KANDIL et al.: AZOPYRAZOLONES
179
lisation of water molecules precedes the decomposition of sulphonylazido group as
revealed by DTA curves of the aqua complexes [12]. It is apparent that volatilisation
of these water molecules would destruct the crystal packing of the aqua complex [19],
*
thereby assists the decomposition of SO N as shown by lowering of its ∆G value.
For copper(II) complexes, the same arguments can be given for the difference be-
2
3
1
*
1
*
–1
tween ∆G1 for [Cu(D –SO N ) (H O)]; ∆G =173.64 kJ mol
and for
2
3
2
2
1
2
*
–1
[
Cu(D –SO N ) (H O) ]; ∆G =118.11 kJ mol . In nickel(II) complexes, the differ-
2
3
2
2
2
1
*
1
*
–1
ence between ∆G values for [Ni(D –SO N ) (H O) ]; ∆G =170.02 kJ mol and for
Ni(D –SO N ) (H O) ]; ∆G =146.94 kJ mol is pronounced, though it is smaller
1
2
3
2
–1
2
2
1
2
*
[
2
3
2
2
2
1
*
than in the cases of copper(II) and cobalt(II) complexes. Since the ∆H values are
reasonably similar as consequences of each having the same kinds and number of do-
1
*
nors, the difference in ∆G for the two complexes should be attributed to the differ-
1
*
*
ence in the ∆S values or more strictlyT∆S . The former complex which has o-OCH
substituent needs more energy to be ordered in structure than that needed for the latter
1
1
3
one which has no o-substituents, in the activated state with respect to the reactants
and/or the reaction of o-CH substituted complex is relatively slow. The close values
3
*
of ∆G of the complexes of the two ligands with the same cation e.g. for
2
1
*
–1
2
*
[
2
Co(D –SO N ) ]; ∆G =242.60 kJ mol and for [Co(D –SO N ) (H O) ]; ∆G =
41.74 kJ mol suggest that the tetracoordinate complexes [M(D–SO N:) ] produced
2 2
2
3
–1
2
2
2
3
2
2
2
2
from the first stage would have the same electronic and geometric structures so that
thermal activation in this stage involves mostly similar groups. On the other hand, the
*
difference in ∆G from one cation to the other for the same ligand is not pronounced.
This suggests that the effect of the ligand is more than the cation on the second stage
decomposition of the complexes.
2
References
1
R. H. Wiley and P. Wiley, Pyrazolones, Pyrazolidones and Derivatives, Wiley, New York
964.
S. A. Ibrahim, M. A. El-Gahami, Z. A. Khafagi and S. A. El-Gyar, J. Inorg. Biochem.,
3 (1991) 1.
1
2
4
3
4
A. Abdel-Razik, International J. Chem., 3 (1992) 35.
N. G. Smaglyuk, S. T. Talipov, Z. A. Pivenko, R. K. Dzhiyanbaeva and A. A. Khodzhaev,
Zh. Anal. Khim., 30 (1975) 1680; 84 (1976) 68981.
5
6
A. A. Saafan, M. A. El-Borai, M. A. Sakran and I. S. El-Kamary, Melliand Textilber.,
7
1 (1990) 25.
A. A. Saafan, M. A. El-Borai, M. A. Sakran and I. S. El-Kamary, Melliand Textilber.,
0 (1989) 254.
7
7
8
K. I. Zamaraev, Zh. Strukt. Khim., 10 (1969) 32; C. A., 70 (1969) 110424.
G. B. El-Hefnawy, M. A. El-Borai, E. A. Aly and A. A. Gaber, Indian J. Fibre and Text. Res.,
1
7 (1992) 87.
9
G. Back, (Ger. Offen. DE 351 2253); C. A., 105 (1986) 7938.
1
1
0 D. R. Williams, Chem. Rev., 72 (1972) 203.
1 A. Furst and R. T. Haro, Prog. Exp. Tumor Res., 12 (1969) 102.
J. Therm. Anal. Cal., 63, 2001