Electrochemical synthesis of adducts of 2-aminopyridine or methanol in metal chelates of a N,N,N-tridentate Schiff base ligand. X-ray crystal structures of the Ni(II) and Zn(II) derivatives

Article abstract of DOI:10.1016/S0277-5387(03)00104-9

The electrochemical syntheses of series of novel adducts of 2-aminopyridine and methanol in Co(II), Ni(II), Cu(II) or Zn(II) chelates of the N,N,N-tridentate basic form of the Schiff base 2-N-tosylamino(2′-tosylaminobenzylidene)aniline (H₂L), [M(L)L′] (M = Co, Ni, Zn, L′ = 2-aminopyridine; M = Cu, L′ = CH₃OH), were performed by using the corresponding metal as a sacrificial anode. The compounds were characterized by elemental analysis, IR spectroscopy, FAB mass spectrometry, ¹H NMR and magnetic measurements. The crystal structures of the Zn and Ni derivatives as well as of the Schiff base have been determined by X-ray diffraction. In the 2-aminopyridine complexes this ligand is bound to the metal through the endocyclic nitrogen whereas the aminogroup is involved in intramolecular N-H?O hydrogen bonds with one of the tosyl SO₂ groups.

Full text of DOI:10.1016/S0277-5387(03)00104-9

Polyhedron 22 (2003) 1335ꢁ1340
/
www.elsevier.com/locate/poly
Electrochemical synthesis of adducts of 2-aminopyridine or methanol
in metal chelates of a N,N,N-tridentate Schiff base ligand.
X-ray crystal structures of the Ni(II) and Zn(II) derivatives
D.A. Garnovskii a, M.F.C. Guedes da Silva a, M.N. Kopylovich a, A.D. Garnovskii b,
J.J.R. Frau´sto da Silva a, A.J.L. Pombeiro a,*
a Centro de Qu´ımica Estrutural, Complexo I, Instituto Superior Te´cnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
b Institute of Physical and Organic Chemistry, Rostov State University, 344000 Rostov-on-Don, Russian Federation
Received 22 November 2002; accepted 10 February 2003
Abstract
The electrochemical syntheses of series of novel adducts of 2-aminopyridine and methanol in Co(II), Ni(II), Cu(II) or Zn(II)
chelates of the N,N,N-tridentate basic form of the Schiff base 2-N-tosylamino(2?-tosylaminobenzylidene)aniline (H2L), [M(L)L?]
(Mꢀ
/
Co, Ni, Zn, L?ꢀ
/
2-aminopyridine; Mꢀ
/
Cu, L?ꢀCH3OH), were performed by using the corresponding metal as a sacrificial
/
anode. The compounds were characterized by elemental analysis, IR spectroscopy, FAB mass spectrometry, 1H NMR and magnetic
measurements. The crystal structures of the Zn and Ni derivatives as well as of the Schiff base have been determined by X-ray
diffraction. In the 2-aminopyridine complexes this ligand is bound to the metal through the endocyclic nitrogen whereas the
aminogroup is involved in intramolecular Nꢀ
/
H
/
ꢀ ꢀ ꢀ
/
O hydrogen bonds with one of the tosyl SO2 groups.
# 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Electrochemical synthesis; 2-Aminopyridine; Methanol; Schiff base
1. Introduction
TsNH, OH or SH; Tsꢀ SO2C6H4CH3-p) in o-posi-
/
ꢀ
/
tions of the phenyl rings can act as tridentate ligands in
either mononuclear or dinuclear coordination com-
The deprotonated (basic) forms of the Schiff bases (I)
that contain two proton donor groups (XH and YHꢀ
/
pounds of the types II and III [1ꢁ5].
/
Among the synthesized complexes of type II those
with aminoheterocycles (L?) are particularly interesting
* Corresponding author. Tel.: ꢂ
846-4455.
E-mail address: pombeiro@ist.utl.pt (A.J.L. Pombeiro).
