Pseudotetrahedral cobalt(II) complexes with thiazoline and thiazine derivative ligands: Synthesis and characterization

Article abstract of DOI:10.1016/j.poly.2004.10.011

The cobalt(II) complexes dichloro[2-(3,4-dichlorophenyl)imino-κN-N- (2-thiazolin-κN-2-yl)thiazolidine]cobalt(II) (1) and dichloro[2-(3,4- dichlorophenyl)imino-κN-N-(2-thiazin-κN-2-yl)thiazolidine]cobalt(II) (2) have been isolated and characterized in the solid state by X-ray diffraction, elemental analysis, IR spectra, magnetic measurements and UV-Vis-NIR diffuse reflectance spectroscopy. In both complexes, the environment around the cobalt(II) ion may be described as a distorted tetrahedral geometry, with the metallic atom coordinated to two chlorine atoms [Co-Cl(1) = 2.213(1) A?; Co-Cl(2) = 2.226(1) A?], one imino nitrogen [Co-N(3) = 1.992(2) A?] and one thiazoline nitrogen [Co-N(1) = 1.974(2) A?] in complex 1 and to two chlorine atoms [Co-Cl(1) = 2.244(2) A?; Co-Cl(2) = 2.226(1) A?], one imino nitrogen [Co-N(3) = 1.970(4) A?] and one thiazine nitrogen [Co-N(1) = 1.946(4) A?] in complex 2.

Full text of DOI:10.1016/j.poly.2004.10.011

Polyhedron 24 (2005) 129–136
www.elsevier.com/locate/poly
Pseudotetrahedral cobalt(II) complexes with thiazoline and
thiazine derivative ligands: synthesis and characterization
*
F.J. Barros-Garcıa, A. Bernalte-Garcıa , A.M. Lozano-Vila, F. Luna-Giles,
´
´
E. Vin˜uelas-Zahınos
´
´ ´
Departamento de Quımica Inorganica, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain
Received 7 September 2004; accepted 25 October 2004
Available online 8 December 2004
Abstract
The cobalt(II) complexes dichloro[2-(3,4-dichlorophenyl)imino-jN-N-(2-thiazolin-jN-2-yl)thiazolidine]cobalt(II) (1) and
dichloro[2-(3,4-dichlorophenyl)imino-jN-N-(2-thiazin-jN-2-yl)thiazolidine]cobalt(II) (2) have been isolated and characterized in
the solid state by X-ray diffraction, elemental analysis, IR spectra, magnetic measurements and UV–Vis–NIR diffuse reflectance
spectroscopy. In both complexes, the environment around the cobalt(II) ion may be described as a distorted tetrahedral geometry,
˚
˚
with the metallic atom coordinated to two chlorine atoms [Co–Cl(1) = 2.213(1) A; Co–Cl(2) = 2.226(1) A], one imino nitrogen
˚
˚
[Co–N(3) = 1.992(2) A] and one thiazoline nitrogen [Co–N(1) = 1.974(2) A] in complex 1 and to two chlorine atoms [Co–
˚
Cl(1) = 2.244(2) A; Co–Cl(2) = 2.226(1) A], one imino nitrogen [Co–N(3) = 1.970(4) A] and one thiazine nitrogen [Co–
˚
˚
˚
N(1) = 1.946(4) A] in complex 2.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Keywords: Crystal structures; Cobalt(II) complexes; Thiazoline; Thiazolidine; Thiazine
1. Introduction
The synthesis of new siderophore analogues consti-
tutes another pharmacological application example.
Microbial siderophores are relatively low molecular
weight compounds synthesized in order to solubilize
and transport iron (III) into the procariotes cells in the
necessary concentrations. New siderophore analogues
are prototypes for the synthesis of chelating agents em-
ployed for clinical use [11]. Thus, there have been char-
acterized siderophores containing thiazoline and
thiazine rings that have been used in the treatment of
acute iron poisoning and in chronic iron overload result-
ing from transfusion therapy of b-thalasemia [12].
