Synthesis of racemic chiral-at-metal complexes of the Group 4 metals

Article abstract of DOI:10.1016/S0022-328X(00)00253-9

A protocol for asymmetric synthesis of chiral-at-metal complexes is described, but enantiomerically-enriched products can not be isolated due to formation of complexes between the Group 4 metallocene products and the borane by-products. An efficient method for synthesis of racemic chiral-at-metal metallocenes, through lithium chloride catalysed ligand redistribution reactions, is described. Sterically-hindered racemic chiral-at-metal complexes are prepared by nucleophilic substitution of prochiral dichlorides.

Full text of DOI:10.1016/S0022-328X(00)00253-9

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 605 (2000) 45–54
Synthesis of racemic chiral-at-metal complexes of the Group 4
metals
Nathaniel W. Alcock, Howard J. Clase, David J. Duncalf, Suzanne L. Hart,
Andrew McCamley, Peter J. McCormack, Paul C. Taylor *
Department of Chemistry, Uni6ersity of Warwick, Co6entry, CV4 7AL, UK
Received 14 February 2000; accepted 16 April 2000
Abstract
A protocol for asymmetric synthesis of chiral-at-metal complexes is described, but enantiomerically-enriched products can not
be isolated due to formation of complexes between the Group 4 metallocene products and the borane by-products. An efficient
method for synthesis of racemic chiral-at-metal metallocenes, through lithium chloride catalysed ligand redistribution reactions,
is described. Sterically-hindered racemic chiral-at-metal complexes are prepared by nucleophilic substitution of prochiral
dichlorides. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Titanocene; Zirconocene; Hafnocene
6a were considered: (i) direct nucleophilic displacement
of chloride from compounds 2–6a; (ii) ligand redistri-
bution reactions between dichlorides 2–6a and dialkyl
or dithiophenolato compounds 7–11b–f; (iii)
transmetalation reactions from boron compounds. The
last method was of particular interest to us as it offers
an opportunity for asymmetric synthesis of non-
racemic complexes.
Herein we first describe the preparation of the
prochiral metallocene dichloride starting materials. The
limitations of the direct nucleophilic displacement
method ((i) above) are then discussed, followed by the
conversion of the dichlorides to some of the dialkyl and
dithiophenolato substrates 7–11b–f for the ligand re-
distribution and transmetalation methods.
1. Introduction
Chiral complexes of Group 4 metals, both racemic
and enantiomerically enriched, have found numerous
applications as catalysts for stereoregular polymerisa-
tions and catalysts and reagents for asymmetric synthe-
sis [1,2]. The majority of these complexes are chiral due
to the presence of one or more centres of chirality in
one or more of the ligands. A further group of com-
plexes are chiral due to conformational restrictions,
notably the so-called ebi and ebthi metallocenes [2].
Our interest lies in a third, little studied class of chiral
complexes of Group 4 metals such as 1 [3], where the
metal atom is the sole centre of chirality. These com-
plexes belong to a general class of metal complexes
which may be described as ‘chiral-at-metal’.
Prominent among the chiral Group 4 complexes
which are employed as catalysts are metallocene dichlo-
rides and dialkyls. The chiral monochloro monoalkyl
metallocenes 2–6b–e were thus potential targets, as
were the related monochloro monothiophenolato com-
plexes 2–6f. Three strategies for synthesis of racemic
compounds 2–6b–f from the prochiral dichlorides 2–
2. Results and discussion
2.1. Synthesis of mixed-ring metallocene dichlorides
All useful syntheses of mixed-ring transition metal
complexes involve the stepwise introduction of the two
rings to the metal centre [4]. The more synthetically
versatile sequence, given that we aimed to have an
unsubstituted Cp ligand in all our targets, is to intro-
* Corresponding author. Fax: +44-2476-524112.
E-mail address: p.c.taylor@warwick.ac.uk (P.C. Taylor).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00253-9

46
N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
duce Cp in the first step followed by the required
substituted ring. Fortunately, for the zirconium and
hafnium series, this was also the higher yielding process
(Scheme 1). Hence, zirconium and hafnium chlorides
reacted with CpSnBu3, according to Abel’s procedure
[4], to yield the half-sandwich intermediates. Displace-
ment of a second chloride ligand with lithium indenide
or Cp%Li led smoothly to the prochiral mixed-ring
complexes 4–6a. The tetramethylcyclopentadienyl zir-
conocene analogue Me4C5HCpZrCl2 was also prepared
and is included in Section 4.
Unfortunately, the procedure in Scheme 1 was not
synthetically useful in our hands for the titanium ana-
logues. Our failure to isolate the target complexes is
consistent with Grubbs’ observation that the second
step leads to ring-exchange by-products (Cp2TiCl2 and
Ind2TiCl2) in the indenyl case [5]. Therefore, it was
necessary to introduce the substituted ring first, via the
tributyltin reagent [4], followed by reaction with lithium
cyclopentadienide (Scheme 2).
trimethylsilylmethyl magnesium chloride or its lithium
analogue, in diethyl ether at low temperature, led
smoothly to the racemic chiral products 2d, 3d and 6d.
That steric hindrance is significant in this reaction is
indicated by the fact that in the cases of 2 and 6, the
bis(trimethylsilylmethyl) product could not be pre-
pared, even with an excess of the nucleophile. Indeed,
as we have previously reported [7], the crystallographic
1
and H-NMR data for compounds 2d and 3d give good
evidence for a strong steric interaction between the
trimethylsilyl group and the cyclopentadienyl
substitutent.
In short, synthesis of the target chiral-at-metal com-
plexes by simple nucleophilic displacement of a chloride
ligand is only useful when there is significant steric
hindrance to addition of a second equivalent of the
nucleophile.
2.3. Synthesis of dialkyl- and dithiophenolato-
mixed-ring metallocenes
2.2. Chiral-at-metal compounds by nucleophilic
displacement of chloride ligands
Our remaining synthetic strategies required the
preparation of dialkyl and diphenylthiolato precursors
7–11b–f. As anticipated [6], we encountered few prob-
lems with the simple substitution of the two chloride
ligands of 2–6a. Nucleophilic displacement of both
chloride ligands of complexes 2–6a was possible using a
range of organolithium and Grignard reagents. With
thiophenol it was possible to carry out chloride dis-
placement reactions directly in the presence of non-nu-
cleophilic organic bases, but reaction with preformed
lithium thiophenolate gave better yields.
