Catalytic dehydrogenation of cyclooctane in homogeneous solution with titanium, zirconium and hafnium complexes containing N,O-chelating ligands

Article abstract of DOI:10.1016/j.molcata.2008.04.005

A series of new titanium, zirconium and hafnium complexes with the heteroatom chelating ligands hydroxyquinolines, hydroxypyridines and hydroxyimines were synthesized. The complexes were activated with MAO and successfully tested for the catalytic CH activation reactions of cyclooctane. They gave TONs of 1.7-18.7 (300 °C, 16 h) in homogeneous solution. The TONs were clearly influenced by the ligand structure. The endothermic CH activation reaction with group 4 metal catalysts is preferably carried out at higher reaction temperatures (300-400 °C).

Full text of DOI:10.1016/j.molcata.2008.04.005

Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Catalytic dehydrogenation of cyclooctane in homogeneous solution with
titanium, zirconium and hafnium complexes containing N,O-chelating ligands
Sandra Taubmann, Helmut G. Alt∗
Laboratorium fu¨r Anorganische Chemie, Universita¨t Bayreuth, Universita¨tsstraße 30, D-95440 Bayreuth, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new titanium, zirconium and hafnium complexes with the heteroatom chelating ligands
hydroxyquinolines, hydroxypyridines and hydroxyimines were synthesized. The complexes were acti-
vated with MAO and successfully tested for the catalytic CH activation reactions of cyclooctane. They gave
TONs of 1.7–18.7 (300 ◦C, 16 h) in homogeneous solution. The TONs were clearly influenced by the ligand
structure. The endothermic CH activation reaction with group 4 metal catalysts is preferably carried out
at higher reaction temperatures (300–400 ◦C).
Received 17 January 2008
Received in revised form 4 April 2008
Accepted 5 April 2008
Available online 12 April 2008
Keywords:
© 2008 Elsevier B.V. All rights reserved.
CH bond activation
Homogeneous catalysts
Dehydrogenation
Titanium
Zirconium
Hafnium
Imines
Heteroatom ligands
MAO
1. Introduction
the generated hydrogen from the reaction equilibrium. This makes
such a reaction inconsiderable for industrial processes. Reports for
The activation and functionalisation of CH bonds of saturated
hydrocarbons is an intensively studied area of research. Currently,
the industrial production of organic chemicals is largely based
on alkenes which are produced by thermal cracking processes of
alkanes [1]. This process is unselective and requires an expensive
separation of the products. Consequently, a new selective method
for alkene production under mild conditions is desirable. The CH
activation of alkanes via oxidative addition to transition metal com-
plexes is one of the most promising approaches to that target.
Significant progress has been made in this area during the past
several years, particularly with late transition metal catalysts [2–8].
Generally, dehydrogenation reactions were carried out with metal
complexes of rhodium [9] and iridium [10]. Currently, the bench-
mark in homogeneous CH activation of cyclooctane amount to more
than 1000 turnovers per 30 min [11]. Like most of the other research
groups [12–16], Brookhart et al. activated cyclooctane via trans-
fer dehydrogenation. This method has the big disadvantage that a
hydrogen acceptor, like tert-butylethylene is necessary to remove
CH activation of alkanes with organometallic compounds are rare
and they describe lower activities than these from transfer dehy-
drogenation reactions [17].
The catalytic CH activation of alkanes with titanium, zirconium
and hafnium complexes is unknown in the literature. These com-
plexes can be activated with a cocatalyst like methylaluminoxane
(MAO) and are then excellent catalysts for olefin polymerisation.
There are hints that such catalysts are also promising candidates for
the activation of saturated hydrocarbons: The oxidative addition of
the alkane on the active center and the ␤-hydrogen elimination
of the alkyl ligand are essential steps in the catalytic CH acti-
vation of alkanes. The latter reaction is often described as side
reaction or chain-termination reaction in the olefin polymerisation
process.
2. Results and discussion
2.1. Complex synthesis
The naphthoxyimine ligand precursors were synthesized via
a condensation reaction of 2-hydroxy-1-naphthaldehyde and an
appropriate aniline [18,19].
