Rhodium(II) trifluoroacetate explained

Rhodium trifluoroacetate is the chemical compound with the formula . 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]

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:

(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]

References

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