The new dimethyl, bis(trimethylsilylmethyl) and
diphenyl complexes were prepared by the reaction of
2.2–2.4 mol equivalents of the corresponding lithium or
Grignard reagent with the dichloride analogue. These
nucleophilic displacement reactions were quite solvent
dependent, with reactions in diethyl ether generally
higher yielding than reactions in thf. The attempted
syntheses of the dibenzyl complexes 4–6c were unsuc-
cessful. It is known that many Group 4 metallocene
dibenzyl complexes, which have substituted cyclopenta-
dienyl rings, are oils, which makes their isolation
difficult [8]. However, we were able to isolate the tita-
nium analogues 2c and 3c. Indeed, compound 2c
proved to be an interesting carbonyl benzylidenation
reagent [9].
A conceptually simple method for preparation of
racemic compounds 2–6b–f is nucleophilic displace-
ment of one of the chlorides of a metallocene dichloride
by a nucleophile X− (using a Grignard reagent,
organolithium reagent or thiophenolate) (Scheme 3) [6].
However, in our experience this reaction is synthetically
useful only in cases where the nucleophile is very steri-
cally demanding; otherwise contamination with the dis-
ubstituted product is inevitable. Hence, reaction of
dichlorides 2a, 3a and 6a with one equivalent of
Scheme 1.
The reactions of 2–6a with 2.2 mol equivalents of
LiSPh led to the formation of the dithiophenolates
7–11f in good yield. The low temperature crystal struc-
tures of 7f and 9f are shown in Fig. 1. Although the
structures are unsurprising per se, there is an intriguing
difference between the titanium and zirconium ana-
logues as regards the orientations of the thiophenyl
groups relative to the t-butyl substituent. It may be that
Scheme 2.
Scheme 3.

N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
47
crystal packing favours the conformation found in the
zirconium compound, but that this arrangement re-
quires too much steric crowding in the tighter coordina-
tion sphere of titanium. Selected bond lengths and
angles for 7f and 9f are given in Table 1.
The low-temperature crystal structure of 10e is
shown in Fig. 2 and selected bond lengths and angles
are given in Table 2. The complex is one of a small
number of crystallographically-characterised com-
pounds containing a phenyl ring h1-bound to zirconium
[10]. The phenyl rings are h1-bound to the zirconium
atom with metal-carbon bond lengths of 2.286(5) and
,
2.289(4) A which are not significantly different. It is
Fig. 2. Low temperature crystal structure of 10e.
Table 2
,
Selected bond lengths (A) and bond angles (°) for 10e
ZrꢀPh
ZrꢀC(1)
ZrꢀC(7)
2.289(4)
2.286(5)
C(7)ꢀZrꢀC(7)
103.09(16)
ZrꢀIndenyl
ZrꢀC(13)
ZrꢀC(14)
ZrꢀC(15)
ZrꢀC(20)
ZrꢀC(21)
ZrꢀC5H5
ZrꢀC(10)
ZrꢀC(11)
ZrꢀC(12)
ZrꢀC(13)
ZrꢀC(14)
2.520(4)
2.527(4)
2.589(4)
2.569(4)
2.478(4)
2.525(5)
2.551(5)
2.527(4)
2.481(4)
2.493(5)
Scheme 4.
Fig. 1. Low temperature crystal structures of 7f and 9f.
interesting that the CꢀZrꢀC bond angle in 10e is rather
large [10], presumably due to the two phenyl groups
being forced into the same plane to avoid unfavourable
interactions with the Cp and indenyl rings.
Table 1
,
Selected bond lengths (A) and bond angles (°) for 7f and 9f
7f
9f
TiꢀS(1)
TiꢀS(2)
TiꢀC(1)
TiꢀC(2)
TiꢀC(3)
TiꢀC(4)
TiꢀC(5)
TiꢀC(10)
TiꢀC(11)
TiꢀC(12)
TiꢀC(13)
TiꢀC(14)
2.414(2)
2.461(2)
2.427(7)
2.363(7)
2.318(7)
2.412(7)
2.483(7)
2.361(7)
2.393(7)
2.400(7)
2.392(7)
2.376(7)
ZrꢀS(1)
ZrꢀS(2)
ZrꢀC(1)
ZrꢀC(2)
ZrꢀC(3)
ZrꢀC(4)
ZrꢀC(5)
ZrꢀC(10)
ZrꢀC(11)
ZrꢀC(12)
ZrꢀC(13)
ZrꢀC(14)
2.5159(5)
2.5198(5)
2.586(2)
2.517(2)
2.466(2)
2.497(2)
2.547(2)
2.516(2)
2.534(2)
2.519(2)
2.470(2)
2.488(2)
2.4. Chiral-at-metal compounds by ligand redistribution
In principle, mixing one equivalent of a dialkyl or
diphenylthiolato compound 7–11b–f with one equiva-
lent of its dichloro precursor 2–6a can lead to the
target complexes by ligand redistribution (Scheme 4).
This reaction has no by-product, which should make
purification of the product simpler. Synthetically useful
ligand redistribution reactions have been reported for
mixtures of Cp2TiCl2 with Cp2TiMe2 and with
Cp2TiPh2 [11]. The analogous reactions of Cp2ZrCl2
with Cp2ZrMe2 and with Cp2ZrPh2 proved much too
S(1)ꢀTiꢀS(2)
96.41
S(1)ꢀZrꢀS(2)
101.28(2)

48
N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
slow to be preparatively important [12]. Rapid ligand
redistribution was noted between Cp2ZrCl2 and
Cp2ZrBr2 [12,13].
We therefore decided to adapt a procedure developed
by Cole for transmetalation from zirconium to boron
[15]. Cole’s group found that monoalkyl- and
monoalkenyl-zirconocene chlorides, prepared by hy-
drozirconation of alkenes and alkynes respectively, re-
act with chloroboranes to yield the corresponding alkyl
or alkenyl boranes (Scheme 6). A chloride ligand is
transferred concomitantly from boron to zirconium.
We reasoned that the parallel reaction of a dialkyl-
metallocene with a boron halide would proceed even
more readily to yield chiral-at-metal products (Scheme
7). This transmetalation procedure was particularly at-
tractive since enantiomerically enriched boron halides
are readily available, thus providing an opportunity for
asymmetric induction.
