Effect of the NH---S Hydrogen Bond on the Nature of Hg−S Bonding in Bis[2-(acylamino)benzenethiolato]mercury(II) and Bis[2,6-bis(acylamino)benzenethiolato]mercury(II) Complexes

2-(Acylamino)benzenethiolate complexes of Hg(II) having an intramolecular NH---S hydrogen bond, Hg[2-(pivaloylamino)benzenethiolato] 2 and Hg[2,6-bis(pivaloylamino)benzenethiolato] 2, were synthesized and the crystal structures were determined. The crystal structure of Hg[2-(pivaloylamino)benzenethiolato] 2 · 1 / 2 H 2 O shows the presence of two distinct conformers with different C−S−(Hg)−S−C torsion angles (81.7 and 176.6°). The crystal structure of Hg[2,6-bis(pivaloylamino)benzenethiolato] 2 indicates the presence of ordinary Hg−S bonds (2.335(2) and 2.342(2) Å) and a straight linear coordination (S−Hg−S = 174.7(1)°) with a weak interaction of one of the amide CO groups toward Hg(II). A weak NH---S hydrogen bond in both complexes is detected from the IR spectra in the solid state. The 199 Hg NMR spectra show the high-field shift with a decrease in the S → Hg(II) ligand-to-metal charge transfer by the NH---S hydrogen bonding. The high-field shift by the double NH---S hydrogen bond is far greater than that by the p -substituent effect of the electron-withdrawing group (OMe, H, NHCOCH 3, Cl, NO 2 ) on the benzenethiolate ring.