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Thermal studies on germanium(IV) complexes of N-alkylcyclohexyl dithiocarbamates
thermochimica acta ELSEVIER
Thermochimica Acta 282/283 (1996) W-508
Thermal studies on germanium(IV) complexes of N-alkylcyclohexyl dithiocarbamates’ Namita
Gandhi,
Reena Jain, N.K. Kaushik
Department
of Chemistry,Delhi
University,
Delhi-210007,
*
India
Abstract Ge(IV) complexes of N-alkylcyclohexyl dithiocarbamates of the type Ge[RCyhxdtc],Cl, _n (Cyhx is cyclohexyl, R is Me, n = 1; R is Pr’, n = 1,4) have been synthesized and characterized by elemental and spectral studies (IR, UV-visible). The course of the thermal degradation of these complexes has been investigated using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The reaction order of the thermal decomposition was calculated from the TG curves using the Coats-Redfern, Piloyan-Novikova and Horowitz-Metzger methods. Heat of reactions of various steps of decomposition and calibration constants were calculated from the DTA curves. Keywords:
Germanium
(IV) complexes;
Dithiocarbamates;
Thermal
studies
1. Introduction The dithiocarbamates are a class of sulphur-donor ligands [l]. Interest in metal dithiocarbamate complexes derives from their diversified applications, including vulcanization accelerators, antioxidants and, in the biochemical field, correction of
chronic alcoholism, insecticides, pesticides and fungicides [2]. rnmnnllnrlr of 6V”“U”‘ l%=rmlnillm are ErlrI-P althn,,nh ~nme U”’ with .I 1111 clithinlimgnclc U’L”‘““&U”UU UVULvv ..,““‘~“U”UU U’ C”“U~” cI”LIl” organogermanium dithiocarbamates have been prepared [l]. The synthesis, IR and Raman spectra of (Me),M(MeDtc) complexes, where M is Si, Ge, Sn, have
* Corresponding author. ’Dedicated to Takeo Ozawa on the Occasion of his 65th Birthday. 0040-6031/96/$15.00
PII
@; 1996 ~
SOO40-6031(96)02880-8
Elsevier Science B.V. All rights reserved
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N. Gandhi et al.lThermochimica
Acta 2821283 (I 996) 501-508
503
chromophore group NCS, [14]. Band I in the 240 nm region is most intense and it attributed to the intraligand ~-7-r* transition of the N=C=S group [l&16]. Band II in the 300 nm region appears as a shoulder and is assigned to the n-z* electronic transition located on the S atom [16]. In the case of complex Ge[S,CNPr’Cyhx],, the co-planarity of the molecule is lost due to the four bulky groups. Consequently the n--n* transition of the N---C---S group is absent and two bands at 206 and 307 nm are observed. In the IR spectra, the 1430- 1440 cm ’region is assigned to the v (C-N) vibration of the S,C-NR, bond. The doublet in the region of lOOO- 1060 cm- ’ is associated with v (C--S) vibrations. The doublet separated by > 20 cm _ ’is indicative of the monodentate nature of the ligand [17].
4. Thermal studies 4.1. Results and discussion 4.1 .I Trichloro (N-methylcyclohexyl dithiocarbamato) germanium(IV) The TG curve for this complex (Fig. 1, curve a) shows that almost 50% mass loss occurs up to 673 K. The initial thermal decomposition step is over the range 400-673 K. At this temperature, the intermediate Ge(SCN),Cl, was formed (calculated Mass loss, 28.1%; found, 30%). The subsequent step at 956 K shows a mass loss; germanium oxide (GeO,) is the end product (calculated mass loss 71.50%; observed, 73%). The DTA curve (Fig. 2, curve a) shows an exothermic peak at T,,, = 605.8 K, which is due to the formation of Ge (SCN), Cl,. An endothermic peak at 872.6 K corresponds to complete decomposition of the complex [9].
