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Mono-and binuclear complexes of malonyl bis(thiosemicarbazide), H 4 MBT, with VO 2+ , Co 2+ , Ni 2+ , Cu 2+ , Cd 2+ and Pt 4+ have been isolated. The elemental analyses, magnetic moments, spectra [u.v.-vis., i.r., e.s.r. (for Cu 2+ ; VO 2+ ) and mass], thermal and voltammetric measurements [for Co 2+ and Ni 2+ ] have been used to characterize the isolated complexes. The ligand behaves as binegative quadridentate with Cu 2+ , Co 2+ and VO 2+ ions, binegative pentadentate with Pt 4+ and hexadentate, either as trinegative in [Cd 2 (HMBT)(OC 2 H 5 )(C 2 H 5 OH)]H 2 O or mononegative in [Ni 2 (H 3 MBT)(OAc) 3 (C 2 H 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 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 2+ complex and a lower one for VO 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 2+ and Pt 4+ thermograms have been calculated.

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