Because of the aforementioned, recently we have been
investigating the coordination chemistry of compounds
containing these heterocycles [13–17]. As a continuation
of this research, we report here the synthesis and charac-
terization by elemental analysis, infrared spectra (IR),
ultraviolet and visible spectra (UV–Vis), proton nuclear
Multidentate ligands containing N,N donors are
extensively used in coordination chemistry with the
aim of obtaining new frameworks having potential bio-
activity [1]. Among these ligands, thiazoline and thiazine
derivative ligands have attracted our attention due to
their biological and pharmaceutical activity. The use
of compounds containing thiazine, thiazoline or/and
thiazolidine rings as antitumoral, analgesic, antibiotic,
antiviral, antihistamine, anti-HIV, antiinflammatory
and sedative agents, is well known [2–9]. In some cases,
the structural and biological properties of the corre-
sponding coordination compounds are more notewor-
thy than those of the ligands [10].
*
Corresponding author. Tel.: +34 924 289394; fax: +34 924 289395.
´
E-mail address: alberga@unex.es (A. Bernalte-Garcıa).
0277-5387/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.10.011

´
F.J. Barros-Garcıa et al. / Polyhedron 24 (2005) 129–136
130
magnetic resonance (1H NMR) and carbon nuclear mag-
netic resonance (13C NMR) of the ligand TdTz
[TdTz = 2-(3,4-dichlorophenyl)imino-N-(2-thiazin-2-yl)-
thiazolidine]. Likewise, the cobalt(II) complexes
[CoCl2(TdTn)] [TdTn = 2-(3,4-dichlorophenyl)imino-
N-(2-thiazolin-2-yl)thiazolidine] and [CoCl2(TdTz)]
have been isolated and their characterization has been
carried out by means of single crystal X-ray diffraction,
elemental analysis, spectroscopic and magnetic
measurements.
a white precipitate had separated out and the reaction
mixture was allowed to cool to room temperature. A
solution of 1.62 g (15.3 mmoles) of sodium carbonate
in 20 ml of water was added and the mixture was stirred
until dissolution of the solid was complete. The phases
were separated and the aqueous layer was extracted with
dichloromethane. The combined organic layers were
dried over anhydrous magnesium sulfate and concen-
trated under reduced pressure to give a solid that was
recrystallized from ethanol 96% (1.5 g; 53%).
1H NMR (deuteriochloroform): d 7.32 (d, J = 8.76
Hz, 1H), 7.07 (d, J = 2.24 Hz, 1H), 6.80 (dd, J = 2.24,
8.76 Hz, 1H), 4.19 (t, J = 7.04 Hz, 2H), 3.72 (t,
J = 5.62 Hz, 2H), 3.15 (t, J = 7.01 Hz, 2H), 2.95 (t,
J = 6.01 Hz, 2H), 1.90 (m, J = 5.88 Hz, 2H); 13C NMR
(deuteriochloroform): d 156.48, 149.61, 148.31, 132.32,
130.42, 126.86, 123.37, 121.03, 51.42, 46.46, 27.07,
26.46, 20.64. Anal. Calc. for C13H13Cl2N3S2: C, 45.09;
H, 3.78; N, 12.13; S, 18.52. Found: C, 45.26; H, 3.78;
N, 11.82; S, 18.07%. UV–Vis (EtOH): kmax, nm; (e,
l molꢀ1 cmꢀ1) 205 (35 140), 247 (19 059), 292 (10 833).
2. Experimental
2.1. Preparation of 2-(3,4-dichlorophenyl)imino-N-(2-
thiazolin-2-yl)thiazolidine (TdTn)
The preparation of TdTn has been carried out as de-
scribed by Outcalt et al. [18]. 1H NMR (deuteriochloro-
form): d 7.37 (d, J = 8.49 Hz, 1H), 7.10 (d, J = 2.45 Hz,
1H), 6.85 (dd, J = 2.45, 2.49 Hz, 1H), 4.33 (t, J = 7.05
Hz, 2H), 4.01 (t, J = 8.28 Hz, 2H), 3.28 (t, J = 7.05
Hz, 2H), 3.23 (t, J = 8.16 Hz, 2H); 13C NMR (deuterio-
chloroform): d 157.58, 155.68, 148.73, 132.47, 130.53,
127.29, 123.30, 120.89, 57.27, 51.30, 33.87, 26.74. Anal.
