Seven-Membered Cyclic Diamidoalumanyls of Heavier Alkali Metals: Structures and C–H Activation of Arenes
Han‐Ying Liu, Michael S. Hill, Mary F. Mahon, Claire L. McMullin, Ryan J. Schwamm
Abstract
High Resolution Image Download MS PowerPoint Slide Like the previously reported potassium-based system, rubidium and cesium reduction of [{SiN Dipp }AlI] ({SiN Dipp } = {CH 2 SiMe 2 NDipp} 2 ) with the heavier alkali metals [M = Rb and Cs] provides dimeric group 1 alumanyl derivatives, [{SiN Dipp }AlM] 2 . In contrast, similar treatment with sodium results in over-reduction and incorporation of a formal equivalent of [{SiN Dipp }Na 2 ] into the resultant sodium alumanyl species. The dimeric K, Rb, and Cs compounds display a variable efficacy toward the C–H oxidative addition of arene C–H bonds at elevated temperatures (Cs > Rb > K, 110 °C) to yield (hydrido)(organo)aluminate species. Consistent with the synthetic experimental observations, computational (DFT) assessment of the benzene C–H activation indicates that rate-determining attack of the Al(I) nucleophile within the dimeric species is facilitated by π-engagement of the arene with the electrophilic M + cation, which becomes increasingly favorable as group 1 is descended.