Hafnium bis(phenoxyimino) dibenzyl complexes and their activation toward olefin polymerization

Article abstract of DOI:10.1021/om060753f

Hf bis(phenoxyimino) dibenzyl complexes bearing benzylimino and perfluorophenylimino groups were prepared by a direct reaction between the desired ligand precursors and Hf(CH₂Ph)₄. In the solid state, the Hf complexes adopt an octahedral configuration where imino nitrogens are in positions cis to each other and oxygens occupy apical vertices of the coordination polyhedron. According to ¹H NMR and 2D-NOESY studies, this cis-N,N configuration was also maintained in solution. In addition, the structures of Hf bis(phenoxyimino) dibenzyl complexes were studied with DFT calculations. Activation of the Hf dibenzyl complexes with B(C₆F ₅)₃ led to the highly air-, moisture-, solvent-, and temperature-sensitive cationic bis(phenoxyimino) Hf monobenzyl species, which were further investigated by ¹H and ¹⁹F NMR, ¹H-¹³C heteronuclear correlation, 2D-NOESY, and ESI-MS methods. It was observed that the cationic, benzylimino-substituted Hf complexes have a propensity toward CH activation. The correlation between the stability of the cationic species toward CH activation and the catalytic behavior of the MAO-activated dibenzyl complexes was established. Accordingly, the MAO-activated Hf bis(phenoxyimino) dibenzyl complexes and their dichloro analogues, depending on the ligand substitution, have from low to very high catalytic activities (up to 14 000 kg of PE/((mol of cat.) h (bar of ethylene))) in ethylene polymerizations. In general, the produced polyethylene had a monomodal molar mass distribution with relatively narrow polydispersity. Polypropylene produced with perfluorophenyl-substituted Hf complexes had a large amount of 2,1-misinsertions in the polymer chains. To further shed light on the catalytic reaction, polymerizations of ethylene and propylene with the cationic species generated from Hf bis-(phenoxyimino) dibenzyl complexes with B(C ₆F₅)₃ were studied with ¹H NMR.

Full text of DOI:10.1021/om060753f

1444
Organometallics 2007, 26, 1444-1460
Hafnium Bis(phenoxyimino) Dibenzyl Complexes and Their
Activation toward Olefin Polymerization
Kirill V. Axenov,† Martti Klinga,† Olli Lehtonen,‡ Harri T. Koskela,§ Markku Leskela¨,† and
Timo Repo*,†
Department of Chemistry, Laboratory of Inorganic Chemistry, P.O. Box 55, UniVersity of Helsinki,
FIN-00014 UniVersity of Helsinki, Finland, Optics and Molecular Materials, Helsinki UniVersity of
Technology, Rakentajanaukio 2 C, FIN-02150 Espoo, Finland, and NMR Laboratory, Finnish Institute for
Verification of the Chemical Weapons ConVention (VERIFIN), P.O. Box 55, UniVersity of Helsinki,
FIN-00014 UniVersity of Helsinki, Finland
ReceiVed August 21, 2006
Hf bis(phenoxyimino) dibenzyl complexes bearing benzylimino and perfluorophenylimino groups were
prepared by a direct reaction between the desired ligand precursors and Hf(CH2Ph)4. In the solid state,
the Hf complexes adopt an octahedral configuration where imino nitrogens are in positions cis to each
1
other and oxygens occupy apical vertices of the coordination polyhedron. According to H NMR and
2D-NOESY studies, this cis-N,N configuration was also maintained in solution. In addition, the structures
of Hf bis(phenoxyimino) dibenzyl complexes were studied with DFT calculations. Activation of the Hf
dibenzyl complexes with B(C6F5)3 led to the highly air-, moisture-, solvent-, and temperature-sensitive
cationic bis(phenoxyimino) Hf monobenzyl species, which were further investigated by 1H and 19F NMR,
1H-13C heteronuclear correlation, 2D-NOESY, and ESI-MS methods. It was observed that the cationic,
benzylimino-substituted Hf complexes have a propensity toward CH activation. The correlation between
the stability of the cationic species toward CH activation and the catalytic behavior of the MAO-activated
dibenzyl complexes was established. Accordingly, the MAO-activated Hf bis(phenoxyimino) dibenzyl
complexes and their dichloro analogues, depending on the ligand substitution, have from low to very
high catalytic activities (up to 14 000 kg of PE/((mol of cat.) h (bar of ethylene))) in ethylene
polymerizations. In general, the produced polyethylene had a monomodal molar mass distribution with
relatively narrow polydispersity. Polypropylene produced with perfluorophenyl-substituted Hf complexes
had a large amount of 2,1-misinsertions in the polymer chains. To further shed light on the catalytic
reaction, polymerizations of ethylene and propylene with the cationic species generated from Hf bis-
1
(phenoxyimino) dibenzyl complexes with B(C6F5)3 were studied with H NMR.
Chart 1
Introduction
Following the successful design of group 4 metallocenes and
their application in homogeneous R-olefin polymerization,1 in
the last few decades nonmetallocene complexes of early and
late transition metals have attracted growing attention as
potential catalyst precursors.2 Many organic and organometallic
ligands, including, for example, amines, imines, and phosphines,
have now been exploited in this area.3 The expansion in choice
of ligands means that the electronic character, geometry, and
steric hindrance around the catalytically active metal center can
be controlled through rational design of the ligand environment.
Recently, new and highly active group 4 polymerization
catalysts based on phenoxyimine ligands (Chart 1) have been
reported in a series of publications by Fujita and co-workers at
Mitsui Chemicals.4 Depending on the nature of the metal and
the ligand substitution, the catalytic properties of MAO- or
* To whom correspondence should be addressed. E-mail: timo.repo@
helsinki.fi. Fax: +358-(0)9-19150198.
† Laboratory of Inorganic Chemistry, University of Helsinki.
‡ Optics and Molecular Materials, Helsinki University of Technology.
§ Finnish Institute for Verification of the Chemical Weapons Convention,
University of Helsinki.
(4) (a) Matsui, S.; Mitani, M.; Saito, J.; Tohi, Y.; Makio, H.; Matsukawa,
N.; Takagi, Y.; Tsuru, K.; Nitabaru, M.; Nakano, T.; Tanaka, H.; Kashiwa,
K.; Fujita, T. J. Am. Chem. Soc. 2001, 123, 6847. (b) Saito, J.; Suzuki, Y.;
Makio, H; Tanaka, H.; Onda, M.; Fujita, T. Macromolecules 2006, 39, 4023.
(c) Mitani, M.; Mohri, J.; Yoshida, Y.; Saito, J.; Ishii, S.; Tsuru, K.; Matsui,
S.; Furuyama, R.; Nakano, T.; Tanaka, H.; Kojoh, S.; Matsugi, T.; Kashiwa,
N.; Fujita, T. J. Am. Chem. Soc. 2002, 124, 3327. (d) Furuyama, R.; Saito,
J.; Ishii, S.; Mitani, M.; Matsui, S.; Tohi, Y.; Makio, H.; Matsukawa, N.;
Tanaka, H.; Fujita, T. J. Mol. Catal., A: Chem. 2003, 200, 31. (e) Furuyama,
R.; Saito, J.; Ishii, S.; Makio, H.; Mitani, M.; Tanaka, H.; Fujita, T. J.
Organomet. Chem. 2005, 690, 4398. (f) Furuyama, R.; Mitani, M.; Mochri,
J.; Mori, R.; Tanaka, H.; Fujita, T. Macromolecules 2005, 38, 1546.
(1) (a) Kaminsky, W.; Arndt, M. In Applied Homogeneous Catalysis with
Organometallic Compounds; Cornils, B.; Herrmann, W. A., Eds.; VCH:
Weinheim, New York, Basel, Cambridge, Tokyo, 1996; Vols. 1 and 2. (b)
Alt, H. G.; Ko¨ppl, A. Chem. ReV. 2000, 100, 1205. (c) Brintzinger, H. H.;
Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth, R. M. Angew. Chem.
1995, 107, 1255. (d) Shapiro, P. J. Coord. Chem. ReV. 2002, 231, 67.
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111, 448; Angew. Chem., Int. Ed. 1999, 38, 428.
(3) Gibson, V. C.; Spitzmesser, K. Chem. ReV. 2003, 103, 283.
10.1021/om060753f CCC: $37.00 © 2007 American Chemical Society
Publication on Web 02/10/2007

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1445
Chart 2
level) were used to gain a further understanding of the dynamic
nature of these catalysts in ethylene polymerization.11
Studies dedicated to the MAO activation of bis(phenoxy-
imino) group 4 metal complexes toward olefin polymerization
were recently reported,12 including a detailed investigation on
the activation of the perfluorophenyl-substituted Ti bis(phe-
noxyimino) dichloro complex with MAO or AlMe3/(CPh3)+B-
-
(C6F5)4 by Bryliakov et al. As a result, cationic monomethyl
complexes with a bulky Me-MAO counteranion on the outer
shell were observed, and these Ti cations reacted further with
ethylene to produce Ti polymeryl species.12b
Although cationic bis(phenoxyimino) complexes are highly
preferable, studies dedicated to them are few. The general
approach developed by Marks et al. to study the activation of
group 4 metal alkyl derivatives with boron activators13 has found
limited use, because the alkyl derivatives of these bis(phenoxy-
imino) complexes have been barely accessible.14 This is due to
the fact that the corresponding alkyl derivatives are not
achievable via straightforward alkylation reactions between the
dichloro complexes and Li, Mg, etc. alkyls. Due to the presence
of the reactive CHdN groups, these alkylation experiments led
regularly to extensive side reactions.14-16 As recently shown,
this synthetic problem can be circumvented when reactions of
Zr tetrabenzyl with free salicylaldimines14b,c or Na salicylaldi-
borane-borate/TIBA-activated Ti, Zr, and Hf bis(phenoxy-
imino) complexes can vary substantially in ethylene and
propylene polymerization. In general, group 4 metal phenoxy-
imino catalysts bearing C6F5 imino substituents are highly active
in ethylene polymerization.5 Intriguingly, analogous MAO-
activated Ti complexes, where Ar is C6H5-xFx (x ) 2, 3, 5)
(Chart 1), can cause living ethylene and propylene polymeriza-
tion.4c,6 While chain-end-controlled syndiotactic polypropylene
can be obtained by MAO-activated Ti and Zr bis(salicylaldi-
minato) complexes having C6F5 groups,7 non-fluoroaryl-
substituted Zr and Hf catalysts produce atactic, low-molar-mass
polypropylene.4a,8
Quite unexpectedly, ethylene polymerization experiments
performed with Zr bis(phenoxyimino) complexes bearing phen-
ylimino groups revealed that these catalysts were able to produce
polyethylene with different modalities (molar mass distribu-
tions), depending on the applied polymerization temperature.9
This multimodal nature of the polymers was referred to the pos-
sibility of bis(phenoxyimino) complexes to possess five differ-
ent isomeric forms (Chart 2). In fact, the structural diversity of
15
minates with Me2TiCl2 were applied. Although preliminary
studies concerning the activation of alkyl bis(phenoxyimino)
complexes with B(C6F5)3 have been reported,14c,15 more detailed
investigations of this process will facilitate direct insight into
the nature and structure of these highly active catalytic species.
In this respect we report herein the synthesis and structure of
various Hf bis(phenoxyimino) dibenzyl complexes as well as
studies on their activation with B(C6F5)3 and the reactivity of
the formed cationic species with ethylene and propylene.
Results and Discussion
Preliminary Studies. An approach to bis(phenoxyimino)
group 4 dialkyl complexes, developed by Scott et al., is based
on the reaction of free phenoxyimino ligands with tetrabenzyl
Ti or Zr.14 A number of relatively stable Zr dibenzyl complexes
were obtained by this method, although such Ti and Zr
complexes had a propensity to migrate of one of the benzyl
groups from the metal center to the imino function of the
phenoxyimino ligands.14,15 In our preliminary studies a similar
procedure was usedsthe metalation of free salicylaldimino
bis(phenoxyimino)-based complexes was demonstrated by 15
N
NMR investigations9 and X-ray crystallographic studies.10 Sim-
ilar multimodal polymerization behavior for arylimino-substi-
tuted Ti bis(phenoxyimino) catalysts was recently observed in
our research group. Computational methods (on the HF/3-21G*
(5) (a) Matsui, S.; Tohi, Y.; Mitani, M.; Saito, J.; Makio, H.; Tanaka,
H.; Nitabaru, M.; Nakano, T.; Fujita, T. Chem. Lett. 1999, 1065. (b) Matsui,
S.; Mitani, M.; Saito, J.; Tohi, Y.; Makio, H.; Tanaka, H.; Fujita, T. Chem.
Lett. 1999, 1263. (c) Matsui, S.; Mitani, M.; Saito, J.; Matsukawa, N.;
Tanaka, H.; Nakano, T.; Fujita, T. Chem. Lett. 2000, 554.
(6) (a) Saito, J.; Mitani, M.; Mohri, J.; Yoshida, Y.; Matsui, S.; Ishii,
S.-I.; Kojoh, S.-I.; Kashiwa, N.; Fujita, T. Angew. Chem., Int. Ed. 2001,
40, 2918. (b) Mitani, M.; Furuyama, R.; Mohri, J.-i.; Saito, J.; Ishii, S.;
Terao, H.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc. 2002, 124, 7888. (c)
Tian, J.; Hustad, P. D.; Coates, G. W. J. Am. Chem. Soc. 2001, 123, 5134.
(7) (a) Mitani, M.; Furuyama, R.; Mohri, J.; Saito, J.; Ishii, S.-I.; Terao,
H.; Nakano, T.; Tanaka, H.; Fujita, T. J. Am. Chem. Soc. 2003, 125, 4293.
(b) Lamberti, M.; Pappalardo, D.; Zambelli, A.; Pellecchia, C. Macromol-
ecules 2002, 35, 658. (c) Milano, G.; Cavallo, L.; Guerra, G. J. Am. Chem.
Soc. 2002, 124, 13368. (d) Tian, J.; Coates, G. W. Angew. Chem., Int. Ed.
2000, 39, 3626. (e) De Rosa, C.; Circelli, T.; Auriemma, F.; Mathers, R.
T.; Coates, G. W. Macromolecules 2004, 37, 9034.
(10) For examples of cis-N,N isomer solid-state structures, see ref 4c.
For structures of trans-N,N isomers, see: (a) Strauch, J.; Warren, T. H.;
Erker, G.; Fro¨hlich, R.; Saarenketo, P. Inorg. Chim. Acta 2000, 300-302,
810. For structure of cis-N,N,cis-O,O isomers, see: (b) Cherian, A. E.;
Lobkovsky, E. B.; Coates, G. W. Macromolecules 2005, 38, 6259.
(11) Pa¨rssinen, A.; Luhtanen, T.; Klinga, M.; Pakkanen, T.; Leskela¨, M.;
Repo, T. Eur. J. Inorg. Chem. 2005, 2100.
(12) (a) Makio, H.; Fuita, T. Macromol. Symp. 2004, 213, 221. (b)
Bryliakov, K. P.; Kravtsov, E. A.; Pennington, D. A.; Lancaster, S. J.;
Bochmann, M.; Brintzinger, H. H.; Talsi, E. P. Organometallics 2005, 24,
5660.
(13) (a) Yang, X.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 1991,
113, 3623. (b) Chen, E. Y.-X.; Marks, T. J. Chem. ReV. 2000, 100, 1391
and references therein. (c) Yang, X.; Stern, C. L.; Marks, T. J. J. Am. Chem.
Soc. 1994, 116, 10015.
(14) (a) Woodman, P. R.; Alcock, N. W.; Munslow, I. J.; Sanders, C. J.;
Scott, P. Dalton Trans. 2000, 3340. (b) Knight, P. D.; O’Shaughnessy, P.
N.; Munslow, I. J.; Kimberley, B. S.; Scott, P. J. Organomet. Chem. 2003,
683, 103. (c) Knight, P. D.; Clarkson, G.; Hammond, M. L.; Kimberley, B.
S.; Scott, P. J. Organomet. Chem. 2005, 690, 5125.
(8) (a) Makio, H.; Tohi, Y.; Saito, J.; Onda, M.; Fujita, T. Macromol.
Rapid Commun. 2003, 24, 894. (b) Makio, H.; Fujita, T. Bull. Chem. Soc.
Jpn. 2005, 78, 52. (c) Ishii, S.-I.; Furujama, R.; Matsukawa, N.; Saito, J.;
Mitani, M.; Tanaka, H.; Fujita, T. Macromol. Rapid Commun. 2003, 24,
452.
(15) Makio, H.; Oshiki, T.; Takai, K.; Fujita, T. Chem. Lett. 2005, 34,
1382.
(9) Tohi, Y.; Makio, H.; Matsui, S.; Onda, M.; Fujita, T. Macromolecules
2003, 36, 523.
(16) Knight, P. D.; Clarke, A. J.; Kimberley, B. S.; Jackson, R. A.; Scott,
P. Chem. Commun. 2002, 352.