∗
Corresponding author. Tel.: +49 921 55 2555; fax: +49 921 55 2044.
E-mail address: helmut.alt@uni-bayreuth.de (H.G. Alt).
1381-1169/$ – see front matter © 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2008.04.005

50
S. Taubmann, H.G. Alt / Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
Scheme 1. Synthesis of complexes 1a–n.
Scheme 2. Synthesis of complex 2a.
Scheme 3. Synthesis of complex 2b.
The complexes were synthesized from the reaction of the
of the isomerisation products dimethylcyclohexane, ethylcyclohex-
ane and methylcycloheptane (Scheme 4).
The titanium, zirconium and hafnium complexes could not be
used directly as catalysts for the dehydrogenation of cyclooctane.
They needed a cocatalyst like MAO. It can be assumed that the acti-
vation step proceeds in an analogous manner (Scheme 5) [23–28]:
sodium salt of the ligand precursors and the metal tetrachlo-
ride. For this purpose, the naphthoxyimine compound and sodium
hydride were reacted. A group IV metal chloride was added
to the sodium alkoxylate in a ratio of M:L = 1:2. After prepara-
tion and workup, the complexes were obtained as yellow solids
(Schemes 1–3).
A similar complex type was synthesized by the reaction of 2-
methyl-8-hydroxyquinoline and 2-hydroxymethyl-pyridine with
NaH followed by the addition of TiCl4 respectively ZrCl4.
Besides bis(2-methyl-8-quinolinato) zirconium dichloride (2c)
[20], bis(8-quinolinato) titanium dichloride (2d) [21] and bis(8-
quinolinato) zirconium dichloride (2e) [22] were synthesized
according to the literature.
2.2. Homogeneous dehydrogenation of cyclooctane
The titanium, zirconium and hafnium complexes were tested as
catalysts for the dehydrogenation of cyclooctane. In a homogeneous
catalytic CH activation reaction they converted cyclooctane into
cyclooctene and bis(3.3.0)cyclooctane along with small amounts
Scheme 4. Catalytic reactions of cyclooctane.

S. Taubmann, H.G. Alt / Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
51
Scheme 5. Activation of a metallocene dichloride complex with MAO.
The exact structure of MAO and the reaction progress are still
unknown except that MAO works as a methylating agent and then
abstracts a methyl anion from the metal to form a cationic species.
Besides this, studies proved that MAO consists of a variety of linear
and cyclic oligomers which exist in a dynamic equilibrium [29–35].
The complexes 1a–n and 2a–e were dissolved or suspended in
cyclooctane and were activated with MAO to form the catalysts
4a–n and 3a–e. The solutions were transferred to an autoclave and
heated to 300 ◦C for 16 h. In order to investigate the temperature
influence on the activities and selectivities, the reaction mixtures
were heated to 375 ◦C.
The catalysts with monochloro substituted imine ligands (4b,
4d, 4m) showed generally higher TONs than catalysts 4a, 4e and 4n.
In both cases, the zirconium containing catalyst gave a higher activ-
ity than the corresponding titanium and hafnium catalysts. The
difference, however, was higher using the monochloro substituted
complexes. Besides the higher activity, the zirconium catalysts
also achieved higher selectivities towards CH activation products
(Scheme 7).
It is evident that most catalysts do not have any longer the
original composition at reaction temperatures of 300–375 ◦C. Nev-
ertheless, the catalysts were active up to 375 ◦C (Table 2) and the
original ligands had a high influence on the activities and selectivi-
ties of the actual catalysts (Scheme 8). It is obvious that the ligands
are involved in the formation and stabilisation of the new active
species.
2.2.1. Dehydrogenation of cyclooctane with N-alcoholate
complexes (3a–e)
The complexes 1a–e were activated with MAO with a ratio
M:Al = 1:50 to form the catalysts 3a–e. The zirconium contain-
ing catalysts showed no catalytic dehydrogenation of cyclooctane
at 300 ◦C, the titanium catalysts effected low conversions of
cyclooctane to cyclooctene respectively bis(3.3.0)cyclooctane. The
activities (given as TONs) and selectivities towards CH activation
products are summarized in the following table (Table 1).
