Benzothiazolylazo derivatives of some β-dicarbonyl compounds and their Cu(II), Ni(II) and Zn(II) complexes

Article abstract of DOI:10.2298/JSC090816040K

The coupling of diazotized 2-aminobenzothiazole with 1,3-dicarbonyl compounds (benzoylacetone, methyl acetoacetate and acetoacetanilide) yielded a new series of tridentate ligand systems (HL). Analytical, IR, ¹H-NMR, 13C-NMR and mass spectral data indicated that the compounds exist in the intramolecularly hydrogen bonded azo-enol tautomeric form in which one of the carbonyl groups of the dicarbonyl moiety had enolised and hydrogen bonded to one of the azo nitrogen atoms. The compounds formed stable complexes with Ni(II), Cu(II) and Zn(II) ions. The Cu(II) complexes conform to [CuL(OAc)] stoichiometry while the Ni(II) and Zn(II) complexes are in agreement with [ML₂] stoichiometry. Analytical, IR, ¹H-NMR, ¹³C-NMR and mass spectral data of the complexes are consistent with the replacement of the chelated enol proton of the ligand with a metal ion, thus leading to a stable six-membered chelate ring involving a cyclic nitrogen, one of the azo nitrogens and the enolate oxygen. The Zn(II) chelates are diamagnetic while Cu(II) and Ni(II) complexes showed a normal paramagnetic moment.

Full text of DOI:10.2298/JSC090816040K

J. Serb. Chem. Soc. 75 (5) 639–648 (2010)
UDC 547.53’788+547.235:546.562’742’472
JSCS–3994
Original scientific paper
Benzothiazolylazo derivatives of some β-dicarbonyl compounds
and their Cu(II), Ni(II) and Zn(II) complexes
1
2
*
KRISHNANNAIR KRISHNANKUTTY , MUHAMMED BASHEER UMMATHUR
and DAMODARAN KAMALAKSHY BABU3
1Department of Chemistry, University of Calicut, Kerala-673635, 2Department of Chemistry,
Unity Women’s College, Manjeri, Kerala-676122 and 3Department of Chemistry,
Zamorin’s Guruvayurappan College, Calicut, Kerala-673014, India
(Received 16 August, revised 4 December 2009)
Abstract: The c oupling of diaz otized 2-aminobenzothiazole with 1,3-dicarbo-
nyl co mpounds (benzoy lacetone, methyl ace toacetate and acetoacetanilide)
yielded a new series of triden tate ligand sy stems (HL). Analy tical, IR, 1H-
-NMR, 13C-NMR and mass spectral data indicated that the compounds exist in
the intramolecularly hydrogen bonded az o-enol tautomeric form in whic h one
of the carbony l groups of the dicarbonyl moiety had enolised and hydrogen
bonded to one of the azo nitrogen ato ms. The compounds formed stable com-
plexes with Ni(II), Cu(II) and Zn(II) ions. The Cu(II) com plexes conform to
[CuL(OAc)] stoichiometry while the Ni(II) and Zn(II) complexes are in agre-
ement with [ML2] stoichiometry. Analytical, IR, 1H-NMR, 13C-NMR and mass
spectral data of the complexes are consistent with the replacement of the che-
lated enol prot on of the ligand with a metal ion, thus leadin g to a stable si x-
-membered chelate ring involv ing a cy clic nitrogen, one of the azo nitrogen s
and the enolate oxygen. The Zn(II) chelates are diamagnetic while Cu(II) and
Ni(II) complexes showed a normal paramagnetic moment.
Keywords: benzothiazolylazo-β-dicarbonyls; azo-enol for m; Cu(II), Ni(II) and
Zn(II) complexes; IR, mass and NMR spectral studies.