As expected [11], the ligand redistribution reactions
of the prochiral titanium compounds 7c and 7f with the
dichloride 2a proceeded smoothly to furnish the
racemic chiral targets 2c and 2f in good yields and
purity. However, contrary to expectations [12], rapid
reaction was also observed for some alkyl zirconocene
analogues. As we have previously communicated [14],
these anomalously fast reactions could be linked to the
presence of lithium chloride as an impurity. We thus
added a small amount of lithium chloride to all the
redistribution reactions which had previously been slow
and, indeed, preparatively useful reaction times (less
than 1 day) were observed in all cases. Pleasingly, three
racemic chiral zirconocenes 5d–f could be prepared in
this manner (Scheme 5). The role of the lithium chlo-
ride in these reactions remains unclear.
In summary, the target chiral metallocene com-
pounds can be prepared racemically by ligand redistri-
bution reactions. For zirconium derivatives, the
presence of lithium chloride is necessary for a syntheti-
cally useful procedure.
2.5. Chiral-at-metal compounds by transmetalation
Our target chiral-at-metal complexes could in princi-
ple be prepared by reaction of prochiral dialkyl or
dithiophenolato metallocenes 7–11 with one equivalent
of a chloride source. Although reactions of this type
have been reported [6], the problems discussed in the
nucleophilic displacement section above pertain here
too and mixtures of mono- and di-substituted com-
pounds result. Nevertheless, we were keen to proceed to
the targets from complexes 7–11 using an external
chloride source, since we wished to attempt to induce
asymmetry in the process.
Model reactions of titanocenes 7c and 7f with achiral
chlorocatecholborane 12 were followed by 1H-NMR
spectroscopy. It was clear, by comparison with authen-
tic samples, that clean transmetalation had occurred to
yield the racemic chiral products 2c and 2f.
Scheme 5.
Scheme 6.
Finally, we attempted reaction of titanocenes 7c and
7f and zirconocenes 10d–f with the commercially avail-
able, enantiomerically-enriched chloroborane DIP-Cl
1
(13). Again, H-NMR spectroscopy showed that in all
five cases the chiral complexes 2c, 2f and 5d–f were the
major products and we thus proceeded to a preparative
scale, with the aim of isolating the, hopefully, enan-
tiomerically-enriched chiral-at-metal metallocenes.
As expected, the preparative scale reactions led
smoothly to mixtures of the chiral-at-metal product and
Scheme 7.

N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
49
Schlenk techniques under an atmosphere of argon, or
in a dry box under an atmosphere of nitrogen. All
solvents were purified and dried by refluxing over a
drying agent, followed by distillation under a nitrogen
atmosphere. The following compounds were prepared
according to literature methods, or simple modifica-
Scheme 8.
t
tions thereof: C5H5MCl3, BuC5H4MCl3 and C9H7MCl3
the by-product DIP-X (X=CH2Ph, CH2SiMe3, Ph,
SPh). However, we were most disappointed to find that
despite numerous attempts, it was not possible to iso-
late the metallocenes free of the chiral DIP-X by-
product and we were thus unable to determine to what
extent, if any, asymmetric induction had occurred. It is
conceivable that this problem is due to formation of a
complex between the product and by-product. Indeed,
kinetic studies [16] show these reactions to be first
order, which is consistent with initial fast reaction of
the reactants to form a complex, followed by slow,
unimolecular reorganisation to a product complex
(Scheme 8). We were unable to isolate and characterise
any such complex and the fact that in some cases some
of the DIP-X by-product could be separated by extrac-
tion into pentane argues against its existence in the
crude product. Nevertheless, the extraction of DIP-X
was remarkably difficult and always incomplete.
It is unfortunate that we were not able to judge the
success or otherwise of our asymmetric synthesis of
chiral-at-metal complexes, but we hope that the proto-
col developed here may be of use in the preparation of
other chiral-at-metal targets in enantiomerically en-
riched form.
[4]; 2a, 3a, 8b, 8c and 8f [4,7]. NMR spectra were
recorded using Bruker ACF-250 and AC-400 spectro-
meters. Spectra were referenced using the resonances
of residual protons in the deuterated solvents.
4.2. [Zr(p5-C5H5)(p5-C5H4t Bu)Cl2] (4a)
To a suspension of CpZrCl3DME (5.00 g, 14.2
mmol) in 3:1 toluene–diethyl ether (70 cm3) at −78°C
was added a suspension of LiC5Ht4Bu (1.92 g, 15.0
mmol) in diethyl ether (50 cm3). A pale yellow suspen-
sion resulted and this mixture was stirred and allowed
to warm to ambient temperature over 12 h. Work-up as
for 5a yielded 2.62 g (53%) of pale yellow micro-crys-
talline 4a. M.p. 152–154°C. Found (calculated for
C14H18Cl2Zr): C, 47.56 (48.26); H, 5.24 (5.21)%. 1H-
NMR (CDCl3): l 6.36 (5H, s, C5H5), 6.34 (2H, m,
t
C5H4), 6.22 (2H, m, C5H4), 1.30 (9H, s, Bu). 13C-
NMR: l 142.41 (Cq of C5H4), 114.50 (C5H5), 113.69
(C5H4), 111.89 (C5H4), 33.28 (CMe3), 31.28 ( CMe3).
MS (m/z): 345/347 [M−1]+.
4.3. [Zr(p5-C5H5)(p5-C9H7)Cl2] (5a)
To a suspension of CpZrCl3DME (10 g, 28.3 mmol)
in 3:1 toluene–diethyl ether (100 cm3) at −78°C was
added a freshly prepared solution of LiC9H7 (3.59 g,
29.5 mmol) in diethyl ether (50 cm3). An orange–red
suspension resulted and this mixture was stirred and
allowed to warm to ambient temperature over 8 h.
After 8 h a bright yellow suspension was obtained. The
solvent was removed under reduced pressure and the
residue was extracted with CH2Cl2 (80 cm3). The result-
ing suspension was cooled to −10°C for 1 h and
filtered cold. The filtrate was reduced in volume to 40
cm3 and pentane (15 cm3) was added to yield a bright
yellow solution. This solution was cooled to −18°C for
12 h to yield bright yellow micro-crystalline 5a upon
filtration. A further crop of 5a could be obtained from
the filtrate by concentrating the filtrate and diluting
with pentane yielding (8.05 g, 83%) of 5a. M.p. 146–
148°C. Found (calculated for C14H12Cl2Zr), C, 48.08
3. Conclusions
A protocol for asymmetric synthesis of chiral-at-
metal complexes has been established, but it is not
synthetically useful for our particular target molecules
due, we propose, to formation of complexes between
the metallocene products and the borane by-products.
