Solubilizing functionalized molecular aluminosilicates

Article abstract of DOI:10.1039/b815291h

Molecular aluminosilicate LAl(SH)(μ-O)Si(OH)(O^tBu) ₂1 (L = [HC{C(Me)N(Ar)}₂]^-, Ar = 2,6- ⁱPr₂C₆H₃) has been prepared from LAl(SH)₂2 and (^tBuO)₂Si(OH)₂ in high yield. When reacted with one equiv. of water, the unique aluminosilicate containing two terminal hydroxy groups LAl(OH·THF)(μ-O)Si(OH)(O ^tBu)₂3 can be isolated. However, when 2 is reacted with the bulkier silanol (^tBuO)₃SiOH, no reaction is observed. The desired LAl(SH)(μ-O)Si(O^tBu)₃6 can be prepared in a two-step synthesis between LAlH₂4 and (^tBuO) ₃SiOH giving first LAl(H)(μ-O)Si(O^tBu)₃5, which reacts further with elemental sulfur to give 6 as the only product. Direct hydrolysis of 6 was conducted to obtain LAl(OH)(μ-O)Si(O^tBu) ₃7, however, such hydrolysis always resulted in a complete decomposition of the starting material. Therefore we used boric acid, which condenses in non-polar solvents and slowly evolve water, to hydrolyze 6 to 7 under mild conditions. Compounds 1, 3 and 5-7 have been characterized by single-crystal X-ray diffraction. The Royal Society of Chemistry 2009.

Full text of DOI:10.1039/b815291h

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www.rsc.org/dalton | Dalton Transactions
Solubilizing functionalized molecular aluminosilicates†
Fernando Rasco´n-Cruz, Rau´l Huerta-Lavorie, Vojtech Jancik,* Rube´n Alfredo Toscano and
Raymundo Cea-Olivares*
Received 2nd September 2008, Accepted 27th October 2008
First published as an Advance Article on the web 8th January 2009
DOI: 10.1039/b815291h
Molecular aluminosilicate LAl(SH)(m-O)Si(OH)(OtBu)2 1 (L = [HC{C(Me)N(Ar)}2]-, Ar =
2,6-iPr2C6H3) has been prepared from LAl(SH)2 2 and (tBuO)2Si(OH)2 in high yield. When reacted with
one equiv. of water, the unique aluminosilicate containing two terminal hydroxy groups
LAl(OH·THF)(m-O)Si(OH)(OtBu)2 3 can be isolated. However, when 2 is reacted with the bulkier
silanol (tBuO)3SiOH, no reaction is observed. The desired LAl(SH)(m-O)Si(OtBu)3 6 can be prepared in
a two-step synthesis between LAlH2 4 and (tBuO)3SiOH giving first LAl(H)(m-O)Si(OtBu)3 5, which
reacts further with elemental sulfur to give 6 as the only product. Direct hydrolysis of 6 was conducted
to obtain LAl(OH)(m-O)Si(OtBu)3 7, however, such hydrolysis always resulted in a complete
decomposition of the starting material. Therefore we used boric acid, which condenses in non-polar
solvents and slowly evolve water, to hydrolyze 6 to 7 under mild conditions. Compounds 1, 3 and 5–7
have been characterized by single-crystal X-ray diffraction.
Introduction
Aluminosilicates are widely found as natural minerals, and build
up an important family of zeolitic materials.1 They are useful
as drying agents and as heterogeneous catalysts in a myriad of
industrial processes.2 Consequently, the development of molecular
aluminosilicate compounds is a promising source of molecular
models for catalytic materials, and secondary building units
(SBU) for heterobimetallic systems, since current methods of
synthesis are not able to tune precisely element distribution in
the final material.3 Molecular aluminosilicates offer advantages
against the abundant aluminosiloxane-based systems,4 because
they obviously represent a more realistic approach as molecular
models for zeolitic materials. In addition, thermal decomposition
Scheme 1 Preparation of compounds 1, 3, L(SH)(m-O)P(OEt)2 and
of Si–O based systems is cleaner than that of Si–C ones, leading
to low carbon content materials.5
[LAl(SLi)(m-O)Si(OLi·2THF)(OtBu)2]2.
Recently, we have reported the preparation of aluminum
as an acceptor for the proton from the OH group on the silicon
atom. Although compound 3 is stable, trace amounts of impurities
can cause its decomposition if stored for longer periods of time.