INTRODUCTION
The chemistry of 2-aminobenzothiazole has gained increasing interest in both
1
synthetic organic chemistry and biological fields. The substitution of an ary l di-
azonium group at the active methy lenic carbon provides for the possibility of
2
azo-hydrazone tautomerism. In rec ent years, a significant num ber of tridenta te
azo compounds containing heteroaryl ring systems have been developed in order
to improve the colouring p roperties and to achieve more specificity and selecti -
3
vity in chemical analysis. Metal dye complexes play a very important role in dye-
*Corresponding author. E-mail: mbummathur@gmail.com
doi: 10.2298/JSC090816040K
639
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KRISHNANKUTTY, UMMATHUR and BABU
4
stuff technology and find application in many other fields, especially in ana ly-
5
tical chemistry. However, structural a spect of many of these pro ducts and their
metal derivatives have rec eived only scanty attention. In continuation of studies
6–11
on arylazo
derivatives of β-dicarbonyl compounds and their metal comple-
xes, the sy nthesis and cha racterization of benzothiazolylazo derivatives of three
β-dicarbonyl compounds: benzoylacetone, methyl acetoacetate and acetoacetani-
lide, are reported herein. Typical Cu (II), Ni(II) and Zn(II) com plexes of these
compounds were also synthesized and characterized.
EXPERIMENTAL
Methods, instruments and materials
Carbon, hy drogen and nitrog en content s we re deter mined by m icroanalyses (Heraeu s
elemental analyzer from RSIC, Central Drug Re search Institute, Luckno w, India, and Ca-
talysis division, Department of Chemistry, Indian Institute of Technology, Chennai, India) and
the metal cont ents of the co mplexes by AAS (Perkin El mer 2380 spe ctrometer). The elec-
tronic spectra of the compounds in methanol (10-4 mol/L) were recorded on a 1601 Shimadzu
UV–Vis. spectr ophotometer, t he IR spectra (KBr di scs) on an 810 1 Shi madzu FTIR sp ec-
1
trophotometer, the H-NMR spectra (CDCl3 or DMSO-d6) on a Varian 300 N MR spectrome-
ter and the mass spectra on a Jeol/SX-102 mass spectrometer (FAB u sing argon and meta-
-nitrobenzyl alcohol as the matrix). The molar conductance of the complexes was determined
in DMF ( ≈10-3 mol/L) at roo m te mperature (301 1 K). The magnetic su sceptibilities were
determined at room temperature on a Guoy type magnetic balance, Sherwood Scientific Ltd.,
England, at room temperature using Hg[Co(NCS)4] as the standard.
Benzoylacetone, methyl acetoacetate, acetoacetanilide, 2-aminobenzothiazole, methanol,
urea and the metal acetates were of AR grade, purchased from Merck, Germany.
General procedure for the preparation of benzothiazolylazo derivatives of
β-dicarbonyl compounds
An aqueous solution of 2-benzothiazoledi azonium ion wa s prepared by a standard me-
thod.12 To a solution of Na NO2 (1.4 g) in H2SO4 (12 M, 20 mL), kept below 278 K, a cooled
(≈278 K) solut ion of 2-a minobenzothiazole ( 1.5 g, 0.010 mol) in 15 mL DMF was ad ded
slowly under stirring. The stirring wa s continued for ≈1 h, a fter which the reaction mixture
was filtered to obtain a clear y ellow diazon ium salt solution. After destr oying the excess
nitrous acid with urea, the diaz onium salt solution (0.010 mol) was ad ded slowly under stir-
ring to an ice-cold (< 27 8 K) solution of the required β-dicarbonyl compound (benzoylace-
tone, methyl acetoacetate or acetoacetanilide, 0.010 mol in 25 mL ethanol). Cooled (< 278 K)
NaOH sol ution (1.0 M, 2 0 mL) was added dropwise to maintain th e p H of the mixture at
around 5. Stirring was continued for about 30 min and the precipitated compound was filtered,
washed several ti mes with deionised w ater a nd recry stallized twice fro m h ot methanol to
obtain chromatographically pure material: 2-(2-benzothiazolylazo)-1-phenyl-1,3-butanedione
(Hbba), methyl 2-(2-benzothiazolyazo)-3-oxobutanoate (Hbma) and 2-(2-b enzothiazolylazo)-
-3-oxo-N-phenylbutanamide (Hban) (TLC on silica gel, acetone as the solvent). All the com-
pounds were cr ystalline in nat ure with a red dish pink colou r and were soluble in co mmon
polar and non-polar organic solvents, such as benzene, methanol, ethanol, chloroform and car-
bon tetrachloride. The co mpounds for med stable co mplexes with Ni(II), Cu(II) and Zn(II)
ions.
