Syntheses, structures and catalytic activity of copper(II) complexes bearing N,O-chelate ligands

Article abstract of DOI:10.1016/j.jorganchem.2005.05.054

Copper complexes [Cu(Lⁿ)₂] 1-4 bearing N,O-chelating β-ketoamine ligands Lⁿ based on condensation products of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with aniline (L¹), α-naphthylamine (L²), o-methylaniline (L³), and p-nitroaniline (L⁴), respectively, were synthesized and characterized by IR, ¹H NMR and X-ray crystallography (except 2). They were shown to catalyze the vinyl polymerization of norbornene when activated by methylaluminoxane (MAO). Both steric and electronic effects are important and influential factors contributing to the catalytic activity of the complexes with the order of 2 > 4 > 3 > 1.

Full text of DOI:10.1016/j.jorganchem.2005.05.054

Journal of Organometallic Chemistry 691 (2006) 821–828
www.elsevier.com/locate/jorganchem
Syntheses, structures and catalytic activity of copper(II)
complexes bearing N,O-chelate ligands
a
b
a,
b,
*
Xing-Qiang Lu , Feng Bao , Bei-Sheng Kang *, Qing Wu
,
¨
a
b
Han-Qin Liu , Fang-Ming Zhu
a
School of Chemistry and Chemical Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou 510275, China
b
Institute of Polymer Science, Sun Yat-Sen (Zhongshan) University, Guangzhou 510275, China
Received 24 November 2004; received in revised form 17 May 2005; accepted 23 May 2005
Available online 10 January 2006
Abstract
Copper complexes [Cu(Ln)2] 1–4 bearing N,O-chelating b-ketoamine ligands Ln based on condensation products of 1-phenyl-3-
methyl-4-benzoyl-5-pyrazolone with aniline (L1), a-naphthylamine (L2), o-methylaniline (L3), and p-nitroaniline (L4), respectively, were
1
synthesized and characterized by IR, H NMR and X-ray crystallography (except 2). They were shown to catalyze the vinyl polymer-
ization of norbornene when activated by methylaluminoxane (MAO). Both steric and electronic effects are important and influential
factors contributing to the catalytic activity of the complexes with the order of 2 > 4 > 3 > 1.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Copper complex; b-Ketoamine; Polymerization; Catalytic activity; Norbornene
1. Introduction
lytic activities. Copper(II) catalysts based on a-diimine [7]
could produce very high-molecular-weight polyethylenes
with moderate activity, which are probably the first such
catalysts reported in the academic literature, although
some have been described in patents [3b].
In recent years there has been an intense search for new-
generation catalysts for the polymerization of olefins in
both academic and industrial research laboratories [1],
especially those containing late transition metals. Com-
pared with the metallocenes based on early transition met-
als, the late transition metal catalysts are less oxophilic and
thus less easily poisoned by polar monomeric contaminants
[2]. Among these, copper(II) complexes present some inter-
esting properties in both homo- and copolymerization of
olefins with functional monomers [3]. Copper alkene chem-
istry is well explored in the literature [4], yet Cu-complexes
used as catalysts in olefin polymerization are not well doc-
umented and the structure of the reactive center is still not
yet disclosed. There were reports that Cu(II) complexes
with benzamidinate [5] or benzimidazolyl [6] ligands have
been used for ethylene polymerization but with low cata-
Complexes containing ligands of N,O-chelate are partic-
ularly interesting and challenging for catalysis by mixed-
donor-ligand-complexes, such as the Ni-based systems
were shown to be effective in ethylene polymerization [8].
b-Ketoamines are important members of the family of
N:O bidentate ligands [9] because of their ease of prepara-
tion and simple modification of both steric and/or elec-
tronic effects. Presently, although the luminescent and
magnetic properties and the biological activity [10] of b-
ketoamino Cu-complexes have been reported, the catalytic
activity toward olefin polymerizations, particularly of the
bicyclic olefin bicyclo[2.2.1]het-2-ene, better known by its
trivial name norbornene (NBE), to our knowledge, has
not been observed before.
