Oxidation of europium with ammonium perfluorocarboxylates in liquid ammonia: pathways to europium(II) carboxylates and hexanuclear europium(III) fluoridocarboxylate complexes

The novel coordination polymer [Eu(O2CCF3)(2)(dmf)(2)](infinity) (1) (dmf = N,N-dimethylformamide) containing europium(II) and the two new compounds (NH4)(2)[Eu6F8(O2CCF3)(12)(CF3COOH)(6)] (2) and (NH4)(2)[Eu6F8(O2CC2F5)(12)(C2F5COOH)(6)]center dot 8C(2)F(5)COOH (3), both based on hexanuclear europiate(III) complexes, were synthesized from precursors with a Eu2+ : Eu3+ ratio >1, obtained by reaction of europium metal with ammonium perfluorocarboxylates in liquid ammonia. In the crystal structure of 1 the europium(II) ions are bridged by carboxylate groups and N,N-dimethylformamide to form polymeric chains with Eu2+center dot center dot center dot Eu2+ distances of 408.39(13)-410.49(13) pm. The compound crystallizes in the triclinic space group P1 (Z = 2). To the best of our knowledge, this is the first example of a (solvated) perfluorocarboxylate containing a lanthanoid in a subvalent oxidation state. In the crystal structures of 2 and 3 the europium(III) ions are bridged by fluoride ions and carboxylate groups to form hexanuclear complex anions with an octahedral arrangement of the cations. The Eu3+center dot center dot center dot Eu3+ distances are in the range of 398.27(15)-400.93(15) pm in 2 and 395.37(4)-399.78(5) pm in 3, respectively. Both compounds crystallize in the monoclinic space group type P2(1)/n (Z = 4) and are the first examples of octahedro-hexanuclear europium carboxylates for which fluoride is reported as a bridging ligand. In all compounds the oxidation state of europium was monitored via Eu-151 Mossbauer and photoluminescene spectroscopy.

Automated summary

The novel coordination polymer [Eu(O2CCF3)(2)(dmf)(2)](infinity) containing europium(II) and the two new compounds based on hexanuclear europiate(III) complexes were synthesized, with the oxidation state of europium monitored via Eu-151 Mossbauer and photoluminescence spectroscopy.