Sterically demanding cyclopentadienyl chemistry: Synthesis of iron and zirconium complexes of 1-phenyl-3-methyl-4,5,6,7-tetrahydroindenyl

Article abstract of DOI:10.1016/S0022-328X(99)00446-5

Reaction of phenyl magnesium bromide with the α,β-unsaturated ketone 3-methyl-2,3,4,5,6,7-hexahydroind-8(9)-en-1-one, followed by an aqueous work-up, generates the pro-chiral tetra-substituted cyclopentadiene, 1-phenyl-3-methyl-4,5,6,7-tetrahydroindene, Cp^?H, a precursor to the η⁵-cyclopentadienyl ligand in (Cp^?)₂Fe and [(Cp^?)Fe(CO)]₂(μ-CO)₂. Both complexes were generated as mixtures of rac-(RR and SS)- and meso-(RS)-isomers, and in either case pure meso-isomer was isolated by crystallisation and characterised by single crystal X-ray structure, both molecules having crystallographic C_i symmetry. Reduction with Na/Hg cleaves meso-(RS)-[(Cp^?)Fe(CO)]₂(μ-CO)₂ and the resulting mixture of (R)- and (S)-[(Cp^?)Fe(CO)₂]^- anions reacts with MeI to give racemic (Cp^?)Fe(CO)₂Me, which was characterised by the X-ray crystal structure. The Cp^? ligand is more electron donating than (η-C₅H₅) as revealed by the reduction potential of the (Cp^?)₂Fe⁺/(Cp^?) ₂Fe couple, E°=-0.127 V (vs. Ag AgCl). Reaction of LiCp^? with ZrCl₄ yields the zirconocene dichloride [Zr(Cp^?)₂Cl₂] as mixture of rac- and meso-isomers, from which pure rac-isomer is obtained as a mixture of RR and SS crystals by recrystallisation. The reaction of rac-[Zr(Cp^?)₂Cl₂] with LiMe gives rac-[Zr(Cp^?)₂Me₂]. The structures of RR-[Zr(Cp^?)₂Cl₂] and rac-[Zr(Cp^?)₂Me₂] have been determined by X-ray diffraction. The structural studies reveal the influence of the bulky substituted cyclopentadienyl ligand on the metal-Cp^? distances and other metric parameters.

Full text of DOI:10.1016/S0022-328X(99)00446-5

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 590 (1999) 169–179
Sterically demanding cyclopentadienyl chemistry: synthesis of iron
and zirconium complexes of
1-phenyl-3-methyl-4,5,6,7-tetrahydroindenyl
Andrei S. Batsanov, Brian M. Bridgewater, Judith A.K. Howard, Andrew K. Hughes *,
Claire Wilson
Department of Chemistry, Uni6ersity Science Laboratories, South Road, Durham DH1 3LE, UK
Received 15 June 1999; accepted 8 July 1999
Abstract
Reaction of phenyl magnesium bromide with the a,b-unsaturated ketone 3-methyl-2,3,4,5,6,7-hexahydroind-8(9)-en-1-one,
followed by an aqueous work-up, generates the pro-chiral tetra-substituted cyclopentadiene, 1-phenyl-3-methyl-4,5,6,7-tetrahy-
droindene, Cp‡H, a precursor to the h5-cyclopentadienyl ligand in (Cp‡)2Fe and [(Cp‡)Fe(CO)]2(m-CO)2. Both complexes were
generated as mixtures of rac-(RR and SS)- and meso-(RS)-isomers, and in either case pure meso-isomer was isolated by
crystallisation and characterised by single crystal X-ray structure, both molecules having crystallographic Ci symmetry. Reduction
with Na/Hg cleaves meso-(RS)-[(Cp‡)Fe(CO)]2(m-CO)2 and the resulting mixture of (R)- and (S)-[(Cp‡)Fe(CO)2]− anions reacts
with MeI to give racemic (Cp‡)Fe(CO)2Me, which was characterised by the X-ray crystal structure. The Cp‡ ligand is more
electron donating than (h-C5H5) as revealed by the reduction potential of the (Cp‡)2Fe+/(Cp‡)2Fe couple, E°= −0.127 V (vs.
Ag ꢀ AgCl). Reaction of LiCp‡ with ZrCl4 yields the zirconocene dichloride [Zr(Cp‡)2Cl2] as mixture of rac- and meso-isomers,
from which pure rac-isomer is obtained as a mixture of RR and SS crystals by recrystallisation. The reaction of rac-[Zr(Cp‡)2Cl2]
with LiMe gives rac-[Zr(Cp‡)2Me2]. The structures of RR-[Zr(Cp‡)2Cl2] and rac-[Zr(Cp‡)2Me2] have been determined by X-ray
diffraction. The structural studies reveal the influence of the bulky substituted cyclopentadienyl ligand on the metalꢀCp‡ distances
and other metric parameters. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Cyclopentadienyl; Ferrocene; Iron carbonyls; Zirconium; Chiral metallocene
ferrocenes [Fe(h-C5R5)2] (R=H, Me) [2]. The greater
steric size (Tolman angle) of the h-C5Me5 ligand is vital
to the stabilisation of monomeric complexes of the
lanthanides [3]. Two recent areas of development in
cyclopentadienyl chemistry have been the design and
synthesis of dicyclopentadienyl ligands for the synthesis
of ansa-metallocenes [4], and the synthesis of chiral and
pro-chiral metallocenes [5], and half-sandwich com-
pounds [6].
This paper describes the synthesis of a bulky pro-chi-
ral cyclopentadiene from a well-established cyclopen-
tenone precursor. The ligand system described here was
selected as being the product of a flexible synthesis,
where changes to the ligand could be made by varying
one of several reagents (cyclohexene, crotonic acid,
PhMgBr). Our initial exploration of the coordination
chemistry of this ligand has involved the synthesis and
1. Introduction
The cyclopentadienyl ligand (h-C5H5) is one of the
most ubiquitous ligands of organotransition-metallic
chemistry [1]. The importance of this ligand is primarily
due to the ease of synthesis of complexes incorporating
one or more cyclopentadienyl rings, the fact that the
ligand produces stable complexes by effectively occupy-
ing three coordination sites at the metal and the wide
variation possible in the steric and electronic properties
of these complexes associated with substitution of one
of more of the hydrogen atoms in the C5H5 ring. Thus,
the peralkylated ligand, C5Me5, is more electron donat-
ing, as revealed in the oxidation potentials of the
* Corresponding author. Fax: +44-191-3861127.
E-mail address: a.k.hughes@durham.ac.uk (A.K. Hughes)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00446-5

170
A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
structural characterisation of some representative exam-
ples of iron and zirconium complexes, and these are
described here.
10% NaOH solution in water to facilitate the decompo-
sition of the polyphosphoric acid rather than solid
ammonium sulphate, the combination of these two
changes increases the yield from 36 to 55%.
Nile and co-workers have reported the synthesis of
alkylated 4,5,6,7-tetrahydroindenes via methylation of
the corresponding cyclopentenones [7]. The synthesis of
cyclopentenones by the Nazarov cyclization [8], and
subsequent alkylation is a route to 4,5,6,7-tetrahydroin-
denes [9] that is significantly more facile and versatile
than hydrogenation of metallated indenyl ligands [10].
Reported here is the synthesis and complexation of a
more sterically demanding 4,5,6,7-tetrahydroindene, 1-
phenyl-3-methyl-4,5,6,7-tetrahydroindene (1), from the
same ketone precursor utilised by Nile.
