Aug 30, 2000 - Vol. 40A, July 2001, pp. 733-737. Synthesis and structure of new cobalt(II) copper(II), nickel(II) copper(II) and cobalt(II) nickel(II) heteronuclear ...
Indian Journal of Chemistry Vol. 40A, July 200 1, pp. 733-737
Synthesis and structure of new cobalt(II) copper(II), nickel(II) copper(II) and cobalt(II) nickel(II) heteronuclear complexes containing monoethanolamine Mamdouh S Masoud Chemistry Department, Facu lty of Science, Alexandria University, Alexandria, Egypt and
Hossien A Motaweh & Alaa E Ali Physics & Chemistry Department, Facu lty of Education" Damanhour", Alexandria University, Egypt Received 30 August 2000; revised 13 March 2001
The heteronuclear COIiCUIl , NiliCU Il and ColiNi li complexes containing monoethanolamine, (MEA), have been prepared using the corresponding metal salts and MEA as starting materials. Both COIiCU Il and NiliCU Il compl exes are heterotrinuclear complexes but the ColiNi li complex is heterodinuclear one. The coordin ation ability of CUll towards MEA is stronger than COli and Ni ll . The separated complexes are of tetrahedral geometry with bridged chlorides and of high stability. The thermal behaviour and thermodynamic parameters of the prepared complexes have been studied. The dependence of the electrical conducti vity on temperat ure is examined and the complexes are found to be of semiconductin g behav iour.
Exploring a new structural class of coordination compounds, namely heteronuclear complexes, may allow the di scovery of agents that possess biological properties quite different from those of mononuclear complexes. Our aim in thi s study was to establi sh an efficient method to obtain desirable heteronuclear complexes containing monoethanolamine, MEA , ligand . In our previous studies, successful methods were reported for the preparation and characterization of numerous homo-nuclear mono-, di- and triethanolamine complexes l - 5 . The program of the present study is the preparati on and characterization of the mixed metal complexes based on mixing the different transition metal salts with MEA in the ratio of 1: 1:1 and 1:1:2 (M t :M 2 :MEA ).
Materials and Methods Synthesis of MEA - heteronuclear complexes The solid metal ethanolamine hetero-nuclear complexes were prepared by mixing the metal chlorides (0.1 mol each) di ssolved in 10mi water with the calculated amount of MEA saturated with ethanol to obtai n 1: I: I and I: 1:2 (M 1:M 2:MEA) ratios. The reaction mixture was refluxed for IOmin and left to cool. The formed complexes were filtered, washed several times with EtOH and dried in a desiccator over an hydrous CaCho
The complexes were digested and decomposed with aqu a regi a. The metal ion contents were determined by atomic absorption spectrophotometer at the central laboratory , Faculty of Science, Alexandria University, Alexandri a, Egypt. The chloride content was estimated by the usual method 6 . The analytical data of the prepared complexes are presented in Table 1. The Infrared spectra were recorded as KBr di sk using Perkin Elmer Spectrophotometer model 1430 covering the frequency range 200-4000 cm -I . The electronic absorption spectral data were recorded using Perkin Elmer Spectrophotometer · model 4B covering the wavelength range 190-900 nm. The complexes were measured in nujol mull, following the method described by Lee et a/ 7 . Molar magnetic susceptibilities, corrected fo r diamagnetic using Pascal's constants, were determined at room temperature (298 K) using Faraday 's method. The apparatus was calibrated with Hg[Co(SCN)4] (ref. 8). Thermogravimetric measurements and differential thermal analysis were performed on a Du Pont 9900 computerized thermal analyzer at Physics Department, Faculty of Science, EI-Menia University. The heating rate was 10degree/min. A 60 mg of the sample was pl aced in a platinum crucible. Dry nitrogen was flowed over the sample at a rate 10 cc/min and a chamber cooling water flow rate was 10 Ith . The speed was 5 mmlmin .