/
351-21-841-9237; fax: ꢂ351-21-
/
[6ꢁ8]. In fact, adducts of the aminoazoles and aminoa-
/
0277-5387/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0277-5387(03)00104-9

1336
D.A. Garnovskii et al. / Polyhedron 22 (2003) 1335ꢁ1340
/
zines with different transition metals provide good
models for natural purine base complexes [9,10]. More-
over, aminoheterocycles containing two or more poten-
tial donor centres play an important role in the study of
competitive reactivity of ambidentate ligand systems
methanol solution (25 ml) contained 0.262 g (1.00
mmol) of the tosylamino-functionalized compound
(H2L), 2-aminopyridine (L?) (0.095 g, 1.00 mmol) and
0.010 g of Et4NClO4 as the electrolyte. The electrolyses
were carried out in a U-shaped glass tube at a current of
10 mA with initial voltage of 8 V for 2 h. After
electrolyses the solid products were filtered off, washed
three times with hot methanol and dried in vacuum. For
complexes IIc, suitable crystals for X-ray diffraction
analysis were obtained in this way. However, for IIb and
H2L, the crystals were obtained by dissolution of the
electrolysis product in methanol/chloroform (1:1) fol-
lowed by slow evaporation.
[11ꢁ26]. In the present work we report the electrosyn-
/
thesis of adducts (type II) of 2-aminopyridine and
methanol in chelates of various first row transition
metal ions with the tridentate basic form (L2ꢃ) of 2-N-
tosylamino(2?-tosylaminobenzylidene)aniline [27] [H2L
i.e. I (Xꢀ
/
YꢀTs)]. The use of the electrochemical
/
procedure with sacrificial electrodes allowed us to
obtain adducts of type II, with 2-aminopyridine (L?)
for Ni(II), Zn(II) and Co(II) and with methanol (L?) in
the case of copper(II). The electrochemical reactions
proceeded under mild conditions (room temperature) in
The electrochemical cell can be summarized as:
(ꢃ
/
)Pt j CH3OHꢂ
/
H2Lꢂ
/
L? j M(ꢂ
/
).
contrast with the usual chemical syntheses [6ꢁ
II complexes which require heating, namely in solvent
refluxing conditions.
/
8] of type
2.2.1. [Co(L)(L?)] (L?ꢀ
/
2-aminopyridine) (IIa)
Under the electrochemical conditions, 22 mg of the
Co sacrificial anode were dissolved (Efꢀ
/
0.5 mol Fꢃ1).
The yield is 76%. Anal. Calc. for C32H29N5O4S2Co: C,
57.30; H, 4.36; N, 10.44; S, 9.56. Found: C, 57.16; H,
2. Experimental
4.30; N, 10.44; S, 10.00. FABꢂ MS, m/z: 599 [Mꢁ
/
L?ꢂ
179ꢁ
180 8C. IR spectrum (selected bands) in KBr, cmꢃ1
3416 nas(NH2), 3343 ns(NH2), 3238 ns(NH2), 1651
d(NH2), 1608 n(CꢁN), 1262 nas(SO2), 1138 ns(SO2).
meff 4.08 B.M.
/
Naꢁ
/
H]ꢂ, 422 [Mꢁ
/
L?ꢁ
/
SO2C6H4CH3-p]ꢂ. M.p.ꢀ
/
/
2.1. Analysis and physical measurements
:
Methanol, 2-aminopyridine, Et4NClO4 are commer-
cially available products and were used as received. The
sheets of metals (Zn, Ni, Co and Cu) were purchased
from Aldrich, and 2-N-tosylamino(2?-tosylaminobenzyl-
idene)aniline (H2L) was prepared according to the
published method [2]. C, H, N, S elemental analyses
were carried out by the Microanalytical Service of the
Instituto Superior Te´cnico. Melting points were deter-
mined on a Kofler table. Positive-ion FAB mass spectra
were obtained on a Trio 2000 instrument by bombard-
ing 3-nitrobenzyl alcohol matrixes of the samples with 8
/
ꢀ
/
2.2.2. [Ni(L)(L?)] (L?ꢀ
Twenty two milligram of the Ni sacrificial anode were
dissolved during the electrolysis (Efꢀ
0.5 mol Fꢃ1). The
/
2-aminopyridine) (IIb)
/
yield is 81%. Anal. Calc. for C32H29N5O4S2Ni: C, 57.32;
H, 4.36; N, 10.45; S, 9.57. Found: C, 57.14; H, 4.35; N,
10.45; S, 9.60. FABꢂ MS, m/z: 670 [M]ꢂ, 598 [Mꢁ
/
L?ꢂ
172ꢁ
173 8C. IR spectrum (selected bands) in KBr, cmꢃ1
3419 nas(NH2), 3344 ns(NH2), 3242 ns(NH2), 1649
d(NH2), 1608 n(CꢁN), 1258 nas(SO2), 1138 ns(SO2).
meff 3.23 B.M.
