Fluoroaryl-substituted ketiminate complexes of aluminum

Article abstract of DOI:10.1016/j.jorganchem.2004.12.011

The ketiminate complex AlCl[OC(Me)CHC(Me)N(p-C₆H ₄F)]₂ (4) has been prepared from the β-aminoenone, O=C(Me)CH=C(Me)N(H)(p-C₆H₄F) (3) by lithiation of 3 with n-BuLi, followed by reaction with AlCl₃ and by the reaction of 3 with Me₂AlCl. A second compound, [AlCl₂{O=C(Me)CH=C(Me)N(H)(p- C₆H₄F)}₄][AlCl₄] (5), was also isolated from the AlCl₃ reaction. The structures of 4 and 5 were determined by X-ray diffraction analysis.

Full text of DOI:10.1016/j.jorganchem.2004.12.011

Journal of Organometallic Chemistry 690 (2005) 1366–1371
www.elsevier.com/locate/jorganchem
Fluoroaryl-substituted ketiminate complexes of aluminum
a
b
a,
a
Piyush Shukla , John C. Gordon , Alan H. Cowley *, Jamie N. Jones
a
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, 1 University Station A5300, Austin, TX 78712, USA
b
Los Alamos National Laboratory, Chemistry Division, MS J514, Los Alamos, NM 87545, USA
Received 16 November 2004; accepted 1 December 2004
Available online 7 February 2005
Abstract
The ketiminate complex AlCl[OC(Me)CHC(Me)N(p-C6H4F)]2 (4) has been prepared from the b-aminoenone,
O@C(Me)CH@C(Me)N(H)(p-C6H4F) (3) by lithiation of 3 with n-BuLi, followed by reaction with AlCl3 and by the reaction of
3 with Me2AlCl. A second compound, [AlCl2{O@C(Me)CH@C(Me)N(H)(p-C6H4F)}4][AlCl4] (5), was also isolated from the AlCl3
reaction. The structures of 4 and 5 were determined by X-ray diffraction analysis.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Ketiminate; b-Aminoenone; Aluminum; Complexes; Syntheses; Structures
1. Introduction
use in organoaluminum chemistry, both with respect
to polymerization catalysis [3] and also for the stabil-
ization of unusual aluminum valence states and coor-
dination numbers [4]. Few studies, however, have
focused on aluminum complexes with ketiminate ligands
[5]. The monoanionic ketiminate ligand (3) normally
binds to metals in a similar fashion to b-diketiminates
and Schiff bases. As a consequence of the formation
of a six-membered chelate ring, the ligation of a keti-
minate causes the metal center to be surrounded by
bulky substituents on only one side of the ring, thus
leaving the other side relatively open. Moreover, li-
gands of the type O–N are particularly interesting be-
cause the oxygen atom provides a site for strong
coordination whereas the nitrogen atom is typically
less strongly bound, thus resulting in ligand hemilabil-
ity and potentially interesting catalytic behavior [6]. In
order to develop catalytic systems with enhanced
activities at the metal centers, it has become increas-
ingly desirable to introduce electron-withdrawing sub-
stituents into the coordination sphere [7]. We have
recently developed a new method for the synthesis
of a-diimines and b-ketiminates bearing fluorinated
aryl substituents [8] and in the present contribution
Due to their pronounced Lewis acidity and ready
availability, aluminum complexes continue to assume a
role of considerable importance, not only for organic
synthesis [1], but also in the field of catalysis [2]. In addi-
tion to the strongly electrophilic character of the alumi-
num atom itself, the supporting ligands of these
complexes can be used to fine-tune both the steric and
electronic properties at the metal center. In this context,
b-diketiminates (1) and Schiff base ligands (2) have
found extensive
Ar
-
N
O
Ar
Ar
Ar
N
O
N
N
-
-
β-diketiminate
ketiminate
Schiff base
3
1
2
*
Corresponding author. Tel.: +5124717484; fax: +5124716822.
