Editing Group 7 element (section)

== Compounds ==

=== Oxides ===

==== Manganese ====

[[File:Manganese(IV)_oxide.jpg|thumb|right|Manganese(IV) oxide]]

Manganese forms a variety of oxides: [[Manganese(II) oxide|MnO]], [[Manganese(II,III) oxide|Mn<sub>3</sub>O<sub>4</sub>]], [[Manganese(III) oxide|Mn<sub>2</sub>O<sub>3</sub>]], [[Manganese dioxide|MnO<sub>2</sub>]], MnO<sub>3</sub> and [[Manganese heptoxide|Mn<sub>2</sub>O<sub>7</sub>]]. Manganese(II) oxide is an inorganic compound that forms green crystals. Like many monoxides, MnO adopts the [[Cubic crystal system#Rock-salt structure|rock salt structure]], where cations and anions are both octahedrally coordinated. Also like many oxides, manganese(II) oxide is often [[nonstoichiometric]]: its composition can vary from MnO to MnO<sub>1.045</sub>.<ref name="G&W" />
Manganese(II,III) oxide is formed when any manganese oxide is heated in air above 1000&nbsp;°C.<ref name="G&W" /> Considerable research has centred on producing nanocrystalline Mn<sub>3</sub>O<sub>4</sub> and various syntheses that involve oxidation of Mn<sup>II</sup> or reduction of Mn<sup>VI</sup>.<ref>Hausmannite Mn<sub>3</sub>O<sub>4</sub> nanorods: synthesis, characterization and magnetic properties Jin Du et al.  Nanotechnology, (2006),17 4923-4928, {{doi| 10.1088/0957-4484/17/19/024}}</ref><ref>One-step synthesis of Mn<sub>3</sub>O<sub>4</sub> nanoparticles: Structural and magnetic study Vázquez-Olmos A.,  Redón R, Rodríguez-Gattorno G., Mata-Zamora M.E., Morales-Leal F, Fernández-Osorio A.L, Saniger J.M.   Journal of Colloid and Interface Science, 291, 1, (2005), 175-180 {{doi|10.1016/j.jcis.2005.05.005}}</ref><ref>{{Cite journal |last1=Sun |first1=Xiaoming |last2=Liu |first2=Junfeng |last3=Li |first3=Yadong |date=2006-02-20 |title=Use of Carbonaceous Polysaccharide Microspheres as Templates for Fabricating Metal Oxide Hollow Spheres |url=https://onlinelibrary.wiley.com/doi/10.1002/chem.200500660 |journal=Chemistry - A European Journal |language=en |volume=12 |issue=7 |pages=2039–2047 |doi=10.1002/chem.200500660 |pmid=16374888 |issn=0947-6539|url-access=subscription }}</ref> Manganese(III) oxide is unlike many other transition metal oxides in that it does not adopt the [[corundum]] ([[aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]]) structure.<ref name="G&W" /> Two forms are generally recognized, α-Mn<sub>2</sub>O<sub>3</sub> and γ-Mn<sub>2</sub>O<sub>3</sub>,<ref name = "Wells">Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford Science Publications {{ISBN|0-19-855370-6}}</ref> although a high pressure form with the CaIrO<sub>3</sub> structure has been reported too.<ref>High Pressure Phase transition in Mn<sub>2</sub>O<sub>3</sub> to the CaIrO<sub>3</sub>-type Phase Santillan, J.; Shim, S. American Geophysical Union, Fall Meeting 2005, abstract #MR23B-0050</ref> Manganese(IV) oxide is a blackish or brown solid occurs naturally as the mineral [[pyrolusite]], which is the main ore of manganese and a component of [[manganese nodule]]s. The principal use for MnO<sub>2</sub> is for dry-cell [[battery (electricity)|batteries]], such as the [[alkaline battery]] and the [[zinc–carbon battery]].<ref name="G&W" /> Manganese(VII) oxide is dark green in its [[crystalline]] form. The liquid is green by reflected light and red by transmitted light.<ref name=brauer>{{cite book|author=H. Lux|chapter=Manganese(VII) Oxide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=1459–1460}}</ref> It is soluble in [[carbon tetrachloride]], and decomposes when in contact with water.