/
Naꢁ
/
H]ꢂ, 421 [Mꢁ
/
L?ꢁ
/
SO2C6H4CH3-p]ꢂ. M.p.ꢀ
/
/
:
keV (:
data system acquisition was achieved using CsI. Infrared
spectra (4000ꢁ
400 cmꢃ1) were recorded on a Bio-Rad
/
1.28ꢄ
1015 J) Xe atoms. Mass calibration for
/
/
/
ꢀ
/
FTS 3000 MX instrument in KBr pellets. 1H NMR
spectra were measured on a Varian Unity 300 spectro-
meter at ambient temperature. The electrolyses were
carried out using an EG&G PAR/173 galvanostat.
Magnetic susceptibilities of Ni(II), Co(II) and Cu(II)
complexes have been determined using the Faraday’s
method on the equipment of the Rostov State Uni-
versity [28]. All the other instruments are at the Centro
de Qu´ımica Estrutural.
2.2.3. [Zn(L)(L?)] (L?ꢀ
Over the period of electrolysis the Zn sacrificial anode
lost 24.0 mg (Efꢀ
0.49 mol Fꢃ1). The yield is 74%.
Anal. Calc. for C32H29N5O4S2Zn: C, 56.76; H, 4.32; N,
10.34; S, 9.47. Found: C, 56.91; H, 4.28; N, 10.07; S,
/
2-aminopyridine) (IIc)
/
9.90. FABꢂ MS, m/z: 608 [Mꢁ
/
L?ꢂ
188 8C. IR spectrum
(selected bands) in KBr, cmꢃ1: 3414 nas(NH2), 3349
N),
/
Naꢂ
/
2H]ꢂ, 605
[Mꢁ
/
L?ꢂ
/
Naꢁ
/
H]ꢂ. M.p.ꢀ
/
187ꢁ
/
ns(NH2), 3239 ns(NH2), 1655 d(NH2), 1608 n(Cꢁ
1259 nas(SO2), 1142 ns(SO2).
/
2.2. Electrosyntheses
The electrosyntheses of the complexes were performed
in methanol solution using a Pt wire as the cathode and
2.2.4. [Cu(L)(CH3OH)] (IId)
The weight of the Cu sacrificial anode reduced by 22
mg (Efꢀ
0.5 mol Fꢃ1). The yield is 63%. Anal. Calc. for
C28H27N3O5S2Cu: C, 54.90; H, 4.40; N, 6.85; S, 10.44.
a metal (M) plate (Mꢀ
/
Cu, Ni, Co, Zn) suspended on a
/
platinum wire as the sacrificial anode, according to a
standard electrochemical procedure [29]. The working
Found: C, 55.01; H, 4.27; N, 7.09; S, 10.46. FABꢂ MS,

D.A. Garnovskii et al. / Polyhedron 22 (2003) 1335ꢁ
/1340
1337
m/z: 582 [Mꢁ
[MꢁCH3OHꢁHꢁ
Hꢁ
2SO2C6H4CH3-p]ꢂ. M.p.ꢀ
trum (selected bands) in KBr, cmꢃ1: 1602 n(Cꢁ
1273 nas(SO2), 1142 ns(SO2). meff 1.92 B.M.
