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

The structures of the title triethanolamine (tea) complexes of Cd-II and Hg-II saccharinates, bis(triethanolamine)-kappa O-3,N,O'; kappa O-4,N,O',O " -cadmium(II) 1,2-benzisothiazol-3(2H)-onate 1,1-dioxide, [Cd(C6H15NO3)(2)](C7H4NO3S)(2), (I), and bis(triethanolamine)-kappa O-3,N,O'; kappa O-4,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.