Isocyanide adducts of tri- and tetravalent uranium metallocenes supported by tetra(isopropyl)cyclopentadienyl ligands

Abstract

Reaction of the uranium(III) metallocenium salt [(Cp^iPr4)₂U][B(C₆F₅)₄] with tert-butyl isocyanide (^tBuNC) yielded the dicationic uranium(IV) complex [(Cp^iPr4)₂U(CN^tBu)₄][B(C₆F₅)₄]₂ (1), which displays a linear metallocene geometry. Use of crude mixtures of [(Cp^iPr4)₂U][B(C₆F₅)₄], which contain a soluble source of iodide, led instead to isolation of the monocationic uranium(IV) iodide complex [(Cp^iPr4)₂U(I)(CN^tBu)₂][B(C₆F₅)₄] (2). Adduct formation with no change in oxidation state was observed upon addition of ^tBuNC to the neutral uranium(III) species (Cp^iPr4)₂UI, resulting in isolation of (Cp^iPr4)₂U(I)(CN^tBu) (3). X-ray crystallographic and IR spectroscopic studies both showed effects ascribed to the presence of multiple strongly donating isocyanide ligands in 1.