0
Fig. 1. TG curves:
200
400 TEMPERATURE
a, Ge[S,CNMeCyhx]Cl,;
600 ( *Cl
000
___+
b,Ge[S,CNPr’Cyhx]Cl,;
c, Ge[S,CNPr’Cyhx],.
N. Gandhi et al./Thermochimica
504
Acta 2821283 (1996) 501-508
1 END0
0
I
I
I
200
400
600
TEMPERATURE
Fig. 2. DTA curves:
a, Ge[S,CNMeCyhx]Cl,;
(‘C)
-
b, Ge[S,CNPr’Cyhx]Cl,;
c, Ge[S,CNPr’Cyhx],
4.1.2. Trichloro (N-isopropyl cyclohexyl dithiocarbamato) germanium(ZV) The TG curve (Fig. 1, curve b) for this complex shows a gradual initial mass loss which accelerates around 454 K and terminates around 545 K. The curve shows almost 50% mass loss at this temperature. At 545 K, the intermediate Ge (SCN),Cl, is formed (calculated mass loss, 33.3%; found, 35%). A further mass loss is observed in the second step to 1073 K. GeO, is the final product after decomposition but the mass loss should be 73.59% (calculated) and actually it is found out to be 65% from the thermogram, which suggests incomplete conversion to oxide at 1073 K. The DTA profile (Fig. 2 curve b) shows a shallow endothermic peak at 493 K, which is due to the initial decomposition of the complex. There is a small exothermic peak at 553 K which is due to further reaction of the intermediate. 4.1.3. Tetrakis (N-isopropyl cyclohexyl dithiocarbamato) yermanium(ZV) The TG curve (Fig. 1, curve c) for this complex shows a completely different trend. The thermal decomposition commences with the increase in temperature. The compound is highly volatile and by 550 K, 100% of the complex is volatilized. The DTA profile (Fig. 2, curve c) for this complex shows an endothermic peak at T max= 483 K, which is due to melting of the complex. The second endothermic peak is = 538.8 K, which is due to the volatilization of the complex. at T,,, Thus from the TG trends it is revealed that the thermal stability of the complexes is in the order: Ge(S,CNPr’Cyhx), < Ge(S,CNMeCyhx)Cl, < Ge(S,CNPr’Cyhx)Cl,. From the TG curves, the reaction order (n) for the first thermal decomposition step has been determined by the methods of Coats and Redfern (Figs. 3 and 4) [lS], Piloyan and Novikova (Figs. 5 and 6) [19] and Horowitz and Metzger (Figs. 7 and 8) [20]. The heat of reaction (AH) can be read directly in microvolts from the DTA curve, obtained from the computer attached to thermoanalyser; this can be converted to kJ
0 0
-/
0
L-
I 2.129
I 2.128
1
2.127
p
Fig. 3. Coats-Redfern
I
I
2.139
-
plot for Ge[S,CNMeCyhx]CI,.
60
b
. ,L-------+.
/
,
18
Fig. 4. Coats-Redfern
I.9
20 lx 103 r
22
21
,
plot for: a, Ge[S,CNPr’Cyhx]Cl,;
b, Ge[S,CNPr’Cyhx:
N. Gandhi et ul./Thermochimica
506
Actu 2821283 (1996) 501-508
1x103 r
2.126 t
-5.5
2.127
,
2x0
2,129
I
-
Fig. 5. Piloyan-Novkova
plot for: Ge[S,CNMeCyhx]Cl,.
-56
Fig. 6. Piloyan-Novikova
plot for: a, Ge[S,CNPr’Cyhx]Cl,;
b, Ge[S,CNPr’Cyhx],.
