Zirconium bis-indenyl compounds. Synthesis and X-ray crystallography study of 1- and 2-substituted bis(R-indenyl)zirconium dichloride metallocenes

Article abstract of DOI:10.1016/S0022-328X(00)00570-2

A series of 1- and 2-substituted indenyl ligands were prepared and used in the synthesis of [1-R-Ind]₂ZrCl₂ [R = Me (2b), Et (4b), ⁱPr (5b), ^tBu (6b), SiMe₃ (8b), Ph (10b), Bz (12b), 1-Naph (14b)] and [2-R-Ind]₂ZrCl₂ [R = Me (1b), Et (3b), SiMe₃ (7b), Ph (9b), Bz (11b), 1-Naph (13b)] metallocenes. An X-ray crystallographic study of 4b and 10b showed the complexes to be the racemic diastereomers (4b, both the R,R and S,S-enantiomers and 10b, the S,S-enantiomer). The X-ray data together with NMR spectral data revealed that the size of the substituent influenced the orientation the two indenyl ligands of the metallocenes. The 4b diastereomers are both found to crystallize with their ethyl groups syn (bis-central) with respect to each other whereas the larger phenyl groups in 10b results in an anti (bis-lateral) orientation of the indenyl ligands.

Full text of DOI:10.1016/S0022-328X(00)00570-2

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Journal of Organometallic Chemistry 616 (2000) 112–127
Zirconium bis-indenyl compounds. Synthesis and X-ray
crystallography study of 1- and 2-substituted
bis(R-indenyl)zirconium dichloride metallocenes
Neil E. Grimmer, Neil J. Coville *, Charles B. de Koning, Jeremy M. Smith,
Leanne M. Cook
Center for Applied Chemistry and Chemical Technology, Department of Chemistry, Uni6ersity of the Witwatersrand, Pri6ate Bag 3,
PO Wits 2050, Johannesburg, South Africa
Received 27 June 2000; accepted 18 August 2000
Abstract
A series of 1- and 2-substituted indenyl ligands were prepared and used in the synthesis of [1-R-Ind]2ZrCl2 [R=Me (2b), Et
i
t
(4b), Pr (5b), Bu (6b), SiMe3 (8b), Ph (10b), Bz (12b), 1-Naph (14b)] and [2-R-Ind]2ZrCl2 [R=Me (1b), Et (3b), SiMe3 (7b), Ph
(9b), Bz (11b), 1-Naph (13b)] metallocenes. An X-ray crystallographic study of 4b and 10b showed the complexes to be the racemic
diastereomers (4b, both the R,R and S,S-enantiomers and 10b, the S,S-enantiomer). The X-ray data together with NMR spectral
data revealed that the size of the substituent influenced the orientation the two indenyl ligands of the metallocenes. The 4b
diastereomers are both found to crystallize with their ethyl groups syn (bis-central) with respect to each other whereas the larger
phenyl groups in 10b results in an anti (bis-lateral) orientation of the indenyl ligands. © 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Zirconium; Indenyl; Metallocene complexes
tuted at the 2-position. Bulky substituents enable these
metallocenes to polymerize sections of atactic and iso-
tactic polypropylene in the same polymer chain. Not
only are these highly effective polymerization catalysts,
but substitution at the 2-position is easily and relatively
cheaply achieved. This result indicates that other 1- or
2-substituted, unbridged bis-indenyl Group 4 metal-
locenes may also have interesting properties. It is to be
noted that reports on the synthesis and application of
such compounds in the synthesis of polymers have been
limited to the papers by Waymouth (vide supra) and a
few other relevant publications that have appeared in
the open literature [16–21].
1. Introduction
The importance of single-center catalysts (SCC) is
reflected by the recent series of reviews on the topic
[1–10]. The major advantage of SCCs lies in the fact
that subtle changes in their molecular architecture lead
to polymers with vastly different properties. For exam-
ple, Waymouth has recently developed a novel catalyst
system in which ligand orientation effects can be con-
trolled resulting in a catalyst that is capable of polymer-
izing propene into elastomeric polypropylene [11–15].
These catalysts consist of zirconium dichloride bonded
to two unconnected, oscillating indene ligands substi-
In this paper we describe the systematic synthesis and
characterization of a series of 1- and 2-substituted
bis(R-indenyl)zirconium dichloride compounds (R=al-
kyl or aryl). A paper on the use of these metallocenes in
the polymerization of ethene and propene is in prepara-
tion [22].
* Corresponding author. Tel.: +27-11-717-6738; fax: +27-11-339-
7967.
E-mail address: ncoville@aurum.chem.wits.ac.za (N.J. Coville).
0022-328X/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00570-2

N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
113
2. Results and discussion
described elsewhere [20,29,31–33]. 2-Ethylindene (3a)
was synthesized by the addition of the Grignard reagent
of 2-ethylbromide to 2-indanone, followed by dehydra-
tion. Similarly, 2- and 3-(1)-naphthyl-indene (13a and
14a) were synthesized by nucleophilic addition of the
Grignard reagent of 1-bromonaphthalene to either 2- or
1-indanone, respectively, followed by dehydration. The
synthesis of 1-methylindene and (2a) and 1-benzylin-
dene (12a) were accomplished by addition of indenyl-
lithium to the electrophiles methyliodide and
benzylbromide, respectively.
2.1. Synthesis of the substituted indene ligands
The synthesis of substituted indene ligands may be
approached via several synthetic routes. Many of these
reactions involve the formation of the five membered
ring as a last step from a suitably substituted benzene
precursor (e.g. via Friedel Crafts methodology), fol-
lowed by a reduction step to form the indene [23–26] or
the cyclization of phenyl substituted allylic cations
[27,28]. We have however preferred to use indene and
1- and 2-indanone as our starting materials for the
synthesis of the substituted indenes described in this
paper. A number of approaches may be followed and
these are summarized in Schemes 1 and 2, which depict
synthetic routes to 1- (and 3-) and 2-substituted indene
compounds respectively. The substituted indene com-
pounds synthesized in this paper are included in these
two schemes.
2.2. Synthesis of the metallocenes
The substituted ligands 1a–14a were used as precur-
sors in the successful synthesis of a series of bis(1-R-in-
i
denyl)zirconium dichloride [R=Me (2b), Et (4b), Pr
t
(5b), Bu (6b), SiMe3 (8b), Ph (10b), Bz (12b), and
1-Naph (14b)] and bis(2-R-indenyl)zirconium dichloride
[R=Me (1b), Et (3b), SiMe3 (7b), Ph (9b), Bz (11b) and
1-Naph (13b)] complexes. The synthetic procedure is
illustrated in Scheme 3, the reaction scheme for the
synthesis of the 1-subsituted metallocenes. In this pro-
cedure, n-butyllithium was allowed to react with the
appropriate indene ligand in THF. The solvent was
then removed in vacuo from the resulting salt, replaced
with toluene, and the metallocene formed by the addi-
tion of ZrCl4, also in toluene.
i
The synthesis of the 1-indene [R=Et (4a) and Pr
(5a)], 3-indene [R=tBu (6a) and Ph (10a)] and 2-indene
[R=Me (1a), Ph (9a) and Bz (11a)] ligands have been
The 1-substituted indene ligands are prochiral and
can yield two diastereomers. A re, re or si, si attach-
ment gives rise to the two racemic (rac) enantiomers
(i.e. these make up the rac-diasteomer) whereas a re, si
attachment gives the meso diastereomer (Scheme 3).
The synthetic approach employed in this study gave the
statistical 50:50 rac:meso isomer ratio. Use of
ZrCl4(THF)2, as the zirconium source, has been sug-
gested to modify the ratio of the diastereomers formed
[17], but this reagent did not influence our ratios for the
synthesis of 4b and 5b. The most probable reason for
this lack of isomer selectivity may relate to the small
size of the indene ligand R-groups (R=ethyl and iso-
propyl). This proposal is reinforced by the observation
that even with the use of ZrCl4, the bulky naphthyl
substituted ligand (14a) attached to the metal to give a
60:40 rac:meso isomeric mixture of 14b. However no
attempt was made to synthesize 14b using ZrCl4(THF)2
to see if this ratio could be improved.
Scheme 1. Synthesis of 1- and 3-substituted indene ligands.
Depending on the nature of the ligand substituent,
different solvents had to be used to achieve successful
purification of the metallocenes and separation of their
diastereomers. There appears to be a relationship be-
tween the size of the indenyl ligand substituent and the
solubility of these metallocenes. Complexes with sub-
stituents smaller than tert-butyl can easily be dissolved
and recrystallized from toluene. More polar solvents,
such as dichloromethane, had to be employed for the
Scheme 2. Synthesis of 2-substituted indene ligands.

