Editing Technetium (section)

==Compounds==
===Pertechnetate and other derivatives===
{{main|Pertechnetate}}
[[File:Pertechnetate1.svg|thumb|left|upright|Pertechnetate is one of the most available forms of technetium. It is structurally related to [[permanganate]].]]
The most prevalent form of technetium that is easily accessible is [[sodium pertechnetate]], Na[TcO<sub>4</sub>]. The majority of this material is produced by radioactive decay from [<sup>99</sup>MoO<sub>4</sub>]<sup>2−</sup>:{{sfn|Schwochau|2000|pp=127–136}}<ref name="nuclmed" />

{{block indent|[<sup>99</sup>MoO<sub>4</sub>]<sup>2−</sup>  →   [<sup>99m</sup>TcO<sub>4</sub>]<sup>−</sup>  + e<sup>−</sup>}}

[[Pertechnetate]] ({{chem|TcO|4|-}}) is only weakly hydrated in aqueous solutions,<ref>{{cite journal |last1=Ustynyuk |first1=Yuri A. |last2=Gloriozov |first2=Igor P. |last3=Zhokhova |first3=Nelly I. |last4=German |first4=Konstantin E. |last5=Kalmykov |first5=Stepan N. |date=2021-11-15 |title=Hydration of the pertechnetate anion. DFT study |journal=Journal of Molecular Liquids |volume=342 |page=117404 |doi=10.1016/j.molliq.2021.117404 |issn=0167-7322 |url=https://www.sciencedirect.com/science/article/pii/S0167732221021280 }}</ref> and it behaves analogously to perchlorate anion, both of which are [[tetrahedral molecular geometry|tetrahedral]]. Unlike [[permanganate]] ({{chem|MnO|4|-}}), it is only a weak [[oxidizing agent]].

Related to pertechnetate is [[Technetium(VII) oxide|technetium heptoxide]]. This pale-yellow, volatile solid is produced by oxidation of Tc metal and related precursors:

{{block indent|4 Tc + 7 O<sub>2</sub> → 2 Tc<sub>2</sub>O<sub>7</sub>}}

It is a molecular metal oxide, analogous to [[manganese heptoxide]]. It adopts a [[Centrosymmetry|centrosymmetric]] structure with two types of Tc−O bonds with 167 and 184&nbsp;pm bond lengths.<ref>{{cite journal |last = Krebs |first = B. |date = 1969 |title = Technetium(VII)-oxid: Ein Übergangsmetalloxid mit Molekülstruktur im festen Zustand |language=de |trans-title=Technetium(VII) oxide, a transition metal oxide with a molecular structure in the solid tate |journal = Angewandte Chemie |volume = 81 |issue = 9 |pages = 328–329 |doi = 10.1002/ange.19690810905 | bibcode=1969AngCh..81..328K }}</ref>

Technetium heptoxide hydrolyzes to pertechnetate and [[pertechnetic acid]], depending on the pH:{{sfn|Schwochau|2000|p=127}}<ref>{{cite book |last1=Herrell |first1=A.Y. |last2=Busey |first2=R.H. |last3=Gayer |first3=K.H. |date=1977 |title=Technetium(VII) Oxide, in Inorganic Syntheses |volume=XVII |pages=155–158|isbn=978-0-07-044327-3 }}</ref>

{{block indent|Tc<sub>2</sub>O<sub>7</sub> + 2 OH<sup>−</sup> → 2 TcO<sub>4</sub><sup>−</sup> + H<sub>2</sub>O}}
{{block indent|Tc<sub>2</sub>O<sub>7</sub> + H<sub>2</sub>O  → 2 HTcO<sub>4</sub>}}

