Thermal properties and crystal structures of cobalt(III)–cyclam complexes with the bis(trifluoromethanesulfonyl)amide anion (cyclam = 1,4,8,11-tetraazacyclotetradecane)

Abstract

The bis(trifluoromethanesulfonyl)amide anion ([Tf2N]−) has frequently been used as a component of ionic liquids. To investigate the effect of this anion and alkyl substituents on the thermal properties of macrocyclic metal complexes, cobalt(III) cyclam complexes [Co(cyclam)Cl2][Tf2N] and its monoalkyl derivatives were prepared (cyclam=1,4,8,11-tetraazacyclotetradecane). The corresponding hexafluorophosphate salts were also prepared and characterized. The salts with propyl and hexyl substituents melted at 171°C and 153°C, respectively, whereas other salts decomposed above 220°C without melting. X-ray crystallography revealed the formation of intermolecular hydrogen bonds involving the NH hydrogens, which are responsible for the high melting points.