Complexation of 3-(2-pyridyl)substituted N-methyl isoxazolidine with Pd(II), Zn(II) and Cu(II): Stereochemistry of co-ordination compounds in solution and solid-state

Article abstract of DOI:10.1016/S0277-5387(02)00840-9

2-Methyl-3-(2-pyridyl)isoxazolidine (L) and its Pd(II), Zn(II) and Cu(II) complexes have been prepared and characterized by IR, ¹H, ¹³C 1D and HMBC, NOESY 2D NMR spectroscopies. The stereochemistry of the 'free' and co-ordinated ligand has been assigned by nuclear Overhauser effect (NOE). The molecular structures of [Zn(cis-L)Cl₂]·0.5CHCl₃ (2a), [Zn(cis-/trans-L)Cl₂] (2a-b) and [Cu(cis-/trans-L)Cl₂]₂ (4a-b) have been established by means of X-ray crystallography. The crystal structure of 2a consists of a racemic mixture of cis-L (3SR,5RS), while the crystal structure of 2b comprises a racemate of cis- and trans-isomeric forms. For both complexes the zinc atoms adopt nearly tetrahedral co-ordination with two chlorine atoms and N,N-bidentate co-ordinated L. The crystal structure of 4a-b consists of dinuclear [Cu(cis-/trans-L)Cl₂]₂ moieties with N,N-bidentate co-ordinated ligands. The square pyramidal co-ordination spheres of copper ions are completed by a bridging chloride ligand at the apex (Cu-Cl 2.79, 2.82 A?).

Full text of DOI:10.1016/S0277-5387(02)00840-9

Polyhedron 21 (2002) 769ꢀ777
/
www.elsevier.com/locate/poly
Complexation of 3-(2-pyridyl)substituted N-methyl isoxazolidine
with Pd(II), Zn(II) and Cu(II): stereochemistry of co-ordination
compounds in solution and solid-state
Andrey B. Lysenko a, Konstantin V. Domasevitch a, Emma Peralta-Pe´rez b,
Fernando Lo´pez-Ortiz b, Jonathan W. Steed c, Rostislav D. Lampeka a,*
a Department of Chemistry, Kiev National University, Vladimirskaja Str. 64, 01033 Kiev, Ukraine
b
´
Area de Qu´ımica Orga´nica, Universidad de Almer´ıa, Carretera Sacramento s/n, 04120 Almer´ıa, Spain
c Department of Chemistry, King’s College London, Strand, London, WC2 R2LS, UK
Received 3 August 2001; accepted 13 December 2001
Abstract
2-Methyl-3-(2-pyridyl)isoxazolidine (L) and its Pd(II), Zn(II) and Cu(II) complexes have been prepared and characterized by IR,
1H, 13C 1D and HMBC, NOESY 2D NMR spectroscopies. The stereochemistry of the ‘free’ and co-ordinated ligand has been
assigned by nuclear Overhauser effect (NOE). The molecular structures of [Zn(cis-L)Cl2]×
/
0.5CHCl3 (2a), [Zn(cis-/trans-L)Cl2] (2aꢀ
/
b) and [Cu(cis-/trans-L)Cl2]2 (4aꢀb) have been established by means of X-ray crystallography. The crystal structure of 2a consists of
/
a racemic mixture of cis-L (3SR,5RS), while the crystal structure of 2b comprises a racemate of cis- and trans-isomeric forms. For
both complexes the zinc atoms adopt nearly tetrahedral co-ordination with two chlorine atoms and N,N-bidentate co-ordinated L.
The crystal structure of 4aꢀb consists of dinuclear [Cu(cis-/trans-L)Cl2]2 moieties with N,N-bidentate co-ordinated ligands. The
/
˚
Cl 2.79, 2.82 A).
square pyramidal co-ordination spheres of copper ions are completed by a bridging chloride ligand at the apex (CuÃ
/
# 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Isoxazolidines; Pd-, Zn-, Cu-complexes; Syntheses; X-ray; NMR
1. Introduction
Very recently, Cu(II)- and Zn(II)-bisoxazoline [21] as
well as (BINOL)ꢀ
/
AlMe complexes (BINOLꢁ2,2?-dihi-
/
Isoxazolidine systems are important in bioscience as
intermediates for organic synthesis of a number of
natural compounds: 1,3-aminoalcohols, alkaloids and
droxy-1,1?-binaphthyl) [22] have been utilized as cata-
lysts in the enantioselective synthesis of isoxazolidines
through 1,3-dipolar cycloadditions of nitrones to elec-
tron-rich olefins. The stereochemistry of the products
has been explained by assuming the formation of a
complex between the nitrone and the catalysts.
Our interest is focused on co-ordination chemistry of
the isoxazolidine systems concerning possible applica-
tion of the metal complexes for the asymmetric 1,3-
dipolar cycloaddition reactions between alkenes and
acyclic nitrones [23,24]. Elaboration of this approach is
closely related with investigation of isoxazolidine co-
ordination compounds themselves because it may give
significant information for understanding the impor-
tance of inherent structure of the co-ordination com-
pounds for 1,3-dipolar cycloaddition and processes of
purification and separation of isomeric isoxazolidines.
amino sugars [1ꢀ/4]. Their pharmacological properties
[5ꢀ9] have stimulated interest on the control of dia-
/
stereo- and enantioselectivity in 1,3-nitrone-olefine di-
polar cycloaddition as the isoxazolidine preparation
method. The last decade has revealed a great deal of
research on improving methods for stereoselective
synthesis of isoxazolidines [10ꢀ18]. Thus, nitrone-
/
tricarbonyl(h6-arene)chromium(0) adducts undergo cy-
cloaddition reactions in a highly stereoselective manner
yielding cis-3,5-disubstituted isoxazolidines [19,20].
* Corresponding author. Fax: ꢂ380-44-463-6417.