Very few examples are known, where the proton from a terminal
Al–OH moiety is involved in an intramolecular hydrogen bond.9
silicate and phosphite precursors LAl(SH)(m-O)Si(OH)(OtBu)2
(1) (L
=
[HC{C(Me)N(Ar)}2]-, Ar
=
2,6-iPr2C6H3) and
LAl(SH)(m-O)P(OEt)2 from LAl(SH)2 (2) and (tBuO)2Si(OH)2
or HP(O)(OEt)2, respectively, together with the correspond-
ing lithium salts [LAl(SLi)(m-O)Si(OLi·2THF)(OtBu)2]2 and
LAl(SLi)(m-O)P(OEt)2]2.6,7 The controlled hydrolysis of 1 led
Results and discussion
to
a
molecular aluminosilicate-hydroxide LAl(OH·THF)(m-
O)Si(OH)(OtBu)2 (3) (Scheme 1). It is known that the compound
LAl(OH)2 is labile and decomposes easily, but the presence of an
Al–(m-O)–M (M = metal) bridge can stabilize the terminal OH
group attached to the aluminum atom.8 In compound 3, such an
hydroxy group is coordinated to a THF molecule, while acting
We decided to investigate the possibility of replacing the
(tBuO)2Si(OH) group with a bulkier homologue (tBuO)3Si in
order to determine the influence of the steric bulk of the silicate
group on the stability and reactivity of the resulting products.
In contrast with the facile synthesis of 1 from LAl(SH)2 210
and (tBuO)2Si(OH)2, no reaction was observed between 2 and
(tBuO)3SiOH, even under harsh conditions as reflux in toluene for
six hours. However, the desired LAl(SH)(m-O)Si(OtBu)3 (6) was
obtained in a two-step synthesis starting from LAlH2 (4)11 and one
equiv. of tri-tert-butoxysilanol (tBuO)3SiOH. This reaction led to
the unprecedented aluminosilicate-hydride LAl(H)(m-O)Si(OtBu)3
(5) in 80% yield (Scheme 2). In this case, the product is formed
Instituto de Qu´ımica, Universidad Nacional Auto´noma de Me´xico, Circuito
Exterior, Ciudad Universitaria, 04510, Me´xico, D. F. Mexico. E-mail:
vjancik@servidor.unam.mx, cea@servidor.unam.mx; Fax: +52 555 616
2217; Tel: +52 555 622 4435
† CCDC reference numbers 628448 (1), 628449 (3) and 700777–700779 (5–
7). For crystallographic data in CIF or other electronic format see DOI:
10.1039/b815291h
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tert-butoxy moieties.13 Absorption of the (Al)S–H moiety was
found at n = 2560 for 1, and 2571 cm-1 for 6, respectively; whereas
˜
the characteristic band for a vibration of (Al)O–H group was
-1
˜
found in at n = 3541 (3) and 3504 (7) cm in the IR spectra. The
-1
˜
Al–H stretching vibration in 5 absorbs at n = 1821 cm . Finally,
˜
absorption of the (Si)O–H group was found at n = 3462 (1) and
3357 cm-1 (3). The presence of two different substituents on the
aluminum center in 1, 3 and 5–7 was confirmed also by the presence
of signals corresponding to the symmetry Cs (two septets and four
doublets) instead of only one septet and two doublets for the
isopropyl groups observed for compound 2 with a C2v symmetry
Scheme 2 Preparation of compounds 5 and 6.
through an intermolecular elimination of H2 and formation of an
Al–O bond, to generate the aluminosilicate backbone.
In the next step—conversion of 5 into 6—harsh conditions were
needed. Reflux in toluene for 16 h of a mixture of 5, two equiv. of
elemental sulfur and a catalytic amount of hexamethylphospho-
ramide, resulted in the formation of 6 as the only product in good
yield (80%) (see Scheme 2). On the other hand, all our efforts
to convert 5 or 6 into LAl(OH)(m-O)Si(OtBu)3 (7) by a direct
reaction with water—in a similar manner as the transformation
of 1 to 3 occurs—always led to the decomposition of the starting
material, although such reactivity has been observed before in
related aluminum compounds.12 To our surprise, N–Al bonds
were more sensitive to the hydrolysis than the Al–H moiety, even
when aluminum hydrides are usually considered to be very reactive
towards hydrolytic reagents. In this case, steric hindrance provided
by the bulky ligand L and the three tert-butoxy groups, as well
as the electron rich ambient at the hydride surroundings may be
responsible for the apparent hydride inertness. To overcome this
difficulty, slow evolution of water through the auto-condensation
of boric acid in toluene was used in the successful conversion of 5
to 7 (Scheme 3) in discrete yield (62%).
1
in the H NMR spectra. The Al–SH protons exhibited singlet
signals at d = -0.45 and -0.29 ppm, for 1 and 6, respectively,
and are shifted downfield in comparison to 2 (-0.88 ppm).10
Corresponding signals for Al–OH were found at d = 0.95 for 3, and
1.40 ppm for 7, which are comparable to that found in LAl(OH)(m-
O)Ti(SH)Cp28 (d = 1.07 ppm), and considerably shifted downfield
when compared to [LAl(OH)]2O13 (d = -0.30 ppm), LAl(OH)2
14
(d = 0.20 ppm), and LAlMe(OH)15 (0.50 ppm). The latter may be
explained by the steric bulk of the tert-butoxy group which shields
the OH moieties and also by the fact, that in both compounds, the
protons from the OH moieties are involved in a hydrogen bond.
