Five new nickel(11) complexes [Ni2L2(N 3)2(H2O)2] (1), [Ni 2L2(NO3)2] (2), [Ni 2L2(O2CPh)(CH3OH) 2]CIO4.0.5CH3OH (3), [Ni3L 2(O2CPh)4] (4), and [Ni2L 2(NO2)2]n (5) have been synthesized by using a tridentate Schiff base ligand, HL (2-[(3-Methylamino-propylimino)- methyl]-phenol), and the polyatomic monoanions N3-, NO3-, PhCOO", or NO2-. The complexes have been structurally and magnetically characterized. The structural analysis reveals that in all five complexes, the Ni(11) ions possess a distorted octahedral geometry. Complexes 1 and 2 are dinuclear with di-μ-1, 1-azido and di-μ2-phenoxo bridges, respectively. Complex 3 is also a di-μ2-phenoxo-bridged dinuclear Ni(11) complex but has an additional syn-syn benzoate bridge. Compound 4 possesses a linear trinuclear structure with the tridentate Schiff base ligand coordinated to the terminal nickel atoms which are linked to the central Ni(11) by phenoxo and carboxylate bridges. Complex 5 consists of a dinuclear entity, bridged by di-μ2-phenoxo together with a c/s-(μ-nitrito-1κO: 2κN) nitrite ion. The dinuclear units are linked each other by another bridging trans-(μ-nitrito-1κO:2κN) nitrite to form a Ni(11) chain that shows the presence of unprecedented alternating cis- and trans-N, O bridging mode of the nitrite anion. Variable-temperature magnetic susceptibility measurements of complex 1 indicate the presence of ferromagnetic exchange interactions within the dimer (J = 23.5(3) cm-1) together with antiferromagnetic interdimer interactions (J = -0.513(3) cm-1), whereas compounds 2 and 3 show intradimer antiferromagnetic interactions (J= -24.27(6) and -16.48(4) cm-1, respectively). Ferromagnetic coupling (J = 6.14(2) cm-1) is observed in complex 4 for the linear centro-symmetric Ni(11) trimer, whereas complex 5 shows an alternating intra-chain antiferromagnetic coupling (J1 = -32.1(1) cm-1 and J2 = -3.2(1) cm-1). © 2009 American Chemical Society.