Cyclic organohydroborate complexes of metallocenes VIII. Triphenylsiloxy derivatives of Group IV organometallic systems, CpM2M(OSiPh 3)X (M=Ti, Zr, Hf; X=Cl, {(μ-H)2BC8 H14})

Article abstract of DOI:10.1016/j.jorganchem.2003.08.010

Group IV metallocene triphenylsiloxy chlorides, Cp₂MCl(OSiPh ₃) (1, M=Ti; 2, M=Zr; 3, M=Hf), and cyclic organohydroborates, Cp₂M(OSiPh₃){(μ-H)₂BC₈ H₁₄} (4, M=Zr; 5, M=Hf), were s

Full text of DOI:10.1016/j.jorganchem.2003.08.010

Journal of Organometallic Chemistry 687 (2003) 69ꢃ77
/
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Cyclic organohydroborate complexes of metallocenes
VIII. Triphenylsiloxy derivatives of Group IV organometallic
systems, Cp2M(OSiPh3)X (Mꢀ
/
Ti, Zr, Hf; XꢀCl, {(m-H)2BC8H14})
/
Fabrice Lacroix, Christine E. Plecnik, Shengming Liu, Fu-Chen Liu,
Edward A. Meyers, Sheldon G. Shore *
Department of Chemistry, Newman and Wolfrom Laboratory, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210-1185, USA
Received 27 May 2003; accepted 5 August 2003
Abstract
Group IV metallocene triphenylsiloxy chlorides, Cp2MCl(OSiPh3) (1, Mꢀ
/
Ti; 2, Mꢀ
/
Zr; 3, MꢀHf), and cyclic organohy-
/
droborates, Cp2M(OSiPh3){(m-H)2BC8H14} (4, MꢀZr; 5, MꢀHf), were synthesized and characterized. The new hafnocene
/
/
chloride derivative 3 was obtained by treating Cp2HfCl2 with triphenylsilanol and piperidine. The 18-electron cyclic
organohydroborates 4 and 5 were afforded by reacting 2 and 3 with K[H2BC8H14], the potassium salt of the 9-BBN dimer.
Reaction of 1 with K[H2BC8H14] causes reduction of the Ti(IV) center and produces the well-known Ti(III), 17-electron,
paramagnetic dimer [Cp2Ti(m-Cl)2TiCp2] (6). Single-crystal X-ray diffraction structures of 3, 4, 5, and 6 were determined.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Group IV metallocene; Triphenylsiloxy; Organohydroborate; Silica model
1. Introduction
In addition to their ability to selectively reduce
organic functionalities (i.e. aldehydes and ketones) [6],
organohydroborate anions are capable of ligating to
metals in a manner similar to that of tetrahydroborate
[7]. For instance, this laboratory has employed cyclic
Grafting [1,2] organometallic systems onto a sup-
port’s surface has been one advancement in the field of
surface organometallic chemistry [3]. Recently, Basset
and co-workers designed ethylene polymerization cata-
lysts by grafting zirconocene alkyl fragments onto the
surface of silica [1a]. Supported catalysts such as these
can be a challenge to study in terms of understanding
reactivity/activity and deciphering structure [3]. More
simplified and easily characterized homogeneous analo-
gues that attempt to simulate the silanol surface of
partially dehydroxylated silica have been developed.
organohydroborate anions [H2BR2]ꢁ (R2ꢀ
C5H10, C8H14) as bidentate ligands (two Mꢁ
bridges) to a variety of metallocenes (MꢀTi, Zr, Hf,
/
C4H8,
Hꢁ
/
/
B
/
Nb) [8]. The properties and reactivity of organohydro-
borate complexes differentiate them from the tetrahy-
droborate analogues. (1) The intramolecular hydrogen
exchange of bridging and Cp hydrogens can be readily
investigated without the interference of a Bꢁ
/
Hb and Bꢁ
/
Reasonable models of isolated silanol sites (ꢀ
can be based on silsesquioxane [4,5] and triphenylsiloxy
ligands [5b].
/
Siꢁ/OH)
Ht fluxional process [8d,8h,9]. (2) The chemistry of the
bridging hydrogens is more easily explored without the
complication of terminal hydrogen (Bꢁ/Ht) reactions.
The reactivity of metallocene organohydroborates with
B(C6F5)3 is of particular interest because this Lewis acid
is a typical co-catalyst in metal-catalyzed olefin poly-
merization and is a traditional alkyl carbanion abstract-
* Corresponding author. Tel.:
2921685.
E-mail address: shore.1@osu.edu (S.G. Shore).
ꢂ
/
1-614-2926000; fax:
ꢂ/1-614-
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00843-X

70
F. Lacroix et al. / Journal of Organometallic Chemistry 687 (2003) 69ꢃ77
/
ing reagent [10]. Previous work demonstrates that the
bridging hydrogens in metallocene cyclic organohydro-
borates are abstracted by B(C6F5)3 [11], and resulting
products include metallocene cations, which have the
potential to function as olefin polymerization catalysts
[12]. The present contribution describes the preparation
of new models of potential homogeneous single-site
metallocene anchored catalysts, namely, triphenylsila-
nolato derivatives of Group IV metallocene cyclic
organohydroborates, Cp2M(OSiPh3){(m-H)2BC8H14}.
siloxy cyclic organohydroborates Cp2M(OSiPh3){(m-
H)2BC8H14} (4, MꢀZr; 5, MꢀHf; Eq. (2)).
