Download Isolation of Cobalt (II) and Copper (II)

Int. J. Engg. Res. & Sci. & Tech. 2014
Ekakitie A O and Osakwe A A, 2014
ISSN 2319-5991 www.ijerst.com
Vol. 3, No. 3, August 2014
© 2014 IJERST. All Rights Reserved
Review Article
ISOLATION OF COBALT (II) AND COPPER (II)
MIXED LIGANDS COMPLEXES OF ACETAMIDE
AND THIOUREA
Ekakitie A O1* and Osakwe A A1
*Corresponding Author: Ekakitie A O  [email protected]
The complexes of CuSO4, Cu (NO3)2, CuCl2, (CH3COO) Cu, CoCl2, Co (NO3) 2 were isolated
from mixed ligands of acetamide and thiourea, stoichiometrically using the molar ratio of
1:1,1:2,2:1. Metal analysis, melting point and decomposition temperature determination, solubility
in various solvent (Ethanol, Methanol, Chloroform, Water, Toluene and Diethylether). Infra-red
Spectroscopy were used for characterization. The percentage yields were about 49.62. CuSO4
Complexes were light green in color, Cu(NO3)2 complexes are green also the CuCl2 complexes.
(CH3COO)Cu are blue while CoCl2 and Co (NO3) 2 complexes are red. The infra-red showed
that the co-ordination to the metal is through the amidenitrogen of actamide and thiourea.
Keywords: Isolation, Cobalt (II), Copper (II), Ligands, Acetamide
INTRODUCTION
ligand complexes in solution. Most authors
recognized the importance of statistical factors
in determining the stability of mixed complexes,
although other factors such as repulsion between
unlike ligand, geometric f actors, dipole
interactions with the solvent, the type of binds
formed and outer versus the inner orbital
coordination have also been looked into (Jacobs,
N E and Margrurn, 1967). A number of
investigators have discovered that the formation
of ternary complexes from two binary complexes
is more favorable than a stabistical distribution of
ligand. This has been explained by phenomena
such as polarization, charges neutralization with
decreased solution and symmetry of ligand field.
Mixed ligands complexes are widely encountered
and are of interest to the wide range of research
workers. The development of computing
techniques has facilitated considerably the
description of the equilibrium in the complex
system formed by a solution of mixed ligand
complexes (I). It is now generally agreed that in
solution containing metal ions and two suitable
ligands, mixed ligand complexes are formed. Note
the word “suitable”, since instances have been
found where mixed ligand complexes cannot be
formed, because of certain properties of the
ligands. Many studies have been directed towards
a better understanding c3f the formation of mixed
1
Department of Chemical Sciences, Novena University Ogume, Delta State, Nigeria.
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Ekakitie A O and Osakwe A A, 2014
formation of stable and solid complexes
confirmed that elemental analysis have been
isolated (Maraus Y and Eliezer, 1969).
Conclusively, research work was carried out on
the synthesis and structural studies of mixed
ligand (8-guinolinalato) (acetylacetanato)
complexes of Vo (IV) Mn(II), Co(II), Ni(II), Cu(II)
and Zn(II) (Mesubi M A and Omotonea B A, 1990).
In this research work, the ternary complexes
Co(q) (acac) 2H2O, Ni(q) (acac) 2H2O and Cu(q)
(acac) H2O were prepared by mixing aqueous
solution of 8-quinolinol and acetylacetone in 1:1:1
molar ratio followed by the addition of 2 equivalent
of KOH in ethanol. The Zn (q) (acac) 2H2O,
Mn(q)(acac) 2H2O and Vo(q) (acac). 2H2O were
obtained by reacting together ethanol solution of
the metal aceta acetonate and hydroxyquinoline
in equimolar ratio and stirring for a few Ni, Cu
and Zn) salts have been carried out in the recent
years. Resulting to the formation of a ternary
complexes of the stoichiometry (m(q)Cl) where
q = 8 - quinolinolato and L=acetyacetone. Although
there is an extensive literature on addition
compound of mg 2 with mono and bidentate
molecules, however, only three papers
concerning synthesis and structural studies are
available on ternary complexes mql. These
include studies on cuql. Ni(q)(acac) and Mn(q)
(dtc) where 1= aminophenyl amine, typtophen
tyrosine or ethylbenzoyl cyanoacetate,
acac=acetylacetonate and dtc= diethyldithiocarbamate.