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TRANSITION METAL COMPLEXES OF BENZOTHIAZOLYLAZO-β-DICARBONYLS
641
Synthesis of the Ni(II), Cu(II) and Zn(II) complexes
A concentrated aqueous solution of metal(II) acetate (0.010 mol) was added under stir-
ring to a methanolic solution of one of the ligands (0.020 mol, 20 mL). Stirring was continued
for the following ≈2 h. Th e precipitated complex was filtered, washed with water, recrystal-
lized from hot chloroform and dried under vacuu m. The Ni(I I), Cu(II) and Zn(II) com plexes
had a greenish black, dark violet and dull white colour, respectively. The complexes were well
soluble in CH3CN, DMSO and DMF but insoluble in methanol, ethanol, carbon tetrachloride
and water.
Determination of magnetic susceptibility
A thin cy lindrical glass tu be filled with the sample was vertically suspended from the
beam of a b alance in a dra ught-free enclosure in such a way that its lo wer end lied bet ween
the poles of an electromagnet. The weight of the sample was determined with the field off and
with the field o n. Corrections for diamagnetism of the constituents were made using Pascal
constants.13 The effective magnetic moments w ere c alculated using t he for mula μeff
=
= 2.83( χMT)1/2(9.274×10-24) A m2, wh ere χM is th e correct ed molar susceptibility and T is
temperature. T he Zn(II) chelates were diam agnetic while the Cu(II) and Ni(II) com plexes
showed a normal paramagnetic moment.
RESULTS AND DISCUSSION
The observed ele mental analytical data of the benzothiazoly lazo derivatives
(Table I) indicate that the diazo-coupling reaction between the diazotized 2-ami-
nobenzothiazole and the β-dicarbonyl compounds occurred in the 1:1 mole ratio.
The analytical data (Table I) together with non-electrolytic nature in DMF (speci-
–1
–3
fic conductance < 10 S cm ; 10 M solution) suggested the for mula [ML ] for
2
the complexes where M(II ) = Zn and Ni, and [ CuL(OAc)] for th e Cu(II) co m-
plexes.
TABLE I. Physical and analytical data of the new b enzothiazolylazo derivatives of β-dicar-
bonyl ligands a nd their metal complexes (Hbba: 2-(2-benzothiazolylazo)-1-phenyl-1,3-buta-
nedione; Hb ma: m ethyl 2-(2-benzothiazolylazo)-3-oxobutanoate; Hban: 2-(2-benzo thiazo-
lylazo)-3-oxo-N-phenylbutanamide; –OAc: acetate)
μeff×1024
Found (Calcd.), %
Compound
Empirical formula
Hbba
C17H13N3SO2
Hbma
Yield
%
60 180
M.p.
°C
A m2
C H
63.10
(63.16)
51.88
N
M
–
–
–
3.98
(4.02)
3.99
12.98
(13.00)
15.05
70 98
–
–
C12H11N3SO3
Hban
C17H14N4SO2
[Ni(bba)2]
C34H24N6NiS2O4
[Ni(bma)2]
C24H20N6NiS2O6
[Ni(ban)2]
(51.99)
60.23
(60.36)
58.20
(58.06)
47.30
(47.16)
55.53
(3.97)
4.14
(4.14)
3.48
(3.42)
3.30
(3.27)
3.54
(15.16)
16.64
(16.57)
11.98
(11.95)
13.65
(13.75)
15.24
70 182
60 170
65 >300
70 270
–
25.8
25.9
26.1
8.50
(8.35)
9.54
(9.61)
8.02
C34H26N8NiS2O4
(55.68)
(3.55)
(15.29)
(8.01)
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KRISHNANKUTTY, UMMATHUR and BABU
TABLE I. Continued
Found (Calcd.)/ %
N
Compound
Empirical formula
Yield
%
M.p.