/
/
ð2Þ
2. Results and discussion
2.1. Preparation of Cp2MCl(OSiPh3) (MꢀTi, Zr, Hf)
/
The anion [H2BC8H14]ꢁ displaces Clꢁ and binds to
Zr and Hf in a bidentate fashion through three-center,
Group IV metallocene chloro triphenylsilanolates
Cp2MCl(OSiPh3) (1, MꢀTi; 2, MꢀZr; 3, MꢀHf)
were synthesized by reacting the corresponding metallo-
cene dichloride with triphenylsilanol and piperidine (Eq.
(1)) [13].
/
/
/
two-electron Mꢁ
/
Hꢁ
/
B bonds. The driving force of this
reaction is KCl precipitation. The reaction is complete
within minutes and no side products are observed by
11B-NMR spectroscopy. Attempts to synthesize pure
sample of another triphenylsilanolato derivative of a
zirconocene cyclic organohydroborate, Cp2Zr(O-
SiPh3){(m-H)2BC5H10}, were unsuccessful [16]. The
complex Cp2ZrH{(m-H)2BC5H10} was combined with
Ph3SiOH and the resulting mixture of products, includ-
ing the desired compound and Cp2Zr(OSiPh3)2, could
not be separated [16]. It appears that the most facile
route toward the zirconocene and hafnocene triphenyl-
siloxy organohydroborates is through Cp2MCl(OSiPh3).
Compounds 4 and 5 are 18-electron, diamagnetic
species. In C6D6, the 11B-NMR resonances of the
organohydroborate ligand appear as unresolved broad
peaks at 5.6 ppm for 4 and 2.3 ppm for 5. The signals for
4 and 5 are upfield comparing with those of the 11B-
NMR resonances of Cp2ZrCl{(m-H)2BC8H14} (17.7
ppm) [8h], Cp2ZrH{(m-H)2BC8H14} (32.5 ppm) [8h],
Cp2HfCl{(m-H)2BC4H8} (12.4 ppm) [8a,8b], and
Cp2HfCl{(m-H)2BC5H10} (9.3 ppm) [8c]. The two brid-
ging protons are inequivalent. One bridging hydrogen
ð1Þ
Compounds 1 and 2 were first prepared according to
this procedure by Dehnicke and co-workers [13]. The
synthetic method was extended to Cp2HfCl2, and a new
hafnocene compound 3 was isolated in 56% yield. The
molecular structure of 3 was determined by single-
crystal X-ray diffraction analysis. Compounds 1, 2,
and 3 were characterized by 1H- and 13C-NMR spectro-
scopies. Cyclopentadienyl protons appear at around d
5.9 and two multiplets centered at d 7.8 and 7.2 are
observed for the phenyl ring hydrogens. The 13C-NMR
spectra possess four resonances for the phenyl carbons
and one for the Cp nuclei. The IR spectrum of 3
peak is broad and upfield at ꢁ
/
0.3 ppm for 4 and ꢂ0.5
/
ppm for 5. The other bridging hydrogen is obscured by
the multiplet (d 2.3 to 1.7) for the b- and g-protons of
the organohydroborate ring. The chemical shift of a-
protons is ca. 1.5 ppm, and the peaks are broad due to
the quadrupolar 11B nuclei [8g]. The proton assignments
possesses a Hfꢁ
/
Oꢁ
/
Si stretch at 977 cmꢁ1 [14], which is
close to the 957 cmꢁ1 frequency recorded for both 1 and
2 [13].
1
are based on integration and a carbon-detected H-13C-
NMR correlation experiment (HETCOR). Phenyl and
Cp proton signals for 4 and 5 are slightly shifted relative
to those of 1 and 2.
2.2. Reactions of 1, 2, and 3 with K[H2BC8H14]
2.2.1. Preparation of Cp2M(OSiPh3){(m-H)2BC8H14}
(Mꢀ/Zr, Hf)
2.2.2. Formation of [Cp2Ti(m-Cl)2TiCp2] (6)
Metathesis reactions of 2 and 3 with K[H2BC8H14]
(the hydroborate anion of the 9-BBN dimer, (m-
H)2(BC8H14)2) [15] afforded the metallocene triphenyl-
Complex 1 and K[H2BC8H14] were mixed in a 1:1
molar ratio in Et2O (Eq. (3)). The reaction solution
progressively changed color from orange to purple then

F. Lacroix et al. / Journal of Organometallic Chemistry 687 (2003) 69ꢃ
/77
71
to dark green with evolution of hydrogen, all of which
are indications of Ti(IV) reduction to Ti(III). The
reaction was monitored by 11B-NMR, and after 15
min the spectrum contained two peaks at 60.8 and 28.8
ppm. After several hours the latter signal, assigned to
the 9-BBN dimer [8g,8h], disappeared and the peak at
60.8 ppm remained. This downfield chemical shift is
characteristic of a trialkyl borane [17]. Green crystals
were isolated from the reaction solution, and single-
crystal X-ray diffraction analysis revealed that the
titanocene product is the paramagnetic, Ti(III), chlor-
ine-bridged dimer [Cp2Ti(m-Cl)2TiCp2] (6) [18]. Proton-
and 13C-NMR spectra of 6 are not valid due to the
paramagnetism of the Ti(III) centers 7e[8g,11b].
2.3. Molecular structures
The molecular structures of 3ꢃ
/
6 were determined by
single-crystal X-ray diffraction analysis; structures are
shown in Figs. 1ꢃ4. Crystallographic data and selected
bond distances and angles are compiled in Tables 1ꢃ4.
/
/
The structures of 1 and 2 were reported by Dehnicke
and co-workers [13]. Complexes 2 and 3 crystallize in the
same trigonal space group, P3. The structure of 6 was
originally elucidated by Stucky and co-workers [18].
