Easy synthesis of new chiral tetradentate N4 Schiff bases and their use as ligands for metal complexes

Article abstract of DOI:10.1002/ejoc.200390182

The chiral N₄ Schiff bases (1R,2R) -N,N′-bis(2-p-tosylaminobenzylidene)-1,2-diaminocyclohexane (H₂CyTs, 1), (1R,2R)-N,N′-bis(2-trifluoromethylsulfonaminobenzylidene)-1, 2-diaminocyclohexane (H₂CyTf, 2), (1R,2R) -N,N′-bis(2

Full text of DOI:10.1002/ejoc.200390182

FULL PAPER
Easy Synthesis of New Chiral Tetradentate N4 Schiff Bases and
Their Use as Ligands for Metal Complexes
[a]
[a]
[b]
[a]
´
´
Iyad Karame, M. Lorraine Tommasino, Rene Faure, and Marc Lemaire*
Keywords: Cobalt / Copper / N ligands / Nickel / Schiff bases
The chiral N4 Schiff bases (1R,2R)-N,NЈ-bis(2-p-tosylamino- NMR spectroscopy. Divalent Co, Cu and Ni complexes 5−8,
benzylidene)-1,2-diaminocyclohexane (H2CyTs, 1), (1R,2R)-
N,NЈ-bis(2-trifluoromethylsulfonaminobenzylidene)-1,2-
diaminocyclohexane (H2CyTf, 2), (1R,2R)-N,NЈ-bis(2-amino-
benzylidene)-1,2-diaminocyclohexane (3) and (1R,2R)-N,NЈ-
bis(2-nitrobenzylidene)-1,2-diaminocyclohexane (4) were
synthesized by a new and easy method in high purity and
good yields. All the organic compounds were characterized
containing the sulfonamide ligands 1 or 2, have been pre-
pared and characterized. The X-ray crystal structures of com-
plexes [Co(1R,2R)-CyTs] (6) and [Ni(1R,2R)-CyTf] (8) have
been solved. These complexes are potential precursors for
homogeneous asymmetric catalysis of a variety of reactions.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
by elemental analysis, mass spectrometry, IR and 1H and 13
C
Introduction
Recently, Moberg described the preparation of tetraden-
tate N4 ligands from chiral aziridines bearing sulfonamido
functionalities. Their titanium complexes catalyse the ad-
dition of diethylzinc to benzaldehyde with high enantiose-
lectivity (80% ee).[10] In the last decade, Noyori demon-
strated that the use of chiral sulfonamide ligands prepared
from chiral diamines gave active and enantioselective ru-
thenium catalysts for hydrogen-transfer reductions of ke-
tones.[11] In other studies, high ee values have been achieved
with bis(sulfonamide) complexes of titanium (additions of
diethylzinc to aldehydes), zinc (cyclopropanation)[12] or alu-
minium (DielsϪAlder cycloadditions).[13]
We are focussing on new chiral Schiff base ligands con-
taining sulfonamido functionalities in place of the phenolic
groups on salen ligands. As the pKa values of
C6H5NHSO2CF3,[14] C6H5NH-tosyl[15] and phenol[16] are
4.45, 8.46 and 9.89, respectively, the acidity of these sulfon-
amides is higher than that of phenol. Deprotonation of the
sulfonamide ligand should therefore be easy and should fa-
cilitate its complexation to transition metals to form chiral
complexes. Very recently, Bermejo and co-workers have de-
scribed a method for the synthesis of the amino-tosylated
Schiff base ligand 1, (1R,2R)-N,NЈ-bis(2-p-tosylaminoben-
zylidene)-1,2-diaminocyclohexane (H2CyTs), with unstable
2-aminobenzaldehyde as intermediate.[17] They described
the X-ray crystal structure of this ligand and of the corre-
sponding Ni and Cu complexes. In this paper we describe
a different method for the synthesis of this type of molecule
starting from 2-nitrobenzaldehyde and (1R,2R)-diaminocy-
clohexane, thus allowing easy modification of the sulfonyl
moiety. This method then allowed us to obtain ligand 2,
(1R,2R)-H2CyTf [(1R,2R)-N,NЈ-bis(2-trifluoromethylsul-
fonaminobenzylidene)-1,2-diaminocyclohexane]. The syn-
The development of efficient catalytic asymmetric reac-
tions is one of the most challenging tasks in current syn-