114
N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
by X-ray crystallography (vide infra). For the remain-
ing 1-substituted metallocenes (5b, 6b, 8b and 14b), the
rac- and meso- diastereomers could be differentiated by
reaction of the isolated diastereomers with methyl-
lithium, replacing the chloride ligands with methyl
groups. As the rac-diastereomer has C2-symmetry, only
one methyl resonance is expected (and observed). How-
ever, as the meso-diastereomer has Cs-symmetry, two
methyl resonances of equal intensity are expected (and
observed).
Attempts at methylating the 1-benzyl substituted
metallocene 12b were not successful, presumably due to
the methyllithium preferentially reacting with the acidic
benzylic methylene protons, even when an excess of
methyllithium was used. The diastereomers of 12b were
therefore assigned using an alternative procedure,
which will be discussed later.
Scheme 3. The prochiral 1- and 3-substituted indene precursors result
in the formation of rac- and meso-metallocene compounds. The
2-substituted metallocenes were synthesized according to the same
route.
For all of the metallocenes, the H-3 signal was
identified as a doublet of doublets through its coupling
to protons H-2 and H-4. H-2 however showed only
vicinal coupling to H-3 and was thus observed as a
simple doublet. For both diastereomers, the H-2 signal
is downfield from H-3 with their corresponding 13C-
NMR spectral data yielding equivalent positions in the
13C-NMR spectra. An exception to this ordering was
found for one of the 6b (R=tBu) diastereomers. In this
case the H-3 resonance (l 6.48) is found downfield from
that of H-2 (d 5.89). Interestingly, C–H correlation
showed that C-3 (l 96.62) is upfield from C-2 (l
Fig. 1. Representation of the symmetry elements of the rac- and
meso-diastereomers.
1
117.65), i.e. opposite to the H-NMR signal order. The
NMR spectral data for the other diastereomer was
consistent with that found for the other metallocenes.
Together with the stereochemical assignments made
earlier, it was possible to assign the H-2 and H-3 signals
to a particular diastereomer. An interesting observation
is that for a sample containing a mixture of rac- and
meso- diastereomers, the ‘inner pair’ of H-2 and H-3
resonances can be assigned to the rac-diastereomer.
Also, the separation between the H-2 and H-3 signals,
Dl, was found to be dependent on the R-group (Table
2). For the rac-diastereomer, Dl becomes smaller as the
electron donating strength of the indenyl substituent
increases and eventually the signal positions intercon-
vert as observed for 6b (R=tBu) where Dl= −0.59.
No linear relationship between Dl and the electronic
properties of the R-substituents could be found (the
Hammett substituent functions |m, |p and F were
considered [34]), which suggests that Dl is also influ-
enced by steric factors.
Using the knowledge of the positioning of the H-2
and H-3 resonances we have tentatively assigned the
stereochemistry for the 1-methyl (2b) and 1-benzyl sub-
stituted metallocene (12b) diastereomers. Thus, for 12b
the rac-isomer has its H-2 and H-3 resonances at l 6.05
and 5.83 (‘inner-pair’), whereas the meso-diastereomer
resonances for the protons are at l 6.29 and 5.29
(‘outer-pair’).
other metallocenes. The exception to this rule was the
benzyl substituted metallocenes (11b and 12b), which
could also be successfully purified from toluene.
The many fractional-crystallization steps undertaken
for the purification of most of the metallocenes incurred
a heavy product-loss penalty. For 2b, the methyl substi-
tuted metallocene, no separation of the diastereomers
could be achieved. The compound was instead purified
as a 50:50 mixture of the rac:meso isomers.
2.3. Characterization of the metallocenes
The rac- and meso-diastereomers are readily distin-
guished from one another by the differing positions of
1
their H-2 and H-3 H-NMR spectroscopy signals (refer
to Table 1 for numbering schemes). Since both rac-
enantiomers have C2-symmetry this results in the H-2
as well as the H-3 protons on each ring being equiva-
lent. In the meso-diastereomer these protons can be
related by a mirror-plane bisecting the Cl–Zr–Cl plane
(Fig. 1). This results in the two H-2 protons and two
H-3 protons in each diastereomer giving rise to one
signal each.
The absolute stereochemical assignment for two of
these metallocenes viz. 4b and 10b, was made possible

Table 1
NMR spectral data for the bis(R-indenyl)zirconium dichloride metallocenes a
b
Metallocene
Code
1H-NMR spectra c
Assignment d
13C-NMR spectra
Assignment d
1b
2.04 (s, 6H)
5.83 (s, 4H)
7.24 (m, 4H)
7.64 (m, 4H)
H8
16.89
106.18
125.14, 125.20
126.17
C8
C1, C3
C4–7
H1, H3
H5, H6
H4, H7
C2
138.12
C3a, C7a
2b
Isomer 1:
Isomer 1:
2.35 (s, 6H)
H8
H3
H2
12.93
Isomer 2:
13.35
Both Isomers:
C8
5.83 (dd, J=2.8, J3–4=0.7 Hz, 2H)
6.07 (d, J=3.1, 2H)
Isomer 2:
C8
2.42 (s, 6H)
H8
H3
H2
98.95, 99.14, 118.17, 121.50,
123.03, 123.72, 123.73, 125.41,
125.44, 125.48, 125.54, 125.84,
125.96, 126.03, 126.76, 127.17
C1–7a
5.70 (dd, J=3.2, J3–4=0.7 Hz, 2H)
6.31 (d, J=3.1 Hz, 2H)
Both Isomers:
/
7.22–7.32, 7.44–7.47, 7.55–7.64 (m, 8H)
H4–7
3b
4b
0.97 (t, J=7.6 Hz, 6H)
2.43 (q, J=7.5, Hz 4H)
5.81 (s, 4H)
H9
H8
H1, H3
H5, H6
H4, H7
14.24
24.27
104.63
125.04
125.44
126.10
145.02
Isomer 1:
13.86
20.99
98.81
121.27
123.81, 125.72
125.35, 126.22
125.30, 125.75
C9
C8
C1, C3
C5, C6
C4, C7
C2
7.24 (m, 4H)
7.67 (dd, J=6.5 4J=3.1 Hz, 4H)
C3a, C7a
e
Isomer 1 (rac) :
1.15 (t, J=7.5 Hz, 6H)
2.84 (m, 4H)
H9
H8
H3
H2
H5, H6
H4, H7
C9
C8
C3
C2
C4, C7
C5, C6
5.82 (dd, J3–2=3.2, 4J3–4=0.7 Hz, 2H)
6.04 (d, J=3.3 Hz, 2H)
7.23–7.32 (m, 4H)
6
)
7.54–7.68 (m, 4H)
Isomer 2 (meso):
2
1.23 (t, J=7.5 Hz, 6H)
2.92 (q, J=7.5 Hz, 4H)
5.62 (dd, J3–2=3.2 Hz,
4J3–4=0.8 Hz, 2H)
H9
H8
H3
127
6.32 (d, J=3.2 Hz, 2H)
7.19–7.49, 7.56–7.57, 7.60–7.62 (m, 8H)
H2
H4–7
f
5b
Isomer 1 (rac) :
Isomer 1:
20.03
24.35
27.10
96.48, 123.99
1.10 (d, J=6.9 Hz, 6H)
1.17 (d, J=6.7 Hz, 6H)
3.51 (dt, J=6.8 Hz, 2H)
5.90 (dd, J3–2=3.2 Hz,
4J3–4=0.5 Hz, 2H)
H9
H9
H8
H3
C3a, C7a
C9
C8
C2, C3
5.91 (d, J=3.3 Hz, 2H)
7.19, 7.34 (m, 4H)
7.54 (d, J4–5=8.5 Hz, 2H)
H2
H5, H6
H4
124.28, 125.20, 125.89, 126.74
123.99
127.83, 132.28
C4–7
C1
C3a, C7a

Table 1 (Continued)
b
Metallocene
Code
1H-NMR spectra c
Assignment d
H7
13C-NMR spectra
Assignment d
7.65 (m, J=8.5 Hz, 2H)
Isomer 2 (meso):
1.15 (d, J=6.9 Hz, 6H)
H9
1.32 (d, J=6.8 Hz, 6H)
H9
3.55 (dq, J=6.8 Hz, 2H)
5.37 (dd, J=3.2 Hz, J3–4=0.7 Hz, 2H)
6.33 (d, J=3.2 Hz, 2H)
H8
H3
H2
7.23, 7.32 (m, 4H)
H5, H6
H4, H7
7.44 (dd, J=8.5 Hz, 4J=0.7 Hz, 2H), 7.60
(dd, J=8.6 Hz, 4J=0.8 Hz, 2H)
f
6b
Isomer 1 (rac) :
1.42 (s, 18H)
H9
H2
H3
H5, H6
H4, H7
30.6
C9
C8
C3
C2
C1
5.89 (d, J=3.0 Hz, 2H)
6.48 (dd, J3–2=3.4 Hz, 4J3–4=0.5 Hz, 2H)
7.17 (m, 2H), 7.31 (m, 2H)
7.67 (d, J=8.5 Hz, 2H), 7.89
(d, J=8.6 Hz, 2H)
34.32
96.62
117.65
121.82
/
Isomer 2 (meso):
1.49 (s, 18H)
124.07, 125.11, 125.33, 125.97
131.04, 132.98
C4–7
C7a, C3a
H9
H3
H2
H4–7
6.05 (dd, J3–2=3.3 Hz, 4J3–4=0.8 Hz, 2H)
6.43 (d, J=6.5 Hz, 2H)
7.25, 7.50, 7.90 (m, 8H)
−0.46
C9
7b
8b
0.074 (s, 18H)
5.97 (s, 4H)
7.29 (m, 4H)
7.80 (m, 4H)
H8
111.73
125.38
125.78
129.36
141.09
C1, C3
C5, C6
C4, C7
C2
H1, H3
H5, H6
H4, H7
C3a, C7a
f
6
Isomer 1 (rac) :
0.35 (s, 18H)
Isomer 1:
−2.53
46.51
104.78, 125.02, 125.87, 126.21,
127.09, 127.57
128.83, 135.75
H8
H3
H2
C8
C1
)
6.37 (dd, J=3.2 Hz, 4J3–4=0.8 Hz, 2H)
6.43 (d, J=3.2 Hz, 2H)
C2, C3, C4–7
1
7.28 (m, 4H), 7.67–7.73 (m, 4H)
Isomer 2 (meso):
H4–7
C3a, C7a
127
0.40 (s, 18H)
H8
H3
H2
H4–7
6.17 (dd, J=3.2 Hz, 4J3–4=0.8 Hz, 2H)
6.58 (d, J=3.2 Hz, 2H)
7.07 (m, 2H), 7.70 (m, 2H)
e
10b
Isomer 1 (rac)
:
Isomer 1:
103.42, 118.94
123.47, 126.09, 126.16, 127.73,
127.84, 127.94, 129.29
117.19, 126.80, 128.80, 134.55
5.93 (dd, J2–1=3.6 Hz, 4J2–4=0.8 Hz, 2H)
6.36 (d, J=3.5 Hz, 2H)
H3
H2
C2, C3
C4–7, C9
7.17 (m, 2H), 7.32–7.65 (m, 14H), 7.77–7.82
(m, 2H)
H4–7, H9
C1, C3a, C7a, C8
Isomer 2 (meso):
5.99 (dd, J2–1=3.5 Hz, 4J2–4=0.8 Hz, 2H)
6.57 (d, J=3.5 Hz, 2H)
H3
H2
7.12–7.66, 7.84–7.89 (m, 18H)
H4–7, H9

