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. 2025 Aug 4;64(30):15760-15773.
doi: 10.1021/acs.inorgchem.5c02587. Epub 2025 Jul 24.

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

Juan Manuel Delgado-Collado  1 , Francisco José Fernández de Córdova  1 , Pilar Palma  1 , Juan Cámpora  1 , Antonio Rodríguez-Delgado  1
Affiliations

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

Juan Manuel Delgado-Collado et al. Inorg Chem. .

Abstract

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 R = H; R' = Me, 1a; R' = Et, 1b; R = Bn; R' = 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 M = 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.

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Figures

1
1. Natural NAD­(P)+/NAD­(P)H System
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2. Synthetic Pathways to BIP-based Dihydropyridinate–Metal Complexes
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3. Irreversible Hydride Transfer from Zn­(II) 1,4-Dihydropyridinates
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1. Synthesis of Cationic Complexes of Type 1 used as Starting Materials in this Work
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4. Reaction of Nonsubstituted Cations 1a,b with Strong Hydride Donors
1
1
ORTEP representation of the structure of compound 2b. Hydrogen atoms have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Al–N(1): 2.218(5); Al–N(2): 1.893(5); Al–N(3): 2.238(5); Al–C(36): 1.993(8); Al–C(34): 1.981(6); N(1)–C(14): 1.274(7); N2–C(15): 1.383(7); C(14)–C(15): 1.451(8); C(13)–C(14): 1.515(8); C(15)–C(16): 1.346(9); C(16)–C(17): 1.485(9); N(2)–Al–N(1): 76.0(2); N(2)–Al–C(36): 136.3(2); N(2)–Al–C(34): 112.7(2); C(34)–Al–C(36): 111.0(3); N(2)–Al–N(3): 76.5(2); N(1)–Al–N(3): 150.9(2).
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5. Regeneration of Cations 1 from Dihydropyridinates 2 with a Trityl Salt
2
2
ORTEP representation of the structure of compound 1b·B­(C 6 F 5 ) 4 . Hydrogen atoms and 2.5 molecules of CH2Cl2 have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Al–N(1): 2.2028(16); Al–N(2): 2.0081(16); Al–N(3): 2.1733(16); Al–C(36): 1.968(3); Al–C(34): 1.970(3); N(1)–C(2): 1.282(2); N2–C(3): 1.342(2); N(2)–C(7): 1.342(2); N(3)–C(8): 1.283(2); C(1)–C(2): 1.493(3); C(3)–C(2): 1.488(3); C(3)–C(4): 1.384(2); C(4)–C(5): 1.384(3); C(5)–C(6): 1.387(3); C(6)–C(7): 1.389(3); C(7)–C(8): 1.487(3); C(8)–C(9): 1.486(3); N(2)–Al–N(1): 74.73(6); N(2)–Al–C(36): 102.30(11); N(2)–Al–C(34): 139.64(11); C(34)–Al–C(36): 117.99­(14); N(2)–Al–N(3): 75.25(6); N(1)–Al–N(3): 147.22(7).
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6. Reaction of the Dihydropyridinate Complexes 2a and 2b with B­(C6F5)3, and Two Alternative Mechanisms to Explain the Formation of Byproducts
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7. Reversible Hydride Addition to the Cationic BnBIP Derivative 1c
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