REACTIONS OF A URANIUM(IV) TERTIARY ALKYL BOND - FACILE LIGAND-ASSISTED REDUCTION AND INSERTION OF ETHYLENE AND CARBON-MONOXIDE

Reaction of (MeC(5)H(4))(3)X (X = Cl, MeC(5)H(4)) with t-BuLi affords the tertiary alkyl complex (MeC(5)H(4))(3)U(t-BU) Despite uranium(IV) generally being the preferred oxidation state in organometallic system s, (MeC(5)H(4))(3)U(t-Bu) reacts with Lewis bases (L = PMe(3), THF, RC N, RNC) to yield the reduced uranium(III) base adducts (MeC(5)H(4))(3) U(L) Carbon monoxide undergoes migratory insertion into the metal tert iary alkyl bond. The resulting acyl derivative decomposes at 90 degree s C to yield insoluble uranium-containing products and a mixture of te rt-butyltoluenes by ring expansion of a methylcyclopentadienyl ligand. Ethylene also undergoes migratory insertion into the metal tertiary a lkyl bond. No subsequent insertion of ethylene into the metal carbon b ond takes place after the first equivalent has inserted. In marked con trast, reaction of various (MeC(5)H(4))(3)ThX (X = Cl, I, MeC(5)H(4), O-2,6-Me(2)C(6)H(3), OTs) compounds with t-BuLi gave intractable mater ials. However, reaction of the cationic species [(RC(5)H(4))(3)Th](BPh (4)) (R = Me(3)Si, t-Bu) with t-BuLi yields the new thorium hydrides ( RC(5)H(4))(3)ThH.