A New Type of Terpene‐Based D₂‐Symmetric Macrocycles, Capable of Selectively Extracting Au, Pd and Pt from Complex Mixtures

Abstract

C2‐symmetric terpene‐based bis(α‐amine oximes) prepared from monoterpene hydrocarbons (+)‐3‐carene, (−)‐α‐pinene and (+)‐limonene, when treated with methylene chloride under phase‐transfer conditions, undergo inter‐ and intramolecular cross‐linking at oxime groups to form D2‐symmetric macrocycles in relatively good preparative yields (35–64 %). The structure of the new compounds was solved by spectroscopic methods and proved by X‐ray crystallography. D2‐symmetric macrocycles are crystalline solids which are well soluble even in small amounts of low‐polar organic solvents. Using Microwave Plasma Atomic Emission Spectrometry the new compounds was found to be able to selectively extract some noble metals (PtIV, AuIII, PdII) from aqueous solutions with pH=1.2 containing complex mixtures of transition elements at with no noticeable extraction of d‐elements (CrVI, MnII, FeIII, CoII, NiII, CuII, ZnII) and other noble metals (RuIII, RhIII, IrIII).