Electrochemical synthesis of MII complexes with a schiff base containing an amido group. Crystal structure of a cobalt(II) complex with a reorganised ligand

Article abstract of DOI:10.1002/zaac.200570034

M(HL)(H₂O)_n complexes have been obtained by the electrochemical reaction of Fe, Co, Ni, Cu, Zn and Cd anodes with the potentially pentadentate and trianionic asymmetrical Schiff base 3-aza-N-{2-[1-aza-2-(5-nitro-2-hydroxylphenyl)-vinyl]phenyl}-4-(5-nitro-2- hydroxyphenyl)but-3-enamide (H₃L), containing a hard amido donor atom. The complexes have been characterized by elemental analysis, mass spectrometry, IR and ¹H NMR spectroscopies, magnetic measurements and molar conductivities. Co(HL)(H₂O) (2) has been found to rearrange in DMF solution into a crystallographically solved octahedral complex, CoL ¹(H₂O)₂ (7) [where H₂L¹ is the symmetrical Schiff base ligand N, N′-(1,2-phenylene)-bis(5-nitro-3- hydroxysalicylidenimine)]. A hydrolysis mechanism is discussed to explain this rearrangement.

Full text of DOI:10.1002/zaac.200570034

Electrochemical Synthesis of MII Complexes with a Schiff Base containing an
Amido Group. Crystal Structure of a Cobalt(II) Complex with a Reorganised
Ligand
a
a
a
a
b
´
´
´
´
M. Jesus Rodrıguez , M. Isabel Fernandez , Ana M. Gonzalez-Noya , Marcelino Maneiro , Rosa Pedrido ,
b
c
b,
´
Miguel Vazquez , Bruno Donnadieu , and Manuel R. Bermejo *
a
´
´
Lugo/Spain, Departamento de Quımica Inorganica, Universidade de Santiago de Compostela
b
´
´
Santiago de Compostela/Spain, Departamento de Quımica Inorganica, Universidade de Santiago de Compostela
c Toulouse/France, Laboratoire de Chimie Coordination, CNRS
Received November 30th, 2004; accepted February 15th, 2005.
Abstract. M(HL)(H2O)n complexes have been obtained by the elec-
trochemical reaction of Fe, Co, Ni, Cu, Zn and Cd anodes with the
potentially pentadentate and trianionic asymmetrical Schiff base 3-
aza-N-{2-[1-aza-2-(5-nitro-2-hydroxylphenyl)-vinyl]phenyl}-4-(5-
nitro-2-hydroxyphenyl)but-3-enamide (H3L), containing a hard
amido donor atom. The complexes have been characterized by ele-
Co(HL)(H2O) (2) has been found to rearrange in DMF solution
into a crystallographically solved octahedral complex, CoL1(H2O)2
(7) [where H2L1 is the symmetrical Schiff base ligand N,NЈ-(1,2-
phenylene)-bis(5-nitro-3-hydroxysalicylidenimine)].
A hydrolysis
mechanism is discussed to explain this rearrangement.
1
mental analysis, mass spectrometry, IR and H NMR spectrosco-
Keywords: Coordination chemistry; Schiff bases; Amides; Electro-
pies, magnetic measurements and molar conductivities.
chemistry
Introduction
work yielded these novel complexes with the metal in its
divalent oxidation state.
In the case of the CoII complex, Co(HL)(H2O), it has
been found to rearrange into a symmetrical complex
CoL1(H2O)2 (where H2L1 is the symmetrical Schiff base
Transition metal compounds containing Schiff base ligands
are very versatile systems, which play an important role in
the developing of coordination chemistry related to cataly-
sis and enzymatic reactions [1Ϫ3], magnetism [4, 5] and mo-
lecular architectures [6Ϫ8]. Attempts to explore new orig-
inal systems, led us to prepare Schiff bases containing am-
ide groups [9, 10]. The study of their manganese complexes
has shown how the amide group may develop different in-
fluences, such as the stabilization of high oxidation states
[10, 11], or the polymerisation of the complexes by μ-amido
bridging [12, 13].
