Transition-metal complexes with monodentate oxime ligands | Poster Board #1202

Ligands with oxime functional groups are noted for their ability to stabilize normally inaccessible oxidation states, such as nickel(III) or copper(III). Previous efforts in our group have focused on tetradentate ligands with three oxime groups. Here, we present work with monodentate ligands having a single oxime functional group (see below). These monodentate ligands are, in fact, the “arms” of our tetradentate ligands. To-date, three ligands have been synthesized and characterized by ¹H-NMR spectroscopy. Also, complexes with three different Cu(II) salts have been synthesized. These complexes have been characterized via pronounced color changes and by UV-Vis spectroscopy. However, attempts to synthesize complexes with Ni(II) salts have proven unsuccessful; this is not unexpected, given the relative reactivity of first-row transition metals (the Irving-Williams series). Oxidations of these complexes have been attempted using ammonium cerium(IV) salts. The observed color changes indicate the absorbances are shifting to shorter wavelengths, suggesting the metal center is in a higher oxidation state. Ultimately, the actual charge of the metal centers will be determined by measuring the number of unpaired electrons with a magnetic susceptibility balance.