Five-coordinate aluminum amides

Article abstract of DOI:10.1021/om9603631

In the present manuscript we will detail the first use of the Salen(^tBu)H₂ ligands with the group 13 elements. This includes the compounds of formula Salen(^tBu)AlCl (where Salen = Salen(N,N′-ethylenebis(3,5-di-tert-butylsalicylideneimine)) (1), Salpen (N,N′-propylenebis-(3,5-di-tert-butylsalicylideneimine)) (2), Salophen CZV7ST-benzenylidenebis(3,5-di-ieri-butyl-salicylideneamine)) (3), and Salomphen (N,N′-(3,4-dimethylbenzenylidene)bis(3,5-di-tert-butylsalicylideneimine)) (4)) and the novel five-coordinate monomeric amides of formula LAINRR′ (where L = Acen (N,N′-ethylenebis((^tBu)salicylidene(nethyl)imine); R, R′ = H, Ph (5); R = R′ = SiMe₃ (6)) and L = Salen (R, R′ = H, ^tBu (7), H, Ph (8), and H, Dipp (2,6-diisopropylphenyl) (9); R = R′ = Me (10), Et (11), and SiMe₃ (12))). Additionally the unique monomeric hydroxy complex Salen(^tBu)AlOH (13) and its condensation product, (Salen(^t-Bu)Al)₂O (14), will be described. All of the compounds were characterized by spectroscopic (¹H, ¹³C, and ²⁷Al NMR, IR) and physical (mp, analyses) techniques. X-ray crystallographic data are presented for 14.

Full text of DOI:10.1021/om9603631

Organometallics 1996, 15, 4417-4422
4417
F ive-Coor d in a te Alu m in u m Am id es
Drew Rutherford and David A. Atwood*
Center for Main Group Chemistry, Department of Chemistry, North Dakota State University,
Fargo, North Dakota 58105
Received May 14, 1996X
In the present manuscript we will detail the first use of the Salen(tBu)H2 ligands with
the group 13 elements. This includes the compounds of formula Salen(tBu)AlCl (where Salen
) Salen(N,N′-ethylenebis(3,5-di-tert-butylsalicylideneimine)) (1), Salpen (N,N′-propylenebis-
(3,5-di-tert-butylsalicylideneimine)) (2), Salophen (N,N′-benzenylidenebis(3,5-di-tert-butyl-
salicylideneamine)) (3), and Salomphen (N,N′-(3,4-dimethylbenzenylidene)bis(3,5-di-tert-
butylsalicylideneimine)) (4)) and the novel five-coordinate monomeric amides of formula
LAlNRR′ (where L ) Acen (N,N′-ethylenebis((tBu)salicylidene(methyl)imine); R, R′ ) H, Ph
t
(5); R ) R′ ) SiMe3 (6)) and L ) Salen (R, R′ ) H, Bu (7), H, Ph (8), and H, Dipp (2,6-
diisopropylphenyl) (9); R ) R′ ) Me (10), Et (11), and SiMe3 (12))). Additionally the unique
monomeric hydroxy complex Salen(tBu)AlOH (13) and its condensation product, (Salen(t-
Bu)Al)2O (14), will be described. All of the compounds were characterized by spectroscopic
(1H, 13C, and 27Al NMR, IR) and physical (mp, analyses) techniques. X-ray crystallographic
data are presented for 14.
In tr od u ction
The Salen1 class of ligands have been used extensively
to support transition metal bonding schemes2 and to a
much lesser extent those of the main group elements.
Some group 13 examples include those incorporating
aluminum3 and gallium4 alkyls, aluminum alkoxides,5
and aluminum cations.6 One considerable limitation in
using the Salen ligands lies in the fact that they are
generally insoluble when bound in a neutral complex.
Occasionally, this problem can be tempered somewhat
by use of the Acen ligand (Figure 1b). In order to avoid
solubility problems entirely we have begun investigating
derivatives that feature pendant alkyl groups. One such
Salen derivative is Salen(tBu)H2, which possesses ter-
tiary butyl groups at two positions on each of the phenol
rings (Figure 1c). Another consequence of the resulting
steric encumberance on the ligand is to favor monomeric
complexes. We envisioned this ligand as being a soluble
F igu r e 1. General depiction of the types of Salen ligands
mentioned in the text.
“platform” upon which unique group 13 chemistry may
be conducted. Indeed, these ligands have had some
degree of success in the realm of transition metal
chemistry.7 Perhaps the most systematically studied
of these complexes are those used as epoxidation
catalysts.8
In the present manuscript we will describe the
compounds of formula Salen(tBu)AlCl (where Salen )
Salen (1), Salpen (2), Salophen (3), Salomphen (4)) and
the novel five-coordinate monomeric amides of formula
LAlNRR′ (where L ) Acen (R, R′ ) H, Ph (5); R ) R′ )
X Abstract published in Advance ACS Abstracts, September 15, 1996.
(1) “Salen” is the name that has historically been used to describe
the entire class of such ligands possessing various diamino backbones.
However, it is also the specific name of the ethyl derivative, SalenH2.
(2) (a) Holm, R. H.; Everett, G. W., J r.; Chakravorty, A. Prog. Inorg.
Chem. 1966, 7, 83. (b) Hobday, M. D.; Smith, T. D. Coord. Chem. Rev.
1972, 9, 311.
(3) Dzugan, S. J .; Goedken, V. L. Inorg. Chem. 1986, 25, 2858.
(4) Chong, K. S.; Rettig, S. J .; Storr, A.; Trotter, J . Can. J . Chem.
1977, 55, 2540.
t
SiMe3 (6)) and L ) Salen(tBu) (R, R′ ) H, Bu (7), H,
Ph (8), and H, Dipp (2,6-diisopropylphenyl) (9); R ) R′
) Me (10), Et (11), and SiMe3 (12))). Additionally, the
unique monomeric hydroxy complex Salen(tBu)AlOH
(13) and its condensation product, (Salen(tBu)Al)2O (14),
will also be reported.
(5) Gurian, P. L.; Cheatham, L. K.; Ziller, J . W.; Barron, A. R. J .
Chem. Soc., Dalton Trans. 1991, 1449.