The reaction of 1 with an excess of phenyl magne-
sium bromide, followed by acid-catalysed dehydration,
yields readily the substituted cyclopentadiene 1-phenyl-
3-methyl-4,5,6,7-tetrahydroindene, (Cp‡H) 2. The
1
product was shown by H-NMR, 13C-NMR and GC
mass spectra to be a mixture of four isomers (one of
which is depicted in Scheme 1), differing by the posi-
tions of double bonds within the five-membered ring. 2
could be purified by distillation, although with a sub-
stantial loss, presumably due to pyrolysis of the diene
in the distillation flask.
The synthesis of a range of cyclopentadienes can be
achieved by varying the Grignard used in the reaction
with 1, although the limit of this flexibility is demon-
strated by PhCH2MgBr, which reacts cleanly with the
a,b-unsaturated ketone 1, to generate, after an acid-
catalysed elimination reaction, a benzylidene substi-
tuted cyclopentene, 4, in which the double bond has
been generated in conjugation with the aromatic ring.
The (Cp‡)− anion (5), can be generated from Cp‡H
(2), by reaction with one equivalent of BuLi in diethyl
ether, and thorough washing to remove any unreacted
BuLi. The planar anion 5 is pro-chiral, and its coordi-
nation to a metal atom can generate either an R or S
enantiomer (the notation [13,14] is illustrated in Fig. 1).
In a non-enantioselective synthesis three isomers are
formed the enantiomers RR (25%) and SS (25%) (com-
2. Results and discussion
The synthesis of 3-methyl-2,3,4,5,6,7-hexahydroind-
8(9)-en-1-one (1) (Scheme 1) follows the Nazarov cy-
clization reaction between crotonic acid and cyclo-
hexene in polyphosphoric acid reported originally by
Dev [11] and later by Nile and co-workers [12]. In our
hands, the yield was optimised by efficiently mixing the
crotonic acid and polyphosphoric acid by mechanical
stirring at 60°C for ca. 30 min before adding the
cyclohexene. Addition of the cyclohexene was carried
out over 30 min and the complete mixture was then
stirred at 60°C for 2 h. This appears to prevent the
occurrence of an exothermic initiation of the cyclization
reported by Nile. The second alteration was the use of
Scheme 1. Preparation of 1-phenyl-3-methyl-4,5,6,7-tetrahydroindene and iron complexes. Reagents: (i) PPA; (ii) PhMgBr, then H2O; (iii) BuLi;
(iv) FeCl2; (v) Fe2(CO)9; (vi) Na/Hg; (vii) MeI; (viii) PhCH2MgBr; then H2O; (ix) HCl.

A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
171
The crystal structure of 6 is centrosymmetric (space
group P21/c). The molecule (see Fig. 2 and for metric
data, Table 1) is located at a crystallographic inversion
centre, thus having the meso (RS) configuration, with
the molecular and crystallographic inversion centres
co-incident, and a distal mutual orientation of the
cyclopentadienyl ligands. Although this conformation
reduces ligand–ligand repulsions, the distance between
the iron atom and the cyclopentadienyl ring plane,
Fig. 1. Absolute configuration of a Cp‡ ligand coordinated to a
transition metal.
,
,
1.672 A is still relatively long (cf. 1.648 A in the triclinic
prising collectively the rac diastereomer) and the meso
diastereomer SR (50%). Due to different packing re-
quirements of chiral and centrosymmetric molecules
[15], rac- and meso-diastereomers crystallise under dif-
ferent thermodynamic conditions and can be separated
by selective crystallisation. Resolution of the RR and
SS enantiomers, indistinguishable by most methods, is
a much more difficult task. Chemically, enantiomers
can be separated in the form of their diastereomeric
(e.g. alkoxide) derivatives [16], i.e. through the intro-
duction of an additional chiral centre. A racemic mix-
ture of enantiomers can crystallise either together in a
racemic crystal (possessing inversion elements of sym-
metry) or separately in right- and left-handed crystals
consisting each of one enantiomer only. Although cen-
trosymmetric crystal structures are much more numer-
ous than chiral [17], such spontaneous resolution is not
as rare as is sometimes believed. However, factors
directing crystallisation towards chiral or racemic struc-
ture, are subtle and by no means fully understood to
the present day [18], even though the spontaneous
resolution of rac-tartaric acid was the starting point of
the whole modern stereochemistry [19].
,
[20] and 1.658 A in the orthorhombic [21] phases of
,
Fe(h-C5H5)2, 1.657 A in Fe(h-C5Me5)2 [22]).
In order to clarify the electronic properties of 6, its
electrochemistry was investigated. The ease of oxida-
tion of substituted ferrocenes relative to the parent
Fe(h-C5H5)2, can be expressed in terms of DE1/2, which
is the difference between E1/2 for the substituted fer-
rocene and Fe(h-C5H5)2. Cyclic voltammetry of 6 and a
mixture of 6 plus Fe(h-C5H5)2 as an internal calibrant,
gave a value for DE1/2 of −0.314 V. It is well estab-
lished that, for substituted ferrocenes, E1/2 decreases
upon the introduction of an alkyl group, and increases
when a phenyl substituent is introduced [23]. Therefore,
the value of DE1/2 for 6 is expected to be less negative
than that for a ferrocene with three alkyl substituents
on each cyclopentadienyl ring and more negative than a
ferrocene with only two alkyl substituents per cyclopen-
tadienyl ring. This is confirmed by comparison with
values of DE1/2= −0.340 V for bis(1-methyl-4,5,6,7-te-
trahydroindenyl)iron(II) and DE1/2= −0.249 V for
bis(4,5,6,7-tetrahydroindenyl)iron(II) [2,24].
Having established the reactivity of the (Cp‡)− anion
5, derived by deprotonation of the cyclopentadiene 2,
The addition of half an equivalent of FeCl2 to a
solution of 5 in THF at 0°C gave the orange substituted
ferrocene (Cp‡)2Fe (6), in moderate yield. The 1H-
NMR spectrum of the crude, unpurified, 6 shows two
sharp singlets characteristic of a cyclopentadienyl pro-
ton, at 3.77 and 3.80 ppm. Since each Cp‡ ligand
contains only one such hydrogen (in position 2), the SS
and RR enantiomers are indistinguishable in NMR and
either has a molecular symmetry C2, the entire rac
isomer should produce only one such resonance. The
same is true for the meso isomer, which has a Ci
molecular symmetry. Crystallisation of crude 6 from
alkane solvents gave two crops of microcrystalline pow-
der (total yield 30%), exhibiting only the l 3.80 ppm
resonance. The first crop contained a small number of
single crystals suitable for X-ray structure determina-
tion (vide infra), which identified the meso isomer. The
X-ray diffraction pattern of the powder proved identi-
cal with the one calculated from the single crystal X-ray
structure. On the basis of all this evidence, 6 was
synthesised as a mixture of the rac and meso isomers in
a ratio (from NMR intensities) of ca. 45:55, although
we could not isolate, in a pure state, the considerably
more soluble rac isomer.
Fig. 2. Molecular structure of 6 (50% displacement ellipsoids). Primed
atoms are symmetrically related via the inversion centre.

