Ambidentate Ligand
A monodentate ligand possessing two different potential donor atoms, either of which may bind.
Unit
Dimensionless
In depth
Only one donor atom coordinates at a time, but which one it is depends on the metal's hard or soft character and on steric factors. The existence of two binding modes gives rise to linkage isomerism, with each isomer having a distinct colour and reactivity.
Examples in the real world
The nitrite ion binding through N as nitro or through O as nitrito; thiocyanate binding through S or N.