Resu lts a n d Discu ssion
(6) (a) Atwood, D. A.; J egier, J . A.; Rutherford, D. J . Am. Chem.
Soc. 1995, 117, 6779. (b) Davidson, M. G.; Lambert, C.; Lopez-Solera,
I.; Raithby, P. R.; Snaith, R. Inorg. Chem. 1995, 34, 3765. (c) Atwood,
D. A.; J egier, J . A.; Rutherford, D. Inorg. Chem. 1996, 35, 63.
(7) (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.
Syn th esis a n d Ch a r a cter iza tion of 1-4. The
monomeric aluminum chloride derivatives can be pre-
(8) For examples see: (a) Lee, N. H.; Muci, A. R.; J acobsen, E. N.
Tetrahedron Lett. 1991, 32, 5055. (b) J acobsen, E. N.; Zhang, W.; Muci,
A. R.; Ecker, J . R.; Deng, L. J . Am. Chem. Soc. 1991, 113, 7063.
S0276-7333(96)00363-9 CCC: $12.00 © 1996 American Chemical Society

4418 Organometallics, Vol. 15, No. 21, 1996
Rutherford and Atwood
Ta ble 1. Selected Sp ectr oscop ic Da ta (p p m ) for Com p ou n d s 1-14
compd
Ph-tBu
backbone
3.74 (m)
4.15 (m)
2.19 (m)
3.64 (m)
4.05 (m)
7.66 (d)
7.77 (m)
2.35 (s)
7.23 (d)
3.73-3.90(m)
3.76 (m)
4.30 (m)
NC-R
27Al (W1/2
)
Salen(tBu)AlCl (1)
1.29 (s)
1.53 (s)
1.29 (s)
1.50 (s)
8.37 (s)
57 (5000)
43 (5300)
Salpen(tBu)AlCl (2)
8.27 (s)
8.97 (s)
Salophen(tBu)AlCl (3)
Salomphen(tBu)AlCl (4)
1.34 (s)
1.59 (s)
1.34 (s)
1.59 (s)
52 (5300)
48 (6500)
8.90 (s)
R ) Me
2.53 (s)
2.48 (s)
AcenAlNHPh (5)
AcenAlN(SiMe3)2 (6)
42 (1212)
43 (2600)
R ) H
Salen(tBu)AlNHtBu (7)
Salen(tBu)AlNHPh (8)
Salen(tBu)AlNHDipp (9)
Salen(tBu)AlNMe2 (10)
Salen(tBu)AlNEt2 (11)
Salen(tBu)AlN(SiMe3)2 (12)
Salen(tBu)AlOH (13)
1.32 (s)
1.56 (s)
1.35 (s)
1.52 (s)
1.35 (s)
1.58 (s)
1.28 (s)
1.51 (s)
1.28 (s)
1.55 (s)
1.29 (s)
1.45 (s)
1.30 (s)
1.32 (s)
1.52 (s)
3.76 (m)
4.16 (m)
3.64 (m)
3.97 (m)
3.53 (m)
8.40 (s)
56 (6800)
42 (1100)
43 (3000)
45 (3500)
55 (6500)
45 (2100)
41 (2500)
8.37 (s)
8.28 (s)
8.37 (s)
8.38 (s)
8.10 (s)
7.86 (s)
4.01 (m)
3.92 (m)
3.49 (m)
4.35 (m)
3.15 (m)
3.30 (m)
4.30 (m)
[Salen(tBu)Al]2O (14)
Sch em e 1. Gen er a l Syn th etic P a th w a y for th e
Sch em e 2. Gen er a l Syn th esis of th e Acen a n d
Sa len (tBu ) Am id es
P r ep a r a tion of 1-4
pared by combining the ligand with R2AlCl in a 1:1 ratio
in toluene (Scheme 1). The compounds are soluble and
can be isolated by precipitation after concentration of
the solution or crystallization after cooling to -30 °C
for a few days. This contrasts with the non-tert-
butylated Salen syntheses in which the SalenAlCl
derivatives precipitate from toluene immediately. In-
deed, the insolubility of these latter complexes, although
nice with regards to obtaining high yields, has made
access to NMR data problematic.6c For compounds 1-4,
however, this is not a difficulty. They are readily
six-coordinate and the ligand is in a bent conformation.6b
Moreover, neutral group 13 chloride reagents will, in
the absence of bridging heteroatoms or steric encum-
berance, adopt chloride-bridged structures.10 Com-
pounds 1-4 fulfill both exceptions; the presence of the
tBu groups negates the possibility of either chloride or
heteroatom bridge-bonding. These suppositions have
been somewhat verified in the crystal structure of
Salcen(tBu)AlCl (Salcen ) (R, R)-N,N′-cyclohexylenebis-
(3,5-di-tert-butylsalicylideneimine)).11
1
soluble in benzene and chloroform. The H NMR data
shows no complexity that may indicate a dimeric or
“open” structure in solution (Table 1). Moreover, the
27Al NMR shifts in the range δ 43-57 ppm are consis-
tent with the presence of five-coordinate aluminum.9 A
monomeric formulation is further supported by cryo-
scopic molecular weight determinations conducted in
benzene. Although it may be intuitive to consider that
the Salen(tBu) ligand would adopt a planar, monomeric
geometry (this property is generally why the ligand is
used in the first place), this is not always the case. For
example, the SalenAlOMe derivatives form dimeric
methoxy-bridged structures in which the aluminum is
Syn th esis a n d Ch a r a cter iza tion of 5-12. The
amides are prepared by the addition of lithium amide
to either AcenAlCl6c or Salen(tBu)AlCl (1) in toluene
(Scheme 2). They can be isolated, after filtration and
solvent removal, as bright orange or yellow solids in
nearly quantitative yield. They are extremely air
sensitive and will undergo protonolysis to form 13. The
level of sensitivity to this process can be correlated to
the degree of steric bulk on the nitrogen. Thus, the least
(9) (a) Delpuech, J . J . In NMR of Newly Accessible Nuclei; Lazlo,
P., Ed.; Academic Press: New York, 1983; Vol. 2, p 153. (b) Benn, R.;
Rufinska, A. Angew. Chem., Int. Ed. Engl. 1983, 22, 779. (c) Benn,
R.; J anssen, E.; Lehmkuhl, H.; Rufinska, A. J . Organomet. Chem. 1987,
333, 155.