E-mail address: cowley@mail.utexas.edu (A.H. Cowley).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.12.011

P. Shukla et al. / Journal of Organometallic Chemistry 690 (2005) 1366–1371
1367
we explore the use of ligand 3 (Ar = p-fluorophenyl) in
the context of aluminum chemistry.
least squares on F2 using the Siemens SHELX PLUS 5.0
(PC) software package [9]. All non-hydrogen atoms
were allowed anisotropic thermal motion and all hydro-
gen atoms, which were included in calculated positions
˚
2. Experimental
(C–H 0.96 A), were refined using a riding model and a
general isotropic thermal parameter. The crystal and
structure refinement details are presented in Table 1.
2.1. General
All manipulations and reactions were performed un-
der a dry, oxygen-free, catalyst-scrubbed argon atmo-
sphere using standard Schlenk techniques or under a
dry, oxygen-free, helium atmosphere in a Vacuum
Atmospheres drybox. All glassware was oven-dried
and vacuum- and argon flow-degassed before use. Tolu-
ene and diethyl ether were distilled under N2 from so-
dium benzophenone ketyl and degassed prior to use.
The syntheses of the ligands are described in a previous
paper [8]; Me2AlCl and AlCl3 were purchased from
commercial sources and used without further
purification.
2.4. AlCl[OC(Me)CHC(Me)N(p-C6H4F)]2 (4)
2.4.1. Method 1
A solution of n-BuLi (2.56 mmol) in hexanes was
added slowly to
a
solution of O@C(Me)CH@
C(Me)N(H)(p-C6H4F) (0.50 g, 2.56 mmol) in 20 ml of
diethyl ether at 0 ꢁC. The reaction mixture was allowed
to come to room temperature over a period of 3 h, after
which time the volatiles were removed in vacuo. The
‘‘O@C(Me)CH@C(Me)N(Li)(p-C6H4F)’’ in 70 ml of
diethyl ether was added slowly to a solution of AlCl3
(0.34 g, 2.55 mmol) in 20 ml of diethyl ether at 0 ꢁC.
The reaction mixture was allowed to come to room tem-
perature and stirred overnight, after which time the vol-
atiles were removed in vacuo, and the resulting pale
yellow residue was extracted with toluene (75 ml). After
filtration through a glass frit covered with a pad of dia-
tomaceous earth, the yellow filtrate was concentrated
and maintained at ambient temperature for 1 week
which resulted in the formation of a crop of colorless
crystals of 4 (0.02 g, 2% yield, m.p. 118–124 ꢁC). 1H
NMR (C6D6, 25 ꢁC): d 7.1 (m, 8H, w1/2 = 30 Hz, aryl-
ring protons), 5.4 (s, 2H, CH), 2.2 (s, 6H, CH3CN),
2.0 (s, 6H, CH3CO). 19F NMR (CDCl3, 25 ꢁC): d
ꢀ118.0 (m, w1/2 = 12 Hz). 27Al NMR (C6D6, 25 ꢁC): d
91 (broad, w1/2 = 100 Hz). MS (CI+, CH4): m/e 447
(M + H), 411 (M ꢀ Cl), 194 [O@C(Me)CH@C(Me)-
N(H)(p-C6H4F) + H]. HRMS (CI, CH4) Calc. for
C22H22AlClF2N2O2: 447.123154. Found: 447.122689.
2.2. Physical measurements
Low-resolution CI mass spectra were obtained on a
Finnigan MAT TSQ-700 mass spectrometer, and high-
resolution CI mass spectra were measured on a VG
Analytical ZAB-VE sector instrument. All MS analyses
were performed on samples that had been sealed in glass
capillaries under argon in a drybox. Solution-phase
NMR spectra were recorded at 298 K on a GE Varian
Unity 300 instrument (1H, 300 MHz; 19F, 282 MHz;
27Al, 78 MHz) at the University of Texas at Austin or
the Los Alamos National Laboratory (LANL). All
NMR samples were run immediately following removal
from the drybox. Benzene-d6 and chloroform-d were
vacuum distilled under argon from sodium benzophe-
1
none ketyl prior to use. The H NMR chemical shifts
are reported relative to tetramethylsilane (d 0.00) and
referenced to solvent. The 19F NMR chemical shifts
are reported relative to freon-11 (d 0.00) and referenced
to C6H5CF3 (d ꢀ63.5 at LANL) or to freon-11 (d 0.00 at
UT-Austin). The 27Al NMR chemical shifts are reported
relative to [Al(H2O)6]3+ (d 0.00).
