A single H-bond triggers the formation of a cleft around EtNH through bond rearrangement and rotations of arms in both Co(III) and Fe(III) complexes.

The single H-bond capable N-H in triethylammonium triggers massive structural rearrangement in an inert Co(III) complex that tetraethylammonium cannot. The rearrangement provides a new way to distinguish two similar cations spectroscopically. The process is identical and instantaneous with labile iron(III) without any spectroscopic change.