The catalytic activities of the zirconium catalysts 3c and 3e
were furthermore investigated at 350 ◦C. As the catalysts gave no
catalytic dehydrogenation at 300 ◦C, a remarkable activation of
cyclooctane was observed at 350 ◦C (Scheme 6). This result sug-
gest that the zirconium complex needs higher activation energy
than the titanium containing catalysts to catalyse the endother-
mic CH activation reaction. It is also very likely that only at higher
temperatures a new efficient active species is formed. Besides the
production of cyclooctene and bis(3.3.0)cyclooctane, the isomeri-
sation of cyclooctane increased at 350 ◦C, so that the products
1,2-dimethylcyclohexane, ethylcyclohexane and methylcyclohep-
tane were produced. The unidentified product with a TON = 21.82
(3e) respectively 6.16 (3c) also seems to be an isomerisation prod-
uct as can be seen from the retention time of the fraction in the GC
analysis.
Catalysts with para-substituted aniline fragments (4f and 4l)
gave the lowest dehydrogenation rates for cyclooctane. A substitu-
tion in the ortho position increased the TONs. The highest catalytic
activity showed the ortho-chloro-substituted catalyst 4d with a
TON of 18.7.
In
a similar manner, olefin polymerisation catalysts like
Cp2ZrCl2/MAO that “decompose” at temperatures above 100 ◦C are
able to activate cyclooctane and other alkanes at higher tempera-
tures but with much better activities (TON = 180, in 5 h, at 300 ◦C
[36]). Preliminary results indicate that in all these cases Zr/Al cages
with various substituents are the active species.
3. Summary and conclusions
The novel titanium, zirconium and hafnium complexes1a–n and
2a–b containing N,O-chelating ligands were synthesized. As lig-
and precursors 2-methyl-8-hydroxyquinoline, 2-hydroxymethyl-
pyridine and different naphthoxyimines were applied. The
naphthoxyimine ligand precursors can be prepared from relatively
inexpensive starting materials.
Titanium, zirconium and hafnium complexes as catalysts for the
catalytic dehydrogenation of cyclooctane have not been reported in
the literature so far. As a consequence, these catalysts can only be
compared with the well-known and expensive iridium, rhodium
and platinum containing catalysts. The group IV metal catalysts
gave lower TONs than the iridium systems (see [37–41]). Nearly
all tested catalysts gave a catalytic CH activation of cyclooctane
in homogeneous solution. They showed TONs of 1.7–18.7 (300 ◦C,
16 h) in homogeneous solution. The TON was clearly influenced
by the ligand structure: catalysts with a para-substituted aniline
fragment (4f and 4l) gave the lowest rates of dehydrogenation
of cyclooctane. A substitution in the ortho position increased the
TONs. An increase of the temperature increased the activities
remarkably: TON (CH activation products) = 86 (3e, 350 ◦C), 71 (3c,
350 ◦C) and 55 (4i, 375 ◦C).
2.2.2. Dehydrogenation of cyclooctane with imine catalysts of
titanium, zirconium and hafnium (4a–n)
The complexes 1a–n were activated with MAO to form the cat-
alysts 4a–n. The investigation of the temperature influence gave
an analogous result as for catalysts 3c and 3e: a higher reaction
temperature resulted in higher TONs as it was expected for an
endothermic reaction. The higher temperatures, especially 350 and
375 ◦C, enhanced the isomerisation of cyclooctane so that the selec-
tivity of catalyst 4i decreased from 60.9 (325 ◦C) to 48.6 (350 ◦C)
respectively to 27.9 (375 ◦C).
The influence of the central metal on the catalytic activity was
also investigated. The titanium, zirconium and hafnium complexes
with monochloro (4b, 4d, 4m) and dichloro (4a, 4e, 4n) substituted
imine ligands were tested at 300 ◦C in an autoclave (Scheme 7).

52
S. Taubmann, H.G. Alt / Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
Table 1
Activities and selectivities of catalysts 3a–e
No.
Complex
Cocatalyst
MAO
TON
4.3
Selectivity (CH activation products) (%)
3a
84.7
3b
3c
MAO
MAO
1.7
1.9
70.8
0.0
3d
3e
MAO
MAO
5.1
0.7
40.8
37.9
Scheme 6. Temperature dependence of the activities of catalysts 2c and 2e.

