Stability constants have been determined for 1,2-dimethylimidazole (dmim) complexes of CoII, NiII, CuII, and ZnII by potentiometric method. Both tetrahedral and octahedral compounds are formed in the series [Co(OH2)n(dmim)x]2+ in aqueous solutions. The configurational equilibrium octahedron ⇌ tetrahedron has also been found for ZnII.