Facile and rational route for high-yield synthesis of titanasiloxanes from aminosilanetriols

Article abstract of DOI:10.1021/om950816m

Reactions of aminosilanetriols RN(SiMe₃)(Si(OH)₃) (R = 2,6-Me₂C₆H₃ (1a), 2,6-1-Pr₂C₆H₃ (1b), 2,4,6-Me₃C₆H₂ (1c)) with titanium orthoesters Ti(OR′)₄ (R′ = Et, i-Pr) in hexane at room temperature afford new cubic titanasiloxanes [RN(SiMe₃)SiO₃Ti(OR′)]₄ (2a-f) in nearly quantitative yield. These compounds have been characterized by mass, IR, and multinuclear NMR spectroscopy. The X-ray crystal structure of [(2,6-i-Pr₂C₆H₃)N(SiMe₃)SiO ₃Ti(OEt)]₄ (2c) is described. The molecular structure of 2c reveals a Si₄Ti₄O₁₂ cubic core. The six Si-O-Ti puckered eight-membered rings in the cubic framework adopt a crown conformation with the two Si and two Ti atoms describing a plane and the four oxygen atoms in an almost parallel plane.

Full text of DOI:10.1021/om950816m

1610
Organometallics 1996, 15, 1610-1613
F a cile a n d Ra tion a l Rou te for High -Yield Syn th esis of
Tita n a siloxa n es fr om Am in osila n etr iols
Andreas Voigt, Ramaswamy Murugavel, Vadapalli Chandrasekhar,†
Norbert Winkhofer, Herbert W. Roesky,* Hans-Georg Schmidt, and Isabel Uso´n
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
37077 Go¨ttingen, Germany
Received October 16, 1995X
Reactions of aminosilanetriols RN(SiMe3)(Si(OH)3) (R ) 2,6-Me2C6H3 (1a ), 2,6-i-Pr2C6H3
(1b), 2,4,6-Me3C6H2 (1c)) with titanium orthoesters Ti(OR′)4 (R′ ) Et, i-Pr) in hexane at
room temperature afford new cubic titanasiloxanes [RN(SiMe3)SiO3Ti(OR′)]4 (2a -f) in nearly
quantitative yield. These compounds have been characterized by mass, IR, and multinuclear
NMR spectroscopy. The X-ray crystal structure of [(2,6-i-Pr2C6H3)N(SiMe3)SiO3Ti(OEt)]4
(2c) is described. The molecular structure of 2c reveals a Si4Ti4O12 cubic core. The six Si-
O-Ti puckered eight-membered rings in the cubic framework adopt a crown conformation
with the two Si and two Ti atoms describing a plane and the four oxygen atoms in an almost
parallel plane.
In tr od u ction
zeolite systems, it was of interest to synthesize metal-
lasiloxanes containing a higher titanium content.
We have recently shown that discrete aminosilanetri-
ols are better synthons for the synthesis of a variety of
metallasiloxanes with a higher metal to silicon ratio (1:
1).7-9 Thus, for example, the reaction of t-BuSi(OH)3
with Re2O7 affords an eight-membered siloxane ring
with pendant OReO3 units bonded to silicon (eq 1).7
There has been considerable interest, in recent times,
in the chemistry of organosilicon compounds containing
the Si-O-M (M ) a transition metal or a main group
element) moiety.1 We2 and others3 have reported on the
synthesis of a number of metallasiloxanes derived from
silanediols R2Si(OH)2 with interesting structural fea-
tures. Feher and co-workers4 have utilized a trisilanol,
[(c-C6H11)7Si7O9(OH)3], with three terminal Si-OH
groups for the construction of a number of corner capped
metallasilsesquioxanes which contain a low metal to
silicon ratio of 1:7. The possible application of these
compounds as models for transition metal complexes
supported on silica surfaces has been discussed.4
4t-BuSi(OH)3 + 4Re2O7 f
[t-BuSiO(OReO3)]4 + 2Re2O7‚6H2O (1)
Interest in titanium-doped zeolite systems has prompted
us to extend the use of this methodology to the synthesis
of titanasiloxanes with cage structures. In a prelimi-
nary communication we have reported strategies for the
synthesis of this class of compounds starting from
discrete silanetriols.9 We now report the details of this
Moreover, recently, there have been reports on the
utility of metal-incorporated silica surfaces as well as
metal-doped zeolites for catalytic purposes.5 Thus, for
example, titanium-doped zeolites have been shown to
catalyze the reactions of H2O2 with diverse substrates
such as alkanes, arenes, alkenes, and amines.6 In view
of the impressive catalytic utility of these modified
(5) (a) Bhaumik, A.; Kumar, R. J . Chem. Soc., Chem. Commun.
