Electrophilic substitution on metal biguanides and metal amidinoureas

Abstract

Electrophilic substitution (halogenation, sulphonation, and nitration) has been carried out on copper(II), nickel(II), cobalt(II), and chromium(III) biguanides. The substitution takes place on nitrogen atoms attached to the metal ions via intermediate formation of higher oxidation state metal species. Several complexes [M(dcbg)_{2 or 3}](dcbg = 2,4-dichlorobiguanide) have been prepared and characterized by elemental analysis and magnetic and spectral studies. X-Ray investigation of [Cu(cbg)₂]Cl₂·2OH₂(cbg = 2-chlorobiguanide) indicates the N–Cl bond distance to be 1.682 Å. Each of the biguanide ligands is planar, allowing delocalization of the π-electron system in the metal biguanide ring. I.r. spectra show lowering of ν(N–C–N) in the ring system due to halogenation. Halogen substitution is also possible on bis(amidinourea)-copper(II) and -nickel(II) complexes.