Synthesis and reactivity of core-functionalized polyhedral titanasiloxanes

Article abstract of DOI:10.1021/om020157v

Condensation reactions of cyclopentadienyl silanetriols with titanium alkoxides yield oligomeric titanasiloxanes in high yields. Two types of polyhedral structures can be obtained by small structural modifications at the reactants (Cp^RSi(OH)

Full text of DOI:10.1021/om020157v

Organometallics 2002, 21, 3009-3017
3009
Syn th esis a n d Rea ctivity of Cor e-F u n ction a lized
P olyh ed r a l Tita n a siloxa n es
Hans Martin Lindemann, Manuela Schneider, Beate Neumann,
Hans-Georg Stammler, Anja Stammler, and Peter J utzi*
Fakulta¨t fu¨r Chemie, Universita¨t Bielefeld, Universita¨tsstrasse 25, 33615 Bielefeld, Germany
Received February 25, 2002
Condensation reactions of cyclopentadienyl silanetriols with titanium alkoxides yield
oligomeric titanasiloxanes in high yields. Two types of polyhedral structures can be obtained
by small structural modifications at the reactants (CpRSi(OH)3, Ti(OR)4) or by variation of
reaction parameters. Thus, reaction of the silanetriols 9-(Me3Si)Fluorenyl-Si(OH)3 (1) and
Cp*Si(OH)3 (2) with Ti(OtBu)4 leads to the cubic Ti4O12Si4 polyhedrons [9-(Me3Si)Fluorenyl-
Si]4O12[TiOtBu]4 (3) and [Cp*Si]4O12[TiOtBu]4 (4), respectively, while co-condensations of 1
with Ti(OiPr)4 afford either the polyhedral titanasiloxane [9-(Me3Si)Fluorenyl-Si]4O12[Ti-
OiPr]6[µ2-iPrO]2[µ3-O]2 (6) or the cubic polyhedron [9-(Me3Si)Fluorenyl-Si]4O12[TiOiPr]4 (5),
depending on the choice of temperature and solvent. Substitution reactions with Ph3SiOH,
Me2NOH, or acetylacetone at the titanium centers proceed selectively under conservation
of the respective TiOSi core structures, whereas substitution reactions at the silicon centers
performed with ethanol, HCl, and water are connected with core degradation. Both the novel
titanasiloxanes and their titanium-functionalized derivatives have been characterized by
IR and NMR spectroscopy as well as by single-crystal X-ray diffraction studies. Thermolysis
of 3 leads to quantitative formation of 9-(Me3Si)Fluorene and 2-methylpropene.
In tr od u ction
three-functional, incompletely condensed oligosilsesqui-
oxanes, Feher et al. synthesized cubic titanasilsesqui-
oxanes in corner-capping reactions;6 these compounds
have a metal-silicon content of 1:7. Roesky et al. used
the co-condensation of silanetriols with titanium(IV)-
alkoxides for the synthesis of mainly cubic titanasilox-
anes with a metal-silicon content of 4:4.7 Although
there are many silanetriols known in the literature,8
only (arylamino)silanetriols of the type [Aryl(Me3Si)-
N]Si(OH)3, (Aryl, e.g., 2,4,6-Me3-phenyl)7 have been
extensively used in co-condensation reactions.
We are particularly interested in polyhedral, cubic
titanasiloxanes possessing eight potential leaving groups
at the corners of the cubic core. Substitution reactions
at the core atoms allow the preparation of novel den-
drimer-type compounds9 and of SiOTi-based hybrid
materials.10 Furthermore, substitution reactions under
elimination of the organic periphery can afford tailor-
made Ti-O-Si phases, in which the cubic precursors
act as secondary building blocks (SBU). In such cubic
titanasiloxanes, attack of electrophiles or nucleophiles
can effect either substitution reactions at the corner
atoms or core opening by Ti-O-Si bond splitting. Core-
Titanasiloxanes containing the Si-O-Ti moiety have
attracted considerable interest in recent years for
several reasons.1 Synthetic titanasilicates are widely
used as heterogeneous catalysts in industrial processes.
They catalyze olefin epoxidation2 and also other oxida-
tion reactions of diverse substrates, such as alkanes,
arenes, and amines.3 In view of the impressive catalytic
utility of these materials, it was of interest to synthesize
soluble molecular titanasiloxanes as models for titana-
silicates and for titanium complexes supported on silica
surfaces. Titanasiloxanes are also considered as precur-
sors for silicone polymers containing metal centers in
the polymer backbone.4 Especially promising compounds
are the polyhedral titanasiloxanes. Their attraction
stems from the appealing combination of an inorganic
core and an organic periphery with potentially useful
functionalities. They serve as model systems for titanium-
doped zeolites.5 Among these, compounds with a cubic
core structure are of particular interest. Starting from
* Corresponding author. Tel: Int. code + (521) 106-6181. Fax: Int.
code + (521) 106-6026. E-mail: Peter.J utzi@Uni-Bielefeld.de.
(1) (a) Gao, X.; Wach, I. E. Catal. Today 1999, 51, 233. (b) Voigt,
A.; Murugavel, R.; Roesky, H. W. Angew. Chem. 1997, 109, 1020. (c)
Kunduk, M. C.; Maschmeyer, T.; Thomas, J . M. Chem. Eur. J . 1999,
5, 1481.
(2) (a) Notari, B. Adv. Catal. 1996, 41, 253. (b) Thomas, J . M.;
Sankar, G. Acc. Chem. Res. 2001, 34, 571-581.
(3) Saxton, P. J .; Chester, W.; Zajacek, J . G.; Crocco, G. L.;
Wijesekera, K. S. U.S. Pat. 5621122, 1997.
(4) (a) Borisov, S. N.; Voronkov, M. G. Organosilicon Heteropolymers
and Heterocompounds; Plenum: New York, 1970. (b) Saam, J . C. In
Silicon Based Polymer Science; Zeigler, J . M., Fearon, F. W. G., Eds.;
Advances in Chemistry 224; American Chemical Society: Washington,
DC, 1999. (c) Abbenhuis, H. C. L.; Krijnen, S.; van Santen, R. A. Chem.
Commun. 1997, 3, 331.
(6) Feher, F. J .; Budzichowski, T. A. Polyhedron 1995, 14, 3239.
(7) (a) Voigt, A.; Murugavel, R.; Chandrasekhar, V.; Winkhofer, N.;
Roesky, H. W.; Schmid, H.-G.; Uso´n, I. Organometallics 1996, 15, 1610.
(b) Winkhofer, N.; Voigt, A.; Roesky, H. W. Angew. Chem., Int. Ed.
Engl. 1994, 33, 1352-4. (c) Murugavel, R.; Voigt, A.; Walawalkar, M.
G.; Roesky, H. W. Chem. Rev. 1996, 96, 2205. (d) Murugavel, R.;
Bhattacharjee, M.; Roesky, H. W. Appl. Organomet. Chem. 1999, 13,
227-243.
(8) Lickiss, P. D. Adv. Inorg. Chem. 1995, 42, 147.
(9) Dittmar, U.; Hendan, B. J .; Flo¨rke, U.; Marsmann, H. C. J .
