ansa-metallocenes with a Ph2Si bridge: Molecular structures of HfCl2[Ph2Si(η5-C13H8) (η5-C5H4)] and HfCl2[Ph2Si(C13H9)(η5 -C5H4)]2

Article abstract of DOI:10.1039/b009280k

A mixture of rac- and meso-HfCl₂[Ph₂Si(η⁵-C₉H₆ )₂] was synthesized by treatment of HfCl₄ with the dilithium salt of di(1H-inden-1-yl)diphenylsilane. These complexes were isolated after fractional crystallization in 15.5 and 8.5% yields, respectively. A sterically strained ansa complex HfCl₂[Ph₂Si(η⁵-C₁₃H₈) (η⁵-C₅H₄)] was synthesized in 62% yield by treatment of HfCl₄ with the dilithium salt of cyclopentadienyl(fluoren-9-yl)diphenylsilane. Both this compound, and the by-product of reaction, HfCl₂[Ph₂Si(C₁₃H₉)(η⁵ -C₅H₄)]₂, were characterized by crystal structure analysis.

Full text of DOI:10.1039/b009280k

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ansa-Metallocenes with a Ph2Si bridge: molecular structures of
HfCl2[Ph2Si(ꢀ5-C13H8)(ꢀ5-C5H4)]andHfCl2[Ph2Si(C13H9)(ꢀ5-C5H4)]2 †
Vyacheslav V. Izmer,a Anton Y. Agarkov,a Valentina M. Nosova,b Lyudmila G. Kuz’mina,c
Judith A. K. Howard,d Irina P. Beletskayaa and Alexander Z. Voskoboynikov*a
a Department of Chemistry, Moscow State University, V-234, Moscow 119899,
Russian Federation. E-mail: voskoboy@org.chem.msu.su
b State Research Institute of Chemistry and Technology of Organoelement Compounds,
38 Shosse Entuziastov, Moscow 111123, Russian Federation
c N.S. Kurnakov Institute of General and Inorganic Chemistry of Russian Academy of Sciences,
31 Leninskii pr., Moscow 117907, Russian Federation
d Department of Chemistry, Durham University, South Road, Durham, UK DH1 3LE
Received 20th November 2000, Accepted 8th February 2001
First published as an Advance Article on the web 16th March 2001
A mixture of rac- and meso-HfCl2[Ph2Si(η5-C9H6)2] was synthesized by treatment of HfCl4 with the dilithium salt
of di(1H-inden-1-yl)diphenylsilane. These complexes were isolated after fractional crystallization in 15.5 and 8.5%
yields, respectively. A sterically strained ansa complex HfCl2[Ph2Si(η5-C13H8)(η5-C5H4)] was synthesized in 62% yield
by treatment of HfCl4 with the dilithium salt of cyclopentadienyl(fluoren-9-yl)diphenylsilane. Both this compound,
and the by-product of reaction, HfCl2[Ph2Si(C13H9)(η5-C5H4)]2, were characterized by crystal structure analysis.
HfCl2[Ph2Si(C13H9)(η5-C5H4)]2 has also been characterized.
1 Introduction
These hafnium complexes can be considered as the precursors
The stereorigid ansa-metallocenes are known to be promising
of efficient polymerization catalysts.
