The use of five-coordinate aluminum alkyls to prepare molecules containing a single Al-O-Si linkage

Article abstract of DOI:10.1021/om9700831

The present work entails the synthesis and first structural characterization of complexes possessing a single Al-O-Si linkage. These are of the formula LAlOSiPh₃ (L = Salen(^tBu) (N,N′-ethylenebis(3, 5-di-tert-butylsalicylideneimine))

Full text of DOI:10.1021/om9700831

Organometallics 1997, 16, 2659-2664
2659
Th e Use of F ive-Coor d in a te Alu m in u m Alk yls To P r ep a r e
Molecu les Con ta in in g a Sin gle Al-O-Si Lin k a ge
David A. Atwood,* Michael S. Hill, J olin A. J egier, and Drew Rutherford
Center for Main Group Chemistry, Department of Chemistry, North Dakota State University,
Fargo, North Dakota 58105
Received February 4, 1997X
The present work entails the synthesis and first structural characterization of complexes
possessing a single Al-O-Si linkage. These are of the formula LAlOSiPh3 (L ) Salen(tBu)
(N,N′-ethylenebis(3, 5-di-tert-butylsalicylideneimine)) (11); Salpen(tBu) N,N′-propylenebis-
(3,5-di-tert-butylsalicylideneimine)) (12); Salophen(tBu) (N,N′-phenylenebis(3,5-di-tert-bu-
tylsalicylideneimine)) (13); and Salomphen(tBu) (N,N′-(3,4-dimethylphenylene)bis(3,5-di-tert-
butylsalicylideneimine)) (14). They are formed by combining the novel five-coordinate
aluminum alkyl starting materials L(tBu)AlR (where L ) Salen(tBu), R ) Me (1), Et (2),
i
iBu (3); Salpen(tBu), R ) Me (4), Salophen(tBu) R ) Me (5), Et (6), Bu (7); and Salomphen,
i
R ) Me (8), Et (9), Bu (10)) with Ph3SiOH in toluene. All of the compounds were
characterized spectroscopically and, in the case of 1, 10, 11, 12, and 13, by X-ray
crystallography.
In tr od u ction
molecules and materials constitute a unique and grow-
ing area of aluminosilicate chemistry.9
Aluminosilicates are ubiquitous in nature, and many
new compositions have been, and continue to be, pre-
pared synthetically.1 They are of importance in a wide
range of catalytic, synthetic and separation applications.
There has been a drive recently to prepare soluble,
molecular aluminosilicates that may act as building
blocks to the solid-state material or as a means of
modeling the behavior of the bulk material. This search
has been partially realized in recent reports of soluble
molecules having core structures similar to that of Linde
type A zeolites.2 Prior to this report, the most relevant
compounds were cubic aluminosilsequioxanes3 and tet-
rameric alkoxide siloxides.4 These compounds are
particularly important considering the fact that molec-
ular group 13 silicates, in general, have not been
extensively explored. Previously published works have
described dimeric structures ([R2M(µ-OSiR′3)]2),5 ex-
amples containing acac supporting ligands,6 those re-
sulting from the insertion of a group 13 moiety into the
Si-O bonds of siloxanes,7 and homoleptic species, Al-
(OSiPh3)3‚base.8 Higher oligomers at the interface of
The present contribution to this area entails the
synthesis and first structural characterization of com-
plexes possessing a single Al-O-Si linkage. These are
of the formula LAlOSiPh3 (where L ) Salen(tBu) (N,N′-
alkylenebis(3,5-di-tert-butylsalicylideneimine). They are
formed by combining the novel five-coordinate alumi-
num alkyl starting materials, LAlR, with Ph3SiOH in
toluene.
Resu lts a n d Discu ssion
F ive-Coor d in a te Alu m in u m Alk yls. Syn th esis
a n d Sp ectr oscop ic Ch a r a cter iza tion . The Salen(t-
Bu) ligand can be envisioned as an extremely soluble
“platform” upon which unique chemistry involving che-
lated metals may be conducted.10,11 When the metal is
coordinated in the N2O2 plane, six-coordinate complexes
can be formed. When the metal is perched above this
plane, only one additional coordination site is generally
available. Since aluminum is a +3 metal, it was
expected that a five-coordinate complex with the alu-
minum perched above the plane would result for the
-AlR derivatives. This geometry was anticipated in the
structure of SalpenAlEt12 and in the recent character-
ization of Salcen(tBu)AlEt.13
X Abstract published in Advance ACS Abstracts, May 15, 1997.
(1) Newsam, J . M. Science 1986, 231, 1093.
(2) (a) Montero, M. L.; Uson, I.; Roesky, H. Angew. Chem., Int. Ed.
Engl. 1994, 33, 2103. (b) Montero, M. L.; Voigt, A.; Teichert, M.; Uson,
I.; Roesky, H. W. Angew. Chem., Int. Ed. Engl. 1995, 34, 2504. (c)
Chandrasekhar, V.; Murugavel, R.; Voigt, A.; Roesky, H.; Schmidt, H.-
G.; Noltemeyer, M. Organometallics 1996, 15, 918.
(3) (a) Feher, F. J .; Budzichowski, T. A.; Weller, K. J . J . Am. Chem.
Soc. 1989, 111, 7288. (b) Feher, F. J .; Weller, K. J . Organometallics
1990, 9, 2638.
(4) Folting, K.; Streib, W. E.; Caulton, K. G.; Poncelet, O.; Hubert-
Pfalzgraf, L. G. Polyhedron 1991, 10, 1639.
(5) (a) Schmidbaur, H.; Schindler, F. Chem. Ber. 1966, 99, 2178. (b)
Schmidbaur, H. Allgem. Prakt. Chem. 1967, 18, 138. (c) Schmidbaur,
H.; Armes, B.; Bergfeld, M. Z. Chem. 1968, 8, 254. (d) Folting, K.;
Streib, W. E.; Caulton, K. G.; Poncelet, O.; Hubert-Pfalzgraf, L. G.