172
A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
Table 1
Geometry of metal–Cp‡ coordination
b
6
7
9
10
10 c
11 b
11 c
,
Bond distances (A)
M aꢀC(1)
MꢀC(2)
2.054(5)
2.070(5)
2.087(5)
2.066(5)
2.058(5)
1.450(7)
1.405(7)
1.397(8)
1.438(7)
1.452(7)
1.474(7)
2.123(1)
2.146(1)
2.188(1)
2.104(1)
2.153(1)
1.434(2)
1.426(2)
1.425(2)
1.435(2)
1.445(2)
1.479(2)
2.113(2)
2.109(2)
2.153(2)
2.118(2)
2.129(2)
1.445(3)
1.419(3)
1.428(3)
1.438(3)
1.421(3)
1.487(3)
2.504(2)
2.492(2)
2.569(2)
2.601(2)
2.607(2)
1.442(3)
1.406(3)
1.421(3)
1.410(3)
1.441(3)
1.478(3)
2.501(2)
2.521(2)
2.527(2)
2.467(2)
2.543(2)
2.605(2)
2.604(2)
1.440(3)
1.407(3)
1.424(3)
1.429(3)
1.426(3)
1.480(3)
2.448(2)
2.570(2)
2.623(2)
2.631(2)
1.432(2)
1.409(2)
1.420(2)
1.418(2)
1.435(2)
1.479(2)
2.483(2)
2.560(2)
2.621(2)
2.625(2)
1.433(2)
1.414(2)
1.423(2)
1.416(2)
1.429(2)
1.478(2)
MꢀC(3)
MꢀC(8)
MꢀC(9)
C(1)ꢀC(2)
C(2)ꢀC(3)
C(3)ꢀC(9)
C(9)ꢀC(8)
C(8)ꢀC(1)
C(1)ꢀC(11)
d
~
(°)
17.4
39.4
54.4
15.9
25.1
27.7
26.3
,
Distances of atoms (A) from the mean plane of C(1), C(2), C(3), C(9) and C(8) [h-Cp moiety]
M
1.672
1.761
1.741
2.245
2.232
2.258
2.254
C(4)
C(7)
C(10)
C(11)
−0.01
−0.14
−0.08
−0.08
−0.09
−0.16
−0.14
−0.14
−0.16
−0.13
−0.10
−0.19
−0.10
−0.19
−0.13
−0.04
−0.11
−0.19
−0.12
−0.09
−0.18
−0.11
−0.12
−0.11
−0.16
−0.26
−0.13
−0.12
,
Distances of atoms (A) from the mean plane of C(4), C(9), C(8) and C(7)
C(5)
C(6)
0.37
−0.44
0.39
−0.36
0.25
−0.47
0.41
−0.36
0.44
−0.35
0.32
−0.45
0.22
−0.53
a M=Fe (6, 7, 9), Zr (10, 11).
b Atoms C(1) to C(16).
c Atoms C(17) to C(32) in the same order.
d Dihedral angle between Cp and Ph ring planes.
inversion centre (Fig. 3, Table 1). The FeꢀFe distance
with metal halide salts, we sought to investigate the
reactivity of the free diene 2 towards metallation reac-
tions. Prolonged reflux of 2 with Fe2(CO)9 in toluene
gave a red–brown solution, from which a dark brown
powder was precipitated by partial removal of the
solvent under reduced pressure. Recrystallisation of this
material from CH3CN gave red–brown crystals iden-
tified by a single-crystal X-ray diffraction study as the
dimer meso-trans-bis(1-phenyl-3-methyl-4,5,6,7-tetrahy-
droindenyl)tetracarbonyldi-iron, [Fe(Cp‡)(CO)2]2 (7).
Using Fe(CO)5 as the iron source instead of Fe2(CO)9,
produced a significantly lower yield of 7.
The solution infrared spectrum of 7 contains two
bands at 1974 and 1933 cm−1 assigned to terminal CO,
and a single band at 1759 cm−1 assigned to a bridging
CO stretch. This pattern of peaks, together with a weak
shoulder at 1796 cm−1, is well documented to be
characteristic of a solution-phase equilibrium between
cis and trans isomers of a [CpFe(CO)2]2 dimer [25].
Only one set of 1H- and 13C-NMR resonances is
observed for the methyl, phenyl and tetramethylene
moieties, indicating that 7 was isolated as a single
isomer. The geometry of compound 7 was established
by a single-crystal X-ray structural study. In common
with compound 6, compound 7 proved to be a meso
isomer, the dinuclear molecule lying at a crystallo-
graphic inversion centre coincident with the molecular
,
of 2.5541(5) is intermediate between 2.534(2) A in
,
trans-[Fe(h-C5H5)(CO)2]2 [26], and 2.560(1) A in trans-
[Fe(h-C5Me5)(CO)2]2 [27] and characteristic for a car-
bonyl-bridged single bond. The bridging is symmetrical:
,
FeꢀC(02) 1.930(1) and FeꢀC(02%) 1.939(1) A, cf.
,
FeꢀC(01) 1.753(2) A for the terminal CO group. The
iron atom to cyclopentadienyl ring plane distance of
,
1.761 A in 7 is close to the corresponding distances in
,
trans-[Fe(h-C5H5)(CO)2]2 (1.754 A) [28] and in trans-
,
[Fe(h-C5Me5)(CO)2]2 (1.765 A) [29].
The dimer 7 can be cleaved using well-established
methodology, and the reductive cleavage with Na/Hg
amalgam gives the sodium salt of the [Fe(Cp‡)(CO)2]−
anion, 8. This salt has not been isolated but was reacted
directly with MeI to yield [Fe(Cp‡)(CO)2Me] (9). Since
the di-iron starting material is the achiral RS (meso)
isomer, cleavage of the iron–iron bond will give a
racemic mixture of iron anions, 8 and hence a racemic
mixture of iron methyl complexes, 9.
The NMR spectra of 9 reveal the presence of a
metal-bound methyl ligand, by a sharp singlet at l=
0.01 ppm in the 1H spectrum, and at l= −13.4 ppm in
the 13C spectrum. The solution infrared spectrum shows
the presence of a cis-dicarbonyl fragment with two
bands at 2025 and 1979 cm−1. Compound 9 is a low
melting solid and was purified by sublimation; the

A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
173
sublimed material usually melted to a red oil (distilla-
tion), but a dark red solid was obtained by careful, slow
sublimation and provided single crystals of suitable
quality to determine the X-ray crystal structure (see
Fig. 4, Table 1).
tempts to isolate pure meso isomer by fractional recrys-
tallisation were unsuccessful, yielding either the pure
1
rac isomer or a mixture of the rac and meso. The H-
and 13C-NMR spectra of the rac-10 were fully assigned
using 1H–1H COSY and 13C–1H HETCOR 2-D
techniques.
The crystal of 9 is racemic, containing both the R
and S enantiomers. The iron atom lies substantially
The X-ray study of 10 proved that it crystallises in a
chiral space group (P212121) that possesses no inversion
symmetry elements and that both Cp‡ ligands in the
molecule have the same absolute configuration. Thus,
rac-10 undergoes a spontaneous resolution upon crys-
tallisation, forming crystals of pure SS and pure RR
enantiomers. The sample chosen for the X-ray study,
has the absolute RR configuration of the molecule,
which was determined directly from the anomalous
X-ray scattering of zirconium atoms.