In view of these results, we were interested in checking
the behaviour of this kind of Schiff bases with other tran-
sition metals. Herein we report the coordination chemistry
of iron, cobalt, nickel, copper, zinc, and cadmium with a
potentially pentadentate and trianionic asymmetrical Schiff
base, 3-aza-N-{2-[1-aza-2-(5-nitro-2-hydroxylphenyl)-vinyl]-
phenyl}-4-(5-nitro-2-hydroxyphenyl)but-3-enamide (H3L,
see Scheme 1). We have already found that this type of
ligand is able to twist and afford a mononuclear single-
stranded helical manganese(III) complex [14]. Now the elec-
trochemical synthetic methodology employed in the present
* Prof. Dr. Manuel R. Bermejo
´
´
´
Departamento de Quımica Inorganica, Facultade de Quımica
Universidade de Santiago de Compostela
E-15782 Santiago de Compostela/ Spain
Fax number: ϩ 34 981597525
E-mail: qimb45@usc.es
Scheme 1 Synthesis of the Schiff base ligand.
Z. Anorg. Allg. Chem. 2005, 631, 2161Ϫ2166
DOI: 10.1002/zaac.200570034
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
2161

´
´
´
´
M. J. Rodrıguez, M. I. Fernandez, A. M. Gonzalez-Noya, M. Maneiro, R. Pedrido, M. Vazquez, B. Donnadieu, M. R. Bermejo
Table 1 Elemental analysis and some selected data for the complexes
Compound
Yield
Colour
Found (Calcd.)
% N
MS (amu)a)
μ (BM)
% C
% H
H3L
65
50
60
60
60
83
96
Yellow
Red
Brown
Green
Green
Orange
Orange
15.2 (15.1)
12.8 (13.1)
12.8 (13.0)
13.4 (13.5)
11.4 (11.7)
12.8 (12.9)
11.6 (11.8)
56.6 (57.0)
49.9 (49.4)
49.9 (49.1)
50.9 (50.8)
44.9 (44.3)
48.9 (48.7)
44.9 (44.6)
3.8 (3.7)
3.3 (3.2)
3.2 (3.2)
3.0 (2.9)
3.1 (3.9)
3.2 (3.1)
2.9 (2.9)
464.0
518.0
520.6
520.4
525.5
526.0
574.0
Ϫ
Fe(HL)(H2O), (1)
Co(HL)(H2O), (2)
Ni(HL), (3)
Cu(HL)(H2O)4, (4)
Zn(HL)(H2O), (5)
Cd(HL)(H2O), (6)
5.0
4.1
db)
1.9
d
d
a) Electrospray for complexes and Electronic Impact for ligand; b) diamagnetic
ligand involving 1,2-phenylenediamine and 5-nitrosalicyl-
aldehyde), of which its structure was solved by single crystal
X-ray analysis.
tonated. This is supported by molar conductivity measure-
ments for the complexes in 10Ϫ3 M DMF solutions, which
are in the range 8-20 ΩϪ1 cm2 molϪ1 (Table 2), indicating
the non-electrolyte nature of these complexes [17], which is
completely consistent with this formulation.
Results and Discussion
Schiff base ligand
Mass Spectrometry and IR spectroscopy
The asymmetrical ligand imine-amide-imine H3L (see
Scheme 1) has been prepared as we previously reported [14].
The synthesis of this ligand was carried out in three steps;
the first step involves a carbodiimide amide coupling of car-
bobenzyloxyglycine with o-phenylenediamine in THF (A1);
the second step implies the removal of the Z protecting
group from the amine by sacrificial hydrogenation using
cyclohexene and palladium on charcoal as catalyst, yielding
the desired amine (A2); and in the last step, the diamine
obtained is employed as the precursor in the preparation of
the Schiff base via conventional condensation reaction with
a commercially available salicylaldehyde. The obtained
Schiff base and the precursors have been satisfactorily
characterized by elemental analysis, mass spectrometry, IR,
1H NMR and 13C NMR spectroscopies.