E-mail address: r.lampeka@clariant.com.ua (R.D. Lampeka).
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 0 8 4 0 - 9

770
A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ777
/
Recently, we have shown that the pyridyl substituted
N-methyl isoxazolidines readily give co-ordination
compounds with d-metal ions [23,25]. The 5-(2-pyri-
dyl)substituted isoxazolidine core may act either as
monodentate ligand through the nitrogen atom of the
pyridyl substituent or as bidentate ligand (N,N for Pd,
Pt; N,O for Zn). In each case, the metal co-ordinates the
pyridyl nitrogen atom and one of the heteroatoms of the
isoxazolidine ring (Scheme 1).
Scheme 2. The possible modes of chelate complexation for 2-methyl-3-
(2-pyridyl)-5-phenylisoxazolidine.
Herein we present our results on the synthesis of
isomeric cis-/trans-2-methyl-3-(2-pyridyl)-5-phenylisox-
azolidine (L) and the study of its co-ordination behavior
with Pd, Zn and Cu metal ions. The presence of one co-
ordinatively active substituent on the isoxazolidine ring
may give rise to different co-ordination modes to the
metals (Scheme 2).
Scheme 3. NOE correlations of L.
2. Results and discussion
(NOEs) (Scheme 3) allows facile determination of both
the configurations for 3,5-disubstituted isoxazolidine
systems.
2.1. Synthesis and structural identification of L
The organic ligand L was obtained through the [3ꢂ
dipolar cycloaddition of N-methyl-C-(2-pyridyl)nitrone
(1) to freshly distilled styrene in refluxing tolueneꢀ
benzene (1:1, v/v) (Scheme 3). Analysis of the crude
reaction showed the presence of two products in an
approximate ratio 67:33 which were identified, respec-
tively, as the cis- and trans-stereoisomers of 2-methyl-3-
(2-pyridyl)-5-phenylisoxazolidine, i.e. a single regioi-
somer was observed. Column chromatography on
/
2]
The 1H NMR spectrum measured in DMSO-d6
showed separate signals for the most significant protons
of both stereoisomers (overlap occurred for the phenyl
protons and H(c) of the 2-pyridyl group). The HMQC
and HMBC correlation spectra allowed the straightfor-
/
1
ward assignment of the H and 13C NMR spectra. The
use of CDCl3 as solvent produced only minor changes in
the chemical shifts of the signals (see Section 4). In
principle, the relative stereochemistry of the stereogenic
centers of L could be established from the observed
coupling constants for the proton at C(5) as it has been
shown for several 3,5-disubstituted isoxazolidines [26]
silicagel (acetoneꢀhexane 1:1) of the crude product
/
afforded pure cis-/trans-L without altering the relative
ratio of isomers.
The IR spectrum of L is similar to the related 5-(2-
pyridyl)isoxazolidine [23] and shows characteristic
(H(5) proton appeared as a double doublet (3JHH 3ꢀ
Hz) for the cis isomer, and a doublet for the trans
derivative (3JHH
5 Hz). Unfortunately, in our case
/
6
strong absorptions at 2990ꢀ
1490ꢀ1590 (n(CÄC) ph, py), 2780ꢀ
cmꢃ1 (n(CÃ
H) and d(CÃH) of the aliphatic groups).
/
3090 (n(CÃ
/
H) ph, py),
Â
/
/
/
/
2960, 1335ꢀ
/
1475
/
/
both isomers produced the same multiplicity pattern for
H(5), a triplet, with the same vicinal couplings (3JHH 7.7
Hz), precluding to draw any stereochemical conclusion
of the configuration of the isoxazolidine moiety. The 2D
NOESY spectrum of the cis-, trans-L mixture allowed
to solve the ambiguity. The major isomer is assigned the
cis stereochemistry based on the intense correlation
observed between H(3) (d 4.19) and H(5) (d 5.32).
1
The H NMR spectrum of L suggests the presence of
two diastereomers. The analysis of the coupling con-
stants in combination with nuclear Overhauser effects
Additionally, the methylene proton at d 2.46 (H(4a), dt,
3
2JHH 12.3, JH4aH3ꢁ3
/
JH4aH5 6.9 Hz) shows the ex-
pected cross peaks with both the 2-pyridyl (d(Hd) 7.58,
see Scheme 2 for labeling) and the phenyl (d(Ho) 7.3)
substituents corresponding to their syn orientation.
Consequently, the double triplet at d 3.23 (2JHH 12.3,
3JH4bH3ꢁ3
methylene proton H(4b) (Scheme 4).
/
JH4bH5 7.7 Hz) is assigned to the other
Scheme 1. Co-ordination features of 5-pyridyl substituted isoxazoli-
dines.

A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ
/777
771
the Na2[PdCl4] complex for palladium. Cooling the
reaction mixture to room temperature afforded a
precipitate which was separated, washed with alcohol
(methanol or 2-propanol) and dried, yielding the metal
complexes [Zn(cis-/trans-L)Cl2] (2aꢀ
L)Cl2] (3aꢀb), and compound [Cu(cis-/trans-L)Cl2]2
(4aꢀb). All the compounds are air stable both as solids
/
b), [Pd(cis-/trans-
/
/
Scheme 4. H(a) defines the proton syn to the 2-pyridyl ring.
and in solution. They are readily soluble in acetonitrile,
N,N-dimethylformamide, dimethyl sulfoxide and al-
most insoluble in hexane.
Therefore, the minor component of the mixture is the
trans isomer. This assignment is supported by the NOE
The 1H and 13C NMR data of compounds 2ꢀ
4
/
3
correlation between H(3) (d 4.04, dd, JH4aH3 6.5,
acquired in DMSO-d6 are given in Table 1. The assign-
ment of the proton and carbon atom signals was easily
made based on the analysis of the 1D (1H, APT) and 2D
(HMQC, HMBC) spectra. The NMR spectra of the
complexes showed two sets of signals derived from the
co-ordinated isomeric cis- and trans-isoxazolidines. The
ratio of isomers was similar to that of the free ligand L
3JH4bH3 7.7 Hz) and the ortho protons (d 7.42, m) of
the phenyl ring linked to C(5) (d 5.07, t, JHH 7.7 Hz).