thetic chemistry, much effort having been devoted to the
creation of new chiral N-ligands and their metal complexes
for evaluation in advanced asymmetric catalysis.[1Ϫ2] Con-
densation between an amine and an aldehyde, forming what
is called a Schiff base, was one of the earliest reported reac-
tions in chemistry.[3] Jacobsen and Katsuki developed tetra-
dentate salen ligands, now one of the most intensely studied
classes of chiral Schiff bases, able to coordinate easily to a
wide variety of metals. The interest in such bases has in-
creased since the discovery of manganese() salen com-
plexes, excellent catalysts for the enantiomeric epoxidation
of unfunctionalized alkenes.[4Ϫ6] The development of chiral
salen metal complexes and catalysts in the last decade has
stimulated very rapid growth.[7Ϫ8] Chiral salen-containing
complexes are now used as catalysts for a variety of enantio-
selective reactions such as oxidation, aziridination, cyclo-
propanation, DielsϪAlder cyclisation, addition of trimeth-
ylsilyl cyanide or zinc derivatives to aldehydes, the Strecker
reaction, and for kinetic resolution of racemic epoxides.[9]
[a]
`
Laboratoire de Catalyse et Synthese Organique, UMR 5622
CNRS/UCB Lyon1, CPE,
43, Bd. du 11 Nov. 1918, 69622 Villeurbanne cedex, France
Fax: (internat.) ϩ 33-4/72431408
E-mail: marc.lemaire@univ-lyon1.fr
[b]
´
ˆ
Laboratoire des Sciences et Strategies Analytiques, Bat
Raulin- RDC,
43, Bd. du 11 Nov. 1918, 69622 Villeurbanne cedex, France
Fax: (internat.) ϩ 33-4/72446202
E-mail: faure@univ-lyon1.fr
1271
Eur. J. Org. Chem. 2003, 1271Ϫ1276  2003 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1434Ϫ193X/03/0407Ϫ1271 $ 20.00ϩ.50/0

´
I. Karame, M. L. Tommasino, R. Faure, M. Lemaire
FULL PAPER
thesis of the complexes Co[(1R,2R)-CyTf] (5), Co[(1R,2R)- TsCl or (CF3SO2)2O (TF2O) to give the C2-symmetric sul-
CyTs] (6), Cu[(1R,2R)-CyTs] (7) and Ni[(1R,2R)-CyTf] (8) fonamides 1 and 2, respectively.
are reported, as well as the X-ray crystal structures of 6 and
8. The method we have developed should allow the easy Synthesis of (1R,2R)-N,NЈ-bis(2-p-tosylaminobenzylidene)-
synthesis of a wide variety of chiral sulfonamides.
1,2-diaminecyclohexane, (1R,2R)-H2CyTs (1)
The method described by Bermejo for the synthesis of
compound 1[17] is shown in Scheme 2. The first step in-
volves the oxidation of 2-aminophenylmethanol by γ-MnO2
to give 2-aminobenzaldehyde,[18] which is a very unstable
Results and Discussion
Synthesis of Ligands
compound
and
rapidly
polymerises
at
room
temperature.[19Ϫ20] Avoidance of the use of this intermedi-
ate therefore allows many synthetic developments. The third
step, condensation between 2-tosylaminobenzaldehyde and
the diaminocyclohexane, is performed at 70 °C and requires
use of a DeanϪStark trap.
The synthesis of chiral sulfonamides that we have devel-
oped is based on the coupling of enantiomerically pure and
commercially available (1R,2R)-diaminocyclohexane with
2-nitrobenzaldehyde (Scheme 1). The C2-symmetric dinitro
compound formed (4) is then reduced to 3, and func-
tionalisation of the diamine groups can be undertaken.
Scheme 2. Synthesis of 1 by Bermejo’s method
We have synthesised compound 1 from compound 3 by
N-tosylation with tosyl chloride in dichloromethane at 0 °C
in presence of triethylamine. Our method is simpler and
easier, since on the one hand it avoids the use of an unstable
intermediate 2-aminobenzaldehyde, while on the other it en-
ables the synthesis of compound 3, which is also potentially
a ligand and can give rise to several other salen-type struc-
tures.
