Synthesis and Structure of Uranium-Silylene Complexes

While carbene complexes of uranium have been known for over a decade, there are no reported examples of complexes between an actinide and aheavy carbene. Herein, we report the syntheses and structures of the first uranium-heavy tetrylene complexes: (CpSiMe3)(3)U-Si[PhC(NR)(2)]R' (R=tBu, R'=NMe2 1; R=iPr, R'=PhC(NiPr)(2) 2). Complex 1 features a kinetically robust uranium-silicon bonding interaction, while the uranium-silicon bond in 2 is easily disrupted thermally or by competing ligands in solution. Calculations reveal polarized sigma bonds, but depending on the substituents at silicon a substantial pi-bonding interaction is also present. The complexes possess relatively high bond orders which suggests primarily covalent bonding between uranium and silicon. These results comprise a new frontier in actinide-heavy main-group bonding.