Likewise, Si–OH chemical shifts vary considerably between 1 (d =
1.53 ppm) and 3 (d = 2.79 ppm), presumably upon substitution of
the Al–SH by Al–OH group and thus different hydrogen bonding
pattern. In addition, the base peak of all compounds belonged
to a singlet signal that integrated either for 18 (1, 3) or 27 (5–7)
protons, corresponding to the tert-butoxy groups bonded to the
silicon atom. Finally, a set of resonances associated to protons of
the b-diketiminato ligand was also found in all the compounds
prepared. All compounds are soluble in common organic solvents
such as toluene, THF, CH2Cl2 and partially soluble in hexane. All
compounds are stable at ambient temperature in the solid state, but
decomposed at higher temperatures (especially during melting).
We have also observed partial decomposition of the compounds
in solution at low concentrations, even if freshly dried solvents are
used.
Molecular description of compounds 1, 3 and 5–7
Single crystals of all compounds were obtained either from
saturated hexane–toluene (1, 3 and 5) or toluene–THF (6 and 7)
solutions at -30 ◦C. Compound 1 crystallizes in the rhombohedral
Scheme 3 Preparation of compound 7.
¯
space group R3 with one molecule of 1 and one third of a
For 7, the free b-diketiminato ligand and 5 were found to be
the main impurities. Thus, rinsing the crude product with pentane
and recrystallization from a toluene–THF mixture led to single
crystals containing the product and a persistent, yet small amount
of 5 (ca. 8%). Due to the isomorphous nature of 5 and 7, it is not
possible to separate these two compounds by crystallization.
Compounds 1, 3 and 5–7 were isolated as crystalline and stable
solids. The formation of the products was confirmed by MS-
EI, where the parent ions were observed at m/z 684 (1), 668
(3), 708 (5), 740 (6) and 724 (7). In addition, the [M - X]+
fragment was observed at m/z 651 in compounds 1 ([M - SH]+)
and 3 ([M - OH]+), whereas for 6 ([M - SH]+) and 7 ([M -
OH]+), it was observed at m/z 707. Moreover, subsequent losses
of m/z 56 were present in all compounds, and were assigned to
isobutene elimination, a common loss in compounds containing
highly disordered hexane molecule in the asymmetric unit, whereas
compound 3 crystallizes in the monoclinic space group P21/n
with one THF molecule in the asymmetric unit, and finally the
isomorphous compounds 5–7 crystallize in the monoclinic space
group P21/c with one molecule in the asymmetric unit, respectively
(Table 1). Further crystal data for compounds 1 and 3 can be found
elsewhere.6 We were not able to crystallize clean 7, therefore crystal
data of compound 7 contaminated by 8% of the starting material
5 were used in the discussion (Fig. 1).
The X-ray analysis confirmed the presence of terminal Al–SH
(compounds 1 and 6) and Al–OH (compounds 3 and 7) moieties
and a terminal hydride in compound 5. In all cases, the protons
from the SH and OH moieties are part of an intra or intermolecular
hydrogen bond. Thus in 1, 6 and 7 the proton of the Al–EH moiety
is involved in an intramolecular Al–E–H ◊ ◊ ◊ OtBu hydrogen bond
1196 | Dalton Trans., 2009, 1195–1200
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Table 1 Crystal data and structure refinement for compounds 5–7
5
6
7
Formula
FW
C41H69AlN2O4Si
709.05
C41H69AlN2O4SSi
741.11
C41H69AlN2O4.92Si
723.77
Crystal system
Space group
Monoclinic
P21/c
12.061(2)
19.621(3)
18.028(3)
90.40(2)
4266(1)
4
0.28 ¥ 0.25 ¥ 0.24
1.104
Monoclinic
P21/c
12.068(2)
19.698(3)
18.023(2)
90.72(2)
4284(1)
4
0.26 ¥ 0.24 ¥ 0.15
1.149
Monoclinic
P21/c
12.061(2)
19.651(3)
18.008(3)
90.24(2)
4268(1)
4
0.32 ¥ 0.28 ¥ 0.08
1.126
˚
a/A
˚
b/A
˚
c/A
b/◦
3
˚
V/A
Z
Size/mm3
r
calcd/g cm-3
m/mm-1
0.115
1552
0.164
1616
0.117
1581
F(000)
q range/◦
Index ranges
1.69–25.00
-14 ≤ h ≤ 14
-23 ≤ k ≤ 23
-21 ≤ l ≤ 21
44 647
7485 (0.0794)
7485/0/467
1.058
0.0591, 0.1232
0.0861, 0.1368
0.352/-0.224
1.53–25.37
-14 ≤ h ≤ 14
-23 ≤ k ≤ 23
-21 ≤ l ≤ 21
34 989
7829 (0.0812)
7829/0/476
1.008
0.0578, 0.1241
0.0889, 0.1396
0.437/-0.261
1.69–25.03
-14 ≤ h ≤ 14
-23 ≤ k ≤ 23
-21 ≤ l ≤ 21
44 646
7520 (0.0598)
7520/140/517
1.027
0.0519, 0.1245
0.0694, 0.1343
0.363/-0.238
No. of reflections collected
No. of independent reflections (Rint
Data/restraints/parameters
GOF on F2
)
R1,a wR2 (I > 2s(I))
b
b
R1,a wR2 (all data)
-3
˚
Largest diffraction peak/hole (e A )
ꢀ
ꢀ
ꢀ
2
a R1 = ꢀFo| - | Fcꢀ/ |Fo|. b wR2 = [ w(Fo - Fc2)2/(Fo2)2]1/2
.
