Reduction of CO to Methanol with Recyclable Organic Hydrides.

The reaction steps for the selective conversion of a transition metal carbonyl complex to a hydroxymethyl complex that releases methanol upon irradiation with visible light have been successfully quantified in acetonitrile solution with dihydrobenzimidazole organic hydride reductants. Dihydrobenzimidazole reductants have been shown to be inactive toward H generation in the presence of a wide range of proton sources and have been regenerated electrochemically or photochemically. Specifically, the reaction of -[Ru(bpy)(CO)] (bpy = 2,2'-bipyridine) with one equivalent of a dihydrobenzimidazole quantitatively yields a formyl complex, -[Ru(bpy)(CO)(CHO)], and the corresponding benzimidazolium on a seconds time scale.