Coordination behaviour of 2-(1-carboxyl-2-hydroxyphenyl)benzothiazoline

Article abstract of DOI:10.1081/SIM-120014857

Reaction of 3-formylsalicylic acid with 2-aminobenzenethiol yielded 2-(1-carboxyl-2-hydroxyphenyl)benzothiazoline, H₂chpbzn, rather than the corresponding Schiff base, 2-(2-mercaptophenyl)(3′-carboxy)salicylaldimine, H₃mpcsalim. The reaction of H₂chpbzn with (π-C₅H₅)₂TiCl₂, (π-C₅H₅)₂ZrCl₂, CrCl₃·6H₂O, FeCl₃ (anhydrous), VOSO₄, VOCl₃, Ni(OAc)₂·4H₂O, Na₂PdCl₄, Me₂TlCl, Ph₂TlCl, BiCl₃ and SbCl₃, under varied reaction conditions, afforded the corresponding Schiff base complexes of the metal ions. For all of the complexes, except those of bismuth and antimony, the dianion of the Schiff base acts as a tridentate NSO donor ligand, while in the bismuth and antimony complexes the neutral benzothiazoline functions as a monodentate N donor ligand. Reactions of [(Hmpcsalim)Ti(π-C₅H₅)Cl], isolated in this study, with Me₃SiE (where E stands for SMe, NMe₂, N₃ and C≡C-Ph) have also been studied leading to the synthesis of many new organotitanium(IV) compounds. The prepared new compounds were characterized by elemental analyses, magnetic susceptibilities, molar conductance values, molecular weights and spectroscopic (UV-Vis, IR and ¹H NMR) data.

Full text of DOI:10.1081/SIM-120014857

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COORDINATION BEHAVIOUR OF 2-(1-CARBOXYL-2-
HYDROXYPHENYL)BENZOTHIAZOLINE
Kamalendu Dey a , Ranabir Bhowmick a & Saikat Sarkar a
a Department of Chemistry , University of Kalyani , Kalyani, West Bengal, 741235, India
Published online: 02 Sep 2006.
To cite this article: Kamalendu Dey , Ranabir Bhowmick & Saikat Sarkar (2002) COORDINATION BEHAVIOUR OF 2-(1-
CARBOXYL-2-HYDROXYPHENYL)BENZOTHIAZOLINE, Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 32:8,
1393-1408, DOI: 10.1081/SIM-120014857
To link to this article: http://dx.doi.org/10.1081/SIM-120014857
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 32, No. 8, pp. 1393–1408, 2002
COORDINATION BEHAVIOUR
OF 2-(1-CARBOXYL-2-
HYDROXYPHENYL)BENZOTHIAZOLINE
Kamalendu Dey,* Ranabir Bhowmick, and Saikat Sarkar
Department of Chemistry, University of Kalyani,
Kalyani-741235, West Bengal, India
ABSTRACT
Reaction of 3-formylsalicylic acid with 2-aminobenzenethiol
yielded 2-(1-carboxyl-2-hydroxyphenyl)benzothiazoline, H2chpbzn,
rather than the corresponding Schiff base, 2-(2-mercapto-
phenyl)(30-carboxy)salicylaldimine, H3mpcsalim. The reaction
of
H2chpbzn
with
FeCl3
(p-C5H5)2TiCl2,
(anhydrous),
(p-C5H5)2ZrCl2,
VOSO4, VOCl3,
CrCl3ꢀ6H2O,
Ni(OAc)2ꢀ4H2O, Na2PdCl4, Me2TlCl, Ph2TlCl, BiCl3 and
SbCl3, under varied reaction conditions, afforded the corre-
sponding Schiff base complexes of the metal ions. For all of the
complexes, except those of bismuth and antimony, the dianion
of the Schiff base acts as a tridentate NSO donor ligand, while
in the bismuth and antimony complexes the neutral ben-
zothiazoline functions as
a
monodentate
N
donor
ligand. Reactions of [(Hmpcsalim)Ti(p-C5H5)Cl], isolated in
*Corresponding author. E-mail: kdey@klyuniv.ernet.in
1393
DOI: 10.1081=SIM-120014857
Copyright # 2002 by Marcel Dekker, Inc.
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com