Organomet. Chem. 1995, 489, 185.
(10) Soler-Illia, G. J . de A. A.; Scolan, E.; Louis, A.; Albouy, P. A.;
Sanchez, C. New J . Chem. 2001, 25, 156.
(5) Thomas, J . M.; Sankar, G. Acc. Chem. Res. 2001, 34, 571-581.
10.1021/om020157v CCC: $22.00 © 2002 American Chemical Society
Publication on Web 06/13/2002

3010 Organometallics, Vol. 21, No. 14, 2002
Lindemann et al.
Sch em e 1
opening finally results in a mixture of oligomeric
products. Thus, reaction conditions have to be found
where substitution reactions under conservation of the
core structure are favored. Useful substitution reactions
on such systems must proceed in nearly quantitative
yields, because otherwise complex mixtures of defi-
ciently substituted compounds would be formed.
functionalization reactions which lead to further novel
titanasiloxanes.
Resu lts a n d Discu ssion
Syn th esis of P olyh ed r a l Tita n a siloxa n es. Two
CpR-functionalized silanetriols and two tetraalkoxy
titanium compounds serve as starting materials for the
synthesis of three-dimensional titanasiloxanes. The
In titanium(IV) chemistry, alkoxy groups have been
shown to be good leaving groups. In silicon(IV) chem-
istry, the potential of cyclopentadienyl ligands as good
leaving groups is well documented.11 Accordingly, our
approach is the preparation of polyhedral titanasilox-
anes with alkoxy groups at the titanium and with CpR
groups at the silicon centers. Changes in the alkoxy
groups as well as in the CpR ligands allow the fine-
tuning of steric properties, thus influencing structure
and reactivity of the correspondingly substituted tita-
nasiloxane.
silanetriols 9-(Me3Si)Fluorenyl-Si(OH)317 (1) and Cp*Si-
18
(OH)3
(2) have been prepared in good yields by
controlled hydrolysis of the corresponding chlorosilanes.
At room temperature, compound 1 shows long-term
stability in the solid state and in solution, whereas
compound 2 decomposes slowly.19 Compound 2 can be
stored at temperatures lower than 0 °C without decom-
position.
Co-condensation of equimolar amounts of the silane-
triols 1 or 2 and of Ti(OtBu)4 in hexane at room
temperature afforded the cubic titanasiloxanes 3 and 4
in nearly quantitative yields (Scheme 1); the cubic
titanasiloxane 5 is formed as the main product by co-
condensation of equimolar amounts of 1 and of Ti(OiPr)4
in THF at room temperature or in hexane at -78 °C.
The compounds 3-5 are obtained as colorless solids,
which are highly soluble in polar and unpolar organic
solvents. The identity of these compounds has been
confirmed by multinuclear NMR and IR spectroscopy,
by elemental analysis, and by single-crystal X-ray
diffraction. In the NMR spectra, the 1H and 13C chemical
shifts are observed within the range expected for η1-
CpR and for OiPr and OtBu groups. The 29Si NMR
spectra exhibit a single resonance for the four SiO3 units
at about δ ) -78 ppm, indicating a high symmetry in
solution. These resonances are observed about 30 ppm
upfield from those of the corresponding silanetriols. IR
spectra of the titanasiloxanes are dominated by the Si-
O-Ti stretching frequencies observed at 900-1000
cm-1. Further spectral data are detailed in the Experi-
mental Section. Single crystals of 3, 4, and 5, suitable
for an X-ray crystal structure determination, were
grown from concentrated solutions in hexane. Selected
bond lengths and bond angles of 3, 4, and 5 are given
in Table 1. The solid state structures differ only slightly
with regard to the inorganic core. As an example, the
structure of 4 is shown in Figure 1. The core structure
can be defined by four silicon and four titanium atoms
There are reports concerning the reactivity of Si-O-
Ti bonds of cyclic, nonpolyhedral titanasiloxanes,12
indicating a strong sensitivity toward hydrolytic ring
cleavage. A substitution reaction under conservation of
the core structure of a cubic silsesquioxane was per-
i
formed by Maschmeyer et al.13 The PrO group at the
Ti moiety of the model compound cHex7Si7O12Ti(OiPr)
was substituted by the MeO group. The above com-
pounds were also shown to be exellent homogeneous
catalysts for olefin epoxidation with tert-butylhydro-
peroxide (TBHP).14 Only recently has a detailed cata-
lytic study been performed with the cubic titanasilses-
quioxane [2,6-iPr2C6H3)(Me3Si)NSi]4O12[TiOEt]4, 15 which
also catalyzes the epoxidation of cyclohexene. In this
study the EtO groups of the above compound were
t
t
selectively substituted by OOtBu, BuO, and BuCH2O
groups.
With this contribution we describe the synthesis of
the first polyhedral titanasiloxanes bearing CpR ligands
at their silicon centers16 and report on selective core-
(11) (a) J utzi, P. Comments Inorg. Chem. 1987, 6, 123. (b) J utzi, P.
J . Organomet. Chem. 1990, 400, 1. (c) J utzi, P.; Reumann, G. J . Chem.
Soc., Dalton Trans. 2000, 2237-2244.
(12) (a) Hoebbel, D.; Nacken, M.; Schmidt, H.; Huch, V.; Veith, M.
J . Mater. Chem. 1998, 8 (1), 171.
(13) Maschmeyer, T.; Klunduk, M. C.; Martin, C. M.; Shephard, D.
S.; Thomas, J . M.; J ohnson, B. F. G. Chem. Commun. 1997, 1874.
(14) (a) Krijnen, S.; Abbenhuis, H. C. L.; Hanssen, R.; van Hooff,
J .; van Santen, R. A. Angew. Chem. 1998, 110, 374. (b) Abbenhuis, H.
C. L.; Krijnen, S.; van Santen, R. A. Chem. Commun. 1997, 3, 331. (c)
Crocker, M.; Herold, R. H. M.; Orpen, A. G. Chem. Comm. 1997, 24,
2411. (d) Crocker, M.; Herold, R. H. M.; Orpen, A. G.; Overgaag, M. T.
A. J . Chem. Soc., Dalton Trans. 1999, 21, 3791. (e) Maschmeyer, T.;
Klunduk, M. C.; Martin, C. M.; Shephard, D. S.; Thomas, J . M.;
J ohnson, B. F. G. Chem. Commun. 1997, 19, 1847.
(16) Preliminary report, see: Schneider, M.; Neumann, B.; Stamm-
ler, H. G.; J utzi, P. In Organosilicon Chemistry-From Molecules to
Materials IV; Auner, N., Weis, J ., Eds.; VCH: Weinheim, 2000.
(17) Schneider, M. Thesis, University Bielefeld, 1999.
(18) J utzi, P.; Strassburger, G.; Schneider, M.; Stammler, H.-G.;
Neumann, B. Organometallics 1996, 15, 2842.
(15) Fujiwara, M.; Wessel, H.; Hyung-Suh, P.; Roesky, H. W.
Tetrahedron 2002, 58, 239.
(19) Cp*H was detected as a decomposition product.