homogeneous catalyst precursors for stereoselective propene
polymerization.1,2 The ansa complexes, particularly fluorenyl-
2 Results and discussion
Synthesis and NMR study of ligands and metal complexes
cyclopentadienyl compounds bridged with the bulky CPh2
group were recently found to have unprecedented catalytic
performance in olefin polymerization.3,4 Similar complexes with
a bulky Ph2Si bridge are poorly studied,5,6 mostly because of
the more difficult preparation. Whereas bis-cyclopentadienyl
ligands with a CPh2 bridge are readily available via nucleophilic
addition of cyclopentadienyllithium to diphenylfulvene, ligands
with a Ph2Si bridge can be prepared only via nucleophilic sub-
stitution at silicon. If nucleophilic substitution at a sterically
hindered silicon center, e.g. in Ph2(CpЈ)SiCl, is slow, attack of
an organolithium or analogous reagent at such a chlorocyclo-
pentadienylsilane is accompanied by transmetallation leading
to decreased yields of the target ligand. In this case, an improve-
ment of yield can be achieved either by optimization of reaction
conditions or by using an alternative approach, which has been
described e.g. for the synthesis of Me2Si(C5Me4H)2 (eqn. 1).7
Di(1H-inden-1-yl)diphenylsilane was synthesized by treatment
of Ph2SiCl2 with 2 equivalents of indenyllithium (eqn. 2). The
desired product was isolated in 21% yield after recrystallization
from cold pentane. This product turned out to be a ca. 50 to 50
1
mixture of isomeric rac and meso compounds. The H NMR
spectrum (in CDCl3) includes characteristic broad triplets at
δ 4.369 (J = 1.9) and 4.414 (J = 1.8 Hz) attributed to allylic
protons H(1) of indenyl fragments. Resonances at δ 6.690
(dd, J = 1.9, J = 14.2 Hz) and 6.680 (J = 1.7, J = 14.3 Hz) can be
attributed to H(2), and multiplets at δ 6.765 and 6.745 are likely
to belong to H(3).
The low yield of the product is accounted for by a metal-
lation side reaction (e.g., eqn. 3; pathway a), which can be faster
(particularly in the case of organolithium reagents) than the
nucleophilic substitution at the sterically hindered silicon center
(eqn. 3; pathway b).
(1)
An attempt to purify the compound using high vacuum
sublimation failed. At 120 ЊC we observed the rearrangement
of isomeric di(1H-inden-1-yl)diphenylsilanes into the more
thermodynamically stable isomer. From the evidence of NMR
spectra, this isomer contains two equivalent indenyl fragments
with silicon at the vinyl position of the indenyl system. This
sigmatropic shift equilibrium sets in within several minutes. So,
the resulting mixture contains up to 70% of this vinylic isomer,
ca. 5% of the isomer with both vinylindenyl and 1H-inden-1-yl
fragments, and ca. 25% of a rac/meso mixture of di(1H-inden-
1-yl)diphenylsilanes. The recrystallization of this mixture from
cold MeOH gave the desired symmetrical vinylic isomer with
ca. 90% purity.
This work is aimed at the synthesis and characterization
of hafnium complexes containing bulky Ph2Si(η5-C13H8)(η5-
C5H4) and Ph2Si(η5-C9H6)2 ligands (C13H8 = fluorenyl, C9H6 =
indenyl). The sterically strained unbridged metallocene
† Electronic supplementary information (ESI) available: characteriz-
ation data for silanes and compounds 1–3. See http://www.rsc.org/
suppdata/dt/b0/b009280k/
It is well known that more electronegative substituents at
Si in cyclopentadienylsilanes should stabilize vinylsilyl isomers
DOI: 10.1039/b009280k
J. Chem. Soc., Dalton Trans., 2001, 1131–1136
This journal is © The Royal Society of Chemistry 2001
1131

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(2)
(3)
Table 1 1H and 13C chemical shifts δ (ppm)a in NMR spectra of
di(1H-inden-3-yl)diphenylsilane in CDCl3
(4)
Fragment
Indenyl
Nucleus No.b
δ(1H) (J/Hz)
δ(13C)c
1
2
4
5
6
7
3.53 (m)
41.21
150.19
123.37
126.08
124.36
123.50
135.91
127.93
129.60
6.92 (t, JHH = 1.71)
7.23 (d, JHH = 7.57)
7.11 (t, JHH = 7.57)
7.18 (t, JHH = 7.32)
Phenyl
11,15
12,14
13
7.69 (m)
7.35 (m)
7.42 (m)
a Relative to TMS. b See atom numbering in eqn. 4. c Signals of quater-
nary atoms 3-C, 8-C, 9-C, and 10-C were not assigned: δ 147.96, 144.46,
140.15 and 134.16.