1995, 869. (b) Zhao, D.; Goldfarb, D. J . Chem. Soc., Chem. Commun.
1995, 875. (c) Gao, H.; Suo, J .; Li, S. J . Chem. Soc., Chem. Commun.
1995, 835. (d) Serano, D. P.; Li, H.-X.; Davis, M. E. J . Chem. Soc.,
Chem. Commun. 1992, 745. (e) Reddy, J . S.; Kumar, R.; Ratnasamy,
P. Appl. Catal. 1990, 58, L1. (f) Reddy, J . S.; Kumar, R. J . Catal. 1991,
130, 440. (g) Perego, G.; Ballussi, G.; Corno, C.; Tamarasso, M.;
Buonomo, F.; Esposito, A. In Studies in Surface Science and Catalysis,
New Developments in Zeolite Science and Technology; Murakami, Y.,
Iijima, A., Word, J . W., Eds.; Elsevier: Amsterdam, 1986. (h) Boccuti,
M. R.; Rao, K. M.; Zecchina, A.; Leofanti, G.; Petrini, G. In Structure
and Reactivity of Surfaces; Morterra, C., Zecchina, A., Costa, G., Eds.;
Elsevier: Amsterdam, 1989; p 133.
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1995, 36, 1903 and references cited therein. (b) Sheldon, R. A.; Dakka,
J . Catal. Today 1994, 19, 215. (c) Sonawane, H. R.; Pol, A. V.; Moghe,
P. P.; Biswas, S. S.; Sudalai, A. J . Chem. Soc., Chem. Commun. 1994,
1215. (d) Kumar, P.; Hedge, V. R.; Pandey, B.; Ravindranathan, T. J .
Chem. Soc., Chem. Commun. 1993, 1553. (e) Blasco, T.; Camblor, M.
A.; Corma, A.; Pe´rez-Pariente, J . J . Am. Chem. Soc. 1993, 115, 11806.
(f) Notari, B. Stud. Surf. Sci. Catal. 1988, 37, 413.
† On sabbatical from the Indian Institute of Technology, Kanpur
208 016, India.
X Abstract published in Advance ACS Abstracts, February 15, 1996.
(1) For recent reviews see: (a) Struchkov, Yu. T.; Lindeman, S. V.
J . Organomet. Chem. 1995, 488, 9. (b) Shakir, M.; Roesky, H. W.
Phosphorus, Sulfur Silicon 1994, 93-94, 13. (c) Voronkov, M. G.;
Maletina, E. A.; Roman, V. K. In Heterosiloxanes; Soviet Scientific
Reviews Supplement, Series Chemistry; Vol’pin, M. E., Ed.; Harwood,
Academic Publishers: London, 1988; Vol. 1.
(2) (a) Gosink, H.-J .; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer,
M.; Irmer, E.; Herbst-Irmer, R. Organometallics 1994, 13, 3420. (b)
Gosink, H.-J .; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G.; Freire-
Erdbru¨gger, F.; Sheldrick, G. M. Chem. Ber. 1993, 126, 279. (c) Roesky,
H. W.; Mazzah, A.; Hesse, D.; Noltemeyer, M. Chem. Ber. 1991, 124,
519. (d) Haoudi-Mazzah, A.; Mazzah, A.; Schmidt, H.-G.; Noltemeyer,
M.; Roesky, H. W. Z. Naturforsch. 1991, 46b, 587.
