Editing Scandium (section)

==Compounds==
{{Category see also|Scandium compounds|Scandium minerals}}
Scandium chemistry is almost completely dominated by the trivalent ion, Sc<sup>3+</sup>. The radii of M<sup>3+</sup> 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.<ref>{{Cite book |last=Horovitz |first=Chaim T. |url=https://books.google.com/books?id=xaPaBwAAQBAJ |title=Biochemistry of Scandium and Yttrium, Part 1: Physical and Chemical Fundamentals |date=2012-12-06 |publisher=Springer Science & Business Media |isbn=978-1-4615-4313-8 |language=en}}</ref>
:{|class="wikitable"
|+ Ionic radius (pm)
|-
|[[aluminium|Al]]||Sc||[[yttrium|Y]]||[[lanthanum|La]]||[[lutetium|Lu]]
|-
|53.5||74.5||90.0||103.2||86.1
|}

===Oxides and hydroxides===
The oxide [[scandium oxide|{{chem|Sc|2|O|3}}]] and the hydroxide {{chem|Sc(OH)|3}} are [[amphoteric]]:<ref>{{cite book|author=Cotton, Simon |title=Lanthanide and actinide chemistry|url=https://books.google.com/books?id=lvQpiVHrb78C&pg=PA108|access-date=2011-06-23|date=2006|publisher=John Wiley and Sons|isbn=978-0-470-01006-8|pages=108–}}</ref>
:{{chem|Sc(OH)|3}} + 3 {{chem|OH|-}} → {{chem|[Sc(OH)|6|]|3−}} (scandate ion)
:{{chem|Sc(OH)|3}} + 3 {{chem|H|+}} + 3 {{chem|H|2|O}} → {{chem|[Sc(H|2|O)|6|]|3+}}

α- and γ-ScOOH are isostructural with their [[aluminium hydroxide oxide]] counterparts.<ref>{{cite journal|last=Christensen|first=A. Nørlund|author2=Stig Jorgo Jensen|date=1967|title=Hydrothermal Preparation of α-ScOOH and of γ-ScOOH. Crystal Structure of α-ScOOH|journal= Acta Chemica Scandinavica|volume=21|pages=1121–126|doi= 10.3891/acta.chem.scand.21-0121|doi-access=free}}</ref> Solutions of {{chem|Sc|3+}} in water are acidic due to [[hydrolysis]].

===Halides and pseudohalides===
The [[halide]]s {{chem2|ScX3}}, where X= [[scandium chloride|Cl]], [[scandium bromide|Br]], or [[scandium triiodide|I]], are very soluble in water, but [[scandium fluoride|{{chem2|ScF3}}]] is insoluble. In all four halides, the scandium is 6-coordinated. The halides are [[Lewis acids]]; for example, [[scandium fluoride|{{chem2|ScF3}}]] dissolves in a solution containing excess fluoride ion to form {{chem2|[ScF6](3−)}}. The coordination number 6 is typical for Sc(III). In the larger Y<sup>3+</sup> and La<sup>3+</sup> ions, [[coordination number]]s of 8 and 9 are common. [[Scandium triflate]] is sometimes used as a [[Lewis acid]] catalyst in [[organic chemistry]].<ref>{{cite journal |doi =10.1055/s-1999-5997 |title= SYNLETT Spotlight 12: Scandium Triflate |author= Deborah Longbottom |journal= [[Synlett]] |year= 1999 |issue= 12 |pages= 2023 |volume =1999|doi-access= free }}</ref>

===Organic derivatives===
{{Main|Organoscandium chemistry}}
Scandium forms a series of organometallic compounds with [[cyclopentadienyl complex|cyclopentadienyl]] ligands (Cp), similar to the behavior of the lanthanides. One example is the chlorine-bridged dimer, {{chem2|[ScCp2Cl]2}} and related derivatives of [[pentamethylcyclopentadienyl]] ligands.<ref>{{cite journal|title=Model Ziegler-Natta ''α''-Olefin Polymerization Catalysts Derived from [{(η<sup>5</sup>-C<sub>5</sub>Me<sub>4</sub>)SiMe<sub>2</sub>(η<sup>1</sup>-NCMe<sub>3</sub>)}(PMe<sub>3</sub>)Sc(μ<sub>2</sub>-H)]<sub>2</sub> and [{(η<sup>5</sup>C<sub>5</sub>Me<sub>4</sub>)SiMe<sub>2</sub>(η<sup>1</sup>NCMe<sub>3</sub>)}Sc(μ<sup>1</sup>CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub>)]<sub>2</sub>. Synthesis, Structures and Kinetic and Equilibrium Investigations of the Catalytically active Species in Solution|last=Shapiro|first=Pamela J.|display-authors=etal|journal=Journal of the American Chemical Society|volume=116|issue=11|page=4623 |date=1994|doi=10.1021/ja00090a011}}</ref>

=== Uncommon oxidation states ===

Compounds that feature scandium in oxidation states other than +3 are rare but well characterized. The blue-black compound {{chem2|CsScCl3}} is one of the simplest. This material adopts a sheet-like structure that exhibits extensive bonding between the scandium(II) centers.<ref>{{cite journal|last=Corbett|first=J. D.|date=1981|title=Extended metal-metal bonding in halides of the early transition metals |journal=Accounts of Chemical Research|volume=14|pages=239–246|doi= 10.1021/ar00068a003|issue=8}}</ref> [[Scandium hydride]] is not well understood, although it appears not to be a [[hydride|saline hydride]] of Sc(II).<ref name="McGuire" /> As is observed for most elements, a diatomic scandium hydride has been observed spectroscopically at high temperatures in the gas phase.<ref name="Smith" /> Scandium borides and carbides are [[non-stoichiometric compound|non-stoichiometric]], as is typical for neighboring elements.<ref name="Holleman">Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.</ref>

Lower oxidation states (+2, +1, 0) have also been observed in organoscandium compounds.<ref>{{cite journal|author=Polly L. Arnold|author2=F. Geoffrey|author3=N. Cloke|author4=Peter B. Hitchcock|author5=John F. Nixon|name-list-style=amp|date=1996|title=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=Journal of the American Chemical Society|volume=118|issue=32|pages=7630–7631|doi= 10.1021/ja961253o|bibcode=1996JAChS.118.7630A }}</ref><ref name="Cloke1991"/><ref>{{cite journal|display-authors=5|author=Ana Mirela Neculai|author2=Dante Neculai|author3=Herbert W. Roesky|author4=Jörg Magull|author5=Marc Baldus|author6=Ovidiu Andronesi|author7=Martin Jansen|date=2002|title=Stabilization of a Diamagnetic Sc<sup>I</sup>Br Molecule in a Sandwich-Like Structure |journal=Organometallics|volume=21|pages=2590–2592|doi= 10.1021/om020090b|issue=13}}</ref><ref>{{cite journal|author=Polly L. Arnold|author2=F. Geoffrey|author3=N. Cloke|author4=John F. Nixon|name-list-style=amp |date=1998|title=The first stable scandocene: synthesis and characterisation of bis(η-2,4,5-tri-tert-butyl-1,3-diphosphacyclopentadienyl)scandium(II) |journal= Chemical Communications|issue=7|pages=797–798|doi= 10.1039/A800089A}}</ref>