New sulfanyl- and selanyl-substituted Schiff bases derived from 2-chalcogenoalkylamines and aromatic aldehydes. Synthesis and complex formation reactions

Article abstract of DOI:10.1134/S1070363213020138

A number of β-phenyl(or benzyl)selanyl- and β-phenylsulfanyl- substituted imines possessing an additional donor nitrogen, oxygen, or sulfur atom were synthesized by reaction of 2-phenylsulfanylethanamine, 2-phenylsulfanylcyclohexanamine, 2-phenylselanylcyclohexanamine, and 2-benzylselanylaniline with salicylaldehyde, 2-pyridinecarbaldehyde, or 2-tert-butylsulfanylbenzaldehyde. The resulting Schiff bases were tested as ligands in the complex formation with nickel(II) and copper(II), and mononuclear (L-H)MCl or LMCl₂ coordination compounds were isolated (L = sulfur- or selenium-containing imine). The redox properties of the selenium-containing ligands and complexes were studied by cyclic voltammetry. The complexes were found to undergo reduction of the metal ion in two one-electron steps. The reduction is reversible for copper complexes and irreversible for nickel complexes.

Full text of DOI:10.1134/S1070363213020138

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 2, pp. 311–318. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.N. Chernysheva, E.K. Beloglazkina, R.L. Antipin, A.A. Moiseeva, N.V. Zyk, 2013, published in Zhurnal Obshchei Khimii, 2013,
Vol. 83, No. 2, pp. 257–264.
New Sulfanyl- and Selanyl-Substituted Schiff Bases
Derived from 2-Chalcogenoalkylamines and Aromatic Aldehydes.
Synthesis and Complex Formation Reactions
A. N. Chernyshevaa, E. K. Beloglazkinaa, R. L. Antipina, A. A. Moiseevaa, and N. V. Zyka, b
a Faculty of Chemistry, Moscow State University, Leninskie gory 1, Moscow, 119992 Russia
e-mail: bel@org.chem.msu.ru
b Institute of Physiologically Active Compounds, Russian Academy of Sciences,
Chernogolovka, Moscow oblast, Russia
Received December 19, 2011
Abstract—A number of β-phenyl(or benzyl)selanyl- and β-phenylsulfanyl-substituted imines possessing an
additional donor nitrogen, oxygen, or sulfur atom were synthesized by reaction of 2-phenylsulfanylethanamine,
2-phenylsulfanylcyclohexanamine, 2-phenylselanylcyclohexanamine, and 2-benzylselanylaniline with salicyl-
aldehyde, 2-pyridinecarbaldehyde, or 2-tert-butylsulfanylbenzaldehyde. The resulting Schiff bases were tested
as ligands in the complex formation with nickel(II) and copper(II), and mononuclear (L–H)MCl or LMCl2
coordination compounds were isolated (L = sulfur- or selenium-containing imine). The redox properties of the
selenium-containing ligands and complexes were studied by cyclic voltammetry. The complexes were found to
undergo reduction of the metal ion in two one-electron steps. The reduction is reversible for copper complexes
and irreversible for nickel complexes.
DOI: 10.1134/S1070363213020138
Organosulfur and organoselenium compounds are
important intermediate products in organic synthesis
and convenient models for studying organic and
bioorganic reaction mechanisms. Low-molecular
weight N,S,Se-containing ligands and coordination
compounds based thereon attract considerable interest
from the viewpoint of their potential catalytic activity,
e.g., as models of natural metalloenzymes. Low-
molecular complexes of transition metals are now used
to catalyze many organic reactions, including
asymmetric synthesis, epoxidation of alkenes [1–3],
cyclopropanation [4], aziridination [5, 6], reactions of
sulfides with diazo esters [7], Diels–Alder
cycloadditions [8], C–H bond activation [9, 10],
oxirane ring opening [11–16], etc.
The present study was aimed at developing
procedures for the preparation of novel N,S- and N,Se-
ligands containing azomethine and alkyl aryl sulfide
(or selenide) fragments, as well as additional donor
oxygen, nitrogen, or sulfur atoms. The structures of the
synthesized Schiff bases are shown below:
N
ХR
N
ХR
N
ХR
N
OH
SBu-t
XR = SPh, SePh, SeBn.
These compounds are tridentate N,O,X-, N,S,X- or
N,N,X-ligands (X = S, Se) potentially capable of
forming mono- and dinuclear coordination compounds,
so that they were brought into complex formation
reactions with nickel(II) and copper(II) salts. With a
view to assess the possibility of using the obtained
311

312
CHERNYSHEVA et al.
complexes as redox catalysts, electrochemical
properties of the ligands and coordination compounds
were studied.
