57 (d, 1H),
4.49 (dq, 1H), and 1.65 (d, 3H) with coupling constants
of 2.9 and 6.8 Hz. The resonances of the imine protons
appear at δ 8.9 and 8.62 for 3 and 4, respectively.
Characteristic resonances for methyl groups bonded to
the zirconium atom are not observed in the spectrum
of compound 3. These spectroscopic features are con-
sistent with a Cs symmetry for compound 2 and C1
symmetry for compounds 3 and 4 and indicate that one
of the two CdN bonds has been methylated.
The 13C NMR spectroscopic data corroborate the
methylation of 2, proceeding through the reduction of
one of the salophen imino groups with the stereospecific
formation of the zirconium amido chiral complex 3. A
significant spectroscopic feature associated with the 13
C
(15) Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements,
2nd ed.; Butterworth Heinemann: Oxford, U.K., 1998.
(16) Matsui, S.; Mitani, M.; Saito, J .; Tohi, Y.; Makio, H.; Mat-
sukawa, N.; Takagi, Y.; Tsuru, K.; Nitabaru, M.; Nakano, T.; Tanaka,
H.; Kashiwa, N.; Fujita, T. J . Am. Chem. Soc. 2001, 123, 6847.
NMR spectra of the substances described here is the
resonance for the imino carbon atom -HCdN-, which
is observed at δ 164.4 and 164.9 for 1 and 4. Almost

Cyclopentadienyl Bis(phenoxo-imino) Zr Complexes
Organometallics, Vol. 23, No. 22, 2004 5327
Sch em e 3
Sch em e 4
titanium and zirconium have also been reported.17 It
has been pointed out that the neutral group 4 diimino
dibenzyl complexes are unstable with respect to a 1,2-
migratory insertion of a benzyl ligand to the imino Cd
N bond. This reaction constitutes a catalyst deactivation
mechanism in the olefin polymerization process cata-
lyzed by these compounds. However, Zr(bis-tBuSalfen)-
(CH2Ph)2 (bis-tBuSalfen ) [Fe{η5-C5H4NdCH(3,5-tBu2-
C6H2)O}2]), in which both zirconium benzyl and imino
ligands are present, has been isolated as a stable
substance at room temperature.18 Alternatively, direct
nucleophilic attack has been proposed to occur at the
electrophilic carbon atom of one of the imino bonds.19
The nucleophilic attack on carbonyl functions (aldehydes
and ketones) as well as imino groups due to coordination
to transition metals20 as well as Lewis acids21 is, of
course, a well-known process.
2. Mon ocyclop en ta d ien yl Der iva tives Con ta in -
in g Tw o P h en oxo-im in o Liga n d s. The reaction of Li-
[EtNdCH(3-tBuC6H3-2-O)], obtained by addition of Lin-
Bu in hexane to the corresponding iminophenol in dry
THF at -78 °C under argon, with the cyclopentadienyl
zirconium compound Zr(η5-C5H5)Cl3‚DME, in THF at
-78 °C, gives the monocyclopentadienyl bis(phenoxo-
imino) monochloro derivative Zr(η5-C5H5)[CH3CH2Nd
CH{(3-tBuC6H3-2-O)}]2Cl (5) (Scheme 4). An analytically
pure sample was obtained by layering a concentrated
dichloromethane solution with light petroleum and
cooling. The compound was obtained as a gray powder
in good yield. Related titanium and zirconium mono-
phenoxo-imino complexes as well as some CpTi com-
pounds containing two Schiff base ligands embedding
the Ti(IV) in a six-coordinate environment have been
recently reported.22 Attempts to alkylate compound 5
did not give isolable products.
In the 1H NMR spectrum of 5, the imino protons
appear at δ 8.05 and 7.99, while the 13C chemical shift
of the imino carbon atoms indicates deshielding com-
pared with the free ligand (∆δ ≈ 7 ppm), indicating that
the nitrogen atoms are coordinated to the metal center,
in contrast with the observations for 2 and 3. These
spectroscopic data are consistent with an asymmetric
geometry for this compound in solution.
The structure of complex 5 was confirmed by a single-
crystal X-ray diffraction study (Figure 1). Selected bond
distances and angles are listed in Table 1. The com-
pound crystallized with a solvent molecule that could
not be resolved (elemental analysis suggests 0.25 CH2-
Cl2).
If the centroid of the cyclopentadienyl ring is consid-
ered as a single coordination site, the geometry around
the titanium center can be well described as octahedral.
The structure shows a trans arrangement of oxygen
atoms, with the Cp ligand in a cis position with respect
to the chlorine atom, and the two nitrogen atoms located
in cis positions. Similar trans oxygen disposition has
been previously observed for bis(phenoxo-imino) tita-
nium and zirconium derivatives,6c,23 and this is the
expected structural trend for the favored geometry
(17) Knight P. D.; Clarke, A. J .; Kimberley, B. S.; J ackson, R. A.;
Scott, P. Chem. Commun. 2002, 352.