1394
DEY, BHOWMICK, AND SARKAR
this study, with Me3SiE (where E stands for SMe, NMe2, N3
and CꢁC–Ph) have also been studied leading to the synthesis
of many new organotitanium(IV) compounds. The prepared
new compounds were characterized by elemental analyses,
magnetic susceptibilities, molar conductance values, molecular
1
weights and spectroscopic (UV-Vis, IR and H NMR) data.
INTRODUCTION
Metal complexes of Schiff bases derived from the condensation of
3-formylsalicylic acid with mono-, di- and polyamines have been studied
extensively by us.[1] Of late, we have initiated work on the metal complexes
of NS and NSO donor ligands of biological importance.[276] In continuation
of that work, we have decided to study the coordination behaviour of
benzothiazolines towards different metal ions, reports of which are rather
few in the literature.[177] The reaction of 3-formylsalicylic acid with
2-aminobenzenethiol led us to synthesize 2-(1-carboxyl-2-hydroxyphenyl)-
benzothiazoline (abbreviated to H2chpbzn). We explored its reactions with
transition and non-transition metal salts=complexes leading to the
preparation of many new complexes of dioxomolybdenum(VI), oxomo-
lybdenum(V), nickel(II), cobalt(II and III) and diorganotin(IV) ions with
the corresponding Schiff base, 2-(2-mercaptophenyl)(30-carboxy)sali-
cylaldimine (H3mpcsalim).[1] The thiazoline (H2chpbzn) and the corre-
sponding Schiff base (H3mpcsalim) may remain in equilibrium in solution
and it is the Schiff base that ultimately forms the metal complexes.[1]
In continuation of this work we have further studied the reactions of
H2chpbzn with (p-C5H5)2TiCl2, (p-C5H5)2ZrCl2, CrCl3ꢀ6H2O, FeCl3 (anhy-
drous), VOSO4, VOCl3, Ni(OAc)2ꢀ4H2O, Na2PdCl4, Me2TlCl, Ph2TlCl, BiCl3
and SbCl3, undervariedreaction conditionsand thispaper records the results of
this investigation. It also includes the reactions of [(Hmpcsalim)Ti(p-C5H5)Cl],
prepared in this study, with Me3SiE (where E stands for SMe, NMe2, N3 and
CꢁC–Ph) affording new organotitanium(IV) compounds.
RESULTS AND DISCUSSION
Syntheses
The reaction of 3-formylsalicylic acid with 2-aminobenzenethiol under
dinitrogen atmosphere and mild reaction conditions afforded light yellow
2-(1-carboxyl-2-hydroxphenyl)benzothiazoline (H2chpbzn) in good yield.[1]

COORDINATION OF BENZOTHIAZOLINE
1395
This benzothiazoline may remain in equilibrium with the corresponding
Schiff base, 2-(2-mercaptophenyl)(30-carboxy)salicylaldimine (H3mpcsalim),
in solution. However, in the solid state the
ð1Þ
benzothiazoline structure has been suggested from the infrared and 1H NMR
spectroscopic data. For all of the complexes (Table I), except the bismuth and
antimony complexes (11) and (12), the dianion of the Schiff base (Hmpcsa-
ꢂ
lim)2 functions as ligand, while in (11) and (12) the neutral benzothiazoline
(H2chpbzn) functions as a monodentate N donor ligand. Benzothiazo-
line, H2chpbzn, reacts smoothly with (p-C5H5)2TiCl2, (p-C5H5)2ZrCl2,
CrCl3ꢀ6H2O,FeCl3 (anhydrous),VOSO4,VOCl3,Ni(OAc)2ꢀ4H2O,Na2PdCl4,
Me2TlCl, Ph2TlCl, BiCl3 and SbCl3 in mixed solvents under varied reaction
conditions affording new coloured complexes of dicyclopentadienyltitan-
ium(IV), dicyclopentadienylzirconium(IV), chromium(III), iron(III), bis-
muth(III), antimony(III), thallium(III), oxovanadium(IV), oxovanadium(V),
palladium(II) and nickel(II) ions involving the corresponding Schiff base,
H3mpcsalim, in its dianionic forms as ONS donor ligand. However, in the
adducts of bismuth(III) (11) and antimony(III) (12) the benzothiazoline acts
as a unidentate N donor neutral ligand (Fig. 1). Such Lewis base behaviour of
benzothiazoline is very rarely encountered in the literature.[1,779] The isolated
metal complexes (1) to (18), excepting the adducts (11) and (12), are stable at
room temperature. The adducts (11) and (12) are susceptible to hydrolysis on
standing in air and decomposed at 149 ꢃC and 168 ꢃC, respectively. The newly
synthesized complexes have been characterised by elemental analyses, mole-
cular weights, molar conductances, magnetic moments values and spectro-
scopic (UV-Vis, IR and 1H NMR) data. The characterization data are shown
in Table I and the reactions are shown in Figs. 1, 2 and 3.
1
IR and H NMR Spectra
The n(COOH), n(OH), n(NH) are observed around 1695 (s), 3450 (br)
and 3250 (br) cmꢂ1, respectively. The complete elimination of n(CHO) at
1660 cmꢂ1 (observed in 3-formylsalicylic acid) and also the absence of
bands around 2500 cmꢂ1 and 1600 cmꢂ1 assignable to n(SH) and n(C¼N),

