The structure and bonding in bisaquamercury(II) trifluoromethanesulfonate, [Hg(OH2)2(CF3SO3)2] ∞, and trisaquathallium(III) trifluoromethanesulfonate, [Tl(OH2)3(CF3SO3)3], have been studied by means of single-crystal X-ray diffraction, EXAFS and vibrational spectroscopy. The crystal structure of bisaquamercury(II) trifluoromethanesulfonate shows an unusual connectivity pattern. The mercury(II) ion strongly binds two water molecules axially with the Hg-O bond distance 2.11 Å, and four oxygen atoms from four trifluoromethanesulfonate ions complete a tetragonally compressed octahedral coordination geometry, at the mean Hg-O distance 2.53 Å. Two trifluoromethanesulfonate ions form double bridges between the bisaquamercury(II) entities giving rise to infinite >Hg(OH2)2 <(CF3SO3)2 >Hg(OH2)2< chains. The parallel chains are held together in layers by relatively strong hydrogen bonds with O(-H)···O distances in the range 2.688(9)-2.735(9) Å. The O-D stretching vibrational frequencies of the hydrogen bonds in the partly deuterated compound occur in a broad band at about 2400 cm-1, bandwidth ca. 170 cm-1. The layers are connected onlyvia van der Waals interactions between the protruding CF3 groups, consistent with the fragile sheet-like structure of the crystalline compound. Trisaquathallium(III) trifluoromethanesulfonate crystallises as molecular complexes where each thallium(III) ion binds three water molecules and three oxygen atoms from trifluoromethanesulfonate ions, with Tl-O bond distances in the range 2.18-2.24 Å. A hydrogen bond network between the water molecules and trifluoromethanesulfonate ions with O(-H)···O distances in the range 2.65(1)-2.80(1) Å holds the structure together. Raman and infrared spectra have been recorded and analysed. The changes in force constants and vibrational frequencies have been correlated with bond lengths for the S-O bond in the coordinated trifluoromethanesulfonate ion and for the Hg-O and Tl-O bonds, also including the hexaaquaions in the comparisons.
|Number of pages||8|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|Publication status||Published - Dec 1 2002|
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