Technetium compounds

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Technetium compounds are chemical compounds containing the chemical element technetium. Technetium can form multiple oxidation states, but often forms in the +4 and +7 oxidation states. Because technetium is radioactive, technetium compounds are extremely rare on Earth.

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Pertechnetate and derivatives

Pertechnetate is one of the most available forms of technetium. It is structurally related to permanganate. Pertechnetate1.svg
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[TcO4]. The majority of this material is produced by radioactive decay from [99MoO4]2−: [1] [2]

[99MoO4]2− → [99mTcO4]− + e−

Pertechnetate (tetroxidotechnetate) TcO−
4 behaves analogously to perchlorate, both of which are tetrahedral. Unlike permanganate (MnO−
4), it is only a weak oxidizing agent.

Related to pertechnetate is technetium heptoxide. This pale-yellow, volatile solid is produced by oxidation of Tc metal and related precursors:

4 Tc + 7 O2 → 2 Tc2O7

It is a molecular metal oxide, analogous to manganese heptoxide. It adopts a centrosymmetric structure with two types of Tc−O bonds with 167 and 184 pm bond lengths. [3]

Technetium heptoxide hydrolyzes to pertechnetate and pertechnetic acid, depending on the pH: [4] [5]

Tc2O7 + 2 OH− → 2 TcO4− + H2O
Tc2O7 + H2O → 2 HTcO4

HTcO4 is a strong acid. In concentrated sulfuric acid, [TcO4]− converts to the octahedral form TcO3(OH)(H2O)2, the conjugate base of the hypothetical triaquo complex [TcO3(H2O)3]+. [6]

Other chalcogenide derivatives

Technetium forms a dioxide, [7] disulfide, diselenide, and ditelluride. An ill-defined Tc2S7 forms upon treating pertechnetate with hydrogen sulfide. It thermally decomposes into disulfide and elemental sulfur. [8] Similarly the dioxide can be produced by reduction of the Tc2O7.

Unlike the case for rhenium, a trioxide has not been isolated for technetium. However, TcO3 has been identified in the gas phase using mass spectrometry. [9]

Simple hydride and halide complexes

Technetium forms the simple complex TcH2−
9. The potassium salt is isostructural with ReH2−
9. [10]

TcCl4 forms chain-like structures, similar to the behavior of several other metal tetrachlorides. Zirconium-tetrachloride-3D-balls-A.png
TcCl4 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, TcF5, TcCl4, TcBr4, TcBr3, α-TcCl3, β-TcCl3, TcI3, α-TcCl2, and β-TcCl2. The oxidation states 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. [11] [12] These compounds are produced by combining the metal and halogen or by less direct reactions.

TcCl4 is obtained by chlorination of Tc metal or Tc2O7 Upon heating, TcCl4 gives the corresponding Tc(III) and Tc(II) chlorides. [12]

TcCl4 → α-TcCl3 + 1/2 Cl2
TcCl3 → β-TcCl2 + 1/2 Cl2

The structure of TcCl4 is composed of infinite zigzag chains of edge-sharing TcCl6 octahedra. It is isomorphous to transition metal tetrachlorides of zirconium, hafnium, and platinum. [12]

Chloro-containing coordination complexes of technetium ( Tc) in various oxidation states: Tc(III), Tc(IV), Tc(V), and Tc(VI) represented. Chloro-containing coordination complexes of technetium (Tc-99).jpg
Chloro-containing coordination complexes of technetium ( Tc) in various oxidation states: Tc(III), Tc(IV), Tc(V), and Tc(VI) represented.

Two polymorphs of technetium trichloride exist, α- and β-TcCl3. The α polymorph is also denoted as Tc3Cl9. It adopts a confacial bioctahedral structure. [13] It is prepared by treating the chloro-acetate Tc2(O2CCH3)4Cl2 with HCl. Like Re3Cl9, the structure of the α-polymorph consists of triangles with short M-M distances. β-TcCl3 features octahedral Tc centers, which are organized in pairs, as seen also for molybdenum trichloride. TcBr3 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. TcI3 has the same structure as the high temperature phase of TiI3, featuring chains of confacial octahedra with equal Tc—Tc contacts. [12]

Several anionic technetium halides are known. The binary tetrahalides can be converted to the hexahalides [TcX6]2− (X = F, Cl, Br, I), which adopt octahedral molecular geometry. [14] 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 Tc4, Tc6, Tc8, and Tc13. The more stable Tc6 and Tc8 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. [15]

Simple carbide complexes

Technetium forms the simple carbon insertion phases with low carbon content up to 17 at.% of C when reacted with grphite [16] or by thermolisys of organic pertechnetates. [17] Tc is considered to be the last d-element to have some low but notable affinity to carbon. [18]

Coordination and organometallic complexes

[[Technetium ( Tc) sestamibi]] ("Cardiolite") is widely used for imaging of the heart. Tc CNCH2CMe2(OMe) 6Cation.png
[[Technetium ( Tc) sestamibi]] ("Cardiolite") is widely used for imaging of the heart.