1396
DEY, BHOWMICK, AND SARKAR

COORDINATION OF BENZOTHIAZOLINE
1397

1398
DEY, BHOWMICK, AND SARKAR
Figure 1. Reactions of H2chpbzn.
respectively, gives further support for the benzothiazoline structure[10712]
(see Fig. 1). The 1H NMR data (in DMSO-d6) showed the
absence of d(CHO) at 9.25 ppm in the thiazoline H2chpbzn which was
found in 3-formylsalicylic acid. No azomethine proton signal d(CH¼N)
could be detected either. The broad d(OH) signal vanishes after the addition
of D2O. The broad signal at d 6.5 ppm to d 7.9 ppm may be assigned to the
phenyl resonance region. It was not possible to assign definitely a resonance

COORDINATION OF BENZOTHIAZOLINE
1399
Figure 2. Reactions of [(p-C5H5)Ti(Hmpcsalim)Cl].
Figure 3. Reaction of H2chpbzn leading to dinuclear complexes.
peak to the hydrogen atom of the CHN linkage of the thiazoline form,
which may possibly be submerged with d(NH) (see Fig. 2). The resonance
peak for the COOH proton could be detected around d 12.06 ppm (broad
signal).[8,13,14] The absence of any bands due to n(SH) and n(C¼N) in the
adducts (11) and (12) indicates that the benzothiazoline ring remains intact
in the adducts also. However, the band due to n(N–H) (see above) of the
free benzothiazolines is shifted in the adducts (11) and (12) and appears as a
weak but broad band at around 3050 cmꢂ1. A band at ꢄ1650 cmꢂ1 is also
observed in the adducts; this may probably be due to the shifting of the
d(NH) bands present in the free benzothiazoline[6] around 1700 cmꢂ1. All
these data support that the adduct formation takes place through

1400
DEY, BHOWMICK, AND SARKAR
1
N-coordination. Due to solubility problems H NMR data of the other
complexes could not be collected.
In the infrared spectra of the complexes the bands due to N–H
vibrations are absent, suggesting the bond formation of the ligand to the
metal through oxygen and nitrogen. In addition, a new band around
1600 cmꢂ1 is observed, assignable to the n(C¼N) vibration. This supports the
fact that the benzothiazoline ring in the presence of metal ions, rearranges to
its Schiff base form and finally acts as a dibasic tridentate ONS donor
ligand in the complexes (Table I). The n(C–S) mode of the ligand around
760–750 cmꢂ1 is shifted to around 730–700 cmꢂ1 in the metal complexes
indicating an M-S linkage. This is further substantiated by the appearance
of new bands in the region 3607320 cmꢂ1 in the metal complexes which are
assignable to n(M–S) (M ¼ metal ions).[15] The appearance of bands in the
region 560–500 cmꢂ1 in the complexes are additional support of N and O
linkage to the metal atoms.[16] The infrared spectra of Na[Me2-
Tl(Hmpcsalim)] (13) and Na[Ph2Tl(Hmpcsalim)] (14) essentially coincide
with those of Me2Sn(Hmpcsalim)1 and Ph2Sn(Hmpcsalim)1, apart from
bands associated with metal-organic radical vibrations, such as the strong
absorptions at about 450 cmꢂ1 in Na[Ph2Tl(Hmpcsalim)] (14), which can be
assigned to a Ph-Tl mode.[17] It may be mentioned here that the stretching
frequencies for coordinated >C¼N– in Na[R2Tl(Hmpcsalim)] are ob-
served at 1600 cmꢂ1 (where R ¼ Ph) and at 1610 cmꢂ1 (where R ¼ Me).
These assignments are based on previously published results.[18] Based on
the above discussion it may be tentatively concluded that the
Na[R2Tl(Hmpcsalim)] complexes in the solid state contain Hmpcsalim2ꢂ
(Schiff base form) coordinating to R2Tl(III) through S, N and O donor
atoms, and that the C-Tl-C skeletons of R2Tl(Hmpcsalim)ꢂ seem to display
a bent configuration. Therefore, we tentatively suggest a trigonal bipyr-
amidal configuration for R2Tl(Hmpcsalim)ꢂ (Fig. 1).[18,19]
Magnetic Properties
The organotitanium(IV) and organozirconium(IV) complexes (1) to
(6), the bismuth(III) complex (11), the antimony(III) complex (12) the
organothallium(III) complexes (13) and (14), the oxovanadium(V) complex
(16) the palladium(II) complex (17) and the nickel(II) complex (18) are all
diamagnetic while the chromium(III), iron(III) and oxovanadium(IV)
complexes (7) to (10) and (15), respectively, are paramagnetic. The magnetic
moment values, 3.85 and 3.88 B.M. found at room temperature for the
chromium(III) complexes (7) and (8) are slightly lower (Table I) than
the spin-only values for a d3 ion and this has been discussed earlier.[20] On