Calc. for C12H11Cl2N3S2: C, 43.38; H, 3.34; N, 12.64;
S, 19.30. Found: C, 43.44; H, 3.36; N, 12.71; S,
Cl
Cl
18.95%. UV–Vis (EtOH): kmax, nm; (e, l molꢀ1 cmꢀ1
)
N
205 (35 087), 239 (17 542), 289 (12 351).
N
Cl
S
N
Cl
S
TdTz
N
2.3. Preparation of [CoCl2(TdTn)]
N
S
N
This complex was isolated from a freshly prepared
ethanol solution (1 ml) of CoCl2 Æ 6H2O (71.6 mg, 0.3
mmol) that was added to an ethanol solution (15 ml)
of TdTn (100 mg, 0.3 mmol). The resulting solution
was allowed to evaporate slowly at room temperature.
After a few days, blue crystals were isolated from the
solution (124 mg, 89.2%). The crystals were separated
by filtration, washed with cold ether and air-dried. Anal.
Calc. for C12H11Cl4CoN3S2: C, 31.19; H, 2.40; N, 9.09;
S, 13.88. Found: C, 31.33; H, 2.42; N, 8.97; S, 14.37%.
S
TdTn
2.2. Preparation of 2-(3,4-dichlorophenyl)imino-N-(2-
thiazin-2-yl)thiazolidine (TdTz)
A solution of 2.01 g (8.1 mmoles) of 2-(3,4-dic-
hlorobenzylamino)-2-thiazoline (that was obtained by
the method of Fanta and Deutsch [19] and by the meth-
od of Outcalt et al. [18]) and 1.38 g (10.2 mmoles) of
3-chloropropylisothiocyanate [20] in 30 ml of toluene
was stirred and heated to reflux for 4 h. At this point,
2.4. Preparation of [CoCl2(TdTz)]
This complex was prepared by reacting an ethanol
solution (1 ml) of CoCl2 Æ 6H2O (68.7 mg, 0.3 mmol)

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F.J. Barros-Garcıa et al. / Polyhedron 24 (2005) 129–136
131
with an ethanol solution (15 ml) of TdTz (100 mg, 0.3
mmol), blue crystals being obtained after a slow evapo-
ration of the solution at room temperature (96.5 mg,
67.5%). The crystals were filtered, washed with cold
ether and air-dried. Anal. Calc. for C13H13Cl4CoN3S2:
C, 32.79; H, 2.75; N, 8.82; S, 13.47. Found: C, 32.76;
H, 2.74; N, 8.58; S, 12.93%.
the 200–2000 nm range were obtained from a pellet of
the samples, using a Shimadzu UV-3101 PC spectropho-
tometer and BaSO4 as a reference. Magnetic measure-
ments were made at room temperature on
a
magnetometer with a pendulum MANICS DSM8,
equipped with a helium continuous-flow cryostat and
an electromagnetometer DRUSCH EAF 16 UE. Data
were corrected for temperature-independent paramag-
netism and diamagnetic contributions, which were esti-
mated from Pascal constants. 1H and 13C NMR
spectra were obtained with a Bruker AM 400 instrument
at 400 and 100 MHz, respectively, in CDCl3 using Me4Si
as internal standard.
2.5. Instrumental procedures
Chemical analyses of carbon, hydrogen, nitrogen and
sulfur were performed by microanalytical methods using
a Leco CHNS-932 microanalyser. IR spectra were re-
corded on a Perkin–Elmer FT-IR 1720 spectrophotom-
eter, from KBr pellets in the 4000–370 cmꢀ1 range and
on a Perkin–Elmer FT-IR 1700X spectrophotometer,
from polyethylene pellets in the 500–150 cmꢀ1 range.
