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The Interplay between Yttrium and Barium or Copper Trifluoroacetates and N-Methyldiethanolamine: Synthesis of a Heterometallic Y3Cu Trifluoroacetate Complex and a Homometallic Ba-TFA 1D Polymer

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Abstract

The reactions between [Y(TFA)3(H2O)3] and either [Cu(TFA)2(MeOH)] or [Ba(TFA)2] in the presence of excess N-methyldiethanolamine (mdeaH2) have been investigated in relation with their use as precursors for high Tc superconductors. They afford the heterometallic Y3Cu complex [CuY33-OH)(μ-η31-mdeaH)33311-mdeaH)22-TFA)(μ,η2-TFA)2](TFA)2(H2O) (1) and the homometallic Ba-TFA 1D polymer [Ba33-mdeaH2)2(μ-η31-mdeaH2)21-TFA)22-TFA)23221-TFA)2]1∞ (2), respectively, in high yield. These compounds were characterised by X-ray diffraction and FT-IR, ESR (for 1) and NMR (for 2) spectroscopy. Single-crystal X-ray diffraction studies show the versatile bonding modes of the trifluoroacetate and N-methyldiethanolamine ligands, with the former acting not only as a terminal (η1 and η2) or bridging-chelating (μ,η2 and μ3221) ligand but also as a counterion, whereas the latter, either protonated or partially deprotonated, binds the metal centres in a chelating (η3) or bridging-chelating (μ,η31 and μ3311) manner. The triangular Y3 unit [3.480(6)–3.550(6) Å] in the cation of 1 consists of one nine-coordinate and two eight-coordinate Y atoms, the former of which are quite scarce in alkoxide chemistry. The unique feature of the 1D polymeric structure of 2 is the secondary F···cation bond, which has not been observed so far for TFA ligands. In addition, it is the only example where the Ba atom is linked to monodentate, bidentate and bridging trifluoroacetate ligands simultaneously. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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