A two-electron reducing reaction of CO2 to an oxalate anion: a theoretical study of delocalized (presolvated) electrons in Al(CH3)n(NH3)m, n = 0–2 and m = 1–6, clusters

Abstract

Presolvated electron possibility in three oxidation states of aluminum – Al(0), Al(I), and Al(II) – has been theoretically investigated for the Al + 6NH₃, Al(CH₃) + 5NH₃, and Al(CH₃)₂ + 4NH₃ reactions. It has been shown that the metal center adopts a tetrahedral shape for its most stable geometric structure, irrespective of the degree of Al oxidation states. Using different analysis techniques (highest occupied molecular orbital shapes, spin density distributions, and electron delocalization ranges), we showed that presolvated (delocalized) electrons are only formed in the Al(CH₃)₂(NH₃)_p coordination complexes when 2 ≤ p ≤ 4. It has also been evidenced that these delocalized electrons being powerful reducing agents allowed two CO₂ molecules to be captured and form an oxalate ion in close contact with the [Al₂(CH₃)₂(CH₂)₂(NH₃)₄]²⁺ dication core.