The Schiff bases were brought into reactions with
nickel(II) and copper(II) chlorides by heating in
boiling ethanol. The structure of the coordination
compounds thus obtained was determined by elemental
analysis, mass spectrometry, and electronic and IR
spectroscopy. Their elemental compositions, yields,
and colors are given in Table 1. The reactions of
nickel(II) and copper(II) chlorides with salicylal-
dehyde derivatives VI and VII gave coordination
compounds XVII–XIX which were assigned the
composition (L–H)MCl on the basis of their elemental
analyses (Table 1). Mononuclear structure of these
complexes was confirmed by the MALDI mass
spectra; according to their electronic absorption spec-
tra, the central metal ion in XVII–XIX has tetrahedral
configuration.
As starting compounds for the synthesis of Schiff
bases V–XVI we used 2-chalcogen-substituted amines
I–IV and aromatic aldehydes, namely salicylaldehyde,
pyridine-2-carbaldehyde, and 2-tert-butylsulfanylbenz-
aldehyde. The latter may be regarded as benzenethiol
derivative protected at the sulfur atom; unlike ArSH
compounds readily oxidizable on exposure to air, S-
tert-butyl derivative is stable to oxygen; on the other
hand, tert-butyl group can readily be removed via
reaction with metal salts (Lewis acid) [17] to afford a
thiolate complex.
The reactions were carried out by heating the
reactants in boiling ethanol or EtOH–CH2Cl2 mixture
over a period of 3–7 h (the progress of reactions was
monitored by TLC following the disappearance of the
initial aldehyde). All Schiff bases V–XVI except for 2-
tert-butylsulfanylbenzaldehyde derivative XIII were
isolated as a single isomer. The E configuration of XIV
was confirmed by NOE experiment: irradiation at a
frequency corresponding to the HC=N resonance (δ
9.13 ppm) gave a response at a δ 4.0 ppm (CH2N).
Compound XIII was formed as a mixture of E and Z
isomers at a ratio of 5:1, which was estimated from the
intensity ratio of the HC=N signals at δ 9.06 and
8.67 ppm in the 1H NMR spectrum.
Ligands IX–XI reacted with nickel(II) and copper(II)
chlorides to produce LMCl2 complexes. Their
electronic absorption spectra also indicated tetrahedral
configuration of the coordination environment. The
results of semiempirical quantum-chemical calcula-
tions (PM3) [18] showed that coordination of two
nitrogen atom of the organic ligand and two halide
ions to the metal ion is energetically more favorable
than coordination modes involving the chalcogen
atom. The propused structures of coordination
compounds XVII–XXII are shown below.
R
R
N
X
Ph
R
M
N
NH2
O
Cl
R
EtOH, Δ
EtOH, Δ
+ RCHO
R
ХPh
ХPh
N
X
Ph
V, VII, IХ, ХIII, ХV
I, III
II
Cl
Cl
M
N
PhSe
NH2
PhSe
N
+ RCHO
R
XVII, XXI, R = H; XVIII–XX, XXII, RR = (CH2)4;
XVII, XX, X = S; XVIII, XIX, XXI, XXII, X = Se;
XVII, XVIII, XXI, M = Ni; XIX, XX, XXII, M = Cu.
VI, Х, ХIV
R
NH2
+ RCHO
SeBn
N
EtOH, Δ
Presumably, the reactions of tert-butylsulfanyl-
substitued ligands XIII–XV with metal chlorides were
accompanied by hydrolysis of the CH=N bond. The
only product isolated in the reaction of XIII with
CuCl2·2H2O was that whose elemental composition
corresponded to copper(II) chloride complex XXIII
with 2-phenylsulfanylcyclohexanamine. Compound
SeBn
IV
VIII, ХII, ХVI
I, V, IX, XIII, X = S; III, VII, XI, XV, X = Se; V–VIII,
R = 2-HOC6H4; IX–XII, R = pyridin-2-yl; XIII–XVI, R =
2-t-BuSC6H4.
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NEW SULFANYL- AND SELANYL-SUBSTITUTED SCHIFF BASES DERIVED
313
Table 1. Compositions, colors, and electronic absorption
spectra of coordination compounds XVII–XXII
XXIII displayed in the IR spectrum absorption bands
at 3220 and 3200 cm–1 due to primary amino group.
Electronic
spectrum,
Ligand
Complex
Color
λ
max, nm
(ε, l mol–1 cm–1)
N
SPh
XVII, (L–Н)NiCl Yellow–green
325.0 (28561)
365.0 (22219)
419.0 (12988)
617.0 (492)
VI
SBu-t
XVIII,
(L–Н)NiCl·2H2O
Yellow–green
Light brown
317.5 (72277)
378.5 (24218)
473.5 (7035)
664.0 (5303)
VII
CuCl2 2H2O
XIX, (L–Н)CuCl
337.0 (94371)
370.5 (65777)
470.0 (4231)
661.0 (3258)
H
H
O
H2N
Cl
SPh
Cl
N
SPh
Cl
XX, LCuCl2
XXI, LNiCl2
Green
Green
327.5 (29966)
711.5 (2689)
IX
X
Cu
Cu
Cl
SBu-t
ХХIII, 24%
344.0 (14314)
398.0 (15031)
736.0 (2831)
We failed to obtain crystalline products by reactions
of benzylselanyl derivatives VIII, XII, and XVI with
metal chlorides under analogous conditions.
