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

Abstract

Converting CO 2 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 CO 2 with LaB m O 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, CB 2 O 2 − , CB 3 O 3 − , and CB 3 O 2 − , which possess B−C bonds, are generated in the reactions of LaB 3,4 O 2 − with CO 2 . When the number of B atoms in the clusters is reduced to 2 or 1, there is only CO-releasing channel, and no CB x O 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 CO 2 . (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 CO 2 transformation driven by clusters containing lanthanide atoms and how to efficiently build B−C bonds under room temperature.