(18) Shafir, A.; Fiedler, D.; Arnold, J . Dalton 2002, 555.
(19) (a) Martin, G. C.; Boncella. J . M. Organometallics 1989, 8, 2968.
(b) Martin, G. C.; Boncella, J . M.; Wucherer, E. J . Organometallics
1991, 10, 2804.
(20) Collmann, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987.
(21) (a) Layer, R. W. Chem. Rev. 1963, 63, 489. (b) Harada, K. In
The Chemistry of the Carbon-Nitrogen Double Bond; Patai, S., Ed.;
Interscience: New York, 1970. (c) March, J . Advanced Organic
Chemistry: Reactions, Mechanisms and Structure, 3rd ed., Inter-
science: New York, 1985.
(22) (a) Bott, R. J . K.; Hughes, D. L.; Schormann, M.; Bochmann,
M.; Lancaster, S. J . J . Organomet. Chem. 2003, 665, 135. (b) Huang,
J .; Lian, B.; Qian, Y.; Zhou, W.; Chen, W.; Zheng, G. Macromolecules
2002, 35, 4871.

5328 Organometallics, Vol. 23, No. 22, 2004
Sanz et al.
Ta ble 2. Eth ylen e P olym er iza tion s Ca ta lyzed w ith
Com p lexes 2, 3, a n d 5/MAOa
d
d
en-
T
t
yield activ-
Mw/ Tf
Tc
c
c
try cat. (°C) (min) (mg) ityb
Mw
Mn
Mn (°C) (°C)
1
2
3
4
5
6
7
8
9
2
3
2
3
2
3
2
3
5e
25
25
50
50
50
50
50
50
25
50
50
5
5
5
5
1
5.2
1.1
11 11.4 234 600 113 500 2.1 139 123
2.2
5
2
15
15
30
30
30
15
49 17.9 321 200 155 400 2.1 139 123
63 22.9 307 400 144 000 2.1 139 124
82 15
140 25.5 376 300 197 000 1.9 139 122
95 32
386 000 177 000 2.2 140 123
10 5e
11 5e
310 207
30 1385 462
F igu r e 1. Molecular structure of 5, showing the atomic
numbering scheme. Hydrogen atoms are omitted for clarity.
a
Conditions: ethylene pressure 1 atm; solvent toluene, 50 mL;
b
MAO:Zr ) 1000:1; catalyst 11.0 µmol. In units of kg of polymer
(mol of Zr)-1 h-1 atm-1
.
c Determined by GPC. Determined by
d
DSC; Tf ) melting point; Tc ) crystallization point. e Catalyst 6
µmol.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 5a
Zr(1)-O(1)
Zr(1)-O(3)
Zr(1)-Cl(6)
Zr(1)-C(51)
Zr(1)-C(54)
Zr(1)-C(5x)
O(3)-C(31)
C(11)-C(12)
N(2)-C(21)
2.040(9)
2.038(7)
2.537(3)
2.628(6)
2.590(10)
2.314
1.368(12)
1.399(14)
1.495(18)
Zr(1)-N(2)
Zr(1)-N(4)
Zr(1)-C(52)
Zr(1)-C(53)
Zr(1)-C(55)
O(1)-C(11)
C(120)-N(2)
C(320)-N(4)
N(4)-C(41)
2.307(8)
2.380(12)
2.58(2)
2.646(7)
2.581(12)
1.341(14)
1.258(15)
1.226(16)
1.516(14)
a Zr-N single bond, indicating significant coordination,
in the solid state, of the imino nitrogen atom to the
metal center, similar to that observed in solution
according to the spectroscopic data. The average Zr-
(1)-O distance of 2.039 Å is as expected for Zr-O bonds
with partial double-bond character due to oxygen π-
donation26 and correlates with a wide average Zr-O-C
bond angle of 144.7°. These Zr-O bond lengths are
intermediate between the ranges observed for bridging
and terminal Zr-OR distances.27
O(1)-Zr(1)-N(2)
O(3)-Zr(1)-O(1)
O(1)-Zr(1)-N(4)
O(1)-Zr(1)-Cl(6)
O(3)-Zr(1)-N(2)
N(2)-Zr(1)-N(4)
N(2)-Zr(1)-Cl(6)
O(3)-Zr(1)-N(4)
C(31)-O(3)-Zr(1)
O(3)-C(31)-C(32)
O(3)-C(31)-C(36)
78.2(3)
157.8(3)
83.7(4)
89.5(2)
90.2(4)
80.0(4)
156.3(3)
75.7(3)
145.5(7)
117.8(9)
121.5(9)
O(3)-Zr(1)-Cl(6)
N(4)-Zr(1)-Cl(6)
O(1)-Zr(1)-C(5x)
N(2)-Zr(1)-C(5x)
O(3)-Zr(1)-C(5x)
N(4)-Zr(1)-C(5x)
Cl(6)-Zr(1)-C(5x)
C(11)-O(1)-Zr(1)
O(1)-C(11)-C(12)
O(1)-C(11)-C(16)
94.2(3)
78.7(3)
100.0
100.9
100.7
176.3
101.1
143.8(7)
117.9(10)
121.1(9)
3. P olym er iza tion Stu d ies. The zirconium com-
plexes 2, 3, and 5 have been studied as catalyst