COORDINATION OF BENZOTHIAZOLINE
1401
the other hand, the iron(III) complexes (9) and (10) at room temperature
have values for effective magnetic moments characteristic for high-spin
octahedral Fe(III) complexes (term 6A1).[21] The low value (meff ¼ 1.28 B.M.)
(compared to the spin-only value of 1.73 B.M.) for the oxovanadium(IV)
complex (15) demonstrates some sort of magnetic interactions between two
oxo-briged oxovanadium(IV) centres in the solid state.[22]
UV-Vis Spectra
The thiazoline ligand showed two intense bands around 260 and
370 nm in solution of DMSO and these are due to the intra-ligand charge
transitions p ? p* and n ? p*, respectively. These bands are very
slightly red-shifted along with other bands in the complexes. The titanium
and zirconium complexes showed another band around 4357445 nm
assignable to charge transfer[23,24] in accordance with the (nꢂ1)d0ns0 elec-
tronic configuration of titanium(IV) and zirconium(IV). The data available
for (1) to (6) suggest the coordination number five for these complexes.[25727]
The electronic absorption spectra of the chromium(III) complexes (7)
and (8) in solution show three absorption bands (in ethanol and DMSO, as
the case may be, depending on the solubility limitations) in the
range 18,000721,000 cmꢂ1 (shoulder), 21,000723,000 cmꢂ1 (e ꢄ3500) and
25,500726,000 cmꢂ1 (e ꢄ5000). Some of these chelates when measured
in Nujol mulls give almost identical spectra, specially in the range
18,000726,000 cmꢂ1. This suggests that the environment of chromium(III) is
almost the same in the solid as well as in the solution state. The bands
observed in the range 18,000726,000 cmꢂ1 may be considered as the split
4
4
components of the T2g (Oh) and T1g (F) (Oh) terms, despite their high
molar extinction coefficients. Similar high molar extinction coefficients were
observed for bands in this region in the chromium(III) complexes of similar
ligands.[28730]
The complexes [Pd2(Hmpcsalim)2] (17) and [Ni2(Hmpcsalim)2] (18) are
possibly sulfur-bridged dinuclear species and the dinuclear nature has been
supported by their molecular weight values. Molar conductance values of
these complexes also indicate their non-electrolytic nature in solution sup-
porting thereby their formulations (Table I). They are diamagnetic which
suggests square-planar geometry. The nickel(II) complex (18) in the visible
region shows two bands in the regions 25,000 and 19,500 cmꢂ1 assignable
1
1
(tentatively) to A1g?1B1g and A1g?1A2g transitions in a square-planar
field.[30,31] A band at 21,000 cmꢂ1 for the palladium(II) complex (17)
is assigned to the A1g?1A2g (dxy?dx2ꢂy2) transition in a square-planar
geometry.
1

