Uranium-Mediated Peroxide Activation and a Precursor toward an Elusive Uranium -Dioxo Fleeting Intermediate.

The activation of chalcogen-chalcogen bonds using organometallic uranium complexes has been well documented for S-S, Se-Se, and Te-Te bonds. In stark contrast, reports concerning the ability of a uranium complex to activate the O-O bond of an organic peroxide are exceedingly rare. Herein, we describe the peroxide O-O bond cleavage of 9,10-diphenylanthracene-9,10-endoperoxide in nonaqueous media, mediated by a uranium(III) precursor [((ArO)N)U(dme)] to generate a stable uranium(V) bis-alkoxide complex, namely, [((ArO)N)U(DPAP)].

Homoleptic Acetylacetonate (acac) and β-Ketoiminate (acnac) Complexes of Uranium.

Transmetalation of potassium salts of differently substituted acetylacetonate (acac) and β-ketoiminate (acnac) with [U(I)(dioxane)] and [U(I)(dioxane)] resulted in the formation of homoleptic, octahedral complexes [U(acnac)] (with acnac = 2,2,6,6-tetramethyl-5-(phenylimino)heptan-3-onate) in the oxidation states +III and +IV and the homoleptic, square prismatic complexes [U(acnac)] (with acnac = 4-(phenylimino)pentan-2-onate) and the homoleptic, square antiprismatic complexes [U(acac)] [with acac = 2,2,6,6-tetramethyl-3,5-heptanedionate (acac), 2,2,6,6-tetramethyl,4-methyl-3,5-heptanedionate (acac), and 2,2,6,6-tetramethyl-4-phenyl-3,5-heptanedionate (acac)] in oxidation states +III, +IV, and +V. Oxidation of [U(acnac)] () with AgOTf yielded [U(acnac)][OTf] (), which was fully characterized by single-crystal X-ray diffraction analysis, a combination of ultraviolet/visible/near-infrared, nuclear magnetic resonance, and infrared spectroscopies, and solid-state superconducting quantum interference device magnetization studies. Complexation of the sterically less encumbering ligand derivative acnac provided access to the tetravalent, square antiprismatic complex [U(acnac)] ().

From Chemical Curiosities and Trophy Molecules to Uranium-Based Catalysis: Developments for Uranium Catalysis as a New Facet in Molecular Uranium Chemistry.

Catalysis remains one of the final frontiers in molecular uranium chemistry. Depleted uranium is mildly radioactive, continuously generated in large quantities from the production and consumption of nuclear fuels and accessible through the regeneration of "uranium waste". Organometallic complexes of uranium possess a number of properties that are appealing for applications in homogeneous catalysis.

Catalytic Carbonylative Rearrangement of Norbornadiene via Dinuclear Carbon-Carbon Oxidative Addition.

Single bonds between carbon atoms are inherently challenging to activate using transition metals; however, ring-strain release can provide the necessary thermodynamic driving force to make such processes favorable. In this report, we describe a strain-induced C-C oxidative addition of norbornadiene. The reaction is mediated by a dinuclear Ni complex, which also serves as a catalyst for the carbonylative rearrangement of norbornadiene to form a bicyclo[3.

Dinuclear oxidative addition reactions using an isostructural series of Ni, Co, and Fe complexes.

A family of low-valent Ni, Co, and Fe naphthyridine-diimine (NDI) complexes is presented. Ligand-based π* orbitals are sufficiently low-lying to fall within the metal 3d manifold, resulting in electronic structures that are highly delocalized across the conjugated [NDI]M system. This feature confers stability to metal-metal interactions during two-electron redox reactions, as demonstrated in a prototypical oxidative addition of allyl chloride.

Well-Defined Models for the Elusive Dinuclear Intermediates of the Pauson-Khand Reaction.

The mechanism of the Pauson-Khand reaction has attracted significant interest due to the unusual dinuclear nature of the Co2 (CO)x active site. Experimental and computational data have indicated that the intermediates following the initial Co2 (CO)6 (alkyne) complex are thermodynamically unstable and do not build up in appreciable concentrations during the course of the reaction. As a consequence, the key steps that control the scope of viable substrates and various aspects of selectivity have remained largely uncharacterized.

Effect of Bronsted Acids and Bases, and Lewis Acid (Sn(2+)) on the Regiochemistry of the Reaction of Amines with Trifluoromethyl-β-diketones: Reaction of 3-Aminopyrrole to Selectively Produce Regioisomeric 1H-Pyrrolo[3,2-b]pyridines.

Reaction of 3-aminopyrrole (as its salt) with trifluoromethyl-β-diketones gave γ-1H-pyrrolo[3,2-b]pyridines via reaction at the less reactive carbonyl group. The trifluoromethyl group increased the electrophilicity of the adjacent carbonyl group and decreased the basicity of the hydroxyl group of the CF3 amino alcohol formed. This amino alcohol was formed faster, but its subsequent dehydration to the β-enaminone was slow resulting in the preferential formation of the γ-regioisomer.

Dinuclear nickel complexes in five states of oxidation using a redox-active ligand.

Redox-active nitrogen donor ligands have exhibited broad utility in stabilizing transition metal complexes in unusual formal oxidation states and enabling multielectron redox reactions. In this report, we extend these principles to dinuclear complexes using a naphthyridine-diimine (NDI) framework. Treatment of ((i-Pr)NDI) with Ni(COD)2 (2.

Four mechanisms in the reactions of 3-aminopyrrole with 1,3,5-triazines: inverse electron demand Diels-Alder cycloadditions vs S(N)Ar reactions via uncatalyzed and acid-catalyzed pathways.

Reaction of 3-aminopyrrole with seven 1,3,5-triazines was studied in a one-step reaction (in situ formation of 3-aminopyrrole) and a two-step reaction (using the tetraphenylborate salt and an amine base). An inverse-electron demand Diels-Alder reaction (IEDDA) was observed with R1 = CF3, CO2Et, and H with the formation of 5H-pyrrolo[3,2-d]pyrimidine derivatives. S(N)Ar was observed when 2,4,6-trifluoro- or 2,4,6-trichloro-1,3,5-triazine were used--1,3,5-triazines that had leaving groups.

A synthesis of α-amino acids via direct reductive carboxylation of imines with carbon dioxide.

A method for the synthesis of α-amino acids by direct reductive carboxylation of aromatic imines with CO2 is described. The protocol employs readily available commercial reagents and serves as a one-step alternative to the Strecker synthesis.