A very practical and efficient method for synthesis of
racemic chiral-at-metal metallocenes, through lithium
chloride catalysed ligand redistribution between prochi-
ral metallocene dichlorides and their dialkyl or dithio-
phenolato
derivatives,
has
been
developed.
Sterically-hindered racemic chiral-at-metal complexes
are most readily prepared by simple nucleophilic substi-
tution of one chloride of prochiral dichlorides.
4. Experimental
1
(49.11); H, 3.60 (3.53)%. H-NMR (C6D6): l 7.35 (2H,
m, C9H7), 6.90 (2H, m, C9H7), 6.48 (1H, t, C9H7), 6.06
(2H, d, C9H7), 5.76 (5H, s, C5H5). 13C-NMR: l 126.00
(Cq of C9H7), 125.64 (C9H7), 125.17 (C9H7), 123.85 (Ca
of C9H7), 115.85 (C5H5), 102.52 (Cb of C9H7). MS (m/z,
+CI(ammonia)): 358/360 [M+NH+4 ].
4.1. General
All manipulations of air- and moisture-sensitive ma-
terials were carried out using standard vacuum and

50
N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
4.4. [Zr(p5-C5H5)(p5-C9H13)Cl2]
1H-NMR (C6D6): l 5.82 (5H, s, C5H5), 5.77 (2H, m,
t
C5H4), 5.74 (2H, m, C5H4), 1.03 (9H, s, Bu), 0.19 (6H,
To a suspension of CpZrCl3DME (5 g, 14.17 mmol)
in thf (70 cm3) at −78°C was added a solution of
LiC5HMe4 (1.92 g, 15.00 mmol) in thf (30 cm3). A pale
yellow suspension resulted and this mixture was stirred
and allowed to warm to ambient temperature over 1 h
and heated to 50°C for 4 h. After 5 h a deep orange
coloured solution was obtained. The solvent was re-
moved under reduced pressure and the residue ex-
tracted with CH2Cl2 (50 cm3). To the resulting
suspension was added dry activated charcoal (0.5 g)
and the mixture was stirred and cooled to 0°C for 1 h.
The suspension was filtered and the pale yelow filtrate
reduced in volume by one half. Pentane (10 cm3) was
added and the solution was cooled to −18°C for 48 h.
Cream coloured micro-crystalline product (3.35 g, 68%)
was isolated upon filtration. M.p. 185–188°C. Found
(calculated for C14H18Cl2Zr): C, 47.75 (48.26); H, 5.37
s, Me). 13C-NMR: l 138.76 (Cq), 113.50 (C5H4), 113.29
(C5H5), 110.15 (C5H4), 45.57 (Me), 31.06 (CMe3), 27.28
(C(CH3)3).
4.7. [Ti(p5-C5H5)(p5-C5H4t Bu)(CH2Ph)2] (7c)
To a solution of 2a (1 g, 0.65 mmol) in diethyl ether
(30 cm3) at −40°C was added dropwise with stirring
PhCH2MgBr (6.6 cm3 of a 1 M solution in diethyl
ether). Work-up as for 7b yielded ca. 0.08 g (60%) of a
brown powder of 7c. M.p. 41°C (dec.). Found(calcu-
lated for C28H32Ti): C, 79.06 (80.56); H, 7.01 (7.97)%.
1H-NMR (C6D6): l 7.26 (4H, m, C6H5), 6.98 (2H, m,
C6H5), 6.90 (4H, m, C6H5), 5.96 (2H, m, C5H4), 5.75
(5H, s, C5H5), 5.67 (2H, m, C5H4), 2.22 (2H, d, J=9.3
Hz, CH2), 1.91 (2H, d, J=9.3 Hz, CH2), 0.94 (9H, s,
tBu). 13C-NMR: l 154.03 (Cq of C6H5), 139.22 (Cq of
C5H4), 125.53 (C6H5), 121.53 (C6H5), 115.38 (C5H5),
114.87 (C5H4), 113.71 (C5H4), 100.34 (C6H5), 73.73
(CH2), 32.50 (C(Me)3), 31.14 (C(CH3)3).
1
(5.21)%. H-NMR (CDCl3): l 6.35 (5H, s, C5H5), 5.96
(1H, s, CH), 2.01 (6H, s, CH3), 1.99 (6H, s, CH3).
13C-NMR: l 130.20 (Cq of C9H13), 122.79 (Cq% of
C9H13), 115.70 (C5H5), 111.69 (CH of C9H13), 14.60
(Mea), 12.42(Meb). MS (m/z): 346/348 [M+], 310 (M+
−HCl), 281/283 (M+−C5H5).
4.8. [Ti(p5-C5H5)(p5-C5H4t Bu)(SPh)2] (7f)
To a solution of 2a (0.2 g, 0.66 mmol) in thf (30 cm3)
at −40°C was added dropwise with stirring LiSPh
(1.32 cm3 of a 1 M solution in thf). The mixture was
stirred for 5 h, allowed to warm to r.t. and the solvent
was removed in vacuo. The resulting residue was ex-
tracted with petroleum ether (15 cm3) and filtered.
Concentrating the solution (20 cm3) and cooling to
−30°C yielded ca. 0.18 g (64%) of purple crystals of 7f.
M.p. 88°C (dec.). Found (calculated for C26H28S2Ti): C,
67.10 (67.27); H, 6.21 (6.59)%]. 1H-NMR (C6D6): l 7.95
(4H, m, C6H5), 7.18 (4H, m, C6H5), 7.01 (2H, m, C6H5),
5.93 (2H, m, C5H4), 5.85 (5H, s, C5H5), 5.81 (2H, m,
4.5. [Hf(p5-C5H5)(p5-C9H7)Cl2] (6a)
To a suspension of CpHfCl3DME (5.00 g, 11.3
mmol) in 3:1 toluene–diethyl ether (70 cm3) at −78°C
was added a solution of LiC9H7 (1.46 g, 12.0 mmol) in
diethyl ether (50 cm3). A cream–yellow suspension
resulted and this mixture was stirred and allowed to
warm to ambient temperature over 15 h. After 15 h a
cream–yellow suspension was obtained. Work-up as
for 5a yielded (3.32 g, 68%) of pale yellow micro-crys-
talline 6a. M.p. 158–160°C. Found (calculated for
1
t
C14H12Cl2Hf): C, 38.80 (39.14); H, 2.84 (2.82)%. H-
C5H4), 1.16 (9H, s, Bu). 13C-NMR: l 149.95 (Cq of
NMR (CDCl3): l 7.67 (2H, m, C9H7), 7.28 (2H, m,
C9H7), 6.90 (1H, t, C9H7), 6.40 (2H, d, C9H7), 6.06 (5H,
s, C5H5). 13C-NMR: l 126.13 (C9H7), 125.51 (C9H7),
124.25 (Ca of C9H7), 114.97 (C5H5), 100.54 (Cb of
C9H7), not observed (Cq of C9H7).
