Rhodium(II) trifluoroacetate

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 * ImageFile = Rh2(tfa)4(H2O)2.svg
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 * IUPACName =
 * OtherNames =Dirhodium tetrakis(trifluoroacetate, rhodium(II) trifluoroacetate dimer
 * Section1={{Chembox Identifiers
 * CASNo = 31126-95-1
 * ChemSpiderID = 380904
 * EC_number = 631-136-4
 * PubChem =10985187
 * StdInChI=1S/4C2HF3O2.2Rh/c4*3-2(4,5)1(6)7;;/h4*(H,6,7);;
 * StdInChIKey = SZQVMUPTZFMHQT-UHFFFAOYSA-N
 * SMILES = 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]
 * Section2={{Chembox Properties
 * Rh = 2|O=8|F=12|C = 8
 * MolarMass =
 * Appearance = green solid
 * Density =
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 * Section3={{Chembox Hazards
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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. 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.

The anhydrous complex is a green volatile solid. It is prepared by dissolving rhodium(II) acetate in hot trifluoroacetic acid:
 * 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, often with 2:1 stoichiometry, with a variety of Lewis bases. The bases bind at the "axial" positions on each of the two Rh(II) center:
 * 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.

Rhodium(II) trifluoroacetate catalyzes cyclopropanation of alkenes by diazo compounds: RCH\dCR'H + CH3CH2O2CCH(N2)  ->  cyclo\s(RCH)(R'CH)(CH3CH2O2CCH)  +  N2