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metal-organic compounds
The structures of trichloro(N,N-dimethylbiguanidium)cobalt(II) [Co(4H12N5)Cl3], (I) and di--chlorobis[chloro(N,N-dimethylbiguanidium)copper(II)], [CuCl2(C4H11N5)], (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]Cl2.2H2O, (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 -electron system in the metal-ligand ring, but not in (I), where the dihedral angle between the two guanidine groups is 68.4 (2)°. The four structures are stabilized by hydrogen bonding and van der Waals interactions.