"Multielectron Redox Transformations Facilitated by Metal-Metal Interactions in Early-Late Heterobimetallic Complexes"

"As a strategy to develop new catalysts for small molecule activation and functionalization, bidentate, bifunctional phosphinoamide ligands have been used to link a Lewis acidic early transition metal (M2) to an electron-rich late transition metal (M1). The resulting heterobimetallic

complexes feature unusual dative M1-->M2 interactions.  The effect of these dative interactions on the electronic environment and redox

activity of the late transition metal center have been explored using electrochemical techniques. It has been found that in Co/Zr complexes,

multielectron reduction of Co is greatly facilitated by dative donation of electrons to Zr, allowing reduction to a formal oxidation state of

cobalt(-I) at mild reduction potentials (~ -1.65 V).  Density functional theory calculations (BP86/LANL2TZ) accurately predict the existence of a Zr-Co interaction and an enhanced metal-metal interaction upon reduction. The effects of ligand substituents on the strength of

metal-metal interactions and, thus, the redox potentials of these complexes will be discussed. In addition, the characterization and

reactivity of chemical reduction products, featuring weakly bound dinitrogen ligands, will be described."