1446 Organometallics, Vol. 26, No. 6, 2007
AxenoV et al.
Table 1. Selected Structural Parameters for Complexes a
Scheme 1
and 10-12
10
11
12
a
Distances (Å)
2.256(5)
M-C
M-O
M-N
2.261(6)
2.313(5)
2.008(3)
2.031(3)
2.362(4)
2.386(4)
2.229(9)
2.274(9)
1.981(5)
1.997(5)
2.398(7)
2.402(6)
2.161(4)
2.006(3)
2.417(5)
1.838(2)
1.891(3)
2.231(3)
Ti-N(amino)
C(imino)-N
1.923(3)
1.294(10) 1.302(5)
1.285(10)
1.292(6)
1.301(6)
1.302(7)
C(amino)-N
1.499(4)
Angles (deg)
94.2(3)
159.21(12) 157.06(19) 157.8(2)
C-Hf-C
O-M-O
N-M-N
Cipso-C-M
97.0(2)
94.6(3)
165.65(12)
129.91(13)
119.3(2)
86.58(13)
109.9(4)
116.5(4)
93.3(2)
115.2(3)
90.6(2)
ligands by metal tetraalkyls. As an example, the reaction
between 2,6-diisopropylphenyl-substituted salicylaldimine and
TiMe4,17 mixed at -78 °C in a 2:1 ratio, gave only a thermally
unstable green LTiMe3-type salicylaldiminato complex (see the
Supporting Information). To further study this method, the
metalation of phenoxyimino ligands with more stable Ti and
117.8(7)
111.4(6)
127.0(6)
125.8(5)
M-N(imino)-C 124.0(3)
126.1(4)
126.1(3)
124.7(3)
Ti-N(amino)-C
C25-C11-C
125.3(2)
111.0(3)
109.0(3)
114.9(3)
C25-C11-N
1
Zr tetrabenzyls was investigated. H NMR and single-crystal
N-C11-C
X-ray studies of the products showed that the obtained Ti and
Zr bis(phenoxyimino) dibenzyl complexes were unstable, as one
of the benzyl substituents tends to migrate from the metal to a
CHdN group (Scheme 1 and Figure 1). In fact, mixtures of
the desired Ti or Zr dibenzyl complexes and migration products
were always obtained.
range for Ti-benzyl complexes,21 and the geometry of the
Ti-CH2Ph moiety (the Ti-C32 distance is ca. 3.164 Å, and
the Ti-C9-C32 angle is 119.3(2)°) indicates η1-benzyl coor-
dination.
On the basis of experimental observations and theoretical
conclusions, it is known that Hf-C bonds are the most stable
among group 4 elements.22 In addition, despite numerous reports
on the synthesis of various Ti and Zr bis(phenoxyimino)
complexes and studies of their catalytic behavior in olefin
polymerization,4-11 the synthesis and catalytic properties of Hf
derivatives are still scarcely described in the scientific literature.8
Therefore, in this respect, we found that Hf bis(phenoxyimino)
dibenzyl complexes should be stable enough for their isolation
and investigation. In present work we focused on the synthesis
and B(C6F5)3 activation studies of Hf bis(phenoxyimino) diben-
zyl derivatives. In order to compare the catalytic behavior of
Hf salicylaldiminates having different substituents at the metal
atom, the corresponding Hf dichloro complexes were also
synthesized and studied in ethylene and propylene polymeri-
zation reactions side by side with their Hf dibenzyl derivatives.
Synthesis of Hf Complexes. For this work, the known tert-
butylsalicylaldimines having CH2Ph (1) or C6F5 (3) imino
groups and analogous new 3,5-dicumylphenoxyimines (2, 4)
In the solid-state structure of the phenoxyimino phenoxyami-
no complex a, the Ti atom has a distorted tetragonal pyramidal
configuration (Figure 1, Tables 1 and 6). As a result of the
benzyl group migration, one of the phenoxyimino ligands is
transformed into a phenoxyamido moiety. The difference
between these two ligands is seen in the relatively short
Ti-N5(amido) bond compared with the Ti-N4(imino) distance
(1.923(3) vs 2.231(3) Å). The former value is typical for
Ti-N(amido) bond lengths in a variety of Ti(IV) amido
complexes,18 while the latter value corresponds to typical
Ti-N(imino) bond lengths in Ti bis(phenoxyimino) com-
plexes.19 The C11-N5 distance (1.499(4) Å) can be assigned
as a single bond,20 and it is longer than the C10-N4 double
bond in the phenoxyimino ligand (1.302(5) Å). Also, the
nonplanar geometry of the C11 atom suggests its sp3 hybridiza-
tion (Table 1). The Ti-C9 distance (2.161(4) Å) is in the normal
(17) TiMe4 is highly thermally sensitive and decomposes at temperatures
above -40 °C. The reagent was prepared and used in situ. See for
example: (a) Thiele, K. H.; Mu¨ller, J. J. Prakt. Chem. 1968, 38, 147. (b)
Kleinhenz, S.; Seppelt, K. Chem. Eur. J. 1999, 5, 3573.
(18) (a) Schrock, R. R.; Schattenmann, F.; Aizenberg, M.; Davis, W.
M. Chem. Commun. 1998, 199 (Ti-N ) 1.962(6) Å). (b) Shafir, A.; Power,
M. P.; Whitener, G. D.; Arnold, J. Organometallics 2001, 20, 1365 (Ti-N
) 1.921(2) Å).
(19) In ref 10, Ti-N ) 2.223(2) Å, and in ref 4c, Ti-N ) 2.234(2) Å.
(20) March, J.; Smith, M. B. AdVanced Organic Chemistry: Reactions,
Mechanisms, and Structure; Wiley: New York, Chichester, Weinheim,
Brisbane, Toronto, Singapore, 2001; p 20 (C(sp3)-N ) 1.47 Å).
(21) (a) Carpentier, J.-F.; Martin, A.; Swenson, D. C.; Jordan, R. F.
Organometallics 2003, 22, 4999 (Ti-C ) 2.190(7) Å). (b) Mahanthappa,
M. K.; Cole, A. P.; Waymouth, R. M. Organometallics 2004, 23, 1405
(Ti-C ) 2.145(4) Å). (c) Minhas, R. K.; Scoles, L.; Wong, S.; Gambarotta,
S. Organometallics 1996, 15, 1113 (Ti-C ) 2.109(4) Å).
(22) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M.
AdVanced Inorganic Chemistry; Wiley: New York, Chichester, Weinheim,
Brisbane, Toronto, Singapore, 1999; pp 877-895.
Figure 1. ORTEP plot of complex a with thermal ellipsoids drawn
at the 50% probability level. All hydrogen atoms were omitted for
clarity.
(23) Bei, X.; Swenson, D. C.; Jordan, R. F. Organometallics 1997, 16,
3282.

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1447
Scheme 2a
Scheme 4
a Legend: (i) BuLi or NaH in Et2O; (ii) HfCl4 in PhCH3.
Scheme 3a
The signals of the Hf-CH2Ph methylene protons in 9-12
have relatively large JHH values (around 11-12 Hz), and in
addition, the CH2 and Cipso signals in the 13C NMR had typical
shifts for η1-bound benzyl groups. Although the JCH constants
were not measured for 9-12, it was possible to conclude that
in solution the benzyl groups coordinate to Hf in a η1 fashion.
In the case of M-η2-CH2Ph coordination in group 4 benzyl
complexes, the signals for ortho Ph protons and CH2 and Cipso
carbons should move to high field.25,26 In addition, the JHH
values should be reduced (<10 Hz), and JCH constants should
be large (>125 Hz) for the methylene protons.25,26
Solid-state structures for the dibenzyl complexes 10-12 were
determined by single-crystal X-ray diffraction methods and
are illustrated in Figures 2-4, respectively. Selected bond
angles and distances are given in Table 1 and crystallographic
data in Table 6. In these structures, Hf adopts a distorted
octahedral configuration, where the apical vertices of the
coordination octahedra are occupied by oxygen atoms and
the equatorial positions are taken by the imino nitrogens and
the Hf-benzyl groups, both in the cis orientation. In fact, this
is common for all of the solid-state structures of dialkyl group
4 metal phenoxyimino derivatives reported so far,15 now
including 10-12. It can be proposed for these alkyl com-
plexes that the cis isomeric structure (A; Scheme 4) presents
a low local minimum of energy compared with the cis,cis
and trans configurations (B and C, respectively; Scheme 4) and
alkyl complexes having structures B and C might be hardly
accessible.
a Legend: (i) Hf(CH2Ph)4 in Et2O; -78 °C.
were chosen as ligand precursors (Scheme 2). The compounds
2 and 4 were prepared via the simple reaction of the corre-
sponding aldehyde and amine in the presence of an acid catalyst.
The deprotonation of 1-4 with NaH or n-BuLi in THF and the
following reaction of the Li or Na salts with HfCl4 in toluene
led to the desired Hf bis(phenoxyimine) dichloro complexes
(5-8) with good yields (Scheme 2). For the bulky substituted
aldimines 2 and 4, the deprotonation with n-BuLi is preferable
because the ligand deprotonation with NaH was not complete,
and thus further reaction with HfCl4 was not selective. Com-
plexes 5-8 were obtained as yellow solid materials, and their
1H and 13C NMR spectra showed the presence of only one
structural isomer in CD2Cl2 solution. As a curiosity, 6 and 8
having bulky cumyl substituents displayed a great affinity to
make solvates with hexane.
The corresponding Hf dibenzyl complexes 9-12 were formed
as a result of separate reactions between the ligand precursors
1-4 and Hf(CH2Ph)4 at -78 °C in Et2O (Scheme 3) and were
isolated as pure compounds with moderate yields. The dibenzyl
complexes were obtained as orange solids, and they were
thermally stable even at temperatures up to 80 °C in C6D5Br
solution. Despite their increased resistance to elevated temper-
atures, the Hf bis(phenoxyimino) dibenzyl complexes were
highly air- and moisture-sensitive; therefore, their isolation and
further reactions were carried out in a glovebox.
Despite their different imino substituents, complexes 10-12
have similar metal-ligand distances between the central atom
and the ligands: Hf-O bonds are around 2.0 Å, Hf-N(imino)
distances are ca. 2.4 Å, and Hf-C bonds are between 2.23 and
2.26 Å (Table 1).27 In the solid state (Figures 2-4), the benzyl
groups in 10-12 coordinate to Hf in an η1 fashion (Hf-Cipso
distances are in the range 3.16-3.25 Å; Cipso-C-Hf angles
1
The dynamic-temperature H NMR analysis revealed that
9-12 were rigid in solution, as no isomerization of the
coordination sphere in the complexes was observed, even at 80
1
°C. In general, the H NMR spectra of 9-12 consist of peaks
(24) Cuomo, C.; Strianese, M.; Cuenca, T.; Sanz, M.; Grassi, A.
Macromolecules 2004, 37, 7469.
(25) Jordan, R. F.; LaPointe, R. E.; Bajgur, C. S.; Echols, S. F.; Willett,
R. J. Am. Chem. Soc. 1987, 109, 4111.
(26) (a) Pelleccia, C.; Immirzi, A.; Grassi, A.; Zambelli, A. Organome-
tallics 1993, 12, 4473. (b) Jordan, R. F.; LaPointe, R. E.; Baenziger, N.;
Hinch, G. D. Organometallics 1990, 9, 1539.
(27) Compare with other Hf benzyl complexes: (a) Morgan, A. R.;
Kloskowski, M.; Kalischewski, F.; Phillips, A. H.; Petersen, J. L. Orga-
nometallics 2005, 24, 5383 (Hf-C ) 2.282(3) Å). (b) Scott, M. J.; Lippard,
S. J. Inorg. Chim. Acta 1997, 263, 287.
in the strong-field region corresponding to t-Bu (in 9, 11) or
cumyl groups (in 10, 12), typical AB patterns for methylene
protons of the Hf-CH2Ph and CHdNCH2Ph substituents,
signals of aryl protons, and a single peak for the CHdN group
at low field (see the Supporting Information). The diastereotopic
behavior of Hf-CH2Ph and CHdNCH2Ph methylene protons
corresponds to the cis orientation of the Hf-benzyl groups and
the benzylimino substituents.24,25