HTcO<sub>4</sub> is a strong acid. In concentrated [[sulfuric acid]], [TcO<sub>4</sub>]<sup>−</sup> converts to the octahedral form TcO<sub>3</sub>(OH)(H<sub>2</sub>O)<sub>2</sub>, the conjugate base of the hypothetical tri[[aquo complex]] [TcO<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>]<sup>+</sup>.<ref>{{cite journal |display-authors=6 |vauthors=Poineau F, Weck PF, German K, Maruk A, Kirakosyan G, Lukens W, Rego DB, Sattelberger AP, KR |name-list-style=vanc |date=2010 |title=Speciation of heptavalent technetium in sulfuric acid: Structural and spectroscopic studies |journal=Dalton Transactions |volume=39 |issue=37 |pmid=20730190 |s2cid=9419843 |pages=8616–8619|doi=10.1039/C0DT00695E |url=http://radchem.nevada.edu/docs/pub/tc%20in%20h2so4%20%28dalton%29%202010-08-23.pdf |access-date=2011-11-14 |url-status=dead |archive-url=https://web.archive.org/web/20170305152213/http://radchem.nevada.edu/docs/pub/tc%20in%20h2so4%20%28dalton%29%202010-08-23.pdf |archive-date=2017-03-05 }}</ref>

===Other chalcogenide derivatives===
Technetium forms a [[technetium(IV) oxide|dioxide]],{{sfn|Schwochau|2000|p=108}} [[metal dichalcogenide|disulfide]], di[[selenide]], and di[[telluride (chemistry)|telluride]]. An ill-defined Tc<sub>2</sub>S<sub>7</sub> forms upon treating [[pertechnate]] with hydrogen sulfide. It thermally decomposes into disulfide and elemental sulfur.{{sfn|Schwochau|2000|pp=112–113}} Similarly the dioxide can be produced by reduction of the Tc<sub>2</sub>O<sub>7</sub>.

Unlike the case for rhenium, a trioxide has not been isolated for technetium. However, TcO<sub>3</sub> has been identified in the gas phase using [[mass spectrometry]].<ref>{{cite journal |last1=Gibson |first1=John K. |year=1993 |title=High-temperature oxide and hydroxide vapor species of technetium |journal=Radiochimica Acta |volume=60 |issue=2–3 |pages=121–126 |doi=10.1524/ract.1993.60.23.121 |s2cid=99795348 }}</ref>

===Simple hydride and halide complexes===
Technetium forms the complex {{chem|TcH|9|2-}}. The potassium salt is [[isostructural]] with [[Potassium nonahydridorhenate|{{chem|ReH|9|2-}}]].{{sfn|Schwochau|2000|p=146}} At high pressure formation of TcH<sub>1.3</sub> from elements was also reported.<ref name="Zhou 2023"/>

[[File:Zirconium-tetrachloride-3D-balls-A.png|thumb|TcCl<sub>4</sub> forms chain-like structures, similar to the behavior of several other metal tetrachlorides.]]
The following binary (containing only two elements) technetium halides are known: [[TcF6|TcF<sub>6</sub>]], TcF<sub>5</sub>, [[TcCl4|TcCl<sub>4</sub>]], TcBr<sub>4</sub>, TcBr<sub>3</sub>, α-TcCl<sub>3</sub>, β-TcCl<sub>3</sub>, TcI<sub>3</sub>, α-TcCl<sub>2</sub>, and β-TcCl<sub>2</sub>. The [[oxidation state]]s range from Tc(VI) to Tc(II). Technetium halides exhibit different structure types, such as molecular octahedral complexes, extended chains, layered sheets, and metal clusters arranged in a three-dimensional network.<ref>{{cite thesis |last=Johnstone |first=E.V. |date=May 2014 |title=Binary Technetium Halides |work=UNLV Theses, Dissertations, Professional Papers, and Capstones |publisher=[[University of Nevada]] |place=Las Vegas, NV |doi=10.34917/5836118 |via=UNLV Theses, Dissertations, Professional Papers, and Capstones |url=http://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=3100&context=thesesdissertations }}</ref><ref name=AS>{{cite journal |last1=Poineau |first1=Frederic |last2=Johnstone |first2=Erik V. |last3=Czerwinski |first3=Kenneth R. |last4=Sattelberger |first4=Alfred P. |year=2014 |title=Recent advances in technetium halide chemistry |journal=Accounts of Chemical Research |volume=47 |issue=2 |pages=624–632 |doi=10.1021/ar400225b |pmid=24393028 }}</ref> These compounds are produced by combining the metal and halogen or by less direct reactions.

