Synthesis, crystal structure and magnetic properties of a new ferromagnetic nickel(II) dimer derived from a hexadentate Schiff base ligand

A new end-on bis(mu-azido) nickel(II) complex of the formula [Ni-2(L-1)(N-3)(4)] (1) (L-1 = hexadentate Schiff base ligand made from the reaction of 2 moles of 2-benzoyl pyridine and I mole of triethylenetetramine) has been prepared and characterized by single crystal X-ray diffraction studies. Each nickel center is coordinated in a distorted octahedral (NiN6) fashion consisting of three nitrogen atoms from the hexadentate ligand moiety, two nitrogen atoms from two end-on azido ligands and the last one from another terminal azido ion. The variable temperature magnetic susceptibility of compound 1 shows that the nickel centers are ferromagnetically coupled. The Ni-N-Ni bridge angles are very similar [98.36(8)degrees and 97.66(9)degrees] and the (NiNi)-Ni-... separation is 3.155(1) Angstrom. The magnetic exchange coupling constant J = 21.8 cm(-1) is consistent with the structure and the value has been compared with some similar reported compounds. (C) 2002 Elsevier Science Ltd. All rights reserved.