(5)
Table
CDCl3
2
Results of NOE for di(1H-inden-3-yl)diphenylsilane in
Irradiated nucleusa
% NOEb(observed nucleus)
1-H
2-H
7-H
9.5 (2-H), 4.4 (7-H)
5.8 (1-H), 4.6 (11/15-H)
11.2 (6-H), 2.4 (1-H)
8.5% yield after crystallization from CH2Cl2–pentane. Crystal-
lization from diethyl ether gave the respective rac isomer 1 in
15.5% yield. From the evidence of NMR spectra, the latter
product was contaminated with ca. 15% of 2.
11/15-H
15.4 (12/14-H), 3.5 (4-H), 2.4 (2-H)
a See atom numbering in eqn. (4). b Calculated assuming 100% for the
The use of NMR helped to resolve the structures for com-
plexes 1 and 2. In the case of analogous ansa complexes with
SiMe2 and CMe2 bridges the determination of the config-
uration, rac or meso, of the respective metallocenes was made
by studying the upfield region of their 1H or 13C NMR spectra.
The racemates have equivalent Me groups in the bridge. On the
other hand the Me groups are not equivalent in the spectra
of meso complexes. The analysis of spectra of complexes with a
SiPh2 bridge is more difficult due to an overlap of resonances
due to protons of Ph fragments of the bridge and aromatic
protons of the indenyl system. However, due to equivalence of
Ph groups in the racemate 1 and non-equivalence of these
groups in the meso complex the assignment can be accom-
plished (assuming free rotation about Si–C(10) and Si–C(10Ј)
bonds). Whereas the resonance of H(11), H(15) of 1 appears at
δ 8.109 (m, AAЈ part of AAЈBBЈC system) the 1H NMR
spectrum of 2 displays two equivalent characteristic multiplets
at δ 8.115 and 8.211 attributed to H(11), H(15) and H(11Ј),
H(15Ј) of two non-equivalent Ph fragments (AAЈBBЈC and
DDЈEEЈF spin systems).
irradiated signal.9,10
at the expense of allylsilyl isomers.8 Thus, possible structures
for the above-mentioned symmetrical vinyl isomer are di(1H-
inden-3-yl)diphenylsilane (eqn. 4, pathway A) or di(1H-inden-
2-yl)diphenylsilane (pathway B).
To assign a correct structure to the obtained isomer, we have
used 1H and 13C (APT, assigned proton test) NMR spectra and
multipulse 2-D-COSY, HETCOR, and 1-D NOE experiments
(Tables 1 and 2). The data confirm the di(1H-inden-3-yl)-
diphenylsilane structure (eqn. 4, pathway A) for the compound
formed. The evidence in favor of this conclusion is as follows.
First, from both 1H NMR spectra and NOE between the
neighboring protons the molecule should include a ᎐CHCH
᎐
2
fragment. Additionally, NOE was observed for H(2) and H(4)
by irradiation of ortho-protons of phenyl rings, i.e. H(11) and
H(15), while NOE for H(4) was not observed by irradiation of
H(2).
HfCl2[Ph2Si(η5-C9H6)2] 1, (rac) and 2 (meso) were prepared
via transmetallation reaction using the organotin reagent
(eqn. 5).11–13 Analytically pure meso complex 2 was isolated in
The second problem under investigation is the synthesis of
the unsymmetrical sterically hindered complex HfCl2[Ph2Si(η5-
1132
J. Chem. Soc., Dalton Trans., 2001, 1131–1136

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Table 3 1H and 13C chemical shifts δ (ppm)a and spin–spin coupling
constants JHH/Hz in NMR spectra of complex 3 in CD2Cl2
(7)
Fragment
Nucleus No.b
δ(1H)c (J/Hz)
δ(13C)d
Cyclopentadienyl
1
2, 5
3, 4
6
7, 18
8, 17
9, 16
10, 15
11, 14
12, 13
19
20, 24
21, 23
22
102.79
110.25
124.41
63.26
127.41
124.51
5.96
6.65
Fluorenyl
Phenyl
6.91 (JHH = 8.61)
7.03 (JHH = 8.61, J 6.84) 128.60
7.60 (JHH = 8.32, J 6.84) 126.85
8.11 (JHH = 8.38)
124.78
128.94
133.02
134.71
129.24
131.27
8.16
7.58
7.61
C(6) atom of the fluorenyl fragment is at δ 63.26, i.e. typical for
a Relative to TMS. b See atom numbering in eqn. (7). c Chemical shifts
for 10/15-H, 21/23-H, and 22-H were obtained from the respective
projections in the HETCOR spectrum, the chemical shift and 3JHH for
10/15-H from NOE (irradiation of 9/16-H). d Signals for 7/18-C, 10/
15-C, 12/13-C, 19-C, and 22-C were assigned on the basis of their
multiplicity in selective double heteronuclear resonance 13C-{1H}15 by
suppression of 8/17-H and 9/16-H with 40H power.
