Electrochemical synthesis and characterization of zinc(II) complexes with [(4-methylphenyl) sulfonyl]-1H-amido-2-phenyl-2-oxazolines

Article abstract of DOI:10.1002/1521-3749(200206)628:5<1210::AID-ZAAC1210>3.0.CO;2-F

A series of [(4-methylphenyl)sulfonyl]-1H-amido-2-phenyl-2-oxazoline ligands, HTs-ROz, has been synthesized by the reaction of substituted 2-(2-aminophenyl)oxazolines and p-toluensulfonyl chloride. The electrochemical oxidation of a sacrificial zinc anode in an acetonitrile solution of the corresponding ligand gave compounds of general formula [Zn(Ts-ROz)₂]. All complexes have been characterized by microanalysis, IR and ¹H NMR spectroscopy and single-crystal X-ray diffraction. In all cases, the metal atom is coordinated by the nitrogen atoms of two monoanionic ligands.

Full text of DOI:10.1002/1521-3749(200206)628:5<1210::AID-ZAAC1210>3.0.CO;2-F

Electrochemical Synthesis and Characterization of Zinc(II) Complexes with
[(4-Methylphenyl)Sulfonyl]-1H-Amido-2-Phenyl-2-Oxazolines
a,*
a
a
b
b
´
´
´
´
´
Jesus Castro , Santiago Cabaleiro , Paulo Perez-Lourido , Jaime Romero , Jose A. Garcıa-Vazquez , and
Antonio Sousab,*
a
´
´
Vigo/Spain, Departamento de Quımica Inorganica, Universidade de Vigo
b
´
´
Santiago de Compostela/Spain, Departamento de Quımica Inorganica, Universidade de Santiago de Compostela
Received December 3rd, 2001.
Dedicated to Professor Joachim Strähle on the Occasion of his 65th Birthday
Abstract. A series of [(4-methylphenyl)sulfonyl]-1H-amido-2-phe-
nyl-2-oxazoline ligands, HTs-ROz, has been synthesized by the re-
action of substituted 2-(2-aminophenyl)oxazolines and p-toluensul-
fonyl chloride. The electrochemical oxidation of a sacrificial zinc
anode in an acetonitrile solution of the corresponding ligand gave
compounds of general formula [Zn(Ts-ROz)2]. All complexes have
been characterized by microanalysis, IR and 1H NMR spectros-
copy and single-crystal X-ray diffraction. In all cases, the metal
atom is coordinated by the nitrogen atoms of two monoanionic li-
gands.
Keywords: Zinc; Electrochemical synthesis; Oxazolines; Sulfona-
mide complexes; Crystal structure
Elektrochemische Synthese und Charakterisierung von Zink(II)-Komplexen mit
[(4-Methylphenyl)sulfonyl]-1H-amido-2-phenyl-2-oxazolinen
Inhaltsübersicht. Eine Serie von [(4-Methylphenyl)sulfonyl]-1H-
amido-2-phenyl-2-oxazolin-Liganden HTs-ROz wurden durch Re-
aktion von substituierten 2-(2-Aminophenyl)oxazolinen mit p-To-
luolsulfonylchlorid synthetisiert. Die elektrochemische Oxidation
von Opfer-Zink-Anoden in Acetonitrillösungen der entsprechen-
den Liganden führt zu Verbindungen der Formel [Zn(Ts-ROz)2].
Alle Komplexe wurden durch Mikroanalysen, IR- und H-NMR-
Spektren und durch Einkristall-Strukturanalysen charakterisiert.
In allen Fällen sind die Metallatome durch die N-Atome zweier
monoanionischer Liganden koordiniert.
1
1 Introduction
atoms, which are capable of chelating behaviour, have been
found to be effective for this type of transformation.
Among the various types of such ligands, those contain-
ing oxazoline rings and a sulfonamide group as donor
centres have been chosen for this study (See scheme 1).
It is very well known that dialkylzinc compounds are used
in the presence of chiral ligands for the asymmetric syn-
thesis of alcohols from prochiral ketones [1]. It has been
suggested that the actual zinc compound is derived from
the interaction of the dialkylzinc and the chiral ligand. For
this reason, an understanding of the enantiomeric excess
produced in the reaction requires an understanding of the
nature of such an intermediate. The work described in this
paper involves the synthesis and elucidation of the molecu-
lar structures of some zinc complexes of nitrogen ligands.
In particular, chiral amines bearing multiple nitrogen
* Prof. J. Castro
Departamento de Quımica Inorganica, Universidade de Vigo,
´
E-36200 Vigo, Galicia/Spain
Tel: ϩ34-986-812-278; Fax: ϩ34-986-813-798;
E-mail: fojo@uvigo.es
Scheme 1
** Prof. A. Sousa
Departamento de Quımica Inorganica, Universidade de Santiago
´
The reason for this choice is that oxazoline rings bearing
chiral centres can be easily prepared and that a sulfonamide
group can be deprotonated. In this way, the proligands can
be transformed into bidentate mononionic ligand systems.
de Compostela,
E-15706, Santiago de Compostela, Galicia/Spain
Tel: ϩ34-981-563-100 ext 14245; Fax: ϩ34-981-597-525; E-mail:
qiansoal@usc.es.
1210
 WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 0044Ϫ2313/02/628/1210Ϫ1217 $ 20.00ϩ.50/0 Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217

Zinc(II) Complexes with [(4-Methylphenyl)Sulfonyl]-1H-Amido-2-Phenyl-2-Oxazolines
Table 1 Summary of crystal data and structure refinement.
