This paper describes the synthesis and reactivity of [η⁵-1,3-(Me₃Si)₂C₅H₃]₂U(P-2,4,6-ⁱPr₃C₆H₂)(OPMe₃) (6) which is accessible from a ligand exchange reaction between [η⁵-1,3-(Me₃Si)₂C₅H₃]₂U(P-2,4,6-ⁱPr₃C₆H₂)(OPPh₃) (2) and Me₃PO at ambient temperature. Phosphinidene 6 exhibits no reactivity towards internal alkynes, but readily reacts with various hetero-unsaturated molecules such as isothiocyanates, aldehydes, nitriles, isonitriles, and organic azides, forming uranium sulfido, oxido, imido, and uranaheterocyclic compounds. Nevertheless, with the bidentate ortho-dicyanobenzene o-C₆H₄(CN)₂ the zwitterionic species [η⁵-1,3-(Me₃Si)₂C₅H₃]₂U[NHC(N){C₆H₄CP(2,4,6-ⁱPr₃C₆H₂)CH₂PMe₂O}] (13) is isolated in good yield. Moreover, 6 converts with Ph₂S₂ to the uranium(III) phenylthiolate compound [η⁵-1,3-(Me₃Si)₂C₅H₃]₂USPh(OPMe₃) (7) in good isolated yield. Furthermore, the influence of the Lewis base on the reactivity of the uranium phosphinidene metallocenes has also been evaluated.