Alkyl Bismuth Cations: Synthesis, Characterization, and Application as Z-Type Ligands.

When compared to their aryl-substituted counterparts, the chemistry of alkyl bismuth cations is still in its infancy. In order to tackle this synthetic challenge and close this gap of knowledge, we have developed protocols for the synthesis of precursors with unusual bismacyclic motifs and cyclopropyl ligands, Bi(CH₂)₅Br and BicPr₂Cl. These and the more common precursor BiiPr₂Cl could be turned into the cationic species [BiR₂(SbF₆)] (R₂ = (CH₂)₅, cPr₂, iPr₂), the first examples of alkyl bismuth cations with longer alkyl chains and cyclic motifs. The ability of these compounds to act as soft Z-type ligands is demonstrated by the formation of metal-only Lewis pairs in reactions with the platinum(0) precursor [Pt(PCy₃)₂]. The products of these reactions [(PCy₃)₂Pt→BiR₂(SbF₆)] show unsupported Pt→Bi bonds, and could be isolated and fully characterized. Pt oxidation and ring-opening of the cyclopropyl ligand were uncovered as a decomposition pathway.