Core-Functionalized Polyhedral Titanasiloxanes
Organometallics, Vol. 21, No. 14, 2002 3011
Ta ble 1. Selected Bon d Len gth s [Å] a n d Bon d An gles [d eg] of 3, 4, a n d 5
3
4
5
d(Si-O)
(O-Si-O)
d(Ti-O)
1.6226(19)-1.6319(19)
108.03(9)-109.69(10)
1.7891(17)-1.8155(17)
endocyclic
1.623(3)-1.640(3)
107.50(16)-109.46(17)
1.797(3)-1.823(3)
endocyclic
1.618(3)-1.636(3)
108.21(13)-109.42(14)
1.783(3)-1.814(2)
endocyclic
1.7456(18)-1.7584(18)
exocyclic
1.756(3)-1.771(3)
exocyclic
1.745(2)-1.754(2)
exocyclic
(Si-O-Ti)
(O-Ti-O)
137.13(11)-163.68(11)
106.55(8)-109.13(9)
1.856(2)-1.870(3)
1.912(3)-1.928(3)
136.92(18)-158.31(19)
105.72(15)-112.22(15)
1.873(4)-1.881(4)
138.32(15)-165.09(16)
106.27(11)-109.13(11)
1.855(3)-1.876(4)
1.906(4)-1.924(4)
d(O3Si-CCpR
)
d(Me3Si-CCpR
)
F igu r e 1. Structure of compound 4. For clarity one of the
four tert-butoxy groups is represented only by an oxygen
atom.
occupying alternate corners of a cube. Each of the 12
Si-Ti edges is bridged by an oxygen atom in a µ2
fashion. There are six Si2Ti2O4 eight-membered rings
that define the faces of the cube, and each of these rings
adopts a pseudo C4 crown conformation. The titanium
and silicon atoms adopt distorted tetrahedral geom-
etries. Although the cage structures of 3, 4, and 5 appear
to be highly symmetric also in the solid state, closer
inspection reveals that they show no symmetry at all.
A strong distortion of the cubes is indicated by the broad
range of the Ti-O-Si angles. The distortion of the Ti-
O-Si angles in 3 and 5 is stronger than that in 4. This
observation can be explained by the greater steric
demand of the 9-(SiMe3)fluorenyl group compared to
that of the Cp* ligand. The average endocyclic (frame-
work) Ti-O bond is slightly longer than the average
exocyclic Ti-O bond. The distortion of the cages is
caused presumably by packing effects in the solid state.
The Ti4Si4O12 polyhedrons are completely enclosed by
hydrophobic CpR and alkoxy groups, thus leading to a
high solubility of these compounds even in nonpolar
solvents such as hexane.
Surprisingly, the co-condensation of equimolar amounts
of 1 and of Ti(OiPr)4 in hexane at room temperature led
to the formation of a mixture of products containing
mainly the polyhedral titanasiloxane 6 and in addition
compound 5 and some polysiloxanes. The ratio of the
three components depends on the reaction conditions
described in the Experimental Section. When the reac-
tants were mixed according to the right stoichiometry
for the formation of compound 6 (4 1, 6 Ti(OiPr)4, 2 H2O),
this species was obtained in quantitative yield and in
analytically pure form (Scheme 2). The identity of 6 has
been confirmed by multinuclear NMR and IR spectros-
F igu r e 2. Side views of the framework of compound 6.
For clarity, 9-(Me3Si)Fluorenyl groups and iso-propyl groups
are represented only by the ipso carbon.
copy, by elemental analysis, and by an X-ray crystal
structure determination. The NMR chemical shifts can
be assigned in accordance with the solid state structure
(see Experimental Section). The IR spectrum is domi-
nated by the typical Si-O-Ti stretching frequencies
around 960 cm-1. Single crystals were obtained from a
concentrated solution in hexane. The structure of 6
resembles a cubelike polyhedron with an additional
“roof”. Figure 2 offers side views, which show how the
addition of this “roof” leads to a distortion of the cage.
The “roof” is created by insertion of a Ti(4)-(µ3-O)2-
Ti(5) fragment into the cube face formed by Si(2), Ti(3),
Si(4), and Ti(6). In Figure 3, a top view of the upper
part of the molecule shows the interconnection between
the Ti(3), Ti(4), Ti(5), and Ti(6) atoms via µ3-O and µ2-

3012 Organometallics, Vol. 21, No. 14, 2002
Lindemann et al.
Sch em e 2
of polysiloxanes and water has to take place. Partial
hydrolysis of Ti-OiPr bonds by the liberated water
followed by condensation reactions results in the con-
nection of Ti-O-Ti units by µ3-O or by µ2-OR bridges.
Interestingly, the described side-reactions can be avoided
by offering the reactants (including water) in the right
stoichometry for the formation of 6.
Our investigations have shown that small modifica-
tions of the alkoxy ligands of the titaniumalkoxide and
the solvent lead to structural changes in the Ti-O-Si
framework of the resulting titanasiloxanes. Thus, co-
condensation of 1 with Ti(OtBu)4 leads to the expected
cubic Ti4Si4O12 polyhedron 3, whereas the products of
the co-condensation of 1 with Ti(OiPr)4 depend on the
reaction parameters. The reaction of 2 with Ti(OtBu)4
afforded the expected cubic compound; the reaction of
2 with Ti(OiPr)4 led to a mixture of oligomeric products
that could not be clearly identified.17
Su bstitu tion Ch em istr y of P olyh ed r a l Tita n a si-
loxa n es. Reactivity studies have been performed with
the titanasiloxanes 3-6. Due to the sensitivity of the
TiOSi core units toward acid- or base-catalyzed oligo-
merizations, the choice of reactants for selective core
functionalizations is strictly limited. Thus, reactions of
the above compounds with ethanol or methanol resulted
in ring cleavage, followed by polycondensation. Despite
these problems, we have found conditions for selective
substitution reactions at the titanium centers, which
proceed under conservation of the core structure of the
respective titanasiloxane. First hints for selective sub-
stitution reactions resulted from experiments with
[9-(Me3Si)Fluorenyl-Si]4O12[TiOtBu]4 (3) and [Cp*Si]4-
O12[TiOtBu]4 (4) as catalysts for the epoxidation of
cyclohexene with TBHP.17 During the catalytic cycle,
OtBu groups have to be substituted by OOtBu groups.
The measured turnover numbers indicated that all four
Ti centers are involved in the catalytic process. The
catalysts could be regained quantitatively, a proof for
the core stability during many catalytic cycles.
The reaction of 3 or 5 with 4 equiv of Ph3SiOH in THF
proceeded readily at room temperature and afforded the
colorless substitution product 7 almost quantitatively,
whereby the corresponding alcohols were liberated
(Scheme 3). Compound 7 has been characterized by
multinuclear NMR and IR spectroscopy, by elemental
analysis, and by an X-ray crystal structure determina-
tion. The 29Si NMR spectrum exhibits sharp resonances
for the SiMe3 (δ ) 4.74 ppm), the SiPh3 (δ ) -12.37
ppm), and the SiO3 group (δ ) -78.21 ppm), indicating
a high symmetry of the cage compound in solution. The
1H NMR and 13C NMR chemical shifts can also be
assigned in accordance with a symmetric structure. The
IR spectrum is dominated by the Si-O-Ti stretching
frequency observed at 917 cm-1. Further spectroscopic
data are given in the Experimental Section. Suitable
single crystals of 7 were grown from a concentrated
solution in hexane, and the crystal structure was
determined. The Ti4Si4O12 polyhedron of 7 is completely
F igu r e 3. Top view of the upper half of 6.
