372
B. Raju, B. N. Sivasankar
Preparation of bis-hydrazine cobalt pyruvate
resulting solution was filtered and heated on a water bath
for 8 h. The resulting solution was concentrated to about
20 mL in a boiling water bath. The concentrated solution
was allowed to crystallize inside a vacuum desiccator. The
dark red crystals formed in the case of cobalt and blue
crystals formed by nickel after a week were removed,
washed with absolute alcohol and dried in the vacuum
desiccator. These complexes are water soluble and
hygroscopic.
and tris-hydrazine nickel, zinc and cadmium pyruvates
To an aqueous solution (20 mL) of the respective metal
nitrate hydrates (0.01 mol), aqueous solution (20 mL) of
pyruvic acid (1.4 mL, 0.02 mol) was added and the
resulting solution was filtered and concentrated to about
20 mL in a boiling water bath. To this hot concentrated
solution, hydrazine hydrate (2 ml, 0.04 mol) was added
drop by drop with vigorous stirring. The complexes thus
formed immediately were allowed to settle and then fil-
tered. The complexes were washed several times with
water, then with alcohol and dried in air.
Physico-chemical studies
The physico-chemical techniques involved in the present
study are similar to those that were reported earlier [3].
Preparation of bis-hydrazine nickel pyruvate
and tris-hydrazine cobalt pyruvate
Results and discussions
An aqueous solution (30 mL) containing a mixture of
pyruvic acid (1.4 mL, 0.02 mol) and hydrazine hydrate
(2 mL, 0.04 mol) was added with stirring to an aqueous
solution (20 mL) of nickel or cobalt nitrate hexa hydrate
(2.91 g, 0.01 mol). The resulting solution was immediately
filtered and the clear solution was kept at room tempera-
ture. The crystalline complex formed was filtered, washed
with water, then with alcohol and dried in air. The cobalt
complex is hygroscopic and hence stored in vacuum
desiccator.
Bis-hydrazine and tris-hydrazine metal pyruvates were
prepared by the aqueous reaction between metal salts and
pyruvic acid in the presence of excess hydrazine hydrate.
The method of preparation and ratio differs for different
metal complexes. The hydrazinium complexes of metal
pyruvates were prepared by the aqueous reaction between
the respective metal ions with aqueous solution containing
a mixture of pyruvic acid and hydrazine hydrate in 1:4
ratio. However, we were able to isolate only cobalt and
nickel complexes. Our attempt to prepare other metal
complexes was not successful and resulted in the formation
of respective metal pyruvates.
Preparation of bis-hydrazine zinc and cadmium
pyruvate
MðCH3COCOOÞ2ðN2H4Þ2 where M ¼ Zn or Cd
The composition of the complexes were assigned on the
basis hydrazine analysis by titrating with standard KIO3
solution and metal analysis by EDTA complexometric
titrations. The observed percentage of hydrazine and metal
are very well in agreement with the calculated values for
the assigned composition. The chemical analysis data of all
the complexes are summarized in Table 1.
To an aqueous solution containing 0.01 mol of zinc nitrate
hexa hydrate or cadmium nitrate tetra hydrate, an aqueous
mixture of pyruvic acid (1.4 mL, 0.02 mol) and hydrazine
hydrate (2 mL, 0.04 mol) was added with constant stirring.
Then to the turbid solution pyruvic acid was added drop by
drop while warming the solution in a water bath. The
precipitate formed was slowly dissolved by the addition of
pyruvic acid. The addition of pyruvic acid was stopped
when the solution become clear. Then the resulting solution
was concentrated to 20 mL and kept at room temperature.
The white crystalline substance that formed after 3 days
was removed, washed with alcohol and dried in air.
Magnetic moment data
The room temperature magnetic moment of all the cobalt
complexes are in the range of 4.6–4.8 BM and for the
nickel complexes, the magnetic moments are in the range
2.9–3.1 BM respectively. These data indicate the high spin
nature of these complexes [10]. The higher magnetic
moment value observed for cobalt complexes are attributed
to the spin orbit coupling. Thus, the cobalt (II) and nickel
(II) ions in these complexes contain three and two unpaired
electrons respectively. Due to the completely filled ‘d’
orbitals both zinc and cadmium complexes are
diamagnetic.
Preparation of hydrazinium cobalt and nickel pyruvates
ðN2H5Þ2MðCH3COCOOÞ4 where M ¼ Co or Ni
To an aqueous solution (20 mL) of cobalt nitrate hexa
hydrate (2.91 g, 0.01 mol), aqueous solution (20 mL)
containing a mixture of pyruvic acid (2.8 mL, 0.04 mol)
and hydrazine hydrate (2 mL, 0.04 mol) was added and the
123