3
Again, the methylene protons are assigned from the
respective correlations with H(3) and H(5) (see Section
4).
(average cis ꢀtrans ratio of 65:35). As for the free ligand,
/
2.2. Synthesis and structural identification of complexes
the relative stereochemistry of the two carbon stereo-
genic centers was unambiguously deduced from the
NOE correlations observed in the corresponding
NOESY spectra. In all cases H(3) and H(5) exhibited
a strong dipolar correlation for the cis isomers, while for
the trans derivatives a correlation of low intensity was
2ꢀ4
/
Complexation of the isomeric mixture of isoxazoli-
dines L with Pd(II), Zn(II) and Cu(II) metal ions was
carried out by heating an alcoholic solution of the ligand
with the corresponding zinc and copper chloride, or with
Table 1
1H and 13C NMR data of complexes 2ꢀ
3
/

772
A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ777
/
detected between H(5) and the ortho protons of the
phenyl substituent on C(3). The methylene protons H(4)
were again assigned through their respective correlations
with the vicinal protons H(3)/H(5).
2.3. Crystal structures of [Zn(cis-L)Cl2]×
(2a), [Zn(cis-/trans-L)Cl2] (2aꢀb) and [Cu(cis-/
trans-L)Cl2]2 (4)
/
0.5CHCl3
/
The NMR results described above indicated that
compounds 2ꢀ4 are mixtures of stereoisomers. Recrys-
The complexation of both ligands is evidenced by the
variations of the proton chemical shifts compared with
/
tallization of the crude products obtained opens up
different possibilities for these systems: resolution of
racemic cis-/trans-isomers, self-resolution of enantio-
mers and co-crystallization of cis- and trans-isomers. In
all cases, further insight into the structural characteristic
of the co-ordination complexes could be gained through
the analysis of the solid state structure (Fig. 1).
Recrystallization of 2 by slow diffusion of 2-propanol
into a chloroform solution of the metal complex
afforded two products suitable for X-ray analysis. One
the free isoxazolidines. In compounds 2aꢀb, the co-
/
ordination of L to Zn(II) produce a broadening of all
proton signals and a partial overlap of the aromatic
protons corresponding to both stereoisomers. Clearly,
for 2aꢀb co-ordination occurred in the proximity of
/
H(3). This is the only proton of the isoxazolidine moiety
showing a significant deshielding effect due to the
complexation
DdH(3)trans (2bꢀ
(DdH(3)cis
L)ꢁ0.12 ppm). Variations on H(4)
(2aꢀ
/
L)ꢁ
/0.14
ppm;
/
/
and H(5) are lower than 0.05 ppm. In principle, the
effect on H(3) is compatible with L acting either as a N-
monodentate or N,N-bidentate ligand. Co-ordination
through the nitrogen of the pyridine is supported by the
deshielding observed for the protons H(b) (DdH(b)cis
of them, [Zn(cis-L)Cl2]×
mic mixture of cis-L (3SR,5RS), while another one
[Zn(cis-/trans-L)Cl2] (2aꢀb) is a racemate including
/
0.5CHCl3 (2a) consists of race-
/
both cis- and trans-forms. These structures are built
up from molecular [Zn(L)Cl2] species, but are dramati-
cally different in the spatial arrangement of the mole-
cules (Figs. 2 and 3). There is a lack of strong
intermolecular interactions such as co-ordination or
hydrogen bonding. However, the packing pattern for
the compounds is determined by stacking interactions
between two aromatic functions of the ligand. Complex
(2aꢀ
and H(c) (DdH(c)cis (2aꢀ
(2bꢀL)ꢁ0.17 ppm) of the heterocycle. On the other
/
L)ꢁ
/
0.07 ppm; DdH(b)trans (2bꢀ
L)ꢁ
/
L)ꢁ
/
0.05 ppm)
/
/
0.16 ppm; DdH(c)trans
/
/
hand, co-ordination to the nitrogen of the isoxazolidine
would prevent rapid inversion of the heteroatom,
originating a new stereogenic center which relative
configuration could be identified in the NOESY spec-
2a consists of dimers sustained by pꢀp, or face-to-face,
/
stacking between pyridine groups. These weak but
commonly encountered interactions contribute to crys-
tal structures of aromatic species [27] and may be loosely
regarded as a kind of ‘supramolecular synthon’ [28].
Two pyridine rings are parallel and the distance between
trum. Indeed, the methyl protons of cis-L in 2aꢀb (d
/
2.74) showed a dipolar correlation with H(3) and H(5),
while for trans-L only the correlation of the methyl
protons at d 2.67 with H(3) was detected. These
evidences indicate that in complex 2aꢀb the ligand is
/
˚
their planes is approximately 3.28 A. Two molecular
Py) evidently
generates a center of inversion in the triclinic crystal,
bonded to the metal in a N,N-bidentate mode.
The same trends have been observed in the proton
complexes being paired in such a way (PyÃ
/
spectrum of the mixture of isomers 3aꢀb. In this case,
/
and the lattice comprises a racemic mixture.
Stacking interactions are also present in the packing
co-ordination of L to palladium produced a much
stronger effect on the proton spectrum of isoxazolidine
and all signals appeared deshielded compared to the free
pattern of complex 2aꢀb but between different func-
/
tions, the pyridyl and phenyl groups. They also appear
to be parallel with interplanar separation at approxi-
ligand. The low field shift ranged from Dd(3aꢀ
0.19ꢀ0.85 ppm for H(4), H(5) and the methyl protons.
