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Electrometric study on La(III) and Ce(III) complexes of furfuryl mercaptan
Notes
3963
the intensity in the region of maximum absorption is decreased markedly with increasing polarity indicating the extensive decrease in enethiol contents. Table 4. Spectral data of some disubstituted dithiobiurets and their sodium derivatives in ethanol '~max
Compound
ET
(nm)
Emax
(kcal/mole)
DPH Na(DP)
289-0 292-0
25,190 18,850
98.93 97.90
DPTH Na(D PT)
285.0 288.0
24,905 18,110
100.30 99.22
POTH Na(POT)
290-0 294.0
17,984 15,850
98.58 97-25
PPTH Na(PPT)
288.0 291.0
21,529 19,325
99.22 98.24
M PTH Na(M PT)
283-0 287.0
22,600 20,510
l 01.00 99.61
Acknowledgements--The thanks of the authors are due to the authorities of B.I.T.S., Pilani for providing necessary facilities.
Department of Chemistry Birla Institute of Technology and Science, Pilani (Rajasthan), India
NARESH K. AGARWAL ARJUN D. TANEJA K. P. SRIVASTAVA
J. inorg, nucl. Chem., 1973, Vol. 35, pp. 3963-3966. Pergamon Press. Printed in Great Britain.
Eiectrometric study on La(IED and Ce(IID complexes of furfuryl mercaptan (Received 21 December 1972) MERCAPTO compounds containing an active -SH group have a wide range of applications including biological, pharmaceutical, industrial and other chemical uses and are well known for their tendency to form complexes with metals. The polarographic behaviour of several such compounds and their metal complexes[I-4] have already been studied in these laboratories. This communication describes the composition and stability constants of La(III) and C¢(III) complexes of fuffuryl mercaptan and the values of AG, AH and AS accompanying the complexation reaction. The literature is, however, silent on this study and hence the present investigation has been undertaken. 1. 2. 3. 4.
R. R. R. R.
S. Saxena and S. Saxena and S. Saxena and S. Saxena and
K. K. U. U.
C. Gupta, Can. J. Chem. 46, 311 (1968). C. Gupta, Aust. J. Chem. 21,641 (1968). S. Chaturvedi, Experientia Suppli. 18, 538 (1971). S. Chaturvedi, J. inorg, nucl. Chem. 34, 2964 (1972).
3964
Notes
EXPERIMENTAL Furfuryl mercaptan (referred herein as FSH) was supplied by Evan's Chemetics, Inc., N.Y. All other chemicals were of Anal-R (BDH) grade. In order to avoid the effects of ageing and air-oxidation, freshly prepared solutions were always used. The study was made in 50 per cent ethanofic media and at an ionic strength of 0.1 M maintained by NaCIO4. A Cambridge Bench type pH meter with a glass-calomel electrode assembly and an electronic eye type conductometer were used for potentiometric and conductometric titrations respectively. The experimental procedure involved a series of potentiometric and conductometric titrations of the solutions conraining metal and ligand mixed in different ratios against standard alkali and Calvin and Melchior's extension of Bjerrum's method was employed for the determination of stability constants of the complexes. RESULTS AND DISCUSSION
Stoichiornetry The stoichiometry of La(IlI) and Ce(IIl) complexes with FSH was established by potentiometric and conductometric titrations of the solutions containing different moles of ligand per mole of metal ion against 0-1 M NaOH. On the addition of NaOH to the ligand solution, the sudden rise in pH was observed indicating the non-titrability of the proton of -SH group under the experimental conditions. The addition of an equimolar concentration of metal ion greatly alters the shape of the free ligand titration curve indicating the complex formation which results in the lowering of buffer region due to the proton displacement. Since the extent of the proton displacement depends on the relative affinities of the ligand for H + and metal ion, it is obvious from the buffer region at pH ~ 74) that the affinity for La 3+ or Ce a÷ is not enough to compete with the concentration of H + up to pH 7 beyond which the affinity of ligand for these metals increases and hence a considerable lowering in buffer region starts. The appearance of a precipitate and the inflection at m = 3.0 show the formation of 1 : 3 complex accompanied by the formation of metal hydroxide as given below : M 3+ + FSH + 3 O H - ~ M ( F S ) a + tM(OH)a + HOH where M stands for La or Ce.
