Complexes of nickel(III) with biguanide and N′-amidinoisoureas

Abstract

The following complexes of nickel(III) with biguanide (Hbg), N′-amidinoisourea (aiu), and O-alkyl-N′-amidinoisoureas [alkyl = Me (Hmaiu) or Et (Heaiu)] have been prepared and isolated: [NiBr₂L₂]Br and [NiCl₂L₂]X (L = Hbg, X = F or Cl); [NiL₂]Cl (L = aiu); and [NiL₂]₂[SO₄]·2H₂O (L = maiu or eaiu). Oxidimetric titrations and the values of the oxidation potentials indicate that the complexes are one-electron oxidizing agents, while polarographic reduction-potential studies suggest nickel(III) complexes rather than nickel (II)-stabilized radical-ligand compounds. Magnetic-susceptibility, e.s.r., and i.r. data also support the presence of Ni^III in these complexes.