Aluminum complexes with bidentate N,N-dialkylaniline-arylamido ligands: Synthesis, structures, and catalytic properties for efficient ring-opening polymerization of ε-caprolactone

Article abstract of DOI:10.1002/ejic.200900158

A number of Al complexes bearing bidentate N,N-dialkylaniline-arylamido ligands, OrMo-(ArNCH₂)C₆H₄NR ₂AlMe₂ (R = Me, Ar = 2,6-iPr₂C ₆H₃, 3a; 2,6-Et₂C_6<

Full text of DOI:10.1002/ejic.200900158

FULL PAPER
DOI: 10.1002/ejic.200900158
Aluminum Complexes with Bidentate N,N-Dialkylaniline–arylamido Ligands:
Synthesis, Structures, and Catalytic Properties for Efficient Ring-Opening
Polymerization of ε-Caprolactone
Aihong Gao,[a] Ying Mu,*[a] Jingshun Zhang,[a] and Wei Yao[a]
Keywords: Aluminum / Ring-opening polymerization / N ligands
A number of Al complexes bearing bidentate N,N-dialk-
ylaniline–arylamido ligands, ortho-(ArNCH2)C6H4NR2AlMe2
(R = Me, Ar = 2,6-iPr2C6H3, 3a; 2,6-Et2C6H3, 3b; 2,6-
Me2C6H3, 3c; 4-MeC6H4, 3d; Ph, 3e; and R = Et, Ar = 2,6-
iPr2C6H3, 3f; 2,6-Me2C6H3, 3g; Ph, 3h), have been synthe-
sized from the reaction of the corresponding free ligands, or-
tho-(ArNHCH2)C6H4NR2 (R = Me, Ar = 2,6-iPr2C6H3, 2a; 2,6-
Et2C6H3, 2b; 2,6-Me2C6H3, 2c; 4-MeC6H4, 2d; Ph, 2e; and R
= Et, Ar = 2,6-iPr2C6H3, 2f; 2,6-Me2C6H3, 2g; Ph, 2h), with
AlMe3 (1 equiv.). All complexes were characterized by 1H
and 13C NMR spectroscopy and elemental analysis. Single-
crystal X-ray diffraction analysis of complexes 3c and 3e re-
vealed that these Al complexes have a distorted tetrahedral
geometry around the metal center. All complexes were found
to be efficient catalysts for the ring-opening polymerization
of ε-caprolactone (CL) in the presence of benzyl alcohol, and
complexes 3a–h catalyze the polymerization of CL in a living
fashion.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
tivity of this type of catalysts was found to decrease with
an increase in the steric hindrance of the ligands. To further
modify the ligand and examine the steric effect of the li-
gand, we have developed a number of new Al complexes
bearing bidentate N,N-dialkylaniline–arylamido ligands.
From a structural point of view, the steric hindrance of the
new ligands should be moderate in comparison to those of
the salicylaldimine ligands and the N-arylanilido–arylimine
ligands. The new Al complexes were found to be efficient
catalysts for the ROP of CL in the presence of benzyl
alcohol (BnOH). In this paper, we wish to report the syn-
Introduction
The synthesis of poly(ε-caprolactone) (PCL) and poly-
(lactide) (PLA) as well as their copolymers have received
considerable attention because of their potential applica-
tions in medicine, pharmaceutics, and tissue engineering
such as delivery medium for the controlled release of drugs,
scaffolds, and the delivery of antibodies and genes.[1] The
signal-site metal complex catalyzed ring-opening polymeri-
zation (ROP) of ε-caprolactone (CL) is the major method
used to synthesize PCL due to its good control over the
molecular weight of the polymerization product.[2]
A
thesis
of
the
Al
complexes
ortho-(ArNCH2)-
number of main-group and transition-metal complexes, in-
cluding magnesium,[3] calcium,[4] aluminum,[5] titanium,[6]
iron,[7] zinc,[8] tin,[9] and rare-earth metal[10] complexes sup-
ported by various ligands have been reported to be efficient
catalysts for the ROP of CL. Among these catalysts, Al
complexes are the most intensely studied catalysts due to
their high Lewis acidity. A series of salicylaldimine–alumi-
num complexes have been reported by Nomura and co-
workers that are efficient catalysts for the ROP of CL, and
the catalytic activity of this type of complexes was found
to increase with increasing steric bulk of their ligands.[11]
Recently, our group reported a similar type of Al catalysts
with N-arylanilido–arylimine ligands.[12] The catalytic ac-
C6H4NR2AlMe2 (R = Me, Ar = 2,6-iPr2C6H3, 3a; 2,6-
Et2C6H3, 3b; 2,6-Me2C6H3, 3c; 4-MeC6H4, 3d; Ph, 3e; and
R = Et, Ar = 2,6-iPr2C6H3, 3f; 2,6-Me2C6H3, 3g; Ph, 3h)
as well as their catalytic properties for the ROP of CL.
Results and Discussion
Synthesis and Spectroscopic Characterization of the Free
Ligands and Their Al Complexes
Al complexes 3a–h were synthesized from the reaction of
corresponding free ligands ortho-(ArNHCH2)C6H4NR2 (R
= Me, Ar = 2,6-iPr2C6H3, 2a; 2,6-Et2C6H3, 2b; 2,6-
Me2C6H3, 2c; 4-MeC6H4, 2d; Ph, 2e; and R = Et, Ar = 2,6-
iPr2C6H3, 2f; 2,6-Me2C6H3, 2g; Ph, 2h) with AlMe3
(1 equiv.), as shown in Scheme 1. ortho-Dimethylami-
nobenzaldehyde (A) and ortho-diethylaminobenzaldehyde
(B) were prepared by treatment of N,N-dimethylaniline and
N,N-diethylaniline with nBuLi (1 equiv.), followed by reac-
[a] State Key Laboratory for Supramolecular Structure and Mate-
rials, School of Chemistry, Jilin University,
2699 Qianjin Street, Changchun 130012, P. R. China
Fax: +86-431-85193421
E-mail: ymu@mail.jlu.edu.cn
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200900158.
Eur. J. Inorg. Chem. 2009, 3613–3621
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3613

A. Gao, Y. Mu, J. Zhang, W. Yao
FULL PAPER
tion with DMF. Preligands 1a–h were synthesized by con- sponding 13C NMR resonances for the carbon atoms of the
densation between A or B and a substituted aniline in meth- AlMe2 group in the regions of δ = –9.78 to –10.51 ppm for
anol. Reduction of preligands 1a–h with LiAlH4 in ethyl 3a–h.
ether gave free ligands 2a–h. Among these compounds, 1d,
1e, 1h, and 2e have been reported previously.[13] All new
compounds were characterized by H and 13C NMR spec-
troscopy along with elemental analyses. The 1H NMR spec-
tra of preligands 1a–c and 1f–g exhibit a resonance in the
range of δ = 8.50–8.80 ppm for the imino N=CH proton,
with the corresponding 13C NMR resonance around δ =
160 ppm. The NH resonance in free ligands 2a–d and 2f–h
appears at characteristically middle field about δ =
3.90 ppm.
1
X-ray Crystallographic Analysis
The molecular structure of complex 3c is shown in Fig-
ure 1. Selected bond lengths and angles for 3c are given in
Table 1. X-ray analysis revealed that the Al center of com-
plex 3c adopts a distorted tetrahedral geometry with the
metal center chelated by the amine and amido nitrogen
atoms of the bidentate ligand. The six-membered chelating
ring has a legless chair geometry and the aluminum atom
occupies the top position of the backrest. The torsion angle
between the plane of N1–Al–N2 and the plane of C6–C7–
N1 is 57.6°, which is an indication of how far the Al atom
is out of the plane of the aniline backbone. The N1–Al–N2
angle [94.23(12)°] in the complex is close to those in related
known Al complexes.[14] The Al–N2 (amido) distance
[1.809(3) Å] is shorter than the Al–N1 (amine) distance
[2.027(3) Å], which indicates the Al–N (amine) coordina-
tion bond character.
Figure 1. The molecular structure of complex 3c. Thermal ellip-
soids are shown at the 30% probability level. Hydrogen atoms are
omitted for clarity.
Scheme 1. Synthetic procedure of ligands 2a–h and complexes 3a–
h.