12'O ~
O
~ e ^
d
c
,o.o / / ? ' ; f '~ pH
2-,'
/
,
d
8"0
6-0 4.0
Z.O
O.O
I
I.O
I
2.0
I
3.0
I
4.0
mole of NoOH / mole of FSH Fig. 1. pH titrations of (a) 4-0 m-mole FSH, (b) 4-0 m-mole FSH + 4-0 m-mole La(NOa)a, (c) 44) m-mole FSH + 2.0 m-mole La(NOa) a, (d) 4.0 m-mole FSH + 1.33 m-mole La(NOa)a and (¢) 4.0 m-mole FSH + 1.0 m-mole La(NO3)a against 0-1 mole NaOH.
(1)
Notes
3965
The formation of M(FS)3 as the highest complex was further confirmed by the inflections at m - 1-5, 1~ and 0-75 when the metal and ligand were mixed in the ratio 1:2, 1:3 and 1:4 respectively. The pH titration curves of ligand solution in absence and presence of La 3+ are shown in Fig. 1. Similar curves were obtained for Ce 3+. The solutions containing ligand and metal in different ratios were also titrated conductometricaily against standard NaOH. The breaks in the curves correspond to the formation of 1 : 3 complex as obtained in pH titrations. Stability constants Calvin and Melchior's[5] extension of Bjerrum's[6] method has been employed for the determination of stability constants of the complexes. The pH titrations of FSH solution in absence and presence of
3.0
~
'(b)
(a)
2-0
1.0--
0.0 3"5
t
L
J
I
4"0
4"5
5"0
5"5
-,og
[A]
Fig. 2. Formation curves at 25°C for (a) La and (b) Ce complexes of FSH.
Table 1. Stability constants and thermodynamic functions for La(III) and Ce(III) complexes of furfuryl mercaptan
Temp. (*C) 25 35 45
La-complexes log K 1 log K 3 (1:1) (1:3) 4-70 4-66 4.58
AG(K cai/mole) AH(K cal/mole) AS(cal/mole/deg)
4.07 4.03 3.98 - 12'27 - 4.37 25.65
Ce complexes log K 1 log K 3 (1:1) (1:3) 5.10 5.03 4.97
4-56 4.52 4-49 - 13-42 - 4-39 29.32
5. M. Calvin and N. C. Melchior, J. Am. chem. Soc. 70, 3270 (1948). 6. J. Bjerrum, Metal Amine Formation in Aqueous Solution. P. Hasse, Copenhagen (1941).
3966
Notes
metal ion were carried out at 25, 35 and 45"C against 0.1 M NaOH and the concentration of bound ligand calculated from the horizontal distance between the corresponding curves was divided by the total metal ion concentration to obtain ~ values. At any pH, the value of [A] was calculated from the relation [A] = [FSH]tomt - [FSH]~u. d [H+---~]+ 1
(2)
Ka
where Ko is the dissociation constant of FSH (pK a = 10.10). The formation curves obtained at different temperatures by plotting h vs - l o g [A] reveal the formation of 1:1 and 1:3 complexes for both the metals. The formation curves at 25°C are shown in Fig. 2 and the log Kst~b values of the complexes have been summarized in Table 1. The stabilities follow the order Ce > La.
Thermodynamic functions The values of change in free energy (AG), enthalpy (AH) and entropy (AS) accompanying the complexation reaction have been determined at 35°C for both the systems by applying the standard equations[7] and are given in Table 1.
