Electronic structures and redox properties of boronated cyanometalates

We have synthesized and structurally characterized homoleptic and heteroleptic tris(pentafluorophenyl)borane adducts of iron, ruthenium, and osmium cyanides. The III/II formal potentials are more than 2.0 V higher in the boronated octahedral complexes; and, in the boronated heteroleptic complexes, the MLCT excited triplets are relatively long-lived (he MLCT absorptions are dramatically blue-shifted).The boronated homoleptic complexes, which are electrochem. reversible, exhibit energy efficiencies of 80% in nonaq. redox flow batteries; and the boronated heteroleptic complexes exhibit cell potentials over 3.0 V in sym-rf batteries.