The reactions of the binary metal chlorides AgCl, RbCl and PbCl₂ at T = 180°C in the ionic liquid [BMIm]Cl · 4AlCl₃ (BMIm = 1-n-butyl-3-methylimidazolium) yielded air-sensitive, colorless, high-quality crystals of their tetrachloridoaluminate(III) salts. Thereby, the obstructions that hinder proper crystallization of these compounds from pristine AlCl₃ melts were circumvented. X-ray diffraction on single-crystals revealed a monoclinic structure (space group P2₁/c) for Ag[AlCl₄], which unexpectedly has a closer relation to Cu[AlCl₄]₂ than to Cu[AlCl₄]. Rb[AlCl₄] crystallizes in the baryte structure type (orthorhombic, Pnma), and Pb[AlCl₄]₂ is isotypic to α-Sr[GaCl₄]₂ (orthorhombic, Pbca).