/
CH3OH]ꢂ, 581 [Mꢁ
SO2C6H4CH3-p]ꢂ, 271 [Mꢁ
174ꢁ175 8C. IR spec-
N),
/
CH3OHꢁ
/
H]ꢂ, 426
/
/
/
/
CH3OHꢁ
/
/
/
/
/
ꢀ
/
2.3. Crystal structure determinations
Diffraction measurements were carried out at room
temperature on an EnrafꢁNonius CAD4 diffractometer,
equipped with a graphite monochromator and Mo Ka
/
˚
0.71069 A). Cell dimensions were ob-
radiation (lꢀ
tained from centered reflections with u between 2 and
258 (H2L, IIc), 1.6 and 248 (IIb). Range of hkl: hꢀ0 to
20, kꢀ 24 to 24, lꢀ0 to 8 (H2L); hꢀ 20 to 20, kꢀ
to 14, lꢀ0 to 29 (IIb); hꢀ 12 to 11, kꢀ 13 to 13,
lꢀ0 to 17 (IIc). The intensities of 4534 (H2L), 9600 (IIb)
or 5576 (IIc) reflections were observed and a total of
2311 (H2L), 9368 (IIb) or 5354 (IIc) (Rint 0.0791,
/
/
/
ꢃ
/
/
/
ꢃ
/
/
0
Fig. 1. Molecular structure of compound H2L.
/
/
ꢃ
/
/
ꢃ
/
/
ꢀ
/
0.0531 and 0.0598, respectively) unique reflections were
used for structures solution and refinement. Structures
were solved by direct methods, by using the SHELXS-97
package [30]. The structure refinements were carried out
with SHELXL-97 [31]. Crystallographic data are sum-
marised in Table 1. Molecular structures with their
respective numbering schemes are shown in Figs. 1ꢁ
/
3
and selected bond lengths and angles in Tables 2ꢁ4. In
/
IIb the single crystal X-ray diffraction analysis shows
the presence of two molecules, A and B, in the
asymmetric unit cell (Fig. 2). In IIc the molecule has
two possible orientations in the crystal and therefore the
Nꢁ
As a consequence, the bond lengths involved in this
group are not perfect, especially N4AꢀC11 which is very
/
CH group is split in two positions as shown in Fig. 3.
Fig. 2. Molecular structure of [Ni{N(SO2C6H4CH3-p)(C6H4)}2(CHꢁ
/
/
N)(NC5H4NH2)] (IIb).
long. Least square refinements with anisotropic thermal
motion parameters for all the non-hydrogen atoms
(except for N4A and N4B atoms in IIc which could
not be refined anisotropically) and isotropic for the
remaining atoms gave R1ꢀ
0.0673 (IIc) [I ꢀ2s(I); R1ꢀ
or 0.1131 (IIc) (all data)].
/
0.0588 (H2L), 0.0757 (IIb) or
/
/0.1422 (H2L), 0.1708 (IIb)
Table 1
Crystallographic data for compound H2L and for the complexes IIb and IIc
Empirical formula
Formula weight
Crystal system
Space group
C
27H25N3O4S2 (H2L)
C32H29N5O4S2Ni (IIb)
670.43
C32H29N5O4S2Zn (IIc)
677.13
Triclinic
519.64
Orthorhombic
P21ab
Monoclinic
P21/n (No. 14)
18.280(3)
13.080(3)
25.381(7)
90
¯
P1 (No. 2)
/
˚
a (A)
