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Lanthanide ion complexes of a ligand derived from salicylaldehyde and malonyl dihydrazone
Polyhedron Vol. 12, No. 9, pp. 10434146, Printed in Great Britain
1993 0
0277-5387193 $6.00+.00 1993 Pergamon Press Ltd
ION COMPLEXES OF A LIGAND DERIVED L-E FROM SALICYLALDEHYDE AND MALONYL DIHYDRAZONE LIANG YONGMIN,
HUANC GUOSHENG
and MA YONGXIANGT
Department of Chemistry, Lanzhou University, Lanzhou 730000, P.R.C. and ZHAO GANG Department of Chemistry, Chengdu University of Science and Technology, Chengdu 610065, P.R.C. (Received 4 November 1992 ; accepted 4 January 1993)
Abstract-The chelates Na2[Ln(C34H28N808)Cl] *nH,O of the malonyl dihydrazone of salicylaldehyde with the lanthanides have been prepared and characterized by elemental analysis, IR, UV, molar conductance and TGA. It is shown that the ligand coordinates to the central ion with one hydrazone unit in the keto form and one chloride ion participates in coordination to the metal ion. These chelates are 1 : 2 electrolytes in DMF and are more thermostable than their ligand due to the formation of chelate rings.
Since Sacconi’ first reported the complexes of nickel (II) with dihydrazones a large number of transition metal complexes of acid dihydrazides have been studied.2-4 However, no work has been performed on the complexes of the lanthanides with dihydrazones. In the present work the reaction of Nsalicylidene derivatives of malonic dihydrazides (H,L) with 11 lanthanide(II1) chlorides in anhydrous ethanol in the presence of sodium hydroxide have been investigated, and the IR, UV, molar conductance and thermal analysis (TGA) of the cornplexes are discussed. EXPERIMENTAL All the solvents were dried by the reported method. 5 Lanthanide(II1) chlorides were prepared from their oxides and hydrochloric acid. The ligand was prepared by the literature method. 6 Preparation of the lanthanide chelates
added to the hydrated lanthanide(II1) chloride (0.5 mmol) in anhydrous ethanol (20 cm3). The mixture was refluxed for 2-3 h until the reaction was complete. The product was separated, washed with warm water, ethanol and diethyl ether, respectively, and dried in vucuu. Yields were 75%. Elemental analyses and some physical properties of the products obtained are listed in Table 1. Measurements
The IR spectra were obtained with a Nicolet 5-DX spectrophotometer using KBr discs in the 4000400 cm-’ region. UV spectra were recorded on a UV-240 spectrometer in the 190-600 mn region using a solution in DMF. Electrolytic conductivities were obtained using a DDS-II A molar conductometer and DMF as the solvent at room temperature. TGA analyses were carried out with a thermal analyser (Japan) between room temperature and 850°C in a nitrogen atmosphere.
H2L (1 mmol) was dissolved in warm ethanol (25 cm3) containing NaOH (2 mmol). This solution was
RESULTS
AND DISCUSSION
These chelates of malonyl dihydrazone of salicyl7 Author to whom correspondence should be addressed. aldehyde with lanthanide are insoluble in non-polar 1043
1044
LIANG
et al.
YONGMIN
Table 1. Analytical and physical data of the compounds
Colour
Yield (%)
Decomposed temperature (“C)
White
88
242
Na,[LaL,Cl] * 3H,O
Yellow
87
321
III
Na,[PrL,C1]*3H,O
Yellow
89
312
IV
Na,[EuL,Cl] - 3H,O
Yellow
75
310
V
NaJYL2CI] - 3H20
Pale yellow
81
286
VI
Na,[ErL,CI]*H,O
Light yellow
78
284
VII
Na,[HoL,Cl]*SH,O
Light red
85
264
Na2[TbL2Cl]
Pale red
91
286
IX
Na,[CeL,Cl] - 3H,O
Red-brown
84
276
X
Na,[LuL,CI] *2H,O
Pale yellow
89
264
Compound I
Formula
(C,,H&@,)
II
VIII
XI
NaJNdL2C1].3H,0
Yellow
92
284
XII
Na,[DyL,Cl]*3H,O
Yellow
78
285
Elemental analysis Found (Calc. %) C N H 60.2 (60.0) 42.7 (42.9) 43.0 (42.9) 42.5 (42.4) 45.6 (45.3) 43.6 (43.3) 40.5 (40.3)
(2;)(E) & (::3, (2) (:::;) (E) d:::,
(Z) 43.1 (42.9) 42.3 (42.1) 42.2 (42.7) 42.6 (42.9)
3.9 (3.8)
12.2 (12.4)
(Z) 3.7 (3.8)
(: ::;, 10.6 (11.0)
(Z) 3.3 (3.6)
(& 11.4 (11.8)
(Z)
(; ::;t,
(Z)
(: ::;,
:::,
(: :::,
‘Calculated values are given in parentheses.