Ta ble 2. Selected Bon d Len gth s [Å] a n d Bon d
An gles [d eg] of 6
d(Ti-OSi
)
1.794(2)-1.866(2) endocyclic
1.751(2)-1.774(2) exocyclic
94.47(9)-111.25(10)
(O-Ti-O)
d(Si-O)
(O-Si-O)
(Si-O-Ti)
µ2-OiPr-Fragment
d(Ti-O)
1.611(2)-1.641(2)
107.42(12)-111.05(12)
134.46(13)-160.82(14)
1.930(2), 1.936(2)
2.104(2), 2.096(2)
102.63(9), 102.87(9)
(Ti-OiPr-Ti)
µ3-O-Fragment
d(Ti-O)
1.962(2), 1.956(2)
2.003(2), 2.009(2)
1.905(2), 1.911(2)
(Ti-O-Ti)
144.49(11), 144.36(11)
107.43(10), 107.09(10)
102.56(10), 102.55(10)
OiPr linkages. A comparison of the different Ti-O bond
i
lengths in the OTi3 and PrOTi2 units with the sum of
the covalent radii of oxygen and titanium suggests that
the µ3-O fragments are connected to the titanium atoms
formally by two covalent and one coordinative bond,
whereas the µ2-OiPr fragments are connected by one
covalent and one coordinative bond. A nearly planar
coordination is observed for the µ3-O units (sum of the
bond angles 354.5° and 354.0°). Compound 6 is the
unique case of a titanasiloxane containing three differ-
ently coordinated Ti centers. While Ti(1) and Ti(2) are
tetrahedrally coordinated, Ti(3) and Ti(6) are trigonal
bipyramidally coordinated and Ti(4) and Ti(5) are
square pyramidally coordinated. The µn-O (n ) 2, 3) and
µ2-OR linkages of Ti atoms found in 6 are also common
structural features in titanium oxo clusters.20 Further
structural parameters are given in Table 2.
The formation of the titanasiloxane 6, possessing
structural elements such as µ3-O units and Ti-O-Ti
linkages, requires side reactions in the co-condensation
process of the silanetriol 1 with Ti(OiPr)4. Thus, auto-
condensation of silanetriol molecules under formation
(20) (a) Day, V. W.; Eberspacher, T. A.; Chen, Y.; Hao, J .; Klemperer,
W. G. Inorg. Chim. Acta 1995, 229, 391. (b) Day, V. W.; Eberspacher,
T. A.; Klemperer, W. G.; Parc, C. W.; Rosenberg, F. S. J . Am. Chem.
Soc. 1991, 113 (21), 8191. (c) Schmied, R.; Mosset, A.; Galy, J . J . Chem.
Soc., Dalton Trans. 1991, 1999.

Core-Functionalized Polyhedral Titanasiloxanes
Organometallics, Vol. 21, No. 14, 2002 3013
Sch em e 3
Sch em e 4
F igu r e 5. Drawing of the structure of compound 8. For
clarity, 9-(Me3Si)Fluorenyl groups are represented by the
ipso carbon atoms.
F igu r e 4. Drawing of the structure of compound 7. For
clarity, 9-(Me3Si)Fluorenyl groups are represented by the
ipso carbon atoms.
or in diethyl ether (9). The solid state structures of 8
and 9 are comparable with regard to their Ti4Si4O12 cage
and their Ti-O-NMe2 moieties. As an example, a
representation of the structure of 8 is shown in Figure
5. The titanium centers of the Ti4Si4O12 polyhedra are
coordinated with dimethylhydroxylamido ligands (ON-
Me2) in a bidentate fashion, whereby Ti-O bonds and
additional Ti-N â-donor bonds are formed. This situ-
ation leads to an overall 5-fold coordination at titanium.
The average N-Ti bond lengths are 2.10 Å (8) and 2.12
Å (9) (∑rvdW: 3.05 Å). The average Ti-O-N angles are
77.50° (8) and 78.05° (9). All framework Ti-O-Si bond
lengths and angles fall in the expected ranges and are
comparable with the values found in the parent com-
pounds 3 and 4. Further structural parameters of
compounds 8 and 9 are given in Table 4.
A few N,N-dialkylhydroxylamido compounds of tita-
nium are known in the literature.21 The solid state
structure of the homoleptic Ti(ONMe2)4 was confirmed
by an X-ray structure investigation. In this symmetric
molecule, the nitrogen atoms serve as â-donors, leading
to an eight-coordinate environment on titanium, achiev-
ing an intramolecular saturation of the coordination
sphere.
Ta ble 3. Selected Bon d Len gth s [Å] a n d Bon d
An gles [d eg] of 7
d(Si-O)
1.626(2)-1.638(2) endocyclic
1.643(1)-1.655(1) exocyclic
107.73(6)-109.20(6)
(O-Si-O)
d(Ti-O)
1.784(1)-1.814(1) endocyclic
1.789(1)-1.796(1) exocyclic
135.59(7)-158.93(8) endocyclic
160.72(9)-172.60(9) exocyclic
104.67(5)-114.61(6)
(Si-O-Ti)
(O-Ti-O)
d(SiO-CFl
)
1.855(2)-1.860(2)
enclosed by hydrophobic 9-(SiMe3)Fluorenyl and OSiPh3
groups, which show a propeller-like conformation. All
bond lengths and angles fall in the expected ranges and
are comparable to those observed for the parent com-
pounds 3 and 5. Figure 4 shows the cubic core structure
of 7 and the arrangement of the pendant OSiPh3 groups
on the titanium moieties. Structural parameters are
given in Table 3.
Treatment of 3 and 4 with 4 equiv of Me2NOH
afforded the compounds 8 and 9, respectively, in high
yields, whereby tert-butyl alcohol was liberated (Scheme
4). The colorless products have been characterized by
multinuclear NMR and IR spectroscopy, by elemental
analysis, and by X-ray crystal structure determination.
The 29Si NMR spectra exhibit one sharp resonance for
the four SiO3 units (δ -77.3 ppm, 8, and δ -73.9 ppm,
The reaction of 4 and 6 with 4 equiv of acetylacetone
afforded the compounds 10 and 11, respectively, whereby
the corresponding alcohols were liberated (Scheme 5).
The identity of the colorless products has been con-
firmed by multinuclear NMR and IR spectroscopy, by
elemental analysis, and by X-ray crystal structure
determination. The 1H NMR and 13C NMR chemical
shifts can be assigned in accordance with the solid state
structure. The 29Si NMR spectrum exhibits a sharp
1
9), and the H NMR and 13C NMR spectra display only
one resonance for the Me2NO ligands, indicating a high
symmetry of the compounds in solution. The IR spectra
show typical Si-O-Ti stretching frequencies around
950 cm-1. Further spectroscopic data are given in the
Experimental Section. Single crystals suitable for an
X-ray crystal structure investigation were grown from
concentrated solutions in dichloromethane/hexane (8)
(21) (a) Wieghardt, K.; Tolksdorf, I.; Weiss, J .; Swiridoff, W. Z.