ES mass spectra show peaks (Table 1) assigned to
[M(HL)]ϩ fragments for all complexes, indicating ligand co-
ordination to the metal centre.
All complexes exhibit similar features in their IR spectra,
which support the coordination of H3L to the metal ions.
The most significant IR bands for H3L are collected in
Table 2. They have been assigned by comparison with the
IR spectrum of the amine precursor A2 and on the basis of
our knowledge in this field [14]. Thus, strong bands at ca.
1600 cmϪ1, characteristic of the ν(CϭN) stretching mode,
show a shift of 11 - 17 cmϪ1 to lower frequencies from the
free ligand values, indicating coordination of the ligand to
the metal through both imine nitrogen atoms. In addition,
bands due to the amide I [ν(CO)] mode undergo positive
shifts whereas the amide II [δ(NH) ϩ ν(CN)] mode bands
undergo negative shifts. This behaviour is compatible with
the participation of the nitrogen amide atom in the coordi-
nation to the metal. Additionally, all spectra show the pres-
ence of the ν(N-H) bands at 3300-3200 cmϪ1, in accordance
with the dianionic nature of the ligand.
Synthesis and characterization of the complexes
The metal complexes 1 - 6 were prepared following an elec-
trochemical method using metal plates as anodes [15, 16].
The electrochemical efficiency of the cell Ef was close to
0.5 mol FϪ1, which is compatible with the following reac-
tion scheme:
Finally, bands centred at ca. 3400 cmϪ1 can be assigned
to a combination of the ν(OH) modes of coordinated and
lattice water.
Cathode: H3L ϩ 2eϪ Ǟ HL2Ϫ ϩ H2
Anode: HL2Ϫ ϩ M Ǟ M(HL) ϩ 2eϪ
Table 2 IR spectroscopy and conductivity measurements for the
ligand and complexes.
b)
Compound IR spectra /cmϪ1 a)
ΛM
ν(OH)
ν(NH) ν(CϭN) ν(amide I) ν(amideII)
The metal complexes formed via this synthetic route ap-
pear to be air-stable in the solid state. These compounds
melt over 350 °C and are insoluble or sparingly soluble in
water and also in common organic solvents, but quite sol-
uble in MeOH, DMF and DMSO. Elemental analyses
(Table 1) of the complexes indicate that the ligand react
with the metals to afford solvated complexes of general stoi-
chiometry M(HL)(H2O)n, suggesting that the complexes are
neutral MII species in which the ligand behaves as bi-depro-
H3L
3380 m, br
3408 m, br
3390 m, br
3385 m, br
3405 m, br
3400 m,br
3406 m, br
3260 m 1617 vs 1676 sh
3247 m 1606 vs 1687 sh
3246 m 1604 s 1686 m
3249 m 1606 vs 1680 sh
3247 m 1605 s 1680 sh
3261 m 1603 vs 1686 sh
3279 m 1600 s 1687 sh
1658 s
Ϫ
11
10
8
20
10
10
1
2
3
4
5
6
1637 m
1636 w
1655 m
1652 m
1655 m
1639 w
a) vs ϭ very strong; s ϭ strong, m ϭ medium, w ϭ weak, sh ϭ shoulder,
br ϭ broad; b) in ΩϪ1 cm2 molϪ1
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Z. Anorg. Allg. Chem. 2005, 631, 2161Ϫ2166

Electrochemical Synthesis of MII Complexes with a Schiff Base
1
Table 3 Some relevant H NMR data (in ppm) for the ligand and the diamagnetic compounds.
