Synthesis, conformation analysis and catalytic properties of chiral zirconium complexes containing etherfunctionalized Cp ligands

Article abstract of DOI:10.1016/S0022-328X(99)00164-3

A novel series of chiral ligands was synthesized having a cyclopentadienyl (Cp) ring attached to an ether moiety. Four chiral monoCp zirconium derivatives contain these ligands in a bidentate Cp/O coordination mode. Complexes 4d, 6d, and 7d bear an aryl g

Full text of DOI:10.1016/S0022-328X(99)00164-3

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 274–285
Synthesis, conformation analysis and catalytic properties of chiral
zirconium complexes containing etherfunctionalized Cp ligands
Adolphus A.H. van der Zeijden *, Chris Mattheis
Institut fu¨r Anorganische Chemie, Martin-Luther-Uni6ersita¨t Halle-Wittenberg, Geusaer Straße, D-06217 Merseburg, Germany
Received 18 January 1999; received in revised form 19 February 1999
Abstract
A novel series of chiral ligands was synthesized having a cyclopentadienyl (Cp) ring attached to an ether moiety. Four chiral
monoCp zirconium derivatives contain these ligands in a bidentate Cp/O coordination mode. Complexes 4d, 6d, and 7d bear an
aryl group at the end of the ether chain. The racemic complexes 3d and 4d show moderate activity for the polymerisation of
ethylene. Complexes 6d and 7d are enantiopure and were used as asymmetric Lewis acid catalysts for the hydrocyanation of
benzaldehyde. The negligible enantiomeric excess thereby is due to decomplexation of the weakly coordinated aryl ether
side-chains during catalysis. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Zirconium; Cyclopentadienyl; Ethylene polymerisation; Hydrocyanation of benzaldehyde
(3)
1. Introduction
Monocyclopentadienyl (Cp) zirconium complexes
can be used both as Lewis acid catalysts in organic
synthesis [1], as well as Ziegler–Natta catalysts for the
polymerisation of a-olefins [2]. Chiral modifications of
the metal complex should allow the control of enan-
tioselectivity and polyolefin-stereoregularity on these
processes. However, the chiral modification of a Cp
ligand is hampered by its high fluctionality, which
makes it difficult to obtain a rigid chiral environment
required for asymmetric transformations [3]. We [4] and
others [5] are therefore investigating the use of func-
tional groups attached to the Cp ring capable of in-
tramolecular coordination, thus giving rise to a more
However, the combination of an amino side-chain
and an oxophilic element like zirconium makes 1 ex-
tremely hydrophilic, which limits its practical use as a
Lewis acid catalyst. Nevertheless, 1 catalyses the Diels–
Alder reaction, although with poor enantioselectivity.
rigid chelate. Following these guidelines we synthesised
Obviously, transfer of chirality from the chiral side-
a chiral monoCp zirconium complex based on the
natural compound ephedrine 1 [4b]:
chain through the relatively small NMe2 group to the
catalytic centre is ineffective in this arrangement.
We recently published the synthesis of an (achiral)
complex 2 bearing an ether side-chain [4d]. This com-
* Corresponding author. Tel.: 49-3461-462105; fax: +49-3461-
plex is much less water sensitive than 1, and it is even
462002.
E-mail address: zeijden@chemie.uni-halle.de (A.A.H. van der Zeij-
den)
possible to conduct Diels–Alder and hydrocyanation
reactions under aerobic conditions.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00164-3

A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
275
The substitution of two or more different substituents
onto a coordinated Cp ring creates an additional
stereogenic centre, and although the resulting metal
complex will be chiral, it is still racemic.
To obtain enantiomerically pure compounds, the lig-
and system either needs to be separated in enantiomers
(which will be difficult) or needs a source of enantiopu-
rity. In the present study this was accomplished either
by introducing a chiral substituent ((1R)-fenchyl) on
the terminal ether group [4c] or by a stereogenic carbon
in the ethylene bridge. In the latter case the terminal
methyl group was substituted for a larger aryl group in
order to amplify the chirality more effectively into the
metal coordination sphere.
Fig. 1. Detail from the X-ray structure of 2 [4d].
2. Results and discussion
The bidentate cyclopentadiene ligand C5H5CH2-
CH2OMe (3a) was synthesised by published methods
[8]. The phenyl-substituted analogue C5H5CH2CH2OPh
(4a) was synthesised by a straightforward reaction be-
tween CpNa and BrCH2CH2OPh. The synthesis of the
chiral ligand C5H5CH2CH2OC10H17 [5a; C10H17=(1R)-
fenchyl] has been published1 recently by us [4c]. The
syntheses of the enantiomerically pure aryl ligands (R)-
C5H5CH2CH(Me)OAr [ArꢀPh (6a), C6H4-4-OMe (7a),
a-naphthyl (8a)] were based on (S)-ethyl lactate as a
starting material (Scheme 1). The conversion to the
A closer look at the crystal structure of 2 reveals a
puckered, and therefore chiral, arrangement of the side-
chain (Fig. 1). In solution, the complex rapidly swings
between the two enantiomeric extremes via a wind-
screen-wiper-wise rotation around the Zr–O axis. Fix-
ing the geometry in one of the extreme conformations
would yield a genuine chiral complex. There are several
options for doing this. First, introducing one or more
substituents onto the Cp ring should favour one of the
enantiomers more than the other, creating a more static
chiral puckering of the side-chain. In the current work,
this was accomplished by substituting two bulky Me3Si
groups in 2,4-position onto the Cp ring [6] (a 1-substi-
tuted indenyl ligand would have the same function) [7].
1
Scheme 1.