(10) Atwood, D. A.; Cowley, A. H.; Schluter, R. D.; Bond, M. R.;
Carrano, C. J . Inorg. Chem. 1995, 34, 2186.
(11) J egier, J . A.; Atwood, D. A. Manuscript in preparation.

Five-Coordinate Aluminum Amides
Organometallics, Vol. 15, No. 21, 1996 4419
sterically encumbered, 10, is the most sensitive (reacting
instantaneously in air) while those incorporating the
Dipp ligand (9) and the SiMe3 groups (12) are the least
air sensitive (decomposing over the course of minutes).
Thus, 7-12 are more air sensitive than the SalenAlR
complexes.3 This difference may be attributed to the
increased steric bulk of the Salen(tBu) ligands combined
with the increased steric requirements of an Al-NR2
group compared to an Al-R group.
The 27Al NMR for 5-12 is consistent with the pres-
ence of monomeric, five-coordinate complexes in solution
(Table 1). The observed chemical shifts in the range δ
40-57 ppm correspond to that of five-coordinate alu-
minum.9 Additionally, cryoscopic molecular weight
determinations support a monomeric formulation. By
comparison, six-coordinate Salen-aluminum complexes
demonstrate chemical shifts in the range δ 3-9 ppm.6c
The primary amides, 5 and 7-9, display an NH stretch-
ing frequency in the expected region of the spectrum
(≈3300 cm-1).
Figu r e 2. Molecular structure and atom-numbering scheme
for [Salen(tBu)Al]2O (14).
Sch em e 3. Rea ction s Lea d in g to th e F or m a tion of
13 a n d 14
The 1H NMR data for compounds 1-4 and 7-14 have
two features in common. They demonstrate two singlets
for the Ph-tBu groups in the range δ 1.28-1.59 ppm.
Moreover, only one singlet is observed for the hydrogen
on the imine carbon. These fall in the relatively broad
range δ 7.86-8.97 ppm. Similarly, compounds 5 and 6
display singlets at δ 2.53 and 2.48 ppm, respectively.
Compound 10 has two resonances in the 1H NMR
spectrum for the N-Me groups. This might be inter-
preted in terms of hindered rotation about the Al-N
bond due to π bonding. Unfortunately, attempts to heat
the compound to observe coalescence of these two peaks
led to decomposition of the compound. Moreover, NMR
spectra obtained to -63 °C were identical to that
obtained at ambient temperature. None of the other
compounds displayed inequivalence of the group on
nitrogen. Further work in this area is aimed at obtain-
ing crystal structures of these compounds for compari-
son to the more traditional three-coordinate12 and four-
coordinate aluminum amides.13
Syn th esis a n d Ch a r a cter iza tion of 13 a n d 14.
Compounds 7-12 are fairly air sensitive and undergo
protonolysis with a limited amount of adventitious
water to form a compound that can be characterized as
Salen(tBu)AlOH (13) (Scheme 3). This compound reacts
with an additional 1 mol of amide to form (Salen-
(tBu)Al)2O (14). Upon further hydrolysis 14, in turn,
converts to 13 which is indefinitely stable in air at 25
°C. Like the amides, it is also very soluble and could
be characterized fully. The 1H NMR data for 13 are
consistent with the other monomeric compounds. Ad-
ditionally, it possesses a νO-H IR stretch centered at ν
3474 cm-1. Compound 13 is a rare example of a group
13 complex with an nonbridging hydroxyl group. One
t
other example is Bu2Ga(THF)OH, which has an OH
stretch of 3285 cm-1 14
It is isolated by the hydrolysis
.
of GatBu3 in coordinating solvents (THF). In contrast,
the presence of a monomeric Ga-OH complex is not
observed in the hydrolysis of Mes3Ga.15
Cr yst a l St r u ct u r e of 14. The X-ray structure of
14 confirms the dimeric arrangement (Figure 2). In
the structure two Salen(tBu)Al units are held together
by a bridging oxygen atom. A C2 rotational axis makes
these two units equivalent. The overall morphology
of 14 is consistent with that observed for (SalenAl)2O5
and (SalenFe)2O.16 However, the Al-O-Al bond angle
in 14 (159.5(5)°) (Table 2) is larger than that observed
in either the Al (152.0(3)°) or Fe (139.1-144.6°) systems.
The larger angle can be attributed to the increase
in steric interactions on going from the Salen to the
Salen(tBu) ligand. The Al-O distance in 14 is act-
ually shorter (1.696(3) Å) than that observed in the
Salen complex (1.705(5) Å). It is also marginally shorter
than the analogous distance in Salen(tBu)AlOSiPh3
(1.719(14) Å).17
(12) (a) Petrie, M. A.; Ruhlandt-Senge, K.; Power, P. P. Inorg. Chem.
1993, 32, 1135. (b) Waggoner, K. M.; Ruhlandt-Senge, K.; Wehms-
chulte, R. J .; He, X.; Olmstead, M. M.; Power, P. P. Inorg. Chem. 1993,
32, 2557. (c) Brothers, P. J .; Wehmschulte, R. J .; Olmstead, M. M.;
Ruhlandt-Senge, K.; Parkin, S. R.; Power, P. P. Organometallics 1994,
13, 2792.
(13) For recently structurally characterized examples, see: (a) J anik,
J . F.; Duesler, E. N.; Paine, R. T. Inorg. Chem. 1988, 27, 4335. (b)
Waggoner, K. M.; Power, P. P. J . Am. Chem. Soc. 1991, 113, 3385. (c)
Choquette, D. M.; Timm, M. J .; Hobbs, J . L.; Rahim, M. M.; Ahmed,
K. J .; Planalp, R. P. Organometallics 1992, 11, 529. (d) Atwood, D.
A.; Cowley, A. H.; J ones, R. A.; Bott, S. G.; Atwood, J . L. Inorg. Chem.