Polyhedron 1991, 10, 1639. (e) Bissinger, P.; Paul, M.; Riede, J .;
Schmidbaur, H. Chem. Ber. 1993, 126, 2579.
(6) Garbauskas, M. F.; Wengrovius, J . H.; Going, R. C.; Kasper, J .
S. Acta Crystallogr. 1984, C40, 1536.
(7) (a) Harvey, S.; Lappert, M. F.; Raston, C. L.; Skelton, B. W.;
Srivastava, G.; White, A. H. J . Chem. Soc., Chem. Commun. 1988,
1216. (b) Apblett, A. W.; Barron, A. R. Organometallics 1990, 9, 2137.
Following procedures similar to those for the prepara-
tion of these two compounds, high yields of Me, Et, and
(8) (a) Apblett, A. W.; Warren, A. C.; Barron, A. R. Can. J . Chem.
1992, 70, 771. (b) Apblett, A. W.; Barron, A. R. J . Crystallogr. Spectrosc.
Res. 1993, 23, 529.
(9) Apblett, A. W.; Warren, A. C.; Barron, A. C. Chem. Mater. 1992,
4, 167.
(10) As supporting ligands in epoxidation catalysts see: (a) J acobsen,
E. N. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.; VCH: New
York, 1993; Chapter 4.2. (b) J acobsen, E. N. In Comprehensive
Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson,
G., Eds.; Pergamon: New York, 1995; Vol. 12, Chapter 11.1. (c)
Katsuki, T. Coord. Chem. Rev. 1995, 140, 189.
(11) For a range of transition-metal derivatives see: (a) Baran, P.;
Bottchner, A.; Elias, H; Haase, W.; Huber, M.; Fuess, H.; Paulus, H.
Z. Naturforsch. 1992, 47B, 1681. (b) Bottcher, A.; Elias, H.; Muller,
L.; Paulus, H. Angew. Chem., Int. Ed. Engl. 1992, 31, 623. (c)
Herrmann, W. A.; Rauch, M. U.; Artus, G. R. Inorg. Chem. 1996, 35,
1988.
S0276-7333(97)00083-6 CCC: $14.00 © 1997 American Chemical Society

2660 Organometallics, Vol. 16, No. 12, 1997
Sch em e 1. Gen er a l Syn th eses of th e F ive-Coor d in a te Alk yl Der iva tives (1-10)a
Atwood et al.
a
The connection between the two nitrogens can be (CH2)2 (for Salen(tBu)), (CH2)3 (for Salpen(tBu)), C6H4 (for Salophen(tBu)),
and 4,5-(Me2)C6H2 (for Salomphen(tBu)).
F igu r e 1. Molecular structure and atom numbering
scheme for Salen(tBu)AlMe (1).
F igu r e 2. Molecular structure and atom numbering
scheme for Salomphen(tBu)AliBu (10).
iBu aluminum derivatives of Salen(tBu) (1-3), Salophen-
(tBu) (5-7), and Salopmphen(tBu) (8-10) can be ob-
tained (Scheme 1). The Salpen(tBu) ligand is problem-
atic in this regard. Reasonable yields of the Me
derivative (4) can be obtained but none for either the
geometry in which the Al atom is located 0.54 Å above
the N2O2 plane (Figure 2). The difference in geometries
of 1 and 10 can be explained in terms of the greater
flexibility of the ethyl backbone in 1 and the tendency
for the hydrogens within this group to adopt a staggered
conformation when possible. In comparison, SalenAlEt
adopts a geometry that can best be described as one that
is intermediary between that of 1 and 10.12 From these
compounds, it is clear that the bulky Salen(tBu) ligands
provide all of the usual attractive features of the Salen
class of ligands but have the improved features of
enhanced solubility. The existence of [Salpen(tBu)-
InOMe]2 is an indication,16 however, that the tBu groups
do not necessarily enforce the formation of a monomer.
The compound (Me3Al)2(diphos) serves as a useful
representative of a four-coordinate Al-Me bond length
(average ) 1.96 Å).17 The lengths in 1 (1.963(17) Å) and
10 (1.972(9) Å) do not differ from this value to any
appreciable extent.
i
Et or Bu derivatives. For the heavier group 13 conge-
ners (Ga and In), this ligand has demonstrated a
tendency to form open, rather than closed, structures.14
The spectroscopic data for these complexes are con-
sistent with monomeric chelated AlR units. For the
methyl derivatives the chemical shifts demonstrate a
slightly greater shielding when incorporated into a
ligand possessing an aryl “backbone” (1, -1.11 ppm; 4,
-0.98 ppm; 5, -1.22 ppm; 8, -1.24 ppm). The same
general trend holds for the ipso-carbon protons in the
Et and iBu derivatives. However, the values also
compared closely to other related complexes containing
a five-coordinate aluminum alkyl, such as SalanAlMe-
(AlMe2)2 (δ -0.35 ppm) and SalomphanAlMe(AlMe2)2
(δ -1.25 ppm).15 In every case, there are two sharp
singlets for the tBu groups of the phenolic portion of the
ligand.