Technetium forms a variety of coordination complexes with organic ligands. Many have been well-investigated because of their relevance to nuclear medicine. [19]

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. [20] The binary carbonyl Tc2(CO)10 is a white volatile solid. [21] In this molecule, two technetium atoms are bound to each other; each atom is surrounded by octahedra of five carbonyl ligands. The bond length between technetium atoms, 303 pm, [22] [23] is significantly larger than the distance between two atoms in metallic technetium (272 pm). Similar carbonyls are formed by technetium's congeners, manganese and rhenium. [24] Interest in organotechnetium compounds has also been motivated by applications in nuclear medicine. [20] Technetium also forms aquo-carbonyl complexes, one prominent complex being [Tc(CO)3(H2O)3]+, which are unusual compared to other metal carbonyls. [20]

See also

Related Research Articles

<span class="mw-page-title-main">Technetium</span> Chemical element with atomic number 43 (Tc)

Technetium is a chemical element; it has symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium and promethium are the only radioactive elements whose neighbours in the sense of atomic number are both stable. All available technetium is produced as a synthetic element. Naturally occurring technetium is a spontaneous fission product in uranium ore and thorium ore, or the product of neutron capture in molybdenum ores. This silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between those of both adjacent elements. The most common naturally occurring isotope is 99Tc, in traces only.

<span class="mw-page-title-main">Group 7 element</span> Group of chemical elements

Group 7, numbered by IUPAC nomenclature, is a group of elements in the periodic table. It contains manganese (Mn), technetium (Tc), rhenium (Re) and bohrium (Bh). This group lies in the d-block of the periodic table, and are hence transition metals. This group is sometimes called the manganese group or manganese family after its lightest member; however, the group itself has not acquired a trivial name because it belongs to the broader grouping of the transition metals.

<span class="mw-page-title-main">Aluminium chloride</span> Chemical compound

Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula AlCl3. It forms a hexahydrate with the formula [Al(H2O)6]Cl3, containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour.

<span class="mw-page-title-main">Rhodium(III) chloride</span> Chemical compound

Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic red-brown solids. The soluble trihydrated (n = 3) salt is the usual compound of commerce. It is widely used to prepare compounds used in homogeneous catalysis.

<span class="mw-page-title-main">Gold(III) chloride</span> Chemical compound

Gold(III) chloride, traditionally called auric chloride, is an inorganic compound of gold and chlorine with the molecular formula Au2Cl6. The "III" in the name indicates that the gold has an oxidation state of +3, typical for many gold compounds. It has two forms, the monohydrate (AuCl3·H2O) and the anhydrous form, which are both hygroscopic and light-sensitive solids. This compound is a dimer of AuCl3. This compound has a few uses, such as an oxidizing agent and for catalyzing various organic reactions.

<span class="mw-page-title-main">Pertechnetate</span> Chemical compound or ion

The pertechnetate ion is an oxyanion with the chemical formula TcO−
4. It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium (Tc). In particular it is used to carry the 99mTc isotope which is commonly used in nuclear medicine in several nuclear scanning procedures.

<span class="mw-page-title-main">Technetium(VII) oxide</span> Chemical compound

Technetium(VII) oxide is the chemical compound with the formula Tc2O7. This yellow volatile solid is a rare example of a molecular binary metal oxide, the other examples being RuO4, OsO4, and the unstable Mn2O7. It adopts a centrosymmetric corner-shared bi-tetrahedral structure in which the terminal and bridging Tc−O bonds are 167pm and 184 pm respectively and the Tc−O−Tc angle is 180°.

<span class="mw-page-title-main">Scandium chloride</span> Chemical compound

Scandium(III) chloride is the inorganic compound with the formula ScCl3. It is a white, high-melting ionic compound, which is deliquescent and highly water-soluble. This salt is mainly of interest in the research laboratory. Both the anhydrous form and hexahydrate (ScCl3•6H2O) are commercially available.

<span class="mw-page-title-main">Ruthenium(III) chloride</span> Chemical compound

Ruthenium(III) chloride is the chemical compound with the formula RuCl3. "Ruthenium(III) chloride" more commonly refers to the hydrate RuCl3·xH2O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a varying proportion of water of crystallization, often approximating to a trihydrate, is a commonly used starting material in ruthenium chemistry.

