Proton-Coupled Electron Transfer at the Pu Couple.

The synthesis and solution and solid-state characterization of [Pu(NPC)], , (NPC = [NPBu(pyrr)]; Bu = C(CH); pyrr = pyrrolidinyl) and [Pu(NPC)][K(2.2.2.

A tetrahedral neptunium(V) complex.

Neptunium is an actinide element sourced from anthropogenic production, and, unlike naturally abundant uranium, its coordination chemistry is not well developed in all accessible oxidation states. High-valent neptunium generally requires stabilization from at least one metal-ligand multiple bond, and departing from this structural motif poses a considerable challenge. Here we report a tetrahedral molecular neptunium(V) complex ([Np(NPC)][B(ArF)], 1-Np) (NPC = [NPBu(pyrr)]; Bu = C(CH); pyrr = pyrrolidinyl (N(CH)); B(ArF) = tetrakis(2,3,4,5,6-pentafluourophenyl)borate).

Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes.

The study of the redox chemistry of mid-actinides (U-Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non-aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=P Bu(pyrr) ] ; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1-M, 2-M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes.

Ligand Control of Oxidation and Crystallographic Disorder in the Isolation of Hexavalent Uranium Mono-Oxo Complexes.

The development of high-valent transuranic chemistry requires robust methodologies to access and fully characterize reactive species. We have recently demonstrated that the reducing nature of imidophosphorane ligands supports the two-electron oxidation of U to U and established the use of this ligand to evaluate the inverse-trans-influence (ITI) in actinide metal-ligand multiple bond (MLMB) complexes. To extend this methodology and analysis to transuranic complexes, new small-scale synthetic strategies and lower-symmetry ligand derivatives are necessary to improve crystallinity and reduce crystallographic disorder.

Elemental chalcogen reactions of a tetravalent uranium imidophosphorane complex: cleavage of dioxygen.

Herein we report the first example of a mononuclear uranium complex, [U(NP(pip))] (1-U), that selectively reduces dioxygen to produce a terminal oxo complex, [UO(NP(pip))] (2-U; [NP(pip)] is tris(piperidinyl)imidophosphorane). Reactions between 1-U and the heavier elemental chalcogens, S or Se, result in six-coordinate U(VI) complexes, [U(κ-E)(NP(pip))] (E = S (3-U) or Se (4-U)).

Pyrrophens: Pyrrole-Based Hexadentate Ligands Tailor-Made for Uranyl (UO) Coordination and Molecular Recognition.

Derivatives of a novel pyrrole-containing Schiff base ligand system (called "pyrrophen") are presented which feature substituted phenylene linkers (R = R = H (); R = R = CH ()) and a binding pocket modeled after macrocyclic species. These ligands bind neutral CHOH in the solid state through pyrrolic hydrogen-bonding. The interaction of the uranyl cation (UO) and yields planar hexagonal bipyramdial uranyl complexes, while the Cu and Zn complexes were found to self-assemble as dinuclear helicate complexes (ML) with under identical conditions.

Bonding Interactions in Uranyl α-Diimine Complexes: A Spectroscopic and Electrochemical Study of the Impacts of Ligand Electronics and Extended Conjugation.

Uranyl complexes of aryl-substituted α-diimine ligands gbha (--) and phen-BIAN () [gbha () = glyoxal bis(2-hydroxyanil); phen-BIAN () = ,'-bis(iminophenol)acenaphthene; R = OMe (), -bu (), H (), Me (), F (), and naphthyl ()] were designed, prepared, and characterized by X-ray diffraction, FT-IR, NMR, UV-vis, and electrochemical methods. These ligand frameworks contain a salen-type O-N-N-O binding pocket but are redox-noninnocent, leading to unusual metal complex behaviors. Here, we describe three solid-state structures of uranyl complexes , , and and observe manifestations of ligand noninnocence for the U(VI) complexes and .

Solid-state structural elucidation and electrochemical analysis of uranyl naphthylsalophen.

A salophen ligand derivative incorporating naphthalene (naphthylsalophen = [H2L]) and the corresponding uranyl (UO22+) complex have been synthesized and characterized both in solution and the solid-state. A hydrogen bonding uranyl tetramer and the electrochemical analysis of [H2L] and UO2[L] are described.