Even though, the shifts for H(3) exceeded 1 ppm
(DdH(3)cis (3ꢀ 1.13 ppm; DdH(3)trans (3ꢀ
L)ꢁ L)ꢁ1.08
/
bꢀ
/
L)ꢁ
/
/
˚
mately 3.45 A. From this point of view, structures 2a
and 2aꢀb may be regarded as supramolecular isomers
(see Fig. 3). For complex 2aꢀb, face-to-face stacking
/
/
/
/
/
/
ppm). Again, the deshielding of the pyridine protons
(see Table 1) and the NOEs measured for the methyl
protons are consistent with L being doubly co-ordinated
to the metal through the nitrogen atoms.
interactions connect the molecules into 1D chain and
unsymmetric pairing results in the absence of a center of
inversion. Nevertheless, the crystal also comprises both
enantiomers that are related by a glide plane.
The differences in line-broadening and range of
chemical shifts variations promoted by Zn versus Pd
co-ordination to L suggest that in DMSO the solvent is
competing with the ligand L for binding to the zinc ion
Another important feature of the structure 2aꢀ
/
b is
disordering of the C(3)ÃPh fragment. This disorder has
/
a clear chemical significance as two components corre-
spond to cis- and trans-isomeric forms of the ligand.
Refinement of partial occupancies suggested contribu-
tions of cis- (72%) and trans- (28%) isomers similar to
that found in the crude product mixture (67 and 33%).
Both isomers have actually the same size, shape and
and therefore, the proton spectrum of 2aꢀb corresponds
/
to the average situation derived from the exchange
between free and complexed ligand which is rapid on the
NMR time scale.

A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ
/777
773
Fig. 1. The 2D NOESY spectrum of [Pd(cis-/trans-L)Cl2] (300 MHz, DMSO-d6/THF-d8).
orientation of functional groups and (Fig. 2) therefore
statistically occupy positions in the crystal. The resulting
structure may be described as a solid-state solution of
isomeric complexes. The existence of such phases may
preclude the possibility of separation of isomeric iso-
xazolidines and their metal complexes by crystallization.
lidine ring in the structures possesses an envelope
conformation. In structure 2a, the methyl group has
an axial orientation to the isoxazolidine ring, while the
phenyl and pyridine substituents are situated in an
equatorial manner (C(6)Ã
(Table 2). In structure 2aꢀ
pyridyl ring are situated in an equatorial manner at the
isoxazolidine cycle (C(10)ÃC(3)ÃC(2)ÃC(1) 153.78)
while the methyl group is located in an axial position
(C(4)ÃN(1)ÃO(1)ÃC(3) ꢃ93.48) (Table 3). The struc-
ture of copper complex 4aꢀb (Fig. 4) consists of a
/
C(7)Ã
/
C(8)Ã
/
C(9) 159.5(4)8)
/
b, the phenyl group and
The zinc atoms in 2aꢀb adopt a nearly tetrahedral co-
/
ordination polyhedron with two chloride ligands and
one N,N-bidentate co-ordinated L. In contrast to the X-
ray data for a related structure of the palladium complex
with trans-2-methyl-5-(2-pyridyl)-3-phenylisoxazolidine,
/
/
/
/
/
/
/
/
the structure of 2a possesses a ZnÃ
A) longer than ZnÃ
/
N(1) bond (2.134(4)
neutral dimers [Cu(cis-/trans-L)Cl2]2. The copper atoms
are co-ordinated in a distorted square pyramid compris-
˚
˚
N(2) 2.049(4) A) [23]. The five-
membered chelate ring in both structures of zinc
/
ing two nitrogen and two chlorine atoms in an
˚
Cl 2.244(2)ꢀ2.262(2) A) and an
complex is almost planar. The atoms Zn(1) and N(1)
˚
deviate by ꢃ0.12 and 0.18 A, respectively, from the
equatorial plane (CuÃ
/
/
/
additional chloride ligand is situated in the apex (CuÃ
/
Cl
2.795(2), 2.818(2) A). Thus two bridging chlorine atoms
˚
mean plane of the other atoms this cycle. The isoxazo-

774
A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ777
/
3. Conclusions
2-Methyl-3-(2-pyridyl)-5-phenylisoxazolidine
been regioselectively synthetized as a 67:33 cis ꢀ
has
trans
/
mixture by reaction of N-methyl-C-(2-pyridyl)nitrone
with styrene. The new ligand readily forms co-ordina-
tion compounds with Zn(II), Cu(II) and Pd(II) chlorides
which solution structure has been assigned through 1D
and 2D NMR spectroscopy. The organic ligand in the
complexes is co-ordinated in a N,N-bidentate chelating
mode, in contrast to isomeric 5-(2-pyridyl)substituted
N-methyl isoxazolidine. The configuration and confor-
mation of the isoxazolidine ring have been determined
by NOE NMR experiments and confirmed by means of
the X-ray diffraction data for zinc and copper chloride
complexes. The crystal structure of [Zn(cis-/trans-L)Cl2]
(2aꢀ
/
b) and [Cu(cis-/trans-L)Cl2] (4aꢀb) revealed the co-
/
crystallization of cis- and trans-isomers of the ligand.
For the zinc complex it has been also possible to isolate
and characterize the co-ordination compound derived
from the cis-isoxazolidine [Zn(cis-L)Cl2]×
/
0.5CHCl3 (2a).