Complex 3e crystallizes with two independent molecules
Al complexes 3a–h were obtained in good yields by al- (assigned as 3e1 and 3e2) in an asymmetric unit cell. The
kane elimination reaction as shown in Scheme 1. The reac- structure of molecule 3e1 is shown in Figure 2, and the
tion of free ligands 2a–h with AlMe3 (1.0 equiv.) affords Al structures of both molecules 3e1 and 3e2 are given in Fig-
complexes 3a–h. The disappearance of the N–H signal of ure S1 (Supporting Information). The two molecules have
the free ligands and the appearance of the resonances for similar conformation and structural parameters. Selected
the protons of AlMe2 (δ = –0.60 to –1.04 ppm) for com- bond lengths and angles for 3e are given in Table 1. The
1
plexes 3a–h in high-field regions in the H NMR spectra structural feature around the Al atom in 3e is similar to
demonstrate the formation of the desired complexes. Com- that in 3c, adopting a distorted tetrahedral geometry with
plexes 3a–h were all characterized by 1H and 13C NMR the four-coordinate metal center chelated by the amine and
spectroscopy and elemental analyses. As mentioned above, amido nitrogen atoms of the bidentate ligand. The torsion
1
the H NMR spectra of complexes 3a–h all exhibit charac- angles between the plane of N1–Al–N2 and the plane of
teristic resonances for the protons of AlMe2, with the corre- C6–C7–N1 are 55.5 and 57.2° for 3e1 and 3e2, respectively.
3614
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3613–3621

Al Complexes with Bidentate N,N-Dialkylaniline–arylamido Ligands
Table 1. Selected bond lengths [Å] and angles [°] for 3c and 3e.
Complex 3c
whereas no reaction takes place in the absence of BnOH
(Table 2, Entries 1–5). The ortho-(ArNCH2)C6H4NMe2-
AlMe2 complexes 3a–e were synthesized and studied as cat-
alysts for the ROP of CL first and it was found that their
catalytic activity under the same conditions is in the order
of 3a Ͼ 3b Ͼ 3c Ͼ 3d Ͼ 3e (Table 2, Entries 6–10). These
results indicate that increasing the steric hindrance of the
aryl group at the amido N atom in the ligands of these
complexes can considerably increase their catalytic activity.
A similar phenomenon has been observed in the salicylald-
imine–aluminum catalyst system.[11] However, reverse re-
sults were obtained with the bulky N-arylanilido–arylimine
Al catalyst system.[12] To systematically examine and cor-
rectly understand the steric effect of the ligands on the cata-
lytic activity of the new type of complexes, ortho-(ArNCH2)-
C6H4NEt2AlMe2 complexes 3f–h were then synthesized and
their catalytic properties for the ROP of CL was studied.
It is interesting to find that the catalytic activities of these
complexes increases first and then decreases with an in-
crease in the steric hindrance of the aryl group at the amido
N atom in their ligands (Table 2, Entries 25–27). These re-
sults indicate that catalysts of this type require their ligands
with adequate steric hindrance to show the highest catalytic
activity. A too-bulky ligand may block the coordination and
insertion of the monomer, whereas a less-bulky ligand
might allow the coordination of the ester linkages in the
polymer chain. For complexes 3a–e, the NMe2 group is
small in size, which results in these complexes requiring a
bulky aryl group at the amido N atom in their ligands to
demonstrate good catalytic activity. To examine the effect
of reaction conditions on the catalytic activity of the new
catalyst system, polymerization experiments under different
conditions were conducted with complex 3a in the presence
of BnOH. The role of BnOH in the ROP of CL has been
studied and reported previously.[12,15] Under similar condi-
tions, the catalytic activity of 3a was observed to change
obviously with the change in the BnOH/Al molar ratio, and
the highest catalytic activity was obtained with a BnOH/Al
molar ratio of 2:1. It was found that the number-averaged
degree of polymerization (DPn) of the obtained polymers
Al–N1
Al–N2
Al–C2
Al–C1
C5–N2
N2–Al–C1
2.027(3)
1.809(3)
1.959(4)
1.952(4)
1.450(4)
119.06(16)
N2–Al–C1
C1–Al–C2
N1–Al–N2
N1–Al–C2
N1–Al–C1
114.52(16)
113.7(2)
94.23(12)
103.22(15)
108.94(16)
Complex 3e1
Complex 3e2
Al1–N1
Al1–N2
2.032(2)
1.863(2)
Al2–N3
Al2–N4
2.035(2)
1.860(2)
Al1–C16
Al1–C17
1.963(2)
1.968(2)
Al2–C33
Al2–C34
1.961(2)
1.965(2)
C9–N2
1.459(3)
C26–N4
1.464(3)
N2–Al1–C16
N2–Al1–C17
C16–Al1–C17
N1–Al1–N2
N1–Al1–C16
N1–Al1–C17
114.77(10)
115.25(10)
115.98(11)
95.82(8)
106.43(10)
105.52(10)
N4–Al2–C33
N4–Al2–C34
C33–Al2–34
N3–Al2–N4
N3–Al2–C33
N3–Al2–C34
114.31(10)
114.81(10)
116.74(11)
96.46(8)
106.97(10)
104.47(10)
The N1–Al–N2 bond angles [95.82(8) and 96.46(8)° for 3e1
and 3e2, respectively] are slightly larger than that in 3c. As
seen in 3c, the Al–N2 (amido) distances [1.863(2) and
1.860(2) Å] are also shorter than the Al–N1 (amine) dis-
tances [2.032(2) and 2.035(2) Å] in 3e. Both the Al–N1 and
Al–N2 distances in 3e are longer than those in 3c. The ob-
served differences in the bond lengths and angles between
3c and 3e may simply result from the packing force, as it
cannot be reasonably explained otherwise.
1
(calculated by H NMR) is close to the CL/BnOH molar
ratio, and the molecular weight (Mn) of the polymers deter-
mined by gel permeation chromatography is proportional
to the CL/BnOH molar ratio (Figure 3). Similar results
have previously been reported for other initiator sys-
tems,[12,16] which have been described as “immortal” poly-
merization. The polymerization reaction was also examined
at different reaction temperatures and the reactivity of com-
plex 3a was found to increase noticeably from 20 to 70 °C.
When the polymerization reaction was carried out at 20 °C
for different times, it was found that the DPn and Mn values
of the obtained polymers increase linearly with an increase
in polymer yields. These results demonstrate the “living”
character of the polymerization process with BnOH as a
Figure 2. The molecular structure of one (3e1) of the two indepen-
dent complexes present in the crystals of 3e. Thermal ellipsoids are
shown at the 30% probability level. Hydrogen atoms are omitted
for clarity.
Ring-Opening Polymerization of ε-Caprolactone Initiated
by 3a–e
Complexes 3a–h were systematically investigated for the co-initiator. In comparison with related known initiator sys-
ROP of CL. Representative experimental results are sum- tems, the reactivity of the present system is similar to that
marized in Table 2. Complexes 3a–h all show high reactivity of the N-arylanilido–arylimine Al catalyst system.[12] The
for catalyzing the ROP of CL in the presence of BnOH, 1H NMR spectrum of a typical PCL sample shows the pres-
Eur. J. Inorg. Chem. 2009, 3613–3621
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3615

A. Gao, Y. Mu, J. Zhang, W. Yao
FULL PAPER
Table 2. Ring-opening polymerization of ε-caprolactone initiated by complexes 3a–h.[a]
[d]
[e]
Entry
Cat. [BnOH]/[Al]/[CL] Temp.