Table 1 (Continued)
b
Metallocene
Code
1H-NMR spectra c
Assignment d
13C-NMR spectra
Assignment d
11b
3.70 (s, 4H)
5.86 (s, 4H)
7.00 (m, 4H)
7.14–7.25 (m, 10H)
7.64 (m, 4H)
H8
37.44
105.74
C8
C1, C2
C4–7, C10
H1, H3
H4, H7
H10
125.35, 125.49, 126.34, 128.44,
128.62
126.26, 139.82, 141.25
H5, H6
C2, C3a, C7a, C9
12b
Isomer 1 (meso):
Isomer 1:
34.11
99.18
4.18 (d, J=15.9 Hz, 2H)
4.26 (d, J=15.9 Hz, 2H)
5.29 (dd, J3–1=3.2 Hz, 4J3–4=0.8 Hz, 2H)
H8
H8
H3
C8
C3
C2
120.78, 121.74
C1
6.29 (d, J=3.2 Hz, 2H)
7.19–7.30 (m, 14H)
7.38 (m, 2H), 7.62 (m, 2H)
Isomer 2 (rac):
H2
123.80, 125.64, 126.38, 126.49,
128.51, 128.90
125.97, 127.48, 139.48
Isomer 2:
C4–7, C10
H5, H6, H10
H4, H7
C3a, C7a, C9
C8
/
4.04 (d, J=15.9 Hz, 2H)
4.23 (d, J=15.9 Hz, 2H)
5.83 (dd, J3–1=3.2 Hz, 4J3–4=0.7 Hz, 2H)
H8
H8
H3
33.96
99.07
122.06
C3
C2
C4–7, C10
C1, C3a, C7a, C9
123.62, 125.62, 125.76, 126.31,
126.44, 128.43, 128.67, 121.63,
126.57, 139.76
6.05 (d, J=3.3 Hz, 2H)
7.11–7.32 (m, 14H)
7.6 (m, 4H)
H2
H5, H6, H10
H4, H7
13b
6.37 (s, 4H)
H1, H3
H4–7, H9
107.82
C1, C3
C4–7, C9
C2, C3a, C7a
C8, C9a
7.21(m. 1H), 7.37–7.41 (m, 1H), 7.46–7.52
(m, 2H), 7.54–7.59 (m, 1H), 7.95 (m, 1H),
7.97–8.00 (m, 1H), 8.18 (m, 20H)
125.08, 125.28, 125.35, 126.21,
126.79, 126.99, 127.28, 128.55,
129.01, 129.51
,
130.52, 131.35, 132.09, 134.31
1
(
1
14b
Isomer 1 (rac):
6.30 (dd, J3–2=3.4 Hz, 4J3–4=0.5 Hz, 2H)
6.43 (d, J=3.5 Hz, 2H)
7.15–7.94 (m, 22H)
H3
H2
H4–7, H9
127
f
Isomer 2 (meso) :
6.06 (dd, J3–2=3.4 Hz, 4J3–4=0.7 Hz, 2H)
6.91 (d, J=3.4 Hz, 2H)
H3
H2
7.21–7.95 (m, 22H)
H4–7, H9
a NMR spectra were recorded in CDCl3 with chemical shifts relative to TMS, d scale. For the 1-substituted metallocenes, the NMR spectral
data given in the table are ordered such that the first diastereomer isolated by the crystallization process is listed first.
b The numbering scheme employed for all the metallocenes is the same as that used for bis(2-methyl-indenyl)zirconium dichloride, 2b.
c All J-values are 3J, unless specified otherwise.

118
N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
2.4. Crystal structures of 4b and 10b
syn-(A), gauche-(B) and anti-(C) conformations, respec-
tively.
X-ray quality crystals were obtained for bis(1-ethyl-
indenyl)zirconium dichloride (4b) and bis(1-phenyl-in-
denyl)zirconium dichloride (10b) and the crystal
structures of these compounds were determined at 173
K. Selected structural parameters are listed in Table 3
and molecular diagrams for these two structures are
depicted in Figs. 2–4.
The crystal structure complex of 4b reveals two
unique molecules in a 1:1 ratio i.e. the R,R (4b-R,R)
and S,S (4b-S,S) racemic enantiomers respectively,
which are similar in many respects. The metal atoms in
these structures are in a pseudotetrahedral environment
formed by the two chlorine ligands and two h5-bonded
indenyl ligands. A slight asymmetry is observed in the
attachment of the indenyl ligands to the zirconium
atoms.
Erker et al. have proposed three possible solid state
conformers for unbridged, rac-bis(1-R-indenyl)-
zirconium dichloride metallocenes [16,17]. These are
depicted in Fig. 5, with the size of the R-substituent
dictating which ligand conformation is adopted. These
workers predicted that metallocenes with small, inter-
mediate and large substituents would adopt the
Fig. 3 (top view of the two enantiomers, looking
down the two five-membered rings of the indenyl lig-
ands) reveals that both 4b enantiomers adopt the syn
conformation with the two ethyl substituents positioned
over the open sector of the metallocene. This conforma-
tion is similar to A in Fig. 5, the structure predicted for
metallocenes with small substituents. In this conforma-
tion there is less steric interaction between the ethyl
substituents and the chloride ligands than if the an-
nelated indenyl six-membered ring were positioned over
them.
Metallocene 10b has C2 symmetry, with the zirco-
nium atom in a pseudotetrahedral environment formed
by the two chlorine ligands and two h5-coordinated
indenyl ligands. The si-faces of the two indenyl ligands
are attached to the metal, creating a metallocene that
has S,S stereochemistry. The Zr–Cl bond lengths are
,
2.429(7) A, which is typical for this class of metal-
locene. However, the Cl–Zr–Cl angle is 98.98(2)°,
which is notably larger than the mean value of 94.77°
for similar 1- or 2-substituted bis(indenyl)zirconium
dichloride metallocenes (determined from the Cam-
bridge Structural Database [35,36]). This implies that
there may be less steric strain in the Cl–Zr–Cl bond
angle in this compound (vide infra). The Cpcen–Zr–
Cpcen bending angle of 128.66(6)° does, however, fall
within the expected range. Of the Zr–CCp bond lengths,
the two bonds to the bridgehead carbons of the indenyl
ligand are the longest. Of the remaining three, the bond
to the five-membered ring carbon atom to which the
substituent is attached, is the longest. This is most
probably a result of the steric strain imposed by the
phenyl groups upon the structure. The difference be-
Table 2
Selected 1H-NMR spectral data for the bis(1-R-indenyl)zirconium
dichloride metallocenes
a
Metallocene
R
Isomer
H-2
H-3
Dl
2b b
Me
rac
meso
6.07
6.31
5.83
5.70
0.24
0.61
4b c
Et
rac
meso
6.04
6.32
5.82
5.62
0.22
0.70
5b d
iPr
rac
meso
5.91
6.33
5.90
5.37
0.01
0.96
tween the longest and shortest Zr–CCp bond is 0.163 A.
,
Although not out of the ordinary, this is larger than
that of the analogous 1-neomenthyl substituted metal-
6b d
tBu
rac
meso
5.89
6.43
6.48
6.05
−0.59
0.38
,
locene, the difference here being 0.103 A [17]. This
8b d
SiMe3
Ph
rac
meso
6.43
6.52
6.37
6.17
0.06
0.35
phenomenon illustrates the size effect of the large and
inflexible phenyl group.
A top view of 10b (Fig. 4b) indicates that an anti-
type structure is adopted, but this conformation is
slightly different from that depicted in Fig. 5. The
crystal structure indicates that the indenyl ligands are
orientated so as to keep the large phenyl substituents
10b c
12b a
14b d
rac
meso
6.36
6.57
5.93
5.99
0.43
0.58
Bz
rac
meso
6.05
6.29
5.83
5.29
0.22
1.00
(1)-Naph
Cy c,e
rac
meso
6.43
6.91
6.30
6.06
0.13
0.85
away from each other with the C(1)–Cpcen–Cpcen
–
C(1A) torsional angle equal to 113.7(8)°. However, this
is significantly smaller than the values of close to 180°
for the analogous bis(1-cyclohexyl-tetrahydroin-
denyl)zirconium dichloride [16] and bis(1-neomenthyl-
rac
meso
5.90
6.30
5.83
5.81
0.07
0.49
a H-2–H-3.
b Tentative assignment of stereochemistry (see text).
indenyl)zirconium
dichloride
[17]
zirconocenes.
c Assignment of stereochemistry made by X-ray crystallography.
d Assignment of stereochemistry made by converting dichloro-
metallocenes to their dimethyl derivatives.
Placement of the phenyl substituents in the crowded
back section of the bent metallocene is most likely a
result of the greater steric strain placed upon the metal-
locene by the more rigid phenyl ring compared to the
e Bis(1-cyclohexyl-indenyl)zirconium dichloride. Metallocene syn-
thesized Kru¨ger et al. [16].

