Conversion of Carbon Dioxide into a Series of CB_xO_y^- Compounds Mediated by LaB_3,4O₂^- Anions: Synergy of the Electron Transfer and Lewis Pair Mechanisms to Construct B-C Bonds

Converting CO₂ into value-added products containing B-C bonds is a great challenge, especially for multiple B-C bonds, which are versatile building blocks for organoborane chemistry. In the condensed phase, the B-C bond is typically formed through transition metal-catalyzed direct borylation of hydrocarbons via C-H bond activation or transition metal-catalyzed insertion of carbenes into B-H bonds. However, excessive amounts of powerful boryl reagents are required, and products containing B-C bonds are complex. Herein, a novel method to construct multiple B-C bonds at room temperature is proposed by the gas-phase reactions of CO₂ with LaB_mO_n^- (m = 1-4, n = 1 or 2). Mass spectrometry and density functional theory calculations are applied to investigate these reactions, and a series of new compounds, CB₂O₂^-, CB₃O₃^-, and CB₃O₂^-, which possess B-C bonds, are generated in the reactions of LaB_3,4O₂^- with CO₂. When the number of B atoms in the clusters is reduced to 2 or 1, there is only CO-releasing channel, and no CB_xO_y^- compounds are released. Two major factors are responsible for this quite intriguing reactivity: (1) Synergy of electron transfer and boron-boron Lewis acid-base pair mechanisms facilitates the rupture of C═O double bond in CO₂. (2) The boron sites in the clusters can efficiently capture the newly formed CO units in the course of reactions, favoring the formation of B-C bonds. This finding may provide fundamental insights into the CO₂ transformation driven by clusters containing lanthanide atoms and how to efficiently build B-C bonds under room temperature.