==== Technetium ====

[[File:Technetium(IV)_oxide.png|thumb|right|Technetium(IV) oxide]]

Technetium's main oxides are [[technetium(IV) oxide]] and [[technetium(VII) oxide]]. Technetium(IV) oxide was first produced in 1949 by electrolyzing a solution of [[ammonium pertechnetate]] under [[ammonium hydroxide]]. It has often been used to separate technetium from [[molybdenum]] and rhenium.<ref name="tc" /><ref name="radio" /><ref name="electro">{{cite journal |author1=L. B. Rogers |title=Electroseparation of Technetium from Rhenium and Molybdenum |journal=Journal of the American Chemical Society |date=1949 |volume=71 |issue=4 |pages=1507–1508 |doi=10.1021/ja01172a520 |language=en}}</ref> More efficient ways are the reduction of ammonium pertechnetate by [[zinc]] metal and [[hydrochloric acid]], [[stannous chloride]], [[hydrazine]], [[hydroxylamine]], [[ascorbic acid]],<ref name="radio">{{cite journal |author1=Edward Anders |title=THE RADIOCHEMISTRY OF TECHNETIUM |url=https://www.osti.gov/biblio/4073069 |website=OSTI.GOV |publisher=U.S. Department of Energy Office of Scientific and Technical Information |access-date=4 November 2022 |page=8 |doi=10.2172/4073069 |date=1960|osti=4073069 }}</ref> by the hydrolysis of [[potassium hexachlorotechnetate]]<ref name="magnet">{{cite journal |author1=C. M. Nelson |author2=G. E. Boyd |author3=Wm. T. Smith Jr. |title=Magnetochemistry of Technetium and Rhenium |journal=Journal of the American Chemical Society |date=1954 |volume=76 |issue=2 |pages=348–352 |doi=10.1021/ja01631a009 |publisher=ACS Publications |language=en}}</ref> or by the decomposition of ammonium pertechnetate at 700&nbsp;°C under an inert atmosphere.<ref name="tc">{{cite book |author1=A. G. Sharpe |author2=H. J. Emeléus |title=Advances in Inorganic Chemistry and Radiochemistry |date=1968 |publisher=Elsevier Science |isbn=9780080578606 |page=21 |url=https://books.google.com/books?id=-SnCsg5jM_kC&pg=PA21}}</ref><ref name="img">{{cite thesis |author1=Bradley Covington Childs |title=Volatile Technetium Oxides: Implications for Nuclear Waste Vitrification |journal=UNLV Theses, Dissertations, Professional Papers, and Capstones |date=2017 |doi=10.34917/10985836}}</ref><ref name="at">{{cite journal |author1=Edward Andrews |title=Technetium and Astatine Chemistry |journal=Annual Review of Nuclear Science |date=1959 |volume=9 |pages=203–220 |doi=10.1146/annurev.ns.09.120159.001223 |publisher=Annual Reviews |language=en|doi-access=free |bibcode=1959ARNPS...9..203A }}</ref> It reacts with oxygen to produce technetium(VII) oxide at 450&nbsp;°C.