1994, 33, 3251. (e) Wang, S.; Trepanier, S. J . J . Chem. Soc., Dalton
Trans. 1995, 2425. (F) Andrianarison, M. M.; Ellerby, M. C.; Gorrell,
I. B.; Hitchcock, P. B.; Smith, J . D.; Stanley, D. R. J . Chem. Soc., Dalton
Trans. 1996, 211.
(14) Power, M. B.; Cleaver, W. M.; Apblett, A. W.; Barron, A. R.;
Ziller, J . W. Polyhedron 1992, 11, 477.
(15) Storre, J .; Klemp, A.; Roesky, H. W.; Schmidt, H.-G.; Noltem-
eyer, M.; Fleischer, R.; Stalke, D. J . Am. Chem. Soc. 1996, 118, 1381.
(16) (a) Gerloch, M.; McKenzie, E. D.; Towl, A. D. C. J . Chem. Soc.
A 1969, 2850. (b) Coggon, P.; McPhail, A. T.; Mabbs, F. E.; McLachlen,
V. N. J . Chem. Soc. A 1971, 1014. (c) Davies, J . E.; Gatehouse, B. M.
Acta Crystallogr., Sect. B 1973, 29, 1934.

4420 Organometallics, Vol. 15, No. 21, 1996
Rutherford and Atwood
608 (s), 444 (m) cm-1. Anal. Calcd for C32H46-N2O2AlCl: C,
69.50; H, 7.91; N, 5.07. Found: C, 69.18; H, 8.02; N, 5.56.
Sa lp en (tBu )AlCl (2). A solution of dimethylaluminum
chloride (0.841 g, 9.191 mmol) in 50 mL of toluene was cooled
to -78 °C and combined with a rapidly stirring solution of
Salpan(tBu)H2 (4.655 g, 9.186 mmol) in 50 mL of toluene also
cooled to -78 °C. The exothermic reaction was allowed to
proceed at -78 °C for 1 h. The solution was brought to room
temperature slowly and stirred overnight. A precipitate
formed, and the solvent was removed under vacuum giving
4.74 g of pale yellow solid (91%): Mp 282-284 °C (dec); 1H
NMR (270 MHz, CDCl3) δ 1.29 (s, 18H, CCH3), 1.50 (s, 18H,
CCH3), 2.17-2.21 (m, 2H, CH2CH2), 3.62-3.67 (m, 2H, NCH2),
4.03-4.08 (m, 2H, NCH2), 7.05 (d, 2H, PhH), 7.54 (d, 2H, PhH),
8.27 (s, 2H, NCH); 27Al NMR (104.15 MHz, CDCl3) δ 43 (W1/2
) 5300 Hz); IR (KBr) 2955, 2905, 2866, 1626, 1557, 1464, 1420,
1391, 1352, 1314, 1260, 1181, 1098, 862, 849, 785, 762, 600,
438. Anal. Calcd for C33H48N2O2AlCl: C, 69.88; H, 8.53.
Found: C, 69.61; H, 8.16.
Sa lop h en (tBu )AlCl (3). A solution of diethylaluminum
chloride (0.108 g, 0.896 mmol) in 20 mL of toluene was added
to a solution of Salophen(tBu)H2 (0.500 g, 0.925 mmol) in 50
mL of toluene. The reaction was refluxed for 2 h. The solution
was then cooled to -30 °C for 2 weeks. At this time a
precipitate had formed so the solvent was removed under
vacuum yielding 0.421 g of a bright yellow solid (78%): Mp
322 °C (dec); 1H NMR (270 MHz, CDCl3) δ 1.34 (s, 18H, CCH3),
1.59 (s, 18H, CCH3), 7.24 (d, 2H, PhH), 7.41 (m, 2H, PhH),
7.66 (d, 2H, PhH), 7.77 (m, 2H, PhH), 8.97 (s, 2H, NCH); 27Al
NMR (104.15 MHz, CDCl3) δ 52 (W1/2 ) 5300 Hz); IR (KBr)
2959, 2907, 2868, 1618, 1586, 1541, 1470, 1397, 1362, 1262,
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [Sa len (tBu )Al]2O (14)
Al(1)-O(1)
Al(1)-O(2)
Al(1)-O(3)
Al(1)-N(1)
Al(1)-N(2)
O(1)-C(1)
1.821(6)
1.793(6)
1.696(3)
2.008(5)
2.035(7)
1.311(10)
O(2)-C(24)
O(3)-Al(1A)
N(1)-C(15)
N(1)-C(16)
N(2)-C(17)
N(2)-C(18)
1.352(10)
1.696(3)
1.284(11)
1.473(9)
1.460(9)
1.274(11)
O(1)-Al(1)-O(2)
O(1)-Al(1)-O(3)
O(2)-Al(1)-O(3)
O(1)-Al(1)-N(1)
O(2)-Al(1)-N(1)
O(3)-Al(1)-N(1)
O(1)-Al(1)-N(2)
O(2)-Al(1)-N(2)
O(3)-Al(1)-N(2)
N(1)-Al(1)-N(2)
Al(1)-O(1)-C(1)
Al(1)-O(2)-C(24)
90.2(3) Al(1)-N(1)-C(15)
104.2(3) Al(1)-N(1)-C(16)
124.2(5)
117.8(5)
117.7(3) C(15)-N(1)-C(16) 117.5(5)
88.0(3) Al(1)-N(2)-C(17)
130.8(3) Al(1)-N(2)-C(18)
110.3(3) C(17)-N(2)-C(18) 120.5(7)
158.2(3) O(1)-C(1)-C(2)
86.9(3) O(1)-C(1)-C(6)
96.2(3) N(1)-C(15)-C(6)
77.7(3) N(1)-C(16)-C(17) 106.1(6)
129.1(5) N(2)-C(17)-C(16) 103.8(7)
132.7(6) N(2)-C(18)-C(19) 123.5(8)
112.6(5)
126.8(5)
121.4(6)
119.7(7)
125.4(6)
Al(1)-O(3)-Al(1A) 159.5(5) O(2)-C(24)-C(19)
O(2)-C(24)-C(23)
120.7(6)
118.7(7)
Con clu sion
We have demonstrated that the Salen(tBu) ligands
are useful in the isolation of unique bonding schemes
for aluminum. Two such complexes were described. The
first are the unique five-coordinate aluminum amides
that were the principal subject of this manuscript. The
second unique complex is the monomeric aluminum
hydroxide. Very few of this type of complex exist in the
literature. It should be a useful starting material to
other monomeric bimetallic complexes possessing an
Al-O-metal linkage.