XXII, LCuCl2
Green
402.0 (11033)
416.0 (6124)
718.5 (3910)
XI
The redox properties of ligands X and XI and
coordination compounds XVII, XVIII, and XXI were
examined by cyclic and rotating disk electrode
voltammetry using glassy carbon and gold electrodes
in DMF with 0.1 M Bu4NClO4 as supporting
electrolyte. The oxidation and reduction potentials are
given in Table 2. Ligands X and XI are reduced in two
steps at potentials higher than 1.0 V and are oxidized
either in two steps at potentials of –1.8 to –1.9 and ca.
–2.5 V. The reduction of pyridine-containing
complexes XXI and XXII occurs at the metal ion in
two one-electron steps; further reduction involves the
ligand. The first oxidation step is oxidation of the
coordinated chloride ion at 1.04–1.16 V (Fig. 1).
Nickel complex XXI is reduced at the first step
irreversibly via single electron transfer, and its one-
electron reduction in the second step is quasi-
reversible. Nickel complexes derived from salicylal-
dehyde imines XVII and XVIII displayed analogous
electrochemical properties. Their oxidation occurred in
two irreversible steps; four irreversible peaks were
observed on the cathodic branch (Fig. 2), the first two
of which corresponded to reduction of the metal ion
(Ni2+ → Ni1+ → Ni0).
Thus the results of electrochemical study showed
that the examined complexes are initially reduced at
the metal ion in two one-electron steps. The reduction
of the copper complexes is reversible, whereas the
nickel complexes are reduced irreversibly.
Copper complex XXII is reduced at the metal ion at
a potential of +0.14 V via transfer of two electrons
(Fig. 1). The subsequent ligand reduction peaks are
strongly shifted to the anodic region compared to the
free ligand, i.e., the presence of copper ion
considerably facilitates reduction of the ligand. The
reduced complex is stable; it remained unchanged in
electrochemical experiments on both glassy carbon and
gold electrodes, as followed from the absence of
copper metal desorption peak on the reverse scan curve
(Fig. 1).
EXPERIMENTAL
1
The H and 13C NMR spectra were recorded at 25°
C on Varian Mercury-400 and Bruker Avance-400
spectrometers at 400 and 100 MHz, respectively. The
IR spectra were measured on a UR-20 spectrometer
from samples dispersed in mineral oil and on a
ThermoNicolet IR200 spectrometer with Fourier
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 2 2013

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CHERNYSHEVA et al.
Table 2. Oxidation (Eox) and reduction potentials (Ered) of
ligands X and XI and coordination compounds XVII,
XVIII, XXI, XXII, XXIV, and XXV, determined by cyclic
voltammetry (relative to Ag|AgCl|KClsat) using a glassy
carbon electrode in DMF (0.1 M Bu4NClO4 as supporting
electrolyte); potential scan rate 200 mV s–1; potentials of
reverse scan peaks are given in parentheses
18000) equipped with a nitrogen laser (λ 337 nm) and
a time-of-flight mass analyzer (accelerating voltage
20 kV); samples were applied to a polished steel
support; positive ions were detected; the resultant
spectrum was the sum of 300 spectra recorded for
different points of a sample; 2,5-dihyidroxybenzoic
acid (99%, Acros) and α-cyano-4-hydroxycinnamic
acid (99%, Acros) were used as matrices. The isotope
ratios for all MS peaks given in Experimental are
consistent with the calculated values.
Comp. no.
Epred
–1.91 (–1.86); –2.67а
Eopx
1.06; 1.30
1.16; 1.46
0.84; 1.08
1.08; 1.21
X
–1.83 (–1.75); –2.51
XI
The electron-impact mass spectra (70 eV) were
recorded on Finnigan MAT SSQ 7000 [25-m quartz
capillary column, stationary phase OV-I, oven tem-
perature programming from 70°C (2 min) to 280°C (10
or 30 min) at a rate of 20 deg /min] and Kratos MS-30
instruments (England) (direct inlet probe, ion source
temperature 200°C).
–1.14; –1.33 (–1.27); –1.89; –2.39
–0.92; –1.36; –1.89; –2.39
XVII
XVIII
XXI
–0.93 (–0.86); –1.21 (–1.16); –1.91; 1.15; 1.23
–2.09 (–2.01)
0.14 (–0.25, 0.49); –1.67; 1.87 (–1.76)b,c
1.17b
XXII
Electrochemical studies were carried out on a PI-
50-1.1 potentiostat coupled with a PR-8 programmer
according to a three-electrode scheme. A glassy carbon
(d = 2 mm), platinum (d = 3 mm), or gold disk (d =
2 mm) was used as working electrode, Ag/AgCl/KCl
(sat.) was used as reference electrode, and secondary
electrode was a platinum plate; supporting electrolyte
0.1 M solution of Bu4NClO4 in DMF. The working
electrode surface was polished with aluminum oxide
powder (particle size <10 μm; Sigma–Aldrich). The
potential scan rate was 200 (cyclic voltammetry) or
a
Additional adsorption prepeaks were also observed at –1.26 and
–2.31 V. b Initial potential 0.7 V. c Additional adsorption prepeak
was observed at –1.43 V.
transform (USA) from films. The electronic absorption
spectra were recorded on Perkin Elmer Lambda 25 and
Hitachi U-2900 spectrophotometers from solutions in
DMF with a concentration of 10–3 M.
