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

[Image: see text] 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.