Aluminum and zinc complexes supported by functionalized phenolate ligands: Synthesis, characterization and catalysis in the ring-opening polymerization of ε-caprolactone and rac-lactide

Article abstract of DOI:10.1016/j.jorganchem.2008.07.002

A series of aluminum and zinc complexes supported by functionalized phenolate ligands were synthesized and characterized. Reaction of 2-(3,5-R₂C₃N₂)C₆H₄NH₂ (R = Me, Ph) with salicylaldehyde or 3,5-di-tert-butylsalicylaldehyde afforded 2-((2-(1H-pyrazol-1-yl)phenylimino)methyl)phenol derivatives 2a-2d. Treatment of 2a-2d with an equiv. of AlR²₃ (R² = Me, Et) gave corresponding aluminum aryloxides 3a-3e, while reaction with an equiv. of ZnEt₂ afforded zinc aryloxides 4a-4d. Treatment of 2c with 0.5 equiv. of ZnEt₂ formed diphenolato zinc complex 5. All new compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analyses. The structures of complexes 3a, 4a and 5 were further characterized by single crystal X-ray diffraction techniques. The catalytic activity of complexes 3-5 toward the ring-opening polymerization of ε-caprolactone was studied. The zinc complexes (4a-4d) exhibited higher catalytic activity than the aluminum complexes (3a-3e). The diphenolato zinc complex 5 showed lower catalytic activity than the ethylzinc complexes 4a-4d. The aluminum complex (3b) is inactive to initiate the ROP of rac-lactide, while the zinc complex (4d) is active initiator for the ROP of rac-lactide, giving atactic polylactide.

Full text of DOI:10.1016/j.jorganchem.2008.07.002

Journal of Organometallic Chemistry 693 (2008) 3151–3158
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Aluminum and zinc complexes supported by functionalized
phenolate ligands: Synthesis, characterization and catalysis
in the ring-opening polymerization of e-caprolactone and rac-lactide
*
Cheng Zhang, Zhong-Xia Wang
Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of aluminum and zinc complexes supported by functionalized phenolate ligands were synthesized
and characterized. Reaction of 2-(3,5-R2C3N2)C6H4NH2 (R = Me, Ph) with salicylaldehyde or 3,5-di-tert-
butylsalicylaldehyde afforded 2-((2-(1H-pyrazol-1-yl)phenylimino)methyl)phenol derivatives 2a–2d.
Treatment of 2a–2d with an equiv. of AlR23 (R2 = Me, Et) gave corresponding aluminum aryloxides 3a–3e,
while reaction with an equiv. of ZnEt2 afforded zinc aryloxides 4a–4d. Treatment of 2c with 0.5 equiv. of
ZnEt2 formed diphenolato zinc complex 5. All new compounds were characterized by 1H and 13C NMR spec-
troscopy and elemental analyses. The structures of complexes 3a, 4a and 5 were further characterized by sin-
gle crystal X-ray diffraction techniques. The catalytic activity of complexes 3–5 toward the ring-opening
Received 28 March 2008
Received in revised form 27 June 2008
Accepted 3 July 2008
Available online 8 July 2008
Keywords:
Aluminum
Zinc
polymerization of e-caprolactone was studied. The zinc complexes (4a–4d) exhibited higher catalytic activity
N,O-ligands
than the aluminum complexes (3a–3e). The diphenolato zinc complex 5 showed lower catalytic activity than
the ethylzinc complexes 4a–4d. The aluminum complex (3b) is inactive to initiate the ROP of rac-lactide,
while the zinc complex (4d) is active initiator for the ROP of rac-lactide, giving atactic polylactide.
Ó 2008 Elsevier B.V. All rights reserved.
e
-Caprolactone
Lactide
Polymerization
1. Introduction
featuring biphenolate and methylenebiphenolate ligands showed
high catalytic activity in the ROP of lactones and lactides [1d,8]. Re-
Synthetic aliphatic polyesters derived from
e
-caprolactone (
e
-
cently it was reported that salicylaldiminato-aluminum and -zinc
complexes (I) were active catalysts in the ROP of -CL or lactides
CL), lactide and glycolide are of great interest for their biomedical
applications due to their biodegradable, biocompatible and perme-
able properties [1,2]. Ring-opening polymerization (ROP) of cyclic
esters initiated by metal complexes is an efficient way to produce
the polyesters. This method can enable control of polymer molecu-
lar weight and polymer architecture and can yield macromolecular
samples with narrow molecular weight distributions [3]. A range of
main group and transition metal complexes have been reported to
be effective catalysts/initiators for the ROP of lactones/lactides, giv-
ing polymers with both high and controlled molecular weights [4].
Among the metals, magnesium, calcium, zinc, aluminum, and tin(II)
are attractive due to their low toxicity [1d,2c,5]. The choice of sup-
porting ligands on central metals is crucial to the catalytic behavior
of the complexes. Alkoxides are the most widely used ligands. Other
chelate ligands are often used as ancillary ligands. These ancillary
ligands are not directly involved in the polymerization but do tune
the properties of the metallic center and minimize the aggregation
processes and side reactions [2c,5i,6]. For example, the metal com-
plexes featuring SALEN or SALAN-type ligands exhibited excellent
stereocontrol in the ROP of lactide [7]; the aluminum complexes
e
[5f,9]. The aluminum and zinc complexes bearing pendant arm tri-
dentate Schiff base (II) [10] and related ligand (III) [11] were also
active catalysts for the ROP of cyclic esters and exhibited good
molecular weight control of polymer. In order to compare catalysis
with I–III, we synthesized aluminum and zinc complexes supported
by ligand IV and evaluated their catalysis toward e-CL and rac-lac-
tide. Here we report the results.
Ar
N
O
N
R
N
MRn
M
R1
O
R1
R1
R1
M = Al, Zn
II
I
N
N
R
N
O
N
R
Zn
But
N
O
R
R1
But
III R = OEt or Et
R1
* Corresponding author. Tel.: +86 551 360 3043; fax: +86 551 360 1592.
E-mail address: zxwang@ustc.edu.cn (Z.-X. Wang).
IV
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.07.002

3152
C. Zhang, Z.-X. Wang / Journal of Organometallic Chemistry 693 (2008) 3151–3158
2. Results and discussion
2.1. Synthesis and characterization of compounds 2a–5
Synthesis of compounds 2a–5 are presented in Scheme 1. Acid
catalyzed reaction of 1a and 1b with salicylaldehyde and 3,5-di-
tert-butylsalicylaldehyde, respectively, in the presence of 4A
molecular sieves afforded 2-((2-(1H-pyrazol-1-yl)phenylimi-
no)methyl)- phenol derivatives 2a–2d in high yields. Treatment
of 2a-2d with AlR3 (R = Me, Et) in toluene afforded N,O-chelate alu-
minum complexes 3a–3e. Reaction of 2a–2d with an equiv. of
ZnEt2 gave N,N,O-chelate ethylzinc complexes 4a–4d; whereas
reaction of 2c with 0.5 equiv. of ZnEt2 formed diphenolato zinc
complex 5. The neutral compounds 2a–2d are air-stable yellow
oil (2a) or orange (2b) or yellow (2c and 2d) solids. They were char-
acterized by elemental analyses and 1H and 13C{1H} NMR spectros-
copy. The proton signals of the OH groups of 2a–2d appeared at
low field regions (from d 11.89 to d 12.67 ppm), showing the exis-
tence of intramolecular hydrogen bonds. The other NMR spectral
signals were consistent with the respective structure. The alumi-
num (3a–3e) and zinc complexes (4a–4d) are air-sensitive crystal-
line solids. Each of them gave satisfactory elemental analysis. The
1H and 13C{1H} NMR spectra were consistent with their structures.
