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H.A. Mohamed et al. / Spectrochimica Acta Part A 64 (2006) 913–917
Scheme 4. The proposed structure of complex 3.
rial sites. Investigation of complex 3 by 1H NMR in DMSO, d6,
nals might be corresponding to two NH groups. The 1H NMR
spectrum of LH2 itself showed a broad signal at 11.30 ppm due
two OH protons, i.e., the ligand existed in solution in an enolic
form (Scheme 1). Therefore, isomer F in Scheme 4 was predom-
inant in solution, while isomer E is the predominant isomer in
the solid state.
Scheme 3. The proposed structure of complex 2.
1
Investigation of complex 1 by H NMR spectroscopy gave
no signal due to its paramagnetic characteristics. Magnetic mea-
surements of the Cr(III), d3, complex at 298 K gave a magnetic
susceptibility value of 2.26 × 10−6 emu g−1 with an effective
magnetic moment (µeff) 1.39 BM. This value is less than the
spin only value of one unpaired electron (1.73 BM). However,
this lowering in µeff could be due to strong antiferromagnetic
coupling between the two Cr(III) centers mediated through the
two (-O) groups.
The reaction of LH2 with [Mo(CO)6] in air resulted in the
O)2MoO2(LH2)] (2). The IR spectrum of the complex (Fig. 1)
displayed a ν(NH) band at 3177 cm−1 and a ν(C O) band at
1650 cm−1 with a corresponding shift from the ligand bands
due to complex formation (Table 2). In addition, the IR spec-
trum of the complex displayed two strong bands at 1549 and
1519 cm−1 due to stretching frequencies of ν(OC NH). Again,
the presence of these bands indicated that the complex existed
850 cm−1 which were assigned owing to symmetric and asym-
metric stretching frequencies of Mo O bond, respectively, for a
cisMoO2 fragmentofadimericstructurehavingthecoreMo2O6
ited two bands at 741 and 690 cm−1 due to two ν(Mo O Mo)
stretching vibrations [17]. Also, the complex 2 showed a ν(OH)
band at 3376 cm−1 indicating that the ligand coordinated to the
3.2. Thermogravimetric analysis
The thermal studies of the chromium, molybdenum and
ruthenium complexes were carried out using thermogravimetry
(TG) and differential thermogravimetry (DTG) techniques. The
TG plot of the complex [(LH)Cr(-O)2Cr(LH)] displayed two
resolved and well-defined decomposition steps. The first decom-
position step occurred in the temperature range 318–428 K with
a net weight loss of 17.77% could be due to elimination of
two moles of oxygen. The second decomposition step occurred
in the temperature range 425–675 K with a net weight loss of
53.33% corresponded to the elimination of a C8H6N4O2 species
to give finally the metallic residue of Cr with a net weight loss of
28.9%.
The TG plot of the of [(LH2)O2Mo(-O)2MoO2(LH2)] dis-
played three decomposition steps in the temperature range
313–1125 K. The first decomposition step occurred in the tem-
perature range 313–472 K with a net weight loss of 6.82% corre-
sponded to the elimination of two H2O molecules. On the other
hand, the second decomposition step occurred in the temperature
range 477–1000 K with a weight loss of 36.93 % and corre-
sponded to the material decomposition of C4H2N4O species.
The third decomposition step occurred in the temperature range
1003–1125 K with a weight loss of 56.25% and corresponded
to the material decomposition of Mo2O6.
The molybdenum complex with Mo(VI), d0, oxidation state
is a diamagnetic. Unfortunately, we were not able to obtain a
1H NMR spectrum for the complex due to its poor solubility.
[Ru3(CO)12] reacted with maleic hydrazide to give the
tricarbonyl derivative [Ru(CO)3(LH2)] (3). The IR spectrum
of 3 displayed the ligand bands with the appropriate shifts
(Fig. 1, Table 2). Furthermore, the IR spectrum of 3 exhibited a
band at 3389 cm−1 due to an OH group. The presence of this OH
group was not observed in the 1H NMR spectrum (vide infra) In
addition, the IR spectrum of 3 showed three bands in the terminal
metal carbonyl region at 2054, 1978 and 1920 cm−1 stretching
vibrations due to three CO groups attached to the metal. From
the number and pattern of the CO groups, it can be concluded
that the ruthenium complex has a trigonal bipyramid structure
and the LH2 ligand coordinated to the metal from two equato-
The [Ru(CO)3(LH2)] complex was found to be thermally
decomposed in a well-defined step in the temperature range
385–598 K with a net weight loss of 47.29% and corresponded
to the elimination of L and CO species to leave a metallic residue
of 52.71%.
4. Conclusion
Maleic hydrazide is an important biologically active sub-
stances. It existed in solution in three different tautomers (keto
and enol forms). Few metal complexes of maleic hydrazide,
which are prepared from the interaction of metal ions, are
reported. The dinuclear oxo complexes [(LH)Cr(-O)2Cr(LH)]
and [(LH2)O2Mo(-O)2MoO2(LH2)] were isolated from the