Time
Yield
[%][b]
TOF[c]
DPn
Mn[e] ϫ103 Mn(SEC)[f] Mn(theor)[g] Mw/Mn
[°C]
ϫ103
ϫ103
1
2
3
4
5
6
7
8
3a
3b
3c
3d
3e
3a
3b
3c
3d
3e
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
4
0:1:100
0:1:100
0:1:100
0:1:100
0:1:100
2:1:100
2:1:100
2:1:100
2:1:100
2:1:100
0.5:1:100
1:1:100
4:1:100
2:1:100
2:1:100
2:1:200
2:1:300
2:1:400
2:1:450
2:1:400
2:1:400
2:1:400
2:1:400
0:1:100
2:1:100
2:1:100
2:1:100
70
70
70
70
70
70
70
70
70
70
70
70
70
50
20
70
70
70
70
20
20
20
20
70
70
70
70
24 h
24 h
24 h
24 h
24 h
0
0
0
0
–
–
–
–
–
–
–
–
–
49
53
56
47
51
197
97
27
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
0
–
–
–
–
–
3 min
4 min
4.7 min
6.5 min
7 min
18 min
14 min
10 min
7 min
12 min
5 min
7 min
9.3 min
12.7 min
9 min
18 min
27 min
36 min
3 min
5.5 min
5 min
8 min
96.5
94.3
95.1
96.7
95.8
93.2
95.7
92.6
94.9
93.4
96.2
98.1
96.3
95.3
46.5
70.2
85.0
92.4
97.1
92.1
94.6
95.2
1930
1414
1214
892
821
311
409
556
813
467
2308
2522
2485
2026
1240
936
755
616
1942
1005
1135
714
11.8
12.7
13.4
11.4
12.3
37.9
19.1
7.51
13.2
11.6
21.4
26.0
39.7
43.7
20.3
28.5
33.8
35.2
11.4
11.1
12.5
12.9
6.6
7.1
7.5
6.3
6.9
21.2
10.7
4.2
7.4
6.5
12.0
14.6
22.2
24.5
11.4
16.0
18.9
19.7
6.4
6.2
7.0
7.2
5.6
5.5
5.5
5.6
5.4
21.4
11.0
2.7
5.5
5.4
11.1
16.9
22.1
24.6
10.7
16.1
19.5
21.2
5.6
5.4
5.5
5.5
1.24
1.18
1.25
1.20
1.12
1.35
1.41
1.56
1.32
1.28
1.35
1.72
1.51
1.74
1.16
1.18
1.19
1.24
1.36
1.27
1.19
1.26
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
55
48
99
159
203
225
95
146
175
187
50
3f
3g
3h
46
52
54
[a] Polymerization conditions: catalyst (0.19 mmol), [CL] = 1  in toluene. [b] Isolated yield. [c] Mole of CL consumed per mol of catalyst
per hour. [d] The number-averaged degree of polymerization calculated by 1H NMR spectroscopy. [e] The molecular weight obtained
from GPC analysis. [f] SEC values of precipitated polymer samples corrected with the coefficient 0.56. [g] Calculated for one growing
polymer chain with Mn(theor) = {[ε-CL]0/[BnOH]0 ϫ114ϫ(conversion)+ 108}.
ence of a benzyl ester group at δ = 5.12 ppm (singlet,
CH2Ph) as the initiating chain end. These results suggest
that BnOH reacts first with the alkyl Al complexes to form
the LAl–OBn complexes as the catalytic active species. To
further confirm that the benzyloxyaluminum complex acts
as the active catalyst, benzyloxyaluminum complex 4 was
synthesized by reaction of 3a with BnOH (2 equiv.) and
used as catalyst for the ROP of CL (Figure 4A). It was
found that complex 4 shows similar catalytic activity to the
catalyst system of 3a/BnOH (1:2). The formation of Al-
[O(CH2)5C=O]nOCH2Ph intermediates during the polyme-
rization was confirmed by 1H NMR spectroscopy (Fig-
ure 4B), in which the signals of the methylene protons (c,
d, e, and f) of the polymer appear at δ = 4.22, 2.46, 1.81,
1.54 ppm, and the sharp signal at δ = 5.27 ppm arises from
the ending benzyl CH2 group.
Figure 3. Plot of Mn vs. [CL]/[BnOH] for the ROP of CL catalyzed
by complex 3a/BnOH in toluene at 70 °C.
On the basis of the above results, a mechanism for the
present polymerization system, similar to the one proposed
previously for the N-arylanilido–arylimine Al catalyst sys-
tem,[12] can be proposed as shown in Scheme 2. The benzyl- BnOH or acetic acid. BnOH acts as a chain initiator as well
oxyaluminum complexes are the active catalysts that are as a chain transfer reagent in the polymerization procedure.
produced by the reaction of the alkylaluminum complexes During the polymerization, excess BnOH (if any) would re-
with BnOH. The polymerization reaction takes place by re- act with the polymerization intermediates LAl–OP to re-
peated coordination of the CL monomer to the metal center place the –OP groups and form the free polymers and new
and insertion into the Al–O bond to form the polymeriza- active species. The formed shorter chain polymers would
tion intermediates LAl–OP (where P refers to the polymer also react with the polymerization intermediates with
chain). Free polymers can be released by the addition of longer polymer chains to produce longer chain free poly-
3616
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3613–3621

Al Complexes with Bidentate N,N-Dialkylaniline–arylamido Ligands
ometry with the metal center chelated by the amine and
amido nitrogen atoms of their bidentate ligands. Complexes
3a–h are all efficient catalysts for the ROP of CL in the
presence of benzyl alcohol and catalyze the polymerization
of CL in a living fashion. The catalytic activity of com-
plexes 3a–e increases with an increase in the steric bulk of
the aryl groups at the amido N atom in the N,N-dimeth-
ylaniline–arylamido ligands, whereas the catalytic activity
of complexes 3f–h increases first and then decreases with
an increase in the steric bulk of the aryl groups in the N,N-
diethylaniline–arylamido ligands. In addition, the catalytic
activity of these catalyst systems increases with an increase
in polymerization temperature from 20 to 70 °C and also
changes with the BnOH/Al molar ratio with the highest
catalytic activity being observed at the BnOH/Al molar ra-
tio of 2:1. Benzyloxyaluminum complex 4 was synthesized
and tested as the active catalyst for the ROP of CL, which
supports the proposed mechanism for the polymerization.
Figure 4. 1H NMR spectra of (A) complex 4 in CDCl3, and (B)
the reaction mixture of complex 4 and CL in CDCl3 at room tem-
perature.
Experimental Section
General: All reactions were performed using standard Schlenk tech-
niques in an atmosphere of high-purity nitrogen or glove-box tech-
niques. Toluene, hexane, and Et2O were dried by heating at reflux
over sodium and benzophenone and then distilled under nitrogen
prior to use. C6D6 and CDCl3 were dried with CaH2 for 48 h and
vacuum-transferred into an air-free flask. nBuLi and AlMe3 were
purchased from Aldrich and used as received. Compounds 1d, 1e,
and 2e were prepared according to a literature procedure.[11] 1H
and 13C NMR spectra were measured using a Varian Mercury-
300 NMR spectrometer. Elemental analyses were performed with
a Perkin–Elmer 2400 analyzer. GPC measurements were performed
with a Waters-410 system using CH2Cl2 as the eluent (flow rate:
1 mLmin–1, at 25 °C). Molecular weights and molecular weight dis-
tributions were calculated using polystyrene as standard.
mers and new polymerization intermediates. Finally, the po-
lymerization reaction stops when the monomer is totally
consumed.
ortho-C6H4(NMe2)CHO (A): After removal of the solvent of nBuLi
(79 mL, 79 mmol), N,N-dimethylaniline (10 mL) was added at 0 °C
with stirring, gently heating to 80 °C for 24 h, during which a yel-
low solid was formed. DMF (6.0 mL) in Et2O (40 mL) was added
to the mixture at 0 °C. After stirring for 12 h, the reaction was
quenched with H2O (30 mL), and the organic phase was separated,
washed with brine, and dried with magnesium sulfate. The solvent
was removed in vacuo to give the crude product as a yellow oil.
Pure product was obtained by column chromatography (10% ethyl
acetate in hexanes) as a yellow oil (9.2 g, 78%). C9H11NO (149.19):
1
Scheme 2. The proposed mechanism for the ROP of CL.
calcd. C 72.46, H 7.43, N 9.39; found C 72.38, H 7.38, N 9.26. H
NMR (300 MHz, CDCl3, 293 K): δ = 10.22 (s, 1 H, CHO), 7.75
(d, 1 H, Ph-H), 7.46 (d, 1 H, Ph-H), 7.06 (d, 1 H, Ph-H), 7.01 (t,
1 H, Ph-H), 2.92 (s, 6 H, NCH3) ppm. 13C{1H} NMR (75 MHz,
CDCl3, 293 K): δ = 191.05, 155.66, 134.49, 130.81, 126.89, 120.49,
117.51, 45.42 ppm.
Conclusions
In conclusion, several Al complexes supported by biden-
tate N,N-dimethylaniline–arylamido ligands and N,N-dieth-
ylaniline–arylamido ligands have been synthesized in good
yields by the reaction of free ligands 2a–h with AlMe3
ortho-C6H4(NEt2)CHO (B): Under an atmosphere of nitrogen,
nBuLi (35 mL, 35 mmol) was added dropwise to a stirred Et2O
solution (50 mL) of N,N-diethylaniline (5 mL) in the presence of
TMEDA (5 mL). The mixture was gently heated to reflux for 24 h.
