The First Dithiolene Complexes of an f-Element, Including the Cyclooctatetraene Derivative [Na(18-crown-6)(THF)][U(η8-C8H8)(C4H4S4)2], a Unique Example of a Uranium(V) Compound with Metal−Sulfur Bonds

Treatment of [U(Cp*) 2 Cl 2 ] and [U(COT)X 2 (THF) n ] (Cp* = η 5 -C 5 Me 5; COT = η 8 -C 8 H 8; X = BH 4 and n = 0, X = I and n = 2) with Na 2 dddt (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) afforded the (dithiolene)uranium (IV) compounds [U(Cp*) 2 (dddt)] ( 1 ) and [Na(18-crown-6)] 2 [U(COT)(dddt) 2 ] ( 2 ); oxidation of 2 with Ag + gave the uranium(V) complex [Na(18-crown-6)(THF)][U(COT)(dddt) 2 ] ( 3 ), the crystal structure of which revealed the exo−endo conformation of the dddt ligands.