Synthesis and characterization of aluminum complexes of 2-pyrazol-1-yl-ethenolate ligands

Article abstract of DOI:10.1016/j.jorganchem.2005.05.049

The synthesis and the characterization of some new aluminum complexes with bidentate 2-pyrazol-1-yl-ethenolate ligands are described. 2-(3,5-Disubstituted pyrazol-1-yl)-1-phenylethanones, 1-PhC(O)CH₂-3,5-R₂C ₃HN₂

Full text of DOI:10.1016/j.jorganchem.2005.05.049

Journal of Organometallic Chemistry 690 (2005) 4080–4086
www.elsevier.com/locate/jorganchem
Synthesis and characterization of aluminum complexes
of 2-pyrazol-1-yl-ethenolate ligands
*
Zhong-Xia Wang , Die Yang
Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, PR China
Received 18 March 2005; accepted 27 May 2005
Available online 19 July 2005
Abstract
The synthesis and the characterization of some new aluminum complexes with bidentate 2-pyrazol-1-yl-ethenolate ligands are
described. 2-(3,5-Disubstituted pyrazol-1-yl)-1-phenylethanones, 1-PhC(O)CH2-3,5-R2C3HN2 (1a, R = Me; 1b, R = But), were pre-
pared by solventless reaction of 3,5-dimethyl pyrazole or 3,5-di-tert-butyl pyrazole with PhC(O)CH2Br. Reaction of 1a or 1b with
AlR13 (R1 = Me, Et) yielded N,O-chelate alkylaluminum complexes ½R12AlOCðPhÞCHfð3; 5-R2C3HN2Þ-1gꢀ (2a, R = R1 = Me; 2b,
R = But, R1 = Me; 2c, R = Me, R1 = Et). Compound 1a was readily lithiated with LiBun in thf or toluene to give lithiated species
3. Treatment of 3 with 0.5 equiv of MeAlCl2 or AlCl3 yielded five-coordinated aluminum complexes [XAl(OC(Ph)CH{(3,5-
Me2C3HN2)-1})2] (4, X = Me; 5, X = Cl). Reaction of 5 with an equiv of LiHBEt3 generated [Al(OC(Ph)CH{(3,5-Me2C3HN2)-
1})3] (6). Complex 6 was also obtained by reaction of 3 with 1/3 equiv of AlCl3. Treatment of 5 with 2 equiv of AlMe3 yielded
complex 2a, whereas with an equiv of AlMe3 afforded a mixture of 2a and [Me(Cl)AlOC(Ph)CH{(3,5-Me2C3HN2)-1}] (7). Compounds
1a, 1b, 2a–2c and 4–6 were characterized by elemental analyses, NMR and IR (for 1a and 1b) spectroscopy. The structures of com-
plexes 2a and 5 were determined by single crystal X-ray diffraction techniques. Both 2a and 5 are monomeric in the solid state. The
coordination geometries of the aluminum atoms are a distorted tetrahedron for 2a or a distorted trigonal bipyramid for 5.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: 2-Pyrazol-1-yl-ethenolate ligands; Aluminum complexes; Synthesis; Structures
1. Introduction
chelate ligands have been investigated as catalysts
for olefin polymerization [1a,6]. Aluminum complexes
with N,O-ligands also showed versatile coordination
mode and unique applications [7]. For example,
tris(8-quinolinolato)aluminum is one of the most
widely used complexes for organic light emitting de-
vices (OLED) [8]. A series of N,O-chelate aluminum
complexes such as ketiminate and SALEN aluminum
complexes exhibited excellent catalytic activity toward
the ring opening polymerization of cyclic esters [7f,9].
N,O-Bidentate ligands were also found to be able to
stabilize cationic monoalkylaluminum species [10].
Here we report synthesis and characterization of alu-
minum complexes stabilized by 2-pyrazol-1-yl-etheno-
late ligands.