1202, 1111, 847, 808, 756, 598, 459. Anal. Calcd for C36H46
N2O2AlCl: C, 71.92; H, 7.71. Found: C, 71.60; H, 7.46.
-
Sa lom p h en (tBu )AlCl (4). A solution of dimethylalumi-
num chloride (0.161 g, 1.76 mmol) in 25 mL of toluene was
added to a rapidly stirring solution of Salomphen(tBu)H2 (1.00
g, 1.76 mmol) in 50 mL of toluene. The reaction was allowed
to stir overnight. A bright orange precipitate was formed. The
solution was filtered, and the solvent was removed from the
precipitate under vacuum, yielding 0.78 g of a bright yellow
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were con-
ducted using Schlenk techniques in conjunction with an inert-
atmosphere glovebox. All solvents were rigorously dried prior
to use. NMR data were obtained on J EOL-GSX-400 and -270
instruments at 270.17 (1H) and 62.5 (13C) MHz. Chemical
shifts are reported relative to SiMe4 and are in ppm. Elemen-
tal analyses were obtained on a Perkin-Elmer 2400 analyzer.
Infrared data were recorded as KBr pellets on a Matheson
Instruments 2020 Galaxy Series spectrometer and are reported
in cm-1. 3,5-Di-tert-butyl-2-hydroxybenzaldehyde18 and Salen-
(tBu)H219 were prepared according to the literature. Cryoscopic
molecular weight determinations were conducted by following
an established procedure.20
Sa len (tBu )AlCl (1). Salen(tBu)H2 (9.268 g, 18.70 mmol)
was dissolved in 50 mL of toluene and cooled to -78 °C, and
then a cooled solution (-78 °C) of dimethylaluminum chloride
(1.96 g, 21.07 mmol) in 50 mL of toluene was added. The
solution was gradually warmed to 25 °C over 2 h and stirred
for an additional 10 h, and then the volatiles were removed
under reduced pressure to give 10.37 g of a pale yellow solid
(99%): Mp 309-310 °C; 1H NMR (270 MHz, CDCl3) δ 1.29 (s,
18H, CCH3), 1.53 (s, 18H, CCH3), 3.74 (m, 2H, NCH2), 4.15
(m, 2H, NCH2), 7.03 (d, 2H, Ph-H), 7.55 (d, 2H, Ph-H), 8.37
(d, 2H, NCH); 13C NMR (100 MHz, CDCl3) δ 29.5 (CCH3), 31.1
(CCH3), 33.8 (CCH3), 35.4 (CCH3), 54.6 (NCH2), 118.4 (Ph),
127.4, 131.6, 139.2, 141.5, 163.3, 170.7 (NCH); 27Al NMR
(104.15 MHz, CDCl3) δ 57 (W1/2 ) 5000 Hz); IR (KBr) 2953
(m), 1624 (vs), 1543 (w), 1398 (w), 1259 (s), 1094 (m), 816 (w),
1
solid (71%): Mp 330 °C (dec); H NMR (270 MHz, CDCl3) δ
1.34 (s, 18H, CCH3), 1.59 (s, 18H, CCH3), 2.35 (s, 6H, PhCH3),
7.23 (d, 2H, PhH), 7.94 (s, 2H, PhH), 7.64 (d, 2H, PhH), 8.90
(s, 2H, NCH); 27Al NMR (104.15 MHz, CDCl3) δ 48 (W1/2
)
6500 Hz); IR (KBr) 2955, 2907, 2868, 1620, 1591, 1553, 1470,
1360, 1256, 1181, 849, 787, 770, 602, 444 cm-1. Anal. Calcd
for C38H50N2O2AlCl: C, 72.53; H, 8.00. Found: C, 72.70; H,
7.93.
Acen AlNHP h (5). Aniline (0.500 mL, 5.49 mmol) was
dissolved in 30 mL of dry THF and cooled to -78 °C. n-BuLi
(2.10 mL, 2.58 M, 5.42 mmol) was added dropwise to the
aniline solution and the reaction stirred at -78 °C for 5 min
and then warmed to 0 °C over 20 min. The solution was
cannulated cold into a stirring suspension of AcenAlCl (1.942
g, 5.45 mmol) in 30 mL of THF. The reaction was stirred at
25 °C for 12 h, after which the THF was filtered off to leave a
yellow solid. The solid was extracted in CH2Cl2, the solution
filtered, and the solvent removed to give 1.02 g of a pale yellow
solid (46%): Mp 208 °C; 1H NMR (270 MHz, CDCl3) δ 2.53 (s,
6H, CH3), 3.73-3.90 (m, 4H, NCH2), 6.19 (d, J ) 8 Hz, 2H,
Ph-H), 6.33 (app t, 1H, Ph-H), 6.70-6.83 (m, 4H, Ph-H), 7.12
(d, J ) 9 Hz, 2H, Ph-H), 7.38 (app t, 2H, Ph-H), 7.62 (d, J )
9 Hz, 2H, Ph-H); 13C NMR (100 MHz, CDCl3) δ 18.1 (CH3),
48.2 (NCH2), 113.7 (Ph), 115.0 (Ph), 116.5 (Ph), 116.6 (Ph),
118.4 (Ph), 120.0 (Ph), 123.9 (Ph), 128.5 (Ph), 129.3 (Ph), 134.9
(Ph), 153.2 (Ph), 164.7 (Ph), 176.4 (CdN); 27Al NMR (104.19
MHz, CDCl3) δ 42 (1212); IR (KBr) 3352 (w), 3028 (m), 2361
(m), 1604 (vs), 1545 (vs), 1334 (vs), 750 (vs), 472 (s) cm-1. Anal.
Calcd for C24H24N3O2Al: C, 69.35; H, 5.94. Found: C, 69.72;
H, 5.85.