1448 Organometallics, Vol. 26, No. 6, 2007
AxenoV et al.
Figure 4. ORTEP plot of 11 with thermal ellipsoids drawn at the
50% probability level. Solvent molecules and all hydrogen atoms
were omitted for clarity.
Figure 2. ORTEP plot of 10 with thermal ellipsoids drawn at the
50% probability level. All hydrogen atoms were omitted for clarity.
due to the absence of differently oriented cumyl substituents,
complex 11 is centrosymmetric in the solid state (Figure 4).
In order to verify the structure of the dibenzyl complexes in
solution, 2D-NOESY NMR methods were applied. As the dia-
stereotopic behavior of the Hf-CH2Ph methylene protons in
1H NMR of 9-12 indicated a cis orientation of the Hf-benzyl
groups (see above), isomers with an axial orientation of the
Hf-CH2Ph substituents were excluded from our considerations.
The isomeric configurations which are possible for Hf bis-
(phenoxyimino) complexes having benzyl groups in cis positions
are shown in Scheme 4. In general, the NOESY spectra of
complexes 9-12 were similar (see the Supporting Information),
showing chemical equivalence of both of the salicylaldiminato
ligands in each structure. The cis,cis configuration (Scheme 4;
B) has two chemically nonequivalent phenoxyimino ligands
1
and can thus be excluded. In the H NMR of 9 and 10 it can
be seen that methylene protons in N-CH2Ph groups are
diastereotopic (analogous to the Hf-CH2 substituents), which
allows us to propose the cis-N,N configuration (Scheme 4; A)
for these complexes. Due to the number of interactions of
neighboring protons observed in the 2D-NOESY spectra of 9
and 11, the presence of relatively close contacts between t-Bu
groups and methylene (from Hf-CH2Ph) protons was recog-
nized. In the solid-state structure of cis-11, the shortest distance
between calculated positions of t-Bu and methylene hydrogens
was found to be ca. 2.4 Å, which corresponds to the 2D-NOESY
data. In addition, the close proximity of Hf-CH2 protons to
protons of the t-Bu groups was observed for calculated Turbo-
mole 5.8 structures of cis-11 and cis-9, while in the calculated
trans isomers of 9 and 11 such groups are placed far from each
other (see the Supporting Information). On the basis of these
observations, it can be proposed that the cis configuration of 9
and 11 is maintained in solution. A comparison of data obtained
from 2D-NOESY, solid-state structural studies and the results
of Turbomole- and ADF-based calculations led to similar
conclusions for complexes 10 and 12 (see the Supporting
information).
Figure 3. ORTEP plot of 12 with thermal ellipsoids drawn at the
50% probability level. All hydrogen atoms were omitted for clarity.
are between 110 and 117°), which is in good agreement with
1
the observed H and 13C NMR spectra.
The coordination octahedron of 10 is distorted. The angle
between trans oxygens (O1-Hf-O3) is reduced to 159.21(12)°,
and angles for the cis-oriented imino nitrogens and the benzyl
groups are 86.58(13) and 97.0(2)°, respectively. Further on, the
possible molecular symmetry of the complex in the solid state
is rather distorted, due to differently oriented cumyl groups.
As a result, the structure of 10 is unsymmetric (Figure 2).
In complexes 11 and 12, the Hf-benzyl groups are orientated
in apical directions (parallel to Hf-O bonds in Figures 3 and
4), whereas the Hf-benzyl groups in the structure of 10 are
placed so that bonds between Cipso and methylene carbons (e.g.,
C80-C81, Figure 2) lie in the equatorial plane (defined by imino
N atoms and C80 and C90 carbons) of the coordination octa-
hedron. The reason for the apical orientation of the Hf-CH2Ph
groups in 11 and 12 can be the repulsion between the electron-
rich phenyl rings of the benzyl substituents and fluorine atoms
in C6F5 acquiring partial negative charges, as a result of strong
C-F bond polarization. The angle between the Hf-CH2Ph
groups in 10 is wider than in 11 and 12 (ca. 94° in 11 and 12
vs 97° in 10, respectively). Unlike the structures of 10 and 12,
Ethylene Polymerization. Although Ti and Zr bis(phenoxy-
imino) complexes have been extensively studied as catalyst
precursors for olefin polymerization over the past few years,
only a few examples of the catalytic behavior of analogous Hf
derivatives have been reported.8 In addition, the published results
were based on ethylene polymerization experiments with short
reaction times, in the range of 5 min. In the present work, the
long-run olefin polymerizations (up to 4 h of polymerization

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1449
Table 2. Ethylene Polymerization Data for Complexes 5-12a
entry
cat.
cat. concn (µmol)
reacn temp (˚C)
MAO concn (M)
yield (g)
activityb
Mn (g/mol)
Mw (g/mol)
PDI
mp (˚C)
1
2
3
4
5
6
7
8
5
5
5
6
6
7
7
8
8
9
10
11
12
2
1
80
30
30
80
30
80
40
80
30
30
30
30
30
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
0.81
12.9
11.1
1.71
0.5
0.54
6.0
1.5
810
7760c
6000d
34000
10000
540
24000
12000
36000
∼100
∼100
56000
24000
1.03 × 104
6.8 × 104
7.4 × 104
3.1 × 104
4.0 × 104
2.1 × 104
8.0 × 104
3.9 × 105
7.1 × 105
2.3 × 105
4.2 × 105
6.6 × 105
8.1 × 104
3.0 × 105
9.5 × 104
2.8 × 105
1.6 × 106
1.9 × 106
22
129
138
137
133
6.2
8.9
2.6
7.5
4.5
3.5
4.0
2.6
0.5
0.1
0.1
2
0.5
0.25
0.25
1
133
135
137
136
9
4.5
10
11
12
13
0.05
∼0.03
14
0.25
0.5
0.25
6.2 × 104
7.2 × 104
4.1 × 105
1.1 × 106
2.1 × 105
2.2 × 106
18
2.9
5.5
3
a Conditions: 200 mL of toluene, pressure of ethylene 4 bar, polymerization time 30 min. b In units of kg of PE/((mol of cat.) h). c Polymerization time
100 min. d Polymerization time 223 min.
Figure 5. Catalytic activity as a function of polymerization
temperature for MAO-activated complexes 5-8 in ethylene po-
lymerization. The numeric values of the observed activities (in kg
of PE/(mmol h)) are given for the corresponding graph points.
time) with activated Hf bis(phenoxyimino) dichloro complexes
Figure 6. GPC curves of polyethylenes obtained with the catalyst
5-8 or their dibenzyl analogues 9-12 were investigated in
7/MAO at different polymerization temperatures: 30, 40, and 80
°C. PDI: molar mass distribution (Mw/Mn).
detail.28
The MAO (methylaluminoxane)-activated hafnium dichloro
salicylaldiminates showed very high activity in ethylene po-
tuted Hf catalysts had high activity, which slightly decreased
lymerization (Table 2), comparable to that of analogous Ti and
during polymerization. The catalysts 5/MAO and 6/MAO
Zr derivatives (FI catalysts)4-8 and well-known metallocene-
showed increased activity when heated from 30 °C up to 60
based catalysts.1 The activation of the perfluorophenyl-
°C, but at higher temperatures the polymerization activity rapidly
substituted complexes 7 and 8 with MAO occurred very quickly,
declined (Figure 5).
and initial polymerization activities with these catalysts were
The properties of the polyethylene produced were investigated
by GPC and DSC methods (Figure 6, Table 2, and the
exceedingly high. After 5-10 min of ethylene polymerization
the activity of 7/MAO and 8/MAO significantly decreased but
Supporting Information). In general, the Hf catalysts appeared
then remained constant at quite a high level until the end of the
to produce monomodal polyethylene with slightly broadened
polymerization run. In addition, these catalysts showed high
molar mass distribution. However, polyethylene with bimodal
sensitivity to increased polymerization temperature, and the
molar mass distribution (run 1, Table 2) was obtained at 80 °C
with 5/MAO. This is connected with the fast decline in catalytic
activity during the polymerization run at 80 °C (see above),
and one possible explanation is a partial decomposition of
maximum ethylene polymerization activity was achieved at quite
low temperatures (Figure 5). In contrast, although ethylene
polymerization with the benzylimino-substituted Hf catalysts
5/MAO and 6/MAO started immediately after addition of the
5/MAO in the course of polymerization. In ethylene polymer-
complex into the reaction mixture, the complete activation of
izations carried out with MAO-activated complexes 5-8 at
the catalyst precursors required a longer time. With 6/MAO
different temperatures, an increase of Mw and visible shouldering
of molar mass distribution curves were recognized when the
polymerization temperature was decreased (Figure 6 and the
Supporting Information). On the basis of these observations, it
5-7 min was needed to achieve the maximum ethylene
consumption, while with 5/MAO at least a few hours was
required. For example, the maximum ethylene consumption with
5/MAO at 30 °C was recorded 4 h after the initiation of
can be concluded for the investigated Hf complexes that the
polymerization. After sufficient time, the benzylimino-substi-
rate of chain termination decreases more slowly than the speed
of chain propagation when the polymerization temperature is
lowered. In addition, unlike the Zr and Ti bis(phenoxyimino)
complexes described earlier,9,11 these catalytic systems did not
show clear dynamic behavior (changes in modality of polymer),
regardless of the wide range of polymerization temperatures
applied (Figure 6).
(28) TIBA/[(PhNHMe2)+B(C6F5)4-] and TIBA/B(C6F5)3 were used as
activators, but the obtained Hf phenoxyimino catalytic systems appeared
to be very sensitive to traces of air and moisture and most probably were
hydrolyzed during the loading of the catalyst solution into the polymerization
autoclave. In contrast, olefin polymerizations carried out in NMR tubes
with Hf bis(phenoxyimino) dibenzyl complexes and B(C6F5)3 (see text)
revealed high polymerization activity.

1450 Organometallics, Vol. 26, No. 6, 2007
Table 3. Propylene Polymerization Data for Complexes 5-12a
AxenoV et al.
entry
cat.
cat. concn (µmol)
reacn temp (°C)
MAO concn (M)
yield (g)
activityb
Mn (g/mol)
Mw (g/mol)
PDI
1
2
3
4
5
6
7
8
5
5
6
6
7
8
8
9
20
20
20
20
20
20
20
20
20
20
20
30
20
20
10
10
20
10
30
30
30
30
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
2000
∼0.1 + dimers
∼0.1 + dimers
0.24 + dimers
0.22 + dimers
4.11
1.02
1.87
inactive
inactive
50c
40c
120c
300c
410
102
190
1584
1278
1272
4459
3415
2418
2.8
2.7
1.9
9
10
11
10
11
12
14.0
0.75
1400
75
1713
1287
4987
2813
2.9
2.2
a Conditions: 200 mL of toluene, pressure of propylene 6 bar, polymerization time 30 min. b In units of kg of PE/((mol of cat.) h). c Activity calculated
on the basis of propylene consumption data.
ization. On the other hand, catalysts having perfluorophen-
ylimino substituents (11/MAO and 12/MAO) showed polym-
erization activities comparable to or even higher than and
polymer properties similar to those recorded for their dichloro
analogues 7/MAO and 8/MAO (compare runs 5 and 10 and
runs 11 and 6, 7 in Table 3).
On the basis of 13C NMR data recorded for the obtained
polymers, the MAO-activated complexes 5-8, 11, and 12
produced different kinds of polypropylene, depending on the
ligand substitution pattern. According to the 13C NMR spectra
of polypropylene obtained with 5/MAO and 6/MAO bearing
Figure 7. Catalytic activity as a function of polymerization
temperature for MAO-activated complexes 5-8 in propylene
polymerization. The numeric values of the observed activities (in
kg of PE/(mol h)) are given for the corresponding graph points.
benzylimino groups, the polymers are atactic, enriched with
syndiotactic stereoregularity (Figure 8a).30 Only traces of
unsaturated end groups were detected, but relatively intense
signals at 22.6-23.7, 25.8, and 48.4 ppm corresponding to
isobutyl end groups were present (Figure 8a). On the basis of
these findings, it can be concluded that the main chain
termination process in propylene polymerization with 5 and 6
is the chain transfer to aluminum (Scheme 5), while the presence
of a few unsaturated end groups indicates occasional â-H
elimination during the polymer chain growth. Similar catalytic
behavior was reported earlier for MAO-activated, perfluoro-
phenyl-substituted Zr bis(phenoxyimino) complexes in propy-
lene polymerization.30 Assuming that each polypropylene
macromolecule has two isobutyl end groups (resulting from a
1,2-1,2 unit sequence), the calculated average length of the
polymer chain was around 50-100 monomer units, depending
on the applied polymerization temperature (Table 4).
The MAO-activated dichloro and dibenzyl complexes 7, 8,
11, and 12 bearing the perfluorophenylimino groups produced
a similar type of polypropylene, which differs from that obtained
with the benzylimino-substituted 5/MAO and 6/MAO (Figure
8b,c). The polymer is poorly stereoregular but has a distinct
syndiotactic type structure (Table 4). The main difference
between polymers produced by the benzylimino- and perfluo-
rophenylimino-substituted catalysts is that the latter give
polypropylene with a large amount of regioerrors, appearing as
2,1-threo and 2,1-erythro microstructures (Table 4, Figure 8b,c,
and Scheme 6).29c Due to the available resolution of the 13C
NMR spectra the precise integration of the peaks is difficult,
but the approximate calculations are presented in Table 4. For
polymers produced with the catalysts 7/MAO and 11/MAO
The MAO-activated dibenzyl complexes 9-12 were also
active in ethylene polymerization. However, the catalytic activity
was strongly dependent on the substitution pattern on the imino
nitrogens. In the case of benzylimino-substituted catalysts
9/MAO and 10/MAO, the polymerization of ethylene started
immediately, but ethylene consumption stayed at a very low
level during polymerization, regardless of the applied polym-
erization time. As a result, only very small amounts of
polyethylene were isolated in polymerization runs. In contrast,
complexes 11/MAO and 12/MAO bearing perfluorophenylimino
groups revealed high polymerization activities and produced
polymers similar to those obtained by their MAO-activated
dichloro analogues 7/MAO and 8/MAO (compare runs 7 and
12 and runs 8 and 13 in Table 2). On the basis of the obtained
polymerization results, it can be proposed that MAO treatment
of the benzylimino-substituted dibenzyl complexes 9 and 10
leads to species which are different from those produced in
MAO activation of analogous dichloro complexes 5 and 6 (see
below).
Propylene Polymerization. The MAO-activated Hf bis-
(phenoxyimino) dichloro complexes 5-8 were also applied to
propylene polymerization with moderate activities (Table 3).
The maximum polymerization activity was observed at low
temperatures (Figure 7). The produced polypropylene had a low
molar mass and relatively narrow molar mass distribution.
Obviously, despite the presence of Hf, the rate of chain
termination is high. The catalysts 5/MAO and 6/MAO, bearing
benzylimino substituents, gave mainly mixtures of propylene
dimers and trimers, and only small amounts of low-molar-mass
polypropylene was obtained (Table 3 and the Supporting
Information).
(29) The analysis of 13C NMR spectra of produced polypropylenes was
performed on the basis of: (a) Zhongde, X.; Mays, J.; Xuexin, C.;
Hadjchristidis, N.; Schilling, F. C.; Bair, H. E.; Pearson, D. S.; Fetters, L.
J. Macromolecules 1985, 18, 2560 (identification of pentads). (b) Resconi,
L.; Cavallo, L.; Fait, A.; Piemontezi, F. Chem. ReV. 2000, 100, 1253. (c)
Busico, V.; Cipullo, R. Prog. Polym. Sci. 2001, 26, 443 (identification of
end groups and regioerrors).
Similarly as in ethylene polymerization, the MAO-activated
dibenzyl complexes 9 and 10, bearing benzylimino groups, had
a significantly lower polymerization activity than their dichloro
analogues and were practically inactive in propylene polymer-
(30) Lamberti, M.; Gliubizzi, R.; Mazzeo, M.; Tedesco, C.; Pellecchia,
C. Macromolecules 2004, 37, 276.