a sp3 carbon, which can be interpreted as evidence in favor of
σ bonding of this carbon with hafnium (see also ref. 16). Crys-
tallographic data, supporting this conclusion, are presented in
the next section.
From the evidence of NMR, if an excess of ligand is used the
synthesis of complex 3 is complicated by the formation of by-
product, which was characterized by crystal structure analysis
to be a complex derived from two mono-metallated cyclo-
pentadienyl(fluoren-9-yl)diphenylsilane molecules (eqn. 8).
Table 4 Results of NOE for complex 3 in CD2Cl2
Irradiated nucleusa
% NOEb (observed nucleus)
(8)
2/5-H
3/4-H
9/16-H
20/24-H
15.5 (3/4-H), 13.9 (20/24-H), 6.9 (8/17-H)
11.4 (8/17-H)
16.3 (10/15-H), 13.1 (8/17-H)
16.7 (21/23-H), 7.2 (2/5-H), 4.5 (8/17-H)
a See atom numbering in eqn. (7). b Calculated assuming 100% for the
irradiated signal.9,10
C13H8)(η5-C5H4)] 3. Cyclopentadienyl(fluoren-9-yl)diphenyl-
silane (a mixture of isomers) has been synthesized by treatment
of Ph2SiCl2 with fluorenyllithium, followed by cyclopentadienyl-
lithium (eqn. 6). This method gave the desired product in 28.5%
Molecular structures of HfCl2[Ph2Si(ꢀ5-C13H8)(ꢀ5-C5H4)] 3 and
HfCl2[Ph2Si(C13H9)(ꢀ5-C5H4)]2 4
(6)
Complexes 3 and 4 were characterized by crystal structure
analysis.The molecular structure of bridged ansa-hafnocene 3
is shown in Fig. 1. Bond lengths are given in Table 5. The
asymmetric unit contains one independent molecule of
hafnocene 3 and one solvent dichloromethane molecule.
Complex 3 possesses an approximate mirror plane symmetry.
The values of the Hf–Cl distances and Cl–Hf–Cl angle
(2.398(3), 2.411(3) Å and 96.4(1)Њ) are comparable with those
found for the closely related compound HfCl2(η5-C5H4CPh2-
η5-C13H8) (2.403(2) Å and 95.6Њ).17 It is of interest that the
inclusion of the short bridging group SiPh2 between cyclo-
pentadienyl and fluorenyl ligands does not distort significantly
the metallocene moiety. Thus, in the structure of 3 the angle
formed by the centroids of C5 rings and Hf atom is equal to
129.8Њ. On the other hand, Si(1)–C(1) and Si(1)–C(6) bonds are
inclined to the least squares planes of C5 rings by 21.2 and
13.8Њ, respectively. The latter results in a decrease of the C(1)–
Si(1)–C(6) angle to 96.3Њ. The Hf–C(6) distance (2.44(1) Å)
is much shorter than Hf–C(12) and Hf–C(13) (2.75(2) and
yield. In this case the side metallation of the formed chloro-
fluorenyldiphenylsilane by CpLi is impossible.14 So, a low
basicity of CpLi favors nucleophilic substitution at silicon atom
and high yield synthesis of the desired ligand. The ansa
complex 3 was prepared by treatment of HfCl4 with 1 equiv-
alent of the dilithium salt of the ligand in toluene (eqn. 7). This
compound was isolated as a yellow crystalline solid in 62% yield.
