Dihydrogen Activation by Lithium- and Sodium-Aluminyls

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Inorganic Synthesis

Background:

• Aluminyl anions, compounds featuring an aluminum-centered anionic species, have historically been limited to isolation as potassium salts.
• The structural diversity and reactivity of main group element anions are crucial for understanding bonding and developing new chemical transformations.

Purpose of the Study:

• To synthesize and characterize novel lithium and sodium aluminyl compounds.
• To investigate the structural features and bonding in these new aluminyl species.
• To explore the reactivity of the full series of alkali metal aluminyls, including their ability to activate dihydrogen.

Main Methods:

• Synthesis of lithium and sodium aluminyls using a specific ligand system (NON^Dipp).
• Crystallization from various solvents to obtain different structural motifs (dimeric and monomeric ion pairs).
• Characterization using techniques suitable for inorganic compounds, including X-ray crystallography.
• Reactivity studies focusing on dihydrogen activation.

Main Results:

• Successful synthesis of lithium and sodium aluminyls, M₂[Al(NON^Dipp)₂] (M=Li, Na).
• Isolation of dimeric structures with slipped contacts and significant M⋅⋅⋅π(aryl) interactions in non-coordinating solvents.
• Formation of monomeric ion pairs, (NON^Dipp)Al-M(Et₂O)₂, containing discrete Al-Li and Al-Na bonds upon isolation from diethyl ether.
• Demonstration of the dihydrogen activation capability across the series of lithium, sodium, and potassium aluminyls.

Conclusions:

• The synthesis of lithium and sodium aluminyls broadens the scope of isolable alkali metal aluminyl compounds.
• The observed structural diversity highlights the influence of solvent and counterion on the aggregation and bonding of these species.
• Alkali metal aluminyls, including the newly synthesized Li and Na variants, are capable of activating dihydrogen, suggesting potential applications in catalysis or synthesis.