Identification code
[Zn(TsOz)2]
[Zn(Ts-5MeOz)2]
[Zn(Ts-4MeOz)2]
[Zn (Ts-4EtOz)2]
[Zn(Ts-4iPrOz)2]
Empirical formula
Formula weight
C32H30N4O6S2Zn
696.09
C34H34N4O6S2Zn
724.17
C34H34N4O6S2Zn
724.17
C36H38N4O6S2Zn
752.22
C38H40N4O6S2Zn
778.23
Temperature
Wavelength
Crystal system, space group
Unit cell dimensions
293(2) K
0.71073 A
triclinic, P1 (#2)
a ϭ 9.7607(1) A
b ϭ 12.1370(1) A
c ϭ 13.7243(2) A
293(2) K
0.71073 A
293(2) K
0.71073 A
293(2) K
0.71073 A
293(2) K
1.54184 A
˚
˚
˚
¯
orthorhombic, Pnaa (#56) monoclinic, P21/n (#14) orthorhombic, Fddd (#70) monoclinic, C2/c (#15)
a ϭ 12.8384(1) A
b ϭ 13.5934(2) A
c ϭ 18.9643(2) A
˚
˚
˚
˚
˚
˚
˚
˚
˚
˚
˚
a ϭ 14.8100(3) A
b ϭ 15.0892(3) A
c ϭ 16.7306(4) A
a ϭ 21.8490(2) A
b ϭ 23.0172(4) A
c ϭ 29.1244(3) A
a ϭ 21.0493(3) A
b ϭ 11.1935(12) A
c ϭ 16.6097(10) A
˚
˚
˚
˚
α ϭ 89.9111(7)°
β ϭ 86.1672(9)°
γ ϭ 72.8279(8)°
1549.62(3) A
2, 1.492 Mg/m3
0.979 mmϪ1
720
α ϭ 90°
β ϭ 90°
γ ϭ 90°
3309.60(7) A
4, 1.453 Mg/m3
0.920 mmϪ1
1504
α ϭ 90°
β ϭ 105.9562(5)°
γ ϭ 90°
3594.76(13) A
4, 1.338 Mg/m3
0.847 mmϪ1
1504
α ϭ 90°
β ϭ 90°
γ ϭ 90°
14646.7(3) A
16, 1.364 Mg/m3
0.834 mmϪ1
6272
α ϭ 90°
β ϭ 100.917(6)°
γ ϭ 90°
3842.7(5) A
4, 1.345 Mg/m3
2.310 mmϪ1
1624
3
3
3
3
3
˚
˚
˚
˚
˚
Volume
Z, Calculated density
Absorption coefficient
F(000)
Crystal size
θ range for data collection
Limiting indices
0.40 ϫ 0.25 ϫ 0.15 mm
1.49 to 28.29°
Ϫ9ՅhՅ13
Ϫ15ՅkՅ16
Ϫ18ՅlՅ15
0.6 ϫ 0.1 ϫ 0.05 mm
1.84 to 28.36°
Ϫ15ՅhՅ17
Ϫ15ՅkՅ18
Ϫ25ՅlՅ18
22446 / 4114
[R(int) ϭ 0.0638]
99.3 %
0.45 ϫ 0.35 ϫ 0.20 mm 0.50 ϫ 0.35 ϫ 0.25 mm
0.25 ϫ 0.15 ϫ 0.10 mm
4.28 to 75.90°
Ϫ26ՅhՅ26
Ϫ14ՅkՅ14
0ՅlՅ20
8089 / 4002
[R(int) ϭ 0.0411]
100.0 %
1.63 to 28.30°
Ϫ18ՅhՅ19
Ϫ20ՅkՅ19
Ϫ21ՅlՅ22
24851 / 8894
[R(int) ϭ 0.0264]
99.5 %
1.46 to 28.20°
Ϫ28ՅhՅ28
Ϫ30ՅkՅ11
Ϫ38ՅlՅ38
Reflections collected / unique 10757 / 7405
[R(int) ϭ 0.0162]
96.1 %
25960 / 4508
[R(int) ϭ 0.0331]
99.8 %
Completeness to θ Max.
Data / restraints / parameters 7405 / 0 / 406
4114 / 0 / 215
1.097
8894 / 0 / 424
1.069
4508 / 0 / 224
1.100
4002 / 0 / 231
1.013
Goodness-of-fit on F2
1.027
Final R indices [I Ͼ 2σ(I)]
R1 ϭ 0.0330
wR2 ϭ 0.0875
R1 ϭ 0.0425
wR2 ϭ 0.0939
R1 ϭ 0.0588
wR2 ϭ 0.1087
R1 ϭ 0.1088
wR2 ϭ 0.1266
R1 ϭ 0.0431
wR2 ϭ 0.0967
R1 ϭ 0.0661
wR2 ϭ 0.1071
R1 ϭ 0.0392
wR2 ϭ 0.1212
R1 ϭ 0.0526
wR2 ϭ 0.1318
1.008 and Ϫ0.347 e·AϪ3
R1 ϭ 0.0422
wR2 ϭ 0.1076
R1 ϭ 0.0914
wR2 ϭ 0.1298
˚
0.498 and Ϫ0.303 e·A
R indices (all data)
Ϫ3
Ϫ3
0.406 and Ϫ0.480 e·AϪ3 0.312 and Ϫ0.326 e·AϪ3
0.303 and Ϫ0.284 e·A
˚
Largest diff. Peak and hole
˚
2 Results and Discussion
Table 2 Selected bond distances/A and angles/° for [Zn(TsOz)2].
The analytical results show that the electrochemical pro-
cedure described (vide infra) is an effective method for the
synthesis of zinc complexes with [(4-methylphenyl)sulfonyl]-
1H-amido-2-phenyl-2-oxazoline ligands and represents a
simple alternative to other standard chemical procedures.