precursors for olefin polymerizations upon activation
with methylaluminoxane (MAO). Since each complex
contains only one Cl ligand, we assume that MAO reacts
under Zr-O bond cleavage, presumably by reaction with
the AlMe3 component of MAO, to generate an active
cationic zirconium alkyl species. Polymerization of eth-
ylene was investigated in toluene as solvent at 25 and
50 °C under 1 atm of ethylene pressure (Al:Zr ) 1000:
1). The results are summarized in Table 2. There was
no polymerization of propylene under identical condi-
tions. The catalytic activities of all three compounds
increase when the temperature is raised from 25 to 50
°C, with the highest activity being observed after 30 min
of polymerization time. Compound 5 is about an order
of magnitude more active than 2 and 3; this may reflect
the less favorable reduction of the imino functionality
reaction and the more facile metal-ligand cleavage and
MAO activation of complexes containing bidentate
rather than tetradentate ligands. The activity of the
amido complex 3 is roughly twice that of 2 under
comparable conditions (entries 7 and 8). The GPC data
indicate small differences in molecular weight of the
resulting polymers with Mw values in the range of
200 000-400 000 and polydispersities close to 2.0. For
2 and 3 the Mw values increased with polymerization
time. The polymers produced by these catalysts exhibit
single DSC endotherms, with melting point Tf ≈ 140
°C.
C(120)-N(2)-C(21) 112.7(11)
C(320)-N(4)-C(41) 113.4(12) C(120)-N(2)-Zr(1) 127.9(8)
C(320)-N(4)-Zr(1) 128.1(9)
C(41)-N(4)-Zr(1)
C(21)-N(2)-Zr(1)
118.7(7)
118.2(8)
a
Esd’s are given in parentheses. C(5x) is the centroid of the Cp
ring, C(51-55).
investigated for zirconium complexes containing bis-
[N,O] bidentate ligands, Zr[N,O]2X2.24 The two trans
components N(2)-Zr(1)-Cl(6) and O(3)-Zr(1)-O(1)
with angle values of 156.3(3) and 157.8(3)°, respectively,
are bent away from the Cp plane, while the Cp-
(centroid)-Zr(1)-N(4) angle is almost linear (176.3°).
The plane of one of the phenoxo-imino ligands, O(1)-
C(11)-C(12)-C(120)-N(2), is nearly parallel to the Cp
plane, while the plane of the second phenoxo-imino
ligand, O(3)-C(31)-C(32)-C(320)-N(4), is nearly per-
pendicular to the Cp plane. The sum of the angles
around N(2) and N(4) are approximately 360°, indicating
sp2 hybridization at both nitrogen atoms. The zirconium-
imino bond distances Zr-N(2) and Zr-N(4) (2.307(8)
and 2.380(12) Å, respectively) are analogous in length
25
to other reported Zr-N(sp3)amino and other Zr-
N(sp2)imino bonding interactions and are consistent with
(23) (a) Tian, J .; Hustad, P. D.; Coates, G. W. J . Am. Chem. Soc.
2001, 123, 5134. (b) Saito, S.; Mitani, M.; Matsui, S.; Kashiwa, N.;
Fujita, T. Macromol. Rapid. Commun. 2000, 21, 1333.
(24) (a) Bei, X.; Swenson, D. C.; J ordan, R. F. Organometallics 1997,
16, 3282 and references therein. (b) J ones, D.; Roberts, A.; Cavell, K.;
Keim, W.; Englert, U.; Skelton, B. W.; White, A. H. J . J . Chem. Soc.,
Dalton Trans. 1998, 255.
(26) (a) Bortolin, R.; Patel, V.; Munday, I.; Taylor, N. J .; Carty, A.
J . J . Chem. Soc., Chem. Commun. 1985, 456. (b) Koch, T.; Blaurock,
S.; Hey-Hawkins, E.; Galan-Fereres, M.; Plat, D.; Eisen, M. S. J .
Organomet. Chem. 2000, 595, 126.
