Ionic radii (pm)
AlScYLaLu
53.574.590.0103.286.1

Scandium compounds are compounds containing the element scandium. The chemistry of scandium is almost completely dominated by the trivalent ion, Sc3+, due to its electron configuration, [Ar] 3d14s2. The radii of M3+ ions in the table below indicate that the chemical properties of scandium ions have more in common with yttrium ions than with aluminium ions. In part because of this similarity, scandium is often classified as a lanthanide-like element.

+3 oxidation state

Oxides and hydroxides

The oxide Sc
2O
3 and the hydroxide Sc(OH)
3 are amphoteric:[1]

Sc(OH)
3 + 3 OH−
 → [Sc(OH)
6]3−
 (scandate ion)
Sc(OH)
3 + 3 H+
 + 3 H
2O → [Sc(H
2O)
6]3+

α- and γ-ScOOH are isostructural with their aluminium hydroxide oxide counterparts.[2] Solutions of Sc3+
 in water are acidic due to hydrolysis.

Halides and pseudohalides

The halides ScX3, where X= Cl, Br, or I, are very soluble in water, but ScF3 is insoluble. In all four halides, the scandium is 6-coordinated. They can be prepared by reacting scandium oxide or scandium hydroxide with the corresponding acid:[3]

Sc(OH)3 + 3 HX → ScX3 + 3 H2O

The halides are Lewis acids; for example, ScF3 dissolves in a solution containing excess fluoride ion to form [ScF6]3−. The coordination number 6 is typical for Sc(III). In the larger Y3+ and La3+ ions, coordination numbers of 8 and 9 are common. Scandium triflate is sometimes used as a Lewis acid catalyst in organic chemistry.

Other oxidation states

Compounds that feature scandium in oxidation states other than +3 are rare but well characterized. The blue-black compound CsScCl3 is one of the simplest. This material adopts a sheet-like structure that exhibits extensive bonding between the scandium(II) centers.[4] Scandium hydride is not well understood, although it appears not to be a saline hydride of Sc(II).[5] As is observed for most elements, a diatomic scandium hydride has been observed spectroscopically at high temperatures in the gas phase.[6] Scandium borides and carbides are non-stoichiometric, as is typical for neighboring elements.[7]

Lower oxidation states (+2, +1, 0) have also been observed in organoscandium compounds.[8][9][10][11]

Organic derivatives

Scandium forms a series of organometallic compounds with cyclopentadienyl ligands (Cp), similar to the behavior of the lanthanides. One example is the chlorine-bridged dimer, [ScCp2Cl]2 and related derivatives of pentamethylcyclopentadienyl ligands.[12]

See also

References

  1. ↑ Cotton, Simon (2006). Lanthanide and actinide chemistry. John Wiley and Sons. pp. 108–. ISBN 978-0-470-01006-8. Retrieved 2011-06-23.
  2. ↑ Christensen, A. Nørlund; Stig Jorgo Jensen (1967). "Hydrothermal Preparation of α-ScOOH and of γ-ScOOH. Crystal Structure of α-ScOOH". Acta Chemica Scandinavica. 21: 1121–126. doi:10.3891/acta.chem.scand.21-0121.
  3. ↑ 无机化学丛书. pp 35. 3.2 卤化钪.
  4. ↑ Corbett, J. D. (1981). "Extended metal-metal bonding in halides of the early transition metals". Accounts of Chemical Research. 14 (8): 239–246. doi:10.1021/ar00068a003.
  5. ↑ McGuire, Joseph C.; Kempter, Charles P. (1960). "Preparation and Properties of Scandium Dihydride". Journal of Chemical Physics. 33 (5): 1584–1585. Bibcode:1960JChPh..33.1584M. doi:10.1063/1.1731452.
  6. ↑ Smith, R. E. (1973). "Diatomic Hydride and Deuteride Spectra of the Second Row Transition Metals". Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences. 332 (1588): 113–127. Bibcode:1973RSPSA.332..113S. doi:10.1098/rspa.1973.0015. S2CID 96908213.
  7. ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  8. ↑ Polly L. Arnold; F. Geoffrey; N. Cloke; Peter B. Hitchcock & John F. Nixon (1996). "The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene Ring". Journal of the American Chemical Society. 118 (32): 7630–7631. doi:10.1021/ja961253o.
  9. ↑ F. Geoffrey N. Cloke; Karl Khan & Robin N. Perutz (1991). "η-Arene complexes of scandium(0) and scandium(II)". Journal of the Chemical Society, Chemical Communications (19): 1372–1373. doi:10.1039/C39910001372.
  10. ↑ Ana Mirela Neculai; Dante Neculai; Herbert W. Roesky; Jörg Magull; Marc Baldus; et al. (2002). "Stabilization of a Diamagnetic ScIBr Molecule in a Sandwich-Like Structure". Organometallics. 21 (13): 2590–2592. doi:10.1021/om020090b.
  11. ↑ Polly L. Arnold; F. Geoffrey; N. Cloke & John F. Nixon (1998). "The first stable scandocene: synthesis and characterisation of bis(η-2,4,5-tri-tert-butyl-1,3-diphosphacyclopentadienyl)scandium(II)". Chemical Communications (7): 797–798. doi:10.1039/A800089A.
  12. ↑ Shapiro, Pamela J.; et al. (1994). "Model Ziegler-Natta α-Olefin Polymerization Catalysts Derived from [{(η5-C5Me4)SiMe2(η1-NCMe3)}(PMe3)Sc(μ2-H)]2 and [{(η5C5Me4)SiMe2(η1NCMe3)}Sc(μ1CH2CH2CH3)]2. Synthesis, Structures and Kinetic and Equilibrium Investigations of the Catalytically active Species in Solution" (PDF). Journal of the American Chemical Society. 116 (11): 4623. doi:10.1021/ja00090a011.
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