Turning the Tables: Ligand-Centered Hydride Shuttling in Organometallic BIP–Al Systems

The reversible storage and release of hydride equivalents remains a central challenge in the design of biomimetic redox systems. Cationic 2,6-bis(imino)pyridine organoaluminum complexes [(4-R-BIP)AlR₂]⁺ (where <i>R</i> = H; <i>R</i>' = Me, 1a; <i>R</i>' = Et, 1b; <i>R</i> = Bn; <i>R</i>' = Me, 1c) and their neutral 2,6-bis(imino)-4-R-dihydropyridinate counterparts [(4-R-HBIP)AlR₂] 2a-c are presented as chemically reversible hydride exchangers. Interconversion between these systems is achieved through strong reducing agents such as M⁺[HBEt₃]^- (where <i>M</i> = Li; Na) or LiAlH₄, while powerful electrophiles like B(C₆F₅)₃ or cationic trityl salts Ph₃C⁺ enable the reverse transformation, with the latter providing complete selectivity. Overall, this reversible hydride exchange mirrors natural NAD(P)H/NADP⁺ cofactor system. These findings establish a new platform for ligand-centered hydride shuttling, where the metal fragment acts as a passive modulator─inverting the traditional roles assigned to metal and ligand.