The enthalpy differences (DeltaHdegrees) of the equilibrium between the octahedral and tetrahedral solvated cobalt(II) complexes were obtained in some primary alkylamines such as propylamine (pa, 36.1 +/- 2.3 kJ mol(-1)), n-hexylamine (ha, 34.9 +/- 1.0 kJ mol(-1)), 2-methoxyethylamine (meea, 44.8 +/-3.1 kJ mol(-1)), and benzylamine (ba, 50.1 +/- 3.6 kJ mol(-1)) by the spectrophotometric method. The differences in the energy levels between the two geometries of the cobalt(II) complexes in the spherically symmetric field (DeltaE(spher)) were estimated from the values of DeltaHdegrees by offsetting the ligand field stabilization energies. It was indicated that the value of DeltaE(spher) is the decisive factor in determining the value of DeltaHdegrees and is largely dependent on the electronic repulsion between the d-electrons and the donor atoms and the interelectronic repulsion in the d orbitals. The comparison between activation enthalpies (DeltaH(not equal)) for the solvent exchange reactions of octahedral cobalt(II) ions in pa and meea revealed that the unexpectedly large rate constant and small DeltaH(not equal) in pa are attributed to the strong electronic repulsion in the ground state and removal of the electronic repulsion in the dissociative transition state, which can give the small DeltaE(spher) between the ground and transition states. Differences in the solvent exchange rates and the DeltaH(not equal) values of the octahedral metal(II) ions in some other solvents are discussed in connection with the electronic repulsive factors.