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

Reaction of the uranium(iii) metallocenium salt [(CpiPr4)2U][B(C6F5)4] with tert-butyl isocyanide (tBuNC) yielded the dicationic uranium(iv) complex [(CpiPr4)2U(CNtBu)4][B(C6F5)4]2 (1), which displays a linear metallocene geometry. Use of crude mixtures of [(CpiPr4)2U][B(C6F5)4], which contain a soluble source of iodide, led instead to isolation of the monocationic uranium(iv) iodide complex [(CpiPr4)2U(I)(CNtBu)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 (CpiPr4)2UI, resulting in isolation of (CpiPr4)2U(I)(CNtBu) (3). X-ray crystallographic and IR spectroscopic studies both showed effects ascribed to the presence of multiple strongly donating isocyanide ligands in 1.