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A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
Scheme 2.
Table 1
1H-NMR data for the SiMe3 derivatives of the Cp ligandsa
Compound
Me
–
C(H)O
3.52(t, 7.1)
4.13
CH2
C5Hx ring
OR
SiMe3
C5H4(CH2CH2OMe)(SiMe3) (3b)
C5H4(CH2CH2OPh)(SiMe3) (4b)
C5H4(CH2CH2Ofenchyl)(SiMe3) (5b)
C5H4(CH2CH(Me)OPh)(SiMe3) (6b)
2.68 (t, 7.1)
2.93
3.26, 6.13, 3.33
6.42, 6.46
3.34, 6.24, 6.93 (3H), 7.27 (2H) −0.02
6.48, 6.55
3.26, 6.12,
6.41, 6.49
−0.06
–
b
–
3.49/3.62 (m) 2.65 (m)
−0.06
1.34
1.30
1.45
–
4.57 (m)
2.70/2.91 (m) 3.31, 6.22, 6.93 (3H), 7.28 (2H) −0.02
6.47, 6.56
C5H4(CH2CH(Me)OC6H4-4-OMe)
(SiMe3) (7b)
C5H4(CH2CH(Me)O-a-naphthyl)
(SiMe3) (8b)
4.42 (m)
2.65/2.90 (m) 3.29, 6.21, 3.74 (3H), 6.84 (4H) −0.01
6.47, 6.54
4.78 (m)
2.82/3.03 (m) 3.30, 6.26, 6.85 (1H), 7.4 (4H),
6.46, 6.60 7.78 (1H), 8.34 (1H)
2.70(t, 7.2)
−0.05
C5H3(CH2CH2OMe)(SiMe3)2 (3c)
3.47 (t, 7.2)
4.09(t, 7.1)
6.13, 6.40, 3.33
6.54
6.24, 6.45, 6.92 (3H), 7.27 (2H) −0.06 (18H)
6.63
6.12, 6.38,
6.56
−0.10 (18H)
C5H3(CH2CH2OPh)(SiMe3)2 (4c)
C5H3(CH2CH2Ofenchyl)(SiMe3)2 (5c)
C5H3(CH2CH(Me)OPh)(SiMe3)2 (6c)
–
2.93(t, 7.1)
–
3.46/3.57 (m) 2.66 (m)
b
−0.10 (18H)
1.32(d, 6.0) 4.53 (m)
1.28(d, 5.9) 4.40 (m)
1.45(d, 6.1) 4.77 (m)
2.68/2.93 (m) 6.21, 6.44, 6.91 (3H), 7.27 (2H) −0.06, −0.07
6.61
C5H3(CH2CH(Me)OC6H4-4-OMe)
(SiMe3)2 (7c)
C5H3(CH2CH(Me)O-a-naphthyl)
(SiMe3)2 (8c)
2.65/2.90 (m) 6.20, 6.44, 3.74 (3H), 6.82 (4H) −0.06, −0.07
6.61
2.86/3.07 (m) 6.28, 6.45, 6.88 (1H), 7.4 (4H),
6.68 7.79 (1H), 8.34 (1H)
−0.05, −0.08
a In CDCl3; all signals (broad) singlets, unless stated otherwise; coupling in Hz in parentheses; the signals for the mono(Me3Si) derivatives were
all slightly broadened.
b Characteristic fenchyl signals at 2.88 (OCH) and 0.89, 1.01, 1.07 (all s, Me).
ing to NMR, although the broadening of the signals
indicates mobility of the Me3Si group. The patterns of
the 1H- and 13C-NMR signals (Tables 1 and 2) are
consistent with an 2-alkyl-5-Me3Si substituted Cp ring.
Compounds 3c–8c also exist as a single isomer. In this
case, the NMR signals are in accord with a 2-alkyl-5,5-
bis(Me3Si) substituted Cp ring.
Deprotonation of 3c and 4c by n-BuLi and the
stoichiometric reaction with ZrCl4 in diethyl ether af-
ford the monoCp zirconium complexes 3d and 4d
(Scheme 3) in good yield. Due to the steric congestion
of the Cp ligands there is no formation of metallocenes
mesylate ester and their SN2-substitution by phenolates
were developed by Burkard and Effenberger [9]. The
chiral esters were reduced to the alcohols by LiAlH4 in
83–90% yield. The alcohols were esterified by me-
sylchloride, and subsequent reaction with CpNa affords
the chiral Cp ligands 6a–7a in 54–60% yield after
distillation (8a could not be distilled without decompo-
sition due to its high boiling point).
The syntheses of the mono- and bis(trimethylsi-
lyl)derivatives 3b–8b and 3c–8c were accomplished by
consecutive reactions with nBuLi and Me3SiCl (Scheme
2). Compounds 3b–8b exist as a single isomer accord-

A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
277
1
by this method. From the analogous reaction with the
fenchyl-substituted ligand 5c we could not isolate a
similar complex. It is possible that C–O bond cleavage
of the bulky ether moiety by the Lewis acidic zirconium
centre is a serious side-reaction here [4d].
ABXY spin system in the H-NMR spectrum for the
ethylene moiety, and by the appearance of two signals
for the Me3Si groups in the H- and 13C-NMR spec-
1
trum. Therefore, the three substituents on the Cp ring
are in an 1,3-bis(Me3Si)-4-alkyl arrangement. In-
tramolecular coordination of the ether side-chain in 3d
is deduced from the low-field 13C-shifts of the CH2O-
moiety (9 ppm) and of the OCH3-moiety (5 ppm) with
respect to those signals in the starting compounds 3a–c.
These coordination shifts are very similar to those of 2
[4d].
Due to the presence of two Me3Si groups on the Cp
ring, compounds 3d and 4d are much more soluble than
2; they even show moderate solubility in pentane. They
are hygroscopic colourless solids that were character-
1
ised by elementary analysis and by their H- and 13C-
NMR spectra in CDCl3 (Tables 3 and 4). As for 2,
compounds 3d and 4d (and 6d, 7d vide infra) are
probably chloride-bridged dimers in the solid state, but
monomeric in solution. The lack of a plane of symme-
try in the molecules is indicated by the presence of an
In 4d there is an even larger similar low-field 13C shift
of the CH2O-moiety of about 14 ppm. In addition, the
phenyl group only shows low-field 13C shifts for the
ortho and para carbons of about 6 and 5 ppm, respec-
Table 2
13C-NMR data for the SiMe3 derivatives of the Cp ligandsa
Compound
Me
C(H)O CH2
C5Hx ring
OR
SiMe3
C5H4(CH2CH2OMe)(SiMe3) (3b)
C5H4(CH2CH2OPh)(SiMe3) (4b)
C5H4(CH2CH2Ofenchyl)(SiMe3) (5b)
C5H4(CH2CH(Me)OPh)(SiMe3) (6b)
–
72.8
30.1
51.2, 128.4, 132.0,
133.8, 141.7
51.53, 128.92, 131.89,
134.11, 141.03
51.17, 128.3, 132.5,
133.6, 141.8
51.23, 129.69, 132.45,
134.02, 141.13
51.09, 129.41, 132.30,
133.74, 141.10
51.23, 129.72, 132.54,
133.98, 141
53.1, 131.8, 132.3,
136.5, 142.1
58.3
−2.19
–
67.76
72.11
73.58
74.69
73.83
73.4
29.82
30.81
36.44
36.51
36.45
29.9
114.55, 120.53, 129.38,
−2.05
158.92d
b
–
−2.05
19.48
19.54
19.31
–
115.84, 120.45, 129.46,
157.99d
55.32, 114.43, 117.17,
−2.18
C5H4(CH2CH(Me)
−2.15
OC6H4-4-OMe)(SiMe3) (7b)
C5H4(CH2CH(Me)O-a-naphthyl)
(SiMe3) (8b)
151.80, 153.67
c
−2.27
C5H3(CH2CH2OMe)(SiMe3)2 (3c)
58.4
−1.0
C5H3(CH2CH2OPh)(SiMe3)2 (4c)
C5H3(CH2CH2Ofenchyl)(SiMe3)2 (5c)
C5H3(CH2CH(Me)OPh)(SiMe3)2 (6c)
–
68.06
72.5
29.67
30.6
56.2, 131.99, 132.17,
136.72, 141.50
51.2, 131.5, 132.7,
136.2, 142.9
54.2, 132.54, 132.91,
136.68, 141.63
55.4?, 132.32, 132.55,
136.33, 141.51
114.56, 120.48, 129.35,
−0.81
158.93d
b
−1.0
19.53
19.49
19.38
73.97
74.99
74.27
36.29
36.25
36.30
115.93, 120.47, 129.50,
158.08d
55.41, 114.42, 117.18,
−0.87, −0.91
−0.88, −0.92
−0.87, −0.94
C5H3(CH2CH(Me)OC6H4-4-
OMe)(SiMe3)2 (7c)
C5H3(CH2CH(Me)O-a-naphthyl)
(SiMe3)2 (8c)
151.79, 153.59
c
56.2?, 132.71, 133.06,
136.70, 141.59
a In CDCl3.
b Fenchyl signals at 20.0/20.7 (C9/10), 25.9/26.1 (C5/6), 31.7 (C8), 39.4 (C3), 41.4 (C7), 48.7 (C4), 49.1 (C1), 93.1 (C2).
c The naphthyl-group has signals between 105 and 155 ppm; due to the presence of impurities (see text) not all signals could be unambiguously
assigned.
d Ortho, para, meta, ipso carbons, respectively.
Scheme 3.