2.4.2. Method 2
A solution of O@C(Me)CH@C(Me)N(H)(p-C6H4F)
(0.32 g, 1.63 mmol) in 3 ml of toluene was added to a
solution of Me2AlCl (0.15 g, 1.62 mmol) in 3 ml of tolu-
ene. Following the cessation of gas evolution, the reac-
tion mixture was stirred overnight at ambient
temperature. Crystals of 4 formed upon slow evapora-
tion of the solvent. (0.12 g, 33% yield). The spectro-
scopic data were identical with those listed above for
Method 1.
2.3. X-ray structure determination of complexes 4 and 5
Crystals of suitable quality were collected under an
argon atmosphere from Schlenk-type flasks, and cov-
ered immediately with degassed perfluorinated polyether
oil. The X-ray data were collected on a Nonius Kappa
CCD diffractometer at 153 K using an Oxford Cryo-
stream low-temperature device and graphite-monochro-
2.5. [AlCl2{O@C(Me)CH@C(Me)N(H)(p-C6H4F)}4]-
[AlCl4] (5)
˚
mated Mo Ka radiation (k = 0.71073 A). A correction
was applied for Lorentz polarization. All structures were
solved by direct methods, and refined by full-matrix
The solution from which the crystals of 4 were grown
(by Method 1) was transferred to a separate Schlenk
flask. The solvent was removed in vacuo and the yellow

1368
P. Shukla et al. / Journal of Organometallic Chemistry 690 (2005) 1366–1371
Table 1
Crystal and structure refinement data for 4 and 5
Compound
4
5
Empirical formula
Formula weight
Temperature (K)
C22H22AlClF2N2O2
446.85
153(2)
C49H49Al2Cl6F4N4O4
1100.58
153(2)
˚
Wavelength (A)
0.71069
Monoclinic
C2/c
0.71069
Monoclinic
Crystal system
Space group
Unit cell dimensions
ꢀ
P1
˚
a (A)
12.140(5)
12.201(5)
11.425(5)
15.731(5)
˚
b (A)
˚
c (A)
14.121(5)
90
17.238(5)
88.003(5)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Volume
Z
Dcalc. (mg mꢀ3
92.150(5)
90
2090.1(14)
78.409(5)
74.750(5)
2927.5(18)
4
1.420
2
1.249
)
Absorption coefficient (mm)
F(000)
Crystal size (mm)
0.264
928
0.378
1134
0.20 · 0.20 · 0.20
3.34–27.62ꢁ
0.2 · 0.2 · 0.2
2.96–28.32ꢁ
h Range for data collection
Index ranges
ꢀ156h614, ꢀ156k615, ꢀ146l618
ꢀ146h614, ꢀ206k616, ꢀ226l622
Reflections collected
Independent reflections [Rint
Completeness to hmax
Maximum/minimum transmission
Refinement method
7153
2421 [0.0845]
99.3%
21380
]
13866 [0.0302]
95.0%
0.8863
Full-matrix least-squares on F2
13866/0/887
1.031
0.9490 and 0.9490
Full-matrix least-squares on F2
2421/0/181
Data/restraints/parameters
Goodness-of-fit on F2
1.144
Final R indices [I > 2r(I)]
R indices (all data)
Largest peak and hole (e A
R1 = 0.0694, wR2 = 0.1360
R1 = 0.1023, wR2 = 0.1472
0.460 and ꢀ0.424
R1 = 0.0952, wR2 = 0.2242
R1 = 0.1524, wR2 = 0.2619
2.397 and ꢀ1.792
ꢀ3
˚
)
residue was taken into the drybox. Following the addi-
tion of 3 ml of C6D6, a crop of yellow crystals of 5
formed over a period of 5 min. (0.15 g, 5%, m.p. 178–
for the same ion. Confirmation of the proposed compo-
sition was provided by X-ray crystallography (see
Tables 1 and 2).
