- Email: [email protected]
Coordination behaviour of benzothiazolines towards stannous ion
Po/yk&on Vol. 4, No. 7, pp. 131 l-1313. Printed in Great Britain
1985 0
0277-5387/85 s3.acl+ .oo 1985 pergsmon Reds Ltd
COORDINATION BEHAVIOUR OF BENZOTHIAZOLINES TOWARDS STANNOUS ION ANIL VARSHNEY and J. P. TANDON* Department of Chemistry, University of Rajasthan, Jaipur-302004, India (Received 19 October 1984; accepted 4 January 1985) Abstract-Bquimolar reactions of tin(H) methoxide with benzothiazolines result in the isolation of a new series of tin(II)comple which further undergo 1: 1 adduct formation with pyridine. The electronic, IR and ‘H NMR spectral studies indicate coordination of tin to the oxygen, azomethine nitrogen and sulphur of the ligand moiety.
The condensation of a o-aminothiophenol with a carbonyl compound does not normally lead to the isolation of the corresponding S&&base, but a benzothiazoline is formed.‘*2 However, in the presence of a metal ion, the cyclic structure of thiazoline or benzothiazoline rearranges to give the S&i&base metal chelate quantitatively.3*4 During the course of the present investigations, an attempt has been made to synthesize tin(H) derivatives by interacting tin(H) methoxide with benzothiazolines derived by the condensation of salicylaldehyde (I), 2hydroxy-1-naphthaldehyde (II), o-hydroxy acetophenone (III), acetylacetone (IV) or benzoyl acetone (V) with o-aminothiophenol. The benzothiazolines used can be structurally depicted as follows :
(Schiff
(Benrothiazoline) R,
=
C6H40H
and
R2
=
II,
R,
=
CmsOH
and
Rp
= H
Et,
R,
=
C6H40H
and
Rp
= CH3(H2A’SP)
I
H
base)
I,
(H2SSP) (t+NSP)
(i)
(ii)
EXPERIMENTAL Tin(H) methoxide was prepared by the reaction of anhydrous SnCl, with an excess of triethylamine in methanol as described by Gsell and Zeldin5 The ligands were prepared by the condensation of aldehydes/ketones with o-aminothiophenol as described earlier.‘j,’ These were purified by recrystallization from ethanol. The complexes were analysed as reported earlier’ and the infrared spectra were recorded on a PerkinElmer 577 IR spectrophotometer in the region, 4000-200 cm-’ using KBr optics. The electro.nic spectra (in methanol) were taken on a Toshniwal spectrophotometer. A Perkin-Elmer (Model RB-12) spectrometer was used for obtaining the PMR spectra employing DMSO-d, as the solvent and TMS as the internal standard Molar conductance measurements were made in anhydrous dimethylformamide at 36 f 1°C using a Systronics Conductivity Bridge Model-305. Molecular weight determinations were carried out by the Rast Method.
/
(Benzothiordine
(Schiff
I
Ip,
R3
=
CH3
Y,
R3
=
CgH5(H2BSPl
base)
lH2ASP)
* To whom all correspondence should be addressed.
Synthesis of tin(II) complexes To a weighed amount of tin(I1) methoxide was added the calculated amount of the ligand in 1: 1 molar ratio using methanol as the reaction medium 1311
1312
A. VARSHNEY and J. P. TANDON Table 1. Synthesis and characteristics of tin(I1) complexes Reactant Tin compound
L&and
Molar ratio
1.
Sn(OMe),
H,SSP
1: 1
2.
Sn(OMe),
H,NSP
1:l
3.
Sn(OMe),
H,A’SP
1: 1
4.
Sn(OMe)z
H,ASP
1: 1
5.
Sn(OMe),
HzBSP
1: 1
6.
SnSSP
Pyridine
1:l
7.
SnNSP
Pyridine
1: 1
8.
SnA’SP
Pyridine
1: 1
9.
&ASP
Pyridine
1: 1
10.