Compound
δ (ϪOH)
δ (ϪNHϪ)
δ (ϪNϭCHϪ)
δ (ϪHarom)
δ (ϪCH2Ϫ)
H3L
14.10 (s), 13.90 (s)
9.80 (s)
9.85 (s)
10.10 (s)
9.70 (s)
8.90 (s), 8.70 (s)
9.10 (s), 8.90 (s)
9.00 (s), 8.80 (s)
8.95 (s), 8.80 (s)
6.00-7.70
6.20-8.80
6.20-8.70
6.70-8.55
4.65 (s)
4.60 (s)
4.65 (s)
4.55 (s)
3
5
6
noa)
no
no
a) non observable
1
Magnetic studies and Electron spectroscopy
The H NMR spectra of 3, 5 and 6 serve to substantiate
the complexation and also the bis-deprotonation of the ligand.
In the absence of suitable crystals to solve their solid-state
structures, physicochemical data clearly show that H3L acts
as a dianionic coordinated ligand in the complexes but it
does not allow basing the coordination environment for the
Zn and Cd diamagnetic complexes. Nevertheless, the avail-
able data for the diamagnetic Ni complex suggest that the
nickel environment is square planar, probably using the com-
partment ONimNimO. Iron, cobalt and copper seem to be in
pseudo-octahedral fields, where the pentadentate ligand
would wrap around the metal ions as we have previously
reported for a similar manganese complex [14], with a water
molecule filling the sixth position. However, it must be noted
that this study does not exclude other possibilities, such as
pentacoordinations and various other non-regular structures.
Values obtained for magnetic measurements at room tem-
perature are shown in Table 1. ZnII and CdII complexes (5
and 6, respectively) are diamagnetic as expected for d10
shell-completed metal ions, but also NiII complex (3) results
diamagnetic. This suggests a square planar geometry for 3.
The magnetic moments for the paramagnetic compounds 1
and 2 are similar to those expected for magnetically diluted
high spin octahedral FeII and CoII complexes, whereas the
value in 4 is in accordance with a distorted octahedral d9
CuII complex.
All complexes display in their electronic spectra (re-
corded in methanol) intense absorption bands in the range
380-450 nm that are clearly charge transfer bands in origin.
These bands overlap the d-d transitions, which should ap-
pear about 400 nm, preventing their accurate assignment.
Crystal structure of 7
Deep green crystals of [Co(L1)(H2O)2]·2DMF 7 [(H2L1
N,NЈ-(1,2-phenylene)-bis(5-nitro-3-hydroxysalicylidenimine)],
suitable for X-ray diffraction studies, were obtained fortu-
itously from a solution of 2 in DMF. Its molecular structure
is shown in Figure 1, and selected bond lengths and angles
are collected in Table 4.
1H NMR spectroscopy
ϭ
1H NMR spectra of H3L and diamagnetic complexes (3, 5
and 6) were recorded in DMSO-d6. Data are listed in Table
3. Assignment of signals is according to our experience with
similar compounds derived from imine-amide ligands [10,
12, 14]. The spectrum of H3L exhibits two singlets at δ 8.90
and 8.70, assigned to the imine hydrogen atoms, corroborat-
ing the formation of CϭN bonds. The spectrum also shows
three singlets in the region of δ 14.1-9.8, which disappears
on deuteration. The aromatic protons lie in the range δ 6.0-
7.7, while the existence of a singlet at δ 4.65 indicates the
presence of the methylene chain.
1
The comparison of the H NMR spectrum of the free
ligand with those of the complexes shows some interesting
aspects:
1. In all cases, it is observed the disappearance of the OH
protons present in the free ligand, in agreement with the
bis-deprotonation of the ligand.
Fig 1 ORTEP view of complex 7. Atoms showing the atomic num-
bering scheme are represented by their 50 % probability ellipsoids.
2. The NH signal remains in the spectra of these com-
plexes, confirming the divalent state for the metal ions
(NiII, ZnII and CdII).
