Formula C8H12O8Rh2 Density 1.13 g/cm³ | Molar mass 441.99 g/mol Appearance Emerald green powder | |
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Related compounds | ||
Rhodium(II) acetate is the chemical compound with the formula Rh2(AcO)4, where AcO− is the acetate ion (CH
3CO−
2). This dark green powder is slightly soluble in polar solvents, including water. It is used as a catalyst for cyclopropanation of alkenes.
Contents
Preparation
Rhodium(II) acetate is usually prepared by the heating of hydrated rhodium(III) chloride in acetic acid (CH3COOH): Rhodium(II) acetate dimer undergoes ligand exchange, the replacement of the acetate group by other carboxylates and related groups.
Rh2(OAc)4 + 4 HO2CR → Rh2(O2CR)4 + 4 HOAcStructure and Properties
The structure of rhodium(II) acetate features a pair of rhodium atoms, each with octahedral molecular geometry, defined by four acetate oxygen atoms, water, and a Rh–Rh bond of length 2.39 Å. The water adduct is exchangeable, and a variety of other Lewis bases bind to the axial positions. Copper(II) acetate and chromium(II) acetate adopt similar structures.
Chemical properties
The application of dirhodium tetraacetate to organic synthesis was pioneered by Teyssie and co-workers. An extensive range of reactions including insertion into O–H and N–H bonds and the cyclopropanation of olefins. and aromatic systems. It selectively binds ribonucleosides (vs. deoxynucleosides) by binding selectively to ribonucleosides at their 2′ and 3′ –OH groups. Rhodium(II) acetate dimer, compared to copper(II) acetate, is more reactive and useful in differentiating ribonucleosides and deoxynucleosides because it is soluble in aqueous solution like water whereas copper(II) acetate only dissolves in non-aqueous solution.
Selected catalytic reactions
Dirhodium tetraacetate is also used as catalyst for insertion into C–H and X–H bonds (X = N, S, O).
- Cyclopropanation
- Aromatic cycloaddition
- C–H insertion
- Oxidation of alcohols
- X–H insertion (X = N, S, O)