Crown compounds for anions. Sandwich complexes of cyclic trimeric perfluoro- o-phenylenemercury with hexacyanoferrate(III) and nitroprusside anions

Abstract

Cyclic trimeric perfluoro- o-phenylenemercury ( o-C 6F 4Hg) 3 ( 1) is able to bind hexacyanoferrate(III) and nitroprusside anions to form complexes {[( o-C 6F 4Hg) 3] 2[Fe(CN) 6]} 3− and {[( o-C 6F 4Hg) 3] 2[Fe(CN) 5NO]} 2−, respectively, which contain one anionic species per two macrocycles. According to X-ray diffraction data, the complexes have unusual sandwich structures wherein the anionic guest is located between the planes of two molecules of 1 and is coordinated to each of these through two types of Fe–C–N–Hg bridges. One type is the simultaneous coordination of a cyanide ligand to all three Hg centres of the cycle. The other type is the coordination of a cyanide group to a single Hg atom of the macrocycle. In both types, the bonding of the anionic guest with the macrocyclic host is accomplished with the participation of π-electrons of the cyanide ligands. The synthesized compounds are the first examples of host–guest complexes of a macrocyclic multidentate Lewis acid with anionic metal complexes.