Complex 5 is air-stable yellow crystals and was characterized by
Fig. 1. ORTEP drawing (30% probability) of complex 3a. Selected bond lengths (Å)
and angles (°): Al(1)–O(1) 1.765(3), Al(1)–N(1) 1.965(3), Al(1)–C(8) 1.943(4), Al(1)–
C(9) 1.939(5), O(1)–C(1) 1.331(4), N(1)–C(7) 1.305(4), N(1)–C(10) 1.438(4), O(1)–
Al(1)–N(1) 95.31(13), O(1)–Al(1)–C(8) 110.43(18), O(1)–Al(1)–C(9) 112.94(19),
C(8)–Al(1)–N(1) 109.01(18), C(9)–Al(1)–N(1) 108.99(18), C(9)–Al(1)–C(8) 117.8(2).
elemental analysis and 1H and 13C{1H} NMR spectroscopy. In addi-
tion, the structures of complexes 3a, 4a and 5 were additionally
characterized by single crystal X-ray diffraction techniques.
The ORTEP drawing of complex 3a is presented in Fig. 1, along
with selected bond lengths and angles. Crystalline 3a is mono-
meric. The ligand coordinates to the central aluminum atom in a
bidentate N,O-chelate mode. The aluminum atom is four-coordi-
nate and has a distorted tetrahedral geometry with angles ranging
from 95.31(13)° to 117.8(2)°. The most acute angle is associated
with the bite angle of the chelate ligand, which is close to corre-
sponding those in [{Sal(But)}AlEt2] [94.97(6)°] [12] and [Me2-
AlOC(Ph)CH{(3,5- Me2C3HN2)-1}] [94.81(13)°] [13]. The fused
six-membered ring Al(1)O(1)C(1)C(6)C(7)N(1) is almost coplanar
with the phenylene moiety. The Al(1)–O(1) distance of 1.765(3) Å
is comparable to those in [{Sal(But)}AlEt2] [1.772(1) Å], [{Sal(But)}-
Al(Me)Cl] [1.750(5) Å] [12] and [Me2AlOC(Ph)CH{(3,5-Me2C3HN2)-
1}] [1.747(3) Å] [13]. The Al(1)–N(1) distance of 1.965(3) Å is close
R
Ph
R
N
O
Ph
N
N
Et
N
Zn
N
N
Zn
N
N
O
N
Ph
O
R1
Ph
5
iv
R1
R1
4a-4d
iii
ii
R
R
N
N
R
N
N
R1
R
N
OH
R1
to that in ½Et2AlfOCðMeÞCHCðMeÞNð2; 6- Pri C6H3Þgꢀ [1.958(2) Å]
2
R1
N
O
[14]. The N(1)–C(7) distance of 1.305(4) Å shows a double bond be-
tween the atoms. The Al(1)–N(3) distance of 4.645 Å is too far to
bond.
Al
R2
R2
The ORTEP drawing of complex 4a is presented in Fig. 2, along
with selected bond lengths and angles. Crystalline 4a exists in a
monomeric form. The ligand bonds to the central zinc atom in a tri-
dentate manner. The Zn atom presents a distorted tetrahedral
coordinate geometry with an acute N1(bridge)–Zn–N(pyrazolyl)
angle (N(1)–Zn(1)–N(3), 82.55(7)°). The Zn(1)–N(1) distance of
2.0629(19) Å is within the normal range for the bidentate Schiff
base zinc complexes such as [Zn{OC6H4(CH@NAr)-o}2] (Ar = m-
NO2C6H4 or p-MeOC6H4) [2.006(2)–2.027(3) Å] [15] and [(SalenMe)-
ZnEt] [2.012(7) and 2.200(9) Å, respectively] [10b]. The Zn(1)–N(3)
distance of 2.105(2) Å is close to that of the Zn–N distances in a
pyrazolyl coordinated zinc complex ½ZnðMeÞfOCðOÞCðN2C3Me2-3;5Þ-
2a-2d
3a-3e
R1 R2
2a Me H
R1 R2
i
R
R
But
But
3d Ph
3e Ph
Me
Et
R
But
2b Me
2c Ph
2d Ph
H
But
4a Me H
N
R
N
But
4b Me
3a Me H Me 4c Ph
H
But
NH2
But
3b Me
3c Ph
Me 4d Ph
1a R = Me
1b R = Ph
ðN2C3But -30; 50Þgꢀ [2.085(7) and 2.104(6) Å, respectively] [16]. The
H
Me
2
Zn–O and Zn–C distances are also normal for a four-coordinate zinc
complex [15–17].
The ORTEP drawing of complex 5 is displayed in Fig. 3, along
with selected bond lengths and angles. The complex is monomeric
in the solid state. Each ligand combines the zinc atom in a biden-
Scheme 1. Synthesis of the ligands and aluminum and zinc complexes. Reagents
and conditions: (i) salicylaldehyde or 3,5-di-tert-butylsalicylaldehyde, 4A molecular
sieves, CH3COOH (cat. amount), toluene, refluxed 20 h; (ii) an equiv. of AlR32
(R2 = Me, Et), toluene, ꢁ80 °C to r.t., 12 h; (iii) an equiv of ZnEt2, toluene, 0 °C, 2 h,
and then r.t., 15 h; (iv) 0.5 equiv. of ZnEt2, toluene, 0–60 °C, 12 h.

C. Zhang, Z.-X. Wang / Journal of Organometallic Chemistry 693 (2008) 3151–3158
3153
Table 1
The ring-opening polymerization of
e
-CL catalyzed by complexes 3a–3ea
c,d
Entry Cat. Solvent
vol. (mL)
Temperature Time
Conv. Mn
Yield PDIc
(%)
(°C)
(min)
(%)b
1
2
3
4
5
6
7
8
9
3a
3a
3a
3b
3b
3c
3c
3c
3d
3e
16
16
20
16
20
16
16
20
16
16
80
110
110
80
110
80
110
110
80
780
100
200
220
80
290
70
160
240
200
55.6
39000 42.8
1.08
88.5 163000 73.6
1.05
1.02
1.07
1.03
1.04
1.07
1.11
1.08
1.05
100
96000 81.7
69.1 123000 51
96.1 109000 80.9
46.5 120000 32.4
71.7 211000 60.6
94.4
100
100
98000 80.8
87000 84.7
143000 87.5
10
80
a
[
e
-CL]0/[Al] = 200:1, [
e-CL] = 13 mmol, solvent:toluene.
b
c
Obtained from the 1H NMR spectral data.
Obtained from GPC analysis and calibrated polystyrene standard.
Using a correcting factor 0.58 for Mn, see Ref. [18].
Fig. 2. ORTEP drawing (50% probability) of complex 4a. Selected bond lengths (Å)
and angles (°): Zn(1)–O(1) 1.9728(16), Zn(1)–N(1) 2.0629(19), Zn(1)–N(3) 2.105(2),
Zn(1)–C(19) 1.981(2), O(1)–C(1) 1.302(3), N(1)–C(7) 1.287(3), N(1)–C(8) 1.428(3),
C(6)–C(7) 1.449(3), N(2)–C(13) 1.428(3), N(2)–N(3) 1.376(3), O(1)–Zn(1)–C(19)
121.18(8), O(1)–Zn(1)–N(1) 90.63(7), C(19)–Zn(1)–N(1) 133.93(9), O(1)–Zn(1)–
N(3) 108.07(7), C(19)–Zn(1)–N(3) 113.07(9), N(1)–Zn(1)–N(3) 82.55(7), N(1)–C(7)–
C(6) 125.3(2), C(7)–N(1)–Zn(1) 124.90(15).
d
mined at a [e-CL]0/cat. ratio of 200:1 in toluene. The polymeriza-
tion process was monitored by 1H NMR spectroscopy, and the
monomer conversion was also determined by 1H NMR spectros-
copy. The catalysis of the aluminum complexes 3a–3e was deter-
mined at first. The data are listed in Table 1. In the catalysis of
complexes 3b–3c the conversion of e-CL can not reach completion
in 16 mL of toluene even at elevated reaction temperature and in
longer reaction time. In 20 mL of toluene these reaction can go to
completion. However, in the reaction catalyzed by 3d and 3e, the
conversion of the monomer can reach 100% in 16 mL of solvent.
