1H and 199Hg NMR spectra of methylmercury(II) complexes. Effects of basicity and ortho substitution in pyridines(L) in complexes [MeHgL]NO3
Linear complexes [MeHgL]NO3 (L = substituted pyridine) have been prepared and their 1H and 199Hg NMR spectra measured and compared with other complexes of this series reported previously. The coupling constant J(1H-199Hg) correlates directly with pKa and with the gas phase enthalpy of ionization [?Gi(g)] of LH+; with J(1H-199Hg) decreasing with increasing pKa or ?Gi(g). The chemical shift, d, for 199Hg does not correlate with either pKa or ?Gi(g). Complexes without substituents in the 2 position of pyridine have d199Hg ca. 80-100 ppm downfield from MeHgNO3, those with one methyl group in the 2 position ca. 125-150 ppm, and those with methyl groups in the 2 and 6 position (or benzyl or 3'-methylpyridyl groups in the 2 position) ca. 160-200 ppm downfield from MeHgNO3. The coupling constant J(1H-199Hg) is found to be more useful than d199Hg in determination of solution structures of MeHg(II) complexes of this type of ligand.
Journal of Organometallic Chemistry