Organoaluminum compounds have attracted much
attention in recent years due to their use as catalysts
or co-catalysts for olefin polymerization [1,2], as initi-
ators in ROP of cyclic esters [3] and as synthetic re-
agents or catalysts [4]. These compounds also
exhibited interesting structure features and versatile
reactivities [5]. N,O-Chelate ligands have been widely
used in main group and transition metal coordination
chemistry. For example, nickel complexes with N,O-
*
Corresponding author. Tel.: +86 551 3603043; fax: +86 551
3601592/3631760.
E-mail address: zxwang@ustc.edu.cn (Z.-X. Wang).
0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.05.049

Z.-X. Wang, D. Yang / Journal of Organometallic Chemistry 690 (2005) 4080–4086
4081
2. Results and discussion
coordinated aluminum complex 4. Similar reaction
between 3 and 0.5 equiv of AlCl3 afforded another
five-coordinated aluminum complex 5. Attempts to
methylate 5 by treatment with MeLi were unsuccessful.
The reaction produced a complicated mixture. Treat-
ment of complex 5 with an equiv of LiHBEt3 in thf
afforded complex 6. The reaction could proceed via a
hydride intermediate I, which transformed into 6 via a
dismutation reaction. The other product of the dismuta-
tion reaction may be AlH3 because no other complexes
can be isolated. Complex 6 was also obtained by reac-
tion of 3 with 1/3 equiv of AlCl3. Reaction of 5 with
an equiv of AlMe3 gave a mixture of 2a and 7. Similar
reaction between 5 and 2 equiv of AlMe3 afforded com-
plex 2a. These are attributed to a redistribution of ligands
and then the methylation of 7 with AlMe3. Ligand redis-
tributions often occur between aluminum complexes. A
number of examples have been reported in the literature
[11–13]. In addition, attempts to prepare complex 7 by
reaction of 3 with an equiv of MeAlCl2 were unsuccess-
ful. The reaction gave a complicated mixture.
Preparation and reactions of 2-(3,5-disubstituted
pyrazol-1-yl)-1-phenylethanones are summerized in
Scheme 1.
A mixture of 3,5-dimethylpyrazole, PhC(O)CH2Br
and Na2CO3 in a motar was ground with a pestle for
20 min to give 2-(3,5-dimethylpyrazol-1-yl)-1-phenyleth-
anone (1a). Similar treatment of 3,5-di-tert-butylpyraz-
ole and PhC(O)CH2Br in the persence of Na2CO3
formed a mixture of 2-(3,5-di-tert-butylpyrazol-1-yl)-1-
phenylethanone (1b) and starting materials. However,
the reaction can reach almost completeness under
microwave radiation conditions. The minor unreacted
starting materials were removed at 80 °C under vacuum.
Both 1a and 1b reacted readily with AlMe3 or AlEt3 in a
1:1 molar ratio, giving four-coordinated N,O-chelate
alkylaluminum complexes 2a–2c. The reactions proceed
along with the elimination of an equivalent of methane
or ethane. However, reaction of 1a or 1b with trimethyl-
aluminum in a 2:1 molar ratio can not form bis(2-pyra-
zol-1-yl-ethenolate) aluminum complexes, only 2a or 2b
being obtained. Compound 1a was readily lithiated with
LiBun in thf or toluene from about ꢁ80 °C to room tem-
perature to give lithiated species, supposing 3. Treat-
ment of 3 with 0.5 equiv of MeAlCl2 prepared [11] in
situ from AlMe3 and AlCl3 in toluene generated five-
Ph
Me
Me
O
N
N
N
Al
H
N
O
Me
Ph
R
Ph
N
Me
N
Me
Me
Me
O
Ph
N
N
I
N
N
Me
O
Al
N
N
Al
Compounds 1a and 1b were characterized by elemental
analyses, 1H and 13C NMR and IR spectroscopy. Each of
complexes 2a–2c and 4–6 was characterized by elemental
Al
Me
O
R
R1
Me
Me
R1
Ph
O
2a R = Me, R1 = Me
2b R = But, R1= Me
2c R = Me, R1=Et
3
4
Ph
6
1
analyses, H and 13C NMR spectroscopy. The NMR
vii
v
spectra of complexes 4 and 5 showed that two 2-pyra-
zol-1-yl- ethenolate ligands are equivalent in the respec-
tive molecule. Complex 6 is six-coordinated in the solid
state shown by single crystal X-ray diffraction (see 6a).