TcCl<sub>4</sub> is obtained by chlorination of Tc metal or Tc<sub>2</sub>O<sub>7</sub>. Upon heating, TcCl<sub>4</sub> gives the corresponding Tc(III) and Tc(II) chlorides.<ref name=AS/>

{{block indent|TcCl<sub>4</sub> → α-TcCl<sub>3</sub> + 1/2 Cl<sub>2</sub>}}
{{block indent|TcCl<sub>3</sub> → β-TcCl<sub>2</sub> + 1/2 Cl<sub>2</sub>}}

The structure of TcCl<sub>4</sub> is composed of infinite zigzag chains of edge-sharing TcCl<sub>6</sub> octahedra. It is isomorphous to transition metal tetrachlorides of [[zirconium]], [[hafnium]], and [[platinum]].<ref name="AS" />

[[File:Chloro-containing coordination complexes of technetium (Tc-99).jpg|thumb|Chloro-containing coordination complexes of technetium (<sup>99</sup>Tc) in various oxidation states: Tc(III), Tc(IV), Tc(V), and Tc(VI) represented.]]
Two polymorphs of [[technetium trichloride]] exist, α- and β-TcCl<sub>3</sub>. The α polymorph is also denoted as Tc<sub>3</sub>Cl<sub>9</sub>. It adopts a confacial [[Octahedral molecular geometry#Bioctahedral molecular geometry|bioctahedral structure]].<ref>{{cite journal |last1=Poineau |first1=Frederic |last2=Johnstone |first2=Erik V.|last3=Weck |first3=Philippe F. |last4=Kim |first4=Eunja |last5=Forster |first5=Paul M. |last6=Scott |first6=Brian L. |last7=Sattelberger |first7=Alfred P. |last8=Czerwinski |first8=Kenneth R. |display-authors=6 |year=2010 |title=Synthesis and structure of technetium trichloride |journal=Journal of the American Chemical Society |volume=132 |issue=45 |pages=15864–15865 |doi=10.1021/ja105730e |pmid=20977207 |bibcode=2010JAChS.13215864P }}</ref> It is prepared by treating the chloro-acetate Tc<sub>2</sub>(O<sub>2</sub>CCH<sub>3</sub>)<sub>4</sub>Cl<sub>2</sub> with HCl. Like [[Trirhenium nonachloride|Re<sub>3</sub>Cl<sub>9</sub>]], the structure of the α-polymorph consists of triangles with short M-M distances. β-TcCl<sub>3</sub> features octahedral Tc centers, which are organized in pairs, as seen also for [[molybdenum trichloride]]. TcBr<sub>3</sub> does not adopt the structure of either trichloride phase. Instead it has the structure of [[molybdenum tribromide]], consisting of chains of confacial octahedra with alternating short and long Tc—Tc contacts. TcI<sub>3</sub> has the same structure as the high temperature phase of [[titanium(III) iodide|TiI<sub>3</sub>]], featuring chains of confacial octahedra with equal Tc—Tc contacts.<ref name=AS/>

Several anionic technetium halides are known. The binary tetrahalides can be converted to the hexahalides [TcX<sub>6</sub>]<sup>2−</sup> (X = F, Cl, Br, I), which adopt [[octahedral molecular geometry]].<ref name=s8/> More reduced halides form anionic clusters with Tc–Tc bonds. The situation is similar for the related elements of Mo, W, Re. These clusters have the nuclearity Tc<sub>4</sub>, Tc<sub>6</sub>, Tc<sub>8</sub>, and Tc<sub>13</sub>. The more stable Tc<sub>6</sub> and Tc<sub>8</sub> clusters have prism shapes where vertical pairs of Tc atoms are connected by triple bonds and the planar atoms by single bonds. Every technetium atom makes six bonds, and the remaining valence electrons can be saturated by one axial and two [[bridging ligand]] halogen atoms such as [[chlorine]] or [[bromine]].<ref>{{cite journal |first1 = K.E. |last1 = German |last2 = Kryutchkov|first2 = S.V. |date = 2002 |title = Polynuclear technetium halide clusters |journal = Russian Journal of Inorganic Chemistry |volume = 47 |issue = 4 |pages = 578–583 |url = http://www.maik.rssi.ru/cgi-perl/search.pl?type=abstract&name=inrgchem&number=4&year=2&page=578 |url-status = dead |archive-url = https://web.archive.org/web/20151222111809/http://www.maik.rssi.ru/cgi-perl/search.pl?type=abstract&name=inrgchem&number=4&year=2&page=578 |archive-date = 2015-12-22 }}</ref>

