title: Synthesis of electron-rich uranium(IV) complexes supported by tridentate Schiff base ligands and their multi-electron redox chemistry.
abstract: The synthesis, structure, and reactivity of a new complex of U(IV) with the tridentate Schiff base ligand Menaphtquinolen are reported. The reduction of the bis-ligand complexes [UX2((Me)naphtquinolen)2] (X = Cl, (1-Cl) ; I (1-I)) with potassium metal affords the U(IV) complex of the new tetranionic hexadentate ligand μ-bis-(Me)naphtquinolen formed through the intramolecular reductive coupling of the imino groups of each (Me)naphtquinolen unit. The solid state structure of the [U(μ-bis-(Me)naphtquinolen)]2 dimer 2 isolated from toluene confirms the presence of a U(IV) complex of the reduced ligand. Reactivity studies with molecular oxygen and 9,10-phenanthrenequinone show that complex 2 can act as a multielectron reducing agent releasing two electrons through the cleavage of the C-C bond to restore the original imino function of the ligand. In the resulting U(IV) and U(VI) complexes [U(9,10-phenanthrenediol)((Me)naphtquinolen)2], 3, and [UO2((Me)naphtquinolen)2], 4, the restored tridentate Schiff base allows for the coordination of the reduced substrate to the metal. Electrochemical studies of complex 2 show the presence of irreversible ligand centered reduction processes and of a reversible U(IV)/U(III) couple.
authors.affiliation: Laboratoire de Reconnaissance Ionique et Chimie de Coordination, SCIB, UMR-E CEA/UJF-Grenoble 1, INAC, CEA-Grenoble, 17 rue des Martyrs, Grenoble, F-38054, France.
authors.forename: Clément
authors.initials: C
authors.lastname: Camp
authors.forename: Julie
authors.initials: J
authors.lastname: Andrez
authors.forename: Jacques
authors.initials: J
authors.lastname: Pécaut
authors.forename: Marinella
authors.initials: M
authors.lastname: Mazzanti