INDIAN J CHEM . SEC A. JULY 200 1
734
Electrical conductivity measurements The data were measured in the temperature range 294-750 K. The complexes were prepared in the form of tablets at a pressure of 4 tons/cm 2• The tablets were of an area 2.54 cm 2 and 0.12 cm thickness. The samples were hold between two copper electrodes with silver paste in between and then inserted with the holder vertically into cylindrical electric furnace. Both ends of the furnace were closed off to reduce drafts. The potential drop across the heater was varied graduall y through variac transformer to produce slow rale of increasing temperature to get accurate temperature measurements. The circuit used to measure the electric conductivity consists of D.C. regulated power suppl y Heat Kit (0-400 volts), Keith multi meter for measuring current with a sensitivity up to 10- 15 ampere. The temperature of the sample was measured within ± 0.1 degree by means of CopperConstant thermocouple. The conductivity was obtained in the case of cooling using the general formula: (J = IdlY e a where, I is the current in ampere, Yc is the potential drop across the sample of cross section area "a" and thickness "d".
Results and Discussion The analytical data of the prepared complexes (Table 1) proved that the product depends on the mode of reaction. The heterotrinuclear complexes, lMCu2L2CI4]; M=Co lI , Ni ll ; HL=MEA, only were form.ed when the ratio of M:Cu:MEA was 1: 1:2. On the other hand, when the ratio was 1: I : I, the same homotrinuclear [Cu3L2CI4] complex was formed. The data proved that the tendency of CUll ion towards
MEA is greater than that of both COli and Ni ll ions. This can be attributed to the more hardness of CUll relative to both COli and Ni ll ions, indicating that MEA reacted as mononegative ligand. Inspite of the different reacted components with the ratios of 1: 1: 1 and I: 1:2 Co:Ni:MEA., both gave the same analytical data of the stoichiometry of [CoNiL2Ch] . The IR spectra of [CoCu2L2Cl4], [NiCu2L2Cl4] and [CoNiL 2Cl 2] comp-Iexes indicated th at the mode of coordination of MEA with CUll occurs through nitrogen and oxygen sites. The stretching vibration bands due to VCu-Nand VCu-O are assigned at 447 and 338 cm- I, respectively, in the first two complexes. The two peaks at 294 and 344 cm-1 indicated VCu-CI and VCo-Ci in [CoCu2L2Cl4] , while both at 294 and 345 cm- I are assigned for the VCu-C1 and VNi-CI in [NiCu2L2Cl4]. In case of [CoNiL 2Cl 2J, the bands due to VCo-N, Vco-o, VNi-N, VNi-O, VNi-CI are assigned at 408, 367,460,385,349 and 344 cm- I, respectively. These data indicated the presence of bridged chlorides in all the complexes 9 . The absence of VOH band expected to lie at -3450 cm- I indicated that MEA reacts as mononegatively charged ligand. The nujol mull electronic spectra of [CoCu2L2Cl4] and [NiCu2L2CI4] gave a main broad band at 680 and 690nm, respectively due to 4A2 --7 4 T I (P) of the tetrahedral COli in the former complex and 3TI (F)-7 3TI(P) for the tetrahedral Ni[J in the latter complex 10. The shoulder in the UY region at 340 nm may be due to the charge transitions.
Table I-Analytical data of the complexes Product HL=MEA. CU 3 L2CI~ . H 2 0
CoCu2L2C1 4. H20
CU3L2 Cl~ . H 2 0
Mode of reaction Co: Cu :MEA 1: 1: 1 1: 1:2 Ni:Cu :MEA 1: 1:1
NiCU2L2Cl4 .H20
1: 1:2
CoN iL 2Cl 2 .H 2O
Co:Ni :MEA 1: 1: 1
CoNiL 2Cl 2 ·H2O
1: 1:2
Colour (m.p.)
~cff.