°C
μeff×1024
A m2
C H
51.40
(51.29)
42.26
M
[Cu(bba)(OAc)]
C19H15CuN3SO4
[Cu(bma)(OAc)]
C14H13CuN3SO5
[Cu(ban)(OAc)]
C19H16CuN4SO4
[Zn(bba)2]
C34H24N6S2O4Zn
[Zn(bma)2]
C24H20N6S2O6Zn
[Zn(ban)2]
65 220
16.2
16.5
16.8
–
3.34
(3.37)
3.23
9.36
(9.45)
10.70
14.19
(14.29)
15.85
65 >300
72 >300
68 208
(42.15)
49.55
(49.61)
57.58
(57.52)
46.56
(46.65)
55.28
(3.26)
3.45
(3.48)
3.38
(3.38)
3.23
(3.24)
3.53
(10.54) (15.94)
12.28 13.75
(12.19) (13.83)
11.80
(11.84)
13.63
9.35
(9.22)
10.72
72 >300
68 225
–
(13.61) (10.59)
–
15.03
8.75
C34H26N8S2O4Zn
(55.18)
(3.52)
(15.15)
(8.84)
IR Spectra
The IR sp ectra of the ben zothiazolylazo derivatives show a stro ng band at
–1
8
≈1640 cm , assignable to the stretching of the enolised acety l carbonyl group
(Fig. 1). The free benzoyl, ester and anilide carbonyl bands of Hbba, Hb ma and
–1
14,15
Hban were observed at 1650, 1738 and 1670 cm , respectively.
In the spec-
tra of all the co mpounds, two medium intensity bands were observed at ≈1280
–1
and 1470 cm , assignabl e to C–O–H in-plane bending and ν(N=N), respecti-
14,15
–1
vely.
The aro matic ν(C=C) vibrations appeared at ≈1580 cm and benzo-
–1
thiazole ring ν(C=N) was observed at ≈1620 cm . The broad ban d in the range
2500–3300 cm indicates the existence of strong intramolecular hydrogen bond-
–1
ing in these co mpounds. Thus, the IR spectra strongly support t he existence of
the compounds in the intramolecularly hydrogen-bonded azo-enol tautomeric form.
Fig. 1. Sche matic view represe nting the geo-
metry of the prepared benzothiazolylazo deri-
vatives, where R = C 6H5 (Hbba); OCH
3
(Hbma); NHC6H5 (Hban).
In the IR spe ctra of all the complexes, the broad free ligand band in the re-
–1
gion 2500–3300 cm had disappeared, indicating the replacement of the en ol
7,8
proton by a metal ion during complexation. Several medium intensity bands
were present in this region of the spectra due to various ν(C–H) vibrations. The
–1
absence of the free ligand band at ≈1270 cm due to C–O–H be nding also sup-
ports the replacement of the enol prot on by a metal ion. The free carbon yl band
of the compounds was only marginally shifted indicating that this carbonyl is not
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TRANSITION METAL COMPLEXES OF BENZOTHIAZOLYLAZO-β-DICARBONYLS
643
involved i n t he coordinati on. However, the band d ue to the h ydrogen b onded
acetyl carbony l gr oup disappeared and instead a new band appeared at ≈1570
–1
cm in the spectra of all the com plexes, supporting the involvement of the eno-
16
lised carbonyl in the bon ding with the metal ion. In the spectra of all the com-
–1
plexes, the band at ≈1470 cm due to ν(N=N) and the band due to benzothiazole
–1
–1
ν(C=N) at ≈1620 cm of the ligands w ere appreciably shifted ( 20–30 cm ) to
lower wave n umbers, indicating the invo lvement of these groups in the bonding
with the metal ion, as shown in Figs. 2 and 3.
Fig. 2. Schematic view representing the
proposed geometry of the metal complexes
of the benzothiazolylazo derivatives
within 1/2 molecules.
Fig. 3. Schematic view representing the
proposed coordination in the Cu(II)
complexes of the benzothiazolylazo
derivatives.
