EPR characterisation of nickel(III) complexes with N2O2 Schiff base ligands derived from naphthaldehyde and their pyridine adducts

Nickel(II) complexes with quadridentate N2O2 Schiff base ligands derived from naphthaldehyde have been synthesised and their oxidative chemistry was studied in N,N'-dimethylformamide and in dimethylsulfoxide. Electrochemical and EPR data for the oxidised solutions have revealed that in these strong coordinating solvents, only the complexes with aliphatic imine bridges were oxidised to low spin six-coordinate nickel(III) complexes, in a (2)A(1)(d(z)(2)) ground state, formulated as [Ni(III)(L). S-2](+), where S stands for a solvent molecule. Upon addition of pyridine to fluid solutions of [Ni(III)(L). S-2](+), new species were formed that on the basis of their EPR spectra can be formulated as [Ni(III)(L). py(2)](+). Extensive electronic characterisation of the NI(III) compounds was made by coupling EPR and electronic spectroscopic data. (C) 1998 Elsevier Science Ltd. All rights reserved.