(3) (a) Abrahams, I.; Motevalli, M.; Shah, S. A.; Sullivan, A. C. J .
Organomet. Chem. 1995, 492, 99 and references cited therein. (b)
Igonin, V. A.; Shchegolikhina, O. I.; Lindeman, S. V.; Levitsky, M. M.;
Struchkov, Yu. T.; Zhdanov, A. A. J . Organomet. Chem. 1992, 423,
351. (c) Levitsky, M. M.; Shchegolikhina, O. I.; Zhdanov, A. A.; Igonin,
V. A.; Ovchinnikov, Yu. E.; Shklover, V. E.; Struchkov, Yu. T. J .
Organomet. Chem. 1991, 401, 199.
(4) (a) Feher, F. J .; Budzichowski, T. A. Polyhedron 1995, 14, 3239.
(b) Feher, F. J .; Gonzales, S. L.; Ziller, J . W. Inorg. Chem. 1988, 27,
3440.
(7) Winkhofer, N.; Roesky, H. W.; Noltemeyer, M.; Robinson, W. T.
Angew. Chem. 1992, 104, 670; Angew. Chem., Int. Ed. Engl. 1992, 31,
599.
(8) (a) Montero, M. L.; Uso´n, I.; Roesky, H. W. Angew. Chem. 1994,
106, 2198; Angew. Chem., Int. Ed. Engl. 1994, 33, 2103. (b) Chan-
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Int. Ed. Engl. 1994, 33, 1352.
0276-7333/96/2315-1610$12.00/0 © 1996 American Chemical Society

Titanasiloxanes
Organometallics, Vol. 15, No. 6, 1996 1611
Sch em e 1
F igu r e 1. IR spectra of the (a) normal and (b) 10% 18O-
enriched samples of the titanasiloxane 2b in the region
800-1200 cm-1. The new shoulder appearing in (b) on 18O
enrichment is labeled with an arrow.
facile procedure using a series of highly stable aminosi-
lanetriols.10 We also report on the X-ray crystal struc-
ture of one of the representative products.
The 1H NMR spectra of 2a -f are consistent with their
structures. It is interesting to note that in compounds
2c,d the methyl groups of the isopropyl moiety on the
aromatic ring show slight nonequivalances. However
for all the compounds the alkoxy group attached to
titanium shows only one set of resonances. The 29Si
NMR spectral data for 2a -f are detailed in the Experi-
mental Section. The resonances due to the SiMe3
groups are observed around 5 ppm. The chemical shifts
of the silicon atoms in the cubic framework occur around
-95 ppm.
Resu lts a n d Discu ssion
Syn th esis. The reaction of silanetriols10 with tita-
nium orthoesters, Ti(OR′)4 (R′ ) Et, i-Pr), proceeds
readily at room temperature within few hours yielding
titanasiloxanes 2a -f nearly quantitatively (Scheme 1).
These compounds are extremely soluble in all organic
solvents including hydrocarbons such as pentane and
hexane.
The compound 2d was also synthesized starting from
the silanetriol 1b and TiCl(O-i-Pr)3 (eq 2).
There has been considerable debate about an IR
stretching frequency observed around 960-970 cm-1 in
Ti-containing zeolites such as TS-1, TS-2, and TiZSM48.
