Synthesis and structural characterization of lanthanide picrate complexes with a new binaphthylamide

Article abstract of DOI:10.1016/S0022-2860(03)00531-3

Solid complexes of lanthanide picrates with N-Ethyl-2-{2′ -[(ethyl-phenyl-carbamoyl)-methoxy]-[1,1′]binaphthalenyl-2-yloxy} -N-phenyl-acetamide (L), [Ln(pic)₃L] (Ln = La, Tb, Y), have been prepared and characterized by elemental analysis, IR and ¹H NMR spectra. The molecular structure of [Tb(pic)3L] shows that the Tb(III) ion is nine-coordinated by four oxygen atoms from the L and five from two bidentate and one unidentate picrates. The complex forms a 1D supramolecular structure along z-axis.

Full text of DOI:10.1016/S0022-2860(03)00531-3

Journal of Molecular Structure 660 (2003) 41–47
www.elsevier.com/locate/molstruc
Synthesis and structural characterization of lanthanide picrate
complexes with a new binaphthylamide
a
a,
a
*
Ya-Wen Wang , Wei-Sheng Liu , Ning Tang ,
Min-Yu Tana, Kai-Bei Yub
aDepartment of Chemistry and National Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering,
Lanzhou University, Lanzhou 730000 ,China
bChengdu Center of Analysis and Measurement, Academia Sinica, Chengdu 610041, China
Received 13 January 2003; accepted 25 July 2003
Abstract
Solid complexes of lanthanide picrates with N-Ethyl-2-{20-[(ethyl-phenyl-carbamoyl)-methoxy]-[1,10]binaphthalenyl-2-
yloxy}-N-phenyl-acetamide (L), [Ln(pic)3L] (Ln ¼ La, Tb, Y), have been prepared and characterized by elemental analysis, IR
1
and H NMR spectra. The molecular structure of [Tb(pic)3L] shows that the Tb(III) ion is nine-coordinated by four oxygen
atoms from the L and five from two bidentate and one unidentate picrates. The complex forms a 1D supramolecular structure
along z-axis.
q 2003 Published by Elsevier B.V.
Keywords: Lanthanide picrate; Complex; Crystal structure; p–p stack; Wave-like supramolecular structure
1. Introduction
organic reactions can be promoted catalytically
rather than stoichiometrically [5–9]. Of the
many chiral ligands developed for preparing
chiral reagents and catalysts in asymmetric syn-
thesis, 1,10-2,20-binaphthol (BINOL) is one of the
most useful ligands, and has a considerable contri-
bution to asymmetric synthesis [10,11]. However,
much less attention has been paid to binaphthyla-
mide, and few of the structures of this kind of
catalysts have been determined by X-ray measure-
ments. Recently, our group synthesized a new
binaphthylamide: N-Ethyl-2-{20-[(ethyl-phenyl-car-
bamoyl)-methoxy]-[1,10]binaphthalenyl-2-yloxy}-N-
phenyl-acetamide (L) and investigated the reaction
of L with lanthanide picrates. As a subsequent study
The importance of lanthanide reagents and
catalysts in organic synthesis has been well-
recognized since the pioneering works by
Kagan and co-workers on the SmI2-promoted
reactions [1,2]. Chiral lanthanide complexes as
new catalysts in asymmetric synthesis are currently
of intense interest. The unique coordination chem-
istry of the f-block elements [3,4], particularly their
high coordination numbers are an advantage as
*
Corresponding author. Tel.: þ86-931-8912552; fax: þ86-931-
8912582.
E-mail address: liuws@lzu.edu.cn (W.-S. Liu).
0022-2860/$ - see front matter q 2003 Published by Elsevier B.V.
doi:10.1016/S0022-2860(03)00531-3