*
The catalytic polymerization of NBE has been reported
to go through three pathways [1d,11] as shown in Scheme 1
Corresponding authors. Tel./fax: +86 20 84110318.
E-mail address: cedc34@zsu.edu.cn (B.-S. Kang).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.05.054

822
X.-Q. Lu¨ et al. / Journal of Organometallic Chemistry 691 (2006) 821–828
N
ROMP
N
n
O
O
RNH2
cationic or radical
vinyl type
n
n
N
N
NR
O
n
Scheme 1. Schematic representation of the three polymerization processes
for norbornene (Ref. [1d]).
N
N
[1d]: the ring-opening metathesis polymerization (ROMP),
the cationic or radical polymerization, and the vinylic poly-
merization. Catalysts containing Pd [12], Ni [13], or Co [14]
and many others have been reported for vinyl-type poly-
merization of NBE, but none of copper complexes has been
documented. The significance of this type of polymeriza-
tion lies in the fact that the polymers formed will have good
mechanical property, high heat resistivity and good solubil-
ity in organic solvents [1d]. Such systems may also find use
in the copolymerization of NBE/olefins. In order to explore
this void field of b-ketoamine-Cu(II) catalysts, herein a ser-
ies of copper(II) complexes have been synthesized, charac-
terized, and their catalytic activities reported for the first
time.
O
NHR
CuCl2
NEt3
N
N
RN
O
Cu
O
NR
N
N
NO2
2. Results and discussion
R
CH3
HL3
2.1. Synthesis and characterization
HL4
HL2
2
HL
HL1
1
The three new b-ketoamine ligands HL1, HL3 and HL4
were synthesized by condensation of the corresponding
amines (see Section 3) with 1-phenyl-3-methyl-4-benzoyl-
5-pyrazolone in good yields. Their enamine conformation
has been exemplified by the single crystal structural study
of a member of HLn obtained with b-methylphenylamine
[15]. HL1–HL4 are very soluble in CH2Cl2 and CHCl3,
but moderately soluble in hot EtOH and MeOH.
Complex
3
4
Scheme 2. Reaction scheme for the syntheses of ligands HLn and the
complexes 1–4.
groups. The large red shift of the absorptions for the car-
bonyl bonds as compared to that for the ligands (1620–
1644 cmꢁ1) may have been caused by coordination thus
weakening of the bonds, and also by the delocalization of
the conjugated six-membered chelate rings. Thermogravi-
metric analysis (TGA) in the range 25–600 ꢁC showed that
1–4 have similar weight loss patterns. The framework
decomposes at temperature over 320 ꢁC where an abrupt
weight loss was observed, followed by a final weight loss
in the 390–600 ꢁC range.
When the deprotonated (by triethylamine) ligands Ln
(n = 1, 3, 4) were allowed to react with CuCl2 or Cu(NO3)2
in either 2:1 or 1:1 molar ratio, the respective bis(b-ketoa-
mino)copper(II) complexes ½CuLn2ꢀ 1, 3 and 4 (Scheme 2) in
70–80% yields were obtained, respectively, suggesting that
the composition of the products are sensitive neither to
the type of anion nor to the ligand-to-metal ratio under
these reaction conditions. Ligand HL2 and complex 2 were
also prepared for catalytic studies, which have been
reported before [16].