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Table 3
1H-NMR data for the zirconium compoundsa
Compound
CH(CH3)
CH2CHxO
CH2CHxO
C5H2 OR
SiMe3
0.34
[C5H2(CH2CH2OMe}(SiMe3)2]ZrCl3 (3d)
–
4.24 (‘dt’,
8.9×5)
4.44 (‘q’,
8.7)
3.04 (2H, ‘t’, 6.4)
6.75
6.87
3.73 (s, 3H)
0.36
[C5H2(CH2CH2OPh)(SiMe3)2]ZrCl3 (4d)
–
4.61 (‘dt’,
8.9×5)
4.88 (‘dt’,
5.4×8.8)
3.12 (‘dt’,
14.2×5.0)
3.23 (ddd,
14.2×8.6×6.2)
6.82
7.03
7.1–7.3 (m, 5H) 0.34
0.42
[C5H2(CH2CH(Me)OPh)(SiMe3)2]ZrCl3 (6d)
(major isomer)
(minor isomer)
1.29 (d, 6.2)
1.18 (d. 5.6)
5.18 (m)
5.32 (m)
3.02 (dd, 14.1×8.6) 6.91
3.25 (dd, 14.1×5.1) 6.93
3.10 (dd, 14×11.3)b 6.81
3.19 (dd, 14×4.3)b 7.07
7.1–7.3 (m)
7.1–7.3 (m)
0.33
0.40
0.33b
0.44
[C5H2(CH2CH(Me)OC6H4-4-OMe}(SiMe3)2]
1.28 (d, 6.2)
1.16 (d, 5.9)
5.19 (m)
5.35 (m)
2.97 (dd, 13.9×8.2) 6.89
6.78 (2H), 7.20
(2H)
0.34
ZrCl3 (7d)
(major isomer)
(minor isomer)
3.25 (dd, 13.9×5.0) 6.91
3.76 (3H)
0.40
0.34b
0.44
3.06 (dd, 14×11.5)b 6.8?b 6.8b, 7.2b
3.20 (dd, 14×3.9)b 7.07
3.74 (3H)
a In CDCl3; coupling in Hz in parentheses
b Poorly resolved.
Table 4
13C-NMR data for the zirconium compoundsa
Compound
Me
C(H)O
C2
Cp (2×CH, 3×C)
129.70, 130.81,
133.90, 137.03, 142.87
129.6, 131.46,
134.94, 137.31, 141.24
129.44, 133.48,
134.4, 137.87, 141.92
128.18, 131.74,
133.5?, 138.8, 141.4
129.48, 133.66
(2x?), 137.79, 141.76
128.12, 131.41,
OR
SiMe3
[C5H2(CH2CH2OMe}(SiMe3)2]ZrCl3 (3d)
[C5H2(CH2CH2OPh)(SiMe3)2]ZrCl3 (4d)
[C5H2(CH2CH(Me)OPh)(SiMe3)2]ZrCl3 (6d)
Idem, minor isomerb
–
82.40
82.40
87.61
87.6?
90.36
89.88
27.48
28.55
36.83
36.62
36.58
36.40
64.18
0.01, 0.23
–
120.64, 125.66,
129.61, 159.27c
122.86, 125.49,
129.28, 155.61c
123.22, 125.5?,
−0.08, 0.29
−0.19, 0.11
−0.27, 0.29
−0.09, 0.14
−0.19, 0.32
20.31
20.25
129.3?, 155.6?c
[C5H2(CH2CH(Me)OC6H4-4-OMe}(SiMe3)2] 20.38
55.48, 114.11,
ZrCl3 (7d)
124.90, 148.76, 157.49d
55.48, 114.05,
Idem, minor isomerb
20.22
133.7?, 138.92, 141.55
125.14, 148.8?, 157.5?d
a In CDCl3.
b Incomplete data due to severe overlap with signals of the major isomer.
c Ortho, para, meta, ipso carbons, respectively.
d OMe, Meta, ortho, ipso, para carbons, respectively.
tively. In contrast, the 13C chemical shifts of the ipso
and meta carbons hardly change upon coordination
(B0.5 ppm). This interesting phenomenon is obviously
a result of mesomeric effects. As the ether group coor-
dinates to the zirconium centre, electron density is
withdrawn from the oxygen atom. Because of reso-
nance this also results in a decrease of electron density
in the ortho and para positions of the phenyl ring and
consequently in a low-field shift for these carbons.
Similar observations were made for instance for the
AlCl3 adduct of MeOPh: the methyl, ortho and para
carbons of the phenyl ring show down-field shifts of 14,
7 and 7 ppm, respectively, in the 13C-NMR spectrum
upon complexation [10].
The conformation of the chelate rings in 3d and 4d
can be deduced from the coupling patterns of the
1
ethylene hydrogens in the H-NMR spectra, that of 4d
being better resolved as that for 3d (Fig. 2 and Table 3).
As for 2, there exist two conformations for the chelate
rings in 3d and 4d (A and B in Fig. 2), but in contrast
to 2 they are not equally likely. This is best seen by the
3JHH couplings: uniform values of about 6–7 Hz (cf. 6.3
Hz in 2) would be expected when conformations A and
B were equally abundant. Since both larger (8.6 Hz)