As in the spectrum of the ligand, the com plexes of Hban showed a band at
–1
≈3400 cm due to t he NH group of anilide. In the spectra of the Cu(II) co m-
–1
plexes, a comparatively strong band at ≈1625 cm and a medium intensity band
–1
at ≈1310 cm appeared due to the antisy mmetric and symmetric stretching of
16,17
the monodentate acetate group, respectively,
as in Fig. 3. The presence of
–1
new medium intensit y bands in the 4 20–490 and 530–560 cm regions, assi-
gnable to ν(M–O) and ν(M–N) in the spectra of all the complexes also support
Figs. 2 and 3. Important bands that appeared in the spectra are given in Table II.
16
NMR Spectra
1
The H-NMR spectra of t he benzothiazolylazo derivatives are characterized
by the presence of a low field, one proton signal at δ 13 ppm , which is consi-
derably lower than that re ported for arylazo derivatives of β-diketones that exist
9–11
in the h ydrazone form.
Since azo-enol prot ons show a signal in the δ range
10–14 ppm, the signal at δ 13 ppm can be assigned to the intramolecularly hydro-
gen bon ded enol proto n of Fig. 1.
8,9,18
The integrated intensities of all other
protons agree well with the structure of the compounds presented in Fig. 1. In the
1
H-NMR spectra of the diamagnetic Zn(II) complexes, the low field signal due to
the chelated hydrogen disappeared, indicating its re placement by the metal ion
8,19
during complexation.
The non-involvement of the ester carbo nyl and the ani-
lide NH groups in the coordination is evident from the observed position of the
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KRISHNANKUTTY, UMMATHUR and BABU
OCH and anilide NH resonance signals, which remain unaltered. The position of
3
the signal of the methyl proton in the chelates is downfield shifted, indicating the
involvement of the acetyl carbonyl in the coordination. The integrated intensities
of all other protons agree well with the structure of the complexes presented in
Fig. 2. The assign ments of the various proton signals observed are ass embled in
Table III.
TABLE II. Characteristic IR stretching bands (cm-1) of the ligands and their metal complexes
(abbreviations as in Table I)
Acetate
Free
Chelated
Compound
ν(C=O) and ν(C=N) ν(N=N) ν(M–N) ν(M–O)
ν(C–O)
ν(C=O) ν(C=O)
Hbba 1650
1640
1572
–
–
1615
1590
1593
1588
1618
1589
1590
1594
1615
1590
1588
1592
1468
1440
1444
1446
1460
1435
1436
1438
1460
1438
1440
1435
–
–
[Ni(bba)2] 1648
[Cu(bba)(OAc)]
[Zn(bba)2] 1652
Hbma 1738
[Ni(bma)2] 1737
[Cu(bma)(OAc)]
[Zn(bma)2] 1734
Hban 1670
548
540
548
–
555
540
540
–
420, 470
428, 490
420, 478
–
430, 468
420, 485
420, 466
–
1645
1735
1666
1566
1570
1644
1574
1566
1568
1638
1565
1562
1574
1622, 1305
–
–
–
1622, 1300
–
–
–
[Ni(ban)2] 1665
[Cu(ban)(OAc)]
[Zn(ban)2] 1668
538
545
550
435, 488
422, 480
428, 477
1620, 1305
–
TABLE III. 1H-NMR spectral data (δ / ppm) of the ligands and their Zn(II) complexes (abbre-
viations as in Table I)
Compound
OH CH
3 R
Benzothiazolyl
(9H, m)
(18H, m)
(3H, s) 6.90–7.50
(6H, s) 7.10–7.60
Hbba 12.80
[Zn(bba)2] –
Hbma 12.52
[Zn(bma)2] –
Hban 12.99
[Zn(ban)2] –
(1H, s, br) 2.61 (3H, s) 6.80–8.07
2.88 (6H, s) 6.98–8.02
(1H, s, br) 2.45 (3H, s) 3.82
2.82 (6H, s) 3.85
(1H, s, br) 2.59 (3H, s) 7.15–7.81 (9H, m), 11.20 (1H, s, anilide NH)
2.85 (6H, s) 7.20–8.01 (18H, m), 11.16 (2H, s, anilide NH)
(4H, m)
(8H, m)
13
The C-NMR spectrum of Hb ma clearly indicates it s existence in the azo-
-enol form. That the two carbonyl groups are in different electronic environments
is evident from the large separation of the carbon yl carbon signals. The com pa-
ratively large chemical shift of the methyl carbon signal in the spectrum indicates
8
the enolised nature of the acetyl group and its involvement in hydrogen bonding.
