Here we report the syntheses and crystal structures of a series of cobalt(II) and nickel(II) complexes derived from (R)NP2 ligands (where R = OMeBz, H-Bz, Br-Bz, Ph) bearing ethylene linkers between a single N and two P donors. The Co-II complexes generally adopt a tetrahedral configuration of general formula [(NP2)Co(I)(2)], wherein the two phosphorus donors are bound to the metal center but the central N-donor remains unbound. We have found one case of structural isomerism within a single crystal structure. The Co-II complex derived from (Bz)NP2 displays dual coordination modes: one in the tetrahedral complex [((Bz)NP2)Co(I)(2)]; and the other in a square pyramidal variant, [((Bz)NP2)Co(I)(2)]. In contrast, the Ni-II complexes adopt a square planar geometry in which the P(Et)N(Et)P donors in the ligand backbone are coordinated to the metal center, resulting in cationic species of formula [((R)NP2)Ni(I)](+) with iodide as counterion. All Ni-II complexes exhibit sharp H-1 and P-31 spectra in the diamagnetic region. The Co-II complexes are high-spin (S = 3/2) in the solid state as determined by SQUID measurements from 4 to 300 K. Solution electron paramagnetic resonance (EPR) experiments reveal a high-spin/low-spin Co-II equilibrium that is dependent on solvent and ligand substituent.