(8m)
Co
Found (Calc.) % Ni Cu
Cl
Green (170)
4.95
Green (>300)
7.43
Green (171 )
4.95
Green (>300)
6.34
Pale green (>300)
6.67
17.86 (17.88)
17.8 1 (17.83)
21.57 (2 1.60)
Pale green (>300)
6.67
17.85 (17.88)
17.79 (17 .83)
2 1.58 (2 1.60)
12.49 ( 12.58)
12.55 ( 12.53)
40.3 1 (40.34)
30.02 (30.00)
27.2 1 (27.23)
30.33 (30.38)
40.32 (40.34)
30.0 1 (30.00)
27.19 (27. 22)
30.33 (30.36)
MASOUD et (II.: CO MPLEX ES OF Co(lJ)Cu(II), Ni(lJ )Cu(lI) & Co(II)Ni(lJ)
The nujol mull electronic spectrum of [CoNiL2CI 2] gave two bands at 628 and 676 nm. The first band assigned to 3T ,(F) ~3T,(P) for the tetrahedral Ni" ion while the second assigned to 4A2 ~ 4 T ,(p) for the tetrahedral COli ion. Thus, these data together with the magnetic moment values suggested the high spin nature of the complexes. The [CoCu2L2CI4] and [NiCu2L2CI4] complexes are green and insoluble in water with the formation of grey precipitate, suggesting hydro lys is. The liberated chloride ions from the hydrol ys is process were determin ed fro m aqueous solution gravimetricall y as AgCl. The [CuL(OH )Cl] complex was separated and identified by elemental analysis and UV spectra indicated tetrahedral geometry of the Cu" ion. Its )..lerreq uals 1.69BM at 298 K. The [CoNiL 2Cbl complex was fo und to be insoluble in water, not affected by hydro lysis. By the analogous previous discussion, one can predict the structural chemistry of the [C u3L2Cl4] complex . This com plex is also affected by hydrolysis.
735
The DT A data of both [CoCu2L2C141 and [NiCu2L2CI4] complexes (Table 2) showed th at th ere is a great similarity of the thermal behaviour of th ese complexes. The [CoCu2L2Cl4J complex gave two DTA peaks at 75 .40 and 105.00 DC with activation energies of 37.40 and 287.60 kllmol and orders of 1.26 and 2.70, respectively. The [NiCu2L2Cl4] complex, (Table 2) gave the same two DT A peaks at 86.70 and 116.10 DC with activ ati on energies of 14.30 and 291.10 kllmol and orders of 1.38 and 1.26, respectively. In both complexes, the first peak was due to the dehydration of the adsorbed water molecules. The second peak was due to MCl 2 [M= Co or Ni] fo rmation on the decomposition as given below :
H2 0
[MCu2L2Cl41 -~~~2[CuL(H20)Cl] + M+2 + 2cr M= Co or Ni H 20
[Cu3L2C14]
2
~ 2[CuL(H 20)Cl] + Cu+ + 2Cl-
The DTA pattern of [CoNiL2Cb] complex (Table 2) gave one peak at 68.30 DC with activati on energy of 26.30 kllmol and order of 3.36. This peak was due to the dehydration of the adsorbed water molecul e. The mechanism of the thermal decomposition was given as follow s:
The difference between the thermal behaviours of the hetero-trinuclear complexes and the heterodinuclear one is that the first peak in the trinu clear complexes is endothermic while that of the dinuclear complex is of exothermic behaviour. Also, the low Eo of the second step in the dinuclear comp lex , [CoNiL2Cbl , which was the main difference, leads to postulate isomerization step. Table 2-Thermal properties o f the mi xed metal amino alcohol complexes Complex
TI K
E. kJmol - 1
n
(3
/1:;*
K s- I
kJ mor l
ICoCu2L2C141.HzO
75.40 105.00
37.40 287.60
1.26 2.7
2.41 3.25
-0.220 -0.196
22.58 408.20
[NiCu2L2CI41 ·H20
86.70 116. 10
14.30 291.10
1.38 1.26
2.55 2.41
-0.206 -0.206
126.44 174.20
[CoNiL 2CI 21· H2O
68.30
26.3
336
3.4 1
-0.226
18.45
INDIAN J CHEM. SEC A . JULY 2001
736
Generally, the simi larity between the thermal behaviours of [CoCu2L2Ci4] and .[NiCu2L2CI4] was due to the great similarity in the chemistry of both Co and Ni in the periodic table. The thermal parameters of the decomposition steps, Ea: activation energy; n: order of the reaction; ~: heating rate; i1St:: entropy of activation and Z: collision number, are gathered in Table 2. The change of entropy of activation values in the range -0.196 to -0.226 kJ/mol for the thermal decomposition steps, showed that the transition states are more ordered, i.e. in a less random molecular configuration, than the reacting complexes. The fractions appearing in the calcu lated order of thermal reactions also confirmed
that the reactions proceeded in complex mechanisms. The values of calculated collision n mbers and that of the calculated act ivation energies showed a direct proportion relation between both .