S. Taubmann, H.G. Alt / Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
53
Scheme 7. Influence of the central metal (4a, 4b, 4d, 4e, 4m, 4n) on the TON and the selectivities towards CH activation products.
4. Experimental
peak (53.80 ppm, the center line of a quintet for CD2Cl2). Elemental
analyses were determined on a VarioEl III instrument. Mass mea-
surements were performed using a VARIAN MAT CH7 instrument
(direct inlet, electron impact ionization, 70 eV). The products of
CH activation experiments were characterized with a GC (Agilent
6890) and GC/MS (FOCUS DSQ Thermo). For GC measurements a
30 m HP-5 column (film 1.5 ␮m) was used. The measuring program
was: 6 min at 35 ◦C (starting phase); 20 ◦C/min (heating phase);
2 min at 200 ◦C (final phase). The products were detected by a
flame ionization detector. For GC/MS measurements a 30 m TR-
5MS column was used. The measuring program was 8 min at 35 ◦C
(starting phase); 15 ◦C/min (heating phase); 2 min at 250 ◦C (final
phase).
4.1. General considerations
Air- and moisture-sensitive reactions were carried out under
an atmosphere of purified argon using conventional Schlenk tech-
niques. NMR spectra were obtained on a Bruker ARX250 instrument
at ambient temperatures (21 ◦C). 1H NMR spectra were reported in
terms of chemical shifts (ı, ppm) relative to the residual solvent
peak (5.31 ppm for CD2Cl2). The multiplicities were designated as
follows: s, singlet; d, doublet; m, multiplet. 13C{1H} NMR spectra
were recorded fully decoupled by broad-band decoupling and are
reported in terms of chemical shifts (ı, ppm) relative to the solvent
Table 2
Temperature dependence of catalyst 4i/MAO
Complex
Temperature (◦C)
TON
Selectivity (%)
300
325
350
375
9.5
12.0
37.7
97.9
56.8
60.9
48.6
27.9

54
S. Taubmann, H.G. Alt / Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
Scheme 8. Activities and selectivities of catalysts 4d–k.
brown powder. Spectroscopic data for 1b: 1H NMR (250 MHz,
4.2. Materials
21 ◦C, CD2Cl2): 8.96 (s, 2H), 8.16–6.53 (m, 20H). MS data for 1b:
•
769 (M +) (13), 732 (100), 697 (8), 653 (5), 443 (61), 324 (23).
Tetrahydrofuran, n-pentane and methylene dichloride were
refluxed over the appropriate drying agents and distilled under
argon. NaH was washed with toluene and pentane before use to
remove residues of mineral oil. Cyclooctane (COA) was degassed
and stored under argon. The organic starting materials were pur-
chased from Aldrich or Arcos and were used without further
purification.
(1c) From 0.56 g (2 mmol) of 1-[[(2-chlorophenyl)imino]
methylenyl]-2-naphthalenol and 0.11 ml (0.19 g, 1 mmol) TiCl4
was obtained an amount of 0.38 g (0.56 mmol, 56%) of 1c as an
•
orange brown powder. MS data for 1c: 680 (M +) (9), 645 (100),
435 (18), 400 (94), 280 (33).
(1d) From 1.13 g (4 mmol) of 1-[[(2-chlorophenyl)imino]
methylenyl]-2-naphthalenol and 0.47 g (2 mmol) ZrCl4 was
obtained an amount of 0.70 g (0.97 mmol, 48%) of 1d as an yellow
powder. NMR data for 1d: 1H NMR (250 MHz, 21 ◦C, CD2Cl2): 9.47
(s, 2H), 8.19 (d, 2H), 7.89–7.75 (m, 2H), 7.60–7.38 (m, 8H), 7.25–7.13
4.3. General procedure for the synthesis of alkoxyimine titanium,
zirconium and hafnium complexes
1
(m, 8H). 13C { H} (62 MHz, 21 ◦C, CD2Cl2): 157.1 (CH), 136.9 (CH),
The desired ligand precursor was dissolved in 50 ml of THF and
1 equiv. NaH was added. After the completion of the hydrogen
evolution, an amount of 0.5 equivalents of MCl4 (M = Ti, Zr, Hf)
was added, and the solution was stirred for 16 h at room tem-
perature. The solvent was evaporated in vacuo; the residue was
suspended in CH2Cl2. After filtration over Na2SO4, the solvent
was evaporated. The residue was washed with 50 ml pentane and
dried in vacuo. The complexes were obtained as yellow or orange
powders.
