Halogen impact into new oxonium benzo-crown ether complexes with tetrachloro- and tetrabromoaurates(iii)

Abstract

Five oxonium tetrahalogenaurate(III) (Hal = Cl, Br) benzo-crown ether (BCE) complexes are prepared and reported. The new compounds are [(H₃O)(B18C6)_0.58(4′-Cl-B18C6)_0.42][AuCl₄] 1, [(H₃O)(B18C6)][AuCl₄] 2, [(H₃O)(4′-Br-B18C6)][AuCl₄] 3, [(H₃O)(4′-Br-B18C6)][AuBr₄] 4, and [(H₃O)(B18C6)][AuBr₄] 5. The reaction medium, distinctive from the previously used aqua regia, allowed avoiding the unwanted nitration of initial macrocycles. The compositions and structures for 1, 3, 4, and 5 were proved by single crystal X-ray crystallography. The complete conversion of tetrachloroaurate(III) to the tetrabromoaurate(III) salts resulted in complex 4 isomorphous and isostructural to 3. All compounds form the laminated structures with alternation of cationic and anionic layers. The robustness of the anionic sheets is sustained by the halogen–halogen interactions and makes crucial impact on extraction of stoichiometric products in the case of tetrabromoaurate(III) salts.