2.2. Crystal structures
Complexes 1–4 showed mC@O absorptions in range 1595–
1597 cmꢁ1, while multiple strong absorptions in range
1560–1380 cmꢁ1 could be caused by the C@N and C@C
The structure of 1 is shown in Fig. 1, while those of 3
and 4 are similar and were shown in Figs. 2 and 3, respec-
tively. Selected atomic distances and bond angles are listed

X.-Q. Lu¨ et al. / Journal of Organometallic Chemistry 691 (2006) 821–828
823
in Table 1. The structure of 2 was not determined since the
complex has been reported previously [16]. In the com-
plexes, the four-coordinate copper atom is arranged in a
distorted square-planar geometry where the two Ln ligands
acting as monoanionic bidentate N,O-chelators lie in the
trans-conformation to create two stable delocalized six-
membered chelate rings (CuOCCCN), with O–Cu–O and
N–Cu–N angles in the range 136–149ꢁ and 141–152ꢁ,
respectively. Weak axial Cuꢂ ꢂ ꢂH–Cedge intramolecular
interaction was observed in the complexes with Cu to the
˚
nearest Cphenyl distances in the range 3.2–4.0 A.
The distances of the Cu(II) ion in 1 to the two least
square chelate planes defined by O1–C7–C8–C11–N3 and
˚
O2–C30–C31–C34–N6 are 0.407 and 0.077 A, respectively.
˚
Similar distances are 0.439 and 0.254 A in 3. The Cu(II) to
˚
chelate-ring distance is increased to 0.481 A in 4 where the
alkyl substituent is p-nitrophenyl (L4). A sequence can be
observed within the series 1, 3 and 4, where the R group
is phenyl, o-methylphenyl, and p-nitrophenyl, respectively,
and the aforementioned Cu-to-chelate-plane distances are
in the order of 1 < 3 < 4. Besides that, the dihedral angles
(127.9ꢁ, 121.0ꢁ and 47.0ꢁ for 1, 3 and 4, respectively) of
the two six-membered chelate rings are in the order of
1 > 3 > 4, which showed a reverse trend. On correlation
of the crystal structure versus catalytic activity (see next
section), a fact is disclosed that with larger and more elec-
tron withdrawing substituent for the R group of the ligand,
such as in 4, higher activity is observed (next section),
which is accompanied by larger Cu-to-chelate distance
and smaller dihedral angle. These results imply that both
steric and electronic effects are important for good catalytic
activity. Although the structure of 2 [16] was not studied, it
can be assumed that 2 will have similar molecular frame-
work by comparison of its spectral data with those of know
structures as discussed in the previous section, and also
shown in Section 3.
Fig. 2. Structure of complex 3 with atomic-labeling scheme. Hydrogen
atoms are omitted for clarity.
Fig. 3. Structure of complex 4 with atomic-labeling scheme. Hydrogen
atoms are omitted for clarity.
There is only weak intramolecular p–p interaction
although there are several aromatic planes present, the
shortest pꢂ ꢂ ꢂp centroid-to-centroid distances are 4.36,
˚
4.01, and 4.19 A for complexes 1, 3, and 4, respectively.
No intermolecular interaction can be observed for any of
the complexes (see Table 2).
Fig. 1. Structure of complex 1 with atomic-labeling scheme. Hydrogen
atoms and the solvate molecule are omitted for clarity.

