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Linkage isomerization changes which atom of an ambidentate ligand is bound to a central atom. Its rate depends on a reaction barrier, whereas the final equilibrium depends on relative free energies.

The N-bound isomer $C$ is the thermodynamically favored form; heating accelerates access to it. Formation of $B$ retains the original metal–oxygen attachment and is a plausible kinetic control outcome. Rearranging that attachment requires overcoming an activation free energy, especially at a substitutionally inert low-spin cobalt(III) center. Raising temperature speeds the linkage isomerization, allowing the more stable N-bound nitro ligand to accumulate. Its stronger ligand field and different covalent bonding help rationalize the stability, but a larger field splitting alone is not a complete calculation of the isomerization Gibbs free energy. The classical crystallographic comparison establishes the different attachments and thermodynamic direction.^[ref]

Begin with the same ammine deprotonation and amido-assisted weakening/cleavage of the Co-S bond, but now SCN${}^{-}$ is already beside the metal. A solvent-caged pair of five-coordinate cobalt amido species and the departing thiocyanate can reorient and recombine through nitrogen before the ligand diffuses into bulk solution. Reprotonation restores the five ammines and gives A.

Thus the essential sequence isWater capture competes to give Co-OH, but rapid internal return of the already associated ligand accounts for the high yield of A. The slower entry into the reactive conjugate-base/dissociation sequence is followed by faster reorientation, capture and proton transfer. This is linkage isomerization, not oxidation or reduction of cobalt.