(25) Doufou, P.; Abboud, K. A.; Boncella, J . M. J . Organomet. Chem.
2000, 603, 213.
(27) Evans, W. J .; Ansari, M. A.; Ziller, J . W. Polyhedron 1998, 17,
869.

Cyclopentadienyl Bis(phenoxo-imino) Zr Complexes
Organometallics, Vol. 23, No. 22, 2004 5329
Syn th esis of tBu 4sa lop h en H2 (1). A solution of 3,5-di-tert-
butyl-salicylaldehyde (14.26 g, 60.84 mmol) in MeOH (340 mL)
was treated successively with formic acid (0.35 mL) and 1,2-
diaminobenzene (3.29 g, 30.47 mmol) with vigorous stirring
at 0 °C. The reaction mixture was stirred at room temperature
overnight, and a yellow solid was formed. After filtration, the
solid was washed twice with cold MeOH and further dried at
64 °C in vacuo overnight (15.28 g, 93%). IR (KBr): ν (cm-1):
3430 (OH), 1617 (CdN). 1H NMR (300 MHz, CDCl3, 25 °C): δ
13.50 (2H, s, OH), 8.65 (2H, s, NdCH), 7.42 (2H, AB spin
system, 4J ) 2.5 Hz, CH phenol), 7.30 (2H, AA′BB′ spin
system, CH phenylene), 7.23 (2H, AA′BB′ spin system, CH
phenylene), 7.20 (2H, AB spin system, 4J ) 2.1 Hz, CH phenol),
1.42 (18H, s, tBu), 1.31 (18H, s, tBu). 1H NMR (300 MHz, C6D6,
25 °C): δ 14.03 (2H, s, OH), 8.11 (2H, s, NdCH), 7.62 (2H,
AB spin system, CH phenol), 7.04 (2H, AB spin system, CH
phenol), 6.98 (2H, AA′BB′ spin system, CH phenylene), 6.72
Con clu d in g Rem a r k s
In this contribution we describe the synthesis and
characterization of the monocyclopentadienyl bis(phe-
noxo-imino) monochloro zirconium derivative Zr(η5-
C5H5)[C6H4-1,2-{NdCH(3,5-tBu2C6H2-2-O)}2]Cl (2), which
contains a tetradentate Schiff base ligand, and the
analogous complex Zr(η5-C5H5)[EtNdCH(3-tBuC6H3-2-
O)]2Cl (5), containing two Schiff base ligands. The
coordination of the phenoxo-imino ligand to the metal
center in the complexes depends on the nature of the
Schiff base studied. When the tetracoordinate ligand is
used, NMR spectroscopy suggests a weak coordination
of the imino nitrogen atom, while significant coordina-
tion is observed in the compound with the bidentate
ligand. The diphenoxo-imino-amido zirconium com-
pound Zr(η5-C5H5)[C6H4-1,2-{NdCH(3,5-tBu2C6H2-2-
O)}{NCH(Me)(3,5-tBu2C6H2-2-O)}] (3) is formed in the
methylation reaction of compound 2 by reduction of the
corresponding imino functionality. The nature of the
tetracoordinated ligand in compound 3 is confirmed by
a hydrolysis reaction, giving a diphenol-amine-imine
compound. The zirconium complexes are catalyst pre-
cursors for the polymerization of ethylene when acti-
vated with MAO under mild conditions.
t
(2H, AA′BB′ spin system, CH phenylene), 1.42 (18H, s, Bu),
t
1.31 (18H, s, Bu). 13C{1H} NMR (75 MHz, CDCl3, 25 °C): δ
164.4 (NdCH), 158.3 (C-OH), 142.5 (ipso-phenylene), 140.1,
137.0, 118.2 (ipso-phenol), 128.0, 127.2, 126.6, 119.7 (phenol
+ phenylene), 35.4, 34.4 (ipso-tBu), 31.7, 29.7 (tBu). 13C{1H}
NMR (75 MHz, C6D6, 25 °C): δ 165.1 (NdCH), 158.3 (C-OH),
143.1 (ipso-phenylene), 140.4, 137.6, 119.1 (ipso-phenol), 128.2,
127.4, 127.3, 120.1 (phenol + phenylene), 35.5, 34.3 (CMe3),
31.6, 29.8 (CMe3). Anal. Calcd for C36H48N2O2: C, 79.96; H,
8.95; N, 5.18. Found: C, 79.97; H, 9.00; N, 5.33.