Str u ctu r a l Ch a r a cter iza tion . In 1, the central
aluminum atom is in a geometry that is best described
as distorted trigonal bipyramidal (Figure 1). The axial
atoms, N(1) and O(2), form somewhat longer bonds to
Al(1) (2.069(10) and 1.831(9) Å, respectively) than the
equatorially disposed N(2) and O(1) (2.025(11) and
1.779(9) Å, respectively). The N(1)-Al(1)-O(2) angle
is 158.7(5)°, while the N(2)-Al(1)-O(1) angle is 130.6-
(5)°. The remaining angles range from 76.4(4)° for
N(1)-Al(1)-N(2) to 116.9(5)° for O(1)-Al(1)-C(33). In
10, the central aluminum adopts a square pyramidal
Molecu les P ossessin g a Sin gle Alu m in osiloxa n e
Lin k a ge. Syn th esis a n d Sp ectr oscop ic Ch a r a c-
ter iza tion . Mixing of any of the alkyl derivatives 1-10
with Ph3SiOH results in the formation of the novel
aluminosiloxane monomers 11-14. There was no ap-
parent difference in reactivity or yield when using either
i
the Me, Et, or Bu derivatives. They are soluble in
toluene and benzene and do not decompose on standing
in air (in solution or as a solid) for several hours.
1
The H NMR data for 11-14 are similar to what was
observed for 1-10 with respect to chemical shifts
associated with the ligand. However, an interesting
1
feature is observed in the H NMR of 11. Three Si-Ph
resonances can be discerned in the region of δ 7.0-7.4
ppm (Figure 1 in the Supporting Information). A view
of the structure (Figure 3) shows that the three phenyl
(12) Dzugan, S. J .; Goedken, V. L. Inorg. Chem. 1986, 25, 2858.
(13) Leung, W.-H.; Chan, E. Y. Y.; Chow, E. K. F.; Williams, I. D.;
Peng, S.-M. J . Chem. Soc., Dalton Trans. 1996, 1229.
(14) Atwood, D. A.; J egier, J . A.; Rutherford, D. Bull. Chem. Soc.
J pn. 1997, in press.
(15) Atwood, D. A.; J egier, J . A.; Martin, K. J .; Rutherford, D.
Organometallics 1995, 14, 1453.
(16) Hill, M. S.; Atwood, D. A. Main Group Chem. 1997, in press.
(17) Bradley, D. C.; Chudzynska, H.; Faktor, M. M.; Frigo, D. M.;
Hursthouse, M. B.; Hussain, B.; Smith, L. M. Polyhedron 1988, 7, 1289.

Preparation of Molecules with a Single Al-O-Si Linkage
Organometallics, Vol. 16, No. 12, 1997 2661
F igu r e 4. Molecular structure and atom numbering
scheme for Salpen(tBu)AlOSiPh3 (12).
(Figure 3), the ligand forms the basal coordination plane
of a square pyramidal geometry about the aluminum.
The aluminum atom is located 0.52 Å above the N2O2
plane. The apical site is occupied by the oxygen of the
siloxane. However, the Al-O3 (1.719(14) Å) distance is
still substantially shorter than those to the ligand
oxygens (1.807(16) and 1.820(19) Å). Compound 13
(Figure 2 in the Supporting Information) adopts the
same structural arrangement. It also demonstrates a
relatively short Al-O (apical) distance of 1.603(9) Å. The
aluminum atom is perched at 0.48 Å above the N2O2
plane. In 12 (Figure 4), the geometry around the
aluminum atom is best described as trigonal bipyrami-
dal. The O1 and N2 atoms occupy the axial sites and
form an angle of 169.5(1) Å. Atoms N1, O2, and O3
occupy equatorial sites and form angles that range from
99.0(1)° (O1-Al-O3) to 120.7(1)° (O2-Al-O3).
These structures are unique because they are the first
instances where a single Al-O-Si linkage has been
structurally characterized. Molecules possessing this
linkage have an almost overwhelming tendency to
aggregate. This has its extreme manifestation in the
bonding within zeolites. Indeed, the metrical param-
eters within 3 bear the most similarity to oligomeric
aluminosilicates. For example, in the structure of [(2,6-
Me2C6H3)N(SiMe3)SiO3Al-dioxane]4,2c which has the
core structure of the Linde type-A zeolite, the Al-O-
Si linkages average 140(5)°. For 11-13, this angle is
157.9(14)°, 166.3(2)°, and 166.8(6)°, respectively. To the
best of our knowledge, these are the widest Al-O-Si
angles ever reported. The distances in the LTA complex
range from 1.703(4) to 1.712(4)Å for Al-O bonds and
1.615(4) to 1.623(4)Å for the Si-O bonds. In 3, the
Al-O and Si-O distances fall within this range (1.719-
(14) and 1.608(13) Å, respectively). By comparison, the
Al-O and Si-O distances for dimeric derivatives such
as [Me2AlOSiH2(C2H)]2 are 1.85(1) and 1.651(2) Å,
respectively.4a
F igu r e 3. Molecular structure and atom numbering
scheme for Salen(tBu)AlOSiPh3 (11).
groups are found in unique environments. Most promi-
nently, the phenyl group (C39...) situated at the concave
side of the Al-O-Si bond is flattened relative to the
other two phenyl groups. This feature is less well-
defined in 12-14. A related complex, AcacenTiOBPh3,
displays similar behavior.18 The 29Si chemical shifts fall
in the narrow range of δ -28.77 to -29.99 ppm. These
are similar to what was observed for Al(OSiPH3)(thf)
(-24.6 ppm) and Al(OSiPh3)3(H2O)(thf)2 (-25.7 ppm).8a
For other molecular aluminosilicates where the Si has
an RSiO3 coordination environment the shifts are ≈ -60
ppm.22
In a previous review, it was predicted that “the
reactvity of five-coodinate complexes would certainly be
different than that of the four-coordinate derivatives.”19
However in the limited number of reactions of four- and
five-coordinate aluminum alkyls with silanols there
appears to be little difference. On the other hand, the
formation of amides through alkane elimination pro-
ceeds readily for the four-coordinate derivatives but not
at all for the five-coordinate ones. These must be
formed through a salt elimination between the five-
coordinate halide and the amido lithium derivative.20
Str u ctu r a l Ch a r a cter iza tion . The monomeric na-
ture of 11, 12, and 14 in the solid state was confirmed
by X-ray analyses. These structures clearly demon-
strate how changing the ligand backbone changes the
resulting coordination of the aluminum atom. In 11
Systems with Si-O bond lengths on the order of 1.6
Å are well-known to possess π-bonding. This is the case,
for instance, in the silsesquioxane, (CySiO)7O2(µ2-O3)-
AlOdPPh3, for which the Si-O distances are 1.593-
1.595 Å.5 The obtuse Al-O-Si bond angles demon-
strated by 11-13 are similar to the Al-O-C angle in
Me2(BHT)Al(PMe3) (164.5(4)°) for which π bonding is
supported by photoelectron spectroscopy.21 In five-
coordinate complexes like 11-14, such π bonding might
(18) Franceschi, F.; Gallo, E.; Solari, E.; Floriani, C.; Chiesi-Villa,
A.; Rizzoli, C.; Re, N.; Sgamellotti, A. Chem. Eur. J . 1996, 2, 1466.