4. Experimental
4.1. Synthesis
Fig. 2. Molecular structure of [Zn(L)Cl2]: (A) cis-isomeric form of the
˚
All solvents were used as supplied or distilled using
standard methods. The starting materials for the synth-
esis of organic ligands and complexes were commercial
products of reagent grade (Fluka, Aldrich). The N-
methyl-C-(2-pyridyl)nitrone (1) was prepared as pre-
viously described [24].
ligand in structure 1a. Selected bond length, A: Zn(1)ÃN(2) 2.049(4);
Zn(1)ÃN(1) 2.134(4); Zn(1)ÃCl(2) 2.208(1); Zn(1)ÃCl(1) 2.209(1); (B)
disordering scheme for CÃC6H5 fragment in structure 1b suggests
presence of cis- and trans-isomeric forms that possess the same shape
˚
and form mixed crystal. Selected bond length, A: Zn(1)ÃN(2) 2.038(3);
Zn(1)ÃN(1) 2.109(4); Zn(1)ÃCl(1) 2.202(1); Zn(1)ÃCl(2) 2.211(1).
4.1.1. 2-Methyl-3-(2-pyridyl)-5-phenylisoxazolidine (L)
Freshly distilled styrene (20.2 ml, 18.36 g, 176.54
connects molecular units [Cu(L)Cl2] into the dimer
(Table 4). The latter one is actually centrosymmetric,
and all three pairs of isoxazolidine asymmetric atoms
within the dimer frame possess opposite chirality. N-co-
ordination of the isoxazolidine to the metal atom also
makes impossible pyramidal inversion at the nitrogen
atom, and the co-ordinated isoxazolidine core possesses
three chiral centers simultaneously. Nevertheless, sys-
tematic absences suggest the chiral space group P212121.
The structure also shows high parameters for thermal
mmol) was added to a C6H5CH3ꢀC6H6 solution (1:1 v/
/
v, 30 ml) of N-methyl-C-(2-pyridyl)nitrone (3.00 g,
22.06 mmol). The reaction mixture was stirred at reflux
for 70 h and then concentrated in vacuo. Undesired side
products were removed by means of column chromato-
graphy on silica gel with C3H6Oꢀ
eluent. The yield of L (yellow oil, mixture of cis ꢀ
60%).
/
C6H14 (1:1) as an
/
trans
isomers in a ratio 67:33) was 3.18 g (Â
/
IR (film between KBr discs, cmꢃ1): 3085, 3065, 3035,
3010, 2990, 2960, 2960, 2915, 2875, 2850, 2780, 1670,
1590, 1570, 1495, 1475, 1450, 1440, 1400.
motion of the isoxazolidine CÃ
/
Ph fragment (Uiso 0.1ꢀ
0.2 A ) that may be ascribed to co-crystallization of cis-
and trans-isomeric forms, by analogy with 2aꢀb. Both
/
2
˚
cis-L, 1H NMR spectrum (CDCl3): d 2.54 (dt, 1H, 3J
7.9, 2J 12.7, H(4a)), 2.84 (s, 3H, NCH3), 3.24 (dt, 1H, 3J
/
2
3
five-membered chelate rings formed are almost planar.
The isoxazolidine ring has an envelope conformation
and the methyl group possesses the axial position in
7.9, J 12.7, H(4b)), 4.17 (t, 1H, J 7.9, H(3)), 5.33 (t,
3
1H, J 7.9, H(5)), 7.15 (m, 1H, Hb), 7.25 (m, 1H, Hp Ã
/
Ph), 7.31 (m, 2H, Hm ÃPh), 7.36 (m, 2H, Ho Ã
/
/
Ph), 7.58
3
(dt, 1H, J 1.0, J 7.9, Hd), 7.66 (dt, 1H, J 1.9, J 7.7,
4
3
4
the
C(3A) 115.08), whereas the pyridyl substituted is located
in an anticlinal arrangement with the C(2)ÃC(3)
bond.
isoxazolidine
ring
(C(1A)Ã
/
N(1A)Ã
/
C(4A)Ã
/
Hc), 8.51 (ddd, 1H, J 1.0, 1.9, J 5, Ha). 13C NMR
(CDCl3): d 44.61 (Me), 45.61 (C(4), 74.28 (C(3)), 78.49
4
3
/
(C(5)), 121.35 (C(d)), 122.46 (C(b)), 126.41 (Co Ã
/Ph),

A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ
/777
775
Fig. 3. Intermolecular interactions in the structures of [Zn(L)Cl2] complex and nature of its supramolecular isomerism: (A) dimeric centrosymmetric
ensemble sustained by pÁ Á Áp stacking interaction between pyridine functions in 1a; (B) polar chain formed by pÁ Á Áp stacking between pyridine and
phenyl groups in structure 1b.
(t, 1H, 3J 7.9, H(5)), 7.21 (m, 1H, Hb), 7.25 (m, 1H, Hp Ã
Ph), 7.35 (m, 2H, Hm ÃPh), 7.43 (m, 2H, Ho Ã
Ph), 7.56
/
Table 2
Selected angles (8) for structure of 2a ([Zn(cis-L)Cl2]×0.5CHCl3)
/
/
(dt, 1H, J 1.0, J 7.9, Hd), 7.69 (dt, 1H, J 1.9, J 7.7,
4
3
4
3
4
3
Hc), 8.57 (ddd, 1H, J 1.0, 1.9, J 5, Ha). 13C NMR
(CDCl3): d 44.25 (C(4)), 46.26 (Me), 74.28 (C(3)), 79.31
Bond angles
N(2)ÃZn(1)ÃN(1)
81.43(16) N(1)ÃC(6)ÃC(5)
110.8(4)
102.3(4)
Cl(2)ÃZn(1)ÃCl(1) 119.97(5) N(1)ÃC(6)ÃC(7)
(C(5)), 121.94 (C(d)), 122.73 (C(b)), 126.68 (Co Ã
/
Ph),
Ph), 136.95 (C(c)), 140.49
Py).