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X.-Q. Lu¨ et al. / Journal of Organometallic Chemistry 691 (2006) 821–828
Table 1
˚
Selected atomic distances (A) and bond angles (ꢁ) for complexes 1 Æ EtOH, 3 and 4
1 Æ EtOH
3
4
˚
Atomic distance (A)
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–N(3)
Cu(1)–N(6)
O(1)–C(7)
O(2)–C(30)
C(7)–C(8)
C(30)–C(31)
C(8)–C(11)
C(31)–C(34)
N(1)–N(2)
1.910(2)
1.890(2)
1.971(2)
1.946(2)
1.275(4)
1.285(4)
1.407(4)
1.415(4)
1.432(4)
1.408(4)
1.395(3)
1.396(3)
1.358(3)
1.355(4)
1.316(4)
1.315(4)
1.320(3)
1.317(3)
1.433(4)
1.408(4)
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–N(3)
Cu(1)–N(6)
O(1)–C(2)
O(2)–C(26)
C(1)–C(2)
C(25)–C(26)
C(1)–C(18)
C(25)–C(42)
N(1)–N(2)
N(4)–N(5)
N(1)–C(2)
N(4)–C(26)
N(2)–C(3)
N(5)–C(27)
N(3)–C(18)
N(6)–C(42)
C(1)–C(3)
1.905(2)
1.906(2)
1.984(2)
1.978(2)
1.280(4)
1.286(3)
1.413(4)
1.421(4)
1.418(4)
1.415(4)
1.388(4)
1.401(3)
1.356(4)
1.343(4)
1.313(4)
1.310(4)
1.315(4)
1.309(4)
1.422(4)
1.434(4)
Cu(1)–O(1)
Cu(1)–N(3)
O(1)–C(7)
C(7)–C(8)
C(8)–C(11)
N(1)–N(2)
N(1)–C(7)
N(2)–C(9)
N(3)–C(11)
C(8)–C(9)
1.9015(15)
1.9914(18)
1.278(2)
1.415(3)
1.411(3)
1.392(2)
1.356(2)
1.309(3)
1.318(3)
1.436(3)
N(4)–N(5)
N(1)–C(7)
N(4)–C(30)
N(2)–C(9)
N(5)–C(32)
N(3)–C(11)
N(6)–C(34)
C(8)–C(9)
C(31)–C(34)
C(25)–C(27)
Bond angle (ꢁ)
O(1)–Cu(1)–O(2)
N(3)–Cu(1)–N(6)
O(1)–Cu(1)–N(3)
O(1)–Cu(1)–N(6)
O(2)–Cu(1)–N(3)
O(2)–Cu(1)–N(6)
136.25(10)
144.20(11)
95.01(8)
94.86(9)
99.97(9)
96.33(9)
O(1)–Cu(1)–O(2)
N(3)–Cu(1)–N(6)
O(1)–Cu(1)–N(3)
O(1)–Cu(1)–N(6)
O(2)–Cu(1)–N(3)
O(2)–Cu(1)–N(6)
145.01(10)
141.43(10)
93.25(10)
97.04(9)
97.90(9)
94.62(9)
O(1)–Cu(1)–O(1)a
N(3)–Cu(1)–N(3)a
O(1)–Cu(1)–N(3)
O (1)a –Cu(1)–N(3)
149.03(9)
151.67(10)
93.74(6)
93.75(6)
Equivalent position for a: ꢁx + 1, y, ꢁz + 3/2.
2.3. Catalytic studies
merization of ethylene. These results imply that both steric
and electronic effects of the ligands play important roles in
catalysis [8b]. Such effects have been discussed in Section
2.2.
Complexes 1–4 showed medium catalytic activities
towards the polymerization of norbornene (NBE) in the
presence of co-catalyst MAO (methylaluminoxane) [17] as
compared to the reported Ni catalysts [13]. However, this
could be the first report of Cu(II) complexes with b-keto-
amine ligands to show fair activities. A summary of the cat-
alytic data are listed in Table 3.
EPR measurements were performed in toluene in which
the polymerization reactions were run. Complexes 1 and 3
were chosen as examples to check on the oxidation state of
the active species – the copper atom. Signals at gi = 2.110
and g^ = 2.065 were observed for the complexes, which
are very similar to the literature values for Cu(II) com-
plexes [18]. These signals persist for both 1 and 3 after
the solution was added with an excess amount of the co-
catalyst MAO, although the intensity is weaker due to dilu-
tion of the solution by the large amount of MAO
(400 molar excess). These experimental facts indicate that
the copper ions in these complexes were in the divalent
state and remained to be Cu(II) after the co-catalyst
MAO was added, no reduction can be observed as that
occurred for the Co catalysts [19].
