Abstract
A re-examination of the N.M.R. spectrum of mercury dimethyl using heteronuclear double resonance techniques confirms the values of the directly bonded and geminal coupling constants obtained by McLauchlan et al. [4]. The use of a locked oscillator system enables the signs and magnitudes of the vicinal and long-range coupling constants to be determined. The values obtained are 3 J 13C--H = -1·9±0·2 c/s and 4 J H---H = +0·45±0·02 c/s respectively. The chemical shifts of the 13C and 199Hg resonances relative to T.M.S. are also given.