The structure of compound 3 was established by NMR spec-
troscopy (Tables 3 and 4). An assignment was made using 2-D
spectra (COSY, HETCOR), 1-D NOE, and selective double
resonance 13C-{1H} experiments (see Table 3 for experimental
details). It is of interest that the resonance of the quarternary
J. Chem. Soc., Dalton Trans., 2001, 1131–1136
1133

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Fig. 1 View of complex 3.
Table 5 Bond lengths (Å) for complex 3
Fig. 2 View of complex 4.
Table 6 Bond lengths (Å) for complex 4
Hf(1)–Cl(1)
Hf(1)–Cl(2)
Hf(1)–C(5)
Hf(1)–C(6)
Hf(1)–C(2)
Hf(1)–C(1)
Hf(1)–C(3)
Hf(1)–C(4)
Hf(1)–C(7)
Hf(1)–C(18)
Hf(1)–C(13)
Hf(1)–C(12)
Si(1)–C(1)
Si(1)–C(19)
Si(1)–C(25)
Si(1)–C(6)
C(1)–C(2)
C(1)–C(5)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(6)–C(18)
C(6)–C(7)
C(7)–C(12)
2.398(3)
2.411(3)
2.45(2)
2.437(12)
2.46(2)
2.48(2)
2.51(2)
2.52(2)
2.552(13)
2.566(13)
2.73(2)
2.75(2)
1.848(13)
1.874(14)
1.868(13)
1.86(2)
1.44(2)
1.46(2)
1.42(2)
1.41(2)
1.44(2)
1.48(2)
1.48(2)
1.43(2)
C(7)–C(8)
C(8)–C(9)
1.45(2)
1.36(2)
1.42(2)
1.36(2)
1.41(2)
1.43(2)
1.41(2)
1.40(2)
1.36(2)
1.40(2)
1.38(2)
1.43(2)
1.41(2)
1.40(2)
1.39(2)
1.37(2)
1.37(2)
1.38(2)
1.38(2)
1.40(2)
1.42(2)
1.37(2)
1.36(2)
1.41(2)
C(8)–C(10)
C(10)–C(11)
C(11)–C(12)
C(12)–C(13)
C(13)–C(14)
C(13)–C(18)
C(14)–C(15)
C(15)–C(16)
C(16)–C(17)
C(17)–C(18)
C(19)–C(20)
C(19)–C(24)
C(20)–C(21)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
C(25)–C(26)
C(25)–C(30)
C(26)–C(27)
C(27)–C(28)
C(28)–C(29)
C(29)–C(30)
Hf(1)–Cl(2)
Hf(1)–Cl(1)
Hf(1)–C(2Ј)
Hf(1)–C(1)
Hf(1)–C(5)
Hf(1)–C(3Ј)
Hf(1)–C(4)
Hf(1)–C(1Ј)
Hf(1)–C(2)
Hf(1)–C(3)
Hf(1)–C(5Ј)
Hf(1)–C(4Ј)
Si(1)–C(25)
Si(1)–C(19)
Si(1)–C(1)
2.413(2)
2.424(2)
2.471(6)
2.489(5)
2.497(6)
2.491(7)
2.496(6)
2.504(6)
2.500(6)
2.515(6)
2.523(6)
2.530(6)
1.875(6)
1.884(7)
1.877(6)
1.924(6)
1.882(6)
1.889(6)
1.896(6)
1.927(6)
1.422(8)
1.429(9)
1.412(9)
1.411(10)
1.425(9)
1.508(10)
1.513(9)
1.413(11)
1.394(11)
1.405(11)
1.37(2)
C(20)–C(21)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
C(25)–C(26)
C(25)–C(30)
C(26)–C(27)
C(27)–C(28)
C(28)–C(29)
C(29)–C(30)
C(1Ј)–C(2Ј)
C(1Ј)–C(5Ј)
C(2Ј)–C(3Ј)
C(3Ј)–C(4Ј)
C(4Ј)–C(5Ј)
C(6Ј)–C(18Ј)
C(6Ј)–C(7Ј)
C(7Ј)–C(8Ј)
C(7Ј)–C(12Ј)
C(8Ј)–C(9Ј)
C(9Ј)–C(10Ј)
C(10Ј)–C(11Ј)
C(11Ј)–C(12Ј)
C(12Ј)–C(13Ј)
C(13Ј)–C(18Ј)
C(13Ј)–C(14Ј)
C(14Ј)–C(15Ј)
C(15Ј)–C(16Ј)
C(16Ј)–C(17Ј)
C(17Ј)–C(18Ј)
C(19Ј)–C(24Ј)
C(19Ј)–C(20Ј)
C(20Ј)–C(21Ј)
C(21Ј)–C(22Ј)
C(22Ј)–C(23Ј)
C(23Ј)–C(24Ј)
C(25Ј)–C(26Ј)
C(25Ј)–C(30Ј)
C(26Ј)–C(27Ј)
C(27Ј)–C(28Ј)
C(28Ј)–C(29Ј)
C(29Ј)–C(30Ј)
1.379(11)
1.396(11)
1.378(11)
1.390(10)
1.400(10)
1.404(9)
1.397(11)
1.374(13)
1.396(13)
1.385(10)
1.416(9)
1.422(8)
1.425(8)
1.426(10)
1.413(9)
1.505(9)
1.528(8)
1.390(10)
1.407(10)
1.402(10)
1.383(12)
1.390(12)
1.400(10)
1.449(9)
1.407(9)
1.409(10)
1.372(12)
1.401(12)