However, its 1H NMR spectrum exhibited two sets of li-
gand signals in a 2:1 integral ratio, showing that two of
the ligands have same coordination environment. Its
27Al NMR spectrum (d 60 ppm) supported a five-coordi-
nated aluminum center [14]. Hence we assume that in the
solution it exists as structure 6b.
vi
iv
ii
Ph
N
R
Me
Me
Me
O
Ph
Ph
N
N
N
iii
N
O
N
O
N
Al
R=Me
N
Li
Me
O
R
Me
Cl
Me
1a R = Me
1b R = But
3
Ph
(not isolated)
5
viii
i
Me
Me
R
Ph
Ph
N
N
N
N
Ph
Ph
N
N
H
Me
O
O
Me
Me
+
Al
N
Al
Me
Me
O
N
N
Ph
Me Me
R
O
N
Me
Cl
Ph
R = Me or But
7
O
N
2a
Me
Al
N
Me
O
Me
Al
O
O
N
Scheme 1. Reagents and conditions: i, PhC(O)CH2Br, grinding
(R = Me) or MW radiation (R = But); ii, AlR31 (R1 = Me, Et), toluene,
r.t., 15 h.; iii, LiBun, thf or toluene, ꢁ80 °C–r.t., 6 h.; iv, 1/2 MeAlCl2,
toluene, ꢁ80 °C–r.t., 15 h.; v, 1/2 AlCl3, thf, ꢁ80 °C–r.t., 15 h.; vi,
LiHBEt3, thf, ꢁ80 °C–r.t., 15 h.; vii, 1/3 AlCl3, thf, ꢁ80 °C–r.t., 15 h;
viii, 1 or 2 equiv. of AlMe3, toluene, r.t., 15 h.
Me
N
N
N
Ph
N
N
Me
Me
Me
Me
Me
Ph
6a
6b

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Z.-X. Wang, D. Yang / Journal of Organometallic Chemistry 690 (2005) 4080–4086
The structures of complexes 2a and 5 were further
to linear. The bite angles N1–Al1–O1 and N3–Al1–O2
(90.30(8)° and 90.89(8), respectively) are narrower than
that in 2a, but wider than those in ½RAlfOCðMeÞ-
CHCðMeÞNð2; 6-Pr2i C6H3Þg2ꢀ (R = Me, Et. av. 87.58°
and 87.43°, respectively) [15]. The Al–N distance of
characterized by single crystal X-ray diffraction. The
structure of 2 is presented in Fig. 1 along with selected
bond lengths and angles. Crystalline 2a is monomeric.
The fused six-membered ring Al1N1N2C6C7O1 is
coplanar with the pyrazolato moiety as well as the phe-
nyl ring. The geometry at the aluminum atom is a dis-
torted tetrahedron with angles ranging from 94.81(13)°
to 114.9(2)°. The most acute angle is associated with
the bite angle of the chelate ligand, which is close to
corresponding those in ½Et2AlfOCðMeÞCHCðMeÞN-
˚
average 2.0317 A is normal for a five-coordinated alumi-
num complex with N,O-chelate ligands. For example,
the Al–N distances in ½RAlfOCðMeÞCHCðMeÞN-
ð2; 6-Pri2C6H3Þg2ꢀ (R = Cl, Me, Et) range from
˚
2.021(12) to 2.0678(17) A [15]. The Al–O distance of
˚
average 1.7463 A is close to that in 2a, but shorter than
ð2; 6-Pri C6H3Þgꢀ [94.56(9)°] [13] and [Et2Al{Sal(But)}]
in the five-coordinated complexes ½RAlfOCðMeÞ-
CHCðMeÞNð2; 6-Pr2i C6H3Þg2ꢀ (R = Cl, Me, Et), which
2
˚
[94.97(6)°] [14]. The Al1–N1 distance of 1.940(3) A is a
˚
ranging between 1.799(9) and 1.8202(16) A.