The compounds are of the general formula [Zn(Ts-ROz)2]
where Ts-ROzϪ represents the anion of the corresponding
ligand. The electrochemical efficiency value, Ef, defined as
the amount of metal dissolved per Faraday of charge, was
always close to 0.5 mol·FϪ1. This fact, along with the evol-
ution of hydrogen at the cathode, is consistent with the fol-
lowing reaction mechanism:
Zn-N(21)
Zn-N(12)
Zn-O(21)
S-O(12)
S(1)-C(110)
N(11)-C(11)
O(13)-C(13)
1.9854(15)
2.0016(14)
2.6801(14)
1.4431(15)
1.7753(19)
1.478(2)
Zn-N(22)
Zn-N(11)
S-O(11)
S(1)-N(12)
N(11)-C(13)
N(12)-C(19)
O(13)-C(12)
2.0001(15)
2.0263(16)
1.4419(15)
1.6021(15)
1.281(2)
1.408(2)
1.458(3)
1.351(2)
N(21)-Zn-N(22)
N(22)-Zn-N(12)
N(11)-Zn-N(22)
N(21)-Zn-O(21)
N(12)-Zn-O(21)
O(11)-S(1)-O(12)
91.98(6)
123.35(6)
122.74(7)
148.67(6)
86.13(5)
N(21)-Zn-N(12)
N(21)-Zn-N(11)
N(12)-Zn-N(11)
N(22)-Zn-O(21)
N(11)-Zn-O(21)
123.28(6)
106.50(6)
90.63(6)
59.85(5)
81.30(6)
116.44(10)
O(11)-S(1)-N(12) 105.68(8)
Cathode: 2 HTs-ROz ϩ 2eϪ Ǟ 2 Ts-ROzϪ ϩ H2
Anode : Zn ϩ 2 Ts-ROzϪ Ǟ [Zn(Ts-ROz)2] ϩ 2eϪ
The compound consists of discrete molecules without sig-
nificant interactions between one another. The zinc atom is
coordinated to two monoanionic bidentate chelating li-
gands, which are bonded to the metal atom through their
sulfonyl and oxazoline nitrogen atoms. Although electron
density data does not normally provide sufficient evidence
to decide if the coordination of the oxazoline ring is
through the nitrogen or the oxygen atom, the fact that the
CϭN double bond is shorter than the CϪO bond leads us
to conclude that the metal is coordinated through the nitro-
gen atom of the oxazoline ring.
2.1 X-ray Structural Studies
Table 1 lists crystal data, experimental details, refinement
results and details of structure determination.
Description of the structure of [Zn(TsOz)2] (1)
The molecular structure of compound 1 is shown in Fig. 1
together with the labelling scheme used. Selected bond
lengths and angles, along with estimated deviations, are
summarised in Table 2.
The coordination sphere around the zinc atom can be
described as slightly distorted tetrahedral with a dihedral
angle between chelate rings of 81.91(6)°, which is not far
Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217
1211

´
´
´
J. Castro, S Cabaleiro, P. Perez-Lourido, J. Romero, J. A Garcıa-Vazquez, A. Sousa
Fig. 2 The molecular structure of [Zn(Ts-5MeOz)2].
˚
Table 3 Selected bond distances/A and angles/° for [Zn(Ts5-
MeOz)2].
Fig. 1 The molecular structure of [Zn(TsOz)2].
Zn-N(1)
Zn-N(2)
Zn-O(2)
S(2)-O(1)
S(2)-N(29
N(1)-C(4)
N(2)-C(10)
O(3)-C(4)
1.988(3)
2.011(2)
2.759(2)
1.435(2)
1.608(3)
1.279(4)
1.402(4)
1.343(4)
Zn-N(1Ј)
Zn-N(2Ј)
Zn-O(2Ј)
S(2)-O(2)
S(2)-C(11)
N(1)-C(1)
N(2)-S(2)
O(3)-C(2)
1.988(3)
2.011(2)
2.759(2)
1.453(3)
1.771(3)
1.468(4)
1.608(3)
1.472(5)
from the theoretical value. The main source of the distor-
tion is the small bite angle of these chelate rings, which is
close to 90°. This situation makes the other angles around
the metal larger than the theoretical value, with the biggest
angle being 123.35(6)° for N(amide)ϪZnϪN(amide). A
weak contact between the zinc atom and the O(21) atom of
the sulfonyl group is also observed, with the bond distance
N(1)-Zn-N(1Ј)
N(1Ј)-Zn-N(2)
N(1Ј)-Zn-N(2Ј)
N(1)-Zn-O(2)
N(2)-Zn-O(2)
N(1)-Zn-O(2Ј)
N(2)-Zn-O(2Ј)
105.66(15)
121.47(10)
91.12(10)
142.21(9)
58.65(9)
76.88(9)
95.87(9)
N(1)-Zn-N(2)
N(1)-Zn-N(2Ј)
N(2)-Zn-N(2Ј)
N(1Ј)-Zn-O(2)
N(2Ј)-Zn-O(2)
N(1Ј)-Zn-O(2Ј)
N(2Ј)-Zn-O(2Ј)
91.12(10)
121.47(10)
126.74(15)
76.88(9)
95.87(9)
142.21(9)
58.65(9)
˚
ZnϪO(21) being 2.6801(14) A. This weak interaction
makes the N(11)ϪZnϪN(22) bond angle, 122.74(7)°,
slightly longer than one would expect for a regular tetra-
hedron. If this interaction is taken into account, the metal
atom would be in a [ZnN4O] five-coordinate environment
with a τ value [2] of 0.42 [τ ϭ (β Ϫ α)/60, where β and α are
the bond angles N(21)ϪZnϪO(21) and N(22)ϪZnϪN(12),
respectively]. This situation suggests that the complex can
be described as being 58 % along the distortion pathway
between a trigonal bipyramid (τ ϭ 1) and a square pyramid
(τ ϭ 0).
Symmetry transformations used to generate equivalent atoms: (Ј)ϭ x, .5Ϫy,
.5Ϫz
presence of the oxygen atom in the coordination sphere of
the metal.
The two ZnϪN(oxazoline) bond distances are slightly
different from each other and have values of 1.9854(15) and
2.0263(16) A. The difference is probably due to steric effects
Description of the structure of [Zn(Ts-5MeOz)2] (2)
˚
The molecular structure of compound 2 is shown in Fig. 2.
Selected bond distances and angles are summarised in Table
3. The substitution of a methyl group for a β-hydrogen
atom in the oxazoline ring causes only minor changes in
the structure of the compound. This complex also exists as
a monomer that does not experience significant contacts
with neighbouring molecules. The coordination polyhedron
around the metal is best described as a tetrahedron, with
small chelate angles of 91.12(10)° and values of the
N(amide)ϪZnϪN(amide) angle of 126.74(15)°.