===Coordination and organometallic complexes===
[[File:Tc CNCH2CMe2(OMe) 6Cation.png|thumb|right|[[Technetium (99mTc) sestamibi|Technetium (<sup>99m</sup>Tc) sestamibi]] ("Cardiolite") is widely used for imaging of the heart.]]
Technetium forms a variety of [[coordination complex]]es with organic ligands. Many have been well-investigated because of their relevance to [[nuclear medicine]].<ref>{{cite journal |last1=Bartholomä |first1=Mark D. |last2=Louie |first2=Anika S. |last3=Valliant |first3=John F. |last4=Zubieta |first4=Jon |year=2010 |title=Technetium and gallium derived radiopharmaceuticals: Comparing and contrasting the chemistry of two important radiometals for the molecular imaging era |journal=Chemical Reviews |volume=110 |issue=5 |pages=2903–20 |doi=10.1021/cr1000755 |pmid=20415476 }}</ref>

Technetium forms a variety of compounds with Tc–C bonds, i.e. organotechnetium complexes. Prominent members of this class are complexes with CO, arene, and cyclopentadienyl ligands.<ref name=Alberto/> The binary carbonyl Tc<sub>2</sub>(CO)<sub>10</sub> is a white volatile solid.<ref>{{cite journal |last1 = Hileman |first1 = J.C. |last2 = Huggins |first2 = D.K. |last3 = Kaesz |first3 = H.D. |date = 1961 |title = Technetium carbonyl |journal = Journal of the American Chemical Society |volume = 83 |issue = 13 |pages = 2953–2954 |doi = 10.1021/ja01474a038|bibcode = 1961JAChS..83.2953H }}</ref> In this molecule, two technetium atoms are bound to each other; each atom is surrounded by [[octahedron|octahedra]] of five carbonyl ligands. The bond length between technetium atoms, 303&nbsp;pm,<ref>{{cite journal |last1 =Bailey |first1 = M.F. |last2 = Dahl |first2 = Lawrence F. |date =1965 |title = The crystal structure of ditechnetium decacarbonyl |journal =Inorganic Chemistry |volume =4 |issue = 8 |pages =1140–1145 |doi =10.1021/ic50030a011 }}</ref><ref>{{cite journal |last1 = Wallach |first1 = D. |date = 1962 |title = Unit cell and space group of technetium carbonyl, Tc2(CO)10 |journal = Acta Crystallographica |volume = 15 |issue = 10 |page = 1058 | bibcode=1962AcCry..15.1058W |doi = 10.1107/S0365110X62002789 }}</ref> is significantly larger than the distance between two atoms in metallic technetium (272&nbsp;pm). Similar [[carbonyl]]s are formed by technetium's [[Congener (chemistry)|congeners]], manganese and rhenium.{{sfn|Schwochau|2000|pp=286, 328}} Interest in organotechnetium compounds has also been motivated by applications in [[nuclear medicine]].<ref name=Alberto>{{cite book |last1=Alberto |first1=Roger |year=2010 |chapter=Organometallic radiopharmaceuticals |title=Medicinal Organometallic Chemistry |volume=32 |pages=219–246 |series=Topics in Organometallic Chemistry |isbn=978-3-642-13184-4 |doi=10.1007/978-3-642-13185-1_9 }}</ref> Technetium also forms aquo-carbonyl complexes, one prominent complex being [Tc(CO)<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>]<sup>+</sup>, which are unusual compared to other metal carbonyls.<ref name="Alberto" />