Synthesis, structural, spectroscopic and magnetic studies of two azido and thiocyanato nickel(II) dinuclear complexes with ferromagnetic interactions

Abstract

From a newly synthesised tridentate ligand [pepci =N′-(2-pyridin-2-ylethyl)pyridine-2-carbaldimine] two new octahedrally co-ordinated nickel(II) dimers, [{Ni(pepci)(N₃)₂}₂]1 and [{Ni(pepci)(NCS)₂}₂]2, have been prepared. The crystal structure 1 has been solved. It crystallizes in space group P2₁/c with four formula weights in a cell measuring a= 9.198(3), b= 17.382(6), c= 19.356(7)Å, and β= 99.57(1)°. The structure consists of isolated dimeric units in which the nickel ions are linked by two azide bridging groups in an end-on fashion. Two pepci ligands and two terminal azide groups complete the co-ordination spheres. Inside the dimer, each Ni(pepci)(N₃)₂ entity is crystallographically non-equivalent. There are two different bridging angles Ni(A)–N(4A)–Ni(B) 102.2(2) and Ni(B)–N(4B)–Ni(A) 101.0(2)°. The co-ordination geometry at each nickel atom is approximately octahedral. The Ni(A)⋯ Ni(B) distance is 3.297(1)Å. For complex 2 a dimeric structure involving end-to-end thiocyanate bridging groups is proposed. Magnetic susceptibility data, measured from 4 to 300 K, were fitted to the Ginsberg equation, giving the parameters (cm^–1): J=+36.3, D=–18.8, z′J′= 0.0 (N₃); and J=+4.9, D=–9.8, z′J′=+0.33 (NCS). The magnetic behaviour of these and related complexes is discussed and some magnetostructural trends are given.