Three crystal structures of the (4-bromo-benz-yl)tri-phenyl-phospho-nium cation with perchlorate, tetra-fluoro-borate and triiodide anions.

The reaction of (4-bromo-benz-yl)tri-phenyl-phospho-nium bromide ([4BrBzTPP][Br]) with excess perchloric, tetra-fluoro-boric or hydro-iodic acid in methanol affords the corresponding anion-exchanged salts. X-ray quality crystals of (4-bromo-benz-yl)tri-phenyl-phospho-nium perchlorate, C25H21BrP+·ClO4 - or [4BrBzTPP][ClO4], (I), (4-bromo-benz-yl)tri-phenyl-phospho-nium tetra-fluoro-borate, C25H21BrP+·BF4 - or [4BrBzTPP][BF4], (II), and (4-bromo-benz-yl)tri-phenyl-phospho-nium triiodide, C25H21BrI3P+·I3 - or [4BrBzTPP][I3], (III), were isolated and characterized by single-crystal X-ray diffraction. Compounds (I) and (II) are isostructural and crystallize in the ortho-rhom-bic space group Pbca, whereas compound (III) crystallizes in the monoclinic space group P21/n. In all three structures, the phospho-nium cation adopts a tetra-hedral geometry at phospho-rus, with C-P-C bond angles in the range 106.09 (11)-112.67 (11)°. Hirshfeld surface analyses show that H⋯H and H⋯C contacts dominate the environments of the (4-bromo-benz-yl)tri-phenyl-phospho-nium cations, whereas the perchlorate, tetra-fluoro-borate and triiodide anions are linked to the surrounding cations primarily through H⋯O, H⋯F and H⋯I contacts, respectively.