N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
119
Table 3
Selected crystallographic structural data for 4b and 10b
a
Parameter
4b-S,S
4b-R,R
10b
Bond lengths
Zr–Cl
Zr(1A)–Cl(1A)
Zr(1A)–Cl(2A)
Zr(1A)–C(3A)
Zr(1A)–C(4A)
Zr(1A)–C(5A)
Zr(1A)–C(6A)
Zr(1A)–C(7A)
Zr(1A)–C(14A)
Zr(1A)–C(15A)
Zr(1A)–C(16A)
Zr(1A)–C(17A)
Zr(1A)–C(18A)
Zr(1A)–CCp(1) (avg)
Zr(1A)–CCp(2) (avg)
Zr(1A)–Cpcen
2.449(5)
2.434(4)
2.571(10)
2.462(9)
2.411(7)
2.492(10)
2.589(11)
2.593(10)
2.532(8)
2.520(10)
2.574(12)
2.618(11)
2.505
Zr(1)–Cl(1)
Zr(1)–Cl(2)
Zr(1)–C(3)
Zr(1)–C(4)
Zr(1)–C(5)
2.442(5)
2.441(4)
2.556(10)
2.468(9)
2.453(8)
2.533(10)
2.595(11)
2.582(11)
2.541(8)
2.542(8)
2.584(9)
2.608(11)
2.521
Zr(1)–Cl(1)
Zr(1)–Cl(2)
Zr(1)–C(1)
Zr(1)–C(2)
Zr(1)–C(3)
Zr(1)–C(4)
Zr(1)–C(9)
2.429(7)
2.429(7)
2.532(1)
2.493(2)
2.473(2)
2.564(2)
2.636(2)
b
Zr–CCp
Zr(1)–C(6)
Zr(1)–C(7)
Zr(1)–C(14)
Zr(1)–C(15)
Zr(1)–C(16)
Zr(1)–C(17)
Zr(1)–C(18)
Zr(1)–CCp(1) (avg)
Zr(1)–CCp(2) (avg)
Zr(1)–Cpcen
C(3)–C(2)
Zr(1)avg–CCp (avg)
2.539
2.567
2.224
1.465(18)
1.534(15)
2.571
2.241
1.484(16)
1.558(16)
c
Zr–Cpcen
Zr(1)–Cpcen
C(1)–C(10)
2.231(0)
1.476(7)
CCp–C(R) d
C(3A)–C(2A)
C(14A)–C(13A)
C(14)–C(13)
Bond angles
Cl–Zr–Cl
Cpcen–Zr–Cpcen
Cl(1A)–Zr(1A)–Cl(2A)
Cpcen–Zr(1A)–Cpcen
C(3A)–Cpcen–Cpcen
–C(14A)
96.45(16) Cl(1)–Zr(1)–Cl(2)
96.18(17) Cl(1)–Zr(1)–Cl(1A)
98.98(2)
128.66(6)
113.7(8)
e
132.72
Cpcen–Zr(1)–Cpcen
C(3)–Cpcen–Cpcen
–C(14)
131.98
29.3(8)
Cpcen–Zr(1)–Cpcen
C(1A)–Cpcen–Cpcen
–C(1)
Cp(R1)–Cpcen–Cpcen
–27.5(9)
–Cp(R2) f
a As the zirconium atom resides on a point of symmetry, the second indenyl ligand was generated by a C2 symmetry operation.
b The distance from the zirconium atom to the carbon atoms in the five-membered ring in the indenyl ligand.
c The average of the two vectors drawn from the metal to the centroid of the five-membered ring in the indenyl ligand.
d The length of the bond that connects the substituent to the indenyl ligand.
e The angle formed between the two ring centroids and the zirconium atom.
f The torsional angle between the R-substituents on the two indenyl ligands when looking along an imaginary line connecting the two indenyl
ring centroids.
Fig. 2. ORTEP diagram of the two racemic enantiomers of bis(1-ethyl-indenyl)zirconium dichloride (4b) with 50% probability thermal ellipsoids
(H-atoms on C12a and C12b omitted for clarity).
locene is the larger Cl–Zr–Cl bond angle observed. To
relieve any overbearing steric strain, the dihedral angle
formed between the least squares planes through the
more flexible cyclohexyl and neomenthyl entities. A
possible concomitant effect of the phenyl rings being
placed further away from the open face of the metal-

120
N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
phenyl ring and the indenyl ligands is 34.93(4)° (the
dihedral angle to the five-membered ring is 32.21(5)°).
This angle is considerably larger than the same angle in
the 2-phenyl substituted metallocene bis(2-phenyl-in-
denyl)zirconium dichloride, which is only 10.44° for the
‘meso-like’ structure and 11.54° for the ‘rac-like’ struc-
tures [11,13]. Even in the di-substituted metallocene,
bis(1-methyl-2-phenyl-indenyl)zirconium
dichloride,
this dihedral angle is only 26.4(8)° (‘meso-like’) and
31.4(8)° (‘rac-like’) [13]. A distinct feature of the latter
two metallocenes, synthesized by the Waymouth
group, is that both the ‘meso-like’ and ‘rac-like’ struc-
tures are found in the same crystal structure implying
that they are similar in energy (Scheme 4). However,
only one stereoisomer of 10b is found in the solid state,
implying unfavorably high steric energies in all other
conformers.
The size of the ligand substituents and eventual
conformation adopted by these ligands has a direct
Fig. 4. (a) ORTEP diagram of bis(1-phenyl-indenyl)zirconium dichlo-
ride (10b) with 40% probability thermal ellipsoids (top) and (b) 10b
viewed down the five-membered rings of the indenyl ligands (bottom).
As the second ligand is generated by symmetry, it is not numbered.
Fig. 5. The ligands in unbridged Group 4 metallocenes can adopt
three conformations with respect to each other. These conformers are
dictated by the size of the substituents on the indenyl ligands.
impact on the space available to reactant molecules in
the reaction sphere of the metallocene during an olefin
polymerization reaction. This issue will be more fully
discussed in a related paper [22].
Fig. 3. Molecular geometry of 4b viewed down the five-membered
rings of the indenyl ligands (a) R,R-enantiomer (top) and (b) S,S-
enantiomer (bottom).

