Synthesis, spectral and thermal studies of monomeric, homobimetallic and polymeric complexes containing benzoyldithiocarbazate

• Published in: Transition metal chemistry (Weinheim) 2003-10, Vol.28 (7), p.749
• Main Author: El-said, Asma I
• Format: Article
• Language: English
• Subjects: Decomposition
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1023/A:1026074223926

New mixed ligand complexes of benzoyldithiocarbazate (H^sub 2^BDT) have been synthesized and characterized by elemental analyses, spectral studies (i.r., u.v.-vis., mass), thermal analysis and electrical conductivity measurements. The complexes have the general formulae: [M^sub 2^(BDT)(OX)^sub 2^] · xH^sub 2^O; [Co^sub 2^(BDT)(OX)^sub 2^(H^sub 2^O)^sub 4^]; [M'(HBDT)(OX)-(H^sub 2^O)], [Ni(BDT)(py)^sub 2^]^sub n^ and [Ni(BDT)(L)]^sub n^ where M = Mn^sup II^, Ni^sup II^ and Cu^sup II^; BDT = dithiocarbazate dianion; OX = 8-hydroxyquinolinate; x = 1 or 2; M' = Zn^sup II^ or Cd^sup II^; HBDT = dithiocarbazate anion and L = 2,2'-bipyridyl or 1,10-o-phenanthroline. For the [M^sub 2^(BDT)(OX)^sub 2^] · xH^sub 2^O, [Co^sub 2^(BDT)(OX)^sub 2^(H^sub 2^O)^sub 4^], [Ni(BDT)(py)^sub 2^]^sub n^ and [Ni(BDT)(L)]^sub n^ complexes, benzoyldithiocarbazate acts as a dibasic-tetradentate ligand in the enol form via the enolic oxygen, the hydrazide nitrogens and the thiolate sulphur, while it acts as a monobasic-tridentate ligand in the keto form in the [M'(HBDT)(OX)(H^sub 2^O)] complexes. The thermal behaviour of the complexes has been studied by t.g.-d.t.g. techniques. Kinetic parameters of the thermal decomposition process have been computed by Coats-Redfern and Horowitz-Metzger methods. It is obvious that the thermal decomposition in the complexes occurs directly at the metal-ligand bonds except for the Zn^sup II^ and Cd^sup II^ complexes in which decomposition seems to be at a point in the benzoyldithiocarbazate moiety. From the calculated kinetic data it can be concluded that the dehydration processes in all complexes have been described as phase-boundary controlled reactions. The activation energy values reveal that the thermal stabilities of the homobimetallic complexes lie in the order: Mn^sup II^ < Ni^sup II^ < Co^sup II^, while the monomeric Cd^sup II^ complex has more enhanced thermal stability than the Zn^sup II^ complex.[PUBLICATION ABSTRACT]