,
closer to the cyclopentadienyl ring plane (1.741 A) than
in 7. The difference can be due to different p acceptor
strengths of the opposing ligands, competing with the
cyclopentadienyl for the d electrons of Fe. Thus, strong
iron–carbonyl d–p* backbonding weakens the iron–
cyclopentadienyl bond in 7 relative to 6, while in 9 the
substitution of a s-methyl ligand (with no p-acceptor
capacity) for a carbonyl group partially relieves the
competition. The iron–methyl s-bond length of
,
2.062(2) A is in agreement with the values of 2.04–2.07
The molecule (see Fig. 5) has a typical non-bridged
Group 4 bent metallocene structure, with two planar
h5-cyclopentadienyl systems forming a dihedral angle
of 56.0° and two chloride ligands lying in the bisectral
plane of this angle. The ZrꢀCp‡ distances (Table 1),
ZrꢀCl(1) and ZrꢀCl(2) bond lengths [2.4470(5) and
,
A in the three previously known structures containing
CpFe(CO)2Me moieties [30]. The FeꢀCO distances of
1.757(2) and 1.748(2) A are unexceptional.
,
Having established the metallation chemistry of both
the neutral tetrahydroindene and lithium tetrahydroin-
denide salt through the synthesis and characterisation
of iron complexes, we explored the chemistry of two
representative examples of Group 4 metallocenes,
[Zr(Cp‡)2X2] (X=Cl, Me). The zirconocene dichloride,
10, was prepared by the reaction of freshly sublimed
,
2.4477(5) A, respectively] are comparable with those
typically found in Zr(h-C5H5)2X2 and Zr(h-C5Me5)2X2
complexes [31]. The Cp‡ ligands do not adopt a distal
configuration as seen in the ferrocene 6, rather the
bulky cyclohexyl groups of both ligands are directed in
the same direction, and the phenyl groups nearly eclipse
the methyl groups.
1
ZrCl4 with LiCp‡ in diethyl ether. The H-NMR spec-
trum of the crude reaction mixture shows two sharp
resonances at l=6.32 and 5.88 ppm, which are as-
signed to the single hydrogen atom attached to the
cyclopentadienyl ring in the rac and meso isomers,
respectively. Crystallisation from toluene followed by
recrystallisation from dichloromethane gave yellow
crystals of the pure (by NMR spectra) rac isomer,
characterised by X-ray crystallography (vide infra). At-
The dimethyl zirconocene, [Zr(Cp‡)2Me2] (11), was
readily prepared via the addition of methyl lithium to
rac-10 (see Scheme 2 for preparation of zirconium
1
complexes). The H-NMR spectrum of the crude reac-
tion mixture possesses a single sharp resonance in the
cyclopentadienyl–CH region at l=4.96 ppm, indicat-
ing the presence of only one isomer in solution. This
Fig. 3. Molecular structure of 7 (50% displacement ellipsoids). Primed atoms are symmetrically related via the inversion centre.

174
A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
Fig. 4. Molecular structure of 9 (50% displacement ellipsoids).
mer by slightly different orientations of the phenyl
rings. Thus the methyl group of one Cp‡ ligand ap-
proaches the phenyl substituent of the other, and vice
versa. The mutual orientation of the two cyclopentadi-
enyl rings is somewhat staggered: the projections of the
C(2)ꢀH and C(18)ꢀH bonds on the XZrX plane form
an angle of 17.5° in 10 and 43.3° in 11.
could be expected to be rac-11, given that the parent
compound was a pure rac isomer and that the optical
inversion (through breaking and reforming of the
metal–cyclopentadienyl bond) would require much
harsher reaction conditions [32]. Recrystallization of 11
from hexanes at −20°C gave colourless single crystals
suitable for an X-ray structure determination, which
confirmed the above expectations. However, unlike the
parent compound, rac-11 does not spontaneously re-
solve into left- and right-hand crystals, but crystallises
The conformation of the Cp‡ ligand in all five struc-
tures displays certain similarities (see Table 1). All the
substituents on the h5-ring are tilted out of the ring
plane and away from the metal atom; this is common
for substituted cyclopentadienyl ligands. The tetrahy-
drobenzene ring adopts a twisted conformation: the
(
instead in a centrosymmetric structure (space group P1)
comprising equal amounts of the SS and RR
enantiomers.
The asymmetric unit contains one molecule 11 (Fig.
6) and half of a n-hexane molecule of crystallisation.
The latter is situated at an inversion centre, with each
carbon atom disordered over two positions with equal
occupancies. Molecule 11 is essentially isostructural
with 10, chlorine atoms being replaced by two methyl
groups, which form s-bonds ZrꢀC(33) 2.264(2) and
‡
,
ZrꢀC(34) 2.270(2) A. The Cp ligands in 11 are slightly
more distant from the metal atom than in 10, probably
due to smaller positive charge on the metal atom result-
ing from lower electronegativity of the methyl group
compared to the chloride ligand (2.4 vs. 3.0 on the
Pauling’s scale) [33]. The alternative, steric, explanation
is less plausible, as although the effective van der Waals
,
radius of a methyl group (2.0 A) is larger than that of
,
a Cl atom (1.8 A) [34], the dihedral angle between the
cyclopentadienyl rings in 11 does not widen (56.1°, cf.
56.0° in 10), while the MeꢀZrꢀMe angle of 96.64(8)° in
11 is actually smaller than the ClꢀZrꢀCl angle 97.78(2)°
in 10.
Both 10 and 11 display approximate (non-crystallo-
graphic) molecular symmetry C2, distorted in the for-
Fig. 5. Molecular structure of 10 (50% displacement ellipsoids).

A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
175
of early transition metal (Groups 3 and 4) complexes of
these ligands are in progress.
4. Experimental
4.1. General remarks
Scheme 2. Preparation of zirconium complexes. Reagents: (i) ZrCl4;
(ii) MeLi.
Air-sensitive compounds were manipulated under a
nitrogen atmosphere using standard Schlenk and glove-
box techniques. NMR spectra were recorded on Varian
XL-200 (1H), Varian Gemini-200 (1H and 13C), Bruker
AC-250 (1H and 13C) or Varian VXR-400 (1H-1H
COSY and 1H-13C HETCOR) instruments. Infrared
spectra were run as liquid films on a Perkin–Elmer
1615 FTIR spectrometer or as solid samples on a
Graseby Specac 10500 Golden Gate coupled to a
Perkin–Elmer 1000 series Paragon spectrometer. Mass
spectroscopy was undertaken on a VG Micromass
7070E instrument operating in EI mode. Gas chro-
matography–mass spectroscopy was carried out using a
Hewlett–Packard 5890 series gas chromatograph cou-
pled to a Finnegan Mass Lab Trio 1000 mass spectrom-
eter operating in EI mode, using a 1.25 m HP methyl
silicone column; column temperature 40°C for 1 min,
then 10°C min−1 to 270°C. CHN analysis was per-
formed on a EAI CE-440 Elemental Analyser. Cyclic
voltammetry was carried out with a EG&G PAR Po-
tentiostat/Galvanostat model 263 using a platinum
bead electrode, an Ag ꢀ AgCl non-aqueous reference
electrode, lithium perchlorate as the supporting elec-
trolyte and acetonitrile as the solvent. Solvents were
predried and distilled from appropriate drying agents.
Unless indicated otherwise all reagents were used as
received. Diiron nonacarbonyl, Fe2(CO)9, was purified
by washing under N2 with, in order, 25% hydrochloric
acid in water, water, ethanol, and diethyl ether, fol-
lowed by drying under reduced pressure.
carbon atoms C(4), C(7), C(8) and C(9) are co-planar,
as required by the sp2-hybridisation of C(8) and C(9);
the C(5) atom is displaced from this plane towards the
metal atom and C(6) to the opposite side. Such a
(relatively stable) conformation may offer some oppor-
tunities for stereo- or enantioselective reactions. On the
other hand, the phenyl ring rotates easily around the
C(1)ꢀC(11) bond, the torsion angle ~ increasing with
the increase of steric congestion within the metal coor-
dination sphere.