little shorter than those found in ½R2AlfOCðMeÞCHC-
i
˚
ðMeÞNð2; 6-Pr2C6H3Þgꢀ (R = Me, 1.954(6) A; R = Et,
The structure of complex 6 was also determined by
single crystal X-ray diffraction, but the data quality is
poor due to the crystal quality. However, the structure
has been solved and proves that the central aluminum
atom is six-coordinated in the solid state as shown in
6a. This coordination mode is different from that in
the solution proved by 1H and 27Al NMR spectroscopy.
t
1.958(2) A) [15] and in [Et2Al{Sal(Bu )}] (1.976(2) A)
˚
˚
˚
[16]. The Al1–O1 distance of 1.747(3) A is also shorter
than corresponding those in ½Me2AlfOCðMeÞCHC-
ðMeÞNð2; 6-Pri C6H3Þgꢀ and [Et2Al{Sal(But)}] (1.795(5)
2
˚
and 1.772(1) A, respectively). However, The distances
of Al1–N1 and Al1–O1 are still within the normal
ranges for a four-coordinated alkyl aluminum complex
˚
[10b,17]. The C6–C7 distance of 1.327(5) A shows a
double bond between the atoms.
3. Experimental
The structure of 5 is presented in Fig. 2 along with se-
lected bond lengths and angles. Complex 5 is monomeric
in the solid state and the aluminum atom is five-coordi-
nated. The coordination geometry is a distorted trigonal
bypyramid with N1 and N3 atoms in axial positions and
Cl1, O1 and O2 atoms in equatorial positions. The Cl1,
O1, O2 and Al1 atoms are coplanar, the total angles of
the trigonal plane being 360°. The N1–Al1–N3 angle of
176.68(8)° shows that the arrange of the atoms is close
3.1. General methods
All experiments were performed under nitrogen using
standard Schlenk and vacuum line techniques. Solvents
were distilled under nitrogen over sodium (toluene),
Fig. 2. ORTEP drawing of complex 5 with 30% probability thermal
ellipsoids. All hydrogen atoms have be omitted for clarity. Selected
˚
bond lengths (A) and bond angles (°): Al1–Cl1 2.1816(9), Al1–O1
Fig. 1. ORTEP drawing of complex 2a with 30% probability thermal
ellipsoids. All hydrogen atoms have be omitted for clarity. Selected
1.7468(16), Al1–N1 2.0347(18), Al1–O2 1.7459(16), Al1–N3
2.0287(19), O1–C7 1.333(3), O2–C20 1.328(2), C6–C7 1.331(3), C19–
C20 1.331(3), C6–N2 1.393(3), C19–N4 1.403(3); Cl1–Al1–O1
118.82(7), Cl1–Al1–O2 117.53(7), Cl1–Al1–N1 91.95(6), Cl1–Al1–N3
91.36(6), N1–Al1–N3 176.67(8), N1–Al1–O1 90.30(8), N1–Al1–O2
87.91(8), N3–Al1–O1 87.79(8), N3–Al1–O2 90.89(8), O1–Al1–O2
123.65(9).
˚
bond lengths (A) and bond angles (°): Al1–C14 1.948(3), Al1–O1
1.747(3), Al1–N1 1.940(3), C7–O1 1.322(4), C6–C7 1.327(5), C6–N2
1.419(4); N1–Al1–O1 94.81(13), O1–Al1–C14 112.54(12), C14–Al1–
C140 114.9(2), N1–Al1–C14 110.16(12), C7–O1–Al1 130.9(2), N2–N1–
Al1 122.6(2), N2–C6–C7 125.6(3).

Z.-X. Wang, D. Yang / Journal of Organometallic Chemistry 690 (2005) 4080–4086
4083
sodium–benzophenone (thf, Et2O and n-hexane) or
3.4. Synthesis of [Me2AlOC(Ph)CH{(3,5-Me2-
C3HN2)-1}] (2a)
CaH2 (CH2Cl2) and degassed prior to use. C6D6 were
purchased from Acros Organics and stored over Na/K
alloy and degassed prior to use. CDCl3 was purchased
A solution of 1a (0.306 g, 1.43 mmol) in toluene
(10 ml) was cooled to about ꢁ80 °C. To the solution
was added AlMe3 (2.3 M solution in hexane, 0.65 ml,
1.49 mmol) with stirring. The mixture was stirred over-
night at room temperature and the resulted solution
was filtered. Concentration of the filtrate afforded color-
less crystals of 2a (0.213 g, 55%), m.p. 160–162 °C. Anal.
