Synthesis of N3-/SCN- bridged polynuclear complexes of nickel(II) using N,N,N′-trimethylethane-1,2-diamine as a blocking ligand:: low temperature magnetic study and single crystal structure of [Ni(μ1,1-N3)(μ1,3-N3)(N,N,N′-Me3en)]n

Seven new complexes of nickel(II), derived from azido, thiocyanato and nitrito bridging ligands and N,N,N'-trimethylethylenediamine (N,N,N'-Me(3)en) as blocking ligand, were synthesised and characterised; four of them are one-dimensional compounds: [Ni(mu (1,3)-N-3)(N,N,N'-Me(3)en)(2)](n)(ClO4)(n) 1, [Ni(mu (1,3)-N-3)(N,N,N'-Me-3 en)(2)](n)(PF6)(n) 2, [Ni mu (1,1)-N-3)(mu (1,3)-N-3)(N,N,N'-Me(3)en)](n) 3, [Ni(mu -SCN)(2)(N,N,N'-Me(3)en)](n) 4, and three mononuclear: [Ni(NCS)(2)(N,N,N'-Me(3)en)(2)] 5, [Ni(NO2)(N,N,N'-Me(3)en)(2)]PF6 6, [Ni(NO2)(2)(N,N,N'-Me(3)en)] 7. Crystal structures for 3 and 6 were determined by X-ray diffraction methods. Compound 3 may be described as a one-dimensional system with double azido bridging ligands alternately in end-on and end-to-end coordination modes. Compound 6 is a mononuclear complex in which a nitrito ligand acts as a chelate. The magnetic properties of all the compounds were studied by susceptibility measurements vs. temperature. The chi (M) vs. T plots for 1 and 2 show the typical shape for moderate antiferromagnetic one-dimensional nickel(II) complexes, while global strong antiferromagnetic behaviour with a maximum at about 200 K is observed for 3 and 4 exhibits a very weak ferromagnetic interaction. Compounds 5, 6, and 7 follow the Curie law, typical behaviour of mononuclear Ni-II compounds. The superexchange parameter J for 1, 2 and 4 was deduced from the spin Hamiltonian -J SigmaS(i)S(i + 1) and from -Sigma (J(AF)S(2i)S(2i + 1) + J(F)S(2i)S(2i - 1)) for 3. J values for 1 and 2 are -15.5 and -16.6 cm(-1), respectively, J(AF) = -132 cm(-1) and J(FM) = 99 cm(-1) for 3, and 1.34 cm(-1) for 4.