Olefin Rearrangements Assisted by a Molecular Metal−Oxo Surface: The Chemistry of Calix[4]arene Tungsten(IV)

This report deals with the olefin rearrangements achieved on a W-calix[4]arene oxo fragment that mimicks a heterogeneous metal−oxo surface both in the results and the chemical pathways. The olefin complexation by the W(IV)-calix[4]arene fragment has been achieved, generating the [{p-But-calix[4]-(O)4}W]-d2 from the reduction of [cis-(Cl)2W{p-But-calix[4]-(O)4}], 1, in the presence of the appropriate olefin. With this method, [{p-But-calix[4]-(O)4}W(η2-C2H4)], 2, [{p-But-calix[4]-(O)4}W(η2-MeC2H3)], 3, and [{p-But-calix[4]-(O)4}W(C6H10)], 4, have been obtained. In the latter complex the very labile cyclohexene can be replaced by another olefin, such as trans-stilbene in [{p-But-calix[4]-(O)4}W(η2-Ph2C2H2)], 5. The ethylene complex, 2, undergoes deprotonation with LiBu, leading to the corresponding anionic alkylidyne [{p-But-calix[4]-(O)4}W⋮CMe]Li, 6, which can be protonated, not back to the starting olefin complex, but rather to the corresponding alkylidene [{p-But-calix[4]-(O)4}WC(H)Me], 7. Complexes 6 an...