1
182 ꢁC). H NMR (C6D6, 25 ꢁC): d 12.3 (br, 4H, NH),
Individual molecules of 4 possess a twofold rotation
axis that lies along the Al(1)–Cl(1) bond and renders
the two chelate rings equivalent (Fig. 1). The aluminum
atom is five-coordinate and adopts a trigonal bipyrami-
dal geometry in which the two nitrogen atoms occupy
the axial positions as evidenced by the fact that the
N(1)–Al(1)–N(2) angle deviates only slightly from linear-
ity [172.44(4)ꢁ]. The equatorial plane comprises one chlo-
rine and two oxygen atoms, for which the sum of bond
angles is 360.00(8)ꢁ. The N–C–C–C–O chelate rings are
close to planar as reflected by the sum of bond angles
(718.78ꢁ). There is a slight deviation of the oxygen atom
6.5 (m, 16H, w1/2 = 43 Hz, aryl-ring protons), 4.7 (s,
4H, CH), 2.3 (s, 12H, CH3C–N), 1.2 (s, 12H, CH3C@O).
19F NMR (CDCl3, 25 ꢁC): d ꢀ113.7 (m, w1/2 = 10 Hz).
27Al (CDCl3, 25 ꢁC): d 86 (sharp; (AlCl4)ꢀ), 2 (sharp;
(AlCl2(ligand)4)+). MS (CI+, CH4): m/e 642 (M ꢀ Cl–li-
gand), 485 [M–(2 ligand)], 194 [O@C(Me)CH@C(Me)-
N(H)(p-fluorophenyl) + H].
3. Results and discussion
˚
Treatment of the free ligand O@C(Me)CH@C(Me)-
N(H)(p-C6H4F) with n-BuLi afforded the lithiated inter-
mediate, ‘‘O@C(Me)CH@C(Me)N(Li)(p-C6H4F)’’, which
in turn was allowed to react in situ with 1 equivalent of
AlCl3. Although the reagents were employed in 1:1 stoi-
chiometry, a disubstituted product, AlCl[OC(Me)CHC-
(Me)N(p-C6H4F)]2 (4), was isolated. The empirical
composition of 4 was indicated by the detection of a
peak corresponding to the molecular ion at m/e 447 in
the CI+ mass spectrum, along with a satisfactory HRMS
(0.078 A) from the mean plane of each ring. The chelate
rings are delocalized as evidenced by the pattern of bond
˚
lengths, [1.314(3) A, O(1)–C(4); 1.350(4) A, C(4)–C(3);
˚
˚
˚
1.431(4) A, C(3)–C(2); 1.320(4) A, C(2)–N(1)]. Com-
pared with the free ligand [8], lengthening of the O(1)–
C(4) and C(3)–C(2) bonds and a shortening of the
N(1)–C(2) bond takes place upon coordination.
In an effort to prepare an aluminum ketiminate
complex with a 1:1 stoichiometry, 1 equivalent of the
protonated form of the free ligand, O@C(Me)CH@C-

P. Shukla et al. / Journal of Organometallic Chemistry 690 (2005) 1366–1371
1369
Table 2
˚
Selected bond lengths (A) and angles (ꢁ)
Compound 4
Bond lengths
Cl(1)–Al(1)
Al(1)–O(1)
Al(1)–N(1)
N(1)–C(2)
N(1)–C(10)
F(13)–C(13)
O(1)–C(4)
C(3)–C(4)
C(3)–C(2)
2.1925(18) C(13)–C(12)
1.361(4)
1.371(4)
1.385(4)
1.388(4)
1.497(4)
1.392(4)
1.501(4)
1.385(4)
1.774(2)
2.034(2)
1.320(4)
1.445(3)
1.370(3)
1.314(3)
1.350(4)
1.431(4)
C(13)–C(14)
C(15)–C(10)
C(15)–C(14)
C(4)–C(5)
C(12)–C(11)
C(2)–C(1)
C(10)–C(11)
Bond angles
O(1)–Al(1)–O(1A)
O(1)–Al(1)–N(1A)
O(1A)–Al(1)–N(1A) 89.97(9)
122.64(15) C(4)–O(1)–Al(1)
132.98(18)
124.8(3)
118.5(3)
123.3(3)
118.3(3)
121.0(3)
123.7(3)
113.7(3)
118.3(3)
121.4(3)
121.9(3)
121.1(3)
119.7(2)
86.40(9)
C(4)–C(3)–C(2)
Fig. 1. Molecular structure of AlCl[OC(Me)CHC(Me)N(p-C6H4F)]2,
(4), showing the atom numbering scheme. The thermal ellipsoids are
shown at the 30% probability level. All hydrogen atoms have been
omitted for clarity.
