- Email: [email protected]
A spectroscopic study of tin(IV) complexes with multidentate Schiff bases
J. inorg,nucl.Chem.,1971,Vol.33, pp. 3781-3786. PergamonPress. Printedin Great Britain
A SPECTROSCOPIC STUDY OF TIN(IV) COMPLEXES WITH MULTIDENTATE SCHIFF BASES N. S. BIRADAR and V. H. K U L K A R N i Department of Chemistry, Karnatak University, Dharwar, India (Received 21 December 1970) A b s t r a c t - T h e complexes of tin(IV) chloride with multidentate Schiff bases have been prepared. The complexes are yellow to orange-yellow in colour. These complexes are characterised by elemental analyses, conductometric and spectral data. Based on these measurements an octahedral structure may be proposed to each one of these complexes. INTRODUCTION
SINCE the initial report on the preparation and characterisation of tin(IV) complexes containing multidentate Schiff bases as ligands there has been considerable amount of activity in the preparation and characterisation of a number of tin(IV) complexes with monodentate and bidentate Schiffbases [1-8]. We wish to report in this paper preparation and properties of tin(IV) complexes with the following multidentate Schiffbases:
/--k
I
II
OH
H
O
~
III IV 1. V . A . Kogan, O. A. Osipov, V. I. Minkin and V. P. Sokolov, Zh. neorg. Khim. 10, 83 (1965). 2. L. A. Kazitsyna, A. A. Nilson, N. B. Kupletskaya and O. A. Reutov, Vestn. Mosk. Univ. Ser. I1, Khim. 21, 95 (1966). 3. A. D. Garnovskii, V. I. Minkin, O. A. Osipov, V. T. Panyushkin, L. K. Isaeva and M. I. Knyazhanskii, Zh. neorg. Khim. 12, 2443 ( 1967); C. A. 68, 8894u (1968). 4. L. V. Orlova, A. D. Garnovskii, O. A. Osipov, O. A. Raevskii, Zh. obshch. Khim. 37, 1787 ( 1967); C. A. 68, 8897x (1968). 5. L. V. Orlova, A. D. Garnovskii, O. A. Osipov and I. I. Kukushkina, Zh. obshch. Khim. 38, 1850 (1968); C.A. 69, 113055q (1968). 6. F. M aggio, R. Bosco, R. Cefalu and R. Barbieri, lnorg. & Nucl. Chem. Left. 4, 389 (1968). 7. G. Faraglia, F. Maggio, R. Bosco, R. Cefalu and R. Barbieri, Inorg. & Nucl. Chem. Lett. 5, 177 (1969). 8. N. S. Biradar and V. H. Kulkarni, J. inorg, nucl. Chem. 33,2451 ( 1971 ). 3781
3782
N . S . BIRADAR and V. H. KULKARNI EXPERIMENTAL
Materials and method
Chemicals used for preparing complexes were of reagent grade p-p'-diaminodiphenylsulphide was prepared by the method known in the literature[9]. Anhydrous tin(IV) chloride of Riedal grade was used as such without further purification. Absolute alcohol used as a solvent was prepared by the standard method [ 10]. An alcoholic solution of tin(IV) chloride (0.01 mole) was added to an alcoholic solution containing 0.02 mole of salicylaldehyde and 0.01 mole of a diamine. The reaction mixture was refluxed for 3-4 hr. Then the mixture was heated at 70-80°C until the solvent vaporised away and subsequently the temperature was raised and maintained between 150-180°C. The heating was continued until the evolution of HCI gas ceased. The product was cooled and extracted with ethanol in soxhlet apparatus. The product thus obtained was dried in vacuum over anhydrous calcium chloride. All the complexes are insoluble in water and most of the organic solvents. They are soluble to a limited extent in DMF and DMSO. Analysis
Tin in these complexes was estimated gravimetricallySnO~. Chloride was determined as AgCI and nitrogen by Kjeldalh method. Physical measurements
The conductance measurements were made with an ELICO C.M. 82 conductivity bridge with a cell having cell constant 0.829 cm -~ manufactured by Electronic Industrial Instruments Company, Hyderabad. The u.v. absorption spectra of the ligands and their complexes were measured with a Hilger UVSPEK H-700 using quartz cells. The i.r. spectra of the ligands and their complexes in Nujol mull were recorded on a Perkin Elmer infracord. RESULTS A N D D I S C U S S I O N T h e e l e m e n t a l a n a l y s e s in T a b l e 1 s h o w t h a t t h e t i n ( I V ) c h l o r i d e f o r m s c o m p l e x e s , l o o s i n g t w o o f its f o u r c h l o r i d e s , w i t h t h e S c h i f f b a s e s ( I - I V ) . T h e m o l a r c o n d u c t a n c e v a l u e s ( T a b l e 1) d e t e r m i n e d in D M F at t h e c o n c e n t r a t i o n 10 -3 M m a k e us to p r e d i c t t h a t t h e s e a r e n o n - e l e c t r o l y t e s in D M F . Electronic spectra