DMF (3.1 mL) in Et2O (20 mL) was added to the mixture at 0 °C.
After stirring for 12 h, the reaction was quenched with H2O
(30 mL), and the organic phase was separated, washed with brine,
and dried with magnesium sulfate. The solvent was removed in
1
(1.0 equiv.). All complexes were fully characterized by H
and 13C NMR spectroscopy along with elemental analyses.
The structures of 3c and 3e were determined by X-ray crys-
tallography, and the structural analysis revealed that the Al
center of these complexes adopts a distorted tetrahedral ge- vacuo to give the crude product as a yellow oil. Pure product was
Eur. J. Inorg. Chem. 2009, 3613–3621
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3617

A. Gao, Y. Mu, J. Zhang, W. Yao
FULL PAPER
obtained by column chromatography (dichloromethane/hexane,
2:1) as a yellow oil (1.7 g, 30%). C11H15NO (177.24): calcd. C
der. C19H24N2 (280.41): calcd. C 81.38, H 8.63, N 9.99; found C
81.41, H 8.67, N 9.92. 1H NMR (300 MHz, CDCl3, 293 K): δ =
74.54, H 8.53, N 7.90; found C 74.49, H 8.50, N 7.94. 1H NMR 8.67 (s, 1 H, CH=N), 8.20 (d, 1 H, Ph-H), 7.45 (t, 1 H, Ph-H),
(300 MHz, CDCl3, 293 K): δ = 10.36 (s, 1 H, CHO), 7.82 (d, 1 H,
7.20–6.95 (m, 5 H, Ph-H), 3.08 (q, 4 H, NCH2CH3), 2.16 (s, 6 H,
Ph-H), 7.49 (t, 1 H, Ph-H), 7.17 (d, 1 H, Ph-H), 7.07 (d, 1 H, Ph- CH3), 0.99 (t, 6 H, NCH2CH3) ppm. 13C{1H} NMR (75 MHz,
H), 3.18 (q, 4 H, NCH2CH3), 1.06 (t, 6 H, NCH2CH3) ppm.
CDCl3, 293 K): δ = 161.87, 152.31, 152.10, 132.35, 131.48, 128.00,
13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 191.72, 154.34, 127.76, 127.18, 123.57, 123.39, 122.46, 48.64, 18.43, 12.33 ppm.
134.02, 128.60, 122.54, 122.15, 121.47, 48.72, 12.09 ppm.
ortho-C6H4(NMe2)CH2NHC6H3iPr2-2,6 (2a): A solution of Li-
ortho-C6H4(NMe2)CH=NC6H3iPr2-2,6 (1a): A solution of ortho- AlH4 (0.681 g, 18.0 mmol) in Et2O (10 mL) was added to a solution
C6H4(NMe2)CHO (2.24 g, 15.0 mmol) and 2,6-diisopropylaniline
(2.83 mL, 15.0 mmol) in MeOH (20 mL) was stirred at room tem-
perature for 12 h. The mixture was then cooled to 0 °C for a couple
of hours to precipitate the product. The precipitate was collected
on a filter and washed with cool MeOH (5 mL) to give the product
as a yellow crystalline material (3.7 g, 80%). C21H28N2 (308.46):
of 1a (3.70 g, 12.0 mmol) in Et2O (30 mL) at 0 °C. The mixture was
warmed to room temperature and stirred for 5 h. The reaction was
quenched with cooled H2O (20 mL), and the organic phase was
separated, washed with brine, and dried with magnesium sulfate.
The solvent was removed in vacuo to give the crude product as a
yellow oil. Pure product was obtained by distillation under reduced
1
calcd. C 81.77, H 9.15, N 9.08; found C 81.74, H 9.14, N 9.12. H
NMR (300 MHz, CDCl3, 293 K): δ = 8.58 (s, 1 H, CH=N), 8.24 C 81.24, H 9.74, N 9.02; found C 81.27, H 9.73, N 9.00. H NMR
pressure as a yellow solid (2.83 g, 76%). C21H30N2 (310.48): calcd.
1
(d, 1 H, Ph-H), 7.47 (t, 1 H, Ph-H), 7.03–7.16 (m, 5 H, Ph-H), 3.04
(300 MHz, CDCl3, 293 K): δ = 7.42 (d, 1 H, Ph-H), 7.28 (t, 1 H,
[m, 2 H, CH(CH3)2], 2.81 (s, 6 H, NCH3), 1.20 [d, 12 H, CH(CH3)2] Ph-H), 7.21 (d, 1 H, Ph-H), 7.05–6.11 (m, 4 H, Ph-H), 4.07 (s, 2
ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 160.26, 154.46, H, CH2N), 3.89 (br., 1 H, NH), 3.40 [m, 2 H, CH(CH3)2], 2.72 (s,
149.26, 137.21, 131.25, 128.74, 127.62, 123.36, 122.42, 122.25,
118.24, 45.27, 27.30, 22.08 ppm.
6 H, NCH3), 1.25 [d, 12 H, CH(CH3)2] ppm. 13C{1H} NMR
(75 MHz, CDCl3, 293 K): δ = 152.83, 143.58, 142.67, 135.16,
129.69, 128.16, 124.01, 123.62, 123.49, 120.01, 53.05, 45.30, 27.49,
24.34 ppm.
ortho-C6H4(NMe2)CH=NC6H3Et2-2,6 (1b): A mixture of ortho-
C6H4(NMe2)CHO (3.13 g, 21.0 mmol) and 2,6-diethylaniline
(3.46 mL, 21.0 mmol) in MeOH (20 mL) was stirred for 12 h. The
solvent was removed in vacuo to give the crude product as a yellow
oil. Pure product was obtained by column chromatography (5%
ethyl acetate in hexanes) as a yellow solid (4.95 g, 84%). C19H24N2
(280.41): calcd. C 81.38, H 8.63, N 9.99; found C 81.35, H 8.60, N
ortho-C6H4(NMe2)CH2NHC6H3Et2-2,6 (2b): This compound was
prepared in the same way as described above for 2a with 1b (3.53 g,
12.6 mmol) and LiAlH4 (0.720 g, 18.9 mmol) as starting materials.
The product (2.92 g, 82%) was obtained as a yellow solid.
C19H26N2 (282.42): calcd. C 80.80, H 9.28, N 9.92; found C 80.83,
10.05. 1H NMR (300 MHz, CDCl3, 293 K): δ = 8.59 (s, 1 H, H 9.26, N 9.91. H NMR (300 MHz, CDCl3, 293 K): δ = 7.47 (d,
1
CH=N), 8.16 (d, 1 H, Ph-H), 7.44 (t, 1 H, Ph-H), 7.04–7.15 (m, 5
1 H, Ph-H), 7.30 (t, 1 H, Ph-H), 7.22 (d, 1 H, Ph-H), 7.08–6.98
H, Ph-H), 2.78 (s, 6 H, NCH3), 2.52 (q, 4 H, CH2CH3), 1.16 (t, 6 (m, 4 H, Ph-H), 4.15 (s, 2 H, CH2N), 3.87 (br., 1 H, NH), 2.74 (s,
H, CH2CH3) ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 6 H, NCH3), 2.54 (q, 4 H, CH2CH3), 1.27 (t, 6 H, CH2CH3) ppm.
171.89, 156.03, 142.46, 136.86, 136.79, 136.14, 129.06, 125.80,
116.01, 115.01, 114.73, 56.84, 18.67, 8.24 ppm.
13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 152.75, 145.34,
136.76, 129.61, 128.04, 126.59, 125.93, 123.82, 122.69, 119.80,
51.25, 45.22, 24.21, 15.05 ppm.
ortho-C6H4(NMe2)CH=NC6H3Me2-2,6 (1c): This compound was
prepared in the same way as described above for 1a with ortho-
C6H4(NMe2)CHO (2.98 g, 20.0 mmol) and 2,6-dimethylaniline
(2.44 mL, 20.0 mmol) as starting materials. The product (3.94 g,
78%) was obtained as a yellow powder. C17H20N2 (252.35): calcd.
ortho-C6H4(NMe2)CH2NHC6H3Me2-2,6 (2c): This compound was
prepared in the same way as described above for 2a with 1c (2.95 g,
11.7 mmol) and LiAlH4 (0.670 g, 17.6 mmol) as starting materials.