All the four copper catalysts afforded the polynorborn-
enes with narrow molecular weight distributions (Mw/
Mn = 2.48–2.70), indicating the presence of a single active
species in the polymerization process [20]. The DSC mea-
surement of the polynorbornenes did not give any endo-
thermal signal in a heating range of 20–400 ꢁC and the
TGA data indicated that these polymers are stable up to
400 ꢁC. No olefinic bonds in the polymers formed can be
Assisted by the co-catalyst MAO, the catalytic activity
of the complexes could reach the highest to
6.35 · 104 g polymer/(mol Cu h) for 2 among the four com-
plexes, and the activity sequence is in the order of
2 > 4 > 3 > 1, with R groups (as shown in Scheme 2) of
a-naphthyl (2), p-nitrophenyl (4), o-methylphenyl (3) and
phenyl (1). A plausible preliminary interpretation for the
activity sequence can be given to the bulkiness of the R-
substituents, since the size of R is in the same order as that
of the activities. In addition to that, the nearly 5-fold
increase of activity of 2 as compared to 1 could be attrib-
uted to the large p-system of the naphthyl ring. Further-
more, complex 4 with an p-nitro-substituent on the
phenyl ring in R is more active than 1 by 3.5-fold, which
could be caused by the electron-withdrawing p-NO2 group
affording the active Cu(II) center more deficient in electron
density. Such electronic effect was also observed by Grubbs
[8a] for the salicylaldiminato Ni(II) complexes in the poly-

X.-Q. Lu¨ et al. / Journal of Organometallic Chemistry 691 (2006) 821–828
825
Table 2
Crystallographic data and structure refinement details for 1 Æ EtOH, 3 and 4
Complex
1 Æ EtOH
3
4
Formula
Formula weight
T (K)
C48H42CuN6O3
814.42
298(2)
C48H40CuN6O2
796.40
293(2)
C46H34CuN8O6
858.35
293(2)
Crystal system
Space group
Crystal size (mm)
Triclinic
Triclinic
Monoclinic
C/2c
ꢀ
ꢀ
P1
P1
0.46 · 0.26 · 0.25
10.673(1)
13.552(2)
15.106(2)
104.858(2)
90.029(2)
97.165(2)
2094.1(5)
2
0.47 · 0.46 · 0.07
10.252(4)
14.207(5)
14.323(5)
76.604(6)
78.247(6)
79.582(6)
1967.0(13)
2
0.46 · 0.39 · 0.21
21.990(9)
15.551(7)
15.181(6)
90
129.021(6)
90
4033(3)
4
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dcalc (g cmꢁ3
)
1.292
0.570
1.345
0.604
1.414
0.603
l (mmꢁ1
)
Reflections collected
Reflections observed I > 2r(I)
Maximum 2h (ꢁ)
Rint
18038
9063
54.22
0.0199
15748
7858
52.72
0.0257
12429
4371
54.08
0.0194
R1 [I > 2r(I)]
wR2
0.0495
0.1384
0.0482
0.1208
0.0375
0.0935
Table 3
Catalytic data in the polymerization of norbornene by the pyrazolone-based Cu(II) complexes 1–4a
Acitivity (104 g molꢁ1 hꢁ1
)
Mn (105)
Mw (105)
Mw/Mn
b
c
No.
Complex
Polymer yield (g)
1
2
3
4
a
1
2
3
4
0.3250
1.5746
0.4734
0.9673
1.31
6.35
2.19
4.48
2.86
2.24
3.20
2.84
7.32
5.55
8.46
7.52
2.56
2.48
2.64
2.65
Reaction conditions: toluene: 20 ml, 60 ꢁC, norbornene: 5 g, Cu complex: 5.4 lmol, MAO as auxiliary catalyst, Al/Cu = 400 (molar ratio) and 4 h.
Mn is the relative number-average molecular weight.
Mw is the relative weight-average molecular weight.
b
c
identified by IR and 1H NMR spectroscopic measure-
internal standard at room temperature. Thermogravimetric
analyses were carried out on a NETZSCH TG 209 Instru-
ment under flowing nitrogen by heating the samples from
25 to 600 ꢁC. EPR spectra were performed on a Bruker
ER-420 spectrometer in toluene at room temperature with
frequency of 9.65 GHz and scan range of 100 mT and cen-
tered at 330 mT.
ments: the presence of bridging methylene group at
1296 cmꢁ1, the absence of bands for C@C absorption in
range 1620–1680 cmꢁ1 in IR [12,13b], and the absence of
1
vinyl proton at ꢃ5.3 ppm in the H NMR spectra [12].