This absorption has been attributed to the TidO stretch
by some authors11 Others have assigned it to an Si-
O- absorption12 or to an Si-Oδ--Tiδ+ unit.13 It has
been suggested that the intensity of this absorption is
related to the Ti content in the modified silicalites. In
all our compounds 2a -f we observe a very strong
absorption in the range of 960-970 cm-1 (Figure 1). We
assign this absorption to a Ti-O-Si stretching vibration
as our compounds do not contain a TidO or a Si-O-
unit.9
4(2,6-i-Pr2C6H3)N(SiMe3)(Si(OH)3) +
1b
4TiCl(O-i-Pr)3 + 4Et3N f
[(2,6-i-Pr2C6H3)N(SiMe3)SiO3Ti(O-i-Pr)]4 +
2d
4Et3N‚HCl + 8i-PrOH (2)
However, this route requires the use of Et3N as HCl
acceptor. Another preparation of titanasiloxane used
OSnMe3 derivatives of the silanetriols such as t-BuSi-
(OSnMe3)3 as starting materials.9
In order to further confirm this assignment we have
carried out 18O-labeling studies for one of the titanasi-
loxanes. From a 10% 18O-enriched sample of the silane-
triol 1a we prepared the titanasiloxane 2b and con-
firmed the enrichment of 18O by mass spectral studies.
We observed that this stretching frequency around 960
cm-1 undergoes considerable broadening on 18O enrich-
ment with a new shoulder appearing at a lower fre-
quency (Figure 1). In views of the unambiguous nature
of the structural assignment of 2a -f by X-ray diffraction
studies (vide infra) and 18O-labeling studies, we are
confident that this absorption is due to a Si-O-Ti
The titanasiloxanes 2a -f have been characterized by
CHN analyses and mass, IR, and multinuclear NMR
spectroscopy. Further, an X-ray structure investigation
was carried out on 2c. The characterization data for 3,
including a single-crystal X-ray structure determination,
have been reported previously.9
Sp ectr a . It is interesting to note that in spite of their
high molecular weights, compounds 2a -f give molecular
ions (M+) with high intensities (often 100%) under
electron impact conditions. The subsequent fragmenta-
tions are due to the loss of methyl groups either from
the aryl ring or from the SiMe3 group. This observation
indicates to the retention of the large cubic cores under
the spectrometer ionization conditions. Moreover, all
the compounds show a high thermal stability and do
not melt below 300 °C.
(11) Huybrechts, D. R. C.; Bruycker, D. L.; J acobs, P. A. Nature
1990, 345, 240.
(12) Camblor, M. A.; Corma, A.; Pe´rez-Pariente, J . J . Chem. Soc.,
Chem. Commun. 1992, 589.
(13) (a) Boccuti, M. R.; Rao, K. M. Stud. Surf. Sci. Catal. 1989, 48,
133. (b) Pe´rez-Pariente, J .; Martens, J . A.; J acobs, P. A. Appl. Catal.
1987, 31, 35. (c) Zhang, G.; Sterte, J .; Schoeman, B. J . Chem. Soc.,
Chem. Commun. 1995, 2259.
(10) Murugavel, R.; Chandrasekhar, V.; Voigt, A.; Roesky, H. W.;
Schmidt, H.-G.; Noltemeyer, M. Organometallics 1995, 14, 5298.

1612 Organometallics, Vol. 15, No. 6, 1996
Voigt et al.
The average Ti-O bond length in the framework is
1.80 Å which is slightly longer than the exocyclic Ti-O
distance of 1.768(3) Å. These values are comparable to
the Ti-O distances found in [t-BuSiO3Ti(MeC5H4)]4 (3).
The average Si-O distance found in 2c (1.63 Å) is
slightly longer than the corresponding distances found
in 3. The Si(1)-N(1) distance of 1.712(4) Å is consider-
ably shorter than the Si(2)-N(1) distance of 1.761(4)
Å. This observation is consistent with the presence of
three electron-withdrawing oxygen atoms attached to
Si(1). The average length of the Si‚‚‚Ti edge of the cube
is 3.32 Å. The body diagonal of the Si4Ti4 cube is 5.75
Å. The framework Si-O-Ti angles in 2c are 150.2(2),
155.3(2), and 145.2(2)°, which compare with the values
found in 3. The Ti and Si atoms adopt nearly ideal
tetrahedral geometries with the average angles around
each of them being 109.5°. The sum of angles around
the nitrogen atom in 2c is 359.9° corresponding to a
trigonal planar geometry.