C(12)–C(13)–F(13)
C(12)–C(13)–C(14)
F(13)–C(13)–C(14)
O(1)–Al(1)–N(1)
O(1A)–Al(1)–N(1)
N(1A)–Al(1)–N(1)
O(1)–Al(1)–Cl(1)
O(1A)–Al(1)–Cl(1)
N(1A)–Al(1)–Cl(1)
N(1)–Al(1)–Cl(1)
C(2)–N(1)–C(10)
C(2)–N(1)–Al(1)
C(10)–N(1)–Al(1)
89.97(9)
86.40(9)
172.44(15) C(10)–C(15)–C(14)
118.68(8)
118.68(8)
93.78(7)
93.78(7)
116.5(2)
O(1)–C(4)–C(3)
O(1)–C(4)–C(5)
C(13)–C(12)–C(11)
N(1)–C(2)–C(3)
N(1)–C(2)–C(1)
significantly better than that realized by salt elimination
(Method 1). The two approaches are summarized in
Scheme 1.
Yu et al. [5] have reported similar reactions with the
bulkier ketiminate ligand [OC(Me)CHC(Me)N(2,6-i-
Pr2C6H3)]ꢀ. However, there are significant differences
in our results. For instance, and probably on account
of the bulkier aryl ligand, these authors were able to ob-
tain both 1:1 and 2:1 ligand:aluminum stoichiometry
products either by the methane elimination or by salt
elimination methodology. There is also a significant dif-
ference in the two AlCl(ketiminate)2 structures.
125.87(19) C(11)–C(10)–N(1)
117.66(17) C(15)–C(10)–N(1)
Compound 5
Bond lengths
C(22)–C(50)
C(22)–C(44)
C(22)–N(15)
C(24)–O(12)
C(24)–C(42)
C(24)–C(49)
C(37)–C(15)
C(37)–C(42)
C(37)–C(59)
C(44)–C(46)
C(46)–C(57)
C(50)–C(53)
1.377(7)
1.392(7)
1.422(6)
1.280(5)
1.392(6)
1.491(7)
1.328(6)
1.405(7)
1.498(7)
1.390(8)
1.377(9)
1.401(8)
C(53)–C(57)
C(57)–F(3)
O(7)–Al(2)
O(11)–Al(2)
O(12)–Al(2)
O(13)–Al(2)
Al(2)–Cl(1)
Al(2)–Cl(2)
Al(4)–Cl(4)
Al(4)–Cl(06)
Al(4)–Cl(07)
Al(4)–Cl(3)
1.371(9)
1.352(6)
1.867(3)
1.889(3)
1.867(3)
1.885(3)
2.2686(19)
2.4238(19)
2.082(3)
2.101(3)
2.103(4)
2.135(3)
Both structures feature trigonal biyramidal alumi-
num centers. However, in contrast to 4, which has
axially disposed nitrogens, in the case of AlCl[OC(Me)-
CHC(Me)N(2,6-i-Pr2C6H3)], the axial positions are
occupied by oxygen atoms with an O–Al–O bond angle
of 168.8(5)ꢁ. A further chemical difference relates to the
fact that a second product was isolated from the reac-
tion of O@C(Me)CH@C(Me)- N(H)(p-C6H4F) with
AlCl3. The 27Al NMR assay of this product (5) evi-
denced sharp resonances at d 86 and 2, the first of which
is indicative of the presence of [AlCl4]ꢀ and the second
of which falls in the region anticipated for hexacoordi-
Bond angles
C(50)–C(22)–N(15)
C(44)–C(22)–N(15)
O(12)–C(24)–C(42)
O(12)–C(24)–C(49)
C(42)–C(24)–C(49)
N(15)–C(37)–C(42)
N(15)–C(37)–C(59)
F(3)–C(57)–C(46)
C(37)–N(15)–C(22)
C(24)–O(12)–Al(2)
O(12)–Al(2)–O(13)
O(12)–Al(2)–O(13)
O(7)–Al(2)–O(13)
119.0(5)
120.7(5)
119.4(4)
119.4(4)
121.2(4)
121.6(4)
118.7(4)
117.8(6)
