CO₂ Capture by 2-(Methylamino)pyridine Ligated Aluminum Alkyl Complexes

A set of novel, easily synthesized aluminum complexes, Al[κ²-N,N-2-(methylamino)pyridine]₂R (R = Et, iBu) are reported. When subjected to 1 atm of CO₂ pressure, each hemilabile pyridine arm dissociates and facilitates cooperative activation of the CO₂ substrate reminiscent of a Frustrated Lewis Pair. This reaction has limited precedent for Al/N based Lewis Pair systems, and this is the first system readily shown to sequester multiple equivalents of CO₂ per aluminum center. The ethyl variant then reacts further, inserting a third equivalent of CO₂ into the aluminum alkyl to generate an aluminum carboxylate. Examples of this type of reactivity are rare under thermal conditions. A joint experimental/computational study supports the proposed reaction mechanism.