Calc. for C15H19N2OAl: C, 66.65; H, 7.08; N, 10.36.
Found: C, 66.48; H, 7.12; N, 10.29%. 1H NMR
(C6D6): d ꢁ0.05 (s, 6H, AlMe2), 1.47 (s, 3H, Me), 2.10
(s, 3H, Me), 5.29 (s, 1H, CH), 6.26 (s, 1H, CH), 7.25-
7.35 (m, 3H, Ph), 7.96–7.99 (m, 2H, Ph). 13C NMR
(C6D6): d ꢁ8.90, 10.42, 12.32, 96.76, 106.35, 125.78,
128.53, 128.67, 138.66, 139.06, 146.31, 149.57.
˚
from Acros Organics and stored over 4 A molecular
sieve. AlMe3, AlEt3, LiBun and LiHBEt3 were pur-
chased from Alfa Acesar and used as received. 3,5-
Disubstituted pyrazoles were prepared according to
the literature [18]. NMR spectra were recorded on a
Bruker av300 spectrometer at ambient temperature.
The chemical shifts of 1H and 13C NMR spectra are ref-
erenced to internal solvent resonances and the 27Al
NMR spectra are referenced to external AlCl3 in D2O.
IR spectra were determined on a Bruker VECTOR-22
spectrometer. Elemental analyses were performed by
the Analytical Center of University of Science and Tech-
nology of China.
3.2. Synthesis of 1-PhC(O)CH2-3,5-Me2C3HN2 (1a)
3.5. Synthesis of [Me2AlOCðPhÞCH{ð3; 5-But2-
C3HN2Þ-1}]ð2bÞ
A mixture of 3,5-dimethylpyrazole (3.84 g, 40 mmol),
PhC(O)CH2 Br (7.96 g, 40 mmol) and Na2CO3 (2.12 g,
20 mmol) in a motar was ground using a pestle for
20 min. The mixture was set aside for 4 h. The resulted
solid was washed with water and dried in air to give
1a ꢂ H2O (6.51 g, 70%), m.p. 80–84 °C. Anal. Calc. for
2b was prepared using a similar method to that for
2a. Reaction of 1b (0.262 g, 0.88 mmol) with AlMe3
(2.3 M solution in hexane, 0.40 ml, 0.92 mmol) in tolu-
ene (10 ml) gave colorless crystals of 2b (0.21 g, 68%),
m.p. 144–148 °C. Calc. for C21H31N2OAl: C, 71.16; H,
1
C13H16N2O2: C, 67.22; H, 6.94; N, 12.06. Found: C,
8.81; N, 7.90. Found: C, 70.74; H, 8.80; N, 7.79%. H
1
67.02; H, 7.14; N, 12.03%. H NMR (CDCl ): d 1.75
NMR (C6D6): d 0.10 (s, 6H, AlMe2), 1.11 (s, 9H, But),
1.41 (s, 9H, But), 6.02 (s, 1H, CH), 7.01 (s, 1H, CH),
7.22–7.34 (m, 3H, Ph), 8.06-8.09 (m, 2H, Ph). 13C
NMR (C6D6): d 1.42, 28.94, 30.98, 31.69, 32.62,
100.62, 102.77, 125.76, 128.17, 128.71, 128.88, 138.44,
150.09, 152.36, 161.33.