SnBSP
Pyridine
1:l
Where : H,SSP = H2NSP = H,A’SP = H,ASP = H,BSP= s= d=
Compound, colour and state SnSSP Yellow solid SnNSP Green solid SnA’SP Yellow solid SnASP Yellow solid SnBSP Orange solid SnSSP - Py Yellow solid SnNSP * Py Green solid SnA’SP - Py Yellow solid SnASP - Py Yellow solid SnBSP - Py
205s 280d 18Od 230d 195s 260s 315s 310s 210s 200s
Analysis observed (Cal.) Sn N S 33.93 (34.34) 29.73 (29.99) 32.56 (32.99) 35.93 (36.67) 30.53 (30.78) 27.85 (27.95) 24.82 (25.01) 26.84 (27.06) 28.86 (29.48) 24.98 (25.54)
3.85 (4.05) 3.02 (3.54) 3.42 (3.89) 3.86 (4.33) 3.31 (3.63) 5.86 (6.59) 5.35 (5.89) 5.86 (6.38) 6.53 (6.95) 5.86 (6.03)
8.86 (9.26) 7.89 (8.09) 8.43 (8.89) 9.43 (9.89) 7.86 (8.29) 6.94 (7.54) 6.34 (6.74) 6.82 (7.29) 7.64 (7.95) 6.34 (6.89)
Mol. wt. observed (Cal.) 330 (345.7) 370 (395.7) 372 (359.7) 340 (323.7) 400 (385.7) 405 (424.7) 440 (474.7) 415 (438.7) 385 (402.7) 443 (464.7)
salicylaldehyde-2-mercaptoanil 2-hydroxy-1-naphthaldehyde-2-mercaptoanil 2 -hydroxy acetophenone-2-mercapaptoanil a&y1 acetone-2-mercaptoanil benzoylacetone-2-mercaptoanil sharp decomposition.
in an oxygen-free nitrogen atmosphere. Immediately, the colour of the solution changed and it was then stirred magnetically for ca 2 h. The excess of the solvent was removed and the compound finally dried in uacuo at a bath temperature of 35 f5”C after being repeatedly washed with dry cyclohexane.
Synthesis of 1: 1 adducts To a weighed amount of tin@) complex was added the calculated amount of pyridine in 1: 1 molar ratio in methanol under an oxygen-free nitrogen atmosphere. The above solution was stirred magnetically for ca * h. The excess solvent was removed and the compound finally dried in uacuo after being repeatedly washed with dry cyclohexane. RESULTS
M.P. “C
AND DISCUSSION
The formation of tin(I1) complexes by the equimolar reactions of tin(H) methoxide and
benzothiazoline and their further adduct formation with pyridine can be depicted by the following equations : Sn(OMe), + ONSH, + Sn(ONS) + 2 MeOH Sn(ONS) + Py + Sn(ONS) * Py (where ONSHz and Py represent the benzothiazoline and pyridine molecules respectively). The resulting new derivatives are coloured solids and found to be soluble in DMF and DMSO. The molar conductance of low3 M solutions of the adducts in DMF lies in the range, 8-14 ohm-’ cm2 mol - I, indicating their non-electrolytic behaviour and the molecular weight determinations indicate their monomeric nature. Electronic spectra The electronic spectra of the ligands show two bands around 250 nm and 315 nm. These bands are consistent with the typical spectrum of benzothiazoline2 (cyclic form) and may be attributed to
Coordination behaviour of benzothiazolines towards stannous ion the +4* and n--k* benzenoid transitionsg*” In the corresponding tin(H) complexes, an additional band around 410 nm due to the nlr* electronic transitions of the azomethine group is also observed. l1 This new band may be due to the isomerization of the ligands on complexation. IR spectra
A comparison of the characteristic IR absorption bands of the benzothiazolines with those of the corresponding tin(I1) complexes reveals the following important features: (1) In the IR spectra of ligands, a strong broad band at 3400-3250 cm- ’ is observed which can be assigned to the association of v (NH) with the phenol& OH vibrations. l2 In the spectra of metal complexes, these bands disappear, indicating the chelation of oxygen as well as nitrogen to the metal atom. (2) A strong band at 1670-1705 cm-’ may be assigned to the N-H deformation vibrations and the absence of v (SH) at - 2500-2600 cm- ’ is indicative of the benzothiazoline rather than the S&&base structure of the ligands. In the spectra of complexes, a new band at - 1605 cm- ’ is observed and which can be assigned to v (C=N) vibrations. The presence of this band clearly indicates that the resulting metal complexes are S&X-base derivatives and these are formed by the rearrangement of the benzothiazoline structure. (3) New bands at - 405 and 360 cm- ’ may be attributed to v (N + Sn) and v (S -+ Sn) bands, while v (0 --, Sn)14isobservedat 645cm-‘inthecomplexes. (4) The formation of the pyridine adduct is evidenced by the appearance of new bands in the region, 650-700 cm- l. Proton magnetic *eSon&ce spectra