C6H5), 140.01 (Cq of C5H4), 132.34 (C6H5), 128.95
(C6H5), 125.05 (C6H5), 112.85 (C5H5), 112.65 (C5H4),
111.50 (C5H4), 33.14 (C(Me)3), 31.50 (C(CH3)3).
4.9. [Zr(p5-C5H5)(p5-C5H4t Bu)(SPh)2] (9f)
4.6. [Ti(p5-C5H5)(p5-C5H4t Bu)Me2] (7b)
To a vigorously stirred suspension of 4a (2.00 g, 5.74
mmol) in diethyl ether (40 cm3) at −78°C was added
LiSPh (12.6 cm3 of a 1 M thf solution) dropwise over a
period of 30 min. The mixture became yellow in colour.
Work-up proceeded as in 10f except that after filtration
the toluene solution was concentrated to 10 cm3 and
layered with 15 cm3 of pentane. Upon standing at r.t.
for 72 h, 1.73 g (61%) of large yellow crystals of 9f were
obtained. M.p. 132–134°C. Found (calculated for
C26H28S2Zr): C, 62.71 (62.98); H, 5.71 (5.69)%. 1H-
NMR (C6D6): 7.93 (4H, m, Ph), 7.16 (4H, m, Ph), 6.99
(2H, m, Ph), 5.89 (2H, m, C5H4), 5.85 (5H, s, C5H5),
To a solution of 2a (0.2 g, 0.65 mmol) in diethyl ether
(30 cm3) at −40°C was added dropwise with stirring
MeMgBr (0.45 cm3 of 3 M solution in diethyl ether).
The mixture was stirred for 5 h, allowed to warm to
room temperature (r.t.) and the solvent was removed in
vacuo. The resulting residue was extracted with toluene
(15 cm3) and filtered. Concentrating the solution and
cooling to −30°C yielded ca. 0.09 g (52%) of yellow
powder 7b. It was not possible to obtain elemental
analysis as the product rapidly decomposed when at r.t.

N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
51
t
5.72 (2H, m, C5H4), 1.14 (9H, s, Bu). 13C-NMR: l
146.12 (Cq of Ph), 140.10 (Cq of C5H4), 132.83 (Ph),
128.24 (Ph), 124.90 (Ph), 111.46 (C5H5) 111.11 (C5H4),
109.29 (C5H4), 32.60 (CMe3), 31.53 (CMe3).
allowed to warm to ambient temperature over that
time. The solvent was removed under reduced pressure
and dry activated charcoal (0.5 g) was added to the
resulting residue. The mixture was extracted with
toluene (30 cm3), stirred for a further hour, and filtered.
The pale yellow filtrate obtained was concentrated to 15
cm3, pentane (10 cm3) was added and the solution was
cooled to −18°C for 24 h. Pale yellow crystals were
obtained and these were washed with pentane to yield
4.10. [Zr(p5-C5H5)(p5-C9H7)Me2] (10b)
To a vigorously stirred suspension of 5a (2.00 g, 5.84
mmol) in diethyl ether (40 cm3) at −78°C was added
MeMgCl (12.8 cm3 of a 1 M diethyl ether solution, 12.8
mmol) dropwise over a period of 30 min. The suspen-
sion changed from a bright yellow to a pale cream
colour. Work-up as for 10e yielded pale yellow micro-
crystalline 10b (0.72 g, 41%). M.p. 72–74°C. Found
(calculated for C16H18Zr): C, 64.56 (63.74); H, 5.37
1
10e (1.42 g, 57%). M.p. 177°C (dec.). H-NMR (C6D6):
l 7.35 (4H, m, Ph), 7.26 (4H, m, Ph), 7.18 (2H, m, Ph),
7.03 (2H, m, C9H7), 6.74 (2H, m, C9H7), 6.68 (1H, t,
C9H7), 6.15 (2H, d, C9H7), 5.47 (5H, s, C5H5). 13C-
NMR: l 184.27 (Cq of Ph), 135.67 (Ph), 126.34 (Ph),
125.39 (Ph), 125.20 (C9H7), 123.66 (C9H7) 122.32 (Ca of
C9H7), 121.51 (Cq of C9H7), 113.60 (C5H5), 102.04 (Cb
of C9H7). MS (m/z, +CI(ammonia)): 365 [M+NH4+
−C6H6], 348 [M+H+−C6H6], 233.
1
(5.98)%. H-NMR (C6D6): l 7.31 (2H, m, C9H7), 6.97
(2H, m, C9H7), 5.94 (2H, d, C9H7), 5.83 (1H, t, C9H7),
5.64 (5H, s, C5H5), −0.43 (6H, s, ZrꢀMe). 13C-NMR:
l 124.58 (C9H7), 124.02 (C9H7), 113.42 (Ca of C9H7),
112.66 (Cq of C9H7), 110.20 (C5H5), 98.67 (Cb of C9H7),
32.66 (ZrꢀMe).
4.13. [Zr(p5-C5H5)(p5-C9H7)(SPh)2] (10f)
To a vigorously stirred suspension of 5a (3.00 g, 8.76
mmol) in diethyl ether (40 cm3) at −78°C was added
LiSPh (19.3 cm3 of a 1 M thf solution) dropwise over a
period of 30 min. The mixture became dark yellow in
colour. The mixture was stirred for 10 h and allowed to
warm to warm to ambient temperature over this period.
The solvent was removed under reduced pressure and
the resulting residue was extracted with toluene (30
cm3) and filtered. The solvent was removed under re-
duced pressure from the dark yellow filtrate to yield a
foaming solid which was cooled to −196°C and
crushed to yield a yellow powder. Diethyl ether (20
cm3) was added to yield a yellow solution, the solution
was warmed to 35°C and pentane (5 cm3) was added.
The resulting solution was slowly cooled to −18°C for
48 h yielding 2.78 g (65%) of 10f as a yellow powder.