T h e s p e c t r a o f t h e s e S c h i f f b a s e s c o n t a i n a c h a r a c t e r i s t i c b a n d in t h e r e g i o n 2 4 0 - 2 6 0 m/x a n d i n t e n s e b r o a d b a n d s in t h e r e g i o n 3 0 0 - 3 8 0 m/x. T h e i n t e n s e b a n d s in t h e r e g i o n 3 0 0 - 3 8 0 m/z o f t h e l i g a n d s a r e r e p l a c e d b y more complicated broad bands of varying intensity when they are coordinated with t h e m e t a l ion. T h e s p e c t r a o f t h e c o m p l e x e s d o n o t r e s e m b l e t h e s p e c t r a o f t h e l i g a n d s , c a n b e t a k e n as a n e v i d e n c e f o r t h e c o m p l e x f o r m a t i o n . T h e b a n d in t h e r e g i o n 2 4 0 - 2 6 0 m/x, a p p e a r i n g in t h e l i g a n d s as well as in t h e i r c o m p l e x e s c a n b e c o n s i d e r e d as a 7r-zr* b e n z e n o i d b a n d , in v i e w o f t h e a s s i g n m e n t m a d e b y C h a t t e r j e e a n d D o u g l a s [ 11 ]. T h e s p e c t r a o f t h e l i g a n d s ( I - I I I ) s h o w a n i n c r e a s e in t h e i n t e n s i t y f r o m I to I I I . T h i s i n c r e a s e in t h e intensity" c a n b e c o r r e l a t e d with t h e n u m b e r o f d o u b l e b o n d s in t h e m o l e c u l e . T h e r e p l a c e m e n t o f C H 2 - C H z h y d r o c a r b o n b r i d g e s u c c e s s i v e l y b y a p h e n y l ring a n d a b i - p h e n y l ring i n c r e a s e t h e n u m b e r o f the 9. s. R. Safir, S. Kushner, L. M. Braucone and Y. Subbaraw, J. org. Chem. 13, 924 (1948). 10. A. I. Vogel, Text Book of Practical Organic Chemistry. Longman's Green, London (1956). 11. K. K. Chatterjee and B. E. Douglas,Spectrochim.Acta 21, 1625 (1965).
A spectroscopic study of tin(l V)
~E
O
"6
--6 e~
e-
¢-
Z ~
tJ _
,.-
.-~Z
3783
3784
N . S . B I R A D A R and V. H. K U L K A R N I
double bonds. Bailar and Busch[12] also have made similar observations in the case of iron(II) azomethine complexes. The intensity of the ligands III and IV almost remains the same though IV contains sulphur in it. This helps us to prove that the sulphur does not act as a conjugate transmitter. The spectra of the complexes (V-VII), under investigation show the same trend in the intensity as seen in the ligands 1-II1. A considerable decrease is observed in the complex VIII, and it falls between V and VI. This decrease in the intensity may be due to the steric hindrance posed by the bulky sulphur atom of the ligand IV. I.R. spectra The i.r. frequencies of the ligands and their complexes are given in Table 2 with their assignments. The spectra of the ligands I - I V show broad and weak band in the region 28002700 cm -1 and it is assigned to the intramolecular hydrogen bonded OH. This assignment agrees with that of Ueno and Martell[13] in the case of bis(salicylidene) ethylenediamine. This broad and weak band disappears in the complexes V - V I I I indicating metal-oxygen bond formation in the complexes. The strong band around 1280 cm-1 is ascribed to the phenolic C - O stretching vibration in analogy with the assignment of Marvel et al.[ 14] and Kovacic [15]. This band in the complexes does not show marked shift indicating that this frequency is not so sensitive to the chelation. Similar observations have been made by Sokolov et al.[16] in the case of titanium(I V) azomethine complexes. A strong band found around 1613 cm -1 in the ligands is attributed to the ~ N stretch in view of the previous assignments [15-17]. This band in the complexes Table 2. I.R. frequencies (in cm -1) of the Schiff bases and their tin(IV) complexes and their assignments
3 4
5
I
V
II
VI
III
VII
IV
VIII
2976 2632
2985
3012 2778
2985
2985 2646
2985
2985 2703
3030
1618 1592 1565 1488 1274
1626 1600 1538 1495 1280
