METFORMINE COMPOUNDS WITH THE IONS CO(II) , CU(II) AND NI(II)

The structures of trichloro(N,N-dimethyibiguanidium)-cobalt(II), [Co(C 4H12N5)Cl-3], (I), and di-mu-chlorobis-[chloro-(N, N-dimethylbiguanide ) copper(II)], [CuCl2(C4C11N5)](2), (II), consist of the metal atom bo und to three Cl atoms and to one or two N atoms, respectively, belongi ng to one metformine ligand. The structures of bis(N,N-dimethylbiguani de)copper(II) dichloride dihydrate [Cu(C4H11N5)(2)]Cl-2.2H(2)O, (III), and bis(N,N-dimethylbiguanide)nickel(II) monohydroxide chloride, [Ni( C4H11N5)(2)](Cl)(OH), (IV), are formed of [M(metformine)(2)](2+) (M = Cu or Ni) and anions (Cl- or OH-). In these compounds, the metal is on a centre of symmetry and forms a square-planar structure comprising f our N atoms of two N,N-dimethylbiguanidine ligands. The metformine lig and is planar in (II), (III) and (IV), allowing delocalization of the pi-electron system in the metal-ligand ring, but not in (I), where the dihedral angle between the two guanidine groups is 68.4 (2)degrees. T he four structures are stabilized by hydrogen bonding and van der Waal s interactions.