Synthesis of (1R,2R)-N,NЈ-bis(2-trifluoromethylsulfon-
aminobenzylidene)-1,2-diamino-cyclohexane, (1R,2R)-
H2CyTf (2)
Scheme 1. General synthesis of N4 Schiff bases 1؊4
The preparation of (1R,2R)-H2CyTf (2) from diamine 3,
The first step (A) is easily performed in anhydrous THF by treatment with Tf2O in dry CH2Cl2 at low temperature
in the presence of molecular sieves, which collect the water (Ͻ Ϫ78 °C), requires the presence of Et3N to neutralise the
formed during the condensation between the 2-nitrobenzal- triflic acid formed during the reaction. The reaction should
dehyde and the diaminocyclohexane. The following step (B) begin at Ϫ78 °C under a water-free atmosphere in order
is a reduction carried out under an atmospheric pressure of to avoid the triflic acid-catalysed hydrolysis of the imine
hydrogen and catalysed by Pd-C (10%). In order to avoid functions. Several tests were carried out at higher tempera-
imine reduction or hydrolysis, it is very important to keep tures (Ϫ20 °C, 0 °C), but resulted in the destruction of com-
the temperature at 0 °C and to use molecular sieves. The pound 3.
selectivity of this reduction step is indeed the key factor of
Just two equivalents of triflic anhydride are enough to
the synthetic pathway. The diamine 3 can then react with convert 3 completely into 2. If an excess of this reagent is
1272
Eur. J. Org. Chem. 2003, 1271Ϫ1276

New Chiral Tetradentate N4 Schiff Bases
FULL PAPER
used, the secondary product 2Ј is also formed Co···O(18), Co···O(36), Ni···O(18) and Ni···O(33) distances
(Scheme 3).[21]
(2.560(3) A, 2.607(3) A, 3.052(3) A and 3.027(3) A) are too
long to be regarded as true coordinated bonds. The metal
environment in 6 could be described as pseudo-tetrahedral
and that in complex 8 as pseudo-square planar. The
˚
˚
˚
˚
N(15)···N(34) distance in complex 6 is shorter than that in
[17]
˚
˚
the free ligand (3.560(4) A for 6 and 5.346(5) A
for 1
[H2CyTs]). In a similar way, the N(15)···N(31) distance in
˚
the free ligand 2 [7.324(8) A] shortened after complexation
˚
to the Ni [2.824(4) A] to produce 8.
Scheme 3
In the 1H NMR spectra, the NH protons appear as broad
signals at δ ϭ 14.8 ppm (for 2), 15 ppm (for 2Ј) and
13.2 ppm (for 1). It is notable that the OH proton in the
salen ligand appears at δ ϭ 13Ϫ13.5 ppm. For ligand 2, we
can assume that the protons should be easily replaceable by
a metal. This trend should facilitate the formation of metal
complexes with sulfonamide Schiff base 2.
The presence of the triflate groups avoids the π-stacking
interactions (face-to-face or face-to-edge) previously ob-
served between the terminal tosyl aromatic rings or between
the tosyl and the benzylidene rings in H2CyTs.[17] These π-
stacking interactions influence the conformation of the
molecule and generate a competitive interaction in ligand
1, thus reducing the available cavity for the metal.
Figure 1. ORTEP view of complex 6
Synthesis of Complexes
The interest in making new salen-type ligands lies in their
ability to form stable complexes with transition metals, thus
serving as potential precursors for homogeneous asymmet-
ric catalysis of a variety of reactions.[7,10] All the complexes
were prepared by addition of the divalent metal salts
Co(AcO)2·4H2O, NiCl2·6H2O or CuCl2·4H2O to a MeOH/
CH2Cl2 (1:1) solution of ligand 1 or a MeOH solution of
ligand 2. The complexes Co[(1R,2R)-CyTf], Co[(1R,2R)-
CyTs],
Cu[(1R,2R)-CyTs]
and
Ni[(1R,2R)-CyTf]
(Scheme 4), which precipitated in MeOH, were obtained
with high purity and in high yields. All these complexes
were characterised by mass spectra.
Figure 2. ORTEP view of complex 8
Conclusion
Scheme 4. General structural formula of complexes 5, 6, 7 and 8
The synthetic route that we have developed has allowed
us to prepare four C2-symmetric Schiff bases 1؊4 in good
yields. The tosylated derivative 1 was also prepared very
Crystal Structure Studies of Complex 6 and Complex 8
ORTEP views of 6 and 8 are shown in Figure 1 and Fig- recently by Bermejo, by a different pathway. The main ad-
ure 2, respectively. Selected bond lengths, distances and vantage of our method is the formation of a stable imine/
angles are displayed in Table 1 for 6 and in Table 2 for 8. amine intermediate that can be easily modified.