It is of interest to compare the structural parameters
of 2c with that of a titana(III)silsesquioxane dimer [(c-
C6H11)7(Si7O12)TiIII
]
(4) prepared by Feher et al.4b
2
F igu r e 2. Structure of [(2,6-i-Pr2C6H3)N(SiMe3)SiO3Ti-
(OEt)]4 (2c). Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ti(1)-O(1)
1.803(3), Ti(1)-O(2A) 1.807(3), Ti(1)-O(3B) 1.803(3), Ti-
(1)-O(4) 1.768(3), Si(1)-O(1) 1.632(3), Si(1)-O(2) 1.622-
(3), Si(1)-O(3) 1.641(3), Si(1)-N(1) 1.712(4); O(4)-Ti(1)-
O(1) 110.9(2), O(4)-Ti(1)-O(3B) 109.5(2), O(1)-Ti(1)-
O(3A) 109.0(2), O(4)-Ti(1)-O(2A) 111.7(2), O(1)-Ti(1)-
O(2A) 107.4(2), O(3B)-Ti(1)-O(2A) 108.2(2), O(2)-Si(1)-
O(1) 107.3(2), O(2)-Si(1)-O(3) 112.3(2), O(1)-Si(1)-O(3)
106.3(2), O(2)-Si(1)-N(1) 109.6(2), O(1)-Si(1)-N(1) 113.3-
(2), O(3)-Si(1)-N(1) 108.0(2), Si(1)-O(1)-Ti(1) 150.2(2),
Si(1)-O(2)-Ti(1B) 155.3(2), Si(1)-O(3)-Ti(1A) 155.3(2).
There is a steric congestion in 4 owing to the presence
of a Ti2O2 four-membered ring which bridges the two
trisilanol moieties. Perhaps as a consequence of this,
along with the fact that Ti is in a lower oxidation state,
the average Ti-O bond length is much longer in 4 (1.904
Å). Moreover the Si-O-Ti angles in the framework in
4 vary from extremely small angles of 131.6° to normal
values of 156.6°.
Con clu sion
We have shown that discrete aminosilanetriols are
excellent synthons for generating a new class of oligo-
meric cage structures containing Ti, O, and Si in the
framework. The X-ray structure of 2c reveals that the
Si and Ti are bridged by oxygen atoms in a three-
dimensional cubic cage structure. The strong absorp-
tion observed for these compounds around 960-970
cm-1 is assigned to the Si-O-Ti stretch. In view of
this assignment, it is possible that the stretching
frequency in the same region observed in titanium-
modified zeolites is also due to a similar absorption.
The synthetic methodology adopted here is likely to
be quite general and can possibly be extended for the
realization of other metal-containing oligomeric silox-
anes. Further, the presence of easily hydrolyzable Si-N
and Ti-O pendant groups offer possible access to
supramolecular cage structures. We are actively pursu-
ing these aspects.
stretching frequency. The high intensities of the 960-
970 cm-1 peak in 2a -f are certainly due to the high Ti
to Si ratio of 1:1, whereas in the modified zeolites this
peak is observed with varying intensities, depending on
the extent of Ti incorporation in the silicalite structure.13
X-r a y Cr ysta l Str u ctu r e of 2c. In order to further
confirm the molecular structure of these titanasiloxanes,
we performed a single-crystal X-ray study of 2c, whose
molecular structure with atom-numbering scheme is
shown in Figure 2 along with the selected structural
parameters. The Ti4Si4O12 polyhedron is completely
enclosed in a hydrophobic sheath of alkyl-substituted
aryl and SiMe3 groups which explains the high solubility
of compounds 2a -f in hydrocarbon solvents such as
pentane.