The product (2.02 g, 68%) was obtained as a yellow oil. C17H22N2
C 80.91, H 7.99, N 11.10; found C 80.88, H 8.07, N 11.05. 1H (254.37): calcd. C 80.27, H 8.72, N 11.01; found C 80.30, H 8.70,
NMR (300 MHz, CDCl3, 293 K): δ = 8.56 (s, 1 H, CH=N), 8.17 N 11.00. 1H NMR (300 MHz, CDCl3, 293 K): δ = 7.39 (d, 1 H,
(d, 1 H, Ph-H), 7.44 (t, 1 H, Ph-H), 7.14–6.95 (m, 5 H, Ph-H), 2.79
Ph-H), 7.26 (t, 1 H, Ph-H), 7.17 (d, 1 H, Ph-H), 7.05 (t, 1 H, Ph-
H), 6.99 (d, 2 H, Ph-H), 6.82 (t, 1 H, Ph-H), 4.17 (s, 2 H, CH2N),
(s, 6 H, NCH3), 2.16 (s, 6 H, CH3) ppm. 13C{1H} NMR (75 MHz,
CDCl3, 293 K): δ = 161.36, 154.59, 151.79, 131.62, 128.82, 127.96, 3.87 (br., 1 H, NH), 2.72 (s, 6 H, NCH3), 2.30 (s, 6 H, CH3) ppm.
127.81, 126.91, 123.25, 122.34, 118.23, 45.50, 18.28 ppm.
13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 152.70, 146.41,
134.95, 129.78, 128.71, 128.71, 128.04, 123.65, 121.83, 119.65,
49.38, 45.18, 18.35 ppm.
ortho-C6H4(NEt2)CH=NC6H3iPr2-2,6 (1f): This compound was
prepared in the same way as described above for 1a with B (0.890 g,
5.0 mmol) and 2,6-diisopropylaniline (0.94 mL, 5.0 mmol) as start-
ing materials. The product (1.13 g, 67%) was obtained as a yellow
powder. C23H32N2 (336.51): calcd. C 82.09, H 9.58, N 8.32; found
ortho-C6H4(NMe2)CH2NHC6H4Me-4 (2d): This compound was
prepared in the same way as described above for 2a with 1d (2.57 g,
10.8 mmol) and LiAlH4 (0.610 g, 16.2 mmol) as starting materials.
The product (2.05 g, 79%) was obtained as a yellow oil. C16H20N2
1
C 82.13, H 9.54, N 8.33. H NMR (300 MHz, CDCl3, 293 K): δ =
8.69 (s, 1 H, CH=N), 8.24 (d, 1 H, Ph-H), 7.47 (t, 1 H, Ph-H), (240.34): calcd. C 79.96, H 8.39, N 11.66; found C 79.90, H 8.38,
7.03–7.16 (m, 5 H, Ph-H), 3.05 [m, 2 H, CH(CH3)2], 3.05 (m, 4 H, N 11.72. 1H NMR (300 MHz, CDCl3, 293 K): δ = 7.37 (d, 1 H,
NCH2CH3), 1.19 [d, 12 H, CH(CH3)2], 0.96 (t, 6 H, NCH2CH3) Ph-H), 7.26–6.97 (m, 5 H, Ph-H), 6.62 (d, 2 H, Ph-H), 4.40 (s, 2
ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 161.19, 152.45, H, CH2N), 3.92 (br., 1 H, NH), 2.76 (s, 6 H, NCH3), 2.24 (s, 3 H,
150.12, 137.88, 132.84, 132.80, 132.76, 131.57, 127.80, 124.02,
123.06, 48.88, 27.98, 23.70, 12.39 ppm.
CH3) ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 152.36,
146.24, 133.34, 129.63, 129.23, 127.82, 126.44, 123.28, 119.15,
113.06, 44.94, 44.84, 20.37 ppm.
ortho-C6H4(NEt2)CH=NC6H3Me2-2,6 (1g): This compound was
prepared in the same way as described above for 1a with B (1.06 g,
6.0 mmol) and 2,6-dimethylaniline (0.73 mL, 6.0 mmol) as starting
materials. The product (1.33 g, 79%) was obtained as a yellow pow-
ortho-C6H4(NEt2)CH2NHC6H3iPr2-2,6 (2f): This compound was
prepared in the same way as described above for 2a with 1f (1.01 g,
3.0 mmol) and LiAlH4 (0.17 g, 4.5 mmol) as starting materials. The
3618
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3613–3621

Al Complexes with Bidentate N,N-Dialkylaniline–arylamido Ligands
product (0.84 g, 83%) was obtained as a yellow oil. C23H34N2
(338.53): calcd. C 81.60, H 10.12, N 8.28; found C 81.53, H 10.15,
N 8.32. H NMR (300 MHz, CDCl3, 293 K): δ = 7.46 (d, 1 H, Ph-
materials. The product (0.50 g, 89%) was obtained as a colorless
crystalline solid. C19H27AlN2 (310.41): calcd. C 73.52, H 8.77, N
9.02; found C 73.50, H 8.75, N 9.00. 1H NMR (300 MHz, C6D6,
1
H), 7.28 (t, 1 H, Ph-H), 7.21–7.12 (m, 5 H, Ph-H), 4.10 (s, 2 H, 293 K): δ = 7.25 (d, 2 H, Ph-H), 7.13 (t, 1 H, Ph-H), 6.93 (m, 3 H,
CH2N), 3.53 (br., 1 H, NH), 3.42 [m, 2 H, CH(CH3)2], 3.06 (q, 4
Ph-H), 6.69 (m, 1 H, Ph-H), 4.32 (s, 2 H, CH2N), 2.52 (s, 6 H,
H, NCH2CH3), 1.24 [d, 12 H, CH(CH3)2], 1.03 (t, 6 H, NCH2CH3) NCH3), 2.36 (s, 6 H, CH3), –0.65 (s, 6 H, AlCH3) ppm. 13C{1H}
ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 142.93, 137.39, NMR (75 MHz, C6D6, 293 K): δ = 150.81, 1415.98, 138.29, 136.26,
129.53, 128.31, 124.16, 123.75, 123.55, 123.07, 122.75, 118.50,
52.46, 48.30, 27.52, 24.37, 12.20 ppm.
130.74, 129.03, 127.40, 127.05, 123.84, 118.62, 57.19, 44.94, 19.57,
–9.78 ppm.
ortho-C6H4(NEt2)CH2NHC6H3Me2-2,6 (2g): This compound was
prepared in the same way as described above for 2a with 1g (1.12 g,
4.0 mmol) and LiAlH4 (0.23 g, 6.0 mmol) as starting materials. The
ortho-C6H4(NMe2)(CH2NC6H4Me-4)AlMe2 (3d): This compound
was prepared in the same way as described above for 3a with 2d
(0.72 g, 3.0 mmol) and AlMe3 (3.0 mL, 3.0 mmol) as starting mate-
product (1.02 g, 91%) was obtained as a yellow oil. C19H26N2 rials. The product (0.82 g, 92%) was obtained as a colorless crystal-
(282.42): calcd. C 80.80, H 9.28, N 9.92; found C 80.83, H 9.23, N
line solid. C18H25AlN2 (296.39): calcd. C 72.94, H 8.50, N 9.45;
9.94. 1H NMR (300 MHz, CDCl3, 293 K): δ = 7.45 (d, 1 H, Ph-
found C 72.96, H 8.45, N 9.48. 1H NMR (300 MHz, CDCl3,
H), 7.26 (t, 1 H, Ph-H), 7.19 (m, 2 H, Ph-H), 7.01 (d, 2 H, Ph-H), 293 K): δ = 7.37–7.28 (m, 6 H, Ph-H), 7.00 (d, 1 H, Ph-H), 6.69
6.84 (t, 1 H, Ph-H), 4.18 (s, 2 H, CH2N), 3.68 (br., 1 H, NH), 3.08 (d, 1 H, Ph-H), 4.49 (s, 2 H, CH2N), 2.92 (s, 6 H, NCH3), 2.25 (s,
(q, 4 H, NCH2CH3), 2.38 (s, 6 H, CH3), 1.06 (t, 6 H, NCH2CH3) 3 H,CH3), –0.85 (s, 6 H, AlCH3) ppm. 13C{1H} NMR (75 MHz,
ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 146.70, 137.80, CDCl3, 293 K): δ = 151.93, 145.32, 134.62, 131.78, 129.62, 128.45,
129.96, 129.60, 128.85, 127.61, 124.30, 123.10, 121.95, 118.03,
65.64, 48.76, 18.56, 12.52 ppm.
