Coordination of isocyanide and reduction of cyclooctatetraene by a homoleptic uranium(III) aryloxide, and characterisation of the heteroleptic uranium(III) dimer [{U(N″)2(thf)(μ-I)}2]

[U(ODtbp)3] (ODtbp = O-2,6-tBu2C6H3) reacts in a 1:1 ratio with the isocyanide CN-Xyl (Xyl = 2,6-Me2C6H3) to form the pseudo-tetrahedral 4-coordinate adduct [U(CNXyl)(ODtbp)3] with νCN 24 cm−1 higher compared to the free isocyanide. Uranium(III) complexes with bulky ligands UX3 (X: ODtbp, N″ = N(SiMe3)2) react with cyclooctatetraene (COT) in a 2:1 U:COT ratio to generate the half-sandwich UIV [U(COT)X2] and [UX4] (which for X = N″ spontaneously converts into the more stable metallacycle [U(N″)2{κ2-N(SiMe3)SiMe2CH2}] and HN″), as opposed to the other potential product, the inverse COT-sandwich [(UX2)2(μ-COT)]. The heteroleptic UIII amido-iodide [{U(N″)2(thf)(μ-I)}2] can be isolated in a low yield (14%) from the 2:1 reaction of KN″ and [UI3(thf)4] in thf, and its molecular structure was shown to be dimeric with iodine atoms bridging the U centres.

No coupling, no sandwiches: reactions of simple, homoleptic U(III) complexes with bulky ligands show the potential limits at which small π-acceptor molecules can be reductively coupled, and at which cyclic δ-acceptor organics can be sandwiched by reductive activation.Figure optionsDownload as PowerPoint slide