In the structure of 2c, a cubic polyhedron can be
defined with four silicon and four titanium atoms
occupying its alternate corners. Each of the Si‚‚‚Ti
edges of the cube is bridged by an oxygen atom in a µ2
fashion which is between 0.38 and 0.52 Å out of the Si-
Ti line. There are six puckered Si2Ti2O4 eight-mem-
bered rings which define the cube, and each of these
rings adopts a pseudo-C4 crown conformation. The four
oxygen atoms on any of these eight-membered rings are
in a plane (mean deviation 0.008 Å) while the two Al
and two Si atoms form an almost parallel plane (mean
deviation 0.01 Å)14 with a dihedral angle of 2.6° between
them.
Exp er im en ta l Section
Gen er a l Da ta . All reactions were carried out in an inert
atmosphere using Schlenk methods. Moisture-sensitive ma-
terials were handled in a dry-box. Solvents were purified and
dried using conventional procedures. Titanium ethoxide
(Merck) and titanium isopropoxide (Riedel) were used as
received. The syntheses of silanetriols 1a -c have been
described previously.10 NMR spectra were recorded on a
Bruker AM 200 or a Bruker AS 400 instrument. Chemical
shifts are reported in ppm with reference to SiMe4 with upfield
shifts being negative. IR spectra were recorded on a Bio-Rad
Digilab FTS7 spectrometer (only strong absorption bands are
given; vide infra). Mass spectra were obtained on a Finnigan
MAT System 8230 and a Varian MAT CH5 mass spectrometer.
(14) SHELXTL-PLUS, Siemens Analytical X-ray Instruments, Madi-
son, WI, 1990.

Titanasiloxanes
Organometallics, Vol. 15, No. 6, 1996 1613
Melting points were obtained on a HWS-SG 3000 apparatus
and are uncorrected. CHN analyses were performed at the
Analytical Laboratory of the Institute of Inorganic Chemistry
at Go¨ttingen, Germany.
[(2,4,6-Me3C6H2)N(SiMe3)SiO3Ti(O-i-P r )]4 (2f). Yield: 1.15
g (99%). IR (Nujol): 1333, 1304, 1259, 1250, 1214, 1154, 1132,
1059, 994, 968, 891, 862, 840, 755, 733, 686, 647, 594, 561,
504, 454 cm-1
.
1H NMR (400 MHz, CDCl3): 0.08 (s, 36H,
Syn th esis of Tita n a siloxa n es 2a -f. The titanasiloxanes
were synthesized by following a general procedure. To a
suspension of RN(SiMe3)(Si(OH)3) (3 mmol) in hexane (20 mL)
was added the titanium orthoester Ti(OR′)4 (3 mmol) using a
syringe. Immediately the solution became clear. The reaction
mixture was further stirred for a period of 4 h at room
temperature. The solvent was stripped off in vacuo, and the
resulting residue was dried thoroughly for 12 h in high
vacuum. The solid material obtained was recrystallized from
a minimum amount of pentane or hexane and was identified
as tetrameric titanasiloxane [RN(SiMe3)SiO3Ti(OR′)]4.
[(2,6-Me2C6H3)N(SiMe3)SiO3Ti(OEt)]4 (2a ). Yield: 0.98
g (90%). IR (Nujol): 1305, 1258, 1201, 1154, 1101, 1056, 1016,
SiMe3), 1.08 (d, 24H, J ) 6.2 Hz, Me), 2.20 (s, 12H, Me), 2.28
(s, 24H, Me), 4.39 (m, 4H, CH), 6.76 (m, 8H, aromatic). 29Si
NMR (49.7 MHz, CDCl3): -96.9 (SiO3), 6.3 (SiMe3). Mass
spectrum (EI, 70 eV): m/e 1557 (M+). Anal. Calcd for
C
60H108N4O16Si8Ti4: C, 46.3; H, 7.0; N, 3.6. Found: C, 46.0;
H, 7.0; N, 3.7.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 2c. Colorless
crystals of 2c suitable for single-crystal X-ray diffraction
studies were obtained from a saturated pentane solution at
room temperature. A 0.75 × 0.75 × 0.40 mm3 sized crystal
was mounted on a glass fiber in a rapidly cooled perfluoropoly-
ether.15 Diffraction data were collected on a Siemens-Stoe
AED2 four-circle instrument at 150(2) K, with graphite-
monochromated Mo KR radiation (λ ) 0.710 73 Å), ω-2θ scans
in the range 7 e 2θ e 50°, on line profile fitting,16 and constant
scan speed. Crystal data for C68H124N4O16Si8Ti4‚4/3C2H6O:
Cubic, I4h3d, unit cell dimensions a ) b ) c ) 31.180(4) Å,
unit cell volume 30313(7) Å3, Fcalcd ) 1.138 g‚cm-3, µ ) 0.454
mm-1; total number of reflections measured 15 157, unique
2901 (Rint ) 0.051). The structure was solved by direct
methods using SHELXS-9017 and refined against F2 on all data
by full-matrix least squares with SHELXL-93.18
970, 928, 903, 843, 765, 728, 687, 640, 588, 555, 509, 455 cm-1
.