C(8)ÃO(1)ÃN(1)
O(1)ÃN(1)ÃC(15) 106.9(4)
O(1)ÃN(1)ÃC(6) 106.3(3)
C(15)ÃN(1)ÃC(6) 111.2(4)
C(8)ÃC(7)ÃC(6)
O(1)ÃC(8)ÃC(7)
C(6)ÃN(1)ÃZn(1) 108.1(3)
C(5)ÃN(2)ÃZn(1) 114.8(3)
N(2)ÃC(5)ÃC(6)
109.5(3)
N(2)ÃZn(1)ÃN(1)ÃC(6) ꢃ21.5(3)
N(1)ÃZn(1)ÃN(2)ÃC(1) ꢃ164.7(4)
127.93 (Cp Ã
/
Ph), 128.52 (Cm Ã
/
(Cipso Ph), 149.40 (C(a)), 159.47 (Cipso
Ã
/
Ã
/
N(1)ÃZn(1)ÃN(2)ÃC(5)
O(1)ÃN(1)ÃC(6)ÃC(5)
Zn(1)ÃN(1)ÃC(6)ÃC(5)
O(1)ÃN(1)ÃC(6)ÃC(7)
C(15)ÃN(1)ÃC(6)ÃC(7)
12.9(3)
145.1(4)
26.4(4)
cis-L, 1H NMR (DMSO-d6): d 2.46 (dt, 1H, 3J 6.9, 2J
12.3, H(4a)), 2.74 (s, 3H, NCH3), 3.23 (dt, 1H, 3J 7.7, 2J
101.9(4)
101.4(4)
20.5(5)
136.5(4)
3
3
12.3, H(4b)), 4.19 (t, 1H, J 6.9, H(3)), 5.32 (t, 1H, J
7.36 (m, 3H, Hm Ã, Hp Ã
/
/
C(8)ÃO(1)ÃN(1)ÃC(15) ꢃ112.5(4)
C(6)ÃC(7)ÃC(8)ÃC(9)
7.7, H(5)), 7.19ꢀ Ph), 7.22 (m,
/
1H, Hb), 7.3 (m, 2H, Ho Ã
/
4
Ph), 7.58 (dt, 1H, J 1.0, J
3
118.4(4)
159.5(4)
7.9, Hd), 7.78 (dt, 1H, 4J 1.9, 3J 7.7, Hc), 8.51 (ddd, 1H,
4J 1.0, 1.9, J 5, Ha). 13C NMR (DMSO-d6): d 45.0
(C(4)), 44.57 (Me), 73.37 (C(3)), 77.95 (C(5)), 121.69
3
Table 3
Selected angles (8) for structure of 2aꢀ
/b
(C(d)), 122.83 (C(b)), 126.90 (Co Ã
/
Ph), 127.81 (Cp Ã
/
Ph),
Ph),
128.62 (Cm Ã
/
Ph), 137.23 (C(c)), 142.02 (Cipso
Ã
/
Bond angles
149.27 (C(a)), 160.78 (Cipso
Ã
/
Py).
N(2)ÃZn(1)ÃN(1)
Cl(1)ÃZn(1)ÃCl(2)
C(3)ÃO(1)ÃN(1)
O(1)ÃN(1)ÃC(4)
O(1)ÃN(1)ÃC(1)
C(3A)ÃO(1)ÃN(1)
81.98(16) C(4)ÃN(1)ÃC(1)
112.0(4)
105.1(3)
102.0(5)
111.2(3)
116.7(3)
101.6(9)
1
trans-L, H NMR (DMSO-d6): d 2.56 (ddd, 1H, J
3
115.82(7)
106.8(4)
106.8(3)
106.6(3)
106.3(5)
N(1)ÃC(1)ÃC(2)
O(1)ÃC(3)ÃC(2)
C(1)ÃN(1)ÃZn(1)
C(5)ÃN(2)ÃZn(1)
O(1)ÃC(3A)ÃC(2)
2
7.7, 8.5, J 12.3, H(4b)), 2.67 (s, 3H, NCH3), 2.88 (ddd,
1H, 3J 6.5, 7.7, 2J 12.3, H(4a)), 4.04 (dd, 1H, 3J 6.5, 8.5,
H(3)), 5.07 (t, 1H, 3J 7.7, H(5)), 7.19ꢀ
/
7.36 (m, 3H, Hm Ã
/
, Hp Ã
/
Ph), 7.33 (m, 1H, Hb), 7.42 (m, 2H, Ho Ã
/
Ph), 7.58
3
(dt, 1H, J 1.0, J 7.9, Hd), 7.82 (dt, 1H, J 1.9, J 7.7,
4
3
4
127.6 (Cp Ã
/
Ph), 128.44 (Cm Ã
/
Ph), 136.95 (C(c)), 141.4
4
3
Hc), 8.55 (ddd, 1H, J 1.0, 1.9, J 5, Ha). 13C NMR
(DMSO-d6): d 44.71 (C(4)), 44.57 (Me), 73.65 (C(3)),
(Cipso
Ã
/
Ph), 149.08 (C(a)), 160.29 (Cipso
Ã
/
Py).
1
3
78.99 (C(5)), 122.37 (C(d)), 123.19 (C(b)), 127.07 (Co Ã
/
trans-L, H NMR (CDCl3): d 2.71 (ddd, 1H, J 7.2,
7.9, 2J 12.7, H(4a)), 2.80 (s, 3H, NCH3), 2.88 (dt, 1H, 3J
Ph), 128.13 (Cp Ã
/
Ph), 128.77 (Cm Ã
/
Ph), 137.34 (C(c)),
Py).
7.9, 2J 12.7, H(4b)), 4.03 (dt, 1H, J 7.2, 7.9 H(3)), 5.22
3
141.15 (Cipso Ph), 149.40 (C(a)), 159.59 (Cipso
Ã
/
Ã
/

776
A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ777
/
˚
Fig. 4. Structure of the dimeric [Cu(L)Cl2]2 complex. Selected bond lengths, A: Cu(1A)ÃN(2A) 1.996(7); Cu(1A)ÃN(1A) 2.077(7); Cu(1A)ÃCl(2A)
2.245(3); Cu(1A)ÃCl(1B) 2.795(2).