3. The imine hydrogen atoms show a shift to lower field for
all these complexes, indicating a withdrawal of charge
from the imine group upon coordination. Therefore,
these imine nitrogen atoms should be coordinated to the
metal ions.
˚
Table 4 Selected bond lengths/A and angles/° for 7.
Co(1)ϪO(1)
Co(1)ϪO(2)
Co(1)ϪN(1)
Co(1) ϪN(2)
Co(1)ϪO(1W)
Co(1)ϪO(2W)
1.872(6)
1.886(7)
1.874(8)
1.892(9)
2.354(14)
1.964(7)
O(1)ϪCo(1)ϪN(1)
O(1)ϪCo(1)ϪO(2)
O(1)ϪCo(1)ϪN(2)
O(2)ϪCo(1)ϪN(2)
N(1)ϪCo(1)ϪO(2)
N(1)ϪCo(1)ϪN(2)
O(1)ϪCo(1)ϪO(2W)
O(2)ϪCo(1)ϪO(2W)
N(2)ϪCo(1)ϪO(2W)
O(2W)ϪCo(1)ϪO(1W)
95.1(3)
82.8(3)
177.5(3)
95.8(3)
177.8(3)
86.4(3)
88.7(3)
90.1(3)
89.3 (3)
178.4(3)
4. The aromatic protons are also affected on coordination.
They are shifted to lower field, showing a drain of charge
from the phenyl ring.
Z. Anorg. Allg. Chem. 2005, 631, 2161Ϫ2166
zaac.wiley-vch.de
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
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M. J. Rodrıguez, M. I. Fernandez, A. M. Gonzalez-Noya, M. Maneiro, R. Pedrido, M. Vazquez, B. Donnadieu, M. R. Bermejo
multistep mechanism with an imine hydrolysis prior to a
subsequent amide hydrolysis. The sequence is shown in
Scheme 2.
The first imine hydrolysis process, possible by the exist-
ence of water in the media, would be favoured by the charge
withdrawal by the coordinated cobalt ion from the imine
nitrogen atom, which made it and its neighbouring primary
carbon more electrophilics. As result of this process, the
amine I would be released.
The second step would involve the amide hydrolysis. Co-
balt [25] has already been found to induce amide hydrolysis
(as well as copper [26] and iron [27]), and no doubt it plays
a determinant role in the present case, although it is diffi-
cult to set up its coordination during the different steps, so
it is omitted in the sequence at the right of Scheme 2.
The amide hydrolysis would originate the amine III,
which after condensation with free 5-nitrosalicylaldehyde
would form the final symmetrical ligand N,NЈ-(1,2-phenyl-
ene)-bis(5-nitro-3-hydroxysalicylidenimine). Despite of
these equilibrium processes would be a priori displaced to
the left, the high stabilization of the symmetrical complex
Scheme 2 Proposed hydrolytic mechanism for the 2 to 7 rearrange-
ment.
7, would be the driving force for the overall process.
The cobalt(II) atom in 7 is hexacoordinated, with two
Experimental Part
nitrogen and four oxygen donor atoms, forming a distorted
octahedral complex. The symmetrical Schiff base occupies
the equatorial plane of the octahedron using its tetradentate
ONNO donor set, yielding a nearly planar entity. The
Co(1)ϪO(1) and Co(1)ϪO(2) bonds of 1.872(6) and
General: Iron, cobalt, nickel, copper, zinc and cadmium were pur-
chased from Aldrich and used as sheets 0.5 mm thick. All reagents
of the highest commercial grade available (Aldrich) and solvents
were used as received without further purification. Elemental
analyses were performed on a Carlo Erba EA 1108 analyser. The
NMR spectra were recorded on a Bruker WM-250 spectrometer
using DMSO-d6 as solvent. IR spectra were recorded as KBr pellets
on a Bruker IFS-66V spectrophotometer in the range 4000-
600 cmϪ1. Mass spectrometry (Electronic Impact) was performed
on a Hewlett Packard 5988A mass spectrometer, whilst Electros-
pray was performed on a Hewlett-Packard LC-MSD 1100 instru-
ment (positive ion mode, 98:2 MeOH-HCOOH as mobile phase, 30
to 100 V). Room temperature magnetic susceptibility was measured
using a Digital Measurement system MSB-MKI, calibrated using
mercury tetrakis(isothiocyanato)cobaltate(II). Conductivity was
obtained at 25 °C from 10Ϫ3 M solution in DMF on a Crison
model Micro CM 2200 instrument. Electronic spectra were re-
corded on a Varian Cary IE spectrophotometer from 10Ϫ3 meth-
anol solutions in the range 300-900 nm.
