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.