1616 1587 1563 1481 1274
1600 1575 1538 1460 1299 1280
1618 1600 1575 1497 1280
1626 1590 1538 1471 1282
1616 1587 1563 1481 1282
Assignments
CH stretch Intramolecular Hbonded OH stretch 1639 C~---Nstretch 1613 C==C stretch 1550 1481 1282 Phenolic C - O stretch
I-IV Schiff bases. V - V I I I Complexes. D. H. Bush and J. C. Bailar, Jr., J. Am. chem. Soc. 78, 1137 (1956). K. Ueno and A. E. Martell, J. phys. Chem. 60, 1270 (1956). C. S. Marvel, S. A. Aspey and E. A. Dudley,J. Am. chem. Soc. 78, 4905 (1956). J. E. Kovacic, Spectrochim. Acta 23A, 183 (1967). V. P. Sokolov, V. A. Kogan, O. A. Osipov and L. G. Kolomin, Zh. neorg. Khim. 14, 2401 (1969); Chem. Abstr. 71, I 19143e (1969). 17. N. S. Biradar and V. H. Kulkarni, Rev. Roumaine Chim. 15, 1993 (1970).
12. 13. 14. 15. 16.
A spectroscopic study of tin(IV)
3785
V, VII and V I I I shows an increase in the ~ N stretch whereas complex VI shows a lowering in the ~ N stretch suggesting coordination of the Schiff base through the azomethine nitrogen. T h e i.r. interpretation has revealed that the coordination bond has been formed between metal ion and two azomethine groups of the ligand and oxygen-metal bonds have been set up. It is known that ligand 1 is stericaily very flexible and can encompass the metal moiety strainlessly[18]. It is also reported that the ligand 1 always prefers to have cis-configuration[19]. In view of the observed non-electrolytic nature and the predominant hexacovalency of tin(IV), the complex V can be regarded as having coordination number 6. When CH2-CH2 hydrocarbon bridge is replaced by a phenyl ring, a more rigid tetradentate il is formed. This is also non-electrolyte and prefers to have cis octahedral form in tin(IV) complex.
cl
,4 In the case of ligand III one can expect the following two structures for the tin(IV) complex.
B
18. F. P. Dwyer, and D. P. Mellor, Chelating Agents and Metal Chelates. Academic Press, New York (1964). 19. A. E. Martell and M. Calvin, Chemistry of Metal Chelate Compounds, Prentice Hall, New Jersey (1962).
3786
N . S . B I R A D A R and V. H. K U L K A R N I
On the steric grounds it can be predicted that the tin(IV) complexes can exist in dimeric form in analogy with the known dimeric complex of zircomnium with the same ligand[20]. Pfeiffer and Pfitzner[21] have also studied extensively the complexes with the similar and substituted ligands and assign dimeric structure for their complexes. Unfortunately the dimeric nature of the complex could not be ascertained by the molecular weight determination because of its limited solubility. The construction ofthemodel shows that the structure B can be formed without any steric hindrance whereas the molecule is terribly strained to form complex A. In view of the above considerations the structure B is more favoured than A. The ligand IV under investigation contains two - ~ N , two - O H and one S groups. This can be compared with the Schiff base formed by the condensation of salicylaldehyde with diamino diethyl sulphide [ 19].
N/-'-k s/---N N
foH Ho: The phenyl rings have been introduced in the place o f - C H 2 - C H ~ - hydrocarbon bridges of the above ligand to result the ligand IV. The ligand IV is comparatively more rigid and bulkier than the one reported by Gills and involves more steric hindrance. Construction of the model shows that though - ~ N groups and - O H groups can surround the single metal ion due to the pyramidal distribution of the sulphur bonds, the sulphur is removed far from the coordination site thus rendering the ligand to behave as tetradentate. The complex is non-electrolyte in DMF and hence has the coordination number six. Acknowledgement-The authors wish to thank Professor D. K. Banerjee, I.I.Sc. for the i.r. spectra. One of the authors (V.H.K.) acknowledges with thanks the financial assistance given by the Karnatak University. 20. C. G. Macarovici, E. Pertic and E. Motiu, Rev. Roumaine Chim. 11, 53, 59 (1966). 21. P. Pfeiffer, and H. Pfitzner, J. prakt. Chem. 145, 243 (1936).
