Crystal Structure Analysis of the l,2,4,7‐anti‐Tetramethyl‐2‐norbornyl Cation: an Unsymmetrically Bridged Carbocation

Classical or nonclassical? This was the question posed repeatedly during the last 30 years concerning the structure the 2-norbornyl cation. New evidence has now been provided by the title compound 1, for which the first X-ray crystal structure analysis of a 2-norbornyl cation has en obtained. Unsymmetrical σ-participation is evident 1. The originally single bond C1-C6 is weakened by nation of electron density to the electron-deficient central C2 and thereby lengthened to 1.74(2)Å. Correspondingly. the bond C1-C2 is shortened to 1.44(2)Å. The C2- distance (2.09(2)Å) also reflects the bridging between these atoms.