Rhodium(II) acetate is the

coordination compound A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

Rh₂(AcO)₄, where AcO⁻ is the

acetate An acetate is a salt formed by the combination of acetic acid with a base (e.g. alkaline, earthy, metallic, nonmetallic, or radical base). "Acetate" also describes the conjugate base or ion (specifically, the negatively charged ion called ...

ion (). This dark green powder is slightly soluble in polar solvents, including water. It is used as a catalyst for

cyclopropanation In organic chemistry, cyclopropanation refers to any chemical process which generates cyclopropane () Ring (chemistry), rings. It is an important process in modern chemistry as many useful compounds bear this motif; for example pyrethroid insectic ...

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

s. It is a widely studied example of a

transition metal carboxylate complex Transition metal carboxylate complexes are coordination complexes with carboxylate (RCO2−) ligands. Reflecting the diversity of carboxylic acids, the inventory of metal carboxylates is large. Many are useful commercially, and many have attracted ...

Preparation

Rhodium(II) acetate is usually prepared by the heating of

hydrated In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

rhodium(III) chloride in a methanol-

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

mixture. The crude product is the bis(methanol) complex, but it is easily desolvated.

Structure and properties

The structure of rhodium(II) acetate features a pair of

rhodium 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 isot ...

atoms, each with

octahedral molecular geometry In chemistry, octahedral molecular geometry, also called square bipyramidal, describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The o ...

, defined by four acetate oxygen atoms, water, and a Rh–Rh bond of length 2.39 Å. The water

adduct In chemistry, an adduct (; alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is ...

is exchangeable, and a variety of other

Lewis base A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

s bind to the axial positions.

Copper(II) acetate Copper(II) acetate, also referred to as cupric acetate, is the chemical compound with the formula where is acetate (). The hydrated derivative, , which contains one molecule of water for each copper atom, is available commercially. Anhydrous co ...

and

chromium(II) acetate Chromium(II) acetate hydrate, also known as chromous acetate, is the coordination compound with the chemical formula, formula Cr2(CH3CO2)4(H2O)2. This formula is commonly abbreviated Cr2(OAc)4(H2O)2. This red-coloured compound features a quadruple ...

adopt similar structures.

Chemical properties

The dimer binds a number of classical

s to form 2:1 adducts: Its

Lewis acidity A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty Non-bonding orbital, orbital which is capable of accepting an electron pair from a Lewis Base (chemistry), base to form a Lewis ...

is eclipsed by the enhanced reactivity of

rhodium(II) trifluoroacetate Rhodium trifluoroacetate is the chemical compound with the formula . 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 ...

, which even binds arenes and alkenes. The acetate group can be replaced by other carboxylates of strong acids. The yields are nearly quantitative. Like almost all rhodium complexes, rhodium(II) acetate catalyzes many reactions such as hydrogenation and hydrosilylation. No evidence exists for mechanisms and the behavior has not motivated further work. The important observation that rhodium(II) acetate catalyzes reactions of diazo compounds has led to considerable research, but mostly focused on the trifluoroacetate or chiral derivatives.

References

{{DEFAULTSORT:Rhodium(II) Acetate Rhodium(II) compounds Acetates Dimers (chemistry) Chemical compounds containing metal–metal bonds Aqua complexes