(17) J egier, J . A.; Remington, M. P.; Rutherford, D.; Atwood, D. A.
To be submitted for publication.
(18) Casiraghi, G.; Casnati, G.; Puglia, G.; Sartori, G.; Terenghi, G.
J . Chem. Soc., Perkin Trans. 1980, 1862.
(19) Deng, L.; J acobsen, E. N. J . Org. Chem. 1992, 57, 4320.
(20) J olly, W. L. The Synthesis and Characterization of Inorganic
Compounds; Waveland Press: Prospect Heights, IL, 1991; p 283.
Acen AlN(SiMe3)2 (6). AcenAlCl (5.00 g, 14.04 mmol) and
LiN(SiMe3)2 (2.50 g, 14.51 mmol) were placed in a 250 mL

Five-Coordinate Aluminum Amides
Organometallics, Vol. 15, No. 21, 1996 4421
round bottom flask, and 100 mL of dry THF was added. The
solution was stirred at 25 °C for 12 h, after which the solvents
were removed in vacuo to give a dark tan solid. The solid was
extracted in CH2Cl2, the solution was filtered, and CH2Cl2 was
removed in vacuo to give a yellow-orange solid (5.86 g, 87%):
Mp 277-279 °C (dec); 1H NMR (270 MHz, CDCl3) δ -0.07 (s,
18H, SiCH3), 2.48 (s, 6H, CH3), 3.76 (m, 2H, NCH2), 4.30 (m,
2H, NCH2), 6.64-7.57 (m, 8H, Ph-H); 13C NMR (100 MHz,
CDCl3) δ 2.5 (SiCH3), 4.9 (SiCH3), 17.2 (CH3), 48.0 (NCH2),
115.8 (Ph), 120.3 (Ph), 123.9 (Ph), 129.2 (Ph), 134.7 (Ph), 165.2
(Ph), 174.6 (CdN); 27Al NMR (104.15 MHz, CDCl3) δ 43 (W1/2
) 2600); IR (KBr) 2953 (m), 1606 (vs), 1447 (s), 1248 (s), 937
(s), 885 (vs), 833 (vs), 754 (vs), 474 (s) cm-1. Anal. Calcd for
CHCH3), 1.35 (s, 18H, CCH3), 1.58 (s, 18H, CCH3), 2.42 (br s,
1H, NH), 2.81 (m, 2H, CHCH3), 3.53 (m, 4H,NCH2), 6.62 (t,
1H, Ph-H), 6.83 (d, 2H, Ph-H), 7.06 (d, 2H, Ph-H), 7.59 (d, 2H,
Ph-H), 8.28 (s, 2H, NCH); 13C NMR (100 MHz, CDCl3) δ 22.9
(CHCH3), 27.5 (CHCH3), 29.8 (CCH3), 31.5 (CCH3), 34.1
(CCH3), 35.7 (CCH3), 55.9 (NCH2), 117.1 (Dipp), 118.7 (Ph-
ligand), 122.0 (Dipp), 127.0 (Ph-ligand), 130.0 (Ph-ligand),
138.3 (Ph-ligand), 139.4 (Dipp), 141.3 (Ph-ligand), 147.4 (Dipp),
163.3 (Ph-ligand), 169.5 (NCH); 27Al NMR (104.15 MHz,
CDCl3) δ 43 (W1/2 ) 3000 Hz); IR (KBr) 3360, 2953, 1626, 1554,
1460, 1390, 1261, 1177, 839, 754, 583 cm-1. Anal. Calcd for
C
44H64N3O2Al: C, 76.19; H, 9.24; N, 6.06. Found: C, 75.93;
H, 8.99; N, 5.34.
Sa len (tBu )AlNMe2 (10). Salen(tBu)AlCl (0.500 g, 0.91
mmol) was suspended in 10 mL of toluene and stirred at 25
°C, and then lithium dimethylamide (0.048 g, 0.94 mmol) was
added as a solid. The solution was stirred at 35 °C for 24 h
and filtered, and the volatiles were removed under reduced
pressure to give 0.496 g of an orange solid (98%): Mp 172 °C
C
24H36N3O2AlSi2: C, 60.20; H, 6.93; N, 8.42. Found: C, 59.88;
H, 7.48; N, 8.73.
Sa len (tBu )AlNHtBu (7). tert-Butylamine (1.0 mL, 9.45
mmol) was dissolved in 20 mL of THF and stirred at -78 °C,
t
and then BuLi (5.5 mL, 1.72 M in pentane, 9.46 mmol) was
added. The solution was warmed to 25 °C, stirred for 4 h, and
then cannulated onto a suspension of Salen(tBu)AlCl (4.95 g,
8.95 mmol) in 50 mL of toluene. The solution changed from a
yellow to orange during the course of the addition and was
stirred for 12 h. The volatiles were removed in vacuo, the
orange solid was extracted in CH2Cl2, the solution was filtered,
and the solvent was removed under reduced pressure to
provide 7 as an orange solid (4.38 g, 83%): Mp 258-261 °C;
1H NMR (270 MHz, CDCl3) δ 1.16 (s, 9H, NCCH3), 1.32 (s,
18H, CCH3), 1.56 (s, 18H, CCH3), 3.76 (m, 2H, NCH2), 4.16
(m, 2H, NCH2), 7.07 (d, 2H, Ph-H), 7.58 (d, 2H, Ph-H), 8.40 (s,
2H, NCH); 13C NMR (100 MHz, CDCl3) δ 29.8 (CCH3), 31.5
1
(dec); H NMR (270 MHz, CDCl3) δ 1.28 (s, 18H, CCH3), 1.51
(s, 18H, CCH3), 2.09 (br s, 3H, NCH3), 2.61 (s, 3H, NCH3), 4.01
(m, 4H, NCH2), 7.03 (s, 2H, Ph-H), 7.52 (s, 2H, Ph-H), 8.37 (s,
2H, NCH); 13C NMR (100 MHz, CDCl3) δ 29.7 (CCH3), 31.4
(CCH3), 34.1 (CCH3), 35.6 (CCH3), 39.1 (NCH3), 43.3 (NCH3),
54.2 (NCH2), 118.5 (Ph), 127.9, 131.5, 138.8, 140.7, 163.0, 170.8
(NCH); 27Al NMR (104.15 MHz, CDCl3) δ 45 (W1/2 ) 4500 Hz);
