Low p Phosphido-Boranes Capture Carbon Dioxide with Exceptional Strength: DFT Predictions Followed by Experimental Validation.

We have developed a class of phosphido-boranes (BoPh's) with formula X[RPBH] that bind CO with exceptional strength (Δ = -8.2 to -24.0 kcal/mol) at ambient conditions. We use quantum mechanics (QM) to determine how the choice of electron-donating versus electron-withdrawing ligand impacts the CO binding strength, in the presence of a donating borane moiety. We also examine the role of the cation in CO binding, finding that the ion position relative to the bound CO dramatically alters binding strength. We find that the BoPh with two ethyl ligands Li[EtPBH] leads to Δ = -24.0 kcal/mol upon CO binding while Li[PhPBH] leads to Δ = -12.8 kcal/mol. We synthesized the BoPh with two phenyl ligands Li[PhPBH] to validate the QM-predicted stability and predicted p.