N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
121
3. Conclusions
NMR spectroscopic analyses of the metallocenes, were
first dried over calcium hydride, subjected to three
freeze–pump–thaw deoxygenating cycles and then col-
lected for use by a trap-to-trap distillation at reduced
pressure. The latter procedures were carried out in an
all-glass manifold. Technical grade indene (Aldrich,
90%) was purified according to the procedure outlined
by Perrin [37]. All indene ligands were distilled under
reduced pressure, from calcium hydride, before use in
the synthesis of the metallocenes. 1-Indanone [38], 2-in-
danone [39], 2-methylindene (1a) [33], 1-ethylindene
(4a) [29], 1-iso-propylindene (5a) [29], 3-tert-butylin-
dene (6a) [32], 2-trimethylsilylindene (8a) [31], 1-
trimethylsilylindene (7a) [33], 2-phenylindene (9a)
[11,30], 3-phenylindene (10a) [30], 2-benzylindene (11a)
[20] and bis(2-phenyl-indenyl)zirconium dichloride (9b)
[11] were synthesized according to literature procedures.
NMR spectra were recorded on either a Bruker AC 200
MHz or Bruker DRX 400 MHz spectrometer. Elemen-
tal analysis was performed by the Agricultural Re-
search Council (Pretoria, South Africa) and
high-resolution mass spectrometry (HR-MS) by the
Cape Technikon (Cape Town, South Africa).
A series of 1- (and 3-) and 2-substituted indene
ligands were synthesized and their lithiated salts reacted
with ZrCl4 to give the corresponding 1- and 2-bis(R-in-
denyl)zirconium dichloride metallocenes. The 1- and
3-substituted indenes are prochiral resulting in two
diastereomers being formed, viz. one meso- and two
rac-enantiomers making up the other diastereomer.
These could be separated and purified by fractional
crystallization.
The crystal structures of two 1-substituted metal-
locenes, 4b and 10b, were successfully determined by
X-ray diffraction at 173 K. The indenyl ligands in 4b
are orientated so as to place the ethyl groups syn with
respect to each other, over the open sector of the
metallocene, pointing between the two chloride atoms.
In 10b, due to the larger size of the phenyl ligand, the
indenyl ligands are orientated to place these sub-
stituents anti to each other towards the back sector of
the bent metallocene.
What is clear from these and related crystal struc-
tures are that the two substituents on the different rings
in the metallocene interact with each other and depend-
ing on their size adopt a specific conformation in the
solid state. This should have implications on the use of
these metallocenes in olefin polymerization studies [22].
4.2. 1-Methylindene (2a)
n-Butyllithium (14.3 ml, 2.4 M, 34.4 mmol) was
added drop-wise to a solution of indene (4.00 g, 34.4
mmol, 4.0 ml) in 80 ml diethyl ether at 0°C. This was
slowly allowed to warm to room temperature and
stirred for 3 h in total. This orange–yellow solution
was then added drop-wise via cannula to iodomethane
(9.6 g, 8.61 ml, 0.138 mol) in 50 ml diethyl ether at 0°C.
This was stirred overnight and the reaction terminated
by the addition of 50 ml of a saturated aqueous NH4Cl
solution. The organic material was extracted into di-
ethyl ether, separated, dried (MgSO4), filtered and the
solvent removed at a rotary-evaporator. The remaining
product was distilled at reduced pressure to give a
colorless oil (2a, 4.34 g, 75%), which turned yellow on
standing at room temperature (r.t.). 1H-NMR (200
MHz, CDCl3): l 7.15–7.43 (m, 4H, arom. H), 6.77 (dd,
4. Experimental
4.1. General procedures
All experimental procedures, unless specified other-
wise, were performed under an argon atmosphere em-
ploying standard Schlenk techniques and apparatus.
Solvents employed in reactions were distilled under a
nitrogen atmosphere from an appropriate drying agent.
,
Tetrahydrofuran and ether were first pre-dried over 4 A
molecular sieves and then distilled from sodium wire/
benzophenone. Toluene was dried by heating under
reflux over molten sodium. Dichloromethane, benzene,
hexane and pentane were distilled from calcium hy-
dride. All solvents were transferred to reaction vessels
via a cannula from solvent collection flasks. The sol-
vents chloroform-d and benzene-d6, employed in the
4
3
3J=5.5 Hz, J=1.9 Hz, 1H, 3-CH), 6.47 (dd, J=5.5
4
Hz, J=1.9 Hz, 1H, 2-CH), 3.48 (m, 1H, 1-CH), 1.31
(d, 3J=7.6 Hz, 3H, CH3). 13C-NMR (50.3 MHz,
CDCl3): l 149.14, 143.26 (C-3a and C-7a), 141.26,
130.11, 126.35, 124.72 (arom. C), 122.56 (C-3), 120.96
(C-2), 45.06 (C-1), 15.95 (CH3).
4.3. 2-Ethylindene (3a)
Bromoethane (4.12 g, 37.8 mmol; 2.82 ml) was added
dropwise, from a pressure-equalizing dropping funnel
to magnesium (0.920 g, 37.8 mmol) suspended in 100
ml of diethyl ether at a rate to effect gentle reflux. Once
all the magnesium had been consumed, 2-indanone
Scheme 4. Both the anti-‘rac-like’ and syn-‘meso-like’ structures are
found in the crystal structure of bis[2-phenylindenyl]zirconium dichlo-
ride.

122
N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
(5.00 g, 37.8 mmol) dissolved in 50 ml of diethyl ether,
was slowly added drop-wise at 0°C via cannula. A
white mixture was formed by the end of the addition,
which was slowly allowed to warm to r.t. and then
stirred overnight. The reaction mixture was cooled to
0°C and the reaction terminated by the addition of 50
ml of a saturated aqueous NH4Cl solution. The organic
layer was extracted with diethyl ether, dried (MgSO4),
filtered and the solvent removed on a rotary-evapora-
tor. The product was taken up in 200 ml of benzene,
p-toluenesulfonic acid hydrate (0.5 g) added and the
solution heated under reflux overnight in a Dean–Stark
apparatus. A saturated aqueous Na2CO3 solution was
added to the remaining benzene, the organic layer
extracted with diethyl ether, separated, dried (MgSO4),
filtered and the solvent removed at the rotary-evapora-
tor. The remaining product was distilled at reduced
pressure to give a colorless oil (3a, 3.2 g, 59%), which
formed during the addition and the reaction stirred
overnight after which a 50 ml saturated aqueous NH4Cl
solution was added, at 0°C, to terminate the reaction.
The organic material was extracted into diethyl ether,
dried (MgSO4), filtered and the solvent removed at the
rotary-evaporator. The remaining product was purified
by passage through a short silica column using hexane
eluent to remove all non-polar products. An ethyl
acetate:hexane (1:1) mixture was then employed to re-
trieve the desired product, which was taken up in
benzene (200 ml) and heated under reflux overnight
together with p-toluenesulfonic acid hydrate (0.6 g) in a
Dean–Stark apparatus. A 50 ml saturated aqueous
Na2CO3 solution was added, the organic layer extracted
into diethyl ether, separated, dried (MgSO4), filtered
and the solvent removed at the rotary-evaporator to
1
leave a yellow–white solid (14a, 6.4 g, 70%). H-NMR
(400 MHz, CDCl3): l 8.25 (m, 1H, arom. H), 7.83 (m,
1H, arom. H), 7.75 (m, 1H, arom. H), 7.40–7.48 (m,
6H, arom. H), 7.30 (m, 1H, arom. H), 7.20 (m, 1H,
arom. H), 7.09 (d, 4J=0.5 Hz, 1H, 3-CH), 3.83 (d,
4J=0.6 Hz, 2H, 1-CH2). 13C-NMR (100.6 MHz,
CDCl3): l 145.88, 145.29, 143.22, 135.64, 133.99 (C-3a,
C-7a, C-1%, C-4% and C-8%), 131.53, 128.43, 127.63,
126.62, 126.10, 125.96, 125.80, 125.22, 124.71, 123.59,
121.02 (arom. C, C-2 and C-3), 42.91 (C-1). Anal. Calc.
for C19H14: C, 94.18; H, 5.82. Found: C, 93.79; H,
5.84%. HR-MS (m/z): Calc. for C19H14 (M+),
242.1096; found (EI), 242.1091.
1
turned yellow on standing at r.t. H-NMR (400 MHz,
4
CDCl3): l 7.05–7.35 (m, 4H, arom. H), 6.48 (t, J=0.6
4
Hz, 1H, 3-CH), 3.28 (d, J=0.5 Hz, 2H, 1-CH2), 2.48
(q, 3J=7.4 Hz, 2H, CH2), 1.20 (t, 3J=7.5 Hz, 3H,
CH3). 13C-NMR (100.6 MHz, CDCl3): l 152.40, 145.71
(C-3a and C-7a), 126.22, 125.17, 123.49, 123.35 (arom.
C), 143.06 (C-2) 119.84 (C-3), 40.92 (C-1), 24.78 (CH2),
14.09 (CH3).
4.4. 1-Benzylindene (12a)
The procedure followed in the synthesis of 1-
n
methylindene (3a) was followed except that BuLi (43
4.6. 3-(1)-Naphthylindene (14a)
ml, 2.0 M, 86.1 mmol) was added to indene (10.0 g,
10.0 ml, 86.1 mmol) in 100 ml of diethyl ether. This
solution was then added drop-wise via cannula to ben-
zylbromide (14.7 g, 10.2 ml, 86.1 ml) in 50 ml of diethyl
ether. After work-up, the desired product was obtained
as a colorless oil (13a, 10.8 g, 61%), which turned
1-Bromonaphthalene (8.62 g, 5.78 ml, 41.6 mmol), in
50 ml of diethyl ether, was added from a pressure-
equalizing dropping funnel to magnesium (1.01 g, 45.8
mmol) suspended in 500 ml of diethyl ether. After all
the magnesium had been consumed, 1-indanone (5.00 g,
37.8 mmol) in 100 ml of diethyl ether was slowly added
drop-wise via a cannula, at 0°C. The white mixture that
formed was stirred overnight at r.t. and the reaction
terminated by the addition of 50 ml of a saturated
aqueous NH4Cl solution at 0°C. The organic material
was extracted into diethyl ether, separated, dried
(MgSO4), filtered and the solvent removed on a rotary-
evaporator to leave an orange oil. This was purified by
passage through a short silica column. Hexane eluent
was first used to remove non-polar side-products and
then an ethyl acetate–hexane (1:1) solvent mixture was
used to retrieve the desired product as a viscous orange
oil. This was taken up in 200 ml of benzene and
refluxed overnight in a Dean–Stark apparatus together
with p-toluenesulfonic acid hydrate (0.6 g). The acid
was neutralized by the addition of a 50 ml saturated
aqueous Na2CO3 solution. The organic material was
extracted into diethyl ether, separated, dried (MgSO4),
filtered and the solvent removed at the rotary-evapora-
1
yellow on standing at r.t. H-NMR (200 MHz, CDCl3):
3
l 7.09–7.35 (m, 9H, arom. H), 6.76 (dd, J=5.5 Hz,
3
3
4J=1.8 Hz, 1H, 3-CH), 6.41 (dd, J=5.6 Hz, J=1.9
2
Hz, 1H, 2-CH), 3.69 (m, 1H, 1-CH), 3.09 (dd, J=13.5
3
2
Hz, J=6.8 Hz, 1H, CHH), 2.68 (dd, J=13.5 Hz,
3J=9.2 Hz, 1H, CHH). 13C-NMR (50.3 MHz, CDCl3):
l 147.03, 144.27, 140.32 (C-3a, C-7a and C-1’), 138.89,
130.92, 129.00, 128.27, 126.64, 126.20, 124.61 (arom.
C), 123.14 (C-3), 121.09 (C-2), 51.75 (C-1), 37.96 (CH2).
4.5. 2-(1)-Naphthylindene (13a)
To magnesium (1.01 g, 41.6 mmol) suspended in 500
ml of diethyl ether, 1-bromonaphthalene (7.83 g, 5.26
ml, 37.8 mmol) in 50 ml of diethyl ether was added
dropwise from a pressure-equalizing dropping funnel.
After all the magnesium had been consumed, 2-in-
danone (5.00 g, 37.8 mmol), in 100 ml of diethyl ether,
was added dropwise over 5 h. A white precipitate

