title: The disproportionation of [Ni(tacn)]2+ in Ni2+ and [Ni(tacn)2]2+ crystallographically demonstrated (tacn = 1,4,7-triazacyclononane).
abstract: From an EtOH/H2O solution, 0.3 M each of Ni(2+) and cyclic triamine tacn (2; tacn = 1,4,7-triazacyclononane), after 10 min refluxing and cooling at room temperature, copious and comparable amounts of blue crystals (containing the complex [Ni(tacn)(H2O)3](2+)) and pink crystals (containing in the same cell both [Ni(H2O)6](2+) and [Ni(tacn)2](2+)) precipitated. This unusual behaviour is ascribed to the fact that at the refluxing temperature the three species are present at the equilibrium in similar concentrations, which are frozen on cooling, due to the inertness of the macrocyclic complexes [Ni(tacn)(H2O)3](2+) and [Ni(tacn)2](2+).
authors.affiliation: Dipartimento di Chimica, Università di Pavia via Taramelli 12, 27100 Pavia, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Amendola
authors.forename: Massimo
authors.initials: M
authors.lastname: Boiocchi
authors.forename: Luigi
authors.initials: L
authors.lastname: Fabbrizzi
authors.forename: Nadia
authors.initials: N
authors.lastname: Fusco
authors.forename: Elisa
authors.initials: E
authors.lastname: Valeri
keywords: crystal structures; inertness; lability; macrocycles; nickel