A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
279
Fig. 2. Conformation analysis on 4d.
and smaller (4 Hz) 3JHH couplings are observed, there is
clearly a preference for one of the conformers. A closer
inspection of the two conformers (Fig. 3) reveals that
there is an unfavourable interference between the
ethylene bridge and the adjacent Me3Si group in con-
formation B, and therefore we believe that 4d and also
3d mainly reside in conformation A. This is corrobo-
rated by molecular modelling studies (PCMODEL), which
predict a somewhat lower energy for conformation A.
When 4d is dissolved in methanol, the coordination
of the ether side chain is lost and a bis(methanol)
solvate is formed (Fig. 2), reminiscent of 2. The en-
hanced mobility of the side chain is nicely seen by the
3JHH couplings which now show a uniform value of 6.9
Hz, being consistent with a more or less free rotation
around the C–C(O) bond.
The enantiomerically pure zirconium compounds 6d
and 7d were prepared from 6c and 7c in a similar way
as for 3d and 4d (Scheme 4). Reactions with the naph-
thyl derivative 8c were unsuccessful. It is possible that
the steric bulk of the naphthyl group prevents the
formation of a stable monoCp zirconium compound.
Compounds 6d and 7d contain a stereogenic carbon
in the chelate ring having R configuration. Because the
triple substituted Cp ring presents a further stereogenic
centre, there are two possible diastereomers. Appar-
ently, the enantiopure carbon in the chelate ring exerts
46% diastereoselectivity on the coordination mode of
the Cp rings, since the two diastereomers are present in
a 73:27 ratio for both 6d and 7d. An explanation for
this diastereoselectivity is hampered by the complexity
of the mechanism of the transmetallation of the biden-
tate ligand, which is largely unknown. For the same
reason one cannot be completely sure whether the
observed diastereomer ratio reflects the difference in the
thermodynamical stability of the two isomers, moreover
since there appears to be no dynamic equilibrium be-
tween the two in solution.
There are four different conformations possible for
the chelate rings in 6d and 7d (two for each
diastereomer). However, conformations A1 and A2 in
Fig. 4 can be ruled out since the methyl groups in the
side chain are in a very unfavourable position. There-
fore, these methyl groups will be trans-positioned to the
Cp unit, and this is corroborated by the coupling
1
patterns of the bridgehead hydrogens in the H-NMR
spectra (Fig. 4). Similar conformations are also found
in Ca[(S)–C5H4CH2CH(R)OMe]2, with R=Me or Ph
[5g]. The conformations of 6d and 7d are therefore
Fig. 3. Possible conformations of 3d and 4d, showing preference for
conformation A over that of B on steric grounds.

280
A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
Scheme 4.
Fig. 4. Conformation analysis on 6d.
much more soluble than 2, the activity of 2 is the same
[4d]. We believe that the strong coordination of the
ether moiety in these compounds saturates the zirco-
nium centre too much, for a significant Ziegler–Natta
ruled by the stereogenic carbon in the chelate ring and
not by the position of the Me3Si groups like in 3d and
4d. However, for the same reasons as in 3d and 4d, it is
obvious that diastereomer B2 is more stable than B1
(Fig. 5), and it is assumed that B2 is the prevalent
isomer. It is noted that for both of the diastereomers of
6d and 7d the aryl group points in the same direction,
and therefore it is expected that during a Lewis acid
catalysed reaction, both diastereomers should exert the
same asymmetric effect on the chiral products.
Compounds 3d and 4d were tested for their activity
on the polymerisation of ethylene. The activity is ca
50–100 g polyethylene/mmol Zr/h/bar ethylene, which
is rather moderate, compared to CpZrCl3 (ca. 1000) or
Cp2ZrCl2 (\10 000) [2b]. Although 3d and 4d are
Fig. 5. Possible conformations of the two diastereomers of 6d,
showing preference for conformation B2 over that of B1.

A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
281
Scheme 5.
Scheme 6.
activity to develop. This is further corroborated by the
fact that the sulphur-analogue of 2 shows significantly
better activity (400), which can be attributed to the
poorer coordination of the thioether to zirconium [11].
As 2 is known to be an active Lewis acid catalyst, we
tested the analogous, chiral complexes 6d and 7d as a
hydrocyanation catalyst (Scheme 5) [12].
solvents like acetone-d6 (68.7 ppm), thf-d8 (69.8),
CD3CN (69.0) and CD3OD (69.6) the aryl ether–zirco-
nium bond in 4d is also broken, whereas in the non-co-
ordinating solvent C6D6 (80.9) it is not (Scheme 6). In
contrast, the coordination of the alkyl ether side-chain
in 3d (and 2) is only broken in methanol-d4, but not in
the other solvents [13]. This sensitivity towards a wide
variety of functional groups of course precludes the use
of the aryl ether complexes 6d and 7d as chiral Lewis
acid catalysts.
Although both zirconium complexes catalyse the re-
action between benzaldehyde and Me3SiCN very well,
the resulting alcohol that was obtained after hydrolysis,
was not enantiomerically enriched. This result was
somewhat surprising, since it might have been expected
that the asymmetric position of the bulky aryl ether
moiety should have some influence on the enantioselec-
tivity. To explain this, we investigated the reaction of
3. Conclusions
Compounds 3d, 4d, 6d, 7d present a unique class of
chiral mono(Cp) zirconium complexes having ether
side-chains attached to the Cp ring. Despite the
renowed oxophilicity of zirconium, the coordination of
the aryl-substituted side-chains in 4d, 6d, and 7d is very
weak compared to that in the alkyl-substituted com-
plexes 3d and 2. Actually, without being supported by
the rigid coordination of the Cp ring, stable coordina-
tion of the aryl ether moieties in the former compounds
does not seem possible. We are currently designing
chiral Cp ligands having SPh and especially PPh2 side-
chains, since the electron-withdrawing effect of the aryl
group should have less effect on the donor capability of
these heavier donor elements.
1
the model compound 4d with benzaldehyde by H- and
13C-NMR. Adding 1–2 equivalents of benzaldehyde
causes severe broadening of all signals for 4d. Upon
addition of five or more equivalents of benzaldehyde,
the signals sharpen up again, but show large differences
compared to the starting situation. Especially, those 13
C
shifts that are characteristic for the coordination of the
ether moiety have returned to the values which they
had in the (noncoordinating) Me3Si precursors, e.g.
72.1 ppm for CH2O, 116.4 ppm for the ortho-phenyl
carbon, and 122.0 ppm for the para-phenyl carbon.
Apparently, under catalytic conditions, with a large
excess of benzaldehyde, the ether moiety is not coordi-
nated anymore and will bent away from the reaction
centre. Transfer of chirality in this arrangement during
catalysis is very unlikely.
4. Experimental
Obviously, the aryl ether moieties in 4d, 6d, and 7d
are much less strongly coordinated than the alkyl ether
groups in 2 and 3d. As can be deduced from the 13C
chemical shift of the CH2O moiety, in coordinating
All manipulations were carried out under an atmo-
sphere of argon using Schlenk glassware. Solvents were
dried and degassed by conventional procedures prior to