1402
DEY, BHOWMICK, AND SARKAR
EXPERIMENTAL
Materials and Instruments
The solvents and chemicals were purified and dried before use by
standard procedures. The elemental analyses were carried out at the
Regional Sophisticated Instrumentation Centre, the Central Drug Research
Institute, Lucknow. The electronic spectra (ethanol or DMSO) were
recorded on a Hitachi 200-20 spectrophotometer and infrared spectra (KBr
or Nujol or hexachlorobutadiene; more than one media were used for
some compounds) on a Perkin-Elmer 1330 spectrophotometer. The molar
conductance was measured using an Elico conductivity bridge. The mag-
netic susceptibility was determined by the Guoy method. Molecular weights
were determined by Rast’s method. Di(p-cyclopentadienyl)titanium di-
chloride, (p-C5H5)2TiCl2, and di(p-cyclopentadienyl)zirconium dichloride,
(p-C5H5)2ZrCl2, were purchased from Alfa Inorganics.
Preparation of the Ligand
Theligand,2-(1-carboxyl-2-hydroxyphenyl)benzothiazoline(H2chpbzn)
was prepared by our previously published method.[1]
Preparation of Complexes
[(p-C5H5)M(Hmpcsalim)(Cl)] {M ¼ Ti, (1) and M ¼ Zr, (2)}
To a solution of the thiazoline ligand H2chpbzn (6.825 g, 25 mmol) in
methanol-nitromethane mixture (50:50, V=V) (40 mL) was added (p-
C5H5)2MCl2 (25 mmol) (M ¼ Ti or Zr) in a chloroform-methanol mixture
(50:50, V=V) (35 mL) with stirring. The mixture was heated under reflux at
neutral pH for 6 h and filtered when hot. A reddish-brown (for Ti) or yel-
low-brown (for Zr) filtrate was obtained from which the solvent was
removed under reduced pressure. n-Hexane (20 mL)ꢃwas then added to this
crude product and the mixture cooled to about ꢂ5 C to obtain orange (1)
or yellow-brown (2) solids. The compounds were collected by filtration,
washed with ethanol and n-hexane and dried in vacuo. Yields, 0.18 g for (1)
and 0.20 g for (2) (about 70%).
[(p-C5H5)Ti(Hmpcsalim)(MeS)] (3)
One equivalent of (1) (0.4195 g, 1 mmol) was added to one equivalent
of MeSH (0.048 g, 1 mmol) in THF-toluene (50:50, V=V) (50 mL) and

COORDINATION OF BENZOTHIAZOLINE
1403
stirred at room temperature in the presence of a stoichiometric amount of
Et3N (0.101 g, 1 mmol) for 3 d. Solid Et3NꢀHCl which had separated and
was removed by filtration and then the volume of the solution was
ꢃ
reduced to half under vacuum. Standing at about ꢂ10 C gave a brown
solid (3). It was filtered, washed with n-hexane and dried in vacuo. Yield,
0.27 g (65%).
[(p-C5H5)Ti(Hmpcsalim)(NMe2)] (4)
The complex (1) (0.4195 g, 1 mmol) was treated with an equimolar
quantity of Me3SiNMe2 (0.117 g, 1 mmol) as described above in the same
solvent system (60 mL) and yellow-brown (4) was isolated. Yield, 0.74 g
(70%).
[(p-C5H5)Ti(Hmpcsalim)(N3)] (5)
The compound (1) (0.4195 g, 1 mmol) when treated with Me3SiN3
(0.115 g, 1 mmol) in THF for 3 d, yielded the light-brown compound (5).
The byproduct Me3SiCl and the solvent were removed by distillation at low
pressure. The crude product (5) was extracted with a n-hexane-THF mix-
ture (50:50, V=V). The solution was cooled and the formed light-brown
solid was filtered off, washed with n-hexane and dried in vacuo. Yield, 0.69 g
(68%).
[(p-C5H5)Ti(Hmpcsalim)(CꢁC-Ph)] (6)
Similar to compound (5), the compound (1) (0.4195 g, 1 mmol), when
treated with Me3SiCꢁC–Ph (0.174 g, 1 mmol) in THF, yielded the light-
brown compound (6). Yield, 0.67 g (58%).
Na[(Hmpcsalim)2Cr] (7) and [(Hmpcsalim)Cr(H2mpcsalim)] (8)
The ligand H2chpbzn (2.73 g, 10 mmol) was dissolved in ethanol
(30 mL) to which a solution of CrCl3ꢀ6H2O (2.665 g, 10 mmol) in the same
solvent (30 mL) was added with stirring followed by the addition of a
stoichiometric amount of CH3COONa (0.82 g, 10 mmol) and the mixture
was refluxed for 2 h. The brown solution thus obtained gave the brown
compound (7) on standing, which was filtered, washed with cold ethanol and
dried in vacuo. Yield, 1.1 g, (48%). The filtrate from (7), on concentration