However, when crystals are grown under different
conditions, 6 exists in a different crystalline form (i.e.
a polymorph with different crystal symmetry and unit
cell parameters). Nevertheless, bond distances and
angles (Table 4) for the two polymorphs are nearly
identical, and the structures will not be discussed further
(see Section 3). Crystals of 6 are twinned.
The coordination geometry about the Zr and Hf
atoms in 3, 4, and 5 is best described as a distorted
tetrahedron, with the two Cp centroids, the oxygen
atom of [OSiPh3]ꢁ, and Cl or B located at the corners of
ð3Þ
the tetrahedron. Structural features in 1ꢃ
/
3 are compar-
able (Table 2), and this is reflected by the narrow Mꢁ
/
O
˚
˚
(1.842(4)ꢃ
/
1.961(6) A) and Mꢁ
/
Cl (2.388(2)ꢃ2.460(3) A)
/
ranges [13]. In compounds 4 and 5, the Cp2M(OSiPh3)
fragment bonds to the {BC8H14} moiety through two
bridging hydrogens. MetalÁ Á Áboron distances (Table 3)
The production of 6 most likely occurs in a stepwise
˚
˚
in 4 (2.71(1) A) and 5 (2.624(8) A) are slightly elongated
relative to those in other zirconocene and hafnocene
fashion:
1) Metathesis. Displacement of [OSiPh3]ꢁ with
[H2BC8H14]ꢁ causes precipitation of K[OSiPh3]
and perhaps forms the intermediate [Cp2TiCl{(m-
H)2BC8H14}]. This metathetical step contrasts the
substitution of Clꢁ by [H2BC8H14]ꢁ in the
zirconocene and hafnocene triphenylsilanolates
(Eq. (2)). It is not immediately clear why replace-
ment of [OSiPh3]ꢁ is favored over Clꢁ in the
titanocene system. However, a comparison of the
organohydroborates,
Cp2ZrCl{(m-H)2BC8H14}
˚
(2.593(3), 2.609(3) A) [8h], Cp2ZrH{(m-H)2BC8H14}
˚
(2.566(2) A) [8h], and Cp2HfCl{(m-H)2BC4H8}
(2.527(5) A) [8b]. This may be a consequence of the
˚
larger steric bulk of the [OSiPh3]ꢁ ligand compared to
Clꢁ and Hꢁ. The Mꢁ
typical for metallocene organohydroborates [8b,8h]. In
/
Hb and Bꢁ
/
Hb bond lengths are
˚
O distances (3, 1.934(5) A;
compounds 1ꢃ
4, 1.985(3) A; 5, 1.993(4) A) and nearly linear Mꢁ
angles (3, 171.9(4)8; 4, 159.4(2)8; 5, 158.3(3)8) suggest
/
5 the short Mꢁ
/
˚
˚
/
OꢁSi
/
average Mꢁ
enthalpies may shed light on the result; Tiꢁ
and TiꢁCl bonds have similar dissociation energies,
whereas ZrꢁOR and HfꢁOR bonds are on average
stronger than the corresponding ZrꢁCl and HfꢁCl
bonds [19].
/
OR and Mꢁ
/
Cl bonds dissociation
/OR
/
/
/
/
/
2) Redox. Although the identity of the actual reducing
agent is unknown, reduction of Ti(IV) to Ti(III) is
not surprising. For example, tetrahydroborate [20]
and organohydroborates [8g] readily reduce
Cp2TiCl2 to yield Ti(III) complexes Cp2Ti{(m-
H)2BR2} (R2ꢀH2, C4H8, C5H10, C8H14). The
/
unidentified trialkyl borane product in Eq. (3)
probably results from rearrangement of the alkyl
groups in the 9-BBN dimer [21]. Chlorine bridges
are constructed to relieve electron deficiency at the
two Ti(III) centers.
Fig. 1. Molecular structure of one of the three independent molecules
of Cp2HfCl(OSiPh3) (3) showing 25% probability thermal ellipsoids.
Hydrogen atoms are omitted for clarity.

72
F. Lacroix et al. / Journal of Organometallic Chemistry 687 (2003) 69ꢃ77
/
observed in the bis(triphenylsiloxy)-substituted systems
˚
(DME)ZrCl2(OSiPh3)2 (Zrꢁ
/
O, 1.91(1) A; Zrꢁ
/
Oꢁ
1,3-
OꢁSi,
/
Si,
171(1)8) [22] and CpƒZrCl(OSiPh3)2 (Cpƒꢀ
/
˚
C5H3(SiMe3)2; Zrꢁ
/
O, 1.921(4), 1.929(5) A; Zrꢁ
/
/
175.3(3), 159.3(2)8) [5b].
3. Experimental
3.1. General procedures
All manipulations were carried out on a standard high
vacuum line or in a dry box under an atmosphere of
nitrogen. Diethyl ether, tetrahydrofuran, and toluene
were dried over sodium-benzophenone and freshly
distilled prior to use. Hexane was stirred over concen-
trated sulfuric acid for 2 days and then decanted and
washed with water. Next, the hexane was stirred over
sodium-benzophenone for 1 week, followed by distilla-
tion into a storage bulb-containing sodium-benzophe-
none. Cp2TiCl2, Cp2ZrCl2, Cp2HfCl2, and Ph3SiOH
were purchased from Aldrich and used as received.