Technetium(VII) oxide can be prepared directly by the oxidation of technetium at 450-500&nbsp;°C.<ref>{{cite book|author1=Herrell, A. Y. |author2=Busey, R. H. |author3=Gayer, K. H. | title = Technetium(VII) Oxide, in Inorganic Syntheses| year = 1977 | volume = XVII| pages = 155–158 | isbn = 0-07-044327-0|doi=10.1002/9780470132487.ch41}}</ref> It is a rare example of a molecular binary metal oxide. Other examples are [[ruthenium(VIII) oxide]] and [[osmium(VIII) oxide]]. It adopts a [[centrosymmetric]] corner-shared bi-tetrahedral structure in which the terminal and bridging  Tc&minus;O bonds are 167pm and 184 pm respectively and the Tc&minus;O&minus;Tc angle is 180°.<ref>{{cite journal|last=Krebs|first=Bernt|title = Technetium(VII)-oxid: Ein Übergangsmetalloxid mit Molekülstruktur im festen Zustand| journal = Angewandte Chemie | year = 1969 | volume = 81| issue = 9| pages = 328–329| doi = 10.1002/ange.19690810905|bibcode=1969AngCh..81..328K}}</ref>

==== Rhenium ====

Rhenium's main oxides are [[rhenium(IV) oxide]] and [[rhenium(VII) oxide]]. Rhenium(IV) oxide is a gray to black crystalline solid that can be formed by [[comproportionation]].<ref>G. Glemser "Rhenium (IV) Oxide" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1480.</ref> At high temperatures it undergoes [[disproportionation]]. It is a laboratory reagent that can be used as a [[catalyst]]. It adopts the [[rutile structure]]. It forms [[perrhenate]]s with alkaline [[hydrogen peroxide]] and [[oxidizing acid]]s.<ref>{{cite web |url=http://www.aaamolybdenum.com/RheniumDioxide.html |title=RHENIUM DIOXIDE - Manufacturer |publisher=Aaamolybdenum.com |accessdate=2012-08-06 |url-status=dead |archiveurl=https://web.archive.org/web/20030209232809/http://www.aaamolybdenum.com/RheniumDioxide.html |archivedate=2003-02-09 }}</ref> In molten sodium hydroxide it forms sodium rhenate:<ref>G. Glemser "Sodium Rhenate (IV)" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1483.</ref>

: 2{{nbsp}}NaOH  +  ReO<sub>2</sub>   →   Na<sub>2</sub>ReO<sub>3</sub>  +  H<sub>2</sub>O

Rhenium(VII) oxide can be formed when rhenium or its oxides or sulfides are oxidized a 500-700&nbsp;°C in air.<ref name=Schmidt>{{cite book |title=Inorganic Syntheses |year=1967 |volume=9 |last1=Schmidt |first1=Max |last2=Schmidbaur |first2=Hubert |chapter=Trimethylsilyl Perrhenate |pages=149–151 |isbn=9780470132401 |doi=10.1002/9780470132401.ch40}}</ref> It dissolves in water to give [[perrhenic acid]]. Heating Re<sub>2</sub>O<sub>7</sub> gives rhenium(IV) oxide, signalled by the appearance of the dark blue coloration.<ref name="Brauer" /> In its solid form, Re<sub>2</sub>O<sub>7</sub> consists of alternating octahedral and tetrahedral Re centres. It is the raw material for all rhenium compounds, being the volatile fraction obtained upon roasting the host ore.<ref>{{Ullmann|doi=10.1002/14356007.a23_199|title=Rhenium and Rhenium Compounds|year=2000|last1=Georg Nadler|first1=Hans|isbn=3527306730}}</ref>

Rhenium, in addition to the +4 and +7 oxidation states, also forms a [[rhenium trioxide|trioxide]]. It can be formed by reducing rhenium(VII) oxide with [[carbon monoxide]] at 200&nbsp;C or elemental rhenium at 4000&nbsp;C.<ref>{{Citation |last1=Nechamkin |first1=H. |title=Rhenium(VI) Oxide (Rhenium Trioxide) |date=Jan 1950|url=https://onlinelibrary.wiley.com/doi/10.1002/9780470132340.ch49 |work=Inorganic Syntheses |volume=3 |pages=186–188 |editor-last=Audrieth |editor-first=Ludwig F. |access-date=2023-08-26 |edition=1 |publisher=Wiley |language=en |doi=10.1002/9780470132340.ch49 |isbn=978-0-470-13162-6 |last2=Hiskey |first2=C. F. |last3=Moeller |first3=Therald |last4=Shoemaker |first4=C. E.|url-access=subscription }}</ref> It can also be reduced with [[dioxane]].<ref name="Glemser">{{cite book|author1=O. Glemser|author2=R. Sauer|chapter=Rhenium(VI) Oxide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY |volume=2 |pages=1482 }}</ref> It is a red solid with a metallic lustre that resembles [[copper]] in appearance, and is the only stable [[trioxide]] of the group 7 elements.

