Metal complexes with disubstituted oxamidic ligands

Three oxamidic ligands have been prepared by reaction of oxalyldichloride with the appropriate amine H2NC6H4P(C6H5)2 (H2A), H2NC2H4(NC5H4) (H2B) and H2NC2H4SC6H5 (H2C). They have been characterized by elemental analyses, IR, NMR, mass spectrometry and for H2B by X-ray diffractometry. The crystals, grown from a tetrahydrofuran/diethylether solution, are monoclinic, space group P21/c, cell dimensions a=9.503(4), b=6.278(4), c=13.083(5) Å and ?=100.24(4)° with Z=2. The asymmetric unit is half of the ligand molecule which shows an inversion centre between the C-C bond of the oxamidic group. The molecule is elongated in a three steps configuration. The reaction of H2A with trans-Pd(C6H5CN)2(Cl)2 forms the white mononuclear cis-Pd(A) and the yellow homodinuclear trans-Pd2(A)(Cl)2 complexes as confirmed by scanning electron microscopy (SEM) and EDX analyses and by an X-ray structure of Pd2(A)(Cl)2. The yellow crystals, grown from alcoholic solution, are monoclinic, space group P21/c, cell dimensions a=10.335(5), b=10.246(5), c=16.480(6) Å and ?=100.81(5)° with Z=2; as for H2B crystals, the asymmetric unit is half of the whole molecule. A distorted square planar coordination around each metal ion is reached by the coordination of a phosphorus, an oxygen and a nitrogen atom of the ligand and a chlorine atom. H2B forms the homodinuclear nickel(II) and copper(II) complexes M(B)(X)2 (X=Cl-, CH3COO-, ClO4-). Crystals of the dinuclear copper(II) complex Cu2(B)(Cl)2(dmso)2, grown from dimethylsulphoxide, are triclinic, space group View the MathML source , cell dimensions a=8.352(5), b=8.361(5), c=9.959(4) Å, ?=83.39(4) ?=85.49(3), ?=75.38(5)° with Z=1. Again the dinuclear entity shows a inversion centre between the two C-C bonds of the oxamide ligand. Each copper(II) ion has a distorted square pyramidal environment formed by two nitrogen atom and an oxygen atom of half oxamidic ligand, a chlorine atom and the oxygen atom of a dimethylsulphoxide molecule; the copper-copper distance is 5.28 Å. An antiferromagnetic interaction was observed for the dinuclear copper(II) complexes. H2C does not form complexes when reacted with transition metal ions.