Rhodium(II) trifluoroacetate

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Rhodium(II) trifluoroacetate
Rh2(tfa)4(H2O)2.svg
Names
Other names
  • Dirhodium tetrakis(trifluoroacetate)
  • Dirhodium tetra(trifluoroacetate)
  • Rhodium(II) trifluoroacetate dimer
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.159.403 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 631-136-4
PubChem CID
  • InChI=1S/4C2HF3O2.2Rh/c4*3-2(4,5)1(6)7;;/h4*(H,6,7);;
    Key: SZQVMUPTZFMHQT-UHFFFAOYSA-N
  • C(=O)(C(F)(F)F)O.C(=O)(C(F)(F)F)O.C(=O)(C(F)(F)F)O.C(=O)(C(F)(F)F)O.[Rh].[Rh]
Properties
C8F12O8Rh2
Molar mass 657.872 g·mol−1
Appearancegreen solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Rhodium trifluoroacetate is the chemical compound with the formula Rh2(O2CCF3)4. It is used as a catalyst in the synthesis of some organic compounds. [1] The compound and its derivatives have been extensively characterized by X-ray crystallography. It adopts the Chinese lantern structure seen for many dimetal carboxylate complexes. This structure accommodates a Rh-Rh bond, the existence of which explains the diamagnetism of this Rh(II) species. The Rh-Rh distance is 238 pm. [2]

The anhydrous complex is a green volatile solid. It is prepared by dissolving rhodium(II) acetate in hot trifluoroacetic acid: [3]

Rh2(O2CCH3)4 + 4 HO2CCF3 → Rh2(O2CCF3)4 + 4 HO2CCH3

This reaction expels acetic acid. The Rh-Rh bond is retained.

Reactions

Rhodium(II) trifluoroacetate forms adducts with a variety of Lewis bases. The structures typically have a 2:1 stoichiometry, with one base binding at the "axial" position on each of the two Rh(II) centers:

Rh2(O2CCF3)4 + 2 L → Rh2(O2CCF3)4L2 (L = CO, RCN, R2SO, R3P, ...)

Rhodium(II) trifluoroacetate binds even very weak bases, moreso than does rhodium(II) acetate. It even forms adducts with hexamethylbenzene and with S8. [4]

Rhodium(II) trifluoroacetate catalyzes cyclopropanation of alkenes by diazo compounds: [1] RCH=CR'H + CH3CH2O2CCH(N2) → cyclo−(RCH)(R'CH)(CH3CH2O2CCH) + N2

Related Research Articles

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Rhodium is a chemical element; it has symbol Rh and atomic number 45. It is a very rare, silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope, which is 103Rh. Naturally occurring rhodium is usually found as a free metal or as an alloy with similar metals and rarely as a chemical compound in minerals such as bowieite and rhodplumsite. It is one of the rarest and most valuable precious metals. Rhodium is a group 9 element.

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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.

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<span class="mw-page-title-main">Palladium(II) acetate</span> Chemical compound

Palladium(II) acetate is a chemical compound of palladium described by the formula [Pd(O2CCH3)2]n, abbreviated [Pd(OAc)2]n. It is more reactive than the analogous platinum compound. Depending on the value of n, the compound is soluble in many organic solvents and is commonly used as a catalyst for organic reactions.

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3
CO
2
). This dark green powder is slightly soluble in polar solvents, including water. It is used as a catalyst for cyclopropanation of alkenes. It is a widely studied example of a transition metal carboxylate complex.

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Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion (CH
3
COCHCOCH
3
) and metal ions, usually transition metals. The bidentate ligand acetylacetonate is often abbreviated acac. Typically both oxygen atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(acac)3 and M(acac)2. Mixed-ligand complexes, e.g. VO(acac)2, are also numerous. Variations of acetylacetonate have also been developed with myriad substituents in place of methyl (RCOCHCOR). Many such complexes are soluble in organic solvents, in contrast to the related metal halides. Because of these properties, acac complexes are sometimes used as catalyst precursors and reagents. Applications include their use as NMR "shift reagents" and as catalysts for organic synthesis, and precursors to industrial hydroformylation catalysts. C
5
H
7
O
2
in some cases also binds to metals through the central carbon atom; this bonding mode is more common for the third-row transition metals such as platinum(II) and iridium(III).

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Copper(II) trifluoroacetate is the trifluoroacetate of divalent copper with the chemical formula Cu(CF3COO)2. It exists as the anhydride, hydrate and adducts of other solvents. The hydrate begins to lose two waters of crystallisation at 108 °C, and loses all crystal water at 173 °C to form the anhydrous form. This begins to decompose at 220 °C. It finds some use as a reagent in organic chemistry.

References

  1. 1 2 Doyle, Michael P.; Davies, Huw M. L.; Manning, James R.; Yu, Yang (2018). "Dirhodium(II) tetrakis(trifluoroacetate)". EEROS. doi:10.1002/047084289X.rd461.pub2. ISBN   978-0-471-93623-7.
  2. Cotton, F. Albert; Dikarev, Evgeny V.; Feng, Xuejun (1995). "Unligated Dirhodium Tetra(trifluoroacetate): Preparation, Crystal Structure and Electronic Structure". Inorganica Chimica Acta. 237 (1–2): 19–26. doi:10.1016/0020-1693(95)04662-S.
  3. Felthouse, Timothy R. (1982). "The Chemistry, Structure, and Metal-Metal Bonding in Compounds of Rhodium(II)". Progress in Inorganic Chemistry. Vol. 29. pp. 73–166. doi:10.1002/9780470166307.ch2. ISBN   978-0-471-09370-1.
  4. Cotton, F. Albert; Dikarev, Evgeny V.; Petrukhina, Marina A. (2001). "Neutral Cyclooctasulfur as a Polydentate Ligand: Supramolecular Structures of [Rh2(O2CCF3)4]n(S8)m (n:m=1:1, 3:2)". Angewandte Chemie International Edition. 40 (8): 1521–1523. doi:10.1002/1521-3773(20010417)40:8<1521::AID-ANIE1521>3.0.CO;2-M.