Department of Chemistry Malaviya Regional Engineering College Jaipur India
R.S. SAXENA S.S. SHEELWANT
7. K. B. Yatsimirskii and V. P. Vasil'Ev, Instability Constants of Complex Compounds. Pergamon Press, Oxford (1960).
J. inorg,nucl. Chem., 1973,Vol. 35, pp. 3966-3968. PergamonPress. Printed in Great Britain.
Thiol derivatives of tricyclopentadienyl cerium(IV) and bishsienyl cerium(IV) (First received 5 January 1973 ; in revised form 26 January 1973) IN CONTINUATIONof our earlier work on the preparation of pseudohalide[ 1], alkyl and aryl[2], carboxyl[3], phenoxy[4] and borohydride[5] derivatives of tricyclopentadienyl cerium(IV) chloride and bisindenyl cerium(IV) dichloride, the preparation and characterization of thiol derivatives of tricyclopentadienyl cerium(IV) and bisindenyl cerium(IV) are reported in this paper. These compounds have been prepared by the interaction of tricyclopentadienyl cerium(IV) chloride and bisindenyl cerium(IV) dichloride with various thiols to give complexes of the type (CsHs)3Ce(R) and (C9HT)2Ce(R)2 wherein R may be SCH3, SC2H5, SC3H~, SC3H~, SC4H[, SC4H~ and SC5 H~ 1 groups. These compounds are generally dark brown in colour, sensitive to moisture, are stable in dry and inert atmosphere. These compounds are nonvolatile, do not sublime even in vacuum and are soluble in common organic solvents viz. acetone, alcohol, benzene, dimethyl formamide, dichloro methane, chloroform, carbon tetrachloride and insoluble in water. 1. 2. 3. 4. 5.
B. L. Kalsotra, R. K. Multani and B. D. Jain, J. inorg, nucl. Chem. 34, 2265 (1972). B. L. Kalsotra, R. K. Multani and B. D. Jain, J. inorg, nucL Chem. In press. B. L. Kalsotra, R. K. Multani and B. D. Jain, J. Chinese chem. Soc. 18, 189 (1971). Shushma Kapur, B. L. Kalsotra and R. K. Multani, J. Chinese chem. Soc. 20, 49 (1972). Shushma Kapur, B. L. Kalsotra, R. K. Multani and B. D. Jain, J. inorg, nucl. Chem. In press.
3963
the intensity in the region of maximum absorption is decreased markedly with increasing polarity indicating the extensive decrease in enethiol contents. Table 4. Spectral data of some disubstituted dithiobiurets and their sodium derivatives in ethanol '~max
Compound
ET
(nm)
Emax
(kcal/mole)
DPH Na(DP)
289-0 292-0
25,190 18,850
98.93 97.90
DPTH Na(D PT)
285.0 288.0
24,905 18,110
100.30 99.22
POTH Na(POT)
290-0 294.0
17,984 15,850
98.58 97-25
PPTH Na(PPT)
288.0 291.0
21,529 19,325
99.22 98.24
M PTH Na(M PT)
283-0 287.0
22,600 20,510
l 01.00 99.61
Acknowledgements--The thanks of the authors are due to the authorities of B.I.T.S., Pilani for providing necessary facilities.
Department of Chemistry Birla Institute of Technology and Science, Pilani (Rajasthan), India
NARESH K. AGARWAL ARJUN D. TANEJA K. P. SRIVASTAVA
J. inorg, nucl. Chem., 1973, Vol. 35, pp. 3963-3966. Pergamon Press. Printed in Great Britain.
Eiectrometric study on La(IED and Ce(IID complexes of furfuryl mercaptan (Received 21 December 1972) MERCAPTO compounds containing an active -SH group have a wide range of applications including biological, pharmaceutical, industrial and other chemical uses and are well known for their tendency to form complexes with metals. The polarographic behaviour of several such compounds and their metal complexes[I-4] have already been studied in these laboratories. This communication describes the composition and stability constants of La(III) and C¢(III) complexes of fuffuryl mercaptan and the values of AG, AH and AS accompanying the complexation reaction. The literature is, however, silent on this study and hence the present investigation has been undertaken. 1. 2. 3. 4.