The MALDI mass spectra were obtained on a
Bruker Autoflex II instrument (FWHM resolution
1
2
2μA
2μA
5μA
Е, V
Fig. 1. Cyclic voltammograms of (1) ligand XI and (2) com-
plex XXII; concentration 10–3 M, glassy carbon electrode,
DMF, Bu4NClO4.
Fig. 2. Cyclic voltammograms of nickel complex XVIII;
concentration 10–3 M, glassy carbon electrode, DMF,
Bu4NClO4.
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NEW SULFANYL- AND SELANYL-SUBSTITUTED SCHIFF BASES DERIVED
315
20 mV/s (rotating disk electrode). The potentials are
given with correction for iR-compensation. The
number of transferred electrons was determined by
comparing the limiting wave current in rotating disk
electrode experiment with the one-electron oxidation
current of ferrocene at the same concentration. All
measurements were performed under dry argon;
samples were dissolved in pre-liminarily deoxygenated
anhydrous solvent. Dimethyl-formamide of pure grade
was purified by stirring for 4 days over freshly
calcined potassium carbonate, followed by distillation
under reduced pressure first over P2O5 and then over
anhydrous CuSO4.
gave 0.63 g (99%) of compound VI as a yellow oily
substance which gradually crystallized on storage. H
1
NMR spectrum (CDCl3), δ, ppm (J, Hz): 12.69 br. s
(1H, OH), 8.30 s (1H, CH=N), 7.60 d (1H, Harom, J =
7.8), 7.52 m (2H, Harom), 7.25 m (3H, Harom), 7.18 t
(1H, Harom, J = 7.4), 6.91 d (1H, Harom, J = 8.4), 6.83 t
(1H, Harom, J = 7.4), 3.89 t (2H, CH2, J = 6.8); 3.04 t
(2H, CH2, J = 7.0).
2-[2-(Phenylselanyl)cyclohexyliminomethyl]phe-
nol (VII). Salicylaldehyde, 0.05 ml (0.5 mmol), was
added under stirring to a solution of 0.13 g (0.5 mmol)
of 2-(phenylselanyl)cyclohexan-1-amine (III) in 7 ml
of ethanol, and the mixture was heated under reflux
until salicylaldehyde disappeared (TLC). The solvent
was removed under reduced pressure to leave 0.16 g
trans-2-(Phenylsulfanyl)cyclohexan-1-amine (I), 2-
(phenylselanyl)ethanamine (II) hydrochloride, and
trans-(2-phenylselanyl)cyclohexan-1-amine (III) were
synthesized as described in [19, 20]; 2-(benzylselanyl)
aniline (IV) was prepared according to [21]; and 2-
tert-butylsulfanylbenzaldehyde was synthesized as
described in [22].
1
(91%) of VII as a yellow oily substance. H NMR
spectrum (C6D6), δ, ppm (J, Hz): 13.57 br. s (1H, OH),
7.98 s (1H, CH=N), 7.58 d.d (2H, Harom, J = 2.2, 7.2),
7.20 m (2H, Harom), 7.07 m (4H, Harom), 6.81 d.d.d (1H,
Harom, J = 0.8, 2.2, 7.2), 3.17 d.t (1H, HCN, J = 4.1,
9.8), 2.99 d. t (1H, HCSe, J = 4.1, 9.8), 2.22 d.d (1H,
3-H, J = 4.1, 13.3), 1.65 d (1H, 6-H, J = 13.3), 1.54 m
(3H, 3-H, 4-H, 6-H), 1.38 m (1H, 5-H), 1.11 m (2H, 4-
H, 5-H).
2-[2-(Phenylsulfanyl)cyclohexyliminomethyl]phe-
nol (V). Salicylaldehyde, 0.09 ml (0.9 mmol), was
added under stirring to a solution of 0.18 g (0.9 mmol)
of 2-(phenylsulfanyl)cyclohexan-1-amine (I) in 10 ml
of ethanol, and the mixture was heated under reflux
until the initial aldehyde disappeared (TLC). The
solvent was removed under reduced pressure to isolate
0.25 g (91%) of compound V as a yellow oily sub-
stance. IR spectrum (film), ν, cm–1: 3070, 1640, 1590.
1H NMR spectrum (CDCl3), δ, ppm (J, Hz): 13.29 br.s
(1H, OH), 8.36 s (1H, CH=N), 7.37 m (2H, Harom),
7.32 d.d.d (1H, Harom, J = 0.8, 1.6, 6.7), 7.27 d.d (1H,
Harom, J = 1.6, 7.6), 7.23–7.17 m (3H, Harom), 6.95 d
(1H, Harom, J = 8.3), 6.89 t (1H, Harom, J = 6.7), 3.21 d.
t (1H, HCN, J = 4.2, 9.7), 3.17 d. t (1H, HCS, J = 4.2,
9.7), 2.23 m (1H, 3-H), 1.95 m (1H, 6-H), 1.83 m (2H,
3-H, 6-H), 1.69 m (1H, 4-H), 1.55–1.40 m (3H, 5-H, 4-
H). Mass spectrum (EI): m/z 311 [M]+.