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1451
Figure 8. 13C NMR spectra of polypropylenes produced by (a) 6/MAO, (b) 7/MAO, and c) 8/MAO. Conditions: polymerization temperature
10 °C, propylene pressure 6 bar, MAO:Hf ratio 2000:1, 200 mL of toluene.
Scheme 5
sterically bulky cumyl groups in the ligand frameworks prevents
close coordination between the MAO- counteranion and the
catalytically active metal center, which is a prerequisite for the
chain transfer to Al. The dominating chain ends in the obtained
polypropylenes were allyl, 1-butenyl, and cis- and trans-2-bute-
nyl (Figure 8c). The allyl groups result from â-H transfer in a
2,1-2,1-... sequence, while 1-butenyl and cis- and trans-2-
butenyl are products of â-H eliminations in a 2,1-1,2-1,2-...
polymer chain.8a Consequently, the chain termination with
catalysts 8/MAO and 12/MAO takes place selectively after 2,1-
insertion of the last monomer, not after 1,2-insertion, which is
in agreement with previously observed results.8a
Generation of Cationic Species. The activation of Hf
dibenzyl complexes 9-12 with B(C6F5)3 was investigated by
NMR methods. The activation experiments were carried out
in NMR tubes in a glovebox at ambient temperature, and dry
C6D5Br was used as a solvent. When the perfluorophenylimino-
substituted Hf dibenzyl complexes 11 and 12 were mixed with
bearing o-tert-butyl groups at the salicylaldiminato rings, the
content of 2,1-threo and 2,1-erythro methyl groups (PR,â) was
around 6-12%. The amount of 2,1-inserted units was signifi-
cantly higher in the polypropylene chains obtained by 8 and
12/MAO having large cumyl substituents at the phenoxy ring
(up to 40%).
The dominating end groups in polymers obtained with
7/MAO and 11/MAO are isobutyl groups, and on the basis of
the ratio of integral intensities, the calculated average polymer
chain length is about 50 monomer units. The obtained average
molar masses, ∼2000 g/mol, are in accordance with the molar
mass values obtained with GPC measurements (compare Tables
3 and 4).
Assuming that 1,2-insertion of propylene is followed by 2,1-
insertion and the chain then transfers to aluminum, the n-butyl
end group should appear (Scheme 6). Although the peaks corre-
sponding to the n-butyl end groups are difficult to assign due
to the increased amount of regioerrors, presumably minor
amounts of n-butyl groups can be present. This means that, after
2,1-insertion of propylene, the polymer chain grows further
(main route), and with 7/MAO and 11/MAO the chain termina-
tion occurs regioselectively, mainly after 1,2-insertion of the
monomer.
However, polymers produced with catalysts 8/MAO and
12/MAO are different, as only traces of isobutyl end groups
were detected. The growing polymer chain is predominantly
terminated by â-H elimination. Probably, the presence of the
1
B(C6F5)3, a reaction occurred immediately. According to H
NMR and 1H-13C heteronuclear correlation measurements (see
the Supporting Information), the abstraction of one of the benzyl
groups from the Hf atom by the boron activator occurred
selectively and, as a result, the “classical” cationic species 14
and 15 were formed (Scheme 7b).
1
In the H NMR spectra of 14, the signal for the methylene
protons belonging to the PhCH2B(C6F5)3- anion was observed
at 3.01 ppm, indicating that one of the benzyl-Hf groups was
abstracted from the metal. The other Hf-CH2Ph group remained
unchanged and gave a signal at 2.84 ppm (see the Supporting
Information). Unlike the spectra of the parent complexes 11
and 12, the peaks corresponding to the methylene protons of
the Hf-benzyl groups in 14 and 15 appeared as simple singlets,
showing that some dynamic processes are present in solution.
The resulting cationic complexes 14 and 15 were rather stable
but were thermally sensitive. The visible decomposition of 14
started at 50 °C and led to another cationic Hf complex having
-
a close interaction with the PhCH2B(C6F5)3 counteranion
(∆δ(F) ) 3.9 ppm). Until the decomposition point no structural
isomerization of 14 was detected. Complex 15 was even less
thermally stable than 14 and decomposed readily at room

1452 Organometallics, Vol. 26, No. 6, 2007
Table 4. 13C NMR Analysis of Polypropylene Produced with 5-8, 11, and 12
AxenoV et al.
misinsertions (%)
reacn
[mm] (%)
[rm] (%)
[rr] (%)
Ma
cat.
temp (°C)
([rmmr]:[mmmr]:[mmmm])
([rmrm]:[mmrm]:[mmrr])
([mrrm]:[rrrm]:[rrrr])
(kg/mol)
PR,â(erythro)
PR,â(threo)
6
6
7
8
8
11
12
30
10
10
20
10
30
30
23 (1:2:1)
25 (1.2:1.8:1)
11 (3.4:3.1:1)
6
3
54 (2:3:1)
54 (2:3:1)
23 (1.7:2:1)
21 (2:2:1)
2
traces
1.8
12
19
18
traces
1.6
9
17
16
6
4.2
2.1
1.3
2.1
2.8
1.5
47
37
38
48
39
42
57
59
42
54
12
7
9
19
17
a Calculated average molar mass based on the ratio between intensities of signals for the chain ends and the methyl groups of the main sequence.
1
diminished and almost disappeared. In H-13C heteronuclear
Table 5. Relative Energies (kJ/mol) of Isomeric Structures
for Hf Bis(phenoxyimino) Dibenzyl Complexes and for the
correlation spectra, the peaks of the methyl group of toluene,
Hf-CH2Ph, the benzylimino substituents, and the BCH2Ph
Corresponding Monobenzyl Cationic Species
complex
Er(cis)
Er(cis,cis)
Er(trans)
moiety can be distinguished (Figure 9). These observations
indicate that the formed cationic species derived from 9 are
unstable toward CH activation processes, which can proceed
by an intramolecular pathway (Scheme 7a).33 Similarly to 14
and 15, the peaks corresponding to methylene protons of the
Hf-benzyl and benzylimino groups in 9/B(C6F5)3 appeared as
simple singlets, showing that some dynamic processes are
present in solution.
In the 1H-13C heteronuclear correlation spectrum the peaks
corresponding to the methylene carbon (73.5 ppm for 9 vs 66.6
ppm in 9/B(C6F5)3) and ortho protons of the Hf-CH2Ph group
(6.9 ppm for 9 vs 6.60 ppm in 9/B(C6F5)3) are noticeably shifted
to high field. This indicates the η2 coordination of the remaining
benzyl group to the Hf atom.31 ESI-MS investigations of the
reaction in THF confirmed the presence of CH activation
processes. The main species in the solution had a molar mass
of 713 g/mol, corresponding to the CH activation product from
the original Hf cation (802 g/mol) (Scheme 7 and the Supporting
Information).
9
-35.1
-35.0a
-8.1
-14.0
-8.7a
-7.7
-17.2
-3
0
0a
0
0
0
0
0
0
0
9/B(C6F5)3
10
10/B(C6F5)3
11
14
12
15
-21.6
-8.3
-32.3
-34.5
-50.9
-19.6
0
-36.0
-26.5
0
a Calculated with the ADF2005.01 program.
Scheme 6
Similar CH activations were observed for 10, bearing the
bulky cumyl groups, when treated with B(C6F5)3. The resulting
cationic complex tended to be even more unstable than
9/B(C6F5)3 species. Only a small amount of the Hf-CH2Ph
protons corresponding to unchanged 10/B(C6F5)3 was found in
1
1
1
temperature. H NMR and H-13C heteronuclear correlation
experiments showed that the signals of the o-phenyl protons
(6.8 ppm in 11 vs 6.5 ppm in 14; 6.9 ppm in 12 vs 5.6 ppm in
15) and the methylene carbon of the Hf-CH2Ph groups in 14
and 15 (81 ppm in 11 vs 76 ppm in 14; 80 ppm in 12 vs 74
ppm in 15) are moved to high field, indicating the η2 coor-
dination between Hf and the benzyl group in 14 and 15.31 The
ESI-MS studies support the efficient formation of the monoben-
zyl Hf cationic species 14 (M ) 953.1 g/mol) and 15 (M )
1314 g/mol), as they were the main components in the solution
(see the Supporting Information).
the H NMR spectrum. The ESI-MS spectrum of 10/B(C6F5)3
showed the CH activation product (M ) 1073 g/mol) as the
main compound in solution (Scheme 7). The observed tendency
of the cationic benzylimino-substituted bis(phenoxyimino) Hf
monobenzyl species to undergo CH activation could be the
reason for the low activity of 9/MAO and 10/MAO in ethylene
and propylene polymerization. After MAO activation of 9 or
10, the formed catalytic species can be instantly deactivated
via the CH activation.
The activation process of complexes 9-12 was also inves-
tigated by 19F NMR. In all cases, at room temperature the
-
formed PhCH2B(C6F5)3 anions stay in the outer coordination
The benzylimino-substituted Hf dibenzyl complex 9 reacted
rapidly with B(C6F5)3. The reaction mixture changed from light
orange to orange and then to yellow, indicating that simulta-
neously with the complex activation some further transforma-
tions took place. In H NMR spectra, the signals of protons
belonging to the PhCH2B(C6F5)3 anion, the remaining
sphere (∆δ(F) ) 2.7 ppm) and, thus, there are no direct contacts
between the cationic Hf centers and the borate anions (Sup-
porting Information). On the other hand, at low temperature
(-80 °C), a weak coordination between Hf cationic species and
1
-
(32) The preparation of samples in a glovebox and use of dry C6D5Br
exclude the possibility of hydrolysis of the formed cationic Hf monobenzyl
species. This is supported by the fact that the similar, extremely highly
sensitive to moisture and air, perfluorophenyl-substituted, cationic Hf
monobenzyl complexes 14 and 15 did not show any sign of hydrolysis in
NMR tubes.
(33) For the intramolecular activation of monobenzyl group 4 metal
cationic species see: (a) Chen, E. Y.-X.; Marks, T. J. Organometallics 1997,
16, 3649. (b) Horton, A. D.; de With, J. Chem. Commun. 1996, 1375. (c)
Wright, J. M.; Landis, C. R.; Ros, M. A. M. P.; Horton, A. D.
Organometallics 1998, 17, 5031. (d) Thorn, M. G.; Etheridge, Z. C.;
Fanwick, P. E.; Rothwell, I. P. J. Organomet. Chem. 1999, 591, 148.
Hf-CH2Ph group, and a peak at 2.44 ppm were found (see the
Supporting Information). The signal at 2.44 ppm can be
attributed to a toluene methyl group, which can appear as a
result of CH activation in “classical” cationic species.32 After
2 h, the intensity of toluene protons increased significantly, while
at the same time the signal of the Hf-CH2Ph group drastically
(31) In addition, JHH values for the Hf-CH2Ph AB pattern (measured
at -80 °C in CD2Cl2) were 8.3 Hz for 9/B(C6F5)3 and 8.7 Hz for 14, which
indicates η2 coordination of the benzyl group to the central atom.23

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1453
Scheme 7
borate counteranions was recognized (∆δ(F) ) 3.1 ppm). It
seems that, as a consequence of the η2 coordination of the
CH2Ph group to Hf, the positively charged metal center becomes
in some extent saturated, and tight contacts with PhCH2B(C6F5)3-
anion are thus prevented.
heteronuclear correlation, and 2D-NOESY spectra of 14 and
9/B(C6F5)3 showed chemical equivalence of the phenoxyimino
ligands and, thus, the cis,cis isomeric structure (Scheme 4, B)
can also be excluded from consideration. As a conclusion, the
cis configuration (Scheme 4, A) can be proposed for cationic
complex 14.
2D-NOESY methods were used to identify solution structures
of the cationic Hf bis(phenoxyimino) benzyl complexes, and
structural identifications were based on calculated structures.
In the NOESY spectrum of 14, it was found that protons from
the tert-butyl substituents interact with methylene and ortho Ph
protons of the Hf-CH2Ph group (see the Supporting Informa-
tion). Whereas the geometry of the calculated cis-14 isomer
corresponds to these observations, Hf-CH2Ph and t-Bu groups
in the calculated trans isomer appeared to be too far from each
other (Figure 10). This excludes the possibility for the trans-
In the 2D-NOESY spectrum of 9/B(C6F5)3, a partial CH
activation of the cationic Hf complex was observed, and as a
result of this, the intensities of the desired signals and, con-
sequently, the interaction reflections for the methylene protons
of the Hf-CH2Ph groups were quite low. In any event, it was
possible to distinguish the interactions between protons of the
t-Bu substituents and the ortho Ph protons of the Hf-CH2Ph
group. On the basis of a comparison of calculated structures of
cis and trans isomers these findings correspond to a cis con-
figuration for 9/B(C6F5)3 in solution (see the Supporting Infor-
mation). Unfortunately, 2D-NOESY spectra of 10/B(C6F5)3 and
15 became too complicated for interpretation due to extensive
CH activation of 10/B(C6F5)3 or thermal decomposition of the
initially formed “classical” cationic species 15. Nevertheless,
the cis-configuration can be expected for all 9-12/B(C6F5)3
species in solution. The DFT calculations, performed with
Turbomole 5.834 and ADF 2005.01b,35 also showed that the cis
configuration is energetically favored for Hf dibenzyl phenoxy-
imino complexes 9-12, as well as for the corresponding cationic
species (see Table 5 and the Supporting Information).
1
1
configuration (Scheme 4, C). In addition, H NMR, H-13C
(34) Ahlrichs, R.; Ba¨r, M.; Ha¨ser, M.; Horn, H.; Ko¨lmel, C. Chem. Phys.
Lett. 1989, 162, 165. See: http://www.cosmologic.de/QuantumChemistry/
main_qChemistry.html.
(35) (a) ADF2005.01b; SCM, Theoretical Chemistry, Vrije Universiteit,
Amsterdam, The Netherlands. See: http://www.scm.com. (b) te Velde, G.;
Bickelhaupt, F. M.; van Gisbergen, S. J. A.; Fonseca Guerra, C.; Baerends,
E. J.; Snijders, J. G.; Ziegler, T. J. Comput. Chem. 2001, 22, 931. (c) Fonseca
Guerra, C.; Snijders, J. G.; te Velde, G.; Baerends, E. J. Theor. Chem. Acc.
1998, 99, 391.
Figure 9. 1H-13C correlation spectrum of 9/B(C6F5)3 in C6D5Br.

1454 Organometallics, Vol. 26, No. 6, 2007
AxenoV et al.
Figure 10. Calculated structures of cis and trans isomers of 14 together with a part of the measured 2D NOESY spectrum. For clarity, one
of the phenoxyimino ligands is omitted from the drawn structures. For both isomers the shortest distances (in Å) between the protons of
Hf-CH2 and the t-Bu groups are shown.
The dynamic behavior of complexes 9/B(C6F5)3 and 14 was
studied by low-temperature 1H NMR. CD2Cl2 was chosen as a
solvent, because the melting point of C6D5Br is too high (-31
°C). The cationic species for these measurements were generated
at -78 °C by the addition of CD2Cl2 to a precooled mixture of
reagents. The cationic species generated from 9 appeared to be
very unstable in CD2Cl2, even at low temperature (-80 °C).
The CH activation in 9/B(C6F5)3 proceeded similarly as in
C6D5Br at room temperature. Above -10 °C, complete decom-
position of the sample in CD2Cl2 was detected. For this reason,
it was difficult to recognize the main dynamic processes within
9/B(C6F5)3, and the thermodynamic characteristics of these
processes were calculated at an approximate level. At 27 °C
and in C6D5Br, methylene protons of the benzylimino and the
Hf-CH2Ph substituents of 9/B(C6F5)3 and the Hf-CH2Ph group
of 14 appear in 1H NMR spectrum as singlets, while at -80 °C
the corresponding signals are seen as AB patterns (Figure 11
and the Supporting Information). In the case of 9/B(C6F5)3, the
signals related to the methylene protons of the benzyl groups
broaden at -30 °C and coalesce at -10 °C. With 14 the
broadening for the AB pattern of the Hf-CH2Ph protons started
already at -70 °C and the coalescence point was recognized at
-60 °C. Above -57 °C, only a singlet for the methylene protons
of the Hf-CH2Ph group was recorded (Figure 11). The
measured JHH value for the benzyl methylene protons in
9/B(C6F5)3 was 8.3 Hz, and for 14 JHH was found to be 8.7
Hz.36 Together with the shift of peaks corresponding to the
methylene and the ortho protons and the carbons of the
Hf-CH2Ph groups in 9/B(C6F5)3 and 14 to strong field (see
above), the values of JHH indicate that Hf is bound to the
Figure 11. Dynamic behavior of the methylene protons of the
HfCH2Ph group in the cationic complex 14. The measurements were
performed in CD2Cl2 at low temperatures and in C6D5Br at 30 °C.
CH2Ph group in an η2 fashion.
For these dynamic processes, the Gibbs energies of activation
(∆Gq) were calculated on the basis of Eyring equations.37 The
∆Gq values found for 9/B(C6F5)3 was ca. 14 kcal/mol, and 10.3
kcal/mol was found for 14. There can be two explanations for
the observed fluxional behavior. The isomerization process
(Scheme 4) can be proposed as has been found for related Zr
bis(phenoxyimino) dichloro complexes. The key feature to
distinguish the structural isomerization of Zr dichloro salicy-
laldiminates is the dynamic behavior of CHdN protons in NMR
studies.9 However, as there are no changes in positions and
shapes of signals for the CHdN protons in these low-
temperature 1H NMR experiments (see the Supporting Informa-
tion), the structural isomerization of 9/B(C6F5)3 and 14 seems
not to be plausible and only the cis isomer (Scheme 4, A) is
present in solution.
It is well-known that six-coordinated, bis(chelate) complexes
can undergo inversion of the configuration at the metal center,
which leads to the interconversion between two, ∆ and Λ,
stereoisomers (Scheme 8).38 Such racemization processes have
been previously recognized for phenoxyimino related Zr and
Hf dibenzyl bis(quinolinates).23 For the cationic bis(phenoxy-
imino) Hf benzyl complexes the presence of ∆/Λ isomerization
should be clearly seen in dynamic 1H NMR spectra as a
temperature-dependent behavior of the methylene protons of
the benzyl substituents.38a In addition, temperature variations
(36) Solvent coordination to the metal center and dynamic exchange
processes between coordinated and uncoordinated solvent can be excluded
from consideration, as no changes in the shape and position of the solvent
1
peak were detected in H NMR spectra at temperatures between -80 and
30 °C.

