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Int. J. Engg. Res. & Sci. & Tech. 2014 Ekakitie A O and Osakwe A A, 2014

ISOLATION OF COBALT (II) AND COPPER (II)MIXED LIGANDS COMPLEXES OF ACETAMIDE

AND THIOUREA

Ekakitie A O1* and Osakwe A A1

The complexes of CuSO4, Cu (NO3)2, CuCl2, (CH3COO) Cu, CoCl2, Co (NO3) 2 were isolatedfrom mixed ligands of acetamide and thiourea, stoichiometrically using the molar ratio of1:1,1:2,2:1. Metal analysis, melting point and decomposition temperature determination, solubilityin various solvent (Ethanol, Methanol, Chloroform, Water, Toluene and Diethylether). Infra-redSpectroscopy 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 showedthat the co-ordination to the metal is through the amidenitrogen of actamide and thiourea.

Keywords: Isolation, Cobalt (II), Copper (II), Ligands, Acetamide

*Corresponding Author: Ekakitie A O [email protected]

INTRODUCTIONMixed 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.

Int. J. Engg. Res. & Sci. & Tech. 2014

ISSN 2319-5991 www.ijerst.comVol. 3, No. 3, August 2014

© 2014 IJERST. All Rights Reserved

Review Article

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 factors, 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.

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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).

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 (Me2Cb-Mpz) and B-

deketonate ion (dike) was prepared. The

formation of stable and solid complexesconfirmed that elemental analysis have beenisolated (Maraus Y and Eliezer, 1969).Conclusively, research work was carried out onthe synthesis and structural studies of mixedligand (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 complexesCo(q) (acac) 2H2O, Ni(q) (acac) 2H2O and Cu(q)(acac) H2O were prepared by mixing aqueoussolution of 8-quinolinol and acetylacetone in 1:1:1molar ratio followed by the addition of 2 equivalentof KOH in ethanol. The Zn (q) (acac) 2H2O,Mn(q)(acac) 2H2O and Vo(q) (acac). 2H2O wereobtained by reacting together ethanol solution ofthe metal aceta acetonate and hydroxyquinolinein equimolar ratio and stirring for a few Ni, Cuand Zn) salts have been carried out in the recentyears. Resulting to the formation of a ternarycomplexes of the stoichiometry (m(q)Cl) whereq = 8 - quinolinolato and L=acetyacetone. Althoughthere is an extensive literature on additioncompound of mg2 with mono and bidentatemolecules, however, only three papersconcerning synthesis and structural studies areavailable on ternary complexes mql. Theseinclude studies on cuql. Ni(q)(acac) and Mn(q)(dtc) where 1= aminophenyl amine, typtophentyrosine or ethylbenzoyl cyanoacetate,acac=acetylacetonate and dtc= diethyldithio-carbamate.

METHODS OF PREPARATIONOF COMPLEXESThe ternary complexes (Co(q) (acac). 2H2O’ Ni(q)

(acac) 2H2O and Cu(q) (acac). 2H2O 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).

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2H2O and Vo (q) (acac). 2H2O were obtained by

reacting ethanolic solution of the metal

acetylacetonate and Hq in Equimolar and stirring

for a few 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).

USES OF MIXED LIGANDSThey 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.

THE SCOPE AND OBJECTIVEOF THIS WORKIt 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).

MATERIALS AND METHODSReagent

Acetamide

Thiourea

Ethanol

Methanol

Toluene

Chloroform

Diethyl ether

Distilled water

Disodium EDTA

Copper II chloride dihydrate

Copper II Sulphate pentahydrate

Copper II Nitrate trihydrate

Copper acetate

Cobalt II Nitrate

Cobalt II chloride

Universal indicator

Solochrome black

Sodium acetate

Murexide indicator

Concentrated tetraoxosulphate VI acid

Concentrated trioxonitrate V acid

Ammonia solution

PREPARATION ANDISOLATION OF METALCOMPLEXESThe 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.

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

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minimum amount of methanol while the

acetamide was dissolved with minimum amount

of methanol.

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.

The crystals were filtered and washed with

water and dried over silica gel in a dessicator.

METAL ANALYSIS:DIGESTION OF METALCOMPLEXESThe 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.

PROCEDURE FORTITRATIONS: CU (II)SULPHATE COMPLEXES (1:)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

complexes such as the copper (II) Chloride,

copper (II) nitrate, copper (II) acetate, cobalt (II)

nitrate.

SAMPLE CALCULATIONMETHOD FOR PERCENTAGEYIELD OF LIGAND (FORMED)1:1 COMPLEXESCuSO4.5H20 + Cs(NH2) 2

Cu(CH3CoNH2)(CS (NH2) )SO4) 5H2O

Molar mass of the complexes = 385 g

Molar of salt used = 0.010

Experimental yield = 0.99 g

Theoretical yield = molar mass x moles

385 x 0.010 = 3.85

100%

Experimental yieldof yield

Theoretical

= 0.99 x 100S

= 3.85

= 2571%

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

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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0.01 x 0.65 x 63.5 x 100

% Cu = 25 x 4 x 0.03 x 1

= 13.75% (found).

CALCULATED PERCENTAGEMETALFor Cu(aceta) (thiou) SO4 5HO (1:1) Compound

Atomic mass of Cu x 100 63.5 % Cu= 16.6%

molar mass of compound 385

Percentage of Carbon

Cu(CH3 CONH2) CS(NH2) 2SO24H2O

12 x 3 % Cn= 100 9.35%

385

19 % of Hydrogen= 100 4.93%

385

14 3 % of Nitrogen= 100 10.90%

385

143



Table 2: Solubility Test for Complexes

144



Table 3: Using Shimadzu Infra Red

PHYSICAL MEASUREMENTDetermination of Melting Point andDecomposition Temperature

Ligand paraffin, thermometer and melting point

tube were employed in the determination of the

point and the decomposition temperature of the

complexes.

The melting point and decomposition

temperature of the complexes is shown in table.

SOLUBILITY OF THE METALCOMPLEXESThe 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) >CO

W(2400-20) B-A(2400-2200)

For Cobalt complexes ranges from 4000-650cm-1 1.1

Cobalt nitrate

A (3550) hydrogen bonded N H group

Al (2800) Thio group stretching

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RESULTS AND DISCUSSIONThe 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.

COLOR OF THE COMPLEXESThe 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 OFLIGANDS AND COMPLEXESThe 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 shif t 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

- 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.

CONCLUSIONThere 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 similarit ies 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.

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