Synthesis, crystal structure and magnetic properties of dinuclear nickel(II) complexes bridged by oxamides

Abstract

Two dinuclear nickel(II) complexes, Ni(obbz)Ni(H 2O) 4·2H 2O ( 1) and Ni (oxen)Ni(en)(SCN) 2 ( 2) (en = ethylenediamine), (where obbz and oxen are N,N′-bis(2-aminobenzoato)oxamide and N,N′-bis(2-aminoethyl)oxamide dianions, respectively), were prepared and characterized by X-ray crystallography, magnetic and spectroscopic measurements. For both the dinuclear compounds, one nickel(II) central atom is located in an approximately square planar environment, the other one is in a distorted octahedral geometry. The structures consist of molecular Ni IINi II units in which the nickel(II) ions are bridged by an oxamidato group in cis conformation. The effective moments of both complexes correspond to a high-spin (S = 1) nickel(II) ion at room temperature but decrease rapidly below 14 K. Analysis of the data showed the decrease to correspond to the effects of single ion anisotropy, and the susceptibility of Ni(obbz)Ni(H 2O) 4·2H 2O ( 1) can be described as resulting from the single-ion anisotropy parameter D = 5.54 cm −1, with the m s = 0 singlet ground state for this complex.