Equilibrium populations of the dinucleating ligand H5(F-HXTA) (5-fluoro-2-hydroxy-1,3-xylene-α,α′-diamine-N,N,N′,N′-tetraacetic acid) in the presence of pairs of divalent metal ions were measured by 19F NMR to assess the relative stability of the heterobimetallic complex [MaMbL]− (L = F-HXTA5−). Homobimetallic Fe(II), Zn(II) and Mg(II) complexes of F-HXTA having the general formula [M(H2O)6][M2(F-HXTA)(H2O)x]2 yH2O have been characterized by single crystal X-ray diffraction (x = 4, y = 14 for Fe(II) and Mg(II); x = 3, y = 10 for Zn(II)) and 1H and 19F NMR data show the complex ions retain their structures in aqueous solution. Equilibrium constants for metal exchange between [Ma2L]− and [Mb2L]− to produce [MaMbL]− were measured to be Kex = 4.4 ± 0.3 for Fe(II)/Zn(II), 4.15 ± 0.07 for Mg(II)/Fe(II) and 5.59 ± 0.09 for Mg(II)/Zn(II). This trend of enhanced relative stability of the heterobimetallic state (Kex > 1) agrees with a previous report on the stability of Fe(II)/Mn(II) F-HXTA complexes. Density functional theory (DFT) and natural bond orbital (NBO) analysis were used to simulate metal exchange in the Zn(II)/Mg(II) system (Kcalc = 13) and revealed increased charge transfer between the bridging phenoxo ligand and metal ions in the lower symmetry environment of the heterobimetallic complex.