All the N-donor atoms in these complexes are bound to the
The two sulfonamide ligands are indeed promising chiral
metal centre. One oxygen atom of each tosyl group seems inductors for asymmetric catalysis. We thus prepared vari-
to have a weak interaction with the metal atom. The ous complexes of Co, Cu and Ni. The X-ray structures
Eur. J. Org. Chem. 2003, 1271Ϫ1276
1273

´
I. Karame, M. L. Tommasino, R. Faure, M. Lemaire
FULL PAPER
188.29 MHz for 19F) or a Bruker AC 300 FT (300.13 MHz for 1H,
75.47 MHz for 13C, 282.45 MHz for 19F) spectrometer; δ values are
given in ppm and J in Hz.
˚
˚
Table 1. Selected distances (A), angles (°) and bond lengths (A) in
complex 6
N(7)···N(26)
2.661(3)
2.790(3)
3.560(4)
2.821(4)
(1R,2R)-N,NЈ-Bis(2-p-tosylaminobenzylidene)-1,2-diaminocyclo-
hexane (1): Compound 3 (0.5 g, 1.56 mmol) was dissolved in
CH2Cl2 (10 mL), Et3N (470µL, 3.28 mmol) was added, and the
mixture was cooled to 0 °C. At this temperature, p-toluenesulfonyl
chloride (0.625 g, 3.28 mmol) was added. The resulting mixture was
stirred overnight (the temperature was allowed to rise at room tem-
perature). CH2Cl2 (10 mL) was added, and the resulting solution
was washed with water (3 ϫ 20 mL). After separation, the organic
layer was dried with Na2SO4 and the solvent was removed under
vacuum. After addition of methanol (10 mL) to the residual oil, a
yellow precipitate formed, and was collected by filtration through
a Millipore filter (vv type, pore size 0.10 µm) and dried under vac-
uum to give ligand 1 (0.444 g). Isolated yield 70%. M.p. 175 °C.
The ligand was recrystallized from CH2Cl2/MeOH to give yellow
crystals suitable for X-ray diffraction. The crystal structure, which
we obtained before publication of the Bermejo study,[17] gave the
same results. [α]D ϭ Ϫ107.2 (c ϭ 0.01 g/mL, CH2Cl2). 1H NMR
(CDCl3, 200 MHz, 25 °C): δ ϭ 13.2 (broad s, 2 H, NH), 8.47(s, 2
N(7)···N(15)
N(15)···N(34)
N(26)···N(34)
N(7)ϪC(1)ϪC(2)ϪN(26)
C(1)ϪC(2)ϪN(26)ϪC(27)
C(2)ϪC(1)ϪN(7)ϪC(8)
CoϪN(7)
CoϪN(26)
CoϪN(15)
CoϪN(34)
N(7)ϪCoϪN(15)
N(7)ϪCoϪN(26)
N(7)ϪCoϪN(34)
N(15)ϪCoϪN(26)
N(15)ϪCoϪN(34)
N(26)ϪCoϪN(34)
Ϫ53.5(3)
Ϫ129.2(4)
Ϫ129.7(3)
2.067(2)
2.052(3)
1.996(3)
1.994(3)
86.7(1)
80.5(1)
138.4(1)
135.6(1)
126.3(1)
88.4(1)
˚
˚
Table 2. Selected distances (A), angles (°) and bond lengths (A) in
complex 8
4
3
H, HCϭN), 7.49 (dd, JH,H ϭ 1.05, JH,H ϭ 8.2 Hz, 2 H, ArϪH),
3
4
7.42 (d, JH,H ϭ 8.2 Hz, 2 H, ArϪH), 7.27 (dd, JH,H ϭ 1.6,
3JH,H ϭ 8.2 Hz, 2 H, ArϪH), 7.2 (ddd, JH,H ϭ 1.6, JH,H ϭ 7.5,
8.2 Hz, 2 H, ArϪH), 6.9 (ddd, JH,H ϭ 1.05; JH,H ϭ 7.5, 8.2 Hz,
2 H, ArϪH), 6.63 (d, JH,H ϭ 8.2 Hz, 2 H, ArϪH), 3.57 (m, 2 H,
4
3
N(7)···N(23)
2.538(4)
2.646(4)
2.704(4)
2.824(4)
47.9(2)
127.3(2)
135.5(2)
1.860(2)
1.874(2)
1.910(2)
1.905(2)
89.15(8)
85.68(8)
168.86(9)
168.97(9)
95.49(9)
91.37(8)
4
3
N(7)···N(15)
3
N(23)···N(31)
N(31)···N(15)
CHϪN), 2.08 (s, 3 H, ArϪCH3), 1.5Ϫ2 (m, 8 H, ϪCH2Ϫ) ppm.
