Organorhenium chemistry

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Organorhenium chemistry describes the compounds with Re-C bonds. Because rhenium is a rare element, relatively few applications exist, but the area has been a rich source of concepts and a few useful catalysts.

General features

Re exists in ten known oxidation states from −3 to +7 except −2, and all but Re(−3) are represented by organorhenium compounds. Most are prepared from salts of perrhenate and related binary oxides.[1] The halides, e.g., ReCl5 are also useful precursors as are certain oxychlorides.

A noteworthy feature of organorhenium chemistry is the coexistence of oxide and organic ligands in the same coordination sphere.[2]

Carbonyl compounds

Dirhenium decacarbonyl is a common entry point to other rhenium carbonyls. The general patterns are similar to the related manganese carbonyls. It is possible to reduce this dimer with sodium amalgam to Na[Re(CO)5] with rhenium in the formal oxidation state −1. Bromination of dirhenium decacarbonyl gives bromopentacarbonylrhenium(I),[3] then reduced with zinc and acetic acid to pentacarbonylhydridorhenium:[4]

Re2(CO)10 + Br2 → 2 Re(CO)5Br
Re(CO)5Br + Zn + HOAc → Re(CO)5H + ZnBr(OAc)

Bromopentacarbonylrhenium(I) is readily decarbonylated. In refluxing water, it forms the triaquo cation:[5]

Re(CO)5Br + 3 H2O → [Re(CO)3(H2O)3]Br + 2 CO

With tetraethylammonium bromide Re(CO)5Br reacts to give the anionic tribromide:[6]

Re(CO)5Br + 2 NEt4Br → [NEt4]2[Re(CO)3Br3] + 2 CO

Cyclopentadienyl complexes

One of the first transition metal hydride complexes to be reported was (C5H5)2ReH. A variety of half-sandwich compounds have been prepared from (C5H5)Re(CO)3 and (C5Me5)Re(CO)3. Notable derivatives include the electron-precise oxide (C5Me5)ReO3 and (C5H5)2Re2(CO)4.

Re-alkyl and aryl compounds

File:Methylrhenium-trioxide-3D-balls.png
Structure of methylrhenium trioxide.

Rhenium forms a variety of alkyl and aryl derivatives, often with pi-donor coligands such as oxide.[7] Well known is methylrhenium trioxide ("MTO"), CH3ReO3 a volatile, colourless solid. This compound has been used as a catalyst in some laboratory experiments. It can be prepared by many routes, a typical method is the reaction of Re2O7 and tetramethyltin:

Re2O7 + (CH3)4Sn → CH3ReO3 + (CH3)3SnOReO3

Analogous alkyl and aryl derivatives are known. MTO catalyses for the oxidations with hydrogen peroxide. Terminal alkynes yield the corresponding acid or ester, internal alkynes yield diketones, and alkenes give epoxides. MTO also catalyses the conversion of aldehydes and diazoalkanes into an alkene.[8]

Rhenium is also able to make complexes with fullerene ligands such as Re2(PMe3)4H8(η2:η2C60).

See also

  • Chemical bonds of carbon with other elements in the periodic table:
CH He
CLi CBe CB CC CN CO CF Ne
CNa CMg CAl CSi CP CS CCl CAr
CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr
CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe
CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn
Fr CRa Rf Db CSg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo
↓
CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu
Ac CTh CPa CU CNp CPu CAm CCm CBk CCf CEs Fm Md No Lr
Chemical bonds to carbon
Core organic chemistry Many uses in chemistry
Academic research, but no widespread use Bond unknown

References

  1. ↑ O. Glemser "Ammonium Perrhenate" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1476-85.
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  7. ↑ Pericles Stavropoulos, Peter G. Edwards, Geoffrey Wilkinson, Majid Motevalli, K. M. Abdul Malik and Michael B. Hursthouse "Oxoalkyls of rhenium-(V) and-(VI). X-Ray crystal structures of (Me4ReO)2Mg(thf)4,[(Me3SiCH2)4ReO]2Mg(thf)2, Re2O3Me6 and Re2O3(CH2SiMe3)6" J. Chem. Soc., Dalton Trans., 1985, pp. 2167-2175. doi:10.1039/DT9850002167
  8. ↑ Hudson, A. "Methyltrioxorhenium" Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons: New York, 2002.
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