(19) Oliver, J . P.; Kumar, R. Polyhedron 1990, 9, 409.
(21) (a) Healy, M. D.; Wierda, D. A.; Barron, A. R. Organometallics
1988, 7, 2543. (b) Lichtenberger, D. L.; Hogan, R. H.; Healy, M. D.;
Barron, A. R. Organometallics 1991, 10, 609.
(20) Rutherford, D.; Atwood, D. A. Organometallics 1996, 15, 4417.

2662 Organometallics, Vol. 16, No. 12, 1997
Atwood et al.
Ta ble 1. Cr ysta l Da ta for Sa len (tBu )AlMe (1), Sa lom p h en (tBu )AliBu (10), Sa len (tBu )AlOSiP h 3 (11),
Sa lp en (tBu )AlOSiP h 3 (12), a n d Sa lop h en (tBu )AlOSiP h 3 (13)
compd
formula
fw
1
C
532.7
10
11
12
13
33H49N2O2Al
C49H67N2O2Al
743.0
C50H61N2O3SiAl
793.1
C58H71N2O3AlSi
899.2
C54H61N2O3AlSi
841.1
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
10.057(3)
18.962(3)
17.595(2)
monoclinic
P21/c
14.156(4)
13.298(1)
24.794(2)
triclinic
P-1
triclinic
P-1
monoclinic
P21/c
18.333(7)
14.261(6)
19.127(7)
10.837(3)
14.055(4)
17.027(4)
96.03(2)
99.74(2)
112.46(2)
2320.8(11)
2
11.6224(6)
14.8998(8)
17.7648(9)
100.030(1)
104.931(1)
109.485(1)
2685.6(2)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
106.53(2)
97.44(2)
108.16(2)
3216.5(11)
4
1.100
4628.4(14)
4
1.066
4751(3)
4
1.176
(0.3)3
0.60
D
calc (g/cm3)
1.135
1.112
0.4 × 0.4 × 0.6
cryst size (mm)
scan range (deg)
0.4 × 0.4 × 0.2
0.8 × 0.5 × 0.4
0.8 × 0.2 × 0.05
0.45
0.60
0.47
no. of reflns collected
no. of indep reflns
no. of obsd reflns with F > xσF; x
no. of params
5413
4199
1155; 5
343
7647
6059
2376; 4
484
7207
6026
1496; 5
424
15523
15523
12244; 4
586
7158
5833
1955; 4
550
R
0.0554
0.0599
2.85
0.0612
0.0619
2.45
0.0961
0.0108
4.37
0.0646
0.0591
1.16
0.0695
0.0765
1.07
Rw
GOF
diff peak (e/Å-3
)
0.22
0.28
0.47
0.53
0.34
C(CH3)3 at 1.87, 1H, AlCH2CH(CH3)2), 2.55 (m, 2H, NCH2),
3.08 (m, 2H, NCH2), 6.90 (d, 2H, PhH), 7.40 (s, 2H, PhH), 7.77
(d, 2H, PhCH); IR 2957 vs (br), 2913 s (br), 2863 s (br), 1645
be envisioned to involve the participation of d orbitals
on aluminum. However, at present, an Al-O-Si π-bond-
ed system for these complexes is not proposed. Current
research is directed toward gathering further evidence
for this type of bonding and determining whether such
bonding might also occur in five-coordinate, monomeric
amides, phosphides, and arsenides.
s, 1620 vs, 1541 s, 1256 s, 1175 s, 837 s, 752 s, 575 s cm-1
.
Sa lp en (tBu )AlMe (4). Reagents: Salpen(tBu)H2 (1.323 g,
2.61 mmol) and Me3Al (0.201, 2.79 mmol) (yield 0.942 g, 66%).
1
4: mp 256 °C dec; H NMR (CDCl3) δ -0.98 (s, 3H, AlCH3),
1.28 (s, 18H, C(CH3)3), 1.45 (s, 18H, C(CH3)3), 2.13 (m, 2H,
CH2), 3.61, 3.78 (m, 4H, NCH2), 6.97 (d, 2H, PhH), 7.45 (d,
2H, PhH), 8.15 (s, 2H, PhCH); IR 2957 vs, 2903 s, 2870 s, 1624
vs, 1555 s, 1460 s, 1416 s, 1316 s, 1260 s, 1177 s, 1098 w, 843
Exp er im en ta l Section
All manipulations were conducted under an inert atmo-
sphere using a combination of drybox and Schlenk line
techniques. Toluene was dried by refluxing over sodium-
benzophenone prior to use. NMR data were obtained on J eol
instruments (270 or 400 MHz) at 270 Hz (1H), 67.81 MHz (13C),
and 53.67 MHz (29Si). Infrared data were obtained on a Galaxy
s, 750 w, 650 s, 565 w cm-1
.