4.1.4. [Cu(cis-/trans-L)Cl2]2 (4aꢀb)
A sample of L (0.065 g, 0.27 mmol) in warm 2-
propanol (5 ml) was added to a C5H11O solution (10 ml)
/
Table 4
Selected angles (8) for structure of 4aꢀ
/b
Bond angles
N(2A)ÃCu(1A)ÃN(1A)
Cl(2A)ÃCu(1A)ÃCl(1A) 94.33(10) C(4A)ÃN(1A)ÃO(1A) 106.3(6)
N(2A)ÃCu(1A)ÃCl(2A) 94.4(2)
N(1A)ÃCu(1A)ÃCl(2A) 148.1(2)
N(2A)ÃCu(1A)ÃCl(1A) 168.9(2)
N(1A)ÃCu(1A)ÃCl(1A) 95.4(2)
C(2A)ÃC(3A)ÃC(4A)
N(1A)ÃC(4A)ÃC(3A)
of CuCl2×
/
2H2O (0.046 g, 0.27 mmol). A light-green
80.6(3)
C(2A)ÃO(1A)ÃN(1A) 105.5(7)
precipitate was formed at once. After cooling to r.t., the
precipitate was separated, washed with cold 2-propanol
and dried in vacuo to afford a solid 0.062 g (74%). Anal.
Found: C, 48.0; H, 4.1; N, 7.4. Calc. for
C15H16Cl2CuN2O: C, 47.94; H, 4.29; N, 7.46%. Crystals
of the complex, green platelets, were grown by the slow
O(1A)ÃN(1A)ÃC(1A) 105.5(7)
C(4A)ÃN(1A)ÃC(1A) 111.8(8)
C(3A)ÃC(2A)ÃO(1A) 107.7(12)
O(1A)ÃN(1A)ÃCu(1A) 102.1(4)
107.6(10) C(1A)ÃN(1A)ÃCu(1A) 116.3(6)
105.1(8)
liquid diffusion in next mixtures CHCl3ꢀ
/
2-propanolꢀ
/
C6H14 and 2-propanolꢀDMF as well as an isothermal
/
evaporation of CHCl3 solution.
4.1.2. [Zn(cis-/trans-L)Cl2] (2aꢀ
/
b)
A warm mixture 2-propanolꢀC3H6O solution (8/4 ml)
/
Table 5
of L (0.090 g, 0.375 mmol) was added to 2-propanol (5
ml) containing ZnCl2 (0.051 g, 0.375 mmol). The red
precipitate was formed immediately. After cooling to
room temperature (r.t.), the precipitate of 1 was
separated, washed with cold 2-propanol and dried in
vacuum. Yield: 0.086 g (61%). Anal. Found: C, 48.4; H,
4.3; N, 7.4. Calc. for C15H16Cl2N2OZn: C, 47.84; H,
Crystal data and structure refinement for compounds 2a, 2aꢀ
/
b and
4aꢀ
/
b
Compound
2a
2aꢀ/b
4aꢀb
/
Temperature (K)
Crystal system
Space group
100(2)
triclinic
¯
P1/
223(2) 293(2)
orthorhombic orthorhombic
/
Pna21
P212121
8.9215(11)
14.9093(18)
25.089(3)
90.00
˚
a (A)
8.5986(4)
9.9688(4)
23.1035(12) 13.1536(9)
16.9776(11)
7.3273(5)
4.28; N, 7.44%. Recrystallization from 2-propanolꢀ
/
˚
b (A)
CHCl3 afforded single crystals of 1a (orange) and 1b
(white).
˚
c (A)
a (8)
b (8)
g (8)
U (A )
Z
80.410(3)
80.170(3)
65.075(3)
90.00
90.00
90.00
90.00
90.00
4.1.3. [Pd(cis-/trans-L)Cl2] (3aꢀb)
/
3
˚
1759.61(14) 1636.3(2)
4
3337.1(7)
8
1.492
A warm methanolic solution (5 ml) of L (0.156 g, 0.65
mmol) was added to a warm MeOH (5 ml) containing
Na2[PdCl4] (0.191 g, 0.65 mmol). A yellow precipitate
was formed at once. The reaction mixture was cooled to
4
Dcalc (Mg mꢃ3
)
1.647
1.931
Reflections collected 10 601
1.529
1.826
8322
2667
0.0622
0.0371
0.0885
m (mmꢃ1
)
1.628
15 181
4761
Reflections unique
6840
r.t., the precipitate of 3aꢀb was filtered, washed with
/
Rint
R1
0.0807
0.0582
0.1757
0.1013
0.0569
0.1325
cold MeOH and dried. Yield: 0.185 g (65%). Anal.
Found: C, 43.2; H, 3.8; N, 6.6. Calc. for
C15H16Cl2N2OPt: C, 43.62; H, 3.93; N, 6.60%.
wR2

A.B. Lysenko et al. / Polyhedron 21 (2002) 769ꢀ
/777
777
4.2. Measurements
(fax: ꢂ44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk
/
or www: http://www.ccdc.cam.ac.uk).
The IR spectrum of liquid L was recorded on a UR-10
(Carl Zeiss, Jena) spectrometer (film between KBr discs;
400ꢀ
/
4000 cmꢃ1).
References
1H (300 MHz), 13C (75.5 MHz) NMR spectra were
recorded at r.t. on a Bruker Avance DPX300 spectro-
meter equipped with a 5 mm QNP-Z probe (1H, 13C,
15N, 31P). The solvents were CDCl3, C3H6O-d6 and
[1] K.B.G. Torssell, Nitrile Oxides, Nitrones, and Nitronates in
Organic Synthesis Novel Strategies in Synthesis, VCH Publishers,
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[2] P. DeShong, W. Li, J.W. Kennington, J.L. Ammon, H.L.