Piperidine was purchased from Aldrich, dried over
sodium-benzophenone, and freshly distilled prior to
use. K[H2BC8H14] was prepared by the literature
procedure [15]. The synthesis of Cp2MCl(OSiPh3) (1,
2), originally prepared by Dehnicke and co-workers [13],
was slightly modified and is detailed below. Elemental
analyses were obtained by Galbraith Laboratories,
Knoxville, TN. 1H-NMR spectra were obtained on
Bruker AM-250 and DPX-400 spectrometers operating
at 250.1 and 400.1 MHz, respectively, and referenced to
residual solvent protons. 13C-NMR spectra were ob-
tained on Bruker AM-250 and DPX-400 spectrometers
operating at 63.0 or 100.6 MHz, respectively, and
referenced to deuterated solvent signals. 11B-NMR
spectra were obtained on a Bruker AM-250 spectro-
meter operating at 80.3 MHz and externally referenced
Fig. 2. Molecular structure of Cp2Zr(OSiPh3){(m-H)2BC8H14} (4)
showing 10% probability thermal ellipsoids. Hydrogens attached to
carbon atoms are omitted for clarity.
Fig. 3. Molecular structure of Cp2Hf(OSiPh3){(m-H)2BC8H14} (5)
showing 25% probability thermal ellipsoids. Hydrogens attached to
carbon atoms are omitted for clarity.
to BF3×
/
OEt2 in C6D6 (dꢀ0.00 ppm). Infrared spectra
/
were recorded on a Mattson Polaris Fourier Transform
Spectrometer with 2 cmꢁ1 resolution.
3.2. X-ray structure determination
Single-crystal X-ray diffraction data were collected on
a Nonius Kappa CCD diffraction system, which em-
Fig. 4. Molecular structure of one of the two independent molecules of
[Cp2Ti(m-Cl)2TiCp2] (6) showing 25% probability thermal ellipsoids.
Hydrogen atoms are shown with arbitrary thermal ellipsoids.
ploys graphite-monochromated Moꢃ
/
Ka radiation (lꢀ
/
˚
0.71073 A). A single crystal of 3, 4, 5, and 6 was
mounted on the tip of a glass fiber coated with Fomblin
oil (a pentafluoropolyether). Unit cell parameters were
obtained by indexing the peaks in the first 10 frames and
refined employing the whole data set. All frames were
integrated and corrected for Lorentz and polarization
ppꢃ
gen p orbitals of [OSiPh3]ꢁ into empty metal d orbitals)
[13,22]. The extent of this ppꢃdp bonding appears to be
/
dp bonding (electron donation from occupied oxy-
/
stronger in 1, 2, and 3; the electron withdrawing effect of
Clꢁ, in contrast to the electron donating ability of
[H2BC8H14]ꢁ, encourages greater donation from
effects using the DENZO-SMN package (Nonius BV,
1999) [23]. Absorption correction was applied using the
SORTAV program [24] provided by MaXus software [25].
[OSiPh3]ꢁ to the metal. Similar ppꢃ
/
dp interactions are

F. Lacroix et al. / Journal of Organometallic Chemistry 687 (2003) 69ꢃ
/77
73
Table 1
Crystal and structure refinement data for Cp2HfCl(OSiPh3) (3), Cp2Zr(OSiPh3){(m-H)2BC8H14} (4), Cp2Hf(OSiPh3){(m-H)2BC8H14} (5), and
[Cp2Ti(m-Cl)2TiCp2] (6)
3×
/
1/6C5H11
N
4
5
6
Empirical formula C28.833H26.833N0.167ClHfOSi
Formula weight (amu) 633.73
C36H41BOSiZr
619.81
C76H90B2Hf2O3Si2
1486.26
C20H20Cl2Ti2
427.06
Temperature (8C)
Crystal system
Space group
ꢁ
Trigonal
P3
/
73
ꢁ
Triclinic
P1
/
10
ꢁ
/
73
ꢁ73
Triclinic
P1
/
Monoclinic
P21/c
Crystal color, habit
˚
Colorless rectangle
35.457(1)
35.457(1)
10.443(1)
90
Colorless block
9.116(1)
9.695(1)
10.696(1)
116.11(1)
92.12(1)
105.92(1)
802.6(1)
1
Colorless rectangle
8.688(1)
17.916(1)
21.138(1)
90
Dark green block
11.393(1)
11.396(1)
13.541(1)
89.98(1)
89.91(1)
89.63 (1)
1758.0(3)
4 b
a (A)
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
V (A )
Z
90
120
90.00(1)
90
3
˚
11371(1)
18 a
1.671
3290.2(4)
4
1.427
Dcalc (g cmꢁ3
)
1.282
0.406
1.614
1.210
m (mmꢁ1
)
4.302
3.232
Crystal size (mm)
2u Range (8)
Index ranges
0.23ꢄ
2.30ꢃ50.04
425h 5
125l 512
66 407
/
0.15ꢄ
/
0.06
0.15ꢄ
4.72ꢃ49.84
105h 5
k 511, ꢁ125
17 422
5443
/
0.08ꢄ
/
0.08
0.27ꢄ
4.54ꢃ50.06
105h 5
21, ꢁ255l 5
69 718
5823
/
0.19ꢄ
/
0.12
0.19ꢄ
5.86ꢃ50.06
135h 5
k 513, ꢁ165
9996
5807
0.0187
93.6
/
0.19ꢄ0.15
/
/
/
/
/
ꢁ/
/
/41, ꢁ
/
425
/
k 5
/
41, ꢁ
/
ꢁ/
/
/10, ꢁ
/
115
/
ꢁ/
/
/10, ꢁ
/
215
/
k 5
/
ꢁ/
/
/13, ꢁ
/
135
/
/
/
/
/
/
l 5
/12
/
/
/25
/
/
/
l 5
/
15
Reflections collected
Independent reflections 13 374
Rint 0.1174
Completeness to u (%) 99.8
0.1288
99.7
0.0482
99.9
Max/min transmission
Data/restraints/para-
meters
0.7824, 0.4378
13 374/0/902
0.9682, 0.9416
5443/3/369
0.6977, 0.4757
5823/0/369
0.8393, 0.8027
5807/0/429
R1 [I ]
/
2.0s(I)] c
0.0587
0.1082
1.185
0.0486
0.1367
1.393
0.0229
0.0604
1.076
0.0265
0.0639
1.040
wR2 (all data) d
Goodness-of-fit on F2
Largest difference peak 1.371, ꢁ
/0.801
0.490, ꢁ/0.683
1.014, ꢁ/1.194
0.292, ꢁ0.348
/
ꢁ3
˚
and hole (e A
)
a
In the asymmetric unit cell, there are three independent molecules of 3, 1/3 of a molecule of C5H11N, and 1/6 of another molecule of C5H11N.