The polymerization of
e-CL catalyzed by 3a proceeded much
slower compared with those of 3b–3e. All these complexes have
lower catalytic activity compared with the reported salicylaldimi-
natoaluminum alkoxides [5f]. In each polymerization reaction the
measured molecular weight of polymer was much higher than cal-
culated value (based on living polymerization). For example, the
polymerization reaction catalyzed by 3a in 20 mL of toluene gave
polymer with Mn = 96000, which means that the polymer chains
contain about 840 e-CL units. This and narrow PDI values imply
the number of active sites of the catalyst is rather small. The other
aluminum complexes gave similar results. It is also seen that the
Mn values do not increase with increase of the e-CL conversion (en-
tries 2, 3, 7 and 8, Table 1). Hence the polymerization reactions did
not take place in a living manner. Due to high molecular weights of
the polymers, we did not observe the signals of the initiating group
in the 1H NMR spectra of the PCLs. In this case we can not obtain
the information of the initiating species. In addition, the catalysis
of 3b toward the ROP of rac-lactide was also tested and the result
showed that the complex was inactive for the polymerization of
rac-lactide.
The catalysis of the zinc complexes (4a–4d) was determined as
above and the results are listed in Table 2. It was noticed that the
zinc complexes displayed higher catalytic activity than the alumi-
num complexes. However, the polymerization catalyzed by the
zinc complexes also gave high molecular weight polymers. This
means that the number of active sites of the catalysts is rather
small. For example, the polymerization reaction catalyzed by 4d
in 28 mL of toluene gave polymer with Mn = 167000, which means
Fig. 3. ORTEP drawing (30% probability) of complex 5. Selected bond lengths (Å)
and angles (°): Zn(1)–N(1) 2.0225(16), Zn(1)–O(1) 1.9092(15), N(1)–C(7) 1.297(3),
Zn(1)ꢂ ꢂ ꢂN(3) 3.841, O(1)–Zn(1)–N(1) 95.79(7), O(1)–Zn(1)–N(1A) 133.54(7), N(1)–
Zn(1)–N(1A) 102.49(9), O(1)–Zn(1)–O(1A) 101.77(10).
tate N,O-chelate manner. The zinc atom is four-coordinate, having
a distorted tetrahedral coordinate geometry. The Zn(1)–N(3) dis-
tance of 3.841 Å shows no bond interaction between the atoms.
The N(1)–Zn(1)–O(1) angle of 95.79(7)° is normal for a N,O-chelate
six-membered metallacycle [15]. Both Zn(1)–N(1) and Zn(1)–O(1)
distances are shorter than corresponding those in complex 4a,
but close to those found in [Zn{OC6H4(CH@NAr)-o}2] (Ar =
m-NO2C6H4 or p-MeOC6H4) [15].
2.2. Catalysis of complexes 3a–5 in the ROP of e-caprolactone
that the polymer chains contain about 1450
value did not increase with increase of the
e
-CL units. That the Mn
e
-CL conversion (entries
Metal alkoxides are often efficient initiators for the ring-open-
ing polymerization of cyclic esters [1d,2a,2b]. We attempted to
prepare aluminum and zinc alkoxides by reaction of the alkyl alu-
minum and alkyl zinc complexes mentioned in Scheme 1 with an
alcohol such as PhCH2OH and PriOH. However, each reaction gave
a mixture. Hence catalysis of complexes 3a–3e and 4a–4d in the
4–10, Table 2) indicates that the polymerization reactions were not
living.
Complex 5 showed much lower catalytic activity compared
with 4a–4d (Table 3). At 80 °C in 36.5 h only 42.9% of monomer
was converted. At a higher temperature (110 °C) the reaction rate
increased obviously, 90.6%
e-CL conversion being reached in
ring-opening polymerization of
catalytic activities for the ROP of
e
-caprolactone was tested. The
430 min. Higher polymerization temperature also led to higher
molecular weights of PCLs. The low activity of 5 may be due to
e
-CL of the complexes were deter-

3154
C. Zhang, Z.-X. Wang / Journal of Organometallic Chemistry 693 (2008) 3151–3158
Table 2
bis(N,O-chelate)zinc complex. These complexes exhibited catalytic
activity toward the ROP of -CL. N,N,O-Chelate zinc complexes
The ring-opening polymerization of e
-CL catalyzed by complexes 4a–4da
e
c,d
behaved higher catalytic activity than the aluminum complexes.
Bis(N,O-chelate)zinc complex 5 displayed relatively low catalytic
activity. The zinc complex (4d) is also active initiator for the ROP
of rac-lactide, giving atactic polylactide. Each polymerization led
to polymer of high molecular weight, and the polymerization did
not take place in a living manner.
Entry Cat. Solvent vol.
(mL)
Time
(min)
Conv.
(%)b
Mn
Yield
(%)
PDI
1
2
3
4
5
6
7
8
9
4a
4a
4a
4b
4b
4c
4c
4c
4d
4d
16
16
24
16
24
16
24
28
16
28
90
110
66
90
160
37
64
160
34
69
86
–
–
75.6
–
–
1.06
–
1.01
1.04
1.10
1.05
1.10
1.11
1.06
98000
–
11.1
51.6
100
57.8
69.6
100
76.6
100
115000 38.7
101000 73.7
138000 48.3
125000 57.3
124000 80.6
181000 71.4
167000 82.5
4. Experimental
4.1. General remarks
10
75
a
[e-CL]0/[Zn] = 200:1, [e-CL] = 13 mmol, solvent:toluene, reaction temperature:
All air or moisture sensitive manipulations were performed un-
der nitrogen, using standard Schlenk techniques. Solvents were
distilled under nitrogen over sodium (toluene) or sodium/benzo-
phenone (n-hexane and diethyl ether) and degassed prior to use.
AlMe3, AlEt3 and ZnEt2 were purchased from Alfa Aesar and used
80 °C.
b
Obtained from the 1H NMR spectral data.
Obtained from GPC analysis and calibrated polystyrene standard.
Using a correcting factor 0.58 for Mn, see Ref. [18].
c
d
as received. e-Caprolactone, purchased from Acros Organics, was
Table 3
The ring-opening polymerization of
e
-CL catalyzed by complex 5a
dried over molecular sieves and distilled under reduced pressure
prior to use. rac-Lactide, purchased from Beijing Yuanshengrong
Company, was recrystallized three times from toluene prior to
use. CDCl3 and C6D6, purchased from Cambridge Isotope Laborato-
ries, Inc., were degassed and stored over activated 4A molecular
sieves (CDCl3) or Na/K alloy (C6D6). Compounds 1a and 1b were
prepared according to literature methods [19]. All other chemicals
were obtained from commercial vendors and used as received.
NMR spectra were recorded on a Bruker Avance300 spectrometer
at ambient temperature. The chemical shifts of 1H and 13C{1H}
NMR spectra are referenced to internal solvent resonances. Ele-
mental analyses were performed by the Analytical Center of Uni-
versity of Science and Technology of China. Molecular weight and
the molecular weight distribution were determined on a Waters
150C gel-permeation chromatograph (GPC) equipped with Ultra-
Styragel columns (103, 104 and 105 Å) and 410 refractive index
detector, using monodispersed polystyrene as calibration standard.
THF (HPLC grade) was used as eluent at a flow rate of 1 mL/min.
Entry Temperature (°C) Time (min) Conv. (%)b Mn
Yield (%) PDI
c,d
1
2
80
110
2190
430
42.9
90.6
25,000 30.4
166,000 80.9
1.03
1.05
a
Polymerization were performed in 10 mL toluene,
[e-CL]0/[Zn] = 200:1,
[
e
-CL] = 13 mmol.
b
Obtained from the 1H NMR spectral data.
c
Obtained from GPC analysis and calibrated polystyrene standard.
d
Using a correcting factor 0.58 for Mn, see Ref. [18].
either the steric hindrance around the zinc atom or the low reactiv-
ity of the zinc–oxygen bonds in the complex. Formation of high
molecular weight polymers also indicates that the number of
active sites of the catalyst remains rather small.