A SPECTROSCOPIC STUDY OF TIN(IV) COMPLEXES WITH MULTIDENTATE SCHIFF BASES N. S. BIRADAR and V. H. K U L K A R N i Department of Chemistry, Karnatak University, Dharwar, India (Received 21 December 1970) A b s t r a c t - T h e complexes of tin(IV) chloride with multidentate Schiff bases have been prepared. The complexes are yellow to orange-yellow in colour. These complexes are characterised by elemental analyses, conductometric and spectral data. Based on these measurements an octahedral structure may be proposed to each one of these complexes. INTRODUCTION
SINCE the initial report on the preparation and characterisation of tin(IV) complexes containing multidentate Schiff bases as ligands there has been considerable amount of activity in the preparation and characterisation of a number of tin(IV) complexes with monodentate and bidentate Schiffbases [1-8]. We wish to report in this paper preparation and properties of tin(IV) complexes with the following multidentate Schiffbases:
/--k
I
II
OH
H
O
~
III IV 1. V . A . Kogan, O. A. Osipov, V. I. Minkin and V. P. Sokolov, Zh. neorg. Khim. 10, 83 (1965). 2. L. A. Kazitsyna, A. A. Nilson, N. B. Kupletskaya and O. A. Reutov, Vestn. Mosk. Univ. Ser. I1, Khim. 21, 95 (1966). 3. A. D. Garnovskii, V. I. Minkin, O. A. Osipov, V. T. Panyushkin, L. K. Isaeva and M. I. Knyazhanskii, Zh. neorg. Khim. 12, 2443 ( 1967); C. A. 68, 8894u (1968). 4. L. V. Orlova, A. D. Garnovskii, O. A. Osipov, O. A. Raevskii, Zh. obshch. Khim. 37, 1787 ( 1967); C. A. 68, 8897x (1968). 5. L. V. Orlova, A. D. Garnovskii, O. A. Osipov and I. I. Kukushkina, Zh. obshch. Khim. 38, 1850 (1968); C.A. 69, 113055q (1968). 6. F. M aggio, R. Bosco, R. Cefalu and R. Barbieri, lnorg. & Nucl. Chem. Left. 4, 389 (1968). 7. G. Faraglia, F. Maggio, R. Bosco, R. Cefalu and R. Barbieri, Inorg. & Nucl. Chem. Lett. 5, 177 (1969). 8. N. S. Biradar and V. H. Kulkarni, J. inorg, nucl. Chem. 33,2451 ( 1971 ). 3781
3782
N . S . BIRADAR and V. H. KULKARNI EXPERIMENTAL
Materials and method
Chemicals used for preparing complexes were of reagent grade p-p'-diaminodiphenylsulphide was prepared by the method known in the literature[9]. Anhydrous tin(IV) chloride of Riedal grade was used as such without further purification. Absolute alcohol used as a solvent was prepared by the standard method [ 10]. An alcoholic solution of tin(IV) chloride (0.01 mole) was added to an alcoholic solution containing 0.02 mole of salicylaldehyde and 0.01 mole of a diamine. The reaction mixture was refluxed for 3-4 hr. Then the mixture was heated at 70-80°C until the solvent vaporised away and subsequently the temperature was raised and maintained between 150-180°C. The heating was continued until the evolution of HCI gas ceased. The product was cooled and extracted with ethanol in soxhlet apparatus. The product thus obtained was dried in vacuum over anhydrous calcium chloride. All the complexes are insoluble in water and most of the organic solvents. They are soluble to a limited extent in DMF and DMSO. Analysis
Tin in these complexes was estimated gravimetricallySnO~. Chloride was determined as AgCI and nitrogen by Kjeldalh method. Physical measurements
The conductance measurements were made with an ELICO C.M. 82 conductivity bridge with a cell having cell constant 0.829 cm -~ manufactured by Electronic Industrial Instruments Company, Hyderabad. The u.v. absorption spectra of the ligands and their complexes were measured with a Hilger UVSPEK H-700 using quartz cells. The i.r. spectra of the ligands and their complexes in Nujol mull were recorded on a Perkin Elmer infracord. RESULTS A N D D I S C U S S I O N T h e e l e m e n t a l a n a l y s e s in T a b l e 1 s h o w t h a t t h e t i n ( I V ) c h l o r i d e f o r m s c o m p l e x e s , l o o s i n g t w o o f its f o u r c h l o r i d e s , w i t h t h e S c h i f f b a s e s ( I - I V ) . T h e m o l a r c o n d u c t a n c e v a l u e s ( T a b l e 1) d e t e r m i n e d in D M F at t h e c o n c e n t r a t i o n 10 -3 M m a k e us to p r e d i c t t h a t t h e s e a r e n o n - e l e c t r o l y t e s in D M F . Electronic spectra