127.64, 123.77, 118.61, 114.38, 53.87, 44.91, 20.52, –10.20 ppm.
ortho-C6H4(NMe2)(CH2NC6H5)AlMe2 (3e): This compound was
prepared in the same way as described above for 3a with 2e (0.56 g,
2.5 mmol) and AlMe3 (2.5 mL, 2.5 mmol) as starting materials. The
product (0.66 g, 93%) was obtained as a colorless crystalline solid.
C17H23AlN2 (282.36): calcd. C 72.31, H 8.21, N 9.92; found C
72.35, H 8.25, N 9.83. 1H NMR (300 MHz, CDCl3, 293 K): δ =
ortho-C6H4(NEt2)CH2NHC6H5 (2h): This compound was prepared
in the same way as described above for 2a with 1h (1.39 g,
5.5 mmol) and LiAlH4 (0.31 g, 8.3 mmol) as starting materials. The
product (1.22 g, 87%) was obtained as a yellow oil. C17H22N2
(254.37): calcd. C 80.27, H 8.72, N 11.01; found C 80.21, H 8.75,
N 11.04. 1H NMR (300 MHz, CDCl3, 293 K): δ = 7.37 (d, 1 H, 7.37–7.30 (m, 4 H, Ph-H), 7.20 (t, 2 H, Ph-H), 6.77 (d, 2 H, Ph-
Ph-H), 7.25–7.17 (m, 4 H, Ph-H), 7.06 (t, 1 H, Ph-H), 6.66 (m, 3
H, Ph-H), 4.40 (s, 2 H, CH2N), 3.65 (br., 1 H, NH), 3.02 (q, 4 H,
H), 6.62 (t, 1 H, Ph-H), 4.50 (s, 2 H, CH2N), 2.93 (s, 6 H, NCH3),
–0.84 (s, 6 H, AlCH3) ppm. 13C{1H} NMR (75 MHz, CDCl3,
NCH2CH3), 1.05 (t, 6 H, NCH2CH3) ppm. 13C{1H} NMR 293 K): δ = 154.03, 154.01, 134.13, 131.53, 128.79, 128.27, 127.41,
(75 MHz, CDCl3, 293 K): δ = 148.58, 136.04, 129.12, 127.36,
123.93, 122.62, 118.28, 117.08, 113.61, 112.8, 48.01, 44.69,
12.62 ppm.
118.37, 114.66, 114.26, 53.39, 44.64, –10.51 ppm.
ortho-C6H4(NEt2) (CH2NC6H3iPr2-2,6)AlMe2 (3f): This com-
pound was prepared in the same way as described above for 3a with
2f (0.34 g, 1.0 mmol) and AlMe3 (1.0 mL, 1.0 mmol) as starting
materials. The product (0.36 g, 92%) was obtained as a colorless
crystalline solid. C25H39AlN2 (394.57): calcd. C 76.10, H 9.96, N
ortho-C6H4(NMe2)(CH2NC6H3iPr2-2,6)AlMe2 (3a): AlMe3 (1.0 
in toluene, 2.0 mL, 2.0 mmol) was added to a solution of 2a (0.62 g,
2.0 mmol) in toluene (20 mL) at –10 °C with stirring. The reaction
mixture was gently heated to 80 °C for 24 h. After removal of the
solvent, the product was recrystallized from hexane to give the de-
sired complex as a colorless crystalline solid (0.62 g, 84%).
1
7.10; found C 76.15, H 9.93, N 7.18. H NMR (300 MHz, CDCl3,
293 K): δ = 7.51 (d, 1 H, Ph-H), 7.36 (m, 3 H, Ph-H), 7.24–7.11
(m, 3 H, Ph-H), 4.35 (s, 2 H, CH2N), 3.69 [m, 2 H, CH(CH3)2],
C23H35AlN2 (366.52): calcd. C 75.37, H 9.63, N 7.64; found C 3.50 (m, 4 H, NCH2CH3), 1.25 [d, 12 H, CH(CH3)2], 1.19 (t, 6 H,
75.40, H 9.61, N 7.65. 1H NMR (300 MHz, CDCl3, 293 K): δ = NCH2CH3), –1.04 (s, 6 H, AlCH3) ppm. 13C{1H} NMR (75 MHz,
7.32 (m, 3 H, Ph-H), 7.02 (m, 1 H, Ph-H), 6.94–6.93 (m, 2 H, Ph- CDCl3, 293 K): δ = 149.52, 142.84, 135.82, 130.81, 129.45, 127.56,
H), 6.71 (m, 1 H, Ph-H), 4.45 (s, 2 H, CH2N), 3.95 [m, 2 H,
126.67, 124.31, 123.15, 121.69, 60.81, 44.40, 27.14, 25.92, 24.38,
CH(CH3)2], 2.41 (s, 6 H, NCH3), 1.41 [q, 12 H, CH(CH3)2], –0.63 9.20, –8.52 ppm.
(s, 6 H, AlCH3) ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ
= 149.12, 147.93, 145.99, 136.09, 130.60, 127.60, 127.16, 124.87,
124.11, 118.74, 60.74, 44.91, 27.52, 26.23, 25.15, –9.97 ppm.
ortho-C6H4(NEt2) (CH2NC6H3Me2-2,6)AlMe2 (3g): This com-
pound was prepared in the same way as described above for 3a with
2g (0.42 g, 1.5 mmol) and AlMe3 (1.5 mL, 1.5 mmol) as starting
materials. The product (0.44 g, 87%) was obtained as a colorless
crystalline solid. C21H31AlN2 (338.47): calcd. C 74.52, H 9.23, N
ortho-C6H4(NMe2)(CH2NC6H3Et2-2,6)AlMe2 (3b): This com-
pound was prepared in the same way as described above for 3a with
2b (0.62 g, 2.2 mmol) and AlMe3 (2.2 mL, 2.2 mmol) as starting
materials. The product (0.65 g, 87%) was obtained as a colorless
crystalline solid. C21H31AlN2 (338.47): calcd. C 74.52, H 9.23, N
1
8.28; found C 74.48, H 9.27, N 8.23. H NMR (300 MHz, CDCl3,
293 K): δ = 7.32 (d, 1 H, Ph-H), 7.29 (t, 1 H, Ph-H), 7.24 (m, 2 H,
Ph-H), 7.05 (d, 2 H, Ph-H), 6.91 (t, 1 H, Ph-H), 4.34 (s, 2 H,
CH2N), 3.55 (m, 4 H, NCH2CH3), 2.31 (s, 6 H, CH3), 1.20 (t, 6 H,
1
8.28; found C 74.39, H 9.32, N 8.34. H NMR (300 MHz, CDCl3,
293 K): δ = 7.32–7.28 (m, 3 H, Ph-H), 6.99–6.94 (m, 3 H, Ph-H), NCH2CH3), –1.03 (s, 6 H, AlCH3) ppm. 13C{1H} NMR (75 MHz,
6.71 (m, 1 H, Ph-H), 4.38 (s, 2 H, CH2N), 3.0 (q, 4 H, CH2CH3), CDCl3, 293 K): δ = 150.84, 143.42, 138.32, 136.09, 130.89, 128.20,
2.40 (s, 6 H, NCH3), 1.38 (t, 6 H, CH2CH3), –0.63 (s, 6 H, AlCH3) 126.94, 126.59, 123.02, 121.66, 57.30, 44.40, 19.18, 9.06, –8.25 ppm.
ppm. 13C{1H} NMR (75 MHz, CDCl3, 293 K): δ = 149.64, 146.00,
144.21, 136.13, 130.69, 127.52, 127.10, 126.68, 124.27, 118.73,
59.37, 45.02, 24.50, 16.38, –9.90 ppm.
ortho-C6H4(NEt2) (CH2NC6H5)AlMe2 (3h): This compound was
prepared in the same way as described above for 3a with 2h (0.51 g,
2.0 mmol) and AlMe3 (2.0 mL, 2.0 mmol) as starting materials. The
ortho-C6H4(NMe2)(CH2NC6H3Me2-2,6)AlMe2 (3c): This com-
pound was prepared in the same way as described above for 3a with
2c (0.46 g, 1.8 mmol) and AlMe3 (1.8 mL, 1.8 mmol) as starting
product (0.52 g, 84%) was obtained as a colorless crystalline solid.
