Synthesis, characterization and crystal structures of four dinuclear Schiff base nickel(II) and copper(II) complexes with versatile bridging groups

Four novel Schiff base nickel(II) and copper(II) complexes, derived from the end-on (mu(1,1)-N-3) azide, end-to-end (mu(1,3)-NCS) thiocyanate, or phenolate oxygen bridges, have been synthesized and their crystal structures determined by X-ray diffraction methods. They are the dinuclear double end-on azide-bridged [Ni-2(L1)(2)(MeCN)(2)(mu(1,1)-N-3)(2)]center dot MeOH (1), the dinuclear double end-on azide-bridged [Ni-2(L2)(2)(MeOH)(2)(mu(1,1)-N-3)(2)][Ni-2(L2)(2)(OH2)(2)-(mu(1,1)-N-3)(2)]center dot MeOH (2), the dinuclear double end-to-end thiocyanatebridged [Cu-2(L3)(2)(mu(1,3)-NCS)(2)] (3), and the dinuclear double phenolate O-bridged [Cu-2(L4)(2)(NCS)(2)] (4), where HL1 HL2, HL3 and HL4 are four tridentate Schiff bases obtained by the condensation of 3,5-dibromosalicylaldehyde with N-ethylethane-1,2-diamine, of 3,5-dichlorosalicylaldehyde with N-methylpropane-1,3-diamine, of 3-bromo-5-chlorosalicylaldehyde with 2-aminomethylpyridine, and of 5-nitrosalicylaldehyde with 2-aminomethylpyridine, respectively. Each nickel(II) atom in 1 and 2 is in an octahedral coordination, while each copper(II) atom in 3 and 4 is in a square pyramidal coordination. There exists crystallographic inversion centre symmetry in each of the complexes.