1.405(10)
1.389(9)
1.387(9)
1.406(9)
1.391(9)
1.402(11)
1.371(11)
1.392(9)
1.390(9)
1.400(9)
1.394(9)
1.375(10)
1.379(11)
1.391(10)
Si(1)–C(6)
Si(2)–C(19Ј)
Si(2)–C(1Ј)
Si(2)–C(25Ј)
Si(2)–C(6Ј)
C(1)–C(5)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(6)–C(18)
C(6)–C(7)
C(7)–C(12)
C(7)–C(8)
2.73(2) Å). The same Zr–fluorenyl bonding is common for ansa-
zirconocene derivatives.17,18
Fig. 2 shows the structure and atom numbering scheme for
compound 4. Bond lengths are given in Table 6. The asym-
metric unit contains one independent molecule of 4 and two
disordered dichloromethane molecules, one of which occupies
an inversion center. The coordination environment of Hf has a
bent sandwich geometry with two chloride ligands lying in the
bisecting plane. Both cyclopentadienyl rings are planar within
0.012 and 0.005 Å. The Hf–Cl and Hf–Cpcent distances are
equal to 2.424(2), 2.413(2) and 2.188, 2.193 Å, respectively. The
Cl–Hf–Cl and Cpcent–Hf–Cpcent angles are 94.29(6) and 129.5Њ.
Analysis of the Cambridge Structural Database (Release
5.1819) shows that the geometry of the central metallocene
fragment in 4 is common for biscyclopentadienyldichloro-
hafnium derivatives (13 entries, excluding short bridged ansa
compounds). Thus, the Hf–Cl, Hf–Cpcent distances and Cl–Hf–
Cl, Cpcent–Hf–Cpcent angles lie within the ranges 2.410–2.431,
2.166–2.207 Å and 92.85–97.64, 125.67–132.42Њ, respectively.
Both silyl substituents in 4 are oriented towards the opposite
lateral sectors of the metallocene moiety (looking down the line
through the Cp ring centroids). The same anti conformation
was previously shown to be characteristic for Zr(RC5H4)2(X)2
(X = halide) derivatives with bulky R substituents.20,21 The
Si(1) and Si(1Ј) atoms deviate slightly (0.268, 0.301 Å) from
the least squares planes of the corresponding Cp rings in the
C(8)–C(9)
C(9)–C(10)
C(10)–C(11)
C(11)–C(12)
C(12)–C(13)
C(13)–C(18)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
C(16)–C(17)
C(17)–C(18)
C(19)–C(24)
C(19)–C(20)
1.39(2)
1.400(10)
1.470(12)
1.403(9)
1.398(12)
1.372(14)
1.418(13)
1.387(11)
1.401(10)
1.414(9)
1.399(10)
directions opposite to the Hf atom. The latter are prob-
ably caused by steric interactions of the bulky silyl substituents
with the opposite Cp rings. Both Si atoms possess distorted
tetrahedral coordination with C–Si–C angles lying in the
range 102.8(3)–119.1(3)Њ. The rotations of the silyl substi-
tuents around Si–C(Cp) bonds are different. The latter makes
the whole molecule asymmetric. Both fluorenyl fragments
1134
J. Chem. Soc., Dalton Trans., 2001, 1131–1136

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Table 7 Crystal data, data collection, structure solution and refine-
ment parameters for complexes 3 and 4
C(6)–C(18) and C(6Ј)–C(18Ј) are planar within 0.121 and
0.185 Å.
