Octahedral μ-oxalato-nickel(II) dinuclear complexes with watet and tridentate amines as blocking ligands: magnetostructural correlations

Abstract

Three nickel( II) dinuclear oxalato (ox) bridged compounds: (μ-ox)[Ni(dpt)(H 2O)] 2(ClO 4) 2 ( 1), (μ-ox)[Ni(Medpt)(H 2O)] 2(ClO 4) 2·2H 2O ( 2) and (μ-ox)[Ni(ept)(H 2O)] 2(ClO 4) 2 ( 3) have been synthesized and characterized where dpt is bis(3-aminopropyl)amine, Medpt is 3,3′-diamino- N-methyl-dipropylamine and ept is N-(2-aminoethyl)-1,3-propanediamine. The crystal structures of 1 and 2 have been solved. Complex 1 crystallizes in the monoclinic system, space group I2/ a, with FW=702.8, a=12.534(4), b=16.871(5), c=13.450(4) Å, β=95.28(7)°, V=2831(3) Å 3, Z=4, R=0.063 and R w=0.068. Complex 2 crystallizes in the monoclinic system, space group P2 1/ n, with FW=766.9, a=6.404(2), b=13.333(4), c=18.687(4) Å, β=97.67(8)°, V=1576(2) Å, Z=2, R=0.063 and R w=0.068. In both complexes the nickel atom is placed in a distorted octahedral environment. The magnetic properties of these compounds have been investigated. The χM T versus T plots for 1–3 exhibit the typical shapes for antiferromagnetically coupled nickel(II) dinuclear complexes. The J values for 1–3 were −24.7, −21.6 and −25.0 cm −1, respectively. These values are significantly lower than those reported for nickel(II) dinuclear complexes when the blocking ligands have four N atoms. The influence of the change in the electronegativity of the peripheral ligand atoms on the magnetic behaviour has been studied by means of extended-Hückel calculations.