Zr (η5-C5H5)[C6H4-1,2-{NdCH(3,5-tBu 2C6H2-2-O)}2]Cl (2)-
.
tBu4salophenH2 (1.51 g, 2.80 mmol) and freshly purified
Exp er im en ta l Section
triethylamine (0.825 mL, 6.03 mmol) in pentane (120 mL) were
added at room temperature to a pentane solution (40 mL) of
Zr(η5-C5H5)Cl3‚DME (1 g, 2.82 mmol). The mixture was re-
fluxed with vigorous stirring for 23 h. After it was cooled to
room temperature, the mixture was evaporated to dryness and
the remaining solid was Soxhlet-extracted with ether. The
resulting solution was evaporated in vacuo, and a yellow-
orange solid was obtained, which was recrystallized from cold
pentane to give an analytically pure yellow solid, characterized
Gen er a l Con sid er a tion s. All manipulations were per-
formed under argon using Schlenk and high-vacuum-line
techniques or in an inert-atmosphere glovebox. The solvents
were of reagent grade and were purified by distillation under
argon before use by employing the appropriate drying/deoxy-
genated agent. Deuterated solvents were stored over activated
4 Å molecular sieves and degassed by several freeze-thaw
cycles. 1,2-Diaminobenzene, 3,5-di-tert-butyl-salicylaldehyde,
formic acid, triethylamine, methylmagnesium chloride, and
chlorotrimethylsilane (Aldrich) were used as received or puri-
fied by literature methods.28 Zr(η5-C5H5)Cl3‚DME14 was pre-
pared by a known procedure. C, H, and N microanalyses were
performed on a Perkin-Elmer 240B and/or Heraeus CHN-O-
Rapid microanalyzer. The IR spectra were recorded at room
temperature on a Perkin-Elmer Spectrum-2000 FT-IR spec-
trophotometer. The NMR spectra were recorded on Varian
Mercury VX-300 PFG and PFG WFG Unity Plus 500 spec-
trometers. The chemical shifts were referenced with respect
to residual proton and carbon resonances of the solvent
(CDCl3: 1H, 7.24 ppm; 13C, 77.0 ppm). The assignment of the
signals in NMR spectra was made by using PFG WFG
TOCSY1D, PFG WFG NOESY1D, PFG WFG HSQC, and PFG
HMBC pulse sequences. Polymerization grade ethylene from
Air Liquide was purified by passage through two columns
packed with activated 4 Å molecular sieves. Methylaluminox-
ane (MAO; 10% solution in toluene) was purchased from
CROMPTON GmbH.
Polymer melt endotherms were determined using a Perkin-
Elmer DSC-4 differential scanning calorimeter and heating
rate of 10 °C/min. Melting points of solid samples placed in a
dried capillary tube sealed under high vacuum are determined
using Thiele’s method (thermometer Fernandez 75 mm im-
mersion, range -10 to +200 °C, 1 °C graduation). The GPC
measurements were performed on a Polymer Laboratories PL-
220 instrument, equipped with a refractive index detector. The
samples were analyzed in trichlorobenzene (TCB) stabilized
with 0.0125% BHT at 160 °C. The flow was 1.0 mL/min. Two
columns of PLgelMIXED B (length 600 mm) were used.
1
as 2 (0.26 g, 13%). H NMR (300 MHz, CDCl3, 25 °C): δ 8.57
(2H, s, NdCH), 7.68 (2H, AA′BB′ spin system, CH phenylene),
7.62 (2H, AB spin system, 4J ) 2.5 Hz, CH phenoxo), 7.49 (2H,
AA′BB′ spin system, CH phenylene), 7.34 (2H, AB spin system,
4J ) 2.1 Hz, CH phenoxo), 6.06 (5H, s, Cp), 1.47 (18H, s, CMe3),
1.34 (18H, s, CMe3). 13C{1H} NMR (75 MHz, CDCl3, 25 °C): δ
164.2 (NdCH), 162.8 (C-O), 143.4 (ipso-phenylene), 139.2,
139.1, 122.1 (ipso-phenoxo), 132.7, 130.7, 128.4, 117.4 (phenoxo
+ phenylene), 114.6 (Cp), 35.5, 34.4 (CMe3), 31.6, 30.2 (CMe3).
Anal. Calcd for C41H51N2O2ClZr: C, 67.41; H, 7.04; N, 3.83.
Found: C, 67.51; H, 7.50; N, 3.88.