3. Conclusions
We have synthesised a bulky cyclopentadiene which
is deprotonated to yield a cyclopentadienyl ligand with
enantiotopic faces. The complexation of this ligand
with iron and zirconium has demonstrated that its
steric demands cause only a relatively small weakening
of the h5-bonding, but at the same time provides inter-
esting possibilities to control the stereochemistry on the
metal centre or to screen an electron-poor metal atom.
To investigate the latter opportunities, further studies
4.2. 3-Methyl-2,3,4,5,6,7-hexahydroind-8(9)-en-1-one
(1)
Cyclohexene (27.3 g, 0.332 mol) was added dropwise
to a mechanically stirred mixture of crotonic acid (28.7
g, 0.333 mol) and polyphosphoric acid (200 g) main-
tained at 60°C. The mixture was stirred at 60°C for 2 h.
A solution of NaOH (10% by mass, 100 cm3) was
added and the slurry stirred for 16 h to facilitate
decomposition of the polyphosphoric acid. The mixture
was extracted with 40–60°C petroleum ether (3×100
cm3), and the combined organic extracts were washed
with 5% ammonia solution in water (50 cm3), followed
by saturated sodium chloride solution (2×50 cm3). The
solution was dried over magnesium sulphate and con-
centrated. Distillation under reduced pressure (b.p.=
58–60°C, ꢀ1 mmHg) afforded 1 as a colourless oil.
Fig. 6. Molecular structure of 11 (50% displacement ellipsoids).

176
A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
1
Yield 27.4 g, 55%. H-NMR: l (ppm, CDCl3) 1.11 (d,
3H, J=6.2 Hz, CH3); 1.30–2.80 (series of overlapping
m, 11H). 13C{1H}-NMR; l (ppm, CDCl3) 19.2, 20.4,
22.1, 22.6, 26.4, 36.7, 43.9 (CH3, CH, 5CH2); 138.3,
177.9, 208.7 (3 quat. C). MS (EI): m/z 150 [M+]. IR:
(cm−1) 1700, 1647 (CO).
1H, ꢁC(Ph)H); 7.10–7.5 (series of m, 5H, phenyl
CH’s). 13C{1H}-NMR: l (CDCl3) 20.2 (CH3); 22.8,
23.1, 23.5, 25.3 (4×CH2); 39.4 (C(Me)H or cyclopen-
tenyl CH2); 41.6 (cyclopentenyl CH2 or C(Me)H);
114.9 (ꢁC(Ph)H); 125.7 (para-CH); 128.4 (meta-CH or
ortho-CH); 128.8 (ortho-CH or meta-CH); 137.0,
139.8, 149.3, 151.4 (quat. C and ipso-C). MS (EI): m/z
224 [M+].
4.3. 1-Phenyl-3-methyl-4,5,6,7-tetrahydroindene (2)
Phenyl magnesium bromide was prepared from bro-
mobenzene (5.50 g, 35 mmol) and magnesium turnings
(0.97 g, 40 mmol) in diethyl ether (100 cm3). The
Grignard solution was cooled to 0°C and 3-methyl-
2,3,4,5,6,7-hexahydroind-8(9)-en-1-one (5 g, 33 mmol)
was slowly added with stirring. The mixture was al-
lowed to warm to room temperature (r.t.) and stirred
for 15 h. After filtration from the excess Mg the solu-
tion was quenched with water (50 cm3) and the organic
layer was extracted with diethyl ether (2×50 cm3). The
combined organic extracts were dried over magnesium
sulphate and filtered. Aqueous HCl (6 M, 0.5 cm3) was
then added and the solution stirred for 2 h. After
washing with water and drying with magnesium sul-
phate the solution was concentrated on a rotary evapo-
rator. Distillation at reduced pressure (b.p.=80–81°C,
ꢀ1 mmHg) provided 1 as an orange–red oil. Yield 3.6
4.5. Bis(1-phenyl-3-methyl-4,5,6,7-tetrahydroindenyl)
iron(II) (6)
Butyl lithium (1.65 M in hexanes, 2.41 ml, 3.91
mmol) was added at 0°C to a solution of 1-phenyl-3-
methyl-4,5,6,7-tetrahydroindene 2 (0.83 g, 3.91 mmol)
in diethyl ether (30 cm3) and the solution was stirred for
4 h at 0°C. The resulting lithium 1-phenyl-3-methyl-
4,5,6,7-tetrahydroindenide was isolated on a sintered
glass filter and washed with diethyl ether (3×10 cm3)
to remove excess butyllithium and organic impurities.
The solid was then dissolved in THF (40 cm3) and the
resulting solution was added to a slurry of anhydrous
FeCl2 (0.25 g, 1.96 mmol) in THF (10 cm3) at 0°C. The
mixture was allowed to warm to r.t. and stirred for 14
h. After quenching with water (50 cm3), the organic
layer was extracted with diethyl ether (2×20 cm3) and
dried over magnesium sulphate. After filtration the
solution was concentrated and recrystallised from low
boiling petroleum ether to give orange crystals of 6.
Yield 0.10 g, 10%. Further concentration and cooling
to −20°C, gave an orange microcrystalline powder,
shown to be the same meso-isomer as the first crop by
powder X-ray diffraction (see text). Yield 0.20 g, 20%.
1
g, 52%. H-NMR, 13C{1H}-NMR and GC–MS indi-
cated the presence of several isomers. GC–MS: 4 iso-
mers detected with base m/z=210 [M+] at retention
times 15.78, 16.35, 17.20 and 17.65 min. Anal. Calc. for
C16H18 (210.32): C, 91.3; H, 8.6. Found: C, 85.7; H,
8.1%. Many samples, including those pure by GC–MS,
consistently gave this low analysis.
1
Total yield 0.30 g, 30%. H-NMR: l (ppm, C6D6) 1.31
4.4. 1-Benzylidene-3-methyl-2,3,4,5,6,7-
hexahydroind-8(9)-ene (4)
(m, 1H, CH2); 1.37 (m, 1H, CH2); 1.54–1.72 (overlap-
ping m, 2H, CH2); 1.58 (s, 3H, CH3); 1.91 (m, 1H,
CH2); 2.15 (m, 1H, CH2); 2.27 (m, 1H, CH2); 2.58 (m,
1H, CH2); 3.80 (s, 1H, CH); 7.09–7.47 (series of m, 5H,
aromatic CH’s). 13C{1H}-NMR: l (ppm, C6D6) 11.2
(CH3); 21.9, 23.1, 24.1, 24.7 (CH2); 70.3 (CH); 81.3,
81.4, 82.6, 86.2 (quat. C); 125.4 (para-CH); 127.5
(meta-CH); 128.6 (ortho-CH); 139.2 (ipso-CH). M.p.
191–192°C. MS (EI): m/z 474 [M+]. Anal. Calc. for
C32H34Fe (474.471): C, 81.0; H, 7.2. Found: C, 80.8; H,
7.2%.
Benzyl magnesium chloride was prepared from ben-
zylchloride (4.43 g, 35 mmol) and magnesium turnings
(0.97 g, 40 mmol) in diethyl ether (100 cm3). The
Grignard solution was cooled to 0°C and neat 1 (5.00 g,
33.3 mmol) was slowly added with stirring. The mixture
was allowed to warm to r.t. and was stirred for 15 h.