Saloph en (tBu )AlMe (5). Reagents: Salophen(tBu)H2 (0.706
g, 1.31 mmol) and Me3Al (0.101 g, 1.40 mmol) (yield 0.696 g,
91.5%). 5: mp 271-274 °C dec; 1H NMR (CDCl3) δ -1.22 (s,
3H, AlCH3), 1.33 (s, 18H, C(CH3)3), 1.55 (s, 18H, C(CH3)3), 7.14
(d, 2H, PhH), 7.37 (m, 2H, PhH), 7.58 (d, 2H, PhH), 7.68 (m,
2H, PhH), 8.79 (s, 2H, PhCH); IR 2958 vs (br), 2922 s, (br),
2868 s (br), 1616 s, 1535 vs, 1471 s, 1386 m, 1359 m, 1261 m,
1180 m, 1101 m, 1030 m, 841 m, 752 s, 621 m, 585 m, 547 m,
FT-IR using KBr and are reported in cm-1
.
Elemental
analyses were conducted on a Perkin-Elmer 2400 unit. The
results are listed in the Supporting Information. Compounds
1-10 were generally prepared and isolated as described for 1
with some minor variations as listed in the Supporting
Information. In all cases, the spectroscopic data for the
isolated solids matched that of the single-crystalline products.
Sa len (tBu )AlMe (1). To a stirred toluene solution (30 mL)
of Salen(tBu)H2 (10.00 g, 20.29 mmol) was added Me3Al (1.46
g, 20.29 mmol) in toluene (10 mL). The exothermic reaction
was allowed to stir at 25 °C for 1 h before being refluxed for 2
h to yield a clear yellow solution. Removal of the solvent under
vacuum yielded a yellow crystalline solid (yield 10.61 g, 98%):
mp 213-218 °C; 1H NMR (CDCl3) δ -1.11 (s, 3H, AlCH3), 1.33
(s, 18H, C(CH3)), 1.53 (s, 18H, C(CH3)), 3.66 (m, 2H, NCH2),
3.94 (m, 2H, NCH2), 7.01 (d, 2H, PhH), 7.51 (d, 2H, PhH), 8.29
(s, 2H, PhCH); IR 2949 vs (br), 2903 s (br), 2868 s (br), 1699
454 m cm-1
.
Sa lop h en (tBu )AlEt (6). Reagents: Salophen(tBu)H2 (2.30
g, 4.26 mmol) and Et3Al (0.48g, 4.26 mmol) (yield 1.44g, 57%).
1
6: mp 258 °C dec; H NMR (CDCl3) δ -0.43 (q, 2H, AlCH2-
CH3), 0.58 (t, 3H, AlCH2CH3, 1.35 (s, 18H, C(CH3)3), 1.58 (s,
18H, C(CH3)3), 7.15 (d, 2H, PhH), 7.40 (m, 2H, PhH), 7.60 (d,
2H, PhH), 7.68 (m,2H,PhH), 8.81 (s, 2H, PhCH); IR 2958 vs,
2935s, 2901 s, 1614 vs, 1583 s, 1535 s, 1469 s, 1384 s, 1359 s,
1261 s, 1201 s, 1178 s, 1095 w, 1026 w, 869 m, 841 m, 750 s,
607 m, 580 m cm-1
.
Sa lop h en (t Bu )AliBu (7). Reagents: Salophen(tBu)H2
s, 1630 vs, 1541 s, 1420 s, 1179 s, 837 s, 750 s cm-1
.
i
(2.30g, 4.26 mmol) and Bu3Al (0.845g, 4.26 mmol) (yield 1.58g,
Sa len (tBu )AlEt (2). Reagents: Salen(tBu)H2 (2.022 g, 4.10
mmol) and Et3Al (1.0 M in hexane, 2.838 g, 4.10 mmol) (yield
1.585 g, 71%). 2: mp 244-248 °C; 1H NMR (CDCl3) δ 0.14 (q,
2H, AlCH2CH3), 1.21 (t, 3H, AlCH2CH3) 1.38 (s, 18H, C(CH3)3),
1.86 (s, 18H, C(CH3)3), 2.54 (m, 2H, NCH2), 3.01 (m, 2H,
NCH2), 6.89 (d, 2H, PhH), 7.39 (d, 2H, PhH), 7.76 (s, 2H,
PhCH); IR 2955 vs, 2907 s, 2864 s, 1645 s, 1624 vs, 1541 s,
60%). 7: mp 208 °C dec; 1H NMR (CDCl3) δ -0.35 (d, 2H,
AlCH2CH(CH3)2), 0.50 (d, 3H, AlCH2CH(CH3)2, 1.38 (s, 18H,
C(CH3)3), 1.56 (s, 18H, C(CH3)3), 7.14 (d, 2H, PhH), 7.40 (m,
2H, PhH), 7.59 (d, 2H, PhH), 7.66 (m, 2H, PhH), 8.77 (s, 2H,
PhCH); IR 2955 vs, 2906s, 2860 s, 1620 vs, 1583 s, 1502, 1469
s, 1386s, 1359 s, 1262 s, 1202s, 1180 s, 1022 m, 872 w, 802 m,
744 s, 657 w, 640 m, 559 m, 547 m, 495 w, 435 w cm-1
.
1443 s, 1414 s, 1310 s, 1256 s, 1175 s cm-1
.
