UNSTABLE COMPOUNDS - SYNTHESIS, STRUCTURE, AND EXPERIMENTAL AND COMPUTATIONAL CARBOCATION CHEMISTRY OF 2-CUMYLADAMANTAN-2-OL AND ITS ETA-6-CR(CO)3 COMPLEX

Structures of the title alcohol (1) and its chromium tricarbonyl complex (1a), were determined by single-crystal X-ray diffraction methods and were found to be very similar. Both of the alcohols were subjected to treatment with strong acids, and the behavior of the resulting carbocations was studied. Little difference between the two systems was noted. Both gave a mixture of predominantly phenyl- and methyl-shifted olefinic and cyclopropane dehydration products under various reaction conditions. These presumably arose from the corresponding rearranged cations. H-1 and C-13 NMR spectra of the cation derived from the title alcohol were obtained under stable ion conditions. Trapping of this species by triethylsilane at -78-degrees-C produced a 96% yield of 2-cumyladamantane. Semiempirical molecular orbital calculations (MNDO, AM1, and PM3) of the energies of the optimized structures of reactants, presumed intermediates, and products of the reactions, together with estimates of the energy barriers for the minimum energy reaction pathways, were used to understand the nature of the reaction mechanism.