However, the compound is now centrosymmetric and
crystallizes in an orthorhombic space group. This is a
consequence of a twist in one of the sulfonyl groups
through the SϪN bond. This twist has the effect of moving
the oxygen atoms of the SO2 away from one another, mean-
ing that they are now related by symmetry. The zinc atom
and, despite this fact, the values are very similar to those
found in other zinc complexes with ligands containing
˚
oxazoline rings; for instance 2.031(4) A in {dichloro-bis[5-
(2-methylallyl)-2-phenyl-1,3-oxazole-N]}zinc(II)
2.066(3) A in {dichloro-[2-(2Ј-(diphenylphosphino) phe-
[3]
or
˚
nyl)]-4,5-dihydro-4-phenyloxazole}zinc(II)
[4].
The
˚
ZnϪN(amide) bond distances, 2.0001(15) and 2.0016(14) A
˚
(average 2.0008 A), are longer than those found in other
complexes containing an amide nitrogen and a zinc atom
˚
in a tetrahedral environment; for instance 1.942(8) A in
{[N,NЈ-bis(butanesulfonamide)-1,2-diaminocyclohexane]-
˚
(2,2Ј-bipyridyl)}zinc(II) [5], or 1.962(3) A in bis{N-[(2-pyr-
rolyl)methylene]-NЈ-tosylbenzene-1,2-diaminato}zinc(II)
[6]. This increase in the bond lengths could be a conse-
quence of the increase in the coordination number due the
1212
Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217

Zinc(II) Complexes with [(4-Methylphenyl)Sulfonyl]-1H-Amido-2-Phenyl-2-Oxazolines
Fig. 4 The molecular structure of [Zn(Ts-4EtOz)2].
Fig. 3 The molecular structure of [Zn(Ts-4MeOz)2].
is coordinated by two amide nitrogens and two nitrogen
atoms from two oxazoline rings. This gives a distorted tetra-
hedral environment, although once again a bonding inter-
action between O(2) and the zinc atom can be envisaged
˚
[ZnϪO(2) ϭ 2.759(2) A]. If this interaction is taken into
account, the coordination polyhedron around the metal can
be described as a distorted trigonal prism. In this case, each
triangular face of the prism would be formed by the N(ox-
azoline) and the N(amide) atoms, both of which belong to
the same ligand, and one oxygen atom from the other li-
gand. The dihedral angle between these two triangular faces
is 18.13(10)° with the zinc atom situated at a distance
˚
1.2856(16) A from each plane.
The crystals of this compound contain complexes
[Zn(R)(R)] and [Zn(S)(S)]. Figure 2 shows the [Zn(S)(S)]
form of the complex.
Description of the structures of [Zn(Ts-4MeOz)2]
(3), [Zn(Ts-4EtOz)2] (4) and [Zn(Ts-4iPrOz)2] (5)
Fig. 5 The molecular structure of [Zn(Ts-4iPrOz)2].
The molecular structures of these complexes are shown in
Figs. 3, 4 and 5, respectively. Selected bond distances and
angles are given in Tables 4 to 6.
relative position of the groups directly attached to the sulfur
atom in the sulfonamide group.
These compounds are monomeric and the ligands show
a coordination behaviour similar to that described above,
with a distorted tetrahedral environment around the metal
atom. However, the replacement of an α-hydrogen atom by
different R groups in the oxazoline ring causes some
changes in the structures of the complexes. For example,
the presence of these substituents causes steric restrictions
in the complex that force the ligand to adopt configuration
A (according to the FujisawaЈs definition [7]). This configu-
ration should be compared with configuration B, which is
adopted by the free ligand [8]. As can be seen in Scheme 2,
the main difference between the two configurations is the
The influence of the nature of the substituent in the ox-
azoline ring is also reflected in the relative positions ad-
opted by the p-toluene rings of the sulfonamide groups in
the structures of the complexes containing substituents. For
example, the angle formed by the carbon atoms bonded to
the sulfur and the metal changes from 114.04° and 158.63°
for 1 and 2 to 79.70°, 83.41°, 81.48° for compounds 3, 4
and 5, respectively. This increases the distance between the
α-carbon of the oxazoline ring and the p-toluene ring car-
bon atom bonded to sulfur in the complexes containing a
˚
substituent (in the range 5.602Ϫ5.861 A) in comparison to
Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217
1213

´
´
´
J. Castro, S Cabaleiro, P. Perez-Lourido, J. Romero, J. A Garcıa-Vazquez, A. Sousa
˚
Table 4 Selected bond distances/A and angles/° for [Zn(Ts4-
MeOz)2].
Zn-N(11)
Zn-N(21)
Zn-O(11)
S(2)-O(22)
S(2)-N(22)
S(1)-O(12)
S(1)-N(12)
2.000(2)
Zn-N(12)
Zn-N(22)
Zn-O(21)
S(2)-O(21)
S(2)-C(211)
S(1)-O(11)
S(1)-C(111)
2.0019(18)
2.0109(18)
2.6768(17)
1.4416(17)
1.772(2)
1.4429(16)
1.772(2)
2.0084(19)
2.6319(16)
1.4415(17)
1.5999(18)
1.4367(17)
1.6062(18)
Scheme 2
N(11)-Zn-N(12)
N(12)-Zn-N(21)
N(12)-Zn-N(22)
N(11)-Zn-O(11)
N(21)-Zn-O(11)
N(11)-Zn-O(21)
N(21)-Zn-O(21)
O(11)-Zn-O(21)
91.05(8)
106.90(8)
142.96(7)
150.36(7)
86.12(7)
88.10(8)
149.71(7)
86.78(5)
N(11)-Zn-N(21)
N(11)-Zn-N(22)
N(21)-Zn-N(22)
N(12)-Zn-O(11)
N(22)-Zn-O(11)
N(12)-Zn-O(21)
N(22)-Zn-O(21)
111.68(9)
112.38(8)
91.13(7)
60.39(6)
89.81(6)
94.93(6)
59.43(6)
substituent on the oxazoline ring and the p-toluene ring. In
this respect, the value of the N(amide)-Zn-N(amide) bond
angle increases up to 150.36(7), 145.81(10) and 145.96(15)
for complexes 3, 4 and 5, respectively, and, consequently,
the extent of distortion of the geometry around the metal
increases.