Electronic spectra of the ligands in solution were mea-
sured on a Shimadzu UV-3101 PC using a 10 mm quartz
cell. UV–Vis–NIR reflectance spectra for complexes in
2.6. Crystal structure determinations
Experimental details of the crystal structure determi-
nations including crystal data, data collection, structure
determination and refinement for complexes 1 and 2 are
listed in Table 1. X-ray diffraction measurements were
Table 1
Crystal data, data collection and refinement details for [CoCl2(TdTn)] (1) and [CoCl2(TdTz)] (2)
[CoCl2 (TdTn)] (1)
[CoCl2(TdTz)] (2)
Crystal shape
Colour
Size (mm)
prism
blue
prism
blue
0.34 · 0.18 · 0.14
C12H11Cl4CoN3S2
0.50 · 0.32 · 0.13
C13H13Cl4CoN3S2
476.11
Chemical formula
Formula weight
Crystal system
Space group
462.09
monoclinic
P21/a
monoclinic
Cc
Unit cell dimensions
˚
a (A)
˚
9.699(1)
17.336(1)
10.825(1)
104.06(1)
1765.4(2)
4
7.637(1)
18.273(2)
13.709(1)
101.54(1)
1874.3(3)
4
b (A)
˚
c (A)
b (ꢁ)
Cell volume (A )
3
˚
Z
T (K)
298(2)
1.739
298(2)
1.687
Dcalc (g cmꢀ3
)
l (mmꢀ1
F (0 0 0)
Diffractometer
)
1.810
924
1.708
956
Bruker SMART CCD
Bruker SMART CCD
˚
˚
Radiation
Mo-Ka (k = 0.71073A)
Mo-Ka (k = 0.71073 A)
Collection method
2h Range
Index ranges
/–x
3.8–56.6
/–x
5.4–51.4
ꢀ10 6 h 6 12, ꢀ22 6 k 6 22, ꢀ12 6 l 6 14
ꢀ6 6 h 6 9, ꢀ22 6 k 6 21, ꢀ16 6 l 6 14
Independent reflections
Observed reflections
Absorption correction
Maximum/minimum transmission
Number of refined parameters
R [I > 2r(I)]a
4222
2298
3220 [F > 4.0r(F)]
empirical
0.7857/0.5781
199
2230 [F > 4.0r(F)]
empirical
0.8085/0.4822
208
0.0347
0.0875
0.0317
0.0844
wR [all data]b
GOFc
1.027
0.824, ꢀ0.679
1.060
0.267, ꢀ0.260
ꢀ3
˚
qmax, qmin (e A
)
P
P
a
R = iFoj ꢀ jFci/ jFoj.
n
P
2
o
1=2
P
2
b
c
wR ¼
½wðF 2o ꢀ F c2Þ ꢁ= ½wðF 2oÞ ꢁ
.
n
o
1=2
P
2
The goodness-of-fit (GOF) equals
½wðF 2o ꢀ F c2Þ ꢁ=ðNrf ln s ꢀ Nparams
Þ
.

´
F.J. Barros-Garcıa et al. / Polyhedron 24 (2005) 129–136
132
Table 2
performed using a Bruker SMART CCD diffractometer.
The first fifty frames were recollected at the end of the
data collection to monitor for decay. Absorption correc-
tions were applied using the program SADABS. The
structures were solved by direct methods and subsequent
Fourier differences using the WINGX package [21] and
refined by full-matrix least-squares. The H atoms were
placed from a differential Fourier synthesis and included
in the final refinement cycles in calculated positions.
