Structure and Bond Dissociation Variations in Dialumenes: A Comparative DFT Study on N,P- versus N,N-Bidentate Ligand Effects.

Herein, we report a comprehensive density functional theory (DFT) calculation to investigate the distinct dissociation behaviors of dialumenes supported by amidophosphine, amidinate, and β-diketiminate (BDI) ligands. Calculations reveal that amidophosphine and amidinate ligands stabilize the Al═Al double bond via a dynamic equilibrium with their aluminyl monomers. Conversely, the BDI ligand preferentially stabilizes mononuclear Al(I) species over dimerization. According to energy decomposition analysis (EDA) and charge decomposition analysis (CDA), this distinct behavior is attributed to the enhanced Pauli's repulsion and diminished orbital interaction between the BDI-stabilized aluminyl fragments. Notably, despite the constrained N-Al-N bite angle imposed by the amidinate ligand, the enhanced stability of the Al═Al bond emerges through limited aluminyl monomer deformation and effective ligand-metal conjugation. A systematic comparison with the hydrogenated amidophosphine ligand systems further demonstrates that the ligand-metal conjugation critically modulates Al═Al bond dissociation, primarily through steric repulsion between the amino lone pairs and Al-Al cores. These key ligand parameters derived from specific ligand systems in this study provide a theoretical foundation for future dialumene design.