The proton magnetic resonance spectra of salicylaldehyde-2-mercaptoanil (H,SSP) and its 1: 1 (SnSSP) derivatives have been recorded in DMSO-d,. The signals at 6 9.25 ppm and 6 4.20 ppm in the case of the ligand are due to the phenolic and NH protons respectively. These, however, disappear from the spectra of tin(I1) complexes indicating the
1313
deprotonation of the functional groups during complexation with the tin atom. The ligand shows a complex multiplet in the region 6 7.40-6.40 ppm for the benzene protons, and it remains at almost the same position in the spectra of the tin(I1) complexes. The proton signal for the azomethine proton at 6 8.30 ppm in the ligand shifts downfield in the spectra of complexes due to the donation of a lone pair ofelectrons by the nitrogen to the central tin atom on account of the formation of a coordinate linkage. Thus on the basis of the above spectral evidence, the following structures can be proposed for the resulting tin(I1) complexes and in which the tin atom is probably in tri- (i) and tetra-coordinated (ii) environments. Acknowledgement-One of us (A.V.) thanks the U.G.C., New Delhi (India) for the financial support. REFERENCES 1. H. Jadamus, R. Fernando and H. Freiser, J. Am. Chem. Sot. 1964,86,3056. 2. R. G. Charles and H. Freiser, J. Org. Chem. 1953,18, 422. 3. P. PfeilTer,W. Offermann and A. Werner, J. Prakt. Chem. 1942,159,313. 4. L. F. Lindoy and S. E. Livingstone, Inorg. Chim. Acta 1967,1,365. 5. R. Gsell and M. Zeldin, J. Inorg. Nucl. Chem. 1975,37, 1133. 6. M. Aggrawal, J. P. Tandon and R. C. Mehrotra, J. Inorg. Nucl. Chem. 1981,43,1070. 7. E. C. Alyea and Abdul Malik, Can. J. Chem. 1975,53, 939. 8. A. Varshney and J. P. Tandon, Indian J. Chem. (in press) (1984). 9. N. S. Biradar, V. B. Mohale and V. H. Kulkami, Znorg. Chim. Acta 1973,7,267.
10. B. Bosnich, J. Am. Chem. Sot. 1968,90,627. 11. G. E. Mecasland and E. C. Horswill, J. Am. Chem. Sot. 1951,73,3923. 12. R. K. Sharma, R. V. Singh and J. P. Tandon, J. Znorg. Nucl. Chem. 1980,42,1267. 13. M. Consiglto, F. Maggie, T. Pizzno and V. Romauo, Inorg. Nucl. Chem. Lutt. 1978,14,135. 14. A. Varshney and J. P. Tandon, Proc. Indian Acad. Sci. (Chem. Sci.) (in press) (1984).
1985 0
0277-5387/85 s3.acl+ .oo 1985 pergsmon Reds Ltd
COORDINATION BEHAVIOUR OF BENZOTHIAZOLINES TOWARDS STANNOUS ION ANIL VARSHNEY and J. P. TANDON* Department of Chemistry, University of Rajasthan, Jaipur-302004, India (Received 19 October 1984; accepted 4 January 1985) Abstract-Bquimolar reactions of tin(H) methoxide with benzothiazolines result in the isolation of a new series of tin(II)comple which further undergo 1: 1 adduct formation with pyridine. The electronic, IR and ‘H NMR spectral studies indicate coordination of tin to the oxygen, azomethine nitrogen and sulphur of the ligand moiety.
The condensation of a o-aminothiophenol with a carbonyl compound does not normally lead to the isolation of the corresponding S&&base, but a benzothiazoline is formed.‘*2 However, in the presence of a metal ion, the cyclic structure of thiazoline or benzothiazoline rearranges to give the S&i&base metal chelate quantitatively.3*4 During the course of the present investigations, an attempt has been made to synthesize tin(H) derivatives by interacting tin(H) methoxide with benzothiazolines derived by the condensation of salicylaldehyde (I), 2hydroxy-1-naphthaldehyde (II), o-hydroxy acetophenone (III), acetylacetone (IV) or benzoyl acetone (V) with o-aminothiophenol. The benzothiazolines used can be structurally depicted as follows :
(Schiff
(Benrothiazoline) R,
=
C6H40H
and
R2
=
II,
R,
=
CmsOH
and
Rp
= H
Et,
R,
=
C6H40H
and
Rp
= CH3(H2A’SP)
I
H
base)
I,
(H2SSP) (t+NSP)
(i)
(ii)
EXPERIMENTAL Tin(H) methoxide was prepared by the reaction of anhydrous SnCl, with an excess of triethylamine in methanol as described by Gsell and Zeldin5 The ligands were prepared by the condensation of aldehydes/ketones with o-aminothiophenol as described earlier.‘j,’ These were purified by recrystallization from ethanol. The complexes were analysed as reported earlier’ and the infrared spectra were recorded on a PerkinElmer 577 IR spectrophotometer in the region, 4000-200 cm-’ using KBr optics. The electro.nic spectra (in methanol) were taken on a Toshniwal spectrophotometer. A Perkin-Elmer (Model RB-12) spectrometer was used for obtaining the PMR spectra employing DMSO-d, as the solvent and TMS as the internal standard Molar conductance measurements were made in anhydrous dimethylformamide at 36 f 1°C using a Systronics Conductivity Bridge Model-305. Molecular weight determinations were carried out by the Rast Method.