282
A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
use—1H- and 13C-NMR: Varian Gemini 300. The H-
and 13C-NMR spectra were measured in CDCl3 unless
stated otherwise (CHCl3: lH=7.24; CDCl3: lC=77.0)
The combustion analyses (C,H) were performed on a
CHNS-932 LECO analyser in our department (consis-
tently lower carbon contents for our zirconium com-
plexes (1–2%) were attributed to the formation of
zirconium carbides during analysis). (R)-EtOOC-
CH(Me)OAr (ArꢀPh, C6H4-4-OMe, a-naphthyl) and
C5H5CH2CH2OMe (3a) were synthesised according to
Refs. [9] and [8], respectively.
4.2.2. (R)–HOCH2CH(Me)OC6H4-4-OMe
1
Pale yellow oil: yield: 83%. 1H-NMR: l=1.20 (d, 6.2
Hz, 3H, CCH3), 3.66 (m, 2H, CH2OH), 3.74 (s, 3H,
OCH3), 4.33 (m, 1H, CHOaryl), 6.82 (m, 4H, aryl-H).
13C-NMR: l=15.47 (CH3), 55.23 (OCH3), 65.65
(CH2OH), 75.67 (CHOaryl), 114.45, 117.55, 151.50,
154.02 (aryl-C).
4.2.3. (R)–HOCH2CH(Me)O-h-naphthyl
1
Greyish oil: yield: 90%. H-NMR: l=1.34 (d, 6.2
Hz, 3H, CH3), 3.85 (m, 2H, CH2OH), 4.69 (m, 1H,
CHOaryl), 6.88 (d, 7.5 Hz, 1H, naphthyl-H), 7.37 (m,
1H, naphthyl-H), 7.45 (m, 3H, naphthyl-H), 7.81 (m,
1H, naphthyl-H), 8.27 (m, 1H, naphthyl-H). 13C-NMR:
l=15.68 (CH3), 66.23 (CH2OH), 75.13 (CHOaryl),
106.89 (naphthyl-C2), 120.68 (naphthyl-C4), 121.95
(naphthyl-C8), 125.27 (naphthyl-C7), 125.83 (naphthyl-
C3), 126.40 (naphthyl-C6), 126.45 (naphthyl-C9), 127.61
(naphthyl-C5), 134.77 (naphthyl-C10), 153.39 (naphthyl-
C1).
4.1. C5H5CH2CH2OPh (4a)
To a solution of CpNa prepared from 3.35 g (146
mmol) of sodium and 13.5 ml (164 mmol) cyclopentadi-
ene in 100 ml of THF, 24.5 g (120 mmol) of
PhOCH2CH2Br was added. After refluxing for 3 h, a
few ml of water was added and the mixture was evapo-
rated to dryness. The residue was extracted with pen-
tane; the pentane extracts were concentrated in vacuo
and the residue was distilled at 200–220°C at 4 mmHg
affording 9.9 g (53 mmol, 44%) of C5H5CH2CH2OPh.
The pale yellow oil was a 1: 1 mixture of two regioiso-
mers. (1H-NMR: l=2.95 (m, 2H, C5H5CH2), 3.05 (s,
2H, C5H5-aliphatic), 4.19 (m, 2H, CH2O), 6.23, 6.38,
6.52, 6.59 (sbr, 3H, C5H5-olefinic), 7.0 (m, 3H, Ph), 7.35
(m, 2H, Ph). 13C-NMR: l=29.79, 30.39 (C5H5CH2),
41.41, 43.75 (C5H5-aliphatic), 67.09, 67.52 (CH2O),
127.74, 128.05, 131.28, 132.34, 133.88, 134.55, 142.99,
145.17 (C5H5-olefinic), 114.50 (o-Ph), 120.58 (p-Ph),
129.35 (m-Ph), 158.80 (ipso-Ph).
4.3. (R)–MeSO3CH2CH(Me)Oaryl (aryl=Ph, C6H4-
4-OMe, h-naphthyl)
4.3.1. (R)–MeSO3CH2CH(Me)OPh
A
solution of 8.60 g (56.6 mmol) of (R)–
HOCH2CH(Me)OPh and 10 ml (72 mmol) of Et3N in
100 ml of CH2Cl2 was cooled to −40°C, upon which
4.8 ml (62 mmol) of MeSO2Cl was added. The colour-
less suspension that formed was stirred for 30 min at
room temperature. Than, water was added resulting in
the formation of two clear, layered solutions. The
CH2Cl2 layer was washed with water several times, than
separated and dried over Na2SO4. Filtration and re-
moval of solvent gave an almost quantitative yield
(12.82 g, 55.8 mmol, 99%) of (R)–MeSO3-
CH2CH(Me)OPh as a pale yellow-brown oil. This ma-
4.2. (R)–HOCH2CH(Me)Oaryl (aryl=Ph, C6H4-4-
OMe, h-naphthyl)
1
terial was used without further purification. H-NMR:
4.2.1. (R)–HOCH2CH(Me)OPh
l=1.34 (d, 6.2 Hz, 3H, CH3), 3.00 (s, 3H, O3SCH3),
4.31 (m, 2H, CH2O), 4.64 (m, 1H, CHOPh), 6.89 (m,
3H, Ph), 7.27 (m, 2H, Ph). 13C-NMR: l=16.03 (CH3),
37.54 (O3SCH3), 71.7 (CH2O and CHOPh), 116.13
(o-Ph), 121.74 (p-Ph), 129.76 (m-Ph), 157.2 (ipso-Ph).
Other mesylates were prepared similarly.
To a solution of 12.92 g (66.6 mmol) of (R)-EtOOC-
CH(Me)OPh in 100 ml of ether was carefully added
small portions of LiAlH4 (waterbath cooling and con-
densor). After 6 h of stirring and the addition of 6.9 g
LiAlH4 the reaction was complete. Water was added
very carefully and than concentrated HCl. The aqueous
layer was extracted with ether; the combined ether
extracts were dried over Na2SO4 and than evaporated
to dryness affording spectroscopically pure (R)–
HOCH2CH(Me)OPh (8.60 g, 56.6 mmol, 85%) as a pale
yellow oil. This material was used without further
4.3.2. (R)–MeSO3CH2CH(Me)OC6H4-4-OMe
1
Pale yellow oil: yield: 100%. H-NMR: l=1.28 (d,
6.2 Hz, 3H, CCH3), 2.99 (s, 3H, O3SCH3), 3.72 (s, 3H,
OCH3), 4.27 (m, 2H, CH2O), 4.47 (m, 1H, CHOaryl),
6.82 (m, 4H, aryl-H). 13C-NMR: l=15.97 (CH3), 37.37
(O3SCH3), 55.46 (OCH3), 71.77 (CH2O), 72.93
(CHOaryl), 114.71, 117.81, 151.08, 154.64 (aryl-C).
1
purification. H-NMR: l=1.25 (d, 6.1 Hz, 3H, CH3),
3.72 (m, 2H, CH2OH), 4.49 (m, 1H, CHOPh), 6.93 (m,
3H, Ph), 7.27 (m, 2H, Ph). 13C-NMR: l=15.66 (CH3),
66.28 (CH2OH), 74.69 (CHOPh), 116.19 (o-Ph), 121.30
(p-Ph), 129.67 (m-Ph), 157.8 (ipso-Ph). Other alcohols
were prepared similarly.
4.3.3. (R)–MeSO3CH2CH(Me)O-h-naphthyl
1
Pale orange oil: yield: 92%. H-NMR: l=1.45 (d,
6.2 Hz, 3H, CH3), 2.95 (s, 3H, O3SCH3), 4.44 (m, 2H,