42
Y.-W. Wang et al. / Journal of Molecular Structure 660 (2003) 41–47
of such complexes, in order to explore
the relationship between structure and property, we
give here the synthesis, characterization of the
complexes [Ln(pic)3L] and the crystal structure of
the terbium complex.
solid complex was filtered, washed with ethanol and
dried in vacuo over P2O5 for 48 h. All the complexes
were obtained as yellow powders. Single crystal of the
terbium complex grew from CHCl3/CH3CH2OH by
slow evaporation at room temperature. After about a
month, yellow crystal formed from the solution.
2.4. X-ray crystallography
For the terbium complex, X-ray measurements
were performed on a P4 four-circle diffractometer
with graphite monochromatized Mo Ka radiation at
295(2) K, using the v=2u scan mode. Lorentz and
polarization corrections were applied, and empirical
absorption correction was made. A summary of
crystallographic date and details of the structure
refinements are listed in Table 1. The structure was
solved by direct methods and refined by full-matrix
N-Ethyl-2-{20-[(ethyl-phenyl-carbamoyl)-meth-
oxy]-[1,10]binaphthalenyl-2-yloxy}-N-phenyl-aceta-
mide (L)
2. Experimental
2.1. Chemical and physical measurements
Table 1
The metal ions were determined by EDTA titration
using xylenal orange as indicator. C, N and H were
determined using an Elementar Vario EL. Conduc-
tivity measurements were carried out with a DDS-307
type conductivity bridge using 1023 mol dm23 sol-
utions in acetone at 25 8C. IR spectra were recorded on
Nicolet Avatar 360 FT-IR instrument using KBr discs
in the 400–4000 cm21 region, 1H NMR spectra were
measured on a Brucker AC 80 spectrometer in CDCl3
solution with TMS as internal standard. Mass spectra
were obtained on a VG-ZAB-HS mass spectrometer.
Crystal data and structure refinement for the complex [Tb(pic)3L]
Empirical formula
Temperature (K)
Crystal color
C58 H42 Tb N11 O25
295(2)
Yellow
Crystal size (mm)
Formula weight
Crystal system
Space group
˚
a (A)
˚
b (A)
0.50 £ 0.44 £ 0.20
1451.95
Monoclinic
P2ð1Þ=c
20.712(4)
36.534(8)
16.382(3)
90
˚
c (A)
a (8)
b (8)
g (8)
106.50(1)
90
2.2. Materials
3
˚
V (A )
11886(4)
8
Z
The Lanthanide picrate was prepared according to
literature method [12]. L as enantiomers was syn-
thesized by using a similar method [13] from 1,10-2,20-
binaphthol. All commercially available chemicals
were of reagent grade and were used without further
purification.
Density (calculated) (mg/m3)
1.623
F (000)
5856
Radiation, graphite-
˚
monochromatized, l (A)
0.71073
Reflections collections
Independent reflection
u range for data collection
Index range
22,807
20,939
1.51–25.008
224 # h # 23
243 # k # 0
0 # l # 19
2.3. General preparation of the complexes
Goodness-of-fit on F2
R½I . 2sðIÞꢀ
0.830
R1 ¼ 0:0483; wR2 ¼ 0:0751
R1 ¼ 0:1253; wR2 ¼ 0:0901
0.855, 20.944
To a solution of 0.2 mmol terbium picrate in 5 ml
of ethanol was added dropwise the solution of
0.2 mmol L in 10 ml of ethanol. The mixture was
stirred at room temperature for 4 h. The precipitated
R (all data)
Largest difference peak
23
˚
and hole[e A
]