solvents, such as pentane nnd benzene, but soluble in DMF, warm methanoj, warm ethanol and hot Their water. These chelates Cre hygroscopic. elemental analyses, molar conductance, IR and UV
spectra and TGA measurements show that LnC13 - nH,O (Ln = lanthanide) forms chelates with the loss of two chloride ions and they conform to the formula Ln(NaL),Cl - nH20.
Table 2. IR spectra of the ligand and its complexes
Compound
H& II III IV V VI VII VIII IX X XI XII
y(HzO)
Y(N-H)
Amide I Y(c----o)
3414vb 3440vb 3440vb 3380b 3410b 3472b 3418b 3427b 3392b 3417b
3283ms 3206b 3240b 3220s 3282m 3282m 3171vb 3282s 3220m 3282s 3281s 3282s
1679~s 1673s” 1631s 1673s 1627s 1630s 1673s 1633s 1673s 1673s 1634s 1635s 1673s 1632s 1673s 1673s 1634s 1679s 1635s 1673s 1632s 1673s 1630s
Y(c=N) 1602s 1609s” 1546s 1608s 1546s 1609s 1546s 1609s 1567s 1609s 1567s 1603s 1560s 1609s 1546s 1546s 1609s 1547s 1616s 1608s 1546s 1609s 1547s
“Another hydrazonebnit of the ligand which is uncoordinated b = broad ; m = medium ; w = weak ; s = strong.
Y(N-N) 969m 101 lm 969~” 1Ollm 969~ 1009m 969w 1012w 969~ 1Ollw 969~ 1012m 963~ 1012w 969m 1Ollw 966~ 1012m 969m 1Ollm 968~ 1Ollm 968~
to the central ions.
y(M-0) 583m 583m 589~ 596~ 596~ 589m 589m 589m 596m 589m 584~
Na,[Ln(C~4H,8NsOrJCl]*nH,0 Table 3. Molar conductivities and UV spectra of the ligand and its complexes in DMF at room temperature
Compound
Molar conductance (Q- ’ cm2 mol- ‘)
UV absorption spectra J. (nm) 1
-
H& II III IV V VI VII VIII IX X XI XII
280.0 287.0 292.0 289.0 286.3 287.0 292.5 287.3 288.0 287.1 286.0 289.0
124.1 131.8 139.8 169.2 158.6 122.8 117.4 134.6 175.8 125.4 139.0
2 322.0 315.5 315.2 315.5 315.8 315.5 315.6 318.5 316.0 320.5 315.0 315.5
3 371.2 374.5 371.5 370.8 372.5 376.5 372.5 371.2 382.0 377.0 373.4
complexes
1045
cm- I, assigned to v(N-H), v(C=O), v(C=N), v(N-N) and v(O-H) (phenol@), respectively.’ In contrast to the parent ligand the IR spectra of these complexes, Ln(NaL),Cl *nHzO, show two bands at ca 1673 and 1630 cm- ’ due to uncoordinated and coordinated v(C=O). In addition, the corresponding band of v(C=N) appears at 1609 and 1560 cm- ’ and that of v(N-N) at 1011 and 969 ctn ‘, respectively. The presence of both the free and coordinated v(C=O), v(C=N) and v(N-N), and also a band due to v(N-H) at ca 3250 err- ‘, suggests that only one of the hydrazone units is coordinated to the lanthanide(II1) ion in the keto form.4 A broad medium band in the region 270& 2800 cm-’ of the ligand, assigned to v(O-H) of salicylaldehyde, disappeared in the complexes. This suggests that one of the hydrogens is replaced by a sodium ion and another by a lanthanide ion, which was confirmed by a new single band at 589 cm- ’ due to v(M-O).’
