Synthesis and characterization of volatile cerium(IV) hexafluoroisopropoxide complexes. Structure of [Hpmdien]2[Ce{OCH(CF3)2}6]

Abstract

The reaction between the cerium isopropoxide [Ce₂(OPrⁱ)₈(PrⁱOH)₂] and hexafluoroisopropyl alcohol (Hhfip) in THF at room temperature resulted in the formation of [Ce(hfip)₄(THF)₂(PrⁱOH)_x]. More stable compounds namely [Ce(hfip)₄(diglyme)], [Ce(hfip)₄(bipy)₂] and [Ce(hfip)₄(tmen)] were obtained if the alcoholysis was achieved in the presence of a Lewis base (diglyme = 2,5,8-trioxanonane, bipy = 2,2′-bipyridine, tmen = N,N,N′,N′-tetramethylethane-1,2-diamine). The use of N,N,N′,N″,N″-pentamethyldiethylenetriamine (pmdien) afforded [Hpmdien]₂[Ce(hfip)₆] and [Ce(hfip)₃(OPrⁱ)(pmdien)]. All compounds were volatile and characterized by elemental analyses, FT-IR, ¹H and ¹⁹F NMR. The pmdien salt was also characterized by X-ray diffraction. The cerium atom is six-co-ordinated [Ce–O 2.183(5)–2.208(5) Å] with the CF₃ groups forming nearly a crown (Ce· · ·F 4.06–4.32 Å). The metallic anion [Ce(hfip)₆]^2– and the [Hpmdien]⁺ cations are associated by a short F· · ·C contact (3.15 Å). The interactions are retained in solution as evidenced by ¹H and ¹⁹F NMR.