A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
283
CH2O), 4.86 (m, 1H, CHOaryl), 6.87 (d, 7.5 Hz, 1H,
naphthyl-H), 7.37 (m, 1H, naphthyl-H), 7.46 (m, 3H,
naphthyl-H), 7.80 (m, 1H, naphthyl-H), 8.25 (m, 1H,
naphthyl-H). 13C-NMR: l=16.19 (CH3), 37.62
(O3SCH3), 71.60/72.07 (CH2O and CHOaryl), 106.90
(naphthyl-C2), 121.20 (naphthyl-C4), 121.93 (naphthyl-
C8), 125.47 (naphthyl-C7), 125.72 (naphthyl-C3), 126.27
(naphthyl-C9), 126.54 (naphthyl-C6), 127.58 (naphthyl-
C5), 134.75 (naphthyl-C10), 152.79 (naphthyl-C1).
4H, CH2 and C5H5-aliphatic), 4.79 (m, 1H, CHOaryl),
6.19, 6.30, 6.34, 6.45, 6.57 (sbr, 3H in total, C5H5-
olefinic), 6.85 (m, 1H, naphthyl-H), 7.35–7.55 (m, 4H,
naphthyl-H), 7.80 (m, 1H, naphthyl-H), 8.31 (m, 1H,
naphthyl-H). 13C-NMR: l=19.60 (CH3), 36.68, 37.49
(CH2CO), 41.38, 44.12 (C5H5-aliphatic), 73.56, 73.88
(CHOaryl), 128.72, 128.94, 131.52, 132.28, 133.79,
134.94, 142.94, 145.1 (C5H5-olefinic), 105.9 (naphthyl-
C2), 119.89 (naphthyl-C4), 122.27/122.35 (naphthyl-C8),
124.94 (naphthyl-C7), 125.81 (naphthyl-C3), 126.21
(naphthyl-C6), 127.38 (naphthyl-C5), 134.69/134.94
(naphthyl-C10), 153.51 (naphthyl-C1), signals for C9
could not be assigned unambiguously.
4.4. (R)–C5H5CH2CH(Me)Oaryl (aryl=Ph, C6H4-4-
OMe, h-naphthyl)
4.4.1. (R)–C5H5CH2CH(Me)OPh
4.5. C5H4(CH2CH2OPh)(SiMe3) (4b) and C5H3(CH2-
CH2OPh)(SiMe3)2 (4c)
To a precooled (−40°C) solution of CpLi in 150 ml
THF obtained by reacting 6.0 ml (73 mmol) of CpH
and 40.0 ml of 1.78 M solution of nBuLi in hexane
(71.2 mmol), was added 12.82 g (56.6 mmol) (R)–
MeSO3CH2CH(Me)OPh. Upon raising the tempera-
ture, a brick-red suspension formed that was stirred
overnight at room temperature. After addition of a few
ml of water, the volatiles were removed in vacuo. The
residue was extracted with pentane and the pentane
extracts were evaporated to dryness in vacuo. The
residue was distilled at 200°C (3 mmHg) affording 6.10
g (30.5 mmol, 54%) of (R)-C5H5CH2CH(Me)OPh as a
pale yellow oil. It exists as a 1:1 mixture of regioiso-
A solution of 6.0 g (32 mmol) of 4a in 30 ml of THF
was cooled to −30°C and 19.5 ml of nBuLi in hexane
(1.78 M, 34.7 mmol) was added. After stirring for 15
min at room temperature, the solution was cooled
again to −30°C and 4.6 ml (36.4 mmol) of Me3SiCl
was added. A precipitate (LiCl) formed and after stir-
ring for 2 h at room temperature a solution containing
virtually pure 4b had formed (NMR data in Tables 1
and 2). After cooling the previous solution to −30°C
23.5 ml of nBuLi in hexane (1.78 M, 41.8 mmol) was
added. After stirring for 30 min at room temperature
the mixture was cooled again to −30°C and 6.0 ml
(47.4 mmol) of Me3SiCl was added. After stirring for 2
h at room temperature a few drops of water were
added, the mixture was filtered and the filtrate was
evaporated to dryness affording 9.5 g (28.8 mmol, 90%)
of spectroscopically pure 4c (NMR data in Tables 1
and 2). The oily substance could not be distilled with-
out decomposition and was therefore used without
further purification. The other SiMe3 derivatives
1
mers. H-NMR: l=1.29 (m, 3H, CH3), 2.6–2.9 (m,
2H, CH2), 2.95 (s, 2H, C5H5-aliphatic), 4.54 (m, 1H,
CHOPh), 6.11, 6.26, 6.41, 6.48 (sbr, 3H in total C5H5-
olefinic), 6.90 (m, 3H, Ph), 7.26 (m, 2H, Ph). 13C-NMR:
l=19.56, 19.58 (CH3), 36.59, 37.38 (CH2CO), 41.28,
44.02 (C5H5-aliphatic), 73.35, 73.66 (CHOPh), 128.65,
128.92, 131.50, 132.38, 133.81, 135.02, 143.10, 145.22
(C5H5-aliphatic), 115.94, 116.04 (o-Ph), 120.63, 120.66
(p-Ph), 129.51, 129.54 (m-Ph), 158.03, 158.07 (ipso-Ph).
Other Cp ligands were prepared similarly.
C5H(5−x)(CH2CH2OR)(SiMe3)x
(x=1,2;
R=Me
(3b,c), fenchyl (5b,c)) and (R)–C5H(5−x)(CH2CH-
(Me)OR)(SiMe3)x (x=1,2; R=Ph (6b,c), C6H4OMe
(7b,c), a-naphthyl (8b,c)) were prepared and handled
similarly. Yields were essentially quantitative. The a-
4.4.2. (R)–C5H5CH2CH(Me)OC6H4-4-OMe
Yellow oil: b.p. 240°C (3 mmHg). Yield: 60%. H-
1
NMR: l=1.28 (m, 3H, CH3), 2.5–2.9 (m, 2H, CH2),
2.96 (s, 2H, C5H5-aliphatic), 3.76 (s, 3H, OCH3), 4.43
(m, 1H, CHOaryl), 6.12, 6.27, 6.29, 6.43, 6.50 (sbr, 3H
in total, C5H5-olefinic), 6.83 (sbr, 4H, aryl-H). 13C-
NMR: l=19.79 (CCH3), 36.74, 37.52 (CH2CO), 41.39,
44.11 (C5H5-aliphatic), 55.66 (OCH3), 74.63, 74.91
(CHOaryl), 128.56, 128.79, 131.43, 132.34, 133.77,
134.95, 143.13, 145.32 (C5H5-olefinic), 114.64, 117.37/
117.52, 151.94, 153.90 (aryl-C).
1
naphthyl derivatives were impure (see above). The H-
and 13C-NMR data are given in Tables 1 and 2.
4.6. Synthesis of organozirconium compounds
4.6.1. [p5:p1-C5H2(CH2CH2OPh)(SiMe3)2]ZrCl3: (4d)
To a solution of 1.70 g (5.2 mmol) of 4c in 25 ml of
diethyl ether was added 3.3 ml of nBuLi in hexane (1.73
M, 5.7 mmol) at room temperature. After stirring for 2
h a clear orange solution emerged. After cooling to
−60°C 1.15 g (4.94 mmol) of freshly sublimed ZrCl4
was added and the resulting colourless suspension was
stirred overnight at room temperature. The mixture was
4.4.3. (R)–C5H5CH2CH(Me)O-h-naphthyl
Due to its high boiling point the brownish, viscous
oil could not be purified. A crude yield of 85% was
obtained, containing an estimated 75% of the wanted
1
product. H-NMR: l=1.45 (m, 3H, CH3), 2.7–3.1 (m,