IR spectra
Electrolytic conductance
The IR spectra of the ligand and its complexes are shown in Table 2. The IR spectra of H,L show bands at 3283, 1679, 1602, 969 and 270&2800
Dissolving the lanthanide chelates in DMF obtained a light yellow to red-brown solution. The molar conductances (Table 3) of these solutions
Table 4. TGA data of the ligand and its complexes Temperature (“C)
Compound
Loss of weight (%)
242.3(dec.)
H&
254.2-271.2
2HOC,H,CH=NNH
402.7437.4
-COCH&O-
Up to 850
No residue
84.3
4H,O
NaJLa(C,,H,,N,O,)CI].3H,O
322.3459.7 459.7-576.2
Na,[Pr(C,,H,,N,O,)Cl]
Loss of groups
-OC,H,-CH=NNH-COCh,-CONH--, Cl 2-C,Hz,--CH=N-
Up to 850
Residue, dLa,O,+Na10
86.1
4H20
* 3H,O
311.9494.5
--OCgH+ZH=NNHCOCH#ZONH-, Cl
494.5-541.5
2-C,H4-CH=N-
Up to 850 a Calculated values are given in parentheses.
Residue, :Pr,O, +Na,O
78.10 (79.4) 21.2 (20.6)
7.3 (7.6) 48.5 (49.8) 20.6 (21.7) 23.7 (23.6) 7.95 (7.56) 49.36 (49.72) 20.08 (21.63) 23.95 (23.80)
1046
LIANG
YONGMIN
approach those reported for 1: 2 electrolytes,g showing that the chloride ion participates in coordination. The complexes are, therefore, formulated as Na2[Ln(CjqHZ8N808)Cl] *nHaO. UV spectra
Important bands in the spectra of the ligand and its complexes in DMF re shown in Table 3. It can be seen that the K aF rption band (7~-+ R* transition) of the ligand a pears at 280 nm, but is shifted to a longer wavele gth by 6-12 mn in the complexes. This may be att ‘buted to the interaction between ligands and meta ions when complexing. The absorption band at 22 nm in the ligand is shifted to a lower wavele gth, 315-321 nm, after chelating, which can be a signable to the rc 4 R* transition on azomethine. 1 his indicates that in the complexes the nitrogen inI the imino group participated in coordination ito the metal ion. In addition, there is a new broad band at ca 372 mn, which is due to the liganb-metal charge-transfer band. 3 Thermal analysis
et al.
but the water content is more than that resulting from the elemental analysis which can be due to their hygroscopic properties. Two -OC6H&H= NNHCOCHICONHgroups and two -C,H, CH=Ngroups are then released at 311.9494.5”C and 494.5-541S”C, respectively. It seems the molecules of the chelates are thermally more stable than its ligand. These results show that the ligand has the following structure : -
Pii CH-NNHCCIi&NIiN-CH
\
\/ 9-
/
(HZL)
9 HO
OH
and forms the complexes with some lanthanide ions, NaJLnL$l] *,nHzO. research has been supported by the National Science Foundation of China.
Acknowledgement-This
REFERENCES 1. L. Sacconi, J. Chem. Sot. 1954,1326. 2. R. A. La1 and N. Kailash, Synth. React. Inorg. Met.Org. Chem. 198&l&837.
The thermal analysis data of the ligand and its complexes are listed in Table 4 ; thermal analyses shows that the ligand de mposes exothermically at 242.3-271.2”C and lose ca 78.1% of its weight. Perhaps this is due to tw 1 HOC6H&H=NNHgroups breaking away fro the molecule. The exothermic peak at 427.4”C is ue to the loss of another decomposition of the part of the molecule. T ligand is complete and the e is no residue. The thermal analysis diagrams of a complexes are different from that of the ligand,/ The diagram of Na, prL,Cl] * 3H20 shows that it loses water at 86.1”C,
3. G. H. Havanur, V. K. Revenkar and V. B. Mahale, Ind. J. Chem. 1988,2lA,
803.
4. M. F. Iskander, I. El. Sayed, A. F. M. Hefry and S. E. Zayan, J. Znorg. Nucl. Chem. 1976,38,2209. 5. A. I. Vogel, A Text Book of Organic Chemistry. Longmans, London (1974).
6. J. J. Blanksma and H. A. Bakels, Rec. Trav. Chim. 1939,58,497.
7. M. Mashima, Bull. Chem. Sot. Japan 1962,35,1882; 1962,35,202;
1963,36,210.
