Insertion of CO2 into the carbon-boron bond of a boronic ester ligand.

New Ru and Zn diazafluorenyl complexes undergo C-H borylation of the diazafluorenyl ligand to form the corresponding diazafluorenylboronic ester complexes, which can insert CO2 into their C-B bonds to form boryl ester functionalities. The relevance of these new reactivities towards catalytic CO2 reduction has also been explored.