3
(s, 2H, H2O), 2.16 (s, 3H, Me), 2.24 (s, 3H, Me), 5.45
(s, 2H, CH2), 5.91 (s, 1H, CH), 7.48–7.53 (m, 2H, Ph),
7.59-7.63 (m, 1H, Ph), 7.96–7.99 (m, 2H, Ph). 13C
NMR (CDCl3): d 11.14, 13.61, 55.45, 106.02, 128.27,
129.06, 134.07, 134.88, 140.69, 148.51, 192.90. IR (KBr
disc): mC@O 1689 cmꢁ1. 1a can be obtained by heating
1a Æ H2O under vacuum.
3.6. Synthesis of [Et2AlOC(Ph)CH{(2,4-Me2-
C3HN2)-1}] (2c)
3.3. Synthesis of 1-PhC(O)CH2-3; 5-But2C3HN2 (1b)
2c was prepared using a similar method to that for 2a.
Reaction of 1a (0.307 g, 1.43 mmol) with AlEt3 (1.8 M
solution in hexane, 1.5 ml, 2.70 mmol) in toluene
(10 ml) gave colorless crystals of 2c (0.136 g, 32%),
m.p. 102–104 °C. Anal. Calc. for C17H23N2OAl: C,
A
mixture of 3,5-di-tert-butylpyrazole (1.29 g,
7.17 mmol), PhC(O)CH2Br (1.43 g, 7.18 mmol) and
Na2CO3 (0.38 g, 3.58 mmol) was radiated using micro-
wave (80 W) for 15 min. The mixture was added water
and extracted with Et2O. The ether layer was dried
with Na2SO4 and then concentrated to give 1b with
minor starting materials. The mixture was heated at
80 °C under vacuum for 1 h and then recrystallized
from Et2O to give colorless crystals of 1b (1.66 g,
78%), m.p. 143–144 °C. Anal. Calc. for C19H26N2O:
C, 76.47; H, 8.78; N, 9.39. Found: C, 76.65; H, 8.98;
N, 9.54%. 1H NMR (CDCl3): d 1.21 (s, 9H, But),
1.22 (s, 9H, But), 5.58 (s, 2H, CH2), 5.88 (s, 1H,
CH), 7.41 (t, J = 7.8 Hz, 2H, Ph), 7.53 (t, J = 7.8 Hz,
1H, Ph), 7.85–7.88 (m, 2H, Ph). 13C NMR (CDCl3):
d 30.41, 30.70, 31.38, 32.05, 57.95, 100.82, 128.12,
128.93, 133.75, 135.21, 152.21, 160.85, 193.75. IR: mC@O
68.44; H, 7.77; N, 9.39. Found: C, 68.54; H, 7.46; N,
1
9.54%. H NMR (C6D ): d 0.48–0.89 (m, 4H, AlCH2),
6
1.49 (s, 3H, Me), 1.50 (t, J = 8.1 Hz, 6H, Me), 2.14 (s,
3H, Me), 5.35 (s, 1H, CH), 6.27 (s, 1H, CH), 7.24–
7.35 (m, 3H, Ph), 7.96–7.99 (m, 2H, Ph). 13C NMR
(C6D6): d 0.99, 9.50, 10.48, 12.25, 96.76, 106.34,
125.72, 128.55, 128.69, 138.62, 139.37, 146.48, 149.92.
3.7. Synthesis of [MeAl(OC(Ph)CH{(2,4-Me2C3HN2)-
1})2 Æ C6H5Me] (4 Æ C6H5Me)
To a suspension of AlCl3 (0.123 g, 0.92 mmol) in tol-
uene (10 ml) was added AlMe3 (2.3 M solution in hex-
ane, 0.20 ml, 0.46 mmol) at room temperature with
1699 cmꢁ1
.

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Z.-X. Wang, D. Yang / Journal of Organometallic Chemistry 690 (2005) 4080–4086
stirring. After stirring for 4 h, the solution was cooled to
about ꢁ80 °C and a solution of [LiOC(Ph)CH{(3,5-
Me2C3HN2)-1}] prepared from 1a (0.59 g, 2.76 mmol)
and LiBun (2.89 M solution in hexane, 0.95 ml,
2.76 mmol) in toluene was added. The mixture was
warmed to room temperature and stirred overnight.
