Metal-Ligand Cooperativity of the Calix[4]pyrrolato Aluminate: Triggerable C-C Bond Formation and Rate Control in Catalysis

Metal-ligand cooperativity (MLC) had a remarkable impact on transition metal chemistry and catalysis. By use of the calix[4]pyrrolato aluminate, [1](-), which features a square-planar Al-III, we transfer this concept into thep-block and fully elucidate its mechanisms by experiment and theory. Complementary to transition metal-based MLC (aromatizationupon substrate binding), substrate binding in [1](-)occurs bydearomatizationof the ligand. The aluminate trapps carbonyls by the formation of C-C and Al-O bonds, but the products maintain full reversibility and outstanding dynamic exchange rates. Remarkably, the C-C bonds can be formed or cleaved by the addition or removal of lithium cations, permitting unprecedented control over the system's constitutional state. Moreover, the metal-ligand cooperative substrate interaction allows to twist the kinetics of catalytic hydroboration reactions in a unique sense. Ultimately, this work describes the evolution of ananti-van't Hoff/Le Belspecies from their being as a structural curiosity to their application as a reagent and catalyst.