N. Gandhi et al.lThermochimica
507
Acta 2821283 (1996) 501-508
-0.3 _I
Fig. 7. Horowitz-Metzger
plot for Ge[S,CNMeCyhx]CI,.
b
I
-II1
-110
x)
Fig. 8 Horowitz-Metzger
mol-’
ul
(-8)-
+-----c-e)
plot for: a, Ge[S,CNPr’Cyhx]CI,;
b, Ge[S,CNPr’Cyhx],
using the expression AH(kJ mol- I) = AH (pV) x 60 x mol.wt. x 10-6/1000
The temperature-dependent tion [21]
calibration
constant
K = - 1.3 x 10m4 x peak temperature The kinetic parameters
are summarized
was obtained
+ 0.2200
in Table 2.
from the Currel equa-
508
N. Gandhi et al.lThermochimica
Table 2 Kinetic parameters
of the complexes
Acta 2821283 (1996) 501-508
for the first step of thermal
decomposition
No.
Compound
Calibration constant K/(kJ cm-‘)
Equations
Order of reaction n
Heat of reaction AH/(kJ mol ‘)
1.
Ge[S,CNMeCyhx]CI,
0.1412
Ge[S,CNPr’Cyhx]Cl,
0.1481
1 1 1 1
AH, = 20.049 x IO-’ AH, = 10.3178 x lo.-’
2.
Coats-Redfern PiloyanNovikova Horowitz-Metzger Coats-Redfern PiloyanNovikova Horowitz-Metzger Coats-Redfern Piloyan-Novikova Horowitz-Metzger
1 1
Not recorded
3.
Ge[S,CNPr’Cyhx],
0.1572
1 1 1
AH=
11.24526x
lo-’
References and S.J. Lippard (Eds.), Progress in Inorganic Chemistry, Vol. XI, Interscience, Ill D. Coucouvanis London, 1970, p. 233. and Related Compounds, Elsevier, New York, PI G.D. Thorn and R.A. Ludwig, the Dithiocarbamates 1962. and S.J. Lippard (Eds.), Progress in Inorganic Chemistry, Vol. 26, Interscience, [31 D. Coucouvanis London, 1979, p. 301. M S. Kato and M. Mizuta, J. Org. Met. Chem., 55 (1973) 121. c51 M.A. Bernard and M.M. Borel, Bull. Sot. Chim. Fr., (1969) 3066. 161 G.D. Ascenzo and W.W. Wendlandt, J. Therm. Anal., 1 (1969) 423. c71 S. Kumar, N.K. Kaushik and I.P. Mittal, in W. Hemminger (Ed.), Thermal Analysis, Proc. 6th ICTA, Bayreuth, 1980, Birkueuser Verlag, Basel, 1980, p. 137. Acta, 41 (1980) 19. PI S. Kumar and N.K. Kaushik, Thermochim. Acta, 106 (1986) 233. c91 S.S. Gupta and N.K. Kaushik, Thermochim. Delhi, 1985. [lOI T.N. Srivastava and P.C. Kamboj, Systematic Analytical Chem, Vishal Publications, p. 366. of Organometallic Compounds, Part 1, Interscience Publications, Cl11 M. Tsutsui, Characterization London, 1969, p. 62. Cl21 H. Gilman and A.H. Blatt, Organic Synthesis, Collective Vol. 1, Wiley, New York, 1958, p. 448. Cl31 S.A.A. Zaidi, K.S. Siddiqui and N. Islam, Indian J. Chem., 12 (1974) 1197. 1141 C.K. Jorgenson, Inorganic Complexes, Academic Press, London, 1963, p. 138. Cl51 C.K. Jorgenson, J. Inorg. Nucl. Chem., 24 (1962) 1571. Inorg. Chim. Acta, 18 (1976) 35. Cl61 C.A. Tsipis and G.E. Manoussakis, Cl71 F. Bonati and R. Ugo, J. Org. Met. Chem., 10 (1976) 257. 1181A.W. Coats and J.P. Redfern, Nature, 201 (1964) 68. Cl91 G.D. Piloyan and I.S. Novikova, Russ. J. Inorg. Chem., 12 (1967) 313. 1201 H. Horowitz and G. Metzger, Anal. Chem., 35 (1964) 1464. c211 B.R. Currel, in R.F. Schwenker and P.D. Garn (Eds.), Thermal Analysis, Vol. 3 Academic Press, New York, 1969, p. 1185.