Anorg. Allg. Chem. 1982, 490, 182. (b) Mitzel, N. W.; Parsons, S.; Blake,
A. J .; Rankin, D. W. H. J . Chem. Soc., Dalton Trans. 1996, 2089.

3014 Organometallics, Vol. 21, No. 14, 2002
Ta ble 4. Selected Bon d Len gth s [Å] a n d Bon d An gles [d eg] of 8 a n d 9
Lindemann et al.
8
9
d(Si-O)
(O-Si-O)
d(Ti-O)
1.617(1)-1.637(1)
108.65(6)-110.53(6)
1.815(1)-1.827(1) endocyclic
1.878(1) exocyclic
2.103(1)
1.618(3)-1.648(3)
106.09(13)-111.16(15)
1.807(2)-1.835(2) endocyclic
1.872(2)-1.882(3) exocyclic
2.108(3)-2.124(3)
d(Ti-N)
(N-O-Ti)
(Si-O-Ti)
(O-Ti-O)
77.50(8)
77.83(19)-78.26(17)
130.18(14)-178.6(2)
99.26(12)-116.24(11)
1.885(3)-1.889(3)
132.61(8)-160.32(8)
97.31(5)-121.79(5)
1.871(1)
d(SiO-CCpR
)
Sch em e 5
F igu r e 7. Drawing of the structure of compound 11. For
clarity, 9-(Me3Si)Fluorenyl and iso-propyl groups are rep-
resented by the ipso carbon atoms.
F igu r e 6. Drawing of the structure of compound 10‚4
dioxane. For clarity, Cp* groups are represented by the ipso
carbon atom.
O-Si angles range from 148.06° to 162.95°, indicating
a distortion of the cage. Further structural parameters
are given in Table 5.
Ta ble 5. Selected Bon d Len gth s [Å] a n d Bon d
An gles [d eg] of 10‚4 d ioxa n e
The core structure of 11 (Figure 7 gives a side view)
is comparable to that of the parent compound 6,
resembling a cubelike polyhedron with an additional
“roof”, created by insertion of the Ti(3)-(µ3-O)2-Ti(3a)
fragment into the cube face formed by Si(1), Ti(2), Si-
(1a), and Ti(2a). Four titanium atoms [Ti(1), Ti(1a), Ti-
(2), and Ti(2a)] possess acetylacetonato substituents,
whereas two titanium atoms [Ti(3), Ti(3a)] are still fixed
to isopropoxy groups. This bonding situation leads to a
five-coordination at Ti(1) and Ti(1a) (with trigonal
bipyramidal geometry), to a six-coordination at Ti(2) and
Ti(2a) (with octahedral geometry), and to five-coordina-
tion at Ti(3) and Ti(3a) (with square pyramidal geom-
etry). A top view of the upper part of the molecule is
presented in Figure 8. Selected structural parameters
are given in Table 6.
d(Ti-OSi
d(Ti-Oacac
d(Ti-Odioxane
(OSi-Ti-OSi
)
1.781(3)-1.833(3)
2.038(3)-2.065(3)
2.237(3)-2.317(3)
99.25(11)-102.34(11)
80.15(10)-81.25(11)
1.603(3)-1.634(2)
107.82(14)-111.48(14)
148.06(16)-162.93(16)
1.884(4)-1.900(4)
)
)
)
(Oacac-Ti-Oacac
)
d(Si-O)
(O-Si-O)
(Si-O-Ti)
d(Si-CCp*
)
resonance for 10 (SiO3 δ ) -80.43 ppm) and two
different resonances (δ ) -61.87, -65.72 ppm) for 11.
IR spectra of both compounds are dominated by the Si-
O-Ti stretching frequencies observed at 900-1000
cm-1. Single crystals of [10‚4 dioxane] could be obtained
from recrystallization from an diethyl ether/dioxane
mixture. Suitable single crystals of 11 were grown from
a concentrated solution in diethyl ether. Crystal struc-
tures of both compounds were determined. Four acetyl-
acetonato ligands are bound to the titanium atoms of
10 (Figure 6) in addition to four dioxane molecules from
the solvent. This bonding situation leads to a six-
coordinate environment at the metal. The average Ti-
Oacac bond length (2.05 Å) is shorter than the average
Ti-Odioxane bond length (2.27 Å). The average Ti-O bond
length in the framework is 1.81 Å. The framework Ti-
We have demonstrated that the polyhedral titanasi-
loxanes 3-6 can be functionalized selectively at their
titanium centers without decomposition of the Si-O-
Ti core structure. The choice of reagents is crucial. The
best results are achieved with substrates that lead to
an increase of the coordination number (chelating
ligands).
In our experiments exploring the reactivity of the CpR
substituents at the silicon centers in the compounds 3

Core-Functionalized Polyhedral Titanasiloxanes
Organometallics, Vol. 21, No. 14, 2002 3015
Con clu sion s
With this contribution we have presented the syn-
thesis of novel polyhedral titanasiloxanes bearing CpR
substituents at silicon and alkoxy substituents at
titanium. The observed reaction pathways are domi-
nated by the steric requirements of the substituents at
silicon and at titanium and even by solvent and tem-
perature. We have shown that titanium centers of
polyhedral titanasiloxanes can be selectively function-
alized. This procedure might be used to attach polym-
erizable organic groups (e.g., allyl groups) to polyhedral
titanasiloxanes. Such side chain functionalized titanasi-
loxanes might serve as structurally well-defined nano-
sized building blocks for the preparation of inorganic-
organic hybrid materials.23 Functionalization of titana-
siloxanes at titanium moieties with chelating ligands
increases the overall stability of the compounds by steric
shielding of the titanium centers. These modifications
might alter the reactivity of the CpR titanasiloxanes in
favor of Cp-Si bond splitting under conservation of the
original core structure. We are currently pursuing
studies concerning this aspect and have obtained first
results supporting this assumption.
F igu r e 8. Upper half of 11.
Ta ble 6. Selected Bon d Len gth s [Å] a n d Bon d
An gles [d eg] of 11
d(Ti-OSi
)
1.790(1)-1.844(1) endocyclic
1.817(1) exocyclic
d(Ti-Oacac
)
1.960(1)-2.107(1)
(OSi-Ti-OSi
)
95.88(5)-113.00(5)
80.10(5)-80.96(5)
(Oacac-Ti-Oacac
)
d(Si-O)
1.613(1)-1.633(1)
107.75(6)-111.87(6)
134.74(7)-164.98(7)
(O-Si-O)
(Si-O-Ti)
µ2-O-fragment
d(Ti-O)
Exp er im en ta l Section
1.942(1)-2.133(1)
100.54(5)
(Ti-OiPr-Ti)
µ3-O-fragment
d(Ti-O)
Gen er a l Com m en ts. All manipulations were carried out
under a purified argon atmosphere using standard vacuum
techniques. The solvents were purified by conventional means
and distilled immediately prior to use. Compounds 1 and 2
were prepared according to the literature.17 Titanium(IV)
ethoxide, titanium(IV) isopropoxide, and titanium(IV) tert-
butoxide (Fluka) were used as received. The melting point
determinations were performed using a Bu¨chi 510 melting
point apparatus and are uncorrected. Elemental analyses were
performed by the Microanalytical Laboratory of the Univer-
sita¨t Bielefeld. NMR spectra were recorded using a Bruker
Avance DRX 500 spectrometer (1H 500.1 MHz, 13C{1H} 125.8
MHz, 29Si{1H} 99.4 MHz). Chemical shifts are reported in ppm
and were referenced to the solvent resonances as internal
standard. IR data were collected using a Bruker Vektor 22-
FT spectrometer over the range 4000-400 cm-1. The samples
were measured as KBr pellets.