Zr (η5-C5H 5)[C6H 4-1,2-{NdCH (3,5-t Bu 2C6H 2-2-O)}{N-
CHCH3(3,5-tBu 2C6H2-2-O)}] (3). Methylmagnesium chloride
(0.2 mL of a 3 M solution in THF, 0.6 mmol) was added
dropwise to a solution of 2 (0.34 g, 0.47 mmol) in pentane (20
mL) at -78 °C. The reaction mixture was slowly warmed to
room temperature with vigorous stirring. The dark red solution
was filtered, and the volatiles were removed in vacuo to give
a red solid, which was recrystallized from cold toluene and
1
characterized as 3 (0.23 g, 69%). H NMR (300 MHz, CDCl3,
25 °C): δ 8.90 (1H, s, NdCH), 7.65 (1H, ABCD spin system,
phenylene), 7.62 (1H, AB spin system, phenoxo), 7.45 (1H, AB
spin system, phenoxo), 7.29 (1H, ABCD spin system, phe-
nylene), 7.23 (1H, AB spin system, phenoxo), 7.05 (1H, AB spin
system, phenoxo), 6.98 (1H, ABCD spin system, phenylene),
6.69 (1H, ABCD spin system, phenylene), 5.85 (5H, s, Cp), 5.00
(1H, q, 3J ) 6.3 Hz, NCH), 1.59, 1.57, 1.38, 1.36 (36H, s, CMe3),
3
1.18 (3H, d, J ) 6.3 Hz, NCHCH3). 13C{1H} NMR (75 MHz,
CDCl3, 25 °C): δ 159.3 (NdCH), 157.7, 154.7, 153.3, 141.0,
140.6, 138.6, 137.5, 134.9, 133.9, 122.3 (ipso-phenoxo + phe-
nylene), 130.0, 129.0, 128.2, 123.3, 122.1, 115.5, 115.2, 114.6
(phenoxo + phenylene), 112.9 (Cp), 58.2 (NCHCH3), 35.9, 35.8,
34.6, 34.5 (CMe3), 32.1, 31.8, 30.5, 30.1 (CMe3), 25.9 (NCHCH3).
(28) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, U.K., 1988.

5330 Organometallics, Vol. 23, No. 22, 2004
Sanz et al.
Anal. Calcd for C42H54N2O2Zr: C, 71.04; H, 7.66; N, 3.94.
Found: C, 70.84; H, 7.63; N, 4.01.
CH2Cl2), 3.62 (2H, m, NCH2CH3), 3.43 (2H, m, NCH2CH3), 1.56
(9H, s, CMe3), 1.49 (9H, s, CMe3), 1.05 (3H, t, J ) 7.3 Hz,
NCH2CH3), 0.93 (3H, t, J ) 7.3 Hz, NCH2CH3). 13C{1H} NMR
(75 MHz, CDCl3, 25 °C): δ 167.8 (NdCH), 165.9 (NdCH),
159.7-117.3 (phenoxo), 115.1 (Cp), 53.7 (NCH2CH3), 53.1
(NCH2CH3), 35.0 (CMe3), 34.7 (CMe3), 30.3 (CMe3), 29.7
(CMe3), 16.2 (NCH2CH3), 15.7 (NCH2CH3). Anal. Calcd for
[C6H4-1,2-{NdCH(3,5-t Bu 2C6H2-2-OH)}{NCH(CH 3)(3,5-
tBu 2C6H2-2-OH)}] (4). Meth od 1. Methylmagnesium chloride
(0.22 mL of a 3 M solution in THF, 0.66 mmol) was added
dropwise to a solution of 1 (0.11 g, 0.20 mmol) in pentane (10
mL) at -78 °C. The reaction mixture was slowly warmed to
room temperature with vigorous stirring overnight. The dark
red solution was neutralized with saturated solutions of NH4-
Cl in water (5 mL) and NaCl in water (2 mL). The organic
layer was washed with water (5 mL) and a saturated solution
of NaCl in water (2 mL), dried over MgSO4, and filtered. All
volatiles were removed in vacuo to give a crude yellow solid,
which was purified by flash column chromatography on silica
gel (40-63 µm), elution with hexane, and recrystallization in
ether, affording yellow crystals which were characterized as
4 (0.10 g, 90%), mp 197 °C dec. 1H NMR (300 MHz, CDCl3, 25
°C): δ 13.01 (1H, s, OH), 9.50 (1H, s, OH), 8.62 (1H, s, Nd
CH), 7.48 (1H, AB spin system, phenol), 7.25 (1H, AB spin
system, phenol), 7.23 (1H, AB spin system, phenol), 7.07 (1H,
ABCD spin system, phenylene), 7.03 (1H, ABCD spin system,
phenylene), 7.00 (1H, AB spin system, phenol), 6.93 (1H,
ABCD spin system, phenylene), 6.85 (1H, ABCD spin system,
phenylene), 4.57 (1H, d, J ) 2.9 Hz, NH), 4.49 (1H, dq, J )
6.8 Hz; 2.9 Hz, NCH), 1.65 (3H, d, J ) 6.8 Hz, NCHCH3), 1.47,
1.38, 1.33, 1.32 (36H, s, CMe3). 13C{1H} NMR (75 MHz, CDCl3,
25 °C): δ 164.9 (NdCH), 158.2, 153.4 (C-OH), 141.3 (ipso-
phenylene-Nimido), 138.8 (ipso-phenylene-Namine), 140.9, 140.8,
136.9, 136.2, 126.5, 118.5 (ipso-phenol), 128.4, 127.7, 126.9,
122.7, 121.7, 121.0, 118.4, 115.9 (CH, phenol + phenylene),
57.7 (NCHCH3), 35.4, 35.3, 34.5, 34.4 (CMe3), 32.0, 31.7, 30.0,
29.7 (CMe3), 22.9 (NCHCH3). Anal. Calcd. for C37H52N2O2: C,
79.81; H, 9.41; N, 5.03. Found: C, 79.67; H, 9.97; N, 4.99.