with the oxygen atom from one free OtBu group as acceptor (1,
obtuse: 158.7(2) and 159.2(2)◦. In compounds 1, 3 and 5–7,
the aluminum and silicon centers have a distorted tetrahedral
geometry, where the silicon environment in all compounds features
lower degree of distortion. In case of aluminum, the N1–Al1–N2
angle has always the largest deviation from the ideal value of 109.5◦
(the observed values are in the range of 95.8(1)◦ in 5, to 97.5(1)◦
in 1). While the first number is significantly smaller than in the
parent compound 4 (96.4(1)◦), the second is comparable to that in
2 (97.3(1)◦). This demonstrates that the substituents attached to
the aluminum center do not have the determining effect on the size
of the N–Al–N angle. In both 3 and 7, the Al–(m-O) bond length
is comparable to the Al–OH, while there is a significant difference
between the Si–(m-O) and Si–OH bond lengths in 1 and 3, as the
˚
E = S, 2.48(3); 6, E = S, 2.43(3); 7, E = O, 2.48(2) A). The proton of
the Si–OH hydroxy group in 1 forms an intermolecular hydrogen
bridge to the free OtBu group of another molecule of 1 forming
a centrosymmetric dimer, whereas in compound 3, it is part of a
˚
hydrogen bridge SiO–H ◊ ◊ ◊ O(H)Al (2.06(2) A). Finally, the proton
from the Al–OH group in 3 is obviously interacting with the THF
molecule located partially in between the iPr groups of the ligand
L. In spite of the disorder over two positions present in the THF
molecule, their orientations and the difficulties in removing the
THF under vacuum confirm the presence of the AlO–H ◊ ◊ ◊ OC4H8
˚
(2.10(2), 2.13(1) A) hydrogen bond.
The analysis of the values for the Al–O–Si angle revealed,
that the presence of an extra OtBu group in compounds 5–7
does not have a determining effect over its size, but that it is
rather influenced by the group attached to the aluminum center.
Thus, the largest values for the Al–O–Si angles correspond to the
presence of the Al–SH moiety in the molecules of 1 146.5(1)◦ and
6 (140.6(1)◦), followed by the angle in 5 138.5(1)◦ containing the
Al–H moiety, whereas the presence of the Al–OH group results
in both cases in the smallest values (136.4(1)◦ in 7 to 132.8(1)◦ in
3). This can be explained by the presence of the strong hydrogen
bonds Si–OH ◊ ◊ ◊ OH–Al in 3 and Al–OH ◊ ◊ ◊ OtBuSi in 7, which
diminish the values for the Al–O–Si angles. A similar effect of an
intramolecular hydrogen bond on the size of the Al–O–Si angle
has been observed in [(iPrOH)Al{(m-O)Si(OtBu)3}3] cocrystalized
with [{(iPrO)2Al(m-OiPr)2}3Al].16 In this compound, the presence
of a hydrogen bond between the OH proton of the coordinated
isopropanol and the oxygen atom from one of the three OtBu
groups of one of the three (m-O)Si(OtBu)3 moieties, reduces the
value of the corresponding Al–O–Si angle to 141.3(1)◦, whereas
the other two angles in the same molecule are significantly more
˚
˚
latter are 0.02 A (1) and 0.025 A (3) longer. For better comparison,
selected bonds and angles for compounds 1, 3 and 5–7 are listed
in Table 2.