130.6 (CH), 129.7 (CH), 128.5 (CH), 128.4 (CH), 127.7 (CH), 124.1
•
+
(CH), 121.4 (CH), 119.5 (CH), 119.3 (CH). MS data for 1d: 722 (M
)
(30), 687 (41), 442 (56), 281 (100), 246 (53).
(1e) From 1.26 g (4 mmol) of 1-[[(2,4-dichlorophenyl)imino]
methylenyl]-2-naphthalenol and 0.47 g (2 mmol) ZrCl4 was
obtained an amount of 0.83 g (1.05 mmol, 52%) of 1e as a yellow
powder. NMR data for 1e: 1H NMR (250 MHz, 21 ◦C, CD2Cl2): 9.47
(s, 2H), 8.20 (d, 2H), 7.90–7.77 (m, 2H), 7.61–7.36 (m, 8H), 7.22–7.00
•
(m, 8H). MS data for 1e: 792 (M +) (14), 755 (19), 476 (25), 314 (82),
280 (54), 126 (100).
(1a) From 0.95 g (3 mmol) of 1-[[(2,4-dichlorophenyl)imino]
methylenyl]-2-naphthalenol and 0.17 ml (0.28 g, 1.5 mmol) TiCl4
was obtained an amount of 0.43 g (0.57 mmol, 38%) of 1a as an
orange brown powder. NMR data for 1a: 1H NMR (250 MHz, 21 ◦C,
(1f) From 0.65 g (2 mmol) of 1-[[(4-bromophenyl)imino]
methylenyl]-2-naphthalenol and 0.23 g (1 mmol) ZrCl4 was
obtained an amount of 0.32 g (0.39 mmol, 39%) of 1f as a yellow
powder. NMR data for 1f: 1H NMR (250 MHz, 21 ◦C, CD2Cl2): 9.40
•
+
CD2Cl2): 9.47 (s, 2H), 8.19–7.05 (m, 20H). MS data for 1a: 748 (M
)
•
(s, 2H), 8.17–6.55 (m, 20H). MS data for 1f: 812 (M +) (100), 777
(9), 713 (100), 677 (8), 434 (52), 314 (58), 263 (31).
(64), 487 (56), 325 (26).
(1g) From 0.71 g (2 mmol) of 1-[[(4-bromo-2,6-dimethylphenyl)
imino]methylenyl]-2-naphthalenol and 0.23 g (1 mmol) ZrCl4 was
(1b) From 1.3 g (4 mmol) of 1-[[(4-bromophenyl)imino]
methylenyl]-2-naphthalenol and 0.22 ml (0.38 g, 2 mmol) TiCl4
was obtained an amount of 0.79 g (1.02 mmol, 51%) of 1b as a

S. Taubmann, H.G. Alt / Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
55
obtained an amount of 0.27 g (0.31 mmol, 31%) of 1g as a yellow
powder. NMR data for 1g: 1H NMR (250 MHz, 21 ◦C, CD2Cl2): 9.19
tane and dried in vacuo. The complexes were obtained as yellow
powders.
•
+
(s, 2H), 8.04–7.03 (m, 16H), 2.24 (s, 12H). MS data for 1g: 868 (M
)
(2), 833 (6), 353 (100), 273 (32).
(2a) From 0.8 g (5 mmol) 2-methyl-8-hydroxyquinoline and
0.275 ml (0.47 g, 2.5 mmol) TiCl4, an amount of 0.63 g (1.45 mmol,
58%) of 2a was obtained as a light yellow powder.