R. R. R. R.
S. Saxena and S. Saxena and S. Saxena and S. Saxena and
K. K. U. U.
C. Gupta, Can. J. Chem. 46, 311 (1968). C. Gupta, Aust. J. Chem. 21,641 (1968). S. Chaturvedi, Experientia Suppli. 18, 538 (1971). S. Chaturvedi, J. inorg, nucl. Chem. 34, 2964 (1972).
3964
Notes
EXPERIMENTAL Furfuryl mercaptan (referred herein as FSH) was supplied by Evan's Chemetics, Inc., N.Y. All other chemicals were of Anal-R (BDH) grade. In order to avoid the effects of ageing and air-oxidation, freshly prepared solutions were always used. The study was made in 50 per cent ethanofic media and at an ionic strength of 0.1 M maintained by NaCIO4. A Cambridge Bench type pH meter with a glass-calomel electrode assembly and an electronic eye type conductometer were used for potentiometric and conductometric titrations respectively. The experimental procedure involved a series of potentiometric and conductometric titrations of the solutions conraining metal and ligand mixed in different ratios against standard alkali and Calvin and Melchior's extension of Bjerrum's method was employed for the determination of stability constants of the complexes. RESULTS AND DISCUSSION
Stoichiornetry The stoichiometry of La(IlI) and Ce(IIl) complexes with FSH was established by potentiometric and conductometric titrations of the solutions containing different moles of ligand per mole of metal ion against 0-1 M NaOH. On the addition of NaOH to the ligand solution, the sudden rise in pH was observed indicating the non-titrability of the proton of -SH group under the experimental conditions. The addition of an equimolar concentration of metal ion greatly alters the shape of the free ligand titration curve indicating the complex formation which results in the lowering of buffer region due to the proton displacement. Since the extent of the proton displacement depends on the relative affinities of the ligand for H + and metal ion, it is obvious from the buffer region at pH ~ 74) that the affinity for La 3+ or Ce a÷ is not enough to compete with the concentration of H + up to pH 7 beyond which the affinity of ligand for these metals increases and hence a considerable lowering in buffer region starts. The appearance of a precipitate and the inflection at m = 3.0 show the formation of 1 : 3 complex accompanied by the formation of metal hydroxide as given below : M 3+ + FSH + 3 O H - ~ M ( F S ) a + tM(OH)a + HOH where M stands for La or Ce.
12'O ~
O
~ e ^
d
c
,o.o / / ? ' ; f '~ pH
2-,'
/
,
d
8"0
6-0 4.0
Z.O
O.O
I
I.O
I
2.0
I
3.0
I
4.0
mole of NoOH / mole of FSH Fig. 1. pH titrations of (a) 4-0 m-mole FSH, (b) 4-0 m-mole FSH + 4-0 m-mole La(NOa)a, (c) 44) m-mole FSH + 2.0 m-mole La(NOa) a, (d) 4.0 m-mole FSH + 1.33 m-mole La(NOa)a and (¢) 4.0 m-mole FSH + 1.0 m-mole La(NO3)a against 0-1 mole NaOH.
(1)
Notes
3965
The formation of M(FS)3 as the highest complex was further confirmed by the inflections at m - 1-5, 1~ and 0-75 when the metal and ligand were mixed in the ratio 1:2, 1:3 and 1:4 respectively. The pH titration curves of ligand solution in absence and presence of La 3+ are shown in Fig. 1. Similar curves were obtained for Ce 3+. The solutions containing ligand and metal in different ratios were also titrated conductometricaily against standard NaOH. The breaks in the curves correspond to the formation of 1 : 3 complex as obtained in pH titrations. Stability constants Calvin and Melchior's[5] extension of Bjerrum's[6] method has been employed for the determination of stability constants of the complexes. The pH titrations of FSH solution in absence and presence of
3.0
~
'(b)
(a)
2-0
1.0--
0.0 3"5
t
L
J
I
4"0
4"5
5"0
5"5
-,og
[A]
Fig. 2. Formation curves at 25°C for (a) La and (b) Ce complexes of FSH.