It has been reported that complex IIIa was very active catalyst
for the ROP of lactide and exhibited good molecular weight control
of polylactide, whereas IIIb was inactive [11a]. The complexes we
have synthesized (4a–4d) have similar skeletal structure to III. It is
of interest to compare their catalytic activity toward the ROP of
lactide. However, as indicated above, we could not obtain zinc alk-
oxide derivatives (6). Hence, we tested the catalysis of complex 4d
toward the ROP of rac-lactide. The reaction was carried out in 8 mL
of toluene at 80 °C with 8.17 mM of catalyst concentration and a
1:60 of catalyst to lactide ratio. After 400 min the 1H NMR spec-
trum showed that conversion of the monomer reached 91.7%.
Gel-permeation chromatography (GPC, versus polystyrene stan-
dards) analysis revealed an Mn of 12000 g/mol and a molecular
weight distribution of 1.03. The homonuclear decoupled 1H NMR
spectrum of methine region of the polymer showed an atactic
microstructure.
4.2. Preparation of compounds
4.2.1. 2-((2-(3,5-Dimethyl-1H-pyrazol-1-yl)- phenylimino)methyl)-
phenol (2a)
To a three necked flask was added successively activated 4A
molecular sieves (30 g), 1-(20-aminophenyl)-3,5-dimethylpyrazole
(2.48 g, 13.25 mmol), o-hydroxylbenzaldealdehyde (1.65 g,
13.55 mmol), toluene (30 mL) and several drops of anhydrous ace-
tic acid. The mixture was refluxed for 20 h and then cooled to room
temperature. The molecular sieves were filtered off and washed
with dichloromethane (3 ꢃ 20 mL). The combined organic solution
were washed with water and then dried over MgSO4. MgSO4 was
removed by filtration and volatiles were removed from the filtrate
by rotary evaporation to give yellow oil (3.47 g, 90%), which was
used without further purification. Anal. Calc. for C18H17N3O: C,
74.20; H, 5.88; N, 14.42. Found: C, 74.08; H, 5.91; N, 14.49%. dH
(CDCl3) 1.93 (3H, s, CH3), 2.15 (3H, s, CH3), 5.86 (1H, s, CH), 6.70
(1H, t, J 7.2, C6H4), 6.78 (1H, d, J 8.1, C6H4), 7.11–7.22 (4H, m,
C6H4), 7.28–7.33 (2H, m, C6H4), 8.36 (1H, s, CH), 12.14 (1H, s,
OH). dC (CDCl3) 11.18, 13.42, 105.54, 117.06, 118.82, 118.93,
119.16, 127.10, 128.84, 129.73, 132.41, 133.30, 133.76, 140.59,
144.92, 149.03, 160.83, 163.85.
N
O
N
R
Zn
R
But
N
O
N
Zn
N
R1
But
OR2
IIIa R = OEt
IIIb R = Et
R
R1
6
4.2.2. 2-((2-(3,5-Dimethyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
4,6-di-tert-butylphenol (2b)
3. Conclusions
Synthesis of compound 2b followed the same procedure as for 2a.
Thus, a mixture of activated 4A molecular sieves (30 g), 1-(20-amino-
phenyl)-3,5-dimethylpyrazole (2.78 g, 14.86 mmol), 3,5-di-tert-
We have synthesized novel functionalized phenolate ligands
and their aluminum and zinc complexes, including N,O-chelate
aluminum complexes, N,N,O-chelate zinc complexes and
a

C. Zhang, Z.-X. Wang / Journal of Organometallic Chemistry 693 (2008) 3151–3158
3155
butylsalicylaldehyde (3.56 g, 15.20 mmol), toluene (40 mL) and sev-
eral drops of anhydrous acetic acid was refluxed for 20 h and then
cooled to room temperature. The molecular sieves were filtered off
and washed with dichloromethane (3 ꢃ 20 mL). The combined or-
ganic layers were washed with water and then dried over MgSO4.
MgSO4 was removed by filtration and volatiles were removed from
the filtrate by rotary evaporation. The residue was dissolved in n-
hexane and concentration of the hexane solution afforded orange
powder (5.09 g, 85%). M.p. 93–94 °C. Anal. Calc. for C26H33N3O: C,
77.38; H, 8.24; N, 10.41. Found: C, 77.44; H, 8.16; N, 10.20%. dH
(CDCl3) 1.23 (9H, s, But), 1.34 (9H, s, But), 2.00 (3H, s, Me), 2.22
(3H, s, Me), 5.87 (1H, s, CH), 7.04 (1H, d, J 2.4, Ar), 7.24–7.29 (2H,
m, Ar), 7.34–7.44 (3H, m, Ar), 8.40 (1H, s, CH), 12.67 (1H, s, OH). dC
(CDCl3) 11.54, 13.62, 29.44, 31.55, 34.24, 35.21, 105.79, 118.28,
119.87, 126.87, 127.09, 128.46, 128.95, 129.95, 133.78, 137.11,
140.43, 141.05, 145.80, 149.35, 158.47, 165.31.
at about ꢁ80 °C. The solution was warmed to room temperature
and stirred overnight. Solvent was removed under vacuum and
the residue was dissolved in Et2O. The mixture was filtered and
the filtrate was concentrated to yield yellow crystals of 3a
(0.42 g, 70.4%). M.p. 124–125 °C. Anal. Calc. for C20H22AlN3O: C,
69.15; H, 6.38; N, 12.10. Found: C, 69.19; H, 6.37; N, 12.00%. dH
(C6D6) ꢁ0.36 (6H, s, AlMe), 1.80 (3H, s, Me), 2.07 (3H, s, Me),
5.54 (1H, s, CH), 6.46 (1H, t, J 6.9, C6H4), 6.78–7.05 (6H, m, C6H4),
7.33 (1H, d, J 8.1, C6H4), 8.16 (1H, s, CH). dC (C6D6) ꢁ8.86, 11.50,
13.37, 106.67, 117.57, 119.11, 122.52, 125.57, 127.92, 129.35,
129.87, 133.68, 135.86, 138.22, 140.93, 143.53, 149.41, 165.71,
175.85.
4.2.6. 2-((2-(3,5-Dimethyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
4,6-di-tert-butyl phenato dimethyl aluminum (3b)
AlMe3 (0.73 mL, a 2.2 M solution in hexane, 1.61 mmol) was
added to a solution of 2b (0.65 g, 1.61 mmol) in toluene (10 mL)
at about ꢁ80 °C. The solution was warmed to room temperature
and stirred overnight. Volatiles were removed under vacuum and
the residue was dissolved in Et2O. The mixture was filtered and
the filtrate was concentrated to about 1 mL. To the solution n-hex-
ane (1 mL) was added. The resultant solution was stored at about
ꢁ30 °C for several days to yield yellow crystals of complex 3b
(0.45 g, 60.9%). M.p. 85–86 °C. Anal. Calc. for C28H38AlN3O: C,
73.17; H, 8.33; N, 9.14. Found: C, 72.94; H, 8.31; N, 9.14%. dH
(C6D6) ꢁ0.32 (6H, s, AlMe), 1.29 (9H, s, But), 1.51 (9H, s, But),1.81
(3H, s, Me), 2.13 (3H, s, Me), 5.49 (1H, s, CH), 6.80–7.03 (4H, m,
Ar), 7.41 (1H, d, J 7.8, Ar), 7.65 (1H, d, J 2.4, Ar), 8.20 (1H, s, CH).
dC (C6D6) ꢁ8.76, 11.43, 13.49, 29.59, 31.49, 34.12, 35.54, 106.66,
118.93, 125.54, 127.57, 129.53, 130.24, 130.39, 133.17, 133.78,
139.22, 140.91, 140.92, 143.91, 149.29, 162.88, 176.62.
4.2.3. 2-((2-(3,5-Diphenyl-1H-pyrazol-1-yl)- phenylimino)methyl)-
phenol (2c)
Synthesis of compound 2c followed the same procedure as for
2a. Thus, a mixture of activated 4A molecular sieves (30 g), 1-(20-
aminophenyl)-3,5-diphenylpyrazole (2.50 g, 8.03 mmol), o-
hydroxylbenzaldealdehyde (1.02 g, 8.36 mmol), toluene (30 mL)
and several drops of anhydrous acetic acid was refluxed for 20 h
and then cooled to room temperature. The molecular sieves were
filtered off and washed with dichloromethane (3 ꢃ 20 mL). The
combined organic layers was washed with water and dried over
MgSO4. MgSO4 was removed by filtration and volatiles were re-
moved from the filtrate by rotary evaporation. The residue was
crystallized from toluene to afford yellow crystals (2.80 g, 84%).
