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

Synthesis of (alpha betaS)-(tetren)Co(idaH(2)/dipicH(2))(3+) (where tetren: tetraethylenepentamine) and kinetics of their complexation reaction with N i(II) leading to formation of binuclear complexes, 1 and 2, have been studi ed by stopped-flow/spectrophotometric method. Both N-protonated and NH-depr otonated forms of ida complex are involved in the formation of (tetren)Co(i da)Ni3+ while only NH-deprotonated form of the complex is involved in the f ormation of (tetren)Co(dipic)Ni3+. The rate data for the formation of binuc lear complexes are consistent with I-d mechanism. As expected, (tetren)Co(d ipic)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).