1H NMR (400 MHz, CDCl3): 0.08 (s, 36H, SiMe3), 1.15 (t, 12H,
J ) 7 Hz, Me), 2.30 (s, 24H, Me), 3.90 (q, 8H, J ) 7 Hz, CH2),
6.92 (m, 12H, aromatic). 29Si NMR (49.7 MHz, CDCl3): -98.4
(SiO3), 5.7 (SiMe3). Mass spectrum (EI, 70 eV): m/e 1446 (M+).
Anal. Calcd for C52H92N4O16Si8Ti4: C, 43.2; H, 6.4; N, 3.9.
Found: C, 43.0; H, 6.2; N, 3.4.
[(2,6-Me2C6H3)N(SiMe3)SiO3Ti(O-i-P r )]4 (2b). Yield: 1.07
g (95%). IR (Nujol): 1333, 1257, 1249, 1200, 1165, 1132, 1117,
1102, 1056, 1010, 953, 905, 860, 841, 765, 743, 728, 686, 643,
All non-hydrogen atoms were refined anisotropically. Hy-
drogen atoms were included in the model at geometrically
calculated positions and refined using a riding model. The unit
cell also contains 16 molecules of ethanol, disordered around
3-fold axes. The three atoms in the asymmetric unit were
refined with the help of similar and rigid bond restraints on
the thermal parameters. Data/restraints/parameters: 2898/
15/253. Final R indices with I > 2σ(I): R1 ) 0.045, wR2 )
0.121. R indices on all data: R1 ) 0.053, wR2 ) 0.135.
Goodness-of-fit S on F2 1.073. Largest difference peak and
hole: 0.053 and -0.254 e‚Å-3. R ) ||Fo| - |Fc||/∑|Fo|; wR2 )
588, 542, 503, 465 cm-1 1H NMR (400 MHz, CDCl3): 0.08 (s,
.
36H, SiMe3), 1.06 (d, J ) 6.5 Hz, 24H, Me2), 2.28 (s, 24H, Me),
4.37 (m, 4H, CH), 6.88 (m, 12H, aromatic). 29Si NMR (49.7
MHz, CDCl3): -97.4 (SiO3), 6.6 (SiMe3). Mass spectrum (EI,
70 eV): m/e 1502 (M+). Anal. Calcd for C56H100N4O16Si8Ti4:
C, 44.8; H, 6.7; N, 3.7. Found: C, 44.5; H, 6.5; N, 3.9.
[(2,6-i-P r 2C6H3)N(SiMe3)SiO3Ti(OEt)]4 (2c). Yield: 1.15
g (92%). IR (Nujol): 1362, 1249, 1183, 1143, 1106, 1042, 1021,
1
998, 968, 958, 905, 841, 802, 756, 646, 603, 511, 468 cm-1. H
NMR (250 MHz, CDCl3): 0.04 (s, 36H, SiMe3), 0.96 (m, 48H,
Me), 1.19 (m, 24H, Me), 3.47 (m, 8H, CH), 3.95 (m, 8H, CH2),
6.98 (m, 12H, aromatic). 29Si NMR (79.5 MHz, CDCl3): -96.6
(SiO3), 6.4 (SiMe3). Mass spectrum (EI, 70 eV): m/e 1669 (M+).
