Publication

Abstract : Octahedrally coordinated monomeric and axially bridged polymeric compounds from four coordinated cobalt(H) species have been synthesized and characterized by elemental analysis, infra red and electronic spectroscopy, magnetic susceptibility measurements and thermal analysis. The four coordinated system used was tetrahedral bis(2-mercaptobenzothiazolatocobalt(II), Co(mbt) 2 and ligands used were bidentate opposite end donors such as 4-aminopyridine, 4,4'-bipyridine and pyrazine. For comparison a monodentate ligand pyridine was also used. The complexes synthesized have the molecular formula [CoCmbt) 2L2] where L= pyridine and 4-aminopyridine and [Co(mbt)2L']n where L'= pyrazine and 4,4'-bipyridine. The infra red and thermal studies indicate that 4-aminopyridine is coordinated through its pyridyl nitrogen only, eventhough it is bidentate while others behave as bridging bidentate. These adducts have a trans octahedral structure which is preferable for extended linear framework, eventhough two isomeric forms are possible viz. cis and trans. The variation of magnetic moment on adduct formation was also carried out The thermal decomposition of Co(mbt)2 is seen taking place in two stages, in nitrogen atmosphere, with CoS, a stable residue. In the case of adducts an additional step was observed due to the loss Lewis bases used. The kinetic and mechanistic parameters were also evaluated from different decomposition stages. In most of the cases it follows Random nucleation, one nucleus on each particle obeying Mampel equation. © 2012 RASÄYAN. All rights reserved.