=== Halides ===

==== Manganese ====

Manganese can form compounds in the +2, +3 and +4 oxidation states. The manganese(II) compounds are often light pink solids. Like some other metal difluorides, MnF<sub>2</sub> crystallizes in the [[rutile]] structure, which features octahedral Mn centers.<ref>{{cite journal |doi=10.1021/ja01650a005|title=The Crystal Structure of MnF<sub>2</sub>, FeF<sub>2</sub>, CoF<sub>2</sub>, NiF<sub>2</sub> and ZnF<sub>2</sub>|first1=J. W.|last1=Stout|first2=Stanley A.|last2=Reed|journal= J. Am. Chem. Soc.|year=1954|volume=76|issue=21|pages=5279–5281}}</ref> and it  is used in the manufacture of special kinds of [[glass]] and [[laser]]s.<ref>
{{Cite book | last1 = Ayres | first1 = D. C. | last2 = Hellier | first2 = Desmond | year = 1997 | title = Dictionary of Environmentally Important Chemicals | publisher = CRC Press | isbn = 0-7514-0256-7 | pages = 195 | url = https://books.google.com/books?id=UTKWehimCkEC&q=%22Manganese(II)+fluoride+%22&pg=PA195 | access-date = 2008-06-18 }}</ref> Scacchite is the natural, anhydrous form of manganese(II) chloride.<ref>{{Cite web|url=https://www.mindat.org/min-3549.html|title=Scacchite}}</ref> The only other currently known mineral systematized as manganese chloride is kempite - a representative of the atacamite group, a group of hydroxide-chlorides.<ref>{{Cite web|url=https://www.mindat.org/min-2183.html|title=Kempite}}</ref> It can be used in place of [[palladium]] in the [[Stille reaction]], which couples two carbon atoms using an [[organotin compound]].<ref name="Mn(II) halide" /> It can be used as a pink pigment or as a source of the manganese ion or iodide ion. It is often used in the lighting industry.<ref name="Mn(II) halide">{{Cite book | last = Cepanec | first = Ivica  | author-link =  | year = 2004 | title = Synthesis of Biaryls | edition = | volume = | series = | publication-place =  | place =  | publisher = Elsevier | id = | isbn = 0-08-044412-1 | doi = | oclc = | pages = 104 | url = https://books.google.com/books?id=UMLOo1wXWdwC&dq=%22Manganese(II)+bromide+%22&pg=PA104 | accessdate = 2008-06-18 }}</ref>