After filtration from the excess Mg, the solution was
quenched with water (50 cm3) and the organic layer was
extracted with diethyl ether (2×50 cm3). The combined
organic extracts were dried over magnesium sulphate
and then filtered. Aqueous HCl (6 M, 0.5 cm3) was then
added and the solution was stirred for 2 h. After
washing with water and drying over MgSO4 the solu-
tion was concentrated on a rotary evaporator. Distilla-
tion at reduced pressure (b.p.=105–107°C, ꢀ1
mmHg) provided 4 as an orange–red oil. Yield 4.8 g,
4.6. Bis(1-phenyl-3-methyl-4,5,6,7-
tetrahydroindenyl)tetracarbonyldiiron (7)
A toluene (250 cm3) solution of 1-phenyl-3-methyl-
4,5,6,7-tetrahydroindene (2) (6.3 g, 30 mmol) and
Fe2(CO)9 (5.0 g, 13.7 mmol) in toluene was refluxed
under nitrogen for 24 h. The solvent was removed
under reduced pressure and hexanes (100 cm3) added.
The resulting suspension was filtered through Celite
1
64%. H-NMR: l (CDCl3) 1.14 (d, 3H, CH3); 1.60–
2.60 (series of br m, 8H, CH2); 2.45 (m, 1H, CHH);
2.80 (br m, 1H, C(Me)H); 3.18 (m, 1H, CHH); 6.16 (s,

A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
177
and the residue was washed with hexanes (20 cm3) to
remove any remaining ligand. The product was ex-
tracted from the residue with toluene (3×50 cm3)
giving a dark red–brown solution. Reduction of the
volume of toluene to ca. 25 cm3 under reduced pressure
followed by filtration gave 7 as a very dark red–brown
was filtered to remove LiCl and reduced in volume to
ca. 5 ml. Cooling to −20°C for 20 h gave yellow–
brown semi-crystalline material, further recrystalliza-
tion from CH2Cl2 at −20°C gave 10 as a yellow
1
crystalline solid. Yield 1.0 g, 72%. H-NMR: l (ppm,
CDCl3) 1.24 (s, 3H, CH3); 1.44 (m, 1H, ꢀCH2CH2-
CH2CH2ꢀ); 1.75 (overlapping m, 2H, ꢀCH2CH2-
CH2CH2ꢀ); 2.03 (m, 1H, ꢀCH2CH2CH2CH2ꢀ); 2.30 (m,
1H, ꢀCH2CH2CH2CH2ꢀ); 2.54 (m, 1H, ꢀCH2CH2-
CH2CH2ꢀ); 2.92 (m, 1H, ꢀCH2CH2CH2CH2ꢀ); 3.33 (m,
1H, ꢀCH2CH2CH2CH2ꢀ). 5.81 (s, 1H, CH); 7.27 (over-
lapping m, 3H, ortho-CH and para-CH); 7.43 (t, 2H,
1
powder. Yield 2.16 g, 25%. H-NMR l (ppm, C6D6)
1.14–3.00 (series of m, 7H, CH2); 1.65 (s, 3H, CH3);
2.74 (m, 1H, CH2); 3.75 (br s, 1H, h5-C5H); 7.11–7.43
(series of m, 5H, phenyl CH’s). Selected IR: w (cm−1
)
1974, 1933, 1796 (sh), 1759. MS (EI): m/z 642 [M+].
Anal. Calc. for C36H34O4Fe2 (642.358): C, 67.3; H, 5.34.
Found: C, 66.8; H, 5.8%.
meta-CH). 13C{1H}-NMR:
(CH3); 21.2 (ꢀCH2CH2CH2CH2ꢀ); 23.0 (ꢀCH2CH2-
CH2CH2ꢀ); 24.0 (ꢀCH2CH2CH2CH2ꢀ); 25.4
l (ppm, CDCl3) 13.3
4.7. (1-Phenyl-3-methyl-4,5,6,7-
tetrahydroindenyl)dicarbonyl(methyl)iron (9)
(ꢀCH2CH2CH2CH2ꢀ); 108.9 (CH); 119.9, 125.7, 131.3,
132.5, 134.1 (quat. C or ipso-C); 126.8 (para-CH);
127.1 (ortho-CH); 128.8 (meta-CH). Anal. Calc. for
C32H34Cl2Zr (580.754): C, 66.2; H, 5.9. Found: C, 66.0;
H, 5.9%.
A solution of bis(1-phenyl-3-methyl-4,5,6,7-tetrahy-
droindenyl) di-iron tetracarbonyl (7) (1.5 g, 2.34 mmol)
in THF (20 cm3) was added dropwise to a sodium
amalgam (0.2 g of Na) under THF (20 cm3) and stirred
at r.t. for 2 h. The THF solution was decanted away
from the amalgam, the amalgam washed with portions
of THF (2×20 cm3) and the THF portions combined.
The solution was cooled to 0°C, and iodomethane (0.65
cm3, 1.4 g, 10 mmol) was added and the reaction
mixture was allowed to warm to r.t. and stirred for 1 h.
Volatiles were removed under reduced pressure and the
residue extracted with hexanes (20 cm3). The mixture
was filtered and the volatiles removed under reduced
pressure to leave an orange oily residue. Sublimation
onto a liquid nitrogen cooled probe gave 9 as an oily
orange solid. Yield 0.67 g, 45%. 1H-NMR l (ppm,
CDCl3) 0.01 (s, 3H, FeꢀCH3); 1.40–2.80 (series of m,
8H, CH2); 1.81 (s, 3H, CH3); 4.85 (s, 1H, CH); 7.28–
7.39 (series of m, 5H, phenyl CH’s). 13C-NMR (ppm,
CDCl3) −13.4 (FeꢀCH3); 10.6 (CH3); 21.2 (CH2); 22.0
(CH2); 22.8 (CH2); 23.1 (CH2); 84.0 (CH); 94.2 (quat.
C); 94.8 (quat. C); 100.0 (quat. C); 100.5 (quat. C);
127.0 (para-phenyl CH); 128.0 (ortho-/meta-phenyl
CH); 128.2 (meta-/ortho-phenyl CH); 134.1 (ipso-
phenyl C); 218.0 (CO); 218.1 (CO). Selected IR: w
(cm−1) 1996 (vs), 1943 (vs). MS (EI): m/z 336 [M+].
Anal. Calc. for C19H20O2Fe (336.214): C, 67.8; H, 6.0.
Found: C, 67.0; H, 5.9%.
4.9. Rac-bis(1-phenyl-3-methyl-4,5,6,7-
tetrahydroindenyl)dimethylzirconium (11)
Methyl lithium (1.6 M in Et2O, 1.25 ml, 2.0 mmol)
was added to a diethyl ether (10 ml) solution of rac-10
(0.23 g, 0.4 mmol) at 0°C. The solution was warmed to
r.t. and stirred for 24 h. The Et2O was removed under
reduced pressure and hexanes (20 ml) added. The solu-
tion was filtered to remove LiCl and reduced in volume
to ca. 5 ml. Cooling to −20°C for 48 h gave colourless
1
crystals of 11. Yield 0.19 g, 86%. H-NMR: l (ppm,
C6D6) −0.20 (s, 3H, ZrꢀCH3); 1.46 (s, 3H, CH3); 1.40,
1.70, 1.85, 2.43, 2.63, 2.78, 2.95 (series of m, 8H, CH2);
4.96 (s, 1H, CH); 7.27 (overlapping m, 3H, ortho-CH
and para-CH); 7.03 (m, 2H, meta-CH). 13C{1H}-
NMR: l (ppm, C6D6) 39.8 (ZrꢀCH3); 12.6 (CH3); 22.3,
23.7, 24.2, 25.0 (CH2); 104.5 (CH); 119.0, 120.0, 123.3,
126.0 (quat. C); 125.9 (para-CH); 126.7 (ortho-CH);
128.7 (meta-CH); 136.3 (ipso-C). Anal. Calc. for
C34H40Zr·(C6H14)1/2 (583.007): C, 76.2; H, 8.1. Found:
C, 76.5; H, 8.1%.
