Rearrangement of imidazolidine to piperazine rings in the presence of Dy^III

The formation of imidazolidines from secondary amines and aldehydes is well known. This small cycle can act as nitrogen donor, and it is usually stable when it coordinates to metal ions. Sometimes, the imidazolidines as ligands undergo breaking of the C-N bond when coordinating to the metal centre, yielding related amines. However, the reorganisation of the imidazolidine to a piperazine ring is a quite unusual process. In this work, we describe the transformation of a zinc complex with a ligand containing two imidazolidine moieties into a zinc complex with two piperazine fragments as donors, in the presence of a dysprosium salt.