Ionic Liquid in Synthesis: A Phase Transfer Reagent and a Redox Mediating Medium

Abstract

AbstractIonic liquids (ILs) with chloride anion or bromide anion were attempted as a phase transfer reagent to depolymerize MX2 (M = Pt, Pd; X = Br, Cl) in chloroform for reaction with 2,2′‐bipyridine (= bpy) to give the (bpy)MX2 product. Supersonic irradiation of equiv‐molar bpy, PdX2, and IL in CHCl3 produced almost quantitative precipitate of (bpy)PdX2 in a short time at ambient temperature, where IL is either [BEIm]Br or [BMIm]Br. That is, ILs and sono‐techniques assisted greatly on the synthesis of (bpy)PdX2. For preparation of (bpy)PtX2, nonetheless, free bpy always remained in mixture even after a long time of supersonic treatment. The system of equiv‐molar bpy, PtBr2, and IL in CHCl3, produced yellow (bpy)PtBr2 and orange (bpy)PtBr4, both being characterized with 1H NMR and 195Pt NMR in d6‐Me2SO as well as with single crystal X‐ray diffraction. Overall for PtX2 reactions with halide anions in highly polar environments attributable to ILs, the redox pathway becomes important in that Pt(II) transforms to Pt(IV) to yield (bpy)PtBr2 and (bpy)PtBr4.