These results showed that the vinylic-type polymerization
process of NBE has occurred when catalyzed by the
MAO/Cu(II) complexes 1–4.
3.1. Syntheses
3. Experimental
3.1.1. Ligands HL1–HL4
All chemicals of reagent grade were commercially avail-
able and used without further purification. Element analy-
ses were performed on a Perkin–Elmer 240C element
analyzer. Infrared spectra were recorded on a Bruker
EQUINOX55 FT-IR spectrophotometer in the region
4000–400 cmꢁ1 in KBr pellets. ES–MS was performed on
a Finnigan LCQDECAXP HPLC-MSn mass spectrometer
with a mass to charge (m/z) range of 2000 using a standard
Ligands HL1–HL4 were obtained by similar procedures
by condensation of 1-phenyl-3-methyl-4-benzoyl-5-pyrazo-
lone (2.50 g, 9.0 mmol) and a suitable amine (9.4–
9.7 mmol) in 35 ml of EtOH under reflux for 6 h. Pure
products were obtained on removal of solvent and recry-
stallzation from 1:1 mixture of ethanol/n-heptane.
3.1.1.1. 5-Methyl-2-phenyl-4-[(2-phenylamino)-phenylm-
ethylene]pyrazol-3(2H)-one (HL1). Aniline (0.9 g) was
used to give HL1 in 60% yield (1.92 g). Anal. Calc. for
C23H19N3O: C, 78.19; H, 5.38; N, 11.90. Found: C,
1
electrospray ion source and toluene as solvent. H NMR
spectra were measured on a Varian Unity INOVA
400NB instrument using CDCl3 as solvent and TMS as

826
X.-Q. Lu¨ et al. / Journal of Organometallic Chemistry 691 (2006) 821–828
78.10; H, 5.56; N, 11.92%. Mp: 142–143 ꢁC. IR (KBr,
cmꢁ1): 1629 (vs), 1584 (s), 1535 (m), 1498 (s), 1385 (vs),
1365 (s), 1227 (w), 1139 (w), 1006 (w), 778 (w), 758 (m),
tion of CuCl2 (9 mg, 0.05 mmol) in EtOH (5 ml) was added
and the mixture kept stirring for 20 min. The resultant
clear brown solution was filtered and left to stand at room
temperature for several days to give black crystalline prod-
uct of 1 in 70% yield. Anal. Calc. for C46H36N6O2Cu: C,
71.91; H, 4.72; N, 10.94. Found: C, 72.22; H, 5.04; N,
10.79%. IR (KBr, cmꢁ1): 1595 (s), 1561 (vs), 1526 (s),
1475 (vs), 1435 (s), 1398 (m), 1377 (s), 1246 (w), 1212
(m), 1153 (w), 1064 (w), 1026 (w), 1006 (w), 980 (w), 850
(w), 791 (w), 757 (m), 706 (m), 659 (w), 589 (m), 513 (w),
481 (w). ES–MS (m/z): 769 (M+ ꢁ H).
3.1.2.2. [Cu(L2)2] (2). 2 was prepared using HL2
(41 mg, 0.1 mmol). Yield: 71%. Anal. Calc. for
C54H40N6O2Cu: C, 74.68; H, 4.64; N, 9.68. Found: C,
74.62; H, 5.14; N, 9.79%. IR (KBr, cmꢁ1): 1595 (m),
1560 (vs), 1526 (s), 1480 (vs), 1435 (s), 1380 (m), 1261
(w), 1225 (w), 1156 (w), 1084 (w), 1025 (w), 805 (w), 763
(m), 693 (m), 658 (w), 631 (w), 595 (w), 511 (w). ES–MS
(m/z): 869 (M+ ꢁ H).
