Abstract
The dimeric potassium alumanyl, [{SiN(Dipp)}AlK](2) ({SiN(Dipp)} = {CH(2)SiMe(2)N(Dipp)}(2); Dipp = 2,6-i-Pr(2)C(6)H(3)), reacts with two equivalents of PhC≡CR (R = Ph or SiMe(3)) with the exclusive formation of the aluminacyclopropene derivatives, [{SiN(Dipp)}Al{η(2)-C(2)(R(1))(R(2))}]. In contrast, reactions with an equal stoichiometry of both alumanyl and alkyne reagents provide the products of not only alkyne cycloaddition but also para-C-H activation of a phenyl substituent. Supported by a theoretical study, this outcome is judged to result from a sequence of cooperative steps and the introduction of a modicum of kinetic discrimination that is suggested to be allosteric in origin.