Table 1. Stability constants and thermodynamic functions for La(III) and Ce(III) complexes of furfuryl mercaptan
Temp. (*C) 25 35 45
La-complexes log K 1 log K 3 (1:1) (1:3) 4-70 4-66 4.58
AG(K cai/mole) AH(K cal/mole) AS(cal/mole/deg)
4.07 4.03 3.98 - 12'27 - 4.37 25.65
Ce complexes log K 1 log K 3 (1:1) (1:3) 5.10 5.03 4.97
4-56 4.52 4-49 - 13-42 - 4-39 29.32
5. M. Calvin and N. C. Melchior, J. Am. chem. Soc. 70, 3270 (1948). 6. J. Bjerrum, Metal Amine Formation in Aqueous Solution. P. Hasse, Copenhagen (1941).
3966
Notes
metal ion were carried out at 25, 35 and 45"C against 0.1 M NaOH and the concentration of bound ligand calculated from the horizontal distance between the corresponding curves was divided by the total metal ion concentration to obtain ~ values. At any pH, the value of [A] was calculated from the relation [A] = [FSH]tomt - [FSH]~u. d [H+---~]+ 1
(2)
Ka
where Ko is the dissociation constant of FSH (pK a = 10.10). The formation curves obtained at different temperatures by plotting h vs - l o g [A] reveal the formation of 1:1 and 1:3 complexes for both the metals. The formation curves at 25°C are shown in Fig. 2 and the log Kst~b values of the complexes have been summarized in Table 1. The stabilities follow the order Ce > La.
Thermodynamic functions The values of change in free energy (AG), enthalpy (AH) and entropy (AS) accompanying the complexation reaction have been determined at 35°C for both the systems by applying the standard equations[7] and are given in Table 1.
Department of Chemistry Malaviya Regional Engineering College Jaipur India
R.S. SAXENA S.S. SHEELWANT
7. K. B. Yatsimirskii and V. P. Vasil'Ev, Instability Constants of Complex Compounds. Pergamon Press, Oxford (1960).
J. inorg,nucl. Chem., 1973,Vol. 35, pp. 3966-3968. PergamonPress. Printed in Great Britain.
Thiol derivatives of tricyclopentadienyl cerium(IV) and bishsienyl cerium(IV) (First received 5 January 1973 ; in revised form 26 January 1973) IN CONTINUATIONof our earlier work on the preparation of pseudohalide[ 1], alkyl and aryl[2], carboxyl[3], phenoxy[4] and borohydride[5] derivatives of tricyclopentadienyl cerium(IV) chloride and bisindenyl cerium(IV) dichloride, the preparation and characterization of thiol derivatives of tricyclopentadienyl cerium(IV) and bisindenyl cerium(IV) are reported in this paper. These compounds have been prepared by the interaction of tricyclopentadienyl cerium(IV) chloride and bisindenyl cerium(IV) dichloride with various thiols to give complexes of the type (CsHs)3Ce(R) and (C9HT)2Ce(R)2 wherein R may be SCH3, SC2H5, SC3H~, SC3H~, SC4H[, SC4H~ and SC5 H~ 1 groups. These compounds are generally dark brown in colour, sensitive to moisture, are stable in dry and inert atmosphere. These compounds are nonvolatile, do not sublime even in vacuum and are soluble in common organic solvents viz. acetone, alcohol, benzene, dimethyl formamide, dichloro methane, chloroform, carbon tetrachloride and insoluble in water. 1. 2. 3. 4. 5.
B. L. Kalsotra, R. K. Multani and B. D. Jain, J. inorg, nucl. Chem. 34, 2265 (1972). B. L. Kalsotra, R. K. Multani and B. D. Jain, J. inorg, nucL Chem. In press. B. L. Kalsotra, R. K. Multani and B. D. Jain, J. Chinese chem. Soc. 18, 189 (1971). Shushma Kapur, B. L. Kalsotra and R. K. Multani, J. Chinese chem. Soc. 20, 49 (1972). Shushma Kapur, B. L. Kalsotra, R. K. Multani and B. D. Jain, J. inorg, nucl. Chem. In press.