(1h) From 0.83 g (3 mmol) of 1-[[(2,3-dimethylphenyl)imino]
methylenyl]-2-naphthalenol and 0.35 g (1.5 mmol) ZrCl4 was
obtained an amount of 0.53 g (0.75 mmol, 50%) of 1h as a yellow
powder. NMR data for 1h: 1H NMR (250 MHz, 21 ◦C, CD2Cl2): 9.32
(s, 2H), 8.16–7.07 (m, 18H), 2.37 (s, 6H), 2.12 (s, 6H). MS data for
•
MS data for 2a: 434 (M +) (11), 399 (100), 383 (6), 348 (21), 276
(36), 240 (26).
(2b) From 0.55 g (5 mmol) 2-hydroxymethyl-pyridine and 1.17 g
(2.5 mmol) ZrCl4, an amount of 0.57 g (1. 5 mmol, 60%) of 2b was
obtained as a light yellow powder. Anal. Calc. for C20H16 Cl2N2O2Ti
(2b) C: 39.82; H: 3.91; N: 7.26. Found: C: 38.09; H: 3.20; N: 7.40.
MS data for 2b: 342 (8), 286 (4), 127 (11), 108 (51).
•
1h: 7108 (M +) (29), 673 (60), 436 (21), 400 (16), 274 (100), 258
(32), 132 (24).
(1i) From 0.66 g (2 mmol) of 1-[[(2,6-diisopropylphenyl)imino]
methylenyl]-2-naphthalenol and 0.23 g (1 mmol) ZrCl4 was
obtained an amount of 0.78 g (0.95 mmol, 95%) of 1i as a yellow
powder. NMR data for 1i: 1H NMR (250 MHz, 21 ◦C, CDCl3): 9.13 (s,
4.5. Homogeneous dehydrogenation of cyclooctane
2H), 8.06–7.06 (m, 18H), 3.10 (septet, 4H), 1.22 (d, 24H). 13C { H}
1
(62 MHz, 21 ◦C, CDCl3): 166.0 (Cq), 162.3 (CH), 144.8 (Cq), 143.0
(CH), 140.0 (Cq), 135.5 (CH), 133.1 (Cq), 130.4 (CH), 130.1 (CH),
129,2 (CH), 128.8 (CH), 127.5 (Cq), 126.0 (CH), 125.1 (CH), 124.4
(CH), 123.4 (CH), 120.7 (CH), 119.0 (CH), 108.5 (Cq), 128.3 (CH),
An amount of 10–50 mg of the corresponding complex was dis-
solved or suspended in 20 ml of cyclooctane and activated with
MAO (M:Al = 1:50). The solution was transferred into a laboratory
autoclave and was heated to 300–400 ◦C. After 16 h, the autoclave
was cooled to room temperature and the gas as well as the solution
were analysed by GC.
•
23.4 (CH3) (isomers). MS data for 1i: 823 (M +) (11), 787 (4), 492
(5), 330 (40), 162 (100).
(1j) From 0.91 g (3 mmol) of 1-[[(2-tert-butylylphenyl)imino]
methylenyl]-2-naphthalenol and 0.35 g (1.5 mmol) ZrCl4 was
obtained an amount of 0.90 g (1.17 mmol, 78%) of 1j as a yellow
powder. NMR data for 1j: 1H NMR (250 MHz, 21 ◦C, CDCl3): 9.28
(s), 9.02 (s), 8.96 (s), 8.21–7.07 (m), 1.46 (s) (isomers). MS data for
Acknowledgment
We thank ConocoPhillips, Bartlesville, USA, for the financial sup-
port of the project.
•
1j: 766 (M +) (18), 731 (20), 464 (7), 302 (100), 281 (29).
(1k) From 0.55 g (2 mmol) of 1-[[(2,6-dimethylphenyl)imino]
methylenyl]-2-naphthalenol and 0.23 g (1 mmol) ZrCl4 was
obtained an amount of 0.36 g (0.50 mmol, 50%) of 1k as a yellow
powder. NMR data for 1k: 1H NMR (250 MHz, 21 ◦C, CDCl3): 9.17
(s), 8.96 (s), 8.18 (s), 8.18–7.10 (m), 2.45 (s), 2.28 (s) (isomers). MS
References
[1] T. Sakakura, T. Sodeyama, M. Tanaka, New J. Chem. 13 (1989) 737.
