= Solution
The near absence of incoming $^{14}$C label means the coordinated thiocyanate usually retains its \b[molecular identity] during linkage change. A mechanism that releases it into a fully mixed solution pool and then captures an arbitrary external thiocyanate would predict much more exchange.
Rapid geminate return within a <solvent cage> explains the result: the original ligand turns and binds through N before an external labeled ligand can intercept the cobalt centre. A continuously bound intramolecular rearrangement is also compatible with low exchange. Therefore the label result supports an intramolecular/cage-local process but does not alone prove that the Co-S bond stays unbroken throughout.
<Base hydrolysis of pentaamminecobalt complexes by W. Gregory Jackson and C. N. Hookey>{ref}
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