8. C. Natarajan and P. Tharmaraj, Synth. React. Znorg. Met.-Org. Chem. 1990, 20, 151.
9. W. J. Geary, Coord. Chem. Rev. 1971,71, 81.
1993 0
0277-5387193 $6.00+.00 1993 Pergamon Press Ltd
ION COMPLEXES OF A LIGAND DERIVED L-E FROM SALICYLALDEHYDE AND MALONYL DIHYDRAZONE LIANG YONGMIN,
HUANC GUOSHENG
and MA YONGXIANGT
Department of Chemistry, Lanzhou University, Lanzhou 730000, P.R.C. and ZHAO GANG Department of Chemistry, Chengdu University of Science and Technology, Chengdu 610065, P.R.C. (Received 4 November 1992 ; accepted 4 January 1993)
Abstract-The chelates Na2[Ln(C34H28N808)Cl] *nH,O of the malonyl dihydrazone of salicylaldehyde with the lanthanides have been prepared and characterized by elemental analysis, IR, UV, molar conductance and TGA. It is shown that the ligand coordinates to the central ion with one hydrazone unit in the keto form and one chloride ion participates in coordination to the metal ion. These chelates are 1 : 2 electrolytes in DMF and are more thermostable than their ligand due to the formation of chelate rings.
Since Sacconi’ first reported the complexes of nickel (II) with dihydrazones a large number of transition metal complexes of acid dihydrazides have been studied.2-4 However, no work has been performed on the complexes of the lanthanides with dihydrazones. In the present work the reaction of Nsalicylidene derivatives of malonic dihydrazides (H,L) with 11 lanthanide(II1) chlorides in anhydrous ethanol in the presence of sodium hydroxide have been investigated, and the IR, UV, molar conductance and thermal analysis (TGA) of the cornplexes are discussed. EXPERIMENTAL All the solvents were dried by the reported method. 5 Lanthanide(II1) chlorides were prepared from their oxides and hydrochloric acid. The ligand was prepared by the literature method. 6 Preparation of the lanthanide chelates
added to the hydrated lanthanide(II1) chloride (0.5 mmol) in anhydrous ethanol (20 cm3). The mixture was refluxed for 2-3 h until the reaction was complete. The product was separated, washed with warm water, ethanol and diethyl ether, respectively, and dried in vucuu. Yields were 75%. Elemental analyses and some physical properties of the products obtained are listed in Table 1. Measurements
The IR spectra were obtained with a Nicolet 5-DX spectrophotometer using KBr discs in the 4000400 cm-’ region. UV spectra were recorded on a UV-240 spectrometer in the 190-600 mn region using a solution in DMF. Electrolytic conductivities were obtained using a DDS-II A molar conductometer and DMF as the solvent at room temperature. TGA analyses were carried out with a thermal analyser (Japan) between room temperature and 850°C in a nitrogen atmosphere.
H2L (1 mmol) was dissolved in warm ethanol (25 cm3) containing NaOH (2 mmol). This solution was
RESULTS
AND DISCUSSION
These chelates of malonyl dihydrazone of salicyl7 Author to whom correspondence should be addressed. aldehyde with lanthanide are insoluble in non-polar 1043
1044
LIANG
et al.
YONGMIN
Table 1. Analytical and physical data of the compounds
Colour
Yield (%)
Decomposed temperature (“C)
White
88
242
Na,[LaL,Cl] * 3H,O
Yellow
87
321
III
Na,[PrL,C1]*3H,O
Yellow
89
312
IV
Na,[EuL,Cl] - 3H,O
Yellow
75
310
V
NaJYL2CI] - 3H20
Pale yellow
81
286
VI
Na,[ErL,CI]*H,O
Light yellow
78
284
VII
Na,[HoL,Cl]*SH,O
Light red
85
264
Na2[TbL2Cl]
Pale red
91
286
IX
Na,[CeL,Cl] - 3H,O
Red-brown
84
276
X
Na,[LuL,CI] *2H,O
Pale yellow
89
264
Compound I
Formula
(C,,H&@,)
II
VIII
XI
NaJNdL2C1].3H,0
Yellow
92
284
XII
Na,[DyL,Cl]*3H,O
Yellow
78
285
Elemental analysis Found (Calc. %) C N H 60.2 (60.0) 42.7 (42.9) 43.0 (42.9) 42.5 (42.4) 45.6 (45.3) 43.6 (43.3) 40.5 (40.3)
(2;)(E) & (::3, (2) (:::;) (E) d:::,
(Z) 43.1 (42.9) 42.3 (42.1) 42.2 (42.7) 42.6 (42.9)
3.9 (3.8)
12.2 (12.4)
(Z) 3.7 (3.8)
(: ::;, 10.6 (11.0)
(Z) 3.3 (3.6)
(& 11.4 (11.8)
(Z)
(; ::;t,
(Z)
(: ::;,
:::,
(: :::,
‘Calculated values are given in parentheses.
