Crystal structure and magnetic interactions in nickel(II) dibridged complexes formed by two azide groups or by both phenolate oxygen-azide, -thiocyanate, -carboxylate, or -cyanate groups

Tridentate/tetradentate Schiff base ligands L-1 and L-2, derived from the condensation of o-vanillin or pyridine-2-aldehyde with N,N-dimethylethylenediammine, react with nickel acetate or perchlorate salt and azide, cyanate, or thiocyanate to give rise to a series of dinuclear complexes of formulas [Ni(L-1)(mu(1,1)-N-3)Ni(L-1)(N-3)(OH2)].H2O (1), {[Ni(L-1)(mu(1,1)-NCS)Ni(L-1)(NCS)(OH2)][Ni(L-1)(mu-CH3COO)Ni(L-1)(NCS)(OH2)]} (2) {[2A][2B]}, [Ni(L-1)(mu(1,1)-NCO)Ni(L-1)(NCO)(OH2)].H2O (3), and [Ni(L-2-OMe)(mu(1,1)-N-3)(N-3)](2) (4), where L-1 = Me2N(CH2)(2)NCHC6H3(O-)(OCH3) and L-2 = Me2N(CH2)(2)NCHC6H3N. We have characterized these complexes by analytical, spectroscopic, and variable-temperature magnetic susceptibility measurements. The coordination geometry around all of the Ni(II) centers is a distorted octahedron with bridging azide, thiocyanate/acetate, or cyanate in a mu(1,1) mode and mu(2)-phenolate oxygen ion for 1-3, respectively, or with a double-bridging azide for 4. The magnetic properties of the complexes were studied by magnetic susceptibility (chi(m)) versus temperature measurements. The chi(m) vs T plot reveals that compounds 1 and 4 are strongly ferromagnetically coupled, 3 shows a weak ferromagnetic behavior, and 2 is very weakly antiferromagnetically coupled.