Kinetics of the Iron(II) Reduction of Glycinatobis(malonato)-, trans-Bis(malonato)bis(pyridine)-, Nitrilotriacetato(malonato)-, and Nitrilotriacetato(oxalato)cobaltates(III)

Article abstract of DOI:10.1246/bcsj.59.3243

The kinetics of the iron(II) reduction of glycinatobis(malonato)-, trans-bis(malonato)bis(pyridine), nitrilotriacetato(malonato)-, and nitrilotriacetato(oxalato)cobaltates(III) have been studied in aqueous perchlorate medium at I=1.0 mol dm^-3 (LiClO4) and 30 deg C in the +> range 0.01-0.90 mol dm^-3.The reductions are found to be second order.The reduction of ^2- and ^- is accelerated by H⁺, while the reduction of ^2- and ^2- is independent of +> in the range 0.1<+><0.9 mol dm^-3.The reduction of ^2- is, however, faster at +><0.1 mol dm^-3.The activation parameters for the reduction of ^2-, ^-, ^2-, and ^2- are respectively as follows: ΔH<*>=49.8+/-4.8, 51.2+/-2.6, 41.1+/-3.2, and 41.4+3.6 kJ mol^-1, ΔS<*>=-98.3+/-8.3, -93.7+/-7.2, -119.2+/-9.7, and -114.6+/-9.6 J K^-1 mol^-1.The proposed mechanism invokes (L-py2 or gly) formed in a H⁺-assisted step as the reactive species for the bis(malonato) complexes. ^2- is proposed to be present as ^- while ^2- remains unaffected by H⁺.