Bis(pentafluoroethyl)arsinous Acid and the Bis(pentafluoroethyl)arsinite─Synthesis, Structural Characterization and Transition-Metal Complexes

Herein we report the syntheses and characterization of bis(pentafluoroethyl)arsinous acid and its conjugate base, bis(pentafluoroethyl)arsinite. Controlled hydrolysis of (diethylamino)bis(pentafluoroethyl)arsane affords the corresponding diethylammonium-arsinite salt [NH₂Et₂][As(C₂F₅)₂O]. The coordination behavior of the arsinite anion was investigated by reaction of the salt with [TiCp₂Cl₂] and [Ni(dppp)Cl₂], yielding the monosubstituted complexes [TiCp₂Cl{OAs(C₂F₅)₂}] and [Ni(dppp)Cl{OAs(C₂F₅)₂}], respectively. Attempts to protonate the arsinite ion by treatment with gaseous HBr did not yield the desired arsinous acid, but resulted in the formation of bromobis(pentafluoroethyl)arsane. However, treatment of the amino arsane with para-toluenesulfonic acid led to the formation of the arsinous acid, which was isolated in 80% yield as a liquid at room temperature. Single crystals of the arsinous acid were grown by in situ crystallization techniques and the molecular structures were determined by single-crystal X-ray diffraction. Quantum-chemical calculations were performed to evaluate equilibria involving arsinous acids.