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 NiIII in these complexes.