1
699 (m), 573 (w), 509 (w). ES–MS (m/z): 354 (M+). H
NMR (CDCl3), d (ppm): 12.99 (s, 1H, –NH); 8.04 (d,
2H), 7.41 (m, 7H), 7.14 (t, 3H), 7.06 (t, 1H), 6.81 (d,
2H), 1.56 (s, 3H).
3.1.1.2. 5-Methyl-2-phenyl-4-[(2-naphthylamino)-phenylm-
ethylene]pyrazol-3(2H)-one (HL2). Ligand HL2 was
obtained by using a-naphthylamine (1.36 g), in 62%
(2.24 g) yield. Anal. Calc. for C27H21N3O: C, 80.37; H,
5.25; N, 10.41. Found: C, 80.34; H, 5.34; N, 10.29%. Mp:
175–176 ꢁC. IR (KBr, cmꢁ1): 1620 (vs), 1587 (s), 1535
(m), 1489 (s), 1460 (w), 1439 (w), 1393 (vs), 1321 (w),
1272 (w), 1250 (w), 1174 (w), 1145 (m), 1004 (w), 797
(m), 764 (m), 698 (w), 588 (w), 561 (w), 511 (w). ES–MS
1
(m/z): 404.3 (M+). H NMR (CDCl3), d (ppm): 13.32 (s,
–NH); 8.25 (d, 1H), 8.08 (d, 2H), 7.82 (d, 1H), 7.60 (m,
2H), 7.53 (m, 1H), 7.43 (t, 2H), 7.35 (m, 1H), 7.28 (m,
4H), 7.18 (t, 1H), 7.12 (t, 1H), 6.84 (d, 1H), 1.62 (s, 3H).
3.1.2.3. [Cu(L3)2] (3). 3 was prepared using HL3
(37 mg, 0.1 mmol). Yield: 67%. Anal. Calc. for
C48H40N6O2Cu: C, 72.39; H, 5.06; N, 10.55. Found: C,
72.52; H, 5.44; N, 10.79%. IR (KBr, cmꢁ1): 1595 (m),
1560 (vs), 1526 (s), 1477 (vs), 1438 (s), 1375 (m), 1220
(w), 1188 (w), 1064 (w), 1028 (w), 843 (w), 758 (m), 722
(w), 704 (w), 658 (w), 598 (w), 511 (w). ES–MS (m/z):
797 (M+ ꢁ H).
3.1.2.4. [Cu(L4)2] (4). 4 was prepared using HL4
(40 mg, 0.1 mmol) with 80% yield (0.78 g). Anal. Calc.
for C46H34N8O6Cu: C, 64.37; H, 3.99; N, 13.05. Found:
C, 64.82; H, 4.34; N, 12.79%. IR (KBr, cmꢁ1): 1597 (m),
1563 (vs), 1519 (s), 1479 (vs), 1436 (s), 1381 (m), 1340 (s),
1251 (w), 1217 (m), 1168 (w), 1107 (w), 1063 (w), 1011
(w), 983 (w), 867 (m), 784 (w), 758 (m), 714 (m), 655 (w),
609 (w), 573 (w), 435 (w). ES–MS (m/z): 859 (M+ ꢁ H).
3.1.1.3.
ene]pyrazol-3(2H)-one
5-Methyl-2-phenyl-4-[(2-o-tolyl)-phenylmethyl-
(HL3). Ligand HL3
was
obtained by using o-toluidine (1.29 g), Yield: 65%
(2.15 g). Anal. Calc. for C24H21N3O: C, 78.45; H, 5.76;
N, 11.44. Found: C, 78.23; H, 6.06; N, 11.14%. Mp: 173–
174 ꢁC. IR (KBr, cmꢁ1): 1626 (vs), 1585 (vs), 1537 (m),
1498 (s), 1463 (m), 1385 (vs), 1237 (w), 1188 (w), 1143
(m), 1051 (w), 1007 (m), 831 (w), 756 (s), 708 (w), 654
(w), 589 (w). ES–MS (m/z): 368 (M+). H NMR (CDCl3),
d (ppm): 12.88 (s, –NH); 8.06 (d, 2H), 7.43 (m, 6H), 7.29 (t,
1H), 7.19 (t, 2H), 7.03 (t, 1H), 6.88 (t,1H), 6.62 (d, 1H),
2.46 (s, 3H),1.63 (s, 3H).
