A Comprehensive Study Concerning the Synthesis, Structure, and Reactivity of Terminal Uranium Oxido, Sulfido, and Selenido Metallocenes

Terminal uranium oxido, sulfido, and selenido metallocenes
were
synthesized, and their reactivity was comprehensively studied. Heating
of an equimolar mixture of [η5-1,2,4-(Me3Si)3C5H2]2UMe2 (2) and [η5-1,2,4-(Me3Si)3C5H2]2U(NH-p-tolyl)2 (3) in the presence of 4-dimethylaminopyridine
(dmap) in refluxing toluene forms [η5-1,2,4-(Me3Si)3C5H2]2UN(p-tolyl)(dmap) (4), which is a useful precursor
for the preparation of the terminal uranium oxido, sulfido, and selenido
metallocenes [η5-1,2,4-(Me3Si)3C5H2]2UE(dmap) (E = O (5), S (6), Se (7)) employing a cycloaddition–elimination
methodology with Ph2CE (E = O, S) or (p-MeOPh)2CSe, respectively. Metallocenes 5–7 are inert toward alkynes, but they act as
nucleophiles in the presence of alkylsilyl halides. The oxido and
sulfido metallocenes 5 and 6 undergo [2
+ 2] cycloadditions with isothiocyanate PhNCS or CS2, while
the selenido derivative 7 does not. The experimental
studies are complemented by density functional theory (DFT) computations.