==== Technetium ====

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|title=Binary Technetium Halides |last=Johnstone|first=E. V. |date=May 2014 |publisher=University of Nevada, Las Vegas |url=http://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=3100&context=thesesdissertations |doi=10.34917/5836118 |via=UNLV Theses, Dissertations, Professional Papers, and Capstones}}</ref><ref name="AS">{{cite journal|doi=10.1021/ar400225b |pmid=24393028|title=Recent Advances in Technetium Halide Chemistry|journal=Accounts of Chemical Research|volume=47|issue=2|pages=624–632 |year=2014|last1=Poineau |first1=Frederic|last2=Johnstone|first2=Erik V.|last3=Czerwinski|first3=Kenneth R.|last4=Sattelberger |first4=Alfred P.}}</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" />
:TcCl<sub>4</sub> → α-TcCl<sub>3</sub> + 1/2 Cl<sub>2</sub>
: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 (Tc-99) 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|doi=10.1021/ja105730e|pmid=20977207|title=Synthesis and Structure of Technetium Trichloride|journal=Journal of the American Chemical Society|volume=132|issue=45|pages=15864–5|year=2010|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.}}</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">{{harvnb|Schwochau|2000|pp=7–9}}</ref> 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.|title = Polynuclear Technetium Halide Clusters|journal = Russian Journal of Inorganic Chemistry|volume = 47|issue = 4|date = 2002|pages = 578–583|url = http://www.maik.rssi.ru/cgi-perl/search.pl?type=abstract&name=inrgchem&number=4&year=2&page=578|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|url-status = dead|archive-date = 2015-12-22}}</ref>

==== Rhenium ====

The most common rhenium chlorides are [[Rhenium hexachloride|ReCl<sub>6</sub>]], [[Rhenium pentachloride|ReCl<sub>5</sub>]], [[Rhenium tetrachloride|ReCl<sub>4</sub>]], and [[Rhenium trichloride|ReCl<sub>3</sub>]].<ref name="G&W">{{Greenwood&Earnshaw2nd}}</ref> The structures of these compounds often feature extensive Re-Re bonding, which is characteristic of this metal in oxidation states lower than VII. Salts of [Re<sub>2</sub>Cl<sub>8</sub>]<sup>2−</sup> feature a [[quadruple bond|quadruple]] metal-metal bond. Although the highest rhenium chloride features Re(VI), fluorine gives the d<sup>0</sup> Re(VII) derivative [[rhenium heptafluoride]]. Bromides and iodides of rhenium are also well known.

Like tungsten and molybdenum, with which it shares chemical similarities, rhenium forms a variety of [[Oxohalide|oxyhalides]]. The oxychlorides are most common, and include ReOCl<sub>4</sub>, ReOCl<sub>3</sub>.

=== Organometallic compounds ===

==== Manganese ====

{{Main article|Organomanganese chemistry}}

Organomanganese compounds were first reported in 1937 by Gilman and Bailee who described the reaction of [[phenyllithium]] and [[manganese(II) iodide]] to form phenylmanganese iodide (PhMnI) and diphenylmanganese (Ph<sub>2</sub>Mn).<ref name="Cahiez2009">{{cite journal|title=Chemistry of Organomanganese(II) Compounds|first1=Gerard|last1=Cahiez|first2=Christophe|last2=Duplais|first3=Julien|last3=Buendia|journal=[[Chem. Rev.]]|year=2009|volume=109 |issue=3 |pages=1434–1476 |doi=10.1021/cr800341a|pmid=19209933 }}</ref>

Following this precedent, other organomanganese halides can be obtained by alkylation of [[manganese(II) chloride]], [[manganese(II) bromide]], and [[manganese(II) iodide]].  Manganese iodide is attractive because the anhydrous compound can be prepared in situ from manganese and [[iodine]] in [[diethyl ether|ether]]. Typical alkylating agents are [[organolithium]] or [[organomagnesium]] compounds.

The chemistry of organometallic compounds of Mn(II) are unusual among the [[transition metal]]s due to the high ionic character of the Mn(II)-C bond.<ref>{{cite journal|first=Richard A.|last=Layfield|title=Manganese(II): The Black Sheep of the Organometallic Family|journal=[[Chem. Soc. Rev.]]|year=2008 |volume=37|issue=6|pages=1098–1107 |doi=10.1039/b708850g |pmid=18497923 }}</ref> The reactivity of organomanganese compounds can be compared to that of [[Organomagnesium chemistry|organomagnesium]] and [[organozinc compound]]s. The [[electronegativity]] of Mn (1.55) is comparable to that of Mg (1.31) and Zn (1.65), making the carbon atom (EN = 2.55) [[nucleophilic]]. The [[reduction potential]] of Mn is also intermediate between Mg and Zn.