M.p. 151–152 °C. Anal. Calc. for C28H21N3O: C, 80.94; H, 5.09; N,
10.11. Found: C, 81.10; H, 5.08; N, 10.02%. dH (CDCl3) 6.68–6.73
(2H, m, Ar+CH), 6.79 (1H, d, J 8.4, Ar), 6.93–7.04 (7H, m, Ar), 7.17–
7.24 (2H, m, Ar), 7.27–7.37 (4H, m, Ar), 7.63 (1H, dd, J 1.8 and 7.2,
Ar), 7.81–7.83 (3H, m, Ar+CH), 11.89 (1H, s, OH). dC (CDCl3)
103.96, 117.24, 118.87, 119.24, 119.97, 126.06, 127.41, 127.83,
128.00, 128.02, 128.32, 128.66, 128.86, 129.97, 130.58, 132.53,
133.22, 133.47, 134.22, 144.91, 146.55, 152.52, 160.91, 164.43.
4.2.7. 2-((2-(3,5-Diphenyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
phenato dimethyl aluminum (3c)
Complex 3c was synthesized using a similar procedure to that
of 3a. Thus, reaction of AlMe3 (0.66 mL, a 2.2 M solution in hexane,
1.44 mmol) with 2c (0.60 g, 1.44 mmol) in toluene (10 mL) from
about ꢁ80 °C to room temperature afforded, after work-up, yellow
crystals of 3c (0.56 g, 82.3%). M.p. 182–183 °C. Anal. Calc. for
C
28H38AlN3O: C, 76.42; H, 5.56; N, 8.91. Found: C, 76.50; H, 5.55;
4.2.4. 2-((2-(3,5-Diphenyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
4,6-di-tert-butylphenol (2d)
N, 8.77%. dH (C6D6) ꢁ0.44 (6H, s, AlMe), 6.45–6.51 (1H, m, Ar),
6.59 (1H, s, CH), 6.80 (1H, dd, J 1.5 and 7.8, Ar), 6.86–7.15 (9H,
m, Ar), 7.24–7.39 (5H, m, Ar), 7.73 (1H, s, CH), 7.74 (1H, d, Ar),
8.01–8.04 (1H, m, Ar). dC (C6D6) ꢁ9.46, 105.51, 117.43, 119.53,
122.47, 126.00, 126.25, 127.92, 128.24, 128.46, 128.87, 129.01,
129.47, 130.02, 130.23, 133.40, 134.00, 136.11, 138.41, 142.72,
146.54, 153.24, 165.89, 174.87.
Synthesis of compound 2d followed the same procedure as for
2a. Thus, a mixture of activated 4A molecular sieves (30 g), 1-(20-
aminophenyl)-3,5-diphenylpyrazole (3.22 g, 10.34 mmol), 3,5-di-
tert-butylsalicylaldehyde (2.52 g, 10.75 mmol), toluene (50 mL)
and several drops of anhydrous acetic acid was refluxed for 20 h.
The molecular sieves were filtered off and washed with dichloro-
methane (3 ꢃ 20 mL). The combined solution was washed with
water and dried over MgSO4. The MgSO4 was removed by filtration
and volatiles were removed from the filtrate by rotary evaporation.
Methanol was added to the residue to give yellow powder (4.80 g,
88%). M.p. 175–176 °C. Anal. Calc. for C36H37N3O: C, 81.94; H, 7.07;
N, 7.96. Found: C, 81.84; H, 7.05; N, 7.90%. dH (CDCl3) 1.19 (9H, s,
But), 1.31 (9H, s, But), 6.70 (1H, s, CH), 6.80 (1H, d, J 2.1, Ar),
6.95–7.07 (6H, m, Ar), 7.22–7.39 (6H, m, Ar), 7.62 (1H, dd, J 1.2
and 7.5, Ar), 7.83–7.86 (2H,m, Ar), 7.92 (1H, s, CH), 12.44 (1H, s,
OH). dC (CDCl3) 29.42, 31.55, 34.18, 35.14, 103.97, 118.36, 120.21,
126.16, 126.96, 127.16, 127.95, 128.19, 128.26, 128.65, 128.80,
129.88, 130.60, 133.38, 134.08, 136.91, 140.28, 145.24, 146.62,
152.56, 158.13, 165.66.
4.2.8. 2-((2-(3,5-Diphenyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
4,6-di-tert-butylphenato dimethyl aluminum (3d)
Complex 3d was synthesized using a similar procedure to that
of 3b. Thus, reaction of AlMe3 (0.50 mL, a 2.2 M solution in hexane,
1.10 mmol) with 2 d (0.58 g, 1.10 mmol) in toluene (10 mL) from
about ꢁ80 °C to room temperature afforded, after similar work-
up, yellow crystals of 3d (0.40 g, 62.4%). M.p. 169–170 °C. Anal.
Calc. for C38H42AlN3O: C, 78.19; H, 7.25; N, 7.20. Found: C, 78.23;
H, 7.52; N, 7.23%. dH (C6D6) ꢁ0.55 (6H, s, AlMe), 1.16 (9H, s, But),
1.53 (9H, s, But), 6.45 (1H, s, CH), 6.64 (1H, d, J 2.4, Ar), 6.80 (1H,
dt, J 1.5 and 7.8, Ar), 6.89 (1H, dt, J 1.8 and 7.8, Ar), 6.98–7.07
(5H, m, Ar), 7.13–7.18 (1H, m, Ar), 7.23–7.30 (4H, m, Ar), 7.65
(1H, d, J 2.7, Ar), 7.67 (1H, s, CH), 7.93–7.97 (2H, m, Ar). dC (C6D6)
ꢁ9.56, 29.58, 31.32, 34.03, 35.53, 105.27, 119.39, 125.78, 126.20,
128.48, 128.93, 128.99, 129.01, 129.68, 129.92, 130.53, 133.35,
133.38, 134.18, 139.17, 140.93, 143.20, 146.89, 153.09, 163.02,
175.54.
4.2.5. 2-((2-(3,5-Dimethyl-1H-pyrazol-1-yl)-phenylimino)methyl)
phenato dimethyl aluminum (3a)
AlMe3 (0.78 mL, a 2.2 M solution in hexane, 1.72 mmol) was
added to a solution of 2a (0.50 g, 1.72 mmol) in toluene (10 mL)

3156
C. Zhang, Z.-X. Wang / Journal of Organometallic Chemistry 693 (2008) 3151–3158
4.2.9. 2-((2-(3,5-Diphenyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
4,6-di-tert-butylphenato diethyl aluminum (3e)
(1H, dd, J 1.2 and 7.8, Ar), 6.81 (1H, dt, J 1.5 and 7.8, Ar), 6.89
(1H, dd, J 0.9 and 8.1, Ar), 6.93 (5H, s, Ph), 7.12–7.19 (3H, m, Ar),
7.36 (2H, t, J 7.5, Ar), 7.84 (1H, s, CH), 8.19 (2H, dd, J 1.2 and 8.4,
Ar). dC (C6D6) ꢁ0.61, 13.43, 107.22, 114.04, 119.89, 122.11,
125.17, 125.79, 128.80, 129.03, 129.10, 129.46, 129.56, 130.13,
131.36, 131.86, 136.02, 136.10, 145.37, 147.34, 154.95, 166.83,
173.11.
AlEt3 (0.66 mL, a 1.8 M solution in hexane, 1.19 mmol) was
added to a solution of 2d (0.63 g, 1.19 mmol) in toluene (10 mL)
at about ꢁ80 °C. The mixture was warmed to room temperature
and stirred for 1 h and then at 60 °C overnight. Volatiles were re-
moved under vacuum and the residue was dissolved in n-hexane.