/
(Benzothiordine
(Schiff
I
Ip,
R3
=
CH3
Y,
R3
=
CgH5(H2BSPl
base)
lH2ASP)
* To whom all correspondence should be addressed.
Synthesis of tin(II) complexes To a weighed amount of tin(I1) methoxide was added the calculated amount of the ligand in 1: 1 molar ratio using methanol as the reaction medium 1311
1312
A. VARSHNEY and J. P. TANDON Table 1. Synthesis and characteristics of tin(I1) complexes Reactant Tin compound
L&and
Molar ratio
1.
Sn(OMe),
H,SSP
1: 1
2.
Sn(OMe),
H,NSP
1:l
3.
Sn(OMe),
H,A’SP
1: 1
4.
Sn(OMe)z
H,ASP
1: 1
5.
Sn(OMe),
HzBSP
1: 1
6.
SnSSP
Pyridine
1:l
7.
SnNSP
Pyridine
1: 1
8.
SnA’SP
Pyridine
1: 1
9.
&ASP
Pyridine
1: 1
10.
SnBSP
Pyridine
1:l
Where : H,SSP = H2NSP = H,A’SP = H,ASP = H,BSP= s= d=
Compound, colour and state SnSSP Yellow solid SnNSP Green solid SnA’SP Yellow solid SnASP Yellow solid SnBSP Orange solid SnSSP - Py Yellow solid SnNSP * Py Green solid SnA’SP - Py Yellow solid SnASP - Py Yellow solid SnBSP - Py
205s 280d 18Od 230d 195s 260s 315s 310s 210s 200s
Analysis observed (Cal.) Sn N S 33.93 (34.34) 29.73 (29.99) 32.56 (32.99) 35.93 (36.67) 30.53 (30.78) 27.85 (27.95) 24.82 (25.01) 26.84 (27.06) 28.86 (29.48) 24.98 (25.54)
3.85 (4.05) 3.02 (3.54) 3.42 (3.89) 3.86 (4.33) 3.31 (3.63) 5.86 (6.59) 5.35 (5.89) 5.86 (6.38) 6.53 (6.95) 5.86 (6.03)
8.86 (9.26) 7.89 (8.09) 8.43 (8.89) 9.43 (9.89) 7.86 (8.29) 6.94 (7.54) 6.34 (6.74) 6.82 (7.29) 7.64 (7.95) 6.34 (6.89)
Mol. wt. observed (Cal.) 330 (345.7) 370 (395.7) 372 (359.7) 340 (323.7) 400 (385.7) 405 (424.7) 440 (474.7) 415 (438.7) 385 (402.7) 443 (464.7)
salicylaldehyde-2-mercaptoanil 2-hydroxy-1-naphthaldehyde-2-mercaptoanil 2 -hydroxy acetophenone-2-mercapaptoanil a&y1 acetone-2-mercaptoanil benzoylacetone-2-mercaptoanil sharp decomposition.
in an oxygen-free nitrogen atmosphere. Immediately, the colour of the solution changed and it was then stirred magnetically for ca 2 h. The excess of the solvent was removed and the compound finally dried in uacuo at a bath temperature of 35 f5”C after being repeatedly washed with dry cyclohexane.