Thermochimica Acta 282/283 (1996) W-508
Thermal studies on germanium(IV) complexes of N-alkylcyclohexyl dithiocarbamates’ Namita
Gandhi,
Reena Jain, N.K. Kaushik
Department
of Chemistry,Delhi
University,
Delhi-210007,
*
India
Abstract Ge(IV) complexes of N-alkylcyclohexyl dithiocarbamates of the type Ge[RCyhxdtc],Cl, _n (Cyhx is cyclohexyl, R is Me, n = 1; R is Pr’, n = 1,4) have been synthesized and characterized by elemental and spectral studies (IR, UV-visible). The course of the thermal degradation of these complexes has been investigated using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The reaction order of the thermal decomposition was calculated from the TG curves using the Coats-Redfern, Piloyan-Novikova and Horowitz-Metzger methods. Heat of reactions of various steps of decomposition and calibration constants were calculated from the DTA curves. Keywords:
Germanium
(IV) complexes;
Dithiocarbamates;
Thermal
studies
1. Introduction The dithiocarbamates are a class of sulphur-donor ligands [l]. Interest in metal dithiocarbamate complexes derives from their diversified applications, including vulcanization accelerators, antioxidants and, in the biochemical field, correction of
chronic alcoholism, insecticides, pesticides and fungicides [2]. rnmnnllnrlr of 6V”“U”‘ l%=rmlnillm are ErlrI-P althn,,nh ~nme U”’ with .I 1111 clithinlimgnclc U’L”‘““&U”UU UVULvv ..,““‘~“U”UU U’ C”“U~” cI”LIl” organogermanium dithiocarbamates have been prepared [l]. The synthesis, IR and Raman spectra of (Me),M(MeDtc) complexes, where M is Si, Ge, Sn, have
* Corresponding author. ’Dedicated to Takeo Ozawa on the Occasion of his 65th Birthday. 0040-6031/96/$15.00
PII
@; 1996 ~
SOO40-6031(96)02880-8
Elsevier Science B.V. All rights reserved
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N. Gandhi et al.lThermochimica
Acta 2821283 (I 996) 501-508
503
chromophore group NCS, [14]. Band I in the 240 nm region is most intense and it attributed to the intraligand ~-7-r* transition of the N=C=S group [l&16]. Band II in the 300 nm region appears as a shoulder and is assigned to the n-z* electronic transition located on the S atom [16]. In the case of complex Ge[S,CNPr’Cyhx],, the co-planarity of the molecule is lost due to the four bulky groups. Consequently the n--n* transition of the N---C---S group is absent and two bands at 206 and 307 nm are observed. In the IR spectra, the 1430- 1440 cm ’region is assigned to the v (C-N) vibration of the S,C-NR, bond. The doublet in the region of lOOO- 1060 cm- ’ is associated with v (C--S) vibrations. The doublet separated by > 20 cm _ ’is indicative of the monodentate nature of the ligand [17].
4. Thermal studies 4.1. Results and discussion 4.1 .I Trichloro (N-methylcyclohexyl dithiocarbamato) germanium(IV) The TG curve for this complex (Fig. 1, curve a) shows that almost 50% mass loss occurs up to 673 K. The initial thermal decomposition step is over the range 400-673 K. At this temperature, the intermediate Ge(SCN),Cl, was formed (calculated Mass loss, 28.1%; found, 30%). The subsequent step at 956 K shows a mass loss; germanium oxide (GeO,) is the end product (calculated mass loss 71.50%; observed, 73%). The DTA curve (Fig. 2, curve a) shows an exothermic peak at T,,, = 605.8 K, which is due to the formation of Ge (SCN), Cl,. An endothermic peak at 872.6 K corresponds to complete decomposition of the complex [9].
0
Fig. 1. TG curves:
200
400 TEMPERATURE
a, Ge[S,CNMeCyhx]Cl,;
600 ( *Cl
000
___+
b,Ge[S,CNPr’Cyhx]Cl,;
c, Ge[S,CNPr’Cyhx],.