3
4
3 Experimental
Empirical formula
C30H22Cl2HfSIؒ
CH2Cl2
744.8
Monoclinic
P21/c
11.0830(2)
8.9801(2)
28.7654(6)
C60H46Cl2HfSi2ؒ
1.5CH2Cl2
1199.93
All manipulations have been done either on a high-vacuum line
in an all-glass apparatus equipped with polytetrafluoroethylene
stopcocks or in an atmosphere of thoroughly purified argon
using the standard Shlenk technique. THF was distilled over
LiAlH4. Toluene and pentane were distilled over Na/K alloy
and kept over CaH2. CH2Cl2, as well CDCl3 and CD2Cl2, were
Formula weight
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
β/Њ
Triclinic
¯
P1
13.5860(9)
14.0886(6)
15.9919(6)
69.997(1)
71.314(2)
89.535(1)
2706.9(2)
2
1
distilled over P4O10 and kept over 3A molecular sieves. H and
13C NMR spectra were recorded with a Bruker AM 360
spectrometer.
101.096(1)
γ/Њ
V/Å3
2809.4(1)
4
4.157
Preparations
Z
µ/mmϪ1
2.257
Di(1H-inden-1-yl)diphenylsilane. To a solution of indenyl-
lithium (prepared from 13.0 ml (11.62 g, 0.10 mol) of indene in
120 ml of THF and 52.0 ml of 1.43 M MeLi in diethyl ether)
was added dropwise for several minutes at Ϫ60 ЊC a solution of
10.5 ml (12.66 g, 0.05 mol) Ph2SiCl2 in 50 ml of THF. The
mixture was stirred at this temperature for 3 h, followed by
overnight at ambient temperature, and finally evaporated to
dryness. The residue was dissolved in 200 ml of toluene and
filtered. The toluene solution was evaporated to dryness and
the product extracted with 500 ml of warm pentane. The white
solid obtained from the pentane solution at Ϫ30 ЊC was filtered
off and dried in vacuum. This procedure gave 4.28 g (21%) of a
rac/meso mixture of di(1H-inden-1-yl)diphenylsilanes.
T/K
150.0(2)
11778
150.0(2)
19863
Reflections collected
Independent reflections
Final R1, wR2 [I > 2σ(I)] 0.0620, 0.1348
(all data) 0.0957, 0.1679
3487 [Rint = 0.1223] 12276 [Rint = 0.0639]
0.0589, 0.1489
0.0762, 0.2142
separated, dried over MgSO4, evaporated to give an orange
solid, which was washed with hot hexane and extracted with
3 × 150 ml of hot methanol. The resulting white solid was dried
in vacuum. Yield: 4.71 g (38%).
HfCl2[Ph2Si(ꢀ5-C13H8)(ꢀ5-C5H4)] 3. To 11.4 g (27.6 mmol)
of cyclopentadienyl(fluoren-9-yl)diphenylsilane in 300 ml of
toluene 22.1 ml a 2.5 M solution of n-BuLi in hexanes was
added dropwise. This mixture was refluxed for 1 h and cooled to
Ϫ40 ЊC. At this temperature 9.0 g (28.0 mmol) of HfCl4 were
added. The resulting mixture was refluxed for 4 h, cooled and
filtered. The precipitate was washed with 4 × 70 ml of toluene.
The combined toluene fractions were evaporated to ca. 300 ml.
