Calculated (11)B–(13)C NMR chemical shift relationship in hypercoordinate methonium and boronium ions

The boronium-carbonium continuum was extended to include hypercoordinated protonated methanes and their boron analogs. The (11)B NMR chemical shifts of the hypercoordinated hydriodo boron compounds and the (13)C NMR chemical shifts of the corresponding isoelectronic and isostructural carbocations were calculated by using the GIAO-MP2 method. The data show good linear correlation between (11)B and (13)C NMR chemical shifts, which indicates that the same factors that determine the chemical shifts of the boron nuclei also govern the chemical shifts of carbon nuclei of these hypercoordinated hydriodo compounds.