Editing Lead (section)

==== Other oxidation states ====
{{see also|Plumbide}}

[[File:Nonaplumbide-anion-from-xtal-3D-balls.png|thumb|left|upright|The [[gyroelongated square pyramid|capped square antiprismatic]] anion [Pb<sub>9</sub>]<sup>4−</sup> from [K(18-crown-6)]<sub>2</sub>K<sub>2</sub>Pb<sub>9</sub>·(en)<sub>1.5</sub>{{sfn|Yong|Hoffmann|Fässler|2006|pp=4774–4778}}|alt=Nine dark gray spheres connected by cylinders of the same color forming a convex shape]]

Some lead compounds exist in formal oxidation states other than +4 or +2. Lead(III) may be obtained, as an intermediate between lead(II) and lead(IV), in larger organolead complexes; this oxidation state is not stable, as both the lead(III) ion and the larger complexes containing it are [[radical (chemistry)|radicals]].{{sfn|Becker|Förster|Franzen|Hartrath|2008|pp=9965–9978}}{{sfn|Mosseri|Henglein|Janata|1990|pp=2722–2726}}{{sfn|Konu|Chivers|2011|pp=391–392}} The same applies for lead(I), which can be found in such radical species.{{sfn|Hadlington|2017|p=59}}

Numerous mixed lead(II,IV) oxides are known. When PbO<sub>2</sub> is heated in air, it becomes Pb<sub>12</sub>O<sub>19</sub> at 293&nbsp;°C, Pb<sub>12</sub>O<sub>17</sub> at 351&nbsp;°C, Pb<sub>3</sub>O<sub>4</sub> at 374&nbsp;°C, and finally PbO at 605&nbsp;°C. A further [[sesquioxide]], Pb<sub>2</sub>O<sub>3</sub>, can be obtained at high pressure, along with several non-stoichiometric phases. Many of them show defective [[fluorite]] structures in which some oxygen atoms are replaced by vacancies: PbO can be considered as having such a structure, with every alternate layer of oxygen atoms absent.{{sfn|Greenwood|Earnshaw|1998|pp=384–386}}

Negative oxidation states can occur as [[Zintl phase|Zintl phases]], as either free lead anions, as in Ba<sub>2</sub>Pb, with lead formally being <!--to avoid false positives in search for 'being led/lead' typo -->lead(−IV),{{sfn|Röhr|2017}} or in oxygen-sensitive ring-shaped or polyhedral cluster ions such as the [[trigonal bipyramidal molecular geometry|trigonal bipyramidal]] Pb<sub>5</sub><sup>2−</sup> ion, where two lead atoms are lead(−I) and three are lead(0).{{sfn|Alsfasser|2007|pp=261–263}} In such anions, each atom is at a polyhedral vertex and contributes two electrons to each covalent bond along an edge from their sp<sup>3</sup> hybrid orbitals, the other two being an external [[lone pair]].{{sfn|King|1995|pp=43–63}} They may be made in [[Ammonia|liquid ammonia]] via the reduction of lead by [[sodium]].{{sfn|Greenwood|Earnshaw|1998|p=393}}

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