The treatment of Ce(OH)₄ in thionyl chloride and dimethoxyethane (DME) resulted in the formation of a highly unstable red Ce(IV) complex with the composition [CeCl₄(DME)₂] (1). From the reaction of 1 with the tripodal Kläui ligand η⁵-cyclopentadienyltris(dimethylphosphonato)cobaltate(III), [Co(η⁵-C₅H₅){P(O)(OMe)₂}₃]– (L_OMe), the two new cerium(III) complexes [Ce(L_OMe)₂(H₂O)₂]Cl·2.5H₂O (2), 1D-[Ce(μ-Cl)(L_OMe)(H₂O)₃]Cl (3) and the cerium(IV) complex [CeCl₂(L_OMe)₂]·acetone (4) were obtained and structurally characterized. The complexes 3 and 4 are the first cerium complexes featuring the L_OMe ligand together with chlorido ligands. Due to the potential exchange of the chloride counterions and ligands in 2 - 4, these complexes could serve as precursors in molecular cerium coordination chemistry. The assigned cerium oxidation states are supported by the bond valence sum (BVS) method. The ³¹P-NMR spectra with d(³¹P) = 160.20 ppm (2) and 159.43 ppm (3) are diagnostic of cerium(III).

The treatment of Ce(OH)₄ in thionyl chloride and dimethoxyethane (DME) resulted in the formation of a highly unstable red Ce(IV) complex with the composition [CeCl₄(DME)₂] (1). From the reaction of 1 with the Na[Co(η⁵-C₅H₅){P(O)(OMe)₂}₃] (NaL_OMe) salt containing the anionic tripodal Kläui ligand η⁵-cyclopentadienyltris(dimethylphosphonato)cobaltate(III), the two new cerium(III) complexes [Ce(L_OMe)₂(H₂O)₂]Cl·2.5H₂O (2), 1D-[Ce(μ-Cl)(L_OMe)(H₂O)₃]Cl (3) and the cerium(IV) complex [CeCl₂(L_OMe)₂]·acetone (4) were obtained and structurally characterized. The complexes 3 and 4 are the first cerium complexes featuring the L_OMe ligand together with chlorido ligands. Due to the potential exchange of the chloride counterions with other ligands in 2−4, these complexes could serve as precursors in molecular cerium coordination chemistry. The assigned cerium oxidation states are supported by the bond valence sum (BVS) method. The ³¹P-NMR spectra with δ(³¹P) = 160.20 ppm (2) and 159.43 ppm (3) are diagnostic of cerium(III).