Y.-W. Wang et al. / Journal of Molecular Structure 660 (2003) 41–47
43
Table 2
Analytical and molar conductance data for the complexes (calculated values in parentheses)
Complex
Analysis (%)
C
Lm (ohm21 cm2 mol21
)
H
N
Ln
9.57 (9.70)
La(pic)3L
Tb(pic)3L
Y(pic)3L
48.26 (48.63)
47.53 (47.97)
50.38 (50.39)
3.13 (2.93)
3.10 (2.89)
2.97 (3.04)
11.39 (10.76)
10.74 (10.61)
11.26 (11.15)
30.7
25.5
26.7
10.48 (10.95)
5.94 (6.44)
least-squares techniques with all non-hydrogen atoms
treated anisotropically. All calculations were per-
formed on an Eclipse S/140 computer with the
program package SHELXTL [14] version 5.10.
the spectra of the complexes suggests that the Ln–O
(carbonyl) bond is stronger than the Ln–O (ether).
The OH out-of-plane bending vibration of the free
Hpic at 1151 cm21 disappears in the spectra of the
complexes indicating that the H atom of the OH group
is replaced by Ln(III). The vibration n(C–O) at
1265 cm21 is shifted towards higher frequency by ca.
12 cm21 in the complexes. This is due to the
following two effects. First, the hydrogen atom of
the OH group is replaced by Ln(III), increasing the p-
bond character in the C–O bond. Secondly, coordi-
nation of the oxygen atom of L to Ln(III) causes the
p-character to be weakened. The free Hpic has
3. Results and discussion
Analytical data for the complex listed in Table 2
conform to a 1:3:1 metal-to-picrate-to-L stoichiometry
Ln(pic)3L. All complexes are soluble in DMF, DMSO,
CH3CO2Et and CHCl3, but slightly soluble in ethanol
and CH3CN. The molar conductances of the com-
plexes in acetone (see Table 2) indicate that all
complexes act as non-electrolytes, implying that all
the picrate groups are in coordination sphere.
nas(NO2) and ns (NO2) at 1555 and 1342 cm21
,
respectively, which splits into two bands at 1586,
1544 cm21 and 1360, 1328 cm21 in the complexes.
This indicates that some of the nitryl O atoms take
part in coordination [15].
3.1. IR spectra
3.2. 1H NMR spectra and mass spectra
The most important data are listed in Table 3. And
the detail of the IR spectra of L and [Tb(pic)3L] are
shown in Fig. 1.
1
The H NMR spectra of the free ligand L and its
The infrared spectrum of L shows strong band at
1676 cm21, which is attributable to stretch vibration
of the carbonyl group of amide (n(CyO)). Two peaks
at 1274 and 1223 cm21 can be assigned to n(yC–O–
C), and the peak at 1104 cm21 to n(C–O–C). The
peaks at 1591 and 1499 cm21 are assigned to the CyC
stretches of naphthalene and phenyl rings, at 1444 and
1414 cm21 assigned to the bending vibration of –
CH2–CO–, and at 750 and 700 cm21 assigned to the
stretch of phenyl ring.
lanthanum complex were determined in CDCl3.
L: 1H NMR (CDCl3): d 7.95–7.78 (m, 4H,
C20H12–), 7.36–7.17 (m, 14H, ArH and C20H12–),
Table 3
The most important IR bands (cm21
)
Compound n(CyO) n(C–O n(C–O) nas(–NO2) ns(–NO2)
–C)
In the IR spectra of the lanthanum complex, the
n(CyO) and n(C–O–C) shift by ca. 59 and 25 cm21
towards lower wave numbers, thus indicating that all
the CyO and ether O atoms take part in coordination
to the metal ion. The larger shift for n(CyO) in
Hpic
L
–
–
1265
–
1555
–
1342
–
1676
1104
1081
1074
1081
La(pic)3L 1615
Tb(pic)3L 1619
1274
1277
1279
1589, 1543 1363, 1327
1585, 1544 1357, 1329
1585, 1546 1361, 1328
Y(pic)3L
1617

44
Y.-W. Wang et al. / Journal of Molecular Structure 660 (2003) 41–47
6.89–6.83 (m, 4H, ArH), 4.13 (s, 4H, –O–CH2–
CO–), 3.63 (q, J ¼ 7.0 Hz, 4H, –N–CH2–), 1.00
(t, J ¼ 7.0 Hz, 6H, –CH3). FABMS: m=z 609
(M þ H), 460, 281, 252.
[La(pic)3·L]: 1H NMR (CDCl3): d 8.95 (s, 6H,
pic2), 8.05–7.98 (m, 4H, C20H12–), 7.77–7.01 (m,
14H, ArH and C20H12–), 6.06 (m, 4H, ArH), 4.76 (d,
J ¼ 16 Hz, 2H, –O–CH2–CO–), 3.76 (d, J ¼ 16 Hz,
2H, –O–CH2–CO–), 3.30 (q, J ¼ 7.0 Hz, 4H, –N–
CH2–), 0.78 (t, J ¼ 7.0 Hz, 6H, –CH3).
The spectrum of the ligand exhibits three multi-
plets at ca. 7.87, 7.27 and 6.86 ppm assigned to
C20H12– and –C6H5 protons, one siglet at 4.13 ppm
to –O–CH2–CO– protons, one quadruplet at 3.49,
3.58, 3.67, 3.76 ppm (J ¼ 7.0 Hz) to –N–CH2–
protons, and one triplet at 0.91, 1.00, 1.08 ppm
(J ¼ 7.0 Hz) to –CH3 protons.
Upon coordination, the proton signal of –O–
CH2–CO– splits into two doublets at 4.86, 4.66 ppm
and 3.86, 3.67 ppm (J ¼ 16 Hz). The signal of –
C6H5, –N–CH2– and –CH3 are shifted to higher field
by 0.80, 0.23 and 0.21 ppm, respectively. The reason
is not clear now.
Fig. 1. Infrared absorption spectra of L and its terbium complex.
The proton signal of OH group in free Hpic
disappears in the complexes, indicating that the H
Fig. 2. The structures of [Tb(pic)3L] as two enantiomers.