IR (KBr) 2955, 1651, 1628, 1541, 1442, 1257, 1175, 1026, 839,
599, 498 cm-1. Anal. Calcd for C34H52N3O2Al: C, 72.73; H,
9.27. Found: C, 72.74; H, 9.36.
Sa len (tBu )AlNEt2 (11). Salen(tBu)AlCl (1.703 g, 3.08
mmol) was suspended in 20 mL of toluene and stirred at 25
°C, and then lithium diethylamide (0.279 g, 3.36 mmol) was
added as a solid. The solution was stirred at 35 °C for 48 h
and filtered, and the volatiles were removed under reduced
pressure to give 1.632 g of an orange solid (90%): Mp 262-
264 °C (dec); 1H NMR (270 MHz, CDCl3) δ 1.10 (t, 6H,
CH2CH3), 1.28 (s, 18H, CCH3), 1.55 (s, 18H, CCH3), 2.64 (br
q, 4H, NCH2CH3), 3.92 (br s, 4H, NCH2), 7.05 (s, 2H, Ph-H),
7.56 (s, 2H, Ph-H), 8.38 (s, 2H, NCH); 13C NMR (100 MHz,
CDCl3) δ 15.5 (CH2CH3), 29.8 (CCH3), 31.4 (CCH3), 34.1
(CCH3), 35.7 (CCH3), 44.0 (NCH2CH3), 54.8 (NCH2), 118.3 (Ph),
127.3, 131.4, 139.0, 141.3, 163.0, 170.4 (NCH); 27Al NMR
(104.15 MHz, CDCl3) δ 55 (W1/2 ) 6500 Hz); IR (KBr) 2953,
2908, 2868, 1622, 1541, 1439, 1314, 1258, 1175, 1018, 854, 752,
578 cm-1. Anal. Calcd for C36H56N3O2Al: C, 73.34; H, 9.51;
N, 7.13. Found: C, 73.67; H, 9.43; N, 6.89.
(CCH3), 32.6 (NCCH3), 34.1 (CCH3), 35.7 (CCH3), 54.8 (NCH2),
27
118.3 (Ph), 127.3, 131.5, 139.0, 141.3, 163.0, 170.5 (NCH);
-
Al NMR (104.15 MHz, CDCl3) δ 56 (W1/2 ) 6800 Hz); IR (KBr)
3243, 2857, 1633, 1622, 1446, 1301, 1168, 1055, 873, 754, 598,
498. Anal. Calcd for C36H57N3O2Al: C, 73.22; H, 9.66; N, 7.11.
Found: C, 72.74; H, 9.73; N, 7.41.
Sa len (t Bu )AlNHP h (8). Aniline (0.174 mL, 1.91 mmol)
was combined with 20 mL of hexane and stirred at 25 °C, and
t
then BuLi (1.1 mL, 1.80 M in pentane, 1.98 mmol) was added
to produce a milky white suspension, which was stirred for 5
min and then cannulated onto a suspension of Salen(tBu)AlCl
(1.06 g, 1.92 mmol) in 20 mL of toluene. The solution changed
from a yellow to orange during the course of the addition and
was stirred for 3 h and filtered, and the volatiles were removed
in vacuo to provide 8 as a pale yellow solid (1.13 g, 97%): Mp,
turned orange at 190 °C and then melted while turning dark
red at 254-256 °C; 1H NMR (270 MHz, CDCl3) δ 1.35 (s, 18H,
CCH3), 1.52 (s, 18H, CCH3), 3.01 (br s, 1H, NH), 3.64 (m, 2H,
NCH2), 3.97 (m, 2H, NCH2), 6.07 (d, 2H, Ph-H), 6.28 (t, 1H,
Ph-H), 6.77 (t, 2H, Ph-H), 7.09 (d, 2H, Ph-H), 7.58 (d, 2H, Ph-
H), 8.37 (s, 2H, NCH); 13C NMR (100 MHz, CDCl3) δ 29.5
(CCH3), 31.2 (CCH3), 33.9 (CCH3), 35.4 (CCH3), 55.4 (NCH2),
113.2 (Ph-amide), 116.4 (Ph-amide), 116.5 (Ph-amide), 118.4
(Ph-ligand), 127.1 (Ph-ligand), 128.8 (Ph-amide), 131.1 (Ph-
ligand), 138.6 (Ph-ligand), 141.5 (Ph-ligand), 154.1 (Ph-amide),
163.4 (Ph-ligand), 170.2 (NCH); 27Al NMR (104.15 MHz,
CDCl3) δ 42 (W1/2 ) 1100 Hz); IR (KBr) 3360, 2859, 1649, 1622,
1442, 1301, 1177, 1056, 874, 755, 755, 598, 498, 434 cm-1. Anal.
Calcd for C38H52N3O2Al: C, 74.88; H, 8.54; N, 6.90. Found:
C, 74.66; H, 8.51; N, 7.22.