Conditions that are necessary for the mixed
ligands formation have been suggested and with
potentials. In some of these works, the changes
in free energy of coordination bonds as a result
of mixed ligand complex formation has been
considered. Studies have been carried out on
mixed complexes of nickel (II) with only amino,
carboxylate and water as the coordinate groups.
The ligands were chosen in order to determine
the effect of change, the effect of a number and
types of groups bounded to the metal before and
after mixed complex forrobon, and the effect of
chelation. This work was used to treat a restricted
system but consider more parameters which
might influence the stability constant than has
been the case in previous studies of mixed ligand
complexes. The parameters are evaluated in
terms of their contribution to the free energy
conformation of the mixed ligand complexes [I].
It has also been discovered that copper (II)
readily forms mixed complexes with various
nitrogen-oxygen co-coordinating ligands but is
reluctant to bind more than two bidentate ligands.
(3) Similar studies have also been carried out on
cobalt (II) in which the reaction acetate, Me — AA
and Et—AA derivatives of Co(II) was carried out
with triamines and hydroxyquinoline resulting to
the isolation of hexacoordinated complexes of
stoichiometry Co(L) 2 (L) 2 (L), where L is a CaC
(AA). Methylacetoacetate (4Ne—AA) or
ethylacetoacetate (Et—AA) and L1 is
ethylenediamine (EA) propylenediamine (Pn) or
8-hydroxy guinoline (3).
METHODS OF PREPARATION
OF COMPLEXES
The ternary complexes (Co(q) (acac). 2H2O’ Ni(q)
(acac) 2 H 2 O and Cu(q) (acac). 2 H 2 O were
prepared by mixing aqueous solution of 8quinolinol and acetylacetone in 1 : 1: 1: molar ratio
followed by the addition of 2 equivalent of KOH in
ethanol. The Zn(q) (acac). 2H2O, Mn(q) (acac).
Further work has been carried on the
synthesis and structural studies of Cobalt (II) and
nickel (II) mixed ligand complexes with 2, 2-bis
(1-pyrazoyl) propane (me2 (bpl) or 2, 2-bis(3) (5)
- pyrazoyl) propane (Me 2 Cb-Mpz) and Bdeketonate ion (dike) was prepared. The
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Ekakitie A O and Osakwe A A, 2014
H2O and Vo (q) (acac). 2H2O were obtained by
reacting ethanolic solution of the metal
acetylacetonate and Hq in Equimolar and stirring
for a f ew minutes. All complexes which
precipitated immediately were suction filtered and
washed successively with 50% ethanol and ether
and finally dried in a vacuum. The complexes
were then analyzed for metal employing standard
procedures (Sharman et al., 1981).
Methanol
USES OF MIXED LIGANDS
Copper II Sulphate pentahydrate
They are essential as true elements for most of
the biological system. The 8-quinolinolate is
extensively used in drug synthesis. It is well known
for its anti-malaria and general antimicrobial
properties and also widely employed in analytical
chemistry for the separation and determination
of metals.
Copper II Nitrate trihydrate
2
Toluene
Chloroform
Diethyl ether
Distilled water
Disodium EDTA
Copper II chloride dihydrate
Copper acetate
Cobalt II Nitrate
Cobalt II chloride
Universal indicator
Solochrome black
THE SCOPE AND OBJECTIVE
OF THIS WORK
Sodium acetate
Murexide indicator
It can be deduced from experimental work that
the percentage yield of the salt of the complexes
is about 37.82 averagely of the acetamide and
thiourea of this mixed ligand is small and that the
isolation of this cobalt (II) and copper (II) is small
also due to their high solubility of the salt. In this
case weak paramagnetism results. This
Temperature Independent Paramagnetism (TIP)
thus resembles diamagnetism in that it is not due
to any magnetic dipole existing in the molecule,
but it is induced when the substance is placed in
the magnetic field (Das R C Behera B, 1983).