solvents, such as pentane nnd benzene, but soluble in DMF, warm methanoj, warm ethanol and hot Their water. These chelates Cre hygroscopic. elemental analyses, molar conductance, IR and UV
spectra and TGA measurements show that LnC13 - nH,O (Ln = lanthanide) forms chelates with the loss of two chloride ions and they conform to the formula Ln(NaL),Cl - nH20.
Table 2. IR spectra of the ligand and its complexes
Compound
H& II III IV V VI VII VIII IX X XI XII
y(HzO)
Y(N-H)
Amide I Y(c----o)
3414vb 3440vb 3440vb 3380b 3410b 3472b 3418b 3427b 3392b 3417b
3283ms 3206b 3240b 3220s 3282m 3282m 3171vb 3282s 3220m 3282s 3281s 3282s
1679~s 1673s” 1631s 1673s 1627s 1630s 1673s 1633s 1673s 1673s 1634s 1635s 1673s 1632s 1673s 1673s 1634s 1679s 1635s 1673s 1632s 1673s 1630s
Y(c=N) 1602s 1609s” 1546s 1608s 1546s 1609s 1546s 1609s 1567s 1609s 1567s 1603s 1560s 1609s 1546s 1546s 1609s 1547s 1616s 1608s 1546s 1609s 1547s
“Another hydrazonebnit of the ligand which is uncoordinated b = broad ; m = medium ; w = weak ; s = strong.
Y(N-N) 969m 101 lm 969~” 1Ollm 969~ 1009m 969w 1012w 969~ 1Ollw 969~ 1012m 963~ 1012w 969m 1Ollw 966~ 1012m 969m 1Ollm 968~ 1Ollm 968~
to the central ions.
y(M-0) 583m 583m 589~ 596~ 596~ 589m 589m 589m 596m 589m 584~
Na,[Ln(C~4H,8NsOrJCl]*nH,0 Table 3. Molar conductivities and UV spectra of the ligand and its complexes in DMF at room temperature
Compound
Molar conductance (Q- ’ cm2 mol- ‘)
UV absorption spectra J. (nm) 1
-
H& II III IV V VI VII VIII IX X XI XII
280.0 287.0 292.0 289.0 286.3 287.0 292.5 287.3 288.0 287.1 286.0 289.0
124.1 131.8 139.8 169.2 158.6 122.8 117.4 134.6 175.8 125.4 139.0
2 322.0 315.5 315.2 315.5 315.8 315.5 315.6 318.5 316.0 320.5 315.0 315.5
3 371.2 374.5 371.5 370.8 372.5 376.5 372.5 371.2 382.0 377.0 373.4
complexes
1045
cm- I, assigned to v(N-H), v(C=O), v(C=N), v(N-N) and v(O-H) (phenol@), respectively.’ In contrast to the parent ligand the IR spectra of these complexes, Ln(NaL),Cl *nHzO, show two bands at ca 1673 and 1630 cm- ’ due to uncoordinated and coordinated v(C=O). In addition, the corresponding band of v(C=N) appears at 1609 and 1560 cm- ’ and that of v(N-N) at 1011 and 969 ctn ‘, respectively. The presence of both the free and coordinated v(C=O), v(C=N) and v(N-N), and also a band due to v(N-H) at ca 3250 err- ‘, suggests that only one of the hydrazone units is coordinated to the lanthanide(II1) ion in the keto form.4 A broad medium band in the region 270& 2800 cm-’ of the ligand, assigned to v(O-H) of salicylaldehyde, disappeared in the complexes. This suggests that one of the hydrogens is replaced by a sodium ion and another by a lanthanide ion, which was confirmed by a new single band at 589 cm- ’ due to v(M-O).’
IR spectra
Electrolytic conductance
The IR spectra of the ligand and its complexes are shown in Table 2. The IR spectra of H,L show bands at 3283, 1679, 1602, 969 and 270&2800
Dissolving the lanthanide chelates in DMF obtained a light yellow to red-brown solution. The molar conductances (Table 3) of these solutions
Table 4. TGA data of the ligand and its complexes Temperature (“C)
Compound
Loss of weight (%)
242.3(dec.)
