Bismuth compounds can be used as Lewis acid catalysts in many areas. Their Lewis acidity can be significantly increased by cationizing suitable bismuth compounds. In the present work, the increase in Lewis acidity is investigated using monocationic bismuth compounds and their coordination chemistry. The increased Lewis acidity of the dimethylbismuth cation enabled the synthesis of a compound exhibiting the first unsupported dative bismuth-platinum interaction. The resulting compound [Pt(PCy3)2(BiMe2)(SbF6)] also shows unprecedented reactivity towards elemental hydrogen. In the course of this reaction, the polarity of the dative bond is reversed due to the activation of hydrogen. In the further course of the work, the influence of the substituents on the bismuth atom on adduct formation with the Pt(0) complex [Pt(PCy3)2] was also investigated. It was found that adduct formation occurs with alkyl-substituted bismuth cations, whereas oxidative aryl transfer takes place with aryl-substituted derivatives.
In order to further increase the Lewis acidity, the first alkyl-substituted bismuth dication [BiMe(thf)5][SbF6]2 was prepared starting from BiMeCl2 and investigated for its Lewis acidity. By coordinating suitable ligands, a compound was generated as an intermediate that exhibits Lewis superacidic properties and can abstract a fluoride atom from SbF6-.
