´
´
´
´
M. Maneiro, B. Fernandez, E. Gomez-Forneas, M. J. Rodrıguez, R. Pedrido, M. J. Romero, M. R. Bermejo
H2L3. Elemental analysis: C18H16Br4N2O2 (M. W. ϭ 611.94): C,
35.5 (35.3); N, 4.2 (4.6); H, 2.6 (2.6) %; m.p. 137 °C.
1H NMR (300 MHz, CDCl3): δ ϭ 1.45 (s, 6H), 3.77 (s, 2H), 7.3-7.7 (m, 4H),
dination mode, which involves both reversibility and the
possibility of undergoing the sulphato reaction.
However, we have also found different SO2 binding modes
among the present series of adducts, proposing SϪbridging
for 10, 12 and 14, and ligand bound for 8, 9 and 13.
8.18 (s, 1H), 8.20 (s, 1H) 14.1 (s, 1H), 15.0 (s, 1H) ppm.
IR (KBr): ν(CNimine) 1625 vs, ν(CO) 1274 s cmϪ1
.
H2L4. Elemental analysis: C18H16Cl4N2O2 (M. W. ϭ 434.14): C,
49.6 (49.8); N, 6.4 (6.5); H, 3.6 (3.7) %; m.p. 150 °C.
1H NMR (300 MHz, CDCl3): δ ϭ 1.46 (s, 6H), 3.80 (s, 2H), 7.1-7.4 (m, 4H),
Experimental Part
8.17 (s, 1H), 8.20 (s, 1H) 14.05 (s, 1H), 14.82 (s, 1H) ppm.
General: Salicylaldehydes (Maybridge) and 1,2-diamino-2-methyl-
propane (Aldrich) were used as received without further purifi-
cation. Manganese (Ega Chemie) was used as ca. 2 x 2 cm2 plate.
IR (KBr): ν(CNimine) 1627 vs, ν(CO) 1293 s cmϪ1
.
H2L5. Elemental analysis: C18H16Br2N4O6 (M. W. ϭ 544.14): C,
39.7 (39.7); N, 10.0 (10.3); H, 3.0 (3.0) %; m.p. 243 °C.
1H NMR (300 MHz, CDCl3): δ ϭ 1.60 (s, 6H), 3.90 (s, 2H), 8.2-8.4 (m, 4H),
Elemental analyses were performed on
a Carlo Erba 1108
CHNSϪO elemental analyser. The IR spectra were recorded as
8.51 (s, 1H), 8.52 (s, 1H) 15.0 (s, 1H), 15.7 (s, 1H) ppm.
1
KBr discs on a Nicolet PC5 FT-IR spectrophotometer. H NMR
IR (KBr): ν(CNimine) 1640 vs, ν(CO) 1328 s cmϪ1
.
spectra were recorded on a Bruker WH 300 MHz spectrometer
using CDCl3 as solvent. FAB mass spectra were recorded on a
Kratos MS50 TC spectrometer connected to a DS90 data system,
using mϪnitrobenzyl alcohol as a matrix. Room-temperature mag-
netic susceptibilities were measured using a Digital Measurement
system 1660 vibrating magnetometer operating at 5000 G.
HgCo(NCS)4 was employed as a susceptibility standard.
H2L6. Elemental analysis: C18H16Br2Cl2N2O2 (M. W. ϭ 523.03): C,
40.9 (41.3); N, 5.2 (5.4); H, 3.2 (3.1) %; m.p. 154 °C.
1H NMR (300 MHz, CDCl3): δ ϭ 1.37 (s, 6H), 3.61 (s, 2H), 7.0-7.4 (m, 4H),
8.03 (s, 1H), 8.09 (s, 1H) 13.9 (s, 1H), 14.7 (s, 1H) ppm.
IR (KBr): ν(CNimine) 1631 vs, ν(CO) 1290 s cmϪ1
.
H2L7. Elemental analysis: C20H22Br2N2O4 (M. W. ϭ 514.20): C,
46.5 (46.7); N, 5.6 (5.4); H, 4.5 (4.3) %. m.p. 133 °C.
1H NMR (300 MHz, CDCl3): δ ϭ 1.42 (s, 6H), 3.72 (s, 2H), 3.88 (s, 6H),
Cyclic and normal pulse voltammetry was performed with a Prin-
ceton Applied Research model 270 potentiostat and potential scan-
ning unit with the operating program ECHEM. A Metrohm graph-
ite disc (area 0.07 cm2) coupled to a Metrohm model 628-10 rotat-
ing electrode device was used as a working electrode; a saturated
calomel electrode was used as a reference and a Pt wire as an auxili-
ary electrode. Voltammograms were obtained from ca. 1 mM solu-
tions of the complexes in DMF using 0.2 M Bu4NPF6 as a support-
ing electrolyte. All experiments were carried out under an atmos-
phere of dry N2. Cyclic voltammetry measurements were per-
formed with a static graphite electrode, whilst direct-current and
pulse voltammograms were recorded with the graphite disc rotating
at 2000 revolutions per minute.