From the space filling diagram of compound 5 (Fig. 2), it can
be seen that the three tert-butoxy groups bound to the silicon
atom, as well as the isopropyl moieties from the b-diketiminato
ligand generate a hydrophobic shell that surrounds the Al–H
unit and limits considerably its reactivity, as we suggested pre-
viously. Moreover, the silicon-bonded tert-butoxy groups offer an
interesting advantage, due to isobutene elimination upon heating
treatment, and could lead to carbon-free materials after suitable
treatment.5e,17
Experimental
General comments
All experiments were performed under an inert atmosphere
of nitrogen using standard Schlenk techniques and a MBraun
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Table 2 Crystal data and structure refinement for compounds 1, 3 and 5–7
1·1/3hexanea
3·THFb
5c
6a
7b
Al(1)–X
Al(1)–O(1)
Al(1)–N(1)
Al(1)–N(2)
Si(1)–O(1)
Si(1)–O(2)
Si(1)–O(3)
Si(1)–O(4)
2.222(1)
1.720(2)
1.885(2)
1.891(2)
1.591(2)
1.611(2)
1.624(2)
1.637(2)
1.31(3)
1.715(3)
1.54(2)
2.225(1)
1.706(2)
1.899(2)
1.903(2)
1.604(2)
1.629(2)
1.616(2)
1.620(2)
1.11(3)
1.706(2)
1.717(2)
1.901(2)
1.901(2)
1.603(2)
1.623(1)
1.618(2)
1.630(2)
0.84(1)
—
96.3(1)
114.2(1)
136.4(1)
114.1(1)
112.9(1)
106.4(1)
105.4(1)
105.7(1)
112.2(1)
—
1.711(2)
1.891(3)
1.894(3)
1.602(2)
1.627(3)
1.623(3)
1.625(3)
0.74(1)
1.715(2)
1.908(2)
1.908(2)
1.600(2)
1.617(2)
1.624(2)
1.624(2)
X–H(z)
—
—
(Si)O(x)–H(2)
N(1)–Al(1)–N(2)
O(1)–Al(1)–X
Al(1)–O(1)–Si(1)
O(1)–Si(1)–O(2)
O(1)–Si(1)–O(3)
O(1)–Si(1)–O(4)
O(2)–Si(1)–O(3)
O(2)–Si(1)–O(4)
O(3)–Si(1)–O(4)
Si(1)–O(x)–H(2)
Al(1)–X–H(z)
0.77(2)
97.5(1)
0.75(1)
97.3(1)
—
95.8(1)
115.7(9)
138.5(1)
112.7(1)
106.4(1)
113.8(1)
112.4(1)
105.2(1)
106.3(1)
—
97.3(1)
114.6(1)
140.6(1)
105.8(1)
112.8(1)
113.5(1)
112.4(1)
106.5(1)
105.8(1)
—
112.9(1)
146.5(1)
109.3(1)
106.3(1)
112.9(1)
112.7(1)
105.2(1)
110.6(1)
123(3)
106.3(1)
132.8(1)
110.4(1)
112.5(1)
106.7(1)
109.8(1)
112.2(2)
105.2(1)
114(1)
92(1)
111(1)
—
99(2)
118(2)
a X = S(1), z = 1. b X = O(5), z = 5. c X = H(1); for 1 x = 4, for 3 x = 2.
Fig. 1 POV-Ray drawing of the molecular structures of compounds 1, 3 and 5–7. Thermal ellipsoids at 50% probability. All carbon-bound hydrogen
atoms, and solvating hexane molecule (in 1) have been omitted for clarity. Only the major position of disordered groups is shown: THF in 3 and tBu in 1
and 7. The hydridic hydrogen atom of 5 in the crystal of 7 could not be localized due to its low content (8%).
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NMR (78.30 MHz, C6D6, 25 ◦C, AlCl3·6H2O): no shifts observed.
29Si NMR (29.94 MHz, C6D6, 20 ◦C, TMS) d/ppm: -106. IR (CsI
-1
˜
disc) n/cm : 3063 w, 2967 vs, 1821 s (n, Al–H), 1523 vs, 1439 sh,
1388 vs, 1319 s, 1254 s, 1197 s, 1058 vs, 1030 sh, 938 vw, 877 w,
830 w, 804 s, 766 w, 706 s, 667 s, 595 vw, 534 vw, 510 sh, 485 w,
456 sh, 389 w, 357 sh, 285 vw. Anal. calcd for C41H69AlN2O4Si
(709.06): C 69.45, H 9.81, N 3.95. Found: C 69.26, H 9.63,
N 4.03%.
Preparation of LAl(SH)(l-O)Si(OtBu)3 (6). Toluene (20 mL)
was added to a mixture of 5 (2.02 g, 2.84 mmol) and sulfur (0.182 g,
5.69 mmol), and after complete dissolution of the sulfur, P(NMe2)3
(0.03 mL, 0.02 mmol) was added. The reaction mixture was heated
at reflux for 12 h, and then allowed to cool to ambient temperature.