N. Gandhi et al./Thermochimica
504
Acta 2821283 (1996) 501-508
1 END0
0
I
I
I
200
400
600
TEMPERATURE
Fig. 2. DTA curves:
a, Ge[S,CNMeCyhx]Cl,;
(‘C)
-
b, Ge[S,CNPr’Cyhx]Cl,;
c, Ge[S,CNPr’Cyhx],
4.1.2. Trichloro (N-isopropyl cyclohexyl dithiocarbamato) germanium(ZV) The TG curve (Fig. 1, curve b) for this complex shows a gradual initial mass loss which accelerates around 454 K and terminates around 545 K. The curve shows almost 50% mass loss at this temperature. At 545 K, the intermediate Ge (SCN),Cl, is formed (calculated mass loss, 33.3%; found, 35%). A further mass loss is observed in the second step to 1073 K. GeO, is the final product after decomposition but the mass loss should be 73.59% (calculated) and actually it is found out to be 65% from the thermogram, which suggests incomplete conversion to oxide at 1073 K. The DTA profile (Fig. 2 curve b) shows a shallow endothermic peak at 493 K, which is due to the initial decomposition of the complex. There is a small exothermic peak at 553 K which is due to further reaction of the intermediate. 4.1.3. Tetrakis (N-isopropyl cyclohexyl dithiocarbamato) yermanium(ZV) The TG curve (Fig. 1, curve c) for this complex shows a completely different trend. The thermal decomposition commences with the increase in temperature. The compound is highly volatile and by 550 K, 100% of the complex is volatilized. The DTA profile (Fig. 2, curve c) for this complex shows an endothermic peak at T max= 483 K, which is due to melting of the complex. The second endothermic peak is = 538.8 K, which is due to the volatilization of the complex. at T,,, Thus from the TG trends it is revealed that the thermal stability of the complexes is in the order: Ge(S,CNPr’Cyhx), < Ge(S,CNMeCyhx)Cl, < Ge(S,CNPr’Cyhx)Cl,. From the TG curves, the reaction order (n) for the first thermal decomposition step has been determined by the methods of Coats and Redfern (Figs. 3 and 4) [lS], Piloyan and Novikova (Figs. 5 and 6) [19] and Horowitz and Metzger (Figs. 7 and 8) [20]. The heat of reaction (AH) can be read directly in microvolts from the DTA curve, obtained from the computer attached to thermoanalyser; this can be converted to kJ
0 0
-/
0
L-
I 2.129
I 2.128
1
2.127
p
Fig. 3. Coats-Redfern
I
I
2.139
-
plot for Ge[S,CNMeCyhx]CI,.
60
b
. ,L-------+.
/
,
18
Fig. 4. Coats-Redfern
I.9
20 lx 103 r
22
21
,
plot for: a, Ge[S,CNPr’Cyhx]Cl,;
b, Ge[S,CNPr’Cyhx:
N. Gandhi et ul./Thermochimica
506
Actu 2821283 (1996) 501-508
1x103 r
2.126 t
-5.5
2.127
,
2x0
2,129
I
-
Fig. 5. Piloyan-Novkova
plot for: Ge[S,CNMeCyhx]Cl,.
-56
Fig. 6. Piloyan-Novikova
plot for: a, Ge[S,CNPr’Cyhx]Cl,;
b, Ge[S,CNPr’Cyhx],.
