Coordination Chemistry of Anticrowns. Synthesis and Structures of Double-Decker Sandwich Complexes of the Three-Mercury Anticrown (o-C6F4Hg)3 with Halide Anions Containing and Not Containing Coordinated Dibromomethane Molecules

The interaction of the three-mercury anticrown (o-C6F4Hg)(3) (1) with [PPh4][BF4] in methanol at room temperature leads to fluoride anion transfer from BF4 to 1 with the formation of a fluoride complex, [PPh4]{[(o-C6F4Hg)(3)](2)F}, having a double-decker sandwich structure. The fluoride ion in this unique adduct is disposed between the mutually parallel planes of the central nine-membered rings of the anticrown units and cooperatively coordinated by all six Hg sites. The iodide anion also forms a double-decker sandwich in the interaction with 1, but this sandwich, [PPh4]-([(o-C6F4Hg)(3)](2)I}, has a wedge-shaped geometry. The reaction of 1 with [(Bu4N)-Bu-n]Cl in dibromomethane at -15 degrees C affords a complex, [(Bu4N)-Bu-n]{[(o-C6F4Hg)(3)](2)Cl(CH2Br2)(2)}, containing one chloride anion and two coordinated CH2Br2 species per two molecules of 1. A similar bromide complex of 1, containing two coordinated CH2Br2 moieties, has also been synthesized and structurally characterized. Both compounds represent wedge-shaped double-decker sandwiches wherein the halide anion is simultaneously bonded to all Hg centers of the anticrown molecules. The dibromomethane species in the isolated adducts are also arranged in the space between the mercuramacrocycles. One of these species is coordinated by each of its bromine atoms to a single Hg site of the adjacent macrocycle while the other interacts by only one bromine atom with a Hg center of the neighboring molecule of 1.