Spectroscopic Identification of a Bidentate Binding Motif in the Anionic Magnesium–CO₂ Complex ([ClMgCO₂]⁻)

Abstract

Abstract A magnesium complex incorporating a novel metal–CO 2 binding motif is spectroscopically identified. Here we show with the help of infrared photodissociation spectroscopy that the complex exists solely in the [ClMg(η 2 ‐O 2 C)] − form. This bidentate double oxygen metal–CO 2 coordination has previously not been observed in neutral nor in charged unimetallic complexes. The antisymmetric CO 2 stretching mode in [ClMg(η 2 ‐O 2 C)] − is found at 1128 cm −1 , which is considerably redshifted from the corresponding mode in bare CO 2 at 2349 cm −1 , suggesting that the CO 2 moiety has a considerable negative charge (∼1.8 e − ). We also employed electronic structure calculations and kinetic analysis to support the interpretation of the experimental results.