The Chemistry of Nickel(II) Complexes Derived from Oximato Ligands and Electrochemistry

Abstract

Abstract Tridentate ligands, HRR'Y, derived from α-hydroxyiminoketone and 1,2-propylenediamine, form high-spin octahedral (NiN6 core; Dq ≃ 1280 cm−1) nickel(II) complexes of the type Ni (HRR'Y)2X2 (X = C104, NO3). Cyclic voltammetry (CV) of Ni (HRR'Y)2 (C104)2 has been thoroughly done in well-buffered aqueous media only over a narrow range of pH 7.00–9.00. Below pH 6.00, the nickel(II) species undergo decomposition. In the pH range 7.00–9.00, two distinct one-electron reversible processes are observed corresponding to Ni(II)—Ni(III) and Ni(III)—Ni(IV) couples. The nickel(II) species involved in each couple is what is expected from dissociation (oxime protons) of Ni(HMe2Y)2+ 2 (pK1 = 8.00; pK2 = 10.40).