Anal. Calcd for C68H124N4O16Si8Ti4: C, 48.9; H, 7.5; N, 3.4.
Found: C, 48.9; H, 7.2; N, 3.2.
2
2
[[∑w(Fo - Fc2)2]/[∑w(Fo2)2]]1/2; S ) [[∑w(Fo - Fc2)2]/[∑(n -
p)]]1/2. The final fractional atomic coordinates are given in the
Supporting Information.
Ack n ow led gm en t. This work was supported by the
Deutsche Forschungsgemeinschaft. R.M. and V.C. thank
the AvH Foundation, Bonn, for research fellowships.
I.U. thanks the European Union for a postdoctoral grant
(ERB CHBG 93 0338).
[(2,6-i-P r 2C6H3)N(SiMe3)SiO3Ti(O-i-P r )]4 (2d). Yield: 1.25
g (98%). IR (Nujol): 1323, 1250, 1183, 1131, 1107, 1056, 993,
968, 905, 861, 842, 722, 644, 604 cm-1 1H NMR (250 MHz,
.
CDCl3): 0.02 (s, 36H, SiMe3), 0.95 (d, 24H, J ) 6.1 Hz, Me),
1.15 (d, 24H, J ) 6.8 Hz, Me), 1.24 (d, 24H, J ) 6.8 Hz, Me),
3.50 (sept, 8H, J ) 6.8 CH), 4.25 (sept, 4H, J ) 6.1 Hz, CH),
6.98 (m, 12H, aromatic). 29Si NMR (49 MHz, CDCl3): -96.5
(SiO3), 6.3 (SiMe3). Mass spectrum (EI, 70 eV): m/e 1725 (M+).
Anal. Calcd for C72H132N4O16Si8Ti4: C, 50.1; H, 7.7; N, 3.3.
Found: C, 50.2; H, 8.4; N, 3.3.
Su p p or tin g In for m a tion Ava ila ble: Listings of crystal
data, atomic coordinates and equivalent isotropic displacement
parameters for all non-hydrogen atoms, hydrogen positional
and thermal parameters, anisotropic displacement parameters,
and bond distances and angles (5 pages). Ordering informa-
tion is given on any current masthead page.
[(2,4,6-Me3C6H2)N(SiMe3)SiO3Ti(OEt)] (2e). Yield: 1.05
g (94%). IR (Nujol): 1259, 1250, 1214, 1153, 1094, 1056, 1000,
969, 959, 889, 841, 755, 734, 687, 647, 594, 562, 506, 452 cm-1
.
OM950816M
1H NMR (400 MHz, CDCl3): 0.09 (s, 36H, SiMe3), 1.18 (t, 12H,
J ) 7.1 Hz, Me), 2.18 (s, 12H, Me), 2.30 (s, 24H, Me), 3.90 (q,
8H, J ) 7.1 Hz, CH2), 6.92 (m, 12H, aromatic). 29Si NMR (49.7
MHz, CDCl3): -97.9 (SiO3), 5.2 (SiMe3). Mass spectrum (EI,
70 eV): m/e 1500 (M+). Anal. Calcd for C56H100N4O16Si8Ti4:
C, 44.8; H, 6.7; N, 3.7. Found: C, 44.9; H, 6.7; N, 3.9.
(15) Kottke, T.; Stalke, D. J . Appl. Crystallogr. 1993, 26, 615.
(16) Clegg, W. Acta Crystallogr., Sect. A 1981, 37, 22.
(17) Sheldrick, G. M. Acta. Crystallogr., Sect. A 1990, 46, 467.
(18) Sheldrick, G. M. SHELXL-93, program for crystal structure
refinement, Go¨ttingen, 1993.