Meth od 2. A 0.05 mL portion of chlorotrimethylsilane (0.43
mmol) was added dropwise to a solution of compound 3 (13
mg, 16.3 µmol) in CHCl3 (0.5 mL), and the reaction mixture
was stirred at room temperature overnight. After completion
(12 h), all volatiles were removed in vacuo to eliminate the
excess of trimethylchlorosilane. The residue was dissolved in
0.5 mL of CHCl3, 1 mL of a 3 M solution of NnBu4F in THF (3
mmol) was added, and the resulting solution was stirred for
30 min. The solvent was completely removed at 50 °C, and
the residue was dissolved in 2 mL of CH2Cl2 and washed with
water (2 mL) and a saturated solution of NaCl in water (1 mL).
The organic layer was washed twice with water (2 mL) and a
saturated solution of NaCl in water (1 mL), dried over MgSO4,
and filtered. All volatiles were removed in vacuo to give a crude
yellow solid, which was purified by flash column chromatog-
raphy on silica gel (40-63 µm); elution with hexane afforded
compound 4 as a yellow solid (ca. 10 mg, 100%) after solvent
removal by evaporation.
C
31H41N2O2ClZr‚0.25CH2Cl2: C, 60.38; H, 6.73; N, 4.51; Cl,
8.56. Found: C, 60.31; H, 6.97; N, 4.15; Cl, 8.50 (these numbers
are very sensitive to the exact amount of CH2Cl2 present in
the analysis sample). M+: m/z 599.4.
Cr ysta l Str u ctu r e An a lysis of Zr (η5-C5H5)[CH3CH2Nd
CH{(3-tBu C6H3-2-O)-KO}]2Cl‚(solven t). Crystal data: C31H41
-
ClN2O2Zr, solvent (unresolved), fw ) 685.5*, orthorhombic,
space group Pna21 (No. 33), a ) 24.474(5) Å, b ) 16.284(3) Å,
c ) 8.623(2) Å, V ) 3436.6(12) Å3. Z ) 4, Dc ) 1.325 g cm-3*,
F(000) ) 1452*, T ) 140(1) K, µ(Mo KR) ) 4.3 cm-1*, λ(Mo
KR) ) 0.710 69 Å. N.B.: asterisks denote values which do not
include any solvent contribution.
Crystals are pale yellow and tetrahedral. A crystal of
dimensions 0.30 × 0.20 × 0.20 mm was coated with oil and
mounted on a glass fiber in the cold nitrogen stream on a
Rigaku R-Axis IIc image plate diffractometer equipped with
a rotating-anode X-ray source (Mo KR radiation) and graphite
monochromator. Using 4° oscillations, 48 exposures of 45 min
each were made. The total number of reflections recorded (not
including absences), to θmax ) 25.4°, was 11 201, of which 6049
were unique (Rint ) 0.048) and 4270 were “observed” with I >
2σI.
Data were processed using the DENZO/SCALEPACK pro-
grams.29 The structure was determined by the direct methods
routines in the SHELXS program and refined by full-matrix
least-squares methods, on F2 values, in SHELXL.30 Refinement
with the Zr, Cl, and O atoms anisotropic gave R1 ) 0.234 and
some poor molecular dimensions. The top difference peaks
were at 4.3 and 4.1 e Å-3 and were recognized as alternative
sites for the Zr and Cl atoms. Extension and refinement of
the alternative structure showed pseudo mirror plane sym-
metry of the two structures at z ) ∼0.18 and ∼0.68 and a ratio
of major to minor component molecules of ca. 63:37. Some atom
sites are common to both molecules. Atoms in sites of at least
0.63 occupancy were refined anisotropically; for lower site
occupancies, atoms were refined isotropically. Further disorder
was found in the major component in the phenyl ring of C(31-
36) and in both ethyl groups; in the minor component, the
atoms of the ethyl groups were not located. A region, believed
to be of solvent (the crystals were recrystallized from a mixture
of CH2Cl2 and hexanes), remains unresolved; 10 carbon atoms
with site occupancies of 0.23-0.78, corresponding to ca. 5
carbon atoms overall, were included in the refinement. Hy-
drogen atoms were included in the major molecule in idealized
positions, and their Uiso values were set to ride on the Ueq
values of the parent carbon atoms. At the conclusion of the
refinement, wR2 ) 0.243 and R1 ) 0.10430b for all 6049
reflections weighted with w ) [σ2(Fo2) + (0.176P)2]-1 with P )
(Fo2 + 2Fc2)/3; for the “observed” data only, R1 ) 0.081. In the
final difference map, the highest peak (ca. 0.8 e Å-3) was close
to O(3).
