Iron(II) reduction of halogenocobalt(III) complexes of 3,8-dimethyl-5,6-benzo-4,7-diazadeca- 3,7-diene- 2,9-dione dioxime: Kinetics and mechanism

341-344The iron(II) reduction of cobalt(III) complexes of the type trans-[Co(DODOHbzo)(s-py)X]ClO4, where DODOHbzo = 3,8-dimethyl-5,6-benzo-4, 7-diazadeca-3,7- diene-2,9-dione dioxime mono anion, s-py = pyridine (py), nicotinamide (nic-CONH2) or isonicotin-amide (isonic-CONH2) and X- = Cl-, Br- or I-, has been studied in DMSO/water (1%, v/v) at 27 ± 0.1°C and I = 0.25 mol dm-3 (LiC1O4) in the [H+] range 0.007-0.100 mol dm-3 under pseudo-first order conditions using an excess of the reductant. The inverse dependence of rate on [H+] suggests an equilibrium between the protonated and unprotonated forms of the complex, the protonated from reacting slower than the unprotonated form. The rate constants reflected the trend Cl- - - and py 2 iso-nic-CONH2 for the axial ligands