Sa lom p h en (tBu )AlMe (8). Reagents: Salomphen(tBu)H2
Sa len (tBu )AliBu (3). Reagents: Salen(tBu)H2 (1.552 g,
i
(1.187 g, 2.09 mmol) and Me3Al (0.150 g, 2.09 mmol) (yield
3.15 mmol) and Bu3Al (0.625 g, 3.15 mmol) (yield 1.395 g,
1
77%). 3: mp 180-185 °C; 1H NMR (C6D6) δ 0.17 (d, 2H,
AlCH2CH(CH3)2), 1.03 (d, 6H, AlCH2CH(CH3)2), 1.37 (s, 18H,
C(CH3)3), 1.87 (s, 18H, C(CH3)3), 1.87 (m, coincident with
0.79 g, 62%). 8: mp 257-259 °C; H NMR (CDCl3) δ -1.24
(s, 3H, AlCH3), 1.31 (s, 18H, C(CH3)3), 1.56 (s, 18H, C(CH3)3),
2.37 (s, 6H, PhCH3), 7.15-7.57 (m, 6H, PhH), 8.75 (s, 2H,

Preparation of Molecules with a Single Al-O-Si Linkage
Organometallics, Vol. 16, No. 12, 1997 2663
Ta ble 2. Bon d Len gth s (Å) a n d An gles (d eg) for
Sa len (tBu )AlMe (1) a n d Sa lom p h en (tBu )AliBu (10)
1.55 (s, 18H, C(CH3)3), 2.36 (s, 6H, PhCH3), 7.13 (d, 2H, PhH),
7.45 (s, 2H, PhH), 7.55 (d, 2H, PhH), 8.76 (s, 2H, PhCH); IR
2960 vs (br), 2914 s, 2858 s, 1618 vs, 1589 s, 1535 s, 1471 s,
1357 m, 1257 s, 1176 s, 1087 s, 1022 m, 844 s, 800 s, 752 s,
1
10
586 m, 559 w cm-1
.
Bond Lengths (Å)
Sa lom p h en (tBu )AliBu (10). Reagents: Salomphen(tBu)-
Al(1)-O(1)
Al(1)-O(2)
Al(1)-N(1)
Al(1)-N(2)
Al(1)-C(33)
O(1)-C(1)
O(2)-C(24)
N(1)-C(15)
N(1)-C(16)
N(2)-C(17)
N(2)-C(18)
1.799(9)
1.831(9)
Al(1)-O(1)
1.809(6)
1.825(5)
2.033(6)
2.056(6)
1.972(9)
1.311(9)
1.321(9)
1.309(10)
1.437(9)
1.420(9)
1.297(15)
i
Al(1)-O(2)
H2 (0.769 g, 1.35 mmol) and Bu3Al (0.268 g, 1.35 mmol) (yield
0.35 g, 40%). 10: mp 197-199 °C dec; 1H NMR (CDCl3) δ
-0.39 (d, 2H, AlCH2CH(CH3)2), 0.49 (d, 6H, AlCH2CH(CH3)2)
1.33 (s, 18H, C(CH3)3), 1.52 (s, 18H, C(CH3)3), 2.37 (s, 6H,
PhCH3), 7.13-7.56 (m, 6H, PhH), 8.73 (s, 2H, PhCH); IR 2959
vs (br), 2864 s, 1622 vs, 1593 s, 1537 s, 1470 s, 1256 s, 1177 s,
2.069(10) Al(1)-N(1)
2.025(11) Al(1)-N(2)
1.963(17) Al(1)-C(39)
1.320(13) O(1)-C(1)
1.309(13) O(2)-C(30)
1.282(14) N(1)-C(15)
1.454(17) N(1)-C(16)
1.455(16) N(2)-C(21)
1.297(15) N(2)-C(24)
845 s, 789 s, 554 s cm-1
.
Sa len (tBu )AlOSiP h 3 (11). Ph3SiOH (1.337 g, 4.84 mmol,
98% pure) was added to a toluene solution (20 mL) of 1 (2.526
g, 4.741 mmol) at 25 °C. The exothermic reaction produced a
cloudy mixture and became a clear yellow solution and then a
yellow precipitate. After being stirred at 25 °C for 2 h, the
mixture was filtered via cannula to yield a light yellow
crystalline solid (3.595 g, 96%). X-ray quality crystals were
obtained by slow evaporation of a CH2Cl2 solution at 25 °C:
mp 268-269 °C dec; 1H NMR (CDCl3) δ 1.33 (s, 18H, C(CH3)3),
1.53 (s, 18H, C(CH3)3), 3.45 (m, 2H, NCH2), 3.55 (m, 2H, NCH2)
6.93 (d, 2H, PhH), 7.20 (m, 15H, SiPhH), 7.53 (d, 2H, PhH);
29Si NMR (CDCl3) δ -29.99; IR 2961 vs (br), 2917 s (br), 2873
s (br), 1647 s, 1622 vs, 1543 vs, 1445 s, 1428 s, 1389 s, 1308 s,
Angles (deg)
O(1)-Al(1)-O(2)
O(1)-Al(1)-N(1)
O(2)-Al(1)-N(1)
O(1)-Al(1)-N(2)
O(2)-Al(1)-N(2)
N(1)-Al(1)-N(2)
91.7(4)
87.4(4)
158.7(5)
130.6(5)
88.3(4)
76.4(4)
O(1)-Al(1)-O(2)
O(1)-Al(1)-N(1)
O(2)-Al(1)-N(1)
O(1)-Al(1)-N(2)
O(2)-Al(1)-N(2)
N(1)-Al(1)-N(2)
90.1(2)
87.7(2)
142.2(3)
150.5(3)
87.1(2)
76.9(2)
O(1)-Al(1)-C(33) 116.9(5)
O(2)-Al(1)-C(33) 103.0(5)
N(1)-Al(1)-C(33) 96.3(5)
N(2)-Al(1)-C(33) 111.1(6)
O(1)-Al(1)-C(39) 110.2(3)
O(2)-Al(1)-C(39) 107.4(3)
N(1)-Al(1)-C(39) 108.6(3)
N(2)-Al(1)-C(39) 98.5(3)
Al(1)-O(1)-C(1)
134.7(8)
Al(1)-O(1)-C(1)
136.2(5)
1258 s, 1177 s, 1111 vs, 1065 s, 708 vs, 583 s, 515 vs cm-1
.