13C NMR (CDCl3, 300Mz, 25 °C): δ ϭ 164 (CϭN), 143, 139, 136
(3Cq), 134 (CϪAr), 129.3 (CϪAr), 127.2 (CϪAr), 122.3 (CϪAr),
120.4 (Cq), 117 (CϪAr), 73.4 (CH), 33.6 (CH2), 24.3 (CH2), 21.3
(CH3) ppm. IR (KBr): ν˜ ϭ 1631 (CϭN), 1157Ϫ1167 (NHSO2)
cmϪ1. HR LSIMS calcd. for C34H36N4O4S2·Hϩ(629.8): 629.2256;
found 629.22553. C34H36N4O4S2 (628.8): calcd. C 64.94, H 5.77, N
8.91, O 10.18, S 10.20; found C 65.09, H 5.92, N 8.97, O 10.60,
S 10.40.
N(7)ϪC(1)ϪC(2)ϪN(23)
C(2)ϪC(1)ϪN(7)ϪC(8)
C(1)ϪC(2)ϪN(23)ϪC(24)
NiϪN(7)
NiϪN(23)
NiϪN(15)
NiϪN(31)
N(7)ϪNiϪN(15)
N(7)ϪNiϪN(23)
N(7)ϪNiϪN(31)
N(15)ϪNiϪN(23)
N(15)ϪNiϪN(31)
N(23)ϪNiϪN(31)
(1R,2R)-N,NЈ-Bis(2-trifluoromethylsulfonaminobenzylidene)-1,2-
diaminocyclohexane (2): Compound 3 (0.47 g, 1.47 mmol) was dis-
solved in dry CH2Cl2 (8 mL), and Et3N (430µL, 2.95 mmol) was
added. After the mixture had been cooled to Ϫ78 °C under an
argon atmosphere, a solution of (CF3SO2)2O (483µL, 2.95 mmol)
in CH2Cl2 (8 mL) was added dropwise. The resulting solution was
stirred overnight (the temperature was allowed to rise to room tem-
perature). The solvent was evaporated and ligand 2 (0.57 g) was
obtained by flash chromatography (silica, ethyl acetate/cyclohex-
ane, 40:60). MW ϭ 584.55. Isolated yield 67%. M.p. 136 °C. Com-
pound 2 was recrystallized from CH2Cl2/cyclohexane to give yellow
crystals suitable for X-ray diffraction study. [α]2D0 ϭ Ϫ537 (c ϭ
0.01 g/mL, CH2Cl2). 1H NMR (CDCl3, 300 MHz, 25 °C): δ ϭ 14.8
show that those Schiff bases act as tetradentate ligands, for-
ming structures with the metal centre and the four N atoms
with pseudo-square-planar geometry for Ni complexes and
pseudo-tetrahedral geometry for Co species.
We are now focusing on the synthesis of other C2-sym-
metric sulfonamide Schiff base ligands.
4
(broad s, 2 H, NH), 8.4 (s, 2 H, HCϭN), 7.7 (dd, JH,H ϭ 0.94,
4
3
3JH,H ϭ 8.3 Hz, 2 H, ArϪH), 7.4 (ddd, JH,H ϭ 1.5, JH,H ϭ 7.2,
Experimental Section
4
3
8.3 Hz, 2 H, ArϪH), 7.3 (dd, JH,H ϭ 1.5 JH,H ϭ 7.8 Hz, 2 H,
4
3
General Remarks: Melting points (m.p., uncorrected) were deter-
mined with a Köffler Bench type WME (). Elemental
ArϪH), 7.1 (ddd, JH,H ϭ 0.9, JH,H ϭ 7.2, 7.8 Hz), 3.6 (m, 2
H, CH-N), 1.3Ϫ2.1 (m, 8 H, ϪCH2Ϫ) ppm. 13C NMR (CDCl3,
analysis (C, H, N, S, O, F) were obtained from the Service Central 300 MHz, 25 °C): δ ϭ 168 (CϭN), 143.7 (Cq), 134.5 (CϪAr), 134.4
1
d’Analyse of the CNRS (Solaize). High-resolution mass spectra
(HR LSIMS: Liquid Secondary Ionisation Mass Spectrometry) (CϪAr), 118.7(Cq), 70.2 (CH), 32.8 (CH2), 23.7 (CH2) ppm. 19F
were carried out on a Finnegan MAT 95xL at the UCBL Centre NMR (CDCl3, 300 MHz, 25 °C): δ ϭ Ϫ77.68 (s, 6F) ppm. IR
de Spectroscopie de Masse. IR spectra (KBr plates) were recorded (KBr): ν˜ ϭ 1651 (CϭN), 1316Ϫ1199 (NHSO2) cmϪ1. HR LSIMS
on a FT PerkinϪElmer spectrometer. [α]D values were determined
calculated for C22H22F6N4O4S2·Hϩ (585.6): 585.10649; found
(CϪAr), 122.9 (CϪAr), 120.2(q, JC,F ϭ323.9 Hz, 2C, CF3), 119
with a PerkinϪElmer 241 polarimeter (l ϭ 1 dm; 25 °C; concen- 585.10773. C22H22F6N4O4S2 (584.5): calcd. C 45.20, H 3.79, F
tration c in g/mL). 1H, 13C and 19F NMR spectra were recorded
19.50, N 9.58, O 10.95, S 10.97; found C 45.27, H 3.90, F 19.43,
N 9.40, S 11.47.