[2] R.H. Crabtree, J. Organomet. Chem. 689 (2004) 4083.
[3] C. Six, B. Gabor, H. Go¨rls, R. Mynott, P. Phillips, W. Leitner, Organometallics 18
(1999) 3316.
[4] J.C.W. Lohrenz, H. Jacobsen, Angew. Chem., Int. 35 (1996) 1305.
[5] U. Flekl, K.L. Goldberg, Adv. Inorg. Chem. 54 (2003) 259.
[6] U. Flekl, W. Kaminsky, K.I. Goldberg, J. Am. Chem. Soc. 125 (2003) 15286.
[7] A.E. Shilov, Activation of Saturated Hydrocarbons by Transition Metal Com-
plexes, D. Reidel, Dordrecht, 1984.
[8] S.S. Stahl, J.A. Labinger, J.E. Bercaw, Angew. Chem., Int. 37 (1998) 2180.
[9] K. Wang, M.E. Goldman, T.J. Emge, A.S. Goldman, J. Organomet. Chem. 518 (1996)
55.
[10] F. Liu, E.B. Pak, B. Singh, C.M. Jensen, A.S. Goldman, J. Am. Chem. Soc. 121 (1999)
4086.
•
data for 1k: 710 (M +) (52), 673 (100), 436 (29), 400 (21), 274 (53).
(1l) From 0.61 g (2 mmol) of 1-[[(4-butylphenyl)imino]
methylenyl]-2-naphthalenol and 0.23 g (1 mmol) ZrCl4 was
obtained an amount of 0.46 g (0.60 mmol, 60%) of 1l as a yellow
powder. NMR data for 1l: 1H NMR (250 MHz, 21 ◦C, CDCl3): 9.37 (s,
2H), 8.14–6.89 (m, 20H), 2,65 (t, 4H), 1,62 (quintett, 4H), 1,45–1,30
1
(m, 4H), 0.95 (t, 6H). 13C { H} (62 MHz, 21 ◦C, CDCl3): 136.1 (CH),
129.5 (CH), 129,2 (CH), 127.9 (CH), 123.4 (CH), 122.2 (CH), 120.2
(CH), 118.9 (CH), 35.1 (CH2), 33.6 (CH2), 22.3 (CH2), 13.7 (CH3). MS
[11] I. Go¨ttker-Schnetmann, P. White, M. Brookhart, J. Am. Chem. Soc. 126 (2004)
•
data for 1l: 766 (M +) (100), 731 (73), 631 (28), 464 (43), 302 (34).
1804.
[12] M.J. Burk, R.H. Crabtree, C.P. Parnell, R.J. Uriarte, Organometallics 3 (1984) 816.
[13] M.J. Burk, R.H. Crabtree, J. Am. Chem. Soc. 109 (1987) 8025.
[14] M. Gupta, C. Hagen, R.J. Flesher, W.C. Kaska, C.M. Jensen, Chem. Commun. (1996)
2083.
[15] J. Belli, C.M. Jensen, Organometallics 15 (1996) 1532.
[16] P. Braunstein, Y. Chauvin, J. Nahring, A. DeCian, J. Fischer, A. Tiripicchio, F. Ugoz-
zoli, Organometallics 15 (1996) 5551.
(1m) From 1.13 g (4 mmol) of 1-[[(2-chlorophenyl)imino]
methylenyl]-2-naphthalenol and 0.64 g (2 mmol) HfCl4 was
obtained an amount of 0.56 g (0.69 mmol, 34%) of 1m as a yellow
powder. NMR data for 1m: 1H NMR (250 MHz, 21 ◦C, CDCl3): 9.47
•
(s, 2H), 8.25–7.13 (m, 20H). MS data for 1m: 810 (M +) (37), 775
(46), 530 (61), 280 (100), 246 (64).
[17] W.-W. Xu, G.P. Rosini, M. Gupta, C.M. Jensen, W.C. Kaska, K. Krogh-Jespersen,
A.S. Goldman, Chem. Commun. (1997) 2273.