The mixture was filtered and the filtrate was concentrated to afford
yellow crystals of 3e (0.62 g, 85.2%). M.p. 167–168 °C. Anal. Calc.
for C40H46AlN3O: C, 78.53; H, 7.58; N, 6.87. Found: C, 78.23; H,
7.51; N, 6.95%. dH (C6D6) ꢁ0.05–0.17 (4H, m, AlCH2), 1.15 (9H, s,
But), 1.26 (3H, t, J 8.1, CH3), 1.56 (9H, s, But), 6.48 (1H, s, CH),
6.68 (1H, d, J 2.4, Ar), 6.78 (1H, dt, J 1.5 and 7.5, Ar), 6.91 (1H, dt,
J 1.5 and 7.5 Hz, Ar), 7.00–7.07 (4H, m, Ar), 7.14–7.31 (5H, m,
Ar), 7.65 (1H, d, J 2.4, Ar), 7.84 (1H, s, CH), 7.94 (1H, s, Ar), 7.96
(1H, d, J 1.5, Ar). dC (C6D6) 0.14, 9.17, 29.14, 30.82, 33.53, 35.06,
104.75, 118.89, 125.32, 125.69, 127.41, 128.37, 128.46, 128.52,
129.24, 129.42, 130.07, 130.18, 132.86, 132.96, 133.65, 138.65,
140.30, 142.75, 146.38, 152.58, 163.01, 175.54.
4.2.13. 2-((2-(3,5-Diphenyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
4,6-di-tert-butylphenato ethyl zinc (4d)
Complex 4d was synthesized using a similar procedure to that
of 4a. Thus, reaction of 2d (0.44 g, 0.83 mmol) with ZnEt2
(0.45 mL, a 1.89 M solution in hexane, 0.83 mmol) in toluene
(10 mL) afforded, after similar work-up, yellow crystals of 4d
(0.42 g, 81.3%). M.p. 230–232 °C. Anal. Calc. for C38H41N3OZn: C,
73.48; H, 6.65; N, 6.76. Found: C, 73.25; H, 6.68; N, 6.81%. dH
(C6D6) 0.76 (2H, q, J 8.1, ZnCH2), 1.38 (9H, s, But), 1.51 (3H, t, J
8.1, CH3), 1.63 (9H, s, But), 6.41–6.53 (2H, m, Ar), 6.43 (1H, s,
CH), 6.65 (1H, dd, J 0.9 and 7.8, Ar), 6.77–6.83 (1H, m, Ar), 6.87
(1H, d, J 2.7, Ar), 6.93 (5H, s, Ph), 7.23–7.29 (1H, m, Ar), 7.45 (2H,
t, J 7.5, Ar), 7.67 (1H, d, J 2.4, Ar), 7.85 (1H, s, CH), 8.23 (2H, d, J
8.1, Ar). dC (C6D6) ꢁ0.75, 13.60, 29.87, 31.72, 34.07, 35.91, 107.00,
119.04, 122.09, 125.31, 127.91, 128.74, 129.10, 129.16, 129.46,
129.53, 129.62, 129.68, 130.21, 130.78, 131.17, 134.92, 142.69,
145.72, 147.27, 154.66, 167.14, 170.95.
4.2.10. 2-((2-(3,5-Dimethyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
phenato ethyl zinc (4a)
A solution of 2a (0.45 g, 1.55 mmol) in toluene (3 mL) was
added to a solution of ZnEt2 (0.82 cm3, a 1.89 M solution in hexane,
1.55 mmol) in toluene (6 mL) at 0 °C. The mixture was stirred at
0 °C for 2 h and at room temperature overnight. Volatiles were re-
moved under vacuum and the residue was dissolved in Et2O. The
solution was filtered and the filtrate was concentrated to yield yel-
low crystals of 4a (0.52 g, 88.3%). M.p. 151–152 °C. Anal. Calc. for
4.2.14. Bis(2-((2-(3,5-diphenyl-1H-pyrazol-1-yl)-phenylimino)-
methyl)phenato)zinc (5)
ZnEt2 (0.32 mL, a 1.89 M solution in hexane, 0.60 mmol) was
added to a solution of 2c (0.50 g, 1.20 mmol) in toluene (20 mL)
at 0 °C. The resultant mixture was stirred at 60 °C overnight. The
solution was filtered and the filtrate was concentrated to yield yel-
low crystals of 5 (0.42 g, 80%). M.p. 285–286 °C. Anal. Calc. for
C20H21N3OZn: C, 62.43; H, 5.50; N, 10.92. Found: C, 62.56; H,
5.49; N, 10.81%. dH (C6D6) 0.75 (2H, q, J 8, ZnCH2), 1.55 (3H, t, J 8,
CH3), 1.65 (3H, s, CH3), 2.33 (3H, s, CH3), 5.46 (1H, s, CH), 6.43
(1H, dt, J 0.9 and 7.1, Ar), 6.56–6.64 (2H, m, Ar), 6.76–6.85 (2H,
m, Ar), 6.92 (1H, dt, J 0.9 and 7.8, Ar), 7.13-7.25 (2H, m, Ar), 7.63
(1H, s, CH). dC (C6D6) ꢁ1.43, 12.39, 13.37, 13.73, 107.92, 113.56,
119.86, 121.99, 125.11, 125.21, 125.82, 129.44, 130.53, 135.90,
136.07, 142.09, 145.36, 150.57, 166.47, 173.25.
C56H40N6O2Zn: C, 75.21; H, 4.51; N, 9.40. Found: C, 75.26; H,
4.40; N, 9.25%. dH (C6D6) 6.15–6.21 (1H, m, Ar), 6.37 (1H, dd,J 1.2
and 7.8, Ar), 6.63 (1H, s, CH), 6.67–6.71 (1H, m, Ar), 6.74–6.93
(7H, m, Ar), 7.04–7.08 (2H, m, Ar), 7.12 (1H, s, CH), 7.18–7.27
(3H, m, Ar), 7.33–7.36 (1H, m, Ar), 7.74–7.77 (2H, m, Ar). dC
(C6D6) 105.88, 113.59, 118.70, 124.26, 125.07, 125.70, 126.02,
126.42, 127.47, 127.85, 127.92, 128.16, 128.23, 128.57, 128.61,
128.72, 129.33, 129.38, 131.55, 133.38, 133.68, 135.97, 136.87,
144.94, 146.18, 153.23, 172.36, 173.12.
4.2.11. 2-((2-(3,5-Dimethyl-1H-pyrazol-1-yl)-phenylimino)methyl)-4,
6-di-tert-butylphenato ethyl zinc (4b)
A solution of 2b (0.40 g, 1.00 mmol) in n-hexane (5 mL) was
added to a solution of ZnEt2 (0.53 mL, a 1.89 M solution in hexane,
1.00 mmol) in n-hexane (10 mL) at 0 °C. The mixture was stirred at
0 °C for 2 h and at room temperature overnight. The resultant yel-
low solution was filtered and the filtrate was concentrated under
vacuum to afford yellow crystals of 4b (0.44 g, 89.7%). M.p. 191–
192 °C. Anal. Calc. for C28H37N3OZn: C, 67.67; H, 7.50; N, 8.45.
Found: C, 67.68; H, 7.44; N, 8.31%. dH (C6D6) 0.79 (2H, q, J 8, ZnCH2),
1.38 (9H, s, But), 1.64 (3H, t, J 8, CH3), 1.65 (3H, s, CH3), 1.77 (9H, s,
But), 2.41 (3H, s, CH3), 5.51 (1H, s, CH), 6.55–6.64 (2H, m, Ar), 6.75
(1H, dt, J 1.5 and 7.8, Ar), 6.80 (1H, d, J 2.4, Ar), 6.89 (1H, dt, J 1.2
and 7.5, Ar), 7.61 (1H, s, CH), 7.66 (1H, d, J 2.7, Ar). dC (C6D6)
ꢁ1.65, 12.39, 13.41, 13.87, 29.97, 31.73, 34.03, 36.07, 107.77,
118.88, 122.19, 125.11, 125.35, 129.40, 129.73, 130.58, 134.49,
141.96, 142.55, 145.90, 150.27, 167.16, 170.85.