1
3.1.1.4. 5-Methyl-2-phenyl-4-[(2-p-nitrophenylamino)-phe-
nylmethylene]-pyrazol-3(2H)-one (HL4). Ligand HL4
was obtained by using p-nitroaniline (1.30 g) and formic
acid (1 ml), the latter was added to ensure acidity of the
solution. Yield: 2.10 g (60%). Anal. Calc. for
C23H18N4O3: C, 69.35; H, 4.52; N, 14.07. Found: C,
69.50; H, 4.68; N, 14.14%. Mp: 202–203 ꢁC. IR (KBr,
cmꢁ1): 1644 (vs), 1581 (vs), 1522 (s), 1497 (vs), 1399 (s),
1372 (s), 1340 (vs), 1312 (s), 1235 (m), 1194 (w), 1141 (m),
1109 (m), 1051 (w), 1008 (w), 933 (w), 858 (w), 830 (s),
779 (m), 754 (s), 726 (m), 709 (m), 689 (m), 647 (w), 610
3.2. X-ray crystallography
Single crystals of 1 Æ EtOH, 3 and 4, obtained from
recystallization in CH2Cl2–EtOH (v/v, 1/2), of suitable
dimensions were mounted onto glass fibers for crystallo-
graphic analyses. All the intensity data were collected on
a Bruker SMART CCD diffractometer (Mo Ka radiation,
(m), 554 (w), 498 (w). ES–MS (m/z): 399 (M+). H NMR
k = 0.71073 A) in U and x scan modes. Structures were
1
˚
(CDCl3), d (ppm): 13.31 (s, 1H, –NH); 7.99 (m, 4H), 7.55
(m, 4H), 7.42 (m, 4H), 6.82 (d, 2H), 1.61 (s, 3H, –CH3).
solved by Patterson methods followed by difference Fou-
rier syntheses, and refined by full-matrix least-squares tech-
niques against F2 using SHELXTL [21a]. Except for atoms
belonging to disordered solvate molecules, all the non-
hydrogen atoms were refined with anisotropic thermal
parameters. The solvate EtOH molecule in 1 Æ EtOH was
disordered over two positions and were refined with frac-
tional site occupancy. Absorption corrections were applied
using SADABS [21b]. All hydrogen atoms were placed in cal-
culated positions and refined isotropically using a riding
3.1.2. Complexes 1–4
Complexes 1–4 were prepared by a similar procedure as
depicted by the synthesis of 1.
3.1.2.1. [Cu(L1)2] (1). The CH2Cl2 solution (5 ml) con-
taining HL1 (36 mg, 0.1 mmol) and Et3N (14 ll, 0.1 mmol)
was stirred for 10 min at room temperature, then the solu-

X.-Q. Lu¨ et al. / Journal of Organometallic Chemistry 691 (2006) 821–828
827
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model. Crystallographic data and refinement parameters
for the complexes are presented in Table 2.
3.3. Catalytic activity measurement
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5. Supplementary material
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic Data
Center, CCDC reference numbers for 1 Æ EtOH, 3 and 4 are
238374, 244299 and 244300, respectively. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ
UK (fax: +44 1223 336033; email: deposit@ccdc.cam.ac.uk
or www: http://www.ccdc.cam.ac.uk). The DSC, IR and
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This work was supported by the National Natural Sci-
ence Foundation of China (20273085) and the Research
Fund for the Doctoral Program of Higher Education of
China (20020558027). Thanks are due to Drs. Zhong-Ning
Chen and Jiang-Gao Mao for assistances in the EPR mea-
surements at FIRSM, Chinese Academy of Sciences.
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