Coordination chemistry of mercury-containing anticrowns. Complexation of nitrate and sulfate anions with the three-mercury anticrown (o-C6F4Hg)3 and the influence of the nature of a countercation on the structure of the resulting nitrate complexes

The interaction of the three-mercury anticrown (o-C6F4Hg)3 (1) with [PPN]NO3 and [PPh4]NO3 in an ethanol solution yields nitrate complexes, [PPN]{[(o-C6F4Hg)3]2(NO3)} (2) and [PPh4]{[(o-C6F4Hg)3]2(NO3)} (3), respectively, having double-decker sandwich structures. In both adducts, the nitrate anion behaves as a tridentate ligand and is coordinated through the oxygen atoms with the Hg sites of each anticrown unit in an η3:η1 fashion. However, whereas complex 3 constitutes a bent sandwich in the crystal, the planes of the anticrown molecules in complex 2 are parallel to each other. The reaction of 1 with [PhNMe3]2SO4 results in the formation of a sulfate complex, [PhNMe3]2{[(o-C6F4Hg)3]2(SO4)} (4), the subsequent recrystallization of which from the acetone/ethanol mixture yields a solvate, 4·Me2CO·3EtOH, representing also a double-decker sandwich according to X-ray crystallography. The sulfate anion in this sandwich is a tetradentate ligand and is bound to each anticrown species by two oxygen atoms in an η3:η1 fashion as well. Like 3, complex 4·Me2CO·3EtOH has a bent sandwich geometry. The complex is characterized also by the presence of H-bonds between two oxygen atoms of the coordinated sulfate anion and two ethanol molecules. The synthesized sandwich compounds 2, 3 and 4·Me2CO·3EtOH are the novel structural type of complexes of an anticrown with nitrate and sulfate anions as well as the first examples of structurally characterized complexes of 1 with oxygen-containing anions.