Concentrated tetraoxosulphate VI acid
Concentrated trioxonitrate V acid
Ammonia solution
PREPARATION AND
ISOLATION OF METAL
COMPLEXES
The complexes of Cu(ll) and cobalt (H) were
isolated. Similar methods of preparation were
used in all cases with Iittle modification when
necessary. Stoichiometric amounts of 1: 1 and
2:1 of mixed ligands to metal salts were used.
The metal salts were all hydrated.
MATERIALS AND METHODS
Reagent
A minimum amount of water was used in
dissolving the metal (II) salt of copper and cobalt.
The solution of thiourea was made up with a
Acetamide
Thiourea
Ethanol
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Ekakitie A O and Osakwe A A, 2014
minimum amount of methanol while the
acetamide was dissolved with minimum amount
of methanol.
complexes such as the copper (II) Chloride,
copper (II) nitrate, copper (II) acetate, cobalt (II)
nitrate.
In the isolation of the metal complexes of 1:1,
1:2 and 2:1 the aqueous solution of the metal salt
was treated with the mixture of stoichiometric
amount of acetamide and thiourea and solution
was buffered with ammonia solution to raise the
pH from acidic to basic medium and stirred for
sometime to allow it crystallize.
SAMPLE CALCULATION
METHOD FOR PERCENTAGE
YIELD OF LIGAND (FORMED)
1:1 COMPLEXES
The crystals were filtered and washed with
water and dried over silica gel in a dessicator.
Molar mass of the complexes = 385 g
Molar of salt used
= 0.010
METAL ANALYSIS:
DIGESTION OF METAL
COMPLEXES
Experimental yield
= 0.99 g
Theoretical yield
= molar mass x moles
385 x 0.010
= 3.85
CuSO4.5H20 + Cs(NH2) 2
Cu(CH3CoNH2)(CS (NH2) )SO4) 5H2O
The metal complexes were digested by heating
0.03 g of the complexes with a 1: 1 ratio of
concentrated trioxonitrate (v) acid and
tetramonosulphate (VI) acid mixtures. There were
heated but not to dryness and diluted with distilled
water and made up to 100 cm in a standard flask.
% of yield 
Experimental yield  100
Theoretical
= 0.99 x 100S
= 3.85
= 2571%
PROCEDURE FOR
TITRATIONS: CU (II)
SULPHATE COMPLEXES (1:)
Sample calculation of percentage of metal in
the complexes.
Cu(acetamide) (thiou)SO4) 5H2O = molarity of
EDTA X Volume of EDTA X Atomic mass of metal
x 100
20 cm3 of the digested solution was pipetted into
a 250 cm conical flask buffered with NH3/NH4CI
solution to raise the pH of the solution to pH 10. A
speck of murexide indicator rnixture was added.
The solution was titrated with EDTA. Co(lI)
chloride complexes (1:) 200 cm3 of the digested
solution was pipetted into a 250 cm3 comical flask,
two or three drops of buffer solution (NH3H4CI)
was added to raise the pH to 10. A speck of
murexide indicator mixture was added. The
solution was titrated with EDTA. Similar
processes were used for the remaining metal salt
Volume of complex pipetted x factor to make
100 x of Sample digested x 1
Average volume of EDTA used = 0.65
Atomic mass of Cu metal = 63.5
Wt of Cu (11) complex digested = 0.03 g
Volume of complex pipetted = 25 cm
Factor = 4
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 % Cu =
=
Ekakitie A O and Osakwe A A, 2014
Percentage of Carbon
0.01 x 0.65 x 63.5 x 100
25 x 4 x 0.03 x 1
Cu(CH3 CONH2) CS(NH2) 2SO24H2O
13.75% (found).
