Reductive Addition of  CO 2 to 9,10‐Phenanthrenequinone

Two molecules of add to electrochemically reduced 9,10‐phenanthrenequinone (PAQ) in to give the bis(carbonate), . In the absence of , PAQ undergoes two reversible, one‐electron reductions at −0.65 and −1.44V vs. SCE in . Addition of occurs at ∼ −0.7V vs. SCE with a rate constant of about 102 M−1s−1. A further one‐electron reduction takes place at the same potential and is followed by addition of a second molecule of . The final addition step is effectively chemically irreversible. Oxidation of the adduct results in the quantitative regeneration of PAQ and . Reduction of PAQ with cobaltocene in the presence of also gives . IR, NMR, and UV‐vis spectroscopy were used to identify and characterize . was also prepared by addition of to independently prepared . Loss of occurs upon addition of either or to a solution of . The expected methylation product, , was synthesized by electrochemical reduction of PAQ in the presence of .