Reductive Cleavage of the CO Molecule by a Reactive Vicinal Frustrated PH/BH Lewis Pair

A dimeric ethylene-bridged PH/BH system reduced carbon monoxide to the -CH₂-O- state. In the presence of B(C₆F₅)₃, the frustrated PH/BH Lewis pair reacted with carbon monoxide by reductive coupling of two CO molecules at the template. Removal of the B(C₆F₅)₃ borane with pyridine liberated one equiv of carbon monoxide to give a cyclic five-membered P(═O)-CH₂-B compound, the product of reductive cleavage of carbon monoxide. It reacted as a borylated Horner P(═O)CH₂B carbon nucleophile with carbon dioxide to give a bicyclic product by P-CH₂ attack on CO₂ combined with internal P═O to boron coordination.