Implications of CO2 Activation by Frustrated Lewis Pairs in the Catalytic Hydroboration of CO2 : A View Using N/Si + Frustrated Lewis Pairs

N von Wolff (1) , G Lefèvre (1) , J.-C Berthet (1) , Pierre Thuéry (1) , T Cantat (1)

1 LCMCE - Laboratoire de Chimie Moléculaire et de Catalyse pour l'Energie (ex LCCEF)

A series of base-stabilized silylium species were synthesized and their reactivity toward CO 2 explored, yielding the characterization of a novel N/ Si + FLP-CO 2 adduct. These silicon species are active catalysts in the hydroboration of CO 2 to the methoxide level with 9-BBN, catecholborane (catBH), and pinacolborane (pinBH). Both experiments and DFT calculations highlight the role of the FLP-CO 2 adduct in the catalysis. Depending on the nature of the hydroborane reductant, two distinct mechanisms have been unveiled. While 9-BBN and catBH are able to reduce an intermediate FLP-CO 2 adduct, the hydroboration of CO 2 with pinBH follows a different and novel path where the B−H bond is activated by the silicon-based Lewis acid catalyst. In these mechanisms, the formation of a highly stabilized FLP-CO 2 adduct is found detrimental to the kinetics of the reaction.

Keywords: organocatalysis; CO 2; hydroboration; mechanisms; DFT calculations

Domains: Material chemistry

N von Wolff, G Lefèvre, J.-C Berthet, Pierre Thuéry, T Cantat. Implications of CO2 Activation by Frustrated Lewis Pairs in the Catalytic Hydroboration of CO2 : A View Using N/Si + Frustrated Lewis Pairs. ACS Catalysis, 2016, 6, pp.4526-4535. ⟨10.1021/acscatal.6b00421⟩. ⟨cea-01338153⟩