4.11. [Zr (p5-C5H5)(p5-C9H7)(CH2SiMe3)2] (10d)
To a vigorously stirred suspension of 5a (2.00 g, 5.84
mmol) in diethyl ether (60 cm3) at −78°C was added
LiCH2SiMe3 (13.0 cm3 of a 1 M pentane solution, 13.0
mmol) dropwise over a period of 1 h. The suspension
changed from a bright yellow to a pale cream–yellow
colour. The mixture was stirred for a further 12 h and
the solvent was removed under reduced pressure to
yield a waxy residue. This residue was extracted with
warm pentane (3×40 cm3) and the extracts were
filtered through a short pad of Celite to yield a pale
yellow solution. The solvent was removed under re-
duced pressure and the resulting solid residue was
dissolved in warm diethyl ether. This solution was
cooled to −18°C for 5 days. Product 10d was isolated
as a pale yellow powder from this solution (0.72 g,
1
M.p. 119–121°C. H-NMR (C6D6): l 7.93 (4H, m, Ph),
7.25 (2H, m, C9H7), 7.15 (4H, m, Ph), 6.99 (2H, m, Ph),
6.77 (2H, m, C9H7), 6.41 (1H, t, C9H7), 6.17 (2H, d,
C9H7), 5.47 (5H, s, C5H5). 13C-NMR: 145.41 (Cq of
Ph), 132.76 (Ph), 128.30 (Ph), 125.05 (Ph), 124.74
(C9H7), 124.55 (C9H7) 122.88 (Ca of C9H7), 121.93 (Cq
of C9H7), 113.01 (C5H5), 100.46 (Cb of C9H7). MS
(m/z): 379 [M+−SPh].
1
41%). M.p. 54–56°C. H-NMR (C6D6): l 7.38 (2H, m,
C9H7), 6.98 (2H, m, C9H7), 6.06 (2H, d, C9H7), 5.79
(5H, s, C5H5), 5.74 (1H, t, C9H7), 0.18 (18H, s,
CH2SiMe3), −0.49 (4H, AB, CH2SiMe3. 13C-NMR: l
124.67 (C9H7), 124.23 (C9H7), 112.51 (C9H7), 112.24
(C9H7), 109.49 (C5H5), 97.81 (C9H7), 47.43 (CH2SiMe3),
3.42 (CH2SiMe3). MS (m/z): 429 [M+−CH3], 357
[M+−CH2SiMe3].
4.14. [Hf (p5-C5H5)(p5-C9H7)Ph2] (11e)
4.12. [Zr(p5-C5H5)(p5-C9H7)Ph2] (10e)
To a vigorously stirred suspension of 6a (1.50 g, 3.49
mmol) in diethyl ether (30 cm3) at −78°C was added
PhMgCl (4.18 cm3 of a 2 M thf solution) dropwise over
a period of 30 min. The suspension changed from a
yellow to a pale grey colour. The mixture was stirred in
the absence of light for a further 15 h and allowed to
warm to ambient temperature over that time. Work-up
as for 10e yielded 0.73 g (40%) of cream coloured
To a vigorously stirred suspension of 5a (2.00 g, 5.84
mmol) in diethyl ether (40 cm3) at −78°C was added
PhMgCl (6.5 cm3 of a 2 M thf solution) dropwise over
a period of 30 min. The suspension changed from a
bright yellow to a pale grey colour. The mixture was
stirred in the absence of light for a further 10 h and

52
N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
crystals. M.p. 180°C (dec.). Found (calculated for
C24H22Hf): C, 60.76 (60.88); H, 4.31 (4.32)%. H-NMR
solid 2f. M.p. 93°C (dec.) was isolated. Found (calcu-
1
lated for C20H23SClTi): C, 62.43 (62.22); H, 5.99
1
(C6D6): 7.43 (4H, m, Ph), 7.34 (4H, m, Ph), 7.19 (2H,
m, Ph), 7.05 (2H, m, C9H7), 6.77 (2H, m, C9H7), 6.71
(1H, t, C9H7), 6.10 (2H, d, C9H7), 5.41 (5H, s, C5H5).
13C-NMR: l 192.57 (Cq of Ph), 137.48 (Ph), 126.65
(Ph), 125.39 (Ph), 125.20 (C9H7), 123.77 (C9H7) 122.06
(Ca of C9H7), (Cq of C9H7) not observed, 113.04
(C5H5), 100.73 (Cb of C9H7). MS (m/z): 514 [M+], 435
[M+−Ph].
(6.32)%. H-NMR (C6D6): l 7.64 (2H, m, C6H5), 7.18
(1H, m, C6H5), 7.00 (2H, m, C6H5), 6.40 (1H, m, Ha),
6.34 (1H, m, Hb), 5.90 (5H, s, C5H5), 5.59 (1H, m, Hc),
t
5.16 (1H, m, Hd), 1.23 (9H, s, Bu). 13C-NMR: l 149.96
(Cq of C6H5), 145.75 (Cq of C5H4), 133.75 (C6H5),
132.56 (C6H5), 127.73 (C6H5), 120.11 (C5H4), 117.12
(C5H4), 115.77 (C5H5), 110.69 (C5H4), 109.49 (C5H4),
30.80 (C(Me)3), 31.33 (C(CH3)3).
4.15. [Hf (p5-C5H5)(p5-C9H7)(SPh)2] (11f)
4.18. [Zr(p5-C5H5)(p5-C9H7)(CH2SiMe3)Cl] (5d)
To a vigorously stirred suspension of 6a (2 g, 4.66
mmol) in diethyl ether (40 cm3) at −78°C was added
LiSPh (10.3 cm3 of a 1 M thf solution) dropwise over a
period of 30 min. The mixture became cream–white in
colour. The mixture was stirred for 15 h and allowed to
warm to ambient temperature over this period. Work-
up as in 10f yielded 11f 1.15 g (43%) as a cream
coloured powder. M.p. 123–125°C. Found (calculated
for C26H22S2Hf): C, 54.77 (54.12) H, 4.24 (3.84)%.
1H-NMR (CDCl3): l 7.96 (4H, m, Ph), 7.26 (2H, m,
C9H7), 7.14 (4H, m, Ph), 6.98 (2H, m, Ph), 6.75 (2H, m,
C9H7), 6.41 (1H, t, C9H7), 6.08 (2H, d, C9H7), 5.38 (5H,
s, C5H5). 13C-NMR: l 143.59 (Cq of Ph), 132.84 (Ph),
128.22 (Ph), 125.25 (Ph), 125.08 (C9H7), 125.01 (C9H7)
122.20 (Ca of C9H7), 121.38 (Cq of C9H7), 111.91
(C5H5), 98.71 (Cb of C9H7). MS (m/z): 467/469 [M−
SPh].