Crystallization at Ϫ30 ЊC gave a yellow-orange crystalline solid
which was separated and dried in vacuum. The crude product
was recrystallized from hexane–CH2Cl2 (1 : 1). Yield: 11.3 g
(62%).
rac- and meso-HfCl2[Ph2Si(ꢀ5-C9H6)2] 1 and 2. To a suspen-
sion of 3.66 g (8.87 mmol) of di(1H-inden-1-yl)diphenylsilane
in 100 ml of ether 10.0 ml, 1.86 M MeLi in ether was added
dropwise for several minutes. This mixture was stirred for 2 h.
Then a solution of 4.28 g (17.7 mmol) SnEt3Cl in 70 ml of
ether was added dropwise for several minutes. The mixture was
stirred for 1 hour and evaporated to dryness in vacuum. The
residue was redissolved in 100 ml of toluene and evaporated
to dryness to remove traces of ether. A new portion of 100 ml
of toluene was added and the mixture filtered. The resultant
toluene solution was added dropwise for 2 h to a suspension of
2.84 g (8.87 mmol) HfCl4 in 50 ml of toluene. This mixture was
stirred for 6 h at 95 ЊC. A yellow precipitate obtained at 0 ЊC
was filtered off, washed by 3 × 15 ml of cold toluene, then by
2 × 50 ml of ether. The ether extracts were combined and
evaporated to ca. 30 ml. Yellow rac complex 1 which precipi-
tated at Ϫ30 ЊC was filtered off and dried in vacuum. Yield
0.91 g (15.5%). The yellowish brown solid residue (after extrac-
tion with toluene and ether) was dissolved in 50 ml of CH2Cl2
and filtered through a G4 frit filter. To this solution 50 ml of
pentane were added. The yellow solid which precipitated at
Ϫ30 ЊC was filtered off and dried in vacuum. This procedure
gave 0.50 g (8.5%) of meso complex 2.
X-Ray diffraction study of complexes 3 and 4
Crystal data, data collection, structure solution and refinement
parameters for compounds 4 and 3 are given in Table 7. For the
structure of 4 all non hydrogen atoms (except solvent dichloro-
methane molecules) were refined with anisotropic thermal
parameters. For compound 3, hafnium, chlorine and silicon
atoms were refined anisotropically and all carbon atoms, in an
isotropic approximation. For both structures, hydrogen atoms
were placed in calculated positions and refined using a riding
model.
CCDC reference numbers 152545 and 152546.
See http://www.rsc.org/suppdata/dt/b0/b009280k/ for crystal-
lographic data in CIF or other electronic format.
Chloro(fluoren-9-yl)diphenylsilane. A solution of fluorenyl-
lithium (prepared from 15.3 g (90 mmol) of fluorene in 200 ml
of THF and 39 ml of 2.3 M n-BuLi in hexanes) was added
dropwise for 5 h to a solution of 27 ml (32.5 g, 128 mmol)
Ph2SiCl2 in 100 ml THF. This mixture was stirred overnight at
rt, then, evaporated to dryness. The red oil was washed with 250
ml of dry hexane. The extract was filtered. Crystallization at
Ϫ30 ЊC gave 26 g (75%) of a yellowish solid.
Acknowledgements
Financial support from the Russian Foundation for Basic
Research (Grant no. 98-03-32978a), President of the Russian
Federation (Grant no. 98-15-96061), International Science and
Technology Center (Grant. no. 1036/99) and ExxonMobil
Chemical Company is gratefully acknowledged. We also thank
Dr A. K. Shestakova.
Cyclopentadienyl(fluoren-9-yl)diphenylsilane. To a solution of
C5H5Li (prepared from 9.92 g (150 mmol) of freshly distilled
cyclopentadiene and 65 ml of a 2.3 M solution of n-BuLi in
hexanes in 200 ml THF) 11.5 g (30 mmol) of chloro(fluoren-9-
yl)diphenylsilane in 100 ml of THF were added dropwise for 2 h
at rt. This mixture was stirred overnight at rt, treated with 50 ml
of water and neutralized with 10% HCl. The organic layer was
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