Stereochemistry of metal tetramethylcyclam complexes directed by an unexpected anion effect

Metal(TMC) complexes (TMC = tetramethylcyclam) exclusively form trans-I diastereoisomers; thus, little is known about the trans-III isomers. Herein, we report a new method to prepare the trans-III-[Cu(TMC)]2+ complex via an anion effect. Our crystallographic, spectroscopic, and computational analyses validated that [Cu(TMC)](NO3)2 produced the trans-III complex, different from the trans-I structure of [Cu(TMC)](ClO4)2.