Cerium(IV) Imido Complexes: Structural, Computational, and Reactivity Studies.

A series of alkali metal capped cerium(IV) imido complexes, [M(solv)x][Ce═N(3,5-(CF3)2C6H3)(TriNOx)] (M = Li, K, Rb, Cs; solv = TMEDA, THF, Et2O, or DME), was isolated and fully characterized. An X-ray structural investigation of the cerium imido complexes demonstrated the impact of the alkali metal counterions on the geometry of the [Ce═N(3,5-(CF3)2C6H3)(TriNOx)]− moiety. Substantial shortening of the Ce═N bond was observed with increasing size of the alkali metal cation. The first complex featuring an unsupported, terminal multiple bond between a Ce(IV) ion and a ligand fragment was also isolated by encapsulation of a Cs+ counterion with 2.2.2-cryptand. This complex shows the shortest recorded Ce═N bond length of 2.077(3) A. Computational investigation of the cerium imido complexes using DFT methods showed a relatively larger contribution of the cerium 5d orbital than the 4f orbital to the Ce═N bonds. The [K(DME)2][Ce═N(3,5-(CF3)2C6H3)(TriNOx)] complex cleaves the Si—O bond in (Me3Si)2O, yielding the [(...