4.3. X-Ray crystallography
Single crystals were mounted in Lindemann capillaries under
nitrogen. Diffraction data were collected on a Siemens CCD area-
detector with graphite-monochromated Mo
K
a
radiation
(k = 0.71073 Å). A semi-empirical absorption correction was ap-
plied to the data. The structures were solved by direct methods
using SHELXS-97 [20] and refined against F2 by full-matrix least-
squares using SHELXL-97 [21]. Hydrogen atoms were placed in calcu-
lated positions. Crystal data and experimental details of the struc-
ture determinations are listed in Table 4.
4.4. Polymerization of e-caprolactone catalyzed by complexes 3a-5
4.2.12. 2-((2-(3,5-Diphenyl-1H-pyrazol-1-yl)-phenylimino)methyl)-
phenato ethyl zinc (4c)
A typical polymerization was exemplified by the synthesis of
PCL catalyzed by complex 3b. Complex 3b (0.0301 g, 0.065 mmol)
was added into a Schlenk tube and followed by injection of a solu-
Complex 4c was synthesized using a similar procedure to that
of 4a. Thus, reaction of 2c (0.46 g, 1.11 mmol) with ZnEt2
(0.59 mL, a 1.89 M solution in hexane, 1.11 mmol) in toluene
(15 mL) afforded, after similar work-up, yellow crystals of 4c
(0.50 g, 89.0%). M.p. 232–234 °C. Anal. Calc. for C30H25N3OZn: C,
70.80; H, 4.95; N, 8.26. Found: C, 70.43; H, 5.03; N, 8.10%. dH
(C6D6) 0.71 (2H, q, J 8.1, ZnCH2), 1.39 (3H, t, J 8.1, CH3), 6.40 (1H,
s, CH), 6.42–6.48 (2H, m, Ar), 6.54 (1H, dd, J 1.2 and 8.1, Ar), 6.64
tion of e-CL (1.49 g, 13.05 mmol) in toluene (16 mL). The flask was
put into an oil-bath which was preset at 80 °C. Samples were taken
from the reaction mixture using syringe at a desired time interval
for 1H NMR spectral analysis. After 220 min the polymerization
was quenched by addition of excess glacial acetic acid (0.2 mL) into
the solution. After stirring for 0.5 h at room temperature, the

C. Zhang, Z.-X. Wang / Journal of Organometallic Chemistry 693 (2008) 3151–3158
3157
Table 4
Summary of crystal data for complexes 3a, 4a and 5
3a
4a
5
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C
20H22AlN3O
C20H21N3OZn
384.77
Monoclinic
C2/c
25.428(5)
9.3262(19)
16.289(3)
108.32(3)
C56H40N6O2Zn
894.31
Monoclinic
C2/c
23.583(3)
9.2133(12)
20.887(3)
95.817(2)
4514.8(10)
4
347.39
Monoclinic
P2(1)/n
13.443(3)
9.279(2)
15.742(4)
90.875(4)
1963.4(8)
b (Å)
c (Å)
b (°)
V (Å3)
3667.1(13)
8
Z
4
T (K)
294(2)
1.175
736
0.115
113(2)
1.394
1600
1.351
294(2)
1.316
1856
0.595
Dcalcd (g/cm3)
F(000)
l
(mmꢁ1
)
h range for data collection (°)
Absorption correction
1.98 to 25.02
Semi-empirical from equivalents
9650
3456 (0.0591)
3456/0/231
1.69 to 27.87
Semi-empirical from equivalents
13739
4370 (0.0373)
4370/0/229
1.74 to 26.43
Semi-empirical from equivalents
12481
4620 (0.0333)
4620/0/294
No. of reflections collected
No. of independent reflections [R(int)
No. of data/restraints/parameters
Goodness-of-fit (GOF) on F2
]
1.026
1.067
1.004
Final R indicesa [I > 2
R indices (all data)
r
(I)]
R1 = 0.0563, wR2 = 0.1253
R1 = 0.1306, wR2 = 0.1646
0.195 and ꢁ0.286
R1 = 0.0451, wR2 = 0.1044
R1 = 0.0509, wR2 = 0.1091
0.744 and ꢁ0.778
R1 = 0.0374, wR2 = 0.0829
R1 = 0.0621, wR2 = 0.0946
0.202 and ꢁ0.238
Largest diff peak and hole [e Åꢁ3
]
h
i
1=2
P
P
P
P
a
2
R1
¼
jjFoj ꢁ jFcjj= jFoj; wR2
¼
wðF2o ꢁ Fc2Þ = wðFo4Þ
.
(c) M.H. Chisholm, J.C. Huffman, K. Phomphrai, J. Chem. Soc., Dalton Trans.
(2001) 222;
(d) M. Cheng, A.B. Attygalle, E.B. Lobkovsky, G.W. Coates, J. Am. Chem. Soc. 121
(1999) 11583.
resulting viscous solution was poured into methanol with stirring.
The white precipitate was washed three times with hexane and
dried under vacuum, giving white solid (0.76 g, 51%).
[5] (a) Z. Zhong, M.J.K. Ankoné, P.J. Dijkstra, C. Birg, M. Westerhausen, J. Feijen,
Polym. Bull. 46 (2001) 51;
Acknowledgements
(b) I. Taden, H.C. Kang, W. Massa, T.P. Spaniol, J. Okuda, Eur. J. Inorg. Chem.
(2000) 441;
(c) M.H. Chisholm, N.J. Patmore, Z.P. Zhou, Chem. Commun. (2005) 127;
(d) H.Y. Ma, G. Melillo, L. Oliva, T.P. Spaniol, U. Englert, J. Okuda, Dalton Trans.
(2005) 721;
(e) Z.Y. Zhong, P.J. Dijkstra, J. Feijen, Angew. Chem., Int. Ed. 41 (2002) 4510;
(f) N. Nomura, T. Aoyama, R. Ishii, T. Kondo, Macromolecules 38 (2005)
5363;
(g) M.L. Hseueh, B.H. Huang, C.C. Lin, Macromolecules 35 (2002) 5763;
(h) D.J. Darensbourg, P. Ganguly, D. Billodeaux, Macromolecules 38 (2005)
5406;
(i) L.M. Alcazar-Roman, B.J. O’Keefe, M.A. Hillymer, W.B. Tolman, Dalton Trans.
(2003) 3082;
This work was supported by the National Natural Science Foun-
dation of China (Grant No. 20572106). The authors thank Profes-
sors H.-B. Song and H.-G. Wang for determining the crystal
structures. CZ acknowledges the support of the Graduate School
of University of Science and Technology of China.
Appendix A. Supplementary material
CCDC 676921, 676921 and 676923 contains the supplementary
crystallographic data for 3a, 4a and 5. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2008.07.002.
(j) Y.C. Liu, B.T. Ko, C.C. Lin, Macromolecules 34 (2001) 6196;
(k) P. Lecomte, F. Stassin, R. Jérôme, Macromol. Symp. 215 (2004) 325;
(l) A. Kowalski, A. Duda, S. Penczek, Macromolecules 33 (2000) 689;
(m) A. Kowalski, J. Libiszowski, A. Duda, S. Penczek, Macromolecules 33 (2000)
1964;
(n) M.H. Chisholm, N.W. Eilerts, J.C. Huffman, S.S. Lyer, M. Pacold, K. Phomphrai,
J. Am. Chem. Soc. 122 (2000) 11845;
(o) T.L. Yu, C.C. Wu, C.C. Chen, B.H. Huang, J.C. Wu, C.C. Lin, Polymer 46 (2005)
5909;
(p) H.Y. Chen, B.H. Huang, C.C. Lin, Macromolecules 38 (2005) 5400;
(q) A. Dumitrescu, B. Martin-Vaca, H. Gornitzka, J.B. Cazaux, D. Bourissou, G.
Bertrand, Eur. J. Inorg. Chem. (2002) 1948;
(r) W. Yao, Y. Mu, A. Gao, Q. Su, Y. Liu, Y. Zhang, Polymer 49 (2008) 2486;
(s) A. Amgoune, L. Lavanant, C.M. Thomas, Y. Chi, R. Welter, S. Dagorne, J.-F.