17.5080(50)
20.3660(50)
7.1180(50)
90
10.1500 (8)
11.1514 (5)
15.0913 (6)
99.250 (3)
102.242 (3)
109.426 (4)
1523.89 (16)
2
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
90
90
98.708(16)
90
5999(2)
3
˚
V (A )
Z
2538.05(20)
4
1.360
8
1.485
rcalc (g cmꢃ3
)
1.476
0.989
0.0673
m(Mo Ka) (mmꢃ1
)
0.249
0.0588
0.833
0.0757
R
wR
0.1396 wꢀ
Pꢀ
/
1/[s2(Fo2)ꢂ
/
(0.0555P)2], 0.1954 wꢀ
/
1/[s2(Fo2)ꢂ
/
(0.0438P)2ꢂ
/
0.1729 wꢀ
2.3370P], Pꢀ
/
1/[s2(Fo2)ꢂ
/
(0.0676P)2ꢂ
/
/
(Fo2ꢂ2Fc2)/3
/
32.3043P], Pꢀ
/
(Fo2ꢂ2Fc2)/3
/
/
(Fo2ꢂ2Fc2)/3
/

1338
D.A. Garnovskii et al. / Polyhedron 22 (2003) 1335ꢁ
/1340
Table 3
Selected bond lengths (A) and angles ( ) for [Ni{N(SO2C6H4CH3-
o
˚
p)(C6H4)}2(CHꢁN)(NC5H4NH2)], IIb
/
Ni1ꢀ
Ni1ꢀ
Ni1ꢀ
Ni1ꢀ
Ni1ꢀ
S11ꢀ
S12ꢀ
N14ꢀ
N14ꢀ
/
O12B
N11
N12
N13
N14
2.459(7)
2.033(8)
1.964(7)
1.989(8)
1.971(8)
1.578(9)
1.594(8)
1.245(12)
1.483(13)
Ni2ꢀ
Ni2ꢀ
Ni2ꢀ
Ni2ꢀ
Ni2ꢀ
S21ꢀ
S22ꢀ
N23ꢀ
N23ꢀ
/
N22
N23
N24
O22A
N21
1.972(8)
1.960(8)
2.001(8)
2.385(6)
2.031(7)
1.600(8)
1.587(8)
1.292(11)
1.450(11)
/
/
/
/
/
/
/
/
/
N13
N12
/N24
/
/N22
/C30
/C51
/C66
/C46
N11ꢀ
N11ꢀ
N12ꢀ
N13ꢀ
N12ꢀ
N11ꢀ
C46ꢀN23ꢀ
/
Ni1ꢀ
Ni1ꢀ
Ni1ꢀ
Ni1ꢀ
Ni1ꢀ
Ni1ꢀ
/
N12
N13
N14
N14
N13
N14
101.8(3)
111.1(3)
90.1(3)
N21ꢀ
N21ꢀ
N22ꢀ
N23ꢀ
N22ꢀ
N21ꢀ
C30ꢀN14ꢀ
/
Ni2ꢀ
Ni2ꢀ
Ni2ꢀ
Ni2ꢀ
Ni2ꢀ
Ni2ꢀ
/
N22
N24
N23
N24
N24
N23
100.9(3)
104.0(3)
90.2(3)
/
/
/
/
/
/
/
/
/
/
83.2(3)
/
/
84.2(3)
/
/
147.0(3)
106.0(3)
121.3(8)
/
/
155.1(3)
106.0(3)
121.5(8)
/
/
/
/
/
/
C51
/
/
C66
Table 4
Selected bond lengths (A) and angles ( ) for [Zn{N(SO2C6H4CH3-
o
˚
p)(C6H4)}2(CHꢁ
/
N)( NC5H4NH2)], IIc
Zn1ꢀ
Zn1ꢀ
Zn1ꢀ
Zn1ꢀ
Zn1ꢀ
/
N1
2.053(5)
1.983(6)
2.000(6)
S2ꢀ
S3ꢀ
N4Aꢀ
/
N2
1.599(6)
1.608(6)
1.24(2)
1.29(2)
/N2
/N3
/N3
/C50A
/N4A
2.059(13) N4Bꢀ
2.064(13)
/C50B
/N4B
N(1)ꢀ
N(1)ꢀ
N(1)ꢀ
N(1)ꢀ
/
Zn(1)ꢀ
Zn(1)ꢀ
Zn(1)ꢀ
Zn(1)ꢀ
/
N(2)
116.0(2)
103.5(2)
112.4(4)
108.4(4)
N(2)ꢀ
N(2)ꢀ
N(2)ꢀ
N(3)ꢀ
N(3)ꢀ
N(4A)ꢀ
/
Zn(1)ꢀ
Zn(1)ꢀ
Zn(1)ꢀ
Zn(1)ꢀ
Zn(1)ꢀ
/
N(3)
140.3(2)
78.3(6)
94.3(5)
90.6(5)
75.9(5)
16.4(7)
/
/N(3)
/
/
N(4A)
N(4B)
N(4A)
N(4B)
Fig. 3. Molecular structure of [Zn{N(SO2C6H4CH3-p)(C6H4)}2(CHꢁ
/
/
/N(4A)
/
/
N)(NC5H4NH2)] (IIc).
/
/N(4B)
/
/
/
/
/
Zn(1)ꢀN(4B)
/
Table 2
Selected bond lengths (A) and angles ( ) for compound H2L
o
˚
S1ꢀ
S1ꢀ
S1ꢀ
S1ꢀ
N3ꢀ
N11ꢀ
/
O4
O5
N3
C19
1.437(7)
1.433(7)
1.593(9)
1.775(9)
1.414(13)
1.245(13)
S2ꢀ
S2ꢀ
S2ꢀ
S2ꢀ
N9ꢀ
N11ꢀ
/
O6
O8
N9
C14
1.427(7)
1.415(7)
1.652(8)
1.732(9)
1.425(11)
1.506(13)
for the basic dianionic form of the tridentate Schiff base.
