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

Ionic liquids (ILs) with chloride anion or bromide anion were attempted as a phase transfer reagent to depolymerize MX 2 (M = Pt, Pd; X = Br, Cl) in chloroform for reaction with 2,2′‐bipyridine (= bpy) to give the (bpy)MX 2 product. Supersonic irradiation of equiv‐molar bpy, PdX 2 , and IL in CHCl 3 produced almost quantitative precipitate of (bpy)PdX 2 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)PdX 2 . For preparation of (bpy)PtX 2 , nonetheless, free bpy always remained in mixture even after a long time of supersonic treatment. The system of equiv‐molar bpy, PtBr 2 , and IL in CHCl 3 , produced yellow (bpy)PtBr 2 and orange (bpy)PtBr 4 , both being characterized with 1 H NMR and 195 Pt NMR in d 6 ‐Me 2 SO as well as with single crystal X‐ray diffraction. Overall for PtX 2 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)PtBr 2 and (bpy)PtBr 4 .