DEPROTONATION REACTIONS OF 2-THIOURACIL WITH [2-(PYRIDIN-2-YL)-PHENYL]MERCURY(II) ACETEATE - STRUCTURAL AND SPECTROSCOPIC EFFECTS

The reaction of [2-(pyridin-2-yl)phenyl]mercury(II) acetate with 2-thi ouracil (H(2)tuc) in 1:1 and 2:1 mole ratio in methanol solution affor ded [Hg(C6H4C5H4N)(H(2)tuc)] and [{Hg(C6H4C5H4N)}(2)(tuc)] respectivel y. The bimetallic complex crystallizes in the monoclinic space group P 2(1)/n with a = 10.706(1), b = 22.043(3), c = 11.126(1) Angstrom, beta = 117.01(1)degrees and Z = 4. The complex molecules are associated in centrosymmetric dimers by weak intermolecular pyridine N ... Hg bond interactions. Of the two organometallic cations, one is bound to the t hiouracil N(3) atom [Hg(1)-N(3) 2.12(1)Angstrom] and the other is S-co -ordinated [Hg(2)-S 2.350(5) Angstrom]. Atom Hg(1) also forms two weak intramolecular bonds with the O and S atoms and another secondary bon d with the pyridine nitrogen of the Hg(1)(C6H4C5H4N) moiety [Hg(1)... N 2.61(2) Angstrom]. This last type of intramolecular bond is also pre sent, though a little longer [Hg(2)... N 2.69(2) Angstrom], in Hg(2)(C 6H4C5H4N), where Hg(2) is located 2.99(1) Angstrom from the non-co-ord inated nitrogen atom of the tuc(2-) anion [N(1)]. On the grounds of a vibrational study of the two complexes; a scheme for IR-based diagnosi s of the co-ordination of the 2-thiouracilate anions is proposed. The H-1 and Hg-199 NMR spectra of the bimetallic complex in CDCl3 solution indicate that the N- and S-bound Hg(C6H4C5H4N) units interchange slow ly, while the pyridine intramolecular N ... Hg interactions remain in both CDCl3 and (CD3)(2)SO solutions.