C19H27AlN2 (310.41): calcd. C 73.52, H 8.77, N 9.02; found C
73.56, H 8.73, N 9.07. 1H NMR (300 MHz, CDCl3, 293 K): δ =
Eur. J. Inorg. Chem. 2009, 3613–3621
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3619

A. Gao, Y. Mu, J. Zhang, W. Yao
FULL PAPER
7.37–7.23 (m, 4 H, Ph-H), 7.17 (t, 2 H, Ph-H), 6.75–6.63 (m, 3 H,
Ph-H), 4.43 (s, 2 H, CH2N), 3.42 (m, 4 H, NCH2CH3), 1.15 (t, 6 H,
NCH2CH3) –0.79 (s, 6 H, AlCH3) ppm. 13C{1H} NMR (75 MHz,
–20 °C. Diffraction data of 3c were collected at 293 K with a Ri-
gaku R-AXIS RAPID IP diffractometer equipped with graphite-
monochromated Mo-Kα radiation (λ = 0.71073 Å). Diffraction
CDCl3, 293 K): δ = 146.88, 135.25, 131.90, 129.27, 128.92, 127.61, data of 3e was collected at 293 K with a Bruker SMART-CCD
127.15, 114.76, 114.67, 90.49, 53.96, 47.48, 10.23, –8.24 ppm.
diffractometer equipped with graphite-monochromated Mo-Kα ra-
diation (λ = 0.71073 Å). Details of the crystal data, data collec-
tions, and structure refinements are summarized in Table 3. The
structures were solved by direct methods and refined by full-matrix
least-squares on F2. All non-hydrogen atoms were refined aniso-
tropically and the hydrogen atoms were included in idealized posi-
tion. All calculations were performed using the SHELXTL[17] crys-
tallographic software packages. CCDC-703530 (for 3c) and -703531
(for 3e) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
ortho-C6H4(NMe2)(CH2NC6H3iPr2-2,6)Al-(OCH2C6H5)2 (4): To a
solution of 3a (0.37 g, 1.0 mmol) in toluene (20 mL) was added
BnOH (1.0  in toluene, 2.0 mL, 2.0 mmol) at –10 °C. The reaction
mixture was allowed to gently warm to room temperature and
stirred for 1 h. After removal of the solvent, the crude product was
recrystallized from n-hexane to give the pure product as a colorless
crystalline solid (0.50 g, 90%). C35H43AlN2O2 (550.71): calcd. C
76.33, H 7.87, N 5.09; found C 76.28, H 7.83, N 5.16. 1H NMR
(300 MHz, CDCl3, 293 K): δ = 7.46–7.08 (m, 17 H, Ph-H), 5.01 (s,
4 H, OCH2), 4.08 (s, 2 H, CH2N), 3.42 [m, 2 H, CH(CH3)2], 2.74
(s, 6 H, NCH3), 1.28 [d, 12 H, CH(CH3)2] ppm. 13C{1H} NMR
(75 MHz, C6D6, 293 K): δ = 152.87, 143.63, 142.69, 130.05, 129.69,
128.73, 128.68, 128.21, 128.15, 124.01, 123.60, 123.49, 120.02,
90.35, 67.15, 53.01, 45.31, 27.50, 24.34 ppm.
Supporting Information (see footnote on the first page of this arti-
cle): Molecular structure of 3e.
General Procedure for the Polymerization of CL: To a rapidly stirred
solution of CL in toluene (the amounts of CL and toluene were
calculated based on the conditions given in Table 2) was added a
solution of a catalyst (0.19 mmol) and appropriate amount of
BnOH in toluene (5 mL) under a nitrogen atmosphere at the de-
sired temperature. After the reaction mixture was stirred for a pre-
scribed period or until the reaction mixture became very viscous
and could not be stirred, the reaction was quenched by the addition
of an excess amount of aqueous acetic acid (1.0 ). The polymer
was then precipitated by adding MeOH (100 mL) into the mixture,
collected on a frit, washed with MeOH (3ϫ10 mL), and dried in
vacuo up to a constant weight.
Acknowledgments
This work was supported by the National Natural Science Founda-
tion of China (Nos. 20772044 and 20674024).
[1] a) E. Chiellini, R. Solaro, Adv. Mater. 1996, 8, 305–313; b) M.
Okada, Prog. Polym. Sci. 2002, 27, 87–133; c) T. Hayashi, Prog.
Polym. Sci. 1994, 19, 663–702.
[2] a) B. J. O’Keefe, M. A. Hillmyer, W. B. Tolman, J. Chem. Soc.,
Dalton Trans. 2001, 2215–2224; b) A. C. Albertsson, I. K.
Varma, Biomacromolecules 2003, 4, 1466–1486; c) J. Wu, T. L.
Yu, C. T. Chen, C. C. Lin, Coord. Chem. Rev. 2006, 250, 602–
626.
[3] a) T. L. Yu, C. C. Wu, C. C. Chen, B. H. Huang, J. C. Wu,
C. C. Lin, Polymer 2005, 46, 5909–5917; b) W. Y. Lee, H. H.
Hsieh, C. C. Hsieh, H. M. Lee, G. H. Lee, J. H. Huang, T. C.
Wu, S. H. Chuang, J. Organomet. Chem. 2007, 692, 1131–1137;
c) M. L. Shueh, Y. S. Wang, B. H. Huang, C. Y. Kuo, C. C.
Lin, Macromolecules 2004, 37, 5155–5162; d) L. F. Sánchez-
Barba, D. L. Hughes, S. M. Humphrey, M. Bochmann, Orga-
nometallics 2006, 25, 1012–1020; e) L. E. Breyfogle, C. K. Wil-
liams, V. G. Young, M. A. Hillmyer, W. B. Tolman, Dalton
Trans. 2006, 928–936.
Crystal Structure Determination: Single crystals of 3c and 3e suit-
able for X-ray structural analysis were obtained from n-hexane at
Table 3. Crystal data and structural refinements details for 3c and
3e.
3c
3e
Formula
Fw
C19H27AlN2
310.41
C17H23AlN2
282.35
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
orthorhombic
P212121
7.9459(16)
15.360(3)
15.453(3)
90
monoclinic
P21/c
17.3507(13)
12.5371(9)
16.7569(12)
90
[4] a) Z. Y. Zhong, S. Schneiderbauer, P. J. Dijkstra, J. Feijen, Po-
lym. Bull. (Berlin) 2003, 51, 175–182.
[5] a) R. C. Yu, C. H. Hung, J. H. Huang, H. Y. Lee, J. T. Chen,
Inorg. Chem. 2002, 41, 6450–6455; b) C. H. Huang, F. C. Wang,
B. T. Ko, T. L. Yu, C. C. Lin, Macromolecules 2001, 34, 356–
361; c) C. T. Chen, C. A. Huang, B. H. Huang, Macromolecules
2004, 37, 7968–7973; d) L. M. Alcazar-Roman, B. J. O’Keefe,
M. A. Hillmyer, W. B. Tolman, Dalton Trans. 2003, 3082–3087;
e) M. L. Hsueh, B. H. Huang, C. C. Lin, Macromolecules 2002,
35, 5763–5768; f) C. T. Chen, C. A. Hung, B. H. Huang, Dalton
Trans. 2003, 3799–3803; g) H. L. Chen, B. T. Ko, B. H. Huang,
C. C. Lin, Organometallics 2001, 20, 5076–5083; h) S. G. Gong,
H. Y. Ma, Dalton Trans. 2008, 3345–3357; i) S. Milione, F.
Grisi, R. Centore, A. Tuzi, Organometallics 2006, 25, 266–274;
j) A. Amgoune, L. Lavanant, C. M. Thomas, Y. Chi, R. Welter,
S. Dagorne, J. F. Carpentier, Organometallics 2005, 24, 6279–
6282; k) D. Chakraborty, E. Y. X. Chen, Organometallics 2003,
22, 769–774; l) S. Dagorne, F. L. Bideau, R. Welter, S.