1404
DEY, BHOWMICK, AND SARKAR
ꢃ
and cooling to ꢂ5 C, gave the yellow-brown compound (8). It was filtered
and washed with cold ethanol and dried in vacuo. Yield, 0.65 g (30%).
Na[(Hmpcsalim)2Fe] (9) and [(Hmpcsalim)Fe(H2mpcsalim)] (10)
Similar to compound (7), the reaction of H2chpbzn (2.73 g, 10 mmol)
with anhydrous FeCl3 (1.625 g, 10 mmol) in dry ethanol (30 mL) and in the
presence of CH3COONa (0.82 g, 10 mmol) gave 1.27 g of the red-brown
compound (9) (56% yield). The filtrate from (9) gave 0.82 g of (10) (36%).
[(BiCl3)(H2chpbzn)] (11) and [(SbCl3)(H2chpbzn)] (12)
The reaction of H2chpbzn (2.73 g, 10 mmol) with BiCl3 (3.155 g,
10 mmol) or SbCl3 (2.285 g, 10 mmol) in dry CCl4 (50 mL under nitrogen
atmosphere at 0 ꢃC gave 1.29 g of light-yellow (11) (60% yield) or 0.79 g of a
light-brown compound (12) (55% yield). The compounds were washed with
petroleum ether and n-hexane and dried in vacuo.
Na[Me2Tl(Hmpcsalim)] (13) and Na[Ph2Tl(Hmpcsalim)] (14)
ToasolutionofMe2TlCl(0.2695 g, 1 mmol)orPh2TlCl (3.94 g, 10 mmol)
in methanol (40 mL) was added a solution of H2chpbzn (2.73 g, 10 mmol) in
methanol (40 mL) and the mixture was heated at 40 ꢃC for 3 h. To this light-
brown solution was added a stoichiometric amount of NaOH (0.4 g, 10 mmol)
in methanol (40 mL) and stirred thoroughly for 2 h. The light-brown com-
pound (13) or (14) was formed. The compounds were washed with methanol
and dried in vacuo. Yield, 1.16 g for (13) and 1.43 g for (14) (60%).
[(Hmpcsalim)VO]2 (15)
The reaction of H2chpbzn (2.73 g, 10 mmol) and VOSO4 (1.63 g,
10 mmol) in methanol (60 mL) under reflux gave 1.5 g of this brown com-
pound in about 68% yield. The compound was washed with methanol and
dried in vacuo. The compound is paramagnetic (meff ¼ 1.28 B.M. at room
temperature).
[(Hmpcsalim)VOCe] (16)
Similar to compound (15), the reaction of H2chpbzn (2.73 g, 10 mmol)
and VOCl3 (1.735 g, 10 mmol) gave 0.89 g of this reddish-brown compound in
65% yield. It was washed with methanol and dried in vacuo. It is diamagnetic.

COORDINATION OF BENZOTHIAZOLINE
1405
[Pd2(Hmpcsalim)2] (17)
A solution of H2chpbzn (5.46 g, 20 mmol) in dry methanol (40 mL)
was added to a solution of Na2PdCl4 (2.94 g, 10 mmol) in the same solvent
ꢃ
(60 mL) and the mixture was stirred at 40 C for 10 h yielding the yellow
solid compound (17). Yield; 3.82 g (69%). It is diamagnetic.
[Ni2(Hmpcsalim)2] (18)
Similar to compound (17), the reaction of H2chpbzn (5.46 g, 20 mmol)
with Ni(OOCCH3)2ꢀ4H2O (2.49 g, 10 mmol) in methanol (50 mL) gave the
brown compound (18). Yield, 0.79 g (72%). It is also diamagnetic.
ACKNOWLEDGMENTS
The authors are thankful to the Regional Sophisticated Instrumenta-
tion Centre, the Central Drug Research Institute, Lucknow for elemental
analyses and spectroscopic data.
REFERENCES
1. Dey, K.; Chakraborty, K.; Bhowmik, R.; Nag, S.K. Synthesis,
Characterization and Coordination Behaviour of 2-(1-Carboxyl-2-
hydroxyphenyl)benzothiazole. In Advances in Metallo Organic Chem-
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Received May 11, 2001
Accepted May 30, 2002
Referee I: G. N. Holder
Referee II: K. Moedritzer