127.7(4)
148.2(3)
O(12)–Al(2)–O(11)
O(7)–Al(2)–O(11)
O(13)–Al(2)–O(11)
O(12)–Al(2)–Cl(1)
O(7)–Al(2)–Cl(1)
O(13)–Al(2)–Cl(1)
O(11)–Al(2)–Cl(1)
Cl(4)–Al(4)–Cl(06)
Cl(4)–Al(4)–Cl(07)
88.34(13)
88.73(14)
168.65(14)
91.77(11)
98.16(11)
95.38(11)
95.91(10)
108.54(16)
109.75(16)
1
nate aluminum [10]. The H and 19F NMR spectra of
5 were similar to those of the free ligand, albeit shifted
due to coordination to aluminum. Of particular signifi-
Cl(06)–Al(4)–Cl(07) 109.57(17)
1
cance was the presence of a peak at d 12.3 in the H
169.89(15) Cl(4)–Al(4)–Cl(3)
Cl(06)–Al(4)–Cl(3)
Cl(07)–Al(4)–Cl(3)
106.65(19)
109.37(14)
112.85(19)
spectrum thus indicating that the amido protons were
still present. In order to elucidate the structure of 5, it
was necessary to appeal to X-ray crystallography. The
solid state of 5 comprises an equimolar mixture of
[AlCl2{O@C(Me)CH@C(Me)N(H)(p-C6H4F)}4]+ and
[AlCl4]ꢀ ions and there are no unusually short interionic
contacts. The structure of 5 is illustrated in Fig. 2. The
geometry around the aluminum center Al(2) is octahe-
dral and the average O–Al–O bond angle in the AlO4
equatorial plane is 89.52(14)ꢁ. The Cl(1)–Al(2)–Cl(2)
92.50(14)
88.50(14)
(Me)N(H)(p-C6H4F), was allowed to react with
Me2AlCl. However, both methyl groups underwent a
methane elimination reaction and the product was
shown to be 4 on the basis of spectroscopic data and
X-ray crystallography. It is worth noting that the yield
of 4 from the methane elimination route (Method 2) is

1370
P. Shukla et al. / Journal of Organometallic Chemistry 690 (2005) 1366–1371
F
1) n-BuLi
2)AlCl3
-2 LiCl
Cl
O
N
N
O
Al
O
HN
F
2
Me 2AlCl
-2 MeH
3
4
F
Scheme 1.
˚
˚
C(42) bond [1.392(6) A] is ꢁ0.03 A shorter than in the
˚
free ligand (1.426(2) A) while the other C–C bond,
˚
C(42)–C(37), undergoes a 0.02 A increase upon coordi-
nation, as does the C–N bond. There are no main group
examples of cations of the type [5]+ in which b-aminoe-
none ligands bind to the metal atom via the ketone func-
tionality rather than as bidentate ketiminate ligands.
There are, however, examples of this type of bonding
in titanium and zirconium chemistry [11,12]. These
Group 4 derivatives were prepared by treatment of the
respective metal tetrahalide with two equivalents of the
free ligand, thus forming the MCl4L2 complexes
(M = Ti, Zr; L = b-aminoenone). Both complexes fea-
ture octahedral geometries; however, unlike [5]+, they
are neutral compounds.
The formation of 5 can best be understood on the ba-
sis of the autoionization reaction shown in Equation 1.
