Synthetic and structural studies have been made for a range of cationic, ten-electron, four-co-ordinate, diarylbis(ligand)bismuth(III) complexes. Reactions between BiPh₂Br, AgBF₄ and 2 equivalents of a two-electron donor ligand L afforded the ionic complexes [BiPh₂L₂][BF₄][L = OPPh₃ or pyridine (py)]. The first was characterised by X-ray crystallography and comprises [BiPh₂(OPPh₃)₂]⁺ cations, tetrafluoroborate anions and CH₂Cl₂ molecules of crystallisation. The bismuth centre is four-co-ordinate with a disphenoidal geometry in which the aryl groups are in equatorial positions with the ligands in axial sites. A long interaction is present between the bismuth centre and one of the fluorines of the BF₄ group. A series of similar reactions were also carried out between BiR₂Br (R = aryl), TlPF₆ and 2 equivalents of L affording the ionic complexes [BiR₂L₂][PF₆][R = Ph, L = OP(NMe₂)₃ or py; R = 4-MeC₆H₄, L = OP(NMe₂)₃; R = 2,4,6-Me₃C₆H₂, L = OP(NMe₂)₃ or OPPh₃]. Two of the complexes have also been characterised by X-ray crystallography, the cations having similar structures to that found in [BiPh₂(OPPh₃)₂][BF₄]. The reaction between BiPhBr₂, 1 equivalent of TlPF₆ and an excess of OP(NMe₂)₃ afforded the ionic complex [BiPh{OP(NMe₂)₃}₄][PF₆]₂. The crystal structure of the dication comprises a square-based pyramidal bismuth centre with an apical phenyl group and four basal OP(NMe₂)₃ ligands. Examples of some dihalogenobismuth cations have also been obtained and their structures are described and compared with those of previously reported examples.