The involvement of the enolate oxygen and hetero nitrogen atoms in the bonding
13
with the metal ion is evi dent from the position of the various signals in the C-
-NMR spectrum of its Zn(II) complex (Table IV).
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TRANSITION METAL COMPLEXES OF BENZOTHIAZOLYLAZO-β-DICARBONYLS
645
TABLE IV. 13C-NMR spectral data (δ / ppm) of Hbma and its Zn(II) complex (abbreviations
as in Table I)
Compound C=O
Hbma
CH3 C–N
Benzothiazolyl
121.7, 122.4, 124.9, 126.9,
132.1, 135.5, 141.7
118.9, 122.0, 124.0, 125.8,
126.6, 127.5, 131.5
165.3
147.2
196.7, 198.3 26.5, 30.8
[Zn(bma)2]
195.7, 196.6 28.2, 33.1
Mass spectra
The formulation of the be nzothiazolylazo derivatives as shown in Fig. 1 is
clearly supported from the presence of an intense molecular ion peak in the mass
spectra. The presence of peaks due to the eli mination of ArN from molecular
2
9,20,21
ion, characteristic of tauto mers,
in the spectra support the azo structure of
the compounds. Fragments due to the elimination of RCO and CH CO are als o
3
present in the spectra of all the ligands. The origin of the peak at m/z 175 in the
mass spectra of the compounds can be explained by the formation of the i on ra-
+
dical BT–N CH] (BT = benzothiazole ring) through the elimination of CH CO
2
3
+
and RCO from P . If the co mpounds existed in the hydrazone form, the most
21
facile reaction would be t he cleavage of the N–N bond and an ion of m/z 175
could not be formed. Thus, all available evidences support the existence of the
compounds in the azo-enol form rather than the keto-hy drazone form. The F AB
mass spectra of the Cu(II) complexes showed molecular ion peaks corresponding
+
+
to [CuL(OAc)] stoichiometry. Peaks co rresponding to [P–RCO] , [P–CH CO] ,
3
+
+
+
+
+
[RCO] , [CH CO] , [CuL] , L and frag ments of L were al so present in the
spectra. The spectra also showed peaks due to [ P–CH COO] . The spectra of all
3
+
3
the chelates contained a number of fragments containing copper in the 3:1 natural
63
65
abundance of Cu and Cu isotopes (Table V).
TABLE V. Mass spectral data of the new ligands and their Cu(II) complexes (abbreviations as
in Table I)
Compound
Mass spectral data (m/z)
Hbba
Hbma
Hban
[Cu(bba)(OAc)]
323, 280, 218, 175, 162, 161, 134, 105, 43
277, 234, 218, 175, 162, 134, 115, 59, 43
338, 295, 218, 176, 175, 162, 134, 120, 43
446, 444, 403, 401, 387, 385, 344, 342, 341, 339, 323,
280, 239, 237, 175, 162, 105
[Cu(bma)(OAc)]
[Cu(ban)(OAc)]
400, 398, 341, 339, 357, 355, 282, 280, 277, 239,
237, 175, 162, 134, 115
461, 459, 402, 400, 341, 339, 418, 416, 282, 280, 239,
237, 338, 295, 176, 175, 162, 120
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KRISHNANKUTTY, UMMATHUR and BABU
Electronic spectral and magnetic measurements data
The UV spectra of the benzothiazolyl azo derivatives show two bro ad bands
with m axima at ≈380 n m and ≈270 nm due to various n → π* and π → π*
transitions. The absorption maxi ma of the metal chelates bore close resemblance
with those of the free ligands, which indicat es that no structural alteration to the
ligand had occurred during complexation. However, the values were shifted to
22
slightly longer wavelength in the spectra of the metal complexes, indicating the
involvement of the carbonyl and azo groups in metal complexation. In the Cu(II)
–1
complexes, the presence of a broad
visible band at ≈15,000 cm (log ε ≈
≈ 0.73) and the measur ed μ values ( Table I) supp ort a square-planar structu-
eff
23
re. The Ni(II) chelates showed three well- separated absorption bands in the
spectra at λ
≈ 810 0 (l og ε = 0. 67–0.72), ≈13200 (log ε = 0 .69–0.84) an d
max
–1
3
3
≈24200 cm (log ε = 0.77–0.82), corresponding to the transitions: A → T ;
2g
2g
3
3
3
3
24
A
2g
→ T (F) and A → T (P), respectively. These, toge ther with thei r
1g 2g 1g
measured μ values (Table I), support the octahedral structure.