The volatiles were removed in vacuo. To remove the excess of sulfur
used in the synthesis, the crude product was recrystallized from a
toluene–hexane mixture (1 : 1)◦as large colourless crystals. Yield:
1.68 g (80.7%). mp: 205–206 C (dec.). EI-MS m/z: 740 [M]+,
Fig. 2 Space filling plot of 5 showing the Al–H proton surrounded by
two iPr, one tBu group and the carbon backbone of the ligand.
707 [M - SH]+, 651 [M - C4H8 - SH]+, 595 [M - 2 C4H8
-
SH]+, 539 [M - 3 C4H8 - SH]+, 523 [M - 3 C4H8 - O - SH]+.
◦
1H NMR (300.53 MHz, CDCl3, 20 C, TMS) d/ppm: 7.22–7.12
Unilab glove box. The solvents were purified according to
the conventional procedures and were freshly distilled prior
to use. Commercially available chemicals were purchased
from Aldrich or Fluka and used as received. (tBuO)3SiOH,18
(tBuO)2Si(OH)2,18 LAl(SH)2 (2)10 and LAlH2 (4)11 were prepared
according to literature procedures. Elemental analyses (C, N
and H) were performed using an CE-440 Exeter Analytical
3
(m, 6 H, Ar–H), 5.33 (s, 1 H, g-H), 3.72 (sept, JH–H = 6.8 Hz,
2H, CHMe2), 3.19 (sept, 3JH–H = 6.8 Hz, 2H, CHMe2), 1.78 (s, 6
3
3
H, Me), 1.33 (d, JH–H = 6.8 Hz, 6H, CHMe2), 1.31 (d, JH–H
=
6.8 Hz, 6H, CHMe2), 1.23 (d, 3JH–H = 6.8 Hz, 6H, CHMe2), 1.06
3
t
(d, JH–H = 6.8 Hz, 6H, CHMe2), 0.90 (s, 27H, Bu), -0.29 (s, 1
H, SH). 13C NMR (75.57 MHz, CDCl3, 20 ◦C, TMS) d/ppm:
171.6 (CN), 145.6, 143.2, 140.4, 127.0, 125.0, 123.9 (Ar), 98.6 (g-
C), 71.5 (CMe3), 31.3 (CMe3), 28.9 (CHMe2), 27.9, 27.3, 24.9,
24.4 (CHMe2), 24.1 (Me). 27Al NMR (78.30 MHz, CDCl3, 20 ◦◦C,
1
instrument. H, 13C, 27Al and 29Si NMR spectra were recorded
on a Jeol Eclipse 300 MHz spectrometer. Benzene-d6 was dried
using Na–K alloy and distilled in vacuo. Chloroform-d was
stirred with phosphorous pentoxide and filtered prior to use. IR
spectra were recorded from 4000–250 cm-1 on a Bruker Tensor
27 FT-IR instrument with all samples being pressed into CsI
disks. Mass spectra (EI-MS) were measured on a JMS-AX505HA
spectrometer. Melting points were measured in sealed glass
capillary tubes.
AlCl3·6H2O) d/ppm: 72. 29Si NMR (29.94 MHz, CDCl3, 20 C,
-1
˜
TMS) d/ppm: -115. IR (CsI disc) n/cm : 3063 w, 2970 s, 2929
sh, 2871 w, 2571 vw (n, S–H), 1523 s, 1438 s, 1385 s, 1319 s, 1251 s,
1195 s, 1057 vs, 937 w, 880 w, 832 w, 804 w, 767 w, 706 s, 643 w, 545
sh, 472 s, 393 w, 335 w, 285 w. Anal. calcd for C41H69AlN2O4SSi
(741.13): C 66.44, H 9.38, N 3.78. Found: C 66.23, H 9.19,
N 3.77%.
Preparation of LAl(EH)(l-O)Si(OH)(OtBu)2 (E = S (1), O
(3)). The preparation of compounds 1 and 3 has been described
previously.6
Preparation of LAl(OH)(l-O)Si(OtBu)3 (7). A mixture of 5
(0.97 g, 1.36 mmol) and anhydrous boric acid (0.086 g, 1.40 mmol)
was set in a flask, and toluene (25 mL) was added via cannula.