Carpentier, Organometallics 24 (2005) 6279;
References
[1] (a) M. Endo, T. Aida, S. Inoue, Macromolecules 20 (1987) 2982;
(b) A. Duda, Z. Florjanczyk, A. Hofman, S. Slomokowski, S. Penczek,
Macromolecules 23 (1990) 1640;
(c) B.T. Ko, C.C. Lin, Macromolecules 32 (1999) 8296;
(d) B.J. O’Keefe, M.A. Hillmyer, W.B. Tolman, J. Chem. Soc., Dalton Trans. (2001)
2215;
(e) E.P. Wasserman, I. Annis, L.J. Chopin III, P.C. Price, Macromolecules 38
(2005) 322;
(t) F. Majoumo-Mbe, E. Smolensky, P. Lönnecke, D. Shpasser, M.S. Eisen, E. Hey-
Hawkins, J. Mol. Catal. A: Chem. 240 (2005) 91;
(u) N. Iwasa, J. Liu, K. Nomura, Catal. Commun. 9 (2008) 1148.
[6] Y. Sarazin, R.H. Howard, D.L. Hughes, S.M. Humphrey, M. Bochmann, Dalton
Trans. (2006) 340.
[7] (a) P. Hormnirun, E.L. Marshall, V.C. Gibson, A.J.P. White, D.J. Williams, J. Am.
Chem. Soc. 126 (2004) 2688;
(f) G.W. Coates, A.F. Mason, J. Am. Chem. Soc. 126 (2004) 10798.
[2] (a) D. Mecerreyes, R. Jérôme, P. Dubois, Adv. Polym. Sci. 147 (1999) 1;
(b) K.M. Stridsberg, M. Ryner, A.-C. Albertsson, Adv. Polym. Sci. 157 (2002)
41;
(c) O. Dechy-Cabaret, B. Martin-Vaca, D. Bourissou, Chem. Rev. 104 (2004) 6147.
[3] (a) F. Majoumo-Mbe, E. Smolensky, P. Lönnecke, D. Shpasser, M.S. Eisen, E.
Hey-Hawkins, J. Mol. Catal. A: Chem. 240 (2005) 91;
(b) K.B. Aubrecht, M.A. Hillmyer, W.B. Tolman, Macromolecules 35 (2002)
644;
(c) J. Wu, T.-L. Yu, C.-T. Chen, C.C. Lin, Coord. Chem. Rev. 250 (2006) 602.
[4] (a) D.K. Han, J.A. Hubbell, Macromolecules 29 (1996) 5233;
(b) B.M. Chamberlain, M. Cheng, D.R. Moore, T.M. Ovitt, E.B. Lobkovsky, G.W.
Coates, J. Am. Chem. Soc. 123 (2001) 3229;
(b) T.M. Ovitt, G.W. Coates, J. Am. Chem. Soc. 121 (1999) 4072;
(c) B.M. Chamberlain, M. Cheng, D.R. Moore, T.M. Ovitt, E.B. Lobkovsky, G.W.
Coates, J. Am. Chem. Soc. 123 (2001) 3229;
(d) T.M. Ovitt, G.W. Coates, J. Am. Chem. Soc. 124 (2002) 1316;
(e) Z. Zhong, P.J. Dijkstra, J. Feijen, Angew. Chem., Int. Ed. 41 (2002) 4510;
(f) Z. Zhong, P.J. Dijkstra, J. Feijen, J. Am. Chem. Soc. 125 (2003) 11291;
(g) C.P. Radano, G.L. Baker, M.R. Smith III, J. Am. Chem. Soc. 122 (2000) 1552;
(h) N. Nomura, R. Ishii, M. Akakura, K. Aoi, J. Am. Chem. Soc. 124 (2002) 5938;
(i) K. Majerska, A. Duda, J. Am. Chem. Soc. 126 (2004) 1026;
(j) J. Belleney, M. Wisniewski, A. Le Borgne, Eur. Polym. J. 40 (2004) 523;

3158
C. Zhang, Z.-X. Wang / Journal of Organometallic Chemistry 693 (2008) 3151–3158
(k) Z. Tang, X. Chen, X. Pang, Y. Yang, X. Zhang, X. Jing, Biomacromolecules 5
(2004) 965;
(b) D. Zhang, J. Xu, L. Alcazar-Roman, L. Greenman, C.J. Cramer, M.A. Hillmyer,
W.B. Tolman, Macromolecules 37 (2004) 5274;
(l) M.R.T. Breteler, Z. Zhong, P.J. Dijkstra, A.R.A. Palmans, J. Peeters, J. Feijen, J.
Polym. Sci. Part A: Polym. Chem. 45 (2007) 429;
(m) N. Nomura, R. Ishii, Y. Yamamoto, T. Kondo, Chem. -Eur. J. 13 (2007) 4433.
(c) K.M. Schreck, M.A. Hillmyer, Tetrahedron 60 (2004) 7177.
[12] M.S. Hill, A.R. Hutchison, T.S. Keizer, S. Parkin, M.A. VanAelstyn, D.A. Atwood, J.
Organomet. Chem. 628 (2001) 71.
[8] (a) M.-L. Hsueh, B.-H. Huang, C.C. Lin, Macromolecules 35 (2002) 5763;
(b) T.-C. Liao, Y.-L. Huang, B.-H. Huang, C.C. Lin, Macromol. Chem. Phys. 204
(2003) 885;
[13] Z.-X. Wang, D. Yang, J. Organomet. Chem. 690 (2005) 4080.
[14] R.-C. Yu, C.-H. Hung, J.-H. Huang, H.-Y. Lee, J.-T. Chen, Inorg. Chem. 41 (2002)
6450.
(c) C.-T. Chen, C.-A. Huang, B.-H. Huang, Macromolecules 37 (2004) 7968;
(d) H.-L. Chen, B.-T. Ko, B.-H. Huang, C.C. Lin, Organometallics 20 (2001)
5076;
[15] L. Tatar, D. Ülkü, O. Atakol, Acta Crystallogr., Sect. C 55 (1999) 508.
[16] I. Hegelmann, A. Beck, C. Eichhorn, B. Weibert, N. Burzlaff, Eur. J. Inorg. Chem.
(2003) 339.
(e) B.-H. Huang, C.-N. Lin, M.-L. Hsueh, T. Athar, C.C. Lin, Polymer 47 (2006)
6622;
[17] (a) A. Dumitrescu, B. Martin-Vaca, H. Gornitzka, J.-B. Cazaux, D. Bourissou, G.
Bertrand, Eur. J. Inorg. Chem. (2002) 1948;
(f) Y.-C. Liu, B.-T. Ko, C.C. Lin, Macromolecules 34 (2001) 6196.
[9] M.H. Chisholm, J.C. Gallucci, H. Zhen, Inorg. Chem. 40 (2001) 5051.
[10] (a) J. Lewinski, P. Horeglad, M. Dranka, I. Justyniak, Inorg. Chem. 43 (2004)
5789;
(b) J.-C. Wu, B.-H. Huang, M.-L. Hsueh, S.-L. Lai, C.-C. Lin, Polymer 46 (2005)
9784.
[11] (a) C.K. Williams, L.E. Breyfogle, S.K. Choi, W. Nam, V.G. Young Jr., M.A.
Hillmyer, W.B. Tolman, J. Am. Chem. Soc. 125 (2003) 11350;
(b) W. Kläui, M. Berghahn, W. Frank, G.J. Reiß, T. Schönherr, G. Rheinwald, H.
Lang, Eur. J. Inorg. Chem. (2003) 2059.
[18] H. Ma, J. Okuda, Macromolecules 39 (2006) 128.
[19] A. Mukherjee, U. Subramanyam, V.G. Puranik, T.P. Mohandas, A. Sarkar, Eur. J.
Inorg. Chem. (2005) 1254.
[20] G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[21] G.M. Sheldrick, SHELXL97, Programs for Structure Refinement, Universität
Göttingen, 1997.