Ammon, J. Org. Chem. 56 (1991) 1364.
DMSO-d6ꢀ
/
THF-d8 mixture (internal standard*TMS).
/
Standard Bruker software and microprograms were
applied for all NMR experiments. The sweep width
[3] H.G. Aurich, M. Geiger, C. Gentes, K. Harms, H. Koster,
Tetrahedron 54 (1998) 3181.
1
covered was 3000 Hz for H, digitalized in 16 K, and
[4] P. DeShong, M.C. Dicken, J.M. Leginus, R.R. Whittle, J. Am.
Chem. Soc. 106 (1984) 5598.
15 000 Hz for 13C, digitalized in 64 K.
Crystallographic measurements were made using a
Siemens SMART CCD area-detector three-circle diffract-
ometer (KappaCCD for 2a). Graphite monochromated
[5] M. Ito, Ch. Kibayashi, Tetrahedron 47 (1991) 9329.
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[7] P. Marino, S. Franco, N. Garces, F.L. Merchan, T. Tejero, Chem.
Commun. (1998) 493.
˚
0.71073 A) was employed. The
Mo Ka radiation (lꢁ
/
[8] E. Colacino, A. Converso, A. De Nino, A. Leggio, A. Liguori, L.
Maiulo, A. Napoli, A. Procopio, C. Siciliano, G. Sindona,
Nucleosides Nucleotides 18 (1990) 581.
data frames were integrated using SAINT [29] and
empirical absorption corrections (SADABS) [29] were
employed. The essential experimental conditions and
resulting crystal data are given in Table 5. All structures
[9] P.N. Canfalone, F. Jin, S.A. Mousa, Bioorg. Med. Chem. Lett. 9
(1999) 55.
[10] G. Broggini, F. Folcio, M. Sardone, G. Zecchi, Tetrahedron 52
(1996) 11849.
were solved by direct methods using the SHELXTL-PLUS
set of programs [30], and refined by full-matrix least-
squares methods. Positions of the hydrogen atoms were
idealized.
The CHCl3 of crystallization in structure 2a have no
close contacts with other atoms and fill up emptiness of
the crystal. These solvate molecules are disordered over
two closely situated positions with partial site occupancy
factors at 0.7 and 0.3.
[11] P. Bravo, L. Bruche, A. Farina, G. Fronza, S.V. Meille, A Merli,
Tetrahedron: Asymmetry 4 (1993) 2131.
[12] P.C.B. Page, M. Purdie, D. Lathbury, Tetrahedron 53 (1997)
7365.
[13] B. Carboni, M. Ollivault, F. Le Bouguenec, R. Carrie, M. Jazouli,
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[14] T. Geffault, U. Bauer, K. Airola, A.M.P. Koskinen, Tetrahedron:
Asymmetry 7 (1996) 3099.
[15] K.V. Gothelf, R.G. Hazell, K.A. Jørgensen, J. Org. Chem. 61
(1996) 346.
In structure 2aꢀ/b high anisotropy of thermal motion
[16] R.C. Bernotas, J.S. Jeffrey, I. Sing, D. Friedrich, Synlett (1999)
653.
for C(3)ÃC6H5 carbon atoms suggested that this frag-
/
ment of the molecule is disordered. The disorder was
resolved under constraining the standard geometry of
the phenyl rings and refinement of partial occupancies
led to values of 0.72 and 0.28. Refinement of the
disorder proceeded smoothly and therefore it was
possible to refine all atoms of the major component
anisotropically, while atoms of the minor component
were left isotropic and the hydrogen atoms of phenyl
cycle were not included. Actually the same problem was
observed for copper complex 4. In this case, all attempts
[17] K.B. Simonsen, K.A. Jorgensen, Q.-S. Hu, L. Pu, Chem.
Commun. (1999) 811.
[18] T. Ishikawa, T. Kudo, K. Shigemori, S. Saito, J. Am. Chem. Soc.
122 (2000) 7633.
[19] C. Mukai, I.J. Kim, W.J. Cho, M. Kido, M. Hanaoka, J. Chem.
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[20] C. Baldoli, P.D. Buttero, E. Licandro, S. Maiorana, A. Papagni,
A. Aibinati, A. Papagni, Tetrahedron: Asymmetry 5 (1994) 809.
[21] K.B. Jensen, R.G. Hazell, K.A. Jorgensen, J. Org. Chem. 64
(1999) 2353.
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Jorgensen, J. Am. Chem. Soc. 121 (1999) 3845.
[23] A.B. Lysenko, O.V. Shishkin, R.D. Lampeka, Z. Naturforsch.
55b (2000) 373.
to divide the oscillatory movement of CÃ
/
C6H5 between
two positions with different partial occupancies were not
successful.
[24] R.D. Lampeka, A.B. Lysenko, Zh. Obshchei Khim. 70 (2000)
1900.
[25] A.B. Lysenko, S.V. Shishkina, O.V. Shishkin, E. Peralta-Pe´rez, F.
Lo´pez-Ortiz, R.D. Lampeka, Polyhedron 20 (2001) 957.
[26] P. DeShong, C.M. Dicken, R.R. Staib, A.J. Freyer, S.M.
Weinreb, J. Org. Chem. 47 (1982) 4397.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
[27] C. Janiak, J. Chem. Soc., Dalton Trans. (2000) 3885.
[28] G.R. Desiraju, Crystal Engineering: The Design of Organic
Solids, Elsevier, New York, 1989.
Data Centre, CCDC No. 164044ꢀ
/
164046 for com-
[29] Siemens X-Ray Instruments, Madison, WI, 1995.
pounds 2a, 2aꢀb and 4. Copies of this information
/
[30] G.M. Sheldrick, SHELXTL PLUS. PC Version. A system of
computer programs for the determination of crystal structure
from X-ray diffraction data, Review 5-02-1994.
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK