Lanthanide-containing POMs are in general less investigated than their 3d-transition-metal analogs, but recently there have been more reports on the former class. POMs-containing lanthanides show interesting properties in areas such as photoluminescence, catalysis, electrochemistry, and magnetism. Due to their larger sizes and consequently larger coordination numbers compared to 3d transitionmetal ions, lanthanide ions exhibit a different coordination mode to lacunary POM precursors resulting in novel and sometimes unexpected structure.
Lacunary POM precursors containing a hetero group with a lone pair of electrons (e. g. AsIII, SbIII) are of particular interest, because the lone pair does not allow the closed Keggin unit to form, resulting in a very different reactivity as compared to lacunary POMs with a tetrahedral hetero group. The claw-shaped [As2W19O67(H2O)]14− (As2W19) precursor is a member of this subclass, and its structure can be rationalized as two [B-α-AsW9O33]9− (AsW9) units linked through a WO6 group via four equatorial W-O-W bonds and trans-related terminal oxo and aqua ligands. The dilacunary polyanion As2W19 was first reported by Tourn´e et al. in 1973, and its structure was confirmed later by our group using single-crystal X-ray diffraction. Incorporation of an additional W-bridge in the dilacunary As2W19 unit results in the monolacunary [As2W20O68(H2O)]10− (As2W20), which was first reported by Herv´e and coworkers. Interaction of As2W19 with di- and trivalent transition metal and main group elements has been investigated by different groups and has resulted in the expected disubstituted products [M2As2W19O67(H2O)3]n− (n = 10; M = Mn2+, Co2+, Ni2+, Cu2+, Zn2+, VO2+; n = 8; M = Mn3+, Fe3+, Ga3+).
Our group has also been working in the area of lanthanide-containing polyoxotungstates, and we have isolated species incorporating between one and twenty lanthanide centers. We have also investigated the interaction of both As2W19 and As2W20 with ytterbium(III) ions in aqueous acidic (pH = 2) medium, resulting in both cases in [YbAs2W20O68(H2O)3]7−. This polyanion consists of two AsW9 units connected by a triangular [YbW2O2(H2O)3]11+ unit which is composed of two 6-coordinated tungsten centers and a 7-coordinated YbIII ion, all carrying one terminal water ligand.
- Mono- and Di-Lanthanide Derivatives of 19-Tungsto-2-Arsenate(III)
Ismail, A. H.; Bassil, B. S.; Römer, I.; Redeker, N. C.; Kortz, U., Z. Naturforsch. B, 2010, 65b, 383-389. [Read Online]
- Synthesis and Structural Characterization of the 28-Isopolytungstate Fragment [H2W28O95]20- Stabilized by two External Lanthanide Ions [Ln2(H2O)10W28O93(OH)2]14-
Ismail, A. H.; Bassil, B. S.; Suchopar, A.; Kortz, U. Eur. J. Inorg. Chem. 2009, 5247-5252. [Read Online]
- The 22-Isopolytungstate Fragment [H2W22O74]14- Coordinated to Lanthanide Ions
Ismail, A. H.; Dickman, M. H.; Kortz, U. Inorg. Chem. 2009, 48, 1559-1565. [Read Online]
- Actinide Polyoxometalates: Incorporation of Uranyl-Peroxo in U-Shaped 36-Tungsto-8-Phosphate
Mal, S. S.; Dickman, M. H.; Kortz, U. Chem. Eur. J. 2008, 14, 9851-9855. [Read Online]
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