Cerium(IV) Phosphido Complexes

Although the development of tetravalent lanthanide complexes has accelerated recently, it still lags far behind that of their trivalent congeners. Herein, we report the synthesis and structural characterization of the first tetravalent lanthanide phosphido complexes, [(Im^tBuN)₃Ce^IVP(SiMe₃)Ar] (Ar = C₆H₅ (1), C₆H₃-2,6-ⁱPr₂ (2)). Single-crystal X-ray diffraction reveals a pyramidal geometry around the phosphorus atom in 1, whereas a trigonal planar geometry and a shorter Ce-P distance in 2 suggest the presence of a Ce-P π-interaction alongside the σ-bond. Computational studies corroborate these findings, revealing polarized Ce-P bonds with significant double-bond character. Notably, f-orbital contributions are substantial for both σ-type (28-51%) and π-type (67%) bonding interactions. Preliminary reactivity studies demonstrate that complex 1 undergoes addition reactions with AdN₃ and Ph₂CN₂, rather than redox processes.