284
A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
filtered and the filtrate evaporated to dryness. The
residue was extracted with toluene, filtered and evapo-
rated to dryness. After washing the residue with cold
(−30°C) pentane 1.32 g (2.50 mmol, 51%) of analyti-
cally pure 4d was obtained as a beige powder.
C19H29Cl3OSi2Zr (527.2): calc. C 43.3, H 5.6, Cl 20.2;
found C 41.2, H 5.6, Cl 20.4. Other zirconium com-
pounds were prepared similarly.
the Bundesland Sachsen-Anhalt (HSP III program) is
gratefully acknowledged. We thank Aventis Research &
Technologies (formerly Hoechst) for performing the
polymerisation experiments.
References
4.6.2. [p5:p1-C5H2(CH2CH2OMe)(SiMe3)2]ZrCl3: (3d)
Yield: 88%: C14H27Cl3OSi2Zr (464.5): calc. C 36.2, H
5.8; Found C 36.1, H 5.9.
[1] (a) G. Erker, C. Sarter, S. Werner, C. Kru¨ger, J. Organomet.
Chem. 377 (1989) C55. (b) G. Erker, C. Sarter, M. Albrecht, S.
Dehnicke, C. Kru¨ger, E. Raabe, R. Schlund, R. Benn, A.
Rufinska, R. Mynott, J. Organomet. Chem. 383 (1990) 89. (c) G.
Erker, J. Organomet. Chem. 400 (1990) 185. (d) G. Erker, A.A.H.
van der Zeijden, Angew. Chem. 102 (1990) 543. (e) G. Erker, J.
Schamberger, A.A.H. van der Zeijden, S. Dehnicke, C. Kru¨ger,
R. Goddard, M. Nolte, J. Organomet. Chem. 459 (1993) 107 (f)
F. Bo¨kman, H. Bertagnolli, O. Schupp, G. Bringmann, J.
Organomet. Chem. 474 (1994) 117.
[2] (a) J.C.W. Chien, B.-P. Wang, J. Polym. Sci. A Polym. Chem. 27
(1989) 1539. (b) ibid., 28 (1990) 15. (c) N. Piccolrovazzi, P. Pino,
G. Consiglio, A. Sironi, M. Moret, Organometallics, 9 (1990) 3098.
(d) C. Pellecchia, A. Proto, P. Longo, A. Zambelli, Makromol.
Chem. Rapid Commun. 12 (1991) 663. (e) C. Pellecchia, P. Longo,
A. Proto, A. Zambelli, Makromol. Chem. Rapid Commun. 13
(1992) 265. (f) ibid., 277. (g) C. Pellecchia, A. Immirzi, A. Grassi,
A. Zambelli, Organometallics 12 (1993) 4473. (h) P. Longo, A.
Proto, L. Oliva, Macromol. Rapid Commun. 15 (1994) 151. (i) Q.
Wang, R. Quyoum, D.J. Gillis, M.-J. Tudoret, D. Jeremic, B.K.
Hunter, M.C. Baird, Organometallics 15 (1996) 693. (j) G. Jimenez
Pindado, M. Thornton-Pett, M. Bouwkamp, A. Meetsma, B.
Hessen, M. Bochmann Angew. Chem. 109 (1997) 2457. (k) R.
Duchateau, S.J. Lancaster, M. Thornton-Pett, M. Bochmann,
Organometallics 16 (1997) 4995. (l) S. Doherty, R.J. Errington,
A.P. Jarvis, S. Collins, W. Clegg, M.R. J. Elsegood, Organometal-
lics 17 (1998) 3408.
4.6.3. [p5:p1-(R)–C5H2(CH2CH(Me)OPh)(SiMe3)2]-
ZrCl3: (6d)
Yield: 48%: C20H31Cl3OSi2Zr (541.2): calc. C 44.4, H
5.8, Cl 19.7; Found C 42.7, H 5.9, Cl 19.7.
4.6.4. [p5:p1-(R)–C5H2(CH2CH(Me)OC6H4-4-OMe)-
(SiMe3)2]ZrCl3: (7d)
Yield: 37%: C21H33Cl3O2Si2Zr (571.2): calc. C 44.2, H
5.8, Cl 18.6; Found C 42.3, H 5.8, Cl 18.9.
Similar reactions with 5c and 8c were unsuccessful;
no monoCp zirconium compound could be isolated.
4.7. Hydrocyanation reactions
A solution of ca. 0.10 g (0.2 mmol) of 6d or 7d in 15
ml of CH2Cl2 was thermostated at +21, −4, or
−35°C. Than 1.0 ml (10 mmol) of benzaldehyde and
1.6 ml of Me3SiCN (12 mmol) were added, and the
reaction was stirred overnight (or 1 week at −35°C),
after which the reaction was complete. Hydrochloric
acid (1 N) was added and the mixture stirred for two
days at room temperature. The CH2Cl2 layer was sepa-
rated and filtered over a short column of silica, after
which it was evaporated to dryness. The yield of
PhCH(CN)OH was usually quantitative. The enan-
[3] R.L. Halterman, Chem. Rev. 92 (1992) 965.
[4] (a) A.A.H. van der Zeijden, Tetrahedron Asymm. 6 (1995) 913.
(b) A.A.H. van der Zeijden, J. Organomet. Chem. 518 (1996) 147.
(c) A.A.H. van der Zeijden, C. Mattheis, Synthesis (1996) 847. (d)
A.A.H. van der Zeijden, C. Mattheis, R. Fro¨hlich, Organometal-
lics 16 (1997) 2651. (e) A.A. H. van der Zeijden, C. Mattheis, J.
Organomet. Chem. 555 (1998) 5.
1
tiomeric excess, as was determined by H-NMR using
[5] (a) Q. Huang, Y. Qian, Synthesis (1987) 910. (b) Q. Huang, Y.
Qian, Y. Tang, Trans. Met. Chem. 14 (1989) 315. (c) B. Rieger,
J. Organomet. Chem. 420 (1991) C17. (d) P. Van de Weghe, C.
Bied, J. Collin, J. Marcalo, I. Santos, J. Organomet. Chem. 475
(1994) 121. (e) H. Adams; N.A. Bailey, M. Colley, P.A. Schofield.
C. White, J. Chem. Soc. Dalton Trans. (1994) 1445. (f) Y.
Kataoka, Y. Saito, K. Nagata, K. Kitamura, A. Shibahara, K.
Tani, Chem. Lett. (1995) 833. (g) G.A. Molander, H. Schumann,
E.C.E. Rosenthal, J. Demtschuk, Organometallics 15 (1996) 3817.
(h) A.A. Trifonov, P. Van der Weghe, J. Collin, A. Domingos, I.
Santos, J. Organomet. Chem. 527 (1997) 225. (i) B. Antelmann,
U. Winterhalter, G. Huttner, B.C. Janssen, J. Vogelsang, J.
Organomet. Chem. 545–546 (1997) 407. (j) B. Antelmann, G.
Huttner, J. Vogelsang, O. Walter, U. Winterhalter, J. Organomet.
Chem. 549 (1997) 139. (k) B. Antelmann, G. Huttner, U. Winter-
halter, J. Organomet. Chem. 555 (1998) 119. (l) L. Schwink, P.
Knochel, T. Eberle, J. Okuda, Organometallics 17 (1998) 7.
[6] M. Enders, R. Rudolph, H. Pritzkow, J. Organomet. Chem. 549
(1997) 251.
Eu(hfc)3 as a chiral shift reagent, was always B1%.
4.8. Polymerisation experiments
A mixture of a few mg (ca. 5–10 mmol) of 3d or 4d
was dissolved in toluene and activated with a 30%
solution of methylaluminoxane in toluene (Al/Zr:
3000–5000/1) This mixture was transfered to an auto-
clave and subjected to 10 bar of ethylene in heptane for
1 h at 40–50°C. The amount of polyethylene (PE)
isolated correlates with a polymerisation activity of 110
g PE/mmol Zr/h/bar ethylene for 3d, and 55 for 4d.
Acknowledgements
[7] (a) T. Kauffmann, K. Berghus, A. Rensing, Chem. Ber. 118 (1985)
3737. (b) ibid., 4507. (c) P. Foster, M.D. Rausch, J.C.W. Chien,
J. Organomet. Chem. 527 (1997) 71. (d) Y. Kataoka, Y.Saito, A.
Financial support by the Deutsche Forschungsge-
meinschaft, the Alexander-von-Humboldt-Stiftung and

