Metformine compounds with the ions Co(II), Cu(II) and Ni(II)

The structures of trichloro(N,N-dimethyibiguanidium)-cobalt(II), [Co(C4H12N5)Cl-3], (I), and di-mu-chlorobis-[chloro-(N, N-dimethylbiguanide) copper(II)], [CuCl2(C4C11N5)](2), (II), consist of the metal atom bound to three Cl atoms and to one or two N atoms, respectively, belonging to one metformine ligand. The structures of bis(N,N-dimethylbiguanide)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 four N atoms of two N,N-dimethylbiguanidine ligands. The metformine ligand 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. The four structures are stabilized by hydrogen bonding and van der Waals interactions.