NMR isotope shifts in the 2-methyl-2-bicyclo[2.1.1]hexyl cation and related systems

NMR isotope shifts at ¹³C nuclei due to deuteriation in the 2-methyl-2-bicyclo2.1.1]hexyl cation are reported. Comparisons are made to the 2-methyl-2-bicyclo2.2.1]heptyl and 2-methyl-2-bicyclo2.2.2]octyl cations, and also to neutral molecules containing the bicyclo2.1.1]hexyl framework. The combination of isotope effects with temperature dependence of ¹³C chemical shifts allows predictions of the shapes of the energy surfaces along the bending coordinate corresponding to bridging in these cations.