From Solid State to Solution: Advancing Chemistry of Bi–Bi and Bi–Rh Paddlewheel Carboxylates

The first successful high-yield solution synthesis of homobimetallic Bi2(O2CCF3)4 (1), as well as heterobimetallic BiRh(O2CCF3)4 (2) and BiRh(O2CCF2CF3)4 (3), complexes is reported. It is based on one-pot reduction reactions starting from Bi(III) and Rh(II) carboxylates and using Bi metal as a reducing agent. The presence of small amounts of diphenyl ether was found to facilitate this reaction, most probably because of its good solubilizing and π-stabilizing abilities. The latter is illustrated by the isolation and structural characterization of a π-adduct of 1 with diphenyl ether, [Bi2(O2CCF3)4·1/2Ph2O]. Importantly, the new approach expands to solution the chemistry of Bi(II) that was previously limited to the solid state only. The solution procedure developed for the preparation of heterometallic BiRh(O2CCF3)4 is now one step shorter and gives the product in excellent yield compared with the previously reported method based on sublimation-deposition technique. It is also performed on a greater scale (∼10–20 times) and makes further scale-up feasible, if needed. Moreover, it eliminates the isolation of the hard-to-handle unsolvated Bi(II) trifluoroacetate used earlier as a starting material. A new polymorph of BiRh(O2CCF3)4 (2) was crystallized from solution in this work. The solution approach was also applied to the synthesis of a new heterobimetallic carboxylate with perfluorinated propionate ligands, BiRh(O2CCF2CF3)4 (3). All products are fully characterized by spectroscopic and single crystal X-ray diffraction methods. Complexes 2 and 3 exhibit similar solid state structures based on heterobimetallic paddlewheel units forming infinite 1D chains through intermolecular Rh···O interactions.