Synthesis, characterisation and complexation reaction of (αβS)-pyridine-2,6-dicarboxylato/iminodiacetato (tetraethylenepentamine) cobalt(III) in aqueous medium-A comparative study

Abstract

Synthesis of (αβS)-(tetren)Co(idaH₂/dipicH₂)³⁺ (where tetren: tetraethylenepentamine) and kinetics of their complexation reaction with Ni(II) leading to formation of binuclear complexes, <b>1</b> and <b>2</b>, have been studied by stopped-flow/spectrophotometric method. Both N-protonated and NH-deprotonated forms of ida complex are involved in the formation of

(tetren)Co(ida) Ni³⁺ while only NH-deprotonated form of the complex is involved in the formation of (tetren)Co(dipic)Ni³⁺. The rate data for the formation of binuclear complexes are consistent with <i>I</i>_dmechanism. As expected, (tetren)Co(dipic)Ni³⁺ (where benzene ring forms a part of 5-membered chelate ring) is ~150 times less stable than its ida analogue (which also forms a 5-membered chelate ring but without benzene ring).