˚
Selected bond lengths (A) and bond angles (ꢁ) for [CoCl2(TdTn)] (1)
Bond lengths
Co–Cl(1)
Co–N(1)
2.213(1)
1.974(2)
1.280(3)
1.382(3)
1.292(3)
Co–Cl(2)
Co–N(3)
N(2)–C(4)
C(7)–N(3)
2.226(1)
1.992(2)
1.381(3)
1.445(3)
C(1)–N(1)
N(2)–C(1)
C(4)–N(3)
Bond angles
Cl(1)–Co–Cl(2)
Cl(2)–Co–N(3)
Cl(2)–Co–N(1)
C(4)–N(2)–C(1)
Co–N(3)–C(4)
C(4)–N(3)–C(7)
C(1)–N(1)–C(2)
N(3)–C(4)–N(2)
114.4(4)
Cl(1)–Co–N(3)
Cl(1)–Co–N(1)
N(3)–Co–N(1)
N(2)–C(4)–N(3)
Co–N(3)–C(7)
Co–N(1)–C(1)
N(2)–C(1)–N(1)
116.6(1)
108.7(1)
90.8(1)
109.4(1)
114.8(1)
126.4(2)
126.3(2)
118.1(2)
112.6(2)
124.5(2)
124.5(2)
115.5(2)
126.9(2)
125.0(2)
3. Results and discussion
3.1. Description of the crystal structures
3.1.1. [CoCl2(TdTn)] (1)
The structure of 1 consists of discrete neutral
monomeric units in which the environment around the
cobalt(II) atom may be described as a distorted tetra-
hedral geometry. The metallic atom is coordinated by
bite angles differ from the ideal value of 109.5ꢁ, varying
between 116.6(1)ꢁ [Cl(1)–Co–N(3)] and 90.8(1)ꢁ [N(3)–
Co–N(1)].
The six-membered chelate ring Co–N(1)–C(1)–N(2)–
C(4)–N(3) is essentially planar with maximum mean-
˚
plane deviation for C(4) (0.020 A). In the organic ligand,
the values of the puckering parameters for the 2-thiazo-
line ring, calculated according to Cremer and Pople [25],
˚
two chlorine atoms [Co–Cl(1) = 2.213(1) A; Co–Cl(2) =
˚
2.226(1) A], one thiazoline nitrogen [Co–N(1) = 1.974(2)
˚
˚
A] and one imino nitrogen [Co–N(3) = 1.992(2) A]. A
diagram of the molecular structure and the atom num-
bering system used is shown in Fig. 1. The most relevant
bond lengths and angles are given in Table 2.
˚
are q = 0.143 A and / = 251.2ꢁ, whereas for the thiazoli-
˚
The Co–Cl bond lengths are similar and comparable
˚
to the calculated average value [2.240(26) A] for 100 tet-
rahedral cobalt(II) complexes with a chromophore
group CoCl2N2, obtained from CONQUEST software
[22] from the Cambridge Structural Database (CSD)
[23]. Likewise, the Co–Nimino bond distance is slightly
dine ring these are q = 0.330 A and / = 289.3ꢁ. These
values indicate that both five-membered rings show a
conformation near to envelope, with the apex at C(3)
˚
[deviating 0.230 A from the plane formed by S(1)–
C(1)–N(1)–C(2), maximum mean plane deviation for
˚
N(1) = 0.001 A] for the 2-thiazoline ring, and at C(6)
˚
[deviating 0.514 A from the plane formed by S(2)–
C(4)–N(2)–C(5), maximum mean plane deviation for
˚
N(2) = 0.004 A] for the thiazolidine ring.
˚
shorter than the mean value [2.027(24) A] calculated
for 16 cobalt(II) complexes with an Cl2N2 environment
collected in the CSD. The Co–Nthiazoline bond distance is
˚
closer to that found in [CoCl2(PyTT)] (1.982 A) [13], but
shorter than those observed in [Co(2,20-bithiazoline)-
3.1.2. [CoCl2(TdTz)] (2)
˚
(N3)2]n (average 2.155 A) [24]. The ligand–metal–ligand
The X-ray study revealed that the crystals of 2 are
made up of monoclinic unit cells, each containing four
complex molecules. A diagram of the molecular struc-
ture and the atom numbering system used is shown in
Fig. 2. Selected bond lengths and angles are given in
Table 3.
