SYNTHESIS, STRUCTURE AND ANION COORDINATION CHEMISTRY OF A NOVEL MACROCYCLIC COBALTOCENIUM RECEPTOR

A new macrocyclic amide-substituted cobaltocenium receptor, enedioxy)b is(ethylene-aminocarbonyl)]cobaltocenium hexafluorophosphate 2 has bee n prepared and its single-crystal X-ray structure determined. Proton N MR anion co-ordination studies revealed that 2 and other new acyclic c obaltocenium derivatives complex chloride and bromide anions with 1:1 stoichiometry. Comparative stability constant evaluations imply that t he macrocyclic receptor 2 forms halide complexes of greatest thermodyn amic stability, suggestive of a 'macrocyclic anion effect'. Cyclic vol tammetric investigations showed the cobaltocenium receptors to electro chemically recognise halide anions.