Titanium(III) chloride is the inorganic compound with the formula TiCl3. At least four distinct species have this formula; additionally hydrated derivatives are known. TiCl3 is one of the most common halides of titanium and is an important catalyst for the manufacture of polyolefins.

<span class="mw-page-title-main">Manganese heptoxide</span> Chemical compound

Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula Mn2O7. Manganese heptoxide is a volatile liquid with an oily consistency. It is a highly reactive and powerful oxidizer that reacts explosively with nearly any organic compound. It was first described in 1860. It is the acid anhydride of permanganic acid.

<span class="mw-page-title-main">Antimony trichloride</span> Chemical compound

Antimony trichloride is the chemical compound with the formula SbCl3. It is a soft colorless solid with a pungent odor and was known to alchemists as butter of antimony.

Trirhenium nonachloride is a compound with the formula ReCl3, sometimes also written Re3Cl9. It is a dark red hygroscopic solid that is insoluble in ordinary solvents. The compound is important in the history of inorganic chemistry as an early example of a cluster compound with metal-metal bonds. It is used as a starting material for synthesis of other rhenium complexes.

<span class="mw-page-title-main">Pertechnetic acid</span> Chemical compound

Pertechnetic acid (HTcO4) is a compound of technetium that is produced by reacting technetium(VII) oxide (Tc2O7) with water or reacting Tc metal or TcO2 with strong oxidizing acids, such as nitric acid, mixture of concentrated sulfuric acid with hydrogen peroxide or aqua regia. The dark red hygroscopic substance is a strong acid, with a pKa of 0.32, as such it exists almost entirely as the pertechnetate ion in aqueous solution. The red color in solution is thought to be due to the formation of the polyoxometallate Tc20O4−68. While fresh HTcO4 is white.

Organotellurium chemistry describes the synthesis and properties of organotellurium compounds, chemical compounds containing a carbon-tellurium chemical bond. Organotellurium chemistry is a lightly studied area, in part because of it having few applications.

<span class="mw-page-title-main">Technetium(IV) chloride</span> Chemical compound

Technetium(IV) chloride is the inorganic compound with the formula TcCl4. It was discovered in 1957 as the first binary halide of technetium. It is the highest oxidation binary chloride of technetium that has been isolated as a solid. It is volatile at elevated temperatures and its volatility has been used for separating technetium from other metal chlorides. Colloidal solutions of technetium(IV) chloride are oxidized to form Tc(VII) ions when exposed to gamma rays.

Niobium(III) chloride also known as niobium trichloride is a compound of niobium and chlorine. The binary phase NbCl3 is not well characterized but many adducts are known.

<span class="mw-page-title-main">Tantalum(III) chloride</span> Chemical compound

Tantalum(III) chloride or tantalum trichloride is non-stoichiometric chemical compound with a range of composition from TaCl2.9 to TaCl3.1 Anionic and neutral clusters containing Ta(III) chloride include [Ta6Cl18]4− and [Ta6Cl14](H2O)4.

Technetium trichloride is an inorganic compound of technetium and chlorine with the formula TcCl3.

Rhenium compounds are compounds formed by the transition metal rhenium (Re). Rhenium can form in many oxidation states, and compounds are known for every oxidation state from -3 to +7 except -2, although the oxidation states +7, +4, and +3 are the most common. Rhenium is most available commercially as salts of perrhenate, including sodium and ammonium perrhenates. These are white, water-soluble compounds. The tetrathioperrhenate anion [ReS4]− is possible.