1.896(1)-1.968(1)
103.24(5)-147.17(6)
(Ti-O-Ti)
(9-(Me3Si)Fluorenyl-substituted) and 4 (Cp*-substi-
tuted), we have indeed observed the substitution of the
CpR ligands, but in most cases so far only with concomi-
tant degradation of the Si-O-Ti core.
In studies performed with compound 4 we found that
the Cp*-Si bonds are easily cleaved by treatment with
stoichometric amounts of ethanol, water, or HCl to
afford Cp*H. In addition these reactions afforded gels
that form insoluble solids after removal of the solvent.
Interestingly, the formation of the protonated ligand
CpRH has not been observed in comparable reactions
performed with 3 possessing (Me3Si)Fluorenyl groups
at the silicon centers. The slow formation of insoluble
solids indicates ring opening followed by oligomerization
reactions.
Interestingly, quantitative cleaving reactions have
also been observed under thermal treatment. Thus
heating of 3 (300 °C) led to the formation of 2-methyl-
propene (from the tert-butyl group) and to the liberation
of the protonated (Me3Si)Fluorenyl ligand. Similarly,
heating (200 °C) of 4 afforded Cp* radicals, which
disproportionate to give Cp*H and tetramethylfulvene,
a well-known process in gase phase decomposition of
Cp*-silanes.22
[Me3SiF lSi]4O12[TiOtBu ]4 (3). At room temperature 0.80
g (2.34 mmol) Ti(OtBu)4 was added dropwise over 10 min to a
suspension of 0.74 g (2.34 mmol) of 1 in hexane (18 mL) using
a syringe. The reaction mixture was stirred for 15 h. A clear
solution was formed immediately, followed by the slow forma-
tion of a colorless precipitate. After removal of volatile
compounds in vacuo a yellow-orange solid remained, which
was dried in vacuo. Single crystals suitable for an X-ray crystal
structure determination were grown from a concentrated
1
solution in hexane (0.97 g, 0.56 mmol, 95%), mp >250 °C. H
NMR (CDCl3): δ -0.20 (s, 36H, Me), 0.96 (s, 36H, tBu), 7.21,
3
3
7.31 (2t, J H-H ) 7.2, 8H, aromat-H), 7.63, 7.83 (2d, J H-H
)
7.7, 7.6, 8H, aromat-H). 13C NMR (CDCl3): δ -2.1 (Me), 32.2
(C(CH3)3), 42.0 (allyl-C), 86.2 (C(CH3)3), 119.4, 124.2, 124.5,
124.8, 125.4 (aromat-C), 140.3, 145.6 (vinyl-C). 29Si NMR
(CDCl3): δ 5.0 (SiMe3), -78.2 (SiO3). IR (KBr): 444 (m), 492
(m), 738 (s), 842 (s), 854 (s), 965 (vs), 1072 (m), 1248 (m), 1262
(m), 1364 (m), 1432 (m), 1445 (m), 2893 (m), 2922 (m), 2967
(m), 3054 (w). MS (ESI, in THF) m/z (Irel): 1737 (100) [M+],
1679 (10) [(M - tBu)+], 1664 (8) [(M - SiMe3)+]. Anal. Calcd
In these heterolytic and homolytic cleavage reactions,
we have not fully identified the structure of the remain-
ing inorganic Ti-O-Si materials so far; detailed studies
are in progress, exploring whether the stripping of the
organic periphery in the described polyhedral titanasi-
loxanes affords novel Si-O-Ti materials not accessible
by the sol-gel process.
(23) (a) Schubert, U. Chem. Mater. 2001, 13, 3487. (b) Sanchez, C.;
Soler-Illia, G. J . de A. A.; Ribot, F.; Lalot, T.; Mayer, C. R.; Cabuil, V.
Chem. Mater. 2001, 13, 3061. (c) Skowronska-Ptasinska, M. D.;
Vorstenbosch, M. L. W.; van Santen, R. A.; Abbenhuis, H. C. L. Angew.
Chem. 2002, 114, 659.
(22) Dahlhaus, J .; J utzi, P.; Frenck, H. J .; Kulisch, W. Adv. Mat.
1993, 5, 377.

3016 Organometallics, Vol. 21, No. 14, 2002
Lindemann et al.
Ta ble 7. Com p osition of th e P r od u ct Mixtu r e (%)
δ -1.8, -1.7 (SiMe3), 22.0, 24.6, 25.0, 25.5, 25.6, 25.65, 25.7
(CH(CH3)2), 42.9, 43.3 (allyl-C), 76.2, 80.2, 81.1, 81.9 (CH-
(CH3)2), 119.1, 119.2, 119.4, 123.8, 123.9, 124.0, 125.2, 125.3,
125.4 (aromat-C), 140.1, 140.2, 140.4, 146.1, 146.3, 146.4, 146.7
(vinyl-C). 29Si NMR (CDCl3): δ 5.2, 4.4 (SiMe3), -69.2, -80.4
(SiO3). IR (KBr): 465 (m), 635 (m), 739 (s), 855 (s), 826 (s),
934 (vs), 955 (vs), 991 (vs), 1054 (s), 1112 (m), 1132 (m), 1172
(m), 1248 (m), 1262 (m), 1365 (w), 1379 (w), 1432 (m), 1445
(m), 2838 (w), 2878 (w), 2927 (m), 2970 (m), 3067 (w). Anal.
reaction
5
6
polysiloxane
a
b
c
d
81.5
66
19
18
33
76
0.5
1
5
100
for C80H104O16Si8Ti4 (1737.92): C, 55.29; H, 6.03. Found: C,
54.04; H, 5.86 (due to the formation of SiC, the carbon content
is low).
Calcd for
C88H124O22Si8Ti6 (2132.09): C, 51.60; H, 6.11.
Found: C, 51.35; H, 6.13.
P olysiloxa n e. 29Si NMR (CDCl3): δ -83.3 (SiO3). IR
(KBr): 1102 (vs).