˚
˚
1.886(7) A and the Mn-Nimine bonds of 1.874(8) and
1.892(9) A are consistent with a tight linkage of the di-
anionic ONNO Schiff base ligand to the CoII ion [18]. Two
capping water molecules fill the axial positions, although in
an outstanding different strength since the Co(1)ϪO(2W)
˚
distance of 1.964(7) A contrasts with the Co(1)ϪO(1W) of
˚
2.354(14) A, which actually provokes the distortion of the
octahedron.
2 Ǟ 7 Rearrangement
The ligand rearrangement that led to 7 from 2 appears as
an interesting novel process. In our experience with metal-
Schiff bases complexes we have found and discussed reor-
ganizations in solution that mainly yielded symmetrical li-
gands from asymmetrical ones [19, 20]. This type of re-
arrangements, known for an assortment of cases concerning
different metal ions such as manganese [19, 20], copper [21],
nickel [22] or platinum [23], are usually explained as hy-
drolysis of the imine groups. However, the versatility shown
by the metal-salen complexes has given rise to novel reor-
ganizations which can not be included into this type. Thus,
for instance, we have recently reported, for a Mn-salen de-
rivative system, a CϪN cleavage which followed a photo-
radical mechanism [24].
Synthesis of N-(2-aminophenyl)-2-[(phenylmethoxy)carbonylamino]-
ethanamide, A1. To a solution of carbobenzyloxyglycine (9.67 g,
46.20 mmol) in THF (100 cm3) were added o-phenylenediamine
(5.00 g, 46.20 mmol) and N,NЈ-dicyclohexylcarbodiimide (9.54 g,
46.20 mmol). This mixture was stirred al room temperature during
four hours. The insoluble N,NЈ-dicyclohexylurea was removed by
filtration and the solvent replaced by ethyl acetate (100 cm3). Ad-
dition of light petroleum (bp ϭ 40-60 °C) afforded 10.80 g,
36.10 mmol (78.5 %) of amine A1. Mp: 145 °C. Analysis: Found:
C, 64.0; H, 5.9; N, 13.7. Calc. for C16H17N3O3: C, 64.2; H, 5.7;
N, 14.0 %.
1H NMR (DMSO-d6, ppm): δ 3.85 (d, 2H), 4.86 (s, 2H), 5.07 (s, 2H), 6.55
(t, 1H), 6.73 (d, 1H), 6.92 (t, 1H), 7.15 (d, 1H), 7.31-7.38 (m, 5H), 7.54 (t,
1H), 9.16 (s, 1H). 13C NMR (DMSO-d6, ppm): δ 48.2 (CH2), 69.6 (CH2),
115.3-140.9 (Carom), 157.8 (CO), 168.2 (CO). IR (KBr, cmϪ1): ν(NH) 3473m,
ν(NH2) 3336s, 3383m and 3268m, ν(amide I) 1708vs, 1684vs and 1674vs,
ν(amide II) 1623vs and 1544vs. Mass spectrometry (EI): m/z 299.3.