To a Schlenk tube charged with 5a (0.5 g, 1.46
mmol), 10d (0.65 g, 1.46 mmol), and LiCl (0.010 g, 0.23
mmol) was added thf (15 cm3) at ambient temperature.
A pale yellow suspension resulted and this mixture was
heated to 40°C and stirred for 15 h. A pale yellow
solution was obtained. The solvent was removed under
reduced pressure and to the resulting residue was added
pentane (30 cm3). The resulting pale yellow suspension
was stirred at 40°C for 1 h and filtered. The solvent was
reduced in volume to one third volume (10 cm3) and the
solution cooled to −18°C for 64 h to yield 5d (0.47 g,
42%) as a pale yellow powder. M.p. 97–99°C (dec.).
Found (calculated for C18H23ClSiZr): C, 53.56 (54.85);
H, 5.36 (5.88)%. 1H-NMR (CDCl3): 7.59 (2H, m,
C9H7), 7.21 (2H, m, C9H7), 6.73 (1H, t, C9H7), 6.55
(1H, m, C9H7), 6.18 (1H, m, C9H7), 5.99 (5H, s, C5H5),
0.74 (1H, d, J 10.4 Hz, CH2SiMe3), 0.35 (1H, d, J 10.4
Hz, CH2SiMe3, 0.05 (9H, s, CH2SiMe3).
4.16. [Ti(p5-C5H5)(p5-C5H4t Bu)(CH2Ph)Cl] (2c)
4.19. [Zr(p5-C5H5)(p5-C9H7)PhCl] (5e)
To a solution of 2a (0.54 g, 1.8 mmol) in toluene (20
cm3) was added dropwise with stirring to a solution of
7c (0.75 g, 1.8 mmol) in toluene (20 cm3). The mixture
was stirred overnight at r.t. After concentrating the
solution (20 cm3) and cooling to −30°C, ca. 0.41 g
(71%) of brown solid of 2c was isolated. M.p. 38°C
(dec.). 1H-NMR (C6D6): l 7.32 (2H, m, C6H5), 7.15
(2H, m, C6H5), 7.00 (1H, m, C6H5), 6.63 (1H, m, Ha),
6.30 (1H, m, Hb), 5.75 (5H, s, C5H5), 5.05 (1H, m, Hc),
4.82 (1H, m, Hd), 2.85 (1H, d, J=9.8 Hz, CH2), 2.20
The procedure described for the preparation of 5d
above was followed with the following exceptions. To a
Schlenk tube charged with 5a (0.5 g, 1.46 mmol), 10e
(0.62 g, 1.46 mmol) and LiCl (0.010 g, 0.23 mmol) was
added thf (15 cm3) at ambient temperature. A pale
yellow suspension resulted and this mixture was heated
to 40°C and stirred in the absence of light for 15 h.
Work-up as in 5d yielded 5e (0.29 g, 52%) as a pale
yellow light sensitive powder. M.p. 143–145°C (dec.).
1H-NMR (C6D6): l 7.36 (2H, m, Ph), 7.25 (2H, m, Ph),
7.27 (1H, m, C9H7), 7.17 (1H, m, C9H7), 7.20 (1H, m,
Ph), 6.87 (2H, m, C9H7), 6.35 (1H, t, C9H7), 6.30 (1H,
m, C9H7), 5.82 (1H, m, C9H7), 5.65 (5H, s, C5H5).
t
(1H, d, J=9.8 Hz, CH2), 1.16 (9H, s, Bu). 13C-NMR:
l 153.20 (Cq of C6H5), 145.97 (Cq of C5H4), 128.89
(C6H5), 126.14 (C6H5), 124.99 (C6H5), 122.55 (C5H4),
119.11 (C5H4), 116.65 (C5H5), 109.60 (C5H4), 105.66
(C5H4), 72.10 (CH2), 33.12 (CMe3), 30.80 (C(CH3)3).
4.20. [Zr(p5-C5H5)(p5-C9H7)(SPh)(Cl)] (5f)
4.17. [Ti(p5-C5H5)(p5-C5Ht4Bu)(SPh)Cl] (2f)
The procedure described for the preparation of 5d
above was followed here with the following exceptions.
To a Schlenk tube charged with 5a (0.5 g, 1.46 mmol),
10f (0.71 g, 1.46 mmol), and LiCl (0.010 g, 0.23 mmol)
was added thf (15 cm3) at ambient temperature. A pale
yellow suspension resulted and this mixture was heated
To a solution of 2a (0.33 g, 1.1 mmol) in toluene (20
cm3) was added dropwise with stirring a solution of 2f
(0.5 g, 1.1 mmol) in toluene (20 cm3). The mixture was
stirred overnight at r.t. After concentrating the solution
(20 cm3) and cooling to −30°C, 0.611 g (73%) of pink

N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
53
to 40°C and stirred for 6 h. Work-up as in 5d yielded 5f
(0.48 g, 67%) as a yellow solid. M.p. 137–139°C (dec.).
1H-NMR (C6D6): l 7.75 (2H, m, SPh), 7.50–7.20 (over
lapping multiplets from C9H7 and SPh), 6.88 (2H, m,
C9H7), 6.39 (1H, t, C9H7), 6.23 (1H, m, C9H7), 5.86
(1H, m, C9H7), 5.64 (5H, s, C5H5).
An empirical absorption correction was carried out
using Tmax,min=1.000, 0.676. Structure solution was
carried out using SHELXTL version 5.0 software [17] on
a Silicon Graphics Indy workstation. Refinements were
by least squares, carried out using SHELXL-96 software,
[17] minimising on the weighted R factor wR2. A total
of 21 786 reflections were collected, with 7933 indepen-
dent reflections. 3516 reflections with I\2|(I) were
used for refinement. Anisotropic thermal parameters
were used for all non-hydrogen atoms, hydrogen atoms
4.21. [Hf(p5-C5H5)(p5-C9H7)(CH2SiMe3)Cl] (6d)
To a solution of 6a (1.0 g, 2.33 mmol) in thf (30 cm3)
at −78°C was added a solution of LiCH2SiMe3 (4.8
cm3 of a 1 M solution in pentane). A pale yellow
solution resulted and this mixture was stirred and al-
lowed to warm to ambient temperature over 15 h. After
15 h a pale yellow solution was obtained. The solvent
was removed under reduced pressure and to the result-
ing residue was added pentane (30 cm3). The resulting
suspension was stirred at 40°C for 1 h and filtered. The
solvent was reduced to one third volume (10 cm3) and
the solution was cooled to −18°C for 48 h to yield 6d
(0.47 g, 42%) as a pale yellow powder. M.p. 108–
were inserted in calculated positions and fixed with
3
,
isotropic thermal parameters U=0.08 A where R=
0.0789 and wR2=0.1731.
