[12]MERCURACARBORAND-4, THE 1ST-REPRESENTATIVE OF A NEW CLASS OF RIGID MACROCYCLIC ELECTROPHILES - THE CHLORIDE-ION COMPLEX OF A CHARGE-REVERSED ANALOG OF [12]CROWN-4

An exceptionally stable anion complex of 1 is produced in high yield from the reaction of the dilithiated carborane 1,2-C2B10H12 with HgCl2. It appears that the Cl- ion acts as a template, because the coordination geometry of the Hg center is strongly distorted. The almost perfectly square-planar coordination geometry of the Cl- ion is unprecedented. The anion can be extracted from the complex by Ag+ ions without causing the decomposition of the host, which suggests new possibilities in the molecular recognition of nucleophiles.