Mechanism of isomerization of Ni(cyclam) in aqueous solutions

Nickel complexes of cyclam and cyclam derivatives isomerize in aqueous solutions via two different mechanisms: i. deprotonation of one of the coordinated amino groups followed by inversion and ii. cleavage of the Ni-N bond followed by inversion. While the first mechanism is relevant for the di- and tri-valent nickel complexes, the second one occurs for the mono-valent complexes, and for complexes with tertiary amines as ligands.