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1455
Scheme 8
in 1H NMR experiments should not influence the proton signals
of the CHdN groups because, despite the ∆/Λ interconversion,
their surroundings and relative orientations do not change
markedly. Thus, the observed temperature-dependent behavior
of 9/B(C6F5)3 and 14 supports the presence of an ∆/Λ
interconversion process. On the basis of the topological and
mechanistic analysis of cis-(AB)2MX2 systems carried out by
Serpone and co-workers, it can be proposed that the ∆/Λ
rearrangement of 9/B(C6F5)3 and 14 occurs via a bond rupture
pathway trough square-pyramidal-axial intermediates.38g The
calculated ∆Gq values for the ∆/Λ isomerization of 9/B(C6F5)3
and 14 are lower but of same order of magnitude as ∆/Λ
racemization barriers found for other rigid six-coordinated group
4 metal complexes.23,38d
Olefin Polymerization with Cationic Hf Bis(phenoxyimino)
Species. In situ generated cationic species 9/B(C6F5)3, 10/B-
(C6F5)3, 14, and 15 were tested for ethylene and propylene
polymerization in NMR tubes using C6D5Br as a solvent.
Depending on the ligand substitution patterns, the activated
complexes behaved differently. The benzylimino-substituted
9/B(C6F5)3 and 10/B(C6F5)3 were faintly active in ethylene
polymerization, and as a result, considerable amounts (on the
NMR scale) of polyethylene were detected only after 10 min
of polymerization (see the Supporting Information). After 20
min of bubbling of ethylene through the reaction mixture, the
solutions in NMR tubes turned to viscous sticky gels due to
polymer formation.39 The benzylimino-substituted complexes
were inactive in propylene polymerization, as after 25 min of
propylene bubbling only dissolved propylene and catalysts were
found in the samples.
Figure 12. Propylene polymerization in a NMR tube using 14 as
catalyst (a) before addition of propylene and (b) after 1 min of
propylene bubbling. Conditions: C6D5Br, temperature 27 °C.
the reaction solutions solidified into polymer gel in 1-1.5 min.
1
In order to get reliable H NMR data, ethylene was bubbled
only for 30-60 s. Interestingly, 1H NMR spectra of 14/ethylene
obtained for such solutions did not show significant changes
(see the Supporting Information). It seems that during the first
30-60 s, only the activation of the catalyst and coordination
of the monomer occurs. After this period the polymerization
starts. The process is very fast, and the polymer gel forms
1
instantaneously, which prevents further H NMR analysis.
Propylene polymerization with 14 and 15 was significantly
slower than ethylene polymerization. After 1-2 min of the
initiation of propylene polymerization, the 1H NMR spectra of
14/propylene and 15/propylene were recorded (Figure 12). The
presence of polypropylene was recognized by 1H NMR. It can
be also noticed for 14 that the intensity of the signal at 2.85
ppm, which corresponds to methylene protons of Hf-CH2Ph,
decreased considerably and, in addition, new peaks appeared
in the aliphatic region at 2.2-2.5 ppm, indicating that the benzyl
group moved from Hf to the end of the formed polypropylene
chain (Figure 12).
Conclusions
Hf bis(phenoxyimino) complexes activated with MAO dis-
played very high activity in ethylene polymerization, comparable
to that of analogous Ti and Zr derivatives (FI catalysts) and
well-known metallocene-based catalysts. The Hf catalysts
bearing perfluorophenylimino groups were rapidly activated with
MAO, and a maximum in catalytic activity is achieved during
the first 5-10 min, followed by a modest decline in ethylene
consumption in longer runs. In comparison, MAO activation
of benzylimino-substituted Hf dichloro complexes required
longer induction times, after which the formed catalytically
active species were relatively stable and highly active in ethylene
polymerization. In addition, MAO-activated Hf bis(phenoxy-
imino) complexes were also capable of polymerizing propylene
with moderate activity, and atactic syndiorich polymers with
low molar mass were obtained. Particularly, perfluorophenyl-
substituted catalysts produced highly regioirregular polypropy-
lene.
Unlike the autoclave experiments performed (see above), in
NMR tubes the cationic complexes 14 and 15 bearing perfluo-
rophenyl groups were well-protected from air and moisture
traces and showed exceedingly high catalytic activity in ethylene
polymerization and were also active toward propylene polym-
erization. The ethylene polymerization occurred quickly,40 and
(37) Spectral simulations were made with the help of the WinDNMR
program. See: http://www.chem.wisc.edu/areas/reich/plt/windnmr.htm. For
calculations the equations and methods described in ref 23 and those of
Bruce et al. (Bruce, M. D.; Coates, G. W.; Hauptman, E.; Waymouth, R.
M.; Ziller, J. W. J. Am. Chem. Soc. 1997, 119, 11174) were used. For
9/B(C6F5)3: ∆νAB ) 28.1 Hz, JAB ) 8.3 Hz, Tc ) 283 K. For 14: ∆νAB
) 48.6 Hz, JAB ) 8.7 Hz, Tc ) 213 K.
(38) (a) Willem, R.; Gielen, M.; Pepermans, H.; Brocas, J.; Fastenakel,
D.; Finocchiaro, P. J. Am. Chem. Soc. 1985, 107, 1146. (b) Willem, R.;
Gielen, M.; Pepermans, H.; Hallenga, K.; Recca, A.; Finocchiaro, P. J. Am.
Chem. Soc. 1985, 107, 1153. (c) Harrod, J. F.; Taylor, K. J. Chem. Commun.
1971, 696. (d) Bickley, D. G.; Serpone, N. Inorg. Chem. 1979, 18, 2200.
(e) Bickley, D. G.; Serpone, N. Inorg. Chem. 1976, 15, 948. (f) Bickley,
D. G.; Serpone, N. Inorg. Chem. 1976, 15, 2577.
The synthesized Hf bis(phenoxyimino) dibenzyl complexes
were thermally rather stable but decomposed rapidly in the
presence of traces of water and air. The reaction of B(C6F5)3
with dibenzyl complexes gave corresponding cationic Hf
(39) Solutions with precipitated polymer gels gave very poor resolution
in 1H NMR measurements. Therefore, the polymerization time was adopted
so that the reaction solutions remained transparent enough to be suitable
(40) During the NMR tube polymerizations the temperatures of reaction
mixtures were noticeably and considerably raised, indicating the high activity
of generated cationic species in ethylene polymerization.
1
for H NMR experiments.

1456 Organometallics, Vol. 26, No. 6, 2007
AxenoV et al.
Organisch-Chemisches Institut, Wesfa¨lische-Wilhelms Universita¨t,
Mu¨nster, Germany (Hf bis(phenoxyimino) dibenzyl complexes).
High-temperature gel permeation chromatography (GPC) of poly-
ethylene and polypropylene samples was performed in 1,2,4-
trichlorobenzene at 160 °C using a Waters Alliance GPCV 2000
equipped with HMW7, 2*HMWGE, and HMW2 Waters Styrogel
columns. DCS of obtained polyethylenes was performed with a
Mettler Toledo Star system. Melting temperatures of PE were
measured from 30 to 230 °C using a heating rate of 10 °C/min.
The melting points were determined from the second heating curve.
The 13C NMR spectra of polypropylene samples dissolved in a
mixture of 1,2,4-trichlorobenzene (90 wt %) and C6D6 (10 wt %)
were recorded on a Varian Gemini 300 MHz at 120 °C.
2,3,4,5,6-Pentafluoroaniline, benzylamine, 2,4-bis(R,R-dimeth-
ylbenzyl)phenol, 3-tert-butylsalicylaldehyde, PhCH2MgCl (1 M
solution in Et2O), and MeMgBr (3 M solution in Et2O) were
purchased from Aldrich and used as received. Tris(perfluorophenyl)-
borane was purchased from Strem, recrystallized from pentane, and
stored in a glovebox. Methylalumoxane (MAO, 30 wt % solution
in toluene) was received from Borealis Polymers Oy. 3,5-Bis(R,R-
dimethylbenzyl)salicylaldehyde10b and Hf(CH2Ph)442 were prepared
according to literature procedures.
monobenzyl species which, depending on the imino substituents,
tended to be partially or completely unstable toward the CH
activation. In accordance with NMR and ESI-MS studies, low
activity of the MAO-activated benzylimino-substituted dibenzyl
complexes 9 and 10 in olefin polymerization reflects the
instability of the corresponding cationic Hf monobenzyl species
toward CH activation. On the other hand, the MAO activation
of Hf dichloro derivatives 5 and 6 should lead to cationic Hf
monomethyl species having structures similar to those of 14
and 15. These catalytic species, it could be suggested, are
resistant toward CH activation, and in contrast to the related
complexes 9 and 10, MAO-activated 5 and 6 displayed high
activity in ethylene polymerization and moderate activity in
propylene polymerization. The synthesized Hf dibenzyl com-
plexes and generated cationic species are rigid in solution at
elevated temperatures (no cis/cis,cis/trans isomerization occurred
under the conditions studied) and, consequently, produce
polymers with monomodal molar mass distribution.
When the olefin monomer is introduced into the catalyst
solution, intensities of signals assigned to the original metal-
1
alkyl substituents decrease in the H NMR and a new set of
peaks corresponding to formed polymer chain end groups
appear. This behavior can be clearly seen in propylene polym-
erization experiments with 14 (see above, Figure 12), proving
that 14 is responsible for the polymerization. On the basis of
the results above, it can be proposed that bis(phenoxyimino)
group 4 metal complexes act under an analogous olefin
polymerization mechanism, which is largely accepted for
metallocene types of homogeneous Ziegler-Natta catalysts.41
Activation of dialkyl bis(phenoxyimino) complexes with B(C6F5)3
or MAO generates the monoalkylated cationic species. These
complexes are responsible for olefin coordination and polymer
chain propagation. According to the accepted mechanism for
the chain propagation, the original metal alkyl substituents are
transferred to the polymer chain end in the course of consecutive
migratory monomer insertions. In fact, this was observed here.
Synthesis of Ligands. (a) N-(3-tert-Butylsalicylidene)benzyl-
amine (1).43 3-tert-Butylsalicylaldehyde (2.0 g, 11.2 mmol) and
benzylamine (1.2 g, 11.2 mmol), Na2SO4 (0.3 g) and two drops of
concentrated H2SO4 were mixed in a 100 mL round-bottom flask.
The reaction mixture was heated to 50 °C and stirred overnight.
After it was cooled, the resulting material was extracted with 70
mL of hexane. The hexane extracts were filtered, and solvent was
evaporated in vacuo to give the product as a yellow oil, which
crystallized in 1 day to give a yellow crystalline solid (2.9 g, 97%).
According to NMR analysis the crude product was pure enough
and was used without additional purification. 1H NMR (200 MHz,
CDCl3, 29 °C): δH 1.43 (s, 9H, t-Bu), 4.80 (s, 2H, CH2Ph), 6.82
(t, JHH ) 7.7 Hz, 1H, 5-H Ar), 7.14 (dd, JHH ) 7.7 Hz, 1H, 4-H
Ar), 7.30-7.42 (m, 6H, Ar H from CH2Ph and 6-H Ph), 8.45 (s,
1H, CHdN), 13.68 (s, 1H, OH). 13C{1H} NMR (50.3 MHz, CDCl3,
29 °C): δC 29.30 (s, CH3 of t-Bu), 34.82 (s, C of t-Bu), 63.18 (s,
CH2Ph), 117.81 (5-C Ar), 123.58 (C-CHdN), 127.31 (p-C from
CH2Ph), 127.88 (o-C from CH2Ph), 128.63 (m-C from CH2Ph),
129.46 (4-C Ar), 129.75 (6-C Ar), 137.41 (C-t-Bu), 138.23
(C-CH2 from CH2Ph), 160.38 (C-OH), 166.25 (CHdN).
Experimental Section
All manipulations were performed under an inert argon atmo-
sphere using standard Schlenk techniques. The hydrocarbon and
ether solvents were refluxed over sodium and benzophenone,
distilled, and stored under an inert atmosphere with pieces of
sodium. C6D6 was refluxed over sodium, and CD2Cl2 and C6D5Br
were refluxed with CaH2; these solvents were then transferred into
storage flasks by evaporation-condensation under vacuum and
stored in a glovebox. EI-mass spectra were measured on a JEOL
SX102 spectrometer. ESI-MS and ESI-HRMS spectra were per-
(b) N-[3,5-Bis(R,R-dimethylbenzyl)salicylidene]benzylamine
(2). 3,5-Bis(R,R-dimethylbenzyl)salicylaldehyde (2.0 g, 5.6 mmol)
and benzylamine (0.6 g, 5.6 mmol), Na2SO4 (0.3 g), and 2 drops
of concentrated H2SO4 were mixed in a 100 mL round-bottom flask.
A 5 mL portion of toluene was then added, and the reaction mixture
was heated to 100 °C and stirred for 2 days. After it was cooled,
the resulting material was extracted at elevated temperature with a
mixture of hexane (60 mL) and CH2Cl2 (20 mL). The extracts were
then filtered, and solvents were removed in vacuo to give the
product as a yellow crystalline solid (2.5 g, 100%). According to
NMR analysis the crude product was pure enough and was used
1
formed with a Bruker-MicroTOF spectrometer. The H, 13C, and
19F NMR spectra were recorded on Varian Gemini 200 MHz, Varian
Gemini 300 MHz, Varian INOVA 500, and Bruker AMX 400
spectrometers. The 1H and 13C NMR spectra were referenced
relative to CHDCl2 (5.28 and 53.73 ppm, respectively), C6D4HBr
(7.29 and 122.25 ppm, respectively), and C6D5H (7.24 and 128.0
ppm, respectively). Fluorine signals were referenced relative to
external B(C6F5)3 in CD2Cl2 (-127.8, -143.4, -160.6 ppm).
Elemental analyses were performed at the Laboratory of Pharma-
ceutical Chemistry, Department of Pharmacy, University of Hel-
sinki, Finland (Hf bis(phenoxyimino) dichloro complexes) and
1
without additional purification. H NMR (200 MHz, CDCl3, 29
°C): δH 1.67 (s, 6H, CH3 of 5-R,R-dimethylbenzyl), 1.71 (s, 6H,
CH3 of 3-R,R-dimethylbenzyl), 4.65 (s, 2H, CH2Ph), 7.03 (d, JHH
) 2.2 Hz, 1H, 4-H Ar), 7.10-7.38 (m, 16H, Ar H), 8.31 (t, JHH
)
1.1 Hz, 1H, CHdN), 12.13 (s, 1H, OH). 13C{1H} NMR (50.3 MHz,
CDCl3, 29 °C): δC 29.37 (s, CH3 of 5-R,R-dimethylbenzyl), 30.93
(s, CH3 of 3-R,R-dimethylbenzyl), 42,11 (s, C of 5-R,R-dimethyl-
benzyl), 42.42 (s, C of 3-R,R-dimethylbenzyl), 63.03 (s, CH2Ph),
125.02 (6-C Ar), 126.04 (Ar), 126.85 (Ar), 125.55 (p-C Ph from
(41) For the mechanism of complex activation (MAO used as activator)
see: (a) Sinn, H.; Kaminsky, W.; Vollmer, H. J.; Woldt, R. Angew. Chem.
1980, 92, 346. (b) Kaminsky, W.; Miri, M.; Sinn, H.; Woldt, R. Macromol.
Chem., Rapid Commun. 1983, 4, 417. For the mechanism of the chain
propagation step, see: (c) Cose´e, P. J. Mol. Catal. 1964, 3, 80. (d) Arlman,
E. J. J. Mol. Catal. 1964, 3, 89. (e) Cose´e, P.; Arlman, E. J. J. Mol. Catal.
1964, 3, 99.
(42) Davies, G. R.; Jarvis, J. A. J.; Kilbourn, B. T. Chem. Commun.
1971, 1511.
(43) The synthesis of ligand 1 was reported in: Matsukawa, N. Eur.
Patent EP-1013674, 2000. Ethanol was used as a solvent. The reported data
1
and our H NMR data for 1 are identical.

