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Ellika Nordin coauthored crystal-structure comparisons of nitrito- and nitropentaamminecobalt(III) salts. The structures distinguish coordination through oxygen from coordination through nitrogen.

This is linkage isomerism: the same ligand composition can bind through different donor atoms. Structural evidence from a solid identifies the coordinated form, while solution interconversion requires separate kinetic evidence.^[ref]

Ingmar Grenthe coauthored research on linkage isomerization.^[ref]

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]