Expanding a family of cobalt bimetallic complexes, we report the synthesis of the Ti(III) metalloligand, Ti[N(o(NCH2P(P-i(r))(2))C6H4)(3)] (abbreviated as Tit), and three heterobimetallics that pair cobalt with an early transition metal ion: CoTiL (1), K(crypt-222) [(N-2)CoVL] (2), and K(crypt-222)[(N-2)CoCrL] (3). The latter two complexes, along with previously reported K(crypt-222)[(N-2)CoAlL] and K(crypt-222) [(N-2)Co2L], constitute an isostructural series of cobalt bimetallics that bind dinitrogen in an end-on fashion, i.e. [(N-2)CoML](-). The characterization of 1-3 includes cyclic voltammetry, X-ray crystallography, and infrared spectroscopy. The [CoTiL](0/-) reduction potential is extremely negative at -3.20 V versus Fc(+)/Fc. In the CoML series where M is a transition metal, the reduction potentials shift anodically as M is varied across the first-row period. Among the [(N-2)CoML](-) compounds, the dinitrogen ligand is weakly activated, as evidenced by N N bond lengths between 1.110(8) and 1.135(4) angstrom and by N-N stretching frequencies between 1971 and 1995 cm(-1). Though changes in nu(N2) are subtle, the extent of N-2 activation decreases across the first-row period. A correlation is found between the [CoML](0/-) reduction potentials and N-2 activation, where the more cathodic potentials correspond to lower N-N frequencies. Theoretical calculations of the [(N-2)CoML](-) complexes reveal important variations in the electronic structure and Co-M interactions, which depend on the exact nature of the supporting metal ion, M.