Editing Lanthanide (section)

====Ln(II) and Ln(IV) compounds====
The most common divalent derivatives of the lanthanides are for Eu(II), which achieves a favorable f<sup>7</sup> configuration. Divalent halide derivatives are known for all of the lanthanides. They are either conventional salts or are Ln(III) "[[electride]]"-like salts. The simple salts include YbI<sub>2</sub>, EuI<sub>2</sub>, and SmI<sub>2</sub>. The electride-like salts, described as Ln<sup>3+</sup>, 2I<sup>−</sup>, e<sup>−</sup>, include LaI<sub>2</sub>, CeI<sub>2</sub> and GdI<sub>2</sub>. Many of the iodides form soluble complexes with ethers, e.g. TmI<sub>2</sub>(dimethoxyethane)<sub>3</sub>.<ref name=Nief>{{cite journal|author=Nief, F. |title=Non-classical divalent lanthanide complexes|journal= Dalton Trans.|year= 2010|volume=39|issue=29|pages= 6589–6598|doi=10.1039/c001280g|pmid=20631944}}</ref> [[Samarium(II) iodide]] is a useful reducing agent. Ln(II) complexes can be synthesized by [[transmetalation]] reactions. The normal range of oxidation states can be expanded via the use of sterically bulky [[cyclopentadienyl ligand]]s, in this way many lanthanides can be isolated as Ln(II) compounds.<ref>{{cite journal|last1=Evans|first1=William J.|title=Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States|journal=Organometallics|date=15 September 2016|volume=35|issue=18|pages=3088–3100|doi=10.1021/acs.organomet.6b00466|doi-access=free}}{{open access}}</ref>

Ce(IV) in [[ceric ammonium nitrate]] is a useful oxidizing agent. The Ce(IV) is the exception owing to the tendency to form an unfilled f shell. Otherwise tetravalent lanthanides are rare. However, recently Tb(IV)<ref>{{cite journal |title=Molecular Complex of Tb in the +4 Oxidation State< |author1=Palumbo, C.T. |author2=Zivkovic, I. |author3=Scopelliti, R. |author4=Mazzanti, M. |date=2019 |pages=9827–9831 |volume=141 |journal=Journal of the American Chemical Society |doi=10.1021/jacs.9b05337 |pmid=31194529 |issue=25 |s2cid=189814301 |url=http://infoscience.epfl.ch/record/268286/files/Palumbo%20ja-2019-05337d%20manuscriptR1.pdf |archive-url=https://web.archive.org/web/20240423040613/https://infoscience.epfl.ch/record/268286/files/Palumbo%20ja-2019-05337d%20manuscriptR1.pdf |url-status=dead |archive-date=23 April 2024 }}</ref><ref>{{Cite journal|last1=Rice|first1=Natalie T.|last2=Popov|first2=Ivan A.|last3=Russo|first3=Dominic R.|last4=Bacsa|first4=John|last5=Batista|first5=Enrique R.|last6=Yang|first6=Ping|last7=Telser|first7=Joshua|last8=La Pierre|first8=Henry S.|date=21 August 2019|title=Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium Complex|journal=Journal of the American Chemical Society|volume=141|issue=33|pages=13222–13233|doi=10.1021/jacs.9b06622|pmid=31352780|osti=1558225|s2cid=207197096|issn=0002-7863|url=https://figshare.com/articles/journal_contribution/9450461 }}</ref><ref>{{cite journal |title= Stabilization of the Oxidation State + IV in Siloxide-Supported Terbium Compounds |author1=Willauer, A.R. |author2=Palumbo, C.T. |author3=Scopelliti, R. |author4=Zivkovic, I. |author5=Douair, I. |author6=Maron, L.  |author7=Mazzanti, M. |date=2020 |pages=3549–3553|volume=59 |journal=Angewandte Chemie International Edition |issue=9 |doi=10.1002/anie.201914733|pmid=31840371 |s2cid=209385870 |url=http://infoscience.epfl.ch/record/275738 }}</ref> and Pr(IV)<ref>{{cite journal |title= Accessing the +IV Oxidation State in Molecular Complexes of Praseodymium. |author1=Willauer, A.R. |author2=Palumbo, C.T. |author3=Fadaei-Tirani, F. |author4=Zivkovic, I. |author5=Douair, I. |author6=Maron, L.  |author7=Mazzanti, M. |date=2020 |pages=489–493|volume=142 |journal=Journal of the American Chemical Society |issue=12 |doi=10.1021/jacs.0c01204|pmid=32134644 |s2cid=212564931 |url=http://infoscience.epfl.ch/record/277306 }}</ref> complexes have been shown to exist.