T h e s p e c t r a o f t h e s e S c h i f f b a s e s c o n t a i n a c h a r a c t e r i s t i c b a n d in t h e r e g i o n 2 4 0 - 2 6 0 m/x a n d i n t e n s e b r o a d b a n d s in t h e r e g i o n 3 0 0 - 3 8 0 m/x. T h e i n t e n s e b a n d s in t h e r e g i o n 3 0 0 - 3 8 0 m/z o f t h e l i g a n d s a r e r e p l a c e d b y more complicated broad bands of varying intensity when they are coordinated with t h e m e t a l ion. T h e s p e c t r a o f t h e c o m p l e x e s d o n o t r e s e m b l e t h e s p e c t r a o f t h e l i g a n d s , c a n b e t a k e n as a n e v i d e n c e f o r t h e c o m p l e x f o r m a t i o n . T h e b a n d in t h e r e g i o n 2 4 0 - 2 6 0 m/x, a p p e a r i n g in t h e l i g a n d s as well as in t h e i r c o m p l e x e s c a n b e c o n s i d e r e d as a 7r-zr* b e n z e n o i d b a n d , in v i e w o f t h e a s s i g n m e n t m a d e b y C h a t t e r j e e a n d D o u g l a s [ 11 ]. T h e s p e c t r a o f t h e l i g a n d s ( I - I I I ) s h o w a n i n c r e a s e in t h e i n t e n s i t y f r o m I to I I I . T h i s i n c r e a s e in t h e intensity" c a n b e c o r r e l a t e d with t h e n u m b e r o f d o u b l e b o n d s in t h e m o l e c u l e . T h e r e p l a c e m e n t o f C H 2 - C H z h y d r o c a r b o n b r i d g e s u c c e s s i v e l y b y a p h e n y l ring a n d a b i - p h e n y l ring i n c r e a s e t h e n u m b e r o f the 9. s. R. Safir, S. Kushner, L. M. Braucone and Y. Subbaraw, J. org. Chem. 13, 924 (1948). 10. A. I. Vogel, Text Book of Practical Organic Chemistry. Longman's Green, London (1956). 11. K. K. Chatterjee and B. E. Douglas,Spectrochim.Acta 21, 1625 (1965).
A spectroscopic study of tin(l V)
~E
O
"6
--6 e~
e-
¢-
Z ~
tJ _
,.-
.-~Z
3783
3784
N . S . B I R A D A R and V. H. K U L K A R N I
double bonds. Bailar and Busch[12] also have made similar observations in the case of iron(II) azomethine complexes. The intensity of the ligands III and IV almost remains the same though IV contains sulphur in it. This helps us to prove that the sulphur does not act as a conjugate transmitter. The spectra of the complexes (V-VII), under investigation show the same trend in the intensity as seen in the ligands 1-II1. A considerable decrease is observed in the complex VIII, and it falls between V and VI. This decrease in the intensity may be due to the steric hindrance posed by the bulky sulphur atom of the ligand IV. I.R. spectra The i.r. frequencies of the ligands and their complexes are given in Table 2 with their assignments. The spectra of the ligands I - I V show broad and weak band in the region 28002700 cm -1 and it is assigned to the intramolecular hydrogen bonded OH. This assignment agrees with that of Ueno and Martell[13] in the case of bis(salicylidene) ethylenediamine. This broad and weak band disappears in the complexes V - V I I I indicating metal-oxygen bond formation in the complexes. The strong band around 1280 cm-1 is ascribed to the phenolic C - O stretching vibration in analogy with the assignment of Marvel et al.[ 14] and Kovacic [15]. This band in the complexes does not show marked shift indicating that this frequency is not so sensitive to the chelation. Similar observations have been made by Sokolov et al.[16] in the case of titanium(I V) azomethine complexes. A strong band found around 1613 cm -1 in the ligands is attributed to the ~ N stretch in view of the previous assignments [15-17]. This band in the complexes Table 2. I.R. frequencies (in cm -1) of the Schiff bases and their tin(IV) complexes and their assignments
3 4
5
I
V
II
VI
III
VII
IV
VIII
2976 2632
2985
3012 2778
2985
2985 2646
2985
2985 2703
3030
1618 1592 1565 1488 1274
1626 1600 1538 1495 1280
1616 1587 1563 1481 1274
1600 1575 1538 1460 1299 1280
