Reductive Silylation of the Uranyl Ion with Ph₃SiOTf

The reaction of 2 equiv of Ph₃SiOTf with UO₂(dbm)₂(THF) (dbm = <i>O</i>C­(Ph)­CHC­(Ph)<i>O</i>) and UO₂(^Aracnac)₂ (^Aracnac = Ar<i>N</i>C­(Ph)­CHC­(Ph)<i>O</i>; Ar = 3,5-^tBu₂C₆H₃) results in the formation of U­(OSiPh₃)₂(dbm)₂(OTf) (<b>1</b>) and [U­(OSiPh₃)₂(^Aracnac)₂]­[OTf] (<b>2</b>), respectively, in good yield

Oxidation of the 14-Membered Macrocycle Dibenzotetramethyltetraaza[14]annulene upon Ligation to the Uranyl Ion

Reaction of Li₂(tmtaa) (tmtaaH₂ = dibenzotetramethyltetraaza[14]­annulene) with 1 equiv of [UO₂Cl₂(THF)₃], in an attempt to form <i>cis</i>-[UO₂(tmtaa)], affords the bis­(uranyl) complex [Li­(THF)₃]­[Li­(THF)₂]­[(UO₂Cl₂)₂(tmtaa)] (<b>1</b>) as a red-brown crystalline solid in modest yield. Complex <b>1</b> can be synthesized rationally by reaction of Li₂(tmtaa) with 2 equiv of [UO₂Cl₂(THF)₃]. Under these conditions, it can be isolated in 44% yield. In the solid state, complex <b>1</b> features two [UO₂Cl₂]­ fragments that are bridged by a highly puckered (tmtaa)^2– ligand. Both uranyl fragments feature normal uranyl metrical parameters (U–O (av.) = 1.78 Å, O–U–O = 176.8(3)° and 178.0(3)°). The most notable structural feature of <b>1</b>, however, is the presence of a lithium cation that coordinates to an oxo ligand from each uranyl fragment. In contrast to the Li₂(tmtaa) reaction, addition of [K­(DME)]₂[tmtaa] to 1 equiv of [UO₂Cl₂(THF)₃] results in formation of the 2e^– oxidation products of (tmtaa)^2–. Three isomers of C₂₂H₂₂N₄ (compounds <b>2</b>, <b>3</b>, and <b>4</b>) were isolated as a mixture of orange crystals in 41% combined yield. All three isomers were characterized by X-ray crystallography. We hypothesize that these ligand oxidation products are formed upon decomposition of the unobserved cis uranyl intermediate, <i>cis</i>-[UO₂(tmtaa)], which undergoes a facile intramolecular redox reaction