on a Bruker AC 200 (200.13 MHz for 1H, 50.32 MHz for 13C,
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Eur. J. Org. Chem. 2003, 1271Ϫ1276

New Chiral Tetradentate N4 Schiff Bases
FULL PAPER
(1R,2R)-N,NЈ-Bis(2-aminobenzylidene)-1,2-diaminocyclohexane (3):
LSIMS calculated for C34H34CoN4O4S2·Hϩ(686.7): 686.14316;
Compound 4 (1.026 g, 2.7 mmol) was dissolved in CH2Cl2 (10 mL), found 686.14309.
˚
and Pd/C(10%) (130 mg) was added, together with 4-A molecular
[Cu(1R,2R)-CyTs] (7): This complex was prepared by the same pro-
sieves. The mixture was stirred under a hydrogen atmosphere at 0
°C. The consumption of hydrogen was steady in the course of time.
After 4 hours, the required volume of H2 had been consumed. The
mixture was filtered through Celite, the solvent was removed by
evaporation, and the residue was washed with methanol and fil-
tered through a Millipore filter (vv type, pore size 0.10 µm). Finally,
it was dried under vacuum to give ligand 3 (0.56 g) as a white solid.
Isolated yield: 65%. M.p. 182 °C. The ligand was recrystallized
from CH2Cl2/MeOH to give colourless crystals suitable for X-ray
diffraction study. [α]2D0 ϭ Ϫ517 (c ϭ 0.01 g/mL, CH2Cl2). 1H NMR
(CDCl3, 300 MHz, 25 °C): δ ϭ 8.3 (s, 2 H, HCϭN), 7.1 (dd,
cedure as used for 6, starting from Cu(O2CMe).H2O. The product
crystallises as a green, microcrystalline solid (yield 75%). No X-ray
study was carried out, since one had just been published.[17] HR
LSISM for C34H34CuN4O4S2·Hϩ(691.3): 690.13980; found
690.13980.
[Ni(1R,2R)-CyTf] (8):This complex was prepared by the same pro-
cedure as for 5, from NiCl2·6H2O (44 mg, 0.184 mmol) and 2
(108 mg, 0.184 mmol) in MeOH (yield 70%). The red crystals ob-
tained were suitable for X-ray diffraction study. 1H NMR (DMSO,
3
300 MHz, 25 °C): δ ϭ 8 (s, 2 H, HCϭN), 7.8(d, JH,H ϭ 7.6 Hz, 2
3
4
4JH,H ϭ 1.3, JH,H ϭ 7.7 Hz, 2 H, ArϪH), 7.07(ddd, JH,H ϭ 1.3,
H, ArϪH), 7.55 (t, 3JH,H ϭ 7.25 Hz, 2 H, ArϪH), 7.35 (d, 3JH,H ϭ
7.6 Hz), 7.3 (t, 3JH,H ϭ 7.5 Hz, 2 H, ArϪH), 2.75 (m, 2 H, CHϪN),
2.4 (m, 2 H, CH2), 1.8 (m, 2 H, CH2), 1.6 (m, 2 H, CH2), 1.3
(m, 2 H, CH2) ppm. 19F NMR (DMSO, 300 MHz, 25 °C): δ ϭ
Ϫ75.84 (s, 6F, CF3) ppm. HR LSIMS calculated for
C22H20F6N4O4S2Ni·Hϩ (642.3): 641.0262; found 641.02424.