N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
123
tor to yellow solid. This was purified by passage
4.9. Bis[2-ethyl-indenyl]zirconium dichloride (3b)
through a short silica column, using hexane as the
eluent to obtain the desired product as a white–yellow
solid (14a, 6.38 g, 67%). H-NMR (200 MHz, CDCl3):
The same synthetic procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(6.3 ml, 2.2 M, 13.9 mmol) was added to 3a (3.00 g,
23.0 mmol) in 80 ml of THF. After removal of the
solvent in vacuo, 60 ml of toluene was added followed
by ZrCl4 (1.62 g, 6.93 mmol) in 60 ml of toluene to give
a yellow mixture. The clear yellow filtrate from the
filtration was concentrated and crystallization effected
at −18°C. The pure product (3b) was collected as
orange–yellow needle-like crystals (1.4 g, 43%). Anal.
1
l 7.81–7.93 (m, 3H, arom. H), 7.05–7.57 (m, 8H,
arom. H), 6.61 (t, 3J=2.1 Hz, 1H, 2-CH), 3.60 (d,
3J=1.9 Hz, 2H, 1-CH2). 13C-NMR (50.3 MHz,
CDCl3): l 145.71, 144.13, 143.93, 134.10, 133.71 (C-3a,
C-7a, C-1%, C-4% and C-8%), 132.99, 128.22, 127.92,
126.51, 126.25, 126.14, 125.81, 125.72, 125.46, 124.83,
123.86 (arom. C), 131.87 (C-3), 120.83 (C-2), 38.55
(C-1). Anal. Calc. for C19H14: C, 94.18; H, 5.82. Found:
C, 93.77; H, 5.82%. HR-MS (m/z): Calc. for C19H14
(M+), 242.1096; found (EI), 242.1106.
Calc. for C22H22Cl2Zr: C, 58.91; H, 4.94. Found: C,
22
59.62; H, 5.11%. HR-MS (m/z): Calc. for C22H Cl920Zr
35
(M+), 446.0146; found (EI), 446.0141.
4.7. Bis[2-methyl-indenyl]zirconium dichloride (1b)
4.10. rac- and meso-Bis[1-ethyl-indenyl]zirconium
dichloride (4b)
n-Butyllithium (6.4 ml, 1.8 M, 11.5 mmol) was added
drop-wise to 1a (1.50 g, 11.5 mmol) in 50 ml of THF at
−78°C. This was slowly allowed to warm to r.t. and
stirred for 4 h in total. The solvent was removed in
vacuo to leave a white–yellow solid to which 70 ml of
toluene was added. The resulting slurry was cooled to
−78°C and ZrCl4 (1.34 g, 5.76 mmol) in 50 ml of
toluene added drop-wise via a cannula. This mixture
was slowly allowed to warm to r.t., developing a ca-
nary-yellow color, and stirred for 18 h. The reaction
mixture was filtered through a 2 cm celite pad in an
inert-air filtration apparatus. The pad was washed with
toluene until the washings were clear. The volume of
clear filtrate solution was reduced in vacuo and crystal-
lization effected at −18°C. The pure product was
collected as yellow needle-like crystals of 1b (0.21 g,
10%). Anal. Calc. for C20H18Cl2Zr: C, 57.13; H, 4.37.
Found: C, 55.93; H, 4.37%. HR-MS (m/z): Calc. for
The same synthetic procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(7.7 ml, 1.8 M, 13.9 mmol) was added to 4a (2.00 g,
13.9 mmol) in 80 ml of THF. After removal of the
solvent in vacuo, 80 ml of toluene was added followed
by ZrCl4 (1.62 g, 6.93mmol), in 60 ml of toluene, to
give an orange colored reaction mixture. NMR spectral
analysis (not shown) of this crude material revealed a
50:50 rac:meso isomer mixture. The clear orange filtrate
from the filtration was concentrated and repeated crys-
tallization from toluene at −18°C gave the two iso-
mers of 4b viz. the rac-isomer as yellow needle-like
crystals (determined by X-ray crystallography) and
meso-isomer as an amorphous yellow solid. Total yield
of 4b was 0.60 g (19%). Anal. Calc. for C22H22Cl2Zr: C,
58.91; H, 4.94. Found: C, 58.39, H, 4.94%. HR-MS
C20H Cl920Zr (M+), 417.9833; found (EI), 417.9835.
(m/z): Calc. for C22H Cl920Zr (M+), 446.0146; found
35
18
35
22
(FAB), 446.01.
4.8. rac- and meso-Bis[1-methyl-indenyl]zirconium
dichloride (2b)
4.11. rac- and meso-Bis[1-iso-propyl-indenyl]zirconium
dichloride (5b)
The same synthetic procedure employed in the syn-
thesis of 1b were followed except that n-butyllithium
(11.5 ml, 2.0 M, 23.0 mmol) was added to 2a (3.00 g,
23.0 mmol) in 80 ml of THF. After removal of the
solvent in vacuo, 60 ml of toluene was added followed
by ZrCl4 (2.68 g, 11.5 mmol) in 60 ml of toluene, this
yielding an orange mixture. NMR spectral analysis (not
shown) of this crude material revealed a 50:50 rac:meso
isomer mix. The clear orange filtrate from the filtration
concentrated in vacuo and crystallization effected at
−18°C. The pure product (2b) was collected as a 1:1
mixture of rac:meso isomers in the form of a yellow
powder (1.1 g, 23%). Anal. Calc. for C20H18Cl2Zr: C,
57.13; H, 4.31. Found: C, 55.97; H, 4.43%. HR-MS
The same synthetic procedures employed in the syn-
thesis of 1b were followed except that n-butyllithium
(8.62 ml, 2.2 M, 19.0 mmol) was added to 5a (3.00 g,
19.0 mmol) in 80 ml of THF. After removal of the
solvent in vacuo, 80 ml of toluene was added followed
by ZrCl4 (2.2 g, 9.48 mmol) in 50 ml of toluene to give
an orange–yellow reaction mixture. The clear yellow–
orange filtrate from the filtration was concentrated in
vacuo with analysis by NMR spectroscopy (not shown)
revealing a 50:50 rac:meso isomer ratio. The first isomer
was recrystallized from toluene, layered with pentane,
as an amorphous yellow powder at −18°C. Continued
crystallization from toluene gave the second isomer as
needle-like yellow crystals. Total yield of 5b was 1.6 g
(35%). Anal. Calc. for C24H26Cl2Zr: C, 60.48; H, 5.50.
(m/z): Calc. for C20H Cl920Zr (M+), 417.9833; found
35
18
(EI), 417.9866.