The 2 Ǟ 7 rearrangement, involving an amido cleavage,
also appears as a different case, which should occur by
other less simple pathway. In fact, we propose a probable
2164
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
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Z. Anorg. Allg. Chem. 2005, 631, 2161Ϫ2166

Electrochemical Synthesis of MII Complexes with a Schiff Base
a)
Table 5 Crystal data and details of refinement of 7
.
rubber bund through which the electrical leads entered. The metal
anode, which had been previously weighed, was suspended from a
platinum wire; a second platinum wire was the cathode. H3L, 0.2 g,
was dissolved with heat in about 80 mL of acetonitrile. Then, a
small amount of tetramethylammonium perchlorate (about 10 mg)
was added as supporting electrolyte (CAUTION: although no
problem has been encountered in this work, all perchlorate com-
pounds are potentially explosive, and should be handled in small
quantities and with great care). Direct current was obtained from
a purpose-built DC power supply. Applied voltages of between 9.7
and 60.4 V allowed sufficient current flow to obtain the solution
of the required mass of metal anodes. The electrolysis time (8340 s)
was calculated with respect to the amount of ligand and in accord-
ance with the following reaction: M(s) ϩ H3L Ǟ M(HL)(H2O)n ϩ
H2(g). Cells can be summarised as: M(ϩ)/MeCN ϩ H3L/Pt(Ϫ).
Formula
M. W.
C26H30CoN6O10
645.49
11.179(4)
11.558(4)
11.982(4)
˚
a/A
˚
b/A
˚
c/A
α/°
β/°
γ/°
74.08(3)
71.76(3)
87.55(3)
1412.4(4)
3
˚
V/A
Z
2
Dc/g cmϪ3
Space group
Crystal system
Crystal size/mm
θ range/°
1.518
PϪ1
triclinic
0.22 x 0.14 x 0.07
3.13 to 23.26
Reflections collected
No. Unique reflections
No. Variables
μ /mmϪ1
8674
4030 [R(int) ϭ 0.1462]
Solid products 1 - 6 were readily isolated from the electrolysis solu-
tion by filtration. The insoluble products obtained were washed with
acetonitrile and diethyl ether to remove any excess of ligand and
vacuum dried. The amount of metal solved was evaluated in order
to postulate an empirical formula for the complexes and the pro-
cesses involved in their synthesis. The calculated Ef value is useful
for the latter. Electrodes were cleaned with a dilute HCl solution.
392
0.675
F(000)
670
Ϫ3
˚
Largest Peak and hole/e A
1.489 and Ϫ0.876
R1 ϭ 0.1097, wR2 ϭ 0.2418
R1 ϭ 0.1751, wR2 ϭ 0.2874
Final R indices [I>2sigma(I)]
R indices (all data)
a) Crystallographic data for the structure reported in this paper have been
deposited with the Cambridge Crystallographic Data Centre as supplemen-
tary publication no. CCDCϪ256412. Copies of the data can be obtained free
on application to The Director, CCDC, 12, Union Road, Cambridge CB2
ϩ (1223)336-033; e-mail for inquiry:
fileserv@ccdc.cam.ac.uk; e-mail for deposition: deposit@ccdc.cam.ac.uk).
X-Ray Crystallographic Studies. Crystals of 7, suitable for X-ray
diffraction studies, were obtained as described above. Data were
collected on a Stoe Imaging Plate Diffraction System (IPDS),
equipped with an Oxford Cryosystems Cryostream Cooler Device
and using a graphite-monochromated Mo-Kα radiation (λ ϭ
1EZ, UK (Fax: int. code
˚
0.71073 A), at T ϭ 180 K. Detailed data collection and refinement
Synthesis of 2-amino-N-(2-aminophenyl)ethanamide, (A2). A solu-
tion of A1 (10.00 g, 33.40 mmol) in methanol (250 cm3) was mixed
with cyclohexene (5 cm3, in excess of the molar proportion re-
quired) and 2.00 g of commercial 10 % Pd-C catalyst (catalyst:sub-
strate ratio 1:5 by weight). The mixture was refluxed for 15 min,
filtered from the catalyst, the catalyst washed with ethanol, and the
combined filtrates evaporated under reduced pressure to give the
deprotected amine A2 (4.03 g, yield 73.2 %). Mp: 149 °C. Analysis:
Found: C, 57.9; H, 6.6; N, 25.5. Calc. for C8H11N3O: C, 58.2; H,
6.7; N, 25.4 %.