3JH,H ϭ 7.7, 7.8 Hz, 2 H, ArϪH), 6.64 (ddd, 4JH,H ϭ 1.5, 3JH,H
ϭ
4
3
7.7, 7.8 Hz, 2 H, ArϪH), 6.6 (dd, JH,H ϭ 1.5 JH,H ϭ 7.7 Hz, 2
H, ArϪH), 6.3 (broad s, 4 H, NH2), 3.3 (m, 2 H, CHϪN), 1.5Ϫ2
(m, 2 H, ϪCH2Ϫ) ppm. 13C NMR (CDCl3, 300 MHz, 25 °C): δ ϭ
163.5 (CϭN), 148.76 (Cq), 133.4 (CϪAr), 130.8 (CϪAr), 118.3
(Cq), 116.2 (CϪAr), 115.8 (CϪAr), 74.8 (CH), 33.9 (CH2), 24.9
(CH2) ppm. IR (KBr): ν˜ ϭ 3248Ϫ3473 (NH2), 1626 (CϭN) cmϪ1
.
X-ray Crystallographic Study: Data were collected on a Nonius
HR LSIMS calculated for C20H24N4·Hϩ(321.4): 321.20792; found
321.20724. C20H24N4 (320.4): calcd. C 74.97, H 7.55, N 17.48;
found C 75.38, H 7.67, N 17.26.
Kappa CCD diffractometer by use of graphite monochromated
˚
Mo-Kα radiation (λ ϭ 0.71070 A) from a fine-focus sealed tube
source. The structures were solved by use of SHELXTL[22] and
refined by full-matrix, least-squares on F2. Absorption corrections
were applied (Multiscan, sortav).[23] All non-hydrogen atoms were
anisotropically refined. All hydrogen atoms were included in the
model at geometrically calculated positions and refined by use of
a riding model. Experimental details are shown in Table 3. CCDC-
194700 and CCDC-194701 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from
the Cambridge Crystallographic Data Centre, 12, Union Road,
(1R,2R)-N,NЈ-Bis(2-nitrobenzylidene)-1,2-diaminocyclohexane (4):
2-Nitrobenzaldehyde (6.7 g, 44.3 mmol) and 4-A molecular sieves
˚
were added to a solution of (1R,2R)-1,2-diaminocyclohexane
(2.6 g, 22.7 mmol) in anhydrous THF (12 mL). The mixture was
stirred overnight at room temperature under an argon atmosphere.
Dichloromethane (12 mL) was added, and the resulting mixture
was filtered through silica (CH2Cl2), the solvents were evaporated,
and the residual oil was dried under vacuum to give product 4
(7.846 g) as a white solid. Isolated yield: 91%. M.p. 75 °C. [α]2D0
ϩ556 (c ϭ 0.01 g/mL, CH2Cl2). H NMR (DMSO, 300 MHz, 25
°C): δ ϭ 8.5 (s, 2 H, HCϭN), 8 (dd, JH,H ϭ 1.1, JH,H ϭ 7.9 Hz,
2 H, ArϪH), 7.9 (dd, JH,H ϭ 1.1, JH,H ϭ 7.5 Hz, 2 H, ArϪH),
ϭ
1
4
3
Table 3. Crystal data and details of the structure determination of
6 and 8
4
3
4
3
7.7 (ddd, JH,H ϭ 1.1, JH,H ϭ 7.4, 7.5 Hz, 2 H, ArϪH), 7.6 (ddd,
4JH,H ϭ 1.1 Hz; JH,H ϭ 7.4 and 8 Hz, 2 H, ArϪH), 3.5 (m, 2
3
6
8
H, CHϪN), 1.5Ϫ1.8 (m, 8 H, ϪCH2Ϫ) ppm. 13C NMR (CDCl3,
200 MHz, 25 °C): δ ϭ 156.8 (CϭN), 148.7 (Cq), 133.6 (CϪAr),
131.35 (Cq), 130.5 (CϪAr), 130 (CϪAr), 124.2 (CϪAr), 54.7 (CH),
32.6 (CH2), 24.3 (CH2) ppm. IR (KBr): ν˜ ϭ 1633 (CϭN),
Empirical formula
Molecular mass [g/mol] 685.7
Crystal system
Space group
C34H34CoN4O4S2 C22H20F6N4NiO4S2
641.25
orthorhombic
P212121
monoclinic
P21
1521Ϫ1339 (NO2) cmϪ1
.
HR LSIMS calculated for
381.15628; found 381.15611.