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1457
3- and 5-R,R-dimethylbenzyls), 125.60 (4-C Ar), 126.70 (m-C Ph
from CH2Ph), 127.22 (p-C Ph from CH2Ph), 127.75 (o-C Ph from
5-R,R-dimethylbenzyl), 127.99 (m-C Ph from 3- and 5-R,R-
dimethylbenzyls), 127.95 (C-CHdN), 128.51 (o-C Ph from 3-R,R-
dimethylbenzyl), 128.95 (3-C Ar), 136.08 (C Ph from CH2Ph),
138.03 (C Ph from 3-R,R-dimethylbenzyl), 139.08 (5-C-Ar), 150.76
(C Ph from 5-R,R-dimethylbenzyl), 157.66 (C-OH), 166.1
(CHdN).
solution of ligand 1 (1.0 g, 3.7 mmol) in 20 mL of dry THF. The
reaction mixture was stirred for 2 h at room temperature. When
deprotonation of the ligand was complete, THF was removed in
vacuo. The residue, the Na salt of ligand 1, was dissolved in 20
mL of dry toluene and HfCl4 (0.6 g, 1.9 mmol) was added to this
solution. The reaction mixture was stirred overnight at room
temperature. Toluene was evaporated in vacuo, and the residue was
extracted twice with a mixture of dry hexane (15 mL) and CH2Cl2
(10 mL). The combined extracts were then filtered under argon,
and solvents were removed in vacuo. The product was isolated as
a white-yellow crystalline solid (1.0 g, 68.5%). Anal. Calcd for
C46H44Cl2N2O2Hf: C, 55.28; H, 5.15; N, 3.58. Found: C, 55.46;
H, 5.53; N, 3.49. 1H NMR (200 MHz, CD2Cl2, 29 °C): δH 1.47 (s,
18H, t-Bu), 4.75 (AB system, JHH ) 14.9 Hz, 4H, CH2Ph), 6.76 (t,
JHH ) 7.7 Hz, 2H, 5-H Ar), 6.90 (br m, 6H, Ar H from CH2Ph and
(c) N-(3-tert-Butylsalicylidene)-2,3,4,5,6-pentafluoroaniline (3).44
3-tert-Butylsalicylaldehyde (2.0 g, 11.2 mmol), 2,3,4,5,6-pentafluo-
roaniline (2.1 g, 11.2 mmol), Na2SO4 (0.3 g), and 2 drops of
concentrated H2SO4 were mixed in a 100 mL round-bottom flask
equipped with a Dean-Stark apparatus. Toluene (50 mL) was then
added, and the reaction mixture was refluxed for 2 days. After the
mixture was cooled, toluene was removed from the resulting
material in vacuo. The yellow residue was then extracted with a
mixture of hexane (50 mL) and CD2Cl2 (20 mL). The extracts were
filtered, and solvents were evaporated in vacuo to give the product
as a yellow crystalline solid (3.2 g, 84%). According to NMR
analysis the crude product was pure enough and was used without
4-H Ph), 7.05-7.18 (m, 6H, Ar H from CH2Ph), 7.52 (d, JHH
)
7.7 Hz, 2H, 6-H Ar), 7.82 (s, 2H, CHdN). 13C{1H} NMR (50.3
MHz, C6D6, 29 °C): δC 29.87 (s, CH3 of t-Bu), 35.28 (s, C of
t-Bu), 62.17 (s, CH2Ph), 119.62 (5-C Ar), 123.78 (C-CHdN),
128.81 (o-C from CH2Ph), 128.90 (m-C from CH2Ph), 133.44 (4-C
Ar), 134.21 (6-C Ar), 135.84 (C-t-Bu), 140.84 (C-CH2 from
CH2Ph), 160.67 (C-OH), 171.32 (CHdN). MS (ESI): m/z
(intensity) 780.7 (110, M+), 744.1 (100, M+ - Cl).
1
additional purification. H NMR (200 MHz, CDCl3, 29 °C): δH
1.45 (s, 9H, t-Bu), 6.91 (t, JHH ) 7.7 Hz, 1H, 5-H Ar), 7.21-7.28
(m, 1H, 4-H Ph), 7.47 (dd, JHH ) 7.7 Hz, 1H, 6-H Ar), 8.81 (s,
1H, CHdN), 11.78 (s, 1H, OH). 13C{1H} NMR (50.3 MHz, CDCl3,
29 °C): δC 29.26 (s, CH3 of t-Bu), 34.97 (s, C of t-Bu), 118.86
(5-C Ar), 131.62 (6-C Ar), 132.22 (4-C Ar), 134.08 (C-CHdN),
135.57 (C-F), 136.30 (C-F), 138.23 (C(Ar)-t-Bu), 138.51
(C-F), 140.47 (C-F), 141.33 (C-F), 143.34 (C-F), 160.99
(C-OH), 171.29 (CHdN). 13F NMR (282.2 MHz, CDCl3, 27 °C):
δF -152.6 (dd, J ) 21.31 Hz, 2F, o-F), -159.09 (t, J ) 21.30 Hz,
1F, p-F), -162.97 (dt, J ) 21.30 Hz, 2F, m-F).
(b) Bis{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]benzyl-
aminato}hafnium Dichloride (6). BuLi (1.6 M solution in hexane,
3.5 mL, 5.6 mmol) was added at 0 °C to a stirred solution of ligand
2 (2.4 g, 5.4 mmol) in 30 mL of dry Et2O. The reaction mixture
was stirred for 2 h at room temperature. When deprotonation of
the ligand was complete, Et2O was removed in vacuo. The residue,
the Li salt of the ligand 2, was dissolved in 30 mL of dry toluene,
and HfCl4 (0.87 g, 2.72 mmol) was added to this solution. The
reaction mixture was stirred overnight at room temperature. Toluene
was evaporated in vacuo, and the residue was extracted twice with
a mixture of dry hexane (20 mL) and CH2Cl2 (10 mL). The
combined extracts were then filtered under argon, and solvents were
removed in vacuo. The product was isolated as a yellow solid (3.0
g, 93%). Anal. Calcd for C64H64Cl2N2O2Hf‚1/2C6H14: C, 67.87; H,
6.04; N, 2.36. Found: C, 67.95; H, 6.44; N, 1.96. The presence of
hexane was also detected by 1H and 13C NMR. 1H NMR (200 MHz,
CD2Cl2, 29 °C): δH 1.61 (br s, 12H, CH3 of 5-R,R-dimethylbenzyl),
1.65 (br s, 12H, CH3 of 3-R,R-dimethylbenzyl), 3.0-4.0 (br m,
4H, CH2Ph), 6.51-7.49 (br m, 34H, Ar H), 7.59 (s, 2H, CHdN).
13C{1H} NMR (50.3 MHz, CD2Cl2, 29 °C): δC 30.89 (br s, CH3
of 5-R,R-dimethylbenzyl), 32.20 (s, CH3 of 3-R,R-dimethylbenzyl),
42.21 (s, C of 5-R,R-dimethylbenzyl), 42.75 (s, C of 3-R,R-
dimethylbenzyl), 61.32 (s, CH2Ph), 125.7 (Ar), 126.04 (Ar); 126.85
(Ar), 126.97 (Ar), 128.04 (Ar), 128.20 (Ar), 128.36 (Ar), 129.27
(Ar), 130.13 (C-CHdN), 131.16 (3-C), 133.82 (C Ph from
CH2Ph), 135.61 (5-C), 139.2 (C Ph from 3-R,R-dimethylbenzyl),
141.5 (C Ph from 5-R,R-dimethylbenzyl), 149.6 (C-OH), 170.9
(CHdN). MS (ESI): m/z (intensity) 1140 (260, M+), 1128 (100,
M+ - Me), 1113 (100, M+ - 2Me), 1106 (540, M+ - Cl), 1089
(200, M+ - Cl-Me), 1069 (M+ - 2Cl).
(c) Bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanili-
nato]hafnium Dichloride (7).45 Ligand 3 (1.0 g, 2.9 mmol) in Et2O
(20 mL) was treated with BuLi in hexane (1.6 M, 1.9 mL, 3.1
mmol), as described for 6. The reaction of the resulting Li salt of
3 with HfCl4 (0.5 g; 1.6 mmol) in toluene (20 mL) and the
separation of the product was carried out as reported for complex
6. The complex 7 was isolated as a yellow solid (0.84 g; 58%). 1H
NMR (200 MHz, CD2Cl2, 29 °C): δH 1.24 (s, 18H, t-Bu), 6.95 (t,
JHH ) 7.7 Hz, 2H, 5-H Ar), 7.27 (dd, JHH ) 1.8 Hz, 2H, 4-H Ph),
7.70 (dd, JHH ) 1.8 Hz, 2H, 6-H Ar), 8.30 (s, 2H, CHdN).
13C{1H} NMR (50.3 MHz, CDCl3, 29 °C): δC 29.07 (s, CH3 of
t-Bu), 35.13 (s, C of t-Bu), 121.16 (5-C Ar), 134.99 (6-C Ar),
137.48 (4-C Ar), 138.82 (C-CHdN), 140.59 (C(Ar)-t-Bu), 161.42
(d) N-[3,5-Bis(R,R-dimethylbenzyl)salicylidene]-2,3,4,5,6-pen-
tafluoroaniline (4). 3,5-Bis(R,R-dimethylbenzyl)salicylaldehyde
(2.0 g, 5.6 mmol), 2,3,4,5,6-pentafluoroaniline (1.0 g, 5.6 mmol),
Na2SO4 (0.3 g), 2 drops of concentrated H2SO4, and toluene (50
mL) were mixed in a 100 mL round-bottom flask equipped with a
Dean-Stark apparatus as described for 3. After the mixture was
cooled, toluene was removed from the resulting material in vacuo.
The yellow residue was then extracted with a mixture of hexane
(50 mL) and CD2Cl2 (20 mL). The extracts were filtered, and
solvents were evaporated in vacuo to give the product as a yellow
crystalline solid (2.6 g, 89%). According to NMR analysis the crude
product was pure enough and was used without additional purifica-
tion. 1H NMR (200 MHz, CDCl3, 29 °C): δH 1.68 (s, 6H, CH3 of
5-R,R-dimethylbenzyl), 1.73 (s, 6H, CH3 of 3-R,R-dimethylbenzyl),
7.15 (d, JHH ) 2.5 Hz, 1H, 4-H Ar), 7.10-7.35 (m, 10H, Ar H),
7.47 (d, JHH ) 2.5 Hz, 1H, 6-H Ar), 8.66 (t, JHH ) 1.2 Hz, 1H,
CHdN), 12.28 (s, 1H, OH). 13C{1H} NMR (50.3 MHz, CDCl3, 29
°C): δC 29.30 (s, CH3 of 5-R,R-dimethylbenzyl), 30.83 (s, CH3 of
3-R,R-dimethylbenzyl), 42,19 (s, C of 5-R,R-dimethylbenzyl), 42.49
(s, C of 3-R,R-dimethylbenzyl), 125.24 (4-C Ar), 125.52 (p-C Ph
from 3-R,R-dimethylbenzyl), 125.58 (m-C Ph from 5-R,R-dimeth-
ylbenzyl), 125.83 (p-C Ph from 5-R,R-dimethylbenzyl), 126.64
(6-C-Ar), 126.67 (o-C Ph from 5-R,R-dimethylbenzyl), 127.85 (m-C
Ph from 3-R,R-dimethylbenzyl), 128.13 (o-C Ph from 3-R,R-
dimethylbenzyl), 131.95 (5-C Ar), 133.74 (C-CHdN), 137.08 (C
Ph from 3-R,R-dimethylbenzyl), 140.77 (5-C Ar), 150.02 (C Ph
from 5-R,R-dimethylbenzyl), 158.28 (C-OH), 171.4 (CHdN). 13
F
NMR (282.2 MHz, CDCl3, 27 °C): δF -152.60 (dd, J ) 21.15
Hz, 2F, o-F), -159.26 (t, J ) 21.36 Hz, 1F, p-F), -162.97 (dt, J
) 21.36 Hz, 2F, m-F).
Synthesis of Hf Bis(phenoxyimino) Dichloro Complexes. (a)
Bis[N-(3-tert-butylsalicylidene)benzylaminato]hafnium Dichlo-
ride (5). NaH (0.1 g, 4.2 mmol) was added at 0 °C to a stirred
(44) The synthesis of ligand 3 was reported in: Matsukawa, N. Patent
WO-2001055231, 2001. Toluene was used as a solvent. The reported data
and our H NMR data for 3 are identical.
1
(45) The complex 7 was first reported in ref 8.

