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 [η ⁵ -1,2,4-(Me ₃ Si) ₃ C ₅ H ₂ ] ₂ UMe ₂ ( 2 ) and [η ⁵ -1,2,4-(Me ₃ Si) ₃ C ₅ H ₂ ] ₂ U(NH- p -tolyl) ₂ ( 3 ) in the presence of 4-dimethylaminopyridine (dmap) in refluxing toluene forms [η ⁵ -1,2,4-(Me ₃ Si) ₃ C ₅ H ₂ ] ₂ U═N( p -tolyl)(dmap) ( 4 ), which is a useful precursor for the preparation of the terminal uranium oxido, sulfido, and selenido metallocenes [η ⁵ -1,2,4-(Me ₃ Si) ₃ C ₅ H ₂ ] ₂ U═E(dmap) (E = O ( 5 ), S ( 6 ), Se ( 7 )) employing a cycloaddition-elimination methodology with Ph ₂ C═E (E = O, S) or ( p -MeOPh) ₂ CSe, 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 CS ₂ , while the selenido derivative 7 does not. The experimental studies are complemented by density functional theory (DFT) computations.