1H NMR (DMSO-d6, ppm): δ 5.00 (s, 2H), 6.53 (t, 1H), 6.72 (d, 1H), 6.80
(d, 1H), 7.05 (t, 1H), 9.20 (s, 1H). 13C NMR (DMSO-d6, ppm): δ 48.6 (CH2),
115.4-146.8 (Carom), 173.8 (CO). IR (KBr, cmϪ1): ν(NH) 3416s, ν(NH2) 3323s
and 3200m, ν(amide I), 1680s, ν(amide II) 1635s. Mass spectrometry (EI):
m/z 165.1.
of the compound are summarized in Table 5. Final unit cell param-
eters were obtained by means of a least-squares refinement of a set
of 8000 well measured reflections, and a crystal decay was moni-
tored during the data collection by measuring 200 reflections by
image, no significant fluctuations of intensities were observed dur-
ing measurement. The structure was solved by means of Direct
Methods using the program SIR92 [29] and subsequent differences
Fourier maps, and then refined by least-squares procedures on a
F2 by using the program SHELXL-97 [30], included in the WinGx
package software [31]. All hydrogen atoms were located on a differ-
ence Fourier maps but introduced in the refinement as fixed con-
tributors, using a riding model with an isotropic thermal parameter
fixed at 20 % higher than those of the Csp2 atoms and 50 % for the
Csp3 atoms to which they were connected. Methyl groups were re-
fined with torsion angle as free variable. Positions of hydrogen
atoms of H2O molecules labelled O(1W) and O(2W) were calcu-
lated using the program XHYDEX [32]. All non-hydrogen atoms
were anisotropically refined and in the last cycles of refinement
weighting schemes have been used, where weights are calculated
from the following formula: Wϭ1/[σ2(Fo2)ϩ(aP)2ϩbP] where Pϭ
(Fo2ϩ2Fc2)/3. Criteria for a satisfactory complete analysis were the
ratios of root mean square shift standard deviation being less than
0.1. The figure was drawn using the program ORTEP3 [33].
Preparation of 3-aza-N-{2-[1-aza-2-(5-nitro-2-hydroxylphenyl)-
vinyl]phenyl}-4-(5-nitro-2-hydroxyphenyl)but-3-enamide, H3L. The
Schiff base ligand was prepared by the reaction of an equimolecular
quantity of the aldehyde with the amine A2. Amine A2 (1.90 g,
11.50 mmol) and 5-nitrosalicylaldehyde (3.86 g, 23.00 mmol) were
dissolved in methanol (200 cm3) and the solution was brought to
reflux. The volume of the resulting solution was reduced over 3
hours to ca. 50 cm3, using a Dean-Stark trap and the solution was
then allowed to cool. The solid which precipitated was collected by
filtration, washed with diethyl ether (3 cm3) and dried in vacuo. We
obtained 3.44 g (65 %) of the Schiff base. The purity of this ligand
was checked by elemental analysis, mass spectrometry (Table 1), IR
(Table 2) and 1H NMR spectroscopy (Table 3). The 13C NMR
spectra of this ligand in DMSO-d6 shows 17 signals corresponding
the aromatic, imine and carbonyl carbon atoms, which lie in the
range δ 115.1-167.5. Additionally, the methylene carbon of the
chain gives a separate signal at δ 58.
Acknowledgements. We thank Xunta de Galicia (PGID-
IT03PXI20901PR and PGIDIT04PXIC20902PN) and Ministerio
´
de Ciencia y Tecnologıa of Spain (BQU2003-00167) for financial
support.
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Z. Anorg. Allg. Chem. 2005, 631, 2161Ϫ2166