KINETICS AND MECHANISM OF FORMATION OF BINARY AND TERNARY COMPLEXES OF NICKEL(II) AND NICKEL(II)-2-AMINOMETHYLBENZIMIDAZOLE WITH 3-NITROSALICYLATE AND CIS-(AMMINE)(3-NITROSALICYLATO) BIS (ETHYLENEDIAMINE)COBALT(III) - EVIDENCE FOR THE SLOW INTERCONVERSION OF THE STRUCTURAL ISOMERS OF THE TERNARY COMPLEXES

The kinetics of complex formation of 3-nitrosalicylate(NSAH(-)) and ci s-(en)(2)(NH3)(3-nitrosalicylato)cobalt(III) with Ni(OH2)(6)(2+) and [ Ni(AMB)(OH2)(4)](2+) (AMB = 2-aminomethylbenzimidazole) have been inve stigated. The formation of the ternary complexes [Ni(AMB)(NSA)(OH2)(2) ] and [(en)(2)(NH3)Co{NSA=Ni(AMB)(OH2)(2)}](3+) displayed biphasic kin etics due to the slow and reversible structural isomerisation (trans-( diaqua) species reversible arrow cis-(diaqua) species). The formation of [Ni(NSA)(OH2)(4)] is chelation-controlled. The isomerisation of the ternary complexes is presumed to involve Ni-N (benzimidazolyl-N) bond cleavage and rearrangement of the intermediate.