The chemical reactions of a family of tetradentate pyridyl/imine ligands, L1, L2, and L3 (L1 = [N,N'-bis(2-pyridinyImethylene)]ethane-1,2-diamine; L2 = [N,N'-bis(pyridin-2-yl)benzylidene]ethane-1,2-diamine; L3 = [N,N'-bis(2-pyridinylmethylene)]propane-1,3-diamine), with Ni-II in the presence of various pseudohalides (N3(-), SCN-, and NCO-) have served to prepare six different complexes, [Ni-2(L1)(2)(N-3)(2)](ClO4)(2)center dot H2O (1), [Ni-2(L2)(2)(N-3)(2)](ClO4)(2) (2), [Ni-2(L2)(2)(NCS)(4)] (3), [Ni-2(L2)(2)(NCO)(2)](ClO4)(2) (4), (Ni-2(L3)(2)(NCO)(2)](ClO4)(2) (5), and [Ni(L3)(N-3)(2)] (6), which have been characterized by X-ray crystallography. Interestingly, four of these complexes are dinuclear and exhibit end-on (EO) pseudohalide bridges (1, 2, 4, and 5), one is dinuclear and bridged exclusively by the tetradentate ligand (3), and one is mononuclear (6). The bulk magnetization of the complexes bridged by EO pseudohalides has been studied, revealing these ligands to mediate ferromagnetic coupling between the Ni-II ions, with modeled coupling constants, J, of +31.62 (1), +28.42 (2), +2.81 (4), and +1.72 (5) cm(-1) (where the convention H = -2JS(1)S(2) was used). The striking difference in the coupling intensity between N-3(-) and NCO-has prompted an investigation by means of density functional theory calculations, which has confirmed the experimental results and provided insight into the reasons for this observation.