==== Technetium ====

{{Main article|Organotechnetium chemistry}}

[[File:Tc CNCH2CMe2(OMe) 6Cation.png|thumb|right|[[Technetium (99mTc) 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|doi=10.1021/cr1000755|pmid=20415476|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|year=2010|last1=Bartholomä|first1=Mark D.|last2=Louie|first2=Anika S.|last3=Valliant|first3=John F.|last4=Zubieta|first4=Jon}}</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|doi = 10.1021/ja01474a038|date = 1961|last1 = Hileman|first1 = J. C.|last2 = Huggins|last3 = Kaesz|journal = Journal of the American Chemical Society |volume = 83|title = Technetium carbonyl|pages = 2953–2954|first2 = D. K.|first3 = H. D.|issue = 13}}</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|title = The Crystal Structure of Ditechnetium Decacarbonyl|doi =10.1021/ic50030a011|date =1965|last1 =Bailey|first1 = M. F.|journal =Inorganic Chemistry|volume =4|pages =1140–1145|last2 = Dahl|first2 = Lawrence F.|issue = 8}}</ref><ref>{{cite journal|doi = 10.1107/S0365110X62002789|title = Unit cell and space group of technetium carbonyl, Tc2(CO)10|date = 1962|last1 = Wallach|first1 = D.|journal = Acta Crystallographica|volume = 15|page = 1058|issue = 10| bibcode=1962AcCry..15.1058W }}</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|doi=10.1007/978-3-642-13185-1_9|chapter=Organometallic Radiopharmaceuticals|title=Medicinal Organometallic Chemistry|volume=32|pages=219–246|series=Topics in Organometallic Chemistry|year=2010 |last1=Alberto|first1=Roger|isbn=978-3-642-13184-4}}</ref> Unusual for other metal carbonyls, Tc forms aquo-carbonyl complexes, prominent being [Tc(CO)<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub>]<sup>+</sup>.<ref name="Alberto" />

==== Rhenium ====

{{Main article|Organorhenium chemistry}}

[[Dirhenium decacarbonyl]] is the most common entry to organorhenium chemistry. Its reduction with sodium [[Amalgam (chemistry)|amalgam]] gives Na[Re(CO)<sub>5</sub>] with rhenium in the formal oxidation state −1.<ref>{{cite journal|doi = 10.1002/cber.19901230103|title = Nucleophile Addition von Carbonylmetallaten an kationische Alkin-Komplexe [CpL2M(η2-RC≡CR)]+ (M = Ru, Fe): μ-η1:η1-Alkin-verbrückte Komplexe|date = 1990|author = Breimair, Josef|journal = Chemische Berichte|volume = 123|page = 7|last2 = Steimann|first2 = Manfred|last3 = Wagner|first3 = Barbara|last4 = Beck|first4 = Wolfgang}}</ref> Dirhenium decacarbonyl can be oxidised with [[bromine]] to [[bromopentacarbonylrhenium(I)]]:<ref>{{cite book|title=Inorganic Syntheses|first=Steven P.|last =Schmidt|author2=Trogler, William C. |author3=Basolo, Fred |chapter=Pentacarbonylrhenium Halides | volume=28|date=1990|pages=154–159|doi=10.1002/9780470132593.ch42|isbn=978-0-470-13259-3}}</ref>
:Re<sub>2</sub>(CO)<sub>10</sub> + Br<sub>2</sub> → 2 Re(CO)<sub>5</sub>Br

Reduction of this pentacarbonyl with [[zinc]] and [[acetic acid]] gives [[pentacarbonylhydridorhenium]]:<ref name="Urb">{{cite book|author=Michael A. Urbancic|author2=John R. Shapley|chapter=Pentacarbonylhydridorhenium |title=Inorganic Syntheses|volume=28|pages=165–168|date=1990|doi =10.1002/9780470132593.ch43|isbn=978-0-470-13259-3}}</ref>
:Re(CO)<sub>5</sub>Br + Zn + HOAc → Re(CO)<sub>5</sub>H + ZnBr(OAc)