The cation [AlCl2]+ is a strong Lewis acid that readily
coordinates with the keto
2AlCl3 ! ½AlCl2ꢂþ þ ½AlCl4ꢂꢀ
ð1Þ
Fig. 2. Molecular structure of [AlCl2{O@C(Me)CH@C(Me)N(H)(p-
C6H4F)}4][AlCl4], (5), showing the atom numbering scheme.
A
functionality of the free ligand in preference to undergo-
ing a hydrogen chloride elimination reaction. This type
of autoionization is observed frequently in systems
where halide abstraction reactions are possible since
they do not involve the transfer of lone pairs and are
therefore defined by Lewis acid and base chemistry
[13]. Clearly, for this type of reaction to occur in the ob-
served manner it requires the absence of the lithiated b-
aminoenone ligand. Either the ligand was reprotonated,
or more likely, the lithiation of the starting b-amino-
enone did not go to completion.
benzene of crystallization has been omitted for clarity. The thermal
ellipsoids are shown at the 30% probability level. All hydrogen atoms
have been omitted for clarity.
bond angle is 175.53(4)ꢁ and the average aluminum–
chlorine bond length of 2.347(19) A is slightly longer
than that observed for 4. The Al–oxygen bond lengths,
˚
˚
which average 1.877(3) A, are slightly longer than that
determined for 4, suggestive of a donor–acceptor rather
than a r-type Al–O bond. This view was confirmed by
the detection of the amino proton atom on N(1) as well
as being consistent with the assignment of the +3 oxida-
tion state Al(2). The bond lengths observed for the b-
aminoenone ligand compare reasonably well with those
reported for the free ligand [8], the main difference being
an increase of the C@O bond length from 1.252(1) to
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre, CCDC Nos. 256864 and 256865 for compounds
˚
1.280(5) A upon coordination. The adjacent C(24)–

P. Shukla et al. / Journal of Organometallic Chemistry 690 (2005) 1366–1371
1371
(d) C.E. Radzewich, M.P. Coles, R.F. Jordan, J. Am. Chem. Soc.
120 (1998) 9384;
4 and 5, respectively. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (Fax: +44
1223 336033; e-mail: deposit@ccdc.cam.ca.uk or www:
http://www.ccdc.cam.ac.uk).
(e) A. LeBorgne, V. Vincens, M. Jouglard, N. Spassky, Makro-
moleculare Chemie, Macromolecular Symposia (1993) 73;
(f) R.N. Prasad, J.P. Tandon, Z. Naturforsch.
565.
B (1974)
[4] (a) M. Stender, B.E. Eichler, N.J. Hardman, P.P. Power, J.
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2794;
Acknowledgements
(b) C. Cui, H.W. Roesky, H. Hao, H.-G. Schmidt, M.
Noltemeyer, Angew. Chem., Int. Ed. Engl. 39 (2000) 1815;
(c) C. Cui, H.W. Roesky, H.-G. Schmidt, M. Noltemeyer,
H. Hao, F. Cimpoesu, Angew. Chem. Int. Ed. Engl. 39
(2000) 4274;
We thank the US Department of EnergyÕs Defense
Programs Office, the Laboratory Directed Research and
Developmental Program at the Los Alamos National
Laboratory, DOEÕs Office of Basic Energy Sciences, the
Robert A. Welch Foundation (Grant F-135), and the Na-
tional Science Foundation (CHE-0240008) for support of
this work. P.S. thanks the G.T. Seaborg Institute for
Transactinium Science at LANL for the award of a Sum-
mer Research Fellowship during 2001 and 2002. Los Ala-
mos National Laboratory is operated by the University of
California under Contract W-7405-ENG-36.
(d) D. Neculai, H.W. Roesky, A.M. Neculai, J. Magull,
B. Walfort, D. Stalke, Angew. Chem., Int. Ed. Engl. 41
(2002) 4294.
[5] R.-C. Yu, C.H. Hung, J.-H. Huang, H.-Y. Lee, J.-T. Chen,
Inorg. Chem. 41 (2002) 6450.
[6] D. Jones, A. Roberts, K. Cavell, W. Keim, U. Englert, B.W.
Skelton, A.H. White, J. Chem. Soc., Dalton Trans. (1998) 255.
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