1458 Organometallics, Vol. 26, No. 6, 2007
AxenoV et al.
(C-OH), 177.88 (CHdN). 13F NMR (282.2 MHz, C6D6, 27 °C):
δF -145.0 (dd; J ) 23.00 Hz, 2F, o-F), -146.6 (br, 2F, o-F),
-158.2 (t, J ) 21.75 Hz, 2F, p-F), -161.07 (t, J ) 22.3 Hz, 2F,
m-F), -164.14 (br, 2F, m-F). MS (ESI): m/z (intensity) 932.3
(3300, M+), 916.3 (500, M+ - F), 893.1 (7100, M+ - 2F), 862
(100, M+ - 2Cl).
12H, CH3 of 5-R,R-dimethylbenzyl), 1.53 (s, 6H, CH3 of 3-R,R-
dimethylbenzyl), 1.91 (s, 6H, CH3 of 3-R,R-dimethylbenzyl), 2.00
(AB system, JHH ) 11 Hz, 4H, Hf-CH2Ph), 3.69 (AB system, JHH
) 16 Hz, 4H, CH2Ph), 6.33 (d, JHH ) 7.15 Hz, 4H, H Ph
from cumyl), 6.51 (d, JHH ) 7.2 Hz, 4H, H Ph from cumyl), 6.56
(d, JHH ) 2.4 Hz, 2H, 4-H Ar), 6.76 (t, JHH ) 7.65 Hz, 2H, p-H Ph
from Hf-CH2Ph), 6.81 (dd, JHH ) 6.5 Hz, 4H, o-H Ph from
Hf-CH2Ph), 6.87 (dd, JHH ) 7.3 Hz, 4H, m-H Ph from
Hf-CH2Ph), 7.0 (t, JHH ) 7.6 Hz, 5H, H Ar and H Ph from cumyl),
7.13 (m, 10H, H Ph from CHdNCH2Ph), 7.25 (d, JHH ) 7.7 Hz,
4H, H Ph from cumyl), 7.42 (d, 4H, 7.42 (d, JHH ) 2.5 Hz, 2H,
CHdN). 13C{1H} NMR (50.3 MHz, C6D6, 29 °C): δC ) 30.9 (d,
CH3 of 5-R,R-dimethylbenzyl), 32.78 (br s, CH3 of 3-R,R-
dimethylbenzyl), 42,46 (s, C of 5-R,R-dimethylbenzyl), 42.74
(s, C of 3-R,R-dimethylbenzyl), 61.38 (s, CH2Ph), 74.75 (s,
Hf-CH2Ph), 124.0 (Ph from Hf-CH2Ph), 125.82 (C-CHdN),
126.08 (m-C Ph from CH2Ph), 126.57 (o-C Ph from CH2Ph), 126.60
(o-C Ph from Hf-CH2Ph), 127.03 (m-C Ph from Hf-CH2Ph),
128.27 (o-C Ph from 5-R,R-dimethylbenzyl), 128.33 (o-C Ph from
3-R,R-dimethylbenzyl), 129.83 (p-C Ph from 3- and 5-R,R-
dimethylbenzyl), 131.28 (3-C), 133.19 (C Ph from CH2Ph), 135.76
(5-C), 138.60 (C Ph from 3-R,R-dimethylbenzyl), 149.33 (ipso-C
from Hf-CH2Ph), 150.10 (C Ph from 5-R,R-dimethylbenzyl),
158.46 (C-OH), 169.0 (CHdN). MS (ESI): m/z (intensity) 1255.4
(200, M+), 1179.5 (250, M+ - Ph), 1113 (1600, L2MCH2+), 1071.5
(1800, M+ - 2CH2Ph).
(c) Bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanili-
nato]hafnium Dibenzyl (11). Ligand 3 (1.26 g, 3.68 mmol) in Et2O
(25 mL) was treated with Hf(CH2Ph)4 (1.00 g, 1.84 mmol) in Et2O
(5 mL), as described for 9. The isolation of the product was carried
out as reported for complex 9. The resulting complex is sparingly
soluble in hexane, and 20 mL portions of hexane (with 1 mL of
Et2O added) were used for complex extraction. The complex 11
was isolated as an orange-yellow solid (0.79 g; 41%). Anal. Calcd
for C48H40F10N2O2Hf: C, 55.15; H, 3.86; N, 2.68. Found: C, 55.56;
H, 3.84; N, 2.22. 1H NMR (500 MHz, C6D5Br, 25 °C): δH 1.2 (s,
18H, t-Bu), 2.39 (AB system, JHH ) 12.3 Hz, 4H, Hf-CH2Ph),
6.79 (t, JHH ) 7.0 Hz, 2H, p-H Ph from Hf-CH2Ph), 6.94 (t, JHH
) 7.7 Hz, 2H, 5-H Ar), 7.19 (m, 4H, H Ph from Hf-CH2Ph), 7.21
(d, JHH ) 7.7 Hz, 2H, 6-H Ph), 7.60 (d, JHH ) 7.7 Hz, 2H, 4-H
Ar), 8.33 (s, 2H, CHdN). 13C{1H} NMR (50.3 MHz, C6D6, 29
°C): δC 29.06 (s, CH3 of t-Bu), 34.87 (s, C of t-Bu), 80.75 (s,
Hf-CH2Ph), 119.90 (5-C Ar), 121.36 (Ph from Hf-CH2Ph), 126.68
(Ph from Hf-CH2Ph), 132.48 (C-CHdN), 134.79 (6-C Ar),
136.18 (4-C Ar), 140.55 (C(Ar)-t-Bu), 148.57 (ipso-C from
Hf-CH2Ph), 161.75 (C-OH), 177.39 (CHdN). 13F NMR (282.2
MHz, C6D6, 27 °C): δF -146.3 (br s, 2F, o-F), -148.4 (br s, 2F,
o-F), -159.2 (t, J ) 21.9 Hz, 2F, p-F), -161.7 (br s, 2F, m-F),
-164.0 (dt, J ) 21.6 Hz, 2F, m-F). MS (ESI): m/z (intensity)
1042.3 (300, M+), 1026.2 (100, M+ - F), 971.2 (240, M+ - Ph).
(d) Bis{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]-2,3,4,5,6-
pentafluoroanilinato}hafnium Dichloride (8). Ligand 4 (2.63 g,
5.02 mmol) in Et2O (30 mL) was treated with BuLi in hexane (1.6
M, 3.2 mL, 5.2 mmol), as described for 6. The reaction of the
resulting Li salt of 4 with HfCl4 (0.8 g, 2.5 mmol) in toluene (30
mL) and the separation of the product was carried out as reported
for complex 6. The complex 8 was isolated as a yellow solid (3.0
g; 81.5%). Anal. Calcd for C52H46Cl2F10N2O2Hf‚2C6H14: C, 61.06;
H, 5.53; N, 1.87. Found: C, 60.94; H, 5.31; N, 1.91. The presence
of hexane was also detected by 1H and 13C NMR. 1H NMR
(200 MHz, CD2Cl2, 29 °C): δH 1.59 (br s, 24H, CH3 of 3- and
5-R,R-dimethylbenzyl), 7.10-7.40 (m, 24H, Ar H), 8.14 (s, 2H,
CHdN). 13C{1H} NMR (50.3 MHz, CD2Cl2, 29 °C): δC 30.48 (br
s, CH3 of 5-R,R-dimethylbenzyl), 32.20 (s, CH3 of 3-R,R-dimeth-
ylbenzyl), 42,53 (s, C of 5-R,R-dimethylbenzyl), 42.70 (s, C of
3-R,R-dimethylbenzyl), 125.76 (p-C Ph from 3-R,R-dimethylben-
zyl), 125.88 (4-C Ar), 126.19 (p-C Ph from 5-R,R-dimethylbenzyl),
126.39 (m-C Ph from 5-R,R-dimethylbenzyl), 126.81 (6-C Ar),
126.89 (m-C Ph from 3-R,R-dimethylbenzyl), 128.15 (o-C Ph from
5-R,R-dimethylbenzyl), 128.45 (o-C Ph from 3-R,R-dimethylben-
zyl), 138.48 (3-C Ar), 139.86 (C Ph from 3-R,R-dimethylbenzyl),
143.12 (C-CHdN), 148.69 (5-C Ar), 149.94 (C Ph from 5-R,R-
dimethylbenzyl), 159.36 (C-OH), 177.65 (CHdN). 13F NMR
(282.2 MHz, C6D6, 27 °C): δF -144.24 (dd; J ) 24 Hz, 2F, o-F),
-146.1 (br, 2F, o-F), -157.8 (t, J ) 22.3 Hz, 2F, p-F), -160.7 (t,
J ) 22.0 Hz, 2F, m-F), -164.4 (br, 2F, m-F). MS (ESI): m/z
(intensity) 1292.5 (1400, M+), 1255.4 (5200, M+ - Cl).
Synthesis of Hf Bis(phenoxyimino) Dibenzyl Complexes. (a)
Bis[N-(3-tert-butylsalicylidene)benzylaminato]hafnium Dibenzyl
(9). A cooled (-20 °C) solution of ligand 1 (1.0 g, 3.7 mmol) in
Et2O (25 mL) was added slowly with a syringe to the cooled (-78
°C) solution of Hf(CH2Ph)4 (1.0 g, 1.8 mmol) and Et2O (5 mL).
The reaction mixture was stirred at -78 °C for 20 min and then
placed into a freezer and kept overnight at -20 °C. The solvent
was removed in vacuo, and the residue was extracted twice with
dry hexane (15 × 2 mL). The combined extracts were then filtered
in a glovebox through a syringe PTFE filter. Hexane was evaporated
in vacuo. The product was isolated as an orange solid (1.0 g, 61%).
Anal. Calcd for C50H54N2O2Hf: C, 67.21; H, 6.09; N, 3.14.
Found: C, 67.14; H, 5.85; N, 3.22. 1H NMR (200 MHz, C6D6, 29
°C): δH 1.78 (s, 18H, t-Bu), 2.77 (AB system, JHH ) 10.7 Hz,
4H, Hf-CH2Ph), 4.45 (AB system, JHH ) 15.2 Hz, 4H, CH2Ph),
6.46 (dd, JHH ) 1.7 Hz, 2H, 6-H Ar), 6.63 (t, JHH ) 6.9 Hz, 2H,
5-H Ar), 6.80-7.10 (m, 20H, Ar H from CH2Ph), 7.33 (s, 2H,
CHdN), 7.48 (dd, JHH ) 1.7 Hz, 2H, 4-H Ar). 13C{1H} NMR (50.3
MHz, C6D6, 29 °C): δC 30.10 (s, CH3 of t-Bu), 35.34 (s, C of
t-Bu), 61.87 (s, CH2Ph), 73.50 (s, Hf-CH2Ph), 118.83 (5-C Ar),
120.41 (Ph from Hf-CH2Ph), 125.64 (C-CHdN), 126.82 (o-C
from CH2Ph), 127.89 (Ph from Hf-CH2Ph), 129.40 (m-C from
CH2Ph), 133.06 (4-C Ar), 133.77 (6-C Ar), 135.41 (C-t-Bu), 141.14
(C-CH2 from CH2Ph), 148.67 (ipso-C from Hf-CH2Ph), 160.59
(C-OH), 168.92 (CHdN). MS (ESI): m/z (intensity) 894.6 (100,
M+), 729.3 (500, L2HfCH2), 713.5 (300, M+ - 2CH2Ph).
(d) Bis{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]-2,3,4,5,6-
pentafluoroanilinato}hafnium Dibenzyl (12). Ligand 4 (1.74 g,
3.31 mmol) in Et2O (25 mL) was treated with Hf(CH2Ph)4 (0.90 g,
1.66 mmol) in Et2O (5 mL), as described for 9. The isolation of
the product was carried out as reported for complex 9. The resulting
complex is sparingly soluble in hexane, and 20 mL portions of
hexane (with 8 mL of Et2O added) were used for complex
extraction. After solvent evaporation, the residue was washed with
hexane to remove the unreacted ligand and Hf(CH2Ph)4. The
complex 12 was isolated as a yellow solid (1.51 g; 65%). Anal.
Calcd for C76H64F10N2O2Hf: C, 66.97; H, 5.88; N, 1.78. Found:
(b) Bis{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]benzyl-
aminato}hafnium Dibenzyl (10). Ligand 2 (1.65 g, 3.68 mmol)
in Et2O (25 mL) was treated with Hf(CH2Ph)4 (1.00 g, 1.84 mmol)
in Et2O (5 mL), as described for 9. The isolation of the product
was carried out as reported for complex 9. The complex 10 was
isolated as an orange solid (1.35 g; 58%). Anal. Calcd for
C78H78N2O2Hf: C, 74.71; H, 6.27; N, 2.23. Found: C, 74.16; H,
1
C, 66.92; H, 5.38; N, 1.30. H NMR (500 MHz, C6D5Br, 30 °C):
δH 1.32 (s, 12H, CH3 of 5-R,R-dimethylbenzyl), 1.37 (d, 12H,
CH3 of 3-R,R-dimethylbenzyl), 1.97 (AB system, JHH ) 11.8 Hz,
4H, Hf-CH2Ph), 6.72 (d, JHH ) 6.7 Hz, 2H, p-H Ph from
Hf-CH2Ph), 6.90-7.30 (m, 28H, Ar H), 7.94 (s, 2H, CHdN).
13C{1H} NMR (75 MHz, C6D5Br, 27 °C): δC 28.05 (s, CH3 of
1
5.94; N, 2.81. H NMR (500 MHz, C6D5Br, 27 °C): δH 1.44 (s,