6.9-7.3 (m, 4H), 8.21 (s, 1H), 8.23 (s, 1H) 13.80 (s, 1H), 14.45 (s, 1H) ppm.
IR (KBr): ν(CNimine) 1632 vs, ν(CO) 1258 s cmϪ1
.
Electrochemical synthesis
The complexes were obtained following an electrochemical pro-
cedure. The cell was a beaker (100 cm3) fitted with a rubber bung,
through which the electrochemical leads entered the cell [30]. A
manganese metal platelet was suspended from a platinum wire and
a platinum wire was used as a cathode. The Schiff base ligand (ca
0.4 g) was dissolved in acetonitrile (40 cm3) and a small amount
of tetramethylammonium perchlorate was added as a supporting
electrolyte. During electrolysis nitrogen was bubbled through the
solution to ensure the presence of an inert atmosphere, with the
current being provided by a purpose built d. c. power supply. The
cells can be summarized as follows: Pt(Ϫ)/MeCN ϩ H2Ln/Mn(ϩ).
During electrolysis hydrogen gas was evolved at the cathode. The
solids were collected by filtration and washed successively with
acetonitrile and diethyl ether before drying in vacuo.
Thermogravimetrical analyses were performed using a CAHN In-
struments TG131 apparatus, the inert gas (nitrogen) flow being
maintained at 50 cm3 minϪ1
.
Synthesis of the Schiff bases
The Schiff bases were prepared by a traditional method by the reac-
tion of the appropriately substituted salicylaldehyde with the diam-
ine, and is typified by the preparation of H2L1. To an ethanolic
solution (100 mL) of 1,2-diamino-2-methylpropane (0.83 mL,
7.8 mmol) was added 3-OEt-salicylaldehyde (2.60 g, 15.60 mmol).
The resultant yellow solution was refluxed for two hours over a
Dean-Stark trap, then was concentrated. The solid which precipi-
tated was collected by filtration, washed with diethylether and dried
in vacuo. The purity of the prepared ligands was checked by elemen-
Reactivity towards SO2 in the solid state
Exposure to SO2 was carried out in a small Rotaflo tube by ob-
serving the increase in mass of a sample (0.20 g) of the complex.
The vessel was initially evacuated and charged with the complex
under an Ar atmosphere. The Ar was removed and the tube was
filled with SO2 at 1 atm pressure. Further SO2 was added over
several days until a constant mass was achieved. Full details of this
procedure have been published previously [31].
1
tal analysis, mass spectrometry, IR and H NMR spectroscopy.
H2L1. Elemental analysis: C22H28N2O4 (M. W. ϭ 384.47): C, 68.8
(68.7); N, 7.1 (7.3); H, 7.0 (7.3) %; m.p. 77 °C.
1H NMR (300 MHz, CDCl3): δ ϭ 1.43 (s, 6H), 1.52 (t, 6H), 3.71 (s, 2H),
4.05 (q, 4H), 6.6-6.9 (m, 6H), 8.26 (s, 2H), 13.70 (s, 2H) ppm.
Reactivity towards SO2 in toluene slurries
IR (KBr): ν(CNimine) 1627 vs, ν(CO) 1272 s cmϪ1
.
H2L2. Elemental analysis: C18H18N4O6 (M. W. ϭ 386.36): C, 55.4
(56.0); N, 14.3 (14.5); H, 4.6 (4.7) %; m.p. 233 °C.
The metal complex (ca. 0.20 g) was placed in a predried round-
bottomed flask fitted with a side arm and ground glass tap against
a flow of Ar. Dry distilled toluene (100 cm3) was added and the
flask was then evacuated. The suspension was saturated with SO2
and the flask was then sealed and the contents stirred for ca. 7
1H NMR (300 MHz, CDCl3): δ ϭ1.43 (s, 6H), 3.91 (s, 2H), 6.9-8.0 (m, 6H),
8.45 (s, 1H), 8.54 (s, 1H) 13.65 (s, 1H), 14.22 (s, 1H) ppm.
IR (KBr): ν(CNimine) 1641 vs, ν(CO) 1330 s cmϪ1
.
2004
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2005, 631, 2000Ϫ2005