Synthesis and small molecule reactivity of uranium(IV) alkoxide complexes with both bound and pendant N-heterocyclic carbene ligands

The syntheses of two tetravalent uranium alkoxide‐carbene complexes are reported, [UIL3], and [UL4] where L=OCMe2CH2[1‐C(NCHCHNiPr)]. The latter shows dynamic behaviour of the alkoxycarbene ligands in solution at room temperature, and the crystal structure of [UL4] shows that one carbene group remains uncoordinated. The unbound N‐heterocyclic carbene group is trapped by a range of reagents such as 16‐valence‐electron metal carbonyl fragments and BH3 moieties, forming, for example, [UL3(μ‐L)W(CO)5], [UL2(μ‐L)2Mo(CO)4], and [ULn(L‐BH3)4−n] (n=1–4), demonstrating the potential for these hemilabile electropositive metal–carbene complexes to participate in the bifunctional activation of small molecules