Metal-stabilized carbocations derived from monoterpenes: dicobalt hexacarbonyl complexes of alkynyl-verbenols

Nucleophilic attack by alkynyl anions on the verbenone skeleton occurs on the face opposite to that occupied by the gem-dimethyl group. The resulting alkynols react with dicobalt octacarbonyl to form tetrahedral (μ2-alkyne)Co2(CO)6 clusters in which the tricarbonylcobalt moieties are diastereotopic, and treatment with dppm tags each of these vertices with a 31P NMR label. Protonation yields a single cobalt-stabilized carbocation, 13a, in which …