[Cp *Si]4O12[TiOtBu ]4 (4). At room temperature 1.14 g (3.36
mmol) of Ti(OtBu)4 was added dropwise over 10 min to a
suspension of 0.72 g (3.36 mmol) of 2 in 18 mL of hexane using
a syringe. The mixture was stirred for 15 h. A clear solution
was formed immediately, and a colorless precipitate was
formed after 15 h. After removal of volatile compounds in vacuo
the remaining slightly yellow solid was rinsed two times with
a minimum of cooled hexane and dried in vacuo. Single crystals
suitable for an X-ray crystal structure determination were
grown from a concentrated solution in hexane (1.12 g, 0.84
mmol, 82%), mp ∼180 °C (dec). 1H NMR (CDCl3): δ 1.14 (s,
12H, Me), 1.27 (s, 36H, tBu), 1.80, 1.91 (2s, 24H, Me). 13C NMR
(CDCl3): δ 11.5, 11.6, 15.2 (Me), 31.4 (C(CH3)3), 51.6 (allyl-C),
84.8 (C(CH3)3), 134.8, 137.1 (vinyl-C). 29Si NMR (CDCl3): δ
-77.5. IR (KBr): 451 (s), 474 (s), 799 (s), 960 (vs), 1068 (s),
1237 (w), 1364 (m), 1455 (w), 2864 (m), 2924 (m), 2974 (m).
MS (ESI, in THF) m/z (Irel): 1329 (3) [M+], 1060 (10) [(M -
2Cp*)+]. Anal. Calcd for C56H96O16Si4Ti4 (1329.23): C, 50.60;
H, 7.28. Found: C, 50.96; H, 7.28.
[Me3SiF lSi]4O12[TiOSiP h 3]4 (7). (a) At 0 °C 0.17 g (0.60
mmol) HOSiPh3 in 5 mL of THF was added dropwise over 10
min to a solution of 0.25 g (0.15 mmol) of 3 in 20 mL of THF
under vigorous stirring. The mixture was stirred for a further
16 h. After removal of volatile compounds in vacuo a colorless
solid was obtained. Single crystals suitable for an X-ray crystal
structure determination were grown from a concentrated
solution in hexane (0.36 g, 0.14 mmol, 93%).
(b) At 0 °C 0.38 g (1.38 mmol) of HOSiPh3 in 10 mL of THF
was added dropwise over 10 min to a solution of 0.58 g (0.35
mmol) of 4 in 40 mL of THF under vigorous stirring. The
mixture was stirred for a further 16 h, then volatile compounds
were removed in vacuo. A colorless solid was obtained. Single
crystals suitable for an X-ray crystal structure determination
were grown from a concentrated solution in hexane (0.86 g,
0.34 mmol, 97%), mp <250 °C. 1H NMR (CDCl3): δ -0.60 (1s,
3
[Me3SiF lSi]4O12[TiOiP r ]4 (5) a n d [Me3SiF lSi]4O12[Ti-
OiP r ]6[µ2-iP r O]2[µ3-O]2 (6). (a) At room temperature, an
equimolar amount of Ti(OiPr)4 was added dropwise over 10
min to a solution of 1 in THF (8 mL per mmol). The mixture
was stirred for 15 h. (See workup procedure and Table 7.)
(b) A suspension of 1 in hexane (6 mL per mmol) was cooled
to -78 °C, and a solution of an equimolar amount Ti(OiPr)4 in
hexane (6 mL per mmol) was added dropwise over 10 min.
The mixture was stirred for 15 h and was allowed to warm to
room temperature. A clear solution was obtained. (See workup
procedure and Table 7.)
(c) At room temperature, an equimolar amount of Ti(OiPr)4
was added dropwise over 10 min to a suspension of 1 in hexane
(8 mL per mmol). The mixture was stirred for 15 h. A clear
solution was obtained. (See workup procedure and Table 7.)
(d) At room temperature 3 equiv of Ti(OiPr)4 was added
dropwise over 10 min to a suspension of 2 equiv of 1 and 1
equiv of H2O in hexane (8 mL per mmol) using a syringe. A
clear solution was formed immediately and was stirred for
15 h.
36 H, Me), 6.79, 6.97 (2t, J H-H ) 7.2, 16H, aromat-H), 7.33
3
(m, 60 H, aromat-H), 7.48, 7.62 (2d, J H-H ) 7.1, 6.8, 16 H,
aromat-H). 13C NMR (CDCl3): δ -2.0 (Me), 40.9 (allyl-C),
119.6, 124.2, 124.4, 125.6, 127.9, 129.8, 130.1, 135.1 (aromat-
C), 139.8, 144.1 (vinyl-C). 29Si NMR (CDCl3): δ 4.74 (-SiMe3),
-12.37 (-SiPh3), -78.21(-SiO3). IR (KBr): 514 (s), 697 (m),
712 (m), 739 (w), 836 (sh), 855 (sh), 917 (vs), 998 (w), 1028
(w), 1119 (w), 1171 (vs), 1187 (w), 1262 (s), 1428 (s), 2924 (m),
2961 (m), 3023 (w), 3067 (m). Anal. Calcd for C136H128Si12O16
Ti4 (2547.09): C, 63.44; H, 5.16. Found: C, 63.48; H, 5.46.
-
[Me3SiF lSi]4O12[TiONMe2]4 (8). At 0 °C 38 µL (0.55 mmol)
of Me2NOH was added dropwise over 10 min to a solution of
0.24 g (0.14 mmol) of 3 in 20 mL of hexane under vigorous
stirring. The mixture was stirred at room temperature for a
further 3 days. After removal of volatile compounds in vacuo
a colorless solid was obtained. Single crystals suitable for an
X-ray crystal structure determination were grown from a CH2-
Cl2/hexane mixture (0.22 g, 0.13 mmol, 93%), mp <250 °C. 1H
NMR (CDCl3): δ -0.25 (s, 36H, Me), 2.37 (s, 24H, Me), 7.22,
3
3
7.31 (2t, J H-H ) 7.2, 8H, aromat-H), 7.65, 7.80 (2d, J H-H
)
7.7, 7.6, 8H, aromat-H). 13C NMR (CDCl3): δ -1.8 (Me), 42.84
(allyl-C), 49.2 (Me), 119.0, 124.0, 125.4, 125.7 (aromat-C),
140.0, 146.5 (vinyl-C). 29Si NMR (CDCl3): δ 5.0 (-SiMe3),
-77.3 (-SiO3). IR (KBr): 539 (w), 598 (w), 654 (s), 689 (w),
722 (sh), 739 (s), 838 (s), 889 (s), 962 (vs), 1048 (vs), 1172 (sh),
1248 (s), 1308 (w), 1434 (s), 1608 (m), 2928 (m), 2956 (m), 3060
(m). Anal. Calcd for C72H92N4O16Si8Ti4 (1685.76): C, 51.31; H,
5.51; N, 3.32. Found: C, 51.13; H, 5.51; N, 3.24.
Wor k u p P r oced u r e for a -d . After removal of all volatile
compounds in vacuo a yellow-orange solid was obtained.
Fractional crystallization from hexane at -30 °C afforded the
compounds 5 and 6 as colorless crystals. The NMR and IR
spectra of the product mixture indicate a polysiloxane as the
third component.