In these compounds the distances between the zinc atom
and one oxygen atom from the sulfonyl group are in the
range 2.6291(16)Ϫ2.6768(17) A. This fact can be inter-
˚
Table 5 Selected bond distances/A and angles/° for [Zn(Ts4-
EtOz)2].
˚
preted in terms of a weak interaction between the two
atoms, as discussed in the cases of compounds 1 and 2.
The crystals of compounds 3 and 5 contain [Zn(R)(R)]
and [Zn(S)(S)] forms and the solved were [Zn(S)(S)] and
[Zn(R)(R)], respectively. Crystals of compound 4 contain
only the [Zn(S)(S)] form.
Zn-N(2Ј)
Zn-N(1Ј)
Zn-O(1Ј)
S-O(2)
S-N(2)
N(1)-C(5)
O(3)-C(5)
2.0069(17)
2.0229(18)
2.6291(16)
1.4338(18)
1.6100(16)
1.282(3)
Zn-N(2)
Zn-N(1)
Zn-O(1)
S-O(1)
S-C(12)
N(1)-C(2)
O(3)-C(1)
2.0069(17)
2.0229(18)
2.6291(16)
1.4495(18)
1.775(2)
1.483(3)
1.439(4)
1.349(2)
N(2)-C(7)
1.407(3)
145.81(10)
107.88(7)
91.28(7)
60.61(6)
N(2Ј)-Zn-N(2)
N(2)-Zn-N(1Ј)
N(2)-Zn-N(1)
N(2Ј)-Zn-O(1Ј)
N(2Ј)-Zn-N(1Ј)
N(2Ј)-Zn-N(1)
N(1Ј)-Zn-N(1)
N(2)-Zn-O(1Ј)
91.28(7)
107.88(7)
111.87(11)
92.97(7)
2.2 Spectroscopic studies
The IR spectra of the complexes do not show a band due
to ν(NϪH), thus confirming that the hydrogen atom of the
amide group is lost during the electrolysis. The IR spectra
N(1Ј)-Zn-O(1Ј)
N(2Ј)-Zn-O(1)
N(1Ј)-Zn-O(1)
O(1Ј)-Zn-O(1)
150.02(6)
92.97(7)
88.30(7)
83.39(9)
N(1)-Zn-O(1Ј)
N(2)-Zn-O(1)
N(1)-Zn-O(1)
88.30(7)
60.61(6)
150.02(6)
of the complexes exhibit
a
strong band in the
1625Ϫ1620 cmϪ1 range, attributed to ν(CϭN), which is
shifted to slightly lower frequency on going from the free
ligand to the complex. Bands at 1130Ϫ1180 cmϪ1 and
1315Ϫ1320 cmϪ1 can be assigned to the symmetric and
Symmetry transformations used to generate equivalent atoms: (Ј) x, 1.5Ϫy,
1.5Ϫz
1
asymmetric ν(SϭO) vibrations, respectively. The H NMR
i
˚
Table 6 Selected bond distances/A and angles/° for [Zn(Ts4- P-
rOz)2].
spectra of the complexes show signals for all hydrogen
atoms of the ligand with the exception of the NH proton.
In the spectra of the free ligand this signal appears at about
12.5Ϫ13.1 ppm. This provides further evidence that the li-
gands are deprotonated in the complexes and coordinate in
their anionic form. Aromatic resonances at 8.0Ϫ6.6 ppm, a
singlet at 2.2 ppm for the ϪCH3 protons of the p-toluensul-
fonic group, and a multiplet at 5.0Ϫ3.2 ppm for the hydro-
gen atoms of the oxazoline ring appear in the spectra of all
compounds. These signals all appear at practically the same
chemical shift as the corresponding signals in the free li-
gand. The complexes also exhibit signals at around of
0.8Ϫ1.5 ppm due to the substituent on the oxazoline ring
groups.
Zn-N(2)
Zn-N(1)
Zn-O(2)
S-O(1)
2.008(2)
2.015(3)
2.660(2)
1.443(2)
1.597(3)
Zn-N(2Ј)
Zn-N(1Ј)
Zn-O(2Ј)
S-O(2)
2.008(2)
2.015(3)
2.660(2)
1.449(2)
1.765(3)
S-N(2)
S-C(12)
N(2)-Zn-N(2Ј)
N(2Ј)-Zn-N(1)
N(2Ј)-Zn-N(1Ј)
N(2)-Zn-O(2)
N(1)-Zn-O(2)
N(2)-Zn-O(2Ј)
N(1)-Zn-O(2Ј)
145.96(15)
106.25(10)
91.23(10)
59.67(8)
147.58(9)
93.67(9)
N(2)-Zn-N(1)
N(2)-Zn-N(1Ј)
N(1)-Zn-N(1Ј)
N(2Ј)-Zn-O(2)
N(1Ј)-Zn-O(2)
N(2Ј)-Zn-O(2Ј)
N(1Ј)-Zn-O(2Ј)
91.23(10)
106.25(10)
118.05(16)
93.67(9)
86.06(9)
59.67(8)
86.06(9)
147.58(9)
Symmetry transformations used to generate equivalent atoms: (Ј) Ϫx, y, .5Ϫz
The FAB mass spectra of all compounds show the molec-
ular ion with appropriate isotope distributions. In many
cases, ions formed by loss of one ligand from the initial
complex are also observed, as well as a peak attributed to
the free ligand.
the corresponding distances in the complexes without a
substituent (in the range 4.563Ϫ5.151 A). This fact surely
reflects a tendency to reduce the interaction between the
˚
1214
Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217

Zinc(II) Complexes with [(4-Methylphenyl)Sulfonyl]-1H-Amido-2-Phenyl-2-Oxazolines
Analytical data for the other ligands
All these data are in accordance with the structures de-
scribed above for the complexes.
[(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-5-methyl-2-
oxazoline), (HTs-5MeOz). Found: C, 62.1; H, 5.6; N, 8.5; S, 9.6.
Calcd. for C17H18N2O3S: C, 61.8; H, 5.5; N, 8.5; S, 9.7 %.