There are two independent molecules in the asymmetric unit cell.
b
c
R1ꢀ
/
a||Fo|ꢁ|Fc||/a|Fo|.
/
1=2
/
wR2ꢀ
/
faw(Fo2 ꢁFc2)2=aw(Fo2)2g
:
d
Structures were solved by direct methods and refined
using SHELXTL-97 (difference electron density calcula-
tion, full-matrix least-squares refinements) structure
solution package [26]. Data merging was performed
using the data preparation program supplied by
SHELXTL-97. For each structure, non-hydrogen atoms
were located and refined anisotropically. Bridging
hydrogen atoms in 4 and 5 were located and refined
isotropically. All other hydrogen atom positions were
calculated using standard geometries.
Piperidine co-crystallizes with 3 (before crystalliza-
tion, the solid was not washed with hexane). In the
asymmetric unit cell, there are three unique molecules of
3, 1/3 of a molecule of C5H11N (N(1), N(2); threefold
rotation about an axis passing through the center of the
piperidine ring generates the entire molecule), and 1/6 of
another molecule of C5H11N (N(3); inversion and
threefold rotation about the center of the ring generates
the entire molecule). In the unit cell, there are 18
Table 2
Selected bond distances (A) and angles (8) for Cp2MCl(OSiPh3) (1,
MꢀTi; 2, MꢀZr; 3, MꢀHf)
˚
/
/
/
a
1
2 a,b
3 b
Bond distances
Average Mꢁ
MꢁCentroid
/C
2.381[10] c
2.076(1),
2.072(1)
1.842(4)
2.388(2)
2.510[8]
2.213(7),
2.220(6)
1.961(6)
2.460(3)
2.482[8]
2.208,
2.202
/
Mꢁ
/
O
1.934(5)
2.441(3)
Mꢁ
/
Cl
Bond angles
CentroidꢁMꢁ
troid
MꢁOꢁ
OꢁMꢁ
/
/Cen-
132.6(1)
127.7(3)
127.9
/
/
Si
164.5(2)
95.9(1)
173.0(4)
98.4(2)
171.9(4)
97.3(2)
/
/Cl
a
Ref. [13].
There are three independent molecules in the asymmetric unit cell.
b
Data are listed for only one molecule.
c
Ref. [28].

74
F. Lacroix et al. / Journal of Organometallic Chemistry 687 (2003) 69ꢃ77
/
Table 3
site occupancy factors, respectively. The disordered
sites, Hf(2?) and Hf(3?), were refined isotropically and
possess 9 and 3% site occupancy factors, respectively.
Disordered THF solvent co-crystallizes with 5. In the
asymmetric unit, there is one molecule of 5 and one half
of a THF molecule (two carbons, Ca, Cb, and an oxygen
(50% s.o.f.). The full THF molecule is represented by
two molecules, each of half occupancy, which share their
four carbon atoms Ca, Cb, Ca , and Cb that are
generated through an inversion center that is located in
the center of the four carbons.
The molecular structure of 6 was previously deter-
mined by Stucky and co-workers [18]. Crystals were
grown by sublimation and data were collected at room
temperature (r.t.). The structure was solved in the
˚
Selected bond distances (A) and angles (8) for Cp2M(OSiPh3){(m-
H)2BC8H14} (4, MꢀZr; 5, MꢀHf)
/
/
4
5
Bond distances
Average M(1)ꢁ
Average M(1)ꢁ
/
C(11ꢃ
C(16ꢃ
/
15)
10)
2.535[8]
2.521[9]
2.251
2.516[4]
2.514[7]
2.214
/
/
M(1)ꢁ
M(1)ꢁ
M(1)ꢁ
/
Centroid(C11ꢁC15)
Centroid(C16ꢁC10)
O(1)
/
2.225
2.214
?
?
/
1.985(3)
2.71(1)
1.74(3)
2.12(7)
1.10(4)
1.22(8)
1.614(3)
1.993(4)
2.624(8)
2.14(8)
2.06(7)
1.10(7)
1.07(8)
1.608(4)
M(1)Á Á ÁB(1)
M(1)ꢁ
M(1)ꢁ
/
H(1A)
/H(1B)
B(1)ꢁ
B(1)ꢁ
O(1)ꢁ
/
H(1A)
/
H(1B)
/
Si(1)
monoclinic space group P21/c (aꢀ
/
13.422(8), bꢀ
/
Bond angles
M(1)ꢁO(1)ꢁ
O(1)ꢁM(1)ꢁ
O(1)ꢁM(1)ꢁ
O(1)ꢁM(1)ꢁ
H(1A)ꢁ
H(1A)ꢁ
Centroidꢁ
˚
/
/
Si(1)
159.4(2)
102.2(2)
89(1)
158.3(3)
102.9(2)
127(2)
80(2)
15.666(11), cꢀ
/
13.083(12) A, bꢀ
/
94.21(4)8), and there
/
/B(1)
are 1.5 independent molecules of 6 in the asymmetric
unit. The authors noted that crystals grown from
benzene solutions were twinned and exhibited pseudo-
fourfold symmetry. The space group of these could not
be determined, and the unit cell was not reported.
In the present work, crystals of 6 were isolated from
/
/H(1A)
/
/H(1B)
128(2)
39(2)
/
M(1)ꢁ
B(1)ꢁH(1B)
M(1)ꢁCentroid
/
H(1B)
46(3)
100(6)
129.8
/
/
71(4)
/
/
126.4
an Et2O solution and data were collected at ꢁ
/
73 8C.
Table 4
The resulting unit cell has triclinic symmetry P1 (aꢀ
/
˚
˚
Selected bond distances (A) and angles (8) for [Cp2Ti(m-Cl)2TiCp2] (6)
11.393(1), bꢀ
/
11.396(1), cꢀ
/
13.541(1) A, aꢀ/89.98(1),
bꢀ89.91(1), gꢀ
/
/
89.63(1)8), with two unique molecules
Bond distances
in the asymmetric unit. Therefore, 6 can exist in two
different crystalline forms (i.e. polymorphs). Although
the unit cell parameters indicate tetragonal symmetry (a
and b are nearly equal and a, b, and g are almost 908),
there are no reflection conditions. The appearance of
pseudo-fourfold symmetry is a result of twinning. The
two parts of the twinned crystal are related by rotation;
Ti(1)Á Á ÁTi(2)
Cl(1)Á Á ÁCl(2)
3.912
3.283
Ti(3)Á Á ÁTi(4)
Cl(3)Á Á ÁCl(4)
3.908
3.276
Ti(1)ꢁ
/
Cl(1)
Cl(1)
2.551(1) Ti(1)ꢁ
2.558(1) Ti(2)ꢁ
2.552[3] Average TiꢁC
2.067
/Cl(2)
2.546(1)
2.560(1)
2.385[2]
2.068
Ti(2)ꢁ
/
/Cl(2)
Average Tiꢁ
Ti(1)ꢁCen-
troid(C11ꢁC15)
Cen-
/
Cl
/
/
Ti(1)ꢁ
troid(C16ꢁC10)
Ti(2)ꢁCen-
troid(C26ꢁC20)
/Cen-
Ti(2)ꢁ
/
2.060
/
2.063
troid(C21ꢁC25)
a 1808 rotation of the parent unit cell through the [ꢁ1,
/
1, 0] axis generates the twin. The twin law was
determined by the ROTAX program [27]. The fractional
contribution of the twin component was refined and
found to be 33.2%.
Bond angles
Cl(1)ꢁ
Ti(1)ꢁ
Centroidꢁ
troid
Centroid(C11ꢁC15)
Ti(1)ꢁCl(1)
Centroid(C16ꢁC10)
Ti(1)ꢁCl(1)
/
Ti(1)ꢁ
/
Cl(2)
80.22(3) Cl(1)ꢁ
99.95(3) Ti(1)ꢁ
Centroidꢁ
troid
Centroid(C11ꢁC15)
Ti(1)ꢁCl(2)
Centroid(C16ꢁC10)
Ti(1)ꢁCl(2)
/
Ti(2)ꢁ
/
Cl(2)
79.81(3)
100.02(3)
/
Cl(1)ꢁ
/
Ti(2)
/
Cl(2)ꢁ
/Ti(2)
/
Ti(1)ꢁ
/Cen- 132.2
/
Ti(2)ꢁCen- 131.3
/
ꢁ
/
107.4
108.9
ꢁ
/
108.3
107.7
3.3. Preparation of Cp2TiCl(OSiPh3) (1)
/
/
ꢁ
/
ꢁ
/
/
/
A 150 ml flask was charged with 1.369 g (5.50 mmol)
of Cp2TiCl2 and 70 ml of Et2O. About 5 ml of THF was
added to mostly dissolve the Cp2TiCl2. A solution of
Ph3SiOH (1.380 g, 5.00 mmol) in 10 ml of Et2O was
slowly added dropwise to the Cp2TiCl2 solution with
stirring. Piperidine (0.56 ml, 5.5 mmol) was added using
a plastic syringe. The reaction mixture was stirred for 6
h. After filtration, the volatiles were removed under
dynamic vacuum, and an orange-red powder was
obtained. The powder was dissolved in 30 ml of toluene.