4.10. X-ray crystallography
4.8. Dichlorobis(1-phenyl-3-methyl-4,5,6,7-
tetrahydroindenyl)zirconium (10)
Single-crystal diffraction experiments were carried
out on a Bruker AXS SMART three-circle diffractometer
with a 1 K CCD area detector, using graphite-
,
A slurry of freshly sublimed ZrCl4 (0.55 g, 2.4 mmol)
in Et2O (20 ml) was added to a slurry of lithium(1-
phenyl-3-methyl-4,5,6,7-tetrahydroindenide) (1.0 g, 4.6
mmol) in Et2O (20 ml) at 0°C under N2. The reaction
mixture was slowly warmed to r.t. and was stirred for
13 h. The Et2O was removed under reduced pressure
and toluene (20 ml) was added. The reaction mixture
monochromated Mo–Ka radiation (u=0.71073 A) and
SMART software [35]. The crystals were cooled using a
Cryostream (Oxford Cryosystems) open-flow N2 gas
cryostat [36]. The data collection nominally covered a
hemisphere of reciprocal space, by a combination of
three or four sets of ꢀ scans (in steps of 0.3° ꢀ) at
different ƒ angles. The reflection intensities were inte-

178
A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
Table 2
Crystal data and structure refinement
Compound
6
7
9
10
11
Empirical formula
Formula weight
T (K)
C32H34Fe
474.44
150
C
642.33
150
36H34Fe2O4
C19H20FeO2
336.20
150
C32H34Cl2Zr
580.71
150
C34H40Zr·12C6H14
582.97
150
Crystal system
Space group
Monoclinic
P21/c (no. 14)
9.021(1)
13.778(1)
9.600(1)
90
94.19(1)
90
1190.0(2)
2
Monoclinic
P21/c (no. 14)
11.444(1)
11.211(1)
11.527(1)
90
103.05(1)
90
1440.7(2)
2
Monoclinic
P21/n (no. 14)
10.359(1)
9.312(1)
17.635(1)
90
106.95(1)
90
1627.3(2)
4
Orthorhombic
P212121 (no. 19)
11.342(1)
14.786(2)
15.814(2)
90
90
90
2652(1)
4
1.454
Triclinic
(
P1 (no. 2)
,
a (A)
11.446(3)
11.451(3)
13.609(4)
106.09(4)
107.57(4)
104.00(3)
1527(1)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
1.324
6.5
504
1.481
10.5
668
1.372
9.3
704
1.268
0.383
618
v (cm−1
F(000)
)
0.636
1200
Crystal size (mm)
Max. 2q (°)
0.30×0.30×0.15
51
0.58×0.48×0.20
60
0.34×0.26×0.20
55
0.38×0.18×0.16
55
0.30×0.24×0.20
55
Reflections collected
Unique reflections
Rint
5882
1935
0.068
14 599
3949
0.036
11 260
3702
0.027
21 504
6091
0.035
10 043
6888
0.012
Observed reflections I\2|(I)
Max./min. transmission
Refined parameters
Goodness-of-fit on F2
R[F2\2|(F2)]
1541
0.9099, 0.7742
167
1.22
0.067
3622
0.8189, 0.5728
258
1.10
0.027
2836
0.8311, 0.7586
279
1.09
0.035
6088
0.8943, 0.8052
453
1.039
0.024
6224
0.9317, 0.8199
502
1.146
0.027
wR(F2), all data
0.189
0.73, −0.52
0.075
0.41, −0.40
0.095
0.79, −0.35
0.050
0.30, −0.29
0.061
0.74, −0.38
−3
,
Residual max., min. Dz (e A
)
grated using SAINT software [35]. Absorption correc-
tions were performed by semi-empirical method based
on multiple scans of equivalent reflections using SAD-
ABS routine [37], or (for 7) by numerical integration
based on face-indexing [38]. The structures were solved
by direct methods and refined by full-matrix least
squares against F2 of all data, using SHELXTL pro-
grams.[37] All non-H atoms were refined in anisotropic
approximation, all H atoms were refined in isotropic
approximation or (for 6 and the disordered hexane in
11) were treated as ‘riding’. The absolute configuration
of 10 was determined by refinement of the Flack
parameter [39], which converged at 0.01(2), the ex-
pected value being 0 for the correct and 1 for the
inverted configuration. Crystal data and experimental
details are listed in Table 2.
application to CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44-1223-336-033; e-mail: deposit@
ccdc.cam.ac.uk).
Acknowledgements
We are grateful to the EPSRC for a studentship (to
B.M.B.), to the Leverhulme Trust for a 1996 visiting
fellowship (to A.S.B.) and to the University of Durham
for
a Sir Derman Christopherson fellowship (to
J.A.K.H.).
References
[1] (a) Ch. Elschenbroich, A. Salzer, Organometallics — A Concise
Introduction, second ed., VCH, Weinheim, 1992. (b) F.A. Cot-
ton, G. Wilkinson, Advanced Inorganic Chemistry, Wiley,
Chichester, 1988 (Chapter 26).
[2] (a) A.J. Deeming, in: E.W. Abel, F.G.A. Stone, G. Wilkinson
(Eds.), Comprehensive Organometallic Chemistry, vol. 4, Perga-
mon, Oxford, 1982, p. 481 (Chapter 31.3). (b) N.J. Long, Metal-
locenes, Blackwell Science, Oxford, 1998, p. 134.
[3] (a) W.J. Evans, Adv. Organomet. Chem. 24 (1985) 131. (b) C.J.
Shaverien, Adv. Organomet. Chem. 36 (1994) 283. (c) F.T.
Edelmann, in: E. Abel, F.G.A. Stone, G. Wilkinson (Eds.),
Comprehensive Organometallic Chemistry II, vol. 4, Pergamon,
Oxford, 1995 (Chapter 2). (d) P.L. Watson, G.W. Parshall, Acc.
Chem. Res. 18 (1985) 51.
5. Supplementary material
Crystallographic data (excluding structure factors)
for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication nos. CCDC
116237–116241 for 6, 7, 9, 10 and 11, respectively.
Copies of the data can be obtained free of charge on

A.S. Batsano6 et al. / Journal of Organometallic Chemistry 590 (1999) 169–179
179
[4] (a) F.R.W.P. Wild, L. Zsolnai, G. Huttner, H.W. Brintzinger, J.
Organomet. Chem. 232 (1982) 233. (b) R.L. Haltermann, A.
Tretyakov, M.A. Khan, J. Organomet. Chem. 568 (1998) 41. (c)
H.G. Alt, K. Fottinger, W. Milius, J. Organomet. Chem. 564
(1998) 109.
