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

Abstract

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 (<b>2</b>) and [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U(NH-<i>p</i>-tolyl)₂ (<b>3</b>) in the presence of 4-dimethylaminopyridine (dmap) in refluxing toluene forms [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂U═N(<i>p</i>-tolyl)(dmap) (<b>4</b>), 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 (<b>5</b>), S (<b>6</b>), Se (<b>7</b>)) employing a cycloaddition-elimination methodology with Ph₂C═E (E = O, S) or (<i>p</i>-MeOPh)₂CSe, respectively. Metallocenes <b>5</b>-<b>7</b> are inert toward alkynes, but they act as nucleophiles in the presence of alkylsilyl halides. The oxido and sulfido metallocenes <b>5</b> and <b>6</b> undergo [2 + 2] cycloadditions with isothiocyanate PhNCS or CS₂, while the selenido derivative <b>7</b> does not. The experimental studies are complemented by density functional theory (DFT) computations.