The reaction mixture was stirred for 12 h. The reaction finishes
when the initial suspension becomes a slightly green solution. After
removing all volatiles, hexanes were added and the mixture was
filtered off. The product was redissolved in a mixture toluene–
THF (1 : 1, 6 mL) and stored at -20 ◦C overnight. The resulting
colourless prismatic crystals were filtered off, washed with cold
THF and dried in vacuo. Yield: 0.61 g (62%), mp: 205–206 ◦C
(dec.). EI-MS m/z: 724 [M]+, 707 [M - OH]+, 651 [M - C4H8 -
Preparation of LAl(H)(l-O)Si(OtBu)3 (5). Toluene (40 mL)
was added to the mixture of freshly sublimed (tBuO)3SiOH (2.82 g,
10.68 mmol) and 2 (3.89 g, 8.74 mmol) at -78 ◦C. After the
addition was complete, the reaction mixture was allowed to warm
to ambient temperature and stirred overnight. The solvent was
removed in vacuo and the remaining white solid was washed with
hexanes (2 ¥ 10 mL) and filtered off. Yield: 4.98 g (80.4%). mp:
201 ◦C. EI-MS: m/z 708 [M]+, 651 [M - C4H8 - H]+, 595 [M - 2
C4H8 - H]+, 539 [M - 3 C4H8 - H]+, 523 [M - 3 C4H8 - O - H]+.
1H NMR (300.53 MHz, C6D6, 20 ◦C, TMS) d/ppm: 7.15–7.11
(m, 6 H, Ar–H), 4.90 (s, 1 H, g-H), 3.44 (sept, 3JH–H = 6.8 Hz, 2
1
OH]+, 595 [M - 2 C4H8 - OH]+, 539 [M - 3 C4H8 - OH]+. H
◦
NMR (300.53 MHz, C6D6, 20 C, TMS) d/ppm: 7.19–7.00 (m,
3
3
H, CHMe2), 3.34 (sept, JH–H = 6.8 Hz, 2 H, CHMe2), 1.54 (d,
6 H, Ar–H), 4.95 (s, 1 H, g-H), 3.93 (sept, JH–H = 6.8 Hz, 2H,
3
3JH–H = 6.8 Hz, 6 H, CHMe2), 1.52 (s, 6 H, Me), 1.48 (d, 3JH–H
=
CHMe2), 3.24 (sept, JH–H = 6.8 Hz, 2H, CHMe2), 1.52 (s, 6 H,
6.8 Hz, 6 H, CHMe2), 1.17 (s, 27 H, tBu) 1.14 (d, 3JH–H = 6.8 Hz,
Me), 1.51 (d, 3JH–H = 6.8 Hz, 6 H, CHMe2), 1.43 (d, 3JH–H = 6.8
Hz, 6H, CHMe2), 1.40 (s, 1H, OH), 1.25 (d, 3JH–H = 6.8 Hz, 6H,
3
6 H, CHMe2), 1.13 (d, JH–H = 6.8 Hz, 6 H, CHMe2). 13C NMR
(75.57 MHz, C6D6, 20 ◦C, TMS) d/ppm: 170.4 (CN), 144.4, 143.7,
140.7, 127.0, 124.4 (Ar), 96.7 (g-C), 71.3 (CMe3), 31.5 (CMe3), 28.2
(CHMe2), 25.9, 25.2, 24.5, 24.1 (CHMe2), 23.4 ppm (Me). 27Al
CHMe2), 1.12 (s, 27H, tBu), 1.09 (d, 3JH–H = 6.8 Hz, 6H, CHMe2).
-1
˜
IR (CsI disc) n/cm : 3504 w (n, O–H), 3059 w, 2919 s, 2860 w,
1545 s, 1412 s, 1297 s, 1258 s, 1215 s, 1195 s, 1019 s, 929 w, 859 w,
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The Royal Society of Chemistry 2009
Dalton Trans., 2009, 1195–1200 | 1199
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813 w, 750 s, 709 w, 653 sh, 613 w, 572 s, 445 w, 383 w, 315 w. Due
to the purity of the sample, elemental analysis was not performed.
References
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X-Ray structure determination
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Angew. Chem., Int. Ed. Engl., 1996, 35, 1420.
4 For a survey on the chemistry of aluminosiloxanes see: R. Duchateau,
R. J. Harmsen, H. C. L. Abbenhuis, R. A. van Santen, A. Meetsma, S.
K.-H. Thiele and M. Kranenburg, Chem.–Eur. J., 1999, 5, 3130.
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Crystals were mounted on Nylon loops and rapidly placed in
a stream of cold nitrogen. Diffraction data were collected on a
Bruker-APEX three-circle diffractometer using MoKa radiation
(l = 0.71073 A) at -100 ◦C. Structures were solved by direct
˚
methods (SHELXS-97)19 and refined against all data by full-
matrix least-squares on F2.20 The hydrogen atoms of C–H bonds
were placed in idealized positions, whereas the hydrogen atoms
from the OH and SH moieties were localized from the difference
electron density map and their position was refined with Uiso
tight to the parent atom with distance restraints (SADI) when
applicable. The disordered hexane (in the crystal of 1) and
THF (in the crystal of 3) molecules as well as the disordered
tBu moieties (in the crystals of 1 and 7) were refined using
geometry and distance restraints (SAME, SADI) together with
the restraints for the Uij values (SIMU, DELU). The twin law
for 3 was determined as 1 0 0 0 -1 0 0 0 -1 and the ratio of
the twin domains was refined to 85 : 15. The hexane content
in the crystal of 1 was refined to two hexane molecules per a
6 V. Jancik, F. Rasco´n-Cruz, R. Cea-Olivares and R. A. Toscano, Chem.
Commun., 2007, 4528.
