Dibismuthates as Linking Units for Bis-Zwitterions and Coordination Polymers

Adducts of bismuth trihalides BiX₃ (X = Cl, Br, I) and the PS ligand (PS = P(C₆H₄-o-CH₂SCH₃)₃) react with HCl to form inorganic/organic hybrids with the general formula [HPSBiX₄]₂. On the basis of their solid-state structures determined by single-crystal X-ray diffraction, these compounds exhibit discrete bis-zwitterionic assemblies consisting of two phosphonium units [HPS]⁺ linked to a central dibismuthate core [Bi₂X₈]^2- via S→Bi dative interactions. Remarkably, the phosphorus center of the PS ligand undergoes protonation with hydrochloric acid. This is in stark contrast to the protonation of phosphines commonly observed with hydrogen halides resulting in equilibrium. To understand the important factors in this protonation reaction, ³¹P NMR experiments and DFT computations have been performed. Furthermore, the dibismuthate linker was utilized to obtain the coordination polymer {[AgPSBiCl₃(OTf)]₂(CH₃CN)₂}_∞, in which dicationic [Ag(PS)]₂²⁺ macrocycles containing five-coordinate silver centers connect the dianionic [Bi₂Cl₆(OTf)₂]^2- dibismuthate fragments. The bonding situation in these dibismuthates has been investigated by single-crystal X-ray diffraction and DFT calculations (NBO analysis, AIM analysis, charge distribution).