2-[2-(Benzylselanyl)cyclohexyliminomethyl]phe-
nol (VIII). Salicylaldehyde, 0.06 ml (0.6 mmol), was
added under stirring to a solution of 0.15 g (0.6 mmol)
of 2-(benzylselanyl)aniline (IV) in 10 ml of CH2Cl2–
EtOH (1:1), and the mixture was heated under reflux
until salicylaldehyde disappeared (TLC). The solvent
was removed under reduced pressure to obtain 0.22 g
(99%) of VIII as a yellow oily substance which
1
gradually crystallized on storage. H NMR spectrum
(CDCl3), δ, ppm (J, Hz): 13.05 br.s (1H, OH), 8.62 s
(1H, HC=N), 7.45 m (2H, Harom), 7.39 m (2H, Harom),
7.31 m (7H, Harom), 7.07 d (1H, Harom, J = 8.4), 6.95 t
(1H, Harom, J = 7.6), 3.73 s (2H, CH2). 13C NMR
spectrum (CDCl3), δC, ppm: 162.58, 138.97, 133.04,
132.16, 129.31, 129.11, 128.40, 126.75, 121.24,
118.76, 117.49, 96.28, 32.53, 27.44.
2-[2-(Phenylselanyl)ethyliminomethyl]phenol (VI).
A solution of 0.12 g (2.1 mmol) of potassium hyd-
roxide in a minimal volume of ethanol was added to a
solution of 0.5 g (2.1 mmol) of 2-(phenylselanyl)
ethanamine (II) hydrochloride in 10 ml of ethanol. The
mixture was stirred until complete precipitation of
potassium chloride (white flakes). The precipitate was
filtered off, 0.22 ml (2.1 mmol) of salicylaldehyde was
added to the filtrate under stirring, and the mixture was
heated under reflux until salicylaldehyde disappeared
(TLC). Removal of the solvent under reduced pressure
2-Phenylsulfanyl-N-(pyridin-2-ylmethylidene)-
cyclohexan-1-amine (IX). Pyridine-2-carbaldehyde,
0.08 ml (0.9 mmol), was added under stirring to a
solution of 0.18 g (0.9 mmol) of 2-(phenylsulfanyl)
cyclohexan-1-amine (I) in 10 ml of ethanol, and the
mixture was heated for 8 h under reflux (TLC) and
evaporated under reduced pressure. Yield 0.23 g
(91%), red oily substance. IR spectrum (nujol), ν, cm–1:
1655, 1590, 1570. 1H NMR spectrum (CDCl3), δ, ppm
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 2 2013

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CHERNYSHEVA et al.
1
(J, Hz): 8.52 d (1H, Py, J = 5.6), 8.27 s (1H, HC=N),
7.78 d (1H, Py, J = 7.9), 7.55 t (1H, Py, J = 7.9), 7.27 d
(2H, Ph, J = 8.2), 7.16 t (1H, Py, J = 5.6), 7.08 t (2H,
Ph, J = 8.2), 7.01 m (1H, Ph), 3.23 m (2H, 1-H, 2-H),
2.12 m (1H, 3-H), 1.77 m (3H, 3-H, 6-H), 1.66 m (1H,
5-H), 1.45–1.36 m (3H, 4-H, 5-H).
on storage. H NMR spectrum (CDCl3), δ, ppm (J,
Hz): 8.66 m (1H, Py), 8.58 s (1H, HC=N), 8.26 t.d
(1H, Py, J = 1.0, 7.9), 7.76 d.d (1H, Py, J = 1.0, 7.9),
7.38 t (2H, Ph, J = 7.9), 7.31 d.d.d (1H, Py, J = 1.0,
4.8, 7.9), 7.27–7.18 m (7H, Ph, Py), 3.66 s (2H, CH2).
13C NMR spectrum (CDCl3), δC, ppm: 160.47, 154.98,
151.09, 149.34, 138.96, 135.99, 129.04, 128.32,
128.16, 126.97, 126.61, 126.48, 124.59, 121.36,
121.09, 96.21, 27.36.
