Bis(triethanolamine)cadmium(II) and -mercury(II) saccharinates: seven-coordinate complexes containing both tri- and...

The structures of the title triethanolamine (tea) complexes of Cd(II) and Hg(II) saccharinates, bis(triethanolamine)-kappa3O,N,O';kappa4O,N,O',O"-cadmium(II) 1,2-benzisothiazol-3(2H)-onate 1,1-dioxide, [Cd(C6H15NO3)2](C7H4NO3S)2, (I), and bis(triethanolamine)-kappa3O,N,O';kappa4O,N,O',O"-mercury(II) 1,2-benzisothiazol-3(2H)-onate 1,1-dioxide, [Hg(C6H15NO3)2](C7H4NO3S)2, (II), or [M(tea)2](sac)2, where M is Cd(II) or Hg(II) and sac is the saccharinate anion, reveal seven-coordinate metal ions in both complexes. Both complex cations, [M(tea)2]2+, adopt a monocapped trigonal prism geometry in which the two tea ligands exhibit different coordination modes to achieve seven-coordination. One tea ligand acts as a tetradentate ligand using all its donor atoms, while the other behaves as a tridentate O,N,O'-donor ligand, with one of its ethanol groups remaining uncoordinated. The H atoms of the free and coordinated hydroxyl groups of the tea ligands are involved in hydrogen bonding with the amine N atom, and with the carbonyl and sulfonyl O atoms of neighbouring sac ions, forming an infinite three-dimensional network. A weak pi-pi interaction between the phenyl rings of the sac ions also occurs.