Hydroxylation of N-heterocycle ligands observed in two unusual mixed-valence Cu(I)/Cu(II) complexes.

Abstract

The chelate ligands 2,2 -bipyridine (bpy), 1,10-phenanthroline (phen), and their substituted derivatives have played an important role in the development of coordination chemistry,[1, 2] and over the decades a number of so-called anomalies have been reported in reactions of their metal complexes. To rationalize the anomalous properties of complexes such as [M(bpy)3] and [M(phen)3] , Gillard borrowed the idea of TMcovalent hydrates∫ from the organic literature and proposed an interesting mechanism,[3] the core of which is nucleophilic attack of a hydroxide ion on a coordinated heterocyclic ligand to form a covalent hydrate (CH); this may react further by intramolecular shift of OH or H2O onto the metal before the formation of the final products (Scheme 1). The mechanism