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 eta(3):eta(1) 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](2)SO4 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 center dot Me2CO center dot 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 eta(3):eta(1) fashion as well. Like 3, complex 4 center dot Me2CO center dot 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 center dot Me2CO center dot 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. (C) 2013 Elsevier B. V. All rights reserved.