A.A.H. 6an der Zeijden, C. Mattheis / Journal of Organometallic Chemistry 584 (1999) 274–285
285
Shibahara, K. Tani, Chem. Lett. (1997) 621. (e) Y. Kataoka, A.
Shibahara, Y. Saito, T. Yamagata, K. Tani, Organometallics 17
(1998) 4338.
[11] A.A.H. van der Zeijden, J. Jimenez, unpublished results.
[12] (a) M.T. Reetz, F. Kunisch, P. Heitmann, Tetrahedron Lett. 27
(1986) 4721. (b) K. Narasaka, T. Yamada, H. Minamikawa,
Chem. Lett. (1987) 2073. (c) H. Minamikawa, S. Hayakawa, T.
Yamada, N. Iwasawa, K. Narasaka, Bull. Chem. Soc. Jpn. 61
(1988) 4379.
[8] W.S. Rees, K. Dippel, Org. Prep. Proc. Int. 24 (1992) 527.
[9] U. Burkard, F. Effenberger, Chem. Ber. 119 (1986) 1594.
[10] L.I. Belen’kii, V.S. Bogdanov, I.B. Karmanova, Izv. Akad.
Nauk SSSR, Se Khim. (1979) 1735; Chem. Abstr. 91 (1979)
166018r.
[13] A.A.H. van der Zeijden, C. Mattheis, R. Fro¨hlich, F. Zippel,
Inorg. Chem. 36 (1997) 4444.
.
.