Bismuth (II) trifluoroacetate, the first inorganic salt of bismuth in the oxidation state +2, can be obtained by both gas-phase and solution approaches through comproportionation reaction of Bi(III) trifluoroacetate and bismuth metal [1]. The solid state structure contains carboxylate-bridged dinuclear units with a single Bi–Bi bond. The compound can act as metalloligand toward transition metal complexes leading to heterometallic paddlewheel carboxylates BiM(O₂CCF₃)₄ (M = Ru, Rh) [2]. The physical and electronic properties of heterometallic molecules can be further tuned by changing the carboxylate environment. Mixed-ligand compounds [BiRh(O₂CCF₃)_x(O₂CR)_4-x] [3] can be synthesized by solid-state reactions between corresponding bismuth and rhodium carboxylates. These molecules maintain a paddle-wheel structure with single bismuth-to-transition metal bonds. The dinuclear units have been shown to remain intact in solution as well as in the vapor phase. The heterometallic trifluoroacetates function as one-ended Lewis acids to afford monoadducts with neutral donors, BiM(O₂CCF₃)₄×L, in which the substrate L is coordinated to the transition metal center only. At the same time, they exhibit a metal-site controlled arene coordination: h⁶ at the Bi-end and h² at the Rh-end. Heterobimetallic Bi-Rh molecules have been shown to exhibit catalytic activity in the transformations of diazo compounds similar to that of homometallic dirhodium complexes.

[1] E. V. Dikarev, B. Li. Inorg. Chem. 2004, 43, 3461.

[2] E. V. Dikarev, T. G. Gray, B. Li Angew. Chem. Int. Ed. 2005, 44, 1721.

[3] E. V. Dikarev, B. Li, H. Zhang J. Am. Chem. Soc. 2006, 128, 2814.