IR (KBr, cmϪ1): 2970(m), 1620(s), 1558(m), 1315(s), 1242(m), 1135(s). 1H-
NMR (CDCl3): 12.4 ppm (s, 1H, NH), 7.9Ϫ6.9 ppm (m, 8H, phenyl),
4.4 ppm (m, H, ϪCH), 3.8 ppm (m, 2H, ϪCH2), 2.3 ppm (s, 3H, ϪCH3
tolyl), 1.3 ppm (s, 3H, ϪCH3). EI MS: m/z: 330 (100 %, Mϩ); 175 (11 %,
MϩϪ{O2S-tolyl}).
3 Experimental
Anthranilonitrile, p-toluenesulfonyl chloride and amino alcohols
were all commercial products and were used as supplied. Aceto-
nitrile, chlorobenzene, dichloromethane and other solvents were
dried by standard methods [9]. Zinc (Aldrich) was used in plate
form (ca. 2 ϫ 2 cm).
Ligands were synthesised under argon using slight modifications
of the standard literature procedure [10] (see Scheme 3). Details are
given for a representative example.
[(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-4-methyl-2-
oxazoline), (HTs-4MeOz). Found: C, 61.7; H, 5.6; N, 8.5; S, 9.8.
Calcd. for C17H18N2O3S: C, 61.8; H, 5.5; N, 8.5; S, 9.7 %.
IR (KBr, cmϪ1): 2977(m), 1634(s), 1506(m), 1340(s), 1261(m), 1161(s). 1H-
NMR (CDCl3): 12.2 ppm (s, 1H, NH), 7.6Ϫ6.9 ppm (m, 8H, phenyl),
4.4 ppm (m, 2H, ϪCH2), 3.8 ppm (m, 1H, ϪCH), 2.3 ppm (s, 3H, ϪCH3
tolyl), 1.3 ppm (s, 3H, ϪCH3). EI MS: m/z: 330 (100 %, Mϩ); 175 (11 %,
MϩϪ{O2S-tolyl})
[(4-methylphenyl)sulfonyl]-1H-amido-(2-phenyl-2-
oxazoline)] (HTs-Oz)
[(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-4-ethyl-2-
oxazoline) (HTs-4EtOz). Found: C, 62.9; H, 5.2; N, 8.0; S, 10.1.
Calcd. for C18H20N2O3S: C, 62.8; H, 5.9; N, 8.1; S, 9.3 %.
2-(2-oxazoline)aniline was prepared by reaction of anthranilonitrile
(3 g, 25 mmol) and 2-aminoethanol (5.0 mL, 82 mmol), in chlorob-
enzene (40 mL), using ZnCl2 (0.5 g, 3.7 mmol) as a catalyst. The
mixture was refluxed under argon during 36 h to give a red solu-
tion. The solvent was removed and the red crude product was dis-
solved in dichloromethane. The organic solution was washed with
water, dried over anhydrous Na2SO4 and the solvent removed un-
der vacuum. The resulting solid was purified by chromatography
on silica gel using hexane/ethyl acetate (19:1) as eluent to obtain
the pure amine (2.8 g, 68 %). A dichloromethane solution of this
amine (1 g, 6.2 mmol) was treated with p-toluenesulfonyl chloride
(1.6 g, 8.4 mmol) in aqueous KOH (0.5 g, 8.9 mmol) and the mix-
ture was stirred for 24 h. The organic layer was separated, dried
and concentrated to dryness to give a crude product, which was
purified by chromatography on silica gel using hexane/ethyl acetate
(4:1) as eluent. The ligand was obtained as a colourless solid (1.8 g,
92 %). Anal. Calcd. for C16H16N2O3S: C, 60.7; H, 5.1; N, 8.9; S,
10.1. Found: C, 60.4; H, 5.2; N, 9.0; S, 10.1 %.
IR (KBr, cmϪ1): 2970(m), 1634(s), 1506(s), 1339(s), 1268(m), 1154(s). 1H-
NMR (CDCl3): 12.4 ppm (s, 1H, NH), 7.8Ϫ6.9 ppm (m, 8H, phenyl),
4.4 ppm (m, H, ϪCH), 3.8 ppm (m, 2H, ϪCH2), 2.3 ppm (s, 3H, ϪCH3
tolyl), 1.7 ppm (m, 2H, ϪCH2(Et)), 1.1 ppm (m, 3H, ϪCH3(Et). EI MS:
m/z: 344 (100 %, Mϩ); 189 (6 %, MϩϪ{O2S-tolyl}).
[(4-Methylphenyl)sulfonyl]-1H-imino-(2-phenyl-4-isopropyl-2-
oxazoline) (HTs-4iPrOz.). Found: C, 63.5; H, 6.0; N, 7.9; S, 9.2,
Calc. for C19H22N2O3S: C, 63.7; H, 6.2; N, 7.8; S, 8.9 %.
IR (KBr, cmϪ1): 2964(m), 1625(s), 1559(m), 1318(s), 1241(m), 1173(s). 1H
NMR (CDCl3): 12.4 ppm (s, 1H, NH), 7.8Ϫ6.7 ppm (m, 8H, phenyl),
4.3 ppm (m, 2H, ϪCH2), 3.9 ppm (m, 1H, ϪCH), 2.3 ppm (s, 3H, ϪCH3
tolyl), 1.5 ppm [s, 1H, ϪCH(isopropyl)], 1.0 ppm [d, 3H, ϪCH3 (isopropyl)],
0.9 ppm [d, 3H, ϪCH3 (isopropyl)]. EI MS: m/z: 358 (68 %, Mϩ); 203 (5 %,
Mϩ Ϫ {O2S-tolyl}).
Electrochemical synthesis
The electrochemical method used in the synthesis of the complexes
was similar to that described by Tuck [11]. The anode consisted of
zinc foil suspended from a platinum wire and the cathode was a
platinum wire. The ligand was dissolved in acetonitrile and a small
IR (KBr, cmϪ1): 2969 (m), 1625 (s), 1560 (s), 1313 (s), 1241 (m), 1132 (s).
