Editing Thorium (section)

===Organothorium compounds===
Most of the work on organothorium compounds has focused on the [[cyclopentadienyl complex]]es and [[cyclooctatetraenide anion|cyclooctatetraenyls]]. Like many of the early and middle actinides (up to [[americium]], and also expected for [[curium]]), thorium forms a cyclooctatetraenide complex: the yellow {{chem2|Th(C8H8)2}}, [[thorocene]]. It is [[isotypic]] with the better-known analogous uranium compound [[uranocene]].{{sfn|Wickleder|Fourest|Dorhout|2006|pp=116–117}} It can be prepared by reacting [[potassium cyclooctatetraenide|{{chem2|K2C8H8}}]] with thorium tetrachloride in [[tetrahydrofuran]] (THF) at the temperature of [[dry ice]], or by reacting thorium tetrafluoride with {{chem2|MgC8H8}}.{{sfn|Wickleder|Fourest|Dorhout|2006|pp=116–117}} It is unstable in air and decomposes in water or at 190&nbsp;°C.{{sfn|Wickleder|Fourest|Dorhout|2006|pp=116–117}} [[Half sandwich compound]]s are also known, such as {{chem2|(η^{8}\-C8H8)ThCl2(THF)2}}, which has a piano-stool structure and is made by reacting thorocene with thorium tetrachloride in tetrahydrofuran.<ref name="CottonSA2006" />

The simplest of the cyclopentadienyls are {{chem2|Th(C5H5)3}} and {{chem2|Th(C5H5)4}}: many derivatives are known. The former (which has two forms, one purple and one green){{sfn|Wickleder|Fourest|Dorhout|2006|pp=116–117}} is a rare example of thorium in the formal +3 oxidation state;{{sfn|Greenwood|Earnshaw|1997|pp=1278–1280}} a formal +2 oxidation state occurs in a derivative.<ref>{{cite journal |first1=Ryan R. |last1=Langeslay |first2=Megan E. |last2=Fieser |first3=Joseph W. |last3=Ziller |first4=Philip |last4=Furche |first5=William J. |last5=Evans |title=Synthesis, structure, and reactivity of crystalline molecular complexes of the {[C<sub>5</sub>H<sub>3</sub>(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub>Th}<sup>1−</sup> anion containing thorium in the formal +2 oxidation state |journal=[[Chemical Science (journal)|Chemical Science]] |volume=6 |year=2015 |issue=1 |pages=517–521 |doi=10.1039/C4SC03033H|pmid=29560172 |pmc=5811171 }}</ref> The chloride derivative {{chem2|[Th(C5H5)3Cl]}} is prepared by heating thorium tetrachloride with [[limiting reagent|limiting]] {{chem2|KC5H5}} used (other univalent metal cyclopentadienyls can also be used). The [[alkyl]] and [[aryl]] derivatives are prepared from the chloride derivative and have been used to study the nature of the Th–C [[sigma bond]].{{sfn|Greenwood|Earnshaw|1997|pp=1278–1280}}

Other organothorium compounds are not well-studied. Tetraallylthorium, {{chem2|Th(CH2CH\dCH2)4}}, is known, but its structures has not been determined. The molecular structure of tetrabenzylthorium, {{chem2|Th(CH2C6H5)4}}, without ancillary ligands has been reported.<ref>{{cite journal |last1=Bart |first1=Suzanne |title=Isolation and Characterization of Elusive Tetrabenzylthorium Complexes |journal=Organometallics |date=August 2, 2023 |volume=42 |issue=15 |page=2079-2086 |doi=10.1021/acs.organomet.3c00248 }}</ref> They decompose slowly at room temperature. Thorium forms the monocapped trigonal prismatic anion {{chem2|[Th(CH3)7](3−)}}, heptamethylthorate(IV), which forms the salt {{chem2|[Li(tmeda)]3[Th(CH3)7]}} (tmeda = {{chem2|(CH3)2NCH2CH2N(CH3)2}}). Although one methyl group is only attached to the thorium atom (Th–C distance 257.1&nbsp;pm) and the other six connect the lithium and thorium atoms (Th–C distances 265.5–276.5&nbsp;pm), they behave equivalently in solution. Tetramethylthorium, {{chem2|Th(CH3)4}}, is not known, but its [[adduct]]s are stabilised by [[phosphine]] ligands.<ref name="CottonSA2006" />