2-Phenylselanyl-N-(pyridin-2-ylmethylidene)-
ethanamine (X). A solution of 0.09 g (1.7 mmol) of
potassium hydroxide in a minimal volume of ethanol
was added to a solution of 0.40 g (1.7 mmol) of 2-
(phenylselanyl)ethanamine (II) hydrochloride in 5 ml
of ethanol. The mixture was stirred until complete
precipitation of potassium chloride (white flakes). The
precipitate was filtered off, 0.16 ml (1.7 mmol) of
pyridine-2-carbaldehyde was added under stirring, and
the mixture was heated for 7 h under reflux (TLC) and
evaporated under reduced pressure. Yield 0.46 g
(94%), brown oily substance which gradually
crystallized on storage. IR spectrum (film), ν, cm–1:
N-[2-(tert-Butylsulfanyl)phenylmethylidene]-2-
(phenylsulfanyl)cyclohexan-1-amine (XIII). 2-tert-
Butylsulfanylbenzaldehyde, 0.14 g (0.7 mmol), was
added under stirring to a solution of 0.15 g (0.7 mmol)
of 2-(phenylsulfanyl)cyclohexan-1-amine (I) in 10 ml
of ethanol. The mixture was heated for 5 h under
reflux (TLC), and the solvent was removed under
reduced pressure. Yield 0.27 g (99%; a mixture of E
and Z isomers at a ratio of 5:1), yellow oily substance.
IR spectrum (film), ν, cm–1: 1640, 1590, 1530. H
1
1
NMR spectrum, CDCl3, δ, ppm (J, Hz): E isomer: 9.06
s (1H, CH=N), 8.00 d.d (1H, Harom, J = 2.2, 7.4), 7.51
d.d (1H, Harom, J = 2.2, 6.6), 7.34 m (4H, Harom), 7.17
m (3H, Harom), 3.33 t (1H, HCN, J = 7.4), 3.25 m (1H,
HCS), 2.23 m (1H, 3-H), 1.79 m (4H, 3-H, 6-H), 1.44
m (3H, 4-H, 5-H), 1.28 s (9H, t-Bu); Z isomer: 8.67 s
(1H, CH=N), 7.94 d (1H, Harom, J = 7.4), 7.83 d (1H,
1650, 1590, 1570. H NMR spectrum, CDCl3, δ, ppm
(J, Hz): 8.63 d (1H, Py, J = 4.9), 8.34 s (1H, HC=N),
7.9 d (1H, Py, J = 7.8), 7.69 t (1H, Py, J = 7.8), 7.51 d.
d (2H, Ph, J = 1.4, 7.8), 7.23 m (4H, Ph, Py), 3.96 t
(2H, CH2, J = 7.8), 3.23 t (CH2, J = 7.8). Mass
spectrum (EI): m/z 290 [M]+.
2-Phenylselanyl-N-(pyridin-2-ylmethylidene)-
cyclohexan-1amine (XI). Pyridine-2-carbaldehyde,
0.05 ml (0.5 mmol), was added under stirring to a
solution of 0.13 g (0.5 mmol) of 2-(phenylselanyl)
cyclohexan-1-amine (III) in 7 ml of ethanol, the
mixture was heated for 3 h under reflux (TLC), and the
solvent was removed under reduced pressure. Yield
0.17 g (99%), brown oily substance. 1H NMR
spectrum (CDCl3), δ, ppm (J, Hz): 8.59 d (1H, Py, J =
4.1), 8.35 s (1H, HC=N), 7.80 d (1H, Py, J = 7.8), 7.62
d.t (1H, Py, J = 1.2, 7.8), 7.47 m (2H, Ph), 7.24 d.d.d
(1H, Py, J = 1.2, 4.1, 7.8), 7.14 m (3H, Harom), 3.46
d.d.d (1H, 1-H, J = 4.1, 9.7, 13.7), 3.33 d. t (1H, 2-H,
J = 4.1, 9.7), 2.21 d (1H, 3-H, J = 4.1), 1.75 m (4H, 3-
H, 4-H, 6-H), 1.55 m (1H, 5-H), 1.38 m (2H, 4-H, 5-
H). Mass spectrum (MALDI-TOF): m/z 344 [M]+.
H
H
arom, J = 7.4), 7.46 d (1H, Harom, J = 6.7), 7.34 m (4H,
arom), 7.09 d (2H, Harom, J = 7.4), 3.33 t (1H, HCN,
J = 7.4), 3.25 m (1H, HCS), 2.23 m (1H, 3-H), 1.74 m
(4H, 3-H, 6-H), 1.51 m (3H, 4-H, 5-H), 1.28 s (9H, t-
Bu). Mass spectrum: m/z 326 [M]+.