The cobalt(II) is bound to two chlorine atoms [Co–
˚
˚
Cl(1) = 2.244(2) A; Co–Cl(2) = 2.226(1) A], one thiazine
˚
nitrogen [Co–N(1) = 1.946(4) A] and one imino nitrogen
˚
[Co–N(3) = 1.970(4) A] in a distorted tetrahedral geom-
etry. The distortion of the tetrahedral environment of
the cobalt(II) ion is smaller than in complex 1, being
indicated by the ligand–metal–ligand bite angles that
vary between 115.1(2)ꢁ [Cl(1)–Co–N(1)] and 92.5(2)ꢁ
[N(3)–Co–N(1)]. This compound is the first structurally
characterized compound having a 1,3-thiazine link to
cobalt(II). The Co-ligand bond lengths were compared
with the same values collected from the CSD used dur-
ing discussion of complex 1. Thus, the Co–Cl bond
Fig. 1. Molecular structure of [CoCl2(TdTn)] (1), showing the atom
numbering scheme. The thermal ellipsoids are drawn at the 50% level.

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F.J. Barros-Garcıa et al. / Polyhedron 24 (2005) 129–136
133
3.2. Physical measurements
A pseudotetrahedral stereochemistry may be assigned
to the two complexes reported in this paper on the basis
of their diffuse reflectance spectra, which closely resem-
ble those of other Co(II) tetrahedral complexes.
Complex 1 exhibits one intense band at 34 720 cmꢀ1
(288 nm), which is assigned to the p ! p* transition of
the organic ligand. Moreover, the spectrum shows two
multicomponent absorptions in the near infrared and
visible regions with intensities consistent with spin-al-
lowed d–d transitions. These bands may be assigned to
m2 [4A2(F) ! T1(F)] (10 800, 8300, 6930 cmꢀ1) and m3
4
4
[4A2(F) ! T1(P)] (18 870 and 16 290 cmꢀ1) transitions,
Fig. 2. Molecular structure of [CoCl2(TdTz)] (2), showing the atom
numbering scheme. The thermal ellipsoids are drawn at the 50% level.
respectively, in an idealized Td symmetry.
The very large splitting for these bands suggests a
marked effect of a low symmetry component of the crys-
tal field, C1, prevailing on the spin-orbit coupling effects,
although such a mechanism may contribute [26].
The ligand field parameters, 10 Dq and B, were calcu-
lated from the average values of the m2 and m3 bands tak-
ing the centre of gravity of the total intensity, using the
following known relationships [27] for tetrahedral d7
complexes:
Table 3
˚
Selected bond lengths (A) and bond angles (ꢁ) for [CoCl2(TdTz)] (2)
Bond lengths
Co–Cl(1)
Co–N(1)
2.244(2)
1.946(4)
1.284(6)
1.403(6)
1.288(6)
Co–Cl(2)
Co–N(3)
N(2)–C(5)
C(8)–N(3)
2.226(1)
1.970(4)
1.384(6)
1.433(6)
C(1)–N(1)
N(2)–C(1)
C(5)–N(3)
Bond angles
Cl(1)–Co–Cl(2)
Cl(2)–Co–N(3)
Cl(2)–Co–N(1)
C(5)–N(2)–C(1)
Co–N(3)–C(5)
C(5)–N(3)–C(8)
C(1)–N(1)–C(2)
N(3)–C(5)–N(2)
112.8(1)
Cl(1)–Co–N(3)
Cl(1)–Co–N(1)
N(3)–Co–N(1)
N(2)–C(5)–N(3)
Co–N(3)–C(8)
Co–N(1)–C(1)
N(2)–C(1)–N(1)
108.2(1)
115.1(2)
92.5(2)
4
m2½4A2ðFÞ ! T1ðFÞꢁ ¼ 15Dq þ ð15=2ÞB
115.0(1)
111.7(1)
127.0(4)
124.4(3)
118.5(4)
119.2(4)
125.6(4)
2
2 1=2
ꢀ 1=2½ðꢀ6Dq þ 15BÞ þ 64ðDqÞ ꢁ
ð1Þ
ð2Þ
125.6(4)
117.1(3)
127.8(3)
122.1(4)
m3½4A2ðFÞ ! T1ðPÞꢁ ¼ 15Dq þ ð15=2ÞB
4
2
2 1=2
þ 1=2½ðꢀ6Dq þ 15BÞ þ 64ðDqÞ ꢁ
The calculated values of the ligand field parameters
10 Dq = 4870 cmꢀ1 and B = 746 cmꢀ1 are in fair agree-
ment with the predicted values for tetrahedral complexes
and are consistent with the presence of a chromophore
group [CoCl2N2] [13,28–30].
lengths are similar to those collected, whereas the Co–
Nimino bond length is shorter to those collected.