7 A. P. Go´mora-Figueroa, V. Jancik, R. Cea-Olivares and R. A. Toscano,
Inorg. Chem., 2007, 46, 10749.
8 V. Jancik and H. W. Roesky, Angew. Chem., Int. Ed., 2005, 44, 6016.
9 We have found only one example of such compound: S. S. Kumar, S.
Singh, H. W. Roesky and J. Magull, Inorg. Chem., 2005, 44, 1199.
10 V. Jancik, Y. Peng, H. W. Roesky, J. Li, D. Neculai, A. M. Neculai and
R. Herbst-Irmer, J. Am. Chem. Soc., 2003, 125, 1452.
11 C. Cui, H. W. Roesky, H. Hao, H.-G. Schmidt and M. Noltemeyer,
Angew. Chem., Int. Ed., 2000, 39, 1815.
12 (a) Y. Peng, G. Bai, H. Fan, D. Vidovic, H. W. Roesky and J. Magull,
Inorg. Chem., 2004, 43, 1217; (b) S. Gonza´lez-Gallardo, V. Jancik, R.
Cea-Olivares, R. A. Toscano and M. Moya-Cabrera, Angew. Chem.,
Int. Ed., 2007, 46, 2895.
¯
cavity centered around the 3 axis. Thus, there is 1/3 of hexane in
the asymmetric unit, which is disordered over three independent
positions (18 for the whole cavity and two hexane molecules).
The sum of the occupancies was controlled using the SUMP
command implemented in the in SHELXL program. The hydridic
hydrogen atom of 5 in the crystal of 7 could not be localized due
to its low content (8%), but it is included in the sum and moiety
formulas.
13 (a) G. Bai, Y. Peng, H. W. Roesky, J. Li and H.-G. Schmidt, Angew.
Chem., Int. Ed., 2003, 42, 1132; (b) H. Zhu, J. Chai, V. Jancik, H. W.
Roesky, W. A. Merrill and P. P. Power, J. Am. Chem. Soc., 2005, 127,
10170.
Conclusions
14 (a) V. Jancik, L. W. Pineda, J. Pinkas, H. W. Roesky, D. Neculai, A. M.
Neculai and R. Herbst-Irmer, Angew. Chem., Int. Ed., 2004, 43, 2142;
(b) G. Bai, H. W. Roesky, J. Li, M. Noltemeyer and H.-G. Schmidt,
Angew. Chem., Int. Ed., 2003, 42, 5502.
15 (a) H. W. Roesky, G. Bai, V. Jancik, and S. Singh, World Pat.
2005090373, 2005; (b) G. Bai, S. Singh, H. W. Roesky, M. Noltemeyer
and H.-G. Schmidt, J. Am. Chem. Soc., 2005, 127, 3449.
16 C. G. Lugmair, K. L. Fujdala and T. D. Tilley, Chem. Mater., 2002, 14,
888.
To summarize, we have prepared five unique soluble functionalized
molecular aluminosilicates. The compounds prepared are stable
even at 150 ◦C in the solid state, and do not suffer self-
condensation, although they contain reactive Al–EH (E = O,
S) and Si–OH functional groups. Compounds 1, 3 and 5–7
are promising starting materials for the preparation of soluble
molecular heterobimetallic aluminosilicates. Preparation of such
compounds is a subject of an ongoing research.
17 For example see: (a) K. L. Fujdala, A. G. Oliver, F. J. Hollander and
T. D. Tilley, Inorg. Chem., 2003, 42, 1140; (b) K. L. Fujdala and T. D.
Tilley, Chem. Mater., 2004, 16, 1035.
18 J. Beckmann, D. Dakternieks, A. Duthie, M. L. Larchin and E. R. T.
Tiekink, Appl. Organomet. Chem., 2003, 17, 52.
Acknowledgements
19 G. M. Sheldrick, SHELXS-97, Program for solution of crystal struc-
tures, University of Go¨ttingen, Germany, 1997.
20 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997.
We are grateful for financial support from UNAM PAPIIT (grant
IN205108). F. R. and R. H. L. thank CONACyT for their doctoral
fellowships.
1200 | Dalton Trans., 2009, 1195–1200
This journal is
The Royal Society of Chemistry 2009
©