[18] H.R. Christen, F. Vo¨gtle, Grundlagen der organischen Chemie, 1st ed., Salle und
Sauerla¨nder, 1989.
[19] F. Chang, D. Zhang, G. Xu, H. Yang, J. Li, H. Song, W.-H. Sun, J. Organomet. Chem.
689 (2004) 936.
[20] X. Bei, D.C. Swenson, R.F. Jordan, Organometallics 16 (1997) 3282.
[21] M.J. Frazer, B. Rimmer, J. Chem. Soc. A: Inorg., Phys., Theor. (1968) 69.
[22] M.X. Qian, M. Wang, H. Wang, R. He, Chin. Chem. Lett. 13 (2002) 843.
[23] W. Kaminsky, A. Bark, R. Steiger, J. Mol. Catal. 74 (1992) 109.
[24] W. Kaminsky, R. Steiger, Polyhedron 7 (1988) 2375.
[25] A.R. Siedle, W.M. Lamanna, J.M. Olofson, B.A. Nerad, R.A. Newmark, Selectivity
in Catalysis, vol. 517, 1993.
(1n) From 1.26 g (4 mmol) of 1-[[(2,4-dimethylphenyl)imino]
methylenyl]-2-naphthalenol and 0.64 g (2 mmol) HfCl4 was
obtained an amount of 0.88 g (1.00 mmol, 50%) of 1n as a yellow
•
powder. MS data for 1n: 880 (M +) (2), 844 (3), 564 (2), 315 (100),
280 (64).
4.4. Synthesis of the alcoholate titanium and zirconium
complexes 2a and 2b
[26] R.F. Jordan, C.S. Bajgur, R. Willett, B. Scott, J. Am. Chem. Soc. 108 (1986)
7410.
[27] R.F. Jordan, W.E. Dasher, S.F. Echols, J. Am. Chem. Soc. 108 (1986) 1718.
[28] R.F. Jordan, C.S. Bajagur, W.E. Dasher, A.L. Rheingold, Organometallics 6 (1987)
1041.
[29] H. Sinn, Chem. Macromol. Symp. 97 (1995) 21.
[30] A.R. Barron, Organometallics 13 (1994) 2957.
[31] A.R. Barron, Macromol. Symp. 97 (1995) 15.
An amount of 5 mmol of the respective ligand precursor was
dissolved in 50 ml Et2O and 0.12 g (5 mmol) NaH was added at
0 ◦C. After completed hydrogen evolution, an amount of 2.5 mmol
MCl4 (M = Ti, Zr) was added and the solution was stirred for 24 h
at room temperature. The solvent was evaporated in vacuo; the
residue was suspended in CH2Cl2. After filtration over Na2SO4, the
solvent was evaporated. The residue was washed with 50 ml pen-
[32] E.Y.-X. Chen, T.J. Marks, Chem. Rev. 100 (2000) 1391.

56
S. Taubmann, H.G. Alt / Journal of Molecular Catalysis A: Chemical 289 (2008) 49–56
[33] W.P. Long, D.S. Breslow, Liebigs Ann. Chem. (1975) 463.
[34] L. Resconi, S. Bossi, L. Abis, Macromolecules 23 (1990) 4489.
[35] A. Nekhaeva, G.N. Bondarrenko, S.V. Rykov, A.I. Nekhaev, B.A.M.I. Krentsel, L.I.
Vyshinskaya, I.M.P. Khrapova, N.N. Korneev, J. Organomet. Chem. 406 (1991)
139.
[38] H.G. Alt, I.K. Bo¨hmer, Angew. Chem. 120 (2008) 2659;
H.G. Alt, I.K. Bo¨hmer, Angew. Chem. Int. Ed. Engl. 47 (2008) 2619.
[39] S. Taubmann, H.G. Alt, J. Mol. Catal. A: Chem. 284 (2008) 134.
[40] S. Taubmann, H.G. Alt, J. Organomet. Chem. 693 (2008) 1808.
[41] S. Taubmann, H.G. Alt, J. Mol. Catal. A: Chem. 287 (2008) 102.
[37] H.G. Alt, C.E. Denner, S. Taubmann, unpublished.