The six membered chelate ring Co–N(1)–C(1)–N(2)–
C(5)–N(3), similarly to complex 1, is essentially planar
with maximum mean-plane deviation for C(1)
The electronic spectra of 1 and 2 resemble each other
closely. Thus, complex 2 shows one intense band at
34 480 cmꢀ1 (290 nm) which can be assigned to the
p ! p* transition of the organic ligand.
˚
(0.047 A). The 1,3-thiazine ring shows a conformation
near to boat with S(1) and C(2) deviating 0.350 and
˚
0.215 A, respectively, above the plane formed by C(1),
N(1), C(3), C(4) [maximum mean-plane deviation for
˚
N(1) = 0.051 A]. This geometry is proved by the pucker-
Likewise, in a similar form to 1, the electronic spec-
trum exhibits a splitting of the m2 and m3 transitions.
Thus, the bands at 18 670 and 16 500 cmꢀ1 are assigned
˚
ing parameters q = 0.336 A, / = 303.4ꢁ and h = 82.9ꢁ
[25]. For the thiazolidine ring, the puckering parameters
4
to the m3 [4A2(F) ! T1(P)] transition, whereas the bands
at 11 130 cmꢀ1, 8200 cmꢀ1 and 7130(sh) cmꢀ1 are as-
˚
q = 0.356 A and / = 303.4ꢁ [25] indicate a conformation
near to envelope with the apex at C(7), deviating 0.546 A
from the plane formed by C(5), N(2), C(6), S(2) [maxi-
4
signed to the m2 [4A2(F) ! T1(F)] transition.
˚
Attention is now given to the splitting of the m2 tran-
sition of 2 (two bands and a shoulder) that is smaller
than that of 1 (three bands). This fact may possibly be
explained in terms of geometrical effects, since in accor-
dance with the X-ray crystallographic results, the distor-
tion of the coordination polyhedron around the
cobalt(II) atom in 1 is greater than that in 2 [31].
˚
mum mean-plane deviation for N(2) = 0.038 A].
Finally, it should be pointed out that the organic
moiety in both complexes presents a different degree of
rotation of the 3,4-dichlorophenyl ring around the
N(3)–C(7) [or N(3)–C(8)] bond, which could be due to
the molecular packing of the crystal structures [torsion
angle C(4)–N(3)–C(7)–C(12) = ꢀ78.5ꢁ in complex 1; tor-
sion angle C(5)–N(3)–C(8)–C(13) = ꢀ119.2ꢁ in complex
2].
The ligand field parameters, 10 Dq and B, were col-
lected in the same way as for 1 using the Eqs. (1) and
(2). Likewise, the calculated values of the ligand field

´
F.J. Barros-Garcıa et al. / Polyhedron 24 (2005) 129–136
134
parameters, 10 Dq = 4861 cmꢀ1 and B = 754 cmꢀ1, are
consistent with the presence of the chromophore group
[CoCl2N2] [13,28–30].
The observed molar magnetic susceptibilities for 1
and 2 were corrected for diamagnetism and tempera-
ture-independent paramagnetism to provide the fully
corrected magnetic moments at room temperature of
4.37 and 4.44 MB, respectively. These values are consis-
tent with an ion with an e4t23 electronic configuration in a
tetrahedral field [32,33].
at 1024 (mn1), 923 (mn2), 891 (mn3), 701 (mn4), 675 (mn5)
and 475 cmꢀ1(dn2) for TdTz [36,37].
Likewise, the spectrum of TdTn exhibits bands
assignable to the thiazoline ring vibrations at 1602
(W1), 985 (W2), 937 (W3), 799 (W4), 733 (W5), 644
(W6), 593 (W8), 526 (W7) and 445 cmꢀ1 (C1) [38],
whereas the spectrum of TdTz shows bands assignable
to the thiazine ring vibrations at 1604 (W1), 1010 (W2),
947 (W3), 823 (W4), 765 (W5), 710 (W6), 628 (W7), 592
(W8) and 528 cmꢀ1 (/1) [14,39,40].