The oxidation of copper in the same conditions resulted
in the formation of the methanol adduct
[Cu(L)(CH3OH)] (IId).
/
/
/
/
/
/
/C12
/C21
/C7
/
C13
The value (see Section 2) of the electrochemical
efficiency, Ef (defined as the number of moles of metal
O4ꢀS1ꢀ
O4ꢀS1ꢀ
O5ꢀS1ꢀ
N3ꢀS1ꢀ
S1ꢀN3ꢀ
C7ꢀ
/
/
O5
N3
N3
120.3(4)
103.6(5)
110.8(5)
105.7(5)
130.2(8)
125.1(9)
O6ꢀS2ꢀ
O6ꢀS2ꢀ
O8ꢀS2ꢀ
N9ꢀS2ꢀ
S2ꢀN9ꢀ
/
/
O8
N9
N9
119.5(4)
104.9(4)
107.1(4)
107.0(4)
118.7(6)
dissolved per Faraday of charge), close to 0.5 mol Fꢃ1
,
/
/
/
/
/
/
/
/
and the liberation of hydrogen at the cathode are in
accord with the following process:
/
/
C19
/
/
C14
C21
/
/
C12
/
/
Cathode: H2Lꢂ2eꢃ 0 L2ꢃ ꢂH2
/
N11ꢀ
/
C13
Anode: M(Co; Ni; Zn)ꢂL2ꢃ ꢂL?
0 [M(L)(L?)]ꢂ2eꢃ
In the case of copper: Anode: CuꢂL2ꢃ ꢂCH3OH
0 [Cu(L)(CH3OH)]ꢂ2eꢃ
3. Results and discussion
The electrochemical oxidation of cobalt, nickel or zinc
metals, used as sacrificial anodes, in the presence of the
potential tridentate species 2-N-tosylamino(2?-tosylami-
nobenzylidene)aniline (H2L) and 2-aminopyridine (L?),
in methanol, led to the complexes of general formula
3.1. X-ray molecular structures
The molecular structures of the sulfonylamino-func-
tionalized imine (H2L) and of its nickel (IIb) and zinc
[M(L)(L?)] (Mꢀ/Co IIa, Ni IIb, Zn IIc) where L stands

D.A. Garnovskii et al. / Polyhedron 22 (2003) 1335ꢁ
/1340
1339
(IIc) complexes were unambiguously established by X-
ray diffraction analyses.
In the H2L molecule the bond distances and angles lie
within normal values [32], with the p-tolyl moieties
being bent due to the steric control induced by the SO2
fragment.
For both molecules II, the ligand L acts as a tridentate
chelating species by means of the two amino- and the
imino-nitrogen atoms. The fourth coordination position
is occupied by the aminopyridine which is bound in a
monodentate fashion through the endocyclic N atom, as
found in other complexes with Lewis acids [11]. The
coordination polyhedra of the metal atoms in both
structures are highly distorted tetrahedrons. In fact, the
aminopyridine and an oxygen atom of a tosylated
fragment of the Schiff base ligand.
The 1H NMR of the Zn(II) complex (IIc) confirms the
4-N environment of the metal centre. In fact, the
spectrum (run in d6-dmso) does not display any reso-
nance assigned to the tosylated amino protons (which in
the free ligand, H2L, appear as two singlets at d 9.6 and
11.4), whereas that of the azomethinic proton occurs at
d 9.0, i.e. shifted to lower field in comparison with that
(at d 8.2) of the free ligand. These observations testify in
favour of the basic form (L2ꢃ) of the ligand and its
tridentate chelation via both the amido-N atoms and the
imino-N atom. In addition, the appearance of a broad
singlet at d 5.9, assigned to the amino protons of 2-
aminopyridine, confirms the presence of this ligand (L?).