Electrical conductivity measuremenrs The dependence of the electrical conductivi ty on temperature is expressed by the following equation: h AE 'IS the activatIOn . . energy f or the a=a °e - t. EIKT were L.l conduction, aO is a constant for the conductivity independent of temperature and K is th e Boltzmann constant. The electrical conductivity behaviour are represented Fig. 1. The data depict that all complexes are of semiconductor behaviour.
-13 ~--------~--------~------~--------~---------r--------~
2.4
22
2.6
2.8
3
3.2
-14
IOoorr
3.4
-15 -16
..stl
[CoCu2L2CI4]
-17 -18
-19
C -20 -21
Fig. I-The electrical conductivity behaviour of the complexes 1.2
A: [CoCU2L2C4]
•
6E = 0.0286 Inao + 0.64/4
B:
6 E/eV
[NiCu2~C I4]
t.E = 0.0407 Ina. + 0.6323
0.8
c: [CoNiL 2CI 2] t.E = 0.0128 Ina. + 0.2576
A:
c:
r---~--~~--------~----------~------~~--------~r------~ B: 10 5 -1 0 -5 -20 -1 5 In a. -0.2
Fig. 2- The M - In
0'0
relation
MASOUD et a/.: COMPLEXES OF Co(II)Cu(Il), Ni(II)Cu(lI) & Co(II)Ni(lI)
The temperature dependence of the conductivity curves of the [CoCu2L2CI4] complex gave three regions with transition temperatures of 75 and lOs oC, respectively. The first break was due to the loss of the adsorbed water molecules, while the second break was due to the separation of CoCI 2 molecule from the complex. Thi s interpretation is in a good agreement with the thermal analysis properties (Table 2). The electrical conductivity pattern of [NiCu2L2C14] complex also gave three regions with transition temperatures of 90.0 and 114.0°C, respectively. The two breaks may be due to the loss of the adsorbed water and the separation of NiCI 2, respectively. The conductivity behaviour of [CoNiL2C1 2] complex gave three conductivity regions with two transItIon temperatures at 68.0 and 97.3°C. The data indicated lower cr values than that of the [CoCu2L2CI4] and [NiCu2L2C14] complexes. This indicates the high mobility of the electrons in the copper containing complexes. This reflects the interaction of Cu-orbitals with the ligands to give new molecular orbitals, which are delocalized over the whole molecular complexes. In addition, based on the insolubility of this complex in water, interaction might occur between adjacent atoms in a metal-atom chain. Best-fit straight lines were obtained by plotting ~E - Incro relations (Fig. 2).
Empirical equations were constructed conductivity of the complexes as follows:
737 for
the
~E=0.0286
In cro+0.6474 for [CoCu2L2CI4] complex .
~E=0.0407
In cro+0.6323 for [NiCu2L2C14] complex.
~E=0.0128
In cro+0.2S76 for [CoNiL2Cb] complex .
References I
Hedewy S, Hoffman S K, Masoud M S & Goslar J, SpeClrosc Lett, 19 ( 1986) 917.
2 3 4 5
Masoud M S, Ibrahim N A, Ali G Y & Aboll Ali S A, 8/11/ Fac of Sci Minia , 1(1987) 37. Masoud M S & EI-Dessouky M A, /raqui Chelll Soc, 12 (1987) I. Masoud M S, EI-Essawi M M & Amr A M, Symh react Inorg & met -org Chern , 20 (1990) 839. Masoud M S, Hafez A M & Ali A E, Spectrosc Lett. 3 1
(1998) 901. 6 Vogel A I, A text book of quantitative inorganic analysis , 4 th Edn Longmann, London 1978, p 116. . 7 Lee R H, Griswold E & Kleinberg J, Inorg G ell/, 3 ( 1964) 1278. 8 Figgis B N & Lewis J, Modern coordination chemistry (Intersciene, New York) 1967, P 403. 9 Nakamoto K, Fujita J, Tanaka S & Kobayas hi M, J Am chell/ Soc, 79 (1957) 4904. 10 Cotton F A & Wilkinson G, Advanced inorganic chell/islly, 2nd Edn (Wiley Eastern, London) 1966, p 878.
