Saccharinate-metal complexes with 1,10-phenanthroline (phen) or 2,2â?²-bipyridine (bipy) as co-ligands; The synthesis, crystal and molecular structures of five new compounds of divalent metals

Five new saccharinate complexes of divalent metals with either phen or bipy as co-ligands have been synthesised, and fully characterised by single crystal X-ray diffraction at low temperature. The complexes [M(phen)2(H 2O)2](sac)2·H2O (M = Co or Zn) are isostructural, while [Hg(bipy)2(sac)2] is isostructural with the analogous cadmium(II) compound, which has been described previously in the literature. Cadmium(II) complex [Cd(phen)2(sac) (H2O)](sac).H2O has an octahedral cation with the unidentate ligands in cis-positions, while [Hg(phen)2(sac)](sac) ·2.5 H2O provides a rare example of a distorted tbp structure for the cation, with five nitrogen donors. The structures are compared with those of related saccharinate complexes. In general, the more sterically demanding phen, when compared with bipy, forces more of the saccharinate anions to be uncoordinated, and for smaller ligands such as H2O to be coordinated to the metal, despite the electrostatic attraction between the positively charged metal and the anion. Intramolecular hydrogen bonding involving saccharinate groups plays an important role in all the hydrated complexes. © 2010 Elsevier B.V. All rights reserved.