Zr (η5 -C 5 H 5 )[C H 3 C H 2 N dC H {(3-t B u C 6 H 3 -2-O )}]2 C l‚
0.25CH2Cl2 (5). A solution of LinBu (1.6 M in hexanes, 3.15
mmol, 2.0 mL) was added dropwise to a stirred solution of
3-tert-butyl-N-ethyl-salicylaldimine (0.62 g, 3 mmol) in THF
(100 mL) at -78 °C. The mixture was stirred at -78 °C for 15
min, allowed to reach room temperature, stirred for a further
1 h, and then cooled to -78 °C. ZrCpCl3‚DME was added as a
suspension in THF (50 mL). The resulting solution was
warmed to room temperature and stirred overnight. The
volatiles were removed under vacuum to give a brown foam,
which was extracted with dichloromethane and the extract
filtered to remove LiCl. The solution was then concentrated
to ∼5-10 mL, carefully layered with light petroleum, and left
at 5 °C to afford yellow crystals of the title compound and some
residual ZrCpCl3 as a gray powder. 1H NMR (300 MHz, CDCl3,
25 °C): δ 8.05 (1H, s, NdCH), 7.99 (1H, s, NdCH), 7.55 (1H,
dd, J ) 7.7 and 1.7 Hz, aryl), 7.52 (1H, dd, J ) 7.7 and 1.7
Hz, aryl), 7.17 (1H, dd, J ) 7.7 and 1.6 Hz, aryl), 7.15 (1H,
dd, J ) 7.7 and 1.6 Hz, aryl), 6.80 (1H, t, J ) 7.6 Hz, aryl),
6.78 (1H, t, J ) 7.6 Hz, aryl), 6.39 (5H, s, Cp), 5.28 (0.5H, s,
Scattering factors for neutral atoms were taken from ref 31.
Computer programs used in this analysis have been noted
above or in Table 4 of ref 32 and were run on a Silicon Graphics
Indy computer at the University of East Anglia or a DEC-
Alpha Station 200 4/100 computer at the Biological Chemistry
Department, J ohn Innes Centre.
(29) Otwinowski, Z.; Minor, W. Methods Enzymol. 1996, 276, 307.
(30) Sheldrick G. M. SHELX-97: Programs for Crystal Structure
Determination (SHELXS) and Refinement (SHELXL); University of
Go¨ttingen, Go¨ttingen, Germany, 1997.
(31) International Tables for X-ray Crystallography; Kluwer Aca-
demic: Dordrecht, The Netherlands, 1992; Vol. C, pp 193, 219, 500.
(32) Anderson, S. N.; Richards, R. L.; Hughes, D. L. J . Chem. Soc.,
Dalton Trans. 1986, 245.

Cyclopentadienyl Bis(phenoxo-imino) Zr Complexes
Organometallics, Vol. 23, No. 22, 2004 5331
P olym er iza tion P r oced u r e. Dried toluene (50 mL) was
introduced under argon into the glass reactor equipped with
a magnetic stirrer and was externally thermostated at the
desired temperature with vigorous stirring over 30 min. MAO
(8 mL, 12.19 mmol) was then injected and the mixture stirred
for 15 min. The argon was replaced by ethylene (1 atm), the
solution was degassed in vacuo, and the reactor was refilled
with the ethylene. This procedure was repeated and the
solution saturated with ethylene (1 atm) over 15 min. The
zirconium complex (6-11 µmol in 1 mL-1 of toluene) was
injected. The polymerization was terminated by methanol
injection. The polymer was precipitated with 100 mL of a 5%
HCl solution in MeOH, stirred, filtered, washed successively
with 50 mL of a 5% HCl solution in MeOH, 100 mL of water,
and 100 mL of MeOH, and finally dried in vacuo at 50 °C for
24 h to constant weight.
Ack n ow led gm en t. Financial support for this re-
search by the European Commission (Contract No.
HPRN-CT2000-00004) and DGICYT (Project No.
MAT2001-1309) is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables giving X-ray
crystallographic data for Zr(η5-C5H5)[CH3CH2NdCH{(3-t-
BuC6H3-2-O)}]2Cl‚(solvent) and a figure giving an additional
view of the structure. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM049596F