Syntheses, crystal structures and magnetic properties of four-coordinate Ni(II) and Cu(II) complexes

In this work, two mononuclear four-coordinate complexes of Ni(II) and Cu(II), formulated as (HNEt3)2[Ni(L)2] (1) and (HNEt3)2[Cu(L)2]·H2O (2) (H2L = N,N'-bis(p-toluenesulfony1)oxamide), have been synthesized and characterized. These complexes are coordinated by two doubly deprotonated oxamide ligands. The crystal structures of both complexes were determined using single-crystal X-ray diffraction, revealing highly irregular coordination geometries around the central metal ions. Complex 1 exhibits a structure closer to a tetrahedral configuration, whereas complex 2 adopts a structure closer to a seesaw configuration. Direct-current (dc) magnetic data demonstrate that 1 possesses an easy-plane anisotropy with a large value for the zero-field splitting (ZFS) parameter D of + 66.3 cm−1.