Slow evaporation of the toluene at r.t. (until 5 ml of
solution remained) yielded orange crystals. The mother
liquor was removed and the crystals were washed with
molecules of 3 and three molecule of C5H11N. The
piperidine molecules are disordered because of symme-
try. As a result, all atoms and their occupancies were
refined as nitrogens (N(1), 92% site occupancy factor;
N(2), 88% site occupancy factor; N(3), 85% site occu-
pancy factor). These site occupancy factors are close to
the theoretical value of 88%. Due to the disorder,
hydrogen atom positions were not calculated. Two
independent molecules of 3 have disordered Hf atoms;
that is, the atoms adopt two alternate positions (Hf(2),
Hf(2?); Hf(3), Hf(3?)). Atoms Hf(1), Hf(2), and Hf(3)
were refined anisotropically and have 100, 91, and 97%
2ꢄ5 ml of hexane. After vacuum drying for 12 h, 1.340
/

F. Lacroix et al. / Journal of Organometallic Chemistry 687 (2003) 69ꢃ
/77
75
1
g (55% yield) of 1 was isolated. H-NMR (250 MHz,
13C-NMR (101 MHz, d8-THF): d 138.7 (s, Ph), 136.0 (s,
Ph), 130.0 (s, Ph), 128.4 (s, Ph), 112.6 (s, Cp), 34.4 (s, b-
C), 28.3 (br s, a-C), 25.6 (br s, g-C). IR (KBr, cmꢁ1):
3101 (vw), 3064 (w), 3046 (w), 3023 (vw), 2980 (w), 2913
(m, sh), 2867 (s), 2823 (ms, sh), 2665 (vw), 2052 (mw,
sh), 2021 (m), 1943 (mw), 1899 (w), 1827 (vw), 1495
(mw), 1428 (m), 1370 (m), 1339 (m), 1291 (m), 1203
(mw), 1110 (ms), 1071 (mw), 1051 (m), 1023 (m), 1015
(m), 961 (vs), 811 (vs), 745 (m), 703 (s), 511 (ms). Anal.
Calc. for C36H41BOSiZr: C, 69.76; H, 6.67; Si, 4.53.
Found: C, 69.16; H, 6.92; Si, 4.44%.
C6D6): d 7.86-7.82 (m, 6H, Ph), 7.26-7.23 (m, 9H, Ph),
5.92 (s, 10H, Cp). 13C-NMR (63 MHz, C6D6): d 137.9
(s, Ph), 136.0 (s, Ph), 130.0 (s, Ph), 128.3 (s, Ph), 118.0 (s,
Cp).
3.4. Preparation of Cp2ZrCl(OSiPh3) (2)
In a procedure similar to the one described above for
1, 1.608 g (5.50 mmol) of Cp2ZrCl2, 1.379 g (5.00 mmol)
of Ph3SiOH, and 0.57 ml (5.5 mmol) of piperidine
afforded 2.112 g (79% yield) of 2 as colorless crystals.
1H-NMR (250 MHz, C6D6): d 7.82-7.78 (m, 6H, Ph),
7.25-7.23 (m, 9H, Ph), 5.90 (s, 10H, Cp). 13C-NMR (63
MHz, C6D6): d 137.4 (s, Ph), 135.6 (s, Ph), 129.9 (s, Ph),
128.2 (s, Ph), 114.4 (s, Cp).
3.7. Preparation of Cp2Hf(OSiPh3){(m-H)2(BC8H14)}
(5)
In a procedure similar to the one described above for
4, 0.622 g (1.00 mmol) of 3 and 0.162 g (1.00 mmol) of
K[H2BC8H14] were reacted in THF. Colorless needlelike
crystals of 5 (0.380 g, 54% yield) were grown from THF.
3.5. Preparation of Cp2HfCl(OSiPh3) (3)
In a procedure similar to the one described above for
1, 2.089 g (5.50 mmol) of Cp2HfCl2, 1.381 g (5.00 mmol)
of Ph3SiOH, and 0.56 ml (5.5 mmol) of piperidine
afforded 1.740 g (56% yield) of 3 as colorless crystals.
1H-NMR (250 MHz, C6D6): d 7.82-7.78 (m, 6H, Ph),
7.25-7.22 (m, 9H, Ph), 5.84 (s, 10H, Cp). 13C-NMR (63
MHz, C6D6): d 137.5 (s, Ph), 135.6 (s, Ph), 129.9 (s, Ph),
128.2 (s, Ph), 113.2 (s, Cp). IR (KBr, cmꢁ1): 3109 (w),
3065 (w), 3046 (w), 3019 (w), 1968 (vw), 1895 (vw), 1830
(vw), 1739 (vw), 1675 (vw), 1623 (vw), 1588 (m), 1567
(vw), 1483 (m), 1427 (s), 1388 (w, sh), 1367 (w), 1332
(vw), 1306 (w), 1261 (mw), 1185 (mw), 1160 (mw, sh),
1116 (s), 1066 (w), 1013(s, sh), 1001 (s, sh), 977 (s), 814
(s), 744 (s), 704 (s), 619 (w), 530 (ms, sh), 511 (s). Anal.
Calc. for C28H25ClHfOSi: C, 54.28; H, 4.08. Found: C,
53.80; H, 4.15%.