H&
254.2-271.2
2HOC,H,CH=NNH
402.7437.4
-COCH&O-
Up to 850
No residue
84.3
4H,O
NaJLa(C,,H,,N,O,)CI].3H,O
322.3459.7 459.7-576.2
Na,[Pr(C,,H,,N,O,)Cl]
Loss of groups
-OC,H,-CH=NNH-COCh,-CONH--, Cl 2-C,Hz,--CH=N-
Up to 850
Residue, dLa,O,+Na10
86.1
4H20
* 3H,O
311.9494.5
--OCgH+ZH=NNHCOCH#ZONH-, Cl
494.5-541.5
2-C,H4-CH=N-
Up to 850 a Calculated values are given in parentheses.
Residue, :Pr,O, +Na,O
78.10 (79.4) 21.2 (20.6)
7.3 (7.6) 48.5 (49.8) 20.6 (21.7) 23.7 (23.6) 7.95 (7.56) 49.36 (49.72) 20.08 (21.63) 23.95 (23.80)
1046
LIANG
YONGMIN
approach those reported for 1: 2 electrolytes,g showing that the chloride ion participates in coordination. The complexes are, therefore, formulated as Na2[Ln(CjqHZ8N808)Cl] *nHaO. UV spectra
Important bands in the spectra of the ligand and its complexes in DMF re shown in Table 3. It can be seen that the K aF rption band (7~-+ R* transition) of the ligand a pears at 280 nm, but is shifted to a longer wavele gth by 6-12 mn in the complexes. This may be att ‘buted to the interaction between ligands and meta ions when complexing. The absorption band at 22 nm in the ligand is shifted to a lower wavele gth, 315-321 nm, after chelating, which can be a signable to the rc 4 R* transition on azomethine. 1 his indicates that in the complexes the nitrogen inI the imino group participated in coordination ito the metal ion. In addition, there is a new broad band at ca 372 mn, which is due to the liganb-metal charge-transfer band. 3 Thermal analysis
et al.
but the water content is more than that resulting from the elemental analysis which can be due to their hygroscopic properties. Two -OC6H&H= NNHCOCHICONHgroups and two -C,H, CH=Ngroups are then released at 311.9494.5”C and 494.5-541S”C, respectively. It seems the molecules of the chelates are thermally more stable than its ligand. These results show that the ligand has the following structure : -
Pii CH-NNHCCIi&NIiN-CH
\
\/ 9-
/
(HZL)
9 HO
OH
and forms the complexes with some lanthanide ions, NaJLnL$l] *,nHzO. research has been supported by the National Science Foundation of China.
Acknowledgement-This
REFERENCES 1. L. Sacconi, J. Chem. Sot. 1954,1326. 2. R. A. La1 and N. Kailash, Synth. React. Inorg. Met.Org. Chem. 198&l&837.
The thermal analysis data of the ligand and its complexes are listed in Table 4 ; thermal analyses shows that the ligand de mposes exothermically at 242.3-271.2”C and lose ca 78.1% of its weight. Perhaps this is due to tw 1 HOC6H&H=NNHgroups breaking away fro the molecule. The exothermic peak at 427.4”C is ue to the loss of another decomposition of the part of the molecule. T ligand is complete and the e is no residue. The thermal analysis diagrams of a complexes are different from that of the ligand,/ The diagram of Na, prL,Cl] * 3H20 shows that it loses water at 86.1”C,
3. G. H. Havanur, V. K. Revenkar and V. B. Mahale, Ind. J. Chem. 1988,2lA,
803.
4. M. F. Iskander, I. El. Sayed, A. F. M. Hefry and S. E. Zayan, J. Znorg. Nucl. Chem. 1976,38,2209. 5. A. I. Vogel, A Text Book of Organic Chemistry. Longmans, London (1974).
6. J. J. Blanksma and H. A. Bakels, Rec. Trav. Chim. 1939,58,497.
7. M. Mashima, Bull. Chem. Sot. Japan 1962,35,1882; 1962,35,202;
1963,36,210.
8. C. Natarajan and P. Tharmaraj, Synth. React. Znorg. Met.-Org. Chem. 1990, 20, 151.
9. W. J. Geary, Coord. Chem. Rev. 1971,71, 81.