N. Gandhi et al.lThermochimica
507
Acta 2821283 (1996) 501-508
-0.3 _I
Fig. 7. Horowitz-Metzger
plot for Ge[S,CNMeCyhx]CI,.
b
I
-II1
-110
x)
Fig. 8 Horowitz-Metzger
mol-’
ul
(-8)-
+-----c-e)
plot for: a, Ge[S,CNPr’Cyhx]CI,;
b, Ge[S,CNPr’Cyhx],
using the expression AH(kJ mol- I) = AH (pV) x 60 x mol.wt. x 10-6/1000
The temperature-dependent tion [21]
calibration
constant
K = - 1.3 x 10m4 x peak temperature The kinetic parameters
are summarized
was obtained
+ 0.2200
in Table 2.
from the Currel equa-
508
N. Gandhi et al.lThermochimica
Table 2 Kinetic parameters
of the complexes
Acta 2821283 (1996) 501-508
for the first step of thermal
decomposition
No.
Compound
Calibration constant K/(kJ cm-‘)
Equations
Order of reaction n
Heat of reaction AH/(kJ mol ‘)
1.
Ge[S,CNMeCyhx]CI,
0.1412
Ge[S,CNPr’Cyhx]Cl,
0.1481
1 1 1 1
AH, = 20.049 x IO-’ AH, = 10.3178 x lo.-’
2.
Coats-Redfern PiloyanNovikova Horowitz-Metzger Coats-Redfern PiloyanNovikova Horowitz-Metzger Coats-Redfern Piloyan-Novikova Horowitz-Metzger
1 1
Not recorded
3.
Ge[S,CNPr’Cyhx],
0.1572
1 1 1
AH=
11.24526x
lo-’
References and S.J. Lippard (Eds.), Progress in Inorganic Chemistry, Vol. XI, Interscience, Ill D. Coucouvanis London, 1970, p. 233. and Related Compounds, Elsevier, New York, PI G.D. Thorn and R.A. Ludwig, the Dithiocarbamates 1962. and S.J. Lippard (Eds.), Progress in Inorganic Chemistry, Vol. 26, Interscience, [31 D. Coucouvanis London, 1979, p. 301. M S. Kato and M. Mizuta, J. Org. Met. Chem., 55 (1973) 121. c51 M.A. Bernard and M.M. Borel, Bull. Sot. Chim. Fr., (1969) 3066. 161 G.D. Ascenzo and W.W. Wendlandt, J. Therm. Anal., 1 (1969) 423. c71 S. Kumar, N.K. Kaushik and I.P. Mittal, in W. Hemminger (Ed.), Thermal Analysis, Proc. 6th ICTA, Bayreuth, 1980, Birkueuser Verlag, Basel, 1980, p. 137. Acta, 41 (1980) 19. PI S. Kumar and N.K. Kaushik, Thermochim. Acta, 106 (1986) 233. c91 S.S. Gupta and N.K. Kaushik, Thermochim. Delhi, 1985. [lOI T.N. Srivastava and P.C. Kamboj, Systematic Analytical Chem, Vishal Publications, p. 366. of Organometallic Compounds, Part 1, Interscience Publications, Cl11 M. Tsutsui, Characterization London, 1969, p. 62. Cl21 H. Gilman and A.H. Blatt, Organic Synthesis, Collective Vol. 1, Wiley, New York, 1958, p. 448. Cl31 S.A.A. Zaidi, K.S. Siddiqui and N. Islam, Indian J. Chem., 12 (1974) 1197. 1141 C.K. Jorgenson, Inorganic Complexes, Academic Press, London, 1963, p. 138. Cl51 C.K. Jorgenson, J. Inorg. Nucl. Chem., 24 (1962) 1571. Inorg. Chim. Acta, 18 (1976) 35. Cl61 C.A. Tsipis and G.E. Manoussakis, Cl71 F. Bonati and R. Ugo, J. Org. Met. Chem., 10 (1976) 257. 1181A.W. Coats and J.P. Redfern, Nature, 201 (1964) 68. Cl91 G.D. Piloyan and I.S. Novikova, Russ. J. Inorg. Chem., 12 (1967) 313. 1201 H. Horowitz and G. Metzger, Anal. Chem., 35 (1964) 1464. c211 B.R. Currel, in R.F. Schwenker and P.D. Garn (Eds.), Thermal Analysis, Vol. 3 Academic Press, New York, 1969, p. 1185.