The solution was filtered and the filtrate was concen-
trated to generate pale yellow crystalline 4 Æ C6H5Me
(0.306 g, 40%), m.p. 190–192 °C. Calc. for C34H37-
N4O2Al: C, 72.84; H, 6.65; N, 9.99. Found: C, 72.87;
7.09–7.23 (m, 7H, Ph + CH), 7.25 (s, 5H, Ph), 7.33 (t,
J = 7.5 Hz, 4H, Ph), 7.87–7.90 (m, 2H, Ph), 8.01 (d,
J = 7.5 Hz, 4H, Ph). 13C NMR (C6D6): d 10.91, 13.03,
14.21, 14.34, 21.42, 96.11, 98.21, 105.59, 106.95,
125.54, 125.70, 125.90, 127.37, 127.57, 127.91, 128.57,
129.34, 135.95, 136.35, 137.25, 137.90, 139.29, 141.69,
146.24, 148.12, 150.79, 151.42. 27Al NMR (C6D6): d 60.
Complex 6 was also obtained by reaction between
lithiated 1a and AlCl3. Compound 1a (0.642 g, 3 mmol)
was lithiated by reaction with LiBun (2.89 M in hexane,
1.04 ml, 3 mmol) in thf. The solution was cooled to
about ꢁ80 °C and AlCl3 (0.133 g, 1 mmol) was added.
The mixture was warmed to room temperature and
stirred overnight. Solvents were removed in vacuo
and the residue was extracted with toluene. The mix-
ture was filtered and the filtrate concentrated to afford
colorless crystalline complex 6 Æ C6H5Me (0.559 g,
74%).
1
H, 6.45; N, 9.88%. H NMR (C6D6): 0.04 (s, 3H, Me),
1.66 (s, 6H, Me), 2.20 (3H, PhMe), 2.68 (s, 6H, Me),
5.66 (s, 2H, CH), 6.52 (s, 2H, CH), 7.10–7.36 (m, 11H,
Ph), 7.90–7.94 (m, 4H, Ph). 13C NMR (C6D6): d 10.60,
14.41, 21.42, 97.80, 106.41, 125.64, 125.70, 126.64,
127.85, 128.56, 129.34, 136.38, 137.90, 140.01, 146.97,
147.70.
3.8. Synthesis of [ClAl(OC(Ph)CH{(2,4-Me2-
C3HN2)-1})2] (5)
3.10. Reaction of complex 5 with AlMe3
LiBun (2.89 M solution in hexane, 0.97 ml,
2.80 mmol) was added to a solution of 1a (0.60 g,
2.80 mmol) in thf (10 ml) at about ꢁ80 °C with stirring.
After stirring for 4 h at room temperature, the solution
was recooled to about ꢁ80 °C and AlCl3 (0.187 g,
1.40 mmol) was added. The mixture was warmed to
room temperature and stirred overnight. Volatiles were
removed in vacuo and the residue was extracted with
CH2Cl2. The mixture was filtered and the filtrate was
concentrated to about 1 ml. Several drops of Et2O was
added to form colorless crystals of 5 (0.50 g, 73%),
m.p. 218–221 °C. Anal. Calc. for C26H26N4O2ClAl: C,
63.68; H, 5.36; N, 11.46. Found: C, 63.72; H, 5.41; N,
To a solution of complex 5 (0.446 g, 0.91 mmol) in
toluene (10 ml) was added AlMe3 (2.3 M solution in
hexane, 0.83 ml, 1.82 mmol) at room temperature with
stirring. The mixture was stirred for 12 h and then
Table 1
Details of the X-ray structure determinations of complexes 2a and 5
2a
5
Empirical formula
FW
C
15H19N2OAl
C26H26ClN4O2Al
488.94
Triclinic
270.30
Orthorhombic
Pnma
9.3911(16)
7.2864(19)
22.101(6)
90
Crystal system
Space group
ꢀ
P1
˚
a (A)
9.6016(16)
9.7544(16)
13.453(2)
83.340(2)
85.521(3)
83.632(3)
1241.0(4)
2
˚
1
b (A)
11.65%. H NMR (CDCl3): d 2.31 (s, 6H, Me), 2.46
˚
c (A)
(s, 6H, Me), 5.97 (s, 2H, CH), 6.63 (s, 2H, CH), 7.18–
7.26 (m, 6H, Ph), 7.54–7.57 (m, 4H, Ph). 13C NMR
(CDCl3): d 11.62, 14.87, 98.10, 107.36, 125.13, 128.01,
128.27, 129.22, 137.03, 138.27, 146.46, 148.33.