N-[2-(tert-Butylsulfanyl)phenylmethylidene]-2-
(phenylsulfanyl)ethanamine (XIV). A solution of
0.03 g (0.5 mmol) of potassium hydroxide in a
minimal amount of ethanol was added to a solution of
0.13 g (0.5 mmol) of 2-(phenylselanyl)ethanamine (II)
hydrochloride in 5 ml of ethanol. The mixture was
stirred until complete precipitation of potassium
chloride as white flakes. The precipitate was filtered
off, 0.11 g (0.5 mmol) of 2-tert-butylsulfanyl-
benzaldehyde was added under stirring, the mixture
was heated for 7 h under reflux (TLC), and the solvent
was removed under reduced pressure. Yield 0.20 g
(99%), amber yellow oily substance. 1H NMR
spectrum (CDCl3), δ, ppm (J, Hz): 9.09 s (1H, CH=N),
2-(Benzylselanyl)-N-(pyridin-2-ylmethylidene)-
aniline (XII). Pyridine-2-carbaldehyde, 0.06 ml
(0.6 mmol), was added under stirring to a solution of
0.15 g (0.6 mmol) of 2-(benzylselanyl)aniline (IV) in
10 ml of CH2Cl2–EtOH (1:1), the mixture was heated
for 7 h under reflux (TLC), and the solvent was
removed under reduced pressure. Yield 0.20 g (99%),
red–brown oily substance which gradually crystallized
8.05 d.d (1H, Harom, J = 2.2, 7.2), 8.01 d.d (1H, Harom
,
J = 2.2, 7.6), 7.64 m (1H, Harom), 7.57 m (2H, Harom),
7.40 d. t (1H, Harom, J = 2.2, 7.2), 7.27 m (3H, Harom),
3.98 d. t (2H, CH2, J = 2.2, 7.6), 3.70 d.t (2H, CH2, J =
2.2, 7.6), 1.31 s (9H, t-Bu).
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NEW SULFANYL- AND SELANYL-SUBSTITUTED SCHIFF BASES DERIVED
317
N-[2-(tert-Butylsulfanyl)phenylmethylidene]-2-
(phenylselanyl)cyclohexan-1-amine (XV). 2-tert-
butylsulfanylbenzaldehyde, 0.1 g (0.5 mmol), was
added under stirring to a solution of 0.13 g (0.5 mmol)
of 2-(phenylselanyl)cyclohexan-1-amine (III) in 7 ml
of ethanol, the mixture was heated for 5 h under reflux
(TLC), and the solvent was removed under reduced
pressure. Yield 0.21 g (98%), yellow oily substance.
1H NMR spectrum (CDCl3), δ, ppm (J, Hz): 9.08 s
(1H, CH=N), 8.07 d.d (1H, Harom, J = 2.2, 7.2), 8.02
d.d (1H, Harom, J = 2.2, 7.2), 7.62 m (2H, Harom), 7.55
m (2H, Harom), 7.40 d.t (1H, Harom, J = 2.2, 7.2), 7.24 m
(2H, Harom), 3.20 d.t (1H, HCN, J = 4.1, 9.8), 2.92 d.t
(1H, HCSe, J = 4.1, 9.8), 2.24 m (1H, 3-H), 1.68 m
(1H, 6-H), 1.50 m (3H, 3-H, 4-H, 6-H), 1.32 m (1H, 5-
H), 1.28 s (9H, t-Bu), 1.09 m (2H, 4-H, 5-H).
{2-[2-(Phenylselanyl)cyclohexyliminomethyl]-
phenolato}nickel(II) chloride dihydrate (XVIII) was
synthesized from 0.08 g (0.2 mmol) of VII, 0.05 g
(0.2 mmol) of NiCl2·6H2O or 0.03 g (0.2 mmol) of
NiCl2. Yield 0.01 g (11%), yellow–green crystals, mp
240°C. IR spectrum (nujol), ν, cm–1: 3480, 1630, 1600,
1565. Mass spectrum (MALDI-TOF): m/z 416 [M]+.
Found, %: C 47.22; H 4.63; N 3.00. C19H20ClN·
NiOSe·2H2O. Calculated, %: C 46.81; H 4.96; N 2.87.
{2-[2-(Phenylselanyl)cyclohexyliminomethyl]-
phenolato}copper(II) chloride (XIX) was syn-
thesized from 0.08 g (0.2 mmol) of VII and 0.04 g
(0.2 mmol) of CuCl2·2H2O or 0.03 g (0.2 mmol) of
CuCl2. Yield 0.04 g (34%), light brown crystals, mp
188°C. IR spectrum (nujol), ν, cm–1: 3420, 1635, 1600,
1560. Mass spectrum (MALDI-TOF): m/z 421 [M]+.
Found, %: C 49.55; H 4.44; N 3.07. C19H20Cl·
CuNOSe. Calculated, %: C 50.01; H 4.42; N 3.07.
2-(Benzylselanyl)-N-[2-(tert-butylsulfanyl)phenyl-
methylidene]aniline (XVI). 2-tert-butylsulfanyl-
benzaldehyde, 0.11 g (0.6 mmol), was added under
stirring to a solution of 0.15 g (0.6 mmol) of 2-
(benzylselanyl)aniline (IV) in 10 ml of CH2Cl2–EtOH
(1:1), the mixture was heated for 7 h under reflux
(TLC), and the solvent was removed under reduced
pressure. Yield 0.24 g (96%), yellow oily substance.
1H NMR spectrum (CDCl3), δ, ppm (J, Hz): 9.30 s
(1H, HC=N), 8.39 d.d (1H, Harom, J = 1.4, 7.7), 7.61 d
(1H, Harom, J = 6.4), 7.51 t (1H, Harom, J = 7.7), 7.42 m
(3H, Harom), 7.28–7.21 m (7H, Harom), 3.69 s (2H, CH2),
1.34 s (9H, t-Bu). 13C NMR spectrum (CDCl3), δC,
ppm: 159.74, 139.56, 130.37, 129.31, 129.06, 128.35,
128.16, 126.63, 125.84, 121.09, 96.24, 31.09, 27.38.