4.24. [Zr(p5-C5H5)(p5-C5H4t Bu)(SPh)2] (9f)
A pale yellow crystal (0.54× 0.30×0.16mm) of 9f
(C26H28S2Zr) was selected, coated in a perfluorinated oil
and mounted at 180 K on a quartz fibre on a Siemens
SMART area detector system equipped with a dry N2
stream low-temperature device. Lattice parameters were
obtained by least-squares refinement of 25 reflections.
1
110°C. H-NMR (C6D6): l 7.45 (1H, m, C9H7), 7.28
,
Graphite monochromated radiation, u=0.71073 A,
(1H, m, C9H7), 6.93 (2H, m, C9H7), 6.33 (1H, t, C9H7),
6.13 (1H, m, C9H7), 5.72 (1H, m, C9H7), 5.64 (5H, s,
C5H5), 0.25 (1H, d, J=11.2 Hz, CH2SiMe3), 0.22 (9H,
s, CH2SiMe3), 0.01 (1H, d, J=11.2 Hz, CH2SiMe3).
13C-NMR: l 125.27 (C9H7), 124.93 (C9H7), 124.74
(C9H7), 124.67 (C9H7), 123.34 (C9H7), 119.22 (C9H7),
111.67 (C5H5), 106.75 (C9H7), 101.13 (C9H7), 97.06
(C9H7), 49.06 (CH2SiMe3), 3.21 (CH2SiMe3).
MoꢀKa. Monoclinic system, space group P21/n, a=
,
12.2071(5), b=13.2027(5), c=14.5879(6) A, i=
3
95.9670(10)°, V=2338.3(2) A , Dcalc=1.408 Mg m−3
,
,
Z=4, v=0.659 mm−1, F(000)=1024.
An empirical absorption correction was carried out
using Tmax,min=0.92, 0.78. Structure solution was car-
ried out using SHELXTL version 5.0 software [17] on a
Silicon Graphics Indy workstation. Refinements were
by least squares, carried out using SHELXL-96 software,
[17] minimising on the weighted R factor wR2. A total
of 13 555 reflections were collected, with 5460 indepen-
dent reflections (Rint=0.0271), 4202 reflections with
I\2|(I) were used for refinement. Anisotropic thermal
parameters were used for all non-hydrogen atoms, hy-
4.22. General procedure for transmetalation with
chloroboranes
To a solution of 7–11 (1 mmol) in toluene (40 cm3)
at r.t. was added chlorocatecholborane or DIPꢀCl (1
mmol) in toluene (10 cm3). The solution was stirred
overnight and the solvent was removed in vacuo. It was
not possible to isolate the chiral-at-metal products 2–6
from the by-product. The product mixtures were char-
drogen atoms were inserted in calculated positions and
3
,
fixed with isotropic thermal parameters U=0.08 A . A
total of 265 parameters were refined, residual electron
density=0.371 and −0.483 e A−3, GOF on F2=
0.959, R=0.0278, wR2=0.0657.
,
1
acterised by H-NMR spectroscopy.
4.23. [Ti(p5-C5H5)(p5-C5H4t Bu)(SPh)2] (7f)
4.25. [Zr(p5-C5H5)(p5-C9H7)(Ph)2] (10e)
A
pink crystal (0.15×0.10×0.10mm) of 7f
A pale yellow crystal of 10e (C26H22Zr) was selected,
coated in a perfluorinated oil and mounted at 180(2) K
on a quartz fibre on a Siemens SMART area detector
system equipped with a dry N2 stream low temperature
device. Lattice parameters were obtained by least
squares refinement of 25 reflections. Graphite
(C26H28S2Ti) was selected, coated in dry Nujol and
mounted at 180 K on a quartz fibre on a Siemens
SMART area detector system equipped with a dry N2
stream low-temperature device. Lattice parameters were
obtained by least squares refinement of 3880 reflections.
,
,
Graphite monochromated radiation, u=0.71073 A,
monochromated radiation, u=0.71073 A, MoꢀKa. Or-
MoꢀKa. Monoclinic system, space group P21/n, a=
thorhombic crystal system, space group Pbca, a=
,
,
12.5217(9), b=12.2106(9), c=29.649(2) A, i=
14.6088(4),
b=15.1651(4),
,
c=17.5486(4)
A,
3
3
90.515(2)°, V=4533.0(6) A , Dcalc=1.326 Mg m−3
,
V=3887.79(17) A , Dcalc=1.454 Mg m−3, Z=8, v=
,
Z=4, v=0.572 mm−1, F(000)=1904.
0.573 mm−1, F(000)=1744.

54
N.W. Alcock et al. / Journal of Organometallic Chemistry 605 (2000) 45–54
A semi-empirical absorption correction was carried
References
out using Tmax,min=0.93, 0.73. Structure solution was
carried out using SHELXTL version 5.0 software [17] on
a Silicon Graphics Indy workstation. Refinements were
by least squares, carried out using SHELXL-96 software
[17], minimising on the weighted R factor wR2. A total
of 21 889 reflections were collected, with 4659 indepen-
dent reflections (Rint=0.0924). Anisotropic thermal
parameters were used for all non-hydrogen atoms, hy-
[1] (a) R.O. Duthaler, A. Hafner, Chem. Rev. 92 (1992) 807. (b)
R.L. Halterman, Chem. Rev. 92 (1992) 965. (c) H.H.
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3
,
fixed with isotropic thermal parameters U=0.08 A .
244 parameters were refined, residual electron den-
sity=0.645 and −0.758 e A−3, GOF on F2=1.016,
,
R=0.0582, wR2=0.1160 (for all data).
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
137689–137691. Copies of this information may be
obtained free of charge from: The Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (Fax: +44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
Acknowledgements
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Organomet. Chem. 584 (1999) 382.
We thank the EPSRC for studentships to SLH and
PJM, the EPSRC and the University of Warwick for
financial support and Dr Peter Scott for helpful discus-
sions. HJC thanks Memorial University of Newfound-
land for granting study leave.
[15] R. Quintanilla, T.E. Cole, Tetrahedron 51 (1995) 4297.
[16] P.J. McCormack, PhD Thesis, University of Warwick.
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University of Go¨ttingen, 1993.
.