1618 1600 1575 1497 1280
1626 1590 1538 1471 1282
1616 1587 1563 1481 1282
Assignments
CH stretch Intramolecular Hbonded OH stretch 1639 C~---Nstretch 1613 C==C stretch 1550 1481 1282 Phenolic C - O stretch
I-IV Schiff bases. V - V I I I Complexes. D. H. Bush and J. C. Bailar, Jr., J. Am. chem. Soc. 78, 1137 (1956). K. Ueno and A. E. Martell, J. phys. Chem. 60, 1270 (1956). C. S. Marvel, S. A. Aspey and E. A. Dudley,J. Am. chem. Soc. 78, 4905 (1956). J. E. Kovacic, Spectrochim. Acta 23A, 183 (1967). V. P. Sokolov, V. A. Kogan, O. A. Osipov and L. G. Kolomin, Zh. neorg. Khim. 14, 2401 (1969); Chem. Abstr. 71, I 19143e (1969). 17. N. S. Biradar and V. H. Kulkarni, Rev. Roumaine Chim. 15, 1993 (1970).
12. 13. 14. 15. 16.
A spectroscopic study of tin(IV)
3785
V, VII and V I I I shows an increase in the ~ N stretch whereas complex VI shows a lowering in the ~ N stretch suggesting coordination of the Schiff base through the azomethine nitrogen. T h e i.r. interpretation has revealed that the coordination bond has been formed between metal ion and two azomethine groups of the ligand and oxygen-metal bonds have been set up. It is known that ligand 1 is stericaily very flexible and can encompass the metal moiety strainlessly[18]. It is also reported that the ligand 1 always prefers to have cis-configuration[19]. In view of the observed non-electrolytic nature and the predominant hexacovalency of tin(IV), the complex V can be regarded as having coordination number 6. When CH2-CH2 hydrocarbon bridge is replaced by a phenyl ring, a more rigid tetradentate il is formed. This is also non-electrolyte and prefers to have cis octahedral form in tin(IV) complex.
cl
,4 In the case of ligand III one can expect the following two structures for the tin(IV) complex.
B
18. F. P. Dwyer, and D. P. Mellor, Chelating Agents and Metal Chelates. Academic Press, New York (1964). 19. A. E. Martell and M. Calvin, Chemistry of Metal Chelate Compounds, Prentice Hall, New Jersey (1962).
3786
N . S . B I R A D A R and V. H. K U L K A R N I
On the steric grounds it can be predicted that the tin(IV) complexes can exist in dimeric form in analogy with the known dimeric complex of zircomnium with the same ligand[20]. Pfeiffer and Pfitzner[21] have also studied extensively the complexes with the similar and substituted ligands and assign dimeric structure for their complexes. Unfortunately the dimeric nature of the complex could not be ascertained by the molecular weight determination because of its limited solubility. The construction ofthemodel shows that the structure B can be formed without any steric hindrance whereas the molecule is terribly strained to form complex A. In view of the above considerations the structure B is more favoured than A. The ligand IV under investigation contains two - ~ N , two - O H and one S groups. This can be compared with the Schiff base formed by the condensation of salicylaldehyde with diamino diethyl sulphide [ 19].
N/-'-k s/---N N
foH Ho: The phenyl rings have been introduced in the place o f - C H 2 - C H ~ - hydrocarbon bridges of the above ligand to result the ligand IV. The ligand IV is comparatively more rigid and bulkier than the one reported by Gills and involves more steric hindrance. Construction of the model shows that though - ~ N groups and - O H groups can surround the single metal ion due to the pyramidal distribution of the sulphur bonds, the sulphur is removed far from the coordination site thus rendering the ligand to behave as tetradentate. The complex is non-electrolyte in DMF and hence has the coordination number six. Acknowledgement-The authors wish to thank Professor D. K. Banerjee, I.I.Sc. for the i.r. spectra. One of the authors (V.H.K.) acknowledges with thanks the financial assistance given by the Karnatak University. 20. C. G. Macarovici, E. Pertic and E. Motiu, Rev. Roumaine Chim. 11, 53, 59 (1966). 21. P. Pfeiffer, and H. Pfitzner, J. prakt. Chem. 145, 243 (1936).