Thus, both IR and NMR data favour a {MN4}
angles around the metal ion are in the range 83.0(3)ꢁ
110.8(3)8 (IIb) and 75.9(5)ꢁ116.0(2)8 (IIc) except for the
NꢀMꢀN angle involving the nitrogen atoms of the two
sulfonylamino groups which is 147.2(4) or 155.2(3)8
(IIb) or 140.3(2)8 (IIc). The metalꢁN distances are not
unusual and are similar to those reported for other Ni or
Zn complexes [33ꢁ37]. In the Zn complex IIc, these
/
/
/
/
coordination for the complexes IIaꢁc with participation
/
of two (deprotonated) amide nitrogen atoms, the nitro-
gen of the imine group and the endocyclic nitrogen of 2-
aminopyridine.
/
/
The FABꢂ mass spectra of the complexes (IIaꢁ
/
c)
H]ꢂ
and the molecular ion is also observed for the Ni(II)
complex IIb. The peak at m/z 582 [Mꢁ
CH3OH]ꢂ is
distances are slightly longer than in the Ni analogue as
observed in other cases [33]. In addition, in each
show the peaks due to the fragment [Mꢁ
/
L?ꢂ
/
Naꢁ
/
structure the Mꢀ
than the other metalꢁ
is of the same order of magnitude as the Znꢀ
/
Npyr bond distances are slightly longer
nitrogen bonds, although in IIc it
N(4A) [or
/
/
detected in the fragmentation of the methanol complex
IId. The values of the magnetic moments (meff) at room
temperature 4.08, 3.23 and 1.92 B.M. for the Co(II),
Ni(II) and Cu(II) complexes, respectively, support the
mononuclear structure of these compounds [38].
/
N(4B)] bond length. In both structures the nitrogen
atom of the NH2 group of the 2-aminopyridine ligand is
oriented towards the oxygen atoms of one of the SO2
groups in such a manner that the N
/
ꢀ ꢀ ꢀ
/
O distances in the
range from 2.907(9) to 3.193(11) A allow us to assume
that the intramolecular hydrogen bonds Nꢀ ꢀ ꢀ ꢀO have
2.2938 A and NHO angles of
˚
/
H
/
/
˚
distances of 2.0551ꢁ
/
4. Supplementary material
164.65ꢁ170.328.
/
Crystallographic data have been deposited to the
Cambridge Crystallographic Data Center as supplemen-
tary publications No. CCDC-197531 (H2L), CCDC-
197532 (IIb), CCDC-197533 (IIc). Copies of the data
can be obtained free of charge on application to CCDC,
3.2. Spectroscopic properties
The IR spectra of the coordination compounds IIaꢁ
IIc are in agreement with the X-ray data discussed
above. In comparison with the IR spectrum of the free
ligand (H2L) they do not exhibit the band at 3297 cmꢃ1
/
12 Union Road, Cambridge CB2 1EZ, UK (fax: ꢂ44-
/
1223-336033: e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
attributable to n(Nꢀ
/
H) of the tosylated amino group
and show a lower frequency shift (10 cmꢃ1) of the
stretching vibration band of the imino group (1618
cmꢃ1 in the ligand). These features can be interpreted as
a result of the participation of both deprotonated
nitrogens of the tosylated fragments and of the imine
nitrogen in coordination to the metal with formation of
a chelate ring. Moreover, the stretching vibration bands
of the amino group of the coordinated 2-aminopyridine
Acknowledgements
This work has been partially supported by Founda-
tion for Science and Technology (F.C.T.) and the
PRAXIS XXI and POCTI Programmes (Portugal).
We also thank Dr Teresa Duarte (I.S.T.) and Dr Matti
Haukka (Joensuu University, Finland) for stimulation
discussions and assistance in the X-ray analysis of IIc,
and Dr M. Caˆndida N. Vaz for the analytical service at
the I.S.T.
appear at 3500ꢁ
3200 cmꢃ1, i.e. at lower frequencies
/
than in the case of the uncoordinated 2-aminopyridine.
Taking into account our previous results [11], this shift
is indicative of an intramolecular hydrogen bond
between an hydrogen atom of the amino group of 2-

1340
D.A. Garnovskii et al. / Polyhedron 22 (2003) 1335ꢁ1340
/
[18] O. Castillo, A. Luque, M. Julve, F. Lloret, P. Roma´n, Inorg.
Chim. Acta 315 (2001) 9.
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