A trinuclear nickel(II) complex with alternating square-planar and octahedral geometries.: Synthesis, crystal structure and magnetic properties of [Ni3(oxen)2(en)][ClO4]2

The reaction of Ni(oxen) [oxen = N,N'-bis (2-aminoethyl) oxamido dianion], NiCl2 and the disodium salt of EDTA (ethylenediamine tetraacetic acid) in 1:1:1 molar ratio gave the trinuclear complex [Ni-3(oxen)(2)(en)][ClO4](2) (en = 1,2-ethylenediamine), where en came from the partial decomposition of oxen. The complex exhibits a curved Ni-3 metal arrangement with the angle Ni(2)-Ni(1)-Ni(2a) of 119.0 degrees. The structure of a Ni-3(II) unit with three nickel(II) atoms chelated and bridged by two oxamidato (oxen) groups in cis-conformation. The central nickel atom has a distorted octahedral geometry whereas the two on the sides have square-planar surroundings. The complex is paramagnetic and its magnetic behaviour can be interpreted by single-ion anisotropy with D = 5.22 cm(-1) and m(s) = 0 singlet ground state. (C) 1998 Elsevier Science Ltd.