Crystal size (mm)
0.5 ϫ 0.25 ϫ 0.25 0.20 ϫ 0.20 ϫ 0.20
C20H20N4O4·Hϩ
(381.4):
˚
a [A]
8.9140(1)
19.4390(3)
9.6870(2)
103.040(1)
1635.27(5)
2
1.393
0.696
173
9.9320(2)
15.2950(2)
16.4420(3)
˚
C20H20N4O4(380.4): calcd. C 63.15, H 5.30, N 14.73, O 16.83;
found C 63.00, H 5.24, N 14.57, O 17.27.
b [A]
˚
c [A]
β [°]
3
˚
[Co(1R,2R)-CyTf] (5): Co(O2CMe)2·4H2O (43 mg, 0.172 mmol)
was added to a solution of 2 (100 mg, 0.17 mmol) in MeOH
(4 mL). The reaction mixture was heated at reflux for 1 hour. The
pink solution turned brown and a copious amount of precipitate
was formed, and the solid was collected and washed with methanol.
Recrystallization from CH2Cl2/MeOH gave red crystals suitable for
X-ray diffraction study (90 mg, yield 82%). HR LSIMS calculated
for C22H20F6N4O4S2Co·Hϩ (642.5): 642.0240; found 642.02424.
V [A ]
2497.70(8)
4
1.705
1.028
295
Z
D (g/cmϪ3
)
µ Mo-Kα (mmϪ1
T (K)
)
Number of reflections
collected
R int
Number of independent 10778
reflections
Number of reflections
I Ͼ 2 σ(I)
R [I Ͼ 2 σ(I)]
R [all data]
Absolute structure
parameter
20905
24709
0.051
0.044
9021
[Co(1R,2R)-CyTs] (6): A solution of Co(O2CMe)2·4H2O (44 mg,
0.176 mmol) in EtOH (2 mL) was added to a solution of 1 (107 mg,
0.17 mmol) in toluene (1 mL). The resulting solution was heated at
reflux for 1.5 hours. The pink solution turned brown, and a copious
amount of precipitate was formed. The solid was collected, washed
with methanol and recrystallized from CH2Cl2/MeOH to give red
crystals suitable for X-ray diffraction study (60 mg, yield 51%). HR
8760
6569
0.059, 0.173
0.075, 0.185
Ϫ0.01(1)
0.045, 0.098
0.072, 0.108
Ϫ0.02(9)
Eur. J. Org. Chem. 2003, 1271Ϫ1276
1275

´
I. Karame, M. L. Tommasino, R. Faure, M. Lemaire
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Acknowledgments
[17]
´
´
´
`
We thank Genevieve Heraud for her analytical advice.
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2Ј: H NMR(CDCl3, 300 MHz, 25 °C): δ ϭ 15 (broad s, 1 H,
[4]
NH), 8.3 (s, 1 H, HCϭN), 8.1 (s, 1 H, HCϭN), 7.7 (m, 1 H,
ArϪH), 7.6 (m, 2 H, ArϪH), 7.5Ϫ7.3 (m, 3 H, ArϪH), 7.1
(m, 1 H, ArϪH), 6.85 (m, 1 H, ArϪH), 3.8 (m, 1 H, CHϪN),
3.4 (m, 1 H, CHϪN), 2.2Ϫ1.2 (m, 8 H, ϪCH2Ϫ) ppm. 13C
NMR (CDCl3, 300 MHz, 25 °C): δ ϭ 168 (CϭN), 161 (Cϭ
N), 152 (CqϪAr), 141 (CqϪAr), 137 (CϪAr), 135.4 (CϪAr),
135.2 (CϪAr), 135 (CϪAr), 133 (CϪAr), 132 (CϪAr), 130
(CqϪAr), 121(CϪAr), 120.8 (CϪAr), 117(CqϪAr), 75
(CHϪN), 67 (CHϪN), 32.9 (CH2), 32.3 (CH2), 24.4 (CH2),
23.8 (CH2) ppm. 19F NMR (CDCl3, 300 MHz, 25 °C): δ ϭ
Ϫ78.13 (NHϪCF3), Ϫ72.35 (NϪCF3), Ϫ72.27 (NϪCF3) ppm.
HR LSIMS calculated for MHϩ: 717.05577; found 717.05535.
G. M. Sheldrick, SHELXT, Structure Analysis Program,
Bruker AXS software package, Madison, WI, 1998.
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[O02562]
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Eur. J. Org. Chem. 2003, 1271Ϫ1276