References

  1. ↑ Schwochau 2000, pp. 127–136.
  2. ↑ Moore, P. W. (April 1984). "Technetium-99 in generator systems" (PDF). Journal of Nuclear Medicine. 25 (4): 499–502. PMID   6100549 . Retrieved 2012-05-11.
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  4. ↑ Schwochau 2000, p. 127.
  5. ↑ Herrell, A. Y.; Busey, R. H.; Gayer, K. H. (1977). Technetium(VII) Oxide, in Inorganic Syntheses. Vol. XVII. pp. 155–158. ISBN   978-0-07-044327-3.
  6. ↑ Poineau F; Weck PF; German K; Maruk A; Kirakosyan G; Lukens W; Rego DB; et al. (2010). "Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies" (PDF). Dalton Transactions. 39 (37): 8616–8619. doi:10.1039/C0DT00695E. PMID   20730190. S2CID   9419843.
  7. ↑ Schwochau 2000, p. 108.
  8. ↑ Schwochau 2000, pp. 112–113.
  9. ↑ Gibson, John K. (1993). "High-Temperature Oxide and Hydroxide Vapor Species of Technetium". Radiochimica Acta. 60 (2–3): 121–126. doi:10.1524/ract.1993.60.23.121. S2CID   99795348.
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  11. ↑ Johnstone, E. V. (May 2014). Binary Technetium Halides (Thesis). University of Nevada, Las Vegas. doi:10.34917/5836118 – via UNLV Theses, Dissertations, Professional Papers, and Capstones.
  12. 1 2 3 4 Poineau, Frederic; Johnstone, Erik V.; Czerwinski, Kenneth R.; Sattelberger, Alfred P. (2014). "Recent Advances in Technetium Halide Chemistry". Accounts of Chemical Research. 47 (2): 624–632. doi:10.1021/ar400225b. PMID   24393028.
  13. ↑ Poineau, Frederic; Johnstone, Erik V.; Weck, Philippe F.; Kim, Eunja; Forster, Paul M.; Scott, Brian L.; Sattelberger, Alfred P.; Czerwinski, Kenneth R. (2010). "Synthesis and Structure of Technetium Trichloride". Journal of the American Chemical Society. 132 (45): 15864–5. doi:10.1021/ja105730e. PMID   20977207.
  14. ↑ Schwochau, K. (2000). Technetium: Chemistry and Radiopharmaceutical Applications. Weinheim, Germany: Wiley-VCH. ISBN   978-3-527-29496-1.
  15. ↑ German, K. E.; Kryutchkov, S. V. (2002). "Polynuclear Technetium Halide Clusters". Russian Journal of Inorganic Chemistry. 47 (4): 578–583. Archived from the original on 2015-12-22.
  16. ↑ German, K. E.; Peretrukhin, V. F.; Gedgovd, K. N.; Grigoriev, M. S.; Tarasov, A. V.; Plekhanov, Yu V.; Maslennikov, A. G.; Bulatov, G. S.; Tarasov, V. P.; Lecomte, M. (2005). "Tc Carbide and New Orthorhombic Tc Metal Phase". Journal of Nuclear and Radiochemical Sciences. 6 (3): 211–214. doi: 10.14494/jnrs2000.6.3_211 .
  17. ↑ Kuznetsov, Vitaly V.; German, Konstantin E.; Nagovitsyna, Olga A.; Filatova, Elena A.; Volkov, Mikhail A.; Sitanskaia, Anastasiia V.; Pshenichkina, Tatiana V. (2023-10-31). "Route to Stabilization of Nanotechnetium in an Amorphous Carbon Matrix: Preparative Methods, XAFS Evidence, and Electrochemical Studies". Inorganic Chemistry. doi:10.1021/acs.inorgchem.3c03001. ISSN   0020-1669.
  18. ↑ Wang, Qinggao; German, Konstantin E.; Oganov, Artem R.; Dong, Huafeng; Feya, Oleg D.; Zubavichus, Ya V.; Murzin, V. Yu (2016-02-08). "Explaining stability of transition metal carbides – and why TcC does not exist". RSC Advances. 6 (20): 16197–16202. doi:10.1039/C5RA24656C. ISSN   2046-2069.
  19. ↑ Bartholomä, Mark D.; Louie, Anika S.; Valliant, John F.; Zubieta, Jon (2010). "Technetium and Gallium Derived Radiopharmaceuticals: Comparing and Contrasting the Chemistry of Two Important Radiometals for the Molecular Imaging Era". Chemical Reviews. 110 (5): 2903–20. doi:10.1021/cr1000755. PMID   20415476.
  20. 1 2 3 Alberto, Roger (2010). "Organometallic Radiopharmaceuticals". Medicinal Organometallic Chemistry. Topics in Organometallic Chemistry. Vol. 32. pp. 219–246. doi:10.1007/978-3-642-13185-1_9. ISBN   978-3-642-13184-4.
  21. ↑ Hileman, J. C.; Huggins, D. K.; Kaesz, H. D. (1961). "Technetium carbonyl". Journal of the American Chemical Society. 83 (13): 2953–2954. doi:10.1021/ja01474a038.
  22. ↑ Bailey, M. F.; Dahl, Lawrence F. (1965). "The Crystal Structure of Ditechnetium Decacarbonyl". Inorganic Chemistry. 4 (8): 1140–1145. doi:10.1021/ic50030a011.
  23. ↑ Wallach, D. (1962). "Unit cell and space group of technetium carbonyl, Tc2(CO)10". Acta Crystallographica. 15 (10): 1058. doi:10.1107/S0365110X62002789.
  24. ↑ Schwochau 2000, pp. 286, 328.
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