Spectral, Magnetic, Electrical and Thermal Studies on Malonyl bis(thiosemicarbazide) Complexes

• Published in: Transition metal chemistry (Weinheim) 2006-02, Vol.31 (1), p.71-78
• Main Authors: El-Metwally, Nashwa M., Gabr, Issam M., El-Asmy, Ahmed A., Abou-Hussen, Azza A.
• Format: Article
• Language: English
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1007/s11243-005-6347-6

Mono- and binuclear complexes of malonyl bis(thiosemicarbazide), H^sub 4^ MBT, with VO^sup 2+^, Co^sup 2+^, Ni^sup 2+^, Cu^sup 2+^, Cd^sup 2+^ and Pt^sup 4^+ have been isolated. The elemental analyses, magnetic moments, spectra [u.v.-vis., i.r., e.s.r. (for Cu^sup 2+^; VO^sup 2+^) and mass], thermal and voltammetric measurements [for Co^sup 2+^ and Ni^sup 2+^] have been used to characterize the isolated complexes. The ligand behaves as binegative quadridentate with Cu^sup 2+^, Co^sup 2+^ and VO^sup 2+^ ions, binegative pentadentate with Pt^sup 4^+ and hexadentate, either as trinegative in [Cd^sub 2^(HMBT)(OC^sub 2^H^sub 5^)(C^sub 2^H^sub 5^OH)]H^sub 2^O or mononegative in [Ni^sub 2^(H^sub 3^MBT)(OAc)^sub 3^(C^sub 2^H^sub 5^OH)]. The lack of thiol and/or enol hydrogen during the complex formation was confirmed pH-metrically. The pK's (10.70, 8.50 and 8.15) of H^sub 4^MBT reveal the removal of CSNH protons in one step and CONH in two steps. Also, the stability constants reveal a higher value for the Cu^sup 2+^ complex and a lower one for VO^sup 2+^. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. The kinetic and thermodynamic parameters for some decomposition steps in VO^sup 2+^and Pt^sup 4+^ thermograms have been calculated[PUBLICATION ABSTRACT]