[2-(Phenylsulfanyl)-N-(pyridin-2-ylmethylidene)-
cyclohexan-1-amine]copper(II) dichloride (XX).
Ethanol, 1 ml, was added to a solution of 0.05 g
(0.2 mmol) of compound IX in 2 ml of methylene
chloride until the mixture separated into layers. A
solution of 0.03 g (0.2 mmol) of CuCl2·2H2O in 2 ml
of EtOH was slowly added, and the mixture was left to
stand in a tightly capped vessel until it became
homogeneous. The resulting solution was transferred
into an open micro test tube which was placed in a
tightly capped vessel charged with diethyl ether and
left to stand therein until crystals separated. Yield 0.06 g
(84%), green crystals, mp 170°C. Found, %: C 50.04;
H 4.84; N 6.41; S 7.19. C18H20Cl2CuN2S. Calculated,
%: C 50.18; H 4.68; N 6.50; S 7.44.
{2-[2-(Phenylselanyl)ethyliminomethyl]phenol-
ato}nickel(II) chloride (XVII). Compound VI, 0.07 g
(0.2 mmol), was dissolved on heating in a minimal
volume of ethanol, a solution of 0.06 g (0.2 mmol) of
nickel(II) chloride hexahydrate or 0.03 g (0.2 mmol) of
anhydrous nickel(II) chloride in 2–3 ml of ethanol was
added, and the mixture was heated for 5 h under reflux.
The precipitate was filtered off, washed with ethanol,
and dried in air. Yield 0.01 g (13%), yellow–green
crystals, mp 142°C. IR spectrum (nujol), ν, cm–1: 3470,
1645, 1600, 1545. Mass spectrum (MALDI-TOF): m/z
362 [M]+.
[2-(Phenylselanyl)-N-(pyridin-2-ylmethylidene)-
ethanamine]nickel(II) dichloride (XXI). A solution
of 0.06 g (0.3 mmol) of CuCl2·2H2O in 5 ml of
ethanol was added to a solution of 0.10 g (0.3 mmol)
of compound X in 5 ml of ethanol. The mixture was
heated for 5 h under reflux and cooled to room
temperature, and the precipitate was filtered off,
washed with small portions of diethyl ether, and dried
in air. Yield 0.05 g (31%), green crystals, mp 170°C
(decomp.). IR spectrum (nujol), ν, cm–1: 1650, 1600,
1575. Mass spectrum (MALDI-TOF): m/z 388 [M]+.
Found, %: C 39.42; H 3.41; N 6.40. C14H14Cl2·
CuN2Se. Calculated, %: C 39.69; H 3.33; N 6.61.
Coordination compounds with ligand VII
(general procedure). Compound VII, 1 equiv, was
dissolved on heating in a minimal volume of ethanol, a
solution of 1 equiv of the corresponding metal chloride
in ethanol was added, and the mixture was heated for
5 h under reflux. The precipitate was filtered off,
washed with ethanol, and dried in air.
[2-(Phenylselanyl)-N-(pyridin-2-ylmethylidene)-
cyclohexan-1-amine]copper(II) dichloride (XXII). A
solution of 0.03 g (0.3 mmol) of CuCl2 in 5 ml of
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318
CHERNYSHEVA et al.
10. Larrow, J.F. and Jacobsen, E.N., J. Am. Chem. Soc.,
ethanol was added to a solution of 0.09 g (0.3 mmol)
of compound XI in 3 ml of ethanol. The mixture was
heated for 4 h under reflux and cooled to room
temperature, and the precipitate was filtered off,
washed with small portions of diethyl ether, and dried
in air. Yield 0.07 g (58%), green crystals, mp 202°C
(decomp.). IR spectrum (nujol), ν, cm–1: 1640, 1595,
1470. Mass spectrum (MALDI-TOF): m/z 442 [M]+.
1994, vol. 116, no. 26, p. 12129.
11. Jacobsen, E.N., Kakiuchi, F., Konsler, R.G., Larrow, J.F.,
and Tokunaga, M., Tetrahedron Lett., 1997, vol. 38,
no. 5, p. 773.
12. Tokunaga, M., Larrow, J.F., Kakiuchi, F., and Jacob-
sen, E.N., Science, 1997, vol. 277, no. 8, p. 936.
13. Leighton, J.L. and Jacobsen, E.N., J. Org. Chem., 1996,
vol. 61, no. 1, p. 389.
ACKNOWLEDGMENTS
14. Martinez, L.E., Leighton, J.L., Carsten, D.H., and
Jacobsen, E.N., J. Am. Chem. Soc., 1995, vol. 117,
no. 21, p. 5897.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 10-03-00677).
15. Paddock, R.L. and Nguyen, S.B.T., J. Am. Chem. Soc.,
2001, vol. 123, no. 46, p. 11498.
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