Triarylarsine halides The reactions of tri(2-, 3-, 4-methylphenyl)-, tri(dimethylphenyl)-, tri(2-, 3-, 4-fluorophenyl)-, tris(2-, 3-, and 4-trifluoromethylphenyl)arsine with halogens (bromine, iodine and iodine bromide) have been studied by conductometric titration in acetonitrile. In general, evidence was obtained for the formation, in solution, of 1:1 and 2:1 adducts (R3AsX2 and R3AsX4). All of the possible 1:1 and 2:1 adducts were isolated as crystalline solids and the electrolytic conductivity of their acetonitrile or nitrobenzene solutions was measured. The molar conductivity value for each compound (at Cm = 0.01 mol dm−3) was calculated. All of the compounds of type R3AsCl2 are weak electrolytes except (2-CH3C6H4) 3AsCl2 which is a medium electrolyte; and all of the R3AsBr2 compounds are weak or medium electrolytes except (2-CH3C6H4) 3AsBr2 which has a molar conductivity value approaching that of a strong electrolyte. The molar conductivity values of the dibromide adducts are always higher than those of the corresponding dichloride adducts. Comparison of the relative values of the molar conductivity of the adducts (YC6H4) 3AsX2 [Y = H, CH3, F, CF3 and X = Cl, Br] with the relative values of acid strengths of the corresponding substituted benzoic acids, YC6H4COOH, is made. The higher molar conductivity of R3AsI2 and R3AsIBr results from their disproportionation R3AsX2 □(→┬ ) 1⁄2 R 3 As + 1⁄2AsX+X3 All of the 2:1 adducts, R3AsX4 are strong electrolytes in acetonitrile solution and are formulated R3AsX+ X3−. The mixed tetrahalides R3AsCl3I and R3AsBr3I, were indicated from the reactions of R3AsCl2 with ICl and R3AsBr2 with IBr, and they can be obtained as solid adducts. These compounds ionise completely in acetonitrile and the halogen of lower atomic number resides, without exception, in the cation R3AsCl3I  R3AsCl+ICl2− R3AsBr3I  R3AsBr+ IBr2− Triarylstibine halides The course of the reactions of tri(2-, 3-, 4-methylphenyl)-, tri(dimethylphenyl)-, tris(2-, and 4-trifluoromethylphenyl)stibine with bromine, iodine and iodine bromide in acetonitrile solution were investigated by conductometric titration in order to observe compounds formation in these systems. All of the 1:1 and 2:1 adducts (R3SbX2 and R3SbX4) whose existence was shown by the titrations were isolated. The electrolytic conductivity of acetonitrile solutions of the adducts were measured and values of molar conductivity were obtained; all of the compounds of general formula R3SbX2 (X = Cl or Br) are either non-electrolytes or very weak electrolytes in acetonitrile. The conductivity of the adducts R3SbI2 and R3SbIBr are high and arise from their disproportionation in acetonitrile: R3SbI2 ⇄ 1⁄2R3Sb + 1⁄2R3SbI+I3− R3SbIBr⇄ 1⁄3R3Sb + 1⁄3R3SbBr2 + 1⁄3R3SbBr+I3− All of the tetrahalides except (4-CF3C6H4)3SbI4 are strong electrolytes. The conductometric titrations of R3SbCl2 with ICl and SbCl5 and R3SbBr2 with IBr [R = (CH3) 2C6H3, 2-CF3C6H4] have been studied in acetonitrile; there is no reaction between R3SbCl2 and ICl but with SbCl5 a highly conducting 2:1 adduct (R3SbCl+ Sb2Cl11−) is formed. With the exception of [(CH3)2C6H3]3SbBr2, the reaction of R3SbBr2 with IBr does not go to completion, but produces an equilibrium mixture of reactants and product: R3AsBr2 + IBr  R3SbBr+ IBr2− No solid adduct was obtained. However the adduct [(CH3)2C6H3]3SbBr3I, suggested from the titration graph, was isolated as a solid. It is a strong electrolyte in acetonitrile solution. Tetraphenylstibonium halides. All of the compounds Ph4SbX (X = F, Cl, Br, I) and Ph4SbX3 (X3 = Br3, IBr2, Icl2) were isolated as crystalline solids. Their electrolytic conductivity was measured in acetonitrile and the molar conductivity was calculated for each compound; Ph4SbF is a very weak electrolyte. Ph4SbCl and Ph4SbBr are weak electrolytes but Ph4Sbl is a strong electrolyte as are all of the trihalides, Ph4SbX3. The conductometric titrations of Ph4SbCl with ICl and Ph4SbBr with Br2 and IBr indicate that the trihalides Ph4SbX3 are formed readily in acetonitrile solution.