Al(1)-O(2)-C(24) 126.5(9)
Al(1)-N(1)-C(15) 125.9(9)
Al(1)-N(1)-C(16) 113.4(7)
Al(1)-O(2)-C(30) 132.3(5)
Al(1)-N(1)-C(15) 126.4(5)
Al(1)-N(1)-C(16) 115.3(4)
Sa lp en (tBu )AlOSiP h 3 (12). This compound was synthe-
sized employing the same general method as for 11 from Ph3-
SiOH (0.51 g, 1.83 mmol) and 4 (1.0 g, 1.83 mmol) in toluene
(10 mL) producing a pale green solution. Stirring was
continued for 12 h, at which point removal of the solvent under
vacuum produced a pale yellow glass. Recrystallization from
a hexane/toluene (3:1) solution at 25 °C yielded pale yellow/
green rectangular crystals suitable for single-crystal X-ray
PhCH); IR 2959 vs (br), 2868 s, 1618 vs, 1593 vs, 1537 vs, 1472
s, 1385 s, 1254 s, 1177 s, 845 s, 789 s, 752 w, 625 s cm-1
.
Sa lom p h en (tBu )AlEt (9). Reagents: Salomphen(tBu)H2
i
(1.760 g, 3.09 mmol) and Bu3Al (0.35 g, 3.09 mmol) (yield 0.38
1
g, 20%). 9: mp 254-56 °C dec; H NMR (CDCl3) δ -0.49 (q,
1
2H, AlCH2CH3), 0.54 (t, 3H, AlCH2CH3) 1.33 (s, 18H, C(CH3)3),
analysis (1.25 g, 85%): mp 150-151 °C; H NMR (CDCl3) δ
Ta ble 3. Bon d Len gth s (Å) a n d An gles (d eg) for Sa len (tBu )AlOSiP h 3 (11), Sa lp en (tBu )AlOSiP h 3 (12), a n d
Sa lop h en (tBu )AlOSiP h 3 (13)
11
12
13
Bond Lengths (Å)
Al(1)-O(1)
Al(1)-O(2)
Al(1)-N(1)
Al(1)-N(2)
Al(1)-O(3)
Si(1)-O(3)
Si(1)-C(33)
Si(1)-C(39)
Si(1)-C(45)
O(1)-C(20)
O(2)-C(10)
N(1)-C(1)
N(1)-C(3)
N(2)-C(17)
N(2)-C(4)
1.807(16)
1.820(19)
1.963(25)
2.057(24)
1.719(14)
1.608(13)
1.874(29)
1.864(33)
1.846(39)
1.333(30)
1.374(30)
1.508(33)
1.260(31)
1.457(40)
1.263(38)
Al(1)-O(1)
1.828(1)
1.764(2)
1.987(1)
2.037(1)
1.726(2)
1.597(2)
1.867(3)
1.888(1)
1.878(3)
1.319(4)
1.334(4)
1.292(4)
1.476(4)
1.458(3)
1.280(4)
Al(1)-O(1)
Al(1)-O(2)
Al(1)-N(1)
Al(1)-N(2)
Al(1)-O(3)
Si(1)-O(3)
Si(1)-C(37)
Si(1)-C(43)
Si(1)-C(49)
O(1)-C(14)
O(2)-C(23)
N(1)-C(7)
N(1)-C(8)
N(2)-C(1)
N(2)-C(2)
1.794(8)
1.806(9)
2.007(13)
2.026(10)
1.702(9)
Al(1)-O(2)
Al(1)-N(1)
Al(1)-N(2)
Al(1)-O(3)
Si(1)-O(3)
Si(1)-C(34)
Si(1)-C(40)
Si(1)-C(46)
O(1)-C(1)
1.603(9)
1.871(15)
1.885(13)
1.875(15)
1.332(15)
1.307(14)
1.450(18)
1.307(15)
1.308(15)
1.420(19)
O(2)-C(21)
N(1)-C(15)
N(1)-C(16)
N(2)-C(18)
N(2)-C(19)
Angles (deg)
N(1)-Al(1)-N(2)
O(1)-Al(1)-O(2)
O(1)-Al(1)-N(1)
O(2)-Al(1)-N(1)
O(1)-Al(1)-N(2)
O(2)-Al(1)-N(2)
N(1)-Al(1)-O(3)
N(2)-Al(1)-O(3)
O(1)-Al(1)-O(3)
O(2)-Al(1)-O(3)
O(3)-Si(1)-C(33)
O(3)-Si(1)-C(39)
C(33)-Si(1)-C(39)
O(3)-Si(1)-C(45)
C(33)-Si(1)-C(45)
C(39)-Si(1)-C(45)
Al(1)-O(3)-Si(1)
79.5(9)
88.9(8)
87.9(8)
159.3(7)
135.6(8)
88.6(9)
N(1)-Al(1)-N(2)
O(1)-Al(1)-O(2)
O(1)-Al(1)-N(1)
O(2)-Al(1)-N(1)
O(1)-Al(1)-N(2)
O(2)-Al(1)-N(2)
N(1)-Al(1)-O(3)
N(2)-Al(1)-O(3)
O(1)-Al(1)-O(3)
O(2)-Al(1)-O(3)
O(3)-Si(1)-C(34)
O(3)-Si(1)-C(40)
C(34)-Si(1)-C(40)
O(3)-Si(1)-C(46)
C(34)-Si(1)-C(46)
C(40)-Si(1)-C(46)
Al(1)-O(3)-Si(1)
83.7(1)
90.7(1)
88.2(1)
125.2(1)
169.5(1)
88.6(1)
113.5(1)
90.4(1)
N(1)-Al(1)-N(2)
O(1)-Al(1)-O(2)
O(1)-Al(1)-N(1)
O(2)-Al(1)-N(1)
O(1)-Al(1)-N(2)
O(2)-Al(1)-N(2)
N(1)-Al(1)-O(3)
N(2)-Al(1)-O(3)
O(1)-Al(1)-O(3)
O(2)-Al(1)-O(3)
O(3)-Si(1)-C(43)
O(3)-Si(1)-C(37)
C(37)-Si(1)-C(43)
O(3)-Si(1)-C(49)
C(37)-Si(1)-C(49)
C(43)-Si(1)-C(49)
Al(1)-O(3)-Si(1)
79.0(9)
88.9(8)
88.2(4)
155.0(5)
145.1(5)
88.5(4)
97.2(8)
96.7(5)
107.4(8)
116.4(8)
102.6(9)
109.0(10)
109.9(11)
112.0(14)
109.7(13)
107.8(14)
108.4(14)
157.9(14)
102.9(4)
110.8(4)
107.3(5)
111.4(6)
108.9(6)
107.8(6)
108.6(5)
109.5(6)
110.6(7)
166.8(6)
99.0(1)
120.7(1)
109.0(1)
112.1(1)
108.5(1)
109.2(1)
108.3(1)
109.7(1)
166.3(2)

2664 Organometallics, Vol. 16, No. 12, 1997
Atwood et al.
