Synthesis and Characterization of a Bridging Cerium(IV) Nitride Complex

Complexes featuring lanthanide-ligand multiple bonds are rare and highly reactive. They are important synthetic targets to understand 4f/5d-bonding in comparison to d-block and actinide congeners. Herein, the isolation and characterization of a bridging cerium(IV)-nitride complex: [(TriNOx)Ce(Li2 mu-N)Ce(TriNOx)][BArF4] is reported, the first example of a molecular cerium-nitride. The compound was isolated by deprotonating a monometallic cerium(IV)-ammonia complex: [CeIV(NH3)-(TriNOx)][BArF4]. The average Ce=N bond length of [(TriNOx)Ce(Li2 mu-N)Ce(TriNOx)][BArF4] was 2.117(3) angstrom. Vibrational studies of the 15N-isotopomer exhibited a shift of the Ce=N=Ce asymmetric stretch from v = 644 cm-1 to 640 cm-1, and X-ray spectroscopic studies confirm the +4 oxidation state of cerium. Computational analyses showed strong involvement of the cerium 4f shell in bonding with overall 16% and 11% cerium weight in the a- and N-bonds of the Ce=N=Ce fragment, respectively.

Automated summary

We report a rare and highly reactive lanthanide-ligand complex with multiple bonds. These complexes are important for understanding 4f/5d-bonding in comparison to d-block and actinide congeners. In this study, we isolated and characterized a bridging cerium(IV)-nitride complex: [(TriNOx)Ce(Li2 mu-N)Ce(TriNOx)][BArF4], which is the first molecular cerium-nitride. The compound was obtained by deprotonating a monometallic cerium(IV)-ammonia complex: [CeIV(NH3)-(TriNOx)][BArF4]. The Ce=N bond length in [(TriNOx)Ce(Li2 mu-N)Ce(TriNOx)][BArF4] was determined to be 2.117(3) angstrom. Vibrational and X-ray spectroscopic studies confirmed the +4 oxidation state of cerium, and computational analyses revealed the strong involvement of the cerium 4f shell in bonding.