Y.-W. Wang et al. / Journal of Molecular Structure 660 (2003) 41–47
45
Fig. 3. The 1D supramolecular structure of [Tb(pic)3L] in the unit cell. All the N-Ethylanilines are omitted for clarity.
Fig. 4. The wave-like structure of [Tb(pic)3L] linked by p–p stacks in the unit cell. All the N-Ethylanilines are omitted for clarity.

46
Y.-W. Wang et al. / Journal of Molecular Structure 660 (2003) 41–47
atom of the OH group is replaced by Ln(III). The
benzene ring protons of the free Hpic exhibit a singlet
at 9.12 ppm. Upon coordination, the signal moves to
higher field. Only one singlet is observed for the
benzene ring protons of the three coordinated picrate
groups, indicating fast exchange among the group in
solution.
Table 4
Selected bond lengths (A) and bond angles (8) for [Tb(pic)3L]
˚
Tb(1)–O(1)
2.288(4) Tb(2)–O(26)
2.649(4) Tb(2)–O(27)
2.569(4) Tb(2)–O(28)
2.282(4) Tb(2)–O(29)
2.262(4) Tb(2)–O(30)
2.624(4) Tb(2)–O(31)
2.316(4) Tb(2)–O(37)
2.679(5) Tb(2)–O(38)
2.274(4) Tb(2)–O(44)
2.307(4)
2.521(4)
2.678(4)
2.309(4)
2.260(4)
2.573(4)
2.331(4)
2.643(4)
2.250(4)
Tb(1)–O(2)
Tb(1)–O(3)
Tb(1)–O(4)
Tb(1)–O(5)
Tb(1)–O(6)
The mass spectrum of L shows a molecular ion at
m=z ¼ 609 (M þ H), confirming the molecular form-
ular of L as C40H36N2O4. Above the mass of C20H12
ðm=z ¼ 252Þ are observed two major fragment ions at
m=z ¼ 460 (M 2 [–CO–NC6H5(C2H5)]), and 281
(M 2 [–CO–NC6H5(C2H5)] 2 [–O–CH2 –CO–
NC6H5(C2H5)]).
Tb(1)–O(12)
Tb(1)–O(13)
Tb(1)–O(19)
O(1)–Tb(1)–O(2)
O(1)–Tb(1)–O(3)
O(1)–Tb(1)–O(5)
61.49(13) O(26)–Tb(2)–O(27) 64.68(13)
80.74(14) O(26)–Tb(2)–O(28) 71.78(13)
92.65(14) O(26)–Tb(2)–O(31) 70.46(13)
O(1)–Tb(1)–O(13) 64.93(14) O(26)–Tb(2)–O(37) 75.25(14)
O(1)–Tb(1)–O(19) 85.91(15) O(26)–Tb(2)–O(44) 97.65(14)
O(2)–Tb(1)–O(3)
O(2)–Tb(1)–O(4)
68.13(12) O(27)–Tb(2)–O(28) 66.49(13)
72.53(13) O(27)–Tb(2)–O(29) 81.42(14)
3.3. X-ray crystal structure
O(2)–Tb(1)–O(19) 67.87(13) O(27)–Tb(2)–O(37) 72.49(14)
O(3)–Tb(1)–O(4) 63.98(13) O(27)–Tb(2)–O(38) 70.91(13)
There are two enantiomers in the crystal structure
of [Tb(pic)3L]. Fig. 2 (a) and (b) shows the structure
and the atomic numbering schemes for the terbium
complex. Fig. 3 shows a 1D supramolecular structure
along z-axis in the unit cell, and the two adjacent
strings represent the two enantiomers. Fig. 4 shows a
wave-like structure. Selected bond lengths and angles
are given in Table 4.
O(3)–Tb(1)–O(12) 72.47(14) O(28)–Tb(2)–O(29) 61.40(13)
O(3)–Tb(1)–O(13) 70.90(13) O(28)–Tb(2)–O(44) 70.27(13)
O(4)–Tb(1)–O(6)
71.21(13) O(29)–Tb(2)–O(30) 93.62(14)
O(4)–Tb(1)–O(12) 76.05(14) O(29)–Tb(2)–O(38) 66.50(14)
O(4)–Tb(1)–O(19) 94.76(15) O(29)–Tb(2)–O(44) 82.29(14)
O(5)–Tb(1)–O(6)
66.20(13) O(30)–Tb(2)–O(31) 66.14(13)