[5] (a) R.L. Halterman, Chem. Rev. 92 (1992) 965. (b) G.A. Molan-
der, H. Schumann, E.C.E. Rosenthal, J. Demtschuk,
Organometallics 15 (1996) 3817. (c) M.A. Giardello, V.P. Conti-
cello, L. Brard, M. Sabat, A.L. Rheingold, C.L. Stern, T.J.
Marks, J. Am. Chem. Soc. 116 (1994) 10 212. (d) M.A. Gia-
rdello, M.S. Eisen, C.L. Stern, T.J. Marks, J. Am. Chem. Soc.
117 (1995) 12 114. (e) J.P. Mitchell, S. Hajela, S.K. Brookhart,
K.I. Hardcastle, L.M. Henling, J.E. Bercaw, J. Am. Chem. Soc.
118 (1996) 1045. (f) L.A. Paquette, M.R. Sivik, E.I. Bzowej, K.J.
Stanton, Organometallics 14 (1995) 4865.
S.L. Buchwald, J. Org. Chem. 62 (1997) 2267. (c) S. Habaue, H.
Sakamoto, Y. Okamoto, Chem. Lett. (1996) 383. (d) M.E.
Huttenloch, B. Dorer, U. Rief, M.H. Prosenc, K. Schmidt, H.H.
Brintzinger, J. Organomet. Chem. 541 (1997) 219.
[17] W.H. Baur, D. Kassner, Acta Crystallogr. Sect. B 48 (1992) 356.
[18] (a) J.D. Dunitz, J. Bernstein, Acc. Chem. Res. 28 (1995) 193. (b)
D. Braga, F. Grepioni, G.R. Desiraju, Chem. Rev. 98 (1998)
1375. (c) M. Avalos, R. Babiano, P. Cintas, J.L. Jime´nez, J.C.
Palacios, Chem. Rev. 98 (1998) 2391.
[19] For a modern retrospection, see: K. Roth, S. HoeftSchleeh,
Chemie in unserer Zeit 29 (1995) 338.
[20] P. Seiler, J.D. Dunitz, Acta Crystallogr. Sect. B 35 (1979) 2020.
[21] P. Seiler, J.D. Dunitz, Acta Crystallogr. Sect. B 38 (1982) 1982.
[22] D.P. Freiberg, J.L. Robbins, K.N. Raymond, J.C. Smart, J. Am.
Chem. Soc. 101 (1979) 892.
[6] (a) L. Schwink, P. Knochel, T. Eberle, J. Okuda, Organometal-
lics 17 (1998) 7. (b) J. Okuda, S. Verch, T.P. Spaniol, R.
Stu¨rmer, Chem. Ber. 129 (1996) 1429. (c) A.A.H. van der
Zeijden, J. Organomet. Chem. 518 (1996) 147. (d) A.L. Mc-
Knight, Md. A. Masood, R.M. Waymouth, D.A. Straus,
Organometallics 16 (1997) 2879. (e) J.A. Ramsden, D.J. Milner,
H. Adams, N.A. Bailey, P.D. Hempstead, C. White, J.
Organomet. Chem. 551 (1998) 355.
[23] H. Grimes, S.R. Logan, Inorg. Chim. Acta 45 (1980) L223.
[24] M.M. Sabbatini, E. Cesarotti, Inorg. Chim. Acta 24 (1977) L9.
[25] A.R. Manning, J. Chem. Soc. A (1969) 1319.
[26] R.F. Bryan, P.T. Greene, J. Chem. Soc. A (1970) 3064.
[27] R.G. Teller, J.M. Williams, Inorg. Chem. 19 (1980) 2770.
[28] (a) A. Mitschler, B. Rees, M.S. Lehmann, J. Am. Chem. Soc.
100 (1978) 3390. (b) R.F. Bryan, P.T. Greene, J. Chem. Soc. A
(1970) 3064.
[7] R.N. Austin, T.J. Clark, T.E. Dickson, C.M. Killian, T.A. Nile,
D.J. Schabacker, A.T. McPhail, J. Organomet. Chem. 491 (1995)
11.
[8] (a) C. Santelli-Rouvier, M. Santelli, Synthesis (1983) 429. (b)
K.L. Habermas, S.E. Denmark, T.K. Jones, Org. React. 45
(1994) 1. (c) M. Ramaiah, Synthesis (1984) 529.
[9] R.L. Halterman, A. Tretyakov, Tetrahedron 51 (1995) 4371.
[10] (a) C.A. Willoughby, W.M. Davis, S.L. Buchwald, J.
Organomet. Chem. 497 (1995) 11. (b) R. Leino, H.J.G. Lut-
tikhedde, A. Lehtonen, P. Ekholm, J.H. Na¨sman, J. Organomet.
Chem. 558 (1998) 181.
[29] R.G. Teller, J.M. Williams, Inorg. Chem. 19 (1980) 2770.
[30] (a) T. Yu. Orlova, V.N. Setkina, V.G. Andrianov, Yu.T.
Struchkov, Bull. Acad. Sci. USSR Div. Khim. Sci. 35 (1986) 405.
(b) J.K. Stille, C. Smith, O.P. Anderson, M.M. Miller,
Organometallics 8 (1989) 1040. (c) K.H. Pannell, J. Cervantes, L.
Parkanyi, F. Cervantes-Lee, Organometallics 9 (1990) 859.
[31] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Wat-
son, R. Taylor, J. Chem. Soc. Dalton Trans. (1989) S1.
[32] S. Collins, B.A. Kuntz, N.J. Taylor, D.G. Ward, J. Organomet.
Chem. 342 (1988) 21.
[33] S.S. Batsanov, Sov. Sci. Rev. Sect. B Chem. Rev. 15 (1990) 3.
[34] (a) L. Pauling, The Nature of the Chemical Bond, third ed.,
Cornell University Press, Ithaca, NY, 1960. (b) R.S. Rowland,
R. Taylor, J. Phys. Chem. 100 (1996) 7384.
[11] S. Dev, J. Ind. Chem. Soc. 34 (1957) 169.
[12] R.N. Austin, T.J. Clark, T.E. Dickson, C.M. Killian, T.A. Nile,
J. Organomet. Chem. 498 (1995) C31.
[13] (a) T.E. Sloan, Top. Stereochem. 12 (1981) 1. (b) K. Stanley,
M.C. Baird, J. Am. Chem. Soc. 97 (1975) 6598. (c) G. Krow,
Top. Stereochem. 5 (1970) 31.
[35] SMART and SAINT, Release 4.05, Area Detector Control and
Integration Software, Bruker AXS, Analytical X-ray Instru-
ments, Madison, WI, USA, 1995.
[14] R.S. Cahn, C. Ingold, V. Prelog, Angew. Chem. Int. Ed. Engl. 5
(1966) 385.
[15] A.I. Kitaigorodskii, Molecular Crystals and Molecules, Aca-
demic Press, New York, 1973.
[16] (a) A. Scha¨fer, E. Karl, L. Zsolnai, G. Huttner, H.H.
Brintzinger, J. Organomet. Chem. 328 (1987) 87. (b) B. Chin,
[36] J. Cosier, A.M. Glazer, J. Appl. Cryst. 19 (1986) 105.
[37] G.M. Sheldrick, SADABS, Program for Scaling and Correction of
Area Detector Data, University of Go¨ttingen, Germany, 1996.
[38] G.M. Sheldrick, SHELXTL, Version 5/VMS, Bruker AXS, Ana-
lytical X-ray Instruments, Madison, WI, USA, 1995.
[39] H.D. Flack, Acta Crystallogr. Sect. A 39 (1983) 876.
.