Synthesis of 1: 1 adducts To a weighed amount of tin@) complex was added the calculated amount of pyridine in 1: 1 molar ratio in methanol under an oxygen-free nitrogen atmosphere. The above solution was stirred magnetically for ca * h. The excess solvent was removed and the compound finally dried in uacuo after being repeatedly washed with dry cyclohexane. RESULTS
M.P. “C
AND DISCUSSION
The formation of tin(I1) complexes by the equimolar reactions of tin(H) methoxide and
benzothiazoline and their further adduct formation with pyridine can be depicted by the following equations : Sn(OMe), + ONSH, + Sn(ONS) + 2 MeOH Sn(ONS) + Py + Sn(ONS) * Py (where ONSHz and Py represent the benzothiazoline and pyridine molecules respectively). The resulting new derivatives are coloured solids and found to be soluble in DMF and DMSO. The molar conductance of low3 M solutions of the adducts in DMF lies in the range, 8-14 ohm-’ cm2 mol - I, indicating their non-electrolytic behaviour and the molecular weight determinations indicate their monomeric nature. Electronic spectra The electronic spectra of the ligands show two bands around 250 nm and 315 nm. These bands are consistent with the typical spectrum of benzothiazoline2 (cyclic form) and may be attributed to
Coordination behaviour of benzothiazolines towards stannous ion the +4* and n--k* benzenoid transitionsg*” In the corresponding tin(H) complexes, an additional band around 410 nm due to the nlr* electronic transitions of the azomethine group is also observed. l1 This new band may be due to the isomerization of the ligands on complexation. IR spectra
A comparison of the characteristic IR absorption bands of the benzothiazolines with those of the corresponding tin(I1) complexes reveals the following important features: (1) In the IR spectra of ligands, a strong broad band at 3400-3250 cm- ’ is observed which can be assigned to the association of v (NH) with the phenol& OH vibrations. l2 In the spectra of metal complexes, these bands disappear, indicating the chelation of oxygen as well as nitrogen to the metal atom. (2) A strong band at 1670-1705 cm-’ may be assigned to the N-H deformation vibrations and the absence of v (SH) at - 2500-2600 cm- ’ is indicative of the benzothiazoline rather than the S&&base structure of the ligands. In the spectra of complexes, a new band at - 1605 cm- ’ is observed and which can be assigned to v (C=N) vibrations. The presence of this band clearly indicates that the resulting metal complexes are S&X-base derivatives and these are formed by the rearrangement of the benzothiazoline structure. (3) New bands at - 405 and 360 cm- ’ may be attributed to v (N + Sn) and v (S -+ Sn) bands, while v (0 --, Sn)14isobservedat 645cm-‘inthecomplexes. (4) The formation of the pyridine adduct is evidenced by the appearance of new bands in the region, 650-700 cm- l. Proton magnetic *eSon&ce spectra
The proton magnetic resonance spectra of salicylaldehyde-2-mercaptoanil (H,SSP) and its 1: 1 (SnSSP) derivatives have been recorded in DMSO-d,. The signals at 6 9.25 ppm and 6 4.20 ppm in the case of the ligand are due to the phenolic and NH protons respectively. These, however, disappear from the spectra of tin(I1) complexes indicating the
1313
deprotonation of the functional groups during complexation with the tin atom. The ligand shows a complex multiplet in the region 6 7.40-6.40 ppm for the benzene protons, and it remains at almost the same position in the spectra of the tin(I1) complexes. The proton signal for the azomethine proton at 6 8.30 ppm in the ligand shifts downfield in the spectra of complexes due to the donation of a lone pair ofelectrons by the nitrogen to the central tin atom on account of the formation of a coordinate linkage. Thus on the basis of the above spectral evidence, the following structures can be proposed for the resulting tin(I1) complexes and in which the tin atom is probably in tri- (i) and tetra-coordinated (ii) environments. Acknowledgement-One of us (A.V.) thanks the U.G.C., New Delhi (India) for the financial support. REFERENCES 1. H. Jadamus, R. Fernando and H. Freiser, J. Am. Chem. Sot. 1964,86,3056. 2. R. G. Charles and H. Freiser, J. Org. Chem. 1953,18, 422. 3. P. PfeilTer,W. Offermann and A. Werner, J. Prakt. Chem. 1942,159,313. 4. L. F. Lindoy and S. E. Livingstone, Inorg. Chim. Acta 1967,1,365. 5. R. Gsell and M. Zeldin, J. Inorg. Nucl. Chem. 1975,37, 1133. 6. M. Aggrawal, J. P. Tandon and R. C. Mehrotra, J. Inorg. Nucl. Chem. 1981,43,1070. 7. E. C. Alyea and Abdul Malik, Can. J. Chem. 1975,53, 939. 8. A. Varshney and J. P. Tandon, Indian J. Chem. (in press) (1984). 9. N. S. Biradar, V. B. Mohale and V. H. Kulkami, Znorg. Chim. Acta 1973,7,267.
10. B. Bosnich, J. Am. Chem. Sot. 1968,90,627. 11. G. E. Mecasland and E. C. Horswill, J. Am. Chem. Sot. 1951,73,3923. 12. R. K. Sharma, R. V. Singh and J. P. Tandon, J. Znorg. Nucl. Chem. 1980,42,1267. 13. M. Consiglto, F. Maggie, T. Pizzno and V. Romauo, Inorg. Nucl. Chem. Lutt. 1978,14,135. 14. A. Varshney and J. P. Tandon, Proc. Indian Acad. Sci. (Chem. Sci.) (in press) (1984).