O(5)–Tb(1)–O(12) 83.60(14) O(30)–Tb(2)–O(37) 82.00(15)
O(5)–Tb(1)–O(13) 73.52(13) O(30)–Tb(2)–O(38) 72.19(14)
O(5)–Tb(1)–O(19) 79.62(14) O(30)–Tb(2)–O(44) 79.46(14)
O(6)–Tb(1)–O(12) 70.88(15) O(31)–Tb(2)–O(37) 70.90(15)
O(6)–Tb(1)–O(19) 72.82(14) O(31)–Tb(2)–O(44) 73.88(14)
O(12)–Tb(1)–O(13) 63.50(14) O(37)–Tb(2)–O(38) 63.95(14)
The Tb(III) ion is nine-coordinated by four oxygen
atoms from the L, five from two bidentate and one
unidentate picrates. The coordination polyhedron is a
tricapped trigonal prism. Due to the space obstacle,
the two naphthalene rings in the molecule are almost
vertical to each other, with mean angle 93.158
between the two rings. The two naphthalene rings of
one complex are almost parallel with two adjacent
molecules. The corresponding dihedral angle is
172.098. The L molecule wraps around the metal ion
with its oxygen atoms and forms a ring-like
coordination structure together with the terbium
atom. The one naphthalene ring of one complex and
a unidentate picrate of the adjacent complex form a
p–p stack, the dihedral angle is 16.88 and the shortest
and the longest distance of the atom-to-centroid are
Tb–O(C–O–C), indicating that Tb–O(CyO) bond is
stronger than Tb–O(C–O–C) one, in agreement with
the IR spectral data.
In conclusion, the new ligand L can form stable
complexes with lanthanide ions. This ligand was
structurally simple, easily synthesized, and finely
tunable [16]. It, therefore, shows high coordination
ability, which could make it a useful catalyst in organic
reaction. Further studies of the ligand are under way.
4. Supplementary data
˚
3.81 and 4.71 A, respectively. There is a wave-like
structure in the unit cell which is from metal to
naphthalene to picrate (the unit revolves three times)
by p–p interaction between naphthalene and picrate.
The average distance between the Tb atom and
˚
the coordinated oxygen atoms are 2.438 A (a)
˚
and 2.430 A (b), where Tb–O(CyO) is shorter than
Crystallographic data for the structures reported in
this paper have been deposited with the Cambridge
Crystallographic data Centre, CCDC no. 200309.
Copies of this information may be obtained free of
charge from the Director CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: þ44-1223-336033;

Y.-W. Wang et al. / Journal of Molecular Structure 660 (2003) 41–47
47
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Acknowledgements
We are grateful to National Natural Science
Foundation of China (projects 29571014 and
20071015), Foundation for University Key Teacher
by the Ministry of Education, and Key Project of the
Ministry of Education of China (01170) for financial
support.
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