Hf Bis(phenoxyimino) Dibenzyl Complexes
Organometallics, Vol. 26, No. 6, 2007 1459
5-R,R-dimethylbenzyl), 29.06 (s, CH3 of 5-R,R-dimethylbenzyl),
30.60 (s, CH3 of 3-R,R-dimethylbenzyl), 42,50 (s, C of 5-R,R-
dimethylbenzyl), 43.70 (s, C of 3-R,R-dimethylbenzyl), 80.23 (s,
Hf-CH2Ph), 121.21 (Ph from Hf-CH2Ph), 123.18 (4-C Ar), 126.17
(p-C Ph from 3-R,R-dimethylbenzyl), 126.38 (p-C Ph from 5-R,R-
dimethylbenzyl), 126.82 (m-C Ph from 5-R,R-dimethylbenzyl),
126.96 (o-C Ph from 5-R,R-dimethylbenzyl), 127.01 (m-C Ph
from 3-R,R-dimethylbenzyl), 128.50 (Ph from Hf-CH2Ph), 128.54
(Ph from Hf-CH2Ph), 131.94 (C-F), 131.95 (5-C Ar), 132.56
(4-C Ar), 136.32 (C-F), 137.08 (C Ph from 3-R,R-dimethyl-
benzyl), 137.80 (C-F), 139.28 (6-C Ar), 139.66 (C-F), 140.18
(C-CHdN), 142.00 (5-C Ar), 143.10 (C-F), 148.70 (Ph from
Hf-CH2Ph), 150.28 (C Ph from 5-R,R-dimethylbenzyl), 159.90
(C-OH), 177.32 (CHdN). 13F NMR (282.2 MHz, CDCl3, 27 °C):
δF -145.82 (br s, 2F, o-F), -158.99 (t, J ) 22 Hz, 1F, p-F),
-163.42 (br s, 2F, m-F). MS (ESI): m/z (intensity) 1401.7 (50,
M+), 1223.3 (150, M+ - 2CH2Ph).
Generation of Cationic Species. (a) Reaction of Bis[N-(3-tert-
butylsalicylidene)benzylaminato]hafnium Dibenzyl (9) with
B(C6F5)3. In a glovebox a NMR tube was charged with dibenzylbis-
[N-(3-tert-butylsalicylidene)benzylaminato]hafnium (9; 36 mg, 40
µmol), after which 0.4 mL of C6D5Br was added via a syringe at
room temperature. B(C6F5)3 (20 mg, 40 µmol) was added to the
solution of the complex in the NMR tube, and the mixture was
vigorously shaken. The color of the solution changed quickly from
orange to yellow. Owing to its high thermal instability and very
high air and moisture sensitivity, this substance could not be
isolated, and the resulting yellow solution was investigated only
by 1H and 19F NMR methods. 1H NMR (200 MHz, C6D5Br,
29 °C, mixture of generated monobenzyl cation and product of
CH activation): δH 1.81 (s, 18H, t-Bu), 2.44 (s, CH3 from
toluene), 3.08 (s, Hf-CH2Ph), 3.64 (s, 2H, CH2 from PhCH2B),
4.45 (s, 4H, CH2Ph), 6.62 (d, JHH ) 7.3 Hz, 2H, o-H Ph from
Hf-CH2Ph), 7.1-7.44 (Ar H), 7.55 (d, JHH ) 7.7 Hz, 2H, 4-H
Ar), 7.78 (s, 2H, CHdN). 19F NMR (282 MHz, C6D5Br, 29 °C,
mixture of generated monobenzyl cation and product of CH
activation): δF -127.7 (m, B(C6F5)3), -130.52 (d, J ) 22.7 Hz,
2F, o-F), -142.20 (m, B(C6F5)3), -159.7 (m, B(C6F5)3), -163.82
(br s, 1F, p-F), -166.62 (t, 2F, m-F). MS (ESI): m/z (intensity)
713.2 (3.2 × 105, L2MH+).
for the reaction of 9 with B(C6F5)3. Owing to its high thermal
instability and very high air and moisture sensitivity, this substance
could not be isolated, and the resulting orange solution was
investigated only by 1H and 19F NMR methods. 1H NMR (200 MHz,
C6D5Br, 29 °C): δH 0.94 (s, 18H, t-Bu), 2.84 (s, 2H, Hf-CH2Ph),
3.01 (s, 2H, CH2 from PhCH2B), 6.50 (d, JHH ) 7.2 Hz, 2H, o-H
Ph from Hf-CH2Ph), 6.7 (d, 1H, BCH2Ph), 6.7 (2H, 5-H Ar), 6.75
(m, 2H, H Ph from Hf-CH2Ph), 6.8 (d, JHH ) 7.8 Hz, 2H, H Ph
from BCH2Ph), 6.9 (d, JHH ) 7.0 Hz, 3H, H Ph from Hf-CH2Ph),
7.0 (d, JHH ) 7.6 Hz, 2H, 4-H Ph), 7.4 (d, JHH ) 7.6 Hz, 2H, 6-H
Ar), 8.1 (s, 2H, CHdN). 19F NMR (282 MHz, C6D5Br, 29 °C): δF
-127.7 (m, B(C6F5)3), -130.97 (d, J ) 22.6 Hz, 6F, o-F), -142.30
(m, B(C6F5)3), -148.7 (d, J ) 20.6 Hz, 4F, o-F), -152.11 (t, J )
22.2 Hz, 2F, p-F), -158.7 (t, J ) 20.70 Hz, 4F, m-F), -159.75
(m, B(C6F5)3), -164.23 (t, J ) 21.0 Hz, 3F, p-F), -167.08 (t, J )
20.4 Hz, 6F, m-F). MS (ESI): m/z (intensity) 953.1 (1.2 × 106,
L2MCH2Ph+), 933.1 (2.5 × 105, L2MCH2Ph+-F), 914.2 (2.0 × 105,
L2MCH2Ph+ - 2F), 897.0 (1.5 × 105, L2MCH2Ph+ - 3F), 880.1
(7.5 × 105, L2MCH2Ph+ - 4F).
(d) Reaction of Bis{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]-
2,3,4,5,6-pentafluoroanilinato}hafnium Dibenzyl (12) with
B(C6F5)3. Dibenzylbis{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]-
2,3,4,5,6-pentafluoroanilinato}hafnium (12; 56 mg, 40 µmol) was
activated with B(C6F5)3 (20 mg, 40 µmol) in C6D5Br (0.4 mL) in
the same way as described for the reaction of 9 with B(C6F5)3.
Owing to its high thermal instability and very high air and moisture
sensitivity, this substance could not be isolated, and the resulting
orange solution was investigated only by 1H and 19F NMR methods.
1H NMR (500 MHz, C6D5Br, 30 °C): δH 1.33 (s, 12H, CH3 of
5-R,R-dimethylbenzyl), 1.69 (d, 12H, CH3 of 3-R,R-dimethylben-
zyl), 2.25 (s, 2H, Hf-CH2Ph), 3.27 (s, 2H, CH2 from PhCH2B),
5.69 (d, JHH ) 5.8 Hz, 2H, H Ph from Hf-CH2Ph), 6.5-6.9 (m,
4H, H Ph from BCH2Ph), 6.9-7.4 (m, 20H, H Ph from ligand, H
Ph from BCH2Ph, H Ph from Hf-CH2Ph), 7.47 (s, 2H, 6-H Ar),
7.87 (s, 2H, 6-H Ar), 8.37 (s, 2H, CHdN). 13F NMR (282.2 MHz,
CDCl3, 27 °C): δC -127.75 (m, B(C6F5)3), -130.97 (d, J ) 20.0
Hz, 6F, o-F), -142.30 (m, B(C6F5)3), -148.33 (d, J ) 14.6 Hz,
4F, o-F), -151.86 (t, J ) 22.6 Hz, 2F, p-F), -158.4 (t, J ) 20.0
Hz, 4F, m-F), -159.7 (m, B(C6F5)3), -164.20 (t, J ) 20.6 Hz, 3F,
p-F), -167.0 (t, J ) 19.9 Hz, 6F, m-F). MS (ESI): m/z (intensity)
1314.3 (2.5 × 104, L2MCH2Ph+), 1294.3 (1.5 × 105, L2MCH2Ph+
- F), 1274.3 (8.0 × 104, L2MCH2Ph+ - 2F).
(b) Reaction of Bis{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]-
benzylaminato}hafnium Dibenzyl (10) with B(C6F5)3. Dibenzylbis-
{N-[3,5-bis(R,R-dimethylbenzyl)salicylidene]benzylaminato}-
hafnium (10; 52 mg, 40 µmol) was activated with B(C6F5)3 (20
mg, 40 µmol) in C6D5Br (0.4 mL) in the same way as described
for the reaction of 9 with B(C6F5)3. Upon addition of B(C6F5)3, the
reaction mixture turned from orange to yellow. Owing to its high
thermal instability and very high air and moisture sensitivity, this
substance could not be isolated, and the resulting yellow solution
was investigated only by 1H and 19F NMR methods. 1H NMR (200
MHz, C6D5Br, 29 °C, product of CH activation): δH 1.90 (s, 12H,
CH3 of 5-R,R-dimethylbenzyl), 2.01 (m, 12H, CH3 of 3-R,R-
dimethylbenzyl), 2.47 (s, 3H, CH3 from toluene), 3.08 (s, traces,
Hf-CH2Ph), 3.64 (s, 2H, CH2 from PhCH2B), 3.75-5.00 (m, 4H,
CH2Ph), 6.18 (d, traces, H Ph from HfCH2Ph), 6.45 (d, JHH ) 7.7
Hz, 2H, CH2 from BCH2Ph), 6.80-7.9 (m, 38H, Ar H and H Ph
from Hf-CH2Ph), 8.09 (m, 2H, CHdN). 19F NMR (282 MHz,
C6D5Br, 29 °C, product of CH activation): δF -127.7 (m,
B(C6F5)3), -130.52 (d, J ) 22.8 Hz, 2F, o-F), -142.20 (m,
B(C6F5)3), -159.7 (m, B(C6F5)3), -163.82 (br s, 1F, p-F), -166.62
(t, 2F, m-F). MS (ESI): m/z (intensity) 1071.5 (2 × 105, L2MH+),
1014.5 (3.2 × 105, L2M+ - 4Me), 999.4 (4.6 × 105, L2M+ - Ph).
Polymerization Experiments. A 1 L Bu¨chi glass autoclave was
charged with 200 mL of toluene and MAO, thermostated at the
required temperature, and saturated with ethylene, after which the
desired amount of complex solution was added. The B(C6F5)3-
activated benzyl complexes exhibited extremely high air and
moisture sensitivity and thermal instability, and even in the presence
of TIBA, used as a scavenger, only very low or no activity was
observed in the corresponding experiments. The preparation of stock
solutions of the complexes was performed in a glovebox. The
catalyst solution was introduced into the autoclave under argon
pressure. The monomer pressure ((50 mbar) and reaction temper-
ature ((0.5 °C) were kept constant during each polymerization run.
The monomer consumption, polymerization temperature, and pres-
sure were controlled by real-time monitoring. The polymerizations
were quenched by pouring the resulting reaction mixture into 400
mL of methanol acidified with aqueous hydrochloric acid. After
precipitation, the polymers were washed several times with
methanol and water and then dried at 60 °C overnight.
The olefin polymerizations in NMR tubes were carried out with
freshly prepared solutions of B(C6F5)3-activated Hf dibenzyl
complexes. The appropriate amounts of complex, C6D5Br, and
activator (B(C6F5)3) were placed into a NMR tube equipped with
a rubber septum (see Generation of Cationic Species). In a glovebox,
the NMR tube with catalyst solution was placed into a Schlenk
flask equipped with a rubber septum. The olefin was bubbled via
(c) Reaction of Bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pen-
tafluoroanilinato]hafnium dibenzyl (11) with B(C6F5)3. Diben-
zylbis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato]-
hafnium (11; 41 mg, 40 µmol) was activated with B(C6F5)3 (20
mg, 40 µmol) in C6D5Br (0.4 mL) in the same way as described

1460 Organometallics, Vol. 26, No. 6, 2007
AxenoV et al.
Table 6. Crystallographic Data for Complexes 10-12 and a
The crystals of 12 were extremely fragile and broke instanta-
neously into smaller crystallites due to very loose van der Waals
connections between molecules, indicating voids and loose con-
nections between molecules inside the crystal structure. The final
residual maximum in 12 implies disorder due to a partially cracked
crystal.
10
11
12
a
formula
C78H78N2- C48H40F10-
C76H64F10- C52H58N2-
O2Hf
N2O2Hf‚
N2O2Hf
1405.78
O2Ti
1.5C4H10O
fw
1253.91
P1h
1156.49
Pbcn
790.90
P21/c
space group
a (Å)
b (Å)
C2/c
Crystallographic data for complexes 10-12 and a are given in
Table 6.
14.608(2)
15.646(2)
15.844(2)
89.03(1)
65.96(1)
73.39(1)
3148.6(8)
1.323
2
1.71
0.710 73
173(2)
0.0839
0.1165
25.253(2)
9.4870(10)
22.630(2)
90.00
90.00
90.00
5421.6(9)
1.417
4
30.721(6)
19.795(4)
22.751(5)
90.00
95.02(3)
90.00
13782.5(5) 4458.5(5)
1.355
8
20.734(1)
12.020(1)
20.224(1)
90.00
117.80(1)
90.00
c (Å)
Calculation Details. Turbomole 5.834 and ADF 2005.0135
quantum chemistry programs were used. All calculations were
performed on a Sipeli supercomputer at the Finnish IT Center for
Science (CSC).50 The Turbomole computations were made at the
B-P (B-P86) level.51 The SVP basis sets were used for all atoms to
calculate the optimized geometries. For the computations with the
Amsterdam density functional program (ADF), triple-ú STO basis
sets (TVZ) were used for all atoms, and calculations were performed
at the BLYP level. In addition, the scalar relativistic correction on
ZORA formalism52 was applied.
R (deg)
â (deg)
γ (deg)
V (Å3)
d
calcd (g cm-3
)
1.178
4
Z
µ (mm-1
λ (Å)
T (K)
Ra
)
2.00
1.59
0.233
0.710 73
173(2)
0.1464
0.1589
0.710 73
173(2)
0.0720
0.1093
0.710 73
173(2)
0.1199
0.1919
b
Rw
a R ) ∑||Fo| - |Fc||/∑|Fo| for observed reflections (I > 2σ(I)). b Rw
)
{∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2 for all data.
2
2
2
Acknowledgment. The work was financially supported by
the Academy of Finland (Project No. 204408) and the Finnish
National Technology Agency (TEKES). Sami Lipponen and
Tapio Saarinen from the Helsinki University of Technology are
gratefully acknowledged for the help in GPC and 13C NMR
measurements of polymer samples. We acknowledge the fol-
lowing: Dr. Sami Heikkinen from the University of Helsinki
for great help and advice in advanced NMR experiments,
facilities, and staff from the Organisch-Chemisches Institut,
Wesfa¨lische-Wilhelms Universita¨t, Mu¨nster, Germany, for
elemental analysis of Hf dibenzyl complexes, Minna Ra¨isa¨nen
for advice concerning ESI-MS measurements, and Mrs. Eeva
Kaija for the DSC measurements.
a long needle through the catalyst solution. The pressure inside
the NMR tube was normalized by a short needle introduced inside
the NMR tube with an open connection to the outside atmosphere.
1
The polymerization process was followed by H NMR.
Single-Crystal X-ray Diffraction Studies. Crystal data of
compounds 10-12 were collected with a Nonius KappaCCD area-
detector diffractometer at 173(2) K using Mo KR radiation (graphite
monochromator, 0.710 73 Å). Software used: data reduction,
COLLECT;46 absorption correction, SADABS;47 structure solution,
SHELX-9748a or SIR 2002,48b direct methods; refinement, SHELX-
97;48a graphics, SHELXTL.49All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were refined on calculated posi-
tions.
In the structure of 11, Et2O solvent molecules are heavily
disordered, and their site occupation factors are 0.25 and 0.50. Both
Et2O molecules were refined with common isotropic atomic
displacement parameters. Hydrogen atoms were placed on calcu-
lated positions, which is one reason for the short contacts. No other
procedure to locate H atoms of the solvent molecules from the data
set was successful.
Supporting Information Available: CIF files giving crystal-
lographic data for 10-12 and a and figures giving 1H and 19F NMR,
LT NMR, HETCOR 2D COSY, 2D NOESY, and ESI-MS spectra
of bis(phenoxyimino) Hf dibenzyl complexes and products of their
activation with B(C6F5)3 and results of GPC studies of produced
polyethylene and polypropylene. This material is available free of
charge via the Internet at http://www.pubs.acs.org.
OM060753F
(46) Nonius, COLLECT; Nonius BV, Delft, The Netherlands, 2002.
(47) Sheldrick, G. M. SADABS; University of Go¨ttingen, Go¨ttingen,
Germany, 1996.
(48) (a) Sheldrick, G. M. SHELX-97; University of Go¨ttingen, Go¨ttingen,
Germany, 1997. (b) Burla, M. C.; Camalli, M.; Carrozzini, G. L.; Cascarano,
G.; Giacovazzo, C.; Polidori, G.; Spagna, R. SIR 2002. J. Appl. Crystallogr.
2003, 36, 1103.
(50) Regarding CSC, see: http://www.csc.fi/suomi/info/index.phtml.en.
(51) Ahlrichs, R.; Furche, F.; Grimme, S. Chem. Phys. Lett. 2000, 325,
317.
(52) (a) van Lenthe, E.; Baerends, E. J.; Sniders, J. G. J. Chem. Phys.
1993, 99, 4597. (b) van Lenthe, E.; Baerends, E. J.; Sniders, J. G. J. Chem.
Phys. 1994, 101, 9783. (c) van Lenthe, E.; Ehlers, A. E.; Baerends, E. J. J.
Chem. Phys. 1999, 110, 8943.
(49) Sheldrick, G. M. SHELXTL, Version 5.10; Bruker AXS Inc.,
Madison, WI, 1997.