Bellemin-Laponnaz, A. Maisse-François, Chem. Eur. J. 2007,
13, 3202–3217; m) J. Y. Liu, N. Iwasa, K. Nomura, Dalton
Trans. 2008, 3978–3988; n) I. Taden, H. C. Kang, W. Massa,
T. P. Spaniol, J. Okuda, Eur. J. Inorg. Chem. 2000, 441–445.
[6] a) A. J. Chmura, M. G. Davidson, M. D. Jones, M. D. Lunn,
M. F. Mahon, Dalton Trans. 2006, 887–889; b) J. Cayuela, V.
β [°]
90
90
1886.0(7)
4
1.093
117.9610(10)
90
3219.6(4)
8
γ [°]
V [Å3]
Z
Dcalcd. [gcm–3]
1.165
F(000)
672
1216
Θ range for data collection
Limiting indices
3.17 to 27.48°
–10 Յ h Յ 9
–19 Յ k Յ 19
–19 Յ l Յ 19
1.33 to 26.03°
–21 Յ h Յ 21
–15 Յ k Յ 6
–20 Յ l Յ 20
6344/0/369
1.023
No. of data/restraints/parameters 4224/0/205
Goodness-of-fit on F2
0.911
[a]
[a]
Final R indices IϾ2σ(I)
R1 = 0.0594
R1 = 0.0549
wR2[b] = 0.0816
wR2[b] = 0.1214
[a]
[a]
R indices (all data)
R1 = 0.1714
R1 = 0.0811
wR2[b] = 0.1067
wR2[b] = 0.1345
Rint
0.1456
0.0414
[a] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [b] wR2 = {Σw(Fo – Fc ) /Σw(Fo2)2}1/2
.
2
2 2
3620
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3613–3621

Al Complexes with Bidentate N,N-Dialkylaniline–arylamido Ligands
Bounor-Legaté, P. Cassagnau, A. Michel, Macromolecules
2006, 39, 1338–1346; c) M. Davidson, M. D. Jones, M. D.
Lunn, M. F. Mahon, Inorg. Chem. 2006, 45, 2282–2287; d) A. J.
Chmura, M. G. Davidson, M. D. Jones, M. D. Lunn, M. F.
Mahon, A. F. Johnson, P. Khunkamchoo, S. L. Roberts, S. S. F.
Wong, Macromolecules 2006, 39, 7250–7257; e) H. Wang, H. S.
Chan, J. Okuda, Z. W. Xie, Organometallics 2005, 24, 3118–
3124; f) F. Gornshtein, M. Kapon, M. Botoshansky, M. S.
Eisen, Organometallics 2007, 26, 497–507; g) L. I. Strunkina,
M. K. Minacheva, K. A. Lyssenko, V. V. Burlakov, W. Baum-
ann, P. Atndt, B. N. Strunin, V. B. Shur, J. Organomet. Chem.
2006, 691, 557–565.
C. Y. Qi, Z. X. Wang, J. Polym. Sci., Part A: Polym. Chem.
2006, 44, 4621–4631; e) A. Kowalski, A. Duda, S. Penczek,
Macromolecules 2000, 33, 689–695.
[10] a) W. M. Stevels, M. J. K. Ankoné, P. J. Dijkstra, J. Feijen,
Macromolecules 1996, 29, 3332–3333; b) A. Otero, J.
Fernández-Baeza, A. Antiñolo, A. Lara-Sánchez, E. Martínez-
Caballero, J. Tejeda, F. L. Sánchez-Barba, C. Alonso-Moreno,
I. López-Solera, Organometallics 2008, 27, 976–983; c) W. Gao,
D. M. Cui, X. M. Liu, Y. Zhang, Y. Mu, Organometallics 2008,
27, 5889–5893; d) M. Wiecko, P. W. Roesky, V. V. Burlakov, A.
Spannenberg, Eur. J. Inorg. Chem. 2007, 876–881; e) D. M.
Lyubov, A. M. Bubnov, G. K. Fukin, F. M. Dolgushin, M. Yu.
Antipin, O. Pelcé, M. Schappacher, S. M. Guillaume, A. A. Tri-
fonov, Eur. J. Inorg. Chem. 2008, 2090–2098; f) Y. j. Luo, Y. M.
Yao, Q. Shen, K. B. Yu, L. H. Weng, Eur. J. Inorg. Chem. 2003,
318–323.
[7] a) B. J. O’Keefe, L. E. Breyfogle, M. A. Hillmyer, W. B. Tol-
man, J. Am. Chem. Soc. 2002, 124, 4384–4393; b) M. Z. Chen,
H. M. Sun, W. F. Li, Z. G. Wang, Q. Shen, Y. Zhang, J. Or-
ganomet. Chem. 2006, 691, 2489–2494.
[8] a) D. A. Walker, T. J. Woodman, M. Schormann, D. L. Hughes,
M. Bochmann, Organometallics 2003, 22, 797–803; b) H. Y.
Chen, B. H. Huang, C. C. Lin, Macromolecules 2005, 38, 5400–
5405; c) Z. Y. Chai, C. Zhang, Z. X. Wang, Organometallics
2008, 27, 1626–1633; d) Y. Sarazin, M. Schormann, M. Boch-
mann, Organometallics 2004, 23, 3296–3302; e) Z. X. Wang,
C. Y. Qi, Organometallics 2007, 26, 2243–2251; f) B. H. Huang,
C. N. Lin, M. L. Hsueh, T. Athar, C. C. Lin, Polymer 2006, 47,
6622–6629; g) F. Majoumo-Mbe, E. Smolensky, P. Lönnecke,
D. Shpasser, M. S. Eisen, E. Hey-Hawkins, J. Mol. Catal. A
2005, 240, 91–98; h) Y. Sarazin, R. H. Howard, H. L. Hughes,
S. M. Humphrey, M. Bochmann, Dalton Trans. 2006, 340–350;
i) Y. D. M. Champouret, W. J. Nodes, J. A. Scrimshire, K.
Singh, G. A. Solan, I. Young, Dalton Trans. 2007, 4565–4575;
j) C. M. Silvernail, L. J. Yao, L. M. R. Hill, M. A. Hillmyer,
W. B. Tolman, Inorg. Chem. 2007, 46, 6565–6574; k) C. Zhang,
Z. X. Wang, J. Organomet. Chem. 2008, 693, 3151–3158.
[9] a) P. Lecomte, F. Stassin, R. Jérme, Macromol. Symp. 2004,
215, 325–338; b) G. Deshayes, F. A. G. Mercier, P. Degée, I.
Verbruggen, M. Biesemans, R. Willem, P. Dubois, Chem. Eur.
[11] N. Nomura, T. Aoyama, R. Ishii, T. Kondo, Macromolecules
2005, 38, 5363–5366.
[12] W. Yao, Y. Mu, A. H. Gao, Q. Su, Y. J. Liu, Y. Y. Zhang, Poly-
mer 2008, 49, 2486–2491.
[13] a) G. Sunagawa, T. Ichii, N. Toshida. Pharmaceutical Bulletin,
1955, NO. 2, pp. 109–113; b) R. L. Bentley, H. Suschitzky, J.
Chem. Soc. Perkin Trans. 1 1976, 1725–1734.
[14] a) W. Yao, Y. Mu, A. H. Gao, W. Gao, L. Ye, Dalton Trans.
2008, 3199–3206; b) X. M. Liu, W. Gao, Y. Mu, G. H. Li, L.
Ye, H. Xia, Y. Ren, S. H. Feng, Organometallics 2005, 24, 1614.
[15] a) M. T. Gamer, P. W. Roesky, I. Palard, M. L. Hellaye, S. M.
Guillaume, Organometallics 2007, 26, 651–657; b) H. L. Chen,
B. T. Ko, B. H. Huang, C. C. Lin, Organometallics 2001, 20,
5076–5083.
[16] a) Z. Y. Zhong, M. J. K. Ankoné, P. J. Dijkstra, C. Birg, M.
Westerhausen, J. Feijen, Polym. Bull. (Berlin) 2001, 46, 51–57;
b) M. Helou, O. Miserque, J. M. Brusson, J. F. Carpentier,
S. M. Guillaume, Chem. Eur. J. 2008, 14, 8772–8775.
[17] G. M. Sheldrick, SHELXTL-97, Program for the Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
Received: February 16, 2009
J. 2003, 9, 4346–4352; c) M. Moller, R. Kange, J. L. Hedrick,
¯
J. Polym. Sci., Part A: Polym. Chem. 2000, 38, 2067–2074; d)
Published Online: July 15, 2009
Eur. J. Inorg. Chem. 2009, 3613–3621
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3621