124
N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
Found: C, 61.10; H, 5.61%. HR-MS (m/z): Calc. for
26
4.13. Bis[2-trimethylsilyl-indenyl]zirconium dichloride
(7b)
C24H Cl920Zr (M+), 474.0459; found (EI), 474.0467.
35
The first diastereomer (0.020 g; 0.0419 mmol), sus-
pended in 10 ml of pentane, was quantitatively con-
verted to its dimethyl analogue by adding
methyllithium (0.084 mmol, 1 M, 0.084 ml) and stirring
at r.t. for 12 h. The solvent was removed in vacuo,
taken up in benzene-d6, and filtered via a glass-filter
paper-tipped cannula into an argon filled NMR tube.
The product was confirmed to have C2-symmetry and
hence the rac-diastereomer due a single Zr–CH3 below
The same synthetic procedure employed in the syn-
thesis of 1b were followed except that n-butyllithium
(2.89 ml, 2.2 M, 6.37 mmol) was added to 7a (1.20 g,
6.37 mmol) in 80 ml of THF. After removal of the
solvent in vacuo, 40 ml of toluene was added followed
by ZrCl4 (0.74 g, 3.18 mmol) in 40 ml of toluene to give
a yellow reaction mixture. The clear yellow–orange
filtrate from the filtration was concentrated in vacuo
and crystallization effected at −18°C from toluene to
give the product as yellow rectangular crystals of 7b
(0.53 g, 31%). Anal. Calc. for C24H30Cl2Si2Zr: C, 53.70;
H, 5.63. Found: C, 53.95; H, 5.62%. HR-MS (m/z):
1
0 ppm. H-NMR (400 MHz, C6D6): l 6.88–7.37 (m,
3
8H, arom. H), 5.51 (d, J=3.3 Hz, 2H, 3-CH), 5.47 (d,
3J=3.2 Hz, 2H, 2-CH), 3.20 (m, 3J=6.8 Hz, 2H,
3
CH(CH3)2), 1.18 (d, J=6.8 Hz, 6H, CH(CH3)(CH3)),
3
1.04 (d, J=6.8 Hz, 6H, CH(CH3)(CH3)) and −1.10
Calc. for C24H Cl2Si290Zr (M+), 534.0310; found (EI),
35
30
(s, 6H, Zr–(CH3)2).
534.0307.
4.12. rac- and meso-Bis[1-tert-butyl-indenyl]zirconium
dichloride (6b)
4.14. rac- and meso-Bis[1-trimethylsilyl-indenyl]zirco-
nium dichloride (8b)
The same synthetic procedure employed in the syn-
thesis of 1b were followed except that n-butyllithium
(4.6 ml, 2.0 M, 9.3 mmol) was added to 6a (1.60 g, 9.29
mmol) in 70 ml of THF. After removal of the solvent in
vacuo, 80 ml of toluene was added followed by ZrCl4
(1.08 g, 4.64 mmol) in 50 ml of toluene to give an
orange–yellow reaction mixture. The clear yellow–or-
ange filtrate from the filtration was concentrated in
vacuo with analysis by NMR spectroscopy (not shown)
revealing a 50:50 rac:meso isomer ratio. Crystallization
from a toluene solution at −18°C gave the first isomer
as an amorphous yellow powder. Dissolving this pow-
der in CH2Cl2 and crystallization at −18°C gave fine
yellow crystals of 6b (0.68 g, 29%). These slowly dark-
ened (\1month) on standing at r.t. to give a dirty-yel-
low product. However, analysis by NMR spectroscopy
indicates that this material still contained substantial
amounts of pure 6b. Due to decomposition in the
mother-liquor none of the second isomer could be
obtained. Anal. Calc. for C26H30Cl2Zr: C, 61.88; H,
5.99. Found: C, 61.11; H, 5.91%. HR-MS (m/z): Calc.
The same synthetic procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(7.53 ml, 1.48 M, 11.2 mmol) was added to 8a (2.10 g,
11.2 mmol) in 80 ml of THF. After removal of the
solvent in vacuo, 80 ml of toluene was added followed
by ZrCl4 (1.29 g, 5.57 mmol) in 50 ml of toluene giving
a yellow mixture. After stirring for 18 h, the toluene
was removed in vacuo and 100 ml of CH2Cl2 added to
the remaining solid, which was then filtered through a 2
cm celite pad in an inert-air filtration apparatus. The
pad was washed with CH2Cl2 until the washings were
clear, a small aliquot was taken from the filtrate and
the solvent removed in vacuo. NMR spectral analysis
(not shown) on this sample revealed a 50:50 rac:meso
isomer mix. The clear orange filtrate was placed in the
freezer and crystallization effected at −18°C to give
yellow needle-like crystals of 8b (0.84 g, 28%). Anal.
Calc. for C24H30Cl2Si2Zr: C, 53.70; H, 5.63. Found: C,
53.16; H, 5.65%. HR-MS (m/z): Calc. for
C24H Cl2Si920Zr (M+), 534.0310; found (EI), 534.0321.
35
30
for C26H Cl920Zr (M+), 502.0772; found (EI), 502.0753.
35
30
The first diastereomer (0.020 g; 0.037 mmol), sus-
The first diastereomer (0.020 g; 0.0396 mmol), sus-
pended in 10 ml of toluene, was quantitatively con-
verted to its dimethyl analogue by adding
methyllithium (0.075 mmol, 1 M, 0.075 ml) and stirring
at r.t. for 12 h. The solvent was removed in vacuo,
taken up in benzene-d6, and filtered via a glass-filter
paper-tipped cannula into an argon filled NMR tube.
The product was confirmed to have C2-symmetry and
hence the rac-diastereomer due a single Zr–CH3 reso-
nance below 0 ppm. 1H-NMR (400 MHz, C6D6): l
pended in 10 ml of pentane, was quantitatively con-
verted to its dimethyl analogue by adding
methyllithium (0.079 mmol, 1 M, 0.08 ml) and stirring
at r.t. for 12 h. The solvent was removed in vacuo,
taken up in benzene-d6, and filtered via a glass-filter
paper-tipped cannula into an argon filled NMR tube.
The product was confirmed to have C2-symmetry and
hence the rac-diastereomer due a single Zr–CH3 reso-
nance below 0 ppm. 1H-NMR (400 MHz, C6D6): l
3
3
7.17–7.62 (m, 8H, arom. H), 6.05 (d, J=2.69 Hz, 2H,
6.57–7.45 (m, 8H, arom. H), 5.47 (d, J=3.3 Hz, 2H,
3-CH), 5.39 (d, 3J=3.07 Hz, 2H, 2-CH), –0.16 (s, 18H,
3
3-CH), 5.4 (d, J=3.2 Hz, 2H, 2-CH), 1.04 (s, 18H,
C(CH3)3), and −1.08 (s, 6H, Zr–(CH3)2).
Si(CH3)3), and –1.08 (s, 6H, Zr–(CH3)2).

N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
125
4.15. rac- and meso-Bis[1-phenyl-indenyl]zirconium
dichloride (10b)
meso-diastereomer as a yellow amorphous solid. The
rac-isomer could be obtained as yellow, irregularly
shaped crystals from CH2Cl2 at −18°C. Total yield of
12b was 1.34 g (32%). Anal. Calc. for C32H26Cl2Zr: C,
67.11; H, 4.57. Found: C, 66.44; H, 4.62%. HR-MS
The same synthetic procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(4.86 ml, 1.85 M, 9.00 mmol) was added to 10a (1.73 g,
9.00 mmol) in 100 ml of THF. After removal of the
solvent in vacuo, 60 ml of toluene was added followed
by ZrCl4 (1.05 g, 4.50 mmol) in 60 ml of toluene giving
a orange mixture on warming to r.t. and stirring for 18
h. The solvent from the clear red filtrate was removed
in vacuo and crystallization effected from CH2Cl2 at
−18°C. A small aliquot was taken from the filtrate
before crystallization and its solvent removed in vacuo.
NMR spectral analysis (not shown) of this sample
revealed a 54:46 rac:meso isomer mixture. The R,R-
enantiomer (as determined by X-ray crystallography)
was obtained as orange rectangular crystals of 10b (0.96
g, 40%). No meso-isomer was obtained due to degrada-
tion of the crystallization liquor during the repeated
crystallisations. Anal. Calc. for C30H22Cl2Zr: C, 65.67;
H, 4.04. Found: C, 65.67; H, 4.13%. HR-MS (m/z):
(m/z): Calc. for C32H Cl920Zr (M+), 570.0459; found
35
26
(EI), 570.0449.
4.18. Bis[2-(1)-naphthyl-indenyl]zirconium dichloride
(13b)
The same synthesis procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(2.3 ml, 2.2 M, 4.95 mmol) was added to 13a (1.2 g,
4.95 mmol) in 80 ml of THF. After removal of the
solvent in vacuo, 40 ml of toluene was added followed
by ZrCl4 (0.557 g, 2.48 mmol) in 30 ml of toluene to
give a yellow mixture reaction mixture on warming to
r.t. and stirring for 18 h. The clear yellow filtrate from
the filtration procedure was concentrated in vacuo and
crystallization from CH2Cl2 effected at −18°C. Pure
product (13b) from the crystallizations was obtained as
either a yellow powder or yellow platelets. Total yield
was 0.47 g (29%). Anal. Calc. for C38H26Cl2Zr: C,
70.78; H, 4.06. Found: C, 70.48; H, 4.31%. HR-MS
Calc. for C30H Cl920Zr (M+), 542.0146; found (EI),
35
22
542.0180.
4.16. Bis[2-benzyl-indenyl]zirconium dichloride (11b)
(m/z): Calc. for C38H Cl920Zr (M+), 642.0459; found
35
26
(EI), 642.0475.
The same synthetic procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(2.1 ml, 1.85 M, 3.88 mmol) was added to 11a (0.800 g,
3.88 mmol) in 50 ml of THF. After removal of the
solvent in vacuo, 50 ml of toluene was added followed
by ZrCl4 (0.451 g, 1.94 mmol) in 50 ml of toluene to
give a yellow mixture on warming to r.t. and stirring
for 18 h. The clear yellow filtrate from the filtration was
concentrated in vacuo and crystallization effected at
−18°C. Pure product (11b) was obtained as a yellow
amorphous solid (0.59 g, 53%). Anal. Calc. for
C32H26Cl2Zr: C, 67.11; H, 4.57. Found: C, 67.48; H,
4.19. rac- and meso-Bis[1-(1)-naphthyl-indenyl]-
zirconium dichloride (14b)
The same synthesis procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(5.6 ml, 2.2 M, 12.38 mmol) was added to 14a (3.00 g,
12.38 mmol) in 100 ml of THF. After removal of the
solvent in vacuo, 60 ml of toluene was added followed
by ZrCl4 (1.44 g, 6.19 mmol) in 50 ml of toluene to give
a yellow reaction mixture on warming to r.t. and
stirring for 18 h. The solvent was removed in vacuo and
replaced with 100 ml of CH2Cl2. The slurry was filtered
through a 2 cm celite pad in an inert-air filtration
apparatus. The solvent was removed from an aliquot
taken from this filtrate and analysis by NMR spec-
troscopy (not shown) revealed a 60:40 rac:meso isomer
ratio. The solvent was removed in vacuo and replaced
with a THF–pentane solvent mixture and crystalliza-
tion effected at −18°C to give a yellow powder. Anal-
ysis by NMR spectroscopy revealed this product to be
the THF adduct (product:THF=1:1.5). The product
could be freed of solvent by crystallization from tolu-
ene. The second diastereomer was obtained by crystal-
lization from toluene. Total yield of 14b was 0.88 g
(22%). Anal. Calc. for C38H26Cl2Zr: C, 70.78; H, 4.06.
Found: C, 70.57; H, 4.21%. HR-MS (m/z): Calc. for
4.62%. HR-MS (m/z): Calc. for C32H Cl920Zr (M+),
35
26
570.0459; found (EI), 570.0440.
4.17. rac- and meso-Bis[1-benzyl-indenyl]zirconium
dichloride (12b)
The same synthetic procedure employed in the syn-
thesis of 1b was followed except that n-butyllithium
(9.80 ml, 1.48 M, 14.5 mmol) was added to 12a (3.00 g,
14.5 mmol) in 100 ml of THF. After removal of the
solvent in vacuo, 60 ml of toluene was added followed
by ZrCl4 (1.69 g, 7.27 mol) in 60 ml of toluene. This
gave an orange mixture on warming to r.t. and stirring
for 18 h. The clear orange filtrate from the filtration
was concentrated in vacuo. Analysis by NMR spec-
troscopy (not shown) revealed a 52:48 rac:meso ratio.
Crystallization from toluene at −18°C first gave the
C38H Cl920Zr (M+), 642.0459; found (EI), 642.0458.
35
26