1.36 (s, 18H, C(CH3)3), 1.43 (s, 18H, C(CH3)3), 1.84 (m, 1H,
CH2(CH2)2), 1.98 (m, 1H, CH2(CH2)2), 3.22, 3.58 (m, 4H, NCH2),
7.02-7.54 (m, 23H, PhH), 8.05 (s, 2H, PhCH); 29Si NMR
(CDCl3) δ -29.22; IR 2957 vs (br), 2903 s, (br), 1645 s, 1620
vs, 1541 m, 1462 s, 1417 m, 1313 s, 1257 s, 1176 m, 1111 vs,
X-r a y Exp er im en ta l Da ta . Details of the crystal data and
a summary of data collection parameters for the complexes
are given in Tables 1-3. Data were collected at ambient
temperature on a Siemens P4 diffractometer for 1 and 10 and
on a SMART CCD unit for 11-13. Both utilized graphite-
monochromated Mo ΚR (0.710 73 Å) radiation. All calculations
were performed on a personal computer using the Siemens
software package, SHELXTL-Plus. The structures were solved
by direct methods and successive interpretation of difference
Fourier maps, followed by least-squares refinement. All non-
hydrogen atoms were refined anisotropically. The hydrogen
atoms were included in the refinement in calculated positions
using fixed isotropic parameters.
1070 vs, 841 m, 740 m, 702 vs, 580 s, 509 vs, 464 m cm-1
.
Sa lop h en (tBu )AlOSiP h 3 (13). This compound was syn-
thesized employing the same general method as for 11 from
Ph3SiOH (0.36 g, 1.29 mmol) and 5 (0.75 g, 1.29 mmol).
Recrystallization from hexane/toluene (3:1) at 25 °C yielded
bright yellow rectangular crystals suitable for single-crystal
X-ray analysis (0.92 g, 85%): mp 294-297 °C; 1H NMR (CDCl3)
δ 1.40 (s, 18H, C(CH3)3), 1.62 (s, 18H, C(CH3)3), 6.97-7.68 (m,
23H, PhH), 8.68 (s, 2H, PhCH); 29Si NMR (CDCl3) δ -28.77;
IR 2958 vs (br), 2910 s (br), 2868 s, 1614 vs, 1583 s, 1537 vs,
1471 s, 1386 s, 1359 s, 1261 m, 1201 m, 1182 m, 1111 vs, 1070
Ack n ow led gm en t. Gratitude is expressed to the
National Science Foundation (Grant No. 9452892) and
the donors of the Petroleum Research Fund (Grant No.
31901-AC3), administered by the American Chemical
Society, for support. The receipt of an NSF-CAREER
award is also gratefully acknowledged. M. Remington
contributed technical assistance to portions of this work.
vs, 842 m, 788 w, 742 m, 704 s, 586 m, 513 s cm-1
.
Sa lom p h en (tBu )AlOSiP h 3 (14). This compound was syn-
thesized employing the same general method as for 11 from
Ph3SiOH (0.178 g, 0.645 mmol) and 8 (0.385 g, 0.632 mmol).
The reaction was allowed to stir at 25 °C for 5 h yielding a
clear orange solution. The solvent was removed under vacuum
to yield an orange crystalline solid (0.45 g, 82%): mp 296-
299 °C; 1H NMR (CDCl3) δ 1.35 (s, 18H, C(CH3)3), 1.61 (s, 18H,
C(CH3)3), 2.35 (s, 6H, PhCH3), 6.89-7.63 (m, 21H, PhH), 8.64
(s, 2H, PhCH); 29Si NMR (CDCl3) δ -29.15; IR 2963 vs (br),
2868 s, 1620 vs, 1593 s, 1537 vs, 1470 s, 1393 vs (br), 1256 s,
Su p p or tin g In for m a tion Ava ila ble: Tables of bond
lengths and angles, positional parameters, anisotropic thermal
parameters, and unit cell views, elemental analyses, a figure
1
of the H NMR spectrum of 11, and a view of the structure of
12 (72 pages). Ordering information is given on any current
masthead page.
1181 s, 1111 vs, 1074 vs, 843 s, 789 s, 708 s, 513 s cm-1
.
OM9700831