Sa len (tBu )AlNHDip p (9). 2,6-Diisopropylaniline (0.380
mL, 2.02 mmol) was combined with 20 mL of hexane and
stirred at 25 °C, and then nBuLi (0.85 mL, 2.5 M in hexane,
2.13 mmol) was added to produce a milky white suspension
which was stirred for 10 min and then cannulated onto a
suspension of Salen(tBu)AlCl (1.134 g, 2.05 mmol) in 20 mL
of toluene. The solution changed from a yellow to orange
during the course of the addition and was stirred for 10 h and
volatiles removed in vacuo. Dissolution of the residue in 40
mL of toluene, followed by filtration, and removal of volatiles
in vacuo provided 9 as a pale yellow solid (1.326 g, 95%): Mp
283-289 °C (dec); 1H NMR (270 MHz, CDCl3) δ 0.81 (d, 12H,
Sa len (tBu )AlN(SiMe3)2 (12). Salen(tBu)AlCl (0.738 g, 1.38
mmol) was suspended in 10 mL of toluene and stirred at 25
°C, and then lithium hexamethyldisilazane (0.252 g, 1.51
mmol) was added as a solid. The solution was stirred at 35
°C for 48 h and filtered, and the volatiles were removed under
reduced pressure to give 0.944 g of a fluorescent yellow solid
(99%): Mp 201-210 °C (dec); 1H NMR (270 MHz, CDCl3) δ
-0.03 (s, 18H, SiCH3), 1.29 (s, 18H, CCH3), 1.45 (s, 18H,
CCH3), 3.49 (m, 2H, NCH2), 4.35 (m, 2H, NCH2), 6.94 (d, 2H,
Ph-H), 7.48 (d, 2H, Ph-H), 8.10 (s, 2H, NCH); 13C NMR (100
MHz, CDCl3) δ 5.09 (SiCH3), 29.9 (CCH3), 31.2 (CCH3), 33.7
(CCH3), 35.2 (CCH3), 53.1 (NCH2), 118.9 (Ph), 127.0, 130.9,
137.8, 140.9, 163.6, 169.5 (NCH); 27Al NMR (104.15 MHz,
CDCl3) δ 45 (W1/2 ) 2100 Hz); 29Si NMR (CDCl3) δ -3.5; IR
(KBr) 2961, 1655, 1624, 1421, 1259, 916, 885, 754, 573 cm-1
.
Anal. Calcd for C38H64N3O2AlSi2: C, 67.16; H, 9.43; N, 6.19.
Found: C, 66.76; H, 8.96; N, 6.34.
Sa len (tBu )AlOH (13). Compound 13 can be prepared by
allowing a solution of 7-12 to stir, without heating, in air for
12 h. It is isolated as a pale yellow solid after removal of the
solvent under vacuum: Mp 310 °C (dec); 1H NMR (270 MHz,
CDCl3) δ 1.30 (s, 18H, CCH3), 1.32 (s, 18H, CCH3), 1.52 (br s,
1H, OH), 3.15 (m, 2H, NCH2), 3.30 (m, 2H, NCH2), 6.87 (d,
2H, Ph-H), 7.34 (d, 2H, Ph-H), 7.86 (s, 2H, NCH); 13C NMR
(100 MHz, CDCl3) δ 29.6 (CCH3), 31.6 (CCH3), 34.0 (CCH3),
35.6 (CCH3), 54.9 (NCH2), 118.7 (Ph), 126.2, 129.0, 136.8,

4422 Organometallics, Vol. 15, No. 21, 1996
Rutherford and Atwood
Ta ble 3. Cr ysta l Da ta for [Sa len (tBu )Al]2O (14)
140.8, 163.9, 167.1 (NCH); 27Al NMR (104.15 MHz, CDCl3) δ
41 (W1/2 ) 2500 Hz); IR (KBr) 3474, 2955, 1631, 1442, 1259,
1174, 1003, 837, 750, 579 cm-1. Anal. Calcd for C32H47N2O3-
Al: C, 71.91; H, 8.80. Found: C, 71.64; H, 8.71.
compd
formula
fw
14
C
32H46AlN2O2.5
525.7
[Sa len (tBu )Al]2O (14). A solution of Salen(tBu)AlNHtBu
(2.02 g, 3.42 mmol) in 40 mL of CH3CN, 40 mL of CH2Cl2, and
40 mL of THF was heated open to the atmosphere until all of
the solid had dissolved and then allowed to stand uncovered
for 3 days until prisms formed (1.355 g, 76%): Mp 305-306
cryst system
space group
a (Å)
b (Å)
c (Å)
monoclinic
C2/c
24.915(3)
17.401(3)
17.573(1)
122.78(1)
6405.2(14)
8
â (°)
1
°C (dec); H NMR (270 MHz, CDCl3) δ 1.29 (s, 18H, CCH3),
V (Å3)
Z
1.52 (s, 18H, CCH3), 3.70-4.30 (v br s, 4H, NCH2), 7.02 (d,
2H, Ph-H), 7.51 (d, 2H, Ph-H), 8.35 (s, 2H, NCH); 13C NMR
(100 MHz, CDCl3) δ 29.7 (CCH3), 31.4 (CCH3), 34.1 (CCH3),
35.7 (CCH3), 55.5 (NCH2), 118.3 (Ph), 127.2, 130.7, 138.2,
140.9, 163.4, 169.8, (NCH); 27Al NMR (104.15 MHz, CDCl3) δ
40 (W1/2 ) 1800 Hz); IR (KBr) 2955, 2904, 2868, 1662, 1632,
D
calc (g/cm3)
1.090
cryst size (mm)
temp (K)
2θ range (deg)
scan type
scan speed (deg/min)
scan range (deg)
reflcns collcd
indp reflcns
obsd reflcns
no. of params
R
0.6 × 0.5 × 0.4
298
3.5-45
2θ-θ
8-60
0.29
4885
4133
1893 (F > 4.0σ(F))
339
1552, 1475, 1445, 1314, 1175, 1003, 837, 750, 577, 498 cm-1
.
Anal. Calcd for C64H92N4O5Al2: C, 73.14; H, 8.76; N, 5.33.
Found: C, 72.83; H, 8.42; N, 5.29.
X-r a y Exp er im en ta l Section
0.0632
0.0647
4.30
Details of the crystal data and a summary of data collection
parameters for the complexes are given in Table 3. Data were
collected on a Siemens P4 diffractometer using graphite-
monochromated Mo KR (0.710 73 Å) radiation. In each case
the check reflections indicated a less than 5% decrease in
intensity over the course of data collection, and hence, no
correction was applied. 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 in-
cluded in the refinement in calculated positions using fixed
isotropic parameters.
Rw
GOF
lar diff peak (e/Å3)
0.23
donors of the Petroleum Research Fund (Grant 30057-
G3), administered by the American Chemical Society,
for support. The receipt of an NSF-CAREER award is
also gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
parameters, positional and thermal parameters, and bond
distances and angles and a unit cell diagram (10 pages).
Ordering information is given on any current masthead page.
Ack n ow led gm en t. Gratitude is expressed to the
National Science Foundation (Grant 9452892) and the
OM9603631