126
N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
The first diastereomer (0.020 g; 0.031 mmol), sus-
Table 4
Crystal data and structure refinement for 4b and 10b
pended in 10 ml of toluene, was quantitatively con-
verted to its dimethyl analogue by adding
methyllithium (0.062 mmol, 1 M, 0.062 ml) and stirring
at r.t. for 12 h. The solvent was removed in vacuo,
taken up in benzene-d6, and filtered via a glass-filter
paper-tipped cannula into an argon filled NMR tube.
The product was confirmed to have C1-symmetry and
hence the meso-diastereomer due two Zr–CH3 reso-
Identification code
4b
10b
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C22H22Cl2Zr
448.52
173(2)
0.71073
Monoclinic
P1n1
C31H24Cl4Zr
629.52
173(2)
0.71073
Monoclinic
C2/c
1
nances below 0 ppm. H-NMR (400 MHz, C6D6): l
Unit cell dimensions
3
,
6.87–7.94 (m, 22H, arom. H), 6.20 (d, J=3.32 Hz,
a (A)
8.1156(4)
13.5223(7)
17.3459(9)
90
91.3650(10)
90
1903.03(17)
4
1.565
90
2H, 3-CH), 5.73 (d, 3J=3.14 Hz, 2H, 2-CH), −0.41 (s,
3H, Zr–CH3), and −0.52 (s, 3H, Zr–CH3).
,
b (A)
109.188(2)
90
90
109.188(2)
90
2712.5(5)
4
,
c (A)
h (°)
i (°)
k (°)
4.20. Crystallography
3
,
Volume (A )
Z
A single crystal (0.28×0.16×0.12 mm) of 4b was
maneuvered to the end of a 0.30 mm Hilgenberg Mark
capillary tube (Glass number 14; Lindemann-glass) and
secured in position using a glass fiber. The glass fiber
was in turn glued to the walls of the capillary. For 10b
a single crystal (0.74×11.5×10 mm) was mounted at
the end of a glass-fiber using epoxy-glue and protected
from the atmosphere by anointing it with a drop of
paraffin oil. Both mounted crystals were then secured
to a brass-collar before moving them to the goniometer.
All of the above procedures were performed in a
Schlenk-tube, under a microscope, with a steady stream
of Argon gas protecting the system.
Dcalc (Mg m−3
Absorption
)
1.542
0.819
0.860
coefficient (mm−1
)
F(000)
Crystal size (mm)
Theta range for data 1.51–28.30
collection (°)
912
1272
0.74×0.23×0.20
5.80–28.30
0.28×0.16×0.12
Index ranges
−105h59;
−165k517;
−225l522
v
−145h514;
−245k524;
−185l518
v
Scan type
Scan width (°)
Scan speed
Reflections collected 11 645
Independent
reflections
0.3
0.3
10 s frame exposures 10 s frame exposures
14 794
6497 [Rint=0.0431] 3341 [Rint=0.0175]
Both crystal data sets were collected on a 1K
SMART Siemens CCD area detector system using
Mo–Ka radiation. X-rays were generated using a regu-
lar sealed tube and a Phillips X-ray generator operating
at 50 kV and 30 mA. A graphite-monochromator fol-
lowed by a 0.5 mm collimator was used. The 9 cm wide
CCD area detector was mounted 4.5 cm from the
crystal and both data sets collected at 173 K. The data
collection nominally covered a full hemisphere of recip-
rocal space, by a combination of three sets of exposures
with 1321 and 2169 frames for 4b and 10b, respectively.
In order to monitor crystal and instrument stability
and to enable crystal decay corrections, the first 50
frames of the first data set were measured again at the
end of the data collection. Crystal decay was found to
be negligible after analyzing the duplicate reflections.
The determination of the unit cell parameters, crystal
orientation and data collection were performed with the
SMART system [40]. The data reduction and absorption
corrections were performed using the program SAINT
[41] and SADABS [42], respectively. The program
SHELXTL-PLUS (Version 5.1) was used for the structure
solution, refinement and publication preparation [43].
Molecular graphics were prepared using ORTEP-3 for
Windows [44]. The structures were solved by direct
methods using Fourier techniques and refined by full
matrix least-squares methods based on F2.
Completeness to
q=28.30
Reflections observed 5211
(\2|)
91.3%
98.8%
3088
Refinement method Full-matrix
Full-matrix
least-squares on F2
6497/15/239
least-squares on F2
3341/0/164
Data/restraints/
parameters
Goodness-of-fit on
1.076
1.026
F2
Final R indices
[I\2|(I)]
R indices (all data)
R1=0.0541,
wR2=0.1053
R1=0.0759,
wR2=0.1163
0.701 and −0.716
R1=0.0199,
wR1=0.0532
R1=0.0224,
wR2=0.0542
0.408 and −0.427
Largest difference
peak and hole
−3
,
(e A
)
The structure of 4b could be refined as a disorder
model in the centrosymmetric space group P21/n. How-
ever, it was possible to resolve the disorder in the space
group P1n1 with Z=4, where the two independent
molecules in the asymmetric unit correspond to two
racemic enantiomers. There is also a large correlation
matrix when the two enantiomers are allowed to refine
in the lower symmetry space group. It was only possible
to arrive at an acceptable solution for 4b by making all
the indenyl carbon atoms isotropic. When the structure

N.E. Grimmer et al. / Journal of Organometallic Chemistry 616 (2000) 112–127
127
[10] M.C. Baird, Chem. Rev. 100 (2000) 1471.
[11] G.W. Coates, R.M. Waymouth, Science 267 (1995) 217.
[12] E. Hauptman, R.M. Waymouth, J. Am. Chem. Soc. 117 (1995)
11586.
[13] R. Kravchenko, A. Masood, R.M. Waymouth, Organometallics
16 (1997) 3635.
was solved in an anisotropic mode C5, C14, C15, C17
and C15a became non-positive definite. The five-mem-
bered ring was also fitted to a regular pentagon (C–
,
C=1.42 A) and allowed to refine as a variable metric
group. Two alternate positions were found for C12a in
the difference electron density map. These were refined
isotropically with a 50% occupancy factor each (viz.
C12a and C12b). The remaining non-hydrogen atoms
were refined anisotropically. The metallocene 10b was
found to inhabit the space group C2/c and all of its
non-hydrogen atoms were refined anisotropically. For
both compounds, the hydrogen atoms were allowed to
refine, by riding on their parent atoms. The data collec-
tion statistics for these two structures are collected in
Table 4.
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Crystallographic data (excluding structure factors)
for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre, CCDC no. 146396 for compound 4b and
CCDC no. 146395 for compound 10b. Copies of this
information may be obtained free of charge from the
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: +44-1223-336-033; e-mail: de-
posit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
Acknowledgements
We would like to thank the University of the Witwa-
tersrand, AECI, THRIP and the Foundation for Re-
search and Development for the funding that has made
this work possible. N.E.G. would also like to thank
these organizations for their generous financial support.
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