[Me3SiF lSi]4O12[TiOiP r ]4 (5). Mp > 250 °C. 1H NMR
3
(CDCl3): δ -0.21 (s, 36H, SiMe3), 0.87 (d, J H-H ) 3.8, 24H,
CH(CH3)2), 4.17 (m, 4H, CH(CH3)2), 7.30 (m, 16H, aromat-H),
7.64, 7.82 (2d, 3J H-H ) 7.6, 8H, aromat-H). 29Si NMR (CDCl3):
δ 5.2 (SiMe3), -78.0 (SiO3). IR (KBr): 447 (m), 492 (m), 740
(s), 855 (s), 968 (vs), 1055 (m), 1103 (m), 1172 (m), 1248 (m),
1262 (m), 1432 (m), 1445 (m), 2880 (m), 2924 (m), 2969 (m),
3057 (w). Anal. Calcd for C76H96O16Si8Ti4 (1681.81): C, 54.28;
H, 5.75. Found: C, 54.12; H, 5.69.
[Cp *Si]4O12[TiONMe2]4 (9). At -78 °C 0.04 g (0.66 mmol)
of Me2NOH in 10 mL of THF was added dropwise over 10 min
to a solution of 0.22 g (0.17 mmol) of 5 in 10 mL of THF. The
colorless solution was allowed to warm to room temperature
and was stirred for 15 h. After removal of volatile compounds
in vacuo a colorless solid was obtained. Single crystals suitable
for an X-ray crystal structure determination were grown from
a concentrated solution in ether (0.21 g, 0.16 mmol, 98%), mp
> 250 °C. 1H NMR (CDCl3): δ 1.15 (s, 12H, Cp*-Me), 1.73,
1.89 (2s, 24H, Cp*-Me), 2.88 (s, 24H, ONMe2). 13C NMR
(CDCl3): δ 11.4, 12.0, 15.5 (Cp*-Me), 49.8 (ONMe2), 51.4 (allyl-
C), 134.1, 138.2 (vinyl-C). 29Si NMR (CDCl3): δ -73.9. IR
(KBr): 443 (m), 456 (m), 658 (m), 798 (m), 956 (vs), 1038 (vs),
1262 (m), 1448 (m), 2862 (m), 2921 (m), 2964 (m). MS (ESI, in
[Me3SiF lSi]4O12[TiOiP r ]6[µ2-iP r O]2[µ3-O]2 (6). Mp > 250
°C. 1H NMR (CDCl3): δ -0.19, -0.16 (2s, 18H, Me), 0.56, 0.78,
0.80, 0.84, 0.87, 0.91, 0.96, 1.09 (8d, 3J H-H ) 5.8-7.0, 6H, CH-
(CH3)2), 3.98 (sept, 4H, CH(CH3)2), 4.39, 4.52 (2sept, 2H,
CH(CH3)2), 7.12, 7.29 (2t, 3J H-H ) 7.5, 7.4, 2H, aromat-H), 7.63,
3
7.76 (2d, J H-H ) 7.7, 2H, aromat-H), 7.21, 7.36 (2m, 6H,
aromat-H), 7.80-7.90 (m, 12H, aromat-H). 13C NMR (CDCl3):

Core-Functionalized Polyhedral Titanasiloxanes
Organometallics, Vol. 21, No. 14, 2002 3017
THF) m/z (Irel): 1315 (100) [(M + K)+], 1300 (76) [(M + Na)+].
Anal. Calcd for C48H84N4O16Si4Ti4 (1277.07): C, 45.14; H, 6.63.
Found: C, 43.68; H, 6.75 (due to the formation of SiC, the
carbon content is low).
X-ray crystal structure determination were grown at -30 °C
from a concentrated solution in ether (0.45 g, 0.20 mmol, 83%),
mp <250 °C. 1H NMR (CDCl3): δ -0.45 to -0.13 (m, 36H, Me),
3
0.90, 0.87, 0.83, 0.69 (d, J H-H ) 3.8, 12H, CH(CH3)2), 1.77-
[Cp *Si]4O12[Tia ca c]4 (10). At 0 °C 0.11 g (1.08 mmol) of
acetylacetone was added dropwise over 10 min to a solution
of 0.36 g (0.27 mmol) of 5 in 40 mL of ether under vigorous
stirring. A yellow solution was formed. The mixture was stirred
for a further 16 h. After removal of volatile compounds in vacuo
a colorless solid was obtained. Single crystals of [10‚4dioxane]
suitable for an X-ray crystal structure determination were
grown from an ether/dioxane mixture (0.45 g, 0.25 mmol, 93%),
mp <250 °C. 1H NMR (CDCl3): δ 1.03 (s, 12H, Me), 1.87, 1.94,
1.96 (3s, 72H, Me), 3.67-3.70 (b, 8H, dioxane) 5.57 (s, 4H,
acac). 13C NMR (CDCl3): δ 11.1, 11.5, 14.5 (Me), 24.6, 25.0
(acac), 51.4 (allyl-C), 68.3 (dioxane), 103.9 (acac), 132.2, 139.7
(vinyl-C), 190.2, 191.9 (acac). 29Si NMR (CDCl3): δ -80.43.
IR (KBr): 430 (s), 530 (m), 657 (m), 665 (m), 875 (sh), 975 (vs),
1057 (sh), 1281 (m), 1365 (s), 1439 (m), 1526 (s), 1596 (s), 2857
(s), 2918 (s). Anal. Calcd for C60H88O20Si4Ti4 (1433.21): C,
50.28; H, 6.19. Found: C, 53.25; H, 6.35 (elemental analyses
not successful due to tenacious retainment of fractional
amounts of solvent).
2.30 (m, 24 H, Me), 3.82 (m, 4H, CH(CH3)2), 7.13-7.24, (m,
16H, aromat-H), 7.65-7.90 (m, 16H, aromat-H). 13C NMR
(CDCl3): δ -2.2 (b, SiMe3), 25.2, 25.7, 26.1(CH(CH3)2), 43.0
(allyl-C), 65.9 (CH(CH3)2, 118.7, 123.3, 124.9, 125.8 (aromat-
C), 139.9, 147.3 (vinyl-C), 190.4 (acac). 29Si NMR (CDCl3): δ
5.01, 4.73, 4.06, -61.87, -65.72. IR (KBr): 447 (m), 499 (w),
689 (w), 541 (w), 663 (m), 739 (m), 800 (s), 948 (m), 1021 (vs),
1102 (sh), 1172 (sh), 1262 (s), 1360 (s), 1433 (m), 1526 (s), 1594
(s), 2963 (m). Anal. Calcd for C96H124Si8O26Ti6 (2206.00): C,
52.27; H, 5.67. Found: C, 49.91; H, 5.67 (due to the formation
of SiC, the carbon content is low).
Ack n ow led gm en t. We gratefully acknowledge sup-
port of this work by the Deutsche Forschungsgemein-
schaft (Schwerpunktprogramm “Silicium-Chemie“), the
University of Bielefeld, and the Fonds der Chemischen
Industrie.
[Me3SiF lSi]4O12[TiOiP r ]2[Tia ca c]4[µ2-iP r O]2[µ3-O]2 (11).
At 0 °C 145 µL (1.41 mmol) of acetylacetone was added
dropwise over 10 min to a solution of 0.50 g (0.24 mmol) of 6
in 30 mL of hexane under vigorous stirring. The mixture was
stirred for a further 16 h. After removal of volatile compounds
a colorless solid was obtained. Single crystals suitable for an
Su p p or tin g In for m a tion Ava ila ble: Tables of structure
crystal data, positional and thermal parameters, and selected
bond lengths and angles of 3-11. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM020157V