a (°)
b (°)
c (°)
90
90
3
˚
V (A )
1512.3(6)
4
1.187
Z
Dcalc. (g/cm3)
F(000)
1.308
512
3.9. Synthesis of [Al(OC(Ph)CH{(3,5-Me2-
C3HN2)-1})3 Æ C6H5Me] (6 Æ C6H5Me)
576
0.128
1.84 to 25
l (mmꢁ1
)
0.220
1.53 to 26.36
h range for data
collections (°)
To a stirred solution of 5 (0.143 g, 0.29 mmol) in thf
(10 ml) was added LiHBEt3 (1 M solution in thf,
0.29 ml, 0.29 mmol) at about ꢁ80 °C. The mixture was
warmed to room temperature and stirred overnight. Sol-
vents were removed and the residue was dissolved in tol-
uene. The solution was filtered and the filtrate was
concentrated to give colorless crystals of complex
6 Æ C6H5Me (0.088 g, 59%), m.p. 194–196 °C. Anal.
Calc. for C46H47N6O3Al: C, 72.80; H, 6.24; N, 11.07.
Found: C, 72.67; H, 6.28; N, 10.98%. 1H NMR
(C6D6): 1.63–1.72 (b, 6H, Me), 1.77 (s, 3H, Me), 2.17
(s, 6H, Me), 2.20 (s, 3H, MePh), 2.30 (s, 3H, Me),
5.58 (s, 1H, CH), 5.66 (s, 2H, CH), 6.60 (s, 1H, CH),
Number of reflections
collected
Number of independent
7372
7161
1448 (0.0496)
1448/0/115
4982 (0.0200)
4982/0/311
reflections (Rint
Number of data/
)
restraints/parameters
Goodness-of-fit on F2
Final R indicesa [I > 2r(I)]
1.150
1.025
R1 = 0.0482
wR2 = 0.1341
R1 = 0.0812
wR2 = 0.1759
0.248 and ꢁ0.336
R1 = 0.0447
wR2 = 0.1144
R1 = 0.0713
wR2 = 0.1344
0.185 and ꢁ0.214
R indices (all data)
Largest difference peak
ꢁ3
˚
and hole (e Æ A
)
2
1=2
a
R1 = RiFo| ꢁ |Fci/R|Fo|; wR2 ¼ ½RwðF 2o ꢁ F c2Þ =RwðF o4Þꢀ
.

Z.-X. Wang, D. Yang / Journal of Organometallic Chemistry 690 (2005) 4080–4086
4085
´ ˆ
(b) D. Mecerreyes, R. Jerome, P. Dubois, Adv. Polym. Sci. 147
(1999) 1.
filtered. The filtrate was concentrated to form colorless
crystalline complex 2a (0.272 g, 55%).
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with an equiv of AlMe3 (2.3 M solution in hexane,
0.16 ml, 0.35 mmol) gave colorless crystals (0.086 g)
identified by NMR spectroscopy as a mixture of 2a
and 7. The ratio of 2a to 7 is about 3.6:1.
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˚
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data and experimental details of the structure determi-
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4. Supplementary materials
(e) N. Jaber, D. Gelman, H. Schumann, S. Dechert, J. Blum,
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Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic
Data Centre CCDC Nos. 266571 and 266572 for 2a
and 5. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ UK (fax: +44 1223 336
033; email: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
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Acknowledgments
We thank the National Natural Science Foundation
of China for financial support (project code 20272056)
and professors H.-G. Wang and H.-B. Song of Nankai
University for carrying out the X-ray structure
determinations.
(b) P.A. Cameron, V.C. Gibson, C. Redshaw, J.A. Segal, G.A.
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