1H NMR (CDCl3): 13.1 ppm (s, 1H, NH), 8.6Ϫ7.6 ppm (m, 8H, phenyl),
5.2Ϫ4.8 ppm (m, 4H, ϪCH2), 3.1 ppm (s, 3H, ϪCH3). EI MS: (m/z): 316
(100 %, Mϩ); 161 (7 %, Mϩ Ϫ {O2S-tolyl}).
Scheme 3
Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217
1215

´
´
´
J. Castro, S Cabaleiro, P. Perez-Lourido, J. Romero, J. A Garcıa-Vazquez, A. Sousa
(s, 6H), 1.5 ppm (m, 4H), 0.9 ppm (m, 6H). FAB (m/z): 751 [Zn(Ts-
amount of tetramethylammonium perchlorate was added to the
4EtOz)2]ϩ; 408 [Zn(Ts-4EtOz)]ϩ; 343 [Ts-4EtOz]ϩ.
solution as an electrolyte carrier. Applied voltages of 10Ϫ15 V al-
lowed sufficient current flow for smooth dissolution of the metal.
Nitrogen was bubbled through the solution during electrolysis to
provide an inert atmosphere and also to stir the reaction mixture.
[Zn(Ts-4iPrOz)2] (5)
A solution of {[(4-methylphenyl)sulfonyl]-1H-amido-(2-phenyl-4-
isopropyl-2-oxazoline)} (0.159 g, 0.44 mmol) in acetonitrile
(50 mL) was electrolysed at 10 mA during 1 h; 12.5 mg of zinc me-
tal was dissolved from the anode, Ef ϭ 0.51 mol·FϪ1. Colourless
crystals, suitable for X-ray studies, were obtained in the cell. The
crystals were recovered by filtration, washed with acetonitrile, dried
and characterised by elemental analysis. Anal. Calcd. for
C38H40ZnN4O6S2: C, 58.6; H, 5.2; N, 7.2; S, 8.2. Found: C, 58.1;
H, 5.6; N, 7.2; S, 8.3 %.
Under these conditions the cell can be summarised as Zn(ϩ)
/
CH3CN ϩ HTsϪROz/Pt(Ϫ)
.
[Zn(TsOz)2] (1)
Electrochemical oxidation of a zinc anode in a solution of [(4-meth-
ylphenyl)sulfonyl]-1H-amido-(2-phenyl-2-oxazoline) (0.236 g,
0.75 mmol) in acetonitrile (50 mL) at 6 V and 10 mA for 2 h,
caused 24.4 mg of zinc to be dissolved, Ef ϭ 0.50 mol·FϪ1. During
the electrolysis hydrogen was evolved at the cathode and at the end
of the experiment a crystalline solid was observed at the bottom
of the vessel. The solid was collected by filtration, washed with
acetonitrile and diethyl ether and dried under vacuum. Anal.
Calcd. for C32H30ZnN4O6S2: C, 55.2; H, 4.3; N, 8.1; S, 9.2. Found:
C, 55.0; H, 4.9; N, 8.3; S, 8.9 %.
IR (KBr, cmϪ1): 2959 (m), 1621 (s), 1560 (m), 1304 (s), 1241 (m), 1139 (s).
1H NMR (CDCl3): 8.0Ϫ6.6 ppm (m, 16H), 5.0Ϫ3.6 ppm (m, 6H), 2.2 ppm
(s, 6H), 1.5 ppm (m, 2H), 0.7 ppm (m, 12H). FAB (m/z): 779 [Zn(Ts-
4iPrOz)2]ϩ; 422 [Zn(Ts-4iPrOz)]ϩ; 357 [Ts-4iPrOz]ϩ.
IR (KBr, cmϪ1): 2978 (m), 1631 (s), 1561 (m), 1320 (s), 1240 (m), 1137 (s).
1H NMR (CDCl3): 8.0Ϫ6.6 ppm (m, 16H), 5.0Ϫ3.2 ppm (m, 8H), 2.2 ppm
(s, 6H). FAB (m/z): 696 [Zn(TsOz)2]ϩ; 379 [Zn(TsOz)]ϩ; 316 [TsOz]ϩ. Crys-
tals suitable for X-ray studies were obtained by crystallisation from chloro-
form.
Physical measurement
Elemental analyses were obtained using a Carlo-Erba EA 1108
microanalyser. IR spectra were recorded on KBr mulls using a
Bruker Vector-22 spectrophotometer. Mass spectra were recorded
on a Kratos-MS-50T spectrophotometer connected to a DS90 data
system. FAB Mass spectra were measured using 3-nitrobenzyl al-
cohol (3-NBA) as a matrix material. The 1H NMR spectra were
recorded on a Bruker ARX-400 MHz spectrometer using CDCl3
as solvent.
[Zn(Ts-5MeOz)2] (2)
An experiment similar to that described above (7.5 V, 10 mA, 2 h)
with the ligand (0.235 g, 0.71 mmol) in acetonitrile (50 mL) led to
the dissolution of 23.3 mg of zinc, Ef ϭ 0.48 mol·FϪ1. The solid
was filtered off, washed with cool acetonitrile, diethyl ether and
dried under vacuum (0.27 g, 86 %). Anal. Calcd. for
C34H34ZnN4O6S2: C, 56.4; H, 4.7; N, 7.7; S, 8.9. Found: C, 55.9;
H, 4.7; N, 7.8; S, 8.9 %.
Crystal structure determination
IR (KBr, cmϪ1): 2966 (m), 1618 (s), 1560 (m), 1316 (m), 1238 (m), 1140 (s).
1H NMR (CDCl3): 8.0Ϫ6.6 ppm (m, 16H), 5.0Ϫ3.3 ppm (m, 6H), 1.5 ppm
(s, 6H), 2.2 ppm (s, 6H). FAB (m/z): 724 [Zn(Ts-5MeOz)2]ϩ; 393 [Zn(Ts-
5MeOz)]ϩ; 329 [Ts-5MeOz]ϩ. Crystals suitable for X-ray studies were ob-
tained by crystallisation from chloroform.
