Metal complexes with disubstituted oxamidic ligands

Abstract

Three oxamidic ligands have been prepared by reaction of oxalyldichloride with the appropriate amine H 2NC 6H 4P(C 6H 5) 2 (H 2A), H 2NC 2H 4(NC 5H 4) (H 2B) and H 2NC 2H 4SC 6H 5 (H 2C). They have been characterized by elemental analyses, IR, NMR, mass spectrometry and for H 2B by X-ray diffractometry. The crystals, grown from a tetrahydrofuran/diethylether solution, are monoclinic, space group P2 1/ c, cell dimensions a=9.503(4), b=6.278(4), c=13.083(5) Å and β=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 H 2A with trans-Pd(C 6H 5CN) 2(Cl) 2 forms the white mononuclear cis-Pd(A) and the yellow homodinuclear trans-Pd 2(A)(Cl) 2 complexes as confirmed by scanning electron microscopy (SEM) and EDX analyses and by an X-ray structure of Pd 2(A)(Cl) 2. The yellow crystals, grown from alcoholic solution, are monoclinic, space group P2 1/ c, cell dimensions a=10.335(5), b=10.246(5), c=16.480(6) Å and β=100.81(5)° with Z=2; as for H 2B 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. H 2B forms the homodinuclear nickel(II) and copper(II) complexes M(B)(X) 2 (X=Cl −, CH 3COO −, ClO 4 −). Crystals of the dinuclear copper(II) complex Cu 2(B)(Cl) 2(dmso) 2, grown from dimethylsulphoxide, are triclinic, space group P 1 ̄ , cell dimensions a=8.352(5), b=8.361(5), c=9.959(4) Å, α=83.39(4) β=85.49(3), γ=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. H 2C does not form complexes when reacted with transition metal ions.