Manganese(II) forms structurally diverse complexes of varying nuclearity with the imidazole-containing Schiff base ligand 5-NO2-salimH(2) [5-NO2-salimH(2) 4-(2-((5-nitrosalicylidene)amino)ethyl)imidazole]. The type of complex formed is determined by the type and stoichiometry of carboxylate added to the reaction mixture. The structures of the complexes Mn(5-NO2-salimH)2, 1, and [Mn(5-NO2-salimH)(mu-HCO2)(CH3OH)](n), 2, have been characterized by X-ray crystallography and are compared to the structure of the linear trinuclear Mn(II) complex Mn-3(5-NO2-salimH)(2)(mu u-CH3CO2)(4), 3, which we reported previously [Baldwin, M. J.; Kampf, J. W.; Pecoraro, V. L. J. Chem. Sec., Chem. Commun. 1993, 1741-1743]. Complex 1 is a mononuclear complex with two meridionally bound ligands. It was crystallized in the orthorhombic space group P2(1)2(1)2(1), with Z = 8, R = 0.0605, and R(w) 0.0590. The unit cell parameters are a 17.170(4) Angstrom, b = 17.811(4) Angstrom, c 18.305(4) Angstrom, and alpha = beta = gamma = 90.000 degrees. Complex 2 is a polymeric chain with equatorial-to-axial formate bridges in the anti-anti configuration, a meridionally bound 5-NO2-salimH in the other equatorial positions, and a methanol ligating in the other axial position. It was crystallized in the orthorhombic space group Pcab (the alternative setting to Pbca), with Z = 8, R = 0.0404, and R(w) = 0.0433. The unit cell parameters are a = 8.070(2) Angstrom, b = 11.895(3) Angstrom, c 34.29(1) Angstrom and alpha = beta = gamma = 90.000 degrees. Complex 3 is a linear trimer with 5-NO2-salimH bound meridionally to each terminal Mn and three bridges from each terminal Mn to the central Mn consisting of the phenolate oxygen of the tridentate ligand, a triatomically bridging acetate, and a monatomically bridging acetate producing a unique (mu-phenolato)(mu-carboxylato-O)(mu-carboxylato-O,O’) bridging set which may be of relevance to the carboxylate shift concept.