The data collection was carried out on an Enraf-Nonius CAD-4
diffractometer using graphite monochromated Cu-Kα radiation
i
˚
(λ ϭ 1.54184 A) for [Zn(Ts-4 PrOz)2], and on a Siemens Smart
CCD area-detector diffractometer using graphite monocromated
˚
Mo-Kα radiation (λ ϭ 0.71073 A) in all other cases. All the struc-
tures were resolved by direct methods and refined by a full-matrix
least-squares based on F2 [12]. Non-hydrogen atoms were refined
with anisotropic displacement parameters. Hydrogen atoms were
included in idealised positions and refined with isotropic displace-
ment parameters. Atomic scattering factors and anomalous disper-
sion corrections for all atoms were taken from the International
Tables for X-ray Crystallography [13]. For the compound [Zn(Ts-
4MeOz)2] (3) the Squeeze program [14] was used to correct the
reflection data for the diffuse scattering due to disorder of the sol-
vent. The crystal parameters and other experimental details regard-
ing data collection and refinement are summarised in Table 1.
Crystallographic data for the structures have been deposited with
Cambridge Crystallographic Data Centre, CCDC, numbers 170824
to 170828 respectively. Copies of the data can be obtained free of
charge on application to The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: int.codeϩ(1223)336-033; e-mail
for inquiry: fileserv@ccdc.cam.ac.uk; e-mail for deposition: de-
posit@ccdc.cam.ac.uk).
[Zn(Ts-4MeOz)2] (3)
Electrolysis of a solution of the ligand (0.251 g, 0.76 mmol) in
acetonitrile (50 mL) at 6.5 V and 10 mA for 2 h dissolved 25.1 mg
of zinc, Ef ϭ 0.51 mol·FϪ1. At the end of the electrolysis colourless
crystals were present in the cell and these were filtered off, washed
with cool acetonitrile, diethyl ether and dried under vacuum. Crys-
tallisation from chloroform gave crystals identified as [Zn(Ts-
4MeOz)2]. Anal. Calcd. for C34H34ZnN4O6S2: C, 56.4; H, 4.7; N,
7.7; S, 8.9. Found: C, 55.8; H, 4.5; N, 7.5; S, 8.5 %.
IR (KBr, cmϪ1): 2967 (m), 1620 (s), 1560 (s), 1313 (s), 1239 (m), 1135 (s).
1H NMR (CDCl3): 8.0Ϫ6.6 ppm (m, 16H), 5.0Ϫ3.6 ppm (m, 6H), 1.5 ppm
(s, 6H), 2.2 ppm (s, 6H). FAB (m/z): 724 [Zn(Ts-4MeOz)2]ϩ; 393 [Zn(Ts-
4MeOz)]ϩ; 329 [Ts-4MeOz]ϩ.
[Zn(Ts-4EtOz)2] (4)
A solution of ligand (0.283 g, 0.79 mmol) in acetonitrile (50 mL)
was electrolysed at 8 V and 10 mA during 2 h; 25.9 mg of zinc was
dissolved from the anode, Ef ϭ 0.53 mol·FϪ1. Colourless crystals,
suitable for X-ray studies, were obtained directly from the cell. The
solid was collected, washed with cool acetonitrile, diethyl ether and
dried under vacuum. Anal. Calcd. for C36H38ZnN4O6S2: C, 57.5;
H, 5.1; N, 7.4; S, 8.5. Found: C, 57.3; H, 4.7; N, 7.5; S, 8.3 %.
Acknowledgements. We thank the Xunta de Galicia
(PGIDT00PXI20305PR) and (PGIDT99PXI20306B) for financial
support.
IR (KBr, cmϪ1): 2964 (m), 1615 (s), 1559 (m), 1318 (s), 1241 (m), 1135 (s).
All the crystallographic calculations were performed on the fergu-
s.uvigo.es system (http://angus.uvigo.es/).
1H NMR (CDCl3): 8.0Ϫ6.6 ppm (m, 16H), 5.0Ϫ3.3 ppm (m, 6H), 2.2 ppm
1216
Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217

Zinc(II) Complexes with [(4-Methylphenyl)Sulfonyl]-1H-Amido-2-Phenyl-2-Oxazolines
´
[8] J. Castro, S. Cabaleiro, P. Perez-Lourido, J. Romero, J.A. Gar-
References
´
´
cıa-Vazquez, A. Sousa, Trans. Met. Chem. 2001, 26, 709.
[9] A. I. Vogel, in Practical Organic Chemistry, ELBS and Long-
man, London, 3rd Ed., 1965, p. 163.
[10] J. V. Allen, G. J. Dawson, C. G. Frost, J. M. J. Williams, Tetra-
hedron 1994, 50, 799.
[11] J. J. Habeeb, D. G. Tuck, F. H. Walters, J. Coord. Chem. 1978,
8, 27.
[12] G. M. Sheldrick, SHELX-97, Program for the solution and
refinement of crystal structures, University of Göttingen, Ger-
many, 1997.
[1] L. Pu, H.-B Yu, Chem. Rev. 2001, 101, 757 and references ther-
ein.
[2] A. W. Addison, T. N. Rao, J. van Reedijk, J. van Rijn, G. C.
Verschoor, J. Chem. Soc., Dalton Trans. 1984, 1349.
[3] B. Hajjem, A. Kallel, I. Svoboda, J. Sakurai, Acta Crystallogr.
1992, C48, 1002.
[4] N. Baltzer, L. Macko, S. Schaffner, M. Zehnder, Helv. Chim.
Acta 1996, 79, 803.
[5] S. E. Denmark, S. P. OЈConnor, S. R. Wilson, Angew. Chem.,
Int. Ed. Engl. 1998, 37, 1149.
[13] International Tables for X-ray Crystallography, Vol. C,
Kluwer, Dordrecht, 1992.
[14] A. L. Spek, Acta Crystallogr. 1990, A46, 34.
´
´
´
[6] J. Romero, J. A. Garcıa-Vazquez, M. L. Duran, A. Casti-
n˜eiras, A. Sousa, A.D. Garnovskii, D. A. Garnovskii, Acta
Chem. Scand. 1997, 51, 672.
[7] T. Ichiyanai, M. Shimizu, T. Fujisawa, Tetrahedron 1997, 53,
9599.
Z. Anorg. Allg. Chem. 2002, 628, 1210Ϫ1217
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