eff
1
13
Thus, the observed analy tical, IR, H-NMR, C-NMR and m ass spectral
data are in conform ity with the structu res given in Fig. 1 for t he benzothiazo -
lylazo derivatives and in Fig. 2 for their Ni(II) and Zn(II) com plexes. The ana-
lytical and spectral data of the Cu(II) complexes are in agreement with Fig. 3.
CONCLUSIONS
Three new arylazo derivatives were prepared by coupling 2-benzothiazoledi-
azonium ion with the active methy lene group of t he β-dicarbonyl com pounds
benzoylacetone, methyl acetoacetate and acetoacetanilide (HL). The analytical and
spectral data of the compounds confirmed their existence in the azo-enol form in
which one of the carbonyl groups of the dicarbonyl moiety was enolised and hyd-
rogen bonded to one of the azo nitrogens. For the Cu(II) complexes, the formulas
[CuL(OAc)] are assumed, while the Ni(II) and Zn(II) co mplexes are represented
with [ML ]. The analytical and spectral data clearly indicated the monobasic tri-
2
dentate nature of the co mpounds and the involvement of the cyclic nitrogen, one
of the azo nitrogens and the enolate oxygen in the bonding with the metal ion.
И З В О Д
БЕНЗОТИОАЗОЛИЛАЗО ДЕРИВАТИ НЕКИХ β-ДИКАРБОНИЛ ЈЕДИЊЕЊА И
ЊИХОВИХ Cu(II), Ni(II) И Zn(II) КОМПЛЕКСА
KRISHNANNAIR KRISHNANKUTTY1, MUHAMMED BASHEER UMMATHUR2
и DAMODARAN KAMALAKSHY BABU3
1Department of Chemistry, University of Calicut, Kerala-673635, 2Department of Chemistry, Unity Women’s
College, Manjeri, Kerala-676122 и 3Department of Chemistry, Zamorin’s Guruvayurappan College,
Calicut, Kerala-673014, India
Купловањем диазотованог 2- аминобензотиазола са 1,3- дикарбонилним једињењима
(бензоилацетоном, метил-ацетоацетатом и ацетоацетанилидом) добијена је нова серија три-
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2010 Copyright (CC) SCS

TRANSITION METAL COMPLEXES OF BENZOTHIAZOLYLAZO-β-DICARBONYLS
647
дентатних лигандних система (HL). Аналитички, IR, 1H-NMR, 13C-NMR
и
масени
спектрални подаци указују да једињења постоје у интрамолекулско водонично везаном азо-
енол таутомерном облику у коме је једна од карболилних група у дикарбонилној околини
енолизована и водонично везана за један од азо азота. Једињења су градила стабилне
комплексе са Ni(II), Cu(II) и Zn(II) јонима. Cu(II) комплексима одговара [CuL(OAc) ]
стехиометрија, док су Ni(I I) и Zn(II) комплекси у складу са [ML ] стехиометријом.
2
Аналитички, IR, 1H-NMR, 13C-NMR и масени спектрални подаци су у складу са заменом
хелатног енолног протона лиганда металним јоном, што доводи до стабилног шесточланог
хелатног прстена укључујући циклични азот, један од азо азота и енолатни кисеоник. Zn(II)
хелати су дијамагнетични, док су Cu(II) и Ni(II) комплекси имали нормални парамагнетични
момент.
(Примљено 16. августа, ревидирано 4. децембра 2009)
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