It should be pointed out that the magnetic moment of
2 is a little higher than that of 1, this fact can be ex-
plained by considering, according to Cotton [34,35], that
the orbital contribution to the spin only value of the
magnetic moment varies inversely with the strength of
the ligand field, and that is lower for 2 than for 1.
The IR spectra of TdTn and TdTz in the 4000–370
cmꢀ1 region show the presence of bands due to thiazoli-
dine ring vibrations at 1027 (mn1), 906 (mn2), 828 (mn3),
704 (mn4), 673 (mn5) and 477 cmꢀ1 (dn2) for TdTn, and
Moreover, the bands of 3,4-dichlorophenyl ring
vibrations are detected at 1586 (8b), 1550 (8a), 1470
(19b), 1384 (19a), 1253 (14), 1131 (1) and 433 cmꢀ1
(16b) for TdTn, and at 1585 (8b), 1548 (8a), 1466
(19b), 1372 (19a), 1244 (14), 1136 (1) and 428 cmꢀ1
(16b) for TdTz [41].
Other relevant bands are registered at 1635
[m(C@N)imine] and 1035 cmꢀ1 [m(C–Cl)orto] for TdTn,
and at 1631 [m(C@N)imine], 1358 [m(C–N)] and 1048
cmꢀ1 [m(C–Cl)orto] for TdTz [42,43].
Table 4
Infrared bands (cmꢀ1) due to ring vibrations of TdTn, [CoCl2(TdTn)] (1), TdTz and [CoCl2(TdTz)] (2)
Assignment
Thiazoline
TdTn
1
TdTz
2
W1
W2
W3
W4
W5
W6
W8
W7
C1
1602 (vs)
985 (w)
937 (w)
799 (w)
733 (vw)
644 (m)
593 (m)
526 (w)
445 (w)
1540 (s)
1001 (w)
949 (m)
774 (w), 753 (vw)
730 (w), 717 (w)
631 (w)
588 (w)
542 (w)
444 (w)
Thiazine
W1
W2
W3
W4
W5
W6
W7
W8
1604 (vs)
1010 (m)
947 (w)
823 (m)
765 (w)
710 (w)
628 (w)
592 (w)
528 (w)
1598 (vs)
1022 (m)
942 (w)
839 (m)
760 (w), 746 (w)
721 (w)
631 (w)
594 (w)
545 (w)
/
1
Thiazolidine
mn1
mn2
mn3
mn4
mn5
dn2
C1
1027 (m)
906 (m)
828 (m)
704 (m)
673 (m)
477 (w)
445 (w)
1024 (m)
923 (m)
891 (m)
701 (w)
675 (w)
475 (w)
1031 (m)
912 (w)
893 (m)
702 (w)
673 (w)
478 (w)
912 (w)
830 (w)
696 (w)
672 (w)
484 (w)
444 (w)
3,4-Dichlorophenyl
8b
8a
1586 (s)
1550 (m)
1470 (s)
1384 (s)
1253 (m)
1131 (m)
1606 (vs)
1558 (m)
1463 (m)
1391 (s)
1585 (s)
1548 (m)
1466 (s)
1372 (m)
1244 (m)
1136 (m)
1563 (m)
1538 (m)
1467 (m)
1377 (s)
1233 (m)
1147 (w)
686 (w)
19b
19a
14
1237 (m)
1121 (m)
1
6a
16a
16b
550 (w)
435 (w)
584 (w)
425 (w)
433 (w)
428 (w)
Abbreviations: (s) strong; (m) medium; (w) weak; (v) very.

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F.J. Barros-Garcıa et al. / Polyhedron 24 (2005) 129–136
135
The IR spectra of 1 and 2 in the 4000–370 cmꢀ1
References
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The two complexes showed a strong m(C@N)imine
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shifted to lower wavenumbers compared with that for
the respective free ligands (Table 4). From this a coordi-
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