The tetradentate “tripod-like” ligand tris(2-diphenylphosphinoethyl)amine (NP3), which has donor atoms that tend to give both low- and high-spin five-coordinate complexes, forms complexes with nickel(II) and cobalt(II) salts of the general formula [M(NP3)X]Y (where X = Cl, Br, I, NCS; Y = X or BPh4). All of the complexes are five-coordinate, probably with a trigonal-bipyramidal structure. The nickel complexes are diamagnetic. The cobalt ones are high spin when X is Cl or Br and low spin when X is NCS. When the set of donor atoms is NPSI, a high-spin complex is obtained when Y is BPh4 and a low-spin complex is formed when Y is I. The set NP3I appears to represent the crossovrr point between high- and low-spin species. In fact, both these high-and low-spin species are present together in solution in inert solvents. © 1968, American Chemical Society. All rights reserved.