% Cn=
CALCULATED PERCENTAGE
METAL
12 x 3
 100  9.35%
385
% of Hydrogen=
For Cu(aceta) (thiou) SO4 5HO (1:1) Compound
% Cu=
Atomic mass of Cu x 100 63.5

 16.6%
molar mass of compound 385
% of Nitrogen=
19
 100  4.93%
385
14  3
 100  10.90%
385
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Table 2: Solubility Test for Complexes
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Table 3: Using Shimadzu Infra Red
The melting point and decomposition
temperature of the complexes is shown in table.
PHYSICAL MEASUREMENT
Determination of Melting Point and
Decomposition Temperature
SOLUBILITY OF THE METAL
COMPLEXES
Ligand paraffin, thermometer and melting point
tube were employed in the determination of the
point and the decomposition temperature of the
complexes.
The solubility test results for the metal complexes in
solvent such as water, toluene, methanol,
chloroform, ethanol, diethyl ether is given in Table 2.
Table 4: Using Shimadzu Infra Red (Infra-red Vibrational Frequencies 1:1)
(In cm-1) Cu Complexes Ranges From 4000 - 650cm-1
C uCI2
Cu(NO3) 2
Acetat
CuSO4
Tentative Assignment
A(3450)
A(3650)
A(3600)
A(3500)
hydrogen bonded
N H group
A1(1655)
A1(1675)
A2(1670)
A1(1650)
W (2400-20)
For Cobalt complexes ranges from 4000-650cm-1
>CO
B-A(2400-2200)
1.1
Cobalt nitrate
A (3550)
hydrogen bonded
N H group
Al (2800)
Thio group stretching
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RESULTS AND DISCUSSION
- 2700 cm–1 in the spectra of the complexes is
not much affected by complexation M - L. The
finger - print region clearly shows that the metal
salt complexes are sensitive to changes in their
functional group. The absence of similar bands
in the correlation chart is an evidence that this
assignment is in order.
The complexes were formed almost immediately
in all cases. The yields are 49.62 in some cases
and 32.45% in others. The low yield of 32.69%
corresponding to Cu (aceta) (Thiou) NO3)3H3O
and others below the above stated value might
be possibly due to high solubility of Cu (aceta)
(thiou) NO3) 3H2O in water. The yields of cobalt
(II) nitrate complexes were moderate of 49.72.
CONCLUSION
There is no significant difference between the
copper (II), Co (II) salt complexes prepared from
acetamide and thiourea in the ratio 1:1. This is
true because of the similarities in
physicochemical properties of the complexes, for
instance, all the complexes are insoluble in most
of the solvents used for solubility test except for
Cu (II) CI, complex which is soluble in water and
sparingly soluble in ethanol and methanol. Some
of the complexes prepared were red, and green
due to the configuration of the metal except for
the acetates. From infrared result, it is obvious
that the same atoms were involved in the
formation of the M - ligand bands for the
complexes. The broadness of the bands around
3400 cm-1 is due to water interference still present
in the molecules.
COLOR OF THE COMPLEXES
The color of the complexes is shown on Table 1.
Generally, the intensity of the color of the
complexes are higher then the starting materials.
The color of the complexes formed were expected
to be all green for copper except that of the Cu
(aceta) (thiou) (CH3COO) H2O which was blue.
The expected color for the cobalt complexes were
red respectively.
INFRARED SPECTRA OF
LIGANDS AND COMPLEXES
The shimadzu infrared absorption bands of
ligands are given in Table 3 and those of the metal
complexes are given in Table 4. Their assignment
were made by comparing the correlation chart of
shimadzu infra red group frequencies with those
of the complexes and by reference to literatures.
The region of interest in both the ligands and
complexes is the region 3500-1600. The important
vibration of these regions are the NH, >CO, thio
group stretching. The presence of the NH
vibration around the region of 1580 - 1490 (W)
often too weak to be noticed and that the vibration
at high frequency is due to NH instead of OH
group. The shift to lower frequency upon
coordination is the indication that NH group of the
acetamide is involved in the formation of C - H.
The vibrational frequency occurs between 2980
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