[[Methylrhenium trioxide]] ("MTO"), CH<sub>3</sub>ReO<sub>3</sub> is a volatile, colourless solid has been used as a [[catalyst]] in some laboratory experiments. It can be prepared by many routes, a typical method is the reaction of Re<sub>2</sub>O<sub>7</sub> and [[tetramethyltin]]:
:Re<sub>2</sub>O<sub>7</sub> + (CH<sub>3</sub>)<sub>4</sub>Sn → CH<sub>3</sub>ReO<sub>3</sub> + (CH<sub>3</sub>)<sub>3</sub>SnOReO<sub>3</sub>
Analogous alkyl and aryl derivatives are known. MTO catalyses for the oxidations with [[hydrogen peroxide]]. Terminal [[alkyne]]s yield the corresponding acid or ester, internal alkynes yield diketones, and [[alkene]]s give epoxides. MTO also catalyses the conversion of [[aldehyde]]s and [[diazoalkane]]s into an alkene.<ref>Hudson, A. (2002) “Methyltrioxorhenium” in ''Encyclopedia of Reagents for Organic Synthesis''. John Wiley & Sons: New York, {{ISBN|9780470842898}}, {{doi|10.1002/047084289X}}.</ref>

=== Polyoxometalates ===

{{Main article|Polyoxometalate#Polyoxotechnetates and rhenates}}

The polyoxotechnetate (polyoxometalate of technetium) contains both Tc(V) and Tc(VII) in ratio 4: 16 and is obtained as the [[hydronium]] salt [H<sub>7</sub>O<sub>3</sub>]<sub>4</sub>[Tc<sub>20</sub>O<sub>68</sub>]·4H<sub>2</sub>O by concentrating an HTcO<sub>4</sub> solution.<ref>{{Cite journal |last1=German |first1=Konstantin E. |last2=Fedoseev |first2=Alexander M. |last3=Grigoriev |first3=Mikhail S. |last4=Kirakosyan |first4=Gayane A. |last5=Dumas |first5=Thomas |last6=Den Auwer |first6=Christophe |last7=Moisy |first7=Philippe |last8=Lawler |first8=Keith V. |last9=Forster |first9=Paul M. |last10=Poineau |first10=Frederic |date=2021-09-24 |title=A 70-Year-Old Mystery in Technetium Chemistry Explained by the New Technetium Polyoxometalate [H 7 O 3 ] 4 [Tc 20 O 68 ] ⋅ 4H 2 O |url=https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102035 |journal=Chemistry – A European Journal |language=en |volume=27 |issue=54 |pages=13624–13631 |doi=10.1002/chem.202102035 |pmid=34245056 |issn=0947-6539|url-access=subscription }}</ref> The first empirically isolated polyoxorhenate was the white [Re<sub>4</sub>O<sub>15</sub>]<sup>2−</sup> and contained Re(VII) in both octahedral and tetrahedral coordination.<ref>{{Cite journal |last1=Volkov |first1=Mikhail A. |last2=Novikov |first2=Anton P. |last3=Borisova |first3=Nataliya E. |last4=Grigoriev |first4=Mikhail S. |last5=German |first5=Konstantin E. |date=2023-08-21 |title=Intramolecular Re···O Nonvalent Interactions as a Stabilizer of the Polyoxorhenate(VII) |url=https://pubs.acs.org/doi/10.1021/acs.inorgchem.3c01863 |journal=Inorganic Chemistry |language=en |volume=62 |issue=33 |pages=13485–13494 |doi=10.1021/acs.inorgchem.3c01863 |pmid=37599582 |issn=0020-1669|url-access=subscription }}</ref>