1
11B-NMR (80 MHz, C6D6): d 2.3 (br t). H-NMR (400
MHz, C6D6): d 7.73-7.70 (m, 6H, Ph), 7.29-7.23 (m, 9H,
Ph), 5.77 (s, 10H, Cp), 2.23-1.75 (m, 13H, b-, g-, m-H),
1.47 (br s, 2H, a-H), 0.5 (br s, 1H, m-H). 13C-NMR (101
MHz, C6D6): d 138.1 (s, Ph), 135.5 (s, Ph), 129.8 (s, Ph),
128.1 (s, Ph), 110.4 (Cp), 34.1 (s, b-C), 27.8 (br s, a-C),
25.2 (br s, g-C). IR (KBr, cmꢁ1): 3119 (vw), 3063 (w),
3044 (w), 3020 (w), 2994 (w), 2952 (w), 2925 (mw), 2867
(m), 2823 (m), 2164 (vw), 2054 (m), 2022 (m, sh), 1943
(m), 1889 (mw, sh), 1818 (w), 1746 (vw), 1587 (mw),
1484 (m), 1441 (m, sh), 1428 (s), 1407 (ms, sh), 1386 (s),
1343 (s), 1310 (w, sh), 1281 (mw), 1204 (mw), 1187 (w),
1110 (s), 1070 (m), 1023 (ms), 1015 (ms), 1001 (s, sh),
972 (vs), 927 (s, sh), 839 (ms), 814 (s), 799 (s, sh), 745 (s),
736 (m, sh), 710 (s), 612 (mw), 526 (ms, sh), 512 (s), 457
(ms) cmꢁ1. Anal. Calc. for C36H41BHfOSi: C, 61.15; H,
5.84. Found: C, 61.75; H, 6.27%.
3.6. Preparation of Cp2Zr(OSiPh3){(m-H)2(BC8H14)}
(4)
In a 50 ml flask, a solution of K[H2BC8H14] (0.225 g,
1.39 mmol) in 10 ml of THF was added dropwise to a
solution of 2 (0.737 g, 1.39 mmol) in 20 ml of THF. The
reaction mixture was stirred for 1 h. The solvent was
removed under dynamic vacuum, and 25 ml of THF was
vacuum transferred into the flask. The solution was
filtered to remove KCl, THF was evaporated, and a
white foamy solid was obtained. The solid was dissolved
in 20 ml of toluene and crystals were grown by slowly
evaporating the solvent until 2 ml of solution remained.
After removal of the mother liquor, the crystal were
washed with 5 ml of hexane and vacuum dried for 12 h.
Compound 4 (0.450 g, 52% yield) was isolated as white
3.8. Reaction of 1 with K[H2BC8H14]. Formation of
[Cp2Ti(m-Cl)2TiCp2] (6)
A 50 ml flask was charged with 0.272 g (0.556 mmol)
of 1, 0.091 g (0.56 mmol) of K[H2BC8H14], and 15 ml of
Et2O. The mixture was stirred for 3 h, during which time
the solution changed color from orange to purple to
dark green and hydrogen evolved. Filtration of the
solution and slow removal of the solvent under vacuum
at r.t. afforded green crystals. The mother liquor (2 ml)
was removed and the crystals were washed with 3ꢄ5 ml
/
1
crystals. 11B-NMR (80 MHz, C6D6): d 5.6 (br t). H-
of cold hexane (ca. ꢁ40 8C) and dried under dynamic
/
vacuum for 3 h (152 mg, 64% yield). 1H-NMR (250
MHz, C6D6): not valid. 13C-NMR (63 MHz, C6D6): not
valid.
NMR (400 MHz, C6D6): d 7.74-7.70 (m, 6H, Ph), 7.27-
7.24 (m, 9H, Ph), 5.82 (s, 10H, Cp), 2.28-1.74 (m, 13H,
b-, g-, m-H), 1.50 (br s, 2H, a-H), ꢁ0.3 (br s, 1H, m-H).
/

76
F. Lacroix et al. / Journal of Organometallic Chemistry 687 (2003) 69ꢃ
/77
119 (1997) 9699;
4. Supplementary material
(d) A. Antinolo, F. Carrillo-Hermosilla, J. Ferna´ndez-Baeza, S.
˜
Garc´ıa-Yuste, A. Otero, A.M. Rodr´ıguez, J. Sa´nchez-Prada, E.
Crystallographic data for the structural analysis
(excluding structure factors) have been deposited with
the Cambridge Crystallographic Data Centre, CCDC
Villasenor, R. Gelabert, M. Moreno, J.M. Lluch, A. Lledo´s,
˜
Organometallics 19 (2000) 3654;
(e) P.A. Chase, W.E. Piers, M. Parvez, Organometallics 19 (2000)
2040.
nos. 211361ꢃ
/
211364 for compounds 3ꢃ6. Copies of this
/
[8] (a) G.T. Jordan, IV, S.G. Shore, Inorg. Chem. 35 (1996) 1087;
(b) G.T. Jordan, IV, F.-C. Liu, S.G. Shore, Inorg. Chem. 36
(1997) 5597;
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (Fax: ꢂ44-1223-336033; e-mail: deposit@ccdc.ca-
/
(c) J. Liu, E.A. Meyers, S.G. Shore, Inorg. Chem. 37 (1998) 496;
(d) F.-C. Liu, J. Liu, E.A. Meyers, S.G. Shore, Inorg. Chem. 37
(1998) 3293;
m.ac.uk or www: http://www.ccdc.cam.ac.uk).
(e) F.-C. Liu, J. Liu, E.A. Meyers, S.G. Shore, Inorg. Chem. 38
(1999) 2169;
Acknowledgements
(f) F.-C. Liu, B. Du, J. Liu, E.A. Meyers, S.G. Shore, Inorg.
Chem. 38 (1999) 3228;
This work was supported by the National Science
Foundation through Grants CHE 99-01115 and CHE
02-13491.
(g) F.-C. Liu, C.E. Plecnik, S. Liu, J. Liu, E.A. Meyers, S.G.
Shore, J. Organomet. Chem. 627 (2001) 109;
(h) X. Chen, S. Liu, C.E. Plenik, F.-C. Liu, G. Fraenkel, S.G.
Shore, Organometallics 22 (2003) 275.
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cyclic organohydroborate metallocene complexes, in: M.G. Da-
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¨

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(Fl ) for the average bond lengths is calculated according to the
following equations from Ref. [27]: Fl ꢀ3m [(lm
l)2/m(mꢁ1)]1/2
where ꢂl is the mean length, lm is the length of the mth bond, and
/
408. The standard deviation
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9/
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/
m is the number of bonds. The standard deviation is written in
brackets.